Multiple Lens Microlensing in OGLE 2K-BUL-038

First posted: 11-July-2000
Last Update: 13-July-2000

The PLANET collaboration has detected an increase in brightness in the anomalous event OGLE 2000-BUL-38 which indicates that event will soon undergo a second caustic crossing. The PLANET collaboration has monitored this event intensively since it was first announced as anomalous by the OGLE team. According to the OGLE data, this event executed a first caustic just before Heliocentric Julian Date (HJD)=2451707. Since then, the source light curve has declined and levelled out in the caustic trough.

An electronic alert was issued by PLANET on 11 July 2000 stating that the event had risen 0.15 magnitudes in two days. The OGLE team confirmed this rise and indicated in their alert that the event may undergo a second crossing soon. As announced in a second PLANET electronic alert, the most recent PLANET data show that the event has brightened 0.23 magnitudes in the last 24 hours, and may indicate a caustic crossing as soon as HJD=2451739.4, although more data are needed for a firm prediction.

PLANET continues to monitor this event.

Event:                  OGLE-2000-BUL-38
RA (J2000):         17:53:19.20
Dec (J2000):     -29:57:33.9

The baseline I magnitude reported by the OGLE team is 17.87.

A postscript finding chart can be downloaded here.

Caustic crossing events can be used to measure source resolution effects, which can allow the determination of the relative proper motion of the lens and, in special circumstances, the limb-darkening of the source star. High magnification events, are especially likely to betray the presence of possible planets orbiting the lens.

Finding charts and future updated information can be found on the PLANET web site at

OGLE information on this event can be found at the OGLE alert web page at

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