TY  - JOUR
A1  - Gvaramadze, V. V.
A1  - Chene, A.-N.
A1  - Kniazev, A. Y.
A1  - Schnurr, O.
A1  - Shenar, Tomer
A1  - Sander, Andreas Alexander Christoph
A1  - Hainich, Rainer
A1  - Langer, N.
A1  - Hamann, Wolf-Rainer
A1  - Chu, Y.-H.
A1  - Gruendl, R. A.
T1  - Discovery of a new Wolf-Rayet star and a candidate star cluster in the Large Magellanic Cloud with Spitzer
JF  - Monthly notices of the Royal Astronomical Society
N2  - We report the first-ever discovery of a Wolf-Rayet (WR) star in the Large Magellanic Cloud via detection of a circular shell with the Spitzer Space Telescope. Follow-up observations with Gemini-South resolved the central star of the shell into two components separated from each other by a parts per thousand 2 arcsec (or a parts per thousand 0.5 pc in projection). One of these components turns out to be a WN3 star with H and He lines both in emission and absorption (we named it BAT99 3a using the numbering system based on extending the Breysacher et al. catalogue). Spectroscopy of the second component showed that it is a B0 V star. Subsequent spectroscopic observations of BAT99 3a with the du Pont 2.5-m telescope and the Southern African Large Telescope revealed that it is a close, eccentric binary system, and that the absorption lines are associated with an O companion star. We analysed the spectrum of the binary system using the non-LTE Potsdam WR (powr) code, confirming that the WR component is a very hot (a parts per thousand 90 kK) WN star. For this star, we derived a luminosity of log L/ L-aS (TM) = 5.45 and a mass-loss rate of 10(- 5.8) M-aS (TM) yr(- 1), and found that the stellar wind composition is dominated by helium with 20 per cent of hydrogen. Spectroscopy of the shell revealed an He iii region centred on BAT99 3a and having the same angular radius (a parts per thousand 15 arcsec) as the shell. We thereby add a new example to a rare class of high-excitation nebulae photoionized by WR stars. Analysis of the nebular spectrum showed that the shell is composed of unprocessed material, implying that the shell was swept-up from the local interstellar medium. We discuss the physical relationship between the newly identified massive stars and their possible membership of a previously unrecognized star cluster.
KW  - line: identification
KW  - binaries: spectroscopic
KW  - stars: massive
KW  - stars: Wolf-Rayet
KW  - ISM: bubbles
Y1  - 2014
U6  - https://doi.org/10.1093/mnras/stu909
SN  - 0035-8711
SN  - 1365-2966
VL  - 442
IS  - 2
SP  - 929
EP  - 945
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Chené, A.-N.
A1  - Wyrick, D.
A1  - Borissova, J.
A1  - Kuhn, M.
A1  - Hervé, A.
A1  - Ramírez Alegría, S.
A1  - Bonatto, C.
A1  - Bouret, J.-C.
A1  - Kurtev, R.
T1  - Improving distances to Galactic Wolf-Rayet stars
JF  - Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.–5. June 2015
N2  - Before GAIA improves the HIPPARCOS survey, direct determination of the distance via parallax is only possible for γ Vel, but the analysis of the cluster or association to which WR stars are associated can give distances with a 50% to a 10% accuracy. The list of Galactic clusters, associations and clusters/association candidates has grown significantly in the last decade with the numerous deep, high resolution surveys of the Milky Way.  In this work, we revisit the fundamental parameters of known clusters with WR stars, and we present the search for new ones. All our work is based on the catalogs from the VVV (from the VISTA telescope) and the UKIDS (from the UKIRT telescope) near infrared surveys. Finally, the relations between the fundamental parameters of clusters with WR stars are explored.
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-87759
SP  - 97
EP  - 100
ER  - 
TY  - JOUR
A1  - Gormaz-Matamala, A. C.
A1  - Hervé, A.
A1  - Chené, A.-N.
A1  - Curé, M.
A1  - Mennickent, R. E.
T1  - Results Of The Spectroscopic Analysis Of WR6 Using CMFGEN
JF  - Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.–5. June 2015
N2  - Using ESPaDOnS optical spectra of WR6, we search variations on the stellar wind parameters during the different phases of the spectral variations. We use the radiative transfer code CMFGEN (Hillier & Miller 1998) to determine the wind parameters. Our work gives mean parameters for WR6, Teff = 55 kK, M = 2.7 × 10^-5 M⊙/yr and v∞ =1700 km/s. Furthermore the line profiles variations at different phases are the consequence of a variation of mass loss rate and temperature un the winds. Effective temperature reaches 59 kK at the highest intensity, whereas the mass-loss rate decreases to 2.5 × 10^-5 M⊙/yr in that case. On the other hand, effective temperature decreases to 52.5 kK and the mass-loss rate increases to 3 × 10^-5 M/⊙yr when the line profile reach its minimum intensity. Results confirm the variable nature of the stellar wind, presented in this case on two of its fundamental parameters: temperature and mass-loss; which could be used to constrain the nature of the instability at the basis of the wind.
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-88422
SP  - 357
ER  - 
TY  - CHAP
A1  - Chené, A.-N.
A1  - Moffat, Anthony F. J.
A1  - Crowther, P. A.
T1  - Rapidly accelerating clumps in the winds of the very hot WNE Stars
N2  - We study the time variability of emission lines in three WNE stars : WR 2 (WN2), WR 3 (WN3ha) and WR152 (WN3). While WR 2 shows no variability above the noise level, the other stars do show variation, which are like other WR stars in WR 152 but very fast in WR 3. From these motions, we deduce a value of β ∼1 for WR 3 that is like that seen in O stars and β ∼2–3 for WR 152, that is intermediate between other WR stars and WR 3.
Y1  - 2007
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-18163
ER  - 
TY  - JOUR
A1  - Ramírez Alegría, S.
A1  - Chené, A.-N.
A1  - Borissova, J.
A1  - Kurtev, R.
A1  - Navarro, C.
A1  - Kuhn, M.
A1  - Carballo-Bello, J. A.
T1  - A not so massive cluster hosting a very massive star
JF  - Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.–5. June 2015
N2  - We present the first physical characterization of the young open cluster VVVCL041. We spectroscopically observed the cluster main-sequence stellar population and a very-massive star candidate: WR62-2. CMFGEN modelling to our near-infrared spectra indicates that WR62-2 is a very luminous (10^6.4±0.2 L⊙)and massive (∼ 80M⊙) star.
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-88477
SP  - 362
ER  - 
TY  - GEN
A1  - Vink, Jorick Sandor
A1  - Heger, Alexander
A1  - Krumholz, Mark R.
A1  - Puls, Joachim
A1  - Banerjee, Shiladitya
A1  - Castro, Norberto
A1  - Chen, K.-J.
A1  - Chenè, A.-N.
A1  - Crowther, P. A.
A1  - Daminelli, A.
A1  - Gräfener, G.
A1  - Groh, J. H.
A1  - Hamann, Wolf-Rainer
A1  - Heap, S.
A1  - Herrero, A.
A1  - Kaper, L.
A1  - Najarro, F.
A1  - Oskinova, Lida
A1  - Roman-Lopes, A.
A1  - Rosen, A.
A1  - Sander, A.
A1  - Shirazi, M.
A1  - Sugawara, Y.
A1  - Tramper, F.
A1  - Vanbeveren, D.
A1  - Voss, R.
A1  - Wofford, A.
A1  - Zhang, Y.
T1  - Very massive stars in the local universe
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Recent studies have claimed the existence of very massive stars (VMS) up to 300 M⊙ in the local Universe. As this finding may represent a paradigm shift for the canonical stellar upper-mass limit of 150 M⊙, it is timely to discuss the status of the data, as well as the far-reaching implications of such objects. We held a Joint Discussion at the General Assembly in Beijing to discuss (i) the determination of the current masses of the most massive stars, (ii) the formation of VMS, (iii) their mass loss, and (iv) their evolution and final fate. The prime aim was to reach broad consensus between observers and theorists on how to identify and quantify the dominant physical processes.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 601 
KW  - stars: massive stars
KW  - stars: mass-loss
KW  - stars: stellar evolution
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-415220
SN  - 1866-8372
IS  - 601
ER  -