Photometric Confirmation of MACHO Large Magellanic Cloud Microlensing Events

We present previously unpublished photometry of three Large Magellanic Cloud(LMC) microlensing events and show that the new photometry confirms themicrolensing interpretation of these events. These events were discovered bythe MACHO Project alert system and were also recovered by the analysis of the5.7 year MACHO data set. This new photometry provides a substantial increase inthe signal-to-noise ratio over the previously published photometry and in allthree cases, the gravitational microlensing interpretation of these events isstrengthened. The new data consist of MACHO-Global Microlensing Alert Network(GMAN) follow-up images from the CTIO 0.9 telescope plus difference imagingphotometry of the original MACHO data from the 1.3m "Great Melbourne" telescopeat Mt. Stromlo. We also combine microlensing light curve fitting withphotometry from high resolution HST images of the source stars to providefurther confirmation of these events and to show that the microlensinginterpretation of event MACHO-LMC-23 is questionable. Finally, we compare ourresults with the analysis of Belokurov, Evans & Le Du who have attempted toclassify candidate microlensing events with a neural network method, and wefind that their results are contradicted by the new data and more powerfullight curve fitting analysis for each of the four events considered in thispaper. The failure of the Belokurov, Evans & Le Du method is likely to be dueto their use of a set of insensitive statistics to feed their neural networks.Comment: 29 pages with 8 included postscript figures, accepted by the Astrophysical Journa