A planetesimal orbiting within the debris disc around a white dwarf star

Many white dwarf stars show signs of having accreted smaller bodies, implying that they may host planetary systems. A small number of these systems contain gaseous debris discs, visible through emission lines. We report a stable 123.4-minute periodic variation in the strength and shape of the Ca ii emission line profiles originating from the debris disc around the white dwarf SDSS J122859.93+104032.9. We interpret this short-period signal as the signature of a solid-body planetesimal held together by its internal strength.

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The Time Dependence of the Phases of the Harmonics Relative to the 1490 sec Fundamental in PG1346+082

International Astronomical Union Colloquium ◽

10.1017/s0252921100099759 ◽

1989 ◽

Vol 114 ◽

pp. 296-299

Author(s):

J. L. Provencal ◽

J. C. Clemens ◽

G. Henry ◽

B. P. Hine ◽

R. E. Nather ◽

...

Keyword(s):

White Dwarf ◽

Compact Object ◽

Detailed Knowledge ◽

Line Profiles ◽

Pressure Broadening ◽

Dwarf Stars ◽

White Dwarf Stars ◽

Adequate Understanding ◽

Magnitude Variation ◽

Hydrogen Lines

White dwarf stars provide important boundary conditions for the understanding of stellar evolution. An adequate understanding of even these simple stars is impossible without detailed knowledge of their interiors. PG1346+082, an interacting binary white dwarf system, provides a unique opportunity to view the interior of one degenerate as it is brought to light in the accretion disk of the second star as the primary strips material from its less massive companion (see Wood et at. 1987).PG1346+082 is a photometric variable with a four magnitude variation over a four to five day quasi-period. A fast Fourier transform (FFT) of the light curve shows a complex, time-dependent structure of harmonics. PG1346+082 exhibits flickering – the signature of mass transfer. The optical spectra of the system contain weak emission features during minimum and broad absorption at all other times. This could be attributed to pressure broadening in the atmosphere of a compact object, or to a combination of pressure broadening and doppler broadening in a disk surrounding the compact accretor. No hydrogen lines are observed and the spectra are dominated by neutral helium. The spectra also display variable asymmetric line profiles.

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New line profiles of sodium and potassium perturbed by helium for brown dwarf and very cool white dwarf stars

10.1063/1.3026467 ◽

2008 ◽

Author(s):

M. Christova ◽

N. F. Allard ◽

J. F. Kielkopf ◽

D. Homeier ◽

F. Allard ◽

...

Keyword(s):

White Dwarf ◽

Line Profiles ◽

Brown Dwarf ◽

Dwarf Stars ◽

White Dwarf Stars ◽

Sodium And Potassium

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

International Astronomical Union Colloquium ◽

10.1017/s0252921100099929 ◽

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).

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Wave propagation in the magnetized cores of white dwarf stars with ultra-relativistic degenerate electrons

Journal of Plasma Physics ◽

10.1017/s0022377811000092 ◽

2011 ◽

Vol 77 (5) ◽

pp. 571-575 ◽

Cited By ~ 14

Author(s):

P. K. SHUKLA ◽

D. A. MENDIS ◽

S. I. KRASHENINNIKOV

Keyword(s):

Wave Propagation ◽

Dispersion Relation ◽

White Dwarf ◽

Low Frequency ◽

Hydrodynamic Equations ◽

Dwarf Star ◽

Dwarf Stars ◽

White Dwarf Stars

AbstractWe discuss the dispersive properties of low-frequency electromagnetic (EM) perturbations in the magnetized core of self-gravitating white dwarf stars with ultra-relativistic degenerate electrons. For our purposes, we derive a dispersion relation by using the hydrodynamic equations for the ions under the action of EM and self-gravitating forces, and the inertialess electrons under the action of EM forces and the gradient of the ultra-relativistic pressure. The dispersion relation admits stability of a white dwarf star against a class of EM perturbations whose wavelengths are shorter than 15000 km.

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Stark Broadening of Carbon and Oxygen Lines in Hot DQ White Dwarf Stars: Recent Results and Applications

Open Astronomy ◽

10.1515/astro-2017-0329 ◽

2011 ◽

Vol 20 (4) ◽

Cited By ~ 2

Author(s):

P. Dufour ◽

N. Ben Nessib ◽

S. Sahal-Bréchot ◽

M. S. Dimitrijević

Keyword(s):

White Dwarf ◽

Line Profiles ◽

Stark Broadening ◽

Atmospheric Parameters ◽

Crucial Importance ◽

Dwarf Stars ◽

White Dwarf Stars ◽

New Family ◽

New Generation ◽

Future Work

AbstractWhite dwarf stars are traditionally found to have surface compositions made primarily of hydrogen or helium. However, a new family has recently been uncovered, the so-called hot DQ white dwarfs, which have surface compositions dominated by carbon and oxygen with little or no trace of hydrogen and helium (Dufour et al. 2007, 2008, 2010). Deriving precise atmospheric parameters for these objects (such as the effective temperature and the surface gravity) requires detailed modeling of spectral line profiles. Stark broadening parameters are of crucial importance in that context. We present preliminary results from our new generation of model atmospheres including the latest Stark broadening calculations for C II lines and discuss the implications as well as future work that remains to be done.

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Hot Wind in the Double Degenerate System AM CVn

International Astronomical Union Colloquium ◽

10.1017/s0252921100105706 ◽

1987 ◽

Vol 93 ◽

pp. 785-794

Author(s):

J.-E. Solheim ◽

O. Kjeldseth-Moe

Keyword(s):

White Dwarf ◽

Optical Spectrum ◽

Rotation Period ◽

Close Binary System ◽

Close Binary ◽

Degenerate System ◽

Line Profiles ◽

Dwarf Stars ◽

White Dwarf Stars ◽

Close Orbit

AbstractThe close binary system Am CVn consists of two helium white dwarf stars in close orbit. Strong flickering in the optical light curve and the observed spin-up in the rotation period indicate that mass transfer takes place (Solheim et al., 1984). The optical spectrum shows broad helium absorption lines (Robinson and Faulkner, 1975) sometimes partly filled in by emission (Voikhanskaya, 1982). The optical spectrum shows no sign of hydrogen, and the line profiles are interpreted as due to an accretion disk of intermediate angle of inclination with a temperature of the order of 20.000 K (Robinson and Faulkner, 1975). Another possibility is direct accretion onto a magnetized BD white dwarf (Voikhanskaya, 1982). In the latter case a magnetic field B ≃ 106 to 109 gauss is needed. Voikhanskaya also reports significant changes in the absorption line profiles from 1978 to 1980.

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Pulsation in the white dwarf HE 1017−1352: confirmation of the class of hot DAV stars

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slaa106 ◽

2020 ◽

Vol 497 (1) ◽

pp. L24-L29

Author(s):

Alejandra D Romero ◽

L Antunes Amaral ◽

S O Kepler ◽

L Fraga ◽

D Kurtz ◽

...

Keyword(s):

White Dwarf ◽

Rotation Period ◽

False Alarm Probability ◽

Dwarf Star ◽

Dwarf Stars ◽

Long Period ◽

White Dwarf Stars ◽

Harmonic Degree ◽

Radial Pulsations ◽

Astrophysical Research

ABSTRACT We report the detection of periodic variations on the $T_\mathrm{eff}\simeq 32\, 000$ K DA white dwarf star HE 1017−1352. We obtained time series photometry using the 4.1-m Southern Astrophysical Research telescope on three separate nights for a total of 16.8 h. From the frequency analysis, we found four periods of 605, 556, 508, and 869 s with significant amplitudes above the 1/1000 false alarm probability detection limit. The detected modes are compatible with low harmonic degree g-mode non-radial pulsations with radial order higher than ∼9. This detection confirms the pulsation nature of HE 1017−1352 and thus the existence of the new pulsating class of hot DA white dwarf stars. In addition, we detect a long period of 1.52 h, compatible with a rotation period of DA white dwarf stars.

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