The 1995 Pilot Campaign of PLANET: Searching for Microlensing Anomalies through Precise, Rapid, Round‐the‐Clock Monitoring

Abstract

PLANET (the Probing Lensing Anomalies NETwork) is a worldwide collaboration of astronomers whose primary goal is to monitor microlensing events densely and precisely in order to detect and study anomalies that contain information about Galactic lenses and sources that would otherwise be unobtainable. The results of PLANET's highly successful first year of operation are presented here. Details of the observational setup, observing procedures, and data reduction procedures used to track the progress in real time at the three participating observing sites in 1995 are discussed. The ability to follow several events simultaneously with a median sampling interval of 1.6 hours and a photometric precision of better than 0.10mag even at I=19 has been clearly demonstrated. During PLANET's 1995 pilot campaign, 10 microlensing events were monitored; the binary nature of one of these, MACHO 95-BLG-12 was recognized by PLANET on the mountain. Another event, OGLE 95-BLG-04, displayed chromaticity that may betray the presence of blending with unresolved stars projected onto the same resolution element. Although lasting only about a month, the campaign may allow constraints to be placed on the number of planets with mass ratios to the parent star of 0.01 or greater.

Realisation of a fully‐deterministic microlensing observing strategy for inferring planet populations

“…A first microlensing follow-up network for planet detection that allows round-the-clock monitoring with hourly sampling was put into place in 1995 by the PLANET (Probing Lensing Anomalies NETwork) collaboration 14 (Albrow et al 1998;Dominik et al 2002). Figure 1 shows the model light curve of the event OGLE-2005-BLG-390 together with data collected at 6 different sites.…”

“…Based on some simple thoughts and experience gained during the course of their observations, PLANET arrived at a rather pragmatic observing strategy that may not be optimal in a mathematical sense, but appears to be a workable match for achieving the science goals of the campaign (Albrow et al 1998;Dominik et al 2002). The fundamental principle behind the adopted strategy is in demanding a fixed photometric accuracy of 1-2 per cent, and selecting an exposure time t exp for each of the targets, so that this can be met.…”

Discovery of a cool planet of 5.5 Earth masses through gravitational microlensing

“…The sensitivity of the microlensing method to lowmass planets is restricted by the finite angular size of the source stars 10,11 , limiting detections to planets of a few M % for giant source stars, but allowing the detection of planets as small as 0.1M % for main-sequence source stars in the Galactic Bulge. The PLANET collaboration 12 maintains the high sampling rate required to detect low-mass planets while monitoring the most promising of the .500 microlensing events discovered annually by the OGLE collaboration, as well as events discovered by MOA. A decade of pioneering microlensing searches has resulted in the recent detections of two Jupiter-mass extrasolar planets 13,14 with orbital separations of a few AU by the combined observations of the OGLE, MOA, MicroFUN and PLANET collaborations.…”

1318 new variable stars in a 0.25 square degree region of the Galactic plane

“…The initial images were taken during 2002 as part of a microlensing followup study by the PLANET collaboration (Albrow et al 1998). A follow-up observation run was made in 2005 in service mode using MPIA time (P.I.…”