Hot Inner Gas Disks Around A-type Stars
Abstract
Since the IRAS discovery of Vega's large thermal infrared excess over the expected photospheric flux, dust disks have been found around a large fraction of main-sequence A-type stars. With the detection of gas giant planets orbiting Alpha PsA, Beta Pic, and HR 8799, we now have evidence that A-type stars can host planetary systems. While dust in A-type star debris disks has been studied extensively with Spitzer, relatively little is known about their connection with circumstellar gas. Circumstellar gas is often observed in debris disk systems, but it is also observed in many A-type stars without debris disks. We have used high-resolution optical and ultraviolet absorption spectroscopy to detect circumstellar gas around nearby A-type stars, but there are still many unanswered questions. What is the origin of the observed circumstellar gas? Is it a gas disk or a gas shell (or both)? Is the gas a remnant of star formation? In the spectra of some A-type dwarfs, three Ti II transitions (3685, 3759, 3761 Å) sometimes appear as narrow absorption lines. These Ti II lines can be used as an additional diagnostics for the origin of the hot inner gas.
- Publication:
-
American Astronomical Society Meeting Abstracts #217
- Pub Date:
- January 2011
- Bibcode:
- 2011AAS...21733920C