2012ApJ...749...42H -
Astrophys. J., 749, 42 (2012/April-2)
Two new tidally distorted white dwarfs.
HERMES J.J., KILIC M., BROWN W.R., MONTGOMERY M.H. and WINGET D.E.
Abstract (from CDS):
We identify two new tidally distorted white dwarfs (WDs), SDSS J174140.49+652638.7 and J211921.96-001825.8 (hereafter J1741 and J2119). Both stars are extremely low mass (ELM, ≤ 0.2 M☉) WDs in short-period, detached binary systems. High-speed photometric observations obtained at the McDonald Observatory reveal ellipsoidal variations and Doppler beaming in both systems; J1741, with a minimum companion mass of 1.1 M☉, has one of the strongest Doppler beaming signals ever observed in a binary system (0.59%±0.06% amplitude). We use the observed ellipsoidal variations to constrain the radius of each WD. For J1741, the star's radius must exceed 0.074 R☉. For J2119, the radius exceeds 0.10 R☉. These indirect radius measurements are comparable to the radius measurements for the bloated WD companions to A-stars found by the Kepler spacecraft, and they constitute some of the largest radii inferred for any WD. Surprisingly, J1741 also appears to show a 0.23% ±0.06% reflection effect, and we discuss possible sources for this excess heating. Both J1741 and J2119 are strong gravitational wave sources, and the time-of-minimum of the ellipsoidal variations can be used to detect the orbital period decay. This may be possible on a timescale of a decade or less.
Abstract Copyright:
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Journal keyword(s):
binaries: close - Galaxy: stellar content - stars: individual (SDSS J174140.49+652638.7, SDSS J211921.96-001825.8) - stars: neutron - stars: variables: general - white dwarfs
Simbad objects:
13
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