New Light on Young Stars:
Spitzer's View of Circumstellar Disks

Debris Disks Among the Shell Stars: Insights from Spitzer

First Author:
Aki Roberge
Email: Aki.Roberge AT nasa.gov
NASA GSFC
Code 667
Greenbelt MD 20881 USA

Abstract

Shell stars are a class of early-type stars with narrow absorption lines in their spectra that appear to arise from circumstellar gas. This observationally defined class contains a variety of objects, including evolved stars and classical Be stars. However, some of the main sequence shell stars harbor debris disks and younger protoplanetary disks, though this aspect of the class has been largely overlooked. We surveyed a set of main sequence shell stars for cool dust using Spitzer MIPS and found four additional systems with IR excesses at both 24 and 70 microns. This indicates that the stars have both circumstellar gas and dust, and are likely to be edge-on debris disks. Our estimate of the disk fraction among nearby main sequence shell stars is 48% +/- 14%. We here discuss the nature of the shell stars and present preliminary results from ground-based optical spectroscopy of the survey target stars. We will also outline our planned studies aimed at further characterization of the shell star class.