Related papers: BAT99-9 -- a WC4 Wolf-Rayet star with nitrogen emi…
[WC]-type CSPNs are hydrogen-deficient Central Stars of Planetary Nebulae showing strong stellar winds and a carbon-rich chemistry. We have analyzed new high-resolution spectra of [WC]-type CSPNs with the Potsdam Wolf-Rayet (PoWR) non-LTE…
We present new Spitzer IRS observations of HD164270 (WC9, WR103). A quantitative analysis of the UV, optical, near- and mid-IR spectrum of HD164270 is presented, allowing for line blanketing and wind clumping, revealing T* ~ 48kK, log…
The evolutionary origin of Wolf-Rayet (WR) stars at Solar metallicity is unclear. Single-star evolution from massive O stars, possibly via a Luminous Blue Variable phase, is challenged by binary period distributions of different WR…
We present spectroscopic observations of the central star clusters in NGC 5253 the aim of which is to search for WC stars. Our observations show the presence of Wolf-Rayet (WR) stars not only of WN but also of WC subtype in two star forming…
High resolution spectra of seven early B-type giant/supergiant stars in the SMC cluster NGC330 are analysed to obtain their chemical compositions relative to SMC field and Galactic B-type stars. It is found that all seven stars are nitrogen…
We report the serendipitous discovery of a heavily reddened Wolf-Rayet star that we name WR142b. While photometrically monitoring a cataclysmic variable, we detected weak variability in a nearby field star. Low-resolution spectroscopy…
We study the evolution, rotation, and surface abundances of O-type dwarfs in the Small Magellanic Cloud. We analyzed the UV and optical spectra of twenty-three objects and derived photospheric and wind properties. The observed binary…
The Small Magellanic Cloud (SMC) is the nearest low-metallicity dwarf galaxy. Its proximity and low reddening has enabled us to detect its Wolf-Rayet (WR) star population with 12 known objects. Quantitative spectroscopy of the stars…
We use integral field spectroscopic (IFS) observations from Gemini North Multi-Object Spectrograph (GMOS-N) of a group of four H II regions and the surrounding gas in the central region of the blue compact dwarf (BCD) galaxy NGC 4670. At…
We present Gemini-N GMOS and CFHT MOS spectroscopy of Wolf-Rayet candidates in the Local Group dwarf galaxy IC10 that were previously identified by Massey et al. and Royer et al. From the present spectroscopic survey, the WC/WN ratio for…
The evolution of massive stars is only partly understood. Observational constraints can be obtained from the study of massive stars located in young massive clusters. The ESO Public Survey VISTA Variables in the Via Lactea (VVV) discovered…
The increasing neutrality of the intergalactic medium at z>6 suppresses Ly-alpha emission, and spectroscopic confirmation of galaxy redshifts requires detecting alternative UV lines. The strong [C III] 1907 + C III] 1909 doublet frequently…
We report the first-ever discovery of an extragalactic Wolf-Rayet (WR)star with Spitzer. A new WR star in the Large Magellanic Cloud (LMC) was revealed via detection of its circumstellar shell using 24 {\mu}m images obtained in the…
Classical Wolf-Rayet (WR) stars are hot, massive stars with depleted hydrogen. At low metallicities (Z), WN3-type WR stars have relatively thin winds and are major sources of ionizing flux. The detection of high-ionization emission lines in…
Photometry at 3.4 and 4.6 micron of 128 Population~I WC type Wolf-Rayet stars in the Galaxy and 12 in the Large Magellanic Cloud (LMC) observed in the WISE NEOWISE-R survey was searched for evidence of circumstellar dust emission and its…
We present a catalogue of non-nuclear regions containing Wolf-Rayet stars in the metal-rich spiral galaxy M83 (NGC5236). From a total of 283 candidate regions identified using HeII 4686 imaging with VLT-FORS2, Multi Object Spectroscopy of…
Wolf-Rayet stars (WR) have been detected in the NW region of the metal-poor starburst galaxy IZw 18. The integrated luminosity and FWHM of the bumps at 4650 A and 5808 A are consistent with the presence of a few individual stars of WC4 or…
We present a comprehensive study of the Magellanic Cloud planetary nebula SMP 61 and of its nucleus, a Wolf-Rayet type star classified [WC 5-6]. We have performed a detailed spectral analysis of the central star, using the Potsdam code for…
We report the serendipitous discovery of a nitrogen-rich, mildly metal-poor ([Fe/H]=-1.08) giant star in a single-lined spectroscopic binary system found in the SDSS-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE-2)…
The nitrogen to carbon (N/C) and nitrogen to oxygen (N/O) ratios are the most sensitive quantities to mixing in stellar interiors of intermediate and massive stars. We further investigate the theoretical properties of these ratios as well…