Variable and Embedded Stars in the Galactic Center

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Abstract
We report results of a time series analysis of high-resolution K-band imaging, photometry, and polarimetry of stars in the Galactic center cluster covering 7 consecutive years. In our statistical sample with mK < 13, about half of the stars show indication of variability consistent with most of them being long-period variable, asymptotic giant branch stars. Some long-period variables already proposed in the literature are confirmed. They are identified with asymptotic giant branch stars. For the first time we show that the bright He I source IRS 16SW is a short-period variable with a period of ~9.72 days. It is most likely an eclipsing binary with a lower mass limit of ≥100 solar masses. This confirms previous modeling of characteristics of the near-infrared spectra, which also indicated that IRS 16SW is a massive, young hot star. We also present the results of a polarization survey covering the central parsec of the Galaxy. Stars whose polarization vectors differ from the overall polarization, which is parallel to the Galactic plane, are mostly situated in the "minispiral,"a region of high thermal flux density at centimeter-radio wavelengths. Some of these sources appear extended in the high-resolution images and have featureless red spectra. We interpret these objects as young stars that may have just recently been formed and are still embedded in a dust shell.