Hot DQ White Dwarfs: Something Different

Dufour, Patrick; Fontaine, G.; Liebert, James; Schmidt, Gary D.; Behara, N. T.

doi:10.1086/589855

Cited by 116 publications

(192 citation statements)

References 44 publications

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“…In summary, the calculations of Córsico et al (2009d) support the diffusive/convective mixing picture for the formation of hot DQs, and in particular, demonstrate that the diffusive/convective mixing scenario is not only able to explain the origin of hot DQ white dwarfs, but also accounts for the variability of these stars. We stress that the conclusions reached in Córsico et al (2009d), and also the results of and Dufour et al (2008a), especially those concerning the location of the blue edge of the DQV instability strip, could be altered substantially if a fully consistent treatment of the interaction between convection and pulsation were included in the stability analysis.…”

Section: Dqvsmentioning

confidence: 89%

Evolutionary and pulsational properties of white dwarf stars

Althaus

Córsico

Isern

et al. 2010

Astron Astrophys Rev

370

372

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White dwarf stars are the final evolutionary stage of the vast majority of stars, including our Sun. Since the coolest white dwarfs are very old objects, the present population of white dwarfs contains a wealth of information on the evolution of stars from birth to death, and on the star formation rate throughout the history of our Galaxy. Thus, the study of white dwarfs has potential applications to different fields of astrophysics. In particular, white dwarfs can be used as independent reliable cosmic clocks, and can also provide valuable information about the fundamental parameters of a wide variety of stellar populations, like our Galaxy and open and globular clusters. In addition, the high densities and temperatures characterizing white dwarfs allow to use these stars as cosmic laboratories for studying physical processes under extreme conditions that cannot be achieved in terrestrial laboratories. Last but not least, since many white dwarf stars undergo pulsational instabilities, the study of their properties constitutes a powerful tool for applications beyond stellar astrophysics. In particular, white dwarfs can be used to constrain fundamental properties of elementary particles such as axions and neutrinos, and to study problems related to the variation of fundamental constants.These potential applications of white dwarfs have led to a renewed interest in the calculation of very detailed evolutionary and pulsational models for these stars. In this work, we review the essentials of the physics of white dwarf stars. We enumerate the reasons that make these stars excellent chronometers and we describe why white dwarfs provide tools for a wide variety of applications. Special emphasis is placed on the physical processes that lead to the formation of white dwarfs as well as on the different energy sources and processes responsible for chemical abundance changes that occur along their evolution. Moreover, in the course of their lives, white dwarfs cross different pulsational instability strips. The existence of these instability strips provides astronomers with an unique opportunity to peer into their internal structure that would otherwise remain hidden from observers. We will show that this allows to measure with unprecedented precision the stellar masses and to infer their envelope thicknesses, to probe the core chemical stratification, and to detect rotation rates and magnetic fields. Consequently, in this work, we also review the pulsational properties of white dwarfs and the most recent applications of white dwarf asteroseismology.

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Section: Dqvsmentioning

confidence: 89%

Evolutionary and pulsational properties of white dwarf stars

Althaus

Córsico

Isern

et al. 2010

Astron Astrophys Rev

370

372

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“…The hot DQ LAWDS 28 is significantly bluer in U −B than all the other WDs. This exceptional color is due to high carbon opacity at wavelengths 1500 Å, which re-distributes the ultraviolet flux into the near-UV (Dufour et al 2008). …”

Section: Observations and Data Reductionmentioning

confidence: 99%

Probing the Lower Mass Limit for Supernova Progenitors and the High-Mass End of the Initial-Final Mass Relation From White Dwarfs in the Open Cluster M35 (Ngc 2168)

Williams¹,

Bolte²,

Koester³

2009

ApJ

203

226

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We present a photometric and spectroscopic study of the white dwarf (WD) population of the populous, intermediateage open cluster M35 (NGC 2168); this study expands upon our previous study of the WDs in this cluster. We spectroscopically confirm 14 WDs in the field of the cluster: 12 DAs, 1 hot DQ, and 1 DB star. For each DA, we determine the WD mass and cooling age, from which we derive each star's progenitor mass. These data are then added to the empirical initial-final mass relation (IFMR), where the M35 WDs contribute significantly to the high-mass end of the relation. The resulting points are consistent with previously published linear fits to the IFMR, modulo moderate systematics introduced by the uncertainty in the star cluster age. Based on this cluster alone, the observational lower limit on the maximum mass of WD progenitors is found to be ∼5.1 M − 5.2 M at the 95% confidence level; including data from other young open clusters raises this limit to as high as 7.1 M , depending on the cluster membership of three massive WDs and the core composition of the most massive WDs. We find that the apparent distance modulus and extinction derived solely from the cluster WDs ((m − M) V = 10.45 ± 0.08 and E(B −V ) = 0.185 ± 0.010, respectively) is fully consistent with that derived from main-sequence fitting techniques. Four M35 WDs may be massive enough to have oxygen-neon cores; the assumed core composition does not significantly affect the empirical IFMR. Finally, the two non-DA WDs in M35 are photometrically consistent with cluster membership; further analysis is required to determine their memberships.

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“…We note, however, that recently, a very low mass (∼ 0.17 M ) variable DA white dwarf was found [15]. The luminosity of each star was calculated from the effective temperature and surface gravity (assuming a mass of 0.6 M for all stars) listed in [9] for GW Vir stars, DBVs, and DAVs, and in [6] for hot DQVs. The evolutionary track was obtained with the MESA code ( [20]).…”

Section: Overview On the Properties Of Pulsations In White Dwarfsmentioning

confidence: 99%

Pulsations in white dwarfs: Selected topics

Saio

2013

EPJ Web of Conferences

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Abstract. This paper presents a very brief overview of the observed properties of g-mode pulsations in variable white dwarfs. We then discuss a few selected topics: Excitation mechanisms (kappa-and convection-mechanisms), and briefly the effect of a strong magnetic field (∼ 1 MG) on g-modes as recently found in a hot DQ (carbon-rich atmosphere) white dwarf. In the discussion of excitation mechanisms, a simple interpretation for the convection mechanism is given.

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Hot DQ White Dwarfs: Something Different

Cited by 116 publications

References 44 publications

Evolutionary and pulsational properties of white dwarf stars

Evolutionary and pulsational properties of white dwarf stars

Probing the Lower Mass Limit for Supernova Progenitors and the High-Mass End of the Initial-Final Mass Relation From White Dwarfs in the Open Cluster M35 (Ngc 2168)

Pulsations in white dwarfs: Selected topics

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