SIMBAD references

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 and 70 µm 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 β 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. To understand the coevolution 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.