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Published July 2009 | Published
Journal Article Open

Spitzer 24 μm Excesses for Bright Galactic Stars in Boötes and First Look Survey Fields


Optically bright Galactic stars (V ≾ 13 mag) having f_ν(24 μm) > 1 mJy are identified in Spitzer mid-infrared surveys within 8.2 deg^2 for the Boötes field of the NOAO Deep Wide-Field Survey and within 5.5 deg^2 for the First Look Survey (FLS). One hundred and twenty-eight stars are identified in Boötes and 140 in the FLS, and their photometry is given. (K – [24]) colors are determined using K magnitudes from the Two Micron All Sky Survey for all stars in order to search for excess 24 μm luminosity compared to that arising from the stellar photosphere. Of the combined sample of 268 stars, 141 are of spectral types F, G, or K, and 17 of these 141 stars have 24 μm excesses with (K – [24]) > 0.2 mag. Using limits on absolute magnitude derived from proper motions, at least eight of the FGK stars with excesses are main-sequence stars, and estimates derived from the distribution of apparent magnitudes indicate that all 17 are main-sequence stars. These estimates lead to the conclusion that between 9% and 17% of the main-sequence FGK field stars in these samples have 24 μm infrared excesses. This result is statistically similar to the fraction of stars with debris disks found among previous Spitzer targeted observations of much brighter, main-sequence field stars.

Additional Information

© 2009 The American Astronomical Society. Received 2008 August 18; accepted 2009 May 7; published 2009 June 8. We thank Lusine Sargsyan for help with data collection, and we thank M. Meyer for providing unpublished stellar coordinates. We also thank the anonymous referee for detailed comments and helpful suggestions. The Spitzer/MIPS Bootes survey was made possible with GTO time provided by the Infrared Spectrograph team and Marcia Rieke. We thank NOAO for supporting the NOAO Deep Wide-Field Survey; A.D. and B.J. acknowledge support from NOAO, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under a cooperative agreement with the National Science Foundation. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France, and the NASA/ IPAC Extragalactic Database (NED). This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. Support for this work by the IRS GTO team at Cornell University was provided by NASA through Contract Number 1257184 issued by JPL/ Caltech. Support was also provided by the US Civilian Research and Development Foundation under grant ARP1-2849-YE-06.

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