The Nature of the Variable Galactic Center Source GCIRS 16SW Revisited: A Massive Eclipsing Binary

We present a re-analysis of our Hand K-band photometry and light-curves for GCIRS 16SW, a regular periodic source near the Galactic center. These data include those presented by DePoy et al. (2004); we correct a sign error in their reduction, finding GCIRS 16SW to be an eclipsing binary with no color variations. We find the system to be an equal mass overcontact binary (both stars overfilling their Roche lobes) with a period P = 19.4513 days, an inclination angle i = 71, and zero eccentricity. This confirms and strengthens the findings of Martins et al. (2006) that GCIRS 16SW is an eclipsing binary composed of two ∼ 50M⊙ stars, implying that there has been recent star formation very close to the Galactic center. Finally, the calculated luminosity of each component is close to the Eddington luminosity, implying that the temperature of 24400 K given by Najarro et al. (1997) might be too high for these evolved stars. Subject headings: Galaxy: center — stars: individual (GCIRS 16SW) — stars: binaries: eclipsing