The Chandra Variable Guide Star Catalog (Abstract)

Volume 37 number 2 (2009)

Joy S. Nichols

David A. Huenemoerder

E. Martin

J. Lauer

D. Morgan

Arne A. Henden

Abstract

(Abstract only) The Chandra X-ray Observatory has observed about 37,000 stars in the wavelength range 4000-9000 Å as guide stars for maintaining pointing control of the satellite. While these guide stars were intended to be non-variable in order to maximize the pointing accuracy, we have found that 673 are variable, generally at the 0.05 magnitude level. The catalog of these variable guide stars includes many types of variable stars, including pulsating stars, detached eclipsing binaries, contact binaries, etc., with spectral types generally in the range A through K. Light curves of these variables are the same length as the X-ray observation performed by Chandra, varying from 1 ksec to 170 ksec. The Chandra Guide Star Catalog includes about 300 stars that appear to be newly discovered variables. A description of the instrumentation is included and interesting examples from the catalog are shown and discussed. We introduce a new collaboration between the Chandra Variable Guide Star Team and members of the AAVSO, who will enhance this catalog with expertise in variable star characteristics. For future investigation, we intend to reprocess all available photometry in order to look for long-term variability and lower amplitude fluctuations that may not be apparent in the visual inspection of the existing time series. This work was supported by NASA contract NAS8-37073.