DISCOVERY OF THE ECLIPSING DETACHED DOUBLE WHITE DWARF BINARY NLTT 11748
- Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106 (United States)
- Kavli Institute for Theoretical Physics, Kohn Hall, University of California, Santa Barbara, CA 93106 (United States)
- National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)
We report the discovery of the first eclipsing detached double white dwarf (WD) binary. In a pulsation search, the low-mass helium core WD NLTT 11748 was targeted for fast ({approx}1 minute) differential photometry with the Las Cumbres Observatory's Faulkes Telescope North. Rather than pulsations, we discovered {approx}180 s 3%-6% dips in the photometry. Subsequent radial velocity measurements of the primary white dwarf from the Keck telescope found variations with a semi-amplitude K{sub 1} = 271 {+-} 3 km s{sup -1} and confirmed the dips as eclipses caused by an orbiting WD with a mass M{sub 2} = 0.648-0.771 M{sub sun} for M{sub 1} = 0.1-0.2 M{sub sun}. We detect both the primary and secondary eclipses during the P{sub orb} = 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 R{sub 1} = 0.043-0.039 R{sub sun} for M{sub 1} = 0.1-0.2 M{sub sun}, consistent with the theoretically expected values for a helium core WD with a thick, stably burning hydrogen envelope. Though nearby (at {approx}150 pc), the gravitational wave strain from NLTT 11748 is likely not adequate for direct detection by the Laser Interferometer Space Antenna. Future observational efforts will determine M{sub 1}, yielding accurate WD mass-radius measurement of both components, as well as a clearer indication of the binary's fate once contact is reached.
- OSTI ID:
- 21451082
- Journal Information:
- Astrophysical Journal Letters, Vol. 716, Issue 2; Other Information: DOI: 10.1088/2041-8205/716/2/L146; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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