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Large numbers of low-to-medium resolution spectra of M-type dwarf stars from both the local Galactic disk and halo are available from various surveys. In order to fully exploit these data, we develop a template-fit method using a set of…

Solar and Stellar Astrophysics · Physics 2020-03-11 Neda Hejazi , Sebastien Lepine , Derek Homeier , R. Michael Rich , Michael M. Shara

We present our first nucleosynthesis results from a numerical simulation of the thermonuclear disruption of a static cold Chandrasekhar-mass C/O white dwarf. The two-dimensional simulation was performed with an adaptive-mesh Eulerian…

Astrophysics · Physics 2009-11-11 E. F. Brown , A. C. Calder , T. Plewa , P. M. Ricker , K. Robinson , J. B. Gallagher

The QCD coupling alpha_s is determined from a combined analysis of experimental e+e- and e-p jet data confronted to theoretical predictions of the energy evolution of the parton-to-hadron fragmentation functions (FFs) moments…

High Energy Physics - Phenomenology · Physics 2015-06-23 Redamy Pérez-Ramos , David d'Enterria

We investigate the energy loss characteristics of warm dense matter (WDM) and dense plasmas concentrating on the influence of electronic correlations. The basis for our analysis is a recently developed ab initio Quantum Monte-Carlo (QMC)…

Plasma Physics · Physics 2020-05-20 Zh. A. Moldabekov , T. Dornheim , M. Bonitz , T. S. Ramazanov

We study a complete, colour-selected sample of double-degenerate binary systems containing extremely low mass (ELM) <0.25 Msol white dwarfs (WDs). We show, for the first time, that Milky Way disk ELM WDs have a merger rate of approximately…

Astrophysics of Galaxies · Physics 2015-05-20 Warren R. Brown , Mukremin Kilic , Carlos Allende Prieto , Scott J. Kenyon

Kowalski & Saumon (2006) identified the missing absorption mechanism in the observed spectra of cool white dwarf stars as the Ly-alpha red wing formed by the collisions between atomic and molecular hydrogen and successfully explained entire…

Solar and Stellar Astrophysics · Physics 2015-05-20 R. D. Rohrmann , L. G. Althaus , S. O. Kepler

There have been discussions in the recent literature regarding the accuracy of the available electron impact excitation rates (equivalently effective collision strengths $\Upsilon$) for transitions in Be-like ions. In the present paper we…

Atomic Physics · Physics 2016-09-07 K. M. Aggarwal , F. P. Keenan , K. D. Lawson

Strongly magnetized, rapidly rotating massive white dwarfs (WDs) emerge as potential outcomes of double degenerate mergers. These WDs can act as sources of non-thermal emission and cosmic rays, gethering attention as WD pulsars. In this…

High Energy Astrophysical Phenomena · Physics 2024-05-08 Aya Bamba , Yukikatsu Terada , Kazumi Kashiyama , Shota Kisaka , Takahiro Minami , Tadayuki Takahashi

Type Ia supernovae (SNe Ia) often show high-velocity absorption features (HVFs) in their early phase spectra; however the origin of the HVFs is unknown. We show that a near-Chandrasekhar-mass white dwarf (WD) develops a silicon-rich layer…

Solar and Stellar Astrophysics · Physics 2018-08-29 Mariko Kato , Hideyuki Saio , Izumi Hachisu

The unprecedented brilliance of X-ray free-electron lasers (XFELs) [1, 2] has enabled first studies of nonlinear interactions in the hard X-ray range. In particular, X-ray-optical mixing [3], X-ray second harmonic generation (XSHG) [4] and…

Infrared excesses due to dusty disks have been observed orbiting white dwarfs with effective temperatures between 7200 K and 25000 K, suggesting that the rate of tidal disruption of minor bodies massive enough to create a coherent disk…

In the first paper of this series (Blouin et al. 2018), we presented our upgraded cool white dwarf atmosphere code. In this second paper, we use our new models to analyze SDSS J080440.63+223948.6 (J0804+2239), the first DZ star to show…

Solar and Stellar Astrophysics · Physics 2018-11-28 Simon Blouin , Patrick Dufour , Nicole F. Allard , Mukremin Kilic

We present a study of the optical response of compact and hollow icosahedral clusters containing up to 868 silver atoms by means of time-dependent density functional theory. We have studied the dependence on size and morphology of both the…

Materials Science · Physics 2016-06-22 Peter Koval , Federico Marchesin , Dietrich Foerster , Daniel Sánchez-Portal

Two of the possibilities for the formation of low-mass ($M_{\star}\lesssim 0.5\,M_{\odot}$) hydrogen-deficient white dwarfs are the occurrence of a very-late thermal pulse after the asymptotic giant-branch phase or a late helium-flash onset…

Solar and Stellar Astrophysics · Physics 2020-07-01 Tiara Battich , Leandro G. Althaus , Alejandro H. Córsico

Approximately 25--50\% of white dwarfs (WDs) exhibit metal absorption lines in their photospheres, interpreted as evidence of ongoing/recent accretion of planetary debris from remnant systems. Previous theoretical studies have suggested…

Solar and Stellar Astrophysics · Physics 2026-04-28 Zhangliang Chen , Xin-Yue Zhang , Di-Chang Chen , Kejun Wang , Bo Ma , Ji-Wei Xie , Ji-Lin Zhou

We study the emission properties of thermonuclear explosions in a helium white dwarf (WD) tidal disruption event (TDE). We consider a TDE where a 0.2 $M_{\odot}$ helium WD is disrupted by a $10^{2.5}\,M_{\odot}$ intermediate-mass black hole…

High Energy Astrophysical Phenomena · Physics 2020-02-24 Kojiro Kawana , Keiichi Maeda , Naoki Yoshida , Ataru Tanikawa

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…

High Energy Astrophysical Phenomena · Physics 2015-06-05 R. Pakmor , P. Edelmann , F. K. Roepke , W. Hillebrandt

We report the white light flare rates for 10 ultracool dwarfs (UCDs) using \textit{Kepler K2} short cadence data. Among our sample stars, two have spectral type M6, three are M7, three are M8 and two are L0. Most of our targets are old low…

Solar and Stellar Astrophysics · Physics 2018-06-06 Rishi R. Paudel , John E. Gizis , D. J. Mullan , Sarah J. Schmidt , Adam J. Burgasser , Peter K. G. Williams , Edo Berger

Brown dwarf companions to white dwarfs are rare, but recent infra-red surveys are slowly reveal- ing examples. We present new observations of the post-common envelope binary WD0137-349, which reveals the effects of irradiation on the ~…

The recent plethora of sky surveys, especially the Sloan Digital Sky Survey, have discovered many low-mass (M < 0.45 Msun) white dwarfs that should have cores made of nearly pure helium. These WDs come in two varieties; those with masses…