A5108166823- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Nuclear Physics and Applications
- Astro and Planetary Science
- Pulsars and Gravitational Waves Research
- Nuclear physics research studies
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Neutrino Physics Research
- Galaxies: Formation, Evolution, Phenomena
- Medical Imaging Techniques and Applications
- Planetary Science and Exploration
- Radiation Therapy and Dosimetry
- Solar and Space Plasma Dynamics
- Astrophysics and Star Formation Studies
- Cosmology and Gravitation Theories
- Relativity and Gravitational Theory
- Nuclear reactor physics and engineering
- Dark Matter and Cosmic Phenomena
- Particle Detector Development and Performance
- X-ray Spectroscopy and Fluorescence Analysis
- Astronomical and nuclear sciences
- Laser-Plasma Interactions and Diagnostics
- Computational Physics and Python Applications
Clemson University
2004-2023
Northwestern University
1995
University of Arizona
1986-1987
The authors examine the uncertainties in mass estimates for Coma cluster derived from position and velocity data galaxies. If distribution is assumed to parallel galaxy distribution, total within 5.4h<SUB>50</SUB><SUP>-1</SUP> Mpc 1.9×10<SUP>15</SUP>h<SUB>50</SUB><SUP>-1</SUP>M_sun; an accuracy of about 30% (for H<SUB>0</SUB> = 50 h<SUB>50</SUB> km/s/Mpc). However, if form not constrained, this region can range between 6×10<SUP>14</SUP>h<SUB>50</SUB><SUP>-1</SUP> M_sun;...
We present a detailed study of s-process nucleosynthesis in massive stars solar-like initial composition and masses 15, 20,25, 30 Msun. update our previous results during the core He-burning these then focus on an analysis under physical conditions encountered shell-carbon burning. show that recent compilation Ne22(alpha,n)Mg25 rate leads to remarkable reduction efficiency He-burning. In particular, this lowest overproduction factor Kr80 found date stars. The yields resulting from shell...
We analyze the nucleosynthesis implications of recent discovery by M. J. Pellin and collaborators that two odd isotopes molybdenum, 95Mo 97Mo, are overabundant in type X SiC grains: grains condensed within expanding supernova interiors. find a rapid release neutrons (on timescale seconds) with fluence τ = 0.07-0.08 mbarn-1 produces observed pattern way abundant production progenitor radioactive Zr isotopes. This suggests condensing matter was shell which burning occurring at time ejection,...
According to standard models supernovae produce radioactive $^{44}$Ti, which should be visible in gamma-rays following decay $^{44}$Ca for a few centuries. $^{44}Ti production is believed the source of cosmic $^{44}$Ca, whose abundance well established. Yet, gamma-ray telescopes have not seen expected young remnants core collapse events. The $^{44}$Ti mean life $τ\simeq$ 89 y and Galactic supernova rate $\simeq$ 3/100 imply several detectable sources, but only one clearly seen, 340-year-old...
Large excesses of 44Ca in certain presolar graphite and silicon carbide grains give strong evidence for 44Ti production supernovae. Furthermore, recent detection the γ line from Cas A supernova remnant by Compton Gamma Ray Observatory Telescope shows that radioactive is produced These make abundance an observable diagnostic Through use a nuclear reaction network, we have systematically varied rates groups to experimentally identify those govern core-collapse nucleosynthesis. We survey...
We present a study of the early (days to weeks) X-ray and UV properties eight Type Ia supernovae (SNe Ia) which have been extensively observed with X-Ray Telescope (XRT) UV/Optical (UVOT) onboard Swift, ranging from 5-132 days after outburst. SN 2005ke is tentatively detected (at 3-3.6 sigma level significance) in X-rays based on deep monitoring XRT 8 120 The inferred luminosity [(2+/-1) x 10^{38} ergs/s; 0.3-2 keV band] likely caused by interaction shock circumstellar material (CSM),...
We generate bolometric light curves for a variety of Type Ia supernova models at late times, simulating gamma-ray and positron transport various assumptions about the magnetic field ionization ejecta. These calculated curve shapes are compared with specific supernovae which there have been adequate observations. The selection is generally not based upon ability to fit observations, but rather because model has demonstrated by other authors approximate spectra early that SN. From these...
We present a comprehensive study of s-process nucleosynthesis in 15, 20, 25, and 30 M☉ stellar models having solar-like initial composition. The stars are evolved up to ignition central neon with 659 species network coupled the models. In this way, composition from one burning phase another is consistently determined, especially respect neutron capture reactions. aim our calculations gain full account yield massive stars. work, we describe code detail then focus primarily on results during...
We present the results of our abundance analysis Fe, Ni, and O in high signal-to-noise ratio, high-resolution Very Large Telescope UVES McDonald 2dcoudé spectra nine dwarfs three giants Hyades open cluster. The difference Fe abundances derived from II I lines ([Fe /H] - [Fe /H]) Ni moderately high-excitation (χ ≈ 4.20 eV) is found to increase with decreasing Teff for dwarfs. Both these findings are concordance previous overexcitation/overionization cool young Oxygen [O I] λ6300 line, careful...
We extend earlier efforts to determine whether the late (t ≥ 60 days) light curves of Type Ia SNe are better explained by escape positrons from ejecta or complete deposition positron kinetic energy in a trapping magnetic field. refine our selection SNe, using those that have extensive BVRI photometry 35 days more after maximum light. Assuming all within given Δm15(B) range form distinct subclass, we fit combined curve for class members with variety models. improve previous calculations rates...
We present a detailed study of the evolution massive stars masses 15, 20, 25, and 30 M☉ assuming solar-like initial chemical composition. The stellar sequences were evolved through advanced burning phases up to end core oxygen burning. careful analysis physical characteristics models. In particular, we investigate effect still-unsettled reaction 12C(α,γ)16O on by using recent compilations this rate. find that rate has significant impact not only during helium phase but also late phases,...
The hard X-ray continuum and gamma-ray lines from a Type Ia supernova dominate its integrated photon emissions can provide unique diagnostics of the mass ejecta, $^{56}$Ni yield spatial distribution, kinetic energy expansion speed, mechanism explosion. Such signatures their time behavior "X-ray" bulk debris field in direct fashion, do not depend upon oftimes problematic elaborate UV, optical, near-infrared spectroscopy radiative transfer that have informed study these events for decades....
The light curves of Type Ia Supernovae (SN Ia) are powered by gamma-rays emitted the decay radioactive elements such as $^{56}$Ni and its products. These downscattered,absorbed, eventually reprocessed into optical emission which makes up bulk all supernova observations. Detection that escape expanding star provide only direct means to study this power source for SN curves. Unfortunately, disagreements between calculations gamma-ray lines have made it difficult interpret any Here we present a...
The short-lived nuclide Ti44 is an important for the understanding of explosive nucleosynthesis. main production reaction, Ca40(α,γ)Ti44, has been studied in inverse kinematics with recoil mass spectrometer DRAGON located at TRIUMF-ISAC facility Vancouver, Canada. temperature range relevant α-rich freeze-out during a core-collapse supernova covered entirely Ca40 beam 0.60 to 1.15 MeV/nucleon. All quantities calculation astrophysical reaction rate have measured directly. Because many...
view Abstract Citations (57) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The 57 CO Abundance in SN 1987A Clayton, Donald D. ; Leising, Mark The, Lih-Sin Johnson, W. N. Kurfess, J. We discuss several astrophysical consequences of the detection by OSSE (Kurfess et al. 1992) ^57^Co gamma radiation from supernova 1987A. Models with low photoelectric absorption cannot account for both data and bolometric luminosity. By burying...
view Abstract Citations (43) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS X- and Gamma-Ray Signatures of Type IA Supernovae Burrows, Adam ; The, Lih-Sin Using a Monte Carlo code, the hard X-ray continuum gamma-ray line emissions various theoretical models Ia supernova explosions are investigated. The influence distributions velocity, mass, Ni-56, heavy elements on spectral temporal evolution radiations (ultimately derived from positrons lines...
We check the consistency of Milgrom's theory Modified Newtonian Dynamics against optical and x-ray data for Coma cluster galaxies. find that viable models containing no dark matter can be constructed. They require an extensive gaseous atmosphere through which galaxies move on near-radial orbits. The gas temperature is predicted to have a shallow minimum near center; this structure may confiict with best spectra cluster. In addition, values "universal" parameter a_0_ are >~ 2h^1.5^_50_ times...
We report a comprehensive light-element (Li, C, N, O, Na, Mg, and Al) abundance analysis of three solar-type main sequence (MS) dwarfs red giant branch (RGB) clump stars in the Hyades open cluster using high-resolution high signal-to-noise spectroscopy. The abundances have been derived self-consistent fashion, for each group (MS or RGB), CNO are found to be excellent star-to-star agreement. Using infer initial composition giants, combined patterns confirm that giants undergone first...
After considerable controversy regarding the 176Lu decay constant (λ176Lu), there is now widespread agreement that (1.867 ± 0.008) × 10−11 yr−1 as confirmed by various terrestrial objects and a 4557 Myr meteorite correct. This leaves 176Hf excesses are correlated with Lu/Hf elemental ratios in meteorites older than ∼4.56 Ga unresolved. We attribute excess to an accelerated of caused excitation long-lived ground state short-lived 176mLu isomer. The energy needed cause this transition ascribed...
Abstract Cosmic multimessenger backgrounds include relic diffuse components created in the early universe and contributions from individual sources. Here, we study both type Ia supernovae (SNe Ia) core-collapse (CCSNe) to neutrino gamma-ray MeV regime referred as DSNB DSGB respectively. We show that SN background is 10 6 times lower (for <?CDATA ${\overline{\nu }}_{e}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover...
The diffuse extragalactic γ-ray background in the MeV region is believed to be due photons from radioactivity produced supernovae throughout history of galaxies universe. In particular, line emission decay chain 56Ni→56Co→56Fe provides dominant photon source (Clayton & Silk). Although iron synthesis occurs all types supernovae, contribution dominated by Type Ia events their higher escape probabilities. Estimates star formation universe suggest a rapid increase factor ~10 present redshift zp...
view Abstract Citations (40) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Hard X-Rays from SN 1993J Leising, M. D. ; Kurfess, J. Clayton, Grabelsky, A. Grove, E. Johnson, W. N. Jung, G. V. Kinzer, R. L. Kroeger, Purcell, Strickman, S. The, -S. Ulmer, P. The Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Observatory observed during three intervals centered approximately 12, 30, and 108 days after its outburst. X-ray...
view Abstract Citations (38) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Cosmic Gamma-Ray Background from Type IA Supernovae The, Lih-Sin ; Leising, Mark D. Clayton, Donald We present an improved calculation of the cumulative γ-ray spectrum 1a supernovae during history universe. follow Clayton & Ward (1975) in using a few Friedmann models and two simple histories average galaxian nucleosynthesis rate, but we improve their by modeling...
We report the discovery of a presolar SiC grain (KJB2-11-17-1) with unusual Si-isotopic composition. The has 29Si/28Si = 1.63 × solar, 30Si/28Si 0.82 12C/13C 265 (= 3 solar), and evidence for presence radiogenic 44Ca from decay 44Ti. A comparison these isotopic signatures stellar models suggests an origin in 15 M☉ Type II supernova. It is possible to achieve very good match between 30Si/28Si, 12C/13C, inferred 44Ti/48Ti ratios KJB2-11-17-1 model predictions if matter different supernova...