@article{RossloweCrowtherClarketal.2015, author = {Rosslowe, C. K. and Crowther, P. A. and Clark, J. S. and Negueruela, I.}, title = {Physical properties of the WR stars in Westerlund 1}, series = {Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.-5. June 2015}, journal = {Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.-5. June 2015}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-87779}, pages = {105 -- 108}, year = {2015}, abstract = {The Westerlund 1 (Wd1) cluster hosts a rich and varied collection of massive stars. Its dynamical youth and the absence of ongoing star formation indicate a coeval population. As such, the simultaneous presence of both late-type supergiants and Wolf-Rayet stars has defied explanation in the context of single-star evolution. Observational evidence points to a high binary fraction, hence this stellar population offers a robust test for stellar models accounting for both single-star and binary evolution. We present an optical to near-IR (VLT \& NTT) spectroscopic analysis of 22 WR stars in Wd 1, delivering physical properties for the WR stars. We discuss how these differ from the Galactic field population, and how they may be reconciled with the predictions of single and binary evolutionary models.}, language = {en} } @article{KehrigVilchezPerezMonteroetal.2015, author = {Kehrig, C. and V{\´i}lchez, J. M. and P{\´e}rez-Montero, E. and Iglesias-P{\´a}ramo, J. and Brinchmann, Jarle and Crowther, P. A. and Durret, F. and Kunth, D.}, title = {PopIII-star siblings in IZw18 and metal-poor WR galaxies unveiled from integral field spectroscopy}, series = {Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.-5. June 2015}, journal = {Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.-5. June 2015}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-87648}, pages = {55 -- 58}, year = {2015}, abstract = {Here, we highlight our recent results from the IFS study of Mrk178, the closest metal-poor WR galaxy, and of IZw18, the most metal-poor star-forming galaxy known in the local Universe. The IFS data of Mrk178 show the importance of aperture effects on the search for WR features, and the extent to which physical variations in the ISM properties can be detected. Our IFS data of IZw18 reveal its entire nebular HeIIλ4686-emitting region, and indicate for the very first time that peculiar, hot (nearly) metal-free ionizing stars (called here PopIII-star siblings) might hold the key to the HeII-ionization in IZw18.}, language = {en} } @article{Crowther2015, author = {Crowther, P. A.}, title = {Wolf-Rayet content of the Milky Way}, series = {Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.-5. June 2015}, journal = {Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.-5. June 2015}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-87562}, pages = {21 -- 26}, year = {2015}, abstract = {An overview of the known Wolf-Rayet (WR) population of the Milky Way is presented, including a brief overview of historical catalogues and recent advances based on infrared photometric and spectroscopic observations resulting in the current census of 642 (vl.13 online catalogue). The observed distribution of WR stars is considered with respect to known star clusters, given that ≤20\% of WR stars in the disk are located in clusters. WN stars outnumber WC stars at all galactocentric radii, while early-type WC stars are strongly biased against the inner Milky Way. Finally, recent estimates of the global WR population in the Milky Way are reassessed, with 1,200±100 estimated, such that the current census may be 50\% complete. A characteristic WR lifetime of 0.25 Myr is inferred for an initial mass threshold of 25 M⊙.}, language = {en} } @article{BibbySharaZureketal.2015, author = {Bibby, J. and Shara, M. and Zurek, D. and Crowther, P. A. and Moffat, Anthony F. J. and Drissen, L. and Wilde, M.}, title = {The Distribution of Massive Stars in M101}, series = {Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.-5. June 2015}, journal = {Wolf-Rayet Stars : Proceedings of an International Workshop held in Potsdam, Germany, 1.-5. June 2015}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-88402}, pages = {355}, year = {2015}, abstract = {75 WR stars and 164 RSGs are identified in a single WFC3 pointing of our M101 survey. We find that within it's large star-forming complex NGC 5462 WR stars are preferentially located in the core whilst RSGs are found in the halo, suggesting two bursts of star-formation. A review of our WR candidates reveals that only ∼30\% are detected in the archival broad-band ACS imaging whilst only ∼50\% are associated with HII regions.}, language = {en} }