Effect of binary sources on the search for massive astrophysical compact halo objects via microlensing

Abstract

view Abstract Citations (113) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Effect of Binary Sources on the Search for Massive Astrophysical Compact Halo Objects via Microlensing Griest, Kim ; Hu, Wayne Abstract If the dark matter in the Galactic halo consists of compact objects in the 10^-6^-10^2^2 M_sun_ mass range, it can be detected as it gravitationally microlenses stars in neighboring galaxies and the Galactic bulge. Though extremely rare, microlensing has several powerful signatures: the light curves follow a well-known function, are time symmetric, and are the same in all filter bands. These signatures, however, may be lost if the source star is a member of a binary system. Since most stars are, in fact, members of binaries, the true microlensing events may be rejected as background. We study the effect of binary sources by using the event geometry and resulting light curves to define several categories of binary microlensing events, and then calculate the probability of each category occurring. We average these probabilities over measured distributions of binary orbital periods and mass ratios, finding ~10%-20% of events on binary sources should be distinguishable from single-source microlensing events (for the LMC). The bulk of binary events should be achromatic and similar to single source light curves, but 2%-5% should have truly unusual light curves and color shifts greater than 0.1 mag. The total microlensing rate is larger by 5%-15% for binary sources and in deriving the MACHO mass from a binary light curve an error of a factor of 2 or more may be made if single source formulae are used. Publication: The Astrophysical Journal Pub Date: October 1992 DOI: 10.1086/171793 Bibcode: 1992ApJ...397..362G Keywords: Binary Stars; Dark Matter; Galactic Structure; Gravitational Lenses; Point Sources; Light Curve; Stellar Color; Stellar Mass; Astrophysics; COSMOLOGY: GRAVITATIONAL LENSING full text sources ADS | Related Materials (1) Erratum: 1993ApJ...407..440G