From planet@astro.rug.nl Wed Jun 2 15:59:54 MET 1999 Subject: PLANET CAUSTIC ALERT: OGLE 99-BLG-11 Date: Wed, 2 Jun 1999 15:58:56 +0200 () Dear Colleagues: Based on analysis of recent data from the PLANET collaboration and data publicly provided by the OGLE team, we estimate that the center of the source star in the on-going binary microlensing event OGLE 1999-BUL-11 will cross the caustic within the next 18 hours. There is a slight chance that it has already done so. The OGLE collaboration has previously alerted the possible binary nature of this event. Early on 1 June, PLANET reported a brightening that suggested a rise toward a second caustic crossing at JD=2451334 +/- 2. OGLE reported a steeping in the brightness of this event in its 2 June data, and this together with our own data from two sites causes us to revise our estimate for the time of the crossing to JD=2451332.3 +/- 0.5. The source star is currently about 2 magnitudes above its OGLE-reported baseline of I=18.5. Event: OGLE 1999-BUL-11 RA (J2000): 18:05:29.59 Dec (J2000): -27:59:14.4 Observations, both photometric and spectrographic are encouraged. Finding charts and future update information can be found on the PLANET web page at: http://www.astro.rug.nl/~planet. OGLE information on this event can be found at the OGLE alert web page at: http://www.astrouw.edu.pl/~ftp/ogle/ogle2/ews/ews.html