TY - JOUR A1 - Shenar, Tomer A1 - Oskinova, Lida A1 - Hamann, Wolf-Rainer A1 - Corcoran, Michael F. A1 - Moffat, Anthony F. J. A1 - Pablo, Herbert A1 - Richardson, Noel D. A1 - Waldron, Wayne L. A1 - Huenemoerder, David P. A1 - Maiz Apellaniz, Jesus A1 - Nichols, Joy S. A1 - Todt, Helge Tobias A1 - Naze, Yael A1 - Hoffman, Jennifer L. A1 - Pollock, Andy M. T. A1 - Negueruela, Ignacio T1 - A coordinated X-Ray and optical campaign of the nearest massive eclipsing binary, delta ORIONIS Aa. IV. A multiwavelength, non-lte spectroscopic analysis JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - 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. KW - binaries: close KW - binaries: eclipsing KW - stars: early-type KW - stars: individual ([HD 36486]delta Ori A) KW - X-rays: stars Y1 - 2015 U6 - https://doi.org/10.1088/0004-637X/809/2/135 SN - 0004-637X SN - 1538-4357 VL - 809 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Pablo, Herbert A1 - Richardson, Noel D. A1 - Moffat, Anthony F. J. A1 - Corcoran, Michael A1 - Shenar, Tomer A1 - Benvenuto, Omar A1 - Fuller, Jim A1 - Naze, Yael A1 - Hoffman, Jennifer L. A1 - Miroshnichenko, Anatoly A1 - Apellaniz, Jesus Maiz A1 - Evans, Nancy A1 - Eversberg, Thomas A1 - Gayley, Ken A1 - Gull, Ted A1 - Hamaguchi, Kenji A1 - Hamann, Wolf-Rainer A1 - Henrichs, Huib A1 - Hole, Tabetha A1 - Ignace, Richard A1 - Iping, Rosina A1 - Lauer, Jennifer A1 - Leutenegger, Maurice A1 - Lomax, Jamie A1 - Nichols, Joy A1 - Oskinova, Lida A1 - Owocki, Stan A1 - Pollock, Andy A1 - Russell, Christopher M. P. A1 - Waldron, Wayne A1 - Buil, Christian A1 - Garrel, Thierry A1 - Graham, Keith A1 - Heathcote, Bernard A1 - Lemoult, Thierry A1 - Li, Dong A1 - Mauclaire, Benjamin A1 - Potter, Mike A1 - Ribeiro, Jose A1 - Matthews, Jaymie A1 - Cameron, Chris A1 - Guenther, David A1 - Kuschnig, Rainer A1 - Rowe, Jason A1 - Rucinski, Slavek A1 - Sasselov, Dimitar A1 - Weiss, Werner T1 - 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 JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - 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. KW - binaries: close KW - binaries: eclipsing KW - stars: early-type KW - stars: individual (delta Ori A) KW - stars: mass-loss KW - stars: variables: general Y1 - 2015 U6 - https://doi.org/10.1088/0004-637X/809/2/134 SN - 0004-637X SN - 1538-4357 VL - 809 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Corcoran, Michael F. A1 - Nichols, Joy S. A1 - Pablo, Herbert A1 - Shenar, Tomer A1 - Pollock, Andy M. T. A1 - Waldron, Wayne L. A1 - Moffat, Anthony F. J. A1 - Richardson, Noel D. A1 - Russell, Christopher M. P. A1 - Hamaguchi, Kenji A1 - Huenemoerder, David P. A1 - Oskinova, Lida A1 - Hamann, Wolf-Rainer A1 - Naze, Yael A1 - Ignace, Richard A1 - Evans, Nancy Remage A1 - Lomax, Jamie R. A1 - Hoffman, Jennifer L. A1 - Gayley, Kenneth A1 - Owocki, Stanley P. A1 - Leutenegger, Maurice A1 - Gull, Theodore R. A1 - Hole, Karen Tabetha A1 - Lauer, Jennifer A1 - Iping, Rosina C. T1 - A coordinated X-Ray and optical campaign of the nearest massive eclipsing binary, delta ORIONIS Aa. I. Overview of thr X-Ray spectrum JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - 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. KW - binaries: close KW - binaries: eclipsing KW - stars: early-type KW - stars: individual (Delta Ori) KW - stars: mass-loss KW - X-rays: stars Y1 - 2015 U6 - https://doi.org/10.1088/0004-637X/809/2/132 SN - 0004-637X SN - 1538-4357 VL - 809 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Leto, Paolo A1 - Trigilio, C. A1 - Oskinova, Lida A1 - Ignace, R. A1 - Buemi, C. S. A1 - Umana, G. A1 - Ingallinera, A. A1 - Leone, Francesco A1 - Phillips, N. M. A1 - Agliozzo, Claudia A1 - Todt, Helge Tobias A1 - Cerrigone, L. T1 - A combined multiwavelength VLA/ALMA/Chandra study unveils the complex magnetosphere of the B-type star HR5907 JF - Monthly notices of the Royal Astronomical Society N2 - We present new radio/millimeter measurements of the hot magnetic star HR5907 obtained with the VLA and ALMA interferometers. We find that HR5907 is the most radio luminous early type star in the cm-mm band among those presently known. Its multi-wavelength radio light curves are strongly variable with an amplitude that increases with radio frequency. The radio emission can be explained by the populations of the non-thermal electrons accelerated in the current sheets on the outer border of the magnetosphere of this fast-rotating magnetic star. We classify HR5907 as another member of the growing class of strongly magnetic fast-rotating hot stars where the gyro-synchrotron emission mechanism efficiently operates in their magnetospheres. The new radio observations of HR5907 are combined with archival X-ray data to study the physical condition of its magnetosphere. The X-ray spectra of HR5907 show tentative evidence for the presence of non-thermal spectral component. We suggest that non-thermal X-rays originate a stellar X-ray aurora due to streams of non-thermal electrons impacting on the stellar surface. Taking advantage of the relation between the spectral indices of the X-ray power-law spectrum and the non-thermal electron energy distributions, we perform 3-D modelling of the radio emission for HR5907. The wavelength-dependent radio light curves probe magnetospheric layers at different heights above the stellar surface. A detailed comparison between simulated and observed radio light curves leads us to conclude that the stellar magnetic field of HR 5907 is likely non-dipolar, providing further indirect evidence of the complex magnetic field topology of HR5907. KW - stars: chemically peculiar KW - stars: early-type KW - stars: individual: HR 5907 KW - stars: magnetic field KW - radio continuum: stars KW - X-rays: stars Y1 - 2018 U6 - https://doi.org/10.1093/mnras/sty244 SN - 0035-8711 SN - 1365-2966 VL - 476 IS - 1 SP - 562 EP - 579 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Evans, Chris J. A1 - van Loon, Jacco Th. A1 - Hainich, Rainer A1 - Bailey, M. T1 - 2dF-AAOmega spectroscopy of massive stars in the Magellanic Clouds The north-eastern region of the Large Magellanic Cloud JF - Astronomy and astrophysics : an international weekly journal N2 - We present spectral classifications from optical spectroscopy of 263 massive stars in the north-eastern region of the Large Magellanic Cloud. The observed two-degree field includes the massive 30 Doradus star-forming region, the environs of SN1987A, and a number of star-forming complexes to the south of 30 Dor. These are the first classifications for the majority (203) of the stars and include eleven double-lined spectroscopic binaries. The sample also includes the first examples of early OC-type spectra (AA Omega 30 Dor 248 and 280), distinguished by the weakness of their nitrogen spectra and by C IV lambda 4658 emission. We propose that these stars have relatively unprocessed CNO abundances compared to morphologically normal O-type stars, indicative of an earlier evolutionary phase. From analysis of observations obtained on two consecutive nights, we present radial-velocity estimates for 233 stars, finding one apparent single-lined binary and nine (>3 sigma) outliers compared to the systemic velocity; the latter objects could be runaway stars or large-amplitude binary systems and further spectroscopy is required to investigate their nature. KW - Magellanic Clouds KW - stars: early-type KW - stars: fundamental parameters KW - open clusters and associations: general Y1 - 2015 U6 - https://doi.org/10.1051/0004-6361/201525882 SN - 1432-0746 VL - 584 PB - EDP Sciences CY - Les Ulis ER -