Spitzer 24 um Excesses for Bright Galactic Stars in Bootes and First Look Survey Fields

TL;DR

This study identifies optically bright Galactic stars with mid-infrared excesses in Spitzer surveys, revealing that approximately 9-17% of FGK main sequence stars have 24 um excesses, similar to previous debris disk findings.

Contribution

First comprehensive analysis of 24 um excesses in optically bright Galactic stars using Spitzer data, establishing the prevalence among FGK main sequence stars.

Findings

17 out of 141 FGK stars show 24 um excesses.

At least 8 of these excess stars are confirmed main sequence stars.

9% to 17% of FGK main sequence stars have 24 um excesses.

Abstract

Optically bright Galactic stars (V < 13 mag) having fv(24 um) > 1 mJy are identified in Spitzer mid-infrared surveys within 8.2 square degrees for the Bootes field of the NOAO Deep Wide-Field Survey and within 5.5 square degrees for the First Look Survey (FLS). 128 stars are identified in Bootes and 140 in the FLS, and their photometry is given. (K-[24]) colors are determined using K magnitudes from the 2MASS survey for all stars in order to search for excess 24 um 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 um excesses with (K-[24]) > 0.2 mag. Using limits on absolute magnitude derived from proper motions, at least 8 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 um 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.