Debris Disks Around Nearby Stars with Circumstellar Gas

TL;DR

This study used the Spitzer Space Telescope to identify debris disks around nearby shell stars, revealing that nearly half of such stars host dust disks, and highlighting the importance of studying gas in these systems for understanding planet formation.

Contribution

First infrared survey of shell stars with Spitzer identifying new debris disk candidates and emphasizing the significance of gas in debris disks for planetary system evolution.

Findings

At least 48% of shell stars have debris disks.

Four new debris disk candidates identified.

The survey doubles the known systems for gas observation in debris disks.

Abstract

We conducted a survey for infrared excess emission from 16 nearby main sequence shell stars using the Multiband Imaging Photometer for Spitzer (MIPS) on the Spitzer Space Telescope. Shell stars are early-type stars with narrow absorption lines in their spectra that appear to arise from circumstellar (CS) gas. Four of the 16 stars in our survey showed excess emission at 24 microns and 70 microns characteristic of cool CS dust and are likely to be edge-on debris disks. Including previously known disks, it appears that the fraction of protoplanetary and debris disks among the main sequence shell stars is at least 48% +/- 14%. While dust in debris disks has been extensively studied, relatively little is known about their gas content. In the case of Beta Pictoris, extensive observations of gaseous species have provided insights into the dynamics of the CS material and surprises about the composition of the CS gas coming from young planetesimals (e.g. Roberge et al. 2006). To understand the co-evolution of gas and dust through the terrestrial planet formation phase, we need to study the gas in additional debris disks. The new debris disk candidates from this Spitzer survey double the number of systems in which the gas can be observed right now with sensitive line of sight absorption spectroscopy.