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Session 102 - Pulsating Stars.
Display session, Thursday, January 18
North Banquet Hall, Convention Center

[102.01] The Macho Project Variables in the Bulge: 1st Year Results

K. Cook, C. Alcock, P. Purdue (LLNL), R. Allsman (ANUSF), D. Alves (UCD/LLNL), T. Axelrod (MSSSO/LLNL), K. Freeman, B. Peterson, A. Rodgers (MSSSO), A. Becker, C. Stubbs (CfPA/U Washington), D. Bennett (CfPA/LLNL), K. Griest, J. Guern, M. Lehner (CfPA/UCSD), S. Marshall, M. Pratt (CfPA/UCSB), P. Quinn (ESO), W. Sutherland (Oxford), D. Welch (McMaster)

The Macho project has analyzed light curves of 12.6 million stars in 12 square degrees of the bulge of the Milky Way in a survey for microlensing. This poster presents a preliminary analysis of the \sim 39,000 variables noted during this analysis. The data spans 190 days in 1993. Individual 0.5 square degree fields containing about 500,000 stars each were sampled from about 60 to about 150 times. We have searched for periodic variability in these light curves, but have been hampered by the short time span in two ways: 1) it has limited our ability to determine the proper period for long period variables and, 2) with, on average, less than one sample per night, this time span allows for aliasing at multiples of 1 day. These problems will be eliminated as the next years of Macho data are analyzed.

Long period and semi-regular variables which are quite red comprise about 47% of the variables. Eclipsing binaries with periods longer than 1 day comprise about 10% of the variables. Type ab RR Lyrae comprise about 4% of the variables. The remaining variables are short period, relatively small amplitude variables including contact binaries, semi-detached binaries, detached binaries and overtone RR Lyrae. This poster will present general properties of various classes of variables---the RR Lyrae (spatial distribution, period distribution, etc.), Cepheids, W Virginis stars, and binaries, as well as the identification of unusual variables.

Work performed under the auspices of the USDOE at LLNL under contract no. W-7405-ENG-48.

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