@article{TownsleyBroosCorcoranetal.2011, author = {Townsley, Leisa K. and Broos, Patrick S. and Corcoran, Michael F. and Feigelson, Eric D. and Gagne, Marc and Montmerle, Thierry and Oey, M. S. and Smith, Nathan and Garmire, Gordon P. and Getman, Konstantin V. and Povich, Matthew S. and Evans, Nancy Remage and Naze, Yael and Parkin, E. R. and Preibisch, Thomas and Wang, Junfeng and Wou, Scott J. and Chu, You-Hua and Cohen, David H. and Gruendl, Robert A. and Hamaguchi, Kenji and King, Robert R. and Mac Low, Mordecai-Mark and McCaughrean, Mark J. and Moffat, Anthony F. J. and Oskinova, Lida and Pittard, Julian M. and Stassun, Keivan G. and Ud-Doula, Asif and Walborn, Nolan R. and Waldron, Wayne L. and Churchwell, Ed and Nictiols, J. S. and Owocki, Stanley P. and Schulz, Norbert S.}, title = {An introduction to the chandra carina complex project}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics ; Supplement series}, volume = {194}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics ; Supplement series}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0067-0049}, doi = {10.1088/0067-0049/194/1/1}, pages = {28}, year = {2011}, abstract = {The Great Nebula in Carina provides an exceptional view into the violent massive star formation and feedback that typifies giant H II regions and starburst galaxies. We have mapped the Carina star-forming complex in X-rays, using archival Chandra data and a mosaic of 20 new 60 ks pointings using the Chandra X-ray Observatory's Advanced CCD Imaging Spectrometer, as a testbed for understanding recent and ongoing star formation and to probe Carina's regions of bright diffuse X-ray emission. This study has yielded a catalog of properties of > 14,000 X-ray point sources;> 9800 of them have multiwavelength counterparts. Using Chandra's unsurpassed X-ray spatial resolution, we have separated these point sources from the extensive, spatially-complex diffuse emission that pervades the region; X-ray properties of this diffuse emission suggest that it traces feedback from Carina's massive stars. In this introductory paper, we motivate the survey design, describe the Chandra observations, and present some simple results, providing a foundation for the 15 papers that follow in this special issue and that present detailed catalogs, methods, and science results.}, language = {en} } @article{ParkinBroosTownsleyetal.2011, author = {Parkin, E. R. and Broos, Patrick S. and Townsley, L. K. and Pittard, J. M. and Moffat, Anthony F. J. and Naze, Y. and Rauw, G. and Oskinova, Lida and Waldron, W. L.}, title = {X-RAY EMISSION FROM THE DOUBLE-BINARY OB-STAR SYSTEM QZ CAR (HD 93206)}, series = {ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES}, volume = {194}, journal = {ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES}, number = {1}, publisher = {IOP PUBLISHING LTD}, address = {BRISTOL}, issn = {0067-0049}, doi = {10.1088/0067-0049/194/1/8}, pages = {11}, year = {2011}, abstract = {X-ray observations of the double-binary OB-star system QZ Car (HD 93206) obtained with the Chandra X-ray Observatory over a period of roughly 2 years are presented. The respective orbits of systems A (O9.7 I+b2 v, P-A = 21 days) and B (O8 III+o9 v, P-B = 6 days) are reasonably well sampled by the observations, allowing the origin of the X-ray emission to be examined in detail. The X-ray spectra can be well fitted by an attenuated three-temperature thermal plasma model, characterized by cool, moderate, and hot plasma components at kT similar or equal to 0.2, 0.7, and 2 keV, respectively, and a circumstellar absorption of similar or equal to 0.2 x 10(22) cm(-2). Although the hot plasma component could be indicating the presence of wind-wind collision shocks in the system, the model fluxes calculated from spectral fits, with an average value of similar or equal to 7x10(-13) erg s(-1) cm(-2), do not show a clear correlation with the orbits of the two constituent binaries. A semi-analytical model of QZ Car reveals that a stable momentum balance may not be established in either system A or B. Yet, despite this, system B is expected to produce an observed X-ray flux well in excess of the observations. If one considers the wind of the O8 III star to be disrupted by mass transfer, the model and observations are in far better agreement, which lends support to the previous suggestion of mass transfer in the O8 III+o9 v binary. We conclude that the X-ray emission from QZ Car can be reasonably well accounted for by a combination of contributions mainly from the single stars and the mutual wind-wind collision between systems A and B.}, language = {en} } @article{NazeBroosOskinovaetal.2011, author = {Naze, Y. and Broos, Patrick S. and Oskinova, Lida and Townsley, L. K. and Cohen, David H. and Corcoran, M. F. and Evans, N. R. and Gagne, M. and Moffat, Anthony F. J. and Pittard, J. M. and Rauw, G. and Ud-Doula, A. and Walborn, N. R.}, title = {GLOBAL X-RAY PROPERTIES OF THE O AND B STARS IN CARINA}, series = {ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES}, volume = {194}, journal = {ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES}, number = {1}, publisher = {IOP PUBLISHING LTD}, address = {BRISTOL}, issn = {0067-0049}, doi = {10.1088/0067-0049/194/1/7}, pages = {20}, year = {2011}, abstract = {The key empirical property of the X-ray emission from O stars is a strong correlation between the bolometric and X-ray luminosities. In the framework of the Chandra Carina Complex Project, 129 O and B stars have been detected as X-ray sources; 78 of those, all with spectral type earlier than B3, have enough counts for at least a rough X-ray spectral characterization. This leads to an estimate of the L-X-L-BOL ratio for an exceptional number of 60 O stars belonging to the same region and triples the number of Carina massive stars studied spectroscopically in X-rays. The derived log(L-X/L-BOL) is -7.26 for single objects, with a dispersion of only 0.21 dex. Using the properties of hot massive stars listed in the literature, we compare the X-ray luminosities of different types of objects. In the case of O stars, the L-X-L-BOL ratios are similar for bright and faint objects, as well as for stars of different luminosity classes or spectral types. Binaries appear only slightly harder and slightly more luminous in X-rays than single objects; the differences are not formally significant (at the 1\% level), except for the L-X-L-BOL ratio in the medium (1.0-2.5 keV) energy band. Weak-wind objects have similar X-ray luminosities but they display slightly softer spectra compared with "normal" O stars with the same bolometric luminosity. Discarding three overluminous objects, we find a very shallow trend of harder emission in brighter objects. The properties of the few B stars bright enough to yield some spectral information appear to be different overall (constant X-ray luminosities, harder spectra), hinting that another mechanism for producing X-rays, besides wind shocks, might be at work. However, it must be stressed that the earliest and X-ray brightest among these few detected objects are similar to the latest O stars, suggesting a possibly smooth transition between the two processes.}, language = {en} } @article{EvansDeGioiaEastwoodGagneetal.2011, author = {Evans, Nancy Remage and DeGioia-Eastwood, Kathleen and Gagne, Marc and Townsley, Leisa and Broos, Patrick S. and Wolk, Scott J. and Naze, Yael and Corcoran, Michael and Oskinova, Lida and Moffat, Anthony F. J. and Wang, Junfeng and Walborn, Nolan R.}, title = {The search for low-mass companions of b stars in the Carina Nebula cluster trumpler 16}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics ; Supplement series}, volume = {194}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics ; Supplement series}, number = {1}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0067-0049}, doi = {10.1088/0067-0049/194/1/13}, pages = {9}, year = {2011}, abstract = {We have developed lists of likely B3-A0 stars (called "late B" stars) in the young cluster Trumpler 16. The following criteria were used: location within 3' of eta Car, an appropriate V and B - V combination, and proper motion (where available). Color and magnitude cuts have been made assuming an E(B - V) = 0.55 mag +/- 0.1, which is a good approximation close to the center of Trumpler 16. These lists have been cross-correlated with X-ray sources found in the Chandra Carina Complex Project. Previous studies have shown that only very rarely (if at all) do late main-sequence B stars produce X-rays. We present evidence that the X-ray-detected sources are binaries with low-mass companions, since stars less massive than 1.4 M-circle dot are strong X-ray sources at the age of the cluster. Both the median X-ray energies and X-ray luminosities of these sources are in good agreement with values for typical low-mass coronal X-ray sources. We find that 39\% of the late B stars based on a list with proper motions have low-mass companions. Similarly, 32\% of a sample without proper motions have low-mass companions. We discuss the X-ray detection completeness. These results on low-mass companions of intermediate-mass stars are complementary to spectroscopic and interferometric results and probe new parameter space of low-mass companions at all separations. They do not support a steeply rising distribution of mass ratios to low masses for intermediate-mass (5 M-circle dot) primaries, such as would be found by random pairing from the initial mass function.}, language = {en} } @article{OskinovaTodtIgnaceetal.2011, author = {Oskinova, Lida and Todt, Helge Tobias and Ignace, Richard and Brown, John C. and Cassinelli, Joseph P. and Hamann, Wolf-Rainer}, title = {Early magnetic B-type stars X-ray emission and wind properties}, series = {Monthly notices of the Royal Astronomical Society}, volume = {416}, journal = {Monthly notices of the Royal Astronomical Society}, number = {2}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0035-8711}, doi = {10.1111/j.1365-2966.2011.19143.x}, pages = {1456 -- 1474}, year = {2011}, abstract = {We present a comprehensive study of X-ray emission by, and wind properties of, massive magnetic early B-type stars. Dedicated XMM-Newton observations were obtained for three early-type B-type stars, xi(1) CMa, V2052 Oph and zeta Cas, with recently discovered magnetic fields. We report the first detection of X-ray emission from V2052 Oph and zeta Cas. The latter is one the softest X-ray sources among the early-type stars, while the former is one of the X-ray faintest. The observations show that the X-ray spectra of our programme stars are quite soft with the bulk of X-ray emitting material having a temperature of about 1 MK. We compile the complete sample of early B-type stars with detected magnetic fields to date and existing X-ray measurements, in order to study whether the X-ray emission can be used as a general proxy for stellar magnetism. We find that the X-ray properties of early massive B-type magnetic stars are diverse, and that hard and strong X-ray emission does not necessarily correlate with the presence of a magnetic field, corroborating similar conclusions reached earlier for the classical chemically peculiar magnetic Bp-Ap stars. We analyse the ultraviolet (UV) spectra of five non-supergiant B stars with magnetic fields (tau Sco, beta Cep, xi(1) CMa, V2052 Oph and zeta Cas) by means of non-local thermodynamic equilibrium (non-LTE) iron-blanketed model atmospheres. The latter are calculated with the Potsdam Wolf-Rayet (PoWR) code, which treats the photosphere as well as the wind, and also accounts for X-rays. With the exception of t Sco, this is the first analysis of these stars by means of stellar wind models. Our models accurately fit the stellar photospheric spectra in the optical and the UV. The parameters of X-ray emission, temperature and flux are included in the model in accordance with observations. We confirm the earlier findings that the filling factors of X-ray emitting material are very high. Our analysis reveals that the magnetic early-type B stars studied here have weak winds with velocities not significantly exceeding upsilon(esc). The mass-loss rates inferred from the analysis of UV lines are significantly lower than predicted by hydrodynamically consistent models. We find that, although the X-rays strongly affect the ionization structure of the wind, this effect is not sufficient in reducing the total radiative acceleration. When the X-rays are accounted for at the intensity and temperatures observed, there is still sufficient radiative acceleration to drive a stronger mass-loss than we empirically infer from the UV spectral lines.}, language = {en} }