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 - 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 - Sturm, R. A1 - Haberl, F. A1 - Oskinova, Lida A1 - Schurch, M. P. E. A1 - Henault-Brunet, V. A1 - Gallagher, J. S. A1 - Udalski, A. T1 - Long-term evolution of the neutron-star spin period of SXP1062 JF - Astronomy and astrophysics : an international weekly journal N2 - Context. The Be/X-ray binary SXP 1062 is of especial interest owing to the large spin period of the neutron star, its large spin-down rate, and the association with a supernova remnant constraining its age. This makes the source an important probe for accretion physics. Aims. To investigate the long-term evolution of the spin period and associated spectral variations, we performed an XMM-Newton target-of-opportunity observation of SXP 1062 during X-ray outburst. Methods. Spectral and timing analysis of the XMM-Newton data was compared with previous studies, as well as complementary Swift/XRT monitoring and optical spectroscopy with the SALT telescope were obtained. Results. The spin period was measured to be P-s = (1071.01 +/- 0.16) s on 2012 Oct. 14. The X-ray spectrum is similar to that of previous observations. No convincing cyclotron absorption features, which could be indicative for a high magnetic field strength, are found. The high-resolution RGS spectra indicate the presence of emission lines, which may not completely be accounted for by the SNR emission. The comparison of multi-epoch optical spectra suggest an increasing size or density of the decretion disc around the Be star. Conclusions. SXP 1062 showed a net spin-down with an average of P-s = ( 2.27 +/- 0.44) s yr(-1) over a baseline of 915 days. KW - pulsars: individual: SXP1062 KW - galaxies: individual: Small Magellanic Cloud KW - stars: emission-line, Be KW - stars: neutron KW - X-rays: binaries Y1 - 2013 U6 - https://doi.org/10.1051/0004-6361/201321755 SN - 0004-6361 VL - 556 IS - 4 PB - EDP Sciences CY - Les Ulis 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 -