@article{GagneFehonSavoyetal.2011, author = {Gagne, Marc and Fehon, Garrett and Savoy, Michael R. and Cohen, David H. and Townsley, Leisa K. and Broos, Patrick S. and Povich, Matthew S. and Corcoran, Michael F. and Walborn, Nolan R. and Evans, Nancy Remage and Moffat, Anthony F. J. and Naze, Yael and Oskinova, Lida}, title = {Carina ob stars: x-ray signatures of wind shocks and magnetic FIELDS}, 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 = {10.1088/0067-0049/194/1/5}, pages = {26}, year = {2011}, abstract = {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 L-X/L-bol 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 that 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 L-X 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.}, 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{CorcoranNicholsPabloetal.2015, author = {Corcoran, Michael F. and Nichols, Joy S. and Pablo, Herbert and Shenar, Tomer and Pollock, Andy M. T. and Waldron, Wayne L. and Moffat, Anthony F. J. and Richardson, Noel D. and Russell, Christopher M. P. and Hamaguchi, Kenji and Huenemoerder, David P. and Oskinova, Lida and Hamann, Wolf-Rainer and Naze, Yael and Ignace, Richard and Evans, Nancy Remage and Lomax, Jamie R. and Hoffman, Jennifer L. and Gayley, Kenneth and Owocki, Stanley P. and Leutenegger, Maurice and Gull, Theodore R. and Hole, Karen Tabetha and Lauer, Jennifer and Iping, Rosina C.}, title = {A coordinated X-Ray and optical campaign of the nearest massive eclipsing binary, delta ORIONIS Aa. I. Overview of thr X-Ray spectrum}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {809}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/809/2/132}, pages = {15}, year = {2015}, abstract = {We present an overview of four deep phase-constrained Chandra HETGS X-ray observations of delta Ori A. Delta Ori A is actually a triple system that includes the nearest massive eclipsing spectroscopic binary, delta Ori Aa, the only such object that can be observed with little phase-smearing with the Chandra gratings. Since the fainter star, delta Ori Aa2, has a much lower X-ray luminosity than the brighter primary (delta Ori Aa1), delta Ori Aa provides a unique system with which to test the spatial distribution of the X-ray emitting gas around delta Ori Aa1 via occultation by the photosphere of, and wind cavity around, the X-ray dark secondary. Here we discuss the X-ray spectrum and X-ray line profiles for the combined observation, having an exposure time of nearly 500 ks and covering nearly the entire binary orbit. The companion papers discuss the X-ray variability seen in the Chandra spectra, present new space-based photometry and ground-based radial velocities obtained simultaneously with the X-ray data to better constrain the system parameters, and model the effects of X-rays on the optical and UV spectra. We find that the X-ray emission is dominated by embedded wind shock emission from star Aa1, with little contribution from the tertiary star Ab or the shocked gas produced by the collision of the wind of Aa1 against the surface of Aa2. We find a similar temperature distribution to previous X-ray spectrum analyses. We also show that the line half-widths are about 0.3-0.5 times the terminal velocity of the wind of star Aa1. We find a strong anti-correlation between line widths and the line excitation energy, which suggests that longer-wavelength, lower-temperature lines form farther out in the wind. Our analysis also indicates that the ratio of the intensities of the strong and weak lines of Fe XVII and Ne X are inconsistent with model predictions, which may be an effect of resonance scattering.}, language = {en} } @article{PabloRichardsonMoffatetal.2015, author = {Pablo, Herbert and Richardson, Noel D. and Moffat, Anthony F. J. and Corcoran, Michael and Shenar, Tomer and Benvenuto, Omar and Fuller, Jim and Naze, Yael and Hoffman, Jennifer L. and Miroshnichenko, Anatoly and Apellaniz, Jesus Maiz and Evans, Nancy and Eversberg, Thomas and Gayley, Ken and Gull, Ted and Hamaguchi, Kenji and Hamann, Wolf-Rainer and Henrichs, Huib and Hole, Tabetha and Ignace, Richard and Iping, Rosina and Lauer, Jennifer and Leutenegger, Maurice and Lomax, Jamie and Nichols, Joy and Oskinova, Lida and Owocki, Stan and Pollock, Andy and Russell, Christopher M. P. and Waldron, Wayne and Buil, Christian and Garrel, Thierry and Graham, Keith and Heathcote, Bernard and Lemoult, Thierry and Li, Dong and Mauclaire, Benjamin and Potter, Mike and Ribeiro, Jose and Matthews, Jaymie and Cameron, Chris and Guenther, David and Kuschnig, Rainer and Rowe, Jason and Rucinski, Slavek and Sasselov, Dimitar and Weiss, Werner}, title = {A coordinated X-Ray and optical campaign of the nearest massive eclipsing binary, delta ORIONIS Aa. III. Analysis of optical photometric (most) and spectroscopic (ground based) variations}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {809}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/809/2/134}, pages = {11}, year = {2015}, abstract = {We report on both high-precision photometry from the Microvariability and Oscillations of Stars (MOST) space telescope and ground-based spectroscopy of the triple system delta Ori A, consisting of a binary O9.5II+early-B (Aa1 and Aa2) with P = 5.7 days, and a more distant tertiary (O9 IV P > 400 years). This data was collected in concert with X-ray spectroscopy from the Chandra X-ray Observatory. Thanks to continuous coverage for three weeks, the MOST light curve reveals clear eclipses between Aa1 and Aa2 for the first time in non-phased data. From the spectroscopy, we have a well-constrained radial velocity (RV) curve of Aa1. While we are unable to recover RV variations of the secondary star, we are able to constrain several fundamental parameters of this system and determine an approximate mass of the primary using apsidal motion. We also detected second order modulations at 12 separate frequencies with spacings indicative of tidally influenced oscillations. These spacings have never been seen in a massive binary, making this system one of only a handful of such binaries that show evidence for tidally induced pulsations.}, language = {en} } @article{ShenarOskinovaHamannetal.2015, author = {Shenar, Tomer and Oskinova, Lida and Hamann, Wolf-Rainer and Corcoran, Michael F. and Moffat, Anthony F. J. and Pablo, Herbert and Richardson, Noel D. and Waldron, Wayne L. and Huenemoerder, David P. and Maiz Apellaniz, Jesus and Nichols, Joy S. and Todt, Helge Tobias and Naze, Yael and Hoffman, Jennifer L. and Pollock, Andy M. T. and Negueruela, Ignacio}, title = {A coordinated X-Ray and optical campaign of the nearest massive eclipsing binary, delta ORIONIS Aa. IV. A multiwavelength, non-lte spectroscopic analysis}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {809}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/809/2/135}, pages = {20}, year = {2015}, abstract = {Eclipsing systems of massive stars allow one to explore the properties of their components in great detail. We perform a multi-wavelength, non-LTE analysis of the three components of the massive multiple system delta Ori A, focusing on the fundamental stellar properties, stellar winds, and X-ray characteristics of the system. The primary's distance-independent parameters turn out to be characteristic for its spectral type (O9.5 II), but usage of the Hipparcos parallax yields surprisingly low values for the mass, radius, and luminosity. Consistent values follow only if delta Ori lies at about twice the Hipparcos distance, in the vicinity of the sigma-Orionis cluster. The primary and tertiary dominate the spectrum and leave the secondary only marginally detectable. We estimate the V-band magnitude difference between primary and secondary to be Delta V approximate to 2.(m)8. The inferred parameters suggest that the secondary is an early B-type dwarf (approximate to B1 V), while the tertiary is an early B-type subgiant (approximate to B0 IV). We find evidence for rapid turbulent velocities (similar to 200 km s(-1)) and wind inhomogeneities, partially optically thick, in the primary's wind. The bulk of the X-ray emission likely emerges from the primary's stellar wind (logL(X)/L-Bol approximate to -6.85), initiating close to the stellar surface at R-0 similar to 1.1 R-*. Accounting for clumping, the mass-loss rate of the primary is found to be log (M) over dot approximate to -6.4 (M-circle dot yr(-1))., which agrees with hydrodynamic predictions, and provides a consistent picture along the X-ray, UV, optical, and radio spectral domains.}, language = {en} }