White Dwarf Mass-radius Relation Research Articles

PG 1258+593 and its common proper motion magnetic white dwarf counterpart

We identify SDSS J130033.48+590407.0 as a common proper motion companion to the well-studied DA white dwarf PG 1258+593 (GD322). The system lies at a distance of 68 +/- 3 pc, where the angular separation of 16.1 +/- 0.1 arcsec corresponds to a minimum binary separation of 1091 +/- 7 AU. SDSS J1300+5904 is a cool (Teff = 6300 +/- 300K) magnetic white dwarf (B ~ 6 MG). PG 1258+593 is a hydrogen-rich (DA) white dwarf with Teff=14790 +/- 77 K and log(g) = 7.87 +/- 0.02. Using the white dwarf mass-radius relation implies the masses of SDSS J1300+5904 and PG 1258+593 are 0.54 +/- 0.06 Msun and 0.54 +/- 0.01 Msun, respectively, and therefore a cooling age difference of 1.67 +/- 0.05 Gyr. Adopting main-sequence life times from stellar models, we derive an upper limit of 2.2 Msun for the mass of the progenitor of PG 1258+593. A plausible range of initial masses is 1.4 - 1.8 Msun for PG 1258+593 and 2 - 3 Msun for SDSS J1300+5904. Our analysis shows that white dwarf common proper motion binaries can potentially constrain the white dwarf initial-final mass relation and the formation mechanism for magnetic white dwarfs. The magnetic field of SDSS J1300+5904 is consistent with an Ap progenitor star. A common envelope origin of the system cannot be excluded, but requires a triple system as progenitor.

Finding White Dwarfs with Transit Searches

We make predictions for the rate of discovery of eclipsing white dwarf-main-sequence (WD-MS) binaries in terrestrial-planet transit searches, taking the planned Kepler and Eddington missions as examples. We use a population synthesis model to characterize the Galactic WD-MS population, and we find that, despite increased noise due to stellar variability compared with the typical planetary case, discovery of 102 nonaccreting, eclipsing WD-MS systems is likely using Kepler and Eddington, with periods of 2-20 days and transit amplitudes of |Δm| ~ 10-4±0.5 mag. Follow-up observations of these systems could accurately test the theoretical white dwarf mass-radius relation or theories of binary star evolution.

Procyon B: Outside the Iron Box

Procyon B is one of a select group of white dwarf stars in visual binaries that are used to put stringent constraints on the fundamental physics of stellar degeneracy. We present Space Telescope Imaging Spectrograph observations of this elusive white dwarf. Our spectra cover 1800-10000 A and contain carbon Swan bands, Mg II, and numerous iron features. Procyon B is therefore a rare DQZ white dwarf. Our analysis of the spectrum yields an effective temperature of 7740 ± 50 K and a radius of 0.01234 ± 0.00032 R☉. We discuss the implications of these results on observational support for the white dwarf mass-radius relation.

Mass‐Radius Relation for Magnetic White Dwarfs

Recently, several white dwarfs with very strong surface magnetic fields have been observed. In this paper we explore the possibility that such stars could have sufficiently strong internal fields to alter their structure. We obtain a revised white dwarf mass-radius relation in the presence of strong internal magnetic fields. We first derive the equation of state for a fully degenerate ideal electron gas in a magnetic field using an Euler-MacLaurin expansion. We use this to obtain the mass-radius relation for magnetic 4He, 12C, and 56Fe white dwarfs of uniform composition.

Testing the White Dwarf Mass‐Radius Relation withHipparcos

We present the Hipparcos parallaxes and resulting radii for 10 white dwarfs in visual binaries or common proper-motion systems and 11 field white dwarfs. For bright stars, Hipparcos parallaxes have uncertainties approaching 1 mas and are thus considerably more accurate than earlier ground-based parallaxes. Overall, our results support the predictions of the white dwarf mass-radius relation and our understanding of stellar degeneracy. Our most important finding for an individual object is the position of 40 Eri B, a well-known puzzle, now consistent with single-star evolution. In addition, we present evidence supporting the existence of a range of atmosphere thicknesses for hydrogen (DA) white dwarfs.

X-Ray Emission from Magnetic Cataclysmic Variables and White Dwarf Mass Estimates

view Abstract Citations (30) References (52) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS X-Ray Emission from Magnetic Cataclysmic Variables and White Dwarf Mass Estimates Wu, Kinwah ; Chanmugam, G. ; Shaviv, G. Abstract We have calculated the temperature and density structures of the postshock regions in accreting magnetic white dwarfs and deduced the related X-ray emission. Our calculations show that the X-rays from structured postshock regions with strong magnetic fields are significantly softer than the X-rays from model emission regions, which are assumed to be homogeneous. Inclusion of these effects, and an improved mass-radius relation for white dwarfs, leads to higher white dwarf masses than estimated by Ishida in his recent work. Publication: The Astrophysical Journal Pub Date: December 1995 DOI: 10.1086/176574 Bibcode: 1995ApJ...455..260W Keywords: ACCRETION; ACCRETION DISKS; HYDRODYNAMICS; STARS: MAGNETIC FIELDS; STARS: WHITE DWARFS; X-RAYS: STARS full text sources ADS | data products SIMBAD (22)

Gravitational redshift determinations for white dwarfs in common proper-motion binaries

view Abstract Citations (30) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Gravitational Redshift Determinations for White Dwarfs in Common Proper-Motion Binaries Wegner, Gary ; Reid, I. N. Abstract Gravitational redshifts determined using the 5 m Hale telescope are given for 23 white dwarfs belonging to common proper-motion binary systems and additional velocities are presented for 14 pairs found not to comprise physical binaries or that have unmeasurable velocities. The mass distribution for the common proper-motion pairs using the gravitational redshifts and the mass-radius relation peaks strongly near 0.55 solar mass, and the main details of the shape agree with earlier determinations using other methods although a problem remains with contamination with optical pairs. The redshifts and radii of a subset of these objects with known distances are consistent with the mass-radius relation for white dwarfs. Publication: The Astrophysical Journal Pub Date: July 1991 DOI: 10.1086/170230 Bibcode: 1991ApJ...375..674W Keywords: Binary Stars; Red Shift; Stellar Gravitation; Stellar Motions; White Dwarf Stars; Mass Distribution; Stellar Mass; Astrophysics; GRAVITATION; STARS: VISUAL MULTIPLES; STARS: WHITE DWARFS full text sources ADS | data products SIMBAD (68)

Short-range effects in large white dwarfs

Recent work of Membrado and Pacheco (1988) on the implication of Yukawa-like effects in small white dwarfs is extended to analyze the very massive case. Although the role of these impurities grows substantially as the radius of the star decreases, when reasonable supergravity parameters are used the predicted change in the white dwarf mass-radius relation is unobservably small. 8 references.