Discovery of the Eclipsing Detached Double White Dwarf Binary NLTT 11748

Details Discovery of the Eclipsing Detached Double White Dwarf Binary NLTT 11748 Discovery of the Eclipsing Detached Double White Dwarf Binary NLTT 11748

Jan 2011

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21712601s&link_type=abstract

American Astronomical Society, AAS Meeting #217, #126.01; Bulletin of the American Astronomical Society, Vol. 43, 2011

Astronomy and Astrophysics

Astronomy

Scientific paper

We report the discovery of the first eclipsing detached double white dwarf (WD) binary, NLTT 11748. In a photometric search for pulsations from this low-mass helium core WD, we discovered approx 180 s 3%--6% dips in the photometry. Subsequent radial velocity measurements found variations with a semi-amplitude K1 = 271 ± 3 km/s (also now reported by Kawka et al. and Kilic et al.) and confirmed the dips as eclipses caused by an orbiting WD with a mass M2 = 0.648--0.771 Msun for M1 = 0.1--0.2 Msun. We detect both the primary and secondary eclipses during the Porb = 5.64 hr orbit and measure the secondary's brightness to be 3.5% ± 0.3% of the primary at SDSS-g'. Assuming that the secondary follows the mass-radius relation of a cold C/O WD and including the effects of microlensing in the binary, the primary eclipse yields a primary radius of R1 = 0.043--0.039 Rsun for M1 = 0.1--0.2 Msun, consistent with the theoretically expected values for a helium core WD with a thick, stably burning hydrogen envelope. I will discuss how our future observational efforts, such as detection of the secondary semi-amplitude K2, multiband high-cadence photometric eclipse observations, and cross system time-delay measurements, will determine M1, yielding accurate WD mass-radius measurement of both components, as well as a clearer indication of the binary's fate once contact is reached.

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