Astro Lunch Talks
Wednesdays, 11:45am-1:00pm, 76-1275 Carlson Learning Center.
Topics will be emailed prior to the talk. Please contact Ben Sargent for more information.
Date/Time: April 16th, 12:30pm 76-1275
Speakers: Valerie Rapson
Title: A Spitzer and Herschel Study of the Protoplanetary Disk Around the Young Nearby System V4046 Sgr
Abstract: We present results from a spectroscopic Spitzer and Herschel mid-to-far-infrared study of the circumbinary disk orbiting V4046 Sgr. V4046 Sgr is a ~12 Myr-old spectroscopic binary that is still surrounded by, and is actively accreting from, a gaseous protoplanetary disk. The disk’s apparent longevity may be evidence for ongoing planet formation, or could be due to the influence of a distant tertiary (stellar) component. We report detections of emission lines of Ne II, Ar II, H2 and HCN in the Spitzer spectrum, as well as tentative detections of H2O and OH. The Herschel spectrum reveals emission from O I, OH, and, tentatively, high-J transitions of CO. Modeling of the silicate dust grains reveals that the inner disk is composed mainly of large amorphous pyroxine and olivine grains (85% by mass) and a small amount of crystalline silicates (15% by mass). These results are consistent with other lines of evidence indicating that planet building is ongoing in regions of the disk within ~30 AU of the central, close binary. We compare these results for V4046 Sgr to those for TW Hya, whose disk is similarly evolved but apparently orbits a single star. Combined with our previous and ongoing X-ray and radio studies of the V4046 Sgr system, the Spitzer and Herschel results will shed much-needed light on protoplanetary disk dissipation and planet formation processes in close binary systems.
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