2005/07/31 by P. Cseresnjes, Patrick Cseresnjes, Arlin P. S. Crotts +9 · 1 citation
Physics and Astronomy · #Astronomy #Astrophysics #Brown dwarf #Bulge #Flux (metallurgy) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Gamma-ray bursts and supernovae #Gravitational microlensing #Halo #Physics #Stars #Stellar, planetary, and galactic studies #Supernova #astro-ph
paper · pdf · doi:10.1086/498501
published as Astrophys.J.633:L105-L108,2005 · Accepted for publication in ApJL. Higher resolution version available at http://www.astro.columbia.edu/~patrick/hst/hst_ml.pdf
arxiv created 2005/10/06 · openalex publication_date 2005/10/24 · openalex created_date 2016/06/24 · arxiv updated 2016/08/30 · openalex updated_date 2026/08/05
We investigate HST /ACS and WFPC2 images at the positions of five candidate microlensing events from a large survey of variability in M31 (MEGA). Three closely match unresolved sources, and two produce only flux upper limits. All are confined to regions of the color-magnitude diagram where stellar variability is unlikely to be easily confused with microlensing. Red variable stars cannot explain these events (although background supernovae are possible for two). If these lenses arise in M31's halo, they are due to masses 0.15 < m / M ☉ < 0.49 (95% certainty, for a δ-function mass distribution), with brown dwarfs for disk lenses and stellar masses for bulge lenses.