Far-infrared properties of M dwarfs

Abstract

We report the mid- and far-infrared properties of nearby M dwarfs. Spitzer/MIPS measurements were obtained for a sample of 62 stars at 24 μm, with subsamples of 41 and 20 stars observed at 70 μm and 160 μm respectively. We compare the results with current models of M star photospheres and look for indications of circumstellar dust in the form of significant deviations of K-[24 μm] colors and 70 μm / 24 μm flux ratios from the average M star values. At 24 μm, all 62 of the targets were detected; 70 μm detections were achieved for 20 targets in the subsample observed; and no detections were seen in the 160 μm subsample. No clear far-infrared excesses were detected in our sample. The average far infrared excess relative to the photospheric emission of the M stars is at least four times smaller than the similar average for a sample of solar-type stars. However,this limit allows the average fractional infrared luminosity in the M-star sample to be similar to that for more massive stars. We have also set low limits (10−4 to 10−9 MEarth depending on location) for the maximum mass of dust possible around our stars.