TY - JOUR A1 - Almeida, Leonardo A. A1 - Sana, H. A1 - Taylor, W. A1 - Barbá, Rodolfo A1 - Bonanos, Alceste Z. A1 - Crowther, Paul A1 - Damineli, Augusto A1 - de Koter, A. A1 - de Mink, Selma E. A1 - Evans, C. J. A1 - Gieles, Mark A1 - Grin, Nathan J. A1 - Hénault-Brunet, V. A1 - Langer, Norbert A1 - Lennon, D. A1 - Lockwood, Sean A1 - Maíz Apellániz, Jesús A1 - Moffat, A. F. J. A1 - Neijssel, C. A1 - Norman, C. A1 - Ramírez-Agudelo, O. H. A1 - Richardson, N. D. A1 - Schootemeijer, Abel A1 - Shenar, Tomer A1 - Soszyński, Igor A1 - Tramper, Frank A1 - Vink, J. S. T1 - The tarantula massive binary monitoring BT - I. Observational campaign and OB-type spectroscopic binaries JF - Astronomy and astrophysics : an international weekly journal N2 - Context: Massive binaries play a crucial role in the Universe. Knowing the distributions of their orbital parameters is important for a wide range of topics from stellar feedback to binary evolution channels and from the distribution of supernova types to gravitational wave progenitors, yet no direct measurements exist outside the Milky Way. Aims: The Tarantula Massive Binary Monitoring project was designed to help fill this gap by obtaining multi-epoch radial velocity (RV) monitoring of 102 massive binaries in the 30 Doradus region. Methods: In this paper we analyze 32 FLAMES/GIRAFFE observations of 93 O- and 7 B-type binaries. We performed a Fourier analysis and obtained orbital solutions for 82 systems: 51 single-lined (SB1) and 31 double-lined (SB2) spectroscopic binaries. Results: Overall, the binary fraction and orbital properties across the 30 Doradus region are found to be similar to existing Galactic samples. This indicates that within these domains environmental effects are of second order in shaping the properties of massive binary systems. A small difference is found in the distribution of orbital periods, which is slightly flatter (in log space) in 30 Doradus than in the Galaxy, although this may be compatible within error estimates and differences in the fitting methodology. Also, orbital periods in 30 Doradus can be as short as 1.1 d, somewhat shorter than seen in Galactic samples. Equal mass binaries (q> 0.95) in 30 Doradus are all found outside NGC 2070, the central association that surrounds R136a, the very young and massive cluster at 30 Doradus’s core. Most of the differences, albeit small, are compatible with expectations from binary evolution. One outstanding exception, however, is the fact that earlier spectral types (O2–O7) tend to have shorter orbital periods than later spectral types (O9.2–O9.7). Conclusions: Our results point to a relative universality of the incidence rate of massive binaries and their orbital properties in the metallicity range from solar (Z⊙) to about half solar. This provides the first direct constraints on massive binary properties in massive star-forming galaxies at the Universe’s peak of star formation at redshifts z ~ 1 to 2 which are estimated to have Z ~ 0.5 Z⊙. KW - stars: early-type KW - stars: massive KW - binaries: spectroscopic KW - binaries: close Y1 - 2017 U6 - https://doi.org/10.1051/0004-6361/201629844 SN - 1432-0746 VL - 598 PB - EDP Sciences CY - Les Ulis ER - 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 - Evans, C. J. A1 - Smartt, S. J. A1 - Lee, J. K. A1 - Lennon, D. J. A1 - Kaufer, A. A1 - Dufton, P. L. A1 - Trundle, C. A1 - Herrero, A. A1 - Simon Díaz, Sergio A1 - de Koter, A. A1 - Hamann, Wolf-Rainer A1 - Hendry, M. A. A1 - Hunter, I. A1 - Irwin, M. J. A1 - Korn, A. J. A1 - Kudritzki, R. P. A1 - Langer, Norbert A1 - Mokiem, M. R. A1 - Najarro, F. A1 - Pauldrach, A. W. A. A1 - Przybilla, Norbert A1 - Puls, J. A1 - Ryans, R. S. I. A1 - Urbaneja, M. A. A1 - Venn, K. A. A1 - Villamariz, M. R. T1 - The VLT-FLAMES survey of massive stars : Observations in the Galactic clusters NGC3293, NGC4755 and NGC6611 N2 - We introduce a new survey of massive stars in the Galaxy and the Magellanic Clouds using the Fibre Large Array Multi- Element Spectrograph ( FLAMES) instrument at the Very Large Telescope ( VLT). Here we present observations of 269 Galactic stars with the FLAMES- Giraffe Spectrograph ( R similar or equal to 25 000), in fields centered on the open clusters NGC3293, NGC4755 and NGC6611. These data are supplemented by a further 50 targets observed with the Fibre- Fed Extended Range Optical Spectrograph ( FEROS, R = 48 000). Following a description of our scientific motivations and target selection criteria, the data reduction methods are described; of critical importance the FLAMES reduction pipeline is found to yield spectra that are in excellent agreement with less automated methods. Spectral classifications and radial velocity measurements are presented for each star, with particular attention paid to morphological peculiarities and evidence of binarity. These observations represent a significant increase in the known spectral content of NGC3293 and NGC4755, and will serve as standards against which our subsequent FLAMES observations in the Magellanic Clouds will be compared Y1 - 2005 ER - TY - JOUR A1 - Henault-Brunet, V. A1 - Oskinova, Lida A1 - Guerrero, Martín A. A1 - Sun, W. A1 - Chu, Y.-H. A1 - Evans, C. J. A1 - Gallagher, J. S. A1 - Gruendl, R. A. A1 - Reyes-Iturbide, J. T1 - Discovery of a Be/X-ray pulsar binary and associated supernova remnant in the wing of the small magellanic cloud JF - Monthly notices of the Royal Astronomical Society N2 - We report on a new Be/X-ray pulsar binary located in the Wing of the Small Magellanic Cloud (SMC). The strong pulsed X-ray source was discovered with the Chandra and XMM-Newton X-ray observatories. The X-ray pulse period of 1062 s is consistently determined from both Chandra and XMM-Newton observations, revealing one of the slowest rotating X-ray pulsars known in the SMC. The optical counterpart of the X-ray source is the emission-line star 2dFS 3831. Its B0-0.5(III)e+ spectral type is determined from VLT-FLAMES and 2dF optical spectroscopy, establishing the system as a Be/X-ray binary (Be-XRB). The hard X-ray spectrum is well fitted by a power law with additional thermal and blackbody components, the latter reminiscent of persistent Be-XRBs. This system is the first evidence of a recent supernova in the low-density surroundings of NGC602. We detect a shell nebula around 2dFS 3831 in H alpha and [OIII] images and conclude that it is most likely a supernova remnant. If it is linked to the supernova explosion that created this new X-ray pulsar, its kinematic age of (2-4) x 10(4) yr provides a constraint on the age of the pulsar. KW - stars: emission-line, Be KW - ISM: supernova remnants KW - Magellanic Clouds KW - X-rays: binaries Y1 - 2012 U6 - https://doi.org/10.1111/j.1745-3933.2011.01183.x SN - 0035-8711 VL - 420 IS - 1 SP - L13 EP - L17 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Oskinova, Lida A1 - Sun, W. A1 - Evans, C. J. A1 - Henault-Brunet, V. A1 - Chu, Y.-H. A1 - Gallagher, J. S. A1 - Guerrero, Martín A. A1 - Gruendl, R. A. A1 - Güdel, M. A1 - Silich, S. A1 - Chen, Y. A1 - Naze, Y. A1 - Hainich, Rainer A1 - Reyes-Iturbide, J. T1 - Discovery of x-ray emission from young suns in the small magellanic cloud JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We report the discovery of extended X-ray emission within the young star cluster NGC 602a in the Wing of the Small Magellanic Cloud (SMC) based on observations obtained with the Chandra X-Ray Observatory. X-ray emission is detected from the cluster core area with the highest stellar density and from a dusty ridge surrounding the H II region. We use a census of massive stars in the cluster to demonstrate that a cluster wind or wind-blown bubble is unlikely to provide a significant contribution to the X-ray emission detected from the central area of the cluster. We therefore suggest that X-ray emission at the cluster core originates from an ensemble of low-and solar-mass pre-main-sequence (PMS) stars, each of which would be too weak in X-rays to be detected individually. We attribute the X-ray emission from the dusty ridge to the embedded tight cluster of the newborn stars known in this area from infrared studies. Assuming that the levels of X-ray activity in young stars in the low-metallicity environment of NGC 602a are comparable to their Galactic counterparts, then the detected spatial distribution, spectral properties, and level of X-ray emission are largely consistent with those expected from low-and solar-mass PMS stars and young stellar objects (YSOs). This is the first discovery of X-ray emission attributable to PMS stars and YSOs in the SMC, which suggests that the accretion and dynamo processes in young, low-mass objects in the SMC resemble those in the Galaxy. KW - Magellanic Clouds KW - ISM: bubbles KW - H II regions KW - stars: winds, outflows KW - stars: pre-main sequence KW - X-rays: stars Y1 - 2013 U6 - https://doi.org/10.1088/0004-637X/765/1/73 SN - 0004-637X VL - 765 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Szécsi, D. A1 - Langer, N. A1 - Sanyal, D. A1 - Evans, C. J. A1 - Bestenlehner, J. M. A1 - Raucq, F. T1 - Do rapidly-rotating massive stars at low metallicity form Wolf–Rayet stars? JF - Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.–5. June 2015 N2 - The evolution of massive stars is strongly influenced by their initial chemical composition. We have computed rapidly-rotating massive star models with low metallicity (∼1/50 Z⊙) that evolve chemically homogeneously and have optically-thin winds during the main sequence evolution. These luminous and hot stars are predicted to emit intense mid- and far-UV radiation, but without the broad emission lines that characterize WR stars with optically-thick winds. We show that such Transparent Wind UV-Intense (TWUIN) stars may be responsible for the high number of He ii ionizing photons observed in metal-poor dwarf galaxies, such as IZw 18. We find that these TWUIN stars are possible long-duration gamma-ray burst progenitors. Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-87997 SP - 189 EP - 192 ER - TY - JOUR A1 - van Loon, J. Th. A1 - Bailey, M. A1 - Tatton, B. L. A1 - Apellaniz, Jesus Maiz A1 - Crowther, P. A. A1 - de Koter, A. A1 - Evans, C. J. A1 - Henault-Brunet, V. A1 - Howarth, I. D. A1 - Richter, Philipp A1 - Sana, Hugues A1 - Simon Díaz, Sergio A1 - Taylor, W. A1 - Walborn, N. R. T1 - The VLT-FLAMES tarantula survey IX. - the interstellar medium seen through diffuse interstellar bands and neutral sodium JF - Astronomy and astrophysics : an international weekly journal N2 - Context. The Tarantula Nebula (a.k.a. 30 Dor) is a spectacular star-forming region in the Large Magellanic Cloud (LMC), seen through gas in the Galactic disc and halo. Diffuse interstellar bands (DIBs) offer a unique probe of the diffuse, cool-warm gas in these regions. Aims. The aim is to use DIBs as diagnostics of the local interstellar conditions, whilst at the same time deriving properties of the yet-unknown carriers of these enigmatic spectral features. Methods. Spectra of over 800 early-type stars from the Very Large Telescope Flames Tarantula Survey (VFTS) were analysed. Maps were created, separately, for the Galactic and LMC absorption in the DIBs at 4428 and 6614 angstrom and - in a smaller region near the central cluster R 136 - neutral sodium (the Na ID doublet); we also measured the DIBs at 5780 and 5797 angstrom. Results. The maps show strong 4428 and 6614 angstrom DIBs in the quiescent cloud complex to the south of 30 Dor but weak absorption in the harsher environments to the north (bubbles) and near the OB associations. The Na maps show at least five kinematic components in the LMC and a shell-like structure surrounding R 136, and small-scale structure in the Milky Way. The strengths of the 4428, 5780, 5797 and 6614 angstrom DIBs are correlated, also with Na absorption and visual extinction. The strong 4428 angstrom DIB is present already at low Na column density but the 6614, 5780 and 5797 angstrom DIBs start to be detectable at subsequently larger Na column densities. Conclusions. The carriers of the 4428, 6614, 5780 and 5797 angstrom DIBs are increasingly prone to removal from irradiated gas. The relative strength of the 5780 and 5797 angstrom DIBs clearly confirm the Tarantula Nebula as well as Galactic high-latitude gas to represent a harsh radiation environment. The resilience of the 4428 angstrom DIB suggests its carrier is large, compact and neutral. Structure is detected in the distribution of cool-warm gas on scales between one and > 100 pc in the LMC and as little as 0.01 pc in the Sun's vicinity. Stellar winds from the central cluster R 136 have created an expanding shell; some infalling gas is also detected, reminiscent of a galactic "fountain". KW - ISM: individual objects: Tarantula Nebula (30 Doradus Nebula) KW - ISM: molecules KW - ISM: kinematics and dynamics KW - ISM: lines and bands KW - ISM: structure KW - local insterstellar matter Y1 - 2013 U6 - https://doi.org/10.1051/0004-6361/201220210 SN - 0004-6361 VL - 550 IS - 9 PB - EDP Sciences CY - Les Ulis ER -