AAS 203rd Meeting, January 2004
Session 127 Variations in Stars
Oral, Thursday, January 8, 2004, 10:00-11:30am, Regency VI

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[127.01] Infrared Absorption By Carbon Monoxide in R CrB Type Stars

E. Tenenbaum (Pomona Coll.& Maria Mitchell Obs.), G.C. Clayton (Louisiana State U. & Maria Mitchell Obs.), C. Englebracht (Steward Obs.), M. Asplund (Mt. Stromlo Obs.)

R Coronae Borealis (RCB) type stars experience massive irregular declines caused by circumstellar dust formation. The dust formation mechanism remains a mystery, and it has been proposed that CO molecules play a cooling role in the dust formation process. The detection of the CO first vibrational overtone (\Delta v=2) absorption band in RCB spectra was first reported by Clayton in 1999. We report on the first attempt to analyze the CO \Deltav=2 band in a large survey of RCB stars. Low-resolution IR spectra of 10 RCB stars, obtained with FSpec on the 90" telescope at Steward Observatory, were analyzed for the presence and, if applicable, equivalent widths of CO \Delta v=2 absorption lines. Effective temperatures of the ten stars range from 3500 to 20000 K. We compared the spectra to line-blanketed model spectra of RCB stars. As predicted by the model, the CO bands are strongest in the coolest RCB stars. No correlation was found between the presence of CO bands and lightcurve declines. This project was supported by the NSF/REU grant AST-0097694 and the Nantucket Maria Mitchell Association.

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.