GALACTIC CEPHEIDS WITH SPITZER. II. SEARCH FOR EXTENDED INFRARED EMISSION
- Department of Physics and Astronomy, University of Western Ontario, London, Ontario N6A 3K7 (Canada)
- Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States)
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
- Department of Physics, Universita di Roma Tor Vergata, via della Ricerca Scientifica 1, I-00133 Roma (Italy)
- Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States)
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1 (Canada)
A deep and detailed examination of 29 classical Cepheids with the Spitzer Space Telescope has revealed three stars with strong nearby extended emission detected in multiple bands which appears to be physically associated with the stars. RS Pup was already known to possess extended infrared emission, while the extended emission around the other two stars (S Mus and {delta} Cep) is newly discovered in our observations. Four other stars (GH Lup, l Car, T Mon, and X Cyg) show tentative evidence for extended infrared emission. An unusual elongated extended object next to SZ Tau appears to be a background or foreground object in a chance alignment with the Cepheid. The inferred mass-loss rate upper limits for S Mus and {delta} Cep are in the range from 10{sup -9} to 10{sup -8} M{sub sun} yr{sup -1}, with the upper limit for RS Pup as high as 10{sup -6} M{sub sun} yr{sup -1}. Mass loss during post-main-sequence evolution has been proposed as a resolution to the discrepancy between pulsational and dynamical masses of Cepheid variable stars: dust in the lost material would make itself known by the presence of an infrared bright nebula or unresolved infrared excess. The observed frequency of infrared circumstellar emission (<24%) and the mass-loss rate we estimate for our sources show that dusty mass loss can only account for part of the Cepheid mass-loss discrepancy. Nevertheless, our direct evidence that mass loss is active during the Cepheid phase is an important confirmation that these processes need to be included in evolutionary and pulsation models of these stars and should be taken into account in the calibration of the Cepheid distance scale.
- OSTI ID:
- 21583259
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 141, Issue 2; Other Information: DOI: 10.1088/0004-6256/141/2/42; ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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