Note that this page of links is assembled automatically via software
algorithm and sometimes it gets a little confused. Also, this is certainly NOT a complete list of resources, its just some of the ones that are easy to retrieve online.
Recent Physics-Related News Articles
These links point to recent Physics-related news articles from the popular press and more "physics oriented" sites.
After Setbacks, Small Successes for Gene Therapy (Fri Nov 6 1:15 am)
Three recent successes, though small, prompted hopes among scientists that a still-experimental idea for correcting genetic disorders might be back.
Treating the Pain Epidemic (Thu Nov 5 2:23 pm)
Chronic pain affects more than 70 million Americans, which makes it more widespread than heart disease, cancer and diabetes combined. So why don't more doctors and researchers take it seriously?
William Belton, Self-Taught Ornithologist, Dies at 95 (Fri Nov 6 1:54 am)
Mr. Belton was almost single-handedly responsible for the current body of knowledge of the bird life of Rio Grande do Sul, the southernmost Brazilian state.
Rules on Modified Corn Skirted, Study Says (Fri Nov 6 2:27 pm)
As many as 25 percent of the American farmers growing genetically engineered corn are no longer complying with federal rules intended to maintain the resistance of the crops to damage from insects.
Democrats Push Climate Bill Through Panel Without G.O.P. Debate (Fri Nov 6 1:49 pm)
The move suggested that President Obama and Democratic supporters of the bill will have serious problems assembling the votes needed to enact it when it comes to the Senate floor.
Groups Press U.S. and China on Carbon (Wed Nov 4 8:06 pm)
Two research organizations want the two countries to put more money into developing use of carbon capture technology.
Qian Xuesen, Father of China’s Space Program, Dies at 98 (Wed Nov 4 12:29 am)
Mr. Qian was a rocket scientist who led China’s space and military rocketry efforts after he was drummed out of the U.S. during the redbaiting of the McCarthy era.
Findings on Mysterious Haze at Galaxy’s Center (Sat Oct 31 2:52 am)
Astronomers said the particles around the core of the Milky Way might be the decayed remains of the long-sought dark matter that constituted a quarter of the universe.
7.3 Billion Years Later, Einstein’s Theory Prevails (Fri Oct 30 4:47 pm)
Astronomers said a contest between gamma rays of differing energies and wavelengths tested a proclamation by Einstein on the speed of light.
NASA Rocket Takes Off as Clouds Break (Fri Oct 30 4:47 pm)
After weather delays, the Ares I-X, a prototype of NASA’s next-generation rocket, zipped off the launch pad.
New Rocket, but Future of Program Is Unclear (Tue Oct 27 9:55 am)
The launching of the Ares I-X is scheduled for Tuesday, less than a week after a report on NASA’s human spaceflight program brought the entire program into question.
For NASA, Possible Shifts in Direction (Fri Oct 23 2:20 am)
A report from a 10-member group said the Ares I was a victim of smaller-than-expected budgets and changing circumstances.
Beyond North and South: Evidence for Magnetic Monopoles (Fri Nov 6 7:00 am)
Editor's note: The original online version of this story was previously posted. Magnets are remarkable exemplars of fairness--every north pole is invariably accompanied by a counterbalancing south pole. Split a magnet in two, and the...
Tweak Gravity: What If There Is No Dark Matter? (Thu Nov 5 1:01 pm)
Theorists and observational astronomers are hot on the trail of dark matter , the invisible material thought to account for puzzling mass disparities in large-scale astronomical structures. For instance, galaxies and galactic clusters behave...
How Noise Can Help Quantum Entanglement (Tue Nov 3 7:00 am)
Wouldn’t it be nice to be an electron? Then you, too, could take advantage of the marvels of quantum mechanics, such as being in two places at once--very handy for juggling the competing demands of modern life. Alas, physicists have long...
The Long-Lost Siblings of the Sun (preview) (Mon Nov 2 7:00 am)
People have often sought solitude in the starry night sky, and it is an appropriate place for that. The night is dark because, in cosmic terms, our sun and its family of planets are very lonely. Neighboring stars are so far away that they look...
Is the nuclear material at Los Alamos safe from an earthquake? (Fri Oct 30 4:30 pm)
Los Alamos National Laboratory conducts much of the nation's nuclear security research, and a new study has found that the plutonium facility may not be equipped to safely ride out an earthquake. [More]
Astronomical Artifact: Most Distant Object Yet Detected Carries Clues from Early Universe (Wed Oct 28 2:01 pm)
A violent explosion picked up by a NASA satellite earlier this year is the oldest object ever seen by astronomers, its light having been emitted some 13 billion years ago. At that time the universe was roughly 5 percent of its present age and...
Novel Analysis Confirms Climate "Hockey Stick" Graph (Wed Oct 28 8:00 am)
The “hockey stick” graph has been both a linchpin and target in the climate change debate. As a plot of average Northern Hemisphere temperature from two millennia ago to the present, it stays relatively flat until the 20th century,...
GREAT RED SPOT NOT AS GREAT (Fri Feb 27 12:02 pm)
GREAT RED SPOT NOT AS GREAT The hurricanes that visit the Gulf and Caribbean in September and even the huge jetstream that dominates winter weath. . .
Bluebeat to battle EMI over Beatles songs (Sat Nov 7 10:10 am)
US online music service Bluebeat said it plans to fight British recording label EMI over rights to stream and sell versions of Beatles songs.
Dinosaur prints found on NZealand's South Island (Sat Nov 7 9:40 am)
Scientists have discovered the first evidence that dinosaurs roamed the South Island of New Zealand with 70-million-year-old footprints found in six locations.
Decision day for health care in the House (Sat Nov 7 9:40 am)
(AP) -- President Barack Obama is trying to close the deal in the House on his health care overhaul, facing a make-or-break vote that's certain to be seen as a test of his presidency.
Prized mushroom collection returns to China (Sat Nov 7 9:10 am)
(AP) -- A Chinese scholar persecuted during the Cultural Revolution for smuggling a rare collection of mushrooms out of China before World War II was honored Saturday when the collection was returned more than 70 years later.
Island village hit by suspected swine flu (Sat Nov 7 9:00 am)
(AP) -- Suspected swine flu is sweeping a traditional Eskimo whaling village on a remote Alaska island - prompting an urgent medical mission to deliver help.
Microsoft websites top spots in September: comScore (Sat Nov 7 9:00 am)
Industry tracker comScore on Friday released a study showing that Internet users in September spent more time at Microsoft websites that at any other online properties.
Brazil blackouts result of cyber hacking: report (Sat Nov 7 8:59 am)
Massive power outages in Brazil in 2005 and 2007 that impacted millions were caused by cyber hackers attacking control systems, the US television network CBS said Sunday.
Russian rocket to launch from French Guiana in 2010 (Sat Nov 7 8:56 am)
A Russian rocket will next year for the first time blast off from a European launch pad in South America, officials said Saturday, as the first rockets headed for the site on board a ship.
Sea lions killed, but Columbia salmon toll rises (Sat Nov 7 8:51 am)
(AP) -- Killing or removing 25 California sea lions over the past two years has not reduced the toll on salmon at the base of Bonneville Dam in the Columbia River.
Seattle team wins $900,000 in Space Elevator Games (Sat Nov 7 8:45 am)
(AP) -- A Seattle team has collected a $900,000 prize in a NASA-backed competition to develop the concept of an elevator to space - an idea spurred by science fiction novels.
Materials in extreme environments (Sun Nov 1 7:00 am)
The study of materials under harsh conditions is essential to meet a range of energy challenges—from creating better turbines, reactors, and batteries to developing future energy systems in dense plasmas.
Human-generated sound and marine mammals (Sun Nov 1 7:00 am)
Loud anthropogenic noises can alter the behavior of whales and other marine mammals, sometimes with fatal consequences
Paul Dirac: Engineer, mathematician, philosopher, physicist (Sun Nov 1 7:00 am)
Dirac practiced theoretical physics for almost 60 years with a unique style: a sometimes baffling combination of intuition, imagination, rectilinear logic, and steam-hammer mathematical power.
One of the things that sets science apart from many other fields of human-endeavor is that to prevent personal opinion from being represented as fact, articles that are submitted to scientific journals are "peer-reviewed", which means the paper is sent to a referee (possibly a scientific "competitor") who disects the article and makes sure its conclusions are valid based on the data presented. The process is not perfect, but it tends to drive a high level of scholarly quality in peer-reviewed journals.
USAGE NOTE: The symbol next to each feed item can be clicked in order to bring up the abstract from the article.
Author(s): Laura Filion, Matthieu Marechal, Bas van Oorschot, Dani?Pelt, Frank Smallenburg, and Marjolein Dijkstra[Phys. Rev. Lett. 103, 199904] Published Fri Nov 06, 2009
Author(s): Tobias GallaDemographic noise has profound effects on evolutionary and population dynamics, as well as on chemical reaction systems and models of epidemiology. Such noise is intrinsic and due to the discreteness of the dynamics in finite populations. We here show that similar noise-sustained trajectories arise ...[Phys. Rev. Lett. 103, 198702] Published Fri Nov 06, 2009
Author(s): J. W. Mullinax and W. G. NoidWe employ a basis set representation for classical force fields to derive an original system of exact integral equations relating each mode in the force field to an associated set of structural correlation functions. This generalized Yvon-Born-Green theory provides a framework for interpreting compl...[Phys. Rev. Lett. 103, 198104] Published Fri Nov 06, 2009
Author(s): Lars Bocklage, Benjamin Kr?, Toru Matsuyama, Markus Bolte, Ulrich Merkt, Daniela Pfannkuche, and Guido MeierA dependence of current-induced domain-wall motion in nanowires on the temporal shape of current pulses is observed. The results show that the motion of the wall is amplified for alterations of the current on a time scale smaller than the intrinsic time scale of the domain wall which is a few nanose...[Phys. Rev. Lett. 103, 197204] Published Fri Nov 06, 2009
Author(s): C. W. Groth, M. Wimmer, A. R. Akhmerov, J. Tworzydło, and C. W. J. BeenakkerWe present an effective medium theory that explains the disorder-induced transition into a phase of quantized conductance, discovered in computer simulations of HgTe quantum wells. It is the combination of a random potential and quadratic corrections ∝p^{2} σ_{z} to the Dirac Hamiltonian that can...[Phys. Rev. Lett. 103, 196805] Published Fri Nov 06, 2009
Author(s): Leonardo Spanu, Sandro Sorella, and Giulia GalliWe compute the interlayer bonding properties of graphite using an ab initio many-body theory. We carry out variational and diffusion quantum Monte Carlo calculations and find an equilibrium interlayer binding energy in good agreement with most recent experiments. We also analyze the behavior of th...[Phys. Rev. Lett. 103, 196401] Published Fri Nov 06, 2009
Author(s): M. Xu, Y. Q. Cheng, H. W. Sheng, and E. MaUsing electronic structure calculations, we demonstrate a global valence alternation in the amorphous Ge_{2} Sb_{2} Te_{5} , a prototype phase-change alloy for data storage. The resulting p bonding profoundly influences the local atomic structure, leading to right-angle components similar to those i...[Phys. Rev. Lett. 103, 195502] Published Fri Nov 06, 2009
Author(s): C. Klempt, O. Topic, G. Gebreyesus, M. Scherer, T. Henninger, P. Hyllus, W. Ertmer, L. Santos, and J. J. ArltWe analyze the spinor dynamics of a ^{87} Rb F=2 condensate initially prepared in the m_{F} =0 Zeeman sublevel. We show that this dynamics, characterized by the creation of correlated atomic pairs in m_{F} =±1, presents an intriguing multiresonant magnetic-field dependence induced by the trap inhom...[Phys. Rev. Lett. 103, 195302] Published Fri Nov 06, 2009
Author(s): O. M. Braun, I. Barel, and M. UrbakhWe propose a model for a description of dynamics of cracklike processes that occur at the interface between two blocks prior to the onset of frictional motion. We find that the onset of sliding is preceded by well-defined detachment fronts initiated at the slider trailing edge and extended across th...[Phys. Rev. Lett. 103, 194301] Published Fri Nov 06, 2009
Author(s): Dam T. Son and Piotr Sur?We consider the hydrodynamic regime of theories with quantum anomalies for global currents. We show that a hitherto discarded term in the conserved current is not only allowed by symmetries, but is in fact required by triangle anomalies and the second law of thermodynamics. This term leads to a numb...[Phys. Rev. Lett. 103, 191601] Published Fri Nov 06, 2009
Author(s): O. Scholten, S. Buitink, J. Bacelar, R. Braun, A. G. de Bruyn, H. Falcke, K. Singh, B. Stappers, R. G. Strom, and R. al YahyaouiParticle cascades initiated by ultrahigh energy neutrinos in the lunar regolith will emit an electromagnetic pulse with a time duration of the order of nanoseconds through a process known as the Askaryan effect. It has been shown that in an observing window around 150 MHz there is a maximum chance ...[Phys. Rev. Lett. 103, 191301] Published Fri Nov 06, 2009
Author(s): Uttam Shrestha, Juha Javanainen, and Janne RuostekoskiWe study numerically the outcome of the phase separation instability of a dual-species Bose-Einstein condensate in an optical lattice. When only one excitation mode is unstable a bound pair of bright and dark solitonlike structures periodically appears and disappears, whereas for more than one unsta...[Phys. Rev. Lett. 103, 190401] Published Fri Nov 06, 2009
Author(s): Lior Turgeman, Shai Carmi, and Eli BarkaiWe derive backward and forward fractional Feynman-Kac equations for the distribution of functionals of the path of a particle undergoing anomalous diffusion. Fractional substantial derivatives introduced by Friedrich and co-workers [Phys. Rev. Lett. 96, 230601 (2006)] provide the correct fractional ...[Phys. Rev. Lett. 103, 190201] Published Fri Nov 06, 2009
Author(s): Gavin W. Morley, Johan van Tol, Arzhang Ardavan, Kyriakos Porfyrakis, Jinying Zhang, and G. Andrew D. Briggs[Phys. Rev. Lett. 103, 199902] Published Thu Nov 05, 2009
Author(s): Kyriacos C. Leptos, Jeffrey S. Guasto, J. P. Gollub, Adriana I. Pesci, and Raymond E. GoldsteinIn contexts such as suspension feeding in marine ecologies there is an interplay between Brownian motion of nonmotile particles and their advection by flows from swimming microorganisms. As a laboratory realization, we study passive tracers in suspensions of eukaryotic swimmers, the alga Chlamydomon...[Phys. Rev. Lett. 103, 198103] Published Thu Nov 05, 2009
Author(s): Enju Lima, Lutz Wiegart, Petra Pernot, Malcolm Howells, Joanna Timmins, Federico Zontone, and Anders MadsenX-ray diffraction microscopy (XDM) is well suited for nondestructive, high-resolution biological imaging, especially for thick samples, with the high penetration power of x rays and without limitations imposed by a lens. We developed nonvacuum, cryogenic (cryo-) XDM with hard x rays at 8 keV and ...[Phys. Rev. Lett. 103, 198102] Published Thu Nov 05, 2009
Author(s): Xiaojing Huang, Johanna Nelson, Janos Kirz, Enju Lima, Stefano Marchesini, Huijie Miao, Aaron M. Neiman, David Shapiro, Jan Steinbrener, Andrew Stewart, Joshua J. Turner, and Chris JacobsenWe report the first image of an intact, frozen hydrated eukaryotic cell using x-ray diffraction microscopy, or coherent x-ray diffraction imaging. By plunge freezing the specimen in liquid ethane and maintaining it below -170 °C, artifacts due to dehydration, ice crystallization, and radiation da...[Phys. Rev. Lett. 103, 198101] Published Thu Nov 05, 2009
Author(s): Ilya Grinberg, Young-Han Shin, and Andrew M. RappeWe use atomistic molecular dynamics simulations to study relaxor behavior in the 0.75PbMg_{1/3} Nb_{2/3} O_{3} -0.25PbTiO_{3} material. Even for a fairly small simulation size of 1000 atoms, the system exhibits frequency dispersion and deviation from the Curie-Weiss law typical of relaxor materials....[Phys. Rev. Lett. 103, 197601] Published Thu Nov 05, 2009
Author(s): K. Namikawa, M. Kishimoto, K. Nasu, E. Matsushita, R. Z. Tai, K. Sukegawa, H. Yamatani, H. Hasegawa, M. Nishikino, M. Tanaka, and K. NagashimaWe have developed a new method to investigate the relaxation time of the dipole moment in polarization clusters in BaTiO_{3} . Time correlation of speckle intensities was measured by the use of a double pulsed soft x-ray laser. The evolution of the relaxation time of the dipole moment near the Curie...[Phys. Rev. Lett. 103, 197401] Published Thu Nov 05, 2009
Author(s): Yi-feng Yang, Ricardo Urbano, Nicholas J. Curro, David Pines, and E. D. BauerWe report Knight-shift experiments on the superconducting heavy-electron material CeCoIn_{5} that allow one to track with some precision the behavior of the heavy-electron Kondo liquid in the superconducting state with results in agreement with BCS theory. An analysis of the ^{115} In nuclear quadru...[Phys. Rev. Lett. 103, 197004] Published Thu Nov 05, 2009
Author(s): Ofer Yuli, Itay Asulin, Yoav Kalcheim, Gad Koren, and Oded MilloThe temperature evolution of the proximity effect in Au/La_{2-x} Sr_{x} CuO_{4} and La_{1.55} Sr_{0.45} CuO_{4} /La_{2-x} Sr_{x} CuO_{4} bilayers was investigated using scanning tunneling microscopy. Proximity-induced gaps, centered at the chemical potential, were found to persist above the supercon...[Phys. Rev. Lett. 103, 197003] Published Thu Nov 05, 2009
Author(s): Dung-Hai LeeThe surface of a topological insulator is a closed two-dimensional manifold. The surface states are described by the Dirac Hamiltonian in curved two-dimensional spaces. For a slablike sample with a magnetic field perpendicular to its top and bottom surfaces, there are chiral states delocalized on th...[Phys. Rev. Lett. 103, 196804] Published Thu Nov 05, 2009
Author(s): M. D. Alaimo, M. A. C. Potenza, M. Manfredda, G. Geloni, M. Sztucki, T. Narayanan, and M. GiglioWe present a novel method to map the two-dimensional transverse coherence of an x-ray beam using the dynamical near-field speckles formed by scattering from colloidal particles. Owing to the statistical nature of the method, the coherence properties of synchrotron radiation from an undulator source ...[Phys. Rev. Lett. 103, 194805] Published Thu Nov 05, 2009
Author(s): Apiano F. Morais, Hansjoerg Seybold, Hans J. Herrmann, and Jos?. Andrade, Jr.We investigate the flow of various non-Newtonian fluids through three-dimensional disordered porous media by direct numerical simulation of momentum transport and continuity equations. Remarkably, our results for power-law (PL) fluids indicate that the flow, when quantified in terms of a properly mo...[Phys. Rev. Lett. 103, 194502] Published Thu Nov 05, 2009
Author(s): Daniel K. Shenfeld, Huafeng Xu, Michael P. Eastwood, Ron O. Dror, and David E. ShawIn computational thermodynamics, a sequence of intermediate states is commonly introduced to connect two equilibrium states. We consider two cases where the choice of intermediate states is particularly important: minimizing statistical error in free-energy difference calculations and maximizing ave...[Phys. Rev. E 80, 046705] Published Mon Oct 19, 2009
Author(s): Timothy E. Saunders and Martin HowardMorphogen profiles play a vital role in biology by specifying position in embryonic development. However, the factors that influence the shape of a morphogen profile remain poorly understood. Since morphogens should provide precise positional information, one significant factor is the robustness of ...[Phys. Rev. E 80, 041902] Published Fri Oct 02, 2009
Author(s): Richard S. Graham and Peter D. OlmstedWe perform kinetic Monte Carlo simulations of flow-induced nucleation in polymer melts with an algorithm that is tractable even at low undercooling. The configuration of the noncrystallized chains under flow is computed with a recent nonlinear tube model. Our simulations predict both enhanced nucle...[Phys. Rev. Lett. 103, 115702] Published Thu Sep 10, 2009
Author(s): G. Vogl, E. Partyka-Jankowska, M. Zając, and A. I. ChumakovWe study the structure of a model surface, i.e., an Fe monolayer on W(110) by nuclear resonant scattering of x rays. We conclude that at room temperature the structure is nearly perfect, whereas when increasing the temperature up to 770 K an increasing fraction of the Fe atoms feels the appearance o...[Phys. Rev. B 80, 115406] Published Fri Sep 04, 2009
Author(s): Christoph Freysoldt, Patrick Rinke, and Matthias SchefflerBy means of quasiparticle-energy calculations in the G_{0} W_{0} approach, we show for the prototypical insulator-semiconductor system NaCl/Ge(001) that polarization effects at the interfaces noticeably affect the excitation spectrum of molecules adsorbed on the surface of the NaCl films. The magnit...[Phys. Rev. Lett. 103, 056803] Published Fri Jul 31, 2009
Author(s): B. P. Abbott et al. LIGO Scientific CollaborationThis paper reports on an all-sky search for periodic gravitational waves from sources such as deformed isolated rapidly spinning neutron stars. The analysis uses 840 hours of data from 66 days of the fifth LIGO science run (S5). The data were searched for quasimonochromatic waves with frequencies ...[Phys. Rev. D 80, 042003] Published Tue Aug 11, 2009
Author(s): Xinguo Ren, Patrick Rinke, and Matthias SchefflerThe adsorption of CO on the Cu(111) surface is investigated in the random phase approximation (RPA) as formulated within the adiabatic connection fluctuation-dissipation theorem. The RPA adsorption energy is obtained by adding a “local exchange-correlation correction” that is extrapolated from c...[Phys. Rev. B 80, 045402] Published Thu Jul 02, 2009
Author(s): N. Bloembergen, C. K. Patel, P. Avizonis, R. G. Clem, A. Hertzberg, T. H. Johnson, T. Marshall, R. B. Miller, W. E. Morrow, E. E. Salpeter, A. M. Sessler, J. D. Sullivan, J. C. Wyant, A. Yariv, R. N. Zare, A. J. Glass, L. C. Hebel, G. E. Pake, M. M. May, W. K. Panofsky, A. L. Schawlow, C. H. Townes, and H. York APS Study Group Participants, APS Council Review Committee[Rev. Mod. Phys. 59, S1] Published Wed Jul 01, 1987
Author(s): Richard Wilson, Kamal J. Araj, Augustine O. Allen, Peter Auer, David G. Boulware, Fred Finlayson, Simon Goren, Clark Ice, Leon Lidofsky, Allen Lee Sessoms, Mary L. Shoaf, Irving Spiewak, Thomas Tombrello, Herbert S. Gutowsky, Andreas Acrivos, Herman Feshbach, and William A. Fowler APS Study Group Participants, APS Council Review Committee[Rev. Mod. Phys. 57, S1] Published Mon Jul 01, 1985
Author(s): Bernard R. Cooper, Wayne R. Gruner, Larry Anderson, Robert H. Davis, Paul Engelking, Jose D. Garcia, Edward Gerjuoy, Robert I. Jaffee, Philip G. Kosky, Leonidas Petrakis, Robert T. Poe, Richard Pollina, C. Dwight Prater, Robert L. Thomas, Sandor Trajmar, G. J. Dienes, Nancy M. O'Fallon, Harvey Brooks, William A. Fowler, Everett Gorin, Norman F. Ramsey, and M. D. Schlesinger APS Study Group Participants, Ex Officio Panel Members, APS Council Review Committee[Rev. Mod. Phys. 53, S1] Published Thu Oct 01, 1981
Author(s): L. Charles Hebel, Eldon L. Christensen, Fred A. Donath, Warren E. Falconer, Leon J. Lidofsky, Ernest J. Moniz, Thomas H. Moss, Robert L. Pigford, Thomas H. Pigford, Gene I. Rochlin, Robert H. Silsbee, McDonald E. Wrenn, Hans Frauenfelder, Theodore L. Cairns, W. K. Panofsky, and M. Gene Simmons APS Study Group Participants, APS Council Review CommitteeUtilization of nuclear fuels and management of nuclear wastes have become major topics of public discussion. Under the auspices of the American Physical Society this study was undertaken as an independent evaluation of technical issues in the use of fissionable materials in nuclear fuel cycles, toge...[Rev. Mod. Phys. 50, S1] Published Sun Jan 01, 1978
Author(s): H. W. Lewis, R. J. Budnitz, A. W. Castleman, D. E. Dorfan, F. C. Finlayson, R. L. Garwin, L. C. Hebel, S. M. Keeny, R. A. Muller, T. B. Taylor, G. F. Smoot, F. von Hippel, Hans Bethe, W. K. Panofsky, and V. F. Weisskopf APS Study Group Participants, APS Council Review CommitteeThe issue of light-water reactor (LWR) safety has been the subject of a part-time, year-long study sponsored by the American Physical Society. The goal of the study was the assessment of some of the technical aspects of the safety of large light-water nuclear power reactors typical of present commer...[Rev. Mod. Phys. 47, S1] Published Wed Jan 01, 1975
Author(s): F. L. Vook, H. K. Birnbaum, T. H. Blewitt, W. L. Brown, J. W. Corbett, J. H. Crawford, A. N. Goland, G. L. Kulcinski, M. T. Robinson, D. N. Seidman, F. W. Young, J. Bardeen, R. W. Balluffi, J. S. Koehler, and G. H. Vineyard APS Study Group Participants, APS Council Review Committee[Rev. Mod. Phys. 47, S1] Published Wed Jan 01, 1975
Author(s): David K. Barton, Roger Falcone, Daniel Kleppner, Frederick K. Lamb, Ming K. Lau, Harvey L. Lynch, David Moncton, David Montague, David E. Mosher, William Priedhorsky, Maury Tigner, and David R. VaughanThis issue of RMP has, as a special supplement, the report of an APS study group on the physics and engineering issues that must be addressed in designing a missile defense system capable of intercepting a hostile missile while it is still burning, the so-called “boost phase.” The challenges for...[Rev. Mod. Phys. 76, S1] Published Tue Oct 05, 2004
Author(s): Burton Richter, David Goldston, George Crabtree, Leon Glicksman, David Goldstein, David Greene, Dan Kammen, Mark Levine, Michael Lubell, Maxine Savitz, Daniel Sperling, Fred Schlachter, John Scofield, and James DawsonThe American Physical Society regularly produces reports on issues of public import that require technical understanding and for which an objective and authoritative analysis would be of particular use to the public and policy makers. This report, entitled Energy Future: Think Efficiency, is the lat...[Rev. Mod. Phys. 80, S1] Published Tue Dec 30, 2008
Author(s): Kaiichiro Ota, Masaki Nomura, and Toshio AoyagiWe demonstrate that the phase response curve (PRC) can be reconstructed using a weighted spike-triggered average of an injected fluctuating input. The key idea is to choose the weight to be proportional to the magnitude of the fluctuation of the oscillatory period. Particularly, when a neuron exhibi...[Phys. Rev. Lett. 103, 024101] Published Wed Jul 08, 2009
Author(s): Evan Monroig, Kazuyuki Aihara, and Yozo FujinoWe examine the problem of reconstructing input-output systems from time series data. Although the method of delays has already been used in the case where both input and output are measured, in some cases, the inputs cannot be measured, and hence, the method of delays cannot be used. On the basis of...[Phys. Rev. E 79, 056208] Published Fri May 08, 2009
Author(s): Johan M. Carlsson, Felix Hanke, Suljo Linic, and Matthias SchefflerWe study the oxidation of vacancies in graphene by ab initio atomistic thermodynamics to identify the dominant reaction mechanisms. Our calculations show that the low-temperature oxidation occurs via a two-step process: Vacancies are initially saturated by stable O groups, such as ether (C-O-C) and...[Phys. Rev. Lett. 102, 166104] Published Thu Apr 23, 2009
Author(s): Martin Gabl, Magdalena Bachmann, Norbert Memmel, and Erminald BertelSilver nanoclusters arranged in quasi-one-dimensional chains with a nearest-neighbor cluster-cluster distance of 1.4 nm were prepared on the R(15?2)-C/W(110) surface. The silver cluster chains form local thermodynamic equilibrium structures. Interactions between neighboring clusters are addressed ...[Phys. Rev. B 79, 153409] Published Mon Apr 27, 2009
Author(s): Hong Jiang, Ricardo I. Gomez-Abal, Patrick Rinke, and Matthias SchefflerMany-body perturbation theory in the GW approach is applied to lanthanide oxides, using the local-density approximation plus a Hubbard U correction (LDA+U) as the starting point. Good agreement between the G_{0} W_{0} density of states and experimental spectra is observed for CeO_{2} and Ce_{2} O_{3...[Phys. Rev. Lett. 102, 126403] Published Tue Mar 24, 2009
Author(s): Nicholas P. Bailey, Thomas B. Schrøder, and Jeppe C. DyreWe study the statistics of flow events in the inherent dynamics in supercooled two- and three-dimensional binary Lennard-Jones liquids. Distributions of changes of the collective quantities energy, pressure, and shear stress become exponential at low temperatures, as does that of the event ?8364;œsize?8364;...[Phys. Rev. Lett. 102, 055701] Published Tue Feb 03, 2009
Author(s): Alexandre Tkatchenko and Matthias SchefflerWe present a parameter-free method for an accurate determination of long-range van der Waals interactions from mean-field electronic structure calculations. Our method relies on the summation of interatomic C_{6} coefficients, derived from the electron density of a molecule or solid and accurate ref...[Phys. Rev. Lett. 102, 073005] Published Fri Feb 20, 2009
S. S. Lin, H. P. He, Y. F. Lu, and Z. Z. Ye Hydrogen is codoped with sodium into ZnO films. X-ray photoelectron spectroscopy and secondary ion mass spectroscopy indicate that the Na concentration decreases as the substrate temperature increases. Hall-effect tests reveal a transition from n-type to p-type conduction when the growth temperature ... [J. Appl. Phys. 106, 093508 (2009)] published Fri Nov 6, 2009.
Oleg A. Louchev and Satoshi Wada The feasibility of cascaded second harmonic generation (SHG) and third harmonic generation (THG) in a monolithic two-sectioned periodically poled lithium tantalate crystal is analyzed. Simulation using a computational nonlinear optical model rigorously coupled with a thermal model suggests that 25%3 ... [J. Appl. Phys. 106, 093106 (2009)] published Fri Nov 6, 2009.
D. P. Adams, M. A. Rodriguez, J. P. McDonald, M. M. Bai, E. Jones, Jr. et al. Nickel/titanium nanolaminates fabricated by sputter deposition exhibited rapid, high-temperature synthesis. When heated locally, self-sustained reactions were produced in freestanding Ni/Ti multilayer foils characterized by average propagation speeds between ~0.1 and 1.4 m/s. The speed of a propagat ... [J. Appl. Phys. 106, 093505 (2009)] published Fri Nov 6, 2009.
M. E. White, O. Bierwagen, M. Y. Tsai, and J. S. Speck By antimony doping tin oxide, SnO:Sb (ATO), below 1.0% Sb concentration, controllable n-type doping was realized. Plasma-assisted molecular beam epitaxy has been used to grow high quality single crystalline epitaxial thin films of unintentionally doped (UID) and Sb-doped SnO on r-plane sapphire subs ... [J. Appl. Phys. 106, 093704 (2009)] published Fri Nov 6, 2009.
Hua Qu, Lixin Cao, Ge Su, Wei Liu, Yuanguang Sun et al. Undoped ZnS and ZnS:Ag nanoparticles have been prepared through hydrothemal synthesis. The changes of luminescence properties induced by ultraviolet irradiation have been investigated. For both samples, the initial slight increase in luminescence is ascribed to the fast electron filling, while the s ... [J. Appl. Phys. 106, 093506 (2009)] published Fri Nov 6, 2009.
N. E. Souza Filho, A. C. Nogueira, J. H. Rohling, M. L. Baesso, A. N. Medina et al. This paper discusses the use of photoacoustic models to obtain the nonradiative relaxation time (tau) and characteristic diffusion time (tau) for a sample showing visible absorption bands from fluorescent ion-doped low-silica calcium aluminosilicate glass. Two models allowing phase shift analyses, t ... [J. Appl. Phys. 106, 093105 (2009)] published Fri Nov 6, 2009.
W. X. Li, R. Zeng, L. Lu, Y. Li, and S. X. Dou The influences of connectivity and disorder on the critical current density J are discussed to clarify the different mechanisms of J(H) enhancement in different magnetic field ranges. Excess Mg in MgB+10 wt % SiC composites effectively improves the connectivity, as evidenced by both the resistivit ... [J. Appl. Phys. 106, 093906 (2009)] published Fri Nov 6, 2009.
M. Martini, M. Montagna, M. Ou, O. Tillement, S. Roux et al. Dye quantum yield is generally measured using the method of Williams, which consists in comparing the absorbance and the emission of the dye to test with those of a reference. Unfortunately, this method is no more applicable when the sample presents some significant scattering which is, for instance ... [J. Appl. Phys. 106, 094304 (2009)] published Fri Nov 6, 2009.
Mohammad Khazaei, Mohammad Saeed Bahramy, Natarajan Sathiyamoorthy Venkataramanan, Hiroshi Mizuseki, and Yoshiyuki Kawazoe Our first-principles calculations show that if the hydrogen atoms on one of the faces of a graphane sheet (prehydrogenated graphene) are substituted with Li atoms, the resulting monolayer attains a good hydrogen storage capacity of around 3.8 wt % close to the revised Department of Energy (DOE) targ ... [J. Appl. Phys. 106, 094303 (2009)] published Fri Nov 6, 2009.
D. Navarro-Urrios, Y. Lebour, O. Jambois, B. Garrido, A. Pitanti et al. Optical properties of directly excited erbium (Er) ions have been studied in silicon rich silicon oxide materials codoped with Er. The spectral dependence of the direct excitation cross section (sigma) of the Er atomic I-->I transition (around 0.98 [mu]m) has been measured by time resolved [mu]-pho ... [J. Appl. Phys. 106, 093107 (2009)] published Fri Nov 6, 2009.
Jaroslaw W. Klos and Maciej Krawczyk We calculate the band structure of a two-dimensional GaAs/AlGaAs superlattice and estimate the ultimate efficiency of solar cells using this type of structure for solar energy conversion. The superlattice under consideration consists of gallium arsenide rods forming a square lattice and embedded in ... [J. Appl. Phys. 106, 093703 (2009)] published Fri Nov 6, 2009.
Olivier Deparis, Jean Pol Vigneron, Otto Agustsson, and Daniel Decroupet The amount of solar energy reaching the active (photovoltaic) layer in a thin-film solar cell can be increased by reducing the Fresnel reflection losses at the interfaces. By using corrugated interfaces (at the wavelength scale), adiabatic propagation of the electromagnetic radiation is achieved ove ... [J. Appl. Phys. 106, 094505 (2009)] published Fri Nov 6, 2009.
D. J. Oliver, J. E. Bradby, S. Ruffell, J. S. Williams, and P. Munroe We have investigated nanoindentation-induced plastic deformation in amorphous germanium (a-Ge) prepared by high-energy self-ion implantation. Using cross-sectional transmission electron microscopy, micro-Raman spectroscopy, and force-displacement curve analysis, we find strong evidence for a pressur ... [J. Appl. Phys. 106, 093509 (2009)] published Fri Nov 6, 2009.
Shotaro Hara, Satoshi Izumi, and Shinsuke Sakai Threshold strain required for a thermally activated dislocation nucleation from a Ni surface step has been measured using an atomistic-based reaction pathway analysis. We show that the saddle-point configuration and the stress-dependent activation energy are strongly influenced by the presence of a ... [J. Appl. Phys. 106, 093507 (2009)] published Fri Nov 6, 2009.
N. K. Bourne, G. T. Gray, III, and J. C. F. Millett The response of four cubic metals to shock loading is reviewed in order to understand the effects of microstructure on continuum response. Experiments are described that link defect generation and storage mechanisms at the mesoscale to observations in the bulk. Four materials were reviewed; these we ... [J. Appl. Phys. 106, 091301 (2009)] published Fri Nov 6, 2009.
H.-S. Zhang and K. Komvopoulos Surface modification of a magnetic recording medium was accomplished by filtered cathodic vacuum arc (FCVA). The carbon overcoat of thin-film disks was removed by Ar ion sputter etching in vacuum to prevent oxidation of the exposed magnetic medium, which was then modified by FCVA carbon plasma under ... [J. Appl. Phys. 106, 093504 (2009)] published Thu Nov 5, 2009.
Shingo Kondo, Shinji Kawai, Wakana Takeuchi, Koji Yamakawa, Shoji Den et al. We synthesized carbon nanowalls (CNWs) using radical injection plasma-enhanced chemical vapor deposition. The initial growth process of CNWs was investigated with and without O gas addition to a CF capacitively coupled plasma with H radical injection. In the case of the CNW synthesis without the add ... [J. Appl. Phys. 106, 094302 (2009)] published Thu Nov 5, 2009.
Tse Nga Ng (吳子雅), Beverly Russo, and Ana Claudia Arias Organic ferroelectric field-effect transistors were fabricated by inkjet printing for use as nonvolatile memory. Changes in device hysteresis were measured for 7 days to determine the limiting properties that restrict memory retention time. It was found that shifts in threshold voltage contributed t ... [J. Appl. Phys. 106, 094504 (2009)] published Thu Nov 5, 2009.
K. Bhattacharyya, S. Varma, A. K. Tripathi, D. Bhattacharyya, O. Mathon et al. A modified sol-gel method for synthesizing vanadium doped titania is being reported. These materials were thoroughly characterized for their oxidation states by electron paramagnetic resonance and x-ray absorption near edge structure and the local environment of the V-atom were investigated by the x ... [J. Appl. Phys. 106, 093503 (2009)] published Thu Nov 5, 2009.
O. Mounkachi, A. Benyoussef, A. El Kenz, E. H. Saidi, and E. K. Hlil Using first-principles density functional calculations, we study the electronic structure and magnetic properties of Mn-doped ZnO, wurtzite crystal structure, with various defects. This allows to understand and to explain the half-metallicity and the ferromagnetism stability, observed in Mn-doped Zn ... [J. Appl. Phys. 106, 093905 (2009)] published Thu Nov 5, 2009.
Muhammad Qazi, Jie Liu, M. V. S. Chandrashekhar, and Goutam Koley Correlations between surface electronic properties of SiC and NO adsorption were investigated using electrostatic force potentiometry. It was observed that surface work function (SWF) of both 6H and 3CSiC changes significantly with NO adsorption. Measurements on semi-insulating 6HSiC revealed that t ... [J. Appl. Phys. 106, 094901 (2009)] published Thu Nov 5, 2009.
J. Lloyd-Hughes, Y. L. Delley, G. Scalari, M. Fischer, V. Liverini et al. Terahertz time-domain spectroscopy is shown to provide a convenient and rapid means to measure the conductivity of individual layers in semiconductor heterostructures such as terahertz quantum cascade lasers. By modeling the complex transmission at terahertz frequencies, the electron density and the ... [J. Appl. Phys. 106, 093104 (2009)] published Thu Nov 5, 2009.
Anurak Prasatkhetragarn, Piyachon Ketsuwan, Santi Maensiri, Rattikorn Yimnirun, Chien-Chih Huang et al. The double perovskite Sr(NiMo)O has been prepared with solid-state reaction and was characterized by x-ray diffraction technique. It has been indicated that the single phase is formed at 1300 degrees C in air. The compound undergoes a phase transition at 280 degrees C, where the structure of the ... [J. Appl. Phys. 106, 094105 (2009)] published Wed Nov 4, 2009.
V. P. S. Awana, Jagdish Kumar Bains, G. S. Okram, Ajay Soni, P. K. Ahluwalia et al. All the samples possess single-phase character and their superconducting transition temperatures (T) are 85, 90, and 72 K, respectively for Bi2212-MQ, Bi2212-N, and Bi2212-O. Though the Bi2212-MQ and Bi2212-N samples are in near optimum doping regime, the Bi2212-O is an overdoped sample. T values ob ... [J. Appl. Phys. 106, 096102 (2009)] published Wed Nov 4, 2009.
Ashutosh Goel, Anna Maria Ferrari, Ishu Kansal, Maria J. Pascual, Luisa Barbieri et al. We report on the synthesis, sintering, and crystallization behaviors of a glass with a composition corresponding to 90 mol % CaMgSiO10 mol % NaFeSiO. The investigated glass composition crystallized superficially immediately after casting of the melt and needs a high cooling rate (rapid quenching ... [J. Appl. Phys. 106, 093502 (2009)] published Wed Nov 4, 2009.
In this work, we present the first results of our imaging campaign at Keck Observatory to identify the host galaxies of "dark" gamma-ray bursts (GRBs), events with no detected optical afterglow or with detected optical flux significantly fainter than expected from the observed X-ray afterglow. We find that out of a uniform sample of 29 Swift bursts rapidly observed by the Palomar 60 inch telescope through 2008 March (14 of which we classify as dark), all events have either a detected optical afterglow, a probable optical host-galaxy detection, or both. Our results constrain the fraction of Swift GRBs coming from very high redshift (z>7), such as the recent GRB 090423, to between 0.2% and 7% at 80% confidence. In contrast, a significant fraction of the sample requires large extinction columns (host-frame AV gsim 1 mag, with several events showing AV > 2-6 mag), identifying dust extinction as the dominant cause of the dark GRB phenomenon. We infer that a significant fraction of GRBs (and, by association, of high-mass...
We present the kinematical properties, distribution of spectroscopic subtypes, and stellar population subcomponents of the white dwarfs within 20 pc of the Sun. We find no convincing evidence of halo white dwarfs in the total 20 pc sample of 129 white dwarfs nor is there convincing evidence of genuine thick disk subcomponent members within 20 parsecs. Virtually, the entire 20 pc sample likely belongs to the thin disk. The total DA to non-DA ratio of the 20 pc sample is 1.6, a manifestation of deepening envelope convection which transforms DA stars with sufficiently thin H surface layers into non-DAs. The addition of five new stars to the 20 pc sample yields a revised local space density of white dwarfs of (4.9 ± 0.5) ?10--3 pc--3 and a corresponding mass density of (3.3 ± 0.3) ?10--3 M sun pc--3. We find that at least 15% of the white dwarfs within 20 parsecs of the Sun (the DAZ and DZ stars) have photospheric metals that possibly originate from accretion of circumstellar material (debris disks) around them....
Surface brightness profiles for 23 M31 star clusters were measured using images from the Wide Field Planetary Camera 2 on the Hubble Space Telescope, and fitted to two types of models to determine the clusters' structural properties. The clusters are primarily young (~108 yr) and massive (~104.5 M sun), with median half-light radius 7 pc and dissolution times of a few Gyr. The properties of the M31 clusters are comparable to those of clusters of similar age in the Magellanic Clouds. Simulated star clusters are used to derive a conversion from statistical measures of cluster size to half-light radius so that the extragalactic clusters can be compared to young massive clusters in the Milky Way. All three sets of star clusters fall approximately on the same age-size relation. The young M31 clusters are expected to dissolve within a few Gyr and will not survive to become old, globular clusters. However, they do appear to follow the same fundamental plane (FP) relations as old clusters; if confirmed with velocity...
We have obtained deep infrared J- and K-band observations of nine 4.9 ?4.9 arcmin fields in the Small Magellanic Cloud (SMC) with the ESO New Technology Telescope equipped with the SOFI infrared camera. In these fields, 34 RR Lyrae stars cataloged by the OGLE collaboration were identified. Using different theoretical and empirical calibrations of the infrared period-luminosity-metallicity relation, we find consistent SMC distance moduli, and find a best true distance modulus to the SMC of 18.97 ± 0.03 (statistical) ±0.12 (systematic) mag, which agrees well with most independent distance determinations to this galaxy, and puts the SMC 0.39 mag more distant than the Large Magellanic Cloud for which our group has recently derived, from the same technique, a distance of 18.58 mag. Based on observations obtained with the ESO NTT for programmes 082.D-0513(A) and 079.D-0482(A).
We present XMM-Newton observations of the type 1 active galactic nucleus (AGN) SDSS 1430 -- 0011 (z = 0.1032). The low signal-to-noise ratio spectrum of this source obtained in a snap shot Chandra observation showed an unusually flat continuum. With the follow-up XMM-Newton observations, we find that the source spectrum is complex; it either has an ionized absorber or a partially covering absorber. The underlying power law is in the normal range observed for AGNs. The low flux of the source during Chandra observations can be understood in terms of variations in the absorber properties. The X-ray and optical properties of this source are such that it cannot be securely classified as either a narrow-line Seyfert 1 or a broad-line Seyfert 1 galaxy, adding to the group of sources in the "in-between" class.
We present a method to estimate and map the two-dimensional distribution of dust extinction in the late-type spiral galaxy NGC 959 from the theoretical and observed flux ratio of optical V and mid-IR (MIR) 3.6 mum images. Our method is applicable to both young and old stellar populations for a range of metallicities, and is not restricted to lines of sight toward star-formation (SF) regions. We explore this method using a pixel-based analysis on images of NGC 959 obtained in the V band at the Vatican Advanced Technology Telescope and at 3.6 mum (L band) with Spitzer/Infrared Array Camera. We present the original and extinction corrected Galaxy Evolution Explorer (GALEX) far-UV (FUV) and near-UV (NUV) images, as well as optical UBVR images of NGC 959. While the dust lanes are not clearly evident at GALEX resolution, our dust map clearly traces the dust that can be seen silhouetted against the galaxy's disk in the high-resolution Hubble Space Telescope (HST) images of NGC 959. The advantages of our method are (1)...
We report extensive spectroscopic and differential V-band photometric observations of the 18.4 day detached double-lined eclipsing binary LV Her (F9 V), which has the highest eccentricity (e sime 0.613) among the systems with well-measured properties. We determine the absolute masses and radii of the components to be M 1 = 1.193 ± 0.010 M sun, M 2 = 1.1698 ± 0.0081 M sun, R 1 = 1.358 ± 0.012 R sun, and R 2 = 1.313 ± 0.011 R sun, with fractional errors of 0.9% or better. The effective temperatures are 6060 ± 150 K and 6030 ± 150 K, respectively, and the overall metallicity is estimated to be [m/H] = +0.08 ± 0.21. A comparison with current stellar evolution models for this composition indicates an excellent fit for an age between 3.8 and 4.2 Gyr, with both stars being near the middle of their main-sequence lifetimes. Full integration of the equations for tidal evolution is consistent with the high eccentricity, and suggests that the stars' spin axes are aligned with the orbital axis, and that their rotations...
The Multi-Array Galactic Plane Imaging Survey is an ongoing project to map out the northern Galactic plane in the 21 cm radio continuum. The survey identified 30 probable supernova remnant candidates in the Galactic plane from 18°
We report the first discovery of a QSO damped Lyalpha system (DLA) by the Galaxy Evolution Explorer (GALEX) satellite. The system was initially identified as an Mg II absorption-line system (z abs = 1.028) in the spectrum of Sloan Digital Sky Survey (SDSS) QSO J0203-0910 (z em = 1.58). The presence of unusually strong absorption due to metal lines of Zn II, Cr II, Mn II, and Fe II clearly suggested that it might be a DLA with N H I >= 2 ?1020 atoms cm--2. Follow-up GALEX NUV grism spectroscopy confirms that the system exhibits a DLA absorption line, with a measured H I column density of N H I = 1.50 ± 0.45 ?1021 atoms cm--2. By combining the GALEX N H I determination with the SDSS spectrum measurements of unsaturated metal-line absorption due to Zn II, which is generally not depleted onto grains, we find that the system's neutral-gas-phase metal abundance is [Zn/H] = --0.70 ± 0.22, or ≈20% solar. By way of comparison, although this system has one of the largest Zn+ column densities, its metal abundances...
We present archival Spitzer Infrared Spectrograph (IRS) spectra of 19 luminous 8 mum selected sources in the Large Magellanic Cloud (LMC). The object classes derived from these spectra and from an additional 24 spectra in the literature are compared with classifications based on Two Micron All Sky Survey (2MASS)/MSX (J, H, K, and 8 mum) colors in order to test the "JHK8" (Kastner et al.) classification scheme. The IRS spectra confirm the classifications of 22 of the 31 sources that can be classified under the JHK8 system. The spectroscopic classification of 12 objects that were unclassifiable in the JHK8 scheme allow us to characterize regions of the color-color diagrams that previously lacked spectroscopic verification, enabling refinements to the JHK8 classification system. The results of these new classifications are consistent with previous results concerning the identification of the most infrared-luminous objects in the LMC. In particular, while the IRS spectra reveal several new examples of asymptotic...
We obtained optical photometry of SN 2003gs on 49 nights, from 2 to 494 days after T(B max). We also obtained near-IR photometry on 21 nights. SN 2003gs was the first fast declining Type Ia SN that has been well observed since SN 1999by. While it was subluminous in optical bands compared to more slowly declining Type Ia SNe, it was not subluminous at maximum light in the near-IR bands. There appears to be a bimodal distribution in the near-IR absolute magnitudes of Type Ia SNe at maximum light. Those that peak in the near-IR after T(B max) are subluminous in the all bands. Those that peak in the near-IR prior to T(B max), such as SN 2003gs, have effectively the same near-IR absolute magnitudes at maximum light regardless of the decline rate Deltam 15(B). Near-IR spectral evidence suggests that opacities in the outer layers of SN 2003gs are reduced much earlier than for normal Type Ia SNe. That may allow gamma rays that power the luminosity to escape more rapidly and accelerate the decline rate. This conclusion...
Sulfur abundances are derived for a sample of 10 B main-sequence star members of the Orion association. The analysis is based on LTE plane-parallel model atmospheres and non-LTE line formation theory by means of a self-consistent spectrum synthesis analysis of lines from two ionization states of sulfur, S II and S III. The observations are high-resolution spectra obtained with the ARCES spectrograph at the Apache Point Observatory. The abundance distribution obtained for the Orion targets is homogeneous within the expected errors in the analysis: A(S) = 7.15 ± 0.05. This average abundance result is in agreement with the recommended solar value (both from modeling of the photospheres in one-dimensional and three-dimensional, and meteorites) and indicates that little, if any, chemical evolution of sulfur has taken place in the last ~4.5 billion years. The sulfur abundances of the young stars in Orion are found to agree well with results for the Orion Nebulae, and place strong constraints on the amount of sulfur...
Using imaging that shows 4 mag of main-sequence stars, we have discovered that the Galactic globular cluster NGC 1851 is surrounded by a halo that is visible from the tidal radius of 700 arcsec (41 pc) to more than 4500 arcsec (>250 pc). This halo is symmetric and falls in density as a power law of r --1.24. It contains approximately 0.1% of the dynamical mass of NGC 1851. There is no evidence for tidal tails. Current models of globular cluster evolution do not explain this feature, although simulations of tidal influences on dwarf spheroidal galaxies qualitatively mimic these results. Given the state of published models, it is not possible to decide between creation of this halo from either isolated cluster evaporation or from tidal or disk shocking, or from destruction of a dwarf galaxy in which this object may have once been embedded.
We report the identification of 2MASS J15500845+1455180 as a 0farcs9 L dwarf visual binary. This source is resolved in Sloan Digital Sky Survey (SDSS) images and in near-infrared imaging with the Infrared Telescope Facility SpeX imager/spectrometer. The two components, oriented along a north-south axis, have similar brightnesses in the near-infrared (DeltaK ≈ 0.2 mag), although the fainter northern component is redder in J--K color. Resolved near-infrared spectroscopy indicates spectral types of L3.5 and L4, consistent with its L3 combined-light optical classification based on the SDSS data. Physical association is confirmed through common proper motion, common spectrophotometric distances and low probability of chance alignment. The projected physical separation of 2MASS J1550+1455AB, 30 ± 3 AU at an estimated distance of 33 ± 3 pc, makes it the widest L dwarf-L dwarf pair identified to date, although such a separation is not unusual among very low mass field binaries. The angular separation and spectral...
We have developed a theoretical description of how of an asteroid's polarization-phase curve will be affected by the removal of the dust from the surface due to a size-dependent phenomenon such as radiation pressure-driven escape of levitated particles. We test our calculations against new observations of four small (D ≈ 1 km) near-Earth asteroids (NEAs; (85236), (142348), (162900), and 2006 SZ217) obtained with the Dual Beam Imaging Polarimeter on the University of Hawaii's 2.2 m telescope, as well as previous observations of (25143) Itokawa and (433) Eros. We find that the polarization of the light reflected from an asteroid is controlled by the mineralogical and chemical composition of the surface and is independent of dust particle. The relation between the slope of the polarization-phase curve beyond the inversion angle and the albedo of an asteroid is thus independent of the surface regolith size distribution and is valid for both Main Belt and NEAs.
The HR Del nova remnant was observed with the IFU-GMOS at Gemini North. The spatially resolved spectral data cube was used in the kinematic, morphological, and abundance analysis of the ejecta. The line maps show a very clumpy shell with two main symmetric structures. The first one is the outer part of the shell seen in Halpha, which forms two rings projected in the sky plane. These ring structures correspond to a closed hourglass shape, first proposed by Harman & O'Brien. The equatorial emission enhancement is caused by the superimposed hourglass structures in the line of sight. The second structure seen only in the [O III] and [N II] maps is located along the polar directions inside the hourglass structure. Abundance gradients between the polar caps and equatorial region were not found. However, the outer part of the shell seems to be less abundant in oxygen and nitrogen than the inner regions. Detailed 2.5-dimensional photoionization modeling of the three-dimensional shell was performed using the mass distribution...
From a study of the editorial log for 251 manuscripts submitted in 2006, we learn that 6% are rejected, 5% are withdrawn, and 88% are eventually accepted for publication. Of the accepted articles, 30% are reviewed once, 58% twice, and 12% are reviewed 3-5 times. The mean time for the first review is 31 days and for the first revision is 44 days. The spread in total reviewing times (dispersion of 16 days) is much shorter than in total revision times (54 days). Important articles, those receiving 31-193 citations in 2 yr, are not reviewed more promptly than others nor revised more promptly. Only in the subfield of high-energy objects do the authors revise their manuscripts marginally more promptly than others.
We present an empirical model of Comptonization for fitting the spectra of X-ray binaries. This model, named simpl, has been developed as a package implemented in XSPEC. With only two free parameters, simpl is competitive as the simplest model of Compton scattering. Unlike the pervasive standard power-law model, simpl incorporates the basic features of Compton scattering of soft photons by energetic coronal electrons. Using a simulated spectrum, we demonstrate that simpl closely matches the behavior of physical Comptonization models that consider the effects of optical depth, coronal electron temperature, and geometry. We present fits to RXTE spectra of the black hole transient H1743-322 and a BeppoSAX spectrum of LMC X-3 using both simpl and the standard power-law model. A comparison of the results shows that simpl gives equally good fits, while eliminating the troublesome divergence of the standard power-law model at low energies. simpl is completely flexible and can be used self-consistently with any seed...
We present a means of characterizing and removing internal reflections between the CCD and other optical surfaces in an astronomical camera. The stellar reflections appear as out-of-focus images and are not necessarily axisymmetric about the star. Using long exposures of very bright stars as calibration images, we are able to measure the position, size, and intensity of reflections as a function of their position on the field. We also measure the extended stellar point-spread function out to 1°. Together this information can be used to create an empirical model of the excess light from bright stars and reduce systematic artifacts in deep surface photometry. We then reduce a set of deep observations of the Virgo cluster with our method to demonstrate its efficacy and to provide a comparison with other strategies for removing scattered light.
This tutorial presents a review of the analytical approach to obtain exact solutions for the populations of n-level ions, and summarizes the ideas behind detailed balance and the statistical physics of collisionally-excited ions. Seaton's analytical solution for the populations of the 3-level ion has been supplanted by matrix methods such as the master equation approach, which are now central to astronomy since there is a need to maintain a parity between improvements in quantum-mechanically calculated values for collision strengths and transition probabilities on the one hand, and three-dimensional (3D) photoionization codes used by astrophysicists for producing nebular diagnostics on the other. We show that the analytical method of solution to the problem using matrices and symbolic mathematics is straightforward, and we illustrate through theoretical, numerical, and empirical checks the validity of its results. First, we recast the equations of thermal statistical equilibrium for the energy level populations...
The repeated discovery of supermassive black holes (SMBHs) at the centers of galactic bulges, and the discovery of relations between the SMBH mass (M) and the properties of these bulges, have been fundamental in directing our understanding of both galaxy and SMBH formation and evolution. However, there are still many underlying questions surrounding the SMBH-galaxy relations. For example, are the scaling relations linear and constant throughout cosmic history, and do all SMBHs lie on the scaling relations? These fundamental questions can only be answered by further high quality direct M estimates from a wide range in redshift, before further refinements to galaxy evolution models can be made. In this article we determine the observational requirements necessary to directly determine SMBH masses, across cosmological distances, using current M modeling techniques. We also discuss the SMBH detection abilities of future facilities. We find that if different M modeling techniques, using different spectral features,...
High-contrast coronagraphic imaging is challenging for telescopes with central obstructions and thick spider vanes, such as the Subaru Telescope. We present in this article the first laboratory demonstration of a high-efficiency PIAA-type coronagraph on such a pupil, using coronagraphic optics which will be part of the Subaru Coronagraphic Extreme-AO (SCExAO) system currently under assembly. Lossless pupil apodization is performed by a set of aspheric PIAA lenses specifically designed to also remove the pupil's central obstruction, coupled with a spider removal plate (SRP) which removes spider vanes by translating four parts of the pupil with tilted plane-parallel plates. An "inverse-PIAA" system, located after the coronagraphic focal plane mask, is used to remove off-axis aberrations and deliver a wide field of view. Our results validate the concept adopted for the SCExAO system, and show that the Subaru Telescope pupil can be properly apodized for high-contrast coronagraphic imaging as close as≈1 lambda/D...
We are undertaking an astrometric search for gas giant planets and brown dwarfs orbiting nearby low-mass dwarf stars with the 2.5 m du Pont Telescope at the Las Campanas Observatory in Chile. We have built two specialized astrometric cameras, the Carnegie Astrometric Planet Search Cameras (CAPSCam-S and CAPSCam-N), using two Teledyne HAWAII-2RG HyViSI arrays, with the cameras' design having been optimized for high-accuracy astrometry of M dwarf stars. We describe two independent CAPSCam data reduction approaches and present a detailed analysis of the observations to date of one of our target stars, NLTT 48256. Observations of NLTT 48256 taken since 2007 July with CAPSCam-S imply that astrometric accuracies of around 0.3 mas hr are achievable, sufficient to detect a Jupiter-mass companion orbiting 1 AU from a late M dwarf 10 pc away with a signal-to-noise ratio (S/N) of about 4. We plan to follow about 100 nearby (primarily within about 10 pc) low-mass stars, principally late M, L, and T dwarfs, for 10 yr or more,...
The 6307 ?emission line in the spectrum of eta Car, found by Martin et al., is blue-shifted [S iii] lambda6313 emission originating from the outer wind structures of the massive binary system. We realized the identification while analyzing multiple forbidden emission lines not normally seen in the spectra of massive stars. The high spatial and moderate spectral resolutions of HST/STIS resolve forbidden lines of Fe, N, Fe, S, Ne, and Ar into spatially and velocity-resolved ropelike features originating from collisionally-excited ions photoionized by UV photons or collisions. While the [Fe ii] emission extends across a velocity range of ±500 km s out to 0.7", more highly ionized forbidden emissions ([N ii], [Fe iii], [S iii], [Ar iii], and [Ne iii]) range in velocity from -500 to +200 km s, but spatially extend out to only 0.4". The [Fe ii] defines the outer regions of the massive primary wind. The [N ii], [Fe iii] emissions define the the outer wind interaction regions directly photoionized by far-UV radiation....
BZ UMa is a cataclysmic variable star whose specific classification has eluded researchers since its discovery in 1968. It has outburst and spectral properties consistent with both U Gem class dwarf novae and intermediate polars. We present new photometric and polarimetric measurements of recent outbursts, including the first detected superoutburst of the system. Statistical analysis of these and archival data from outbursts over the past 40 years presents a case for BZ UMa as a nonmagnetic, U Gem class, SU UMa subclass dwarf nova.
We present the results of a search for periodic variables within 4078 time-series light curves and an analysis of the period-color plane for stars in the field of the open cluster NGC 2301. One hundred thirty-eight periodic variables were discovered, of which five are eclipsing binary candidates with unequal minima. The remaining 133 periodic variables appear to consist mainly of late-type stars whose variation is due to rotation modulated by star spot activity. The determined periods range from less than a day to over 14 days and have nearly unreddened B-R colors in the range of 0.8 to 2.8. The Barnes (2003) interpretation of the period-color plane of late type stars is tested with our data. Our data did not show distinct I and C sequences, likely due to nonmember field stars contaminating in the background, as we estimate the total contamination to be 43%. Using different assumptions, the gyrochronological age of the cluster is calculated to be 210±25 Myr, which falls in the range of age values (164-250 Myr)...
This article describes the assembly of an optical (RGB) all-sky mosaic image with an image scale of 36pixel, a limiting magnitude of approximately 14 mag, and an 18 bit dynamic range. Using a portable low-cost CCD camera system, 70 fields (each covering 40°?7°) were imaged over a time span of 22 months from dark-sky locations in South Africa, Texas, and Michigan. The fields were photometrically calibrated against standard catalog stars. Using sky background data from the Pioneer 10 and 11 space probes, gradients resulting from artificial light pollution, airglow, and zodiacal light were eliminated, while the large-scale galactic and extragalactic background resulting from unresolved sources was preserved. The 648 megapixel image is a valuable educational tool, being able to fully utilize the resolution and dynamic range of modern full-dome planetarium projection systems.
We have analyzed the light curves of 3C 279 at 22 GHz, 37 GHz, optical R band, and X-ray (2-10 KeV), and found evidence of quasi-periodic outbusts. The light curves show that 3C 279 is an extremely active object. A period of P=130.6±1.3 days was consistently confirmed by three methods: the power-spectrum method, the discrete correlation function (DCF) method, and the Jurkevich method. Based on the relationship between observed period P and the precession period P given by Rieger and our result, the precession period of jet in 3C 279 is P~=29.6 yr, which is completely consistent with the precession period of jet of about 30 yr obtained by Carrara et al.. This suggests that there is a precession jet in 3C 279 and the variability period of about 130.6 days that we obtained is most likely caused by the helical motion of the jet.
We discuss the critical importance of black hole mass indicators based on scaling relations in active galaxies. We highlight outstanding uncertainties in these methods and potential paths to substantial progress in the next decade.
A Suzaku observation of a giant radio galaxy, 3C 326, which has a physical size of about 2 Mpc, was conducted on 2008 January 19-21. In addition to several X-ray sources, diffuse emission was significantly detected and associated with its west lobe, but the east lobe was contaminated by an unidentified X-ray source WARP J1552.4+2007. After careful evaluation of the X-ray and non-X-ray background, the 0.4-7 keV X-ray spectrum of the west lobe is described by a power-law model modified with the Galactic absorption. The photon index and 1 keV flux density were derived as Gamma = 1.82+0.26 --0.24 ± 0.04 and S X = 19.4+3.3 --3.2 ± 3.0 nJy, respectively, where the first and second errors represent the statistical and systematic ones. The diffuse X-rays were attributed to be inverse Compton (IC) radiation by the synchrotron radio electrons scattering off the cosmic microwave background photons. This radio galaxy is the largest among those with lobes detected through IC X-ray emission. A comparison of the radio to...
We present the results of AKARI observations of the O-rich supernova remnant (SNR) G292.0+1.8 using six Infrared Camera (IRC) and four Far-Infrared Surveyor bands covering 2.7-26.5 mum and 50-180 mum, respectively. The AKARI images show two prominent structures; a bright equatorial ring (ER) structure along the east-west direction and an outer elliptical shell structure surrounding the remnant. The ER structure is clumpy and incomplete with its western end opened. The outer shell is almost complete and slightly squeezed along the north-south direction. The central position of the outer shell is ~1' northwest from the embedded pulsar and coincides with the center of the ER structure. In the northern and southwestern regions, there is also faint emission with a sharp boundary beyond the bright shell structure. The ER and the elliptical shell structures were partly visible in optical and/or X-rays, but they are much more clearly revealed in our AKARI images. There is no evident difference in infrared colors of the...
Using the volume-limited Main galaxy sample of the Sloan Digital Sky Survey Data Release 6, we have explored the dependence of clustering properties of galaxies on the star formation activity. It is found that star-forming galaxies preferentially form isolated, close double and multiple systems, while passive galaxies preferentially inhabit the dense groups and clusters. We also construct the two samples with the same galaxy number and number density, and reach the same conclusion, which shows that our statistical conclusion is robust.
We investigate further a model of the accreting millisecond X-ray pulsars we proposed earlier. In this model, the X-ray-emitting regions of these pulsars are near their spin axes but move. This is to be expected if the magnetic poles of these stars are close to their spin axes, so that accreting gas is channeled there. As the accretion rate and the structure of the inner disk vary, gas is channeled along different field lines to different locations on the stellar surface, causing the X-ray-emitting areas to move. We show that this "nearly aligned moving spot model" can explain many properties of the accreting millisecond X-ray pulsars, including their generally low oscillation amplitudes and nearly sinusoidal waveforms; the variability of their pulse amplitudes, shapes, and phases; the correlations in this variability; and the similarity of the accretion- and nuclear-powered pulse shapes and phases in some. It may also explain why accretion-powered millisecond pulsars are difficult to detect, why some are intermittent,...
Black hole accretion and jet production are areas of intensive study in astrophysics. Recent work has found a relation between radio luminosity, X-ray luminosity, and black hole mass. With the assumption that radio and X-ray luminosities are suitable proxies for jet power and accretion power, respectively, a broad fundamental connection between accretion and jet production is implied. In an effort to refine these links and enhance their power, we have explored the above relations exclusively among black holes with direct, dynamical mass-measurements. This approach not only eliminates systematic errors incurred through the use of secondary mass measurements, but also effectively restricts the range of distances considered to a volume-limited sample. Further, we have exclusively used archival data from the Chandra X-ray Observatory to best isolate nuclear sources. We find log LR = (4.80 ± 0.24) + (0.78 ± 0.27)log M BH + (0.67 ± 0.12)log LX , in broad agreement with prior efforts. Owing to the nature of our sample,...
We present constraints on the nonlinear coupling parameter f nl with the Wilkinson Microwave Anisotropy Probe (WMAP) data. We use an updated method based on the spherical Mexican hat wavelet (SMHW) which provides improved constraints on the f nl parameter. This paper is a continuation of a previous work by Curto et al., where several third-order statistics based on the SMHW were considered. In this paper, we use all the possible third-order statistics computed from the wavelet coefficient maps evaluated at 12 angular scales. The scales are logarithmically distributed from 6.9 arcmin to 500 arcmin. Our analysis indicates that f nl is constrained to --18 < f nl < +80 at 95% confidence level (CL) for the combined V+W WMAP map. This value has been corrected by the presence of undetected point sources, which adds a positive contribution of Deltaf nl = 6 ± 5. Our result excludes at ~99% CL the best-fitting value f nl = 87 reported by Yadav & Wandelt. We have also constrained f nl for the Q, V, and W frequency bands...
The usual procedure for estimating the significance of a peak in a power spectrum is to calculate the probability of obtaining that value or a larger value by chance (known as the "p-value"), on the assumption that the time series contains only noise---typically that the measurements are derived from random samplings of a Gaussian distribution. However, since the use of p-values in other contexts is known to be misleading, it seems prudent to examine the implications of using p-values for significance estimation of power spectra. We really need to know the probability that the time series is---or is not---compatible with the "null hypothesis" that the measurements are derived from noise. This probability can be calculated by Bayesian analysis, but this requires one to specify and evaluate a second hypothesis that the time series does contain a contribution other than noise. We show that the requirement that the p-value should be identical to the probability that the null hypothesis is true leads to an unacceptable...
The masses of coronal mass ejections (CMEs) have traditionally been determined from white-light coronagraphs (based on Thomson scattering of electrons), as well as from extreme ultraviolet (EUV) dimming observed with one spacecraft. Here we develop an improved method of measuring CME masses based on EUV dimming observed with the dual STEREO/EUVI spacecraft in multiple temperature filters that includes three-dimensional volume and density modeling in the dimming region and background corona. As a test, we investigate eight CME events with previous mass determinations from STEREO/COR2, of which six cases are reliably detected with the Extreme Ultraviolet Imager (EUVI) using our automated multi-wavelength detection code. We find CME masses in the range of m CME = (2-7) ?1015 g. The agreement between the two EUVI/A and B spacecraft is mA /mB = 1.3 ± 0.6 and the consistency with white-light measurements by COR2 is m EUVI/m COR2 = 1.1 ± 0.3. The consistency between EUVI and COR2 implies no significant mass backflows...
We report the detection of variable emission from Sgr A* in almost all wavelength bands (i.e., centimeter, millimeter, submillimeter, near-IR, and X-rays) during a multi-wavelength observing campaign. Three new moderate flares are detected simultaneously in both near-IR and X-ray bands. The ratio of X-ray to near-IR flux in the flares is consistent with inverse Compton scattering of near-IR photons by submillimeter emitting relativistic particles which follow scaling relations obtained from size measurements of Sgr A*. We also find that the flare statistics in near-IR wavelengths is consistent with the probability of flare emission being inversely proportional to the flux. At millimeter wavelengths, the presence of flare emission at 43 GHz (7 mm) using the Very Long Baseline Array with milliarcsecond spatial resolution indicates the first direct evidence that hourly timescale flares are localized within the inner 30 ?70 Schwarzschild radii of Sgr A*. We also show several cross-correlation plots between near-IR,...
We have made a search for common proper motion (CPM) companions to the wide binaries in the solar vicinity. We found that the binary GJ 282AB has a very distant CPM companion (NLTT 18149) at a separation s = 1fdg09. Improved spectral types and radial velocities are obtained, and ages determined for the three components. The Hipparcos trigonometric parallaxes and the new radial velocities and ages turn out to be very similar for the three stars, and provide strong evidence that they form a physical system. At a projected separation of 55,733 AU from GJ 282AB, NLTT 18149 ranks among the widest physical companions known.
We present Keck laser guide star adaptive optics imaging of the M8+M8 binary 2MASS J2206 -- 2047AB. Together with archival Hubble Space Telescope, Gemini-North, and Very Large Telescope data, our observations span 8.3 yr of the binary's 35+6 --5 yr orbital period, and we determine a total dynamical mass of 0.15+0.05 --0.03 M sun, with the uncertainty dominated by the parallax error. Using the measured total mass and individual luminosities, the Tucson and Lyon evolutionary models both give an age for the system of 0.4+9.6 --0.2 Gyr, which is consistent with its thin disk space motion derived from the Besan? Galactic structure model. Our mass measurement combined with the Tucson (Lyon) evolutionary models also yields precise effective temperatures, giving 2660+90 --100 K and 2640+90 --100 K (2550+90 --100 K and 2530+90 --100 K) for components A and B, respectively. These temperatures are in good agreement with estimates for other M8 dwarfs (from the infrared flux method and the M8 mass benchmark LHS 2397aA), but...
We present constraints on the nature of the first galaxies selected at 350 mum. The sample includes galaxies discovered in the deepest blank-field survey at 350 mum (in the Bo? Deep Field) and also later serendipitous detections in the Lockman Hole. In determining multiwavelength identifications, the 350 mum position and map resolution of the second generation Submillimeter High Angular Resolution Camera are critical, especially in the cases where multiple radio sources exist and the 24 mum counterparts are unresolved. Spectral energy distribution templates are fitted to identified counterparts, and the sample is found to comprise IR-luminous galaxies at 1 < z < 3 predominantly powered by star formation. The first spectrum of a 350 mum selected galaxy provides an additional confirmation, showing prominent dust grain features typically associated with star-forming galaxies. Compared to submillimeter galaxies selected at 850 and 1100 mum, galaxies selected at 350 mum have a similar range of far-infrared color temperatures....
The Spectrograph for Photometric Imaging with Numeric Reconstruction sounding rocket experiment was launched on 2000 August 4 to record far-ultraviolet (912-1450 - spectral and spatial information for the giant reflection nebula in the Upper Scorpius region. The data were divided into three arbitrary bandpasses (912-1029 - 1030-1200 - and 1235-1450 - for which stellar and nebular flux levels were derived. These flux measurements were used to constrain a radiative transfer model and to determine the dust albedo for the Upper Scorpius region. The resulting albedos were 0.28 ± 0.07 for the 912-1029 ?bandpass, 0.33 ± 0.07 for the 1030-1200 ?bandpass, and 0.77 ± 0.13 for the 1235-1450 ?bandpass.
We report the result of a search for the infrared counterparts of 37 planetary nebulae (PNs) and PN candidates in the Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire II (GLIMPSE II) survey. The photometry and images of these PNs at 3.6, 4.5, 5.8, 8.0, and 24 mum, taken through the Infrared Array Camera (IRAC) and the Multiband Imaging Photometer for Spitzer (MIPS), are presented. Most of these nebulae are very red and compact in the IRAC bands, and are found to be bright and extended in the 24 mum band. The infrared morphology of these objects are compared with Halpha images of the Macquarie-AAO-Strasbourg (MASH) and MASH II PNs. The implications for morphological difference in different wavelengths are discussed. The IRAC data allow us to differentiate between PNs and H II regions and be able to reject non-PNs from the optical catalog (e.g., PNG 352.1 -- 00.0). Spectral energy distributions are constructed by combing the IRAC and MIPS data with existing near-, mid-, and far-IR photometry measurements....
We report the results of simultaneous radio continuum and water maser observations toward the NGC 2071IR star-forming region, carried out with the VLA in its A configuration. We detect continuum emission toward the infrared sources IRS 1 and IRS 3 at 1.3 and 3.6 cm. In addition, a new continuum source, VLA 1, is also detected at both wavelengths, which is located between IRS 1 and IRS 3. IRS 1 breaks up into three continuum peaks (IRS 1E, 1C, and 1W), aligned in the east-west direction (P.A. = 100°). IRS 1 is the central source, while the sources E and W seem to be condensations ejected by IRS 1. In the same way, IRS 3 is also forming a triple system (IRS 3N, 3C and 3S), which is elongated in the northeast-southwest direction and the condensations, IRS 3N and IRS 3S, are symmetrically located along the major axis. Based on the morphology and the continuum emission, we suggest that both IRS 1 and IRS 3 are radio jets, which have ejected condensations into the interstellar medium. Moreover, IRS 1 and IRS 3 seem...
This paper investigates the evolution of the plasma density fluctuations of the fast and slow solar wind from the solar corona into the interplanetary space. The study is performed by comparing the low-frequency spectra and the phase correlation of the proton density oscillations, measured in the inner heliosphere with the Helios 2 in situ instrumentation, with those due to the large-scale density perturbations observed with UVCS/SOHO in the outer corona. We find that the characteristics of density fluctuations of the fast solar wind are maintained in the transition from the outer corona to the inner heliosphere, thus suggesting a coronal imprint for the heliospheric large-scale 1/f 2 noise spectrum. In contrast, a quick dynamical evolution is observed in the slow wind, which, starting from large-scale fluctuations with strong phase correlations in the outer corona, gives rise to a Kolmogorov-like spectrum and an accumulation of density structures at small scales at 0.3 AU. This can be explained in the framework...
We present the log N-log S and spatial distributions of X-ray point sources in seven Galactic bulge (GB) fields within 4° from the Galactic center (GC). We compare the properties of 1159 X-ray point sources discovered in our deep (100 ks) Chandra observations of three low extinction Window fields near the GC with the X-ray sources in the other GB fields centered around Sgr B2, Sgr C, the Arches Cluster, and Sgr A* using Chandra archival data. To reduce the systematic errors induced by the uncertain X-ray spectra of the sources coupled with field-and-distance-dependent extinction, we classify the X-ray sources using quantile analysis and estimate their fluxes accordingly. The result indicates that the GB X-ray population is highly concentrated at the center, more heavily than the stellar distribution models. It extends out to more than 1fdg4 from the GC, and the projected density follows an empirical radial relation inversely proportional to the offset from the GC. We also compare the total X-ray and infrared...
We report on the results of Hubble Space Telescope optical and UV imaging, Spitzer mid-IR photometry, and optical spectroscopy of a sample of 30 low-redshift (z ~ 0.1 to 0.3) galaxies chosen from the Sloan Digital Sky Survey and Galaxy Evolution Explorer surveys to be accurate local analogs of the high-redshift Lyman break galaxies. The Lyman break analogs (LBAs) are similar in stellar mass, metallicity, dust extinction, star formation rate (SFR), physical size, and gas velocity dispersion, thus enabling a detailed investigation of many processes that are important in star-forming galaxies at high redshift. The main optical emission-line properties of LBAs, including evidence for outflows, are also similar to those typically found at high redshift. This indicates that the conditions in their interstellar medium are comparable. In the UV, LBAs are characterized by complexes of massive clumps of star formation, while in the optical they most often show evidence for (post-)mergers and interactions. In six cases,...
We present observations at 1.2 mm with Max-Planck Millimetre Bolometer Array (MAMBO-II) of a sample of z gsim 2 radio-intermediate obscured quasars, as well as CO observations of two sources with the Plateau de Bure Interferometer. The typical rms noise achieved by the MAMBO observations is 0.55 mJy beam--1 and five out of 21 sources (24%) are detected at a significance of >=3sigma. Stacking all sources leads to a statistical detection of langS 1.2 mmrang = 0.96 ± 0.11 mJy and stacking only the non-detections also yields a statistical detection, with langS 1.2 mmrang = 0.51 ± 0.13 mJy. At the typical redshift of the sample, z = 2, 1 mJy corresponds to a far-infrared luminosity L FIR~4 ?1012 L sun. If the far-infrared luminosity is powered entirely by star formation, and not by active galactic nucleus heated dust, then the characteristic inferred star formation rate is ~700 M sun yr--1. This far-infrared luminosity implies a dust mass of M d~3 ?108 M sun, which is expected to be distributed on ~kpc scales. We...
We report the results of spectroscopic mapping observations carried out toward protostellar outflows in the BHR71, L1157, L1448, NGC 2071, and VLA 1623 molecular regions using the Infrared Spectrograph (IRS) of the Spitzer Space Telescope. These observations, covering the 5.2-37 mum spectral region, provide detailed maps of the eight lowest pure rotational lines of molecular hydrogen and of the [S I] 25.25 mum and [Fe II] 26.0 mum fine-structure lines. The molecular hydrogen lines, believed to account for a large fraction of the radiative cooling from warm molecular gas that has been heated by a non-dissociative shock, allow the energetics of the outflows to be elucidated. Within the regions mapped toward these five outflow sources, total H2 luminosities ranging from 0.02 to 0.75 L sun were inferred for the sum of the eight lowest pure rotational transitions. By contrast, the much weaker [Fe II] 26.0 mum fine-structure transition traces faster, dissociative shocks; here, only a small fraction of the fast shock...
Using Hubble Space Telescope (HST)/Advanced Camera for Surveys (ACS) slitless grism spectra from the PEARS program, we study the stellar populations of morphologically selected early-type galaxies in the GOODS North and South fields. The sample---extracted from a visual classification of the (v2.0) HST/ACS images and restricted to redshifts z > 0.4---comprises 228 galaxies (i F775W < 24 mag, AB) out to z lsim 1.3 over 320 arcmin2, with a median redshift z M = 0.75. This work significantly increases our previous sample from the GRAPES survey in the HUDF (18 galaxies over ~11 arcmin2). The grism data allow us to separate the sample into "red" and "blue" spectra, with the latter comprising 15% of the total. Three different grids of models parameterizing the star formation history are used to fit the low-resolution spectra. Over the redshift range of the sample---corresponding to a cosmic age between 5 and 10 Gyr---we find a strong correlation between stellar mass and average age, whereas the spread of ages (defined...
The Interferometric Bidimensional Spectrometer (IBIS) installed at the Dunn Solar Telescope of the NSO/SP is used to investigate the morphology and dynamics of the lower chromosphere and the virtually non-magnetic fluctosphere below. The study addresses in particular the structure of magnetic elements that extend into these layers. We choose different quiet-Sun regions inside and outside the coronal holes. In inter-network regions with no significant magnetic flux contributions above the detection limit of IBIS, we find intensity structures with the characteristics of a shock wave pattern. The magnetic flux elements in the network are long lived and seem to resemble the spatially extended counterparts to the underlying photospheric magnetic elements. We suggest a modification to common methods to derive the line-of-sight magnetic field strength and explain some of the difficulties in deriving the magnetic field vector from observations of the fluctosphere.
Oxygen is one of the major rock-forming elements in the solar system and the third most abundant element of the Sun. Oxygen isotopic composition of the Sun, however, is not known due to a poor resolution of astronomical spectroscopic measurements. Several Delta17O values have been proposed for the composition of the Sun based on (1) the oxygen isotopic measurements of the solar wind implanted into metallic particles in lunar soil (< --200/00 by Hashizume & Chaussidon and ~ +260/00 by Ireland et al.), (2) the solar wind returned by the Genesis spacecraft (--270/00 ± 60/00 by McKeegan et al.), and (3) the mineralogically pristine calcium-aluminum-rich inclusions (CAIs) (--23.30/00 ± 1.90/00 by Makide et al. and --350/00 by Gounelle et al.). CAIs are the oldest solar system solids, and are believed to have formed by evaporation, condensation, and melting processes in hot nebular region(s) when the Sun was infalling (Class 0) or evolved (Class 1) protostar. Corundum (Al2O3) is thermodynamically the first condensate...
The nova-like cataclysmic binary AE Aqr, which is currently understood to be a former supersoft X-ray binary and current magnetic propeller, was observed for over two binary orbits (78 ks) in 2005 August with the High-Energy Transmission Grating (HETG) on board the Chandra X-ray Observatory. The long, uninterrupted Chandra observation provides a wealth of details concerning the X-ray emission of AE Aqr, many of which are new and unique to the HETG. First, the X-ray spectrum is that of an optically thin multi-temperature thermal plasma; the X-ray emission lines are broad, with widths that increase with the line energy from sigma ≈ 1 eV (510 km s--1) for O VIII to sigma ≈ 5.5 eV (820 km s--1) for Si XIV; the X-ray spectrum is reasonably well fit by a plasma model with a Gaussian emission measure distribution that peaks at log T(K) = 7.16, has a width sigma = 0.48, an Fe abundance equal to 0.44 times solar, and other metal (primarily Ne, Mg, and Si) abundances equal to 0.76 times solar; and for a distance...
This paper presents the results of collisional evolution calculations for the Kuiper Belt starting from an initial size distribution similar to that produced by accretion simulations of that region---a steep power-law large object size distribution that breaks to a shallower slope at r ~ 1-2 km, with collisional equilibrium achieved for objects r lsim 0.5 km. We find that the break from the steep large object power law causes a divot, or depletion of objects at r ~ 10-20 km, which, in turn, greatly reduces the disruption rate of objects with r gsim 25-50 km, preserving the steep power-law behavior for objects at this size. Our calculations demonstrate that the roll-over observed in the Kuiper Belt size distribution is naturally explained as an edge of a divot in the size distribution; the radius at which the size distribution transitions away from the power law, and the shape of the divot from our simulations are consistent with the size of the observed roll-over, and size distribution for smaller bodies. Both...
Non Peer-Reviewed Preprints
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Bonacich centrality measures the number of attenuated paths between nodes in a network. We use this metric to study network structure, specifically, to rank nodes and find community structure of the network. To this end we extend the modularity-maximization method for community detection to use this centrality metric as a measure of node connectivity. Bonacich centrality contains a tunable parameter that sets the length scale of interactions. By studying how rankings and discovered communities change when this parameter is varied allows us to identify globally important nodes and structures. We apply the proposed method to several benchmark networks and show that it leads to better insight into network structure than earlier methods.
Social order cannot be considered as a stable phenomenon because it contains an order of reproduced expectations. When the expectations operate upon one another, they generate a non-linear dynamics that processes meaning. Specific meaning can be stabilized, for example, in social institutions, but all meaning arises from a horizon of possible meanings. Using Luhmann's (1984) social systems theory and Rosen's (1985) theory of anticipatory systems, I submit equations for modeling the processing of meaning in inter-human communication. First, a self-referential system can use a model of itself for the anticipation. Under the condition of functional differentiation, the social system can be expected to entertain a set of models; each model can also contain a model of the other models. Two anticipatory mechanisms are then possible: one transversal between the models, and a longitudinal one providing the modeled systems with meaning from the perspective of hindsight. A system containing two anticipatory mechanisms...
In this work we present a simplified description and calculation of the Kerr-Newman black hole basic dynamical (horizons) and thermo-dynamical (Bekenstein-Hawking entropy, Bekenstein entropy/surface quantization, Hawking temperature and radiation) characteristics. Also, a possibility of the fission of nearly extremal black hole is considered in full analogy with remarkable, simple Bohr-Wheeler theory of the nuclear fission. Given black is physically based on the well-known principles of the classical physics (mechanics, thermodynamics and electro-dynamics). It includes the non-relativistic quantum mechanics and statistical mechanics too. Finally, it includes the elementary form of the general relativistic equivalence principle only. Also, suggested simplified description includes mathematically, practically, only simple algebraic equations. Here many steps are extremely simplified and formal, representing, in fact, a linear approximation of the quantum gravity theories (black hole entropy and temperature can...
This paper presents a new framework for track fitting which is usable in a wide range of experiments, independent of the specific event topology, detector setup, or magnetic field arrangement. This goal is achieved through a completely modular design. Fitting algorithms are implemented as interchangeable modules. At present, the framework contains a validated Kalman filter. Track parameterizations and the routines required to extrapolate the track parameters and their covariance matrices through the experiment are also implemented as interchangeable modules. Different track parameterizations and extrapolation routines can be used simultaneously for fitting of the same physical track. Representations of detector hits are the third modular ingredient to the framework. The hit dimensionality and orientation of planar tracking detectors are not restricted. Tracking information from detectors which do not measure the passage of particles in a fixed physical detector plane, e.g. drift chambers or TPCs, is used without...
We model a social network by a random graph whose nodes represent agents and links between two of them stand for a reciprocal interaction; each agent is also associated to a binary variable which represents a dichotomic opinion or attribute. We consider both the case of pair-wise (p=2) and multiple (p>2) interactions among agents and we study the behavior of the resulting system by means of the energy-entropy scheme, typical of statistical mechanics methods. We show, analytically and numerically, that the connectivity of the social network plays a non-trivial role: while for pair-wise interactions (p=2) the connectivity weights linearly, when interactions involve contemporary a number of agents larger than two (p>2), its weight gets more and more important. As a result, when p is large, a full consensus within the system, can be reached at relatively small critical couplings with respect to the p=2 case usually analyzed, or, otherwise stated, relatively small coupling strengths among agents are sufficient...
A new application-specific integrated circuit (ASIC), the high-speed charge-to-time converter (QTC) IWATSU CLC101, provides three channels, each consisting of preamplifier, discriminator, low-pass filter, and charge integration circuitry, optimized for the waveform of a photomultiplier tube (PMT). This ASIC detects PMT signals using individual built-in discriminators and drives output timing signals whose width represents the integrated charge of the PMT signal. Combined with external input circuits composed of passive elements, the QTC provides full analog signal processing for the detector's PMTs, ready for further processing by time-to-digital converters (TDCs). High-rate (>1MHz) signal processing is achieved by short-charge-conversion-time and baseline-restoration circuits. Wide-range charge measurements are enabled by offering three gain ranges while maintaining a short cycle time. QTC chip test results show good analog performance, with efficient detection for a single photoelectron signal, four...
We use compressed sensing to demonstrate theoretically the reconstruction of sub-wavelength features from measured far-field, and provide experimental proof-of-concept. The methods can be applied to non-optical microscopes, provided the information is sparse.
The observed abundances of Li7 and He4 are significantly inconsistent with the predictions from Big Bang Nucleosynthesis (BBN) when using the LCDM cosmological model together with the value for Omega_Bh^2 = 0.0224 +/- 0.0009 from WMAP CMB fluctuations, with the value from BBN required to fit observed abundances being 0.009<Omega_Bh^2<0.013. The dynamical 3-space theory is shown to predict a 20% hotter universe in the radiation-dominated epoch, which then results in a remarkable parameter-free agreement between the BBN and the WMAP value for Omega_Bh^2. The dynamical 3-space also gives a parameter-free fit to the supernova redshift data, and predicts that the LCDM model would require Omega_L=0.73 and Omega_M=0.27 to fit the 3-space dynamics Hubble expansion, and independently of the supernova data. These results amount to the discovery of new physics for the early universe that is matched by numerous other successful observational and experimental tests.
We report studies of photon-stimulated desorption (PSD), also known as light-induced atomic desorption (LIAD), of sodium atoms from a vacuum cell glass surface used for loading a magneto-optical trap (MOT). Fluorescence detection was used to record the trapped atom number, which can be used for monitoring the desorption rate. We observed a steep wavelength dependence of the desorption process near a photoelectric threshold of $2.7\unit{eV}$ photon energy, a result significant for estimations of sodium vapor density in the lunar atmosphere. Our data fit well to a simple model for the loading of the MOT dependent only on the sodium desorption rate and residual gas density. Up to $3.7 \times 10^7$ Na atoms were confined under ultra-high vacuum conditions, creating promising loading conditions for a vapor cell based atomic Bose-Einstein condensate of sodium.
Although Luhmann formulated with modesty and precaution, for example in Die Wissenschaft der Gesellschaft (1990a, at pp. 412f.), that his theory claims to be a universal one because it is self-referential, the "operational closure" that follows from this assumption easily generates a problem for empirical research. Can a theory which considers society--and science as one of its subsystems--operationally closed, nevertheless contribute to the project of Enlightenment which Popper (1945) so vigorously identified as the driver of an open society? How can a theory which proclaims itself to be circular and universal nevertheless claim to celebrate "the triumph of the Enlightenment" Luhmann, (1990a, at p. 548)? Is the lack of an empirical program of research building on Luhmann's theory fortuitous or does it indicate that this theory should be considered as a philosophy rather than a heuristic for the explanation of operations in social systems?
Based on the Science Citation IndexExpanded webversion, the USA is still by far the strongest nation in terms of scientific performance. Its relative decline in percentage share of publications is largely due to the emergence of China and other Asian nations. In 2006, China has become the second largest nation in terms of the number of publications within this database. In terms of citations, the competitive advantage of the American domestic market is diminished, while the European Union EU is profiting more from the enlargement of the database over time than the US. However, the USA is still outperforming all other countries in terms of highly cited papers and citationpublication ratios, and it is more successful than the EU in coordinating its research efforts in strategic priority areas like nanotechnology. In this field, the Peoples Republic of China PRC has become second largest nation in both numbers of papers published and citations behind the USA.
In response to the call for a science of science policy, we discuss the contribution of indicators at the macro-level of nations from a scientometric perspective. In addition to global trends such as the rise of China, one can relate percentages of world share of publications to government expenditure in academic research. The marginal costs of improving one's share are increasing over time. Countries differ considerably in terms of the efficiency of turning (financial) input into bibliometrically measurable output. Both funding schemes and disciplinary portfolios differ among countries. A price per paper can nevertheless be estimated. The percentages of GDP spent on academic research in different nations are significantly correlated to historical contingencies such as the percentage of researchers in the population. The institutional dynamics make strategic objectives such as the Lisbon objective of the EU--that is, spending 3% of GDP for R&D in 2010--unrealistic.
Quantification of human group-behavior has so far defied an empirical, falsifiable approach. This is due to tremendous difficulties in data acquisition of social systems. Massive multiplayer online games (MMOG) provide a fascinating new way of observing hundreds of thousands of simultaneously socially interacting individuals engaged in virtual economic activities. We have compiled a data set consisting of practically all actions of all players over a period of three years from a MMOG played by 300,000 people. This large-scale data set of a socio-economic unit contains all social and economic data from a single and coherent source. Players have to generate a virtual income through economic activities to `survive' and are typically engaged in a multitude of social activities offered within the game. Our analysis of high-frequency log files focuses on three types of social networks, and tests a series of social-dynamics hypotheses. In particular we study the structure and dynamics of friend-, enemy- and communication...
We demonstrate how to explicitly calculate the QED path integral and associated Green functions, exactly, in curved spacetime, with retention of the boundary terms, to infinite order, for any and all spacetime manifolds with sufficient symmetry to admit the application of Pontryagin duality as a form of harmonic analysis. In the process we show how gauge symmetry itself greatly facilitates the ability to conduct harmonic analysis in curved spacetime and to do exact calculations with Pontryagin duality. We also show how non-Abelian, Yang-Mills gauge theories emerge naturally, if somewhat surprisingly, from this analysis.
The ISI subject categories classify journals included in the Science Citation Index (SCI). The aggregated journal-journal citation matrix contained in the Journal Citation Reports can be aggregated on the basis of these categories. This leads to an asymmetrical transaction matrix (citing versus cited) which is much more densely populated than the underlying matrix at the journal level. Exploratory factor analysis leads us to opt for a fourteen-factor solution. This solution can easily be interpreted as the disciplinary structure of science. The nested maps of science (corresponding to 14 factors, 172 categories, and 6,164 journals) are brought online at this http URL An analysis of interdisciplinary relations is pursued at three levels of aggregation using the newly added ISI subject category of "Nanoscience & nanotechnology". The journal level provides the finer grained perspective. Errors in the attribution of journals to the ISI subject categories are averaged out so that the factor analysis can reveal...
International co-authorship relations and university-industry-government ("Triple Helix") relations have hitherto been studied separately. Using Japanese (ISI) publication data for the period 1981-2004, we were able to study both kinds of relations in a single design. In the Japanese file, 1,277,823 articles with at least one Japanese address were attributed to the three sectors, and we know additionally whether these papers were co-authored internationally. Using the mutual information in three and four dimensions, respectively, we show that the Japanese Triple-Helix system has continuously been eroded at the national level. However, since the middle of the 1990s, international co-authorship relations have contributed to a reduction of the uncertainty. In other words, the national publication system of Japan has developed a capacity to retain surplus value generated internationally. In a final section, we compare these results with an analysis based on similar data for Canada. A relative uncoupling of local...
A journal set in an interdisciplinary or newly developing area can be determined by including the journals classified under the most relevant ISI Subject Categories into a journal-journal citation matrix. Despite the fuzzy character of borders, factor analysis of the citation patterns enables us to delineate the specific set by discarding the noise. This methodology is illustrated using communication studies as a hybrid development between political science and social psychology. The development can be visualized using animations which support the claim that a specific journal set in communication studies is increasingly developing, notably in the "being cited" patterns. The resulting set of 28 journals in communication studies is smaller and more focused than the 45 journals classified by the ISI Subject Categories as "Communication". The proposed method is tested for its robustness by extending the relevant environments to sets including many more journals.
The sociological domain is different from the psychological one insofar as meaning can be communicated at the supra-individual level (Schutz, 1932; Luhmann, 1984). The computation of anticipatory systems enables us to distinguish between these domains in terms of weakly and strongly anticipatory systems with a structural coupling between them (Maturana, 1978). Anticipatory systems have been defined as systems which entertain models of themselves (Rosen, 1985). The model provides meaning to the modeled system from the perspective of hindsight, that is, by advancing along the time axis towards possible future states. Strongly anticipatory systems construct their own future states (Dubois, 1998a and b). The dynamics of weak and strong anticipations can be simulated as incursion and hyper-incursion, respectively. Hyper-incursion generates "horizons of meaning" (Husserl, 1929) among which choices have to be made by incursive agency.
We theoretically prove that electromagnetic beams propagating through a nonlinear cubic metamaterial can exhibit a power flow whose direction reverses its sign along the transverse profile. This effect is peculiar of the hitherto unexplored extreme nonlinear regime where the nonlinear response is comparable or even greater than the linear contribution, a condition achievable even at relatively small intensities. We propose a possible metamaterial structure able to support the extreme conditions where the polarization cubic nonlinear contribution does not act as a mere perturbation of the linear part.
It has recently been shown that silicon nanophotonic waveguides can be used to construct all of the components of a photonic data transmission system on a single chip. These components can be integrated together with CMOS electronics to create complex electronic-photonic integrated circuits. It has also emerged that the high field confinement of silicon nanoscale guides enables exciting new applications, from chipscale nonlinear optics to biosensors and light-force activated devices. To date, most of the experiments in silicon waveguides have been at wavelengths in the near-infrared, ranging from 1.1-2 microns. Here we show that single-mode silicon nano-waveguides can be used at mid-infrared wavelengths, in particular at 4.5 microns, or 2222.2 1/cm. This idea has appeared in theoretical literature, but experimental realization has been elusive. This result represents the first practical integrated waveguide system for the mid-infrared in silicon, and enables a range of new applications.
Pulsars are amongst the most stable rotators known in the Universe. Over many years some millisecond pulsars rival the stability of atomic clocks. Comparing observations of many such stable pulsars may allow the first direct detection of gravitational waves, improve the Solar System planetary ephemeris and provide a means to study irregularities in terrestrial time scales. Here we review the goals and status of current and future pulsar timing array projects.
We used archieval RXTE PCA data to investigate the timing and spectral character istics of the transient XTE J1817-330. The data pertains to observations made during 27th January 2006 to 2nd August 2006 with 160 PCA pointings. A detailed analysis of Quasi Periodic Oscillation (QPOs) in the transient black hole X-ray binary XTE J 1817-330 was carried out. Power density spectra were obtained using lightcurves of the source. QPOs have been detected in 12 of the observations. In 8 of these observations, QPOs are also present in 8-14 keV energy band and in 5 observation in 15-25 keV band. XTE J1817-330 is the third black hole source from which low frequency QPOs are clearly detected in hard X-rays. The QPO frequency lies in ~ 5 to 9 Hz band and rms amplitude in 3 to 19% range, amplitude being higher at higher energy. We have fitted the PDS of the observations with lorentzian and powerlaw models. The energy spectra of the source are derived for those observations in which QPOs are detected to investigate any dependence...
A self-consistent global fitting method based on the Markov Chain Monte Carlo technique to study the dark matter (DM) property associated with the cosmic ray electron/positron excesses was developed in our previous work. In this work we further improve the previous study to include the hadronic branching ratio of DM annihilation/decay. The PAMELA $\bar{p}/p$ data are employed to constrain the hadronic branching ratio. We find that the 95% ($2\sigma$) upper limits of the quark branching ratio allowed by the PAMELA $\bar{p}/p$ data is $\sim 0.032$ for DM annihilation and $\sim 0.044$ for DM decay respectively. This result shows that the DM coupling to pure leptons is indeed favored by the current data. Based on the global fitting results, we further study the neutrino emission from DM in the Galactic center. Our predicted neutrino flux is some smaller than previous works since the constraint from $\gamma$-rays is involved. However, it is still capable to be detected by the forth-coming neutrino detector such as...
We present a spectral variability study of the XMM-Newton and Suzaku observations of one of the most extreme Narrow Line Seyfert 1 galaxies, IRAS13224-3809. The X-ray spectrum is characterized by two main peculiar features, i) a strong soft excess with a steep rise below about 1.3 keV and ii) a deep drop in flux above 8.2 keV. These two sharp and peculiar features can be reproduced by two relativistic emission lines due to Fe K and Fe L. The lines are produced in the inner accretion disc and independently yield consistent disc parameters. Moreover, their intensity ratio is broadly consistent with atomic physics models at all source flux levels, indicating that they belong to a single ionized reflection component. The spectral shape, X-ray flux, and variability properties are very similar in the XMM-Newton and Suzaku observations, performed about 5 years apart. The overall X-ray spectrum and variability can be described by a simple two-component model comprising a steep power law continuum plus its ionised reflection...
We discuss the different dust components of a protoplanetary disk with a special emphasis on grain composition, size and structure. The paper will highlight the role dust grains play in protoplanetary disks, as well as observational results supporting this knowledge. First, the path dust travels from the interstellar medium into the CS disk is described. Then dust condensation sequences from the gas are introduced, to determine the most likely species that occur in a disk. The characteristics of silicates are handled in detail: composition, lattice structure, magnesium to iron ratio and spectral features. The other main dust-forming component of the interstellar medium, carbon, is presented in its many forms, from molecules to more complex grains. Observational evidence for PAHs is given for both young stars and solar system material. We show how light scattering theory and laboratory data can be used to provide the optical properties of dust grains. From the observer's point of view, we discuss how infrared...
We present our optical observations of {\em Swift} GRB 070518 afterglow obtained at the 0.8-m Tsinghua University-National Astronomical Observatory of China telescope (TNT) at Xinglong Observatory. Our follow-up observations were performed from 512 sec after the burst trigger. With the upper limit of redshift $\sim$0.7, GRB 070518 is found to be an optically dim burst. The spectra indices $\beta_{ox}$ of optical to X-ray are slightly larger than 0.5, which implies the burst might be a dark burst. The extinction $A_{V}$ of the host galaxy is 3.2 mag inferred from the X-ray hydrogen column density with Galactic extinction law, and 0.3 mag with SMC extinction law. Also, it is similar to three other low-redshift optically dim bursts, which belong to XRR or XRF, and mid-term duration($T_{90}<10$, except for GRB 070419A, $T_{90}$=116s). Moreover, its $R$ band afterglow flux is well fitted by a single power-law with an index of 0.87. The optical afterglow and the X-ray afterglow in the normal segment might have the...
Active galactic nuclei (AGN) found at the centers of clusters of galaxies are a possible source for weak cluster-wide magnetic fields. To evaluate this scenario, we present 3D adaptive mesh refinement MHD simulations of a cool-core cluster that include injection of kinetic, thermal, and magnetic energy via an AGN-powered jet. Using the MHD solver in FLASH 2, we compare several sub-resolution approaches that link the estimated accretion rate as measured on the simulation mesh to the accretion rate onto the central black hole and the resulting feedback. We examine the effects of magnetized outflows on the accretion history of the black hole and discuss the ability of these models to magnetize the cluster medium.
Formation-flying studies to date have required continuous and minute corrections of the orbital elements and attitudes of the spacecraft.This increases the complexity, and associated risk, of controlling the formation, which often makes formation-flying studies infeasible for technological and economic reasons. Passive formation-flying is a novel space-flight concept, which offers a remedy to those problems. Spacecraft in a passive formation are allowed to drift and rotate slowly, but by using advanced metrology and statistical modelling methods, their relative positions, velocities, and orientations are determined with very high accuracy. The metrology data is used directly by the payloads to compensate for spacecraft motions in software. The normally very stringent spacecraft control requirements are thereby relaxed, which significantly reduces mission complexity and cost. Space-borne low-frequency radio astronomy has been identified as a key science application for a conceptual pathfinder mission using this...
We simulate the formation and evolution of galaxies with a self-consistent 3D hydrodynamical model including star formation, supernova feedback, and chemical enrichment. Hypernova feedback plays an essential role not only in solving the [Zn/Fe] problem, but also reproducing the cosmic star formation rate history and the mass-metallicity relations. In a Milky-Way type galaxy, kinematics and chemical abundances are different in bulge, disk, and thick disk because of different star formation histories and the contribution of Type Ia Supernovae.
This study presents a tomographic survey of a subset of the outer halo (10-40 kpc) drawn from the Sloan Digital Sky Survey Data Release 6. Halo substructure on spatial scales of $>3$ degrees is revealed as an excess in the local density of sub-giant stars. With an appropriate assumption of a model stellar isochrone it is possible for us to then derive distances to the sub-giant population. We describe three new candidate halo substructures; the 160- and 180-degree over-densities (at distances of 17 and 19 kpc respectively and radii of 1.3 and 1.5 kpc respectively) and an extended feature at 28 kpc that covers at least 162 square degrees, the Virgo Equatorial Stream. In addition, we recover the Sagittarius dwarf galaxy (Sgr) leading arm material and the Virgo Over-density. The derived distances, together with the number of sub-giant stars associated with each substructure, enables us to derive the integrated luminosity for the features. The tenuous, low surface brightness of the features strongly suggests...
We present new integrated light spectroscopy of globular clusters (GCs) in NGC 5128 in order to measure radial velocities and derive ages, metallicities, and alpha-element abundance ratios. Using Gemini-S 8-m/GMOS, we obtained spectroscopy in the range of ~3400-5700 AA for 72 GCs with S/N > 30 /AA and we have also discovered 35 new GCs within NGC 5128 from our radial velocity measurements. We measured and compared the Lick indices from HdeltaA through Fe5406 with the single stellar population (SSP) models of Thomas et al.(2003,2004). We also measure Lick indices for 41 Milky Way GCs from Puzia et al. (2002) and Schiavon et al. (2005) with the same methodology for direct comparison. Our results show that 68% of the NGC 5128 GCs have old ages (> 8 Gyr), 14% have intermediate ages (5-8 Gyr), and 18% have young ages (< 5 Gyr). However, when we look at the metallicity of the GCs as a function of age, we find 92% of metal-poor GCs and 56% of metal-rich GCs in NGC 5128 have ages > 8 Gyr, indicating that...
We present a study of the acceleration phase of line-driven winds in AGNs, in order to examine the physical conditions for the existence of such winds for a wide variety of initial conditions. We built a simple and fast non-hydrodynamic model, QWIND, where we assume that a wind is launched from the accretion disc at supersonic velocities of the order of a few 10^2 km/s and we concentrate on the subsequent supersonic phase. We show that this model can produce a wind with terminal velocities of the order of 10^4 km/s. There are three zones in the wind, only the middle one of which can launch a wind: in the inner zone the wind is too ionized and so experiences only the Compton radiation force which is not effective in accelerating gas. This inner failed wind however plays an important role in shielding the next zone, lowering the ionization parameter there. In the middle zone the lower ionization of the gas leads to a much larger radiation force and the gas achieves escape velocity This middle zone is quite thin...
Aims: Our primary goal is to search for planets around intermediate mass stars. We are also interested in studying the nature of radial velocity (RV) variations of K giant stars. Methods: We selected about 55 early K giant (K0 - K4) stars brighter than fifth magnitude that were observed using BOES, a high resolution spectrograph attached to the 1.8 m telescope at BOAO (Bohyunsan Optical Astronomy Observatory). BOES is equipped with $I_2$ absorption cell for high precision RV measurements. Results: We detected a periodic radial velocity variations in the K0 III star \gam1leo with a period of P = 429 days. An orbital fit of the observed RVs yields a period of P = 429 days, a semi-amplitude of K = 208 \mps, and an eccentricity of e = 0.14. To investigate the nature of the RV variations, we analyzed the photometric, CaII $\lambda$ 8662 equivalent width, and line-bisector variations of \gam1leo. We conclude that the detected RV variations can be best explained by a planetary companion with an estimated mass of m...
We use direct numerical simulations of forced MHD turbulence with a forcing function that produces two different signs of kinetic helicity in the upper and lower parts of the domain. We show that the mean flux of magnetic helicity from the small-scale field between the two parts of the domain can be described by a Fickian diffusion law with a diffusion coefficient that is approximately independent of the magnetic Reynolds number and about one third of the estimated turbulent magnetic diffusivity. The data suggest that the turbulent diffusive magnetic helicity flux can only be expected to alleviate catastrophic quenching at Reynolds numbers of more than several thousands. We further calculate the magnetic helicity density and its flux in the domain for three different gauges. We consider the Weyl gauge, in which the electrostatic potential vanishes, the pseudo-Lorenz gauge, where the speed of light is replaced by the sound speed, and the `resistive gauge' in which the Laplacian of the magnetic vector potential...
Non-zero neutrino mass would affect the evolution of the Universe in observable ways, and a strong constraint on the mass can be achieved using combinations of cosmological data sets. We focus on the power spectrum of cosmic microwave background (CMB) anisotropies, the Hubble constant H_0, and the length scale for baryon acoustic oscillations (BAO) to investigate the constraint on the neutrino mass, m_nu. We analyze data from multiple existing CMB studies (WMAP5, ACBAR, CBI, BOOMERANG, and QUAD), recent measurement of H_0 (SHOES), with about two times lower uncertainty (5%) than previous estimates, and recent treatments of BAO from the Sloan Digital Sky Survey (SDSS). We obtained an upper limit of m_nu < 0.2eV (95% C.L.), for a flat LambdaCDM model. This is a 40% reduction in the limit derived from previous H_0 estimates and one-third lower than can be achieved with extant CMB and BAO data. We also analyze the impact of smaller uncertainty on measurements of H_0 as may be anticipated in the near term, in combination...
The recent detection of blazar 3C279 by MAGIC has confirmed previous indications by H.E.S.S. that the Universe is more transparent to very-high-energy gamma rays than previously thought. We show that this fact can be reconciled with standard blazar emission models provided photon oscillations into a veri light Axion-Like Particle occur in extragalactic magnetic fields. A quantitative estimate of this effect explains the observed spectrum of 3C279. Our prediction can be tested in the near future by the satellite-borne GLAST detector as well as by the ground-based Imaging Atmospheric Cherenkov Telescpoes H.E.S.S., MAGIC, CANGAROO III, VERITAS and by the Extensive Air Shower arrays ARGO-YBJ and MILAGRO.
We explore cosmological consequences of two quintessence models in which the current cosmic acceleration is a transient phenomenon. We argue that one of them (in which the EoS parameter switches from freezing to thawing regimes) may reconcile the slight preference of observational data for freezing potentials with the impossibility of defining observables in String/M-theory due to the existence of a cosmological event horizon in asymptotically de Sitter universes.
The blazar PG 1553+113 is a well known TeV gamma-ray emitter. In this paper, we determine its spectral energy distribution using simultaneous multi-frequency data in order to study its emission processes. An extensive campaign was carried out between March and April 2008, where optical, X-ray, high-energy (HE) gamma-ray, and very-high-energy (VHE) gamma-ray data were obtained with the KVA, Abastumani, REM, RossiXTE/ASM, AGILE and MAGIC telescopes, respectively. This is the first simultaneous broad-band (i.e., HE+VHE) gamma-ray observation, though AGILE did not detect the source. We combine data to derive source's spectral energy distribution and interpret its double peaked shape within the framework of a synchrotron self compton model
Recent measurements of ultra-high energy cosmic rays and neutrinos are briefly reviewed. With several new large scale observatories nearing completion or becoming fully operational only very recently, a large body of high quality and high statistics data is growing up now. Already these first data have started to open up a new window to the high energy Universe giving us first direct clues about the origin of the most energetic particles with energies of about 10^{20} eV as well as about their interactions from extragalactic sources to Earth. Also, for the first time full sky views of high energy neutrinos have become available with neutrino telescopes operating on either Hemisphere. While a "smoking gun" is still missing on galactic sources of cosmic rays, constraining upper limits to neutrino fluxes from various source candidates are reported. Thus, future neutrino telescopes, such as KM3NeT in the Mediterranean should aim at volumes significantly larger than one cubic kilometer. Besides seeking the sources...
The generation of primordial magnetic seed fields during inflation is studied in a theory derived from the one-loop vacuum polarization effective action of the photon in a curved background. This includes terms which couple the curvature to the Maxwell tensor. The resulting magnetic field strength is estimated in a model where the inflationary phase is directly matched to the standard radiation dominated era. The allowed parameter region is analyzed and compared with the bounds necessary to seed the galactic magnetic field. It is found that magnetic fields of cosmologically interesting field strengths can be generated.
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