THE FREQUENCY OF WARM DEBRIS DISKS AND TRANSITION DISKS IN A COMPLETE SAMPLE OF INTERMEDIATE-MASS GLIMPSE STARS: PLACING CONSTRAINTS ON DISK LIFETIMES

Abstract

The incidence of dusty debris disks around low- and intermediate-mass stars has been investigated numerous times in order to understand the early stages of planet formation. Most notably, the Infrared Astronomical Satellite (IRAS) mission observed the entire sky at mid- and far-infrared (IR) wavelengths, identifying the first debris disk systems, but was unable to detect a statistically significant sample of warm debris disks due to its limited sensitivity at 12 μm. Using Tycho-2 Spectral Catalog stars previously shown to exhibit 8 μm mid-IR circumstellar excesses confirmed at 24 μm in the Spitzer Galactic Legacy Infrared MidPlane Survey Extraordinaire (GLIMPSE) survey, we investigate the frequency of mid-IR excesses among intermediate-mass (2-4 M ☉) stars in a complete volume-limited sample. Our study of 338 stars is four times larger than a complete sample of 12 μm sources from the IRAS Point Source Catalog. We find that 0.3% ± 0.3% of intermediate-mass stars exhibit a signature of a possible terrestrial-temperature debris disks at wavelengths of 8 μm and greater. We also find that 1.2% ± 0.6% of intermediate-mass stars exhibit evidence for circumstellar disks undergoing inner disk clearing, i.e., candidate transition disk systems. Using stellar lifetimes and the frequency of transition and primordial disks within a given spectral type, we find that pre-main-sequence disks around intermediate-mass stars dissipate in 5 ± 2 Myr, consistent with other studies.