TY - JOUR A1 - Gagne, Marc A1 - Fehon, Garrett A1 - Savoy, Michael R. A1 - Cohen, David H. A1 - Townsley, Leisa K. A1 - Broos, Patrick S. A1 - Povich, Matthew S. A1 - Corcoran, Michael F. A1 - Walborn, Nolan R. A1 - Evans, Nancy Remage A1 - Moffat, Anthony F. J. A1 - Naze, Yael A1 - Oskinova, Lida T1 - Carina ob stars: x-ray signatures of wind shocks and magnetic FIELDS JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Supplement series N2 - 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. KW - open clusters and associations: individual (Cl Bochum 10, Cl Bochum 11, Cl Collinder 228, Cl Trumpler 14, Cl Trumpler 15, Cl Trumpler 16) KW - stars: early-type KW - stars: individual (HD 93250, HD 93129A, HD 93403, HD 93205, HD 93343, QZ Car, SS73 24, FO 15, Cl Trumpler 16 22, CPD-59 2610, HD 93501) KW - X-rays: stars Y1 - 2011 U6 - https://doi.org/10.1088/0067-0049/194/1/5 SN - 0067-0049 VL - 194 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Hubrig, Swetlana A1 - Oskinova, Lida A1 - Schoeller, M. T1 - First detection of a magnetic field in the fast rotating runaway Oe star zeta Ophiuchi JF - Astronomische Nachrichten = Astronomical notes N2 - The star zeta Ophiuchi is one of the brightest massive stars in the northern hemisphere and was intensively studied in various wavelength domains. The currently available observational material suggests that certain observed phenomena are related to the presence of a magnetic field. We acquired spectropolarimetric observations of zeta Oph with FORS 1 mounted on the 8-m Kueyen telescope of the VLT to investigate if a magnetic field is indeed present in this star. Using all available absorption lines, we detect a mean longitudinal magnetic field < B(z)>(all) = 141 +/- 45 G, confirming the magnetic nature of this star. We review the X-ray properties of zeta Oph with the aim to understand whether the X-ray emission of zeta Oph is dominated by magnetic or by wind instability processes. KW - stars: mass-loss KW - stars: early-type KW - stars: magnetic field KW - stars: kinematics and dynamics KW - X-rays: stars KW - stars: individual: zeta Ophiuchi Y1 - 2011 U6 - https://doi.org/10.1002/asna.201111516 SN - 0004-6337 VL - 332 IS - 2 SP - 147 EP - 152 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Parkin, E. R. A1 - Broos, Patrick S. A1 - Townsley, L. K. A1 - Pittard, J. M. A1 - Moffat, Anthony F. J. A1 - Naze, Y. A1 - Rauw, G. A1 - Oskinova, Lida A1 - Waldron, W. L. T1 - X-RAY EMISSION FROM THE DOUBLE-BINARY OB-STAR SYSTEM QZ CAR (HD 93206) JF - ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES N2 - 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. KW - hydrodynamics KW - stars: early-type KW - stars: individual (QZ Carinae) KW - stars: massive KW - stars: winds, outflows KW - X-rays: stars Y1 - 2011 U6 - https://doi.org/10.1088/0067-0049/194/1/8 SN - 0067-0049 VL - 194 IS - 1 PB - IOP PUBLISHING LTD CY - BRISTOL ER - TY - JOUR A1 - Schoeller, M. A1 - Hubrig, Swetlana A1 - Ilyin, Ilya A1 - Kharchenko, N. V. A1 - Briquet, Maryline A1 - Gonzalez, J. F. A1 - Langer, Norbert A1 - Oskinova, Lida T1 - Magnetic field studies of massive main sequence stars JF - Astronomische Nachrichten = Astronomical notes N2 - We report on the status of our spectropolarimetric observations of massive stars. During the last years, we have discovered magnetic fields in many objects of the upper main sequence, including Be stars, beta Cephei and Slowly Pulsating B stars, and a dozen O stars. Since the effects of those magnetic fields have been found to be substantial by recent models, we are looking into their impact on stellar rotation, pulsation, stellar winds, and chemical abundances. Accurate studies of the age, environment, and kinematic characteristics of the magnetic stars are also promising to give us new insight into the origin of the magnetic fields. Furthermore, longer time series of magnetic field measurements allow us to observe the temporal variability of the magnetic field and to deduce the stellar rotation period and the magnetic field geometry. Studies of the magnetic field in massive stars are indispensable to understand the conditions controlling the presence of those fields and their implications on the stellar physical parameters and evolution. KW - stars: early-type KW - stars: magnetic fields KW - stars: kinematics KW - techniques: polarimetric Y1 - 2011 U6 - https://doi.org/10.1002/asna.201111606 SN - 0004-6337 VL - 332 IS - 9-10 SP - 994 EP - 997 PB - Wiley-Blackwell CY - Malden ER -