The MACHO Project II: Data Reduction and Analysis of 6 Million Lightcurves

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Session 72 -- High Z Line Measurements; Gravitational Microlensing: Distance Determination
Display presentation, Friday, January 14, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[72.06] The MACHO Project II: Data Reduction and Analysis of 6 Million Lightcurves

D. P. Bennett (CfPA/LLNL), C. Alcock, R. Allsman, T. Axelrod, K. Cook, H.-S. Park (LLNL), K. Freeman, B. Peterson, P. Quinn, A. Rodgers (MSSSO), C. Akerlof, K. Griest, S. Marshall, S. Perlmutter, C. Stubbs, W.Sutherland (CfPA)

We present details of the analysis of 6 million stellar lightcurves spanning about a year with (typically) 300 two-color observations per star collected in our ongoing search for microlensing by MAssive Compact Halo Objects (MACHOs) in the Milky Way halo. By observing stars in the LMC and galactic bulge, we are sensitive to the time-varying amplification due to MACHOs with masses between $10^{-6}$ and $\sim 1$ solar masses moving through the galactic halo along the line of sight to the LMC and galactic bulge. Our primary photometric measurements are performed by SoDOPHOT, a very fast point-spread function fitting photometry routine originally adapted from DOPHOT. The reduced data is then assembled into a lightcurve database which is culled for candidate microlensing events using matched filters and a number of ``cut" criteria such as high signal to noise, good light curve coverage, achromaticity, and an acceptable fit to a microlensing light curve. The photometric efficiency is determined by adding fake stars with a range of amplifications to a number of images of the same field. These photometric efficiencies are then used to determine our microlensing detection efficiency by adding fake events to our lightcurve database using the measured distribution of photometric errors. These detection efficiencies can then be used to convert our distribution of candidate events to information on the abundance and properties of MACHOs in the galactic halo. Details of the MACHO instrumental system, candidate microlensing events and their implications, and variable star astronomical results are presented in accompanying posters.

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