Identification of a class of low-mass asymptotic giant branch stars struggling to become carbon stars in the Magellanic Clouds

Journal Article · Thu Sep 10 04:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/810/2/116· OSTI ID:22882691

Boyer, Martha L.; Sonneborn, George ^[1]; McDonald, Iain; Zijlstra, Albert ^[2]; Srinivasan, Sundar ^[3]; Loon, Jacco Th. van ^[4]; Olsen, Knut A. G., ^[5]

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1. Observational Cosmology Lab, Code 665, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
2. Jodrell Bank Centre for Astrophysics, Alan Turing Building, University of Manchester, M13 9PL (United Kingdom)
3. Institute for Astronomy and Astrophysics, Academia Sinica, 11F, Astronomy-Mathematics Building, No. 1, Roosevelt Rd., Sec 4, Taipei 10617, Taiwan (China)
4. Lennard-Jones Laboratories, Keele University, Staffordshire ST5 5BG (United Kingdom)
5. National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)

We have identified a new class of Asymptotic Giant Branch (AGB) stars in the Small and Large Magellanic Clouds (SMC/LMC) using optical to infrared photometry, light curves, and optical spectroscopy. The strong dust production and long-period pulsations of these stars indicate that they are at the very end of their AGB evolution. Period–mass–radius relations for the fundamental-mode pulsators give median current stellar masses of 1.14M{sub ⊙} in the LMC and 0.94M{sub ⊙} in the SMC (with dispersions of 0.21 and 0.18 M{sub ⊙}, respectively), and models suggest initial masses of <1.5 M{sub ⊙} and <1.25 M{sub ⊙}, respectively. This new class of stars includes both O-rich and C-rich chemistries, placing the limit where dredge-up allows carbon star production below these masses. A high fraction of the brightest among them should show S star characteristics indicative of atmospheric C/O ≈ 1, and many will form O-rich dust prior to their C-rich phase. These stars can be separated from their less-evolved counterparts by their characteristically red J−[8] colors.

• OSTI ID: 22882691
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 810; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CARBON STARS
COSMIC DUST
DISPERSIONS
MAGELLANIC CLOUDS
MASS
PHOTOMETRY
SPECTROSCOPY
STELLAR WINDS