Optical Identification of Close White Dwarf Binaries in the LISA Era

摘要

The Laser Interferometer Space Antenna (LISA) is expected to detect closewhite dwarf binaries (CWDBs) through their gravitational radiation. Around 3000binaries will be spectrally resolved at frequencies > 3 mHz, and theirpositions on the sky will be determined to an accuracy ranging from a few tensof arcminutes to a degree or more. Due to the small binary separation, theoptical light curves of >~ 30% of these CWDBs are expected to show eclipses,giving a unique signature for identification in follow-up studies of the LISAerror boxes. While the precise optical location improves binary parameterdetermination with LISA data, the optical light curve captures additionalphysics of the binary, including the individual sizes of the stars in terms ofthe orbital separation. To optically identify a substantial fraction of CWDBsand thus localize them very accurately, a rapid monitoring campaign isrequired, capable of imaging a square degree or more in a reasonable time, atintervals of 10--100 seconds, to magnitudes between 20 and 25. While thedetectable fraction can be up to many tens of percent of the total resolvedLISA CWDBs, the exact fraction is uncertain due to unknowns related to thewhite dwarf spatial distribution, and potentially interesting physics, such asinduced tidal heating of the WDs due to their small orbital separation.