Searching for IR excesses in Sun-like stars observed by WISE

Abstract

We present the results of a search of infrared excess candidates in a comprehensive (29\,000 stars) magnitude limited sample of dwarf stars, spanning the spectral range F2-K0, and brighter than V$=$15 mag. We searched the sample within the {\em WISE} all sky survey database for objects within 1 arcsecond of the coordinates provided by SIMBAD database and found over 9\,000 sources detected in all {\em WISE} bands. This latter sample excludes objects that are flagged as extended sources and those images which are affected by various optical artifacts. For each detected object, we compared the observed W4/W2 (22$\mu$m/4.6$\mu$m) flux ratio with the expected photospheric value and identified 197 excess candidates at 3$\sigma$. For the vast majority of candidates, the results of this analysis represent the first reported evidence of an IR excess. Through the comparison with a simple black-body emission model, we derive estimates of the dust temperature, as well as of the dust fractional luminosities. For more than 80% of the sample this temperature is higher than 120 K, suggesting the presence of warm circumstellar dust. Complementary observations at longer wavelengths (far-IR and sub-mm) are required for better characterising and explaining the origin of this emission.