SCYON Abstract

Received on October 7 2009

Debris Disks in the Upper Scorpius OB Association

AuthorsJohn M. Carpenter (1), Eric E. Mamajek (2), Lynne A. Hillenbrand (1), and Michael R. Meyer (3)
Affiliation(1) Caltech
(2) University of Rochester
(3) Institute for Astronomy, ETH
Accepted byAstrophysical Journal
Contactjmc@astro.caltech.edu
URLhttp://arxiv.org/abs/0909.4124
Links

Abstract

We present MIPS 24μm and 70μm photometry for 205 members of the Upper Scorpius OB Association. These data are combined with published MIPS photometry for 15 additional association members to assess the frequency of circumstellar disks around 5 Myr old stars with spectral types between B0 and M5. Twelve stars have a detectable 70μm excess, each of which also has a detectable 24μm excess. A total of 54 stars are identified with a 24μm excess more than 32% above the stellar photosphere. The MIPS observations reveal 19 excess sources -- 8 A/F/G stars and 11 K/M stars -- that were not previously identified with an 8μm or 16μm excess. The lack of short-wavelength emission and the weak 24μm excess suggests that these sources are debris systems or the remnants of optically thick primordial disks with inner holes. Despite the wide range of luminosities of the stars hosting apparent debris systems, the excess characteristics are consistent with all stars having dust at similar orbital radii after factoring in variations in the radiation blowout particle size with spectral type. The results for Upper Sco are compared to similar photometric surveys from the literature to re-evaluate the evolution of debris emission. After considering the completeness limits of published surveys and the effects of stellar evolution on the debris luminosity, we find that the magnitude of the 24μm excess around F-type stars increases between ages of 5 and 17 Myr as found by previous studies, but at <2.6σ confidence. For B7-A9 and G0-K5 stars, any variations in the observed 24μm excess emission over this age range are significant at less than 2σ confidence.