A 12 minute orbital period detached white dwarf eclipsing binary

Abstract

We have discovered a detached pair of white dwarfs (WDs) with a 12.75 minute orbital period and a 1315kms-1 radial velocity amplitude. We measure the full orbital parameters of the system using its light curve, which shows ellipsoidal variations, Doppler boosting, and primary and secondary eclipses. The primary is a 0.25 M⊙ tidally distorted helium WD, only the second tidally distorted WD known. The unseen secondary is a 0.55 M⊙ carbon-oxygen WD. The two WDs will come into contact in 0.9Myr due to loss of energy and angular momentum via gravitational wave radiation. Upon contact the systems may merge (yielding a rapidly spinning massive WD), form a stable interacting binary, or possibly explode as an underluminous Type Ia supernova. The system currently has a gravitational wave strain of 10-22, about 10,000 times larger than the Hulse-Taylor pulsar; this system would be detected by the proposed Laser Interferometer Space Antenna gravitational wave mission in the first week of operation. This system's rapid change in orbital period will provide a fundamental test of general relativity. © 2011. The American Astronomical Society. All rights reserved.