HST imaging of MEGA Microlensing Candidates in M31
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 supernova are possible for two). If these lenses arise in M31's halo, they are due to masses 0.08 < m/M{sub {circle_dot}} < 0.85 (95% certainty, for a {delta}-function mass distribution), brown dwarfs for disk/disk, and stellar masses for disk/bulge ''self-lensing''.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-76SF00515
- OSTI ID:
- 878838
- Report Number(s):
- SLAC-PUB-11360; ASJOAB; astro-ph/0507287; TRN: US200612%%174
- Journal Information:
- Astrophysical Journal, Vol. 633; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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