Carina OB Stars: X-ray Signatures of Wind Shocks and Magnetic Fields

Marc Gagne$^1$, Garrett Fehon$^1$, Michael R. Savoy$^1$, David H. Cohen$^2$, Leisa K. Townsley$^3$, Patrick S. Broos$^3$, Matthew S. Povich$^3$, Michael F. Corcoran$^4$, Nolan R. Walborn$^5$, Nancy Remage Evans$^6$, Anthony F.J. Moffat$^7$, Yael Naze$^8$ and Lida M. Oskinova$^9$

1 - Department of Geology and Astronomy, West Chester University, West Chester, PA 19383
2 - Department of Physics and Astronomy, Swarthmore College, Swarthmore, PA 19081
3 - Department of Astronomy & Astrophysics, 525 Davey Laboratory, Pennsylvania State University, University Park, PA 16802
4 - CRESST and X-ray Astrophysics Laboratory, NASA/GSFC, Greenbelt, MD 20771
5 - Space Telescope Science Institute, Baltimore, MD 21218
6 - Smithsonian Astrophysical Observatory, MS 4, 60 Garden St., Cambridge, MA 02138
7 - Departement de Physique, Universite de Montreal, Succursale Centre-Ville, Montr'eal, QC, H3C 3J7, Canada
8 - GAPHE, D'epartement AGO, Universit'e de Li`ege, Allee du 6 Aout 17, Bat. B5C, B4000-Liege, Belgium and Research Associate FRS-FNRS
9 - Institute for Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany

The Chandra Carina Complex contains 200 known O- and B type stars. The Chandra survey detected 68 of the 70 O stars and 61 of 127 known B0-B3 stars. We have assembled a publicly available optical/X-ray database to identify OB stars that depart from the canonical Lx/Lbol relation, or whose average X-ray temperatures exceed 1 keV. Among the single O stars with high kT we identify two candidate magnetically confined wind shock sources: Tr16-22, O8.5 V, and LS 1865, O8.5 V((f)). The O4 III(fc) star HD 93250 exhibits strong, hard, variable X-rays, suggesting it may be a massive binary with a period of >30 days. The visual O2 If* binary HD 93129A shows soft 0.6 keV and hard 1.9 keV emission components, suggesting embedded wind shocks close to the O2 If* Aa primary, and colliding wind shocks between Aa and Ab. Of the 11 known O-type spectroscopic binaries, the long orbital-period systems HD 93343, HD 93403 and QZ Car have higher shock temperatures than short-period systems such as HD 93205 and FO 15. Although the X-rays from most B stars may be produced in the coronae of unseen, low-mass pre-main-sequence companions, a dozen B stars with high Lx cannot be explained by a distribution of unseen companions. One of these, SS73 24 in the Treasure Chest cluster, is a new candidate Herbig Be star.

Reference: arXiv:1103.1149
Status: Manuscript has been accepted


Comments: be published in a special issue of the Astrophysical Journal Supplement on the Chandra Carina Complex Project to appear in May, 2011.