TY - JOUR A1 - Evans, C. J. A1 - Hainich, Rainer A1 - Oskinova, Lida A1 - Gallagher, J. S. A1 - Chu, Y.-H. A1 - Gruendl, R. A. A1 - Hamann, Wolf-Rainer A1 - Henault-Brunet, V. A1 - Todt, Helge Tobias T1 - A rare early-type star revealed in the wing of the small megellanic cloud JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - Sk 183 is the visually brightest star in the N90 nebula, a young star-forming region in the Wing of the Small Magellanic Cloud (SMC). We present new optical spectroscopy from the Very Large Telescope which reveals Sk 183 to be one of the most massive O-type stars in the SMC. Classified as an O3-type dwarf on the basis of its nitrogen spectrum, the star also displays broadened He I absorption, which suggests a later type. We propose that Sk 183 has a composite spectrum and that it is similar to another star in the SMC, MPG 324. This brings the number of rare O2- and O3-type stars known in the whole of the SMC to a mere four. We estimate physical parameters for Sk 183 from analysis of its spectrum. For a single-star model, we estimate an effective temperature of 46 +/- 2 kK, a low mass-loss rate of similar to 10(-7) M-circle dot yr(-1), and a spectroscopic mass of 46(-8)(+ 9) M-circle dot (for an adopted distance modulus of 18.7 mag to the young population in the SMC Wing). An illustrative binary model requires a slightly hotter temperature (similar to 47.5 kK) for the primary component. In either scenario, Sk 183 is the earliest-type star known in N90 and will therefore be the dominant source of hydrogen-ionizing photons. This suggests Sk 183 is the primary influence on the star formation along the inner edge of the nebula. KW - open clusters and associations: individual (NGC 602) KW - stars: early-type KW - stars: fundamental parameters KW - stars: individual (Sanduleak 183) Y1 - 2012 U6 - https://doi.org/10.1088/0004-637X/753/2/173 SN - 0004-637X VL - 753 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Ignace, Richard A1 - Oskinova, Lida A1 - Massa, D. T1 - A report on the X-ray properties of the tau Sco-like stars JF - Monthly notices of the Royal Astronomical Society N2 - An increasing number of OB stars have been shown to possess magnetic fields. Although the sample remains small, it is surprising that the magnetic and X-ray properties of these stars appear to be far less correlated than expected. This contradicts model predictions, which generally indicate that the X-rays from magnetic stars are harder and more luminous than their non-magnetic counterparts. Instead, the X-ray properties of magnetic OB stars are quite diverse. tau Sco is one example where the expectations are better met. This bright main-sequence, early B star has been studied extensively in a variety of wavebands. It has a surface magnetic field of around 500 G, and Zeeman Doppler tomography has revealed an unusual field configuration. Furthermore, tau Sco displays an unusually hard X-ray spectrum, much harder than similar, non-magnetic OB stars. In addition, the profiles of its UV P Cygni wind lines have long been known to possess a peculiar morphology. Recently, two stars, HD 66665 and HD 63425, whose spectral types and UV wind line profiles are similar to those of tau Sco, have also been determined to be magnetic. In the hope of establishing a magnetic field - X-ray connection for at least a subset of the magnetic stars, we obtained XMM-Newton European Photon Imaging Camera spectra of these two objects. Our results for HD 66665 are somewhat inconclusive. No especially strong hard component is detected; however, the number of source counts is insufficient to rule out hard emission. Longer exposure is needed to assess the nature of the X-rays from this star. On the other hand, we do find that HD 63425 has a substantial hard X-ray component, thereby bolstering its close similarity to tau Sco. KW - stars: early-type KW - stars: individual: HD 63425 KW - stars: individual: HD 66665 KW - stars: magnetic field KW - X-rays: stars Y1 - 2013 U6 - https://doi.org/10.1093/mnras/sts358 SN - 0035-8711 VL - 429 IS - 1 SP - 516 EP - 522 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Bozzo, Enrico A1 - Ferrigno, Carlo A1 - Oskinova, Lida A1 - Ducci, Lorenzo T1 - Accretion of a clumped wind from a red supergiant donor on to a magnetar is suggested by the analysis of the XMM-Newton and NuSTAR observations of the X-ray binary 3A 1954+319 JF - Monthly notices of the Royal Astronomical Society N2 - 3A 1954+319 has been classified for a long time as a symbiotic X-ray binary, hosting a slowly rotating neutron star and an aged M red giant. Recently, this classification has been revised thanks to the discovery that the donor star is an M supergiant. This makes 3A 1954+319 a rare type of high-mass X-ray binary consisting of a neutron star and a red supergiant donor. In this paper, we analyse two archival and still unpublished XMM-Newton and NuSTAR observations of the source. We perform a detailed hardness ratio-resolved spectral analysis to search for spectral variability that could help investigating the structures of the inhomogeneous M supergiant wind from which the neutron star is accreting. We discuss our results in the context of wind-fed supergiant X-ray binaries and show that the newest findings on 3A 1954+319 reinforce the hypothesis that the neutron star in this system is endowed with a magnetar-like magnetic field strength (greater than or similar to 10(14) G). KW - accretion KW - stars: massive KW - stars: neutron KW - X-rays: binaries KW - X-rays: individual: 3A 1954+319 KW - X-rays: stars KW - accretion discs Y1 - 2021 U6 - https://doi.org/10.1093/mnras/stab3688 SN - 0035-8711 SN - 1365-2966 VL - 510 IS - 3 SP - 4645 EP - 4653 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Townsley, Leisa K. A1 - Broos, Patrick S. A1 - Corcoran, Michael F. A1 - Feigelson, Eric D. A1 - Gagne, Marc A1 - Montmerle, Thierry A1 - Oey, M. S. A1 - Smith, Nathan A1 - Garmire, Gordon P. A1 - Getman, Konstantin V. A1 - Povich, Matthew S. A1 - Evans, Nancy Remage A1 - Naze, Yael A1 - Parkin, E. R. A1 - Preibisch, Thomas A1 - Wang, Junfeng A1 - Wou, Scott J. A1 - Chu, You-Hua A1 - Cohen, David H. A1 - Gruendl, Robert A. A1 - Hamaguchi, Kenji A1 - King, Robert R. A1 - Mac Low, Mordecai-Mark A1 - McCaughrean, Mark J. A1 - Moffat, Anthony F. J. A1 - Oskinova, Lida A1 - Pittard, Julian M. A1 - Stassun, Keivan G. A1 - Ud-Doula, Asif A1 - Walborn, Nolan R. A1 - Waldron, Wayne L. A1 - Churchwell, Ed A1 - Nictiols, J. S. A1 - Owocki, Stanley P. A1 - Schulz, Norbert S. T1 - An introduction to the chandra carina complex project JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Supplement series N2 - 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. KW - H II regions KW - stars: massive KW - stars: pre-main sequence KW - X-rays: individual (Carina) KW - X-rays: ISM KW - X-rays: stars Y1 - 2011 U6 - https://doi.org/10.1088/0067-0049/194/1/1 SN - 0067-0049 VL - 194 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Ignace, R. A1 - Hole, K. T. A1 - Oskinova, Lida A1 - Rotter, J. P. T1 - An X-Ray Study of Two B plus B Binaries: AH Cep and CW Cep JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - AH Cep and CW Cep are both early B-type binaries with short orbital periods of 1.8. days and 2.7. days, respectively. All four components are B0.5V types. The binaries are also double-lined spectroscopic and eclipsing. Consequently, solutions for orbital and stellar parameters make the pair of binaries ideal targets for a study of the colliding winds between two B. stars. Chandra ACIS-I observations were obtained to determine X-ray luminosities. AH. Cep was detected with an unabsorbed X-ray luminosity at a 90% confidence interval of (9-33) x 10(30) erg s(-1), or (0.5-1.7) x 10(-7) L-Bol , relative to the combined Bolometric luminosities of the two components. While formally consistent with expectations for embedded wind shocks, or binary wind collision, the near-twin system of CW Cep was a surprising nondetection. For CW Cep, an upper limit was determined with L-X/L-Bol < 10(-8), again for the combined components. One difference between these two systems is that AH Cep is part of a multiple system. The X-rays from AH. Cep may not arise from standard wind shocks nor wind collision, but perhaps instead from magnetism in any one of the four components of the system. The possibility could be tested by searching for cyclic X-ray variability in AH. Cep on the short orbital period of the inner B. stars. KW - stars: early-type KW - stars: individual (AH Cep, CW Cep) KW - stars: massive KW - stars: winds KW - outflows X-rays: binaries Y1 - 2017 U6 - https://doi.org/10.3847/1538-4357/aa93ea SN - 0004-637X SN - 1538-4357 VL - 850 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Gimenez-Garcia, Angel A1 - Torrejon, Jose Miguel A1 - Eikmann, Wiebke A1 - Martinez-Nunez, Silvia A1 - Oskinova, Lida A1 - Rodes-Roca, Jose Joaquin A1 - Bernabeu, Guillermo T1 - An XMM-Newton view of FeK alpha in high-mass X-ray binaries JF - Astronomy and astrophysics : an international weekly journal N2 - We present a comprehensive analysis of the whole sample of available XMM-Newton observations of high-mass X-ray binaries (HMXBs) until August 2013, focusing on the FeK alpha emission line. This line is key to better understanding the physical properties of the material surrounding the X-ray source within a few stellar radii (the circumstellar medium). We collected observations from 46 HMXBs and detected FeK alpha in 21 of them. We used the standard classification of HMXBs to divide the sample into different groups. We find that (1) different classes of HMXBs display different qualitative behaviours in the FeK alpha spectral region. This is visible especially in SGXBs (showing ubiquitous Fe fluorescence but not recombination Fe lines) and in gamma Cass analogues (showing both fluorescent and recombination Fe lines). (2) FeK alpha is centred at a mean value of 6.42 keV. Considering the instrumental and fits uncertainties, this value is compatible with ionization states that are lower than Fe xviii. (3) The flux of the continuum is well correlated with the flux of the line, as expected. Eclipse observations show that the Fe fluorescence emission comes from an extended region surrounding the X-ray source. (4) We observe an inverse correlation between the X-ray luminosity and the equivalent width of FeK alpha (EW). This phenomenon is known as the X-ray Baldwin effect. (5) FeK alpha is narrow (sigma(line) < 0.15 keV), reflecting that the reprocessing material does not move at high speeds. We attempt to explain the broadness of the line in terms of three possible broadening phenomena: line blending, Compton scattering, and Doppler shifts (with velocities of the reprocessing material V similar to 1000 km s(-1)). (6) The equivalent hydrogen column (N-H) directly correlates to the EW of FeK alpha, displaying clear similarities to numerical simulations. It highlights the strong link between the absorbing and the fluorescent matter. (7) The observed NH in supergiant X-ray binaries (SGXBs) is in general higher than in supergiant fast X-ray transients (SFXTs). We suggest two possible explanations: different orbital configurations or a different interaction compact object - wind. (8) Finally, we analysed the sources IGR J16320-4751 and 4U 1700-37 in more detail, covering several orbital phases. The observed variation in NH between phases is compatible with the absorption produced by the wind of their optical companions. The results clearly point to a very important contribution of the donor's wind in the FeK alpha emission and the absorption when the donor is a supergiant massive star. KW - surveys KW - X-rays: binaries KW - binaries: general KW - circumstellar matter KW - stars: winds, outflows KW - stars: early-type Y1 - 2015 U6 - https://doi.org/10.1051/0004-6361/201425004 SN - 0004-6361 SN - 1432-0746 VL - 576 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Steinke, Martin A1 - Oskinova, Lida A1 - Hamann, Wolf-Rainer A1 - Sander, Andreas Alexander Christoph A1 - Liermann, A. A1 - Todt, Helge Tobias T1 - Analysis of the WN star WR102c, its WR nebula, and the associated cluster of massive stars in the Sickle Nebula JF - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth N2 - Context. The massive Wolf-Rayet type star WR102c is located near the Quintuplet Cluster, one of the three massive star clusters in the Galactic centre region. Previous studies indicated that WR102c may have a dusty circumstellar nebula and is among the main ionising sources of the Sickle Nebula associated with the Quintuplet Cluster. Aims. The goals of our study are to derive the stellar parameters of WR102c from the analysis of its spectrum and to investigate its stellar and nebular environment. Methods. We obtained observations with the ESO VLT integral field spectrograph SINFONI in the K-band, extracted the stellar spectra, and analysed them by means of stellar atmosphere models. Results. Our new analysis supersedes the results previously reported for WR102c. We significantly decrease its bolometric luminosity and hydrogen content. We detect four early OB type stars close to WR102c. These stars have radial velocities similar to that of WR102c. We suggest that together with WR102c these stars belong to a distinct star cluster with a total mass of similar to 1000 M-circle dot. We identify a new WR nebula around WR102c in the SINFONI map of the di ff use Br gamma emission and in the HST Pa ff images. The Br gamma line at di ff erent locations is not significantly broadened and similar to the width of nebular emission elsewhere in the H i i region around WR102c. Conclusions. The massive star WR102c located in the Galactic centre region resides in a star cluster containing additional early-type stars. The stellar parameters of WR102c are typical for hydrogen-free WN6 stars. We identify a nebula surrounding WR102c that has a morphology similar to other nebulae around hydrogen-free WR stars, and propose that the formation of this nebula is linked to interaction of the fast stellar wind with the matter ejected at a previous evolutionary stage of WR102c. KW - stars: early-type KW - stars: individual: WR 102c KW - stars: Wolf KW - Rayet KW - Galaxy: center KW - HII regions KW - infrared: stars Y1 - 2016 U6 - https://doi.org/10.1051/0004-6361/201527692 SN - 1432-0746 VL - 588 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Schöller, Markus A1 - Hubrig, Swetlana A1 - Fossati, L. A1 - Carroll, Thorsten Anthony A1 - Briquet, Maryline A1 - Oskinova, Lida A1 - Järvinen, S. A1 - Ilyin, Ilya A1 - Castro, N. A1 - Morel, T. A1 - Langer, N. A1 - Przybilla, N. A1 - Nieva, M. -F. A1 - Kholtygin, A. F. A1 - Sana, H. A1 - Herrero, A. A1 - Barba, R. H. A1 - de Koter, A. T1 - B fields in OB stars (BOB) BT - Concluding the FORS2 observing campaign JF - Astronomy and astrophysics : an international weekly journal N2 - Aims. The B fields in OB stars (BOB) Collaboration is based on an ESO Large Programme to study the occurrence rate, properties, and ultimately the origin of magnetic fields in massive stars. Methods. In the framework of this program, we carried out low-resolution spectropolarimetric observations of a large sample of massive stars using FORS2 installed at the ESO VLT 8m telescope. Results. We determined the magnetic field values with two completely independent reduction and analysis pipelines. Our in-depth study of the magnetic field measurements shows that differences between our two pipelines are usually well within 3 sigma errors. From the 32 observations of 28 OB stars, we were able to monitor the magnetic fields in CPD -57 degrees 3509 and HD164492C, confirm the magnetic field in HD54879, and detect a magnetic field in CPD -62 degrees 2124. We obtain a magnetic field detection rate of 6 +/- 3% for the full sample of 69 OB stars observed with FORS 2 within the BOB program. For the preselected objects with a nu sin i below 60 km s(-1), we obtain a magnetic field detection rate of 5 +/- 5%. We also discuss X-ray properties and multiplicity of the objects in our FORS2 sample with respect to the magnetic field detections. KW - polarization KW - stars: early-type KW - stars: magnetic field KW - stars: massive Y1 - 2017 U6 - https://doi.org/10.1051/0004-6361/201628905 SN - 1432-0746 VL - 599 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Castro, Norberto A1 - Fossati, Luca A1 - Hubrig, Swetlana A1 - Simon Díaz, Sergio A1 - Schoeller, Markus A1 - Ilyin, Ilya A1 - Carrol, Thorsten A. A1 - Langer, Norbert A1 - Morel, Thierry A1 - Schneider, Fabian R. N. A1 - Przybilla, Norbert A1 - Herrero, Artemio A1 - de Koter, Alex A1 - Oskinova, Lida A1 - Reisenegger, Andreas A1 - Sana, Hugues T1 - B fields in OB stars (BOB) Detection of a strong magnetic field in the O9.7 V star HD 54879 JF - Astronomy and astrophysics : an international weekly journal N2 - The number of magnetic stars detected among massive stars is small; nevertheless, the role played by the magnetic field in stellar evolution cannot be disregarded. Links between line profile variability, enhancements/depletions of surface chemical abundances, and magnetic fields have been identified for low-mass B-stars, but for the O-type domain this is almost unexplored. Based on FORS 2 and HARPS spectropolarimetric data, we present the first detection of a magnetic field in HD54879, a single slowly rotating O9.7 V star. Using two independent and different techniques we obtained the firm detection of a surface average longitudinal magnetic field with a maximum amplitude of about 600 G, in modulus. A quantitative spectroscopic analysis of the star with the stellar atmosphere code FASTWIND results in an effective temperature and a surface gravity of 33 000 +/- 1000K and 4.0 +/- 0.1 dex. The abundances of carbon, nitrogen, oxygen, silicon, and magnesium are found to be slightly lower than solar, but compatible within the errors. We investigate line-profile variability in HD54879 by complementing our spectra with spectroscopic data from other recent OB-star surveys. The photospheric lines remain constant in shape between 2009 and 2014, although H alpha shows a variable emission. The H alpha emission is too strong for a standard O9.7 V and is probably linked to the magnetic field and the presence of circumstellar material. Its normal chemical composition and the absence of photospheric line profile variations make HD54879 the most strongly magnetic, non-variable single O-star detected to date. KW - stars: atmospheres KW - stars: evolution KW - stars: magnetic field KW - stars: massive KW - stars: individual: HD 54879 Y1 - 2015 U6 - https://doi.org/10.1051/0004-6361/201425354 SN - 1432-0746 VL - 581 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Przybilla, Norbert A1 - Fossati, Luca A1 - Hubrig, Swetlana A1 - Nieva, M. -F. A1 - Jaervinen, S. P. A1 - Castro, Norberto A1 - Schoeller, M. A1 - Ilyin, Ilya A1 - Butler, Keith A1 - Schneider, F. R. N. A1 - Oskinova, Lida A1 - Morel, T. A1 - Langer, N. A1 - de Koter, A. T1 - B fields in OB stars (BOB): Detection of a magnetic field in the He-strong star CPD-57 degrees 3509 JF - Organic letters N2 - Methods. Spectropolarimetric observations with FORS2 and HARPSpol are analysed using two independent approaches to quantify the magnetic field strength. A high-S/N FLAMES/GIRAFFE spectrum is analysed using a hybrid non-LTE model atmosphere technique. Comparison with stellar evolution models constrains the fundamental parameters of the star. Results. We obtain a firm detection of a surface averaged longitudinal magnetic field with a maximum amplitude of about 1 kG. Assuming a dipolar configuration of the magnetic field, this implies a dipolar field strength larger than 3.3 kG. Moreover, the large amplitude and fast variation (within about 1 day) of the longitudinal magnetic field implies that CPD-57 degrees 3509 is spinning very fast despite its apparently slow projected rotational velocity. The star should be able to support a centrifugal magnetosphere, yet the spectrum shows no sign of magnetically confined material; in particular, emission in H alpha is not observed. Apparently, the wind is either not strong enough for enough material to accumulate in the magnetosphere to become observable or, alternatively, some leakage process leads to loss of material from the magnetosphere. The quantitative spectroscopic analysis of the star yields an effective temperature and a logarithmic surface gravity of 23 750 +/- 250 K and 4.05 +/- 0.10, respectively, and a surface helium fraction of 0.28 +/- 0.02 by number. The surface abundances of C, N, O, Ne, S, and Ar are compatible with the cosmic abundance standard, whereas Mg, Al, Si, and Fe are depleted by about a factor of 2. This abundance pattern can be understood as the consequence of a fractionated stellar wind. CPD-57 degrees 3509 is one of the most evolved He-strong stars known with an independent age constraint due to its cluster membership. KW - stars: abundances KW - stars: atmospheres KW - stars: evolution KW - stars: magnetic field KW - stars: individual: CPD-57 degrees 3509 KW - stars: massive Y1 - 2016 U6 - https://doi.org/10.1051/0004-6361/201527646 SN - 1432-0746 VL - 587 PB - EDP Sciences CY - Les Ulis ER -