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Debris disks in the nearest OB association

Chen, C (STScI)
Monday 09 November 2009, 12:20-12:40



We have obtained Spitzer Space Telescope Multiband Imaging Photometer for Spitzer (MIPS) 24 micron and 70 micron photometry and high spectral resolution Magellan MIKE visual spectra (3500-9500 A; R~50,000) of 113 nearby (within 150 pc from the sun), Hipparcos F- and G-type common proper motion members of the nearest OB association, Scorpius-Centaurus. We measure 24 micron disk fractions of 6/18 (33% +/- 14%), 19/49 (39% +/- 9%), and 8/46 (17% +/- 6%) for Upper Scorpius (~5 Myr), Lower Centaurus Crux (~16 Myr), and Upper Centaurus Lupus (~17 Myr), respectively. The magnitude of these excesses (up to 200 times the predicted photospheric flux) is comparable to that expected to be generated by parent bodies at distances similar to the Jovian planets during the epoch of terrestrial planet formation, consistent with the models of Kenyon & Bromley. Since young solar-like stars are expected to possess strong stellar winds, we searched for an anti-correlation between disk fractional infrared luminosity, LIR/L*, and (1) stellar fractional x-ray luminosity, LX/L*, (2) stellar rotational velocity, v sin i, and (3) the calcium activity index, R'HK, to determine whether stellar wind drag is an important grain removal mechanism. We find evidence suggesting that stellar wind drag may play an important role in grain dynamics around 5-20 Myr old solar-like stars.

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