scholarly journals The High Resolution Spectrum of the Pulsating, Pre-White Dwarf Star PG 1159-035 (GW VIR)

1989 ◽  
Vol 114 ◽  
pp. 384-387
Author(s):  
James Liebert ◽  
F. Wesemael ◽  
D. Husfeld ◽  
R. Wehrse ◽  
S. G. Starrfield ◽  
...  
Keyword(s):  
High Resolution ◽  
Effective Temperature ◽  
White Dwarf ◽  
White Dwarfs ◽  
High Resolution Spectrum ◽  
Dwarf Star ◽  
Dwarf Stars ◽  
New Class ◽  
White Dwarf Stars ◽  
Nonradial Pulsation

First reported at the IAU Colloquium No. 53 on White Dwarfs (McGraw et al. 1979), PG 1159-035 (GW Vir) is the prototype of a new class of very hot, pulsating, pre-white dwarf stars. It shows complicated, nonradial pulsation modes which have been studied exhaustively, both observationally and theoretically. The effective temperature has been crudely estimated as 100,000 K with log g ~ 7 (Wesemael, Green and Liebert 1985, hereafter WGL).

scholarly journals Hot DQ white dwarfs: a pulsational test of the mixing scenario for their formation

2009 ◽  
Vol 5 (H15) ◽  
pp. 370-370
Author(s):  
A. Romero ◽  
A. H. Córsico ◽  
L. G. Althaus ◽  
E. García-Berro
Keyword(s):  
Stability Analysis ◽  
White Dwarf ◽  
White Dwarfs ◽  
Evolutionary Models ◽  
Instability Strip ◽  
Dwarf Stars ◽  
Photometric Variability ◽  
New Class ◽  
White Dwarf Stars ◽  
Born Again

Hot DQ white dwarfs constitute a new class of white dwarf stars, uncovered recently within the framework of SDSS project. There exist nine of them, out of a total of several thousands white dwarfs spectroscopically identified. Recently, three hot DQ white dwarfs have been reported to exhibit photometric variability with periods compatible with pulsation g-modes. In this contribution, we presented the results of a non-adiabatic pulsation analysis of the recently discovered carbon-rich hot DQ white dwarf stars. Our study relies on the full evolutionary models of hot DQ white dwarfs recently developed by Althaus et al. (2009), that consistently cover the whole evolution from the born-again stage to the white dwarf cooling track. Specifically, we performed a stability analysis on white dwarf models from stages before the blue edge of the DBV instability strip (Teff ≈ 30000 K) until the domain of the hot DQ white dwarfs (18000-24000 K), including the transition DB→hot DQ white dwarf. We explore evolutionary models with M*= 0.585M⊙ and M* = 0.87M⊙, and two values of thickness of the He-rich envelope (MHe = 2 × 10−7M* and MHe = 10−8M*).

scholarly journals Progress and Problems in the Study of the Pulsating White Dwarf Stars

1986 ◽  
Vol 7 ◽  
pp. 221-228
Author(s):  
D. E. Winget
Keyword(s):  
Effective Temperature ◽  
White Dwarf ◽  
White Dwarfs ◽  
Variable Stars ◽  
Compact Stars ◽  
Dwarf Stars ◽  
White Dwarf Stars ◽  
Pulsating Variable Stars ◽  
Constant Radius ◽  
Cooling Phase

We currently know of at least three distinct classes of degenerate pulsating variable stars; they occur with a practically uniform spacing in the log of the effective temperature and span nearly the full sweep of the white dwarf cooling sequence in the H-R diagram. The hottest of these variable stars are the pulsating PG 1159-035 stars. Extremely hot, compact, stars, they appear to be contracting and cooling on their way to becoming white dwarf stars. These proto-white dwarfs have photometric properties similar to the pulsating white dwarf stars, and are reviewed separately in these proceedings by A. N. Cox. The two remaining classes of compact pulsating variables are found in relatively narrow instability strips occupying distinct portions of the white dwarf cooling sequence after the constant radius, purely cooling, phase has been reached. These two classes of variable stars are the topic of this review. In this work I will use the concise notation introduced by Sion et al. (1983) to indicate the two classes of variables: the ZZ Ceti’s, and the pulsating DB white dwarfs, become simply the DAV, and the DBV stars, respectively.

scholarly journals White Dwarf Stars

2017 ◽  
Vol 45 ◽  
pp. 1760023
Author(s):  
S. O. Kepler ◽  
Alejandra Daniela Romero ◽  
Ingrid Pelisoli ◽  
Gustavo Ourique
Keyword(s):  
White Dwarf ◽  
Final Stage ◽  
White Dwarfs ◽  
Sloan Digital Sky Survey ◽  
Dwarf Stars ◽  
Multiple Systems ◽  
White Dwarf Stars ◽  
Sky Survey ◽  
Data Release ◽  
Low Mass

White dwarf stars are the final stage of most stars, born single or in multiple systems. We discuss the identification, magnetic fields, and mass distribution for white dwarfs detected from spectra obtained by the Sloan Digital Sky Survey up to Data Release 13 in 2016, which lead to the increase in the number of spectroscopically identified white dwarf stars from 5[Formula: see text]000 to 39[Formula: see text]000. This number includes only white dwarf stars with [Formula: see text], i.e., excluding the Extremely Low Mass white dwarfs, which are necessarily the byproduct of stellar interaction.

scholarly journals Asteroseismological Probing of the Thermal Evolution of White Dwarf Stars

1992 ◽  
Vol 9 ◽  
pp. 643-645
Author(s):  
G. Fontaine ◽  
F. Wesemael
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Main Sequence ◽  
Thermal Evolution ◽  
Sequence Evolution ◽  
Helium Burning ◽  
Dwarf Stars ◽  
White Dwarf Stars ◽  
The Galaxy ◽  
Low Mass

AbstractIt is generally believed that the immediate progenitors of most white dwarfs are nuclei of planetary nebulae, themselves the products of intermediate- and low-mass main sequence evolution. Stars that begin their lifes with masses less than about 7-8 M⊙ (i.e., the vast majority of them) are expected to become white dwarfs. Among those which have already had the time to become white dwarfs since the formation of the Galaxy, a majority have burnt hydrogen and helium in their interiors. Consequently, most of the mass of a typical white dwarf is contained in a core made of the products of helium burning, mostly carbon and oxygen. The exact proportions of C and 0 are unknown because of uncertainties in the nuclear rates of helium burning.

Results on (UN)Published Wet Runs on Pulsating DB White Dwarfs

2003 ◽  
Vol 12 (1) ◽  
Author(s):  
G. Handler
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Archival Data ◽  
Dwarf Stars ◽  
Preliminary Results ◽  
White Dwarf Stars ◽  
The Future

AbstractI have collected all the WET archival data on the pulsating DB white dwarf stars (DBVs) and re-reduced them. In addition, the WET has recently observed three DBVs. Preliminary results on PG 1115+158, PG 1351+489, KUV 05134+2605, PG 1654+160 and PG 1456+103 are presented, and the future use of the data is outlined.

scholarly journals The Distribution of Masses and Radii of White-Dwarf Stars

1978 ◽  
Vol 80 ◽  
pp. 117-120
Author(s):  
Harry L. Shipman
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Model Atmosphere ◽  
Selection Effects ◽  
Dwarf Stars ◽  
White Dwarf Stars ◽  
The Status ◽  
The Mean

The status of determinations of white dwarf radii by model atmosphere methods is reviewed in this paper. Details will appear elsewhere (Shipman 1978). In brief, the results are that (i) the mean radius of a sample of 95 hydrogen-rich stars with parallaxes is 0.0131 R⊙; (ii) the mean radius of a sample of 13 helium-rich stars is 0.011 R⊙, indistinguishably different from the radius of the hydrogen-rich stars; and (iii) that the most serious limitation on our knowledge of the mean radius of white dwarfs is the influence of selection effects. An estimate of the selection effects indicates that the true mean white dwarf radius is near 0.011 R⊙.

scholarly journals A search for a new class of pulsating DA white dwarf stars in the DB gap

2008 ◽  
Vol 389 (4) ◽  
pp. 1771-1779 ◽  
Author(s):  
D. W. Kurtz ◽  
H. Shibahashi ◽  
V. S. Dhillon ◽  
T. R. Marsh ◽  
S. P. Littlefair
Keyword(s):  
White Dwarf ◽  
Dwarf Stars ◽  
New Class ◽  
White Dwarf Stars

The high-resolution spectrum of the pulsating, pre-white dwarf star PG 1159-035 (GW VIR)

1989 ◽  
Vol 97 ◽  
pp. 1440 ◽  
Author(s):  
James Liebert ◽  
F. Wesemael ◽  
D. Husfeld ◽  
R. Wehrse ◽  
S. G. Starrfield ◽  
...  
Keyword(s):  
High Resolution ◽  
White Dwarf ◽  
High Resolution Spectrum ◽  
Dwarf Star

scholarly journals 11. Effective Temperatures of White Dwarfs

1971 ◽  
Vol 42 ◽  
pp. 67-76 ◽  
Author(s):  
J. B. Oke ◽  
H. L. Shipman
Keyword(s):  
Chemical Composition ◽  
White Dwarf ◽  
White Dwarfs ◽  
Dwarf Stars ◽  
Evolved Stars ◽  
White Dwarf Stars ◽  
Effective Temperatures ◽  
Highly Evolved

White dwarf stars are among the most challenging and interesting objects which can be studied. Because they represent the interiors of highly-evolved stars, the chemical composition can be enormously variable from object to object. Furthermore, because of the very large gravities, the composition of the atmosphere may be very different from that in the interior. The theory of the degenerate interior provides a relation among mass, radius and chemical composition. Since temperatures, effective gravities, and redshifts can, for certain stars, provide further relations between mass and radius, one can hope to make checks on the theory which are not possible with ordinary stars.

scholarly journals Towards Ensemble Asteroseismology of the Pulsating DB White Dwarf Stars

2002 ◽  
Vol 185 ◽  
pp. 608-609
Author(s):  
G. Handler ◽  
M.A. Wood ◽  
A. Nitta ◽  
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
The Other ◽  
Archival Data ◽  
Dwarf Stars ◽  
Helium Atmosphere ◽  
Individual Stars ◽  
White Dwarf Stars ◽  
Binary Evolution ◽  
Insight Into

The origin of the helium-atmosphere DB white dwarfs is still a matter of debate. In particular, the question is unresolved whether binary evolution produces a significant number of DBs. The pulsating DB white dwarfs (DBV stars) offer a complementary insight into this problem through asteroseismology; DBs descending from binaries will have different interior structures than DBs originating from single stars (Nitta & Winget, 1998).GD 358 is by far the best-observed pulsating DBV star, and the only one for which asteroseismology has been performed to date. This star’s structure has been shown to be inconsistent with an origin from binary evolution (Nitta & Winget, 1998), but most of the other DBVs are relatively poorly studied.We therefore analysed archival data on all DBVs and obtained new measurements of stars with very little data available (Table 1), firstly to identify suitable targets for asteroseismological investigations and secondly to examine the pulsation spectra of the DBVs as a group, following the works of Clemens (1994) and Kleinman (1995) on the pulsating DA white dwarfs. Our study also produced new seismological results on individual stars and promising targets for future Whole Earth Telescope (WET, Nather et al., 1990) runs.

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