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Sample records for astrophysics stellar collapse

  1. Astrophysical Implications of Equation of State for Hadron-Quark Mixed Phase: Compact Stars and Stellar Collapses

    CERN Document Server

    Nakazato, Ken'ichiro; Yamada, Shoichi

    2008-01-01

    We construct an equation of state including the hadron-quark phase transition. The mixed phase is obtained by the Gibbs conditions for finite temperature. We adopt the equation of state based on the relativistic mean field theory for the hadronic phase taking into account pions. As for the quark phase, the MIT bag model of the deconfined 3-flavor strange quark matter is used. As a result, our equation of state is thermodynamically stable and exhibits qualitatively the desired properties of hadron-quark mixed matter, such as the temperature dependence of the transition density. The pions raise the transition density because they make the equation of state softer. Using the equation of state constructed here, we study its astrophysical implications. The maximum mass of compact stars is investigated, and our equation of state is consistent with recent observations. We also compute the collapse of a massive star with 100 solar masses using our equation of state and find that the interval time from the bounce to t...

  2. Computational Astrophysics at the Bleeding Edge: Simulating Core Collapse Supernovae

    Science.gov (United States)

    Mezzacappa, Anthony

    2013-04-01

    Core collapse supernovae are the single most important source of elements in the Universe, dominating the production of elements between oxygen and iron and likely responsible for half the elements heavier than iron. They result from the death throes of massive stars, beginning with stellar core collapse and the formation of a supernova shock wave that must ultimately disrupt such stars. Past, first-principles models most often led to the frustrating conclusion the shock wave stalls and is not revived, at least given the physics included in the models. However, recent progress in the context of two-dimensional, first-principles supernova models is reversing this trend, giving us hope we are on the right track toward a solution of one of the most important problems in astrophysics. Core collapse supernovae are multi-physics events, involving general relativity, hydrodynamics and magnetohydrodynamics, nuclear burning, and radiation transport in the form of neutrinos, along with a detailed nuclear physics equation of state and neutrino weak interactions. Computationally, simulating these catastrophic stellar events presents an exascale computing challenge. I will discuss past models and milestones in core collapse supernova theory, the state of the art, and future requirements. In this context, I will present the results and plans of the collaboration led by ORNL and the University of Tennessee.

  3. Evolution and seismic tools for stellar astrophysics

    CERN Document Server

    Monteiro, Mario JPFG

    2008-01-01

    A collection of articles published by the journal "Astrophysics and Space Science, Volume 316, Number 1-4", August 2008. This work covers 10 evolution codes and 9 oscillation codes. It is suitable for researchers and research students working on the modeling of stars and on the implementation of seismic test of stellar models.

  4. Biological effects of stellar collapse neutrinos

    CERN Document Server

    Collar, J I

    1996-01-01

    Massive stars in their final stages of collapse radiate most of their binding energy in the form of MeV neutrinos. The recoil atoms that they produce in elastic scattering off nuclei in organic tissue create a radiation damage which is highly effective in the production of irreparable DNA harm, leading to cellular mutation, neoplasia and oncogenesis. Using a conventional model of the galaxy and of the collapse mechanism, the periodicity of nearby stellar collapses and the radiation dose are calculated. The possible contribution of this process to the paleontological record of mass extinctions is examined.

  5. Computational Models of Stellar Collapse and Core-Collapse Supernovae

    CERN Document Server

    Ott, C D; Burrows, A; Livne, E; O'Connor, E; Löffler, F

    2009-01-01

    Core-collapse supernovae are among Nature's most energetic events. They mark the end of massive star evolution and pollute the interstellar medium with the life-enabling ashes of thermonuclear burning. Despite their importance for the evolution of galaxies and life in the universe, the details of the core-collapse supernova explosion mechanism remain in the dark and pose a daunting computational challenge. We outline the multi-dimensional, multi-scale, and multi-physics nature of the core-collapse supernova problem and discuss computational strategies and requirements for its solution. Specifically, we highlight the axisymmetric (2D) radiation-MHD code VULCAN/2D and present results obtained from the first full-2D angle-dependent neutrino radiation-hydrodynamics simulations of the post-core-bounce supernova evolution. We then go on to discuss the new code Zelmani which is based on the open-source HPC Cactus framework and provides a scalable AMR approach for 3D fully general-relativistic modeling of stellar col...

  6. Precision Stellar Astrophysics in the Kepler Era

    CERN Document Server

    Huber, Daniel

    2016-01-01

    The study of fundamental properties (such as temperatures, radii, masses, and ages) and interior processes (such as convection and angular momentum transport) of stars has implications on various topics in astrophysics, ranging from the evolution of galaxies to understanding exoplanets. In this contribution I will review the basic principles of two key observational methods for constraining fundamental and interior properties of single field stars: the study stellar oscillations (asteroseismology) and optical long-baseline interferometry. I will highlight recent breakthrough discoveries in asteroseismology such as the measurement of core rotation rates in red giants and the characterization of exoplanet systems. I will furthermore comment on the reliability of interferometry as a tool to calibrate indirect methods to estimate fundamental properties, and present a new angular diameter measurement for the exoplanet host star HD219134 which demonstrates that diameters for stars which are relatively well resolved...

  7. Stellar and Galactic Astrophysics with SIM

    Science.gov (United States)

    Gould, A.

    2001-05-01

    SIM will revolutionize stellar and Galactic astrophysics by tackling new questions that could never previously be addressed and making order of magnitude improvements in key parameters. SIM will measure R0 and Theta0 to measurements of the Milky Way mass and rotation curve. It will probe the Galactic 3-D mass distribution by 2 independent methods. By calibrating the RR Lyrae MV-[Fe/H] relation as well as obtaining direct distances to clusters and halo field objects, SIM will precisely date halo and globular-cluster formation as a function of metallicity. SIM will obtain 1 measurements for 200 stars of all types ranging from brown dwarfs (BD) to O stars from a broad range of metallicities, including both binaries and single stars, and it will yield precision measurements of white dwarf (WD) and black hole (BH) remnants as well. SIM microlensing will take an unbiased census of all objects in the Galactic bulge, both dark (BD WD NS BH) and luminous, and will resolve the nature of the dark-halo (MACHO) candidates currently being detected toward the LMC.

  8. A general method of estimating stellar astrophysical parameters from photometry

    CERN Document Server

    Belikov, A N

    2008-01-01

    Applying photometric catalogs to the study of the population of the Galaxy is obscured by the impossibility to map directly photometric colors into astrophysical parameters. Most of all-sky catalogs like ASCC or 2MASS are based upon broad-band photometric systems, and the use of broad photometric bands complicates the determination of the astrophysical parameters for individual stars. This paper presents an algorithm for determining stellar astrophysical parameters (effective temperature, gravity and metallicity) from broad-band photometry even in the presence of interstellar reddening. This method suits the combination of narrow bands as well. We applied the method of interval-cluster analysis to finding stellar astrophysical parameters based on the newest Kurucz models calibrated with the use of a compiled catalog of stellar parameters. Our new method of determining astrophysical parameters allows all possible solutions to be located in the effective temperature-gravity-metallicity space for the star and se...

  9. Measuring Stellar Temperatures: An Astrophysical Laboratory for Undergraduate Students

    Science.gov (United States)

    Cenadelli, D.; Zeni, M.

    2008-01-01

    While astrophysics is a fascinating subject, it hardly lends itself to laboratory experiences accessible to undergraduate students. In this paper, we describe a feasible astrophysical laboratory experience in which the students are guided to take several stellar spectra, using a telescope, a spectrograph and a CCD camera, and perform a full data…

  10. Search for stellar gravitational collapses with the MACRO detector

    CERN Document Server

    Ambrosio, M; Baldini, A; Barbarino, G C; Barish, B C; Battistoni, G; Bellotti, R; Bemporad, C; Bernardini, P; Bilokon, H; Bloise, C; Bower, C; Brigida, M; Bussino, S; Cafagna, F; Campana, D; Carboni, M; Cecchini, S; Cei, F; Chiarella, V; Choudhary, B C; Coutu, S; Cozzi, M; De Cataldo, G; De Marzo, C; De Mitri, I; De Vincenzi, M; Dekhissi, H; Derkaoui, J; Di Credico, A; Favuzzi, C; Forti, C; Fusco, P; Giacomelli, G; Giannini, G; Giglietto, N; Giorgini, M; Grassi, M; Grillo, A; Gustavino, C; Habig, A; Hanson, K; Heinz, R; Iarocci, E; Katsavounidis, E; Katsavounidis, I; Kearns, E; Kim, H; Kyriazopoulou, S; Lamanna, E; Lane, C; Levin, D S; Lipari, P; Longley, N P; Longo, M J; Loparco, F; Maaroufi, F; Mancarella, G; Mandrioli, G; Margiotta, A; Marini, A; Martello, D; Marzari-Chiesa, A; Mazziotta, M N; Michael, D G; Monacelli, P; Montaruli, T; Monteno, M; Mufson, S; Musser, J; Nicolò, D; Nolty, R; Orth, C; Osteria, G; Palamara, O; Patera, V; Patrizii, L; Pazzi, R; Peck, C W; Perrone, L; Petrera, S; Popa, V; Raino, J A; Reynoldson, J; Ronga, F; Satriano, C; Scapparone, E; Scholberg, K; Sciubba, A; Sioli, M; Sirri, G; Sitta, M; Spinelli, P; Spinetti, M; Spurio, M; Steinberg, R; Stone, J L; Sulak, L R; Surdo, A; Tarle, G; Togo, V; Vakili, M; Walter, C W; Webb, R; 10.1140/epjc/s2004-01981-3

    2004-01-01

    We present the final results of the search for stellar gravitational collapses obtained by the MACRO experiment. The detector was active for a stellar collapse search for more than 11 years and it was sensitive to collapses occurring all over in our galaxy for 8.6 years. A real time system for a prompt recognition of neutrino bursts was developed and was operating on-line for almost the whole life of the experiment. No signal compatible with a neutrino burst from a galactic supernova was observed.

  11. Stellar Astrophysics for the Local Group

    Science.gov (United States)

    Aparicio, A.; Herrero, A.; Sánchez, F.

    2011-06-01

    1. Fundamentals of stellar evolution theory: understanding the HRD C. Chiosi; 2. Observations of the most luminous stars in local group galaxies P. Massey; 3. Quantitative spectroscopy of the brightest blue supergiant stars in galaxies R. P. Kudritzki; 4. Calibration of the extragalactic distance scale B. F. Madore and W. L. Freedman; 5. Dwarf galaxies G. S. Da Costa; 6. Resolved stellar populations of the luminous galaxies in the local group M. Mateo; 7. Chemical evolution of the ISM in nearby galaxies E. D. Skillman; 8. Populations of massive stars and the interstellar medium C. Leitherer.

  12. Stellar core collapse. I - Infall epoch

    Science.gov (United States)

    van Riper, K. A.; Lattimer, J. M.

    1981-10-01

    Simulations of the collapse of the central iron core of a 15-solar-mass spherically symmetric star are reported. In this paper the infall epoch, between the onset of collapse and core bounce, is considered. The models use the recent equation of state of Lamb, Lattimer, Pethick, and Ravenhall and general-relativistic hydrodynamics. The electron capture rates on nuclei proceed rapidly for densities less than 10 to the 11th g/cu cm, but are suppressed at higher densities where the neutron number of the nucleus, N, exceeds 40 (Fuller, Fowler, and Newman). Neutrino transport is treated by a leakage scheme. The effects of changes in the neutrino trapping density and of qualitative changes in the electron capture reactions on the evolution are explored. Greater lepton loss during collapse leads to larger pressure deficits, more rapid collapse, and smaller inner homologous cores. The entropy change during the infall is small, the absolute value of delta s being less than 0.8. The mass of inner core is given, to about 20%, by the formula of Goldreich and Weber. Because the collapsing core is far from equilibrium, the effects of general relativity are small.

  13. A Riccati equation in radiative stellar collapse

    CERN Document Server

    Rajah, S S

    2008-01-01

    We model the behaviour of a relativistic spherically symmetric shearing fluid undergoing gravitational collapse with heat flux. It is demonstrated that the governing equation for the gravitational behaviour is a Riccati equation. We show that the Riccati equation admits two classes of new solutions in closed form. We regain particular models, obtained in previous investigations, as special cases. A significant feature of our solutions is the general spatial dependence in the metric functions which allows for a wider study of the physical features of the model, such as the behaviour of the causal temperature in inhomogeneous spacetimes.

  14. Eclipsing Binary Stars: the Royal Road to Stellar Astrophysics

    CERN Document Server

    Southworth, John

    2012-01-01

    Russell (1948) famously described eclipses as the "royal road" to stellar astrophysics. From photometric and spectroscopic observations it is possible to measure the masses and radii (to 1% or better!), and thus surface gravities and mean densities, of stars in eclipsing binary systems using nothing more than geometry. Adding an effective temperature subsequently yields luminosity and then distance (or vice versa) to high precision. This wealth of directly measurable quantities makes eclipsing binaries the primary source of empirical information on the properties of stars, and therefore a cornerstone of stellar astrophysics. In this review paper I summarise the current standing of eclipsing binary research, present an overview of useful analysis techniques, and conclude with a glance to the future.

  15. Modules for Experiments in Stellar Astrophysics (MESA): Binaries, Pulsations, and Explosions

    CERN Document Server

    Paxton, Bill; Schwab, Josiah; Bauer, Evan B; Bildsten, Lars; Cantiello, Matteo; Dessart, Luc; Farmer, R; Hu, H; Langer, N; Townsend, R H D; Townsley, Dean M; Timmes, F X

    2015-01-01

    We substantially update the capabilities of the open-source software instrument Modules for Experiments in Stellar Astrophysics (MESA). MESA can now simultaneously evolve an interacting pair of differentially rotating stars undergoing transfer and loss of mass and angular momentum, greatly enhancing the prior ability to model binary evolution. New MESA capabilities in fully coupled calculation of nuclear networks with hundreds of isotopes now allow MESA to accurately simulate advanced burning stages needed to construct supernova progenitor models. Implicit hydrodynamics with shocks can now be treated with MESA, enabling modeling of the entire massive star lifecycle, from pre-main sequence evolution to the onset of core collapse and nucleosynthesis from the resulting explosion. Coupling of the GYRE non-adiabatic pulsation instrument with MESA allows for new explorations of the instability strips for massive stars while also accelerating the astrophysical use of asteroseismology data. We improve treatment of ma...

  16. New Discoveries in Stars and Stellar Evolution through Advances in Laboratory Astrophysics

    CERN Document Server

    Brickhouse, AAS WGLA: Nancy; Drake, Paul; Federman, Steven; Ferland, Gary; Frank, Adam; Herbst, Eric; Olive, Keith; Salama, Farid; Savin, Daniel Wolf; Ziurys, Lucy

    2009-01-01

    As the Stars and Stellar Evolution (SSE) panel is fully aware, the next decade will see major advances in our understanding of these areas of research. To quote from their charge, these advances will occur in studies of the Sun as a star, stellar astrophysics, the structure and evolution of single and multiple stars, compact objects, SNe, gamma-ray bursts, solar neutrinos, and extreme physics on stellar scales. Central to the progress in these areas are the corresponding advances in laboratory astrophysics, required to fully realize the SSE scientific opportunities within the decade 2010-2020. Laboratory astrophysics comprises both theoretical and experimental studies of the underlying physics that produces the observed astrophysical processes. The 6 areas of laboratory astrophysics, which we have identified as relevant to the CFP panel, are atomic, molecular, solid matter, plasma, nuclear physics, and particle physics. In this white paper, we describe in Section 2 the scientific context and some of the new s...

  17. MODULES FOR EXPERIMENTS IN STELLAR ASTROPHYSICS (MESA): BINARIES, PULSATIONS, AND EXPLOSIONS

    Energy Technology Data Exchange (ETDEWEB)

    Paxton, Bill; Bildsten, Lars; Cantiello, Matteo [Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States); Marchant, Pablo; Langer, N. [Argelander Institut für Astronomie, Universitat Bonn, Auf dem Hügel 71, D-53121 Bonn (Germany); Schwab, Josiah [Physics Department, University of California, Berkeley, CA 94720 (United States); Bauer, Evan B. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Dessart, Luc [Laboratoire Lagrange, UMR7293, Université Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d’Azur, F-06300 Nice (France); Farmer, R.; Timmes, F. X. [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Hu, H. [SRON, Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht (Netherlands); Townsend, R. H. D. [Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706 (United States); Townsley, Dean M., E-mail: pablo@astro.uni-bonn.de [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL 35487 (United States)

    2015-09-15

    We substantially update the capabilities of the open-source software instrument Modules for Experiments in Stellar Astrophysics (MESA). MESA can now simultaneously evolve an interacting pair of differentially rotating stars undergoing transfer and loss of mass and angular momentum, greatly enhancing the prior ability to model binary evolution. New MESA capabilities in fully coupled calculation of nuclear networks with hundreds of isotopes now allow MESA to accurately simulate the advanced burning stages needed to construct supernova progenitor models. Implicit hydrodynamics with shocks can now be treated with MESA, enabling modeling of the entire massive star lifecycle, from pre-main-sequence evolution to the onset of core collapse and nucleosynthesis from the resulting explosion. Coupling of the GYRE non-adiabatic pulsation instrument with MESA allows for new explorations of the instability strips for massive stars while also accelerating the astrophysical use of asteroseismology data. We improve the treatment of mass accretion, giving more accurate and robust near-surface profiles. A new MESA capability to calculate weak reaction rates “on-the-fly” from input nuclear data allows better simulation of accretion induced collapse of massive white dwarfs and the fate of some massive stars. We discuss the ongoing challenge of chemical diffusion in the strongly coupled plasma regime, and exhibit improvements in MESA that now allow for the simulation of radiative levitation of heavy elements in hot stars. We close by noting that the MESA software infrastructure provides bit-for-bit consistency for all results across all the supported platforms, a profound enabling capability for accelerating MESA's development.

  18. Solar, Stellar and Galactic Connections between Particle Physics and Astrophysics

    CERN Document Server

    Carraminana, Alberto

    2007-01-01

    This book collects extended and specialized reviews on topics linking astrophysics and particle physics at a level intermediate between a graduate student and a young researcher. The book includes also three reviews on observational techniques used in forefront astrophysics and short articles on research performed in Latin America. The reviews, updated and written by specialized researchers, describe the state of the art in the related research topics. This book is a valuable complement not only for research but also for lecturers in specialized course of high energy astrophysics, cosmic ray astrophysics and particle physics.

  19. New Kepler Data Products At MAST For Stellar Astrophysics

    Science.gov (United States)

    Fleming, Scott W.; Shiao, B.; Tseng, S.; Million, C.; Thompson, R.; Seibert, M.; Abney, F.; Donaldson, T.; Dower, T.; Fraquelli, D. A.; Handy, S.; Koekemoer, A. M.; Levay, K.; Matuskey, J.; McLean, B.; Quick, L.; Rogers, A.; Wallace, G.; White, R. L.

    2014-01-01

    The Kepler Mission has collected high-precision, time-series photometry of over 200,000 stars. The reduced lightcurves, target pixel files, and a variety of catalog metadata are already available at MAST. We present new data products and services at MAST that will further aid researchers as Kepler begins its transition to a legacy mission, particularly in the realm of stellar astrophysics. New photometric catalogs to accompany the Kepler targets have arrived at MAST within the past year, and several more will be coming in the relative future. These include the second half of the Kepler INT survey (U,g,r,i,H_alpha; available now), an improved GALEX source catalog (NUV and FUV; available now), PanSTARRS (g,r,i,z; available soon), and WISE (3.4, 4.6, 12, and 22 microns; planned). We expect searches for variability will become one of the most active areas of archive use, so MAST is including a wide range of variability statistics as part of the archive database. In addition to being searchable through database queries and web forms, each Preview page will now include a summary of these variability indices for each of the target's lightcurves within a Quarter. Along with updated NUV and FUV fluxes, a new tool at MAST called gPhoton will allow users to create time-series lightcurves, including animated movies and intensity images, from any set of GALEX photons with arbitrary aperture and bin sizes. We show some examples of the ways GALEX UV lightcurves generated with gPhoton can be used in conjunction with the Kepler data. Finally, MAST has released an initial version of its Data Discovery Portal. This one-stop, interactive web application gives users the ability to search and access data from any of MAST's missions (HST, GALEX, Kepler, FUSE, IUE, JWST, etc.), as well as any data available through the Virtual Observatory. It includes filtering options, access to interactive displays, an accompanying AstroViewer with data footprints on-sky, the ability to upload your own

  20. The r-process of stellar nucleosynthesis: Astrophysics and nuclear physics achievements and mysteries

    CERN Document Server

    Arnould, M; Takahashi, K

    2007-01-01

    The r-process, or the rapid neutron-capture process, of stellar nucleosynthesis is called for to explain the production of the stable (and some long-lived radioactive) neutron-rich nuclides heavier than iron that are observed in stars of various metallicities, as well as in the solar system. A very large amount of nuclear information is necessary in order to model the r-process. This concerns the static characteristics of a large variety of light to heavy nuclei between the valley of stability and the vicinity of the neutron-drip line, as well as their beta-decay branches or their reactivity. The enormously challenging experimental and theoretical task imposed by all these requirements is reviewed, and the state-of-the-art development in the field is presented. Nuclear-physics-based and astrophysics-free r-process models of different levels of sophistication have been constructed over the years. We review their merits and their shortcomings. For long, the core collapse supernova of massive stars has been envi...

  1. The r-process of stellar nucleosynthesis: Astrophysics and nuclear physics achievements and mysteries

    Science.gov (United States)

    Arnould, M.; Goriely, S.; Takahashi, K.

    2007-09-01

    The r-process, or the rapid neutron-capture process, of stellar nucleosynthesis is called for to explain the production of the stable (and some long-lived radioactive) neutron-rich nuclides heavier than iron that are observed in stars of various metallicities, as well as in the solar system. A very large amount of nuclear information is necessary in order to model the r-process. This concerns the static characteristics of a large variety of light to heavy nuclei between the valley of stability and the vicinity of the neutron-drip line, as well as their beta-decay branches or their reactivity. Fission probabilities of very neutron-rich actinides have also to be known in order to determine the most massive nuclei that have a chance to be involved in the r-process. Even the properties of asymmetric nuclear matter may enter the problem. The enormously challenging experimental and theoretical task imposed by all these requirements is reviewed, and the state-of-the-art development in the field is presented. Nuclear-physics-based and astrophysics-free r-process models of different levels of sophistication have been constructed over the years. We review their merits and their shortcomings. The ultimate goal of r-process studies is clearly to identify realistic sites for the development of the r-process. Here too, the challenge is enormous, and the solution still eludes us. For long, the core collapse supernova of massive stars has been envisioned as the privileged r-process location. We present a brief summary of the one- or multidimensional spherical or non-spherical explosion simulations available to-date. Their predictions are confronted with the requirements imposed to obtain an r-process. The possibility of r-nuclide synthesis during the decompression of the matter of neutron stars following their merging is also discussed. Given the uncertainties remaining on the astrophysical r-process site and on the involved nuclear physics, any confrontation between predicted r

  2. The r-process of stellar nucleosynthesis: Astrophysics and nuclear physics achievements and mysteries

    Energy Technology Data Exchange (ETDEWEB)

    Arnould, M. [Institut d' Astronomie et d' Astrophysique, Universite Libre de Bruxelles, CP226, B-1050 Brussels (Belgium)], E-mail: marnould@astro.ulb.ac.be; Goriely, S.; Takahashi, K. [Institut d' Astronomie et d' Astrophysique, Universite Libre de Bruxelles, CP226, B-1050 Brussels (Belgium)

    2007-09-15

    The r-process, or the rapid neutron-capture process, of stellar nucleosynthesis is called for to explain the production of the stable (and some long-lived radioactive) neutron-rich nuclides heavier than iron that are observed in stars of various metallicities, as well as in the solar system. A very large amount of nuclear information is necessary in order to model the r-process. This concerns the static characteristics of a large variety of light to heavy nuclei between the valley of stability and the vicinity of the neutron-drip line, as well as their beta-decay branches or their reactivity. Fission probabilities of very neutron-rich actinides have also to be known in order to determine the most massive nuclei that have a chance to be involved in the r-process. Even the properties of asymmetric nuclear matter may enter the problem. The enormously challenging experimental and theoretical task imposed by all these requirements is reviewed, and the state-of-the-art development in the field is presented. Nuclear-physics-based and astrophysics-free r-process models of different levels of sophistication have been constructed over the years. We review their merits and their shortcomings. The ultimate goal of r-process studies is clearly to identify realistic sites for the development of the r-process. Here too, the challenge is enormous, and the solution still eludes us. For long, the core collapse supernova of massive stars has been envisioned as the privileged r-process location. We present a brief summary of the one- or multidimensional spherical or non-spherical explosion simulations available to-date. Their predictions are confronted with the requirements imposed to obtain an r-process. The possibility of r-nuclide synthesis during the decompression of the matter of neutron stars following their merging is also discussed. Given the uncertainties remaining on the astrophysical r-process site and on the involved nuclear physics, any confrontation between predicted r

  3. Experimental simulation of a stellar photon bath by bremsstrahlung the astrophysical $\\gamma$-process

    CERN Document Server

    Mohr, P J; Babilon, M; Enders, J; Hartmann, T; Hutter, C; Rauscher, T; Volz, S; Zilges, A

    2000-01-01

    The nucleosynthesis of heavy proton-rich nuclei in a stellar photon bath at temperatures of the astrophysical $\\gamma$-process was investigated where the photon bath was simulated by the superposition of bremsstrahlung spectra with different endpoint energies. The method was applied to derive ($\\gamma$,n) cross sections and reaction rates for several platinum isotopes.

  4. Self-gravitating stellar collapse: explicit geodesics and path integration

    Directory of Open Access Journals (Sweden)

    Jayashree Balakrishna

    2016-11-01

    Full Text Available We extend the work of Oppenheimer-Synder to model the gravitational collapse of a star to a black hole by including quantum mechanical effects. We first derive closed-form solutions for classical paths followed by a particle on the surface of the collapsing star in Schwarzschild and Kruskal coordinates for space-like, time-like and light-like geodesics. We next present an application of these paths to model the collapse of ultra-light dark matter particles, which necessitates incorporating quantum effects. To do so we treat a particle on the surface of the star as a wavepacket and integrate over all possible paths taken by the particle. The waveform is computed in Schwarzschild coordinates and found to exhibit an ingoing and an outgoing component, where the former contains the probability of collapse, while the latter contains the probability that the star will disperse. These calculations pave the way for investigating the possibility of quantum collapse that does not lead to black hole formation as well as for exploring the nature of the wavefunction inside r = 2M.

  5. Towards optical intensity interferometry for high angular resolution stellar astrophysics

    CERN Document Server

    Nunez, Paul D

    2012-01-01

    Most neighboring stars are still detected as point sources and are beyond the angular resolution reach of current observatories. Methods to improve our understanding of stars at high angular resolution are investigated. Air Cherenkov telescopes (ACTs), primarily used for Gamma-ray astronomy, enable us to increase our understanding of the circumstellar environment of a particular system. When used as optical intensity interferometers, future ACT arrays will allow us to detect stars as extended objects and image their surfaces at high angular resolution. Optical stellar intensity interferometry (SII) with ACT arrays, composed of nearly 100 telescopes, will provide means to measure fundamental stellar parameters and also open the possibility of model-independent imaging. A data analysis algorithm is developed and permits the reconstruction of high angular resolution images from simulated SII data. The capabilities and limitations of future ACT arrays used for high angular resolution imaging are investigated via ...

  6. Minisuperspace Stellar Collapse in Semi-Classical Gravity

    CERN Document Server

    Balakrishna, Jayashree; Moran, Christine Corbett

    2015-01-01

    We compute the Schr\\"odinger and WKB propagators for the semi-classical collapse of a sphere of dust. This extends the work by Redmount and Suen (1993) from the free particle case to nontrivial gravity. In the Oppenheimer-Snyder model, a star can be idealised as a collapsing dust sphere of uniform density and zero pressure. The particles that make up the star have the attributes of classical dust where each particle is assumed to be infinitesimal in size and to interact only gravitationally with other matter. We include quantum mechanical effects, which lift some of these assumptions. This allows for the possibility that some configurations will not collapse to black holes. We find analytic, closed-form solutions for classical paths of a particle on the surface of a collapsing star in Schwarzschild and Kruskal geometries. Kruskal coordinates can be used to study the wavefunction inside the apparent horizon. The propagator is written in closed form in Schwarzschild coordinates in both the WKB and in the Schr\\"...

  7. Understanding Astrophysical Noise from Stellar Surface Magneto-Convection

    CERN Document Server

    Cegla, H M; Shelyag, S; Mathioudakis, M

    2014-01-01

    To obtain cm/s precision, stellar surface magneto-convection must be disentangled from observed radial velocities (RVs). In order to understand and remove the convective signature, we create Sun-as-a-star model observations based on a 3D magnetohydrodynamic solar simulation. From these Sun-as-a-star model observations, we find several line characteristics are correlated with the induced RV shifts. The aim of this campaign is to feed directly into future high precision RV studies, such as the search for habitable, rocky worlds, with forthcoming spectrographs such as ESPRESSO.

  8. Comments on Biological Effects of Stellar Collapse Neutrinos

    CERN Document Server

    Abbas, S; Abbas, Samar; Abbas, Afsar

    1996-01-01

    Extraterrestrial processes like neutrinos from collapsing stars, cosmic rays from supernovae and cosmic rays from neutron star mergers etc. have recently been proposed as models to explain the periodic mass extinctions such as that which wiped out the dinosaurs at the K-T boundary. Here we show that these models fail to give any reasonable explanation of several empirically established facts related to these mass extinctions.

  9. The Nonlinear Evolution of Massive Stellar Core Collapses That ``Fizzle''

    Science.gov (United States)

    Imamura, James N.; Pickett, Brian K.; Durisen, Richard H.

    2003-04-01

    Core collapse in a massive rotating star may pause before nuclear density is reached, if the core contains total angular momentum J>~1049 g cm2 s-1. In such aborted or ``fizzled'' collapses, temporary equilibrium objects form that, although rapidly rotating, are secularly and dynamically stable because of the high electron fraction per baryon Ye>0.3 and the high entropy per baryon Sb/k~1-2 of the core material at neutrino trapping. These fizzled collapses are called ``fizzlers.'' In the absence of prolonged infall from the surrounding star, the evolution of fizzlers is driven by deleptonization, which causes them to contract and spin up until they either become stable neutron stars or reach the dynamic instability point for barlike modes. The barlike instability case is of current interest because the bars would be sources of gravitational wave (GW) radiation. In this paper, we use linear and nonlinear techniques, including three-dimensional hydrodynamic simulations, to study the behavior of fizzlers that have deleptonized to the point of reaching dynamic bar instability. The simulations show that the GW emission produced by bar-unstable fizzlers has rms strain amplitude r15h=10-23 to 10-22 for an observer on the rotation axis, with wave frequency of roughly 60-600 Hz. Here h is the strain and r15= (r/15 Mpc) is the distance to the fizzler in units of 15 Mpc. If the bars that form by dynamic instability can maintain GW emission at this level for 100 periods or more, they may be detectable by the Laser Interferometer Gravitational-Wave Observatory at the distance of the Virgo Cluster. They would be detectable as burst sources, defined as sources that persist for ~10 cycles or less, if they occurred in the Local Group of galaxies. The long-term behavior of the bars is the crucial issue for the detection of fizzler events. The bars present at the end of our simulations are dynamically stable but will evolve on longer timescales because of a variety of effects, such as

  10. UVESP: Ultraviolet Visible Echellé Spectropolarimeter for Stellar Astrophysics.

    Science.gov (United States)

    Yushkin, Maxim; Sachkov, Mikhail; Gomez De Castro, Ana; Marcos-Arenal, Pablo; Belén Perea Abarca, G.; Panchuk, Vladimir

    2016-07-01

    UVESP is an efficient instrument designed for mid resolution (30,000) spectropolarimetric observations in the 119-888nm wavelength range. Simultaneous spectropolarimetry in the optical and ultraviolet (UV) range is the only tool to study the precise characteristics of stellars magnetic fields and their connection with atmospheric structures, outflows, envelopes. The UV range is very rich in atomic and molecular lines. Moreover, hot stars radiation peaks in the UV range. The visible (VIS) spectrum provides information of the surface of the stars. Simultaneous UV and visible wavelength coverage will allow the extension of Doppler mapping methods into the winds, chromospheres and discs of stars, providing the 3D maps of their magnetospheres and immediate environments. The formation of planets around stars and the environmental conditions for emergence of life on these planets can be studied by monitoring the UV spectrum and the magnetic activity. In this contribution, we describe the optical design of UVESP. The instrument is fed by the radiation of an F/13 telescope that goes through an on-focus single polarimeter. The two spectrographs (UV and VIS) are fed by light coming from the polarimeter. The polarimeter splits the incoming beam into two states of polarization At the entrance of the instrument, a beam splitter divides the beam into the ultraviolet (UV) and the visible (VIS) channels with wavelength ranges of 355 nm to 888 nm for the VIS channel and 119 to 320 nm for the UV channel. In the VIS channel the beam continues to the slit and then a collimator is placed in order to illuminate a prism (double pass) with a collimated beam. After the prism an Echellé-grating and a a concave diffraction grating are allocated . After the grating, objective lenses are allocated. In the UV channel the beam continues from the slit to a collimator mirror. After, an Echelle-grating is allocated. The cross-dispersion is made with a toroidal diffraction grating. This design is

  11. Three-dimensional simulations of stellar core collapse in full general relativity: Nonaxisymmetric dynamical instabilities

    CERN Document Server

    Shibata, M; Shibata, Masaru; Sekiguchi, Yu-ichirou

    2005-01-01

    We perform fully general relativistic simulations of rotating stellar core collapse in three spatial dimension. A parametric equation of state is adopted following Dimmelmeier et al. The early stage of the collapse is followed by an axisymmetric code. When the stellar core becomes compact enough, we start a 3-dimensional simulation adding a bar-mode nonaxisymmetric density perturbation. In the axisymmetric simulations, it is clarified that the maximum value of $\\beta \\equiv T/W$ achieved during the stellar collapse and depends sensitively on the velocity profile and total mass of the initial core, and equations of state. It is also found that for all the models with high degree of differential rotation, a funnel structure is formed around the rotational axis after the formation of neutron stars. For selected models in which the maximum value of $\\beta$ is larger than $\\sim 0.27$, 3-dimensional simulations are performed. It is found that the bar-mode dynamical instability sets in for the case that the followin...

  12. The p-process of stellar nucleosynthesis: astrophysics and nuclear physics status

    Science.gov (United States)

    Arnould, M.; Goriely, S.

    2003-09-01

    The p-process of stellar nucleosynthesis is aimed at explaining the production of the stable neutron-deficient nuclides heavier than iron that are observed up to now in the solar system exclusively. Various scenarios have been proposed to account for the bulk p-nuclide content of the solar system, as well as for deviations (`anomalies') with respect to the bulk p-isotope composition of some elements discovered in primitive meteorites. The astrophysics of these models is reviewed, and the involved nuclear physics is discussed, including a brief account of recent experimental efforts. Already published results are complemented with new ones. A specific attention is paid to the very rare odd-odd nuclides 138La and 180Tam, as well as to the puzzling case of the light Mo and Ru isotopes. Astrophysics and nuclear physics prospects of improvements in the p-process modeling are presented.

  13. The p-process of stellar nucleosynthesis: astrophysics and nuclear physics status

    Energy Technology Data Exchange (ETDEWEB)

    Arnould, M.; Goriely, S

    2003-09-01

    The p-process of stellar nucleosynthesis is aimed at explaining the production of the stable neutron-deficient nuclides heavier than iron that are observed up to now in the solar system exclusively. Various scenarios have been proposed to account for the bulk p-nuclide content of the solar system, as well as for deviations ('anomalies') with respect to the bulk p-isotope composition of some elements discovered in primitive meteorites. The astrophysics of these models is reviewed, and the involved nuclear physics is discussed, including a brief account of recent experimental efforts. Already published results are complemented with new ones. A specific attention is paid to the very rare odd-odd nuclides {sup 138}La and {sup 180}Ta{sup m}, as well as to the puzzling case of the light Mo and Ru isotopes. Astrophysics and nuclear physics prospects of improvements in the p-process modeling are presented.

  14. Capture reactions of astrophysical relevance in the CNO-cycles and in stellar helium burning

    CERN Document Server

    Hammer, J W; Jäger, M; Kunz, R; Mayer, A; Morlock, R; Schreiter, R; Staudt, G; Mohr, P J; Butt, Y; Parker, P D; Kratz, K L; Pfeiffer, B

    2000-01-01

    In the DYNAMITRON laboratory of the University of Stuttgart capture reactions have been investigated which are important for the nucleosynthesis of the elements. Various stellar models describing nucleosynthesis require nuclear reaction rates at burning temperatures with sufficient accuracy. Applying techniques of high sensitivity to cross section measurements one is straining to extend these measurements as far as possible into the astrophysically relevant range at low energies. But despite all these efforts one often has to apply extrapolations or one has to investigate mirror nuclei in cases where the target nucleus is not available in sufficient amounts.

  15. Effects of stellar rotation on star formation rates and comparison to core-collapse supernova rates

    CERN Document Server

    Horiuchi, Shunsaku; Bothwell, Matt S; Thompson, Todd A

    2013-01-01

    We investigate star formation rate (SFR) calibrations in light of recent developments in the modeling of stellar rotation. Using new published non-rotating and rotating stellar tracks, we study the integrated properties of synthetic stellar populations and find that the UV to SFR calibration for the rotating stellar population is 30% smaller than for the non-rotating stellar population, and 40% smaller for the Halpha to SFR calibration. These reductions translate to smaller SFR estimates made from observed UV and Halpha luminosities. Using the UV and Halpha fluxes of a sample of ~300 local galaxies, we derive a total (i.e., sky-coverage corrected) SFR within 11 Mpc of 120-170 Msun/yr and 80-130 Msun/yr for the non-rotating and rotating estimators, respectively. Independently, the number of core-collapse supernovae discovered in the same volume requires a total SFR of 270^{+110}_{-80} Msun/yr, suggesting a mild tension with the SFR estimates made with rotating calibrations. More generally, when compared with t...

  16. Effects of binary stellar populations on direct collapse black hole formation

    CERN Document Server

    Agarwal, Bhaskar; Khochfar, Sadegh; Klessen, Ralf; Glover, Simon; Johnson, Jarrett

    2016-01-01

    The critical Lyman-Werner (LW) flux required for direct collapse blackholes (DCBH) formation, or J$_{\\rm crit}$, depends on the shape of the irradiating spectral energy distribution (SED). The SEDs employed thus far have been representative of realistic single stellar populations. We study the effect of binary stellar populations on the formation of DCBH, as a result of their contribution to the LW radiation field. Although binary populations with ages $>$ 10 Myr yield a larger LW photon output, we find that the corresponding values of J$_{\\rm crit}$ can be up to 100 times higher than single stellar populations. We attribute this to the shape of the binary SEDs as they produce a sub-critical rate of H$^-$ photodetaching 0.76 eV photons as compared to single stellar populations, reaffirming the role that H$^-$ plays in DCBH formation. This further corroborates the idea that DCBH formation is better understood in terms of a critical region in the H$_2$-H$^-$ photodestruction rate parameter space, rather than a ...

  17. Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars

    CERN Document Server

    Paxton, Bill; Arras, Phil; Bildsten, Lars; Brown, Edward F; Dotter, Aaron; Mankovich, Christopher; Montgomery, M H; Stello, Dennis; Timmes, F X; Townsend, Richard

    2013-01-01

    We substantially update the capabilities of the open source software package Modules for Experiments in Stellar Astrophysics (MESA), and its one-dimensional stellar evolution module, MESA Star. Improvements in MESA Star's ability to model the evolution of giant planets now extends its applicability down to masses as low as one-tenth that of Jupiter. The dramatic improvement in asteroseismology enabled by the space-based Kepler and CoRoT missions motivates our full coupling of the ADIPLS adiabatic pulsation code with MESA Star. This also motivates a numerical recasting of the Ledoux criterion that is more easily implemented when many nuclei are present at non-negligible abundances. This impacts the way in which MESA Star calculates semi-convective and thermohaline mixing. We exhibit the evolution of 3-8 Msun stars through the end of core He burning, the onset of He thermal pulses, and arrival on the white dwarf cooling sequence. We implement diffusion of angular momentum and chemical abundances that enable cal...

  18. A Comprehensive Stellar Astrophysical Study of the Old Open Cluster M67 with Kepler

    Science.gov (United States)

    Mathieu, Robert D.; Vanderburg, Andrew; K2 M67 Team

    2016-06-01

    M67 is among the best studied of all star clusters. Being at an age and metallicity very near solar, at an accessible distance of 850 pc with low reddening, and rich in content (over 1000 members including main-sequence dwarfs, a well populated subgiant branch and red giant branch, white dwarfs, blue stragglers, sub-subgiants, X-ray sources and CVs), M67 is a cornerstone of stellar astrophysics.The K2 mission (Campaign 5) has obtained long-cadence observations for 2373 stars, both within an optimized central superaperture and as specified targets outside the superaperture. 1,432 of these stars are likely cluster members based on kinematic and photometric criteria.We have extracted light curves and corrected for K2 roll systematics, producing light curves with noise characteristics qualitatively similar to Kepler light curves of stars of similar magnitudes. The data quality is slightly poorer than for field stars observed by K2 due to crowding near the cluster core, but the data are of sufficient quality to detect seismic oscillations, binary star eclipses, flares, and candidate transit events. We are in the process of uploading light curves and various diagnostic files to MAST; light curves and supporting data will also be made available on ExoFOP.Importantly, several investigators within the M67 K2 team are independently doing light curve extractions and analyses for confirmation of science results. We also are adding extensive ground-based supporting data, including APOGEE near-infrared spectra, TRES and WIYN optical spectra, LCOGT photometry, and more.Our science goals encompass asteroseismology and stellar evolution, alternative stellar evolution pathways in binary stars, stellar rotation and angular momentum evolution, stellar activity, eclipsing binaries and beaming, and exoplanets. We will present early science results as available by the time of the meeting, and certainly including asteroseismology, blue stragglers and sub-subgiants, and newly discovered

  19. Hans A. Bethe Prize Talk: Neutron stars and stellar collapse: the physics of strongly interacting Fermi systems

    Science.gov (United States)

    Pethick, C. J.

    2011-04-01

    The talk will touch on a number of themes in the application of many-body theory to neutron stars and stellar collapse. One of these will be the composition and equation of state of nuclear matter. Specific topics will include nuclei in neutron stars, superfluidity and superconductivity of nuclear matter, and inhomogeneous phases of nuclear matter. A second major theme will be neutrino processes in dense matter: neutrino emission is the most powerful cooling mechanism for young neutron stars, and rates of neutrino processes are a key ingredient in simulations of stellar collapse.

  20. ASTROPHYSICAL SHRAPNEL: DISCRIMINATING AMONG NEAR-EARTH STELLAR EXPLOSION SOURCES OF LIVE RADIOACTIVE ISOTOPES

    Energy Technology Data Exchange (ETDEWEB)

    Fry, Brian J.; Fields, Brian D. [Department of Astronomy, University of Illinois, Urbana, IL 61801 (United States); Ellis, John R. [Theoretical Physics and Cosmology Group, Department of Physics, King' s College London, London WC2R 2LS (United Kingdom)

    2015-02-10

    We consider the production and deposition on Earth of isotopes with half-lives in the range 10{sup 5}-10{sup 8} yr that might provide signatures of nearby stellar explosions, extending previous analyses of Core-Collapse Supernovae (CCSNe) to include Electron-Capture Supernovae (ECSNe), Super-Asymptotic Giant Branch (SAGB) stars, Thermonuclear/Type Ia Supernovae (TNSNe), and Kilonovae/Neutron Star Mergers (KNe). We revisit previous estimates of the {sup 60}Fe and {sup 26}Al signatures, and extend these estimates to include {sup 244}Pu and {sup 53}Mn. We discuss interpretations of the {sup 60}Fe signals in terrestrial and lunar reservoirs in terms of a nearby stellar ejection ∼2.2 Myr ago, showing that (1) the {sup 60}Fe yield rules out the TNSN and KN interpretations, (2) the {sup 60}Fe signals highly constrain SAGB interpretations but do not completely them rule out, (3) are consistent with a CCSN origin, and (4) are highly compatible with an ECSN interpretation. Future measurements could resolve the radioisotope deposition over time, and we use the Sedov blast wave solution to illustrate possible time-resolved profiles. Measuring such profiles would independently probe the blast properties including distance, and would provide additional constraints for the nature of the explosion.

  1. Neutrinos from Stellar Collapse Comparison of the effects of three and four flavour mixings

    CERN Document Server

    Dutta, G; Murthy, M V N; Rajasekaran, G; Dutta, Gautam

    2000-01-01

    We study the effect of non-vanishing masses and mixings among neutrino flavours on the detection of neutrinos from stellar collapse by a water Cerenkov detector. We consider a frame-work in which there are four neutrino flavours, including a sterile neutrino, whose mass squared differences and mixings are constrained by the present understanding of solar, atmospheric and laboratory neutrino detection. We also include the effects of high density matter within the supernova core. Unlike in the three flavour scenario, we find that the number of events due to the dominant process involving electron-antineutrinos changes dramatically for some allowed mixing parameters. Furthermore, contributions from charged-current scattering off oxygen nuclei in the detector can be considerably enhanced due to flavour mixing. We also present a comparison between the two possible scenarios, namely, when only three active neutrino flavours are present and when they are accompanied by a fourth sterile neutrino.

  2. He-like ions as practical astrophysical plasma diagnostics: From stellar coronae to active galactic nuclei

    CERN Document Server

    Porquet, Delphine; Grosso, Nicolas; 10.1007/s11214-010-9731-2

    2011-01-01

    We review X-ray plasma diagnostics based on the line ratios of He-like ions. Triplet/singlet line intensities can be used to determine electronic temperature and density, and were first developed for the study of the solar corona. Since the launches of the X-ray satellites Chandra and XMM-Newton, these diagnostics have been extended and used (from CV to Si XIII) for a wide variety of astrophysical plasmas such as stellar coronae, supernova remnants, solar system objects, active galactic nuclei, and X-ray binaries. Moreover, the intensities of He-like ions can be used to determine the ionization process(es) at work, as well as the distance between the X-ray plasma and the UV emission source for example in hot stars. In the near future thanks to the next generation of X-ray satellites (e.g., Astro-H and IXO), higher-Z He-like lines (e.g., iron) will be resolved, allowing plasmas with higher temperatures and densities to be probed. Moreover, the so-called satellite lines that are formed closed to parent He-like ...

  3. Core-Collapse Astrophysics with a Five-Megaton Neutrino Detector

    CERN Document Server

    Kistler, Matthew D; Ando, Shin'ichiro; Beacom, John F; Suzuki, Yoichiro

    2008-01-01

    The legacy of solar neutrinos suggests that large neutrino detectors should be sited underground. However, to instead go underwater bypasses the need to move mountains, allowing much larger contained water Cherenkov detectors. Reaching a scale of ~5 Megatons, the size of the proposed Deep-TITAND, would permit observations of "mini-bursts" of neutrinos from supernovae in the nearby universe on a yearly basis. Importantly, these mini-bursts would be detected over backgrounds without the need for optical evidence of the supernova, guaranteeing the beginning of time-domain MeV neutrino astronomy. The ability to identify, to the second, every core collapse would allow a continuous "death watch" of all stars within ~5 Mpc, making previously-impossible tasks practical. These include the abilities to promptly detect otherwise-invisible prompt black hole formation, provide advance warning for supernova shock-breakout searches, define tight time windows for gravitational-wave searches, and identify "supernova impostors...

  4. Estimations of the Distances of Stellar Collapses in the Galaxy by Analyzing the Energy Spectrum of Neutrino Bursts

    CERN Document Server

    Kemp, Ernesto; Fulgione, Walter; 10.1142/S0218301311040591

    2012-01-01

    The neutrino telescopes of the present generation, depending on their specific features, can reconstruct the neutrino spectra from a galactic burst. Since the optical counterpart could be not available, it is desirable to have at hand alternative methods to estimate the distance of the supernova explosion using only the neutrino data. In this work we present preliminary results on the method we are proposing to estimate the distance from a galactic supernova based only on the spectral shape of the neutrino burst and assumptions on the gravitational binding energy released an a typical supernova explosion due to stellar collapses.

  5. Neutrino Astrophysics

    CERN Document Server

    Volpe, Cristina

    2016-01-01

    We summarize the progress in neutrino astrophysics and emphasize open issues in our understanding of neutrino flavor conversion in media. We discuss solar neutrinos, core-collapse supernova neutrinos and conclude with ultra-high energy neutrinos.

  6. Numerical simulations of stellar collapse in scalar-tensor theories of gravity

    CERN Document Server

    Gerosa, Davide; Ott, Christian D

    2016-01-01

    We present numerical-relativity simulations of spherically symmetric core collapse and compact-object formation in scalar-tensor theories of gravity. The additional scalar degree of freedom introduces a propagating monopole gravitational-wave mode. Detection of monopole scalar waves with current and future gravitational-wave experiments may constitute smoking gun evidence for strong-field modifications of General Relativity. We collapse both polytropic and more realistic pre-supernova profiles using a high-resolution shock-capturing scheme and an approximate prescription for the nuclear equation of state. The most promising sources of scalar radiation are protoneutron stars collapsing to black holes. In case of a Galactic core collapse event forming a black hole, Advanced LIGO may be able to place independent constraints on the parameters of the theory at a level comparable to current Solar-System and binary-pulsar measurements. In the region of the parameter space admitting spontaneously scalarised stars, tr...

  7. Atomic Data for Stellar Astrophysics: from the UV to the IR

    Science.gov (United States)

    Wahlgren, Glenn M.

    2011-01-01

    The study of stars and stellar evolution relies heavily on the analysis of stellar spectra. The need for atomic line data from the ultraviolet (UV) to the infrared (lR) regions is greater now than ever. In the past twenty years, the time since the launch of the Hubble Space Telescope, great progress has been made in acquiring atomic data for UV transitions. The optical wavelength region, now expanded by progress in detector technology, continues to provide motivation for new atomic data. In addition, investments in new instrumentation for ground-based and space observatories has lead to the availability of high-quality spectra at IR wavelengths, where the need for atomic data is most critical. In this review, examples are provided of the progress made in generating atomic data for stellar studies, with a look to the future for addressing the accuracy and completeness of atomic data for anticipated needs.

  8. Core-Collapse Supernovae: Reflections and Directions

    CERN Document Server

    Janka, H -Thomas; Huedepohl, Lorenz; Marek, Andreas; Mueller, Bernhard; Obergaulinger, Martin

    2012-01-01

    Core-collapse supernovae are among the most fascinating phenomena in astrophysics and provide a formidable challenge for theoretical investigation. They mark the spectacular end of the lives of massive stars and, in an explosive eruption, release as much energy as the sun produces during its whole life. A better understanding of the astrophysical role of supernovae as birth sites of neutron stars, black holes, and heavy chemical elements, and more reliable predictions of the observable signals from stellar death events are tightly linked to the solution of the long-standing puzzle how collapsing stars achieve to explode. In this article our current knowledge of the processes that contribute to the success of the explosion mechanism are concisely reviewed. After a short overview of the sequence of stages of stellar core-collapse events, the general properties of the progenitor-dependent neutrino emission will be briefly described. Applying sophisticated neutrino transport in axisymmetric (2D) simulations with ...

  9. Relativistic astrophysics

    CERN Document Server

    Demianski, Marek

    2013-01-01

    Relativistic Astrophysics brings together important astronomical discoveries and the significant achievements, as well as the difficulties in the field of relativistic astrophysics. This book is divided into 10 chapters that tackle some aspects of the field, including the gravitational field, stellar equilibrium, black holes, and cosmology. The opening chapters introduce the theories to delineate gravitational field and the elements of relativistic thermodynamics and hydrodynamics. The succeeding chapters deal with the gravitational fields in matter; stellar equilibrium and general relativity

  10. Principles of astrophysics using gravity and stellar physics to explore the cosmos

    CERN Document Server

    Keeton, Charles

    2014-01-01

    This book gives a survey of astrophysics at the advanced undergraduate level.  It originates from a two-semester course sequence at Rutgers University that is meant to appeal not only to astrophysics students but also more broadly to physics and engineering students.  The organization is driven more by physics than by astronomy; in other words, topics are first developed in physics and then applied to astronomical systems that can be investigated, rather than the other way around. The first half of the book focuses on gravity.  Gravity is the dominant force in many astronomical systems, so a tremendous amount can be learned by studying gravity, motion and mass.  The theme in this part of the book, as well as throughout astrophysics, is using motion to investigate mass.  The goal of Chapters 2-11 is to develop a progressively richer understanding of gravity as it applies to objects ranging from planets and moons to galaxies and the universe as a whole. The second half uses other aspects of physics to addr...

  11. Stellar electron capture rates on neutron-rich nuclei and their impact on core-collapse

    CERN Document Server

    Raduta, Ad R; Oertel, M

    2016-01-01

    During the late stages of gravitational core-collapse of massive stars, extreme isospin asymmetries are reached within the core. Due to the lack of microscopic calculations of electron capture (EC) rates for all relevant nuclei, in general simple analytic parameterizations are employed. We study here several extensions of these parameterizations, allowing for a temperature, electron density and isospin dependence as well as for odd-even effects. The latter extra degrees of freedom considerably improve the agreement with large scale microscopic rate calculations. We find, in particular, that the isospin dependence leads to a significant reduction of the global EC rates during core collapse with respect to fiducial results, where rates optimized on calculations of stable $fp$-shell nuclei are used. Our results indicate that systematic microscopic calculations and experimental measurements in the $N\\approx 50$ neutron rich region are desirable for realistic simulations of the core-collapse.

  12. Stellar Astrophysics Using Ultra-High Precision CCD Time Series Photometry

    Science.gov (United States)

    Howell, S.; Everett, M.; Huber, M.; Ciardi, D.; van Belle, G.

    2001-05-01

    Using time-series CCD photometry and a wide-field imager, we have extended the techniques of differential photometry to provide robust photometric precisions for each star over the entire field of view. Reaching photometric precisions of 2 milli-magnitudes, we produced high cadence light curves for over 12,000 stars at mid- and high galactic latitude. The fraction of stars seen to be variable is higher than the canonical wisdom, being 10-14 will present the details of our techniques, sample light curves, methods to access the data, and a summary of astrophysical uses of such high precision data.

  13. Numerical simulations of stellar collapse in scalar-tensor theories of gravity

    Science.gov (United States)

    Gerosa, Davide; Sperhake, Ulrich; Ott, Christian D.

    2016-07-01

    We present numerical-relativity simulations of spherically symmetric core collapse and compact-object formation in scalar-tensor theories of gravity. The additional scalar degree of freedom introduces a propagating monopole gravitational-wave mode. Detection of monopole scalar waves with current and future gravitational-wave experiments may constitute smoking gun evidence for strong-field modifications of general relativity. We collapse both polytropic and more realistic pre-supernova profiles using a high-resolution shock-capturing scheme and an approximate prescription for the nuclear equation of state. The most promising sources of scalar radiation are protoneutron stars collapsing to black holes. In case of a galactic core collapse event forming a black hole, Advanced LIGO may be able to place independent constraints on the parameters of the theory at a level comparable to current solar-system and binary-pulsar measurements. In the region of the parameter space admitting spontaneously scalarised stars, transition to configurations with prominent scalar hair before black-hole formation further enhances the emitted signal. Although a more realistic treatment of the microphysics is necessary to fully investigate the occurrence of spontaneous scalarisation of neutron star remnants, we speculate that formation of such objects could constrain the parameters of the theory beyond the current bounds obtained with solar-system and binary-pulsar experiments.

  14. Three-Dimensional General-Relativistic Hydrodynamic Simulations of Binary Neutron Star Coalescence and Stellar Collapse with Multipatch Grids

    CERN Document Server

    Reisswig, C; Ott, C D; Abdikamalov, E; Moesta, P; Pollney, D; Schnetter, E

    2013-01-01

    We present a new three-dimensional general-relativistic hydrodynamic evolution scheme coupled to dynamical spacetime evolutions which is capable of efficiently simulating stellar collapse, isolated neutron stars, black hole formation, and binary neutron star coalescence. We make use of a set of adapted curvi-linear grids (multipatches) coupled with flux-conservative cell-centered adaptive mesh refinement. This allows us to significantly enlarge our computational domains while still maintaining high resolution in the gravitational-wave extraction zone, the exterior layers of a star, or the region of mass ejection in merging neutron stars. The fluid is evolved with a high-resolution shock capturing finite volume scheme, while the spacetime geometry is evolved using fourth-order finite differences. We employ a multi-rate Runge-Kutta time integration scheme for efficiency, evolving the fluid with second-order and the spacetime geometry with fourth-order integration, respectively. We validate our code by a number ...

  15. A New Open-Source Code for Spherically-Symmetric Stellar Collapse to Neutron Stars and Black Holes

    CERN Document Server

    O'Connor, Evan

    2009-01-01

    We present the new open-source spherically-symmetric general-relativistic (GR) hydrodynamics code GR1D. It is based on the Eulerian formulation of GR hydrodynamics (GRHD) put forth by Romero-Ibanez-Gourgoulhon and employs radial-gauge, polar-slicing coordinates in which the 3+1 equations simplify substantially. We discretize the GRHD equations with a finite-volume scheme, employing piecewise-parabolic reconstruction and an approximate Riemann solver. GR1D is intended for the simulation of stellar collapse to neutron stars and black holes and will also serve as a testbed for modeling technology to be incorporated in multi-D GR codes. Its GRHD part is coupled to various finite-temperature microphysical equations of state in tabulated form that we make available with GR1D. An approximate deleptonization scheme for the collapse phase and a neutrino-leakage/heating scheme for the postbounce epoch are included and described. We also derive the equations for effective rotation in 1D and implement them in GR1D. We pr...

  16. Two effects relevant for the study of astrophysical reaction rates: gamma transitions in capture reactions and Coulomb suppression of the stellar enhancement

    CERN Document Server

    Rauscher, T

    2008-01-01

    Nucleosynthesis processes involve reactions on several thousand nuclei, both close to and far off stability. The preparation of reaction rates to be used in astrophysical investigations requires experimental and theoretical input. In this context, two interesting aspects are discussed: (i) the relevant gamma transition energies in astrophysical capture reactions, and (ii) the newly discovered Coulomb suppression of the stellar enhancement factor. The latter makes a number of reactions with negative Q value more favorable for experimental investigation than their inverse reactions, contrary to common belief.

  17. Magnetic field amplification and magnetically supported explosions of collapsing, non-rotating stellar cores

    CERN Document Server

    Obergaulinger, Martin; Toras, Miguel Angel Aloy

    2014-01-01

    We study the amplification of magnetic fields in the collapse and the post-bounce evolution of the core of a non-rotating star of 15 solar masses in axisymmetry. To this end, we solve the coupled equations of magnetohydrodynamics and neutrino transport in the two-moment approximation. The pre-collapse magnetic field is strongly amplified by compression in the infall. Initial fields of the order of 1010 G translate into proto-neutron star fields similar to the ones observed in pulsars, while stronger initial fields yield magnetar-like final field strengths. After core bounce, the field is advected through the hydrodynamically unstable neutrino-heating layer, where non-radial flows due to convection and the standing accretion shock instability amplify the field further. Consequently, the resulting amplification factor of order five is the result of the number of small-eddy turnovers taking place within the time scale of advection through the post-shock layer. Due to this limit, most of our models do not reach e...

  18. The First Feedback and Stellar Tidal Disruptions by Direct Collapse Black Holes

    CERN Document Server

    Kashiyama, Kazumi

    2016-01-01

    We analyze the early growth stage of direct-collapse black holes (DCBHs) with $\\sim 10^{5} \\ \\rm M_\\odot$, which are formed by collapse of supermassive stars in atomic-cooling halos at $z \\gtrsim 10$. A nuclear accretion disk around a newborn DCBH is gravitationally unstable and fragments into clumps with a few $10 \\ \\rm M_\\odot$ at $\\sim 0.01-0.1 \\ \\rm pc$ from the center. Such clumps evolve into massive metal-poor stars with a few $10-100 \\ \\rm M_\\odot$ via successive gas accretion and a nuclear star cluster is formed. Radiative and mechanical feedback from an inner slim disk and the star cluster will significantly reduce the gas accretion rate onto the DCBH within $\\sim 10^6$ yr. Some of the nuclear stars can be scattered onto the loss cone orbits also within $\\lesssim 10^6$ yr and tidally disrupted by the central DCBH. The jet luminosity powered by such tidal disruption events can be $L_{\\rm j} \\gtrsim 10^{50} \\ \\rm erg \\ s^{-1}$. The prompt emission will be observed in X-ray bands with a peak duration of...

  19. Pulsar Recoil and Gravitational Radiation due to Asymetrical Stellar Collapse and Explosion

    Science.gov (United States)

    Burrows, Adam; Hayes, John C.

    1995-12-01

    New data imply that the average velocity of radio pulsars is high. Under the assumption that these data imply that a pulsar is born with an ``intrinsic'' kick, we investigate whether such kicks can be a consequence of asymmetrical collapse and explosion. We conclude that they can. The neutron star recoils in the direction opposite to that in which the ejecta preferentially emerge. In addition, we calculate the gravitational wave (GW) signature of such asymmetries due to anisotropic neutrino radiation and mass motions. We predict that any recoils imparted to the neutron star at birth will result in a gravitational wave strain, h() TT_zz, that does not go to zero with time. Hence, there may be a ``memory'' in the gravitational waveform from a protoneutron star that is correlated with its recoil and neutrino emissions. In principle, the recoil, neutrino emissions, and gravitational radiation can all be measured for a galactic supernova.

  20. Emerging Science Capabilities of Modern Adaptive Optics Systems for Exoplanet and Stellar Astrophysics

    Science.gov (United States)

    Jensen-Clem, Rebecca M.

    2017-01-01

    In this dissertation talk, I discuss new science capabilities enabled by the latest generation of adaptive optics systems in the context of faint companion detection and characterization. I address two regimes of adaptive optics: 1) extreme-AO systems that are combined with coronagraphs to detect companions many times fainter than their parent stars; 2) AO systems that are designed to maximize observing efficiency. GPI and SPHERE, two recent extreme-AO high contrast spectro-polarimeters, embody the first regime. These instruments’ design and sensitivity open up the possibility of a new observable for exoplanet characterization: polarized radiation from self-luminous, directly imaged exoplanets in the near-infrared. As part of my dissertation, I demonstrated that GPI can detect linear polarizations on the 1% scale predicted for cloudy, oblate gas giant exoplanets. Future polarimetric surveys will provide the empirical data needed to build the next generation of cloudy atmospheric models, shedding new light on the compositions of exoplanet atmospheres. The second regime of efficiency-optimized adaptive optics is embodied by Robo-AO, a robotic laser guide star AO system newly installed at the Kitt Peak 2.1-m telescope. Capable of observing over 1000 targets per week, Robo-AO enables LGS-AO surveys of unprecedented scale. I exploited Robo-AO’s efficiency to study the origins of stellar angular momentum: by resolving binaries from among the 700+ Pleiades members observed by K2, I related binary separations to K2’s photometrically determined rotation periods. In this talk, I will also describe Robo-AO’s commissioning at the 2.1-m and subsequent pipeline development.

  1. The spin rate of pre-collapse stellar cores: wave driven angular momentum transport in massive stars

    CERN Document Server

    Fuller, Jim; Lecoanet, Daniel; Quataert, Eliot

    2015-01-01

    The core rotation rates of massive stars have a substantial impact on the nature of core collapse supernovae and their compact remnants. We demonstrate that internal gravity waves (IGW), excited via envelope convection during a red supergiant phase or during vigorous late time burning phases, can have a significant impact on the rotation rate of the pre-SN core. In typical ($10 \\, M_\\odot \\lesssim M \\lesssim 20 \\, M_\\odot$) supernova progenitors, IGW may substantially spin down the core, leading to iron core rotation periods $P_{\\rm min,Fe} \\gtrsim 50 \\, {\\rm s}$. Angular momentum (AM) conservation during the supernova would entail minimum NS rotation periods of $P_{\\rm min,NS} \\gtrsim 3 \\, {\\rm ms}$. In most cases, the combined effects of magnetic torques and IGW AM transport likely lead to substantially longer rotation periods. However, the stochastic influx of AM delivered by IGW during shell burning phases inevitably spin up a slowly rotating stellar core, leading to a maximum possible core rotation perio...

  2. Songlines from Direct Collapse Seed Black Holes: Effects of X-rays on Black Hole Growth and Stellar Populations

    CERN Document Server

    Aykutalp, Aycin; Spaans, Marco; Meijerink, Rowin

    2014-01-01

    In the last decade, the growth of supermassive black holes (SMBHs) has been intricately linked to galaxy formation and evolution and is a key ingredient in the assembly of galaxies. To investigate the origin of SMBHs, we perform cosmological simulations that target the direct collapse black hole (DCBH) seed formation scenario in the presence of two different strong Lyman-Werner (LW) background fields. These simulations include the X-ray irradiation from a central massive black hole (MBH), $\\rm{H}_2$ self-shielding and stellar feedback from metal-free and metal-enriched stars. We find in both simulations that local X-ray feedback induces metal-free star formation $\\sim 0.5$ Myr after the MBH forms. The MBH accretion rate reaches a maximum of $10^{-3}$ $M_{\\odot}$ yr$^{-1}$ in both simulations. However, the duty cycle differs which is derived to be $6\\%$ and $50\\%$ for high and low LW cases, respectively. The MBH in the high LW case grows only $\\sim 6\\%$ in 100 Myr compared to $16\\%$ in the low LW case. We find...

  3. Songlines from Direct Collapse Seed Black Holes: Effects of X-Rays on Black Hole Growth and Stellar Populations

    Science.gov (United States)

    Aykutalp, Aycin; Wise, John H.; Spaans, Marco; Meijerink, Rowin

    2014-12-01

    In the last decade, the growth of supermassive black holes (SMBHs) has been intricately linked to galaxy formation and evolution and is a key ingredient in the assembly of galaxies. To investigate the origin of SMBHs, we perform cosmological simulations that target the direct collapse black hole seed formation scenario in the presence of two different strong Lyman-Werner (LW) background fields. These simulations include the X-ray irradiation from a central massive black hole (MBH), H2 self-shielding, and stellar feedback from metal-free and metal-enriched stars. We find in both simulations that local X-ray feedback induces metal-free star formation ~0.5 Myr after the MBH forms. The MBH accretion rate reaches a maximum of 10-3 M ⊙ yr-1 in both simulations. However, the duty cycle differs and is derived to be 6% and 50% for the high and low LW cases, respectively. The MBH in the high LW case grows only ~6% in 100 Myr compared to 16% in the low LW case. We find that the maximum accretion rate is determined by the local gas thermodynamics, whereas the duty cycle is determined by the large-scale gas dynamics and gas reservoir. We conclude that radiative feedback from the central MBH plays an important role in star formation in the nuclear regions and stifling initial MBH growth relative to the typical Eddington rate argument, and that initial MBH growth might be affected by the local LW radiation field.

  4. Modeling Core Collapse Supernovae

    Science.gov (United States)

    Mezzacappa, Anthony

    2017-01-01

    Core collapse supernovae, or the death throes of massive stars, are general relativistic, neutrino-magneto-hydrodynamic events. The core collapse supernova mechanism is still not in hand, though key components have been illuminated, and the potential for multiple mechanisms for different progenitors exists. Core collapse supernovae are the single most important source of elements in the Universe, and serve other critical roles in galactic chemical and thermal evolution, the birth of neutron stars, pulsars, and stellar mass black holes, the production of a subclass of gamma-ray bursts, and as potential cosmic laboratories for fundamental nuclear and particle physics. Given this, the so called ``supernova problem'' is one of the most important unsolved problems in astrophysics. It has been fifty years since the first numerical simulations of core collapse supernovae were performed. Progress in the past decade, and especially within the past five years, has been exponential, yet much work remains. Spherically symmetric simulations over nearly four decades laid the foundation for this progress. Two-dimensional modeling that assumes axial symmetry is maturing. And three-dimensional modeling, while in its infancy, has begun in earnest. I will present some of the recent work from the ``Oak Ridge'' group, and will discuss this work in the context of the broader work by other researchers in the field. I will then point to future requirements and challenges. Connections with other experimental, observational, and theoretical efforts will be discussed, as well.

  5. Modification of magicity towards the dripline and its impact on electron-capture rates for stellar core-collapse

    CERN Document Server

    Raduta, Ad R; Oertel, M

    2015-01-01

    The importance of microphysical inputs from laboratory nuclear experiments and theoretical nuclear structure calculations in the understanding of the core collapse dynamics, and the subsequent supernova explosion, is largely recognized in the recent literature. In this work, we analyze the impact of the masses of very neutron rich nuclei on the matter composition during collapse, and the corresponding electron capture rate. To this aim, we introduce an empirical modification of the popular Duflo-Zuker mass model to account for possible shell quenching far from stability, and study the effect of the quenching on the average electron capture rate. We show that the preeminence of the $N=50$ and $N=82$ closed shells in the collapse dynamics is considerably decreased if the shell gaps are reduced in the region of $^{78}$Ni and beyond. As a consequence, local modifications of the overall electron capture rate up to 30\\% can be expected, with integrated values strongly dependent on the stiffness of magicity quenchin...

  6. Studies of Stellar Collapse and Black Hole Formation with the Open-Source Code GR1D

    CERN Document Server

    Ott, Christian D; 10.1063/1.3485130

    2010-01-01

    We discuss results from simulations of black hole formation in failing core-collapse supernovae performed with the code GR1D, a new open-source Eulerian spherically-symmetric general-relativistic hydrodynamics code. GR1D includes rotation in an approximate way (1.5D), comes with multiple finite-temperature nuclear equations of state (EOS), and treats neutrinos in the post-core-bounce phase via a 3-flavor leakage scheme and a heating prescription. We chose the favored K_0=220 MeV-variant of the Lattimer & Swesty (1990) EOS and present collapse calculations using the progenitor models of Limongi & Chieffi (2006). We show that there is no direct (or ``prompt'') black hole formation in the collapse of ordinary massive stars (8 M_Sun ~< M_ZAMS ~< 100 M_Sun) and present first results from black hole formation simulations that include rotation.

  7. Stellar GADGET: A smooth particle hydrodynamics code for stellar astrophysics and its application to Type Ia supernovae from white dwarf mergers

    CERN Document Server

    Pakmor, R; Roepke, F K; Hillebrandt, W

    2012-01-01

    Mergers of two carbon-oxygen white dwarfs have long been suspected to be progenitors of Type Ia Supernovae. Here we present our modifications to the cosmological smoothed particle hydrodynamics code Gadget to apply it to stellar physics including but not limited to mergers of white dwarfs. We demonstrate a new method to map a one-dimensional profile of an object in hydrostatic equilibrium to a stable particle distribution. We use the code to study the effect of initial conditions and resolution on the properties of the merger of two white dwarfs. We compare mergers with approximate and exact binary initial conditions and find that exact binary initial conditions lead to a much more stable binary system but there is no difference in the properties of the actual merger. In contrast, we find that resolution is a critical issue for simulations of white dwarf mergers. Carbon burning hotspots which may lead to a detonation in the so-called violent merger scenario emerge only in simulations with sufficient resolutio...

  8. Observational astrophysics

    CERN Document Server

    Smith, Robert C

    1995-01-01

    Combining a critical account of observational methods (telescopes and instrumentation) with a lucid description of the Universe, including stars, galaxies and cosmology, Smith provides a comprehensive introduction to the whole of modern astrophysics beyond the solar system. The first half describes the techniques used by astronomers to observe the Universe: optical telescopes and instruments are discussed in detail, but observations at all wavelengths are covered, from radio to gamma-rays. After a short interlude describing the appearance of the sky at all wavelengths, the role of positional astronomy is highlighted. In the second half, a clear description is given of the contents of the Universe, including accounts of stellar evolution and cosmological models. Fully illustrated throughout, with exercises given in each chapter, this textbook provides a thorough introduction to astrophysics for all physics undergraduates, and a valuable background for physics graduates turning to research in astronomy.

  9. Particle astrophysics

    CERN Document Server

    Krauss, Lawrence M

    1997-01-01

    Astrophysics and cosmology provide fundamental testing grounds for many ideas in elementary particle physics, and include potential probes which are well beyond the range of current or even planned accelerators. In this series of 3 lectures, I will give and overview of existing constraints, and a discussion of the potential for the future. I will attempt whenever possible to demonstrate the connection between accelerator-based physics and astrophysicas/cosmology. The format of the kectures will be to examine observables from astrophysics, and explore how these can be used to constrain particle physics. Tentatively, lecture 1 will focus on the age and mass density of the universe and galaxy. Lecture 2 will focus on stars, stellar evolution, and the abundance of light elements. Lecture 3 will focus on various cosmic diffuse backgrounds, including possibly matter, photons, neutrinos and gravitational waves.

  10. The Dominance of Dynamic Barlike Instabilities in the Evolution of a Massive Stellar Core Collapse That ``Fizzles''

    Science.gov (United States)

    Imamura, James N.; Durisen, Richard H.

    2001-03-01

    Core collapse in a massive rotating star may halt at subnuclear density if the core contains angular momentum J>~1049 g cm2 s-1. An aborted collapse can lead to the formation of a rapidly rotating equilibrium object, which, because of its high electron fraction, Ye>0.4, and high entropy per baryon, Sb/k~1-2, is secularly and dynamically stable. The further evolution of such a ``fizzler'' is driven by deleptonization and cooling of the hot, dense material. These processes cause the fizzler both to contract toward neutron star densities and to spin up, driving it toward instability points of the barlike modes. Using linear stability analyses to study the latter case, we find that the stability properties of fizzlers are similar to those of Maclaurin spheroids and polytropes despite the nonpolytropic nature and extreme compressibility of the fizzler equation of state. For fizzlers with the specific angular momentum distribution of the Maclaurin spheroids, secular and dynamic barlike instabilities set in at T/|W|~0.14 and 0.27, respectively, where T is the rotational kinetic energy and W is the gravitational energy of the fizzler, the same limits as found for Maclaurin spheroids. For fizzlers in which angular momentum is more concentrated toward the equator, the secular stability limits drop dramatically. For the most extreme angular momentum distribution we consider, the secular stability limit for the barlike modes falls to T/|W|~0.038, compared with T/|W|~0.09-0.10 for the most extreme polytropic cases known previously (Imamura et al.). For fixed equation-of-state parameters, the secular and dynamic stability limits occur at roughly constant mass over the range of typical fizzler central densities. Deleptonization and cooling decrease the limiting masses on timescales shorter than the growth time for secular instability. Consequently, unless an evolving fizzler reaches neutron star densities first, it will always encounter dynamic barlike instabilities before

  11. UV-Bright Stellar Populations and Their Evolutionary Implications in the Collapsed-Core Cluster M15

    CERN Document Server

    Haurberg, Nathalie C; Cohn, Haldan N; Lugger, Phyllis M; Anderson, Jay; Cool, Adrienne M; Serenelli, Aldo; 10.1088/0004-637X/722/1/158

    2010-01-01

    We performed deep photometry of the central region of Galactic globular cluster M15 from archival Hubble Space Telescope data taken on the High Resolution Channel and Solar Blind Channel of the Advanced Camera for Surveys. Our data set consists of images in far-UV (FUV$_{140}$; F140LP), near-UV (NUV$_{220}$; F220W), and blue (B$_{435}$; F435W) filters. The addition of an optical filter complements previous UV work on M15 by providing an additional constraint on the UV-bright stellar populations. Using color-magnitude diagrams (CMDs) we identified several populations that arise from non-canonical evolution including candidate blue stragglers, extreme horizontal branch stars, blue hook stars (BHks), cataclysmic variables (CVs), and helium-core white dwarfs (He WDs). Due to preliminary identification of several He WD and BHk candidates, we add M15 as a cluster containing a He WD sequence and suggest it be included among clusters with a BHk population. We also investigated a subset of CV candidates that appear in...

  12. Theoretical astrophysics an introduction

    CERN Document Server

    Bartelmann, Matthias

    2013-01-01

    A concise yet comprehensive introduction to the central theoretical concepts of modern astrophysics, presenting hydrodynamics, radiation, and stellar dynamics all in one textbook. Adopting a modular structure, the author illustrates a small number of fundamental physical methods and principles, which are sufficient to describe and understand a wide range of seemingly very diverse astrophysical phenomena and processes. For example, the formulae that define the macroscopic behavior of stellar systems are all derived in the same way from the microscopic distribution function. This function it

  13. Astrophysics in a nutshell

    CERN Document Server

    Maoz, Dan

    2007-01-01

    A concise but thorough introduction to the observational data and theoretical concepts underlying modern astronomy, Astrophysics in a Nutshell is designed for advanced undergraduate science majors taking a one-semester course. This well-balanced and up-to-date textbook covers the essentials of modern astrophysics--from stars to cosmology--emphasizing the common, familiar physical principles that govern astronomical phenomena, and the interplay between theory and observation. In addition to traditional topics such as stellar remnants, galaxies, and the interstellar medium, Astrophysics in a N

  14. Astrophysics: Birth of stellar siblings

    Science.gov (United States)

    Plunkett, Adele

    2016-10-01

    Binary and multiple star systems result from the fragmentation of dense material in young molecular clouds. Observations reveal that this can occur on small scales, supporting a previous model of star formation. See Letter p.483

  15. Recognition of compact astrophysical objects

    Science.gov (United States)

    Ogelman, H. (Editor); Rothschild, R. (Editor)

    1977-01-01

    NASA's Laboratory for High Energy Astrophysics and the Dept. of Physics and Astrophysics at the Univ. of Md. collaberated on a graduate level course with this title. This publication is an edited version of notes used as the course text. Topics include stellar evolution, pulsars, binary stars, X-ray signatures, gamma ray sources, and temporal analysis of X-ray data.

  16. Neutrinos as astrophysical probes

    CERN Document Server

    Cavanna, F; Palamara, O; Vissani, F; Cavanna, Flavio; Costantini, Maria Laura; Palamara, Ornella; Vissani, Francesco

    2003-01-01

    The aim of these notes is to provide a brief review of the topic of neutrino astronomy and in particular of neutrinos from core collapse supernovae. They are addressed to a curious reader, beginning to work in a multidisciplinary area that involves experimental neutrino physics, astrophysics, nuclear physics and particle physics phenomenology. After an introduction to the methods and goals of neutrinos astronomy, we focus on core collapse supernovae, as (one of) the most promising astrophysical source of neutrinos. The first part is organized almost as a tale, the last part is a bit more technical. We discuss the impact of flavor oscillations on the supernova neutrino signal (=the change of perspective due to recent achievements) and consider one specific example of signal in detail. This shows that effects of oscillations are important, but astrophysical uncertainties should be thought as an essential systematics for a correct interpretation of future experimental data. Three appendices corroborate the text ...

  17. An Account of Stellar Spectroscopy and John S. Plaskett’s Leadership within Early 20th-Century Astrophysics in Canada

    Science.gov (United States)

    Ihor Oakes, Andrew

    2017-01-01

    From the perspective of the science of astronomy, the interpretation of the light spectrum was a fundamental development in the chemical analysis of celestial starlight. The breakthrough discovery with the application of spectroscopy in 1859, inaugurated a new period in astronomy that evolved into astrophysics. It launched a continuing episode of new astronomy that was later embraced in early 20th-century Canada where it was spearheaded by Canadian physicist and scientist, John S. Plaskett (1865-1941). The research work of John Plaskett at the Dominion Observatory in Ottawa, Ontario, from 1903 and, later, the Dominion Astrophysical Observatory in Victoria, British Columbia, from 1918, brought international recognition to Canada’s early efforts in astrophysics. Plaskett’s determination and personal boldness led to the establishment of a small cadre of Canadian astronomers who worked on their astrophysical research programs under Plaskett as their supervisor. Despite its small population at the time and a relatively infinitesimal number of professional astronomers, Canada did become recognized for its early spectrographic work in astrophysics, which was due to developing a professional status equal to its international colleagues. Plaskett improved the techniques of celestial spectroscopy during his scientific work at the Dominion Observatory and, again later, at its newly-built sister facility, the Dominion Astrophysical Observatory. Historically, Plaskett found himself to be the right person, in the right place, at the right time, and with the right temperament during the review period spanning 1903 to 1935.

  18. Physics of stellar evolution and cosmology

    Science.gov (United States)

    Goldberg, H. S.; Scadron, M. D.

    Astrophysical phenomena are examined on a fundamental level, stressing basic physical laws, in a textbook suitable for a one-semester intermediate course. The ideal gas law, the meaning of temperature, black-body radiation, discrete spectra, and the Doppler effect are introduced and used to study such features of the interstellar medium as 21-cm radiation, nebulae and dust, and the galactic magnetic field. The phases of stellar evolution are discussed, including stellar collapse, quasi-hydrostatic equilibrium, the main sequence, red giants, white dwarves, neutron stars, supernovae, pulsars, and black holes. Among the cosmological topics covered are the implications of Hubble's constant, the red-shift curve, the steady-state universe, the evolution of the big bang (thermal equilibrium, hadron era, lepton era, primordial nucleosynthesis, hydrogen recombination, galaxy formation, and the cosmic fireball), and the future (cold end or big crunch).

  19. Gravitational waves from gravitational collapse

    Energy Technology Data Exchange (ETDEWEB)

    Fryer, Christopher L [Los Alamos National Laboratory; New, Kimberly C [Los Alamos National Laboratory

    2008-01-01

    Gravitational wave emission from stellar collapse has been studied for nearly four decades. Current state-of-the-art numerical investigations of collapse include those that use progenitors with more realistic angular momentum profiles, properly treat microphysics issues, account for general relativity, and examine non-axisymmetric effects in three dimensions. Such simulations predict that gravitational waves from various phenomena associated with gravitational collapse could be detectable with ground-based and space-based interferometric observatories. This review covers the entire range of stellar collapse sources of gravitational waves: from the accretion induced collapse of a white dwarf through the collapse down to neutron stars or black holes of massive stars to the collapse of supermassive stars.

  20. Gravitational Waves from Gravitational Collapse

    Directory of Open Access Journals (Sweden)

    Chris L. Fryer

    2011-01-01

    Full Text Available Gravitational-wave emission from stellar collapse has been studied for nearly four decades. Current state-of-the-art numerical investigations of collapse include those that use progenitors with more realistic angular momentum profiles, properly treat microphysics issues, account for general relativity, and examine non-axisymmetric effects in three dimensions. Such simulations predict that gravitational waves from various phenomena associated with gravitational collapse could be detectable with ground-based and space-based interferometric observatories. This review covers the entire range of stellar collapse sources of gravitational waves: from the accretion-induced collapse of a white dwarf through the collapse down to neutron stars or black holes of massive stars to the collapse of supermassive stars.

  1. The Masses and Spins of Neutron Stars and Stellar-Mass Black Holes

    CERN Document Server

    Miller, M Coleman

    2014-01-01

    Stellar-mass black holes and neutron stars represent extremes in gravity, density, and magnetic fields. They therefore serve as key objects in the study of multiple frontiers of physics. In addition, their origin (mainly in core-collapse supernovae) and evolution (via accretion or, for neutron stars, magnetic spindown and reconfiguration) touch upon multiple open issues in astrophysics. In this review, we discuss current mass and spin measurements and their reliability for neutron stars and stellar-mass black holes, as well as the overall importance of spins and masses for compact object astrophysics. Current masses are obtained primarily through electromagnetic observations of binaries, although future microlensing observations promise to enhance our understanding substantially. The spins of neutron stars are straightforward to measure for pulsars, but the birth spins of neutron stars are more difficult to determine. In contrast, even the current spins of stellar-mass black holes are challenging to measure. ...

  2. Fundamental stellar parameters

    CERN Document Server

    Wittkowski, M

    2004-01-01

    I present a discussion of fundamental stellar parameters and their observational determination in the context of interferometric measurements with current and future optical/infrared interferometric facilities. Stellar parameters and the importance of their determination for stellar physics are discussed. One of the primary uses of interferometry in the field of stellar physics is the measurement of the intensity profile across the stellar disk, both as a function of position angle and of wavelength. High-precision fundamental stellar parameters are also derived by characterizations of binary and multiple system using interferometric observations. This topic is discussed in detail elsewhere in these proceedings. Comparison of observed spectrally dispersed center-to-limb intensity variations with models of stellar atmospheres and stellar evolution may result in an improved understanding of key phenomena in stellar astrophysics such as the precise evolutionary effects on the main sequence, the evolution of meta...

  3. Simulation of the spherically symmetric stellar core collapse, bounce, and postbounce evolution of a star of 13 solar masses with boltzmann neutrino transport, and its implications for the supernova mechanism.

    Science.gov (United States)

    Mezzacappa, A; Liebendörfer, M; Messer, O E; Hix, W R; Thielemann, F K; Bruenn, S W

    2001-03-05

    With exact three-flavor Boltzmann neutrino transport, we simulate the stellar core collapse, bounce, and postbounce evolution of a 13M star in spherical symmetry, the Newtonian limit, without invoking convection. In the absence of convection, prior spherically symmetric models, which implemented approximations to Boltzmann transport, failed to produce explosions. We consider exact transport to determine if these failures were due to the transport approximations made and to answer remaining fundamental questions in supernova theory. The model presented here is the first in a sequence of models beginning with different progenitors. In this model, a supernova explosion is not obtained.

  4. Minicourses in Astrophysics, Modular Approach, Vol. II.

    Science.gov (United States)

    Illinois Univ., Chicago.

    This is the second of a two-volume minicourse in astrophysics. It contains chapters on the following topics: stellar nuclear energy sources and nucleosynthesis; stellar evolution; stellar structure and its determination; and pulsars. Each chapter gives much technical discussion, mathematical treatment, diagrams, and examples. References are…

  5. Nuclear structure and astrophysics

    Energy Technology Data Exchange (ETDEWEB)

    Grawe, H [Gesellschaft fuer Schwerionenforschung (GSI), D-64291 Darmstadt (Germany); Langanke, K [Gesellschaft fuer Schwerionenforschung (GSI), D-64291 Darmstadt (Germany); MartInez-Pinedo, G [Gesellschaft fuer Schwerionenforschung (GSI), D-64291 Darmstadt (Germany)

    2007-09-15

    The nuclear structure in regions of the Segre chart which are of astrophysical importance is reviewed. The main emphasis is put on those nuclei that are relevant for stellar nucleosynthesis in fusion processes, and in slow neutron capture, both located close to stability, rapid neutron capture close to the neutron dripline and rapid proton capture near the proton dripline. The basic features of modern nuclear structure, their importance and future potential for astrophysics and their level of predictibility are critically discussed. Recent experimental and theoretical results for shell evolution far off the stability line and consequences for weak interaction processes, proton and neutron capture are reviewed.

  6. Some aspects of neutrino astrophysics

    CERN Document Server

    Athar, H

    2002-01-01

    Selected topics in neutrino astrophysics are reviewed. These include the production of low energy neutrino flux from cores of collapsing stars and the expected high energy neutrino flux from some other astrophysical sites such as the galactic plane as well as the center of some distant galaxies. The expected changes in these neutrino fluxes because of neutrino oscillations during their propagation to us are described. Observational signatures for these neutrino fluxes with and without neutrino oscillations are discussed.

  7. Nuclear reactions in astrophysics

    Energy Technology Data Exchange (ETDEWEB)

    Arnould, M.; Rayet, M. (Universite Libre de Bruxelles (BE))

    1990-06-01

    At all times and at all astrophysical scales, nuclear reactions have played and continue to play a key role. This concerns the energetics as well as the production of nuclides (nucleosynthesis). After a brief review of the observed composition of various objects in the universe, and especially of the solar system, the basic ingredients that are required in order to build up models for the chemical evolution of galaxies are sketched. Special attention is paid to the evaluation of the stellar yields through an overview of the important burning episodes and nucleosynthetic processes that can develop in non-exploding or exploding stars. Emphasis is put on the remaining astrophysical and nuclear physics uncertainties that hamper a clear understanding of the observed characteristics, and especially compositions, of a large variety of astrophysical objects.

  8. Nuclear astrophysics: the unfinished quest for the origin of the elements

    Energy Technology Data Exchange (ETDEWEB)

    Jose, Jordi [Departament de Fisica i Enginyeria Nuclear, EUETIB, Universitat Politecnica de Catalunya, E-08036 Barcelona (Spain); Iliadis, Christian, E-mail: jordi.jose@upc.edu, E-mail: iliadis@unc.edu [Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599 (United States)

    2011-09-15

    Half a century has passed since the foundation of nuclear astrophysics. Since then, this discipline has reached its maturity. Today, nuclear astrophysics constitutes a multidisciplinary crucible of knowledge that combines the achievements in theoretical astrophysics, observational astronomy, cosmochemistry and nuclear physics. New tools and developments have revolutionized our understanding of the origin of the elements: supercomputers have provided astrophysicists with the required computational capabilities to study the evolution of stars in a multidimensional framework; the emergence of high-energy astrophysics with space-borne observatories has opened new windows to observe the Universe, from a novel panchromatic perspective; cosmochemists have isolated tiny pieces of stardust embedded in primitive meteorites, giving clues on the processes operating in stars as well as on the way matter condenses to form solids; and nuclear physicists have measured reactions near stellar energies, through the combined efforts using stable and radioactive-ion beam facilities. This review provides comprehensive insight into the nuclear history of the Universe and related topics: starting from the Big Bang, when the ashes from the primordial explosion were transformed to hydrogen, helium and a few trace elements, to the rich variety of nucleosynthesis mechanisms and sites in the Universe. Particular attention is paid to the hydrostatic processes governing the evolution of low-mass stars, red giants and asymptotic giant-branch stars, as well as to the explosive nucleosynthesis occurring in core-collapse and thermonuclear supernovae, {gamma}-ray bursts, classical novae, x-ray bursts, superbursts and stellar mergers.

  9. The astrophysically important 3{sup +} state in {sup 18}Ne and the {sup 17}F(p,{gamma}){sup 18}Ne stellar rate

    Energy Technology Data Exchange (ETDEWEB)

    Bardayan, D. W.; Blackmon, J. C.; Brune, C. R.; Champagne, A. E.; Chen, A. A.; Cox, J. M.; Davinson, T.; Hansper, V. Y.; Hofstee, M. A.; Johnson, B. A. (and others)

    2000-11-01

    Knowledge of the {sup 17}F(p,{gamma}){sup 18}Ne reaction rate is important for understanding stellar explosions, but it was uncertain because the properties of an expected but previously unobserved 3{sup +} state in {sup 18}Ne were not known. This state would provide a strong s-wave resonance for the {sup 17}F+p system and, depending on its excitation energy, could dominate the stellar reaction rate at temperatures above 0.2 GK. We have observed this missing 3{sup +} state by measuring the {sup 1}H({sup 17}F,p){sup 17}F excitation function with a radioactive {sup 17}F beam at the ORNL Holifield Radioactive Ion Beam Facility (HRIBF). We find that the state lies at a center-of-mass energy of E{sub r}=599.8{+-}1.5{sub stat}{+-}2.0{sub sys} keV (E{sub x}=4523.7{+-}2.9keV) and has a width of {Gamma}=18{+-}2{sub stat}{+-}1{sub sys}keV. The measured properties of the resonance are only consistent with a J{sup {pi}}=3{sup +} assignment.

  10. Essential astrophysics

    CERN Document Server

    Lang, Kenneth R

    2013-01-01

    Essential Astrophysics is a book to learn or teach from, as well as a fundamental reference volume for anyone interested in astronomy and astrophysics. It presents astrophysics from basic principles without requiring any previous study of astronomy or astrophysics. It serves as a comprehensive introductory text, which takes the student through the field of astrophysics in lecture-sized chapters of basic physical principles applied to the cosmos. This one-semester overview will be enjoyed by undergraduate students with an interest in the physical sciences, such as astronomy, chemistry, engineering or physics, as well as by any curious student interested in learning about our celestial science. The mathematics required for understanding the text is on the level of simple algebra, for that is all that is needed to describe the fundamental principles. The text is of sufficient breadth and depth to prepare the interested student for more advanced specialized courses in the future. Astronomical examples are provide...

  11. Chaos and complexity in astrophysics

    CERN Document Server

    Regev, Oded

    2007-01-01

    Methods and techniques of the theory of nonlinear dynamical systems and patterns can be useful in astrophysical applications. Some works on the subjects of dynamical astronomy, stellar pulsation and variability, as well as spatial complexity in extended systems, in which such approaches have already been utilized, are reviewed. Prospects for future directions in applications of this kind are outlined.

  12. Indirect methods in nuclear astrophysics

    CERN Document Server

    Bertulani, C A; Mukhamedzhanov, A; Kadyrov, A S; Kruppa, A; Pang, D Y

    2015-01-01

    We discuss recent developments in indirect methods used in nuclear astrophysics to determine the capture cross sections and subsequent rates of various stellar burning processes, when it is difficult to perform the corresponding direct measurements. We discuss in brief, the basic concepts of Asymptotic Normalization Coefficients, the Trojan Horse Method, the Coulomb Dissociation Method, (d,p), and charge-exchange reactions.

  13. Astrophysics on the Lab Bench

    Science.gov (United States)

    Hughes, Stephen W.

    2010-01-01

    In this article some basic laboratory bench experiments are described that are useful for teaching high school students some of the basic principles of stellar astrophysics. For example, in one experiment, students slam a plastic water-filled bottle down onto a bench, ejecting water towards the ceiling, illustrating the physics associated with a…

  14. Stellar progenitors of black holes: insights from optical and infrared observations

    CERN Document Server

    Mirabel, I F

    2016-01-01

    Here are reviewed the insights from observations at optical and infrared wavelengths for low mass limits above which stars do not seem to end as luminous supernovae. These insights are: (1) the absence in archived images of nearby galaxies of stellar progenitors of core-collapse supernovae above 16-18 solar masses, (2) the identification of luminous-massive stars that quietly disappear without optically bright supernovae, (3) the absence in the nebular spectra of supernovae of type II-P of the nucleosynthetic products expected from progenitors above 20 solar masses, (4) the absence in color magnitude diagrams of stars in the environment of historic core-collapse supernovae of stars with >20 solar masses. From the results in these different areas of observational astrophysics, and the recently confirmed dependence of black hole formation on metallicity and redshift of progenitors, it is concluded that a large fraction of massive stellar binaries in the universe end as binary black holes.

  15. High Energy Density Laboratory Astrophysics

    CERN Document Server

    Lebedev, Sergey V

    2007-01-01

    During the past decade, research teams around the world have developed astrophysics-relevant research utilizing high energy-density facilities such as intense lasers and z-pinches. Every two years, at the International conference on High Energy Density Laboratory Astrophysics, scientists interested in this emerging field discuss the progress in topics covering: - Stellar evolution, stellar envelopes, opacities, radiation transport - Planetary Interiors, high-pressure EOS, dense plasma atomic physics - Supernovae, gamma-ray bursts, exploding systems, strong shocks, turbulent mixing - Supernova remnants, shock processing, radiative shocks - Astrophysical jets, high-Mach-number flows, magnetized radiative jets, magnetic reconnection - Compact object accretion disks, x-ray photoionized plasmas - Ultrastrong fields, particle acceleration, collisionless shocks. These proceedings cover many of the invited and contributed papers presented at the 6th International Conference on High Energy Density Laboratory Astrophys...

  16. Astrophysical Conditions for Planetary Habitability

    CERN Document Server

    Guedel, M; Erkaev, N; Kasting, J; Khodachenko, M; Lammer, H; Pilat-Lohinger, E; Rauer, H; Ribas, I; Wood, B E

    2014-01-01

    With the discovery of hundreds of exoplanets and a potentially huge number of Earth-like planets waiting to be discovered, the conditions for their habitability have become a focal point in exoplanetary research. The classical picture of habitable zones primarily relies on the stellar flux allowing liquid water to exist on the surface of an Earth-like planet with a suitable atmosphere. However, numerous further stellar and planetary properties constrain habitability. Apart from "geophysical" processes depending on the internal structure and composition of a planet, a complex array of astrophysical factors additionally determine habitability. Among these, variable stellar UV, EUV, and X-ray radiation, stellar and interplanetary magnetic fields, ionized winds, and energetic particles control the constitution of upper planetary atmospheres and their physical and chemical evolution. Short- and long-term stellar variability necessitates full time-dependent studies to understand planetary habitability at any point ...

  17. LUNA: Nuclear astrophysics underground

    Energy Technology Data Exchange (ETDEWEB)

    Best, A. [Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali del Gran Sasso, Assergi (Italy)

    2015-02-24

    Underground nuclear astrophysics with LUNA at the Laboratori Nazionali del Gran Sasso spans a history of 20 years. By using the rock overburden of the Gran Sasso mountain chain as a natural cosmic-ray shield very low signal rates compared to an experiment on the surface can be tolerated. The cross sectons of important astrophysical reactions directly in the stellar energy range have been successfully measured. In this proceeding we give an overview over the key accomplishments of the experiment and an outlook on its future with the expected addition of an additional accelerator to the underground facilities, enabling the coverage of a wider energy range and the measurement of previously inaccessible reactions.

  18. Astrophysical black holes

    CERN Document Server

    Gorini, Vittorio; Moschella, Ugo; Treves, Aldo; Colpi, Monica

    2016-01-01

    Based on graduate school lectures in contemporary relativity and gravitational physics, this book gives a complete and unified picture of the present status of theoretical and observational properties of astrophysical black holes. The chapters are written by internationally recognized specialists. They cover general theoretical aspects of black hole astrophysics, the theory of accretion and ejection of gas and jets, stellar-sized black holes observed in the Milky Way, the formation and evolution of supermassive black holes in galactic centers and quasars as well as their influence on the dynamics in galactic nuclei. The final chapter addresses analytical relativity of black holes supporting theoretical understanding of the coalescence of black holes as well as being of great relevance in identifying gravitational wave signals. With its introductory chapters the book is aimed at advanced graduate and post-graduate students, but it will also be useful for specialists.

  19. Numerical Relativity Beyond Astrophysics

    CERN Document Server

    Garfinkle, David

    2016-01-01

    Though the main applications of computer simulations in relativity are to astrophysical systems such as black holes and neutron stars, nonetheless there are important applications of numerical methods to the investigation of general relativity as a fundamental theory of the nature of space and time. This paper gives an overview of some of these applications. In particular we cover (i) investigations of the properties of spacetime singularities such as those that occur in the interior of black holes and in big bang cosmology. (ii) investigations of critical behavior at the threshold of black hole formation in gravitational collapse. (iii) investigations inspired by string theory, in particular analogs of black holes in more than 4 spacetime dimensions and gravitational collapse in spacetimes with a negative cosmological constant.

  20. Numerical relativity beyond astrophysics

    Science.gov (United States)

    Garfinkle, David

    2017-01-01

    Though the main applications of computer simulations in relativity are to astrophysical systems such as black holes and neutron stars, nonetheless there are important applications of numerical methods to the investigation of general relativity as a fundamental theory of the nature of space and time. This paper gives an overview of some of these applications. In particular we cover (i) investigations of the properties of spacetime singularities such as those that occur in the interior of black holes and in big bang cosmology. (ii) investigations of critical behavior at the threshold of black hole formation in gravitational collapse. (iii) investigations inspired by string theory, in particular analogs of black holes in more than 4 spacetime dimensions and gravitational collapse in spacetimes with a negative cosmological constant.

  1. Nuclear astrophysics

    CERN Document Server

    Arnould, M

    1999-01-01

    Nuclear astrophysics is that branch of astrophysics which helps understanding some of the many facets of the Universe through the knowledge of the microcosm of the atomic nucleus. In the last decades much advance has been made in nuclear astrophysics thanks to the sometimes spectacular progress in the modelling of the structure and evolution of the stars, in the quality and diversity of the astronomical observations, as well as in the experimental and theoretical understanding of the atomic nucleus and of its spontaneous or induced transformations. Developments in other sub-fields of physics and chemistry have also contributed to that advance. Many long-standing problems remain to be solved, however, and the theoretical understanding of a large variety of observational facts needs to be put on safer grounds. In addition, new questions are continuously emerging, and new facts endanger old ideas. This review shows that astrophysics has been, and still is, highly demanding to nuclear physics in both its experime...

  2. Nuclear Data for Astrophysical Modeling

    CERN Document Server

    Pritychenko, Boris

    2016-01-01

    Nuclear physics has been playing an important role in modern astrophysics and cosmology. Since the early 1950's it has been successfully applied for the interpretation and prediction of astrophysical phenomena. Nuclear physics models helped to explain the observed elemental and isotopic abundances and star evolution and provided valuable insights on the Big Bang theory. Today, the variety of elements observed in stellar surfaces, solar system and cosmic rays, and isotope abundances are calculated and compared with the observed values. Consequently, the overall success of the modeling critically depends on the quality of underlying nuclear data that helps to bring physics of macro and micro scales together. To broaden the scope of traditional nuclear astrophysics activities and produce additional complementary information, I will investigate applicability of the U.S. Nuclear Data Program (USNDP) databases for astrophysical applications. EXFOR (Experimental Nuclear Reaction Data) and ENDF (Evaluated Nuclear Dat...

  3. Recent results in nuclear astrophysics

    CERN Document Server

    Coc, Alain; Kiener, Juergen

    2016-01-01

    In this review, we emphasize the interplay between astrophysical observations, modeling, and nuclear physics laboratory experiments. Several important nuclear cross sections for astrophysics have long been identified e.g. 12C(alpha,gamma)16O for stellar evolution, or 13C(alpha,n)16O and 22Ne(alpha,n)25Mg as neutron sources for the s-process. More recently, observations of lithium abundances in the oldest stars, or of nuclear gamma-ray lines from space, have required new laboratory experiments. New evaluation of thermonuclear reaction rates now includes the associated rate uncertainties that are used in astrophysical models to i) estimate final uncertainties on nucleosynthesis yields and ii) identify those reactions that require further experimental investigation. Sometimes direct cross section measurements are possible, but more generally the use of indirect methods is compulsory in view of the very low cross sections. Non-thermal processes are often overlooked but are also important for nuclear astrophysics,...

  4. The Wisconsin Plasma Astrophysics Laboratory

    CERN Document Server

    Forest, C B; Brookhart, M; Cooper, C M; Clark, M; Desangles, V; Egedal, J; Endrizzi, D; Miesch, M; Khalzov, I V; Li, H; Milhone, J; Nornberg, M; Olson, J; Peterson, E; Roesler, F; Schekochihin, A; Schmitz, O; Siller, R; Spitkovsky, A; Stemo, A; Wallace, J; Weisberg, D; Zweibel, E

    2015-01-01

    The Wisconsin Plasma Astrophysics Laboratory (WiPAL) is a flexible user facility designed to study a range of astrophysically relevant plasma processes as well as novel geometries which mimic astrophysical systems. A multi-cusp magnetic bucket constructed from strong samarium cobalt permanent magnets now confines a 10 m$^3$, fully ionized, magnetic-field free plasma in a spherical geometry. Plasma parameters of $ T_{e}\\approx5-20$ eV and $n_{e}\\approx10^{11}-5\\times10^{12}$ cm$^{-3}$ provide an ideal testbed for a range of astrophysical experiments including self-exciting dynamos, collisionless magnetic reconnection, jet stability, stellar winds, and more. This article describes the capabilities of WiPAL along with several experiments, in both operating and planning stages, that illustrate the range of possibilities for future users.

  5. Recent advances in neutrino astrophysics

    CERN Document Server

    Volpe, Cristina

    2014-01-01

    Neutrinos are produced by a variety of sources that comprise our Sun, explosive environments such as core-collapse supernovae, the Earth and the Early Universe. The precise origin of the recently discovered ultra-high energy neutrinos is to be determined yet. These weakly interacting particles give us information on their sources, although the neutrino fluxes can be modified when neutrinos traverse an astrophysical environment. Here we highlight recent advances in neutrino astrophysics and emphasise the important progress in our understanding of neutrino flavour conversion in media.

  6. Nuclear physics in astrophysics; La physique nucleaire en astrophysique

    Energy Technology Data Exchange (ETDEWEB)

    Arnould, M. [Universite Libre de Bruxelles (Belgium). Inst. d' Astronomie et d' Astrophysique; Samyn, M. [Universite Libre de Bruxelles (Belgium). Inst. d' Astronomie et d' Astrophysique; Fonds National de la Recherche Scientifique, Brussels (Belgium)

    2001-07-01

    In this review the following topics are covered: nuclei in astrophysics, weak and electromagnetic interactions in nuclei, primordial nucleosynthesis, big bang, stellar evolution and stellar structure and stability, non-explosive stellar nucleosynthesis, element abundances, explosive nucleosynthesis in massive stars, supernovae (WL)

  7. Astrophysical Concepts

    CERN Document Server

    Harwit, Martin

    2006-01-01

    This classic text, aimed at senior undergraduates and beginning graduate students in physics and astronomy, presents a wide range of astrophysical concepts in sufficient depth to give the reader a quantitative understanding of the subject. Emphasizing physical concepts, the book outlines cosmic events but does not portray them in detail: it provides a series of astrophysical sketches. For this fourth edition, nearly every part of the text has been reconsidered and rewritten, new sections have been added to cover recent developments, and others have been extensively revised and brought up to date. The book begins with an outline of the scope of modern astrophysics and enumerates some of the outstanding problems faced in the field today. The basic physics needed to tackle these questions are developed in the next few chapters using specific astronomical processes as examples. The second half of the book enlarges on these topics and shows how we can obtain quantitative insight into the structure and evolution of...

  8. Astrophysical Black Holes in the Physical Universe

    CERN Document Server

    Zhang, Shuang-Nan

    2010-01-01

    In this chapter I focus on asking and answering the following questions: (1) What is a black hole? Answer: There are three types of black holes, namely mathematical black holes, physical black holes and astrophysical black holes. An astrophysical black hole, with mass distributed within its event horizon but not concentrated at the singularity point, is not a mathematical black hole. (2) Can astrophysical black holes be formed in the physical universe? Answer: Yes, at least this can be done with gravitational collapse. (3) How can we prove that what we call astrophysical black holes are really black holes? Answer: Finding direct evidence of event horizon is not the way to go. Instead I propose five criteria which meet the highest standard for recognizing new discoveries in experimental physics and observational astronomy. (4) Do we have sufficient evidence to claim the existence of astrophysical black holes in the physical universe? Answer: Yes, astrophysical black holes have been found at least in some galac...

  9. Nuclear astrophysics

    Energy Technology Data Exchange (ETDEWEB)

    Arnould, M. [Institut d' Astronomie et d' Astrophysique, Universite Libre de Bruxelles, Bruxelles (Belgium); Takahashi, K. [Max-Planck-Institut fuer Astrophysik, Garching (Germany)

    1999-03-01

    Nuclear astrophysics is that branch of astrophysics which helps understanding of the Universe, or at least some of its many faces, through the knowledge of the microcosm of the atomic nucleus. It attempts to find as many nuclear physics imprints as possible in the macrocosm, and to decipher what those messages are telling us about the varied constituent objects in the Universe at present and in the past. In the last decades much advance has been made in nuclear astrophysics thanks to the sometimes spectacular progress made in the modelling of the structure and evolution of the stars, in the quality and diversity of the astronomical observations, as well as in the experimental and theoretical understanding of the atomic nucleus and of its spontaneous or induced transformations. Developments in other subfields of physics and chemistry have also contributed to that advance. Notwithstanding the accomplishment, many long-standing problems remain to be solved, and the theoretical understanding of a large variety of observational facts needs to be put on safer grounds. In addition, new questions are continuously emerging, and new facts endangering old ideas. This review shows that astrophysics has been, and still is, highly demanding to nuclear physics in both its experimental and theoretical components. On top of the fact that large varieties of nuclei have to be dealt with, these nuclei are immersed in highly unusual environments which may have a significant impact on their static properties, the diversity of their transmutation modes, and on the probabilities of these modes. In order to have a chance of solving some of the problems nuclear astrophysics is facing, the astrophysicists and nuclear physicists are obviously bound to put their competence in common, and have sometimes to benefit from the help of other fields of physics, like particle physics, plasma physics or solid-state physics. Given the highly varied and complex aspects, we pick here some specific nuclear

  10. Nuclear astrophysics

    Science.gov (United States)

    Arnould, M.; Takahashi, K.

    1999-03-01

    Nuclear astrophysics is that branch of astrophysics which helps understanding of the Universe, or at least some of its many faces, through the knowledge of the microcosm of the atomic nucleus. It attempts to find as many nuclear physics imprints as possible in the macrocosm, and to decipher what those messages are telling us about the varied constituent objects in the Universe at present and in the past. In the last decades much advance has been made in nuclear astrophysics thanks to the sometimes spectacular progress made in the modelling of the structure and evolution of the stars, in the quality and diversity of the astronomical observations, as well as in the experimental and theoretical understanding of the atomic nucleus and of its spontaneous or induced transformations. Developments in other subfields of physics and chemistry have also contributed to that advance. Notwithstanding the accomplishment, many long-standing problems remain to be solved, and the theoretical understanding of a large variety of observational facts needs to be put on safer grounds. In addition, new questions are continuously emerging, and new facts endangering old ideas. This review shows that astrophysics has been, and still is, highly demanding to nuclear physics in both its experimental and theoretical components. On top of the fact that large varieties of nuclei have to be dealt with, these nuclei are immersed in highly unusual environments which may have a significant impact on their static properties, the diversity of their transmutation modes, and on the probabilities of these modes. In order to have a chance of solving some of the problems nuclear astrophysics is facing, the astrophysicists and nuclear physicists are obviously bound to put their competence in common, and have sometimes to benefit from the help of other fields of physics, like particle physics, plasma physics or solid-state physics. Given the highly varied and complex aspects, we pick here some specific nuclear

  11. Plasma astrophysics

    CERN Document Server

    Kaplan, S A; ter Haar, D

    2013-01-01

    Plasma Astrophysics is a translation from the Russian language; the topics discussed are based on lectures given by V.N. Tsytovich at several universities. The book describes the physics of the various phenomena and their mathematical formulation connected with plasma astrophysics. This book also explains the theory of the interaction of fast particles plasma, their radiation activities, as well as the plasma behavior when exposed to a very strong magnetic field. The text describes the nature of collective plasma processes and of plasma turbulence. One author explains the method of elementary

  12. Nuclear Astrophysics

    Science.gov (United States)

    Drago, Alessandro

    2005-04-01

    The activity of the Italian nuclear physicists community in the field of Nuclear Astrophysics is reported. The researches here described have been performed within the project "Fisica teorica del nucleo e dei sistemi a multi corpi", supported by the Ministero dell'Istruzione, dell'Università e della Ricerca.

  13. Underground Nuclear Astrophysics in China

    Science.gov (United States)

    Liu, Weiping

    Underground Nuclear Astrophysics in China (JUNA) will take the advantage of the ultra-low background in Jinping underground lab. High current accelerator with an ECR source and detectors will be set up. We plan to study directly a number of nuclear reactions important to hydrostatic stellar evolution at their relevant stellar energies, such as 25Mg(p,γ)26Al, 19F(p,α)16O, 13C(α,n)16O and 12C(α,γ)16O.

  14. Underground nuclear astrophysics studies with CASPAR

    Directory of Open Access Journals (Sweden)

    Robertson Daniel

    2016-01-01

    Full Text Available The drive of low-energy nuclear astrophysics laboratories is to study the reactions of importance to stellar burning processes and elemental production through stellar nucleosynthesis, over the energy range of astrophysical interest. As laboratory measurements approach the stellar burning window, the rapid drop off of cross-sections is a significant barrier and drives the need to lower background interference. The natural background suppression of underground accelerator facilities enables the extension of current experimental data to lower energies. An example of such reactions of interest are those thought to be sources of neutrons for the s-process, the major production mechanism for elements above the iron peak. The reactions 13C(α,n16O and 22Ne(α,n25Mg are the proposed initial focus of the new nuclear astrophysics accelerator laboratory (CASPAR currently under construction at the Sanford Underground Research Facility, Lead, South Dakota

  15. Underground nuclear astrophysics studies with CASPAR

    Science.gov (United States)

    Robertson, Daniel; Couder, Manoel; Greife, Uwe; Strieder, Frank; Wiescher, Michael

    2016-02-01

    The drive of low-energy nuclear astrophysics laboratories is to study the reactions of importance to stellar burning processes and elemental production through stellar nucleosynthesis, over the energy range of astrophysical interest. As laboratory measurements approach the stellar burning window, the rapid drop off of cross-sections is a significant barrier and drives the need to lower background interference. The natural background suppression of underground accelerator facilities enables the extension of current experimental data to lower energies. An example of such reactions of interest are those thought to be sources of neutrons for the s-process, the major production mechanism for elements above the iron peak. The reactions 13C(α,n)16O and 22Ne(α,n)25Mg are the proposed initial focus of the new nuclear astrophysics accelerator laboratory (CASPAR) currently under construction at the Sanford Underground Research Facility, Lead, South Dakota

  16. The Astrophysical Multipurpose Software Environment

    CERN Document Server

    Pelupessy, F I; de Vries, N; McMillan, S L W; Drost, N; Zwart, S F Portegies

    2013-01-01

    We present the open source Astrophysical Multi-purpose Software Environment (AMUSE, www.amusecode.org), a component library for performing astrophysical simulations involving different physical domains and scales. It couples existing codes within a Python framework based on a communication layer using MPI. The interfaces are standardized for each domain and their implementation based on MPI guarantees that the whole framework is well-suited for distributed computation. It includes facilities for unit handling and data storage. Currently it includes codes for gravitational dynamics, stellar evolution, hydrodynamics and radiative transfer. Within each domain the interfaces to the codes are as similar as possible. We describe the design and implementation of AMUSE, as well as the main components and community codes currently supported and we discuss the code interactions facilitated by the framework. Additionally, we demonstrate how AMUSE can be used to resolve complex astrophysical problems by presenting exampl...

  17. astrophysical significance

    Directory of Open Access Journals (Sweden)

    Dartois E.

    2014-02-01

    Full Text Available Clathrate hydrates, ice inclusion compounds, are of major importance for the Earth’s permafrost regions and may control the stability of gases in many astrophysical bodies such as the planets, comets and possibly interstellar grains. Their physical behavior may provide a trapping mechanism to modify the absolute and relative composition of icy bodies that could be the source of late-time injection of gaseous species in planetary atmospheres or hot cores. In this study, we provide and discuss laboratory-recorded infrared signatures of clathrate hydrates in the near to mid-infrared and the implications for space-based astrophysical tele-detection in order to constrain their possible presence.

  18. Scaling extreme astrophysical phenomena to the laboratory - a tutorial

    Science.gov (United States)

    Remington, Bruce A.

    2007-11-01

    The ability to experimentally study scaled aspects of the explosion dynamics of core-collapse supernovae (massive stars that explode from the inside out) or the radiation kinetics of accreting neutron stars or black holes on high energy density (HED) facilities, such as high power lasers and magnetic pinch facilities, is an exciting scientific development over the last two decades. [1,2] Additional areas of research that become accessible on modern HED facilities are studies of fundamental properties of matter in conditions relevant to planetary and stellar interiors, protostellar jet dynamics, and with the added tool of thermonuclear ignition on the National Ignition Facility, excited state (``multi-hit'') nuclear physics, possibly relevant to nucleosynthesis. Techniques and methodologies for studying aspects of the physics of such extreme phenomena of the universe in millimeter scale parcels of plasma in the laboratory will be discussed. [1] ``Experimental astrophysics with high power lasers and Z pinches,'' B.A. Remington, R.P. Drake, D.D. Ryutov, Rev. Mod. Phys. 78, 755 (2006). [2] ``High energy density laboratory astrophysics,'' B.A. Remington, Plasma Phys. Cont. Fusion 47, A191 (2005).

  19. Stellar evolution, nuclear astrophysics, and nucleogenesis

    CERN Document Server

    Cameron, AGW

    2013-01-01

    ""The content of this work, which was independently presented by Burbidge, Burbidge, Fowler, and Hoyle in 1957, represents one of the major advances in the natural sciences in the twentieth century. It effectively answered, in one fell swoop, several interrelated questions that humans have been asking since the beginning of inquiry, such as 'What are stars?' 'How does the sun shine?' 'Why is gold so rare?' 'Where did the elements in our world and in our bodies come from?'"" - Alan A. Chen, Associate Professor, McMaster UniversityHarvard professor A. G. W. Cameron - who helped develop the Giant

  20. Solar-stellar astrophysics and dark matter

    Institute of Scientific and Technical Information of China (English)

    Sylvaine Turck-Chièze; Ilídio Lopes

    2012-01-01

    In this review,we recall how stars contribute to the search for dark matter and the specific role of the Sun.We describe a more complete picture of the solar interior that emerges from neutrino detections,gravity and acoustic mode measurements of the Solar and Heliospheric Observatory (SOHO) satellite,becoming a reference for the most common stars in the Universe.The Sun is a unique star in that we can observe directly the effect of dark matter.The absence of a signature related to Weakly Interacting Massive Particles (WIMPs) in its core disfavors a WIMP mass range below 12 GeV.We give arguments to continue this search on the Sun and other promising cases.We also examine another dark matter candidate,the sterile neutrino,and infer the limitations of the classical structural equations.Open questions on the young Sun,when planets formed,and on its present internal dynamics are finally discussed.Future directions are proposed for the next decade:a better description of the solar core,a generalization to stars coming from seismic missions and a better understanding of the dynamics of our galaxy which are all crucial keys for understanding dark matter.

  1. Astrophysical Jets and Outflows

    CERN Document Server

    De Gouveia dal Pino, E M

    2004-01-01

    Highly collimated supersonic jets and less collimated outflows are observed to emerge from a wide variety of astrophysical objects. They are seen in young stellar objects (YSOs), proto-planetary nebulae, compact objects (like galactic black holes or microquasars, and X-ray binary stars), and in the nuclei of active galaxies (AGNs). Despite their different physical scales (in size, velocity, and amount of energy transported), they have strong morphological similarities. What physics do they share? These systems either hydrodynamic or magnetohydrodynamic (MHD) in nature and are, as such, governed by non-linear equations. While theoretical models helped us to understand the basic physics of these objects, numerical simulations have been allowing us to go beyond the one-dimensional, steady-state approach extracting vital information. In this lecture, the formation, structure, and evolution of the jets are reviewed with the help of observational information, MHD and purely hydrodynamical modeling, and numerical si...

  2. Astrophysical formulae

    CERN Document Server

    Lang, Kenneth R

    1978-01-01

    This volume is a reference source of fundamental formulae in physics and astrophysics. In contrast to most of the usual compendia it carefully explains the physical assumptions entering the formulae. All the important results of physical theories are covered: electrodynamics, hydrodynamics, general relativity, atomic and nuclear physics, and so on. Over 2100 formulae are included, and the original papers for the formulae are cited together with papers on modern applications in a bibliography of over 1900 entries. For this new edition, a chapter on space, time, matter and cosmology has been included and the other chapters have been carefully revised.

  3. The solar-stellar connection

    Science.gov (United States)

    Giampapa, Mark S.

    2016-07-01

    A review of some principal results achieved in the area of stellar astrophysics with its origins in solar physics - the Solar-Stellar Connection - is presented from the perspective of an observational astronomer. The historical origins of the Solar-Stellar Connection are discussed followed by a review of key results from observations of stellar cycles analogous to the solar cycle in terms of parameters relevant to dynamo theory. A review of facets of angular momentum evolution and irradiance variations, each of which is determined by emergent, dynamo-generated magnetic fields, is given. Recent considerations of the impacts of stellar magnetic activity on the ambient radiative and energetic particle environment of the habitable zone of exoplanet systems are summarized. Some anticipated directions of the Solar-Stellar Connection in the new era of astronomy as defined by the advent of transformative facilities are presented.

  4. Collapsing Containers.

    Science.gov (United States)

    Brown, Justina L.; Battino, Rubin

    1994-01-01

    Describes variations on atmospheric pressure demonstrations and some systematic studies. Demonstrations use steam, generated either externally or internally to the container, to sweep out residual air. Preferred vessels collapsed slowly. Demonstrations use plastic milk jugs set in layers of aluminum foil, pop bottles immersed in 4-L beakers…

  5. Astrophysics with Presolar Stardust

    Science.gov (United States)

    Clayton, Donald D.; Nittler, Larry R.

    2004-09-01

    Meteorites and interplanetary dust particles contain presolar stardust grains: solid samples of stars that can be studied in the laboratory. The stellar origin of the grains is indicated by enormous isotopic ratio variations compared with Solar System materials, explainable only by nuclear reactions occurring in stars. Known presolar phases include diamond, SiC, graphite, Si3N4, Al2O3, MgAl2O4, CaAl12O19, TiO2, Mg(Cr,Al)2O4, and most recently, silicates. Subgrains of refractory carbides (e.g., TiC), and Fe-Ni metal have also been observed within individual presolar graphite grains. We review the astrophysical implications of these grains for the sciences of nucleosynthesis, stellar evolution, grain condensation, and the chemical and dynamic evolution of the Galaxy. Unique scientific information derives primarily from the high precision (in some cases <1%) of the measured isotopic ratios of large numbers of elements in single stardust grains. Stardust science is just now reaching maturity and will play an increasingly important role in nucleosynthesis applications.

  6. Astrophysics with Microarcsecond Accuracy Astrometry

    Science.gov (United States)

    Unwin, Stephen C.

    2008-01-01

    Space-based astrometry promises to provide a powerful new tool for astrophysics. At a precision level of a few microarcsonds, a wide range of phenomena are opened up for study. In this paper we discuss the capabilities of the SIM Lite mission, the first space-based long-baseline optical interferometer, which will deliver parallaxes to 4 microarcsec. A companion paper in this volume will cover the development and operation of this instrument. At the level that SIM Lite will reach, better than 1 microarcsec in a single measurement, planets as small as one Earth can be detected around many dozen of the nearest stars. Not only can planet masses be definitely measured, but also the full orbital parameters determined, allowing study of system stability in multiple planet systems. This capability to survey our nearby stellar neighbors for terrestrial planets will be a unique contribution to our understanding of the local universe. SIM Lite will be able to tackle a wide range of interesting problems in stellar and Galactic astrophysics. By tracing the motions of stars in dwarf spheroidal galaxies orbiting our Milky Way, SIM Lite will probe the shape of the galactic potential history of the formation of the galaxy, and the nature of dark matter. Because it is flexibly scheduled, the instrument can dwell on faint targets, maintaining its full accuracy on objects as faint as V=19. This paper is a brief survey of the diverse problems in modern astrophysics that SIM Lite will be able to address.

  7. Radioactive ion beams in nuclear astrophysics

    Science.gov (United States)

    Gialanella, L.

    2016-09-01

    Unstable nuclei play a crucial role in the Universe. In this lecture, after a short introduction to the field of Nuclear Astrophysics, few selected cases in stellar evolution and nucleosynthesis are discussed to illustrate the importance and peculiarities of processes involving unstable species. Finally, some experimental techniques useful for measurements using radioactive ion beams and the perspectives in this field are presented.

  8. Stark broadening data for stellar plasma research.

    Science.gov (United States)

    Dimitrijević, M. S.

    Results of an effort to provide to astrophysicists and physicists an as much as possible complete set of Stark broadening parameters needed for stellar opacity calculations, stellar atmosphere modelling, abundance determinations and diagnostics of different plasmas in astrophysics, physics and plasma technology, are presented. Stark broadening has been considered within the semiclassical perturbation, and the modified semiempirical approaches.

  9. Collapsed City

    DEFF Research Database (Denmark)

    Allen, Nacho Ruiz

    2015-01-01

    Currently, when the socio-economic circumstances seem to announce another change of cultural paradigm for the 21st century, the interest in the urban fact seems to have been renewed in architecture. However, this is no longer focused on models of growth and efficiency, as happened in the 70s....... Nowadays the situation is quite different. The enthusiasm for the economic growth which had characterized late capitalism and much of the postmodern cultural production has disappeared, and has given place to some global unease on a possible system collapse. Once the economy does not grow, but threatens...... with its imminent breakdown, the architectural interests have shifted to urban environments like Tokyo, Detroit, Lagos or Rio de Janeiro; places that demonstrate, somehow, an urban culture of collapse....

  10. Temperature evolution during dissipative collapse

    Indian Academy of Sciences (India)

    S D Maharaj; G Govender; M Govender

    2011-09-01

    We investigate the gravitational collapse of a radiating sphere evolving into a final static configuration described by the interior Schwarzschild solution. The temperature profiles of this particular model are obtained within the framework of causal thermodynamics. The overall temperature evolution is enhanced by contributions from the temperature gradient induced by perturbations as well as relaxational effects within the stellar core.

  11. The Link between Rare-Earth Peak Formation and the Astrophysical Site of the R Process

    Science.gov (United States)

    Mumpower, Matthew R.; McLaughlin, Gail C.; Surman, Rebecca; Steiner, Andrew W.

    2016-12-01

    The primary astrophysical source of the rare-earth elements is the rapid neutron capture process (r process). The rare-earth peak that is seen in the solar r-process residuals has been proposed to originate as a pile-up of nuclei during the end of the r process. We introduce a new method utilizing Monte Carlo studies of nuclear masses in the rare-earth region, that includes self-consistently adjusting β-decay rates and neutron capture rates, to find the mass surfaces necessary for the formation of the rare-earth peak. We demonstrate our method with two types of astrophysical scenario, one corresponding to conditions typical of hot winds from core-collapse supernovae and stellar-mass accretion disks, and one corresponding to conditions typical of the ejection of the material from the tidal tails of neutron star mergers. In each type of astrophysical condition, this method successfully locates a region of enhanced stability in the mass surface that is responsible for the rare-earth peak. For each scenario, we find that the change in the mass surface has qualitatively different features, thus future measurements can shed light on the type of environment in which the r process occurred.

  12. The masses and spins of neutron stars and stellar-mass black holes

    Energy Technology Data Exchange (ETDEWEB)

    Miller, M. Coleman, E-mail: miller@astro.umd.edu [University of Maryland, Department of Astronomy and Joint Space-Science Institute, College Park, MD 20742-2421 (United States); Miller, Jon M. [University of Michigan, Department of Astronomy, 500 Church Street, Ann Arbor, MI 48109-1042 (United States)

    2015-01-10

    Stellar-mass black holes and neutron stars represent extremes in gravity, density, and magnetic fields. They therefore serve as key objects in the study of multiple frontiers of physics. In addition, their origin (mainly in core-collapse supernovae) and evolution (via accretion or, for neutron stars, magnetic spindown and reconfiguration) touch upon multiple open issues in astrophysics. In this review, we discuss current mass and spin measurements and their reliability for neutron stars and stellar-mass black holes, as well as the overall importance of spins and masses for compact object astrophysics. Current masses are obtained primarily through electromagnetic observations of binaries, although future microlensing observations promise to enhance our understanding substantially. The spins of neutron stars are straightforward to measure for pulsars, but the birth spins of neutron stars are more difficult to determine. In contrast, even the current spins of stellar-mass black holes are challenging to measure. As we discuss, major inroads have been made in black hole spin estimates via analysis of iron lines and continuum emission, with reasonable agreement when both types of estimate are possible for individual objects, and future X-ray polarization measurements may provide additional independent information. We conclude by exploring the exciting prospects for mass and spin measurements from future gravitational wave detections, which are expected to revolutionize our understanding of strong gravity and compact objects.

  13. Einstein Toolkit for Relativistic Astrophysics

    Science.gov (United States)

    Collaborative Effort

    2011-02-01

    The Einstein Toolkit is a collection of software components and tools for simulating and analyzing general relativistic astrophysical systems. Such systems include gravitational wave space-times, collisions of compact objects such as black holes or neutron stars, accretion onto compact objects, core collapse supernovae and Gamma-Ray Bursts. The Einstein Toolkit builds on numerous software efforts in the numerical relativity community including CactusEinstein, Whisky, and Carpet. The Einstein Toolkit currently uses the Cactus Framework as the underlying computational infrastructure that provides large-scale parallelization, general computational components, and a model for collaborative, portable code development.

  14. Gravitational collapse: The story so far

    Indian Academy of Sciences (India)

    Pankaj S Joshi

    2000-10-01

    An outstanding problem in gravitation theory and relativistic astrophysics today is to understand the final outcome of an endless gravitational collapse. Such a continual collapse would take place when stars more massive than few times the mass of the sun collapse under their own gravity on exhausting their nuclear fuel. According to the general theory of relativity, this results either in a black hole, or a naked singularity – which can communicate with far away observers in the universe. While black holes are (almost) being detected and are increasingly used to model high energy astrophysical phenomena, naked singularities have turned into a topic of active discussion, aimed at understanding their structure and implications. Recent developments here are reviewed, indicating future directions.

  15. ACCESS: Enabling an Improved Flux Scale for Astrophysics

    CERN Document Server

    Kaiser, Mary Elizabeth; McCandliss, Stephan R; Sahnow, David J; Barkhouser, Robert H; Van Dixon, W; Feldman, Paul D; Moos, H Warren; Orndorff, Joseph; Pelton, Russell; Riess, Adam G; Rauscher, Bernard J; Kimble, Randy A; Benford, Dominic J; Gardner, Jonathan P; Hill, Robert J; Woodgate, Bruce E; Bohlin, Ralph C; Deustua, Susana E; Kurucz, Robert; Lampton, Michael; Perlmutter, Saul; Wright, Edward L

    2010-01-01

    Improvements in the precision of the astrophysical flux scale are needed to answer fundamental scientific questions ranging from cosmology to stellar physics. The unexpected discovery that the expansion of the universe is accelerating was based upon the measurement of astrophysical standard candles that appeared fainter than expected. To characterize the underlying physical mechanism of the "Dark Energy" responsible for this phenomenon requires an improvement in the visible-NIR flux calibration of astrophysical sources to 1% precision. These improvements will also enable large surveys of white dwarf stars, e.g. GAIA, to advance stellar astrophysics by testing and providing constraints for the mass-radius relationship of these stars. ACCESS (Absolute Color Calibration Experiment for Standard Stars) is a rocket-borne payload that will enable the transfer of absolute laboratory detector standards from NIST to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of R = 5...

  16. Underground nuclear astrophysics: Why and how

    Energy Technology Data Exchange (ETDEWEB)

    Best, A.; Laubenstein, M. [Laboratori Nazionali del Gran Sasso, INFN, Assergi (AQ) (Italy); Caciolli, A. [Universita di Padova, Dipartimento di Fisica e Astronomia, Padova (Italy); INFN, Padova (Italy); Fueloep, Zs.; Gyuerky, Gy. [Institute for Nuclear Research (MTA Atomki), Debrecen (Hungary); Napolitani, E. [Universita di Padova, Dipartimento di Fisica e Astronomia, Padova (Italy); Laboratori Nazionali di Legnaro, INFN, Legnaro (Italy); Rigato, V. [Laboratori Nazionali di Legnaro, INFN, Legnaro (Italy); Roca, V. [Universita di Napoli ' ' Federico II' ' , Dipartimento di Fisica, Napoli (Italy); INFN, Napoli (Italy); Szuecs, T. [Helmholtz-Zentrum Dresden - Rossendorf (HZDR), Dresden (Germany)

    2016-04-15

    The goal of nuclear astrophysics is to measure cross-sections of nuclear physics reactions of interest in astrophysics. At stars temperatures, these cross-sections are very low due to the suppression of the Coulomb barrier. Cosmic-ray-induced background can seriously limit the determination of reaction cross-sections at energies relevant to astrophysical processes and experimental setups should be arranged in order to improve the signal-to-noise ratio. Placing experiments in underground sites, however, reduces this background opening the way towards ultra low cross-section determination. LUNA (Laboratory for Underground Nuclear Astrophysics) was pioneer in this sense. Two accelerators were mounted at the INFN National Laboratories of Gran Sasso (LNGS) allowing to study nuclear reactions close to stellar energies. A summary of the relevant technology used, including accelerators, target production and characterisation, and background treatment is given. (orig.)

  17. Underground nuclear astrophysics: why and how

    CERN Document Server

    Best, A; Fülöp, Zs; Gyürky, Gy; Laubenstein, M; Napolitani, E; Rigato, V; Roca, V; Szücs, T

    2016-01-01

    The goal of nuclear astrophysics is to measure cross sections of nuclear physics reactions of interest in astrophysics. At stars temperatures, these cross sections are very low due to the suppression of the Coulomb barrier. Cosmic ray induced background can seriously limit the determination of reaction cross sections at energies relevant to astrophysical processes and experimental setups should be arranged in order to improve the signal-to-noise ratio. Placing experiments in underground sites, however, reduces this background opening the way towards ultra low cross section determination. LUNA (Laboratory for Underground Nuclear Astrophysics) was pioneer in this sense. Two accelerators were mounted at the INFN National Laboratories of Gran Sasso (LNGS) allowing to study nuclear reactions close to stellar energies. A summary of the relevant technology used, including accelerators, target production and characterisation, and background treatment is given.

  18. Trends in Nuclear Astrophysics

    OpenAIRE

    Schatz, Hendrik

    2016-01-01

    Nuclear Astrophysics is a vibrant field at the intersection of nuclear physics and astrophysics that encompasses research in nuclear physics, astrophysics, astronomy, and computational science. This paper is not a review. It is intended to provide an incomplete personal perspective on current trends in nuclear astrophysics and the specific role of nuclear physics in this field.

  19. Trends of Stellar Entropy along Stellar Evolution

    CERN Document Server

    de Avellar, Marcio G B; Horvath, Jorge E

    2015-01-01

    This paper is devoted to discuss the difference in the thermodynamic entropy budget {\\it per baryon} in each type of stellar object found in Universe. We track and discuss the actual {\\it decrease} of the stored baryonic thermodynamic entropy from the most primitive molecular cloud up to the final fate of matter in the black holes, passing through evolved states of matter as found in white dwarfs and neutron stars. We then discuss the case of actual stars of different masses throughout their {\\it evolution}, clarifying the role of virial equilibrium condition for the decrease of the entropy and related issues. Finally, we discuss how gravity ultimately drives composition, hence structural changes along the stellar evolution all the way until the ultimate collapse to black holes, which may increase dramatically their entropy because of the gravitational contribution itself.

  20. Bayesian parameter estimation of core collapse supernovae using gravitational wave simulations

    CERN Document Server

    Edwards, Matthew C; Christensen, Nelson

    2014-01-01

    Using the latest numerical simulations of rotating stellar core collapse, we present a Bayesian framework to extract the physical information encoded in noisy gravitational wave signals. We fit Bayesian principal component regression models with known and unknown signal arrival times to reconstruct gravitational wave signals, and subsequently fit known astrophysical parameters on the posterior means of the principal component coefficients using a linear model. We predict the ratio of rotational kinetic energy to gravitational energy of the inner core at bounce by sampling from the posterior predictive distribution, and find that these predictions are generally very close to the true parameter values, with $90\\%$ credible intervals $\\sim 0.04$ and $\\sim 0.06$ wide for the known and unknown arrival time models respectively. Two supervised machine learning methods are implemented to classify precollapse differential rotation, and we find that these methods discriminate rapidly rotating progenitors particularly w...

  1. Simulations of Astrophysical Hydrodynamics: Supernova Remnant Evolution and Star Formation

    Science.gov (United States)

    Truelove, John Kelly

    Many problems in astrophysical hydrodynamics are analytically intractable. In such cases, numerical simulation can provide valuable insight into the nature of the solution. We consider two such problems: the interaction of stellar ejecta and ambient gas in an evolving supernova remnant (SNR), and the collapse and fragmentation of molecular clouds to form stars. We first study the dynamics of SNR evolution from the ejecta-dominated stage through the Sedov-Taylor stage, the stages which precede the onset of dynamically significant radiative losses. We emphasize that all nonradiative SNRs of a given power-law structure evolve according to a unified solution, and we discuss this general property in detail. We present 1-D numerical simulations of the flow and use these to aid the development of approximate analytic solutions for the motions of the SNR shocks. We elucidate the dependence of the evolution on the ejecta power-law index n by developing a general trajectory for all n and explaining its relation to the solutions of Chevalier (1982) & Nadyozhin (1985) for n > 5 and Hamilton & Sarazin (1984) for n = 0. These solutions should be valuable in describing relatively young SNRs at intermediate points of nonradiative evolution. We then turn to 3-D simulation of star formation using adaptive mesh refinement (AMR). We demonstrate that perturbations arising from discretization of the equations of self-gravitational hydrodynamics can grow into artificial fragments. This can be avoided by ensuring the ratio of cell size to Jeans length, which we call the Jeans number, J ≡Δ x/λJ, is kept below 0.25. We refer to the constraint that λJ be resolved as the Jeans condition. We find that it is not possible a priori to have confidence that results of calculations which employ artificial viscosity to halt collapse are relevant to the astrophysical problem. Finally, we describe our new AMR code in detail. This code employs multiple grids at multiple levels of resolution and

  2. Towards 21st Century Stellar Models: Star Clusters, Supercomputing, and Asteroseismology

    DEFF Research Database (Denmark)

    Campbell, S. W.; Constantino, T. N.; D'Orazi, V.;

    2016-01-01

    Stellar models provide a vital basis for many aspects of astronomy and astrophysics. Recent advances in observational astronomy -- through asteroseismology, precision photometry, high-resolution spectroscopy, and large-scale surveys -- are placing stellar models under greater quantitative scrutin...

  3. Advancing Underground Nuclear Astrophysics with CASPAR

    Science.gov (United States)

    Robertson, Daniel; Couder, Manoel; Greife, Uwe; Strieder, Frank; Wells, Doug; Wiescher, Michael

    2015-04-01

    The advancement of experimental nuclear astrophysics techniques and the requirement of astrophysical network models for further nuclear data over greater energy ranges, has led to the requirement for the better understanding of nuclear reactions in stellar burning regimes. For those reactions of importance to stellar burning processes and elemental production through stellar nucleosynthesis, the energy range of astrophysical interest is always problematic to probe. As reaction measurements approach the burning window of interest, the rapid drop off in cross-section hampers laboratory investigation. The natural background suppression of underground accelerator facilities enables the extension of current experimental data to lower energies. An example of such reactions of interest are those thought to be sources of neutrons for the s-process, the major production mechanism for elements above the iron peak. The reactions 13 C(α,n)16 O and 22 Ne(α,n)25 Mg are the proposed initial focus of the new nuclear astrophysics accelerator laboratory (CASPAR) currently under construction at the Sanford Underground Research Facility, Lead, SD. With thanks to funding provided by South Dakota Science and Technology Authority and the NSF under Grant Number PHY-1419765.

  4. The impact of companions on stellar evolution

    CERN Document Server

    De Marco, Orsola

    2016-01-01

    Stellar astrophysicists are increasingly taking into account the effects of orbiting companions on stellar evolution. New discoveries, many thanks to systematic time-domain surveys, have underlined the role of binary star interactions in a range of astrophysical events, including some that were previously interpreted as due uniquely to single stellar evolution. Here, we review classical binary phenomena such as type Ia supernovae, and discuss new phenomena such as intermediate luminosity transients, gravitational wave-producing double black holes, or the interaction between stars and their planets. Finally, we examine the reassessment of well-known phenomena in light of interpretations that include both single and binary stars, for example supernovae of type Ib and Ic or luminous blue variables. At the same time we contextualise the new discoveries within the framework and nomenclature of the corpus of knowledge on binary stellar evolution. The last decade has heralded an era of revival in stellar astrophysic...

  5. Astrophysical jets and outflows

    Science.gov (United States)

    de Gouveia Dal Pino, Elisabete M.

    Highly collimated supersonic jets and less collimated outflows are observed to emerge from a wide variety of astrophysical objects. They are seen in young stellar objects (YSOs), proto-planetary nebulae, compact objects (like galactic black holes or microquasars, and X-ray binary stars), and in the nuclei of active galaxies (AGNs). Despite their different physical scales (in size, velocity, and amount of energy transported), they have strong morphological similarities. What physics do they share? These systems are either hydrodynamic or magnetohydrodynamic (MHD) in nature and are, as such, governed by non-linear equations. While theoretical models helped us to understand the basic physics of these objects, numerical simulations have been allowing us to go beyond the one-dimensional, steady-state approach extracting vital information. In this lecture, the formation, structure, and evolution of the jets are reviewed with the help of observational information, MHD and purely hydrodynamical modeling, and numerical simulations. Possible applications of the models particularly to YSOs and AGN jets are addressed.

  6. The astrophysical gravitational wave stochastic background

    Institute of Scientific and Technical Information of China (English)

    Tania Regimbau

    2011-01-01

    A stochastic background of gravitational waves with astrophysical origins may have resulted from the superposition of a large number of unresolved sources since the beginning of stellar activity.Its detection would put very strong constraints on the physical properties of compact objects, the initial mass function and star formarion history.On the other hand, it could be a ‘noise' that would mask the stochastic background of its cosmological origin.We review the main astrophysical processes which are able to produce a stochastic background and discuss how they may differ from the primordial contribution in terms of statistical properties.Current detection methods are also presented.

  7. Role of clusters in nuclear astrophysics with Cluster Nucleosynthesis Diagram (CND)

    Science.gov (United States)

    Kubono, S.; Binh, Dam N.; Hayakawa, S.; Hashimoto, H.; Kahl, D.; Yamaguchi, H.; Wakabayashi, Y.; Teranishi, T.; Iwasa, N.; Komatsubara, T.; Kato, S.; Chen, A.; Cherubini, S.; Choi, S. H.; Hahn, I. S.; He, J. J.; Khiem, Le Hong; Lee, C. S.; Kwon, Y. K.; Wanajo, S.; Janka, H.-T.

    2013-04-01

    The role of nuclear clustering in stellar reactions is discussed, with Cluster Nucleosynthesis Diagram (CND) proposed before, for nucleosynthesis in stellar evolution and explosive stellar phenomena. Special emphasis is placed on α-induced stellar reactions. We report here the first experimental evidence that a cluster resonances dominate the (α,p) stellar reaction cross sections that is crucial for the vp-process in core-collapse supernovae.

  8. The final outcome of dissipative collapse in the presence of

    Indian Academy of Sciences (India)

    S Thirukkanesh; S Moopanar; M Govender

    2012-08-01

    We investigate the role played by the cosmological constant during gravitational collapse of a radiating star with vanishing Weyl stresses in the interior. We highlight the role played by the cosmological constant during the latter stages of collapse. The evolution of the temperature of the collapsing body is studied by employing causal heat transport equation. We show that the inclusion of the cosmological constant enhances the temperature within the stellar core.

  9. Frontiers in nuclear astrophysics

    Science.gov (United States)

    Bertulani, C. A.; Kajino, T.

    2016-07-01

    The synthesis of nuclei in diverse cosmic scenarios is reviewed, with a summary of the basic concepts involved before a discussion of the current status in each case is made. We review the physics of the early universe, the proton to neutron ratio influence in the observed helium abundance, reaction networks, the formation of elements up to beryllium, the inhomogeneous Big Bang model, and the Big Bang nucleosynthesis constraints on cosmological models. Attention is paid to element production in stars, together with the details of the pp chain, the pp reaction, 3He formation and destruction, electron capture on 7Be, the importance of 8B formation and its relation to solar neutrinos, and neutrino oscillations. Nucleosynthesis in massive stars is also reviewed, with focus on the CNO cycle and its hot companion cycle, the rp-process, triple- α capture, and red giants and AGB stars. The stellar burning of carbon, neon, oxygen, and silicon is presented in a separate section, as well as the slow and rapid nucleon capture processes and the importance of medium modifications due to electrons also for pycnonuclear reactions. The nucleosynthesis in cataclysmic events such as in novae, X-ray bursters and in core-collapse supernovae, the role of neutrinos, and the supernova radioactivity and light-curve is further discussed, as well as the structure of neutron stars and its equation of state. A brief review of the element composition found in cosmic rays is made in the end.

  10. Hierarchical Cluster Assembly in Globally Collapsing Clouds

    CERN Document Server

    Vazquez-Semadeni, Enrique; Colin, Pedro

    2016-01-01

    We discuss the mechanism of cluster formation in a numerical simulation of a molecular cloud (MC) undergoing global hierarchical collapse (GHC). The global nature of the collapse implies that the SFR increases over time. The hierarchical nature of the collapse consists of small-scale collapses within larger-scale ones. The large-scale collapses culminate a few Myr later than the small-scale ones and consist of filamentary flows that accrete onto massive central clumps. The small-scale collapses form clumps that are embedded in the filaments and falling onto the large-scale collapse centers. The stars formed in the early, small-scale collapses share the infall motion of their parent clumps. Thus, the filaments feed both gaseous and stellar material to the massive central clump. This leads to the presence of a few older stars in a region where new protostars are forming, and also to a self-similar structure, in which each unit is composed of smaller-scale sub-units that approach each other and may merge. Becaus...

  11. Life Cycles of Magnetic Fields in Stellar Evolution

    CERN Document Server

    Uzdensky, D; Balbus, S; Blackman, E; Goodman, J; Medvedev, M; Spitkovsky, A; Stone, J

    2009-01-01

    This is a white paper submitted to the Stars and Stellar Evolution (SSE) Science Frontier Panel (SFP) of the NRC's Astronomy and Astrophysics 2010 Decadal Survey. The white paper is endorsed by the American Physical Society's (APS) Topical Group on Plasma Astrophysics (GPAP).

  12. On plasma radiative properties in stellar conditions

    CERN Document Server

    Turck-Chièze, S; Gilles, D; Loisel, G; Piau, L; 10.1016/j.hedp.2009.06.007

    2012-01-01

    The knowledge of stellar evolution is evolving quickly thanks to an increased number of opportunities to scrutinize the stellar internal plasma properties by stellar seismology and by 1D and 3D simulations. These new tools help us to introduce the internal dynamical phenomena in stellar modeling. A proper inclusion of these processes supposes a real confidence in the microscopic physics used, partly checked by solar or stellar acoustic modes. In the present paper we first recall which fundamental physics has been recently verified by helioseismology. Then we recall that opacity is an important ingredient of the secular evolution of stars and we point out why it is necessary to measure absorption coefficients and degrees of ionization in the laboratory for some well identified astrophysical conditions. We examine two specific experimental conditions which are accessible to large laser facilities and are suitable to solve some interesting questions of the stellar community: are the solar internal radiative inte...

  13. Collapsing granular suspensions

    OpenAIRE

    Kadau, D.; Andrade Jr, J. S.; Herrmann, H. J.

    2009-01-01

    A 2D contact dynamics model is proposed as a microscopic description of a collapsing suspension/soil to capture the essential physical processes underlying the dynamics of generation and collapse of the system. Our physical model is compared with real data obtained from in situ measurements performed with a natural collapsing/suspension soil. We show that the shear strength behavior of our collapsing suspension/soil model is very similar to the behavior of this collapsing suspension soil, for...

  14. Transition regions in solar system and astrophysical plasmas

    Science.gov (United States)

    Eastman, Timothy E.

    1990-01-01

    A brief review is presented of basic particle and field characteristics of plasmas observed within the solar system, especially near transition regions, and their parameter ranges are compared with those inferred for stellar winds and the interstellar medium. Parameter ranges for solar system and astrophysical plasmas are found to have considerable overlap. In addition, astrophysics provides unique, global perspectives of large-scale systems, whereas solar-system space physics provides for direct quantitative testing of physical processes. Astrophysics and solar-system space physics studies thus have complementary and synergistic roles.

  15. Astrophysical Applications of Gravitational Microlensing

    CERN Document Server

    Mao, Shude

    2012-01-01

    Since the first discovery of microlensing events nearly two decades ago, gravitational microlensing has accumulated tens of TBytes of data and developed into a powerful astrophysical technique with diverse applications. The review starts with a theoretical overview of the field and then proceeds to discuss the scientific highlights. (1) Microlensing observations toward the Magellanic Clouds rule out the Milky Way halo being dominated by MAssive Compact Halo Objects (MACHOs). This confirms most dark matter is non-baryonic, consistent with other observations. (2) Microlensing has discovered about 20 extrasolar planets (16 published), including the first two Jupiter-Saturn like systems and the only "cold Neptunes" yet detected. They probe a different part of the parameter space and will likely provide the most stringent test of core accretion theory of planet formation. (3) Microlensing provides a unique way to measure the mass of isolated stars, including brown dwarfs to normal stars. Half a dozen or so stellar...

  16. The Astrometric Foundation of Astrophysics

    CERN Document Server

    Høg, Erik

    2014-01-01

    Astrophysical studies require a knowledge of very accurate positions, motions and distances of stars. A brief overview is given of the significance and development of astrometry by ESA's two astrometric satellites, Hipparcos and Gaia, launched in respectively 1989 and 2013. The astrometric foundation of all branches of astronomy from the solar system and stellar systems to compact galaxies, quasars and dark matter is being revolutionized by the observations from these satellites. The future of fundamental astrometry must be considered in a time frame of 50 years, therefore science issues for a Gaia successor mission in twenty years are discussed in an extensive report: "Absolute Astrometry in the Next 50 Years" available at https://dl.dropbox.com/u/49240691/GaiaRef.pdf.

  17. Blue straggler formation at core collapse

    CERN Document Server

    Banerjee, Sambaran

    2016-01-01

    Among the most striking feature of blue straggler stars (BSS) is the presence of multiple sequences of BSSs in the colour-magnitude diagrams (CMDs) of several globular clusters. It is often envisaged that such a multiple BSS sequence would arise due a recent core collapse of the host cluster, triggering a number of stellar collisions and binary mass transfers simultaneously over a brief episode of time. Here we examine this scenario using direct N-body computations of moderately massive star clusters (of order 10^4 Msun ). As a preliminary attempt, these models are initiated with approx. 8-10 Gyr old stellar population and King profiles of high concentrations, being "tuned" to undergo core collapse quickly. BSSs are indeed found to form in a "burst" at the onset of the core collapse and several of such BS-bursts occur during the post-core-collapse phase. In those models that include a few percent primordial binaries, both collisional and binary BSSs form after the onset of the (near) core-collapse. However, t...

  18. Relativistic axions from collapsing Bose stars

    CERN Document Server

    Levkov, D G; Tkachev, I I

    2016-01-01

    The substructures of light bosonic (axion-like) dark matter may condense into compact Bose stars. We study collapses of the critical-mass stars caused by attractive self-interaction of the axion-like particles and find that these processes proceed in an unexpected universal way. First, nonlinear self-similar evolution (similar to "wave collapse" in plasma physics) forces the particles to fall into the star center. Second, collisions in the dense center create an outgoing stream of mildly relativistic particles which carries away an essential part of the star mass. The collapse stops when the star remnant is no longer able to support the self-similar infall feeding the collisions. We shortly discuss possible astrophysical and cosmological implications of these phenomena.

  19. Relativistic Axions from Collapsing Bose Stars

    Science.gov (United States)

    Levkov, D. G.; Panin, A. G.; Tkachev, I. I.

    2017-01-01

    The substructures of light bosonic (axionlike) dark matter may condense into compact Bose stars. We study the collapse of critical-mass stars caused by attractive self-interaction of the axionlike particles and find that these processes proceed in an unexpected universal way. First, nonlinear self-similar evolution (called "wave collapse" in condensed matter physics) forces the particles to fall into the star center. Second, interactions in the dense center create an outgoing stream of mildly relativistic particles which carries away an essential part of the star mass. The collapse stops when the star remnant is no longer able to support the self-similar infall feeding the collisions. We shortly discuss possible astrophysical and cosmological implications of these phenomena.

  20. Nuclear Clusters in Astrophysics

    Energy Technology Data Exchange (ETDEWEB)

    Kubono, S.; Binh, Dam N.; Hayakawa, S.; Hashimoto, H.; Kahl, D.; Wakabayashi, Y.; Yamaguchi, H. [Center for Nuclear Study (CNS), University of Tokyo, Wako Branch at RIKEN 2-1 Hirosawa, Wako, Saitama, 351-0198 (Japan); Teranishi, T. [Department of Physics, Kyushu University, Fukuoka, 812-8581 (Japan); Iwasa, N. [Department of Physics, Tohoku University, Sendai, 980-8578 (Japan); Komatsubara, T. [Department of Physics, Tsukuba University, Ibaraki, 305-8571 (Japan); Kato, S. [Department of Physics, Yamagata University, Yamagata, 990-8560 (Japan); Khiem, Le H. [Institute of Physics, Vietnam Academy for Science and Technology, Hanoi (Viet Nam)

    2010-03-01

    The role of nuclear clustering is discussed for nucleosynthesis in stellar evolution with Cluster Nucleosynthesis Diagram (CND) proposed before. Special emphasis is placed on alpha-induced stellar reactions together with molecular states for O and C burning.

  1. Particle Physics & Astrophysics (PPA)

    Data.gov (United States)

    Federal Laboratory Consortium — Scientists at SLAC's Particle Physics and Astrophysics develop and utilize unique instruments from underground to outer space to explore the ultimate laws of nature...

  2. Seismological challenges for stellar structure

    CERN Document Server

    Christensen-Dalsgaard, J

    2010-01-01

    Helioseismology has provided very detailed information about the solar interior, and extensive data on a large number of stars, although at less detail, are promised by the ongoing and upcoming asteroseismic projects. In the solar case there remain serious challenges in understanding the inferred solar structure, particularly in the light of the revised determinations of the solar surface composition. Also, a secure understanding of the origins of solar rotation as inferred from helioseismology, both in the radiative interior and in the convection zone, is still missing. In the stellar case challenges are certain to appear as the data allow more detailed inferences of the properties of stellar cores. Large remaining uncertainties in modelling concerns the properties of convective cores and other processes that may cause mixing. As a result of developing asteroseismic signatures addressing these and other issues, we can look forward to a highly challenging, and hence exciting, era of stellar astrophysics.

  3. Planets, stars and stellar systems

    CERN Document Server

    Bond, Howard; McLean, Ian; Barstow, Martin; Gilmore, Gerard; Keel, William; French, Linda

    2013-01-01

    This is volume 3 of Planets, Stars and Stellar Systems, a six-volume compendium of modern astronomical research covering subjects of key interest to the main fields of contemporary astronomy. This volume on “Solar and Stellar Planetary Systems” edited by Linda French and Paul Kalas presents accessible review chapters From Disks to Planets, Dynamical Evolution of Planetary Systems, The Terrestrial Planets, Gas and Ice Giant Interiors, Atmospheres of Jovian Planets, Planetary Magnetospheres, Planetary Rings, An Overview of the Asteroids and Meteorites, Dusty Planetary Systems and Exoplanet Detection Methods. All chapters of the handbook were written by practicing professionals. They include sufficient background material and references to the current literature to allow readers to learn enough about a specialty within astronomy, astrophysics and cosmology to get started on their own practical research projects. In the spirit of the series Stars and Stellar Systems published by Chicago University Press in...

  4. Magnetic Modulation of Stellar Angular Momentum Loss

    CERN Document Server

    Garraffo, Cecilia; Cohen, Ofer

    2014-01-01

    Angular Momentum Loss is important for understanding astrophysical phenomena such as stellar rotation, magnetic activity, close binaries, and cataclysmic variables. Magnetic breaking is the dominant mechanism in the spin down of young late-type stars. We have studied angular momentum loss as a function of stellar magnetic activity. We argue that the complexity of the field and its latitudinal distribution are crucial for angular momentum loss rates. In this work we discuss how angular momentum is modulated by magnetic cycles, and how stellar spin down is not just a simple function of large scale magnetic field strength.

  5. Radial velocity planet detection biases at the stellar rotational period

    OpenAIRE

    2016-01-01

    Future generations of precise radial velocity (RV) surveys aim to achieve sensitivity sufficient to detect Earth mass planets orbiting in their stars' habitable zones. A major obstacle to this goal is astrophysical radial velocity noise caused by active areas moving across the stellar limb as a star rotates. In this paper, we quantify how stellar activity impacts exoplanet detection with radial velocities as a function of orbital and stellar rotational periods. We perform data-driven simulati...

  6. Compact stars in the braneworld: A new branch of stellar configurations with arbitrarily large mass

    Science.gov (United States)

    Lugones, Germán; Arbañil, José D. V.

    2017-03-01

    We study the properties of compact stars in the Randall-Sundrum type-II braneworld (BW) model. To this end, we solve the braneworld generalization of the stellar structure equations for a static fluid distribution with spherical symmetry considering that the spacetime outside the star is described by a Schwarzschild metric. First, the stellar structure equations are integrated employing the so-called causal limit equation of state (EOS), which is constructed using a well-established EOS at densities below a fiducial density, and the causal EOS P =ρ above it. It is a standard procedure in general relativistic stellar structure calculations to use such EOSs for obtaining a limit in the mass radius diagram, known as the causal limit, above which no stellar configurations are possible if the EOS fulfills the condition that the sound velocity is smaller than the speed of light. We find that the equilibrium solutions in the braneworld model can violate the general relativistic causal limit, and for sufficiently large mass they approach asymptotically to the Schwarzschild limit M =2 R . Then, we investigate the properties of hadronic and strange quark stars using two typical EOSs: a nonlinear relativistic mean-field model for hadronic matter and the Massachusetts Institute of Technology (MIT) bag model for quark matter. For masses below ˜1.5 M⊙- 2 M⊙ , the mass versus radius curves show the typical behavior found within the frame of general relativity. However, we also find a new branch of stellar configurations that can violate the general relativistic causal limit and that, in principle, may have an arbitrarily large mass. The stars belonging to this new branch are supported against collapse by the nonlocal effects of the bulk on the brane. We also show that these stars are always stable under small radial perturbations. These results support the idea that traces of extra dimensions might be found in astrophysics, specifically through the analysis of masses and

  7. Nuclear astrophysics: a new era

    Energy Technology Data Exchange (ETDEWEB)

    Wiescher, Michael; Aprahamian, Ani [Department of Physics, University of Notre Dame (United States); Regan, Paddy [Department of Physics, University of Surrey (United Kingdom)

    2002-02-01

    The latest generation of radioactive-ion-beam facilities promises to shed light on the complex nuclear processes that control the evolution of stars and stellar explosions. The most fundamental question in nature is where do we come from, or, put another way, what are we made of? The late Carl Sagan poetically said that we are all made of stardust, but the origin of the elements has fascinated scientists for thousands of years. Many of the greatest medieval and renaissance scientists dabbled in alchemy, trying to create the elements that make up the cosmos, but we had to wait until the early 20th century to recognize that elements are really defined by the number of protons in the nucleus. According to our current understanding, after the big bang most of the normal or baryonic material in the universe consisted of the lightest two elements, hydrogen and helium, with only trace amounts of lithium and beryllium. All the heavier elements that occur naturally on Earth were created from this original material via a series of nuclear reactions in the cores of stars or in stellar explosions. Over the last decade, ground-based telescopes and satellite-based Observatories have opened new windows on the stars across the electromagnetic spectrum, from infrared to gamma radiation. New technology now makes it possible to observe and analyse short-lived stellar explosions. Indeed, the distribution of elements in 'planetary nebula' and in the ejecta of supernovae and novae give a direct glimpse of individual nucleosynthesis processes. In the February issue of Physics World, Michael Wiescher, Paddy Regan and Ani Aprahamian describe how sate-of-the-art facilities are set to plug many of the gaps in our understanding of nuclear astrophysics. (U.K.)

  8. Collapsing granular suspensions.

    Science.gov (United States)

    Kadau, D; Andrade, J S; Herrmann, H J

    2009-11-01

    A 2D contact dynamics model is proposed as a microscopic description of a collapsing suspension/soil to capture the essential physical processes underlying the dynamics of generation and collapse of the system. Our physical model is compared with real data obtained from in situ measurements performed with a natural collapsing/suspension soil. We show that the shear strength behavior of our collapsing suspension/soil model is very similar to the behavior of this collapsing suspension soil, for both the unperturbed and the perturbed phases of the material.

  9. Astronomical optical interferometry, II: Astrophysical results

    Directory of Open Access Journals (Sweden)

    Jankov S.

    2011-01-01

    Full Text Available Optical interferometry is entering a new age with several ground- based long-baseline observatories now making observations of unprecedented spatial resolution. Based on a great leap forward in the quality and quantity of interferometric data, the astrophysical applications are not limited anymore to classical subjects, such as determination of fundamental properties of stars; namely, their effective temperatures, radii, luminosities and masses, but the present rapid development in this field allowed to move to a situation where optical interferometry is a general tool in studies of many astrophysical phenomena. Particularly, the advent of long-baseline interferometers making use of very large pupils has opened the way to faint objects science and first results on extragalactic objects have made it a reality. The first decade of XXI century is also remarkable for aperture synthesis in the visual and near-infrared wavelength regimes, which provided image reconstructions from stellar surfaces to Active Galactic Nuclei. Here I review the numerous astrophysical results obtained up to date, except for binary and multiple stars milliarcsecond astrometry, which should be a subject of an independent detailed review, taking into account its importance and expected results at microarcsecond precision level. To the results obtained with currently available interferometers, I associate the adopted instrumental settings in order to provide a guide for potential users concerning the appropriate instruments which can be used to obtain the desired astrophysical information.

  10. An invitation to astrophysics

    CERN Document Server

    Padmanabhan, Thanu

    2006-01-01

    This unique book provides a clear and lucid description of several aspects of astrophysics and cosmology in a language understandable to a physicist or beginner in astrophysics. It presents the key topics in all branches of astrophysics and cosmology in a simple and concise language. The emphasis is on currently active research areas and exciting new frontiers rather than on more pedantic topics. Many complicated results are introduced with simple, novel derivations which strengthen the conceptual understanding of the subject. The book also contains over one hundred exercises which will help s

  11. Bubble Chambers for Experiments in Nuclear Astrophysics

    CERN Document Server

    DiGiovine, B; Holt, R J; Rehm, K E; Raut, R; Robinson, A; Sonnenschein, A; Rusev, G; Tonchev, A P; Ugalde, C

    2015-01-01

    A bubble chamber has been developed to be used as an active target system for low energy nuclear astrophysics experiments. Adopting ideas from dark matter detection with superheated liquids, a detector system compatible with gamma-ray beams has been developed. This detector alleviates some of the limitations encountered in standard measurements of the minute cross sections of interest to stellar environments. While the astrophysically relevant nuclear reaction processes at hydrostatic burning temperatures are dominated by radiative captures, in this experimental scheme we measure the time-reversed processes. Such photodisintegrations allow us to compute the radiative capture cross sections when transitions to excited states of the reaction products are negligible. Due to the transformation of phase space, the photodisintegration cross sections are up to two orders of magnitude higher. The main advantage of the new target-detector system is a density several orders of magnitude higher than conventional gas tar...

  12. Collapse and Outflow Towards an Integrated Theory of Star Formation

    CERN Document Server

    Pudritz, R E; Ouyed, R

    1997-01-01

    Observational advances over the last decade reveal that star formation is associated with the simultaneous presence of gravitationally collapsing gas, bipolar outflow, and an accretion disk. Two theoretical views of star formation suppose that either stellar mass is determined from the outset by gravitational instability, or by the outflow which sweeps away the collapsing envelope of initially singular density distributions. Neither picture appears to explain all of the facts. This contribution examines some of the key issues facing star formation theory.

  13. Outflows and inflows in astrophysical systems

    CERN Document Server

    Shen, Y; Shen, Yue; Lou, Yu-Qing

    2004-01-01

    We seek for self-similar solutions describing the time-dependent evolution of self-gravity systems with either spherical symmetry or axisymmetric disk geometry. By assuming self-similar variable $x\\equiv r/at$ where $a$ is isothermal sound speed we find self-similar solutions extending from the initial instant $t=0$ to the final stage $t\\to \\infty$ using standard semi-analytical methods. Different types of solutions are constructed, which describe overall expansion or collapse, envelope expansion with core collapse (EECC), the formation of central rotationally supported quasi-equilibrium disk as well as shocks. Though infinitely many, these self-similarity solutions have similar asymptotic behaviors which may impose diagnosis on the velocity and density structures in astrophysical systems.

  14. Stereo pairs in Astrophysics

    CERN Document Server

    Vogt, Frédéric

    2011-01-01

    Stereoscopic visualization is seldom used in Astrophysical publications and presentations compared to other scientific fields, e.g., Biochemistry, where it has been recognized as a valuable tool for decades. We put forth the view that stereo pairs can be a useful tool for the Astrophysics community in communicating a truer representation of astrophysical data. Here, we review the main theoretical aspects of stereoscopy, and present a tutorial to easily create stereo pairs using Python. We then describe how stereo pairs provide a way to incorporate 3D data in 2D publications of standard journals. We illustrate the use of stereo pairs with one conceptual and two Astrophysical science examples: an integral field spectroscopy study of a supernova remnant, and numerical simulations of a relativistic AGN jet. We also use these examples to make the case that stereo pairs are not merely an ostentatious way to present data, but an enhancement in the communication of scientific results in publications because they prov...

  15. Astrophysics Decoding the cosmos

    CERN Document Server

    Irwin, Judith A

    2007-01-01

    Astrophysics: Decoding the Cosmos is an accessible introduction to the key principles and theories underlying astrophysics. This text takes a close look at the radiation and particles that we receive from astronomical objects, providing a thorough understanding of what this tells us, drawing the information together using examples to illustrate the process of astrophysics. Chapters dedicated to objects showing complex processes are written in an accessible manner and pull relevant background information together to put the subject firmly into context. The intention of the author is that the book will be a 'tool chest' for undergraduate astronomers wanting to know the how of astrophysics. Students will gain a thorough grasp of the key principles, ensuring that this often-difficult subject becomes more accessible.

  16. Theoretical physics and astrophysics

    CERN Document Server

    Ginzburg, VL

    1979-01-01

    The aim of this book is to present, on the one hand various topics in theoretical physics in depth - especially topics related to electrodynamics - and on the other hand to show how these topics find applications in various aspects of astrophysics. The first text on theoretical physics and astrophysical applications, it covers many recent advances including those in X-ray, &ggr;-ray and radio-astronomy, with comprehensive coverage of the literature

  17. High energy astrophysical neutrinos

    OpenAIRE

    Athar, H.

    2002-01-01

    High energy neutrinos with energy typically greater than tens of thousands of GeV may originate from several astrophysical sources. The sources may include, for instance, our galaxy, the active centers of nearby galaxies, as well as possibly the distant sites of gamma ray bursts. I briefly review some aspects of production and propagation as well as prospects for observations of these high energy astrophysical neutrinos.

  18. Astrophysical Black Holes: Evidence of a Horizon?

    Science.gov (United States)

    Colpi, Monica

    In this Lecture Note we first follow a short account of the history of the black hole hypothesis. We then review on the current status of the search for astrophysical black holes with particular attention to the black holes of stellar origin. Later, we highlight a series of observations that reveal the albeit indirect presence of supermassive black holes in galactic nuclei, with mention to forthcoming experiments aimed at testing directly the black hole hypothesis. We further focus on evidences of a black hole event horizon in cosmic sources.

  19. 3D Immersive Visualization with Astrophysical Data

    Science.gov (United States)

    Kent, Brian R.

    2017-01-01

    We present the refinement of a new 3D immersion technique for astrophysical data visualization.Methodology to create 360 degree spherical panoramas is reviewed. The 3D software package Blender coupled with Python and the Google Spatial Media module are used together to create the final data products. Data can be viewed interactively with a mobile phone or tablet or in a web browser. The technique can apply to different kinds of astronomical data including 3D stellar and galaxy catalogs, images, and planetary maps.

  20. Dimensional analysis and group theory in astrophysics

    CERN Document Server

    Kurth, Rudolf

    2013-01-01

    Dimensional Analysis and Group Theory in Astrophysics describes how dimensional analysis, refined by mathematical regularity hypotheses, can be applied to purely qualitative physical assumptions. The book focuses on the continuous spectral of the stars and the mass-luminosity relationship. The text discusses the technique of dimensional analysis, covering both relativistic phenomena and the stellar systems. The book also explains the fundamental conclusion of dimensional analysis, wherein the unknown functions shall be given certain specified forms. The Wien and Stefan-Boltzmann Laws can be si

  1. Stellar remnants

    CERN Document Server

    Kawaler, S D; Srinivasan, G

    1997-01-01

    This volume examines the internal structure, origin and evolution of white dwarfs, neutron stars and black holes, all objects at the final stage of stellar evolution. It covers topics such as: pulsation of white dwarfs; millisecond pulsars; and the dynamics around black holes.

  2. Stellar Populations

    NARCIS (Netherlands)

    Peletier, Reynier F.

    2013-01-01

    This is a summary of my lectures during the 2011 Canary Islands Winter School in Puerto de la Cruz. I give an introduction to the field of stellar populations in galaxies, and highlight some new results. Since the title of the Winter School is Secular Evolution in Galaxies I mostly concentrate on ne

  3. General polytropic self-gravitating cylinder free-fall and accreting mass string with a chain of collapsed objects

    Science.gov (United States)

    Lou, Yu-Qing; Hu, Xu-Yao

    2016-06-01

    We present a theoretical model framework for general polytropic (GP) hydrodynamic cylinder under self-gravity of infinite length with axial uniformity and axisymmetry. For self-similar dynamic solutions, we derive valuable integrals, analytic asymptotic solutions, sonic critical curves, shock conditions, and global numerical solutions with or without expansion shocks. Among others, we investigate various dynamic solutions featured with central free-fall asymptotic behaviours, corresponding to a collapsed mass string with a sustained dynamic accretion from a surrounding mass reservoir. Depending on the allowed ranges of a scaling index a Physically, such a collapsed mass string or filament would break up into a sequence of sub-clumps and segments as induced by gravitational Jeans instabilities. Depending on the scales involved, such sub-clumps would evolve into collapsed objects or gravitationally bound systems. In diverse astrophysical and cosmological contexts, such a scenario can be adapted on various temporal, spatial and mass scales to form a chain of collapsed clumps and/or compact objects. Examples include the formation of chains of proto-stars, brown dwarfs and gaseous planets along molecular filaments; the formation of luminous massive stars along magnetized spiral arms and circum-nuclear starburst rings in barred spiral galaxies; the formation of chains of compact stellar objects such as white dwarfs, neutron stars, and black holes along a highly condensed mass string. On cosmological scales, one can perceive the formation of chains of galaxies, chains of galaxy clusters or even chains of supermassive and hypermassive black holes in the Universe including the early Universe. All these chains referred to above include possible binaries.

  4. Constraints of noncommutativity from Astrophysical studies

    CERN Document Server

    Garcia-Aspeitia, Miguel A; Ortiz, C; Hinojosa-Ruiz, Sinhue; Rodriguez-Meza, Mario A

    2015-01-01

    This paper is devoted to study the astrophysical consequences of noncommutativity, focusing in stellar dynamics and rotational curves of galaxies. We start exploring a star filled with an incompressible fluid and a noncommutative fluid under the Tolman-Oppenheimer-Volkoff background. We analyze the effective pressure and mass, resulting in a constraint for the noncommutative parameter. Also we explore the rotation curves of galaxies assuming that the dark matter halo is a noncommutative fluid, obtaining an average value of the noncommutative parameter through an analysis of twelve LSB galaxies; our results are compared with traditional models like Pseudoisothermal, Navarro-Frenk-White and Burkert. As a final remark, we summarize our results as: $\\sqrt{\\theta}>0.075R$, from star constraints which is strong dependent of the stellar radius and $\\langle\\sqrt{\\theta}\\rangle\\simeq2.666\\rm kpc$ with standard deviation $\\sigma\\simeq1.090\\rm kpc$ from the galactic constraints.

  5. Electromagnetic wave collapse in a radiation background.

    Science.gov (United States)

    Marklund, Mattias; Brodin, Gert; Stenflo, Lennart

    2003-10-17

    The nonlinear interaction, due to quantum electrodynamical (QED) effects between an electromagnetic pulse and a radiation background, is investigated by combining the methods of radiation hydrodynamics with the QED theory for photon-photon scattering. For the case of a single coherent electromagnetic pulse, we obtain a Zakharov-like system, where the radiation pressure of the pulse acts as a driver of acoustic waves in the photon gas. For a sufficiently intense pulse and/or background energy density, there is focusing and the subsequent collapse of the pulse. The relevance of our results for various astrophysical applications are discussed.

  6. Radial Velocity Planet Detection Biases at the Stellar Rotational Period

    CERN Document Server

    Vanderburg, Andrew; Johnson, John Asher; Ciardi, David R; Swift, Jonathan; Kane, Stephen R

    2016-01-01

    Future generations of precise radial velocity (RV) surveys aim to achieve sensitivity sufficient to detect Earth mass planets orbiting in their stars' habitable zones. A major obstacle to this goal is astrophysical radial velocity noise caused by active areas moving across the stellar limb as a star rotates. In this paper, we quantify how stellar activity impacts exoplanet detection with radial velocities as a function of orbital and stellar rotational periods. We perform data-driven simulations of how stellar rotation affects planet detectability and compile and present relations for the typical timescale and amplitude of stellar radial velocity noise as a function of stellar mass. We show that the characteristic timescales of quasi-periodic radial velocity jitter from stellar rotational modulations coincides with the orbital period of habitable zone exoplanets around early M-dwarfs. These coincident periods underscore the importance of monitoring the targets of RV habitable zone planet surveys through simul...

  7. Astrophysical applications of gravitational microlensing

    Institute of Scientific and Technical Information of China (English)

    Shude Mao

    2012-01-01

    Since the first discovery of microlensing events nearly two decades ago,gravitational microlensing has accumulated tens of TBytes of data and developed into a powerful astrophysical technique with diverse applications.The review starts with a theoretical overview of the field and then proceeds to discuss the scientific highlights.(1) Microlensing observations toward the Magellanic Clouds rule out the Milky Way halo being dominated by MAssive Compact Halo Objects (MACHOs).This confirms most dark matter is non-baryonic,consistent with other observations.(2) Microlensing has discovered about 20 extrasolar planets (16 published),including the first two Jupiter-Saturn like systems and the only five "cold Neptunes" yet detected.They probe a different part of the parameter space and will likely provide the most stringent test of core accretion theory of planet formation.(3) Microlensing provides a unique way to measure the mass of isolated stars,including brown dwarfs and normal stars.Half a dozen or so stellar mass black hole candidates have also been proposed.(4) High-resolution,target-of-opportunity spectra of highly-magnified dwarf stars provide intriguing "age" determinations which may either hint at enhanced helium enrichment or unusual bulge formation theories.(5) Microlensing also measured limb-darkening profiles for close to ten giant stars,which challenges stellar atmosphere models.(6) Data from surveys also provide strong constraints on the geometry and kinematics of the Milky Way bar (through proper motions); the latter indicates predictions from current models appear to be too anisotropic compared with observations.The future of microlensing is bright given the new capabilities of current surveys and forthcoming new telescope networks from the ground and from space.Some open issues in the field are identified and briefly discussed.

  8. Deriving stellar inclination of slow rotators using stellar activity

    Energy Technology Data Exchange (ETDEWEB)

    Dumusque, X., E-mail: xdumusque@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2014-12-01

    Stellar inclination is an important parameter for many astrophysical studies. Although different techniques allow us to estimate stellar inclination for fast rotators, it becomes much more difficult when stars are rotating slower than ∼2-2.5 km s{sup –1}. By using the new activity simulation SOAP 2.0 which can reproduce the photometric and spectroscopic variations induced by stellar activity, we are able to fit observations of solar-type stars and derive their inclination. For HD 189733, we estimate the stellar inclination to be i=84{sub −20}{sup +6} deg, which implies a star-planet obliquity of ψ=4{sub −4}{sup +18} considering previous measurements of the spin-orbit angle. For α Cen B, we derive an inclination of i=45{sub −19}{sup +9}, which implies that the rotational spin of the star is not aligned with the orbital spin of the α Cen binary system. In addition, assuming that α Cen Bb is aligned with its host star, no transit would occur. The inclination of α Cen B can be measured using 40 radial-velocity measurements, which is remarkable given that the projected rotational velocity of the star is smaller than 1.15 km s{sup –1}.

  9. Deriving stellar inclination of slow rotators using stellar activity

    CERN Document Server

    Dumusque, X

    2014-01-01

    Stellar inclination is an important parameter for many astrophysical studies. Although different techniques allow us to estimate stellar inclinationt for fast rotators, it becomes much more difficult when stars are rotating slower than $\\sim2$-2.5 \\kms. By using the new activity simulation SOAP 2.0 that can reproduce the photometric and spectroscopic variations induced by stellar activity, we are able to fit observations of solar-type stars and derive their inclination. For HD189733, we estimate the stellar inclination to be $i=84^{+6}_{-20}$ degrees, which implies a star-planet obliquity of $\\psi=4^{+18}_{-4}$ considering previous measurements of the spin-orbit angle. For $\\alpha$ Cen B, we derive an inclination of $i=45^{+9}_{-19}$, which implies that the rotational spin of the star is not aligned with the orbital spin of the $\\alpha$ Cen binary system. In addition, assuming that $\\alpha$ Cen Bb is aligned with its host star, no transit would occur. The inclination of $\\alpha$ Cen B can be measured using 40...

  10. Maximum stellar iron core mass

    Indian Academy of Sciences (India)

    F W Giacobbe

    2003-03-01

    An analytical method of estimating the mass of a stellar iron core, just prior to core collapse, is described in this paper. The method employed depends, in part, upon an estimate of the true relativistic mass increase experienced by electrons within a highly compressed iron core, just prior to core collapse, and is significantly different from a more typical Chandrasekhar mass limit approach. This technique produced a maximum stellar iron core mass value of 2.69 × 1030 kg (1.35 solar masses). This mass value is very near to the typical mass values found for neutron stars in a recent survey of actual neutron star masses. Although slightly lower and higher neutron star masses may also be found, lower mass neutron stars are believed to be formed as a result of enhanced iron core compression due to the weight of non-ferrous matter overlying the iron cores within large stars. And, higher mass neutron stars are likely to be formed as a result of fallback or accretion of additional matter after an initial collapse event involving an iron core having a mass no greater than 2.69 × 1030 kg.

  11. PREFACE: Nuclear Physics in Astrophysics III

    Science.gov (United States)

    Bemmerer, D.; Grosse, E.; Junghans, A. R.; Schwengner, R.; Wagner, A.

    2008-01-01

    The Europhysics Conference `Nuclear Physics in Astrophysics III' (NPA3) took place from 26 31 March 2007 in Dresden, Germany, hosted by Forschungszentrum Dresden-Rossendorf. The present special issue of Journal of Physics G: Nuclear and Particle Physics contains all peer-reviewed contributions to the proceedings of this conference. NPA3 is the third conference in the Nuclear Physics in Astrophysics series of conferences devoted to the interplay between nuclear physics and astrophysics. The first and second editions of the series were held in 2002 and 2005 in Debrecen, Hungary. NPA3 has been organized under the auspices of the Nuclear Physics Board of the European Physical Society as its XXI Divisional Conference. The conference marks the 50th anniversary of the landmark paper B2FH published in 1957 by E M Burbidge, G R Burbidge, W A Fowler and F Hoyle. A public lecture by Claus Rolfs (Ruhr-Universität Bochum, Germany) commemorated the progress achieved since 1957. NPA3 aimed to bring together experimental and theoretical nuclear physicists, astrophysicists and astronomers to address the important part played by nuclear physics in current astrophysical problems. A total of 130 participants from 71 institutions in 26 countries attended the conference, presenting 33 invited and 38 contributed talks and 25 posters on six subject areas. The astrophysical motivation and the nuclear tools employed to address it are highlighted by the titles of the subject areas: Big Bang Nucleosynthesis Stellar Nucleosynthesis and Low Cross Section Measurement Explosive Nucleosynthesis and Nuclear Astrophysics with Photons Nuclei far from Stability and Radioactive Ion Beams Dense Matter in Neutron Stars and Relativistic Nuclear Collisions Neutrinos in Nuclear Astrophysics The presentations and discussions proved that Nuclear Astrophysics is a truly interdisciplinary subject. The remarkable progress in astronomical observations achieved in recent years is matched by advances in

  12. A Novel Approach to Constraining Uncertain Stellar Evolution Models

    Science.gov (United States)

    Rosenfield, Philip; Girardi, Leo; Dalcanton, Julianne; Johnson, L. C.; Williams, Benjamin F.; Weisz, Daniel R.; Bressan, Alessandro; Fouesneau, Morgan

    2017-01-01

    Stellar evolution models are fundamental to nearly all studies in astrophysics. They are used to interpret spectral energy distributions of distant galaxies, to derive the star formation histories of nearby galaxies, and to understand fundamental parameters of exoplanets. Despite the success in using stellar evolution models, some important aspects of stellar evolution remain poorly constrained and their uncertainties rarely addressed. We present results using archival Hubble Space Telescope observations of 10 stellar clusters in the Magellanic Clouds to simultaneously constrain the values and uncertainties of the strength of core convective overshooting, metallicity, interstellar extinction, cluster distance, binary fraction, and age.

  13. Stereo pairs in Astrophysics

    Science.gov (United States)

    Vogt, Frédéric; Wagner, Alexander Y.

    2012-01-01

    Stereoscopic visualization is seldom used in Astrophysical publications and presentations compared to other scientific fields, e.g., Biochemistry, where it has been recognized as a valuable tool for decades. We put forth the view that stereo pairs can be a useful tool for the Astrophysics community in communicating a truer representation of astrophysical data. Here, we review the main theoretical aspects of stereoscopy, and present a tutorial to easily create stereo pairs using Python. We then describe how stereo pairs provide a way to incorporate 3D data in 2D publications of standard journals. We illustrate the use of stereo pairs with one conceptual and two Astrophysical science examples: an integral field spectroscopy study of a supernova remnant, and numerical simulations of a relativistic AGN jet. We also use these examples to make the case that stereo pairs are not merely an ostentatious way to present data, but an enhancement in the communication of scientific results in publications because they provide the reader with a realistic view of multi-dimensional data, be it of observational or theoretical nature. In recognition of the ongoing 3D expansion in the commercial sector, we advocate an increased use of stereo pairs in Astrophysics publications and presentations as a first step towards new interactive and multi-dimensional publication methods.

  14. Study of the {sup 44}Ti(α,p){sup 47}V reaction and implications for core collapse supernovae

    Energy Technology Data Exchange (ETDEWEB)

    Margerin, V., E-mail: vincent.margerin@ed.ac.uk [School of Physics and Astronomy, The University of Edinburgh, Edinburgh, EH9 3JZ (United Kingdom); Murphy, A.St.J.; Davinson, T. [School of Physics and Astronomy, The University of Edinburgh, Edinburgh, EH9 3JZ (United Kingdom); Dressler, R. [Laboratory of Radiochemistry and Environmental Chemistry, Paul Scherrer Institut, CH-5232 (Switzerland); Fallis, J. [TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada); Kankainen, A. [Department of Physics, University of Jyväskylä, P.O. Box 35, FI-40014 University of Jyväskylä (Finland); Helsinki Institute of Physics, P.O. Box 64, FI-00014 University of Helsinki (Finland); Laird, A.M. [Department of Physics, University of York, York, YO10 5DD (United Kingdom); Lotay, G.; Mountford, D.J.; Murphy, C.D. [School of Physics and Astronomy, The University of Edinburgh, Edinburgh, EH9 3JZ (United Kingdom); Seiffert, C. [CERN (Organisation Européenne pour la Recherche Nucléaire), CH-1211 Genève 23 (Switzerland); Schumann, D.; Stowasser, T. [Laboratory of Radiochemistry and Environmental Chemistry, Paul Scherrer Institut, CH-5232 (Switzerland); Stora, T. [CERN (Organisation Européenne pour la Recherche Nucléaire), CH-1211 Genève 23 (Switzerland); Wang, C.H.-T. [Department of Physics, Aberdeen University, Aberdeen, AB24 3UE (United Kingdom); Woods, P.J. [School of Physics and Astronomy, The University of Edinburgh, Edinburgh, EH9 3JZ (United Kingdom)

    2014-04-04

    The underlying physics triggering core collapse supernovae is not fully understood but observations of material ejected during such events helps to solve this puzzle. In particular, several satellite based γ-ray observations of the isotope {sup 44}Ti have been reported recently. Conveniently, the amount of this isotope in stellar ejecta is thought to depend critically on the explosion mechanism. The most influential reaction to the amount of {sup 44}Ti in supernovae is {sup 44}Ti(α,p){sup 47}V. Here we report on a direct study of this reaction conducted at the REX-ISOLDE facility, CERN. The experiment was performed with a {sup 44}Ti beam at E{sub lab}=2.16 MeV/u, corresponding to an energy distribution, for reacting α-particles, centred on E{sub cm}=4.15 with a 1σ width of 0.23 MeV. This is, for the first time, well within the Gamow window for core collapse supernovae. The material from which the {sup 44}Ti beam was extracted originates from highly irradiated components of the SINQ spallation neutron source of the Paul Scherrer Institute. No yield above background was observed, enabling an upper limit for the rate of this reaction to be determined. This result is below expectation, suggesting that the {sup 44}Ti(α,p){sup 47}V reaction proceeds more slowly than previously thought. Implications for astrophysical events, and remnant age, are discussed.

  15. Astrophysics Source Code Library

    CERN Document Server

    Allen, Alice; Berriman, Bruce; Hanisch, Robert J; Mink, Jessica; Teuben, Peter J

    2012-01-01

    The Astrophysics Source Code Library (ASCL), founded in 1999, is a free on-line registry for source codes of interest to astronomers and astrophysicists. The library is housed on the discussion forum for Astronomy Picture of the Day (APOD) and can be accessed at http://ascl.net. The ASCL has a comprehensive listing that covers a significant number of the astrophysics source codes used to generate results published in or submitted to refereed journals and continues to grow. The ASCL currently has entries for over 500 codes; its records are citable and are indexed by ADS. The editors of the ASCL and members of its Advisory Committee were on hand at a demonstration table in the ADASS poster room to present the ASCL, accept code submissions, show how the ASCL is starting to be used by the astrophysics community, and take questions on and suggestions for improving the resource.

  16. Augmented Reality in Astrophysics

    CERN Document Server

    Vogt, Frédéric P A

    2013-01-01

    Augmented Reality consists of merging live images with virtual layers of information. The rapid growth in the popularity of smartphones and tablets over recent years has provided a large base of potential users of Augmented Reality technology, and virtual layers of information can now be attached to a wide variety of physical objects. In this article, we explore the potential of Augmented Reality for astrophysical research with two distinct experiments: (1) Augmented Posters and (2) Augmented Articles. We demonstrate that the emerging technology of Augmented Reality can already be used and implemented without expert knowledge using currently available apps. Our experiments highlight the potential of Augmented Reality to improve the communication of scientific results in the field of astrophysics. We also present feedback gathered from the Australian astrophysics community that reveals evidence of some interest in this technology by astronomers who experimented with Augmented Posters. In addition, we discuss p...

  17. Surprises in astrophysical gasdynamics

    CERN Document Server

    Balbus, Steven A

    2016-01-01

    Much of astrophysics consists of the study of ionised gas under the influence of gravitational and magnetic fields. Thus, it is not possible to understand the astrophysical universe without a detailed knowledge of the dynamics of magnetised fluids. Fluid dynamics is, however, a notoriously tricky subject, in which it is all too easy for one's a priori intuition to go astray. In this review, we seek to guide the reader through a series of illuminating yet deceptive problems, all with an enlightening twist. We cover a broad range of topics including the instabilities acting in accretion discs, the hydrodynamics governing the convective zone of the Sun, the magnetic shielding of a cooling galaxy cluster, and the behaviour of thermal instabilities and evaporating clouds. The aim of this review is to surprise and intrigue even veteran astrophysical theorists with an idiosynchratic choice of problems and counterintuitive results. At the same time, we endeavour to bring forth the fundamental ideas, to set out import...

  18. Transfer reaction measurements and the stellar nucleosynthesis of 26Al and 44Ti

    CERN Document Server

    AUTHOR|(CDS)2086831

    Progress in the description of stellar evolution is driven by the collaborative effort of nuclear physics, astrophysics and astronomy. Using those developments, the theory of the origin of elements in the Universe is challenged. This thesis addresses the problem behind the abundance of 44Ti and the origin of 26Al. The mismatch between the predicted abundance of 44Ti as produced by the only sites known to be able to create 44Ti, core collapse supernovae (CCSNe), and the observations, highlight the current uncertainty that exists in the physics of these stars. Several satellite based gamma-ray observations of the isotope 44Ti have been reported in recent times and conrm the disagreement. As the amount of this isotope in stellar ejecta is thought to critically depend on the explosion mechanism, the ability to accurately model the observed abundance would be a pivotal step towards validating that theory. The most in influential reaction to the amount of 44Ti in supernovae is 44Ti(alpha, p)47V. Here we report on a...

  19. A multiphysics and multiscale software environment for modeling astrophysical systems

    CERN Document Server

    Zwart, Simon Portegies; Harfst, Stefan; Groen, Derek; Fujii, Michiko

    2008-01-01

    We present MUSE, a software framework for combining existing computational tools for different astrophysical domains into a single multiphysics, multiscale application. MUSE facilitates the coupling of existing codes written in different languages by providing inter-language tools and by specifying an interface between each module and the framework that represents a balance between generality and computational efficiency. This approach allows scientists to use combinations of codes to solve highly-coupled problems without the need to write new codes for other domains or significantly alter their existing codes. MUSE currently incorporates the domains of stellar dynamics, stellar evolution and stellar hydrodynamics for studying generalized stellar systems. We have now reached a ``Noah's Ark'' milestone, with (at least) two available numerical solvers for each domain. MUSE can treat multi-scale and multi-physics systems in which the time- and size-scales are well separated, like simulating the evolution of plan...

  20. Astrophysics in a nutshell

    CERN Document Server

    Maoz, Dan

    2016-01-01

    Winner of the American Astronomical Society's Chambliss Award, Astrophysics in a Nutshell has become the text of choice in astrophysics courses for science majors at top universities in North America and beyond. In this expanded and fully updated second edition, the book gets even better, with a new chapter on extrasolar planets; a greatly expanded chapter on the interstellar medium; fully updated facts and figures on all subjects, from the observed properties of white dwarfs to the latest results from precision cosmology; and additional instructive problem sets. Throughout, the text features the same focused, concise style and emphasis on physics intuition that have made the book a favorite of students and teachers.

  1. Coronal seismology waves and oscillations in stellar coronae

    CERN Document Server

    Stepanov, Alexander; Nakariakov, Valery M

    2012-01-01

    This concise and systematic account of the current state of this new branch of astrophysics presents the theoretical foundations of plasma astrophysics, magneto-hydrodynamics and coronal magnetic structures, taking into account the full range of available observation techniques -- from radio to gamma. The book discusses stellar loops during flare energy releases, MHD waves and oscillations, plasma instabilities and heating and charged particle acceleration. Current trends and developments in MHD seismology of solar and stellar coronal plasma systems are also covered, while recent p

  2. Constraining the astrophysical origin of the p-nuclei through nuclear physics and meteoritic data

    CERN Document Server

    Rauscher, T; Dillmann, I; Fröhlich, C; Fülöp, Zs; Gyürky, Gy

    2013-01-01

    A small number of naturally occurring, proton-rich nuclides (the p-nuclei) cannot be made in the s- and r-process. Their origin is not well understood. Massive stars can produce p-nuclei through photodisintegration of pre-existing intermediate and heavy nuclei. This so-called gamma-process requires high stellar plasma temperatures and occurs mainly in explosive O/Ne burning during a core-collapse supernova. Although the gamma-process in massive stars has been successful in producing a large range of p-nuclei, significant deficiences remain. An increasing number of processes and sites has been studied in recent years in search of viable alternatives replacing or supplementing the massive star models. A large number of unstable nuclei, however, with only theoretically predicted reaction rates are included in the reaction network and thus the nuclear input may also bear considerable uncertainties. The current status of astrophysical models, nuclear input, and observational constraints is reviewed. After an overv...

  3. Stellar evolution

    CERN Document Server

    Meadows, A J

    2013-01-01

    Stellar Evolution, Second Edition covers the significant advances in the understanding of birth, life, and death of stars.This book is divided into nine chapters and begins with a description of the characteristics of stars according to their brightness, distance, size, mass, age, and chemical composition. The next chapters deal with the families, structure, and birth of stars. These topics are followed by discussions of the chemical composition and the evolution of main-sequence stars. A chapter focuses on the unique features of the sun as a star, including its evolution, magnetic fields, act

  4. Surprises in astrophysical gasdynamics

    Science.gov (United States)

    Balbus, Steven A.; Potter, William J.

    2016-06-01

    Much of astrophysics consists of the study of ionized gas under the influence of gravitational and magnetic fields. Thus, it is not possible to understand the astrophysical universe without a detailed knowledge of the dynamics of magnetized fluids. Fluid dynamics is, however, a notoriously tricky subject, in which it is all too easy for one’s a priori intuition to go astray. In this review, we seek to guide the reader through a series of illuminating yet deceptive problems, all with an enlightening twist. We cover a broad range of topics including the instabilities acting in accretion discs, the hydrodynamics governing the convective zone of the Sun, the magnetic shielding of a cooling galaxy cluster, and the behaviour of thermal instabilities and evaporating clouds. The aim of this review is to surprise and intrigue even veteran astrophysical theorists with an idiosyncratic choice of problems and counterintuitive results. At the same time, we endeavour to bring forth the fundamental ideas, to set out important assumptions, and to describe carefully whatever novel techniques may be appropriate to the problem at hand. By beginning at the beginning, and analysing a wide variety of astrophysical settings, we seek not only to make this review suitable for fluid dynamic veterans, but to engage novice recruits as well with what we hope will be an unusual and instructive introduction to the subject.

  5. The NASA Astrophysics Program

    Science.gov (United States)

    Zebulum, Ricardo S.

    2011-01-01

    NASA's scientists are enjoying unprecedented access to astronomy data from space, both from missions launched and operated only by NASA, as well as missions led by other space agencies to which NASA contributed instruments or technology. This paper describes the NASA astrophysics program for the next decade, including NASA's response to the ASTRO2010 Decadal Survey.

  6. Surprises in astrophysical gasdynamics.

    Science.gov (United States)

    Balbus, Steven A; Potter, William J

    2016-06-01

    Much of astrophysics consists of the study of ionized gas under the influence of gravitational and magnetic fields. Thus, it is not possible to understand the astrophysical universe without a detailed knowledge of the dynamics of magnetized fluids. Fluid dynamics is, however, a notoriously tricky subject, in which it is all too easy for one's a priori intuition to go astray. In this review, we seek to guide the reader through a series of illuminating yet deceptive problems, all with an enlightening twist. We cover a broad range of topics including the instabilities acting in accretion discs, the hydrodynamics governing the convective zone of the Sun, the magnetic shielding of a cooling galaxy cluster, and the behaviour of thermal instabilities and evaporating clouds. The aim of this review is to surprise and intrigue even veteran astrophysical theorists with an idiosyncratic choice of problems and counterintuitive results. At the same time, we endeavour to bring forth the fundamental ideas, to set out important assumptions, and to describe carefully whatever novel techniques may be appropriate to the problem at hand. By beginning at the beginning, and analysing a wide variety of astrophysical settings, we seek not only to make this review suitable for fluid dynamic veterans, but to engage novice recruits as well with what we hope will be an unusual and instructive introduction to the subject.

  7. Reconstructing core-collapse supernovae waveforms with advanced era interferometers

    Science.gov (United States)

    McIver, Jessica; LIGO Scientific Collaboration

    2015-04-01

    Among of the wide range of potentially interesting astrophysical sources for Advanced LIGO and Advanced Virgo are galactic core-collapse supernovae. Although detectable core-collapse supernovae have a low expected rate (a few per century, or less) these signals would yield a wealth of new physics in the form of many messengers. Of particular interest is the insight into the explosion mechanism driving core-collapse supernovae that can be gleaned from the reconstructed gravitational wave signal. A well-reconstructed waveform will allow us to assess the likelihood of different explosion models, perform model selection, and potentially map unexpected features to new physics. This talk will present a study evaluating the current performance of the reconstruction of core-collapse supernovae gravitational wave signals. We used simulated waveforms modeled after different explosion mechanisms that we first injected into fake strain data re-colored to the expected Advanced LIGO/Virgo noise curves and then reconstructed using the pipelines Coherent Waveburst 2G and BayesWave. We will discuss the impact of these results on our ability to accurately reconstruct core-collapse supernovae signals, and by extension, other potential astrophysical generators of rich, complex waveforms.

  8. Stellar Opacity

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, F J; Iglesias, C A

    1999-11-07

    The monochromatic opacity, {kappa}{sub v}, quantifies the property of a material to remove energy of frequency v from a radiation field. A harmonic average of {kappa}{sub v}, known as the Rosseland mean, {kappa}{sub R}, is frequently used to simplify the calculation of energy transport in stars. The term ''opacity'' is commonly understood to refer to {kappa}{sub R}. Opacity plays an important role in stellar modeling because for most stars radiation is the primary mechanism for transporting energy from the nuclear burning region in the core to the surface. Depending on the mass, convection and electron thermal conduction can also be important modes of stellar energy transport. The efficiency of energy transport is related to the temperature gradient, which is directly proportional to the mean radiative opacity in radiation dominated regions. When the radiative opacity is large, convection can become the more efficient energy transport mechanism. Electron conductive opacity, the resistance of matter to thermal conduction, is inversely proportional to electron thermal conductivity. Thermal conduction becomes the dominant mode of energy transport at high density and low temperature.

  9. Simulating Convection in Stellar Envelopes

    Science.gov (United States)

    Tanner, Joel

    Understanding convection in stellar envelopes, and providing a mathematical description of it, would represent a substantial advance in stellar astrophysics. As one of the largest sources of uncertainty in stellar models, existing treatments of convection fail to account for many of the dynamical effects of convection, such as turbulent pressure and asymmetry in the velocity field. To better understand stellar convection, we must be able to study and examine it in detail, and one of the best tools for doing so is numerical simulation. Near the stellar surface, both convective and radiative process play a critical role in determining the structure and gas dynamics. By following these processes from first principles, convection can be simulated self-consistently and accurately, even in regions of inefficient energy transport where existing descriptions of convection fail. Our simulation code includes two radiative transfer solvers that are based on different assumptions and approximations. By comparing simulations that differ only in their respective radiative transfer methods, we are able to isolate the effect that radiative efficiency has on the structure of the superadiabatic layer. We find the simulations to be in good general agreement, but they show distinct differences in the thermal structure in the superadiabatic layer and atmosphere. Using the code to construct a grid of three-dimensional radiation hydrodynamic simulations, we investigate the link between convection and various chemical compositions. The stellar parameters correspond to main-sequence stars at several surface gravities, and span a range in effective temperatures (4500 matches the thermodynamics of the simulations. In particular, we consider adjusting the mixing length parameter such that the specific entropy of the model matches that of an equivalent simulation eliminates the need to arbitrarily set the parameter, and in principle will produce stellar models with more accurate radii. By

  10. Collapse of axion stars

    Science.gov (United States)

    Eby, Joshua; Leembruggen, Madelyn; Suranyi, Peter; Wijewardhana, L. C. R.

    2016-12-01

    Axion stars, gravitationally bound states of low-energy axion particles, have a maximum mass allowed by gravitational stability. Weakly bound states obtaining this maximum mass have sufficiently large radii such that they are dilute, and as a result, they are well described by a leading-order expansion of the axion potential. Heavier states are susceptible to gravitational collapse. Inclusion of higher-order interactions, present in the full potential, can give qualitatively different results in the analysis of collapsing heavy states, as compared to the leading-order expansion. In this work, we find that collapsing axion stars are stabilized by repulsive interactions present in the full potential, providing evidence that such objects do not form black holes. In the last moments of collapse, the binding energy of the axion star grows rapidly, and we provide evidence that a large amount of its energy is lost through rapid emission of relativistic axions.

  11. Collapse of Axion Stars

    CERN Document Server

    Eby, Joshua; Suranyi, Peter; Wijewardhana, L C R

    2016-01-01

    Axion stars, gravitationally bound states of low-energy axion particles, have a maximum mass allowed by gravitational stability. Weakly bound states obtaining this maximum mass have sufficiently large radii such that they are dilute, and as a result, they are well described by a leading-order expansion of the axion potential. Heavier states are susceptible to gravitational collapse. Inclusion of higher-order interactions, present in the full potential, can give qualitatively different results in the analysis of collapsing heavy states, as compared to the leading-order expansion. In this work, we find that collapsing axion stars are stabilized by repulsive interactions present in the full potential, providing evidence that such objects do not form black holes. These dense configurations, which are the endpoints of collapse, have extremely high binding energy, and as a result, decay through number changing $3\\,a\\rightarrow a$ interactions with an extremely short lifetime.

  12. Description of anomalous Zeeman patterns in stellar astrophysics

    CERN Document Server

    Pain, Jean-Christophe

    2013-01-01

    The influence of a magnetic field on the broadening of spectral lines and transition arrays in complex spectra is investigated. The anomalous absorption or emission Zeeman pattern is a superposition of many profiles with different relative strengths, shifts, widths, asymmetries and sharpnesses. The "sigma" and "pi" profiles can be described statistically, using the moments of the Zeeman components. We present two statistical modellings: the first one provides a diagnostic of the magnetic field and the second one can be used to include the effect of a magnetic field on simulated atomic spectra in an approximate way.

  13. New GALEX UV Data Products At MAST For Stellar Astrophysics

    Science.gov (United States)

    Shiao, Bernie; Fleming, S. W.; Million, C.; Seibert, M.; Bianchi, L.; Thompson, R.; Tseng, S.; Adler, W. J.; Hubbard, M.; Levay, K.; Madore, B. F.; Martin, C. D.; Nieto-Santisteban, M. A.; Sahai, R.; Schiminovich, D.; White, R. L.; Wyder, T. K.

    2014-01-01

    The Galaxy Evolution Explorer (GALEX) mission ended in June 2013 after ten years in orbit. Its FUV and NUV microchannel plate detectors were used to conduct a variety of direct imaging and spectroscopic astronomical surveys with various depths and sky coverage, recording individual photon events with a time resolution of five thousandths of a second. Although the mission has ended, MAST is continuing to provide new data products as the mission transitions to a legacy archive. One product is the GCAT (Seibert et al., in prep), a catalog of GALEX sources across the entire GR6 data release that removes duplicate objects found in the GALEX MCAT. The GCAT defines "primary" NUV and FUV fluxes within the AIS and MIS surveys 40 million and 22 million sources, respectively), accounting for tile overlaps, and with visual inspection of every tile to flag artifacts and conduct other quality control checks. Another catalog of unique sources is that of Bianchi et al. (2013). Similar to the GCAT, their catalog produces a list of distinct GALEX sources in both the FUV and NUV from the AIS and MIS surveys, and includes data from GR7 (through the end of 2012). They have also cross-matched their sources with SDSS DR9, GSC-II, PanSTARRS, and 2MASS. We review access options for these catalogs, including updated matches between the GCAT and SDSS / Kepler available at MAST. In addition to these unique GALEX source catalogs, MAST will provide a database and software package that archives each of the ~1.5 trillion photon events detected over the lifetime of the mission. For the first time, users will be able to create calibrated lightcurves, intensity maps, and animated movies from any set of photons selected across any tile, and with specified aperture sizes, coordinates, and time steps. Users can access the data using either a python-based command-line software package, through a web interface at MAST, or (eventually) through CasJobs using direct SQL queries. We present some example GALEX lightcurves and images using this new data product to highlight just some of the possibilities available for users to mine the GALEX photon database, particularly with variable sources.

  14. KROME - a package to embed chemistry in astrophysical simulations

    CERN Document Server

    Grassi, T; Schleicher, D R G; Prieto, J; Seifried, D; Simoncini, E; Gianturco, F A

    2013-01-01

    Chemistry plays a key role in many astrophysical situations, and therefore needs to be included in astrophysical simulations modelling such environments. In particular, the chemical evolution regulates the cooling, and the thermal properties of the gas, which are relevant during gravitational collapse, the evolution of disks and the fragmentation process. At the same time, the chemistry of the gas also determines the observational appearance, in particular with respect to the emission through atomic, ionic or molecular lines. In order to simplify the usage of chemical networks in large numerical simulations, we present the chemistry package KROME, consisting of a Python pre-processor which generates a subroutine for the solution of chemical networks which can be embedded in any numerical code. For the solution of the rate equations, we make use of the high-order solver DLSODES, which was shown to be both accurate and efficient for sparse networks, which are typical in astrophysical applications. KROME also pr...

  15. Alba Patera Collapse Pits

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. This image of the Alba Patera region has both lava tube collapse pits (running generally east/west) and subsidence related collapse within structural grabens. Image information: IR instrument. Latitude 26.9, Longitude 256.5 East (103.5 West). 100 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science

  16. Lava Tube Collapse Pits

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. These collapse pits are found in the southern hemisphere of Mars. They are likely lava tube collapse pits related to flows from Hadriaca Patera. Image information: VIS instrument. Latitude -36.8, Longitude 89.6 East (270.4 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D

  17. On the Quantification of Incertitude in Astrophysical Simulation Codes

    Science.gov (United States)

    Hoffman, Melissa; Katz, Maximilian P.; Willcox, Donald E.; Ferson, Scott; Swesty, F. Douglas; Calder, Alan

    2017-01-01

    We present a pedagogical study of uncertainty quantification (UQ) due to epistemic uncertainties (incertitude) in astrophysical modeling using the stellar evolution software instrument MESA (Modules and Experiments for Stellar Astrophysics). We present a general methodology for UQ and examine the specific case of stars evolving from the main sequence to carbon/oxygen white dwarfs. Our study considers two epistemic variables: the wind parameters during the Red Giant and Asymptotic Giant branch phases of evolution. We choose uncertainty intervals for each variable, and use these as input to MESA simulations. Treating MESA as a "black box," we apply two UQ techniques, Cauchy deviates and Quadratic Response Surface Models, to obtain bounds for the final white dwarf masses. Our study is a proof of concept applicable to other computational problems to enable a more robust understanding of incertitude. This work was supported in part by the US Department of Energy under grant DE-FG02-87ER40317.

  18. Laboratory Astrophysics and the State of Astronomy and Astrophysics

    CERN Document Server

    Brickhouse, AAS WGLA: Nancy; Drake, Paul; Federman, Steven; Ferland, Gary; Frank, Adam; Haxton, Wick; Herbst, Eric; Olive, Keith; Salama, Farid; Savin, Daniel Wolf; Ziurys, Lucy

    2009-01-01

    Laboratory astrophysics and complementary theoretical calculations are the foundations of astronomy and astrophysics and will remain so into the foreseeable future. The impact of laboratory astrophysics ranges from the scientific conception stage for ground-based, airborne, and space-based observatories, all the way through to the scientific return of these projects and missions. It is our understanding of the under-lying physical processes and the measurements of critical physical parameters that allows us to address fundamental questions in astronomy and astrophysics. In this regard, laboratory astrophysics is much like detector and instrument development at NASA, NSF, and DOE. These efforts are necessary for the success of astronomical research being funded by the agencies. Without concomitant efforts in all three directions (observational facilities, detector/instrument development, and laboratory astrophysics) the future progress of astronomy and astrophysics is imperiled. In addition, new developments i...

  19. Dawes Review 6: The Impact of Companions on Stellar Evolution

    Science.gov (United States)

    De Marco, Orsola; Izzard, Robert G.

    2017-01-01

    Astrophysicists are increasingly taking into account the effects of orbiting companions on stellar evolution. New discoveries have underlined the role of binary star interactions in a range of astrophysical events, including some that were previously interpreted as being due uniquely to single stellar evolution. We review classical binary phenomena, such as type Ia supernovae, and discuss new phenomena, such as intermediate luminosity transients, gravitational wave-producing double black holes, and the interaction between stars and their planets. Finally, we reassess well-known phenomena, such as luminous blue variables, in light of interpretations that include both single and binary stars. At the same time we contextualise the new discoveries within the framework of binary stellar evolution. The last decade has seen a revival in stellar astrophysics as the complexity of stellar observations is increasingly interpreted with an interplay of single and binary scenarios. The next decade, with the advent of massive projects such as the Square Kilometre Array, the James Webb Space Telescope, and increasingly sophisticated computational methods, will see the birth of an expanded framework of stellar evolution that will have repercussions in many other areas of astrophysics such as galactic evolution and nucleosynthesis.

  20. Electromagnetically-Induced Frame-Dragging around Astrophysical Objects

    CERN Document Server

    Ruiz, Andrés F Gutiérrez

    2015-01-01

    Frame dragging (Lense-Thirring effect) is generally associated with rotating astrophysical objects. However, it can also be generated by electromagnetic fields if electric and magnetic fields are simultaneously present. In most models of astrophysical objects, macroscopic charge neutrality is assumed and the entire electromagnetic field is characterized in terms of a magnetic dipole component. Hence, the purely electromagnetic contribution to the frame dragging vanishes. However, strange stars may posses independent electric dipole and neutron stars independent electric quadrupole moments that may lead to the presence of purely electromagnetic contributions to the frame dragging. Moreover, recent observations have shown that in stars with strong electromagnetic fields, the magnetic quadrupole may have a significant contribution to the dynamics of stellar processes. As an attempt to characterized and quantify the effect of electromagnetic frame-dragging in this kind of astrophysical objects, an analytic soluti...

  1. Numerically determined transport laws for fingering ("thermohaline") convection in astrophysics

    CERN Document Server

    Traxler, Adrienne; Stellmach, Stephan

    2010-01-01

    We present the first three-dimensional simulations of fingering convection performed in a parameter regime close to the one relevant for astrophysics, and reveal the existence of simple asymptotic scaling laws for turbulent heat and compositional transport. These laws can straightforwardly be extrapolated to the true astrophysical regime. Our investigation also indicates that thermocompositional "staircases," a key consequence of fingering convection in the ocean, cannot form spontaneously in stellar interiors. Our proposed empirically-determined transport laws thus provide simple prescriptions for mixing by fingering convection in a variety of astrophysical situations, and should, from here on, be used preferentially over older and less accurate parameterizations. They also establish that fingering convection does not provide sufficient extra mixing to explain observed chemical abundances in RGB stars.

  2. Astrophysical evidence on physics beyond the standard model

    CERN Document Server

    Dar, Arnon

    1995-01-01

    Astrophysics and cosmology can be used to test the standard model of particle physics under conditions and over distance and time scales not accessible to laboratory experiments. Most of the astrophysical observations are in good agreement with the standard model. In particular, primordial nucleosynthesis, supernova explosions, stellar evolution and cosmic background radiations have been used to derive strong limits on physics beyond the standard model. However, the solution of some important astrophysical and cosmological problems may require new physics beyond the standard model. These include the origin of the initial conditions, large scale structure formation, the baryon asymmetry in the observed Universe, the dark matter problem, the solar neutrino problem and some cosmic ray puzzles. Here I review some important developments relevant to some of these problems, which took place most recently.

  3. Experimental astrophysics with high power lasers and Z pinches

    Energy Technology Data Exchange (ETDEWEB)

    Remington, B A; Drake, R P; Ryutov, D D

    2004-12-10

    With the advent of high energy density (HED) experimental facilities, such as high-energy lasers and fast Z-pinch, pulsed-power facilities, mm-scale quantities of matter can be placed in extreme states of density, temperature, and/or velocity. This has enabled the emergence of a new class of experimental science, HED laboratory astrophysics, wherein the properties of matter and the processes that occur under extreme astrophysical conditions can be examined in the laboratory. Areas particularly suitable to this class of experimental astrophysics include the study of opacities relevant to stellar interiors; equations of state relevant to planetary interiors; strong shock driven nonlinear hydrodynamics and radiative dynamics, relevant to supernova explosions and subsequent evolution; protostellar jets and high Mach-number flows; radiatively driven molecular clouds and nonlinear photoevaporation front dynamics; and photoionized plasmas relevant to accretion disks around compact objects, such as black holes and neutron stars.

  4. Ascraeus Mons Collapse Pits

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. These collapse pits are found on the flank of Ascraeus Mons. The pits and channels are all related to lava tube formation and emptying. Image information: IR instrument. Latitude 8, Longitude 253.9 East (106.1 West). 100 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal

  5. Sulci Collapse Pits

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. This is the Noctis Labyrinthus region of Mars. These collapse pits are forming along structural fractures that are allowing the release of volatiles from the subsurface. This is believed to be the way that chaos terrain forms on Mars. This area represents the early stage of chaos formation. Image information: VIS instrument. Latitude -12.6, Longitude 264 East (96 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project

  6. Tharsis Collapse Pits

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. These collapse pits are found within the extensive lava flows of the Tharsis region. They are related to lava tubes, likely coming from Ascraeus Mons. Image information: VIS instrument. Latitude 22.8, Longitude 266.8 East (93.2 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington

  7. Tractus Catena Collapse Pits

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. These collapse pits are found in graben located in Tractus Catena. These features are related to subsidence after magma chamber evacuation of Alba Patera. Image information: VIS instrument. Latitude 35.8, Longitude 241.7 East (118.3 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science

  8. Nuclear astrophysics at DRAGON

    Energy Technology Data Exchange (ETDEWEB)

    Hager, U. [Colorado School of Mines, Golden, Colorado (United States)

    2014-05-02

    The DRAGON recoil separator is located at the ISAC facility at TRIUMF, Vancouver. It is designed to measure radiative alpha and proton capture reactions of astrophysical importance. Over the last years, the DRAGON collaboration has measured several reactions using both radioactive and high-intensity stable beams. For example, the 160(a, g) cross section was recently measured. The reaction plays a role in steady-state helium burning in massive stars, where it follows the 12C(a, g) reaction. At astrophysically relevant energies, the reaction proceeds exclusively via direct capture, resulting in a low rate. In this measurement, the unique capabilities of DRAGON enabled determination not only of the total reaction rates, but also of decay branching ratios. In addition, results from other recent measurements will be presented.

  9. Astrophysical terms in Armenian

    Science.gov (United States)

    Yeghikian, A. G.

    2015-07-01

    There are quite a few astrophysical textbooks (to say nothing about monographs) in Armenian, which are, however out of date and miss all the modern terms concerning space sciences. Many terms have been earlier adopted from English and, especially, from Russian. On the other hand, teachers and lecturers in Armenia need scientific terms in Armenian adequately reproducing either their means when translating from other languages or (why not) creating new ones. In short, a permanently updated astrophysical glossary is needed to serve as explanation of such terms. I am not going here to present the ready-made glossary (which should be a task for a joint efforts of many professionals) but instead just would like to describe some ambiguous examples with comments where possible coming from my long-year teaching, lecturing and professional experience. A probable connection between "iron" in Armenian as concerned to its origin is also discussed.

  10. CASPAR - Nuclear Astrophysics Underground

    Science.gov (United States)

    Strieder, Frank; Robertson, Daniel; Couder, Manoel; Greife, Uwe; Wells, Doug; Wiescher, Michael

    2015-10-01

    The work of the LUNA Collaboration at the Laboratori Nationali del Gran Sasso demonstrated the research potential of an underground accelerator for the field of nuclear astrophysics. Several key reactions could be studied at LUNA, some directly at the Gamow peak for solar hydrogen burning. The CASPAR (Compact Accelerator System for Performing Astrophysical Research) Collaboration will implement a high intensity 1 MV accelerator at the Sanford Underground Research Facility (SURF) and overcome the current limitation at LUNA. The installation of the accelerator in the recently rehabilitated underground cavity at SURF started in Summer 2015 and first beam should be delivered by the end of the year. This project will primarily focus on the neutron sources for the s-process, e.g. 13C(α , n) 16O and 22Ne(α , n) 25Mg , and lead to unprecedented measurements compared to previous studies. A detailed overview of the science goals of CASPAR will be presented.

  11. Astrophysics a new approach

    CERN Document Server

    Kundt, Wolfgang

    2005-01-01

    For a quantitative understanding of the physics of the universe - from the solar system through the milky way to clusters of galaxies all the way to cosmology - these edited lecture notes are perhaps among the most concise and also among the most critical ones: Astrophysics has not yet stood the redundancy test of laboratory physics, hence should be wary of early interpretations. Special chapters are devoted to magnetic and radiation processes, supernovae, disks, black-hole candidacy, bipolar flows, cosmic rays, gamma-ray bursts, image distortions, and special sources. At the same time, planet earth is viewed as the arena for life, with plants and animals having evolved to homo sapiens during cosmic time. -- This text is unique in covering the basic qualitative and quantitative tools, formulae as well as numbers, needed for the precise interpretation of frontline phenomena in astrophysical research. The author compares mainstream interpretations with new and even controversial ones he wishes to emphasize. The...

  12. Recent Efforts in Data Compilations for Nuclear Astrophysics

    CERN Document Server

    Dillmann, I

    2008-01-01

    Some recent efforts in compiling data for astrophysical purposes are introduced, which were discussed during a JINA-CARINA Collaboration meeting on "Nuclear Physics Data Compilation for Nucleosynthesis Modeling" held at the ECT* in Trento/ Italy from May 29th- June 3rd, 2007. The main goal of this collaboration is to develop an updated and unified nuclear reaction database for modeling a wide variety of stellar nucleosynthesis scenarios. Presently a large number of different reaction libraries (REACLIB) are used by the astrophysics community. The "JINA Reaclib Database" on http://www.nscl.msu.edu/\\~nero/db/ aims to merge and fit the latest experimental stellar cross sections and reaction rate data of various compilations, e.g. NACRE and its extension for Big Bang nucleosynthesis, Caughlan and Fowler, Iliadis et al., and KADoNiS. The KADoNiS (Karlsruhe Astrophysical Database of Nucleosynthesis in Stars, http://nuclear-astrophysics.fzk.de/kadonis) project is an online database for neutron capture cross sections...

  13. Processes in astrophysical fluids. On the occasion of the 60th birthday of Giora Shaviv. Proceedings. International Conference on Astrophysical Fluids: From Atomic Nuclei to Stars and Galaxies, Haifa (Israel), 12 - 15 Jan 1998.

    Science.gov (United States)

    Regev, O.

    1999-04-01

    The following topics were dealt with: nuclear processes, solar neutrino problem, gravity waves and solar neutrino problem, primordial He abundance, radiation processes, fluid dynamics processes, astrophysical jets, advection dominated accretion flows, stellar structure, planetary nebula structure, extrasolar planets, gravitational radiation, interacting binary stars, cataclysmic variables, massive supernovae in binaries, stellar mergers in globular clusters, nova outbursts, extragalactic systems, stellar bars in disk galaxies, Lyman α clouds, massive black holes, quasars, accretion disks, IGM enrichment.

  14. Matter and gravitons in the gravitational collapse

    Directory of Open Access Journals (Sweden)

    Roberto Casadio

    2016-12-01

    Full Text Available We consider the effects of gravitons in the collapse of baryonic matter that forms a black hole. We first note that the effective number of (soft off-shell gravitons that account for the (negative Newtonian potential energy generated by the baryons is conserved and always in agreement with Bekenstein's area law of black holes. Moreover, their (positive interaction energy reproduces the expected post-Newtonian correction and becomes of the order of the total ADM mass of the system when the size of the collapsing object approaches its gravitational radius. This result supports a scenario in which the gravitational collapse of regular baryonic matter produces a corpuscular black hole without central singularity, in which both gravitons and baryons are marginally bound and form a Bose–Einstein condensate at the critical point. The Hawking emission of baryons and gravitons is then described by the quantum depletion of the condensate and we show the two energy fluxes are comparable, albeit negligibly small on astrophysical scales.

  15. Matter and gravitons in the gravitational collapse

    Science.gov (United States)

    Casadio, Roberto; Giugno, Andrea; Giusti, Andrea

    2016-12-01

    We consider the effects of gravitons in the collapse of baryonic matter that forms a black hole. We first note that the effective number of (soft off-shell) gravitons that account for the (negative) Newtonian potential energy generated by the baryons is conserved and always in agreement with Bekenstein's area law of black holes. Moreover, their (positive) interaction energy reproduces the expected post-Newtonian correction and becomes of the order of the total ADM mass of the system when the size of the collapsing object approaches its gravitational radius. This result supports a scenario in which the gravitational collapse of regular baryonic matter produces a corpuscular black hole without central singularity, in which both gravitons and baryons are marginally bound and form a Bose-Einstein condensate at the critical point. The Hawking emission of baryons and gravitons is then described by the quantum depletion of the condensate and we show the two energy fluxes are comparable, albeit negligibly small on astrophysical scales.

  16. Cosmology and astrophysics 1992

    CERN Document Server

    Krauss, L M

    1992-01-01

    I review recent developments in cosmology and astrophysics relevant to particle physics, focussing on the following questions: What's new in 1992? What have we learned since the last ICHEP meeting in 1990? and What are the prospects for the future? AMong the topics explicitly discussed are: COBE, Large Scale Structure, and Dark Matter; Bib Bang Nucleosynthesis; the Solar Neutrino Problem; and High Energy Gamma Ray PHysics.

  17. Inferring Core-Collapse Supernova Physics with Gravitational Waves

    CERN Document Server

    Logue, J; Heng, I S; Kalmus, P; Scargill, J

    2012-01-01

    Stellar collapse and the subsequent development of a core-collapse supernova explosion emit bursts of gravitational waves (GWs) that might be detected by the advanced generation of laser interferometer gravitational-wave observatories such as Advanced LIGO, Advanced Virgo, and LCGT. GW bursts from core-collapse supernovae encode information on the intricate multi-dimensional dynamics at work at the core of a dying massive star and may provide direct evidence for the yet uncertain mechanism driving supernovae in massive stars. Recent multi-dimensional simulations of core-collapse supernovae exploding via the neutrino, magnetorotational, and acoustic explosion mechanisms have predicted GW signals which have distinct structure in both the time and frequency domains. Motivated by this, we describe a promising method for determining the most likely explosion mechanism underlying a hypothetical GW signal, based on Principal Component Analysis and Bayesian model selection. Using simulated Advanced LIGO noise and ass...

  18. Optics in Astrophysics

    CERN Document Server

    Foy, Renaud

    2005-01-01

    Astrophysics is facing challenging aims such as deep cosmology at redshift higher than 10 to constrain cosmology models, or the detection of exoplanets, and possibly terrestrial exoplanets, and several others. It requires unprecedented ambitious R&D programs, which have definitely to rely on a tight cooperation between astrophysics and optics communities. The book addresses most of the most critical interdisciplinary domains where they interact, or where they will do. A first need is to collect more light, i.e. telescopes still larger than the current 8-10 meter class ones. Decametric, and even hectometric, optical (from UV to IR wavelengths) telescopes are being studied. Whereas up to now the light collecting surface of new telescopes was approximately 4 times that of the previous generation, now this factor is growing to 10 to 100. This quantum leap urges to implement new methods or technologies developed in the optics community, both in academic labs and in the industry. Given the astrophysical goals a...

  19. Astrophysical fluid dynamics

    Science.gov (United States)

    Ogilvie, Gordon I.

    2016-06-01

    > These lecture notes and example problems are based on a course given at the University of Cambridge in Part III of the Mathematical Tripos. Fluid dynamics is involved in a very wide range of astrophysical phenomena, such as the formation and internal dynamics of stars and giant planets, the workings of jets and accretion discs around stars and black holes and the dynamics of the expanding Universe. Effects that can be important in astrophysical fluids include compressibility, self-gravitation and the dynamical influence of the magnetic field that is `frozen in' to a highly conducting plasma. The basic models introduced and applied in this course are Newtonian gas dynamics and magnetohydrodynamics (MHD) for an ideal compressible fluid. The mathematical structure of the governing equations and the associated conservation laws are explored in some detail because of their importance for both analytical and numerical methods of solution, as well as for physical interpretation. Linear and nonlinear waves, including shocks and other discontinuities, are discussed. The spherical blast wave resulting from a supernova, and involving a strong shock, is a classic problem that can be solved analytically. Steady solutions with spherical or axial symmetry reveal the physics of winds and jets from stars and discs. The linearized equations determine the oscillation modes of astrophysical bodies, as well as their stability and their response to tidal forcing.

  20. Integrating Out Astrophysical Uncertainties

    CERN Document Server

    Fox, Patrick J; Weiner, Neal

    2010-01-01

    Underground searches for dark matter involve a complicated interplay of particle physics, nuclear physics, atomic physics and astrophysics. We attempt to remove the uncertainties associated with astrophysics by developing the means to map the observed signal in one experiment directly into a predicted rate at another. We argue that it is possible to make experimental comparisons that are completely free of astrophysical uncertainties by focusing on {\\em integral} quantities, such as $g(v_{min})=\\int_{v_{min}} dv\\, f(v)/v $ and $\\int_{v_{thresh}} dv\\, v g(v)$. Direct comparisons are possible when the $v_{min}$ space probed by different experiments overlap. As examples, we consider the possible dark matter signals at CoGeNT, DAMA and CRESST-Oxygen. We find that expected rate from CoGeNT in the XENON10 experiment is higher than observed, unless scintillation light output is low. Moreover, we determine that S2-only analyses are constraining, unless the charge yield $Q_y< 2.4 {\\, \\rm electrons/keV}$. For DAMA t...

  1. Collisions of Dark Matter Axion Stars with Astrophysical Sources

    Energy Technology Data Exchange (ETDEWEB)

    Eby, Joshua [Fermilab; Leembruggen, Madelyn [Cincinnati U.; Leeney, Joseph [Cincinnati U.; Suranyi, Peter [Cincinnati U.; Wijewardhana, L. C.R. [Cincinnati U.

    2017-01-05

    If QCD axions form a large fraction of the total mass of dark matter, then axion stars could be very abundant in galaxies. As a result, collisions with each other, and with other astrophysical bodies, can occur. We calculate the rate and analyze the consequences of three classes of collisions, those occurring between a dilute axion star and: another dilute axion star, an ordinary star, or a neutron star. In all cases we attempt to quantify the most important astrophysical uncertainties; we also pay particular attention to scenarios in which collisions lead to collapse of otherwise stable axion stars, and possible subsequent decay through number changing interactions. Collisions between two axion stars can occur with a high total rate, but the low relative velocity required for collapse to occur leads to a very low total rate of collapses. On the other hand, collisions between an axion star and an ordinary star have a large rate, $\\Gamma_\\odot \\sim 3000$ collisions/year/galaxy, and for sufficiently heavy axion stars, it is plausible that most or all such collisions lead to collapse. We identify in this case a parameter space which has a stable region and a region in which collision triggers collapse, which depend on the axion number ($N$) in the axion star, and a ratio of mass to radius cubed characterizing the ordinary star ($M_s/R_s^3$). Finally, we revisit the calculation of collision rates between axion stars and neutron stars, improving on previous estimates by taking cylindrical symmetry of the neutron star distribution into account. Collapse and subsequent decay through collision processes, if occurring with a significant rate, can affect dark matter phenomenology and the axion star mass distribution.

  2. Photometric entropy of stellar populations and related diagnostic tools

    CERN Document Server

    Buzzoni, A

    2005-01-01

    We discuss, from a statistical point of view, some leading issues that deal with the study of stellar populations in fully or partially unresolved aggregates, like globular clusters and distant galaxies. A confident assessment of the effective number and luminosity of stellar contributors can provide, in this regard, a very useful interpretative tool to properly assess the observational bias coming from crowding conditions or surface brightness fluctuations. These arguments have led us to introduce a new concept of "photometric entropy" of a stellar population, whose impact on different astrophysical aspects of cluster diagnostic has been reviewed here.

  3. Plasma physics of extreme astrophysical environments.

    Science.gov (United States)

    Uzdensky, Dmitri A; Rightley, Shane

    2014-03-01

    Among the incredibly diverse variety of astrophysical objects, there are some that are characterized by very extreme physical conditions not encountered anywhere else in the Universe. Of special interest are ultra-magnetized systems that possess magnetic fields exceeding the critical quantum field of about 44 TG. There are basically only two classes of such objects: magnetars, whose magnetic activity is manifested, e.g., via their very short but intense gamma-ray flares, and central engines of supernovae (SNe) and gamma-ray bursts (GRBs)--the most powerful explosions in the modern Universe. Figuring out how these complex systems work necessarily requires understanding various plasma processes, both small-scale kinetic and large-scale magnetohydrodynamic (MHD), that govern their behavior. However, the presence of an ultra-strong magnetic field modifies the underlying basic physics to such a great extent that relying on conventional, classical plasma physics is often not justified. Instead, plasma-physical problems relevant to these extreme astrophysical environments call for constructing relativistic quantum plasma (RQP) physics based on quantum electrodynamics (QED). In this review, after briefly describing the astrophysical systems of interest and identifying some of the key plasma-physical problems important to them, we survey the recent progress in the development of such a theory. We first discuss the ways in which the presence of a super-critical field modifies the properties of vacuum and matter and then outline the basic theoretical framework for describing both non-relativistic and RQPs. We then turn to some specific astrophysical applications of relativistic QED plasma physics relevant to magnetar magnetospheres and to central engines of core-collapse SNe and long GRBs. Specifically, we discuss the propagation of light through a magnetar magnetosphere; large-scale MHD processes driving magnetar activity and responsible for jet launching and propagation in

  4. Plasma physics of extreme astrophysical environments

    Science.gov (United States)

    Uzdensky, Dmitri A.; Rightley, Shane

    2014-03-01

    Among the incredibly diverse variety of astrophysical objects, there are some that are characterized by very extreme physical conditions not encountered anywhere else in the Universe. Of special interest are ultra-magnetized systems that possess magnetic fields exceeding the critical quantum field of about 44 TG. There are basically only two classes of such objects: magnetars, whose magnetic activity is manifested, e.g., via their very short but intense gamma-ray flares, and central engines of supernovae (SNe) and gamma-ray bursts (GRBs)—the most powerful explosions in the modern Universe. Figuring out how these complex systems work necessarily requires understanding various plasma processes, both small-scale kinetic and large-scale magnetohydrodynamic (MHD), that govern their behavior. However, the presence of an ultra-strong magnetic field modifies the underlying basic physics to such a great extent that relying on conventional, classical plasma physics is often not justified. Instead, plasma-physical problems relevant to these extreme astrophysical environments call for constructing relativistic quantum plasma (RQP) physics based on quantum electrodynamics (QED). In this review, after briefly describing the astrophysical systems of interest and identifying some of the key plasma-physical problems important to them, we survey the recent progress in the development of such a theory. We first discuss the ways in which the presence of a super-critical field modifies the properties of vacuum and matter and then outline the basic theoretical framework for describing both non-relativistic and RQPs. We then turn to some specific astrophysical applications of relativistic QED plasma physics relevant to magnetar magnetospheres and to central engines of core-collapse SNe and long GRBs. Specifically, we discuss the propagation of light through a magnetar magnetosphere; large-scale MHD processes driving magnetar activity and responsible for jet launching and propagation in

  5. Growth cone collapse assay.

    Science.gov (United States)

    Cook, Geoffrey M W; Jareonsettasin, Prem; Keynes, Roger J

    2014-01-01

    The growth cone collapse assay has proved invaluable in detecting and purifying axonal repellents. Glycoproteins/proteins present in detergent extracts of biological tissues are incorporated into liposomes, added to growth cones in culture and changes in morphology are then assessed. Alternatively purified or recombinant molecules in aqueous solution may be added directly to the cultures. In both cases after a defined period of time (up to 1 h), the cultures are fixed and then assessed by inverted phase contrast microscopy for the percentage of growth cones showing a collapsed profile with loss of flattened morphology, filopodia, and lamellipodia.

  6. Astrophysical and cosmological doomsdays

    CERN Document Server

    Tavakoli, Yaser

    2014-01-01

    In this dissertation we study two well known gravitational scenarios in which singularities may appear; the final state of gravitational collapse and the late time evolution of the universe. In the first scenario, we study a spherically symmetric space-time whose matter content includes a tachyon scalar field and a barotropic fluid. By employing a dynamical system analysis, we find classical solutions corresponding to a naked singularity or a black hole formation. We then investigate, in a semiclassical manner, loop quantum gravity induced effects on the fate of the classical singularities. By employing an inverse triad correction, we identify a subset which corresponds to an outward flux of energy, thus avoiding either a naked singularity or a black hole formation. Within a holonomy correction, we obtain the semiclassical counterpart of our (classical) general relativistic collapse in which, classical singularity is resolved and replaced by a bounce. In addition, we find a threshold scale for non-singular bl...

  7. {alpha}-{alpha} interaction reexamined in the context of the Sao Paulo potential: possible applications in astrophysics?

    Energy Technology Data Exchange (ETDEWEB)

    Gasques, L.R.; Chamon, L.C.; Botero, D.F.M. [Universidade de Sao Paulo (DFN/USP), SP (Brazil). Dept. de Fisica Nuclear; Alves, L.F.M. [Instituto Federal de Educacao, Ciencia e Tecnologia (Brazil); Carlson, B.V. [Instituto Tecnologico de Aeronautica (CTA/ITA), Sao Jose dos Campos, SP (Brazil). Dept. de Fisica Nuclear; Rossi Junior, E.S. [Centro Universitario FIEO(UNIFIEO), SP (Brazil)

    2012-07-01

    Full text: We have analyzed a large set of {alpha}-{alpha} elastic scattering data for bombarding energies ranging from 0.6 to 29.5 MeV. The complete lack of open reaction channels at these somehow low energies results in a vanishing imaginary part for the optical interaction. This characteristic makes the {alpha}-{alpha} reaction particularly interesting as the corresponding elastic scattering cross sections and phase shifts become very sensitive to the real part of the interaction. The data were analyzed within the context of the velocity-dependent Sao Paulo potential, which is a successful theoretical model for the description of heavy-ion reactions from sub-barrier to intermediate energies. We have shown that, even in this low energy region, the velocity dependence of the Sao Paulo potential model is a necessary ingredient for describing the data. Despite the reasonable description obtained with the Sao Paulo potential, the analyses indicate the necessity of an additional weak dependence of the interaction on the angular momentum. These important characteristics open the possibility for studying reactions with astrophysical interested. In particular, predictions of the astrophysical S-factor for the {sup 12}C({alpha},{gamma}) reaction will be presented. The understanding of the reaction rate for the {alpha}-capture process by a {sup 12}C nucleus is a crucial ingredient for predicting the stellar helium burning and the subsequent fate of stars as this reaction determines the ratio of carbon to oxygen towards the end of the Red Giants phase. It is well known that low mass stars evolve to White Dwarfs and this ratio determines the final abundance composition in White Dwarf matter and sets the trigger conditions for type Ia supernova explosions. The carbon-oxygen ratio also dictates the subsequent sequence of burning processes during the final stages of stellar evolution for massive stars. Thus, it has a key role in the determination of the abundance composition in

  8. Goddard's Astrophysics Science Divsion Annual Report 2014

    Science.gov (United States)

    Weaver, Kimberly (Editor); Reddy, Francis (Editor); Tyler, Pat (Editor)

    2015-01-01

    The Astrophysics Science Division (ASD, Code 660) is one of the world's largest and most diverse astronomical organizations. Space flight missions are conceived, built and launched to observe the entire range of the electromagnetic spectrum, from gamma rays to centimeter waves. In addition, experiments are flown to gather data on high-energy cosmic rays, and plans are being made to detect gravitational radiation from space-borne missions. To enable these missions, we have vigorous programs of instrument and detector development. Division scientists also carry out preparatory theoretical work and subsequent data analysis and modeling. In addition to space flight missions, we have a vibrant suborbital program with numerous sounding rocket and balloon payloads in development or operation. The ASD is organized into five labs: the Astroparticle Physics Lab, the X-ray Astrophysics Lab, the Gravitational Astrophysics Lab, the Observational Cosmology Lab, and the Exoplanets and Stellar Astrophysics Lab. The High Energy Astrophysics Science Archive Research Center (HEASARC) is an Office at the Division level. Approximately 400 scientists and engineers work in ASD. Of these, 80 are civil servant scientists, while the rest are resident university-based scientists, contractors, postdoctoral fellows, graduate students, and administrative staff. We currently operate the Swift Explorer mission and the Fermi Gamma-ray Space Telescope. In addition, we provide data archiving and operational support for the XMM mission (jointly with ESA) and the Suzaku mission (with JAXA). We are also a partner with Caltech on the NuSTAR mission. The Hubble Space Telescope Project is headquartered at Goddard, and ASD provides Project Scientists to oversee operations at the Space Telescope Science Institute. Projects in development include the Neutron Interior Composition Explorer (NICER) mission, an X-ray timing experiment for the International Space Station; the Transiting Exoplanet Sky Survey (TESS

  9. Nuclear astrophysics with secondary (radioactive) beams

    CERN Document Server

    Gai, M

    1995-01-01

    Some problems in nuclear astrophysics are discussed with emphasize on the ones central to the field which were not solved over the last two decades, including Helium Burning in Massive stars (the 12C(a,g)16O reaction) and the 8B Solar Neutrino Flux Problem (the 7Be(p,g)8B reaction). We demonstrate that a great deal of progress was achieved by measuring the time reverse process(es): the beta-delayed alpha-particle emission of 16N and the Coulomb dissociation of 8B, using radioactive beams (of 16N and 8B). In this way an amplification of the sought for cross section was achieved, allowing a measurement of the small cross section(s) of relevance for stellar (solar) process(es).

  10. Maser Radiation in an Astrophysical Context (Overview)

    CERN Document Server

    Gentry, Eric S

    2013-01-01

    In this paper we will look at the phenomenon of Microwave Amplification by Stimulated Emission of Radiation (a maser system). We begin by deriving amplification by stimulated emission using time-dependent perturbation theory, in which the perturbation provided by external radiation. When this perturbation is applied to an ensemble of particles exhibiting a population inversion, the result is stimulated microwave radiation. We will explore both unsaturated and saturated masers and compare their properties. By understanding their gain, as well as the effect of line broadening, astronomers are to identify astrophysical masers. By studying such masers, we gain new insight into poorly understood physical environments, particularly those around young and old stars, and compact stellar bodies.

  11. VI European Summer School on Experimental Nuclear Astrophysics

    Science.gov (United States)

    The European Summer School on Experimental Nuclear Astrophysics has reached the sixth edition, marking the tenth year's anniversary. The spirit of the school is to provide a very important occasion for a deep education of young researchers about the main topics of experimental nuclear astrophysics. Moreover, it should be regarded as a forum for the discussion of the last-decade research activity. Lectures are focused on various aspects of primordial and stellar nucleosynthesis, including novel experimental approaches and detectors, indirect methods and radioactive ion beams. Moreover, in order to give a wide educational offer, some lectures cover complementary subjects of nuclear astrophysics such as gamma ray astronomy, neutron-induced reactions, short-lived radionuclides, weak interaction and cutting-edge facilities used to investigate nuclear reactions of interest for astrophysics. Large room is also given to young researcher oral contributions. Traditionally, particular attention is devoted to the participation of students from less-favoured countries, especially from the southern coast of the Mediterranean Sea. The school is organised by the Catania Nuclear Astrophysics research group with the collaboration of Dipartimento di Fisica e Astromomia - Università di Catania and Laboratori Nazionali del Sud - Istituto Nazionale di Fisica Nucleare.

  12. The molecular universe: from astronomy to laboratory astrophysics and back

    Science.gov (United States)

    van Dishoeck, Ewine

    2015-08-01

    Molecules are found in a wide range of astronomical environments, fromour Solar System to distant starburst galaxies at the highest redshifts. Thanks to the opening up of the infrared and (sub)millimeter wavelength regime, culminating with Herschel and ALMA, more than 180 different species have now been found throughout the various stages of stellar birth and death: diffuse and dense interstellar clouds, protostars and disks, the envelopes of evolved stars and planetary nebulae, and exo-planetary atmospheres. Molecules and solid-state features are now also routinely detected in the interstellar medium of external galaxies, near and far.There are many motivations for studying this molecular universe. From the chemical perspective, interstellar space provides a unique laboratory to study basic molecular processes under very different conditions from those normally found in a laboratory on Earth. For astronomers, molecules are unique probes of the many environments where they are found, providing information on density, temperature, dynamics, ionization fractions and magnetic fields. Molecules also play an important role in the cooling of clouds allowing them to collapse, including the formation of the very first stars and galaxies. Finally, the molecular composition is sensitive to the history of the material, and ultimately provides critical information on our origins.This talk will summarize a number of recent observational highlights and provide examples of cases where the availability of new laboratory data proved crucial in the analysis. This includes basic data such as spectroscopy and collisional rate coefficients, but also an improved understanding of photoprocesses in the gaseous and solid state. Much of the chemistry in star- and planet-forming regions is now thought to be driven by gas-grain chemistry rather than pure gas-phase chemistry, and a few examples of the close link between models and laboratory experiments will be given. In spite of lingering

  13. General relativity and relativistic astrophysics

    CERN Document Server

    Mukhopadhyay, Banibrata

    2016-01-01

    Einstein established the theory of general relativity and the corresponding field equation in 1915 and its vacuum solutions were obtained by Schwarzschild and Kerr for, respectively, static and rotating black holes, in 1916 and 1963, respectively. They are, however, still playing an indispensable role, even after 100 years of their original discovery, to explain high energy astrophysical phenomena. Application of the solutions of Einstein's equation to resolve astrophysical phenomena has formed an important branch, namely relativistic astrophysics. I devote this article to enlightening some of the current astrophysical problems based on general relativity. However, there seem to be some issues with regard to explaining certain astrophysical phenomena based on Einstein's theory alone. I show that Einstein's theory and its modified form, both are necessary to explain modern astrophysical processes, in particular, those related to compact objects.

  14. Rydberg atoms in astrophysics

    CERN Document Server

    Gnedin, Yu N; Ignjatovic, Lj M; Sakan, N M; Sreckovic, V A; Zakharov, M Yu; Bezuglov, N N; Klycharev, A N; 10.1016/j.newar.2009.07.003

    2012-01-01

    Elementary processes in astrophysical phenomena traditionally attract researchers attention. At first this can be attributed to a group of hemi-ionization processes in Rydberg atom collisions with ground state parent atoms. This processes might be studied as a prototype of the elementary process of the radiation energy transformation into electrical one. The studies of nonlinear mechanics have shown that so called regime of dynamic chaos should be considered as typical, rather than exceptional situation in Rydberg atoms collision. From comparison of theory with experimental results it follows that a such kind of stochastic dynamic processes, occurred during the single collision, may be observed.

  15. Investigating High Field Gravity using Astrophysical Techniques

    Energy Technology Data Exchange (ETDEWEB)

    Bloom, Elliott D.; /SLAC

    2008-02-01

    The purpose of these lectures is to introduce particle physicists to astrophysical techniques. These techniques can help us understand certain phenomena important to particle physics that are currently impossible to address using standard particle physics experimental techniques. As the subject matter is vast, compromises are necessary in order to convey the central ideas to the reader. Many general references are included for those who want to learn more. The paragraphs below elaborate on the structure of these lectures. I hope this discussion will clarify my motivation and make the lectures easier to follow. The lectures begin with a brief review of more theoretical ideas. First, elements of general relativity are reviewed, concentrating on those aspects that are needed to understand compact stellar objects (white dwarf stars, neutron stars, and black holes). I then review the equations of state of these objects, concentrating on the simplest standard models from astrophysics. After these mathematical preliminaries, Sec. 2(c) discusses 'The End State of Stars'. Most of this section also uses the simplest standard models. However, as these lectures are for particle physicists, I also discuss some of the more recent approaches to the equation of state of very dense compact objects. These particle-physics-motivated equations of state can dramatically change how we view the formation of black holes. Section 3 focuses on the properties of the objects that we want to characterize and measure. X-ray binary systems and Active Galactic Nuclei (AGN) are stressed because the lectures center on understanding very dense stellar objects, black hole candidates (BHCs), and their accompanying high gravitational fields. The use of x-ray timing and gamma-ray experiments is also introduced in this section. Sections 4 and 5 review information from x-ray and gamma-ray experiments. These sections also discuss the current state of the art in x-ray and gamma-ray satellite

  16. Astrophysics with Extraterrestrial Materials

    Science.gov (United States)

    Nittler, Larry R.; Ciesla, Fred

    2016-09-01

    Extraterrestrial materials, including meteorites, interplanetary dust, and spacecraft-returned asteroidal and cometary samples, provide a record of the starting materials and early evolution of the Solar System. We review how laboratory analyses of these materials provide unique information, complementary to astronomical observations, about a wide variety of stellar, interstellar and protoplanetary processes. Presolar stardust grains retain the isotopic compositions of their stellar sources, mainly asymptotic giant branch stars and Type II supernovae. They serve as direct probes of nucleosynthetic and dust formation processes in stars, galactic chemical evolution, and interstellar dust processing. Extinct radioactivities suggest that the Sun's birth environment was decoupled from average galactic nucleosynthesis for some tens to hundreds of Myr but was enriched in short-lived isotopes from massive stellar winds or explosions shortly before or during formation of the Solar System. Radiometric dating of meteorite components tells us about the timing and duration over which solar nebula solids were assembled into the building blocks of the planets. Components of the most primitive meteoritical materials provide further detailed constraints on the formation, processing, and transport of material and associated timescales in the Sun's protoplanetary disk as well as in other forming planetary systems.

  17. Dancing building prevents collapse

    NARCIS (Netherlands)

    Visscher, R.

    2007-01-01

    In future, anybody caught inside a building during an earthquake need no longer fear the roof collapsing on them. Thanks to the use of composite materials, all the building will do is dance along, riding the waves of the earthquake. At least, according to Professor Ir. Adriaan Beukers of the Aerospa

  18. Scapholunate advanced collapse.

    Science.gov (United States)

    Pomeranz, Stephen J; Salazar, Peter

    2015-01-01

    This case study reviews the pathophysiology of scapholunate advanced collapse (SLAC), which is the most common etiology of degenerative arthritis in the wrist. The scapholunate ligament serves a critical role in stability of the carpus. Disruption of the scapholunate ligament, its sequela, and the magnetic resonance imaging evaluation are discussed, with review of the defining features of this disease and its progression.

  19. Impact Crater Collapse

    Science.gov (United States)

    Melosh, H. J.; Ivanov, B. A.

    The detailed morphology of impact craters is now believed to be mainly caused by the collapse of a geometrically simple, bowl-shaped "transient crater." The transient crater forms immediately after the impact. In small craters, those less than approximately 15 km diameter on the Moon, the steepest part of the rim collapses into the crater bowl to produce a lens of broken rock in an otherwise unmodified transient crater. Such craters are called "simple" and have a depth-to-diameter ratio near 1:5. Large craters collapse more spectacularly, giving rise to central peaks, wall terraces, and internal rings in still larger craters. These are called "complex" craters. The transition between simple and complex craters depends on 1/g, suggesting that the collapse occurs when a strength threshold is exceeded. The apparent strength, however, is very low: only a few bars, and with little or no internal friction. This behavior requires a mechanism for temporary strength degradation in the rocks surrounding the impact site. Several models for this process, including acoustic fluidization and shock weakening, have been considered by recent investigations. Acoustic fluidization, in particular, appears to produce results in good agreement with observations, although better understanding is still needed.

  20. Collapsible Geostrut Structure

    Science.gov (United States)

    Robertson, Glen A.

    1994-01-01

    Portable truss structure collapsible into smaller volume for storage and transportation. At new site, reerected quickly, without need to reassemble parts. Structure could be tent, dome, tunnel, or platform. Key element in structure joint, called "geostrut joint," includes internal cable. Structure is network of struts attached to geostrut joints. Pulling cables taut in all joints makes structure rigid. Releasing cables relaxes structure.

  1. Nuclear Cluster Aspects in Astrophysics

    Science.gov (United States)

    Kubono, Shigeru

    2010-03-01

    The role of nuclear clustering is discussed for nucleosynthesis in stellar evolution with Cluster Nucleosynthesis Diagram (CND) proposed before. Special emphasis is placed on α-induced stellar reactions together with molecular states for O and C burning.

  2. Core-Collapse Supernovae: Modeling between Pragmatism and Perfectionism

    CERN Document Server

    Janka, H T; Kitaura Joyanes, F S; Marek, A; Rampp, M

    2004-01-01

    We briefly summarize recent efforts in Garching for modeling stellar core collapse and post-bounce evolution in one and two dimensions. The transport of neutrinos of all flavors is treated by iteratively solving the coupled system of frequency-dependent moment equations together with a model Boltzmann equation which provides the closure. A variety of progenitor stars, different nuclear equations of state, stellar rotation, and global asymmetries due to large-mode hydrodynamic instabilities have been investigated to ascertain the road to finally successful, convectively supported neutrino-driven explosions.

  3. High Energy Astrophysics Program (HEAP)

    Science.gov (United States)

    Angelini, Lorella; Corcoran, Michael; Drake, Stephen; McGlynn, Thomas A.; Snowden, Stephen; Mukai, Koji; Cannizzo, John; Lochner, James; Rots, Arnold; Christian, Eric; Barthelmy, Scott; Palmer, David; Mitchell, John; Esposito, Joseph; Sreekumar, P.; Hua, Xin-Min; Mandzhavidze, Natalie; Chan, Kai-Wing; Soong, Yang; Barrett, Paul

    1998-01-01

    This report reviews activities performed by the members of the USRA contract team during the 6 months of the reporting period and projected activities during the coming 6 months. Activities take place at the Goddard Space Flight Center, within the Laboratory for High Energy Astrophysics. Developments concern instrumentation, observation, data analysis, and theoretical work in astrophysics. Supported missions include advanced Satellite for Cosmology and Astrophysics (ASCA), X-Ray Timing Experiment (XTE), X-Ray Spectrometer (XRS), Astro-E, High Energy Astrophysics Science Archive Research Center (HEASARC) and others.

  4. Improving 1D Stellar Models with 3D Atmospheres

    CERN Document Server

    Mosumgaard, Jakob Rørsted; Weiss, Achim; Christensen-Dalsgaard, Jørgen; Trampedach, Regner

    2016-01-01

    Stellar evolution codes play a major role in present-day astrophysics, yet they share common issues. In this work we seek to remedy some of those by the use of results from realistic and highly detailed 3D hydrodynamical simulations of stellar atmospheres. We have implemented a new temperature stratification extracted directly from the 3D simulations into the Garching Stellar Evolution Code to replace the simplified atmosphere normally used. Secondly, we have implemented the use of a variable mixing-length parameter, which changes as a function of the stellar surface gravity and temperature -- also derived from the 3D simulations. Furthermore, to make our models consistent, we have calculated new opacity tables to match the atmospheric simulations. Here, we present the modified code and initial results on stellar evolution using it.

  5. Neoclassical impurity transport in stellarator geometry

    CERN Document Server

    García-Regaña, J M; Beidler, C D; berg, H Maaß; Helander, P; Turkin, Y

    2012-01-01

    The impurity dynamics in stellarators has become an issue of moderate concern due to the, \\textit{a priori}, inherent tendency of the impurities to accumulate in the core when the neoclassical ambipolar radial electric field points radially inwards (ion root regime). This accumulation can lead to collapse of the plasma due to radiative losses, and thus limit high performance plasma discharges in non-axisymmetric devices. Theoretically, a quantitative description of the neoclassical impurity transport is complicated by the breakdown of the assumption of small $q \\tilde{\\Phi}/T$ for impurities, where $q$ is the electric charge, $T$ the temperature in energy units, and $\\tilde{\\Phi}$ the electrostatic potential variation within the flux surface. The present work describes quantitatively the particle transport of impurities in the frame of local neoclassical theory when $q\\tilde{\\Phi}/T=O(1)$ in the Large Helical Device (LHD) stellarator. %and the Wendelstein 7-X stellarators. The central numerical tool used is t...

  6. Electron capture cross sections for stellar nucleosynthesis

    CERN Document Server

    Giannaka, P G

    2015-01-01

    In the first stage of this work, we perform detailed calculations for the cross sections of the electron capture on nuclei under laboratory conditions. Towards this aim we exploit the advantages of a refined version of the proton-neutron quasi-particle random-phase approximation (pn-QRPA) and carry out state-by-state evaluations of the rates of exclusive processes that lead to any of the accessible transitions within the chosen model space. In the second stage of our present study, we translate the above mentioned $e^-$-capture cross sections to the stellar environment ones by inserting the temperature dependence through a Maxwell-Boltzmann distribution describing the stellar electron gas. As a concrete nuclear target we use the $^{66}Zn$ isotope, which belongs to the iron group nuclei and plays prominent role in stellar nucleosynthesis at core collapse supernovae environment.

  7. The Radiative Tail of Realistic Gravitational Collapse

    CERN Document Server

    Hod, S

    2000-01-01

    An astrophysically realistic model of wave dynamics in black-hole spacetimes must involve a {\\it non}-spherical background geometry with {\\it angular momentum}. We consider the evolution of {\\it gravitational} (and electromagnetic) perturbations in {\\it rotating} Kerr spacetimes. We show that a rotating Kerr black hole becomes ``bald'' {\\it slower} than the corresponding spherically-symmetric Schwarzschild black hole. Moreover, our results {\\it turn over} the traditional belief (which has been widely accepted during the last three decades) that the late-time tail of gravitational collapse is universal. In particular, we show that different fields have {\\it different} decaying rates. Our results are also of importance both to the study of the no-hair conjecture and the mass-inflation scenario (stability of Cauchy horizons).

  8. Collapse in the Endurance Athlete

    Institute of Scientific and Technical Information of China (English)

    Robert Sallis

    2005-01-01

    @@ KEY POINTS · Most cases of collapse are benign in nature and occur after an athlete crosses the finish line or stops exercising. Athletes who collapse before finishing are more likely to have a serious condition.

  9. Shock induced cavity collapse

    Science.gov (United States)

    Skidmore, Jonathan; Doyle, Hugo; Tully, Brett; Betney, Matthew; Foster, Peta; Ringrose, Tim; Ramasamy, Rohan; Parkin, James; Edwards, Tom; Hawker, Nicholas

    2016-10-01

    Results from the experimental investigation of cavity collapse driven by a strong planar shock (>6km/s) are presented. Data from high speed framing cameras, laser backlit diagnostics and time-resolved pyromety are used to validate the results of hydrodynamic front-tracking simulations. As a code validation exercise, a 2-stage light gas gun was used to accelerate a 1g Polycarbonate projectile to velocities exceeding 6km/s; impact with a PMMA target containing a gas filled void results in the formation of a strong shockwave with pressures exceeding 1Mbar. The subsequent phenomena associated with the collapse of the void and excitation of the inert gas fill are recorded and compared to simulated data. Variation of the mass density and atomic number of the gas fill is used to alter the plasma parameters furthering the extent of the code validation.

  10. Rigid collapsible dish structure

    Science.gov (United States)

    Palmer, William B. (Inventor); Giebler, Martin M. (Inventor)

    1982-01-01

    A collapsible dish structure composed of a plurality of rows of rigid radial petal assemblies concentric with the axis of the dish. The petal assemblies consist of a center petal and two side petals, the center petal hinged on an axis tangent to a circle concentric with the axis of the dish and the side petals hinged to the center petal at their mating edge. The center petal is foldable inwardly and the side petals rotate about their hinges such that the collapsed dish structure occupies a much smaller volume than the deployed dish. Means of controlling the shape of the dish to compensate for differential expansion of the deployed dish are also provided.

  11. Inhomogeneous electromagnetic gravitational collapse

    Energy Technology Data Exchange (ETDEWEB)

    Stein-Schabes, J.A.

    1985-04-15

    The collapse of an inhomogeneous dust cloud in the presence of an electromagnetic field is investigated in detail. The possibility of a naked singularity arising is studied using some known solutions for a spherical charged inhomogeneous dust cloud. It is found that locally naked singularities may develop when the arbitrary functions in the solution are chosen in a special way, but that a global naked singularity will not form. Also the role of the electromagnetic pressure is discussed.

  12. Essential Magnetohydrodynamics for Astrophysics

    CERN Document Server

    Spruit, H C

    2013-01-01

    This text is intended as an introduction to magnetohydrodynamics in astrophysics, emphasizing a fast path to the elements essential for physical understanding. It assumes experience with concepts from fluid mechanics: the fluid equation of motion and the Lagrangian and Eulerian descriptions of fluid flow. In addition, the basics of vector calculus and elementary special relativity are needed. Not much knowledge of electromagnetic theory is required. In fact, since MHD is much closer in spirit to fluid mechanics than to electromagnetism, an important part of the learning curve is to overcome intuitions based on the vacuum electrodynamics of one's high school days. The first chapter (only 36 pp) is meant as a practical introduction including exercises. This is the `essential' part. The exercises are important as illustrations of the points made in the text (especially the less intuitive ones). Almost all are mathematically unchallenging. The supplement in chapter 2 contains further explanations, more specialize...

  13. Basics of plasma astrophysics

    CERN Document Server

    Chiuderi, Claudio

    2015-01-01

    This book is an introduction to contemporary plasma physics that discusses the most relevant recent advances in the field and covers a careful choice of applications to various branches of astrophysics and space science. The purpose of the book is to allow the student to master the basic concepts of plasma physics and to bring him or her up to date in a number of relevant areas of current research. Topics covered include orbit theory, kinetic theory, fluid models, magnetohydrodynamics, MHD turbulence, instabilities, discontinuities, and magnetic reconnection. Some prior knowledge of classical physics is required, in particular fluid mechanics, statistical physics, and electrodynamics. The mathematical developments are self-contained and explicitly detailed in the text. A number of exercises are provided at the end of each chapter, together with suggestions and solutions.

  14. High energy astrophysical techniques

    CERN Document Server

    Poggiani, Rosa

    2017-01-01

    This textbook presents ultraviolet and X-ray astronomy, gamma-ray astronomy, cosmic ray astronomy, neutrino astronomy, and gravitational wave astronomy as distinct research areas, focusing on the astrophysics targets and the requirements with respect to instrumentation and observation methods. The purpose of the book is to bridge the gap between the reference books and the specialized literature. For each type of astronomy, the discussion proceeds from the orders of magnitude for observable quantities. The physical principles of photon and particle detectors are then addressed, and the specific telescopes and combinations of detectors, presented. Finally the instruments and their limits are discussed with a view to assisting readers in the planning and execution of observations. Astronomical observations with high-energy photons and particles represent the newest additions to multimessenger astronomy and this book will be of value to all with an interest in the field.

  15. Optical coherence in astrophysics

    CERN Document Server

    Moret-Bailly, Jacques

    2013-01-01

    Many physicists and most astrophysicists assume that the photon is a small particle which, in a very low pressure gas can only interact with a single molecule. Thus, the interaction of light with this gas is incoherent. W. E.Lamb Jr, W. P. Schleich, M. O. Scully and C. H. Townes (Reviews of Modern Physics 71, S263, 1999) have criticized this view: In accordance with quantum electrodynamics the photon is a pseudo-particle resulting from the quantization of a deterministic exchange of energy between identical molecules and a normal mode of electromagnetic field. Following Lamb et al., we study models in which some variables have an unusual value for a spectroscopist: extremely low pressure hydrogen, but huge light paths, extremely hot sources. However, the magnitudes of the spectral radiances and column densities can be similar in astrophysics and in a laboratory using lasers. Thus, several coherent effects must be taken into account: superradiance, multiphoton interactions, impulsive stimulated Raman scatterin...

  16. NASA's Astrophysics Data Archives

    Science.gov (United States)

    Hasan, H.; Hanisch, R.; Bredekamp, J.

    2000-09-01

    The NASA Office of Space Science has established a series of archival centers where science data acquired through its space science missions is deposited. The availability of high quality data to the general public through these open archives enables the maximization of science return of the flight missions. The Astrophysics Data Centers Coordinating Council, an informal collaboration of archival centers, coordinates data from five archival centers distiguished primarily by the wavelength range of the data deposited there. Data are available in FITS format. An overview of NASA's data centers and services is presented in this paper. A standard front-end modifyer called `Astrowbrowse' is described. Other catalog browsers and tools include WISARD and AMASE supported by the National Space Scince Data Center, as well as ISAIA, a follow on to Astrobrowse.

  17. Astrophysics Faces the Millennium

    Science.gov (United States)

    Trimble, Virginia

    2001-03-01

    The Medieval synthesis of Aristotelian philosophy and church doctrine, due largely to Thomas Aquinas, insisted that the universe outside the earth's atmosphere must be immutable, single-centered, fully inventoried, immaculate or perfect, including perfectly spherical, and much else that sounds strange to modern ears. The beginnings of modern astronomy can be largely described as the overthrow of these various concepts by a combination of new technologies and new ways of thinking, and many current questions in astrophysics can be directly tied to developments of those same concepts. Indeed they probably all can be, but not over time, ending with questions like: Do other stars have spots? What does it mean when quasar jets look like they are moving faster than the speed of light? Is there anything special about our star, our galaxy, our planet, or our universe? How did these all form, and what is their long-term fate?

  18. Exotic nuclei and astrophysics

    Directory of Open Access Journals (Sweden)

    Penionzhkevich Yu.

    2012-12-01

    Full Text Available In recent years, nuclear physics investigations of the laws of the microscopic world contributed significantly to extension of our knowledge of phenomena occurring in the macroscopic world (Universe and made a formidable contribution to the development of astrophysical and cosmological theories. First of all, this concerns the expanding universe model, the evolution of stars, and the abundances of elements, as well as the properties of various stars and cosmic objects, including “cold” and neutron stars, black holes, and pulsars. Without claiming to give a full account of all cosmological problems, we will dwell upon those of them that, in my opinion, have much in common with nuclear-matter properties manifesting themselves in nuclear interactions.

  19. Experiments in Particle Astrophysics

    Energy Technology Data Exchange (ETDEWEB)

    Boratav, M

    2004-07-01

    During the last decade, the field of what is currently called particle astrophysics (that I prefer to the shaky neologism astroparticle physics) has experienced a surprising growth. It is interesting to understand why the cosmic rays, the poor man's accelerator not no long ago, are becoming the object of scrutiny for a continuously growing community of theoreticians and experimentalists. In this article, we made an arbitrary choice of a small number of experiments to illustrate today's state of the art and the future perspectives in this domain. Our choice is based on three facts: the objects detected in each experiment are different, all the selected experiments are in their starting phase and all are spectacular for various reasons. Our aim is to convince the reader of the enormous discovery potential of these ongoing projects and share with him the excitement experienced by those involved in them. (Author) 37 refs.

  20. Theoretical Astrophysics at Fermilab

    Science.gov (United States)

    2004-01-01

    The Theoretical Astrophysics Group works on a broad range of topics ranging from string theory to data analysis in the Sloan Digital Sky Survey. The group is motivated by the belief that a deep understanding of fundamental physics is necessary to explain a wide variety of phenomena in the universe. During the three years 2001-2003 of our previous NASA grant, over 120 papers were written; ten of our postdocs went on to faculty positions; and we hosted or organized many workshops and conferences. Kolb and collaborators focused on the early universe, in particular and models and ramifications of the theory of inflation. They also studied models with extra dimensions, new types of dark matter, and the second order effects of super-horizon perturbations. S tebbins, Frieman, Hui, and Dodelson worked on phenomenological cosmology, extracting cosmological constraints from surveys such as the Sloan Digital Sky Survey. They also worked on theoretical topics such as weak lensing, reionization, and dark energy. This work has proved important to a number of experimental groups [including those at Fermilab] planning future observations. In general, the work of the Theoretical Astrophysics Group has served as a catalyst for experimental projects at Fennilab. An example of this is the Joint Dark Energy Mission. Fennilab is now a member of SNAP, and much of the work done here is by people formerly working on the accelerator. We have created an environment where many of these people made transition from physics to astronomy. We also worked on many other topics related to NASA s focus: cosmic rays, dark matter, the Sunyaev-Zel dovich effect, the galaxy distribution in the universe, and the Lyman alpha forest. The group organized and hosted a number of conferences and workshop over the years covered by the grant. Among them were:

  1. Collapse, environment, and society.

    Science.gov (United States)

    Butzer, Karl W

    2012-03-06

    Historical collapse of ancient states poses intriguing social-ecological questions, as well as potential applications to global change and contemporary strategies for sustainability. Five Old World case studies are developed to identify interactive inputs, triggers, and feedbacks in devolution. Collapse is multicausal and rarely abrupt. Political simplification undermines traditional structures of authority to favor militarization, whereas disintegration is preconditioned or triggered by acute stress (insecurity, environmental or economic crises, famine), with breakdown accompanied or followed by demographic decline. Undue attention to stressors risks underestimating the intricate interplay of environmental, political, and sociocultural resilience in limiting the damages of collapse or in facilitating reconstruction. The conceptual model emphasizes resilience, as well as the historical roles of leaders, elites, and ideology. However, a historical model cannot simply be applied to contemporary problems of sustainability without adjustment for cumulative information and increasing possibilities for popular participation. Between the 14th and 18th centuries, Western Europe responded to environmental crises by innovation and intensification; such modernization was decentralized, protracted, flexible, and broadly based. Much of the current alarmist literature that claims to draw from historical experience is poorly focused, simplistic, and unhelpful. It fails to appreciate that resilience and readaptation depend on identified options, improved understanding, cultural solidarity, enlightened leadership, and opportunities for participation and fresh ideas.

  2. MOSAIC at the E-ELT: A multi-object spectrograph for astrophysics, IGM and cosmology

    NARCIS (Netherlands)

    F. Hammer; B. Barbuy; J.G. Cuby; L. Kaper; S. Morris; C.J. Evans; P. Jagourel; G. Dalton; P. Rees; M. Puech; M. Rodriques; D. Pearson; K. Disseau

    2014-01-01

    The Universe is comprised of hundreds of billions of galaxies, each populated by hundreds of billions of stars. Astrophysics aims to understand the complexity of this almost incommensurable number of stars, stellar clusters and galaxies, including their spatial distribution, formation, and current i

  3. Perspectives on Core-Collapse Supernova Theory

    CERN Document Server

    Burrows, Adam

    2012-01-01

    Core-collapse theory brings together many facets of high-energy and nuclear astrophysics and the numerical arts to present theorists with one of the most important, yet frustrating, astronomical questions: "What is the mechanism of core-collapse supernova explosions?" A review of all the physics and the fifty-year history involved would soon bury the reader in minutiae that could easily obscure the essential elements of the phenomenon, as we understand it today. Moreover, much remains to be discovered and explained, and a complicated review of an unresolved subject in flux could grow stale fast. Therefore, in this paper I describe what I think are various important facts and perspectives that may have escaped the attention of those interested in this puzzle. Furthermore, I attempt to describe the modern theory's physical underpinnings and briefly summarize the current state of play. In the process, I identify a few myths (as I see them) that have crept into modern discourse. However, there is much more to do ...

  4. Null fluid collapse in brane world models

    Science.gov (United States)

    Harko, Tiberiu; Lake, Matthew J.

    2014-03-01

    The brane world description of our Universe entails a large extra dimension and a fundamental scale of gravity that may be lower than the Planck scale by several orders of magnitude. An interesting consequence of this scenario occurs in the nature of spherically symmetric vacuum solutions to the brane gravitational field equations, which often have properties quite distinct from the standard black hole solutions of general relativity. In this paper, the spherically symmetric collapse on the brane world of four types of null fluid, governed by the barotropic, polytropic, strange quark "bag" model and Hagedorn equations of state, is investigated. In each case, we solve the approximate gravitational field equations, obtained in the high-density limit, determine the equation which governs the formation of apparent horizons and investigate the conditions for the formation of naked singularities. Though, naively, one would expect the increased effective energy density on the brane to favor the formation of black holes over naked singularities, we find that, for the types of fluid considered, this is not the case. However, the black hole solutions differ substantially from their general-relativistic counterparts and brane world corrections often play a role analogous to charge in general relativity. As an astrophysical application of this work, the possibility that energy emission from a Hagedorn fluid collapsing to form a naked singularity may be a source of GRBs in the brane world is also considered.

  5. Multiplicity in Early Stellar Evolution

    CERN Document Server

    Reipurth, Bo; Boss, Alan P; Goodwin, Simon P; Rodriguez, Luis Felipe; Stassun, Keivan G; Tokovinin, Andrei; Zinnecker, Hans

    2014-01-01

    Observations from optical to centimeter wavelengths have demonstrated that multiple systems of two or more bodies is the norm at all stellar evolutionary stages. Multiple systems are widely agreed to result from the collapse and fragmentation of cloud cores, despite the inhibiting influence of magnetic fields. Surveys of Class 0 protostars with mm interferometers have revealed a very high multiplicity frequency of about 2/3, even though there are observational difficulties in resolving close protobinaries, thus supporting the possibility that all stars could be born in multiple systems. Near-infrared adaptive optics observations of Class I protostars show a lower binary frequency relative to the Class 0 phase, a declining trend that continues through the Class II/III stages to the field population. This loss of companions is a natural consequence of dynamical interplay in small multiple systems, leading to ejection of members. We discuss observational consequences of this dynamical evolution, and its influenc...

  6. Collapsing spherical stars in f(R) gravity

    CERN Document Server

    Goswami, Rituparno; Maharaj, Sunil D; Ghosh, Sushant G

    2014-01-01

    We perform a careful investigation of the problem of physically realistic gravitational collapse of massive stars in f(R)-gravity. We show that the extra matching conditions that arise in the modified gravity imposes strong constraints on the stellar structure and thermodynamic properties. In our opinion these constraints are unphysical. We prove that no homogeneous stars with non-constant Ricci scalar can be matched smoothly with a static exterior for any nonlinear function f(R). Therefore, these extra constraints make classes of physically realistic collapse scenarios in general relativity, non-admissible in these theories. We also find an exact solution for an inhomogeneous collapsing star in the Starobinski model that obeys all the energy and matching conditions. However, we argue that such solutions are fine-tuned and unstable to matter perturbations. Possible consequences on black hole physics and the cosmic censorship conjecture are also discussed.

  7. Gravitational Waves Signals from the Collapse of the First Stars

    CERN Document Server

    Schneider, R; Ciardi, B; Ferrari, V; Matarrese, S

    1999-01-01

    We study the gravitational wave emission from the first stars which are assumed to be Very Massive Objects (VMOs). We take into account various feedback (both radiative and stellar) effects regulating the collapse of objects in the early universe and thus derive the VMO initial mass function and formation rate. If the final fate of VMOs is to collapse, leaving very massive black hole remnants, then the gravitational waves emitted during each collapse would be seen as a stochastic background. The predicted spectral strain amplitude in a critical density Cold Dark Matter universe peaks in the frequency range \\approx 5 \\times 10^{-4}-5 \\times 10^{-3} Hz where it has a value in the range \\approx 10^{-20}-10^{-19} Hz^{-1/2}, and might be detected by LISA. The expected emission rate is roughly 4000 events/yr, resulting in a stationary, discrete sequence of bursts, i.e. a shot--noise signal.

  8. On the dynamics of dust during protostellar collapse

    Science.gov (United States)

    Bate, Matthew R.; Lorén-Aguilar, Pablo

    2017-02-01

    The dynamics of dust and gas can be quite different from each other when the dust is poorly coupled to the gas. In protoplanetary discs, it is well known that this decoupling of the dust and gas can lead to diverse spatial structures and dust-to-gas ratios. In this paper, we study the dynamics of dust and gas during the earlier phase of protostellar collapse, before a protoplanetary disc is formed. We find that for dust grains with sizes ≲ 10 μm, the dust is well coupled during the collapse of a rotating, pre-stellar core and there is little variation of the dust-to-gas ratio during the collapse. However, if larger grains are present, they may have trajectories that are very different from the gas during the collapse, leading to mid-plane settling and/or oscillations of the dust grains through the mid-plane. This may produce variations in the dust-to-gas ratio and very different distributions of large and small dust grains at the very earliest stages of star formation, if large grains are present in pre-stellar cores.

  9. Advanced stellarator power plants

    Energy Technology Data Exchange (ETDEWEB)

    Miller, R.L.

    1994-07-01

    The stellarator is a class of helical/toroidal magnetic fusion devices. Recent international progress in stellarator power plant conceptual design is reviewed and comparisons in the areas of physics, engineering, and economics are made with recent tokamak design studies.

  10. Direct Collapse Black Holes Can Launch Gamma-Ray Bursts and Get Fat to Supermassive Black Holes?

    CERN Document Server

    Matsumoto, Tatsuya; Ioka, Kunihito; Heger, Alexander; Nakamura, Takashi

    2015-01-01

    The existence of black holes (BHs) of mass ~ 10^{9} M_sun at z > 6 is a big puzzle in astrophysics because even optimistic estimates of the accretion time are insufficient for stellar mass BHs of ~ 10 M_sun to grow into such supermassive BHs. A resolution of this puzzle might be the direct collapse of supermassive stars with mass M ~ 10^{5} M_sun into massive seed BHs. We find that if a jet is launched from the accretion disk around the central BH, the jet can break out the star because of the structure of the radiation pressure-dominated envelope. Such ultra-long gamma-ray bursts with duration of ~ 10^{4} - 10^{6} s and flux of 10^{-11} - 10^{-8} erg s^{-1} cm^{-2} could be detectable by Swift. We estimate an event rate of 10^{55} - 10^{56} erg. The resulting negative feedback delays the growth of the remnant BH by about 70 Myr or evacuates the host galaxy completely.

  11. The Einstein Toolkit: A Community Computational Infrastructure for Relativistic Astrophysics

    CERN Document Server

    Löffler, Frank; Bentivegna, Eloisa; Bode, Tanja; Diener, Peter; Haas, Roland; Hinder, Ian; Mundim, Bruno C; Ott, Christian D; Schnetter, Erik; Allen, Gabrielle; Campanelli, Manuela; Laguna, Pablo

    2011-01-01

    We describe the Einstein Toolkit, a community-driven, freely accessible computational infrastructure intended for use in numerical relativity, relativistic astrophysics, and other applications. The Toolkit, developed by a collaboration involving researchers from multiple institutions around the world, combines a core set of components needed to simulate astrophysical objects such as black holes, compact objects, and collapsing stars, as well as a full suite of analysis tools. The Einstein Toolkit is currently based on the Cactus Framework for high-performance computing and the Carpet adaptive mesh refinement driver. It implements spacetime evolution via the BSSN evolution system and general-relativistic hydrodynamics in a finite-volume discretization. The toolkit is under continuous development and contains many new code components that have been publicly released for the first time and are described in this article. We discuss the motivation behind the release of the toolkit, the philosophy underlying its de...

  12. Stellarator status, 1989

    Energy Technology Data Exchange (ETDEWEB)

    Lyon, J.F. (Oak Ridge National Lab., TN (USA)); Grieger, G.; Rau, F. (Max-Planck-Institut fuer Plasmaphysik, Garching (Germany, F.R.)); Iiyoshi, A. (National Inst. for Fusion Science, Nagoya (Japan)); Navarro, A.P. (Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas, Madrid (Spain)); Kovrizhnykh, L.M. (AN SSSR, Moscow (USSR). Inst. Obshchey Fiziki); Pavlichenko, O.S. (AN Ukrain

    1990-07-01

    The present status of stellarator experiments and recent progress in stellarator research (both experimental and theoretical) are reported by groups in the United States, the USSR, Japan, Australia, and the European Community (the Federal Republic of Germany and Spain). Experiments under construction and studies of large, next-generation stellarators are also described. 73 refs., 11 figs., 4 tabs.

  13. The explosion mechanism of core-collapse supernovae: progress in supernova theory and experiments

    CERN Document Server

    Foglizzo, Thierry; Guilet, Jérôme; Masset, Frédéric; González, Matthias; Krueger, Brendan K; Novak, Jérôme; Oertel, Micaela; Margueron, Jérôme; Faure, Julien; Martin, Noël; Blottiau, Patrick; Peres, Bruno; Durand, Gilles

    2015-01-01

    The explosion of core-collapse supernova depends on a sequence of events taking place in less than a second in a region of a few hundred kilometers at the center of a supergiant star, after the stellar core approaches the Chandrasekhar mass and collapses into a proto-neutron star, and before a shock wave is launched across the stellar envelope. Theoretical efforts to understand stellar death focus on the mechanism which transforms the collapse into an explosion. Progress in understanding this mechanism is reviewed with particular attention to its asymmetric character. We highlight a series of successful studies connecting observations of supernova remnants and pulsars properties to the theory of core-collapse using numerical simulations. The encouraging results from first principles models in axisymmetric simulations is tempered by new puzzles in 3D. The diversity of explosion paths and the dependence on the pre-collapse stellar structure is stressed, as well as the need to gain a better understanding of hydr...

  14. Astrophysical components from Planck maps

    CERN Document Server

    Burigana, Carlo; Paoletti, Daniela; Mandolesi, Nazzareno; Natoli, Paolo

    2016-01-01

    The Planck Collaboration has recently released maps of the microwave sky in both temperature and polarization. Diffuse astrophysical components (including Galactic emissions, cosmic far infrared (IR) background, y-maps of the thermal Sunyaev-Zeldovich (SZ) effect) and catalogs of many thousands of Galactic and extragalactic radio and far-IR sources, and galaxy clusters detected through the SZ effect are the main astrophysical products of the mission. A concise overview of these results and of astrophysical studies based on Planck data is presented.

  15. Book Review: "Inside Stars. A Theory of the Internal Constitution of Stars, and the Sources of Stellar Energy According to General Relativity" (Letters to Progress in Physics

    Directory of Open Access Journals (Sweden)

    Millette P. A.

    2014-01-01

    Full Text Available This book provides a general relativistic theory of the internal constitution of liquid stars. It is a solid contribution to our understanding of stellar structure from a general relativistic perspective. It raises new ideas on the constitution of stars and planetary systems, and proposes a new approach to stellar structure an d stellar energy generation which is bound to help us better understand stellar astrophysics.

  16. Trojan Horse Method: recent results in nuclear astrophysics

    Science.gov (United States)

    Spitaleri, C.; Lamia, L.; Gimenez Del Santo, M.; Burjan, V.; Carlin, N.; Li, Chengbo; Cherubini, S.; Crucilla, V.; Gulino, M.; Hons, Z.; Kroha, V.; Irgaziev, B.; La Cognata, M.; Mrazek, J.; Mukhamedzhanov, M.; Munhoz, M. G.; Palmerini, S.; Pizzone, R. G.; Puglia, M. R.; Rapisarda, G. G.; Romano, S.; Sergi, L.; Zhou, Shu-Hua; Somorjai, E.; Souza, F. A.; Tabacaru, G.; Szanto de Toledo, A.; Tumino, A.; Wen, Qungang; Wakabayashi, Y.; Yamaguchi, H.

    2015-07-01

    The accurate knowledge of thermonuclear reaction rates is important in understanding the energy generation, the neutrinos luminosity and the synthesis of elements in stars. The physical conditions under which the majority of astrophysical reactions proceed in stellar environments make it difficult or impossible to measure them under the same conditions in the laboratory. That is why different indirect techniques are being used along with direct measurements. The Trojan Horse Method (THM) is introduced as an independent technique to obtain the bare nucleus astrophysical S(E)-factor. As examples the results of recent the application of THM to the 2H(11B, σ08Be)n and 2H(10B, σ07Be)n reactions are presented.

  17. Nuclear Theory for Astrophysics, Stockpile Stewardship, and Homeland Security

    Science.gov (United States)

    Hayes, Anna

    2004-10-01

    A large number of problems key to astrophysics, stockpile stewardship, and homeland defense rely on knowledge of nuclear physics in regimes inaccessible to experiment. In stellar and nuclear explosions unstable nuclei and nuclear isomers are produced in copious quantities and are used to diagnose the explosion. Similarly, analysis of the unstable nuclei from the debris will be key to attribution in the event of a terrorist domestic nuclear attack. In the case of nuclear non-proliferation a number of new schemes are being considered by the IAEA to address the ever greater needs, including neutrino monitoring of the plutonium content of reactors. For all of these problems detailed nuclear theory is required. In this talk I discuss the theoretical physics needs for the type of problems of overlapping interest to astrophysics and national security.

  18. Astrophysical Dynamics 1999/2000 Merging Research and Education

    CERN Document Server

    Romeo, A B

    2000-01-01

    The workshop `Astrophysical Dynamics 1999/2000' followed a homonymous advanced research course, and both activities were organized by me. In this opening paper of the proceedings book, I describe them and document their strong impact on the academic life of the local institutions. The advanced research course was open to graduate students, senior researchers, and motivated under-graduate students with good background in physics and mathematics. The course covered several multi-disciplinary issues of modern research on astrophysical dynamics, and thus also of interest to physicists, mathematicians and engineers. The major topic was gas dynamics, viewed in context with stellar dynamics and plasma physics. The course was complemented by parallel seminars on hot topics given by experts in such fields, and open to a wide scientific audience. In particular, I gave a friendly introduction to wavelets, which are becoming an increasingly powerful tool not only for processing signals and images but also for analysing f...

  19. GenASiS: General Astrophysical Simulation System. I. Fundamentals

    CERN Document Server

    Cardall, Christian Y; Endeve, Eirik; Mezzacappa, Anthony

    2012-01-01

    GenASiS (General Astrophysical Simulation System) is a new code being developed initially and primarily, though by no means exclusively, for the simulation of core-collapse supernovae on the world's leading capability supercomputers. Using the features of Fortran 2003 that allow for object-oriented programming, its classes are grouped into three major divisions: (1) Basics, which contains some basic utilitarian functionality for large-scale simulations on distributed-memory supercomputers; (2) Mathematics, which includes generic mathematical constructs and solvers that are as agnostic as possible with regard to the specifics of any particular system; and (3) Physics, which sets up physical spaces associated with various theories of spacetime (including gravity), defines various forms of stress-energy, and combines these into `universes.' To provide a foundation for subsequent papers focusing on the implementation of various pieces of physics needed for the simulation of core-collapse supernovae and other astr...

  20. Atoms in astrophysics

    CERN Document Server

    Eissner, W; Hummer, D; Percival, I

    1983-01-01

    It is hard to appreciate but nevertheless true that Michael John Seaton, known internationally for the enthusiasm and skill with which he pursues his research in atomic physics and astrophysics, will be sixty years old on the 16th of January 1983. To mark this occasion some of his colleagues and former students have prepared this volume. It contains articles that de­ scribe some of the topics that have attracted his attention since he first started his research work at University College London so many years ago. Seaton's association with University College London has now stretched over a period of some 37 years, first as an undergraduate student, then as a research student, and then, successively, as Assistant Lecturer, Lecturer, Reader, and Professor. Seaton arrived at University College London in 1946 to become an undergraduate in the Physics Department, having just left the Royal Air Force in which he had served as a navigator in the Pathfinder Force of Bomber Command. There are a number of stories of ho...

  1. Byurakan Astrophysical Observatory

    Science.gov (United States)

    Mickaelian, A. M.

    2016-09-01

    This booklet is devoted to NAS RA V. Ambartsumian Byurakan Astrophysical Observatory and is aimed at people interested in astronomy and BAO, pupils and students, BAO visitors and others. The booklet is made as a visiting card and presents concise and full information about BAO. A brief history of BAO, the biography of the great scientist Viktor Ambartsumian, brief biographies of 13 other deserved scientists formerly working at BAO (B.E. Markarian, G.A. Gurzadyan, L.V. Mirzoyan, M.A. Arakelian, et al.), information on BAO telescopes (2.6m, 1m Schmidt, etc.) and other scientific instruments, scientific library and photographic plate archive, Byurakan surveys (including the famous Markarian Survey included in the UNESCO Memory of the World International Register), all scientific meetings held in Byurakan, international scientific collaboration, data on full research staff of the Observatory, as well as former BAO researchers, who have moved to foreign institutions are given in the booklet. At the end, the list of the most important books published by Armenian astronomers and about them is given.

  2. Visualizing multiwavelength astrophysical data.

    Science.gov (United States)

    Li, Hongwei; Fu, Chi-Wing; Hanson, Andrew J

    2008-01-01

    With recent advances in the measurement technology for allsky astrophysical imaging, our view of the sky is no longer limited to the tiny visible spectral range over the 2D Celestial sphere. We now can access a third dimension corresponding to a broad electromagnetic spectrum with a wide range of allsky surveys; these surveys span frequency bands including long wavelength radio, microwaves, very short X-rays, and gamma rays. These advances motivate us to study and examine multiwavelength visualization techniques to maximize our capabilities to visualize and exploit these informative image data sets. In this work, we begin with the processing of the data themselves, uniformizing the representations and units of raw data obtained from varied detector sources. Then we apply tools to map, convert, color-code, and format the multiwavelength data in forms useful for applications. We explore different visual representations for displaying the data, including such methods as textured image stacks, the horseshoe representation, and GPU-based volume visualization. A family of visual tools and analysis methods is introduced to explore the data, including interactive data mapping on the graphics processing unit (GPU), the mini-map explorer, and GPU-based interactive feature analysis.

  3. Fingerprinting Hydrogen in Core-Collapse Supernovae

    Science.gov (United States)

    Nance, Sarafina; Parrent, Jerod; Soderberg, Alicia Margarita

    2016-01-01

    This is a preliminary report on the mass of remaining hydrogen envelopes for stars massive enough to explode under core collapse. Using the stellar evolution code, MESA, our initial findings suggest that a significant fraction of massive stars with M_ZAMS = 20-60 Msun lose all but 10^-3 Msun -10^-1 Msun as they near eventual core collapse. This result is dependent on the mass-loss prescription, degree of rotation, metallicity, rates of nuclear burning in the core, and the final stellar configuration. Nevertheless, each of our test cases include a few stars that retain trace amounts of surface hydrogen, which would then be detected as faint H in type IIb/Ib/Ic supernova spectra. We also compare our findings to the progenitor candidate identified for iPTF13bvn using the most recent photometric corrections. We agree with the previous conclusion found by Groh et al. (2013) that the progenitor had an initial mass of 32 Msun, but now with an additional condition of 0.06 Msun of hydrogen on its surface just prior to the explosion. We demonstrate through our study that not all Type Ib supernovae are fully devoid of hydrogen at the time of explosion, which has implications for the nature of the progenitor star and thus provides impetus for a revised classification scheme for 'stripped envelope' supernovae. This work was supported in part by the NSF REU and DoD ASSURE programs under NSF grant no. 1262851 and by the Smithsonian Institution.

  4. An introduction to observational astrophysics

    CERN Document Server

    Gallaway, Mark

    2016-01-01

    Observational Astrophysics follows the general outline of an astrophysics undergraduate curriculum targeting practical observing information to what will be covered at the university level. This includes the basics of optics and coordinate systems to the technical details of CCD imaging, photometry, spectography and radio astronomy.  General enough to be used by students at a variety of institutions and advanced enough to be far more useful than observing guides targeted at amateurs, the author provides a comprehensive and up-to-date treatment of observational astrophysics at undergraduate level to be used with a university’s teaching telescope.  The practical approach takes the reader from basic first year techniques to those required for a final year project. Using this textbook as a resource, students can easily become conversant in the practical aspects of astrophysics in the field as opposed to the classroom.

  5. The Fermilab Particle Astrophysics Center

    Energy Technology Data Exchange (ETDEWEB)

    2004-11-01

    The Particle Astrophysics Center was established in fall of 2004. Fermilab director Michael S. Witherell has named Fermilab cosmologist Edward ''Rocky'' Kolb as its first director. The Center will function as an intellectual focus for particle astrophysics at Fermilab, bringing together the Theoretical and Experimental Astrophysics Groups. It also encompasses existing astrophysics projects, including the Sloan Digital Sky Survey, the Cryogenic Dark Matter Search, and the Pierre Auger Cosmic Ray Observatory, as well as proposed projects, including the SuperNova Acceleration Probe to study dark energy as part of the Joint Dark Energy Mission, and the ground-based Dark Energy Survey aimed at measuring the dark energy equation of state.

  6. Statistical Methods for Characterizing Variability in Stellar Spectra

    Science.gov (United States)

    Cisewski, Jessi; Yale Astrostatistics

    2017-01-01

    Recent years have seen a proliferation in the number of exoplanets discovered. One technique for uncovering exoplanets relies on the detection of subtle shifts in the stellar spectra due to the Doppler effect caused by an orbiting object. However, stellar activity can cause distortions in the spectra that mimic the imprint of an orbiting exoplanet. The collection of stellar spectra potentially contains more information than is traditionally used for estimating its radial velocity curve. I will discuss some statistical methods that can be used for characterizing the sources of variability in the spectra. Statistical assessment of stellar spectra is a focus of the Statistical and Applied Mathematical Sciences Institute (SAMSI)'s yearlong program on Statistical, Mathematical and Computational Methods for Astronomy's Working Group IV (Astrophysical Populations).

  7. Nuclear astrophysics: the unfinished quest for the origin of the elements

    CERN Document Server

    Jose, Jordi

    2011-01-01

    Half a century has passed since the foundation of nuclear astrophysics. Since then, this discipline has reached its maturity. Today, nuclear astrophysics constitutes a multidisciplinary crucible of knowledge that combines the achievements in theoretical astrophysics, observational astronomy, cosmochemistry and nuclear physics. New tools and developments have revolutionized our understanding of the origin of the elements: supercomputers have provided astrophysicists with the required computational capabilities to study the evolution of stars in a multidimensional framework; the emergence of high-energy astrophysics with space-borne observatories has opened new windows to observe the Universe, from a novel panchromatic perspective; cosmochemists have isolated tiny pieces of stardust embedded in primitive meteorites, giving clues on the processes operating in stars as well as on the way matter condenses to form solids; and nuclear physicists have measured reactions near stellar energies, through the combined eff...

  8. New Discoveries in the Galactic Neighborhood through Advances in Laboratory Astrophysics

    CERN Document Server

    WGLA, AAS; Cowan, John; Drake, Paul; Federman, Steven; Ferland, Gary; Frank, Adam; Herbst, Eric; Olive, Keith; Salama, Farid; Savin, Daniel Wolf; Ziurys, Lucy

    2009-01-01

    As the Galactic Neighborhood (GAN) panel is fully aware, the next decade will see major advances in our understanding of this area of research. To quote from their charge, these advances will occur in studies of the galactic neighborhood, including the structure and properties of the Milky Way and nearby galaxies, and their stellar populations and evolution, as well as interstellar media and star clusters. Central to the progress in these areas are the corresponding advances in laboratory astrophysics that are required for fully realizing the GAN scientific opportunities within the decade 2010-2020. Laboratory astrophysics comprises both theoretical and experimental studies of the underlying physics and chemistry that produces the observed astrophysical processes. The 5 areas of laboratory astrophysics that we have identified as relevant to the GAN panel are atomic, molecular, solid matter, plasma, and nuclear physics. In this white paper, we describe in Section 2 some of the new scientific opportunities and ...

  9. PREFACE: Collapse Calderas Workshop

    Science.gov (United States)

    Gottsmann, Jo; Aguirre-Diaz, Gerardo

    2008-10-01

    Caldera-formation is one of the most awe-inspiring and powerful displays of nature's force. Resultant deposits may cover vast areas and significantly alter the immediate topography. Post-collapse activity may include resurgence, unrest, intra-caldera volcanism and potentially the start of a new magmatic cycle, perhaps eventually leading to renewed collapse. Since volcanoes and their eruptions are the surface manifestation of magmatic processes, calderas provide key insights into the generation and evolution of large-volume silicic magma bodies in the Earth's crust. Despite their potentially ferocious nature, calderas play a crucial role in modern society's life. Collapse calderas host essential economic deposits and supply power for many via the exploitation of geothermal reservoirs, and thus receive considerable scientific, economic and industrial attention. Calderas also attract millions of visitors world-wide with their spectacular scenic displays. To build on the outcomes of the 2005 calderas workshop in Tenerife (Spain) and to assess the most recent advances on caldera research, a follow-up meeting was proposed to be held in Mexico in 2008. This abstract volume presents contributions to the 2nd Calderas Workshop held at Hotel Misión La Muralla, Querétaro, Mexico, 19-25 October 2008. The title of the workshop `Reconstructing the evolution of collapse calderas: Magma storage, mobilisation and eruption' set the theme for five days of presentations and discussions, both at the venue as well as during visits to the surrounding calderas of Amealco, Amazcala and Huichapan. The multi-disciplinary workshop was attended by more than 40 scientist from North, Central and South America, Europe, Australia and Asia. Contributions covered five thematic topics: geology, geochemistry/petrology, structural analysis/modelling, geophysics, and hazards. The workshop was generously supported by the International Association of Volcanology and the Chemistry of The Earth's Interior

  10. An introduction to astrophysical hydrodynamics

    CERN Document Server

    Shore, Steven N

    1992-01-01

    This book is an introduction to astrophysical hydrodynamics for both astronomy and physics students. It provides a comprehensive and unified view of the general problems associated with fluids in a cosmic context, with a discussion of fluid dynamics and plasma physics. It is the only book on hydrodynamics that addresses the astrophysical context. Researchers and students will find this work to be an exceptional reference. Contents include chapters on irrotational and rotational flows, turbulence, magnetohydrodynamics, and instabilities.

  11. Neutrinos in Astrophysics and Cosmology

    CERN Document Server

    Balantekin, A B

    2016-01-01

    Neutrinos play a crucial role in many aspects of astrophysics and cosmology. Since they control the electron fraction, or equivalently neutron-to-proton ratio, neutrino properties impact yields of r-process nucleosynthesis. Similarly the weak decoupling temperature in the Big Bang Nucleosynthesis epoch is exponentially dependent on the neutron-to-proton ratio. In these conference proceedings, I briefly summarize some of the recent work exploring the role of neutrinos in astrophysics and cosmology.

  12. FOREWORD: Nuclear Physics in Astrophysics V

    Science.gov (United States)

    Auerbach, Naftali; Hass, Michael; Paul, Michael

    2012-02-01

    the conference dinner banquet at the Dan hotel. An excursion to the 'Red Canyon' in the Eilat Mountains on Wednesday afternoon was one of the social highlights of the conference. A total number of 140 scientists attended NPA5 and about 30 accompanying persons; about 25% of these were young participants (less than 36 years old). 23 participants were from Israel, and 27 were from outside of Europe (including two from Africa). The subjects covered at the conference in Eilat concentrated mainly on the spirit of the original idea - to probe experimental and theoretical activity in nuclear structure and reactions that is directly related to the physics of the Universe. There were also sessions of general interest in astrophysics, as well as a poster session on Tuesday evening featuring 40 posters. The topics included: Nuclear Structure - Theory and Experiment Big-Bang Nucleosynthesis and Formation of First Stars Stellar Reactions and Solar Neutrinos Explosive Nucleosynthesis, Radioactive Beams and Exotic Nuclei-New Facilities and Future Possibilities for Astrophysics Neutrino Physics - the Low and High-Energy Frontiers Rare events, Dark Matter, Double beta-decay, Symmetries The conference started with an excellent exposé of the progress made in the discovery of super-heavy elements and the study of their properties. The progress in this field is enormous, and this subject should be communicated to more general audiences. The role of the nuclear equation of state and of the precise determination of nuclear masses in nucleosynthesis was emphasized in several talks. The role of neutrinos in astrophysics was discussed extensively in several sessions. One of the highlights of this was the presentation about the IceCube and DeepCore detectors operating deep in the Antarctic ice. These facilities are able to detect cosmogenic neutrinos in a wide energy range, from 10 GeV to 1010 GeV. The subject of solar neutrinos was discussed in a number of talks. Topics related to properties

  13. Hierarchical Visual Analysis and Steering Framework for Astrophysical Simulations

    Institute of Scientific and Technical Information of China (English)

    肖健; 张加万; 原野; 周鑫; 纪丽; 孙济洲

    2015-01-01

    A framework for accelerating modern long-running astrophysical simulations is presented, which is based on a hierarchical architecture where computational steering in the high-resolution run is performed under the guide of knowledge obtained in the gradually refined ensemble analyses. Several visualization schemes for facilitating ensem-ble management, error analysis, parameter grouping and tuning are also integrated owing to the pluggable modular design. The proposed approach is prototyped based on the Flash code, and it can be extended by introducing user-defined visualization for specific requirements. Two real-world simulations, i.e., stellar wind and supernova remnant, are carried out to verify the proposed approach.

  14. J-PAS: The Javalambre Physics of the Accelerated Universe Astrophysical Survey

    Science.gov (United States)

    Cepa, J.; Benítez, N.; Dupke, R.; Moles, M.; Sodré, L.; Cenarro, A. J.; Marín-Franch, A.; Taylor, K.; Cristóbal, D.; Fernández-Soto, A.; Mendes de Oliveira, C.; Abramo, L. R.; Alcaniz, J. S.; Overzier, R.; Hernández-Monteagudo, A.; Alfaro, E. J.; Kanaan, A.; Carvano, M.; Reis, R. R. R.; J-PAS Team

    2016-10-01

    The Javalambre Physics of the Accelerated Universe Astrophysical Survey (J-PAS) is a narrow band, very wide field Cosmological Survey to be carried out from the Javalambre Observatory in Spain with a purpose-built, dedicated 2.5 m telescope and a 4.7 sq.deg. camera with 1.2 Gpix. Starting in late 2016, J-PAS will observe 8500 sq.deg. of Northern Sky and measure Δz˜0.003(1+z) photo-z for 9× 107 LRG and ELG galaxies plus several million QSOs, sampling an effective volume of ˜ 14 Gpc3 up to z=1.3 and becoming the first radial BAO experiment to reach Stage IV. J-PAS will detect 7× 105 galaxy clusters and groups, setting constraints on Dark Energy which rival those obtained from its BAO measurements. Thanks to the superb characteristics of the site (seeing ˜ 0.7 arcsec), J-PAS is expected to obtain a deep, sub-arcsec image of the Northern sky, which combined with its unique photo-z precision will produce one of the most powerful cosmological lensing surveys before the arrival of Euclid. J-PAS's unprecedented spectral time domain information will enable a self-contained SN survey that, without the need for external spectroscopic follow-up, will detect, classify and measure σz˜ 0.5 redshifts for ˜ 4000 SNeIa and ˜ 900 core-collapse SNe. The key to the J-PAS potential is its innovative approach: a contiguous system of 54 filters with 145 Å width, placed 100 Å apart over a multi-degree FoV is a powerful redshift machine, with the survey speed of a 4000 multiplexing low resolution spectrograph, but many times cheaper and much faster to build. The J-PAS camera is equivalent to a 4.7 sq.deg. IFU and it will produce a time-resolved, 3D image of the Northern Sky with a very wide range of Astrophysical applications in Galaxy Evolution, the nearby Universe and the study of resolved stellar populations.

  15. Minicourses in Astrophysics, Modular Approach, Vol. I.

    Science.gov (United States)

    Illinois Univ., Chicago.

    This is the first volume of a two-volume minicourse in astrophysics. It contains chapters on the following topics: planetary atmospheres; X-ray astronomy; radio astrophysics; molecular astrophysics; and gamma-ray astrophysics. Each chapter gives much technical discussion, mathematical treatment, diagrams, and examples. References are included with…

  16. Failure of a neutrino-driven explosion after core-collapse may lead to a thermonuclear supernova

    CERN Document Server

    Kushnir, Doron

    2014-01-01

    We demonstrate that $\\sim10$ seconds after core-collapse of a massive star, a thermonuclear explosion of the outer shells is possible for some (tuned) initial density and composition profiles, assuming the neutrinos failed to explode the star. The explosion may lead to a successful supernova, as first suggested by Burbidge, Burbidge, Fowler and Hoyle (1957). We perform a series of one-dimensional (1D) calculations of collapsing massive stars with simplified initial density profiles (similar to the results of stellar evolution calculations) and various compositions (not similar to 1D stellar evolution calculations). We assume that the neutrinos escaped with negligible effect on the outer layers, which inevitably collapse. As the shells collapse, they compress and heat up adiabatically, enhancing the rate of thermonuclear burning. In some cases, where significant shells of mixed helium and oxygen are present with pre-collapsed burning times of $\\lesssim100\\,\\textrm{s}$ ($\\approx10$ times the free-fall time), a ...

  17. On collapsibilities of Yule's measure

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    impson's paradox reminds people that the statistical inference in a low-dimensional space probably distorts the reality in a high one seriously.To study the paradox with respect to Yule's measure,this paper discusses simple collapsibility,strong collapsibility and consecutive collapsibility,and presents necessary and sufficient conditions of them.In fact,these conditions are of great importance for observational and experimental designs,eliminating confounding bias,categorizing discrete variables and so on.

  18. Collapse in self-gravitating turbulent fluids

    Science.gov (United States)

    Murray, Daniel W.; Chang, Philip; Murray, Norman W.; Pittman, John

    2017-02-01

    Motivated by the non-linear star formation efficiency found in recent numerical simulations by a number of workers, we perform high-resolution adaptive mesh refinement simulations of star formation in self-gravitating turbulently driven gas. As we follow the collapse of this gas, we find that the character of the flow changes at two radii, the disc radius rd and the radius r*, where the enclosed gas mass exceeds the stellar mass. Accretion starts at large scales and works inwards. In line with recent analytical work, we find that the density evolves to a fixed attractor, ρ(r, t) → ρ(r), for rd structure on to a sporadically gravitationally unstable disc and from thence on to the star. In the bulk of the simulation box, we find that the random motions vT ∼ rp with p ∼ 0.5 are in agreement with Larson's size-linewidth relation. In the vicinity of massive star-forming regions, we find p ∼ 0.2-0.3, as seen in observations. For r < r*, vT increases inwards, with p = -1/2. Finally, we find that the total stellar mass M*(t) ∼ t2 is in line with previous numerical and analytic work that suggests a non-linear rate of star formation.

  19. Astrophysics and air travel

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, G. [National Physical Laboratory (United Kingdom)

    2003-04-01

    If you have a fear of flying, then probably the last thing on your mind when you are 10 km above the ground is what might be going on in the depths of the galaxy. But airline pilots and cabin crew might want to brush up on their astroparticle physics. High-energy particles coming from violent galactic events mean that radiation exposure for aircrew is higher than it is for most people classified as radiation workers. But the type of radiation that they are exposed to is very different. The majority of the exposure comes from cosmic radiation that originates outside our solar system. Violent events such as stellar flares, supernovae and the explosion of galactic nuclei produce a concoction of subatomic particles, primarily protons and electrons. The energies of these particles can be greater than 10{sup 20} eV - billions of times higher than in the most powerful particle accelerators - although such energetic particles are very rare. Nuclear particles, which comprise about 98% of the radiation, typically have energies that are between 100 MeV and 10 GeV per nucleon. Proportional counter that can measure cosmic radiation is described. (U.K.)

  20. Frontiers in Nuclear Astrophysics

    CERN Document Server

    Bertulani, Carlos A

    2016-01-01

    The synthesis of nuclei in diverse cosmic scenarios is reviewed, with a summary of the basic concepts involved before a discussion of the current status in each case is made. We review the physics of the early universe, the proton to neutron ratio influence in the observed helium abundance, reaction networks, the formation of elements up to beryllium, the inhomogeneous Big Bang model, and the Big Bang nucleosynthesis constraints on cosmological models. Attention is paid to element production in stars, together with the details of the pp chain, the pp reaction, $^3$He formation and destruction, electron capture on $^7$Be, the importance of $^8$B formation and its relation to solar neutrinos, and neutrino oscillations. Nucleosynthesis in massive stars is also reviewed, with focus on the CNO cycle and its hot companion cycle, the rp-process, triple-$\\alpha$ capture, and red giants and AGB stars. The stellar burning of carbon, neon, oxygen, and silicon is presented in a separate section, as well as the slow and r...

  1. SIGNATURES OF STAR CLUSTER FORMATION BY COLD COLLAPSE

    Energy Technology Data Exchange (ETDEWEB)

    Kuznetsova, Aleksandra; Hartmann, Lee [Department of Astronomy, University of Michigan, 1085 S. University Ave., Ann Arbor, MI 48109 (United States); Ballesteros-Paredes, Javier, E-mail: kuza@umich.edu [Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Apdo. Postal 72-3 (Xangari), Morelia, Michocán 58089, México (Mexico)

    2015-12-10

    Subvirial gravitational collapse is one mechanism by which star clusters may form. Here we investigate whether this mechanism can be inferred from observations of young clusters. To address this question, we have computed smoothed particle hydrodynamics simulations of the initial formation and evolution of a dynamically young star cluster through cold (subvirial) collapse, starting with an ellipsoidal, turbulently seeded distribution of gas, and forming sink particles representing (proto)stars. While the initial density distributions of the clouds do not have large initial mass concentrations, gravitational focusing due to the global morphology leads to cluster formation. We use the resulting structures to extract observable morphological and kinematic signatures for the case of subvirial collapse. We find that the signatures of the initial conditions can be erased rapidly as the gas and stars collapse, suggesting that kinematic observations need to be made early in cluster formation and/or at larger scales, away from the growing cluster core. Our results emphasize that a dynamically young system is inherently evolving on short timescales, so that it can be highly misleading to use current-epoch conditions to study aspects such as star formation rates as a function of local density. Our simulations serve as a starting point for further studies of collapse including other factors such as magnetic fields and stellar feedback.

  2. Measurement of reaction rates of interest in stellar structure and evolution

    Energy Technology Data Exchange (ETDEWEB)

    Terrasi, F.; D`Onofrio, A. [Dipt. di Scienze Ambientali, Seconda Univ. di Napoli, Caserta (Italy)]|[INFN, Napoli (Italy); Campajola, L.; Imbriani, G. [INFN, Napoli (Italy)]|[Dipt. di Scienze Fisiche, Univ. Federico II, Napoli (Italy); Gialanella, L. [INFN, Napoli (Italy)]|[Dipt. di Scienze Fisiche, Univ. Federico II, Napoli (Italy)]|[Inst. fuer Experimentalphysik III, Ruhr-Univ. Bochum, Bochum (Germany); Greife, U.; Rolfs, C.; Strieder, F.; Trautvetter, H.P. [Inst. fuer Experimentalphysik III, Ruhr-Univ. Bochum, Bochum (Germany); Roca, V.; Romano, M. [INFN, Napoli (Italy)]|[Dipt. di Scienze Fisiche, Univ. Federico II, Napoli (Italy); Straniero, O. [Osservatorio Astronomico di Collurania, Teramo (Italy)

    1998-06-01

    Accurate determinations of reaction rates at astrophysical energies are very important in stellar structure and evolution studies. The cases of two key reactions, namely {sup 7}Be(p,{gamma}){sup 8}B and {sup 12}C({alpha},{gamma}){sup 16}O are discussed, both from the point of view of their astrophysical interest and of the experimental difficulties in the measurement of their cross section. (orig.)

  3. High energy astrophysics. An introduction

    Energy Technology Data Exchange (ETDEWEB)

    Courvoisier, Thierry J.L. [Geneva Univ., Versoix (Switzerland). ISDC, Data Centre for Astrophysics

    2013-07-01

    Based on observational examples this book reveals and explains high-energy astrophysical processes. Presents the theory of astrophysical processes in a didactic approach by deriving equations step by step. With several attractive astronomical pictures. High-energy astrophysics has unveiled a Universe very different from that only known from optical observations. It has revealed many types of objects in which typical variability timescales are as short as years, months, days, and hours (in quasars, X-ray binaries, and other objects), and even down to milli-seconds in gamma ray bursts. The sources of energy that are encountered are only very seldom nuclear fusion, and most of the time gravitation, a paradox when one thinks that gravitation is, by many orders of magnitude, the weakest of the fundamental interactions. The understanding of these objects' physical conditions and the processes revealed by high-energy astrophysics in the last decades is nowadays part of astrophysicists' culture, even of those active in other domains of astronomy. This book evolved from lectures given to master and PhD students at the University of Geneva since the early 1990s. It aims at providing astronomers and physicists intending to be active in high-energy astrophysics a broad basis on which they should be able to build the more specific knowledge they will need. While in the first part of the book the physical processes are described and derived in detail, the second part studies astrophysical objects in which high-energy astrophysics plays a crucial role. This two-pronged approach will help students recognise physical processes by their observational signatures in contexts that may differ widely from those presented here.

  4. The differing locations of massive stellar explosions

    CERN Document Server

    Fruchter, A S; Burud, I; Castro-Tirado, A J; Cerón, J M C; Conselice, C J; Dahlen, T; Ferguson, H C; Fynbo, J P U; Garnavich, P M; Gibbons, R A; Gorosabel, J; Gull, T R; Hjorth, J; Holland, S T; Kouveliotou, C; Levan, A J; Levay, Z; Livio, M; Metzger, M R; Nugent, P; Petro, L; Pian, E; Rhoads, J E; Riess, A G; Sahu, K C; Smette, A; Strolger, L; Tanvir, N R; Thorsett, S E; Vreeswijk, P M; Wijers, R A M J; Woosley, S E

    2006-01-01

    When massive stars exhaust their fuel they collapse and often produce the extraordinarily bright explosions known as core-collapse supernovae. On occasion, this stellar collapse also powers an even more brilliant relativistic explosion known as a long-duration gamma-ray burst. One would then expect that gamma-ray bursts and supernovae should be found in similar environments. Here we show that this expectation is wrong. Using Hubble Space Telescope imaging of the host galaxies of long-duration gamma-ray bursts and core-collapse supernovae, we find that the gamma-ray bursts are far more concentrated on the very brightest regions of their hosts than are the supernovae. Furthermore, the host galaxies of the gamma-ray bursts are significantly fainter and more irregular than the hosts of the supernovae. Together these results suggest that long-duration gamma-ray bursts are associated with the very most massive stars and may be restricted to galaxies of limited chemical evolution. Our results directly imply that lon...

  5. Resolved Host Studies of Stellar Explosions

    CERN Document Server

    Levesque, Emily M

    2016-01-01

    The host galaxies of nearby (z<0.3) core-collapse supernovae and long-duration gamma-ray bursts offer an excellent means of probing the environments and populations that produce these events' varied massive progenitors. These same young stellar progenitors make LGRBs and SNe valuable and potentially powerful tracers of star formation, metallicity, the IMF, and the end phases of stellar evolution. However, properly utilizing these progenitors as tools requires a thorough understanding of their formation and, consequently, the physical properties of their parent host environments. This review looks at some of the recent work on LGRB and SN hosts with resolved environments that allows us to probe the precise explosion sites and surrounding environments of these events in incredible detail.

  6. The Massive End of the Stellar Mass Function

    CERN Document Server

    D'Souza, R; Kauffmann, G

    2015-01-01

    We derive average flux corrections to the \\texttt{Model} magnitudes of the Sloan Digital Sky Survey (SDSS) galaxies by stacking together mosaics of similar galaxies in bins of stellar mass and concentration. Extra flux is detected in the outer low surface brightness part of the galaxies, leading to corrections ranging from 0.05 to 0.32 mag for the highest stellar mass galaxies. We apply these corrections to the MPA-JHU (Max-Planck Institute for Astrophysics - John Hopkins University) stellar masses for a complete sample of half a million galaxies from the SDSS survey to derive a corrected galaxy stellar mass function at $z=0.1$ in the stellar mass range $9.5<\\log(M_\\ast/M_\\odot)<12.0$. We find that the flux corrections and the use of the MPA-JHU stellar masses have a significant impact on the massive end of the stellar mass function, making the slope significantly shallower than that estimated by Li \\& White (2009), but steeper than derived by Bernardi et al. (2013). This corresponds to a mean comov...

  7. White Paper on Nuclear Astrophysics

    CERN Document Server

    Arcones, Almudena; Beers, Timothy; Berstein, Lee; Blackmon, Jeff; Bronson, Messer; Brown, Alex; Brown, Edward; Brune, Carl; Champagne, Art; Chieffi, Alessandro; Couture, Aaron; Danielewicz, Pawel; Diehl, Roland; El-Eid, Mounib; Escher, Jutta; Fields, Brian; Frohlich, Carla; Herwig, Falk; Hix, William Raphael; Iliadis, Christian; Lynch, William; McLaughlin, Gail; Meyer, Bradley; Mezzacappa, Anthony; Nunes, Filomena; O'Shea, Brian; Prakash, Madappa; Pritychenko, Boris; Reddy, Sanjay; Rehm, Ernst; Rogachev, Grigory; Rutledge, Robert; Schatz, Hendrik; Smith, Michael; Stairs, Ingrid; Steiner, Andrew; Strohmayer, Tod; Timmes, Frank; Townsley, Dean; Wiescher, Michael; Zegers, Remco; Zingale, Michael

    2016-01-01

    This white paper informs the nuclear astrophysics community and funding agencies about the scientific directions and priorities of the field and provides input from this community for the 2015 Nuclear Science Long Range Plan. It summarizes the outcome of the nuclear astrophysics town meeting that was held on August 21-23, 2014 in College Station at the campus of Texas A&M University in preparation of the NSAC Nuclear Science Long Range Plan. It also reflects the outcome of an earlier town meeting of the nuclear astrophysics community organized by the Joint Institute for Nuclear Astrophysics (JINA) on October 9- 10, 2012 Detroit, Michigan, with the purpose of developing a vision for nuclear astrophysics in light of the recent NRC decadal surveys in nuclear physics (NP2010) and astronomy (ASTRO2010). The white paper is furthermore informed by the town meeting of the Association of Research at University Nuclear Accelerators (ARUNA) that took place at the University of Notre Dame on June 12-13, 2014. In summ...

  8. The Dynamical Evolution of Stellar-Mass Black Holes in Dense Star Clusters

    Science.gov (United States)

    Morscher, Maggie

    Globular clusters are gravitationally bound systems containing up to millions of stars, and are found ubiquitously in massive galaxies, including the Milky Way. With densities as high as a million stars per cubic parsec, they are one of the few places in the Universe where stars interact with one another. They therefore provide us with a unique laboratory for studying how gravitational interactions can facilitate the formation of exotic systems, such as X-ray binaries containing black holes, and merging double black hole binaries, which are produced much less efficiently in isolation. While telescopes can provide us with a snapshot of what these dense clusters look like at present, we must rely on detailed numerical simulations to learn about their evolution. These simulations are quite challenging, however, since dense star clusters are described by a complicated set of physical processes occurring on many different length and time scales, including stellar and binary evolution, weak gravitational scattering encounters, strong resonant binary interactions, and tidal stripping by the host galaxy. Until very recently, it was not possible to model the evolution of systems with millions of stars, the actual number contained in the largest clusters, including all the relevant physics required describe these systems accurately. The Northwestern Group's Henon Monte Carlo code, CMC, which has been in development for over a decade, is a powerful tool that can be used to construct detailed evolutionary models of large star clusters. With its recent parallelization, CMC is now capable of addressing a particularly interesting unsolved problem in astrophysics: the dynamical evolution of stellar black holes in dense star clusters. Our current understanding of the stellar initial mass function and massive star evolution suggests that young globular clusters may have formed hundreds to thousands of stellar-mass black holes, the remnants of stars with initial masses from 20 - 100

  9. Radiative Magnetic Reconnection in Astrophysics

    CERN Document Server

    Uzdensky, Dmitri A

    2015-01-01

    I review a new rapidly growing area of high-energy plasma astrophysics --- radiative magnetic reconnection, i.e., a reconnection regime where radiation reaction influences reconnection dynamics, energetics, and nonthermal particle acceleration. This influence be may be manifested via a number of astrophysically important radiative effects, such as radiation-reaction limits on particle acceleration, radiative cooling, radiative resistivity, braking of reconnection outflows by radiation drag, radiation pressure, viscosity, and even pair creation at highest energy densities. Self-consistent inclusion of these effects in magnetic reconnection theory and modeling calls for serious modifications to our overall theoretical approach to the problem. In addition, prompt reconnection-powered radiation often represents our only observational diagnostic tool for studying remote astrophysical systems; this underscores the importance of developing predictive modeling capabilities to connect the underlying physical condition...

  10. Astrophysics a very short introduction

    CERN Document Server

    Binney, James

    2016-01-01

    Astrophysics is the physics of the stars, and more widely the physics of the Universe. It enables us to understand the structure and evolution of planetary systems, stars, galaxies, interstellar gas, and the cosmos as a whole. In this Very Short Introduction, the leading astrophysicist James Binney shows how the field of astrophysics has expanded rapidly in the past century, with vast quantities of data gathered by telescopes exploiting all parts of the electromagnetic spectrum, combined with the rapid advance of computing power, which has allowed increasingly effective mathematical modelling. He illustrates how the application of fundamental principles of physics - the consideration of energy and mass, and momentum - and the two pillars of relativity and quantum mechanics, has provided insights into phenomena ranging from rapidly spinning millisecond pulsars to the collision of giant spiral galaxies. This is a clear, rigorous introduction to astrophysics for those keen to cut their teeth on a conceptual trea...

  11. Towards 21st Century Stellar Models: Star Clusters, Supercomputing, and Asteroseismology

    DEFF Research Database (Denmark)

    Campbell, S. W.; Constantino, T. N.; D'Orazi, V.;

    2016-01-01

    Stellar models provide a vital basis for many aspects of astronomy and astrophysics. Recent advances in observational astronomy -- through asteroseismology, precision photometry, high-resolution spectroscopy, and large-scale surveys -- are placing stellar models under greater quantitative scrutin...... a brief overview of the evolution, importance, and substantial uncertainties of core helium burning stars in particular and then briefly discuss a range of methods, both theoretical and observational, that we are using to advance the modelling....

  12. Advances in astronomy and astrophysics

    CERN Document Server

    Kopal, Zdenek

    1968-01-01

    Advances in Astronomy and Astrophysics, Volume 6 brings together numerous research works on different aspects of astronomy and astrophysics. This volume is composed of five chapters, and starts with the description of improved methods for analyzing and classifying families of periodic orbits in a conservative dynamical system with two degrees of freedom. The next chapter describes the variation of fractional luminosity of distorted components of close binary systems in the course of their revolution, or the accompanying changes in radial velocity. This topic is followed by discussions on vari

  13. Advances in astronomy and astrophysics

    CERN Document Server

    Kopal, Zdenek

    1963-01-01

    Advances in Astronomy and Astrophysics, Volume 2 brings together numerous research works on different aspects of astronomy and astrophysics. This volume is composed of six chapters and begins with a summary of observational record on twilight extensions of the Venus cusps. The next chapter deals with the common and related properties of binary stars, with emphasis on the evaluation of their cataclysmic variables. Cataclysmic variables refer to an object in one of three classes: dwarf nova, nova, or supernova. These topics are followed by discussions on the eclipse phenomena and the eclipses i

  14. White Paper on Nuclear Astrophysics

    OpenAIRE

    Arcones, Almudena; Bardayan, Dan W.; Beers, Timothy C.; Berstein, Lee A.; Blackmon, Jeffrey C.; Messer, Bronson; Brown, B. Alex; Brown, Edward F; Brune, Carl R.; Champagne, Art E.; Chieffi, Alessandro; Couture, Aaron J.; Danielewicz, Pawel; Diehl, Roland; El-Eid, Mounib

    2016-01-01

    This white paper informs the nuclear astrophysics community and funding agencies about the scientific directions and priorities of the field and provides input from this community for the 2015 Nuclear Science Long Range Plan. It summarizes the outcome of the nuclear astrophysics town meeting that was held on August 21-23, 2014 in College Station at the campus of Texas A&M University in preparation of the NSAC Nuclear Science Long Range Plan. It also reflects the outcome of an earlier town mee...

  15. Nuclear astrophysics lessons from INTEGRAL.

    Science.gov (United States)

    Diehl, Roland

    2013-02-01

    Measurements of high-energy photons from cosmic sources of nuclear radiation through ESA's INTEGRAL mission have advanced our knowledge: new data with high spectral resolution showed that characteristic gamma-ray lines from radioactive decays occur throughout the Galaxy in its interstellar medium. Although the number of detected sources and often the significance of the astrophysical results remain modest, conclusions derived from this unique astronomical window of radiation originating from nuclear processes are important, complementing the widely-employed atomic-line based spectroscopy. We review the results and insights obtained in the past decade from gamma-ray line measurements of cosmic sources in the context of their astrophysical questions.

  16. Advances in astronomy and astrophysics

    CERN Document Server

    Kopal, Zdenek

    1966-01-01

    Advances in Astronomy and Astrophysics, Volume 4 brings together numerous research works on different aspects of astronomy and astrophysics. This volume is composed of five chapters, and starts with a description of objective prism and its application in space observations. The next chapter deals with the possibilities of deriving reliable models of the figure, density distribution, and gravity field of the Moon based on data obtained through Earth-bound telescopes. These topics are followed by a discussion on the ideal partially relativistic, partially degenerate gas in an exact manner. A ch

  17. Stellar matter with pseudoscalar condensates

    Energy Technology Data Exchange (ETDEWEB)

    Andrianov, A.A. [Saint-Petersburg State University, St. Petersburg (Russian Federation); Universitat de Barcelona, Departament d' Estructura i Constituents de la Materia and Institut de Ciencies del Cosmos (ICCUB), Barcelona, Catalonia (Spain); Andrianov, V.A.; Kolevatov, S.S. [Saint-Petersburg State University, St. Petersburg (Russian Federation); Espriu, D. [Universitat de Barcelona, Departament d' Estructura i Constituents de la Materia and Institut de Ciencies del Cosmos (ICCUB), Barcelona, Catalonia (Spain)

    2016-03-15

    In this work we consider how the appearance of gradients of pseudoscalar condensates in dense systems may possibly influence the transport properties of photons in such a medium as well as other thermodynamic characteristics. We adopt the hypothesis that in regions where the pseudoscalar density gradient is large the properties of photons and fermions are governed by the usual lagrangian extended with a Chern-Simons interaction for photons and a constant axial field for fermions. We find that these new pieces in the lagrangian produce non-trivial reflection coefficients both for photons and fermions when entering or leaving a region where the pseudoscalar has a non-zero gradient. A varying pseudoscalar density may also lead to instability of some fermion and boson modes and modify some properties of the Fermi sea. We speculate that some of these modifications could influence the cooling rate of stellar matter (for instance in compact stars) and have other observable consequences. While quantitative results may depend on the precise astrophysical details most of the consequences are quite universal and consideration should be given to this possibility. (orig.)

  18. Laboratory Plasma Source as an MHD Model for Astrophysical Jets

    Science.gov (United States)

    Mayo, Robert M.

    1997-01-01

    The significance of the work described herein lies in the demonstration of Magnetized Coaxial Plasma Gun (MCG) devices like CPS-1 to produce energetic laboratory magneto-flows with embedded magnetic fields that can be used as a simulation tool to study flow interaction dynamic of jet flows, to demonstrate the magnetic acceleration and collimation of flows with primarily toroidal fields, and study cross field transport in turbulent accreting flows. Since plasma produced in MCG devices have magnetic topology and MHD flow regime similarity to stellar and extragalactic jets, we expect that careful investigation of these flows in the laboratory will reveal fundamental physical mechanisms influencing astrophysical flows. Discussion in the next section (sec.2) focuses on recent results describing collimation, leading flow surface interaction layers, and turbulent accretion. The primary objectives for a new three year effort would involve the development and deployment of novel electrostatic, magnetic, and visible plasma diagnostic techniques to measure plasma and flow parameters of the CPS-1 device in the flow chamber downstream of the plasma source to study, (1) mass ejection, morphology, and collimation and stability of energetic outflows, (2) the effects of external magnetization on collimation and stability, (3) the interaction of such flows with background neutral gas, the generation of visible emission in such interaction, and effect of neutral clouds on jet flow dynamics, and (4) the cross magnetic field transport of turbulent accreting flows. The applicability of existing laboratory plasma facilities to the study of stellar and extragalactic plasma should be exploited to elucidate underlying physical mechanisms that cannot be ascertained though astrophysical observation, and provide baseline to a wide variety of proposed models, MHD and otherwise. The work proposed herin represents a continued effort on a novel approach in relating laboratory experiments to

  19. Drying Induced Hydrophobic Polymer Collapse

    OpenAIRE

    ten Wolde, Pieter Rein; Chandler, David

    2002-01-01

    We have used computer simulation to study the collapse of a hydrophobic chain in water. We find that the mechanism of collapse is much like that of a first-order phase transition. The evaporation of water in the vicinity of the polymer provides the driving force for collapse, and the rate limiting step is the nucleation of a sufficiently large vapor bubble. The study is made possible through the application of transition path sampling and a coarse-grained treatment of liquid water. Relevance ...

  20. A grid of one-dimensional low-mass star formation collapse models

    Science.gov (United States)

    Vaytet, N.; Haugbølle, T.

    2017-02-01

    Context. Numerical simulations of star formation are becoming ever more sophisticated, incorporating new physical processes in increasingly realistic set-ups. These models are being compared to the latest observations through state-of-the-art synthetic renderings that trace the different chemical species present in the protostellar systems. The chemical evolution of the interstellar and protostellar matter is very topical, with more and more chemical databases and reaction solvers available online to the community. Aims: The current study was developed to provide a database of relatively simple numerical simulations of protostellar collapse as a template library for observations of cores and very young protostars, and for researchers who wish to test their chemical modelling under dynamic astrophysical conditions. It was also designed to identify statistical trends that may appear when running many models of the formation of low-mass stars by varying the initial conditions. Methods: A large set of 143 calculations of the gravitational collapse of an isolated sphere of gas with uniform temperature and a Bonnor-Ebert-like density profile was undertaken using a 1D fully implicit Lagrangian radiation hydrodynamics code. The parameter space covered initial masses from 0.2 to 8 M⊙, temperatures of 5-30 K, and radii 3000 ≤ R0 ≤ 30 000 AU. Results: A spread due to differing initial conditions and optical depths, was found in the thermal evolutionary tracks of the runs. Within less than an order of magnitude, all first and second Larson cores had masses and radii essentially independent of the initial conditions. Radial profiles of the gas density, velocity, and temperature were found to vary much more outside of the first core than inside. The time elapsed between the formation of the first and second cores was found to strongly depend on the first core mass accretion rate, and no first core in our grid of models lived for longer than 2000 years before the onset of

  1. Stellar feedback efficiencies: supernovae versus stellar winds

    CERN Document Server

    Fierlinger, Katharina M; Ntormousi, Evangelia; Fierlinger, Peter; Schartmann, Marc; Ballone, Alessandro; Krause, Martin G H; Diehl, Roland

    2015-01-01

    Stellar winds and supernova (SN) explosions of massive stars ("stellar feedback") create bubbles in the interstellar medium (ISM) and insert newly produced heavy elements and kinetic energy into their surroundings, possibly driving turbulence. Most of this energy is thermalized and immediately removed from the ISM by radiative cooling. The rest is available for driving ISM dynamics. In this work we estimate the amount of feedback energy retained as kinetic energy when the bubble walls have decelerated to the sound speed of the ambient medium. We show that the feedback of the most massive star outweighs the feedback from less massive stars. For a giant molecular cloud (GMC) mass of 1e5 solar masses (as e.g. found in the Orion GMCs) and a star formation efficiency of 8% the initial mass function predicts a most massive star of approximately 60 solar masses. For this stellar evolution model we test the dependence of the retained kinetic energy of the cold GMC gas on the inclusion of stellar winds. In our model w...

  2. The Stellar Imager (SI) - A Mission to Resolve Stellar Surfaces, Interiors, and Magnetic Activity

    Science.gov (United States)

    Christensen-Dalsgaard, Jorgen; Carpenter, Kenneth G.; Schrijver, Carolus J.; Karovska, Margarita

    2012-01-01

    The Stellar Imager (SI) is a space-based, UV/Optical Interferometer (UVOI) designed to enable 0.1 milli-arcsecond (mas) spectral imaging of stellar surfaces and of the Universe in general. It will also probe via asteroseismology flows and structures in stellar interiors. SI will enable the development and testing of a predictive dynamo model for the Sun, by observing patterns of surface activity and imaging of the structure and differential rotation of stellar interiors in a population study of Sun-like stars to determine the dependence of dynamo action on mass, internal structure and flows, and time. SI's science focuses on the role of magnetism in the Universe and will revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magnetohydrodynamically controlled processes in the Universe. SI is a "LandmarklDiscovery Mission" in the 2005 Heliophysics Roadmap, an implementation of the UVOI in the 2006 Astrophysics Strategic Plan, and a NASA Vision Mission ("NASA Space Science Vision Missions" (2008), ed. M. Allen). We present here the science goals of the SI Mission, a mission architecture that could meet those goals, and the technology development needed to enable this mission

  3. Nuclear astrophysics of light nuclei

    DEFF Research Database (Denmark)

    Fynbo, Hans Otto Uldall

    2013-01-01

    A review of nuclear astrophysics of light nuclei using radioactive beams or techniques developed for radioactive beams is given. We discuss Big Bang nucleosynthesis, with special focus on the lithium problem, aspects of neutrino-physics, helium-burning and finally selected examples of studies...

  4. The Stellar Imager (SI) Vision Mission

    CERN Document Server

    Carpenter, K G; Karovska, M; SI Vision Mission Team; Carpenter, Kenneth G.; Schrijver, Carolus J.; Karovska, Margarita; Team, SI Vision Mission

    2006-01-01

    The Stellar Imager (SI) is a UV-Optical, Space-Based Interferometer designed to enable 0.1 milli-arcsecond (mas) spectral imaging of stellar surfaces and of the Universe in general and asteroseismic imaging of stellar interiors. SI is identified as a "Flagship and Landmark Discovery Mission" in the 2005 Sun Solar System Connection (SSSC) Roadmap and as a candidate for a "Pathways to Life Observatory" in the Exploration of the Universe Division (EUD) Roadmap (May, 2005). SI will revolutionize our view of many dynamic astrophysical processes: its resolution will transform point sources into extended sources, and snapshots into evolving views. SI's science focuses on the role of magnetism in the Universe, particularly on magnetic activity on the surfaces of stars like the Sun. SI's prime goal is to enable long-term forecasting of solar activity and the space weather that it drives. SI will also revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant p...

  5. Parametric initial conditions for core-collapse supernova simulations

    CERN Document Server

    Suwa, Yudai

    2016-01-01

    We investigate a method to construct parametrized progenitor models for core-collapse supernova simulations. Different from all modern core-collapse supernova studies, which rely on progenitor models from stellar evolution calculations, we follow the methodology of Baron & Cooperstein (1990) to construct initial models. Choosing parametrized spatial distributions of entropy and electron fraction as a function of mass coordinate and solving the equation of hydrostatic equilibrium, we obtain the initial density structures of our progenitor models. First, we calculate structures with parameters fitting broadly the evolutionary model s11.2 of Woosley et al. (2002). We then demonstrate the reliability of our method by performing general relativistic hydrodynamic simulations in spherical symmetry with the isotropic diffusion source approximation to solve the neutrino transport. Our comprehensive parameter study shows that initial models with a small central entropy ($\\lesssim 0.4\\,k_B$ nucleon$^{-1}$) can explo...

  6. Atmospheric heat redistribution and collapse on tidally locked rocky planets

    CERN Document Server

    Wordsworth, Robin

    2014-01-01

    Atmospheric collapse is likely to be of fundamental importance to tidally locked rocky exoplanets but remains understudied. Here, general results on the heat transport and stability of tidally locked terrestrial-type atmospheres are reported. First, the problem is modeled with an idealized 3D general circulation model (GCM) with gray gas radiative transfer. It is shown that over a wide range of parameters the atmospheric boundary layer, rather than the large-scale circulation, is the key to understanding the planetary energy balance. Through a scaling analysis of the interhemispheric energy transfer, theoretical expressions for the day-night temperature difference and surface wind speed are created that reproduce the GCM results without tuning. Next, the GCM is used with correlated-k radiative transfer to study heat transport for two real gases (CO2 and CO). For CO2, empirical formulae for the collapse pressure as a function of planetary mass and stellar flux are produced, and critical pressures for atmospher...

  7. International Olympiad on Astronomy and Astrophysics

    Science.gov (United States)

    Soonthornthum, B.; Kunjaya, C.

    2011-01-01

    The International Olympiad on Astronomy and Astrophysics, an annual astronomy and astrophysics competition for high school students, is described. Examples of problems and solutions from the competition are also given. (Contains 3 figures.)

  8. Unveiling the High Energy Obscured Universe: Hunting Collapsed Objects Physics

    Science.gov (United States)

    Ubertini, P.; Bazzano, A.; Cocchi, M.; Natalucci, L.; Bassani, L.; Caroli, E.; Stephen, J. B.; Caraveo, P.; Mereghetti, S.; Villa, G.

    2005-01-01

    A large part of energy from space is coming from collapsing stars (SN, Hypernovae) and collapsed stars (black holes, neutron stars and white dwarfs). The peak of their energy release is in the hard-X and gamma-ray wavelengths where photons are insensitive to absorption and can travel from the edge the Universe or the central core of the Galaxy without loosing the primordial information of energy, time signature and polarization. The most efficient process to produce energetic photons is gravitational accretion of matter from a "normal" star onto a collapsed companion (LGxMcollxdMacc/dtx( 1Rdisc)-dMacc/dt x c2), exceeding by far the nuclear reaction capability to generate high energy quanta. Thus our natural laboratory for "in situ" investigations are collapsed objects in which matter and radiation co-exist in extreme conditions of temperature and density due to gravitationally bent geometry and magnetic fields. This is a unique opportunity to study the physics of accretion flows in stellar mass and super-massive Black Holes (SMBHs), plasmoids generated in relativistic jets in galactic microQSOs and AGNs, ionised plasma interacting at the touching point of weakly magnetized NS surface, GRB/Supernovae connection, and the mysterious origins of "dark" GRB and X-ray flash.

  9. On the dynamics of dust during protostellar collapse

    CERN Document Server

    Bate, Matthew R

    2016-01-01

    The dynamics of dust and gas can be quite different from each other when the dust is poorly coupled to the gas. In protoplanetary discs, it is well known that this decoupling of the dust and gas can lead to diverse spatial structures and dust-to-gas ratios. In this paper, we study the dynamics of dust and gas during the earlier phase of protostellar collapse, before a protoplanetary disc is formed. We find that for dust grains with sizes < 10 micron, the dust is well coupled during the collapse of a rotating, pre-stellar core and there is little variation of the dust-to-gas ratio during the collapse. However, if larger grains are present, they may have trajectories that are very different from the gas during the collapse, leading to mid-plane settling and/or oscillations of the dust grains through the mid-plane. This may produce variations in the dust-to-gas ratio and very different distributions of large and small dust grains at the very earliest stages of star formation, if large grains are present in pr...

  10. Precise calculations of astrophysically important allowed and forbidden transitions of Xe VIII

    CERN Document Server

    Bhowmik, Anal; Roy, Sourav

    2016-01-01

    The present work reports astrophysically important transition line parameters for Xe VIII. The relativistic coupled-cluster method is employed here to calculate the E1, E2, and M1 transition line parameters with a high accuracy. The E1 oscillator strengths and probabilities of E2 and M1 transitions are determined using theoretical amplitudes and experimental energy values. The calculated branching ratios and the lifetimes are supplement to the transition parameters. The accurate presentations of these calculated data are crucial for the density estimations in several stellar and inter-stellar mediums.

  11. A new type of stellar explosion

    CERN Document Server

    Perets, H B; Mazzali, P; Arnett, D; Kagan, D; Filippenko, A V; Li, W; Cenko, S B; Fox, D B; Leonard, D C; Moon, D -S; Sand, D J; Soderberg, A M; Foley, R J; Ganeshalingam, M; Anderson, J P; James, P A; Ofek, E O; Bildsten, L; Nelemans, G; Shen, K J; Weinberg, N N; Metzger, B D; Piro, A L; Quataert, E; Kiewe, M; Poznanski, D

    2009-01-01

    The explosive deaths of stars (supernovae; SNe) are generally explained by two physical processes. Young massive stars (more than eight solar masses, M_Sun) undergo gravitational core-collapse and appear as type Ib/c and II SNe. Type Ia SNe result from thermonuclear explosions of older, Chandrasekhar-mass carbon-oxygen white dwarfs (WDs). Even the most underluminous SNe Ia eject ~1 M_Sun of C/O burning products. Here we report our discovery of the faint type Ib SN 2005E in the halo of the nearby isolated galaxy, NGC 1032. The lack of any trace of recent star formation near the SN location, and the very low ejected mass we find (~0.3 M_Sun) argues strongly against a core-collapse origin of this event. Our spectroscopic observations and the derived nucleosynthetic output show that the SN ejecta is dominated by helium-burning products, indicating that SN 2005E was neither a subluminous nor a regular SNe Ia. We have therefore found a new type of stellar explosion, arising from a low-mass, old stellar system. The ...

  12. Black holes formed by direct collapse: observational evidences

    CERN Document Server

    Mirabel, I F

    2016-01-01

    Binary black holes as the recently detected sources of gravitational waves can be formed from massive stellar binaries in the field or by dynamical interactions in clusters of high stellar density, if the black holes are the remnants of massive stars that collapsed without natal kicks that would disrupt the binary system or eject the black holes from the cluster before binary black hole formation. Here are summarized and discussed the kinematics in three dimensions of space of five Galactic black hole X-ray binaries. For Cygnus X-1 and GRS 1915+105 it is found that the black holes of ~15 and ~10 solar masses in these sources were formed in situ, without energetic kicks. These observations suggest that binary black holes with components of ~10 solar masses may have been prolifically produced in the universe.

  13. Geophysical observations at cavity collapse

    OpenAIRE

    Jousset, Philippe; Bazargan-Sabet, Behrooz; Lebert, François; Bernardie, Séverine; Gourry, Jean-Christophe

    2010-01-01

    International audience; In Lorraine region (France) salt layers at about 200 meters depth are exploited by Solvay using solution mining methodology which consists in extracting the salt by dissolution, collapsing the cavern overburden during the exploitation phase and finally reclaiming the landscape by creating a water area. In this process, one of the main challenges for the exploiting company is to control the initial 120-m diameter collapse so as to minimize possible damages. In order to ...

  14. Precision laboratory measurements in nuclear astrophysics

    Energy Technology Data Exchange (ETDEWEB)

    Gai, M. [Connecticut Univ., Storrs, CT (United States). Dept. of Physics

    2000-07-01

    After reviewing some of the basic concepts, nomenclatures and parametrizations of astronomy, astrophysics, cosmology, and nuclear physics, we introduce a few central problems in nuclear astrophysics, including the hot-CNO cycle, helium burning and solar neutrinos. We demonstrate that in this new era of precision nuclear astrophysics secondary or radioactive nuclear beams allow for progress. (orig.)

  15. Vibrational Collapse of Hexapod Packings

    Science.gov (United States)

    Zhao, Yuchen; Ding, Jingqiu; Barés, Jonathan; Dierichs, Karola; Behringer, Robert

    2016-11-01

    Columns made of convex noncohesive grains like sand collapse after being released from a confining container. However, structures built from concave grains can be stable without external support. Previous research show that the stability of the columns depends on column diameter and height, by observing column stability after carefully lifting their confinement tubes. Thinner and taller columns collapse with higher probability. While the column stability weakly depends on packing density, it strongly depends on inter-particle friction. Experiments that cause the column to collapse also reveal similar trends, as more effort (such as heavier loading or shearing) is required to destabilize columns that are intrinsically more stable. In the current experiments, we invesitage the effect of vibration on destructing a column. Short columns collapse following the relaxation dynamics of disorder systems, which coincides with similar experiments on staple packings. However, tall columns collapse faster at the beginning, in addition to the relaxation process coming after. Using high-speed imaging, we analyze column collapse data from different column geometries. Ongoing work is focusing on characterizing the stability of hexapod packings to vibration. We thanks NSF-DMR-1206351 and the William M. Keck Foundation.

  16. Double-helix stellarator

    Energy Technology Data Exchange (ETDEWEB)

    Moroz, P.E.

    1997-09-01

    A new stellarator configuration, the Double-Helix Stellarator (DHS), is introduced. This novel configuration features a double-helix center post as the only helical element of the stellarator coil system. The DHS configuration has many unique characteristics. One of them is the extreme low plasma aspect ratio, A {approx} 1--1.2. Other advantages include a high enclosed volume, appreciable rotational transform, and a possibility of extreme-high-{beta} MHD equilibria. Moreover, the DHS features improved transport characteristics caused by the absence of the magnetic field ripple on the outboard of the torus. Compactness, simplicity and modularity of the coil system add to the DHS advantages for fusion applications.

  17. Hydrodynamic Instability, Integrated Code, Laboratory Astrophysics, and Astrophysics

    Science.gov (United States)

    Takabe, Hideaki

    2016-10-01

    This is an article for the memorial lecture of Edward Teller Medal and is presented as memorial lecture at the IFSA03 conference held on September 12th, 2003, at Monterey, CA. The author focuses on his main contributions to fusion science and its extension to astrophysics in the field of theory and computation by picking up five topics. The first one is the anomalous resisitivity to hot electrons penetrating over-dense region through the ion wave turbulence driven by the return current compensating the current flow by the hot electrons. It is concluded that almost the same value of potential as the average kinetic energy of the hot electrons is realized to prevent the penetration of the hot electrons. The second is the ablative stabilization of Rayleigh-Taylor instability at ablation front and its dispersion relation so-called Takabe formula. This formula gave a principal guideline for stable target design. The author has developed an integrated code ILESTA (ID & 2D) for analyses and design of laser produced plasma including implosion dynamics. It is also applied to design high gain targets. The third is the development of the integrated code ILESTA. The forth is on Laboratory Astrophysics with intense lasers. This consists of two parts; one is review on its historical background and the other is on how we relate laser plasma to wide-ranging astrophysics and the purposes for promoting such research. In relation to one purpose, I gave a comment on anomalous transport of relativistic electrons in Fast Ignition laser fusion scheme. Finally, I briefly summarize recent activity in relation to application of the author's experience to the development of an integrated code for studying extreme phenomena in astrophysics.

  18. Space and Astrophysical Plasmas : Space and astrophysical plasmas: Pervasive problems

    Indian Academy of Sciences (India)

    Chanchal Uberoi

    2000-11-01

    The observations and measurements given by Earth orbiting satellites, deep space probes, sub-orbital systems and orbiting astronomical observatories point out that there are important physical processes which are responsible for a wide variety of phenomena in solar-terrestrial, solar-system and astrophysical plasmas. In this review these topics are exemplified both from an observational and a theoretical point of view.

  19. The Iron Project:. Radiative Atomic Processes in Astrophysics

    Science.gov (United States)

    Nahar, Sultana N.

    2011-06-01

    Astronomical objects, such as, stars, galaxies, blackhole environments, etc are studied through their spectra produced by various atomic processes in their plasmas. The positions, shifts, and strengths of the spectral lines provide information on physical processes with elements in all ionization states, and various diagnostics for temperature, density, distance, etc of these objects. With presence of a radiative source, such as a star, the astrophysical plasma is dominated by radiative atomic processes such as photoionization, electron-ion recombination, bound-bound transitions or photo-excitations and de-excitations. The relevant atomic parameters, such as photoionization cross sections, electron-ion recombination rate coefficients, oscillator strengths, radiative transition rates, rates for dielectronic satellite lines etc are needed to be highly accurate for precise diagnostics of physical conditions as well as accurate modeling, such as, for opacities of astrophysical plasmas. for opacities of astrophysical plasmas. This report illustrates detailed features of radiative atomic processes obtained from accurate ab initio methods of the latest developments in theoretical quantum mechanical calculations, especially under the international collaborations known as the Iron Project (IP) and the Opacity Project (OP). These projects aim in accurate study of radiative and collsional atomic processes of all astrophysically abundant atoms and ions, from hydrogen to nickel, and calculate stellar opacities and have resulted in a large number of atomic parameters for photoionization and radiative transition probabilities. The unified method, which is an extension of the OP and the IP, is a self-consistent treatment for the total electron-ion recombination and photoionization. It incorporates both the radiative and the dielectronic recombination processes and provides total recombination rates and level-specific recombination rates for hundreds of levels for a wide range of

  20. Ludwig Franz Benedikt Biermann: the doyen of German post-war astrophysics

    Science.gov (United States)

    Wielebinski, Richard

    2015-11-01

    Ludwig Biermann was a major figure in theoretical astrophysics in Germany in the twentieth century. His work on stellar interiors, comets and magnetic fields advanced our knowledge. He also predicted the existence and the nature of the solar wind. His predictions were vindicated by space probes. Ludwig Biermann also was an important figure behind the scenes working on the revival of German astronomy after the demise of WWII. For his work he earned important national and international honors.

  1. On the formation of massive stellar clusters

    CERN Document Server

    Tenorio-Tagle, G; Silich, S A; Medina-Tanco, G A; Muñoz-Tunón, C; Tenorio-Tagle, Guillermo; Palous, Jan; Silich, Sergiy; Medina-Tanco, Gustavo A.; Munoz-Tunon, Casiana

    2003-01-01

    Here we model a star forming factory in which the continuous creation of stars results in a highly concentrated, massive (globular cluster-like) stellar system. We show that under very general conditions a large-scale gravitational instability in the ISM, which triggers the collapse of a massive cloud, leads with the aid of a spontaneous first generation of massive stars, to a standing, small-radius, cold and dense shell. Eventually, as more of the collapsing matter is processed and incorporated, the shell becomes gravitationally unstable and begins to fragment, allowing the formation of new stars, while keeping its location. This is due to a detailed balance established between the ram pressure from the collapsing cloud which, together with the gravitational force exerted on the shell by the forming cluster, acts against the mechanical energy deposited by the collection of new stars. We analyze the mass spectrum of fragments that result from the continuous fragmentation of the standing shell and show that it...

  2. The CASPAR underground accelerator facility for the study of low energy nuclear astrophysics

    Science.gov (United States)

    Robertson, Daniel; Couder, Manoel; Greife, Uwe; Strieder, Frank; Wiescher, Michael

    2016-09-01

    The drive of nuclear astrophysics is to push the limits of reaction measurements into the burning regime of astrophysical interest. As current laboratory experiments approach the stellar burning window, the rapid drop off of cross-sections is a significant barrier and drives the need for higher intensity accelerators, more robust and isotopically enriched target material and lower background interference. The natural background suppression of underground accelerator facilities enables the extension of current experimental data to the lower energies needed. The CASPAR facility is the first and only underground accelerator facility in the US, focused on the study of low energy reactions of nuclear astrophysical interest. Support provided by NSF Grant No. PHY 1419765, JINA-CEE Grant No. PHY 1430152 and the South Dakota Science and Technology Authority.

  3. Stellar ages from asteroseismology

    CERN Document Server

    Lebreton, Yveline

    2008-01-01

    Asteroseismology provides powerful means to probe stellar interiors. The oscillations frequencies are closely related to stellar interior properties via the density and sound speed profiles. Since these are tightly linked with the mass and evolutionary state, we can expect to determine the age and mass of a star from the comparison of its oscillation spectrum with predictions of stellar models. Such a comparison suffers both from the problems we face when modeling a particular star (as the uncertainties on global parameters and chemical composition) and from our misunderstanding of processes at work in stellar interiors (as the transport processes that may lead to core mixing and affect the model ages). For stars where observations have provided precise and numerous oscillation frequencies together with accurate global parameters and additional information (as the radius or the mass if the star is in a binary system, the interferometric radius or the mean density if the star is an exoplanet host), we can also...

  4. Stellar Chromospheric Activity

    Directory of Open Access Journals (Sweden)

    Hall Jeffrey C.

    2008-03-01

    Full Text Available The Sun, stars similar to it, and many rather dissimilar to it, have chromospheres, regions classically viewed as lying above the brilliant photosphere and characterized by a positive temperature gradient and a marked departure from radiative equilibrium. Stellar chromospheres exhibit a wide range of phenomena collectively called activity, stemming largely from the time evolution of their magnetic fields and the mass flux and transfer of radiation through the complex magnetic topology and the increasingly optically thin plasma of the outer stellar atmosphere. In this review, I will (1 outline the development of our understanding of chromospheric structure from 1960 to the present, (2 discuss the major observational programs and theoretical lines of inquiry, (3 review the origin and nature of both solar and stellar chromospheric activity and its relationship to, and effect on, stellar parameters including total energy output, and (4 summarize the outstanding problems today.

  5. Geophysical observations at cavity collapse

    Science.gov (United States)

    Jousset, Philippe; Bazargan-Sabet, Behrooz; Lebert, François; Bernardie, Séverine; Gourry, Jean-Christophe

    2010-05-01

    In Lorraine region (France) salt layers at about 200 meters depth are exploited by Solvay using solution mining methodology which consists in extracting the salt by dissolution, collapsing the cavern overburden during the exploitation phase and finally reclaiming the landscape by creating a water area. In this process, one of the main challenges for the exploiting company is to control the initial 120-m diameter collapse so as to minimize possible damages. In order to detect potential precursors and understand processes associated with such collapses, a wide series of monitoring techniques including micro seismics, broad-band seismology, hydro-acoustic, electromagnetism, gas probing, automatic leveling, continuous GPS, continuous gravity and borehole extensometry was set-up in the frame of an in-situ study carried out by the "Research Group for the Impact and Safety of Underground Works" (GISOS, France). Equipments were set-up well before the final collapse, giving a unique opportunity to analyze a great deal of information prior to and during the collapse process which has been successfully achieved on February the 13th, 2009 by controlling the cavity internal pressure. In this work, we present the results of data recorded by a network of 3 broadband seismometers, 2 accelerometers, 2 tilt-meters and a continuously gravity meter. We relate the variations of the brine pumping rate with the evolutions of the induced geophysical signals and finally we propose a first mechanical model for describing the controlled collapse. Beyond the studied case, extrapolation of the results obtained might contribute to the understanding of uncontrolled cavity collapses, such as pit-craters or calderas at volcanoes.

  6. Advanced Stellar Compass

    DEFF Research Database (Denmark)

    Madsen, Peter Buch; Jørgensen, John Leif; Thuesen, Gøsta;

    1997-01-01

    This document describes all interface properties for the Advanced Stellar Compass, developed for the German Research Satellite "CHAMP". Basic operations, modes, software protocol, calibration methods and closed loop test strategies are described.......This document describes all interface properties for the Advanced Stellar Compass, developed for the German Research Satellite "CHAMP". Basic operations, modes, software protocol, calibration methods and closed loop test strategies are described....

  7. Particle Acceleration in Astrophysical Sources

    CERN Document Server

    Amato, Elena

    2015-01-01

    Astrophysical sources are extremely efficient accelerators. Some sources emit photons up to multi-TeV energies, a signature of the presence, within them, of particles with energies much higher than those achievable with the largest accelerators on Earth. Even more compelling evidence comes from the study of Cosmic Rays, charged relativistic particles that reach the Earth with incredibly high energies: at the highest energy end of their spectrum, these subatomic particles are carrying a macroscopic energy, up to a few Joules. Here I will address the best candidate sources and mechanisms as cosmic particle accelerators. I will mainly focus on Galactic sources such as Supernova Remnants and Pulsar Wind Nebulae, which being close and bright, are the best studied among astrophysical accelerators. These sources are held responsible for most of the energy that is put in relativistic particles in the Universe, but they are not thought to accelerate particles up to the highest individual energies, $\\approx 10^{20}$ eV...

  8. Lecture notes: Astrophysical fluid dynamics

    CERN Document Server

    Ogilvie, Gordon I

    2016-01-01

    These lecture notes and example problems are based on a course given at the University of Cambridge in Part III of the Mathematical Tripos. Fluid dynamics is involved in a very wide range of astrophysical phenomena, such as the formation and internal dynamics of stars and giant planets, the workings of jets and accretion discs around stars and black holes, and the dynamics of the expanding Universe. Effects that can be important in astrophysical fluids include compressibility, self-gravitation and the dynamical influence of the magnetic field that is 'frozen in' to a highly conducting plasma. The basic models introduced and applied in this course are Newtonian gas dynamics and magnetohydrodynamics (MHD) for an ideal compressible fluid. The mathematical structure of the governing equations and the associated conservation laws are explored in some detail because of their importance for both analytical and numerical methods of solution, as well as for physical interpretation. Linear and nonlinear waves, includin...

  9. Large Eddy Simulations in Astrophysics

    CERN Document Server

    Schmidt, Wolfram

    2014-01-01

    In this review, the methodology of large eddy simulations (LES) is introduced and applications in astrophysics are discussed. As theoretical framework, the scale decomposition of the dynamical equations for neutral fluids by means of spatial filtering is explained. For cosmological applications, the filtered equations in comoving coordinates are also presented. To obtain a closed set of equations that can be evolved in LES, several subgrid scale models for the interactions between numerically resolved and unresolved scales are discussed, in particular the subgrid scale turbulence energy equation model. It is then shown how model coefficients can be calculated, either by dynamical procedures or, a priori, from high-resolution data. For astrophysical applications, adaptive mesh refinement is often indispensable. It is shown that the subgrid scale turbulence energy model allows for a particularly elegant and physically well motivated way of preserving momentum and energy conservation in AMR simulations. Moreover...

  10. Astrophysical Applications of Fractional Calculus

    Science.gov (United States)

    Stanislavsky, Aleksander A.

    The paradigm of fractional calculus occupies an important place for the macroscopic description of subdiffusion. Its advance in theoretical astrophysics is expected to be very attractive too. In this report we discuss a recent development of the idea to some astrophysical problems. One of them is connected with a random migration of bright points associated with magnetic fields at the solar photosphere. The transport of the bright points has subdiffusive features that require the fractional generalization of the Leighton's model. Another problem is related to the angular distribution of radio beams, being propagated through a medium with random inhomogeneities. The peculiarity of this medium is that radio beams are trapped because of random wave localization. This idea can be useful for the diagnostics of interplanetary and interstellar turbulent media.

  11. Magnetic Reconnection in Astrophysical Environments

    CERN Document Server

    Lazarian, A; Vishniac, E; Kowal, G

    2014-01-01

    Magnetic reconnection is a process that changes magnetic field topology in highly conducting fluids. Traditionally, magnetic reconnection was associated mostly with solar flares. In reality, the process must be ubiquitous as astrophysical fluids are magnetized and motions of fluid elements necessarily entail crossing of magnetic frozen in field lines and magnetic reconnection. We consider magnetic reconnection in realistic 3D geometry in the presence of turbulence. This turbulence in most astrophysical settings is of pre-existing nature, but it also can be induced by magnetic reconnection itself. In this situation turbulent magnetic field wandering opens up reconnection outflow regions, making reconnection fast. We discuss Lazarian \\& Vishniac (1999) model of turbulent reconnection, its numerical and observational testings, as well as its connection to the modern understanding of the Lagrangian properties of turbulent fluids. We show that the predicted dependences of the reconnection rates on the level of...

  12. Focusing Telescopes in Nuclear Astrophysics

    CERN Document Server

    Ballmoos, Peter von

    2007-01-01

    This volume is the first of its kind on focusing gamma-ray telescopes. Forty-eight refereed papers provide a comprehensive overview of the scientific potential and technical challenges of this nascent tool for nuclear astrophysics. The book features articles dealing with pivotal technologies such as grazing incident mirrors, multilayer coatings, Laue- and Fresnel-lenses - and even an optic using the curvature of space-time. The volume also presents an overview of detectors matching the ambitious objectives of gamma ray optics, and facilities for operating such systems on the ground and in space. The extraordinary scientific potential of focusing gamma-ray telescopes for the study of the most powerful sources and the most violent events in the Universe is emphasized in a series of introductory articles. Practicing professionals, and students interested in experimental high-energy astrophysics, will find this book a useful reference

  13. Selected methods of nuclear astrophysics

    CERN Document Server

    Dubovichenko, S B

    2012-01-01

    The book covers the certain questions of nuclear physics and nuclear astrophysics of light atomic nuclei and their processes at low and ultralow energies. Some methods of calculation of nuclear characteristics of the thermonuclear processes considered in nuclear astrophysics are given here. The obtained results are directly applicable to the solution of certain nuclear astrophysics problems in the field of description of the thermonuclear processes in the Sun, the stars and the Universe. The book is based on the results of approximately three-four tens of scientific papers generally published in recent five-seven years and consists of three sections. The first of them covers the description of the general methods of calculation of certain nuclear characteristics for the bound states or the continuum of quantum particles. The second section deals with the methods, the computer programs and the results of the phase shift analysis of elastic scattering in the p3He, p6Li, p12C, n12C, p13C, 4He4He and 4He12C nucle...

  14. Rounding Up the Astrophysical Weeds

    Science.gov (United States)

    McMillan, James P.

    New instruments used for astronomy such as ALMA, Herschel, and SOFIA have greatly increased the quality of available astrophysical data. These improved data contain spectral lines and features which are not accounted for in the quantum mechanical (QM) catalogs. A class of molecules has been identified as being particularly problematic, the so-called "weeds". These molecules have numerous transitions, of non-trivial intensity, which are difficult to model due to highly perturbed low lying vibrational states. The inability to properly describe the complete contribution of these weeds to the astrophysical data has led directly to the misidentification of other target molecules. Ohio State's Microwave Laboratory has developed an alternative approach to this problem. Rather than relying on complex QM calculations, we have developed a temperature dependent approach to laboratory based terahertz spectroscopy. We have developed a set of simple packages, in addition to traditional line list catalogs, that enable astronomers to successfully remove the weed signals from their data. This dissertation will detail my laboratory work and analysis of three keys weeds: methanol, methyl formate and methyl cyanide. Also, discussed will be the analytical technique I used to apply these laboratory results to astrophysical data.

  15. High energy astrophysics an introduction

    CERN Document Server

    Courvoisier, Thierry J -L

    2013-01-01

    High-energy astrophysics has unveiled a Universe very different from that only known from optical observations. It has revealed many types of objects in which typical variability timescales are as short as years, months, days, and hours (in quasars, X-ray binaries, and other objects), and even down to milli-seconds in gamma ray bursts. The sources of energy that are encountered are only very seldom nuclear fusion, and most of the time gravitation, a paradox when one thinks that gravitation is, by many orders of magnitude, the weakest of the fundamental interactions. The understanding of these objects' physical conditions and the processes revealed by high-energy astrophysics in the last decades is nowadays part of astrophysicists' culture, even of those active in other domains of astronomy. This book evolved from lectures given to master and PhD students at the University of Geneva since the early 1990s. It aims at providing astronomers and physicists intending to be active in high-energy astrophysics a broad...

  16. Collapse in Self-gravitating Turbulent Fluids

    CERN Document Server

    Murray, Daniel W; Pittman, John

    2015-01-01

    We perform simulations of star formation in self-gravitating turbulently driven gas. We find that star formation is not a self-similar process; two length scales enter, the radius of the rotationally supported disk $r_d$, and the radius $r_*$ of the sphere of influence of the nascent star, where the enclosed gas mass exceeds the stellar mass. The character of the flow changes at these two scales. We do not see any examples of inside-out collapse. Rather, the accretion of mass starts at large scales where we see large infall velocities $|u_r(r)| \\approx (1/3) v_{ff} \\sim (1/3)\\sqrt{GM(r)/r}\\gtrsim c_s$ out to $r \\sim 1 \\, \\rm{pc}$ hundreds of thousands of years before a star forms. The density evolves to a fixed attractor, $\\rho(r,t ) \\rightarrow \\rho(r)$, for $r_dr_d$ and rotational support becomes important for $r

  17. The Power of Principled Bayesian Methods in the Study of Stellar Evolution

    CERN Document Server

    von Hippel, Ted; Stenning, David C; Robinson, Elliot; Jeffery, Elizabeth; Stein, Nathan; Jefferys, William H; O'Malley, Erin

    2016-01-01

    It takes years of effort employing the best telescopes and instruments to obtain high-quality stellar photometry, astrometry, and spectroscopy. Stellar evolution models contain the experience of lifetimes of theoretical calculations and testing. Yet most astronomers fit these valuable models to these precious datasets by eye. We show that a principled Bayesian approach to fitting models to stellar data yields substantially more information over a range of stellar astrophysics. We highlight advances in determining the ages of star clusters, mass ratios of binary stars, limitations in the accuracy of stellar models, post-main-sequence mass loss, and the ages of individual white dwarfs. We also outline a number of unsolved problems that would benefit from principled Bayesian analyses.

  18. Eclipsing binary systems as tests of low-mass stellar evolution theory

    CERN Document Server

    Feiden, Gregory A

    2015-01-01

    Stellar fundamental properties (masses, radii, effective temperatures) can be extracted from observations of eclipsing binary systems with remarkable precision, often better than 2%. Such precise measurements afford us the opportunity to confront the validity of basic predictions of stellar evolution theory, such as the mass-radius relationship. A brief historical overview of confrontations between stellar models and data from eclipsing binaries is given, highlighting key results and physical insight that have led directly to our present understanding. The current paradigm that standard stellar evolution theory is insufficient to describe the most basic relation, that of a star's mass to its radius, along the main sequence is then described. Departures of theoretical expectations from empirical data, however, provide a rich opportunity to explore various physical solutions, improving our understanding of important stellar astrophysical processes.

  19. Towards 21st Century Stellar Models: Star Clusters, Supercomputing, and Asteroseismology

    CERN Document Server

    Campbell, S W; D'Orazi, V; Meakin, C; Stello, D; Christensen-Dalsgaard, J; Kuehn, C; De Silva, G M; Arnett, W D; Lattanzio, J C; MacLean, B T

    2015-01-01

    Stellar models provide a vital basis for many aspects of astronomy and astrophysics. Recent advances in observational astronomy -- through asteroseismology, precision photometry, high-resolution spectroscopy, and large-scale surveys -- are placing stellar models under greater quantitative scrutiny than ever. The model limitations are being exposed and the next generation of stellar models is needed as soon as possible. The current uncertainties in the models propagate to the later phases of stellar evolution, hindering our understanding of stellar populations and chemical evolution. Here we give a brief overview of the evolution, importance, and substantial uncertainties of core helium burning stars in particular and then briefly discuss a range of methods, both theoretical and observational, that we are using to advance the modelling.

  20. Towards 21st century stellar models: Star clusters, supercomputing and asteroseismology

    Science.gov (United States)

    Campbell, S. W.; Constantino, T. N.; D'Orazi, V.; Meakin, C.; Stello, D.; Christensen-Dalsgaard, J.; Kuehn, C.; De Silva, G. M.; Arnett, W. D.; Lattanzio, J. C.; MacLean, B. T.

    2016-09-01

    Stellar models provide a vital basis for many aspects of astronomy and astrophysics. Recent advances in observational astronomy - through asteroseismology, precision photometry, high-resolution spectroscopy, and large-scale surveys - are placing stellar models under greater quantitative scrutiny than ever. The model limitations are being exposed and the next generation of stellar models is needed as soon as possible. The current uncertainties in the models propagate to the later phases of stellar evolution, hindering our understanding of stellar populations and chemical evolution. Here we give a brief overview of the evolution, importance, and substantial uncertainties of core helium burning stars in particular and then briefly discuss a range of methods, both theoretical and observational, that we are using to advance the modelling. This study uses observational data from from HST, VLT, AAT, Kepler, and supercomputing resources in Australia provided by the National Computational Infrastructure (NCI) and Pawsey Supercomputing Centre.

  1. BONNSAI: correlated stellar observables in Bayesian methods

    Science.gov (United States)

    Schneider, F. R. N.; Castro, N.; Fossati, L.; Langer, N.; de Koter, A.

    2017-02-01

    accounting for correlations is essential in order to derive reliable stellar parameters including robust uncertainties and will be vital when entering an era of precision stellar astrophysics thanks to the Gaia satellite.

  2. Stellar Pulsations in Beyond Horndeski Gravity Theories

    CERN Document Server

    Sakstein, Jeremy; Koyama, Kazuya

    2016-01-01

    Theories of gravity in the beyond Horndeski class recover the predictions of general relativity in the solar system whilst admitting novel cosmologies, including late-time de Sitter solutions in the absence of a cosmological constant. Deviations from Newton's law are predicted inside astrophysical bodies, which allow for falsifiable, smoking-gun tests of the theory. In this work we study the pulsations of stars by deriving and solving the wave equation governing linear adiabatic oscillations to find the modified period of pulsation. Using both semi-analytic and numerical models, we perform a preliminary survey of the stellar zoo in an attempt to identify the best candidate objects for testing the theory. Brown dwarfs and Cepheid stars are found to be particularly sensitive objects and we discuss the possibility of using both to test the theory.

  3. Gravitational collapse and naked singularities

    Indian Academy of Sciences (India)

    Tomohiro Harada

    2004-10-01

    Gravitational collapse is one of the most striking phenomena in gravitational physics. The cosmic censorship conjecture has provided strong motivation for research in this field. In the absence of a general proof for censorship, many examples have been proposed, in which naked singularity is the outcome of gravitational collapse. Recent developments have revealed that there are examples of naked singularity formation in the collapse of physically reasonable matter fields, although the stability of these examples is still uncertain. We propose the concept of `effective naked singularities', which will be quite helpful because general relativity has limitation in its application at the high-energy end. The appearance of naked singularities is not detestable but can open a window for the new physics of strongly curved space-times.

  4. Magnetic Flux Transport by turbulent reconnection in astrophysical flows

    CERN Document Server

    Pino, Elisabete M de Gouveia Dal; Santos-Lima, Reinaldo; Guerrero, Gustavo; Kowal, Grzegorz; Lazarian, Alex

    2011-01-01

    The role of MHD turbulence in astrophysical environments is still highly debated. An important question that permeates this debate is the transport of magnetic flux. This is particularly important, for instance, in the context of star formation. When clouds collapse gravitationally to form stars, there must be some magnetic flux transport. otherwise the new born stars would have magnetic fields several orders of magnitude larger than the observed ones. Also, the magnetic flux that is dragged in the late stages of the formation of a star can remove all the rotational support from the accretion disk that grows around the protostar. The efficiency of the mechanism which is often invoked to allow the transport of magnetic fields in the different stages of star formation, namely, the ambipolar diffusion, has been lately put in check. We here discuss an alternative mechanism for magnetic flux transport which is based on turbulent fast magnetic reconnection. We review recent results obtained from 3D MHD numerical si...

  5. Beryllium Drive Disc Characterization for Laboratory Astrophysics Experiments

    Science.gov (United States)

    Ditmar, J. R.; Drake, R. P.; Kuranz, C. C.; Grosskopf, M. J.

    2009-11-01

    Laboratory Astrophysics scales large-scale phenomena, such as core-collapse supernovae shocks, down to the sub-millimeter scale for investigation in a laboratory setting. In some experiments, targets are constructed with a 20μm thick beryllium disc attached to a polyimide tube. A shockwave is created by irradiating the Be disc with ˜ 4kJ of energy from the Omega Laser. The Be material is rolled into a 20μm sheet and then machined to a 2.5mm diameter. Characterizing the roughness and knowing if there are any major features on the initial surface could affect interpretations of data taken during experiments. Structure in the Beryllium discs could become an important parameter in future high-fidelity computer simulations. Surfaces were characterized with a Scanning Electron Microscope and an Atomic Force Microscope.

  6. Moduli destabilization via gravitational collapse

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Dong-il [Sogang Univ., Seoul (Korea, Republic of). Center for Quantum Spacetime; Pedro, Francisco G. [Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany). Theory Group; Yeom, Dong-han [Sogang Univ., Seoul (Korea, Republic of). Center for Quantum Spacetime; Kyoto Univ. (Japan). Yukawa Inst. for Theoretical Physics

    2013-06-15

    We examine the interplay between gravitational collapse and moduli stability in the context of black hole formation. We perform numerical simulations of the collapse using the double null formalism and show that the very dense regions one expects to find in the process of black hole formation are able to destabilize the volume modulus. We establish that the effects of the destabilization will be visible to an observer at infinity, opening up a window to a region in spacetime where standard model's couplings and masses can differ significantly from their background values.

  7. Ekpyrotic collapse with multiple fields

    CERN Document Server

    Koyama, K; Koyama, Kazuya; Wands, David

    2007-01-01

    A scale invariant spectrum of isocurvature perturbations is generated during collapse in the scaling solution in models where two or more fields have steep negative exponential potentials. The scale invariance of the spectrum is realised by a tachyonic instability in the isocurvature field. We show that this instability is due to the fact that the scaling solution is a saddle point in the phase space. The late time attractor is identified with a single field dominated ekpyrotic collapse in which a steep blue spectrum for isocurvature perturbations is found. Although quantum fluctuations do not necessarily to disrupt the classical solution, an additional preceding stage is required to establish classical homogeneity.

  8. Collapse and dispersal of a homogeneous spin fluid in Einstein-Cartan theory

    Science.gov (United States)

    Hashemi, M.; Jalalzadeh, S.; Ziaie, A. H.

    2015-02-01

    In the present work, we revisit the process of gravitational collapse of a spherically symmetric homogeneous dust fluid which is described by the Oppenheimer-Snyder (OS) model (Oppenheimer and Snyder in Phys Rev D 56:455, 1939). We show that such a scenario would not end in a spacetime singularity when the spin degrees of freedom of fermionic particles within the collapsing cloud are taken into account. To this purpose, we take the matter content of the stellar object as a homogeneous Weyssenhoff fluid. Employing the homogeneous and isotropic FLRW metric for the interior spacetime setup, it is shown that the spin of matter, in the context of a negative pressure, acts against the pull of gravity and decelerates the dynamical evolution of the collapse in its later stages. Our results show a picture of gravitational collapse in which the collapse process halts at a finite radius, whose value depends on the initial configuration. We thus show that the spacetime singularity that occurs in the OS model is replaced by a non-singular bounce beyond which the collapsing cloud re-expands to infinity. Depending on the model parameters, one can find a minimum value for the boundary of the collapsing cloud or correspondingly a threshold value for the mass content below which the horizon formation can be avoided. Our results are supported by a thorough numerical analysis.

  9. Physical effects of gas envelopes with different extension on the collapse of a gas core

    CERN Document Server

    Arreaga-Garcia, Guillermo

    2013-01-01

    In this paper we study the gravitational collapse of a molecular hydrogen gas cloud composed of a core plus a gas envelope surrounding the core. We numerically simulate the collapse of four cloud models to take a glimpse to the time evolution of several dynamic variables, such as the angular momentum and the $aem$ ratio, as well as the ratios between the thermal and rotational energies with respect to the potential gravitational energy, denoted as $\\alpha$ and $\\beta$, respectively, among others. We re-take those models introduced by Arreaga et.al (Astronomy and Astrophysics, {\\bf Vol. 509}, (2010), pag. A96.) in the present paper in order to produce different outcomes of the collapsing cloud characterized in terms of the aforementioned dynamical variables. Such characterization was missing in the paper by Arreaga et.al (Astronomy and Astrophysics, {\\bf Vol. 509}, (2010), pag. A96.), and here we show that the gas envelope extension effects on the collapsing core can be quantitatively compared.

  10. Astrophysical Sources of Statistical Uncertainty in Precision Radial Velocities and Their Approximations

    CERN Document Server

    Beatty, Thomas G

    2015-01-01

    We investigate astrophysical contributions to the statistical uncertainty of precision radial velocity measurements of stellar spectra. We analytically determine the uncertainty in centroiding isolated spectral lines broadened by Gaussian, Lorentzian, Voigt, and rotational profiles, finding that for all cases and assuming weak lines, the uncertainty is the line centroid is $\\sigma_V\\approx C\\,\\Theta^{3/2}/(W I_0^{1/2})$, where $\\Theta$ is the full-width at half-maximum of the line, $W$ is the equivalent width, and $I_0$ is the continuum signal-to-noise ratio, with $C$ a constant of order unity that depends on the specific line profile. We use this result to motivate approximate analytic expressions to the total radial velocity uncertainty for a stellar spectrum with a given photon noise, resolution, wavelength, effective temperature, surface gravity, metallicity, macroturbulence, and stellar rotation. We use these relations to determine the dominant contributions to the statistical uncertainties in precision ...

  11. Hair of astrophysical black holes

    CERN Document Server

    Lyutikov, Maxim

    2012-01-01

    The "no hair" theorem is not applicable to black holes formed from collapse of a rotating neutron star. Rotating neutron stars can self-produce particles via vacuum breakdown forming a highly conducting plasma magnetosphere such that magnetic field lines are effectively "frozen-in" the star both before and during collapse. In the limit of no resistivity, this introduces a topological constraint which prohibits the magnetic field from sliding off the newly-formed event horizon. As a result, during collapse of a neutron star into a black hole, the latter conserves the number of magnetic flux tubes N_B = e \\Phi_\\infty /(\\pi c \\hbar), where \\Phi_\\infty is the initial magnetic flux through the hemispheres of the progenitor and out to infinity. The black hole's magnetosphere subsequently relaxes to the split monopole magnetic field geometry with self-generated currents outside the event horizon. The dissipation of the resulting equatorial current sheet leads to a slow loss of the anchored flux tubes, a process that...

  12. Asymmetries in core-collapse supernovae from maps of radioactive 44Ti in Cassiopeia A

    DEFF Research Database (Denmark)

    Grefenstette, B W; Harrison, F A; Boggs, S E;

    2014-01-01

    and iron X-ray emission, the latter being visible only in shock-heated material. The observed spatial distribution rules out symmetric explosions even with a high level of convective mixing, as well as highly asymmetric bipolar explosions resulting from a fast-rotating progenitor. Instead......Asymmetry is required by most numerical simulations of stellar core-collapse explosions, but the form it takes differs significantly among models. The spatial distribution of radioactive (44)Ti, synthesized in an exploding star near the boundary between material falling back onto the collapsing...

  13. A different approach to anisotropic spherical collapse with shear and heat radiation

    CERN Document Server

    Ivanov, B V

    2015-01-01

    In order to study the type of collapse, mentioned in the title, we introduce a physically meaningful object, called the horizon function. It directly enters the expressions for many of the stellar characteristics. The main junction equation, which governs the collapse, transforms into a Riccati equation with simple coefficients for the horizon function. We integrate this equation in the geodesic case. The same is done in the general case when one or another of the coefficients vanish. It is shown how to build classes of star models in this formulation of the problem and simple solutions are given.

  14. The Theoretical Astrophysical Observatory: Cloud-Based Mock Galaxy Catalogues

    CERN Document Server

    Bernyk, Maksym; Tonini, Chiara; Hodkinson, Luke; Hassan, Amr H; Garel, Thibault; Duffy, Alan R; Mutch, Simon J; Poole, Gregory B

    2014-01-01

    We introduce the Theoretical Astrophysical Observatory (TAO), an online virtual laboratory that houses mock observations of galaxy survey data. Such mocks have become an integral part of the modern analysis pipeline. However, building them requires an expert knowledge of galaxy modelling and simulation techniques, significant investment in software development, and access to high performance computing. These requirements make it difficult for a small research team or individual to quickly build a mock catalogue suited to their needs. To address this TAO offers access to multiple cosmological simulations and semi-analytic galaxy formation models from an intuitive and clean web interface. Results can be funnelled through science modules and sent to a dedicated supercomputer for further processing and manipulation. These modules include the ability to (1) construct custom observer light-cones from the simulation data cubes; (2) generate the stellar emission from star formation histories, apply dust extinction, a...

  15. Nuclear problems in astrophysical q-plasmas and environments

    CERN Document Server

    Coraddu, M; Quarati, P; Scarfone, A M

    2009-01-01

    Experimental measurements in terrestrial laboratory, space and astrophysical observations of variation and fluctuation of nuclear decay constants, measurements of large enhancements in fusion reaction rate of deuterons implanted in metals and electron capture by nuclei in solar core indicate that these processes depend on the environment where take place and possibly also on the fluctuation of some extensive parameters and eventually on stellar energy production. Electron screening is the first important environment effect. We need to develop a treatment beyond the Debye-Huckel screening approach, commonly adopted within global thermodynamic equilibrium. Advances in the description of these processes can be obtained by means of q-thermostatistics and/or superstatistics for metastable states. This implies to handle without ambiguities the case q<1.

  16. Ionization Modeling Astrophysical Gaseous Structures. I. The Optically Thin Regime

    CERN Document Server

    Churchill, Christopher W; Medina, Amber; Vliet, Jacob R Vander

    2014-01-01

    We present a code for modelling the ionization conditions of optically thin astrophysical gas structures. Given the gas hydrogen density, equilibrium temperature, elemental abundances, and the ionizing spectrum, the code solves the equilibrium ionization fractions and number densities for all ions from hydrogen to zinc. The included processes are photoionization, Auger ionization, direct collisional ionization, excitation auto-ionization, charge exchange ionization, two-body radiative recombination, dielectronic recombination, and charge exchange recombination. The ionizing spectrum can be generalized to include the ultraviolet background (UVB) and/or Starburst99 stellar populations of various masses, ages, metallicities, and distances. The ultimate goal with the code is to provide fast computation of the ionization conditions of gas in N-body + hydrodynamics cosmological simulations, in particular adaptive mesh refinement codes, in order to facilitate absorption line analysis of the simulated gas for compari...

  17. 25 Years of Self-Organized Criticality: Solar and Astrophysics

    CERN Document Server

    Aschwanden, Markus J; Dimitropoulou, Michaila; Georgoulis, Manolis; Hergarten, Stefan; MdAteer, James; Milovanov, Alexander V; Mineshige, Shin; Morales, Laura; Nishizuka, Naoto; Pruessner, Gunnar; Sanchez, Raul; Sharma, Surja; Strugarek, Antoine; Uritsky, Vadim

    2014-01-01

    Shortly after the seminal paper {\\sl "Self-Organized Criticality: An explanation of 1/f noise"} by Bak, Tang, and Wiesenfeld (1987), the idea has been applied to solar physics, in {\\sl "Avalanches and the Distribution of Solar Flares"} by Lu and Hamilton (1991). In the following years, an inspiring cross-fertilization from complexity theory to solar and astrophysics took place, where the SOC concept was initially applied to solar flares, stellar flares, and magnetospheric substorms, and later extended to the radiation belt, the heliosphere, lunar craters, the asteroid belt, the Saturn ring, pulsar glitches, soft X-ray repeaters, blazars, black-hole objects, cosmic rays, and boson clouds. The application of SOC concepts has been performed by numerical cellular automaton simulations, by analytical calculations of statistical (powerlaw-like) distributions based on physical scaling laws, and by observational tests of theoretically predicted size distributions and waiting time distributions. Attempts have been und...

  18. Progress of Jinping Underground laboratory for Nuclear Astrophysics (JUNA)

    Science.gov (United States)

    Liu, WeiPing; Li, ZhiHong; He, JiangJun; Tang, XiaoDong; Lian, Gang; An, Zhu; Chang, JianJun; Chen, Han; Chen, QingHao; Chen, XiongJun; Chen, ZhiJun; Cui, BaoQun; Du, XianChao; Fu, ChangBo; Gan, Lin; Guo, Bing; He, GuoZhu; Heger, Alexander; Hou, SuQing; Huang, HanXiong; Huang, Ning; Jia, BaoLu; Jiang, LiYang; Kubono, Shigeru; Li, JianMin; Li, KuoAng; Li, Tao; Li, YunJu; Lugaro, Maria; Luo, XiaoBing; Ma, HongYi; Ma, ShaoBo; Mei, DongMing; Qian, YongZhong; Qin, JiuChang; Ren, Jie; Shen, YangPing; Su, Jun; Sun, LiangTing; Tan, WanPeng; Tanihata, Isao; Wang, Shuo; Wang, Peng; Wang, YouBao; Wu, Qi; Xu, ShiWei; Yan, ShengQuan; Yang, LiTao; Yang, Yao; Yu, XiangQing; Yue, Qian; Zeng, Sheng; Zhang, HuanYu; Zhang, Hui; Zhang, LiYong; Zhang, NingTao; Zhang, QiWei; Zhang, Tao; Zhang, XiaoPeng; Zhang, XueZhen; Zhang, ZiMing; Zhao, Wei; Zhao, Zuo; Zhou, Chao

    2016-04-01

    Jinping Underground laboratory for Nuclear Astrophysics (JUNA) will take the advantage of the ultra-low background of CJPL lab and high current accelerator based on an ECR source and a highly sensitive detector to directly study for the first time a number of crucial reactions occurring at their relevant stellar energies during the evolution of hydrostatic stars. In its first phase, JUNA aims at the direct measurements of 25Mg(p, γ)26Al, 19F(p, α)16O, 13C(α, n)16O and 12C(α, γ)16O reactions. The experimental setup, which includes an accelerator system with high stability and high intensity, a detector system, and a shielding material with low background, will be established during the above research. The current progress of JUNA will be given.

  19. Protostellar jets the best laboratories for investigating astrophysical jets

    CERN Document Server

    De Gouveia dal Pino, E M

    1995-01-01

    Highly collimated supersonic jets are observed to emerge from a wide variety of astrophysical objects, ranging from Active Nuclei of Galaxies (AGN's) to Young Stellar Objects (YSOs) within our own Galaxy. Despite their different physical scales (in size, velocity, and amount of energy transported), they have strong morphological similarities. Thanks to the proximity and relatively small timescales, which permit direct observations of evolutionary changes, YSO jets are, perhaps, the best laboratories for cosmic jet investigation. In this lecture, the formation, structure, and evolution of the YSO jets are reviewed with the help of observational information, MHD and purely hydrodynamical modeling, and numerical simulations. Possible applications of the models to AGN jets are also addressed.

  20. Critical behavior of collapsing surfaces

    DEFF Research Database (Denmark)

    Olsen, Kasper; Sourdis, C.

    2009-01-01

    We consider the mean curvature evolution of rotationally symmetric surfaces. Using numerical methods, we detect critical behavior at the threshold of singularity formation resembling that of gravitational collapse. In particular, the mean curvature simulation of a one-parameter family of initial...

  1. Annual Report: Hydrodynamics and Radiative Hydrodynamics with Astrophysical Applications

    Energy Technology Data Exchange (ETDEWEB)

    R. Paul Drake

    2005-12-01

    We report the ongoing work of our group in hydrodynamics and radiative hydrodynamics with astrophysical applications. During the period of the existing grant, we have carried out two types of experiments at the Omega laser. One set of experiments has studied radiatively collapsing shocks, obtaining high-quality scaling data using a backlit pinhole and obtaining the first (ever, anywhere) Thomson-scattering data from a radiative shock. Other experiments have studied the deeply nonlinear development of the Rayleigh-Taylor (RT) instability from complex initial conditions, obtaining the first (ever, anywhere) dual-axis radiographic data using backlit pinholes and ungated detectors. All these experiments have applications to astrophysics, discussed in the corresponding papers either in print or in preparation. We also have obtained preliminary radiographs of experimental targets using our x-ray source. The targets for the experiments have been assembled at Michigan, where we also prepare many of the simple components. The above activities, in addition to a variety of data analysis and design projects, provide good experience for graduate and undergraduates students. In the process of doing this research we have built a research group that uses such work to train junior scientists.

  2. Introduction to stellar structure

    CERN Document Server

    Maciel, Walter J

    2016-01-01

    In the first part of this book, the author presents the basic properties of the stellar interior and describes them thoroughly, along with deriving the main stellar structure equations of temperature, density, pressure and luminosity, among others. The process and application of solving these equations is explained, as well as linking these results with actual observations.  The second part of the text describes what happens to a star over time, and how to determine this by solving the same equations at different points during a star’s lifetime. The fate of various stars is quite different depending on their masses, and this is described in the final parts of the book. This text can be used for an upper level undergraduate course or an introductory graduate course on stellar physics.

  3. Origins of Stellar Halos

    Science.gov (United States)

    Johnston, Kathryn V.

    2016-08-01

    This contribution reviews ideas about the origins of stellar halos. It includes discussion of the theoretical understanding of and observational evidence for stellar populations formed ``in situ'' (meaning formed in orbits close to their current ones), ``kicked-out'' (meaning formed in the inner galaxy in orbits unlike their current ones) and ``accreted'' (meaning formed in a dark matter halo other than the one they currently occupy). At this point there is general agreement that a significant fraction of any stellar halo population is likely ``accreted''. There is modest evidence for the presence of a ``kicked-out'' population around both the Milky Way and M31. Our theoretical understanding of and the observational evidence for an ``in situ'' population are less clear.

  4. Las Campanas Stellar Library

    Science.gov (United States)

    Chilingarian, Igor; Zolotukhin, Ivan; Beletsky, Yuri; Worthey, Guy

    2015-08-01

    Stellar libraries are fundamental tools required to understand stellar populations in star clusters and galaxies as well as properties of individual stars. Comprehensive libraries exist in the optical domain, but the near-infrared (NIR) domain stays a couple of decades behind. Here we present the Las Campanas Stellar Library project aiming at obtaining high signal-to-noise intermediate-resolution (R=8000) NIR spectra (0.83libraries, INDO-US and UVES-POP and followed up about 400 non-variable stars in the NIR in order to get complete optical-NIR coverage. Worth mentioning that our current sample includes about 80 AGB stars and a few dozens of bulge/LMC/SMC stars.

  5. Asteroseismology of Stellar Populations in the Milky Way

    CERN Document Server

    Eggenberger, Patrick; Girardi, Léo; Montalbán, Josefina

    2015-01-01

    The detection of radial and non-radial solar-like oscillations in thousands of G-K giants with CoRoT and Kepler is paving the road for detailed studies of stellar populations in the Galaxy. The available average seismic constraints allow largely model-independent determination of stellar radii and masses, and can be used to determine the position and age of thousands of stars in different regions of the Milky Way, and of giants belonging to open clusters. Such a close connection between stellar evolution, Galactic evolution, and asteroseismology opens a new very promising gate in our understanding of stars and galaxies.  This book represents a natural progression from the collection of review papers presented in the book 'Red Giants as Probes of the Structure and Evolution of the Milky Way', which appeared in the  Astrophysics and Space Science Proceedings series in 2012. This sequel volume contains review papers on spectroscopy, seismology of red giants, open questions in Galactic astrophysics, and discu...

  6. Solar astrophysics. 3. rev. ed.

    Energy Technology Data Exchange (ETDEWEB)

    Foukal, Peter V. [CRI, Nahant, MA (United States)

    2013-06-01

    This third, revised edition describes our current understanding of the sun - from its deepest interior, via the layers of the directly observable atmosphere to the solar wind, right up to its farthest extension into interstellar space. It includes a comprehensive account of the history of solar astrophysics, and the evolution of solar instruments. This account now includes the most up- to-date implementation of modern solar instruments in facilities on the ground and in space. The revised book now also provides an overview of recent results on ''space weather'' and on sun-climate relations, both of which are fields of increasing societal importance.

  7. Astrophysics Source Code Library Enhancements

    CERN Document Server

    Hanisch, Robert J; Berriman, G Bruce; DuPrie, Kimberly; Mink, Jessica; Nemiroff, Robert J; Schmidt, Judy; Shamir, Lior; Shortridge, Keith; Taylor, Mark; Teuben, Peter J; Wallin, John

    2014-01-01

    The Astrophysics Source Code Library (ASCL; ascl.net) is a free online registry of codes used in astronomy research; it currently contains over 900 codes and is indexed by ADS. The ASCL has recently moved a new infrastructure into production. The new site provides a true database for the code entries and integrates the WordPress news and information pages and the discussion forum into one site. Previous capabilities are retained and permalinks to ascl.net continue to work. This improvement offers more functionality and flexibility than the previous site, is easier to maintain, and offers new possibilities for collaboration. This presentation covers these recent changes to the ASCL.

  8. Astrophysics and Cosmology: International Partnerships

    Science.gov (United States)

    Blandford, Roger

    2016-03-01

    Most large projects in astrophysics and cosmology are international. This raises many challenges including: --Aligning the sequence of: proposal, planning, selection, funding, construction, deployment, operation, data mining in different countries --Managing to minimize cost growth through reconciling different practices --Communicating at all levels to ensure a successful outcome --Stabilizing long term career opportunities. There has been considerable progress in confronting these challenges. Lessons learned from past collaborations are influencing current facilities but much remains to be done if we are to optimize the scientific and public return on the expenditure of financial and human resources.

  9. Gravitational Lensing & Stellar Dynamics

    CERN Document Server

    Koopmans, L V E

    2005-01-01

    Strong gravitational lensing and stellar dynamics provide two complementary and orthogonal constraints on the density profiles of galaxies. Based on spherically symmetric, scale-free, mass models, it is shown that the combination of both techniques is powerful in breaking the mass-sheet and mass-anisotropy degeneracies. Second, observational results are presented from the Lenses Structure & Dynamics (LSD) Survey and the Sloan Lens ACS (SLACS) Survey collaborations to illustrate this new methodology in constraining the dark and stellar density profiles, and mass structure, of early-type galaxies to redshifts of unity.

  10. Sparse field stellar photometry.

    Science.gov (United States)

    Reid, N.

    The past few years have seen substantial developments in the capability of high speed measuring machines in the field of automated stellar photometry. In this review, after describing some of the limitations on photometric precision, empirical results are used to demonstrate the sort of accuracies that are possible with the UK Schmidt plate plus COSMOS/APM images-scan combination. The astronomical results obtained to date from these machines are discussed, and some consideration is given to the future role of measuring machines in stellar astronomy.

  11. The Kepler Catalog of Stellar Flares

    Science.gov (United States)

    Davenport, James R. A.

    2016-09-01

    A homogeneous search for stellar flares has been performed using every available Kepler light curve. An iterative light curve de-trending approach was used to filter out both astrophysical and systematic variability to detect flares. The flare recovery completeness has also been computed throughout each light curve using artificial flare injection tests, and the tools for this work have been made publicly available. The final sample contains 851,168 candidate flare events recovered above the 68% completeness threshold, which were detected from 4041 stars, or 1.9% of the stars in the Kepler database. The average flare energy detected is ˜1035 erg. The net fraction of flare stars increases with g - i color, or decreasing stellar mass. For stars in this sample with previously measured rotation periods, the total relative flare luminosity is compared to the Rossby number. A tentative detection of flare activity saturation for low-mass stars with rapid rotation below a Rossby number of ˜0.03 is found. A power-law decay in flare activity with Rossby number is found with a slope of -1, shallower than typical measurements for X-ray activity decay with Rossby number.

  12. Observing stellar mass and supermassive black holes

    Science.gov (United States)

    Cherepashchuk, A. M.

    2016-07-01

    During the last 50 years, great progress has been made in observing stellar-mass black holes (BHs) in binary systems and supermassive BHs in galactic nuclei. In 1964, Zeldovich and Salpeter showed that in the case of nonspherical accretion of matter onto a BH, huge energy releases occur. The theory of disk accretion of matter onto BHs was developed in 1972-1973 by Shakura and Sunyaev, Pringle and Rees, and Novikov and Thorne. Up to now, 100 years after the creation of Albert Einstein's General Theory of Relativity, which predicts the existence of BHs, the masses of tens of stellar-mass BHs ( M_BH=(4-35) M_⊙) and many hundreds of supermassive BHs ( M_BH=(10^6-1010) M_⊙) have been determined. A new field of astrophysics, so-called BH demography, is developing. The recent discovery of gravitational waves from BH mergers in binary systems opens a new era in BH studies.

  13. The Kepler Catalog of Stellar Flares

    CERN Document Server

    Davenport, James R A

    2016-01-01

    A homogeneous search for stellar flares has been performed using every available Kepler light curve. An iterative light curve de-trending approach was used to filter out both astrophysical and systematic variability to detect flares. The flare recovery completeness has also been computed throughout each light curve using artificial flare injection tests, and the tools for this work have been made publicly available. The final sample contains 851,168 candidate flare events recovered above the 68% completeness threshold, which were detected from 4041 stars, or 1.9% of the stars in the Kepler database. The average flare energy detected is ~$10^{35}$ erg. The net fraction of flare stars increases with $g-i$ color, or decreasing stellar mass. For stars in this sample with previously measured rotation periods, the total relative flare luminosity is compared to the Rossby number. A tentative detection of flare activity saturation for low-mass stars with rapid rotation below a Rossby number of ~0.03 is found. A power...

  14. High-Energy Astrophysics: An Overview

    Science.gov (United States)

    Fishman, Gerald J.

    2007-01-01

    High-energy astrophysics is the study of objects and phenomena in space with energy densities much greater than that found in normal stars and galaxies. These include black holes, neutron stars, cosmic rays, hypernovae and gamma-ray bursts. A history and an overview of high-energy astrophysics will be presented, including a description of the objects that are observed. Observing techniques, space-borne missions in high-energy astrophysics and some recent discoveries will also be described. Several entirely new types of astronomy are being employed in high-energy astrophysics. These will be briefly described, along with some NASA missions currently under development.

  15. High Energy Astrophysics Science Archive Research Center

    Data.gov (United States)

    National Aeronautics and Space Administration — The High Energy Astrophysics Science Archive Research Center (HEASARC) is the primary archive for NASA missions dealing with extremely energetic phenomena, from...

  16. Progresses of Laboratory Astrophysics in China

    Institute of Scientific and Technical Information of China (English)

    ZHAO Gang; ZHANG Jie

    2011-01-01

    The exciting discoveries in astronomy such as the accelerating expansion of the universe, the atmospheric composition of exoplanets, and the abundance trends of various types of stars rely upon advances in laboratory astrophysics. These new discoveries have occurred along with dramatic improvements in measurements by ground- based and space-based instruments of astrophysical processes under extreme physical conditions. Laboratory astrophysics is an exciting and rapidly growing field emerging since the beginning of this century, which covers a wide range of scientific areas such as astrophysics,

  17. QCD deconfinement phase transitions and collapsing quark stars

    CERN Document Server

    Bednarek, I; Manka, R; Bednarek, Ilona; Biesiada, Marek; Manka, Ryszard

    1996-01-01

    In this paper we discuss the QCD phase-transitions in the nontopological soliton model of quark confinement and explore possible astrophysical consequences. Our key idea is to look at quark stars (which are believed to exist since the quark matter is energetically preferred over the ordinary matter) from the point of view of soliton model. We propose that the phase transition taking place during the core collapse of massive evolved star may provide a new physical effect not taken into account in modeling the supernova explosions. We also point out the possibility that merging quark stars may produce gamma-ray bursts energetic enough to be at cosmological distances. Our idea based on the finite-temperature nontopologiocal soliton model overcomes major difficulties present in neutron star merger scenario --- the baryon loading problem and nonthermal spectra of the bursts.

  18. Gravitational Collapse in Repulsive $R+\\mu^4/R$ Gravity

    CERN Document Server

    Fathi, Mohsen

    2016-01-01

    In this paper we work out collapsing conditions for a spherical star in the weak field limit of the $R+\\mu^4/R$ gravity and discuss the importance of the parameter $\\mu$ to generate different criteria in the theory. Such criteria are proved to be resulting in a variety of different fates for the evolution of the outer shells of stars. Furthermore, we investigate the special case of violating the first junction condition and point out corresponding contradictions to the normal cases. These results show that the consistency of the $R+\\mu^4/R$ theory of gravity with the common astrophysical predictions relies highly on the adoption of the parameter $\\mu$ and satisfaction/violation of the first junction condition. For those anomalous results, further observational attempts are mandatory.

  19. PREFACE: A Stellar Journey A Stellar Journey

    Science.gov (United States)

    Asplund, M.

    2008-10-01

    The conference A Stellar Journey was held in Uppsala, Sweden, 23 27June 2008, in honour of Professor Bengt Gustafsson's 65th birthday. The choice of Uppsala as the location for this event was obvious given Bengt's long-standing association with the city stemming back to his school days. With the exception of a two-year postdoc stint in Copenhagen, five years as professor at Stockholm University and two years as director of the Sigtuna foundation, Bengt has forged his illustrious professional career at Uppsala University. The symposium venue was Museum Gustavianum, once the main building of the oldest university in Scandinavia. The title of the symposium is a paraphrasing of Bengt's popular astronomy book Kosmisk Resa (in English: Cosmic Journey) written in the early eighties. I think this aptly symbolizes his career that has been an astronomical voyage from near to far, from the distant past to the present. The original book title was modified slightly to reflect that most of his work to date has dealt with stars in one way or another. In addition it also gives credit to Bengt's important role as a guiding light for a very large number of students, colleagues and collaborators, indeed for several generations of astronomers. For me personally, the book Kosmisk Resa bears particular significance as it has shaped my life rather profoundly. Although I had already decided to become an astronomer, when I first read the book as a 14-year-old I made up my mind then and there that I would study under Bengt Gustafsson and work on stars. Indeed I have remained true to this somewhat audacious resolution. I suspect that a great number of us have similar stories how Bengt has had a major influence on our lives, whether on the professional or personal level. Perhaps Bengt's most outstanding characteristic is his enthralling enthusiasm. This is equally true whether he is pondering some scientific conundrum, supervising students or performing in front of an audience, be it an

  20. Large Eddy Simulations in Astrophysics

    Science.gov (United States)

    Schmidt, Wolfram

    2015-12-01

    In this review, the methodology of large eddy simulations (LES) is introduced and applications in astrophysics are discussed. As theoretical framework, the scale decomposition of the dynamical equations for neutral fluids by means of spatial filtering is explained. For cosmological applications, the filtered equations in comoving coordinates are also presented. To obtain a closed set of equations that can be evolved in LES, several subgrid-scale models for the interactions between numerically resolved and unresolved scales are discussed, in particular the subgrid-scale turbulence energy equation model. It is then shown how model coefficients can be calculated, either by dynamic procedures or, a priori, from high-resolution data. For astrophysical applications, adaptive mesh refinement is often indispensable. It is shown that the subgrid-scale turbulence energy model allows for a particularly elegant and physically well-motivated way of preserving momentum and energy conservation in adaptive mesh refinement (AMR) simulations. Moreover, the notion of shear-improved models for in-homogeneous and non-stationary turbulence is introduced. Finally, applications of LES to turbulent combustion in thermonuclear supernovae, star formation and feedback in galaxies, and cosmological structure formation are reviewed.

  1. Hierarchical gravitational fragmentation. I. Collapsing cores within collapsing clouds

    CERN Document Server

    Romero, Raúl Naranjo; Loughnane, Robert M

    2015-01-01

    We investigate the Hierarchical Gravitational Fragmentation scenario through numerical simulations of the prestellar stages of the collapse of a marginally gravitationally unstable isothermal sphere immersed in a strongly gravitationally unstable, uniform background medium. The core developes a Bonnor-Ebert (BE)-like density profile, while at the time of singularity (the protostar) formation the envelope approaches a singular-isothermal-sphere (SIS)-like $r^-2$ density profile. However, these structures are never hydrostatic. In this case, the central flat region is characterized by an infall speed, while the envelope is characterized by a uniform speed. This implies that the hydrostatic SIS initial condition leading to Shu's classical inside-out solution is not expected to occur, and therefore neither should the inside-out solution. Instead, the solution collapses from the outside-in, naturally explaining the observation of extended infall velocities. The core, defined by the radius at which it merges with t...

  2. Presupernova neutrinos: realistic emissivities from stellar evolution

    Science.gov (United States)

    Patton, Kelly; Lunardini, Cecilia; Farmer, Rob; Timmes, Frank

    2017-01-01

    We present a calculation of neutrino emissivities and energy spectra from a presupernova, a massive star going through the advanced stages of nuclear burning before becoming a supernova. Neutrinos produced from beta decay and electron capture, as well as pair annihilation, plasmon decay, and the photoneutrino process are included. We use the state of the art stellar evolution code MESA to obtain realistic conditions for temperature, density, electron fraction, and nuclear isotopic composition. We have found that beta processes contribute significantly to the neutrino flux at potentially detectable energies of a few MeV. Estimates for the number of events at several current and future detectors are presented for the last few hours before collapse.

  3. Atomic and Molecular Data for Optical Stellar Spectroscopy

    CERN Document Server

    Heiter, U; Asplund, M; Barklem, P S; Bergemann, M; Magrini, L; Masseron, T; Mikolaitis, Š; Pickering, J C; Ruffoni, M P

    2015-01-01

    High-precision spectroscopy of large stellar samples plays a crucial role for several topical issues in astrophysics. Examples include studying the chemical structure and evolution of the Milky Way galaxy, tracing the origin of chemical elements, and characterizing planetary host stars. Data are accumulating from instruments that obtain high-quality spectra of stars in the ultraviolet, optical and infrared wavelength regions on a routine basis. These instruments are located at ground-based 2- to 10-m class telescopes around the world, in addition to the spectrographs with unique capabilities available at the Hubble Space Telescope. The interpretation of these spectra requires high-quality transition data for numerous species, in particular neutral and singly ionized atoms, and di- or triatomic molecules. We rely heavily on the continuous efforts of laboratory astrophysics groups that produce and improve the relevant experimental and theoretical atomic and molecular data. The compilation of the best available ...

  4. Stellar Structure and Evolution

    CERN Document Server

    Kippenhahn, Rudolf; Weiss, Achim

    2013-01-01

    This long-awaited second edition of the classical textbook on Stellar Structure and Evolution by Kippenhahn and Weigert is a thoroughly revised version of the original text. Taking into account modern observational constraints as well as additional physical effects such as mass loss and diffusion, Achim Weiss and Rudolf Kippenhahn have succeeded in bringing the book up to the state-of-the-art with respect to both the presentation of stellar physics and the presentation and interpretation of current sophisticated stellar models. The well-received and proven pedagogical approach of the first edition has been retained. The book provides a comprehensive treatment of the physics of the stellar interior and the underlying fundamental processes and parameters. The models developed to explain the stability, dynamics and evolution of the stars are presented and great care is taken to detail the various stages in a star’s life. Just as the first edition, which remained a standard work for more than 20 years after its...

  5. Gravitational lensing & stellar dynamics

    NARCIS (Netherlands)

    Koopmans, L. V. E.; Mamon, GA; Combes, F; Deffayet, C; Fort, B

    2006-01-01

    Strong gravitational lensing and stellar dynamics provide two complementary and orthogonal constraints on the density profiles of galaxies. Based on spherically symmetric, scale-free, mass models, it is shown that the combination of both techniques is powerful in breaking the mass-sheet and mass-ani

  6. Stellar magnetic cycles

    Science.gov (United States)

    Baliunas, S. L.

    2004-05-01

    Is hope for understanding the solar magnetic cycle to be found in stars? Observations of stars with significant sub-surface convective zones -- masses smaller than about 1.5 solar masses on the lower main sequence and many types of cool, post-main-sequence stars -- indicate the presence of surface and atmospheric inhomogeneities analogous to solar magnetic features, making stellar magnetic activity a cosmically widespread phenomenon. Observations have been made primarily in visible wavelengths, and important information has also been derived from the ultraviolet and x-ray spectrum regions. Interannual to interdecadal variability of spectrum indicators of stellar magnetic features is common, and in some cases similar in appearance to the 11-year sunspot cycle. Successful models of the physical processes responsible for stellar magnetic cycles, typically cast as a magnetohydrodynamic dynamo, require advances in understanding not only convection but also the magnetic field's interaction with it. The observed facts that underpin the hope for models will be summarized. Properties of stellar magnetic cycles will be compared and contrasted with those of the sun, including inferences from paleo-environmental reservoirs that contain information on solar century- to millennial-scale magnetic variability. Partial support of this research came from NASA NAG5-7635, NRC COBASE, CRDF 322, MIT-MSG 5710001241, JPL 1236821, AF 49620-02-1-0194, Richard Lounsberry Foundation, Langley-Abbot, Rollins, Scholarly Studies and James Arthur Funds (Smithsonian Institution) and several generous individuals.

  7. The spatial structure of young stellar clusters

    Science.gov (United States)

    Kuhn, Michael A.

    Star formation is an extremely active area of astronomical research, and young stellar clusters in our Galaxy offer a useful laboratory where star-formation processes can be studied. Young stars form from the the gravitational collapse of molecular clouds that have a hierarchical spatial structure. This leads to stars forming in clustered environments, often with thousands of other young stars in environments that are strongly affected by feedback from massive O-type stars. The environments in these massive star-forming regions (MSFR) can affect how stars form and whether the young stellar clusters remain bound after star formation ends, both of which are questions that have received considerable attention from researchers. Studies of stellar populations in Galactic MSFRs are made difficult due to large numbers of fields stars in the Galactic Plane, large areas of the sky that must be surveyed, high optical extinction from dust, and nebulosity in the the optical and infrared. The Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX) uses multiwavelength observations to overcome some of these difficulties, providing some of the most complete, clean membership lists for 20 MSFRs within 3.6 kpc of the Sun. I described X-ray catalogs and mid-infrared catalogs that were used in this survey. The spatial distribution of young stars in 17 MYStIX regions are used to probe the origin and dynamics of the young stellar clusters. Intrinsic stellar surface-density maps are made for each region, which reveal complex structures with dense subclusters. I examine in detail one of the nearest MYStIX young stellar clusters, W 40 (d = 500 pc), which has properties similar to many of the subclusters in more massive and more distant star-forming regions. The cluster in W 40 has a simple structure with mass segregation, indicating that it has undergone dynamical evolution, even though its young age (~0.8 Myr) is insufficient for relaxation from two-body interactions

  8. How fast is protein hydrophobic collapse?

    OpenAIRE

    Sadqi, Mourad; Lapidus, Lisa J.; Muñoz, Victor

    2003-01-01

    One of the most recurring questions in protein folding refers to the interplay between formation of secondary structure and hydrophobic collapse. In contrast with secondary structure, it is hard to isolate hydrophobic collapse from other folding events. We have directly measured the dynamics of protein hydrophobic collapse in the absence of competing processes. Collapse was triggered with laser-induced temperature jumps in the acid-denatured form of a simple protein and monitored by fluoresce...

  9. Sh2-205: II. Its quiescent stellar formation activity

    CERN Document Server

    Romero, G A

    2009-01-01

    We present a study of active stellar forming regions in the environs of the HII region Sh2-205. The analysis is based on data obtained from point source catalogues and images extracted from 2MASS, MSX, and IRAS surveys. Complementary data are taken from CO survey. The identification of primary candidates to stellar formation activity is made following colour criteria and the correlation with molecular gas emission. A number of stellar formation tracer candidates are projected on two substructures of the HII region: SH148.83-0.67 and SH149.25-0.00. However, the lack of molecular gas related to these structures casts doubts on the nature of the sources. Additional infrared sources may be associated with the HI shell centered at (l,b) = (149\\degr 0\\arcmin, -1\\degr 30\\arcmin). The most striking active area was found in connection to the HII region LBN 148.11-0.45, where stellar formation candidates are projected onto molecular gas. The analytical model to the "collect and collapse" process shows that stellar form...

  10. UNIFYING THE ZOO OF JET-DRIVEN STELLAR EXPLOSIONS

    Energy Technology Data Exchange (ETDEWEB)

    Lazzati, Davide; Blackwell, Christopher H. [Department of Physics, NC State University, 2401 Stinson Drive, Raleigh, NC 27695-8202 (United States); Morsony, Brian J. [Department of Astronomy, University of Wisconsin-Madison, 2535 Sterling Hall, 475 N. Charter Street, Madison WI 53706-1582 (United States); Begelman, Mitchell C. [JILA, University of Colorado, 440 UCB, Boulder, CO 80309-0440 (United States)

    2012-05-01

    We present a set of numerical simulations of stellar explosions induced by relativistic jets emanating from a central engine sitting at the center of compact, dying stars. We explore a wide range of durations of the central engine activity, two candidate stellar progenitors, and two possible values of the total energy release. We find that even if the jets are narrowly collimated, their interaction with the star unbinds the stellar material, producing a stellar explosion. We also find that the outcome of the explosion can be very different depending on the duration of the engine activity. Only the longest-lasting engines result in successful gamma-ray bursts. Engines that power jets only for a short time result in relativistic supernova (SN) explosions, akin to observed engine-driven SNe such as SN2009bb. Engines with intermediate durations produce weak gamma-ray bursts, with properties similar to nearby bursts such as GRB 980425. Finally, we find that the engines with the shortest durations, if they exist in nature, produce stellar explosions that lack sizable amounts of relativistic ejecta and are therefore dynamically indistinguishable from ordinary core-collapse SNe.

  11. On collapsibilities of Yule's measure

    Institute of Scientific and Technical Information of China (English)

    GUO; Jianhua

    2001-01-01

    [1]Simpson,E.H.,The interpretation of interaction in contingency tables,J.R.Statist.Soc.B,1951,13:238-241.[2]Bishop,Y.M.M.,Effects of collapsing multidimensional contingency tables,Biometrics,1971,27:545-562.[3]Whittemore,A.S.,Collapsibility of multidimensional contingency tables,J.R.Statist.Soc.B,1978,40:328-340.[4]Good,I.J.,Mittal,Y.,The amalgamation and geometry of two-by-two contingency tables,Ann.Statist.,1987,15:694-711.[5]Gail,M.H.,Adjusting for covariates that have the same distribution in exposed and unexposed cohorts,Modern Statistical Methods in Chronic Disease Epidemiology (eds.Moolgavkar,S.H.,Prentice,R.L.),New York:Wiley,1986,3-18.[6]Wermuth,N.,Parametric collapsibility and the lack of moderating effects in contingency tables with a dichotomous response variable,J.R.Statist.Soc.B,1987,49:353-364.[7]Wermuth,N.,Moderating effects of subgroups in linear models,Biometrika,1989,76:81-92.[8]Ducharme,G.R.,Lepage,Y.,Testing collapsibility in contingency tables,J.R.Statist.Soc.B,1986,48:197-205.[9]Geng Zhi,Collapsibility of relative risk in contingency tables with a response variable,J.R.Statist.Soc.B,1992,54:585-593.[10]Guo Jianhua,Geng Zhi,Collapsibility of logistic regression coefficients,J.R.Statist.Soc.B,1995,57:263-267.[11]Rosenbaum,P.,Rubin,D.B.,The central role of the propensity score in observational studies for causal effects,Biometrika,1983,70:41-55.[12]Greenland,S.,Robins,J.M.,Pearl,J.,Confounding and collapsibility in causal inference,Statist.Sci.,1999,14:29-46.[13]Freedman,D.,From association to causation:some remarks on the history of statistics,Statist.Sci.,1999,14:243-258.[14]Geng,Z.,Guo,J.H.,Lau,T.S.et al.,Confounding,consistency and collapsibility for causal effects in epidemiologic studies,To appear in Statist.Sinica,2001.[15]Yule,G.U.,Notes on the theory of association of attributes in statistics,Biometrika,1903,2:121-134.[16]Lancaster,H.O.,The Chi-squared Distribution

  12. Spreadsheets and the Financial Collapse

    CERN Document Server

    Croll, Grenville J

    2009-01-01

    We briefly review the well-known risks, weaknesses and limitations of spreadsheets and then introduce some more. We review and slightly extend our previous work on the importance and criticality of spreadsheets in the City of London, introducing the notions of ubiquity, centrality, legality and contagion. We identify the sector of the financial market that we believed in 2005 to be highly dependant on the use of spreadsheets and relate this to its recent catastrophic financial performance. We outline the role of spreadsheets in the collapse of the Jamaican banking system in the late 1990's and then review the UK financial regulator's knowledge of the risks of spreadsheets in the contemporary financial system. We summarise the available evidence and suggest that there is a link between the use of spreadsheets and the recent collapse of the global financial system. We provide governments and regulating authorities with some simple recommendations to reduce the risks of continued overdependence on unreliable spr...

  13. Understanding Core-Collapse Supernovae

    CERN Document Server

    Burrows, A

    2004-01-01

    I summarize, in the form of an extended abstract, the ongoing efforts at the University of Arizona (and in collaboration) to understand core-collapse supernovae theoretically. Included are short discussions of 1D (SESAME) and 2D (VULCAN/2D) codes and results, as well as discussions of the possible role of rotation. Highlighted are recent developments in multi-dimensional radiation hydrodynamics and the essential physics of the neutrino-driven mechanism.

  14. Collapsing floating-point operations

    OpenAIRE

    Defour, David

    2004-01-01

    This paper addresses the issue of collapsing dependent floating-point operations. The presentation focuses on studying the dataflow graph of benchmark involving a large number of floating-point instructions. In particular, it focuses on the relevance of new floating-point operators performing two dependent operations which are similar to "fused multiply and add". Finally, this paper examines the implementation cost and critical path reduction from this strategy.

  15. Astrophysics at the Highest Energy Frontiers

    CERN Document Server

    Stecker, F W

    2002-01-01

    I discuss recent advances being made in the physics and astrophysics of cosmic rays and cosmic gamma-rays at the highest observed energies as well as the related physics and astrophysics of very high energy cosmic neutrinos. I also discuss the connections between these topics.

  16. Astrophysics with small satellites in Scandinavia

    DEFF Research Database (Denmark)

    Lund, Niels

    2003-01-01

    The small-satellites activities in the Scandinavian countries are briefly surveyed with emphasis on astrophysics research. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.......The small-satellites activities in the Scandinavian countries are briefly surveyed with emphasis on astrophysics research. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved....

  17. Nuclear Astrophysics with the Trojan Horse Method

    Science.gov (United States)

    Tumino, A.; Spitaleri, C.; Lamia, L.; Pizzone, R. G.; Cherubini, S.; Gulino, M.; La Cognata, M.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Spartá, R.

    2016-01-01

    The Trojan Horse Method (THM) represents the indirect path to determine the bare nucleus astrophysical S(E) factor for reactions between charged particles at astrophysical energies. This is done by measuring the quasi free cross section of a suitable three body process. The basic features of the THM will be presented together with some applications to demonstrate its practical use.

  18. Long gamma-ray bursts and core-collapse supernovae have differentenvironments

    Energy Technology Data Exchange (ETDEWEB)

    Fruchter, A.S.; Levan, A.J.; Strolger, L.; Vreeswijk, P.M.; Thorsett, S.E.; Bersier, D.; Burud, I.; Castro Ceren, J.M.; Castro-Tirado, A.J.; Conselice, C.; Dahlen, T.; Ferguson, H.C.; Fynbo,J.P.U.; Garnavich, P.M.; Gibbons, R.A.; Gorosabel, J.; Gull, T.R.; Hjorth, J.; Holland, S.T.; Kouveliotou, C.; Levay, Z.; Livio, M.; Metzger, M.R.; Nugent, P.E.; Petro, L.; Pian, E.; Rhoads, J.E.; Riess,A.G.; Sahu, K.C.; Smette, A.; Tanvir, N.R.; Wijers, R.A.M.J.; Woosley, S.E.

    2006-05-01

    When massive stars exhaust their fuel they collapse andoften produce the extraordinarily bright explosions known ascore-collapse supernovae. On occasion, this stellar collapse also powersan even more brilliant relativistic explosion known as a long-durationgamma-ray burst. One would then expect that long gamma-ray bursts andcore-collapse supernovae should be found in similar galacticenvironments. Here we show that this expectation is wrong. We find thatthe long gamma-ray bursts are far more concentrated on the very brightestregions of their host galaxies than are the core-collapse supernovae.Furthermore, the host galaxies of the long gamma-ray bursts aresignificantly fainter and more irregular than the hosts of thecore-collapse supernovae. Together theseresults suggest thatlong-duration gamma-ray bursts are associated with the most massive starsand may be restricted to galaxies of limited chemical evolution. Ourresults directly imply that long gamma-ray bursts are relatively rare ingalaxies such as our own MilkyWay.

  19. Axions in astrophysics and cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Sikivie, P.

    1984-07-01

    Axion models often have a spontaneously broken exact discrete symmetry. In that case, they have discretely degenerate vacua and hence domain walls. The properties of the domain walls, the cosmological catastrophe they produce and the ways in which this catastrophe may be avoided are explained. Cosmology and astrophysics provide arguments that imply the axion decay constant should lie in the range 10/sup 8/ GeV less than or equal to f/sub a/ less than or equal to 10/sup 12/ GeV. Reasons are given why axions are an excellent candidate to constitute the dark matter of galactic halos. Using the coupling of the axions to the electromagnetic field, detectors are described to look for axions floating about in the halo of our galaxy and for axions emitted by the sun. (LEW)

  20. Multivariate Evolutionary Analyses in Astrophysics

    CERN Document Server

    Fraix-Burnet, Didier

    2011-01-01

    The large amount of data on galaxies, up to higher and higher redshifts, asks for sophisticated statistical approaches to build adequate classifications. Multivariate cluster analyses, that compare objects for their global similarities, are still confidential in astrophysics, probably because their results are somewhat difficult to interpret. We believe that the missing key is the unavoidable characteristics in our Universe: evolution. Our approach, known as Astrocladistics, is based on the evolutionary nature of both galaxies and their properties. It gathers objects according to their "histories" and establishes an evolutionary scenario among groups of objects. In this presentation, I show two recent results on globular clusters and earlytype galaxies to illustrate how the evolutionary concepts of Astrocladistics can also be useful for multivariate analyses such as K-means Cluster Analysis.

  1. Focusing telescopes in nuclear astrophysics

    Energy Technology Data Exchange (ETDEWEB)

    Von Ballmoos, P.; Knodlseder, R.; Sazonov, S.; Griffiths, R.; Bastie, P.; Halloin, H.; Pareschi, G.; Ramsey, B.; Jensen, C.; Buis, E.J.; Ulmer, M.; Giommi, P.; Colafrancesco, S.; Comastri, A.; Barret, D.; Leising, M.; Hernanz, M.; Smith, D.; Abrosimov, N.; Smither, B.; Ubertini, P.; Olive, J.F.; Lund, N.; Pisa, A.; Courtois, P.; Roa, D.; Harrison, F.; Pareschi, G.; Frontera, F.; Von Ballmoos, P.; Barriere, N.; Rando, N.; Borde, J.; Hinglais, E.; Cledassou, R.; Duchon, P.; Sghedoni, M.; Huet, B.; Takahashi, T.; Caroli, E.; Quadrinin, L.; Buis, E.J.; Skinner, G.; Krizmanic, J.; Pareschi, G.; Loffredo, G.; Wunderer, C.; Weidenspointner, G.; Wunderer, C.; Koechlin, L.; Bignami, G.; Von Ballmoos, P.; Tueller, J.; Andritschke, T.; Laurens, A.; Evrard, J

    2005-07-01

    The objective of this workshop is to consider the next generation of instrumentation to be required within the domain of nuclear astrophysics. A small, but growing community has been pursuing various techniques for the focusing of hard X-rays and gamma-rays with the aim of achieving a factor of up to 100 improvement in sensitivity over present technologies. Balloon flight tests of both multilayer mirrors and a Laue lens have been performed and ideas abound. At present, implementation scenarios for space missions are being studied at Esa, CNES, and elsewhere. The workshop will provide a first opportunity for this new community to meet, exchange technological know-how, discuss scientific objectives and synergies, and consolidate implementation approaches within National and European Space Science programs. This document gathers the slides of all the presentations.

  2. Large-Scale Astrophysical Visualization on Smartphones

    Science.gov (United States)

    Becciani, U.; Massimino, P.; Costa, A.; Gheller, C.; Grillo, A.; Krokos, M.; Petta, C.

    2011-07-01

    Nowadays digital sky surveys and long-duration, high-resolution numerical simulations using high performance computing and grid systems produce multidimensional astrophysical datasets in the order of several Petabytes. Sharing visualizations of such datasets within communities and collaborating research groups is of paramount importance for disseminating results and advancing astrophysical research. Moreover educational and public outreach programs can benefit greatly from novel ways of presenting these datasets by promoting understanding of complex astrophysical processes, e.g., formation of stars and galaxies. We have previously developed VisIVO Server, a grid-enabled platform for high-performance large-scale astrophysical visualization. This article reviews the latest developments on VisIVO Web, a custom designed web portal wrapped around VisIVO Server, then introduces VisIVO Smartphone, a gateway connecting VisIVO Web and data repositories for mobile astrophysical visualization. We discuss current work and summarize future developments.

  3. Quantifying Stellar Mass Loss with High Angular Resolution Imaging

    CERN Document Server

    Ridgway, Stephen; Creech-Eakman, Michelle; Elias, Nicholas; Howell, Steve; Hutter, Don; Karovska, Margarita; Ragland, Sam; Wishnow, Ed; Zhao, Ming

    2009-01-01

    Mass is constantly being recycled in the universe. One of the most powerful recycling paths is via stellar mass-loss. All stars exhibit mass loss with rates ranging from ~10(-14) to 10(-4) M(sun) yr-1, depending on spectral type, luminosity class, rotation rate, companion proximity, and evolutionary stage. The first generation of stars consisted mostly of hydrogen and helium. These shed material - via massive winds, planetary nebulae and supernova explosions - seeding the interstellar medium with heavier elements. Subsequent generations of stars incorporated this material, changing how stars burn and providing material for planet formation. An understanding of mass loss is critical for modeling individual stars as well as answering larger astrophysical questions. Understanding mass loss is essential for following the evolution of single stars, binaries, star clusters, and galaxies. Mass loss is one of our weakest areas in the modeling of fundamental stellar processes. In large part this is owing to lack of co...

  4. Estimating stellar parameters and interstellar extinction from evolutionary tracks

    Science.gov (United States)

    Sichevsky, S.; Malkov, O.

    Developing methods for analyzing and extracting information from modern sky surveys is a challenging task in astrophysical studies. We study possibilities of parameterizing stars and interstellar medium from multicolor photometry performed in three modern photometric surveys: GALEX, SDSS, and 2MASS. For this purpose, we have developed a method to estimate stellar radius from effective temperature and gravity with the help of evolutionary tracks and model stellar atmospheres. In accordance with the evolution rate at every point of the evolutionary track, star formation rate, and initial mass function, a weight is assigned to the resulting value of radius that allows us to estimate the radius more accurately. The method is verified for the most populated areas of the Hertzsprung-Russell diagram: main-sequence stars and red giants, and it was found to be rather precise (for main-sequence stars, the average relative error of radius and its standard deviation are 0.03% and 3.87%, respectively).

  5. Development and Application of Tools to Characterize Transiting Astrophysical Systems

    Science.gov (United States)

    Beky, Bence

    2014-06-01

    Since the discovery of the first exoplanets (planets outside our Solar System) more than 20 years ago, there has been an increasing need for photometric and spectroscopic models to characterize these systems. While imaging has been used extensively for Solar System bodies and extended objects like galaxies, the small angular extent of typical planetary systems makes it difficult or impossible to resolve them. Spatially integrated observations like measuring the total brightness or spectrum, however, can be conducted at a resonable cost. This thesis focuses on photometric models in the context of transiting systems, which exhibit a number of phenomena that can be exploited for characterization. First, we showcase the popular methods of transiting exoplanet discovery and characterization by ground based observations on the hot Jupiter HAT-P-27b. We demonstrate how transits allow us to constrain planetary mass, radius, and orbital inclination, which would not be possible based only on, for example, radial velocity measurements. Next, we perform reflection spectroscopy on HAT-P-1b, another hot Jupiter, using the binary companion of the host star as a reference to remove systematic errors from the signal. Here the transiting nature of the system allows us to look for the very faint light reflected by the planet. We also apply the idea of planetary transits to investigate the feasibility of transit observations in astrophysical systems of very different scale: stars in galactic nuclei potentially transiting the accretion disk of the supermassive black hole in the galactic center. Finally, we focus on mapping spots on the stellar surface using transits. This method has been used for a decade, and helped constrain stellar rotation or orbital geometry in a number systems. We study starspots on HAT-P-11 not only to learn more about stellar rotation, but also to investigate the size and contrast of the spots themselves.

  6. Fine-grid calculations for stellar electron and positron capture rates on Fe isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Nabi, Jameel-Un, E-mail: jameel@giki.edu.pk [Ghulam Ishaq Khan Institute of Engineering Sciences and Technology, Faculty of Engineering Sciences (Pakistan); Tawfik, Abdel Nasser, E-mail: a.tawfik@eng.mti.edu.eg [MTI University, Egyptian Center for Theoretical Physics (ECTP) (Egypt)

    2013-03-15

    The acquisition of precise and reliable nuclear data is a prerequisite to success for stellar evolution and nucleosynthesis studies. Core-collapse simulators find it challenging to generate an explosion from the collapse of the core of massive stars. It is believed that a better understanding of the microphysics of core-collapse can lead to successful results. The weak interaction processes are able to trigger the collapse and control the lepton-to-baryon ratio (Y{sub e}) of the corematerial. It is suggested that the temporal variation of Y{sub e} within the core of a massive star has a pivotal role to play in the stellar evolution and a fine-tuning of this parameter at various stages of presupernova evolution is the key to generate an explosion. During the presupernova evolution of massive stars, isotopes of iron, mainly {sup 54-56}Fe, are considered to be key players in controlling Y{sub e} ratio via electron capture on these nuclides. Recently an improved microscopic calculation of weak-interaction-mediated rates for iron isotopes was introduced using the proton-neutron quasiparticle random-phase-approximation (pn-QRPA) theory. The pn-QRPA theory allows a microscopic state-by-state calculation of stellar capture rates which greatly increases the reliability of calculated rates. The results were suggestive of some fine-tuning of the Y{sub e} ratio during various phases of stellar evolution. Here we present for the first time the fine-grid calculation of the electron and positron capture rates on {sup 54-56}Fe. The sensitivity of the pn-QRPA calculated capture rates to the deformation parameter is also studied in this work. Core-collapse simulators may find this calculation suitable for interpolation purposes and for necessary incorporation in the stellar evolution codes.

  7. Irreversible gravitational collapse: black stars or black holes?

    CERN Document Server

    Corda, Christian

    2011-01-01

    It is well known that the concept of black hole has been considered very fascinating by scientists even before the introduction of Einstein's general relativity. They should be the final result of an irreversible gravitational collapse of very massive bodies. However, an unsolved problem concerning such objects is the presence of a space-time singularity in their core. Such a problem was present starting by the first historical papers concerning black holes. It is a common opinion that this problem could be solved when a correct quantum gravity theory will be, finally, constructed. In this work we review a way to remove black hole singularities at a classical level i.e. without arguments of quantum gravity. By using a particular non-linear electrodynamics Lagrangian, an exact solution of Einstein field equations is shown. The solution prevents the collapsing object to reach the gravitational radius, thus the final result becomes a black star, i.e. an astrophysical object where both of singularities and event ...

  8. Colloquium: Perspectives on core-collapse supernova theory

    Science.gov (United States)

    Burrows, Adam

    2013-01-01

    Core-collapse theory brings together many facets of high-energy and nuclear astrophysics and the numerical arts to present theorists with one of the most important, yet frustrating, astronomical questions: “What is the mechanism of core-collapse supernova explosions?” A review of all the physics and the 50-year history involved would soon bury the reader in minutiae that could easily obscure the essential elements of the phenomenon, as we understand it today. Moreover, much remains to be discovered and explained, and a complicated review of an unresolved subject in flux could grow stale fast. Therefore, this paper describes various important facts and perspectives that may have escaped the attention of those interested in this puzzle. Furthermore, an attempt to describe the modern theory’s physical underpinnings and a brief summary of the current state of play are given. In the process, a few myths that have crept into modern discourse are identified. However, there is much more to do and humility in the face of this age-old challenge is clearly the most prudent stance as its eventual resolution is sought.

  9. Where Does the Physics of Extreme Gravitational Collapse Reside?

    Directory of Open Access Journals (Sweden)

    Carlos Barceló

    2016-05-01

    Full Text Available The gravitational collapse of massive stars serves to manifest the most severe deviations of general relativity with respect to Newtonian gravity: the formation of horizons and spacetime singularities. Both features have proven to be catalysts of deep physical developments, especially when combined with the principles of quantum mechanics. Nonetheless, it is seldom remarked that it is hardly possible to combine all these developments into a unified theoretical model, while maintaining reasonable prospects for the independent experimental corroboration of its different parts. In this paper we review the current theoretical understanding of the physics of gravitational collapse in order to highlight this tension, stating the position that the standard view on evaporating black holes stands for. This serves as the motivation for the discussion of a recent proposal that offers the opposite perspective, represented by a set of geometries that regularize the classical singular behavior and present modifications of the near-horizon Schwarzschild geometry as the result of the propagation of non-perturbative ultraviolet effects originated in regions of high curvature. We present an extensive exploration of the necessary steps on the explicit construction of these geometries, and discuss how this proposal could change our present understanding of astrophysical black holes and even offer the possibility of detecting genuine ultraviolet effects in gravitational-wave experiments.

  10. Thermal Physics, Cloud Geometry, and the Stellar IMF

    CERN Document Server

    Larson, R B

    2004-01-01

    The thermal properties of star-forming clouds have an important influence on how they fragment into stars, and it is suggested in this paper that the low-mass stellar IMF, which appears to be almost universal, is determined largely by the thermal physics of these clouds. In particular, it is suggested that the characteristic stellar mass, a little below one solar mass, is determined by the transition from an initial cooling phase of collapse to a later phase of slowly rising temperature that occurs when the gas becomes thermally coupled to the dust. Numerical simulations support the hypothesis that the Jeans mass at this transition point plays an important role in determining the peak mass of the IMF. A filamentary geometry may also play a key role in the fragmentation process because the isothermal case is a critical one for the collapse of a cylinder: the collapse and fragmentation of a cylinder can continue freely as long as the temperature continues to decrease, but not if it begins to increase. The limit...

  11. New Astrophysical Reaction Rate for the $^{12}\\textrm{C}(\\alpha,\\gamma)^{16}\\textrm{O}$ Reaction

    CERN Document Server

    An, Z D; Fan, G T; Li, Y J; Chen, Z P; Sun, Y Y

    2016-01-01

    A new astrophysical reaction rate for $^{12}$C($\\alpha,\\gamma$)$^{16}$O has been evaluated on the basis of a global R-matrix fitting to the available experimental data. The reaction rates of $^{12}$C($\\alpha,\\gamma$)$^{16}$O for stellar temperatures between 0.04 $\\leq$ $T_9$ $\\leq$ 10 are provided in a tabular form and by an analytical fitting expression. At $T_9$ = 0.2, the reaction rate is (7.83 $\\pm$ 0.35)$\\times10^{15}$ $\\rm{cm^3 mol^{-1} s^{-1}}$, where stellar helium burning occurs.

  12. Stellar Collisions in Young Clusters: Formation of (Very) Massive Stars?

    CERN Document Server

    Freitag, Marc

    2007-01-01

    In young star clusters, the density can be high enough and the velocity dispersion low enough for stars to collide and merge with a significant probability. This has been suggested as a possible way to build up the high-mass portion of the stellar mass function and as a mechanism leading to the formation of one or two very massive stars (M > 150 Msun) through a collisional runaway. I quickly review the standard theory of stellar collisions, covering both the stellar dynamics of dense clusters and the hydrodynamics of encounters between stars. The conditions for collisions to take place at a significant rate are relatively well understood for idealised spherical cluster models without initial mass segregation, devoid of gas and composed of main-sequence (MS) stars. In this simplified situation, 2-body relaxation drives core collapse through mass segregation and a collisional phase ensues if the core collapse time is shorter than the MS lifetime of the most massive stars initially present. The outcome of this p...

  13. Stellar populations in star clusters

    CERN Document Server

    Li, Chengyuan; Deng, Licai

    2016-01-01

    Stellar populations contain the most important information about star clus- ter formation and evolution. Until several decades ago, star clusters were believed to be ideal laboratories for studies of simple stellar populations (SSPs). However, discoveries of multiple stellar populations in Galactic globular clusters have expanded our view on stellar populations in star clusters. They have simultaneously generated a number of controversies, particularly as to whether young star clusters may have the same origin as old globular clusters. In addition, extensive studies have revealed that the SSP scenario does not seem to hold for some intermediate-age and young star clusters either, thus making the origin of multiple stellar populations in star clusters even more complicated. Stellar population anomalies in numerous star clusters are well-documented, implying that the notion of star clusters as true SSPs faces serious challenges. In this review, we focus on stellar populations in massive clusters with different ...

  14. Microinstabilities in stellarator plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Rafiq, T.; Nasim, M.H.; Persson, M. [Department of Electromagnetics and Euratom/VR Association, Chalmers University of Technology, Goeteborg (Sweden)

    2003-07-01

    Linear stability and localization of ion temperature gradient modes in fully 3-dimensional stellarator plasmas is calculated in the electrostatic limit. A ballooning mode formalism with WKB assumption is applied to reduce the equations into ordinary differential equation along the field lines which are solved numerically for different plasma parameters. The results are correlated with the geometrical effects such as magnetic curvature, local magnetic shear and its integrated value along the field line and the effects of trapped electrons are also investigated. The eigenfunctions of the most unstable modes are found to be localized but the nodes in the amplitude of the eigenfunctions may be large depending upon the location on the magnetic surface. The results are compared and contrasted with calculations in tokamak geometry and the implications on future stellarator design is also discussed. (orig.)

  15. First targeted search for gravitational-wave bursts from core-collapse supernovae in data of first-generation laser interferometer detectors

    Science.gov (United States)

    Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.; Allen, B.; Allocca, A.; Altin, P. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Babak, S.; Bacon, P.; Bader, M. K. M.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bavigadda, V.; Bazzan, M.; Behnke, B.; Bejger, M.; Bell, A. S.; Bell, C. J.; Berger, B. K.; Bergman, J.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Birney, R.; Biscans, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blair, C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogaert, G.; Bogan, C.; Bohe, A.; Bojtos, P.; Bond, C.; Bondu, F.; Bonnand, R.; Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brown, N. M.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Cahillane, C.; Calderón Bustillo, J.; Callister, T.; Calloni, E.; Camp, J. B.; Cannon, K. C.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Casanueva Diaz, J.; Casentini, C.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C. B.; Cerboni Baiardi, L.; Cerretani, G.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, H. Y.; Chen, Y.; Cheng, C.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, S.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Collette, C. G.; Cominsky, L.; Constancio, M.; Conte, A.; Conti, L.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corpuz, A.; Corsi, A.; Cortese, S.; Costa, C. A.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J.-P.; Countryman, S. T.; Couvares, P.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Cripe, J.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Darman, N. S.; Dattilo, V.; Dave, I.; Daveloza, H. P.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; DeBra, D.; Debreczeni, G.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; DeSalvo, R.; Dhurandhar, S.; Díaz, M. C.; Di Fiore, L.; Di Giovanni, M.; Di Girolamo, T.; Di Lieto, A.; Di Pace, S.; Di Palma, I.; Di Virgilio, A.; Dojcinoski, G.; Dolique, V.; Donovan, F.; Dooley, K. L.; Doravari, S.; Douglas, R.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Ducrot, M.; Dwyer, S. E.; Edo, T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Engels, W.; Essick, R. C.; Etzel, T.; Evans, M.; Evans, T. M.; Everett, R.; Factourovich, M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fiorucci, D.; Fisher, R. P.; Flaminio, R.; Fletcher, M.; Fournier, J.-D.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.; Frey, R.; Frey, V.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H. A. G.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S. G.; Garufi, F.; Gaur, G.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.; George, J.; Gergely, L.; Germain, V.; Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.; Glaefke, A.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gonzalez Castro, J. M.; Gopakumar, A.; Gordon, N. A.; Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Grado, A.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hacker, J. J.; Hall, B. R.; Hall, E. D.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Hartman, M. T.; Haster, C.-J.; Haughian, K.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Hofman, D.; Hollitt, S. E.; Holt, K.; Holz, D. E.; Hopkins, P.; Hosken, D. J.; Hough, J.; Houston, E. A.; Howell, E. J.; Hu, Y. M.; Huang, S.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Idrisy, A.; Indik, N.; Ingram, D. R.; Inta, R.; Isa, H. N.; Isac, J.-M.; Isi, M.; Islas, G.; Isogai, T.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jang, H.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jiménez-Forteza, F.; Johnson, W. W.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Haris, K.; Kalaghatgi, C. V.; Kalmus, P.; Kalogera, V.; Kamaretsos, I.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Karki, S.; Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kaur, T.; Kawabe, K.; Kawazoe, F.; Kéfélian, F.; Kehl, M. S.; Keitel, D.; Kelley, D. B.; Kells, W.; Kennedy, R.; Key, J. S.; Khalaidovski, A.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, Chunglee; Kim, J.; Kim, K.; Kim, Nam-Gyu; Kim, Namjun; Kim, Y.-M.; King, E. J.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Kleybolte, L.; Klimenko, S.; Koehlenbeck, S. M.; Kokeyama, K.; Koley, S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Kringel, V.; Krishnan, B.; Królak, A.; Krueger, C.; Kuehn, G.; Kumar, P.; Kuo, L.; Kutynia, A.; Lackey, B. D.; Landry, M.; Lange, J.; Lantz, B.; Lasky, P. D.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lebigot, E. O.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, K.; Lenon, A.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levin, Y.; Levine, B. M.; Li, T. G. F.; Libson, A.; Littenberg, T. B.; Lockerbie, N. A.; Loew, K.; Logue, J.; Lombardi, A. L.; Lord, J. E.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lück, H.; Lundgren, A. P.; Luo, J.; Lynch, R.; Ma, Y.; MacDonald, T.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magaña-Sandoval, F.; Magee, R. M.; Mageswaran, M.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandel, I.; Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A. S.; Maros, E.; Martelli, F.; Martellini, L.; Martin, I. W.; Martin, R. M.; Martynov, D. V.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Mastrogiovanni, S.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McGuire, S. C.; McIntyre, G.; McIver, J.; McManus, D. J.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Meidam, J.; Melatos, A.; Mendell, G.; Mendoza-Gandara, D.; Mercer, R. A.; Merilh, E. L.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.; Metzdorff, R.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, A. L.; Miller, J.; Millhouse, M.; Minenkov, Y.; Ming, J.; Mirshekari, S.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moggi, A.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, B. C.; Moore, C. J.; Moraru, D.; Moreno, G.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.; Mukherjee, S.; Mukund, K. N.; Mullavey, A.; Munch, J.; Murphy, D. J.; Murray, P. G.; Mytidis, A.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Necula, V.; Nedkova, K.; Nelemans, G.; Neri, M.; Neunzert, A.; Newton, G.; Nguyen, T. T.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. K.; Oberling, J.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oliver, M.; Oppermann, P.; Oram, Richard J.; O'Reilly, B.; O'Shaughnessy, R.; Ott, C. D.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, H.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Paoli, A.; Papa, M. A.; Paris, H. R.; Parker, W.; Pascucci, D.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patricelli, B.; Patrick, Z.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.; Penn, S.; Pereira, R.; Perreca, A.; Phelps, M.; Piccinni, O. J.; Pichot, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Poggiani, R.; Popolizio, P.; Post, A.; Powell, J.; Prasad, J.; Predoi, V.; Premachandra, S. S.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Pürrer, M.; Qi, H.; Qin, J.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raja, S.; Rakhmanov, M.; Rapagnani, P.; Raymond, V.; Razzano, M.; Re, V.; Read, J.; Reed, C. M.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Rew, H.; Ricci, F.; Riles, K.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, J. D.; Romano, R.; Romanov, G.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sachdev, S.; Sadecki, T.; Sadeghian, L.; Salconi, L.; Saleem, M.; Salemi, F.; Samajdar, A.; Sammut, L.; Sanchez, E. J.; Sandberg, V.; Sandeen, B.; Sanders, J. R.; Santamaria, L.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Sauter, O. E. S.; Savage, R. L.; Sawadsky, A.; Schale, P.; Schilling, R.; Schmidt, J.; Schmidt, P.; Schnabel, R.; Schofield, R. M. S.; Schönbeck, A.; Schreiber, E.; Schuette, D.; Schutz, B. F.; Scott, J.; Scott, S. M.; Sellers, D.; Sentenac, D.; Sequino, V.; Sergeev, A.; Serna, G.; Setyawati, Y.; Sevigny, A.; Shaddock, D. A.; Shahriar, M. S.; Shaltev, M.; Shao, Z.; Shapiro, B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.; Siellez, K.; Siemens, X.; Sieniawska, M.; Sigg, D.; Silva, A. D.; Simakov, D.; Singer, A.; Singer, L. P.; Singh, A.; Singh, R.; Singhal, A.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, J. R.; Smith, N. D.; Smith, R. J. E.; Son, E. J.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Srivastava, A. K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stephens, B. C.; Stone, R.; Strain, K. A.; Straniero, N.; Stratta, G.; Strauss, N. A.; Strigin, S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sutton, P. J.; Swinkels, B. L.; Szczepańczyk, M. J.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tápai, M.; Tarabrin, S. P.; Taracchini, A.; Taylor, R.; Theeg, T.; Thirugnanasambandam, M. P.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Tomlinson, C.; Tonelli, M.; Torres, C. V.; Torrie, C. I.; Töyrä, D.; Travasso, F.; Traylor, G.; Trifirò, D.; Tringali, M. C.; Trozzo, L.; Tse, M.; Turconi, M.; Tuyenbayev, D.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; van Bakel, N.; van Beuzekom, M.; van den Brand, J. F. J.; Van Den Broeck, C.; Vander-Hyde, D. C.; van der Schaaf, L.; van Heijningen, J. V.; van Veggel, A. A.; Vardaro, M.; Vass, S.; Vasúth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vinciguerra, S.; Vine, D. J.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Voss, D. V.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade, M.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, M.; Wang, X.; Wang, Y.; Ward, R. L.; Warner, J.; Was, M.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Weßels, P.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D. J.; Whiting, B. F.; Williams, R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Worden, J.; Wright, J. L.; Wu, G.; Yablon, J.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yap, M. J.; Yu, H.; Yvert, M.; ZadroŻny, A.; Zangrando, L.; Zanolin, M.; Zendri, J.-P.; Zevin, M.; Zhang, F.; Zhang, L.; Zhang, M.; Zhang, Y.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, X. J.; Zucker, M. E.; Zuraw, S. E.; Zweizig, J.; LIGO Scientific Collaboration; Virgo Collaboration

    2016-11-01

    We present results from a search for gravitational-wave bursts coincident with two core-collapse supernovae observed optically in 2007 and 2011. We employ data from the Laser Interferometer Gravitational-wave Observatory (LIGO), the Virgo gravitational-wave observatory, and the GEO 600 gravitational-wave observatory. The targeted core-collapse supernovae were selected on the basis of (1) proximity (within approximately 15 Mpc), (2) tightness of observational constraints on the time of core collapse that defines the gravitational-wave search window, and (3) coincident operation of at least two interferometers at the time of core collapse. We find no plausible gravitational-wave candidates. We present the probability of detecting signals from both astrophysically well-motivated and more speculative gravitational-wave emission mechanisms as a function of distance from Earth, and discuss the implications for the detection of gravitational waves from core-collapse supernovae by the upgraded Advanced LIGO and Virgo detectors.

  16. A First Targeted Search for Gravitational-Wave Bursts from Core-Collapse Supernovae in Data of First-Generation Laser Interferometer Detectors

    CERN Document Server

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Rollins, J G; Roma, V J; Romano, J D; Romano, R; Romanov, G; Romie, J H; Rosi'nska, D; Rowan, S; R"udiger, A; Ruggi, P; Ryan, K; Sachdev, S; Sadecki, T; Sadeghian, L; Salconi, L; Saleem, M; Salemi, F; Samajdar, A; Sammut, L; Sanchez, E J; Sandberg, V; Sandeen, B; Sanders, J R; Santamaria, L; Sassolas, B; Sathyaprakash, B S; Saulson, P R; Sauter, O E S; Savage, R L; Sawadsky, A; Schale, P; Schilling, R; Schmidt, J; Schmidt, P; Schnabel, R; Schofield, R M S; Sch"onbeck, A; Schreiber, E; Schuette, D; Schutz, B F; Scott, J; Scott, S M; Sellers, D; Sentenac, D; Sequino, V; Sergeev, A; Serna, G; Setyawati, Y; Sevigny, A; Shaddock, D A; Shahriar, M S; Shaltev, M; Shao, Z; Shapiro, B; Shawhan, P; Sheperd, A; Shoemaker, D H; Shoemaker, D M; Siellez, K; Siemens, X; Sieniawska, M; Sigg, D; Silva, A D; Simakov, D; Singer, A; Singer, L P; Singh, A; Singh, R; Singhal, A; Sintes, A M; Slagmolen, B J J; Smith, J R; Smith, N D; Smith, R J E; Son, E J; Sorazu, B; Sorrentino, F; Souradeep, T; Srivastava, A K; Staley, A; Steinke, M; Steinlechner, J; Steinlechner, S; Steinmeyer, D; Stephens, B C; Stone, R; Strain, K A; Straniero, N; Stratta, G; Strauss, N A; Strigin, S; Sturani, R; Stuver, A L; Summerscales, T Z; Sun, L; Sutton, P J; Swinkels, B L; Szczepa'nczyk, M J; Tacca, M; Talukder, D; Tanner, D B; T'apai, M; Tarabrin, S P; Taracchini, A; Taylor, R; Theeg, T; Thirugnanasambandam, M P; Thomas, E G; Thomas, M; Thomas, P; Thorne, K A; Thorne, K S; Thrane, E; Tiwari, S; Tiwari, V; Tokmakov, K V; Tomlinson, C; Tonelli, M; Torres, C V; Torrie, C I; T"oyr"a, D; Travasso, F; Traylor, G; Trifir`o, D; Tringali, M C; Trozzo, L; Tse, M; Turconi, M; Tuyenbayev, D; Ugolini, D; Unnikrishnan, C S; Urban, A L; Usman, S A; Vahlbruch, H; Vajente, G; Valdes, G; van Bakel, N; van Beuzekom, M; Brand, J F J van den; Broeck, C Van Den; Vander-Hyde, D C; van der Schaaf, L; van Heijningen, J V; van Veggel, A A; Vardaro, M; Vass, S; Vas'uth, M; Vaulin, R; Vecchio, A; Vedovato, G; Veitch, J; Veitch, P J; Venkateswara, K; Verkindt, D; Vetrano, F; Vicer'e, A; Vinciguerra, S; Vine, D J; Vinet, J -Y; Vitale, S; Vo, T; Vocca, H; Vorvick, C; Voss, D V; Vousden, W D; Vyatchanin, S P; Wade, A R; Wade, L E; Wade, M; Walker, M; Wallace, L; Walsh, S; Wang, G; Wang, H; Wang, M; Wang, X; Wang, Y; Ward, R L; Warner, J; Was, M; Weaver, B; Wei, L -W; Weinert, M; Weinstein, A J; Weiss, R; Welborn, T; Wen, L; Wessels, P; Westphal, T; Wette, K; Whelan, J T; Whitcomb, S E; White, D J; Whiting, B F; Williams, R D; Williamson, A R; Willis, J L; Willke, B; Wimmer, M H; Winkler, W; Wipf, C C; Wittel, H; Woan, G; Worden, J; Wright, J L; Wu, G; Yablon, J; Yam, W; Yamamoto, H; Yancey, C C; Yap, M J; Yu, H; Yvert, M; zny, A Zadro; Zangrando, L; Zanolin, M; Zendri, J -P; Zevin, M; Zhang, F; Zhang, L; Zhang, M; Zhang, Y; Zhao, C; Zhou, M; Zhou, Z; Zhu, X J; Zucker, M E; Zuraw, S E; Zweizig, J

    2016-01-01

    We present results from a search for gravitational-wave bursts coincident with a set of two core-collapse supernovae observed between 2007 and 2011. We employ data from the Laser Interferometer Gravitational-wave Observatory (LIGO), the Virgo gravitational-wave observatory, and the GEO 600 gravitational-wave observatory. The targeted core-collapse supernovae were selected on the basis of (1) proximity (within approximately 15 Mpc), (2) tightness of observational constraints on the time of core collapse that defines the gravitational-wave search window, and (3) coincident operation of at least two interferometers at the time of core collapse. We find no plausible gravitational-wave candidates. We present the probability of detecting signals from both astrophysically well-motivated and more speculative gravitational-wave emission mechanisms as a function of distance from Earth, and discuss the implications for the detection of gravitational waves from core-collapse supernovae by the upgraded Advanced LIGO and V...

  17. Quantum dust collapse in 2 +1 dimension

    Science.gov (United States)

    Sarkar, Souvik; Vaz, Cenalo; Wijewardhana, L. C. R.

    2016-02-01

    In this paper we will examine the consequence of a canonical theory of quantum dust collapse in 2 +1 dimensions. The solution of the Wheeler-DeWitt equation describing the collapse indicates that collapsing shells outside the apparent horizon are accompanied by outgoing shells within the apparent horizon during their collapse phase and stop collapsing once they reach the apparent horizon. Taking this picture of quantum collapse seriously, we determine a static solution with energy density corresponding to a dust ball whose collapse has terminated at the apparent horizon. We show that the boundary radius of the ball is larger than the Banados-Teitelboim-Zanelli radius confirming that no event horizon is formed. The ball is sustained by radial pressure which we determine and which we attribute to the Unruh radiation within it.

  18. The DEMO Quasisymmetric Stellarator

    OpenAIRE

    McFadden, Geoffrey B.; Garabedian, Paul R.

    2010-01-01

    The NSTAB nonlinear stability code solves differential equations in conservation form, and the TRAN Monte Carlo test particle code tracks guiding center orbits in a fixed background, to provide simulations of equilibrium, stability, and transport in tokamaks and stellarators. These codes are well correlated with experimental observations and have been validated by convergence studies. Bifurcated 3D solutions of the 2D tokamak problem have been calculated that model persistent disruptions, neo...

  19. DOLPHOT: Stellar photometry

    Science.gov (United States)

    Dolphin, Andrew

    2016-08-01

    DOLPHOT is a stellar photometry package that was adapted from HSTphot for general use. It supports two modes; the first is a generic PSF-fitting package, which uses analytic PSF models and can be used for any camera. The second mode uses ACS PSFs and calibrations, and is effectively an ACS adaptation of HSTphot. A number of utility programs are also included with the DOLPHOT distribution, including basic image reduction routines.

  20. Seeing a Stellar Explosion in 3D

    Science.gov (United States)

    2010-08-01

    Astronomers using ESO's Very Large Telescope have for the first time obtained a three-dimensional view of the distribution of the innermost material expelled by a recently exploded star. The original blast was not only powerful, according to the new results. It was also more concentrated in one particular direction. This is a strong indication that the supernova must have been very turbulent, supporting the most recent computer models. Unlike the Sun, which will die rather quietly, massive stars arriving at the end of their brief life explode as supernovae, hurling out a vast quantity of material. In this class, Supernova 1987A (SN 1987A) in the rather nearby Large Magellanic Cloud occupies a very special place. Seen in 1987, it was the first naked-eye supernova to be observed for 383 years (eso8704), and because of its relative closeness, it has made it possible for astronomers to study the explosion of a massive star and its aftermath in more detail than ever before. It is thus no surprise that few events in modern astronomy have been met with such an enthusiastic response by scientists. SN 1987A has been a bonanza for astrophysicists (eso8711 and eso0708). It provided several notable observational 'firsts', like the detection of neutrinos from the collapsing inner stellar core triggering the explosion, the localisation on archival photographic plates of the star before it exploded, the signs of an asymmetric explosion, the direct observation of the radioactive elements produced during the blast, observation of the formation of dust in the supernova, as well as the detection of circumstellar and interstellar material (eso0708). New observations making use of a unique instrument, SINFONI [1], on ESO's Very Large Telescope (VLT) have provided even deeper knowledge of this amazing event, as astronomers have now been able to obtain the first-ever 3D reconstruction of the central parts of the exploding material. This view shows that the explosion was stronger and

  1. Oscillations in stellar superflares

    CERN Document Server

    Balona, L A; Kosovichev, A; Nakariakov, V M; Pugh, C E; Van Doorsselaere, T

    2015-01-01

    Two different mechanisms may act to induce quasi-periodic pulsations (QPP) in whole-disk observations of stellar flares. One mechanism may be magneto-hydromagnetic (MHD) forces and other processes acting on flare loops as seen in the Sun. The other mechanism may be forced local acoustic oscillations due to the high-energy particle impulse generated by the flare (known as `sunquakes' in the Sun). We analyze short-cadence Kepler data of 257 flares in 75 stars to search for QPP in the flare decay branch or post-flare oscillations which may be attributed to either of these two mechanisms. About 18 percent of stellar flares show a distinct bump in the flare decay branch of unknown origin. The bump does not seem to be a highly-damped global oscillation because the periods of the bumps derived from wavelet analysis do not correlate with any stellar parameter. We detected damped oscillations covering several cycles (QPP), in seven flares on five stars. The periods of these oscillations also do not correlate with any ...

  2. Semi-analytic stellar structure in scalar-tensor gravity

    Science.gov (United States)

    Horbatsch, M. W.; Burgess, C. P.

    2011-08-01

    Precision tests of gravity can be used to constrain the properties of hypothetical very light scalar fields, but these tests depend crucially on how macroscopic astrophysical objects couple to the new scalar field. We study the equations of stellar structure using scalar-tensor gravity, with the goal of seeing how stellar properties depend on assumptions made about the scalar coupling at a microscopic level. In order to make the study relatively easy for different assumptions about microscopic couplings, we develop quasi-analytic approximate methods for solving the stellar-structure equations rather than simply integrating them numerically. (The approximation involved assumes the dimensionless scalar coupling at the stellar center is weak, and we compare our results with numerical integration in order to establish its domain of validity.) We illustrate these methods by applying them to Brans-Dicke scalars, and their generalization in which the scalar-matter coupling slowly runs — or `walks' — as a function of the scalar field: a(phi) simeq as+bsphi. (Such couplings can arise in extra-dimensional applications, for instance.) The four observable parameters that characterize the fields external to a spherically symmetric star are the stellar radius, R, mass, M, scalar `charge', Q, and the scalar's asymptotic value, phi∞. These are subject to two relations because of the matching to the interior solution, generalizing the usual mass-radius, M(R), relation of General Relativity. Since phi∞ is common to different stars in a given region (such as a binary pulsar), all quantities can be computed locally in terms of the stellar masses. We identify how these relations depend on the microscopic scalar couplings, agreeing with earlier workers when comparisons are possible. Explicit analytical solutions are obtained for the instructive toy model of constant-density stars, whose properties we compare to more realistic equations of state for neutron star models.

  3. Massive stars as thermonuclear reactors and their explosions following core collapse

    CERN Document Server

    Ray, Alak

    2009-01-01

    Nuclear reactions transform atomic nuclei inside stars. This is the process of stellar nucleosynthesis. The basic concepts of determining nuclear reaction rates inside stars are reviewed. How stars manage to burn their fuel so slowly most of the time are also considered. Stellar thermonuclear reactions involving protons in hydrostatic burning are discussed first. Then I discuss triple alpha reactions in the helium burning stage. Carbon and oxygen survive in red giant stars because of the nuclear structure of oxygen and neon. Further nuclear burning of carbon, neon, oxygen and silicon in quiescent conditions are discussed next. In the subsequent core-collapse phase, neutronization due to electron capture from the top of the Fermi sea in a degenerate core takes place. The expected signal of neutrinos from a nearby supernova is calculated. The supernova often explodes inside a dense circumstellar medium, which is established due to the progenitor star losing its outermost envelope in a stellar wind or mass trans...

  4. SpECTRE: A Task-based Discontinuous Galerkin Code for Relativistic Astrophysics

    CERN Document Server

    Kidder, Lawrence E; Foucart, Francois; Schnetter, Erik; Teukolsky, Saul A; Bohn, Andy; Deppe, Nils; Diener, Peter; Hébert, François; Lippuner, Jonas; Miller, Jonah; Ott, Christian D; Scheel, Mark A; Vincent, Trevor

    2016-01-01

    We introduce a new relativistic astrophysics code, SpECTRE, that combines a discontinuous Galerkin method with a task-based parallelism model. SpECTRE's goal is to achieve more accurate solutions for challenging relativistic astrophysics problems such as core-collapse supernovae and binary neutron star mergers. The robustness of the discontinuous Galerkin method allows for the use of high-resolution shock capturing methods in regions where (relativistic) shocks are found, while exploiting high-order accuracy in smooth regions. A task-based parallelism model allows efficient use of the largest supercomputers for problems with a heterogeneous workload over disparate spatial and temporal scales. We argue that the locality and algorithmic structure of discontinuous Galerkin methods will exhibit good scalability within a task-based parallelism framework. We demonstrate the code on a wide variety of challenging benchmark problems in (non)-relativistic (magneto)-hydrodynamics. We demonstrate the code's scalability i...

  5. Examining the Accuracy of Astrophysical Disk Simulations with a Generalized Hydrodynamical Test Problem

    Science.gov (United States)

    Raskin, Cody; Owen, J. Michael

    2016-11-01

    We discuss a generalization of the classic Keplerian disk test problem allowing for both pressure and rotational support, as a method of testing astrophysical codes incorporating both gravitation and hydrodynamics. We argue for the inclusion of pressure in rotating disk simulations on the grounds that realistic, astrophysical disks exhibit non-negligible pressure support. We then apply this test problem to examine the performance of various smoothed particle hydrodynamics (SPH) methods incorporating a number of improvements proposed over the years to address problems noted in modeling the classical gravitation-only Keplerian disk. We also apply this test to a newly developed extension of SPH based on reproducing kernels called CRKSPH. Counterintuitively, we find that pressure support worsens the performance of traditional SPH on this problem, causing unphysical collapse away from the steady-state disk solution even more rapidly than the purely gravitational problem, whereas CRKSPH greatly reduces this error.

  6. Examining the Accuracy of Astrophysical Disk Simulations With a Generalized Hydrodynamical Test Problem

    CERN Document Server

    Raskin, Cody

    2016-01-01

    We discuss a generalization of the classic Keplerian disk test problem allowing for both pressure and rotational support, as a method of testing astrophysical codes incorporating both gravitation and hydrodynamics. We argue for the inclusion of pressure in rotating disk simulations on the grounds that realistic, astrophysical disks exhibit non-negligible pressure support. We then apply this test problem to examine the performance of various smoothed particle hydrodynamics (SPH) methods incorporating a number of improvements proposed over the years to help SPH better address problems noted in modeling the classical gravitation only Keplerian disk. We also apply this test to a newly developed extension of SPH based on reproducing kernels called CRKSPH. Counterintuitively, we find that pressure support worsens the performance of traditional SPH on this problem, causing unphysical collapse away from the steady-state disk solution even more rapidly than the purely gravitational problem, whereas CRKSPH greatly redu...

  7. Magnetic fields greater than 10 to the 20th power gauss. [in astrophysical systems

    Science.gov (United States)

    Lerche, I.; Schramm, D. N.

    1977-01-01

    Zaumen (1976) found that spontaneous pair production in a uniform magnetic field should be a feasible process for field strengths at least of the order of 10 to the 20th power gauss. This note points out that a magnetic field of this order of magnitude is most unlikely to occur in realistic astrophysical situations because of the large dynamical and quantum-mechanical effects such a field would produce. It is suggested that Zaumen's calculation would probably have little bearing on the suspected evolution of astrophysical systems since other processes (either dynamical or quantum-mechanical) apparently limit the field strength before such high magnetic fields would be reached. An upper limit of about 10 to the 16th power gauss is obtained by considering the isotropy of the 3-K blackbody radiation, the formation of collapsed objects in very high magnetic fields, and magnetic bremsstrahlung processes in quantum electrodynamics.

  8. r-Process Nucleosynthesis in Jet-driven Core-Collapse Supernovae

    Science.gov (United States)

    Halevi, Goni; Moesta, Philipp

    2017-01-01

    We investigate rapidly rotating, strongly magnetized core-collapse supernova (CCSN) explosions as a site for the production of heavy elements through r-process nucleosynthesis. While CCSNe have long been considered a potential astrophysical site of this process explaining the origin of observed abundances for stable nuclei heavier than iron, the neutron-rich conditions necessary have not been robustly produced in simulations. There remain large uncertainties in quantifying the fraction of all core-collapse events that produce r-process material and the quantity of ejected material in a typical explosion.We perform three-dimensional (3D) dynamical-spacetime general-relativistic magnetohydrodynamic (GRMHD) simulations of jet-driven CCSNe. These simulations are run using the Einstein toolkit, an open-source community-driven numerical relativity and computational relativistic astrophysics code. They include microphysical finite-temperature equation of state effects and employ a leakage scheme that captures the overall energetics and lepton number exchange due to postbounce neutrino emission. The nuclear products of the simulated explosions are then calculated using SkyNet, a self-heating nuclear reaction network. We explore the robustness of r-process production in magnetorotational core-collapse and the properties of the ejected material.

  9. Stellar-mass black holes in young massive and open stellar clusters and their role in gravitational-wave generation

    CERN Document Server

    Banerjee, Sambaran

    2016-01-01

    The dynamical processes involving stellar-remnant black holes (BH) in stellar clusters has always drawn attention due to the BHs' potential in a number of astrophysical phenomena, especially the dynamical formation of binary black holes (BBH), which would potentially coalesce via radiation of gravitational waves (GW). This study presents a preliminary set of evolutionary models of compact stellar clusters with initial masses ranging over $1.0\\times10^4M_\\odot-5.0\\times10^4M_\\odot$, and half-mass radius of 2 pc or 1 pc, that is typical for young massive and starburst clusters. They have metallicities between $0.05Z_\\odot-Z_\\odot$. Including contemporary schemes for stellar wind and remnant-formation, such model clusters are evolved, for the first time, using the state-of-the-art direct N-body evolution program NBODY7, until their dissolution or at least for 10 Gyr. That way, a self-regulatory behaviour in the effects of dynamical interactions among the BHs, especially while heating and expanding the cluster an...

  10. The Multi-Dimensional Character of Core-Collapse Supernovae

    CERN Document Server

    Hix, W R; Bruenn, S W; Mezzacappa, A; Messer, O E B; Endeve, E; Blondin, J M; Harris, J A; Marronett, P; Yakunin, K N

    2016-01-01

    Core-collapse supernovae, the culmination of massive stellar evolution, are spectacular astronomical events and the principle actors in the story of our elemental origins. Our understanding of these events, while still incomplete, centers around a neutrino-driven central engine that is highly hydrodynamically unstable. Increasingly sophisticated simulations reveal a shock that stalls for hundreds of milliseconds before reviving. Though brought back to life by neutrino heating, the development of the supernova explosion is inextricably linked to multi-dimensional fluid flows. In this paper, the outcomes of three-dimensional simulations that include sophisticated nuclear physics and spectral neutrino transport are juxtaposed to learn about the nature of the three dimensional fluid flow that shapes the explosion. Comparison is also made between the results of simulations in spherical symmetry from several groups, to give ourselves confidence in the understanding derived from this juxtaposition.

  11. Thermodynamics of a collapsed object

    Energy Technology Data Exchange (ETDEWEB)

    Chaubey, N. (Inst. of Science and Techn., Sultanpur (India). Technological Faculty); De Sabbata, V. (Bologna Univ. (Italy). Ist. di Fisica)

    1981-06-20

    Here is presented a thermodynamic study in the Reissner-Nordstroem blackhole which leads to a beautiful conclusion that the product of surface gravities of the outer horizon and the inner horizon of the blackhole is equal to the inverse square of charge distribution over it. If one considers a more general collapsed object wherein rotation is also considered, a similar inference is that the product of surface gravities of the inner and the outer horizon is equal to the inverse of the sum of squares of the charge distribution and angular momentum per unit mass of the rotation.

  12. Design of Pneumatic Collapsible Steering

    Directory of Open Access Journals (Sweden)

    Anish Nair

    2013-08-01

    Full Text Available The steering wheel is the important cause of fatal injury for drivers in frontal collision. When frontal collision occurs, due to the kinetic energy of driver or occupant body, it moves forward against steering wheel and wind shield. Actually in a frontal collision forces will be first transmitted through driver’s feet which act as fulcrum so the body will rotate about it. For the taller driver steering works as fulcrum. Driver head & chest hit the steering or windshield which may cause severe injury or death. Considering the injury potential of steering wheel we are presenting a new idea Pneumatic Collapsible Steering Column (PCS.

  13. Spherically symmetric scalar field collapse

    Indian Academy of Sciences (India)

    Koyel Ganguly; Narayan Banerjee

    2013-03-01

    It is shown that a scalar field, minimally coupled to gravity, may have collapsing modes even when the energy condition is violated, that is, for ( + 3) < 0. This result may be useful in the investigation of the possible clustering of dark energy. All the examples dealt with have apparent horizons formed before the formation of singularity. The singularities formed are shell focussing in nature. The density of the scalar field distribution is seen to diverge at singularity. The Ricci scalar also diverges at the singularity. The interior spherically symmetric metric is matched with exterior Vaidya metric at the hypersurface and the appropriate junction conditions are obtained.

  14. A Comparison of the Citation Counts in the Science Citation Index and the NASA Astrophysics Data System

    Science.gov (United States)

    Abt, Helmut A.

    2006-01-01

    From a comparison of 1000+ references to 20 papers in four fields of astronomy (solar, stellar, nebular, galaxy), we found that the citation counts in Science Citation Index (SCI) and Astrophysics Data System (ADS) agree for 85% of the citations. ADS gives 15% more citation counts than SCI. SCI has more citations among physics and chemistry journals, while ADS includes more from conferences. Each one misses less than 1% of the citations.

  15. Scaling Extreme Astrophysical Phenomena to the Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Remington, B A

    2007-11-01

    High-energy-density (HED) physics refers broadly to the study of macroscopic collections of matter under extreme conditions of temperature and density. The experimental facilities most widely used for these studies are high-power lasers and magnetic-pinch generators. The HED physics pursued on these facilities is still in its infancy, yet new regimes of experimental science are emerging. Examples from astrophysics include work relevant to planetary interiors, supernovae, astrophysical jets, and accreting compact objects (such as neutron stars and black holes). In this paper, we review a selection of recent results in this new field of HED laboratory astrophysics and provide a brief look ahead to the coming decade.

  16. Plasma Astrophysics, Part I Fundamentals and Practice

    CERN Document Server

    Somov, Boris V

    2012-01-01

    This two-part book is devoted to classic fundamentals and current practices and perspectives of modern plasma astrophysics. This first part uniquely covers all the basic principles and practical tools required for understanding and work in plasma astrophysics. More than 25% of the text is updated from the first edition, including new figures, equations and entire sections on topics such as magnetic reconnection and the Grad-Shafranov equation. The book is aimed at professional researchers in astrophysics, but it will also be useful to graduate students in space sciences, geophysics, applied physics and mathematics, especially those seeking a unified view of plasma physics and fluid mechanics.

  17. Nuclear Astrophysics Measurements with Radioactive Beams

    Science.gov (United States)

    Smith, Michael S.; Ernst Rehm, K.

    Radioactive nuclei play an important role in a diverse range of astrophysical phenomena including the early universe, the sun, red giant stars, nova explosions, X-ray bursts, supernova explosions, and supermassive stars. Measurements of reactions with beams of short-lived radioactive nuclei can, for the first time, probe the nuclear reactions occurring in these cosmic phenomena. This article describes the astrophysical motivation for experiments with radioactive beams, the techniques to produce these beams and perform astrophysically relevant measurements, results from recent experiments, and plans for future facilities.

  18. New Astrophysical Reaction Rates for 18F(p, α)15O and 18F(p, γ)19Ne

    Institute of Scientific and Technical Information of China (English)

    SHU Neng-Chuan(舒能川); D. W. Bardayan; J. C. Blackmon; CHEN Yong-Shou(陈永寿); R. L. Kozub; P. D. Parker; M. S. Smith

    2003-01-01

    The rates of the thermonuclear 18F(p, α)15O and 18F(p,γ)19Ne reactions in hot astrophysical environments are needed to understand gamma-ray emission from nova explosions. The rates for these reactions have been uncertain due to discrepancies in recent measurements, as well as to a lack of a comprehensive examination of the available structure information in the compound nucleus 19Ne. We have examined the latest experimental measurements with radioactive and stable beams, and made estimates of the unmeasured 19Ne nuclear level parameters, to generate new rates with uncertainties for these reactions. The rates are expressed as numerical values over the temperature range relevant for stellar explosions, as well as analytical expressions as functions of temperature in a format suitable for use in astrophysical simulations. Comparisons with the previous rate calculations are carried out, and the astrophysical implications are briefly discussed.

  19. Geotechnical properties of Egyptian collapsible soils

    Directory of Open Access Journals (Sweden)

    Khaled E. Gaaver

    2012-09-01

    Full Text Available The risk of constructing structures on collapsible soils presents significant challenges to geotechnical engineers due to sudden reduction in volume upon wetting. Identifying collapsible soils when encountered in the field and taking the needed precautions should substantially reduce the risk of such problems usually reported in buildings and highways. Collapsible soils are those unsaturated soils that can withstand relatively high pressure without showing significant change in volume, however upon wetting; they are susceptible to a large and sudden reduction in volume. Collapsible soils cover significant areas around the world. In Egypt, collapsible soils were observed within the northern portion of the western desert including Borg El-Arab region, and around the city of Cairo in Six-of-October plateau, and Tenth-of-Ramadan city. Settlements associated with development on untreated collapsible soils usually lead to expensive repairs. One method for treating collapsible soils is to densify their structure by compaction. The ongoing study presents the effect of compaction on the geotechnical properties of the collapsible soils. Undisturbed block samples were recovered from test pits at four sites in Borg El-Arab district, located at about 20 km west of the city of Alexandria, Egypt. The samples were tested in both unsoaked and soaked conditions. Influence of water inundation on the geotechnical properties of collapsible soils was demonstrated. A comparative study between natural undisturbed and compacted samples of collapsible soils was performed. An attempt was made to relate the collapse potential to the initial moisture content. An empirical correlation between California Bearing Ratio of the compacted collapsible soils and liquid limit was adopted. The presented simple relationships should enable the geotechnical engineers to estimate the complex parameters of collapsible soils using simple laboratory tests with a reasonable accuracy.

  20. Energy Conservation and Gravity Waves in Sound-proof Treatments of Stellar Interiors: Part I Anelastic Approximations

    CERN Document Server

    Brown, Benjamin P

    2012-01-01

    Typical flows in stellar interiors are much slower than the speed of sound. To follow the slow evolution of subsonic motions, various sound-proof equations are in wide use, particularly in stellar astrophysical fluid dynamics. These low-Mach number equations include the anelastic equations. Generally, these equations are valid in nearly adiabatically stratified regions like stellar convection zones, but may not be valid in the sub-adiabatic, stably stratified stellar radiative interiors. Understanding the coupling between the convection zone and the radiative interior is a problem of crucial interest and may have strong implications for solar and stellar dynamo theories as the interface between the two, called the tachocline in the Sun, plays a crucial role in many solar dynamo theories. Here we study the properties of gravity waves in stably-stratified atmospheres. In particular, we explore how gravity waves are handled in various sound-proof equations. We find that some anelastic treatments fail to conserve...

  1. Using Graphics Processing Units to solve the classical N-body problem in physics and astrophysics

    CERN Document Server

    Spera, Mario

    2014-01-01

    Graphics Processing Units (GPUs) can speed up the numerical solution of various problems in astrophysics including the dynamical evolution of stellar systems; the performance gain can be more than a factor 100 compared to using a Central Processing Unit only. In this work I describe some strategies to speed up the classical N-body problem using GPUs. I show some features of the N-body code HiGPUs as template code. In this context, I also give some hints on the parallel implementation of a regularization method and I introduce the code HiGPUs-R. Although the main application of this work concerns astrophysics, some of the presented techniques are of general validity and can be applied to other branches of physics such as electrodynamics and QCD.

  2. Bremsstrahlung photons - an ideal tool in nuclear structure and nuclear astrophysics

    Energy Technology Data Exchange (ETDEWEB)

    Babilon, Mario [Institut fur Kernphysik, Darmstadt (Germany)

    2005-07-01

    Full text of publication follows. Bremsstrahlung photons, produced by decelerating electrons, are a very useful probe to investigate current topics in nuclear structure and nuclear astrophysics. The photon scattering facility of the superconducting electron accelerator S-DALINAC at the Darmstadt University of Technology allows for high resolution Nuclear Resonance Fluorescence (NRF) experiments up to 10 MeV. One current topic of interest in nuclear structure is the investigation of Pygmy Dipole Resonances (PDR), which are located near the particle threshold. Recently, experiments have been carried out on Ca isotopes [1] as well as on several N=82 nuclei [2] in order to understand the structure of the PDR. Moreover, important astrophysical questions can be investigated using real photons (g,n) reaction rates, which play a major role in nucleosynthesis, can be measured at the S-DALINAC by simulating a quasi-stellar photon bath with variable temperature [3,4].

  3. Partition functions and equilibrium constants for diatomic molecules and atoms of astrophysical interest

    CERN Document Server

    Barklem, Paul S

    2016-01-01

    Partition functions and dissociation equilibrium constants are presented for 291 diatomic molecules for temperatures in the range from near absolute zero to 10000 K, thus providing data for many diatomic molecules of astrophysical interest at low temperature. The calculations are based on molecular spectroscopic data from the book of Huber and Herzberg with significant improvements from the literature, especially updated data for ground states of many of the most important molecules by Irikura. Dissociation energies are collated from compilations of experimental and theoretical values. Partition functions for 284 species of atoms for all elements from H to U are also presented based on data collected at NIST. The calculated data are expected to be useful for modelling a range of low density astrophysical environments, especially star-forming regions, protoplanetary disks, the interstellar medium, and planetary and cool stellar atmospheres. The input data, which will be made available electronically, also prov...

  4. Modeling Pressure-Ionization of Hydrogen in the Context of Astrophysics

    CERN Document Server

    Saumon, D S; Wagner, D J; Xie, X

    1999-01-01

    The recent development of techniques for laser-driven shock compression of hydrogen has opened the door to the experimental determination of its behavior under conditions characteristic of stellar and planetary interiors. The new data probe the equation of state (EOS) of dense hydrogen in the complex regime of pressure ionization. The structure and evolution of dense astrophysical bodies depend on whether the pressure ionization of hydrogen occurs continuously or through a ``plasma phase transition'' (PPT) between a molecular state and a plasma state. For the first time, the new experiments constrain predictions for the PPT. We show here that the EOS model developed by Saumon and Chabrier can successfully account for the data, and we propose an experiment that should provide a definitive test of the predicted PPT of hydrogen. The usefulness of the chemical picture for computing astrophysical EOS and in modeling pressure ionization is discussed.

  5. Influence of pions and hyperons on stellar black hole formation

    CERN Document Server

    Peres, Bruno; Novak, Jerome

    2013-01-01

    We present numerical simulations of stellar core-collapse with spherically symmetric, general relativistic hydrodynamics up to black hole formation. Using the CoCoNuT code, with a newly developed grey leakage scheme for the neutrino treatment, we investigate the effects of including pions and Lambda-hyperons into the equation of state at high densities and temperatures on the black hole formation process. Results show small but non-negligible differences between the models with reference equation of state without any additional particles and models with the extended ones. For the latter, the maximum masses supported by the proto-neutron star are smaller and the collapse to a black hole occurs earlier. A phase transition to hyperonic matter is observed when the progenitor allows for a high enough accretion rate onto the proto-neutron star.

  6. Silo Collapse under Granular Discharge

    Science.gov (United States)

    Gutiérrez, G.; Colonnello, C.; Boltenhagen, P.; Darias, J. R.; Peralta-Fabi, R.; Brau, F.; Clément, E.

    2015-01-01

    We investigate, at a laboratory scale, the collapse of cylindrical shells of radius R and thickness t induced by a granular discharge. We measure the critical filling height for which the structure fails upon discharge. We observe that the silos sustain filling heights significantly above an estimation obtained by coupling standard shell-buckling and granular stress distribution theories. Two effects contribute to stabilize the structure: (i) below the critical filling height, a dynamical stabilization due to granular wall friction prevents the localized shell-buckling modes to grow irreversibly; (ii) above the critical filling height, collapse occurs before the downward sliding motion of the whole granular column sets in, such that only a partial friction mobilization is at play. However, we notice also that the critical filling height is reduced as the grain size d increases. The importance of grain size contribution is controlled by the ratio d /√{R t }. We rationalize these antagonist effects with a novel fluid-structure theory both accounting for the actual status of granular friction at the wall and the inherent shell imperfections mediated by the grains. This theory yields new scaling predictions which are compared with the experimental results.

  7. New mechanism of acceleration of particles by stellar black holes

    CERN Document Server

    Osmanov, Z

    2016-01-01

    In this paper we study efficiency of particle acceleration in the magnetospheres of stellar mass black holes. For this purpose we consider the linearized set of the Euler equation, continuity equation and Poisson equation respectively. After introducing the varying relativistic centrifugal force, we show that the charge separation undergoes the parametric instability, leading to generation of centrifugally excited Langmuir waves. It is shown that these waves, via the Langmuir collapse damp by means of the Landau damping, as a result energy transfers to particles accelerating them to energies of the order of $10^{16}$eV.

  8. Astrophysics: Unexpected X-ray flares

    Science.gov (United States)

    Campana, Sergio

    2016-10-01

    Two sources of highly energetic flares have been discovered in archival X-ray data of 70 nearby galaxies. These flares have an undetermined origin and might represent previously unknown astrophysical phenomena. See Letter p.356

  9. Stellar structure of magnetars

    Science.gov (United States)

    Dong, JianMin; Zuo, Wei; Gu, JianZhong; Shang, XinLe

    2016-04-01

    Magnetars are strong magnetized neutron stars which could emit quiescent X-ray, repeating burst of soft gamma ray, and even the giant flares. We investigate the effects of magnetic fields on the structure of isolated magnetars. The stellar structure together with the magnetic field configuration can be obtained at the same time within a self-consistent procedure. The magnetar mass and radius are found to be weakly enhanced by the strong magnetic fields. Unlike other previous investigations, the magnetic field is unable to violate the mass limit of the neutron stars.

  10. THE ADVANCED STELLAR COMPASS

    DEFF Research Database (Denmark)

    Jørgensen, John Leif; Liebe, Carl Christian

    1997-01-01

    The science objective of the Danish Geomagnetic Research Satellite "Ørsted" is to map the magnetic field of the Earth, with a vector precision of a fraction of a nanotesla. This necessitates an attitude reference instrument with a precision of a few arcseconds onboard the satellite. To meet...... this demand the Advanced Stellar Compass (ASC), a fully autonomous miniature star tracker, was developed. This ASC is capable of both solving the "lost in space" problem and determine the attitude with arcseconds precision. The development, principles of operation and instrument autonomy of the ASC...

  11. Gray Models of convection in core collapse supernovae

    CERN Document Server

    Swesty, F D

    1998-01-01

    One of the major difficulties encountered in modeling core collapse supernovae is obtaining an accurate description of the transport of neutrinos through the collapsed stellar core. The behavior of the neutrino distribution function transitions from an LTE distribution in the center of the core to a non-LTE distribution in the outer regions of the core. One method that has been recently employed in order to model the flow of neutrinos in 2-D models is the gray approximation. This approximation assumes that the neutrino distribution can be described by a function that is parameterized in terms of a neutrino temperature and a neutrino chemical potential. However, these parameters must be assumed. Furthermore, the parameters will also differ between the LTE and NLTE regions. Additionally, within the gray approximation the location at which the neutrino distribution function transitions from LTE to NLTE must be assumed. By considering a series of models where the LTE/NLTE decoupling point is varied we show that t...

  12. Parametric initial conditions for core-collapse supernova simulations

    Science.gov (United States)

    Suwa, Yudai; Müller, Ewald

    2016-08-01

    We investigate a method to construct parametrized progenitor models for core-collapse supernova simulations. Different from all modern core-collapse supernova studies, which rely on progenitor models from stellar evolution calculations, we follow the methodology of Baron & Cooperstein to construct initial models. Choosing parametrized spatial distributions of entropy and electron fraction as a function of mass coordinate and solving the equation of hydrostatic equilibrium, we obtain the initial density structures of our progenitor models. First, we calculate structures with parameters fitting broadly the evolutionary model s11.2 of Woosley et al. (2002). We then demonstrate the reliability of our method by performing general relativistic hydrodynamic simulations in spherical symmetry with the isotropic diffusion source approximation to solve the neutrino transport. Our comprehensive parameter study shows that initial models with a small central entropy (≲0.4 kB nucleon-1) can explode even in spherically symmetric simulations. Models with a large entropy (≳6 kB nucleon-1) in the Si/O layer have a rather large explosion energy (˜4 × 1050 erg) at the end of the simulations, which is still rapidly increasing.

  13. FINDING THE FIRST COSMIC EXPLOSIONS. II. CORE-COLLAPSE SUPERNOVAE

    Energy Technology Data Exchange (ETDEWEB)

    Whalen, Daniel J. [Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Joggerst, Candace C. [T-2, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Fryer, Chris L. [CCS-2, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Stiavelli, Massimo [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Heger, Alexander [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); Holz, Daniel E. [Enrico Fermi Institute, Department of Physics, and Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637 (United States)

    2013-05-01

    Understanding the properties of Population III (Pop III) stars is prerequisite to elucidating the nature of primeval galaxies, the chemical enrichment and reionization of the early intergalactic medium, and the origin of supermassive black holes. While the primordial initial mass function (IMF) remains unknown, recent evidence from numerical simulations and stellar archaeology suggests that some Pop III stars may have had lower masses than previously thought, 15-50 M{sub Sun} in addition to 50-500 M{sub Sun }. The detection of Pop III supernovae (SNe) by JWST, WFIRST, or the TMT could directly probe the primordial IMF for the first time. We present numerical simulations of 15-40 M{sub Sun} Pop III core-collapse SNe performed with the Los Alamos radiation hydrodynamics code RAGE. We find that they will be visible in the earliest galaxies out to z {approx} 10-15, tracing their star formation rates and in some cases revealing their positions on the sky. Since the central engines of Pop III and solar-metallicity core-collapse SNe are quite similar, future detection of any Type II SNe by next-generation NIR instruments will in general be limited to this epoch.

  14. Gravitational wave signatures in black-hole forming core collapse

    CERN Document Server

    Cerdá-Durán, Pablo; Aloy, Miguel A; Font, José A; Obergaulinger, Martin

    2013-01-01

    We present numerical simulations in general relativity of collapsing stellar cores. Our initial model consists of a low metallicity rapidly-rotating progenitor which is evolved in axisymmetry with the latest version of our general relativistic code CoCoNuT, which allows for black hole formation and includes the effects of a microphysical equation of state (LS220) and a neutrino leakage scheme to account for radiative losses. The motivation of our study is to analyze in detail the emission of gravitational waves in the collapsar scenario of long gamma-ray bursts. Our simulations show that the phase during which the proto-neutron star (PNS) survives before ultimately collapsing to a black hole is particularly optimal for gravitational wave emission. The high-amplitude waves last for several seconds and show a remarkable quasi-periodicity associated with the violent PNS dynamics, namely during the episodes of convection and the subsequent nonlinear development of the standing-accretion shock instability (SASI). ...

  15. GRAVITATIONAL WAVE SIGNATURES IN BLACK HOLE FORMING CORE COLLAPSE

    Energy Technology Data Exchange (ETDEWEB)

    Cerdá-Durán, Pablo; DeBrye, Nicolas; Aloy, Miguel A.; Font, José A.; Obergaulinger, Martin, E-mail: pablo.cerda@uv.es [Departamento de Astronomia y Astrofísica, Universidad de Valencia, c/Dr. Moliner 50, E-46100-Burjassot (Spain)

    2013-12-20

    We present general relativistic numerical simulations of collapsing stellar cores. Our initial model consists of a low metallicity rapidly-rotating progenitor which is evolved in axisymmetry with the latest version of our general relativistic code CoCoNuT, which allows for black hole formation and includes the effects of a microphysical equation of state (LS220) and a neutrino leakage scheme to account for radiative losses. The motivation of our study is to analyze in detail the emission of gravitational waves in the collapsar scenario of long gamma-ray bursts. Our simulations show that the phase during which the proto-neutron star (PNS) survives before ultimately collapsing to a black hole is particularly optimal for gravitational wave emission. The high-amplitude waves last for several seconds and show a remarkable quasi-periodicity associated with the violent PNS dynamics, namely during the episodes of convection and the subsequent nonlinear development of the standing-accretion shock instability (SASI). By analyzing the spectrogram of our simulations we are able to identify the frequencies associated with the presence of g-modes and with the SASI motions at the PNS surface. We note that the gravitational waves emitted reach large enough amplitudes to be detected with third-generation detectors such as the Einstein Telescope within a Virgo Cluster volume at rates ≲ 0.1 yr{sup –1}.

  16. Relativistic Structure, Stability and Gravitational Collapse of Charged Neutron Stars

    CERN Document Server

    Ghezzi, C R

    2005-01-01

    Charged stars have the potential of becoming charged black holes or even naked singularities. It is presented a set of numerical solutions of the Tolman-Oppenheimer-Volkov equations that represents spherical charged compact stars in hydrostatic equilibrium. The stellar models obtained are evolved forward in time integrating the Einstein-Maxwell field equations. It is assumed an equation of state of a neutron gas at zero temperature. The charge distribution is taken as been proportional to the rest mass density distribution. The set of solutions present an unstable branch, even with charge to mass ratios arbitrarily close to the extremum case. It is performed a direct check of the stability of the solutions under strong perturbations, and for different values of the charge to mass ratio. The stars that are in the stable branch oscillates and do not collapse, while models in the unstable branch collapse directly to form black holes. Stars with a charge greater or equal than the extreme value explode. When a cha...

  17. Probing nonlinear electrodynamics in slowly rotating spacetimes through neutrino astrophysics

    Science.gov (United States)

    Mosquera Cuesta, Herman J.; Lambiase, Gaetano; Pereira, Jonas P.

    2017-01-01

    Huge electromagnetic fields are known to be present during the late stages of the dynamics of supernovae. Thus, when dealing with electrodynamics in this context, the possibility may arise to probe nonlinear theories (generalizations of the Maxwellian electromagnetism). We firstly solve Einstein field equations minimally coupled to an arbitrary (current-free) nonlinear Lagrangian of electrodynamics (NLED) in the slow rotation regime a ≪M (black hole's mass), up to first order in a /M . We then make use of the robust and self-contained Born-Infeld Lagrangian in order to compare and contrast the physical properties of such NLED spacetime with its Maxwellian counterpart (a slowly rotating Kerr-Newman spacetime), especially focusing on the astrophysics of both neutrino flavor oscillations (νe→νμ , ντ ) and spin-flip (νl→νr, "l " stands for "left" and "r " stands for "right", change of neutrino handedness) mass level crossings, the equivalent to gyroscopic precessions. Such analysis proves that in the spacetime of a slowly rotating nonlinear charged black hole (RNCBH), intrinsically associated with the assumption the electromagnetism is nonlinear, the neutrino dynamics in core-collapse supernovae could be significantly changed. In such an astrophysical environment, a positive enhancement (reduction of the electron fraction Yeatomic number and amount, of the decaying nuclides. Finally, we envisage some physical scenarios that may lead to short-lived charged black holes with high charge-to-mass ratios (associated with unstable highly magnetized neutron stars) and ways to possibly disentangle theories of the electromagnetism from other black hole observables (by means of light polarization measurements).

  18. A Legacy Magellanic Clouds Star Clusters Sample for the Calibration of Stellar Evolution Models

    Science.gov (United States)

    Fouesneau, Morgan

    2014-10-01

    Stellar evolution models are fundamental to all studies in astrophysics. These models are the foundations of the interpretation of colors and luminosities of stars necessary to address problems ranging from galaxy formation to determining the habitable zone of planets and interstellar medium properties. For decades the standard calibration of these models relied on a handful of star clusters. However, large uncertainties remain in the fundamental parameters underlying stellar evolution models. The project we propose is two-fold. First we propose to generate a new high quality reference dataset of the resolved stars in 121 Magellanic Cloud clusters, selected from 18 past programs to efficiently sample a large grid of stellar evolution models. Our team will measure the photometry of individual stars in those clusters and characterize individual completeness and photometric uncertainties. Second, we will migrate the calibration of the stellar evolution into a fully probabilistic framework, that will not only reflect the state-of-the-art, but will also be published with fully characterized uncertainties, based on the entire reference data set, rather than a few select clusters.We have entered an era dominated by large surveys {e.g. SDSS, PanSTARRS, Gaia, LSST} where the variations between families of stellar models are greater than the nominal precision of the instruments. Our proposed program will provide a library needed for a convergence in the stellar models and our understanding of stellar evolution.

  19. Nuclear Physics and Astrophysics of Neutrino Oscillations

    CERN Document Server

    Balantekin, A B

    2016-01-01

    For a long time very little experimental information was available about neutrino properties, even though a minute neutrino mass has intriguing cosmological and astrophysical implications. This situation has changed in recent decades: intense experimental activity to measure many neutrino properties took place. Some of these developments and their implications for astrophysics and cosmology are briefly reviewed with a particular emphasis on neutrino magnetic moments and collective neutrino oscillations

  20. Probing New Physics with Astrophysical Neutrinos

    OpenAIRE

    Bell, Nicole F.

    2008-01-01

    We review the prospects for probing new physics with neutrino astrophysics. High energy neutrinos provide an important means of accessing physics beyond the electroweak scale. Neutrinos have a number of advantages over conventional astronomy and, in particular, carry information encoded in their flavor degree of freedom which could reveal a variety of exotic neutrino properties. We also outline ways in which neutrino astrophysics can be used to constrain dark matter properties, and explain ho...