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White dwarf

About: White dwarf is a research topic. Over the lifetime, 15004 publications have been published within this topic receiving 430597 citations. The topic is also known as: degenerate dwarf.


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TL;DR: In this article, the authors investigated the feasibility of triggering a secondary core detonation by shock convergence in low-mass CO WDs and the observable consequences of such a detonation.
Abstract: Thermonuclear explosions may arise in binary star systems in which a carbon‐oxygen (CO) white dwarf (WD) accretes helium-rich material from a companion star. If the accretion rate allows a sufficiently large mass of helium to accumulate prio r to ignition of nuclear burning, the helium surface layer may detonate, giving rise to an astrophysical transient. Detonation of the accreted helium layer generates shock waves that propagate into the underlying CO WD. This might directly ignite a detonation of the CO WD at its surface (an edge-lit secondary detonation) or compress the core of the WD sufficiently to tri gger a CO detonation near the centre. If either of these ignition mechanisms works, the two detonations (helium and CO) can then release sufficient energy to completely unbind the W D. These “double-detonation” scenarios for thermonuclear explosion of WDs have previously been investigated as a potential channel for the production of type Ia supernovae from WDs of around one solar mass. Here we extend our 2D studies of the double-detonation model to significantly less massive CO WDs, the explosion of which could produce fainter, more rapidly evolving transients. We investigate the feasibility of triggering a secondary core detonation by shock convergence in low-mass CO WDs and the observable consequences of such a detonation. Our results suggest that core detonation is probable, even for the lowest CO core masses that are likely to be realized in nature. To quantify the observable signatures of core detonation, we compute spectra and light curves for models in which either an edge-lit or compression-triggered CO detonation is assumed to occur. We compare these to synthetic observables for models in which no CO detonation was allowed to occur. If significant sh ock compression of the CO WD occurs prior to detonation, explosion of the CO WD can produce a sufficiently large mass of radioactive iron-group nuclei to significantly affe ct the light curves. In particular, this can lead to relatively slow post-maximum decline. If the secondary detonation is edge-lit, however, the CO WD explosion primarily yields intermediate-mass elements that affect the observables more subtly. In this case, near-infrared obser vations and detailed spectroscopic analysis would be needed to determine whether a core detonation occurred. We comment on the implications of our results for understanding peculiar astrophysical transients including SN 2002bj, SN 2010X and SN 2005E.

159 citations

Journal ArticleDOI
TL;DR: A detailed survey of the local population of white dwarfs lying within 20 pc of the Sun is presented in this article, which contains 27 white dwarf not included in a previous list from 2002, as well as new and recently published trigonometric parallaxes.
Abstract: We have conducted a detailed new survey of the local population of white dwarfs lying within 20 pc of the Sun. A new revised catalog of local white dwarfs containing 122 entries (126 individual degenerate stars) is presented. This list contains 27 white dwarfs not included in a previous list from 2002, as well as new and recently published trigonometric parallaxes. In several cases new members of the local white dwarf population have come to light through accurate photometric distance estimates. In addition, a suspected new double degenerate system (WD 0423+120) has been identified. The 20 pc sample is currently estimated to be 80% complete. Using a variety of recent spectroscopic, photometric, and trigonometric distance determinations, we re-compute a space density of 4.8 ± 0.5 × 10–3 pc–3 corresponding to a mass density of 3.2 ± 0.3 × 10–3 M ☉ pc–3 from the complete portion of the sample within 13 pc. We find an overall mean mass for the local white dwarfs of 0.665 M ☉, a value larger than most other non-volume-limited estimates. Although the sample is small, we find no evidence of a correlation between mass and temperature in which white dwarfs below 13,000 K are systematically more massive than those above this temperature. Within 20 pc 25% of the white dwarfs are in binary systems (including double degenerate systems). Approximately 6% are double degenerates and 6.5% are Sirius-like systems. The fraction of magnetic white dwarfs in the local population is found to be 13%.

158 citations

Journal ArticleDOI
TL;DR: In this article, Maoz et al. explored collisions between two white dwarfs as a pathway for making Type IaSupernovae (SNIa) and found that such collisions produce 0.4 M of 56 Ni, making such events potential candidates for underluminous SNIa or a new class of transient between Novae and SNIA.
Abstract: We explore collisions between two white dwarfs as a pathway for making Type IaSupernovae (SNIa). White dwarf number densities in globular clusters allow 10 100redshift . 1 collisions per year, and observations by (Chomiuk et al.2008) of globularclusters in the nearby S0 galaxy NGC 7457 have detected what is likely to be a SNIaremnant. We carry out simulations of the collision between two 0.6M white dwarfsat various impact parameters and mass resolutions. For impact parameters less thanhalf the radius of the white dwarf, we nd such collisions produce ˇ 0.4 M of 56 Ni,making such events potential candidates for underluminous SNIa or a new class oftransients between Novae and SNIa.Key words: hydrodynamics { nuclear reactions, nucleosynthesis, abundances {(stars:) white dwarfs { (stars:) supernovae: general. 1 INTRODUCTIONType Ia supernovae (henceforth SNIa) play a key role inastrophysics as premier distance indicators for cosmology(Phillips 1993; Riess et al.1998; Perlmutter et al.1999), asdirect probes of low-mass star formation rates at cosmologi-cal distances (Scannapieco et al.2005; Mannucci et al.2006;Maoz 2008) and as signi cant contributors to iron-groupelements in the cosmos (Wheeler et al.1989; Timmes etal.1995; Feltzing et al.2001; Strigari 2006). Our current un-derstanding is that there are two major progenitor systemsfor these events. The rst possibility, the single-degeneratescenario, consists of a carbon-oxygen white dwarf in a bi-nary system evolving to the stage of central ignition by massoverow from a low-mass stellar companion (Whelan & Iben1973; Nomoto 1982; Hillebrandt & Niemeyer 2000). The sec-ond possibility, the double-degenerate scenario, consists ofthe merger of two white dwarfs in a binary system (Iben& Tutukov 1984; Webbink 1984; Yoon et al.2007). It is un-known at what relative frequency both of these channelsoperate (Livio 2000; Maoz 2008).Collisions between two white dwarfs, are likely to hap-pen less frequently than binary mergers. However, as dis-cussed in Timmes (2009) and Rosswog et al.(2009), theywill occur in globular clusters where the stellar densities areextremely high. For a typical globular cluster velocity dis-persion of ˇ5-10 km s

158 citations

Journal ArticleDOI
TL;DR: In this article, the properties of white dwarfs accreting hydrogen-rich matter were revisited by constructing steady-state models, in which hydrogen shell burning consumes hydrogen at the same rate as the white dwarf accretes it.
Abstract: We revisit the properties of white dwarfs accreting hydrogen-rich matter by constructing steady-state models, in which hydrogen shell burning consumes hydrogen at the same rate as the white dwarf accretes it. We obtain such steady-state models for various accretion rates and white dwarf masses. We confirm that these steady models are thermally stable only when the accretion rate is higher than \sim 10^{-7} M_sun/yr. We show that recent models of ``quiescent burning'' in the ``surface hydrogen burning'' at a much wider range of accretion rates results from the too large zone mass in the outer part of the models; hydrogen burning must occur in a much thinner layer. A comparison of the positions on the HR diagram suggests that most of the luminous supersoft X-ray sources are white dwarfs accreting matter at rates high enough that the hydrogen burning shell is thermally stable. Implications on the progenitors of Type Ia supernovae are discussed.

158 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023367
2022667
2021495
2020557
2019548
2018515