A Search for Pre-Main Sequence Eclipsing Binary Stars in the Lagoon Nebula

Abstract

We report time-series CCD I-band photometry for the pre-main-sequence cluster NGC 6530, located within the Lagoon Nebula. The data were obtained with the 4Kx4K imager on the SMARTS 1.0m telescope at CTIO on 36 nights over the summers of 2005 and 2006. In total we have light curves for ~50,000 stars in an area ~1 deg2, with a sampling cadence of ~1 hour. Approximately 1,000 of these stars have been identified as bona fide members of the cluster with masses in the range 0.25-4.0 Msun, assuming a distance of 1.25 kpc to the cluster. Our goals are to measure rotation periods for these stars and to identify eclipsing binary candidates. Here we present light curves of the 223 stars in our sample found by us to be periodically variable, and we present the distribution of the stellar rotation periods derived from these light curves. We also present 16 potential eclipsing binary star systems that, through follow-up work, will provide direct measurements of the masses and radii of the stars for testing of stellar evolutionary models. This work has been supported by the National Science Foundation under Career grant AST-0349075.