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SPITZER SAGE-Spec: NEAR INFRARED SPECTROSCOPY, DUST SHELLS, AND COOL ENVELOPES IN EXTREME LARGE MAGELLANIC CLOUD ASYMPTOTIC GIANT BRANCH STARS
Ist Teil von
The Astronomical journal, 2014-11, Vol.148 (5), p.1-15
Ort / Verlag
United States
Erscheinungsjahr
2014
Link zum Volltext
Quelle
EZB Electronic Journals Library
Beschreibungen/Notizen
K-band spectra are presented for a sample of 39 Spitzer Infrared Spectrograph (IRS) SAGE-Spec sources in the Large Magellanic Cloud. The spectra exhibit characteristics in very good agreement with their positions in the near-infrared-Spitzer color-magnitude diagrams and their properties as deduced from the Spitzer IRS spectra. Specifically, the near-infrared spectra show strong atomic and molecular features representative of oxygen-rich and carbon-rich asymptotic giant branch stars, respectively. A small subset of stars was chosen from the luminous and red extreme "tip" of the color-magnitude diagram. These objects have properties consistent with dusty envelopes but also cool, carbon-rich "stellar" cores. Modest amounts of dust mass loss combine with the stellar spectral energy distribution to make these objects appear extreme in their near-infrared and mid-infrared colors. One object in our sample, HV 915, a known post-asymptotic giant branch star of the RV Tau type, exhibits CO 2.3 mu m band head emission consistent with previous work that demonstrates that the object has a circumstellar disk.