1999A&A...344L..49A

AgapeZ1 is the brightest and the shortest duration microlensing candidate event found to date in the Agape experiment. It occurred only 42'' from the centre of M31 at RA=00:42:41.47 and Dec=+41°16'39.1" (J2000). Our photometry shows that the half intensity duration of the event is 5.3days and at maximum brightness its magnitude is R=17.9 (M_R~-6) with B-R=0.80mag colour. A search on HST archives produced a single resolved star within the projected event position error box. Its magnitude is R=22, and its colour is compatible with that of the event at the 2 σ level. If this event is identified with the HST star, the implied amplification is about 4 magnitudes or 40 in brightness. This would lead to an Einstein crossing time radius of about 60 days. AgapeZ1 could be a bulge/bulge microlensing event involving a binary star. The photometric properties of the object are inconsistent with classical M31 variable stars such as Miras, classical novae, dwarf-novae, and bumpers. However, we cannot rule out the possibility that AgapeZ1 is in fact an odd variable star.