TY  - JOUR
A1  - Steinke, Martin
A1  - Oskinova, Lida
A1  - Hamann, Wolf-Rainer
A1  - Sander, Andreas Alexander Christoph
A1  - Liermann, A.
A1  - Todt, Helge Tobias
T1  - Analysis of the WN star WR102c, its WR nebula, and the associated cluster of massive stars in the Sickle Nebula
JF  - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth
N2  - Context. The massive Wolf-Rayet type star WR102c is located near the Quintuplet Cluster, one of the three massive star clusters in the Galactic centre region. Previous studies indicated that WR102c may have a dusty circumstellar nebula and is among the main ionising sources of the Sickle Nebula associated with the Quintuplet Cluster. Aims. The goals of our study are to derive the stellar parameters of WR102c from the analysis of its spectrum and to investigate its stellar and nebular environment. Methods. We obtained observations with the ESO VLT integral field spectrograph SINFONI in the K-band, extracted the stellar spectra, and analysed them by means of stellar atmosphere models. Results. Our new analysis supersedes the results previously reported for WR102c. We significantly decrease its bolometric luminosity and hydrogen content. We detect four early OB type stars close to WR102c. These stars have radial velocities similar to that of WR102c. We suggest that together with WR102c these stars belong to a distinct star cluster with a total mass of similar to 1000 M-circle dot. We identify a new WR nebula around WR102c in the SINFONI map of the di ff use Br gamma emission and in the HST Pa ff images. The Br gamma line at di ff erent locations is not significantly broadened and similar to the width of nebular emission elsewhere in the H i i region around WR102c. Conclusions. The massive star WR102c located in the Galactic centre region resides in a star cluster containing additional early-type stars. The stellar parameters of WR102c are typical for hydrogen-free WN6 stars. We identify a nebula surrounding WR102c that has a morphology similar to other nebulae around hydrogen-free WR stars, and propose that the formation of this nebula is linked to interaction of the fast stellar wind with the matter ejected at a previous evolutionary stage of WR102c.
KW  - stars: early-type
KW  - stars: individual: WR 102c
KW  - stars: Wolf
KW  - Rayet
KW  - Galaxy: center
KW  - HII regions
KW  - infrared: stars
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201527692
SN  - 1432-0746
VL  - 588
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Hubrig, Swetlana
A1  - Kholtygin, A.
A1  - Ilyin, Ilya
A1  - Schöller, M.
A1  - Oskinova, Lida
T1  - THE FIRST SPECTROPOLARIMETRIC MONITORING OF THE PECULIAR O4 Ief SUPERGIANT zeta PUPPIS
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - The origin of the magnetic field in massive O-type stars is still under debate. To model the physical processes responsible for the generation of O star magnetic fields, it is important to understand whether correlations between the presence of a magnetic field and stellar evolutionary state, rotation velocity, kinematical status, and surface composition can be identified. The O4 Ief supergiant zeta Pup is a fast rotator and a runaway star, which may be a product of a past binary interaction, possibly having had an encounter with the cluster Trumper 10 some 2 Myr ago. The currently available observational material suggests that certain observed phenomena in this star may be related to the presence of a magnetic field. We acquired spectropolarimetric observations of zeta Pup with FORS 2 mounted on the 8 m Antu telescope of the Very Large Telescope to investigate if a magnetic field is indeed present in this star. We show that many spectral lines are highly variable and probably vary with the recently detected period of 1.78 day. No magnetic field is detected in zeta Pup, as no magnetic field measurement has a significance level higher than 2.4 sigma. Still, we studied the probability of a single sinusoidal explaining the variation of the longitudinal magnetic field measurements.
KW  - stars: atmospheres
KW  - stars: early-type
KW  - stars: individual (zetaPup)
KW  - stars: magnetic field
KW  - stars: variables: general
Y1  - 2016
U6  - https://doi.org/10.3847/0004-637X/822/2/104
SN  - 0004-637X
SN  - 1538-4357
VL  - 822
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  -