Chandra Observations of Associates of η Carinae. II. Spectra

• Published in: The Astrophysical journal 2004-09, Vol.612 (2), p.1065-1080
• Main Authors: Evans, Nancy Remage, Schlegel, Eric M, Waldron, Wayne L, Seward, Frederick D, Krauss, Miriam I, Nichols, Joy, Wolk, Scott J
• Format: Article
• Language: English
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; Pre-main sequence objects, young stellar objects (yso's) and protostars (t tauri stars, orion population, herbig-haro objects, bok globules, bipolar outflows, cometary nebulae, etc.); Stars
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/422543

The low-resolution X-ray spectra around eta Car covering Trumpler 16 and part of Trumpler 14 have been extracted from a Chandra CCD ACIS image. Various analysis techniques have been applied to the spectra based on their count rates. The spectra with the greatest number of counts (HD 93162 = WR 25, HD 93129 AB, and HD 93250) have been fitted with a wind model, which uses several components with different temperatures and depths in the wind. Weaker spectra have been fitted with Raymond-Smith models. The weakest spectra are simply intercompared with strong spectra. In general, fits produce reasonable parameters based on knowledge of the extinction from optical studies and on the range of temperatures for high- and low-mass stars. Direct comparisons of spectra confirm the consistency of the fitting results and also hardness ratios for cases of unusually large extinction in the clusters. The spectra of the low- mass stars are harder than the more massive stars. Stars in the sequence evolving from the main sequence (HD 93250) through the system containing the O supergiant (HD 93129 AB) and then through the Wolf-Rayet stage (HD 93162), presumably ending in the extreme example of eta Car, share the property of being unusually luminous and hard in X-rays. For these X-ray-luminous stars, their high mass and evolutionary status (from the very last stages of the main sequence and beyond) is the common feature. Their binary status is mixed, and their magnetic status is still uncertain.