CERN Accelerating science

Article
Report number	astro-ph/0102080
Title	A Short Timescale Candidate Microlensing Event in the POINT-AGAPE Pixel Lensing Survey of M31
Author(s)	Auriere, M. ; Baillon, P. (CERN) ; Bouquet, A. ; Carr, Bernard J. ; Creze, M. ; Evans, N.W. ; Giraud-Heraud, Y. ; Gould, A. ; Hewett, Paul C. ; Kaplan, J. ; Kerins, E. ; Lastennet, E. ; Du, Y.Le ; Melchior, A.L. ; Paulin-Henriksson, S. ; Smartt, S.J. ; Valls-Gabaud, D.
Publication	2001
Imprint	5 Feb 2001
Number of pages	20
Note	20 pages, 4 figures, submitted to The Astrophysical Journal (Letters)
In:	Astrophys. J. 553 (2001) 2
DOI	10.1086/320681
Subject category	Astrophysics and Astronomy
Abstract	We report the discovery of a short-duration microlensing candidate in the northern field of the POINT-AGAPE pixel lensing survey towards M31. The full-width half-maximum timescale is very short, just 1.8 days. Almost certainly, the source star has been identified on Hubble Space Telescope archival images, allowing us to infer an Einstein crossing time of 10.4 days, a maximum magnification of about 18, and a lens-source proper motion greater than 0.3 microarcsec/day. The event lies projected at 8' from the center of M31, which is beyond the bulk of the stellar lens population. The lens is likely to reside in one of three locations. It may be a star in the M31 disk, or a massive compact halo object (Macho) in either M31 or the Milky Way. The most probable mass is 0.06 solar masses for an M31 Macho, 0.02 solar masses for a Milky Way Macho and 0.2 solar masses for an M31 stellar lens. Whilst the stellar interpretation is plausible, the Macho interpretation is the most probable for halo fractions above 20%.

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