THE INFRARED SPECTRAL PROPERTIES OF MAGELLANIC CARBON STARS
- Cornell Center for Astrophysics and Planetary Science, Cornell Univ., Ithaca, NY 14853-6801 (United States)
- Institute for Scientific Research, Boston College, 140 Commonwealth Avenue, Chestnut Hill, MA 02467 (United States)
- Jodrell Bank Centre for Astrophysics, Univ. of Manchester, Manchester M13 9PL (United Kingdom)
- Koninklijke Sterrenwacht van België, Ringlaan 3, B-1180 Brussels (Belgium)
- Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia)
- Observatoire de la Côte d’Azur, F-06300, Nice (France)
- CRESST and Observational Cosmology Lab, Code 665, NASA Goddard Space Flight Center, Greenbelt, MD, 20771 (United States)
- Academia Sinica, Institute of Astronomy and Astrophysics, 11F Astronomy-Mathematics Building, NTU/AS, No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan, R.O.C. (China)
- School of Physics and Astronomy, Cardiff University, Queen’s Buildings, The Parade, Cardiff, CF24 3AA (United Kingdom)
- Jet Propulsion Laboratory, California Institute of Technology, MS 183-900, Pasadena, CA 91109 (United States)
- Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States)
- Lennard Jones Laboratories, Keele University, Staffordshire ST5 5BG (United Kingdom)
The Infrared Spectrograph on the Spitzer Space Telescope observed 184 carbon stars in the Magellanic Clouds. This sample reveals that the dust-production rate (DPR) from carbon stars generally increases with the pulsation period of the star. The composition of the dust grains follows two condensation sequences, with more SiC condensing before amorphous carbon in metal-rich stars, and the order reversed in metal-poor stars. MgS dust condenses in optically thicker dust shells, and its condensation is delayed in more metal-poor stars. Metal-poor carbon stars also tend to have stronger absorption from C{sub 2}H{sub 2} at 7.5 μ m. The relation between DPR and pulsation period shows significant apparent scatter, which results from the initial mass of the star, with more massive stars occupying a sequence parallel to lower-mass stars, but shifted to longer periods. Accounting for differences in the mass distribution between the carbon stars observed in the Small and Large Magellanic Clouds reveals a hint of a subtle decrease in the DPR at lower metallicities, but it is not statistically significant. The most deeply embedded carbon stars have lower variability amplitudes and show SiC in absorption. In some cases they have bluer colors at shorter wavelengths, suggesting that the central star is becoming visible. These deeply embedded stars may be evolving off of the asymptotic giant branch and/or they may have non-spherical dust geometries.
- OSTI ID:
- 22666065
- Journal Information:
- Astrophysical Journal, Vol. 826, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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