Multiple-peak structure in OGLE 2004-BLG-368

Multiple-peak structure in OGLE 2004-BLG-368

First posted on homepage: 28-Jun-2004
Moved to news archive: 26-Jul-2004

As reported in PLANET anomaly alert 2004 #10 (issued 28-Jun, 23:55 UT), data collected by PLANET with the Danish 1.54m telescope at ESO LaSilla (Chile) from HJD=2453184.5 to HJD=2453184.9 (28-Jun, 2004) and data taken by the MicroFUN collaboration independently suggest two peaks which are estimated to have occured at HJD=2453184.25 +/- 0.25 and at HJD=2453185.0 +/- 0.25 but were not observed themselves.

With data from the Danish 1.54m telescope at ESO LaSilla (Chile) collected between HJD=2453185.4 and HJD=2453185.9 (28-Jun, 2004) having become available, PLANET anomaly update 2004 #10-1 (issued 29-Jun, 9:30 UT) was circulated. These data provide evidence that the event is still undergoing an anomaly. An apparent peak was observed at HJD 2453185.6 with a magnification of about 3 mag above baseline and the event has subsequently faded by 0.3 mag until the end of the night.

Further PLANET data collected with the Danish 1.54m telescope at ESO LaSilla (Chile) from HJD=2453185.4 to HJD=2453186.7 (29-Jun, 2004) show that OGLE 2004-BLG-368 has exited a caustic and continues to decline, expected to approach an ordinary lightcurve. This has been reported in PLANET anomaly update 2004 #10-2 (issued 30-Jun, 9:40 UT).

PLANET anomaly update 2004 #10-3 (issued 5-Jul, 8:30 UT) reported that reduction of data collected by PLANET with the Canopus 1.0m telescope near Hobart (Tasmania, Australia) during the two consecutive nights starting on 28-Jun and 29-Jun reveal additional important information about the observed caustic passage. Two points on the rise following the observed caustic entry at HJD=2453184.75 +/- 0.01 (28-Jun, 6:00 UT +/- 15 min) indicate a peak around HJD=2453185.25 (28-Jun, 18:00 UT) at more than 3.5 mag above baseline, after which the event dropped to a magnification of 2.85 mag at HJD=2453185.55 (29-Jun, 1:10 UT) and rose again to a peak at 3.0 mag at HJD=2453185.65 (29-Jun, 3:35 UT). The Tasmanian data favour a slope dicontinuity marking the end of the caustic passage at HJD=2453186.13 +/- 0.01 (29-Jun, 15:07 UT +/- 15 min), so that the caustic passage lasted about 33 hours. The structure of the observed caustic passage is typical for events where the source center passes close to a cusp and the leading limb starts exiting before the trailing limb has entered.

A lightcurve with PLANET and OGLE data is regularly updated.

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