Interacting Binary White Dwarf Stars

This group of stars consists of 4 systems, also called helium cataclysmics. Three of them show photometric variations and have been studied by the Whole Earth Telescope (WET), which have revealed multiperiodic light curves showing the signature of g-mode non-radial pulsations on the accreting star. The combination of accretion and g-mode pulsations gives a unique opportunity to test models for the accreator's structural changes in response to accretion. IUE-spectra provide additional physical parameters.

Amplitude and frequency variability of the pulsating DB white dwarf stars KUV 05134+2605 and PG 1654+160 observed with the Whole Earth Telescope

Monthly Notices of the Royal Astronomical Society ◽

10.1046/j.1365-8711.2003.06373.x ◽

2003 ◽

Vol 340 (3) ◽

pp. 1031-1038 ◽

Cited By ~ 16

Author(s):

G. Handler ◽

D. O'Donoghue ◽

M. Muller ◽

J.- E. Solheim ◽

J. M. Gonzalez-Perez ◽

...

Keyword(s):

White Dwarf ◽

Dwarf Stars ◽

White Dwarf Stars ◽

Discovery of the sixth DBV Star: CBS 114

10.1017/s0252921100099735 ◽

1989 ◽

Vol 114 ◽

pp. 290-292

Author(s):

D. E. Winget ◽

C. F. Claver

Keyword(s):

White Dwarf ◽

Compact Objects ◽

Rich Source ◽

Light Curves ◽

Dwarf Stars ◽

Temperature Variations ◽

White Dwarf Stars

Though widely spread across the H-R diagram the compact pulsators have much in common. All are multi-periodic, and most have extremely complex light curves. All appear to be pulsating in nonradial g-modes, with temperature variations responsible for the bulk of the light modulations. The g-modes are global in nature and, typically, many are excited in each pulsator, so they are a rich source of seismological information about the interior regions of the white dwarf stars.The pulsating DB white dwarf stars (DBV’s) form one of the three distinct classes of pulsating compact objects currently known. We find these classes nearly uniformly distributed in log Te spanning virtually the whole range of the white dwarf cooling sequence, from the hot DOV stars at log Te ~ 5 to the DAV (ZZ Ceti) stars at log Te ~ 4; the DBV stars, with logTe ~ 4.5, fall in the middle.

Asteroseismology of White Dwarf Stars with the Whole Earth Telescope

White Dwarfs ◽

10.1007/978-94-011-3230-5_13 ◽

1991 ◽

pp. 129-141 ◽

Cited By ~ 3

Author(s):

D. E. Winget

Keyword(s):

White Dwarf ◽

Dwarf Stars ◽

White Dwarf Stars ◽

The Whole Earth Telescope

10.1017/s0252921100099371 ◽

1989 ◽

Vol 114 ◽

pp. 109-114 ◽

Cited By ~ 1

Author(s):

R. Edward Nather

Keyword(s):

Star Formation ◽

Light Curve ◽

Early Universe ◽

White Dwarf ◽

Dwarf Stars ◽

Detailed History ◽

White Dwarf Stars ◽

Observational Technique ◽

History Of ◽

AbstractThe history of our galaxy and the detailed history of star formation in the early universe is written in the white dwarf stars. Recently we have learned how to reach beneath their exposed surfaces by observing white dwarfs that are intrinsic variables. We use the stellar equivalent of seismology to probe their interiors, and thus to unravel the history they hold inside. We have designed and placed into operation an observational technique that uses the whole earth as a telescope platform, defeating the effects of daylight which, until now, had seriously limited the length of a single light curve, and therefore the amount of information we could hope to extract from it. This paper describes our new telescope and presents preliminary results from our first observing run in March, 1988.

Searching for ZZ Ceti white dwarfs in the Gaia survey

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320000265 ◽

2019 ◽

Vol 15 (S357) ◽

pp. 123-126

Author(s):

Olivier Vincent ◽

Pierre Bergeron ◽

David Lafrenière

Keyword(s):

White Dwarf ◽

White Dwarfs ◽

Physical Parameters ◽

Hydrogen Line ◽

Instability Strip ◽

Dwarf Stars ◽

White Dwarf Stars ◽

Effective Temperatures

AbstractThe Gaia satellite recently released parallax measurements for nearly 400,000 white dwarf stars, allowing for precise measurements of their physical parameters. By combining these parallaxes with Pan-STARRS and CFIS-u photometry, we measured the effective temperatures and surface gravities for all white dwarfs within 100 pc and identified a sample of ZZ Ceti white dwarf candidates within the instability strip. We report the results of a photometric follow-up, currently under way, aimed at identifying new ZZ Ceti stars among this sample using the PESTO camera attached to the 1.6-m telescope at the Mont Mégantic Observatory. Our goal is to verify that ZZ Ceti stars occupy a region in the logg-Teff plane where no nonvariable stars are found, supporting the idea that ZZ Ceti pulsators represent a phase through which all hydrogen-line (DA) white dwarfs must evolve.

White Dwarf.Org - Establishing a Permanent Endowment for the Whole Earth Telescope

Open Astronomy ◽

10.1515/astro-2017-0053 ◽

2003 ◽

Vol 12 (2) ◽

Author(s):

Travis S. Metcalfe

Keyword(s):

White Dwarf ◽

Fund Raising ◽

Current Status ◽

Dwarf Stars ◽

Non Profit ◽

White Dwarf Stars ◽

Funding Sources ◽

Governmental Funding ◽

AbstractWhite Dwarf Research Corporation is a non-profit organization dedicated to scientific research and public education on topics relevant to white dwarf stars. It was founded in 1999 in Austin, Texas to help fulfill the need for an alternative research center where scarce funding dollars could be used more efficiently, and to provide a direct link between astronomers who study white dwarf stars and the general public. Due to its administrative simplicity, WDRC can facilitate the funding of multi-institutional and international collaborations, provide seamless grant portability, minimize overhead rates, and actively seek non-governmental funding sources. I describe the motivation for, and current status of, one of the long-term goals of WDRC: to establish a permanent endowment for the operation of the Whole Earth Telescope. I pay particular attention to fund-raising efforts through the website at http://WhiteDwarf.org/donate/.

Non Crystallized Regions of White Dwarfs. Thermodynamics. Opacity. Turbulent Convection

10.1017/s025292110002635x ◽

1994 ◽

Vol 147 ◽

pp. 144-160 ◽

Cited By ~ 1

Author(s):

I. Mazzitelli

Keyword(s):

White Dwarf ◽

Chemical Compositions ◽

Surface Chemical ◽

Convective Envelope ◽

Dwarf Stars ◽

Heat Flows ◽

White Dwarf Stars ◽

Test Models ◽

Present Generation ◽

Thermal Content

AbstractThe evolution of White Dwarf stars along their cooling sequences is governed not only by their thermal content, but also by the rate at which heat flows through the external, partially degenerate and non-isothermal layers. In particular, cooling is found to be largely influenced both by the optical atmosphere, and by the convective envelope. The first one, in fact, determines the internal density stratification, down to the point at which electron degeneracy takes over, while the second one affects the temperature stratification in the same layers. The reliability of the present generation of models of White Dwarf envelopes is discussed, on the grounds of the main physical inputs (thermodynamics, opacity, convection theory), for both H-rich and He-rich surface chemical compositions. The conclusion is that, below Log L/L⊙ ≤ −3, we can build little more than test models

The Internal Structure of White Dwarf Stars Using the Whole Earth Telescope

10.1017/s0252921100117051 ◽

1993 ◽

Vol 139 ◽

pp. 117-119

Author(s):

P.A. Bradley

Keyword(s):

Internal Structure ◽

Stellar Evolution ◽

White Dwarf ◽

White Dwarfs ◽

Dwarf Stars ◽

White Dwarf Stars ◽

History Of ◽

The Way ◽

AbstractWhite dwarfs are the final end state for the majority of stars, and hold clues to help solve many current pressing astrophysical problems. We can perform asteroseismology on the pulsating white dwarfs to better understand their internal structure and input physics, paving the way to a better understanding of astrophysics, stellar evolution, and the history of our Galaxy. I describe briefly the potential of asteroseismology by using it to infer the internal structure of PG1159-035.

Non-Radial Pulsations in White Dwarf Stars

Nature Physical Science ◽

10.1038/physci239002a0 ◽

1972 ◽

Vol 239 (88) ◽

pp. 2-7 ◽

Cited By ~ 60

Author(s):

BRIAN WARNER ◽

EDWARD L. ROBINSON

Keyword(s):

White Dwarf ◽

Dwarf Stars ◽

White Dwarf Stars ◽

Radial Pulsations

THE PULSATING WHITE DWARF G 185-32

International Journal of Modern Physics D ◽

10.1142/s021827180400533x ◽

2004 ◽

Vol 13 (07) ◽

pp. 1213-1216

Author(s):

BÁRBARA GARCIA CASTANHEIRA ◽

S. O. KEPLER

Keyword(s):

White Dwarf ◽

White Dwarfs ◽

Light Curves ◽

Stellar Structure ◽

Dwarf Stars ◽

White Dwarf Stars ◽

Non Linear ◽

Linear Effects

We study the structure of pulsating white dwarf stars, which present multi-periodic light variations with periods around minutes, defining instability strips along their cooling sequence. We analyze the ultraviolet (HST) and optical (WET) light curves of the pulsating white dwarf G185-32. Among all pulsating white dwarfs, this star has the shortest periodicity so far observed. We detected 18 periodicities, including non-linear effects, which can be used to study the stellar structure, constraining the physics of the degenerate matter.