CERN Accelerating science

Article
Report number	astro-ph/0206387
Title	A Candidate M31/M32 Intergalactic Microlensing Event
Author(s)	Paulin-Henriksson, S. ; 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. ; Du, Y.Le ; Melchior, A.L. ; Smartt, S.J. ; Valls-Gabaud, D.
Affiliation	(CERN) ; (College de France,) ; (IoA Cambridge,) ; (LERMA, Obs. de Paris,) ; (Liverpool John Moores U.,) ; (Obs. Midi-Pyrenees) ; (Ohio State,) ; (Oxford,) ; (Queen Mary, U. London,) ; (U. Bretagne-Sud,)
Publication	2002
Imprint	21 Jun 2002
Number of pages	13
Note	Submitted to ApJ Letters. 13 pages, 2 figures
In:	Astrophys. J. 576 (2002) L121-L124
DOI	10.1086/343887
Subject category	Astrophysics and Astronomy
Abstract	We report the discovery of a microlensing candidate projected 2'54" from the center of M32, on the side closest to M31. The blue color (R-I= 0.00 +/- 0.14) of the source argues strongly that it lies in the disk of M31, while the proximity of the line of sight to M32 implies that this galaxy is the most likely host of the lens. If this interpretation is correct, it would confirm previous arguments that M32 lies in front of M31. We estimate that of order one such event or less should be present in the POINT-AGAPE data base. If more events are discovered in this direction in a dedicated experiment, they could be used to measure the mass function of M32 up to an unknown scale factor. By combining microlensing observations of a binary-lens event with a measurement of the M31-M32 relative proper motion using the astrometric satellites SIM or GAIA, it will be possible to measure the physical separation of M31 and M32, the last of the six phase-space coordinates needed to assign M32 an orbit.

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