 The Chandra survey of Carina OB stars; ; et al (2011, July 01) We have combined 22 deep Chandra ACIS-I pointings to map over one square degree of the Carina complex. Our x-ray survey detects 69 of 70 known O-type stars and 61 of 130 known early B stars. The majority ... [more ▼] We have combined 22 deep Chandra ACIS-I pointings to map over one square degree of the Carina complex. Our x-ray survey detects 69 of 70 known O-type stars and 61 of 130 known early B stars. The majority of single O stars display soft X-ray spectra and have a mean log L[SUB]X[/SUB]/L[SUB]bol[/SUB] ~ -7.5 suggesting shocks embedded in the O-star winds. Over OB stars show unusually high X-ray luminosities, high shock temperatures or time variability, not predicted for embedded wind shocks. [less ▲] Detailed reference viewed: 10 (1 ULg) Spectroscopic follow-up of the colliding-wind binary WR 140 during the 2009 January periastron passage; ; et al in Neiner, Coralie; Wade, G.; Meynet, G. (Eds.) et al Active OB stars: structure, evolution, mass loss and critical limits (2011, July 01) We present the results from the spectroscopic follow-up of WR140 (WC7 + O4-5) during its last periastron passage in january 2009. This object is known as the archetype of colliding wind binaries and has a ... [more ▼] We present the results from the spectroscopic follow-up of WR140 (WC7 + O4-5) during its last periastron passage in january 2009. This object is known as the archetype of colliding wind binaries and has a relatively large period (~=8 years) and eccentricity (~=0.89). We provide updated values for the orbital parameters, new estimates for the WR and O star masses and new constraints on the mass-loss rates. [less ▲] Detailed reference viewed: 10 (1 ULg)  An Introduction to the Chandra Carina Complex Project; ; et al in Astrophysical Journal. Supplement Series (2011), 194 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 ... [more ▼] 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. [less ▲] Detailed reference viewed: 9 (1 ULg)Carina OB Stars: X-ray Signatures of Wind Shocks and Magnetic Fields; ; et al in Astrophysical Journal. Supplement Series (2011), 194 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 ... [more ▼] 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 [SUB]X[/SUB]/L [SUB]bol[/SUB] 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 [SUB]X[/SUB] 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. [less ▲] Detailed reference viewed: 3 (0 ULg)A period and a prediction for the Of ? p spectrum alternator HD 191612; ; Rauw, Grégor  et alin Astrophysical Journal (2004), 617(1, Part 2), 61-64 The observational picture of the enigmatic O-type spectrum variable HD 191612 has been sharpened substantially. A symmetrical, low-amplitude light curve with a period near 540 days has recently been ... [more ▼] The observational picture of the enigmatic O-type spectrum variable HD 191612 has been sharpened substantially. A symmetrical, low-amplitude light curve with a period near 540 days has recently been reported from Hipparcos photometry. This period satisfies all of the spectroscopy since at least 1982, including extensive new observations during 2003 and 2004, and it has predicted the next transition during 2004 September - October. Measurements of the Ha equivalent width reveal a sharp emission peak in the phase diagram, in contrast to the apparently sinusoidal light curve. The He II absorption-line strength is essentially constant, while He I varies strongly, possibly filled in by emission in the O6 state, thus producing the apparent spectral type variations. The O8 state appears to be the "normal" one. Two intermediate O7 observations have been obtained, which fall at the expected phases, but these are the only modern observations of the transitions so far. The period is too long for rotation or pulsation; although there is no direct evidence as yet for a companion, a model in which tidally induced oscillations drive an enhanced wind near periastron of an eccentric orbit appears promising. Further observations during the now predictable transitions may provide a critical test. Ultraviolet and X-ray observations during both states will likely also prove illuminating. [less ▲] Detailed reference viewed: 13 (4 ULg)Coordinated monitoring of the eccentric O-star binary Iota Orionis: the X-ray analysis; ; et al in Monthly Notices of the Royal Astronomical Society (2000), 319 We analyse two ASCA observations of the highly eccentric O9 III+B1 III binary Iota Orionis obtained at periastron and apastron. Based on the assumption of a strong colliding-wind shock between the stellar ... [more ▼] We analyse two ASCA observations of the highly eccentric O9 III+B1 III binary Iota Orionis obtained at periastron and apastron. Based on the assumption of a strong colliding-wind shock between the stellar components, we expected to see significant variation in the X-ray emission between these phases. The observations proved otherwise: the X-ray luminosities and spectral distributions were remarkably similar. The only noteworthy feature in the X-ray data was the hint of a proximity effect during periastron passage. Although this `flare' is of relatively low significance, it is supported by the notable proximity effects seen in the optical, and the phasing of the X-ray and optical events is in very good agreement. However, other interpretations are also possible. In view of the degradation of the SIS instrument and source contamination in the GIS data we discuss the accuracy of these results, and also analyse archival ROSAT observations. We investigate why we do not see a clear colliding-wind signature. A simple model shows that the wind attenuation to the expected position of the shock apex is negligible throughout the orbit, which poses the puzzling question of why the expected 1/D variation (i.e. a factor of 7.5) in the intrinsic luminosity is not seen in the data. Two scenarios are proposed: either the colliding-wind emission is unexpectedly weak such that intrinsic shocks in the winds dominate the emission, or, alternatively, the emission observed is colliding-wind emission but in a more complex form than we would naively expect. Complex hydrodynamical models are then analysed. Despite strongly phase-variable emission from the models, both are consistent with the observations. We find that if the mass-loss rates of the stars are low then intrinsic wind shocks could dominate the emission. However, when we assume higher mass-loss rates of the stars, we find that the observed emission could also be consistent with a purely colliding-wind origin. A summary of the strengths and weaknesses of each interpretation is presented. To distinguish between the different models X-ray observations with improved phase coverage will be necessary. [less ▲] Detailed reference viewed: 6 (0 ULg)Coordinated monitoring of the eccentric O-star binary Iota Orionis: optical spectroscopy and photometry; Rauw, Grégor ; et alin Monthly Notices of the Royal Astronomical Society (2000), 317 With the objective of investigating the wind-wind collision phenomenon and supporting contemporaneous X-ray observations, we have organized a large-scale, coordinated optical monitoring campaign of the ... [more ▼] With the objective of investigating the wind-wind collision phenomenon and supporting contemporaneous X-ray observations, we have organized a large-scale, coordinated optical monitoring campaign of the massive, highly eccentric O9III+B1III binary Iota Orionis. Successfully separating the spectra of the components, we refine the orbital elements and confirm the rapid apsidal motion in the system. We also see strong interaction between the components during periastron passage and detect phase-locked variability in the spectrum of the secondary star. However, we find no unambiguous signs of the bow shock crashing on the surface of the secondary, despite the predictions of hydrodynamic simulations. Combining all available photometric data, we find rapid, phase-locked variations and model them numerically, thus restricting the orbital inclination to 50°<~i<~70°. [less ▲] Detailed reference viewed: 16 (0 ULg) |
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