TY  - JOUR
A1  - Hubrig, Swetlana
A1  - Scholz, Kathleen
A1  - Hamann, Wolf-Rainer
A1  - Schoeller, M.
A1  - Ignace, R.
A1  - Ilyin, Ilya
A1  - Gayley, K. G.
A1  - Oskinova, Lida
T1  - Searching for a magnetic field in Wolf-Rayet stars using FORS 2 spectropolarimetry
JF  - Monthly notices of the Royal Astronomical Society
N2  - To investigate if magnetic fields are present in Wolf-Rayet stars, we selected a few stars in the Galaxy and one in the Large Magellanic Cloud (LMC). We acquired low-resolution spectropolarimetric observations with the European Southern Observatory FORS 2 (FOcal Reducer low dispersion Spectrograph) instrument during two different observing runs. During the first run in visitor mode, we observed the LMC Wolf-Rayet star BAT99 7 and the stars WR 6, WR 7, WR 18, and WR 23 in our Galaxy. The second run in service mode was focused on monitoring the star WR 6. Linear polarization was recorded immediately after the observations of circular polarization. During our visitor observing run, the magnetic field for the cyclically variable star WR 6 was measured at a significance level of 3.3 sigma (< B-z > = 258 +/- 78 G). Among the other targets, the highest value for the longitudinal magnetic field, < B-z > = 327 +/- 141 G, was measured in the LMC star BAT99 7. Spectropolarimetric monitoring of the star WR 6 revealed a sinusoidal nature of the < B-z > variations with the known rotation period of 3.77 d, significantly adding to the confidence in the detection. The presence of the rotation-modulated magnetic variability is also indicated in our frequency periodogram. The reported field magnitude suffers from significant systematic uncertainties at the factor of 2 level, in addition to the quoted statistical uncertainties, owing to the theoretical approach used to characterize it. Linear polarization measurements showed no line effect in the stars, apart from WR 6. BAT99 7, WR 7, and WR 23 do not show variability of the linear polarization over two nights.
KW  - techniques: polarimetric
KW  - stars: individual: WR 6
KW  - stars: magnetic field
KW  - stars: variables: general
KW  - stars: Wolf-Rayet
Y1  - 2016
U6  - https://doi.org/10.1093/mnras/stw558
SN  - 0035-8711
SN  - 1365-2966
VL  - 458
SP  - 3381
EP  - 3393
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Toala, Jesús Alberto
A1  - Oskinova, Lida
A1  - Gonzalez-Galan, Ana
A1  - Guerrero, Martín A.
A1  - Ignace, R.
A1  - Pohl, Martin
T1  - X-RAY OBSERVATIONS OF BOW SHOCKS AROUND RUNAWAY O STARS. THE CASE OF zeta OPH AND BD+43 degrees 3654
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - Non-thermal radiation has been predicted within bow shocks around runaway stars by recent theoretical works. We present X-ray observations toward the runaway stars zeta Oph by Chandra and Suzaku and of BD+43 degrees 3654 by XMM-Newton to search for the presence of non-thermal X-ray emission. We found no evidence of non-thermal emission spatially coincident with the bow shocks; nonetheless, diffuse emission was detected in the vicinity of zeta Oph. After a careful analysis of its spectral characteristics, we conclude that this emission has a thermal nature with a plasma temperature of T approximate to 2 x 10(6) K. The cometary shape of this emission seems to be in line with recent predictions of radiation-hydrodynamic models of runaway stars. The case of BD+43 degrees 3654 is puzzling, as non-thermal emission has been reported in a previous work for this source.
KW  - stars: individual (zeta Oph, BD+43 degrees 3654)
KW  - stars: winds, outflows
Y1  - 2016
U6  - https://doi.org/10.3847/0004-637X/821/2/79
SN  - 0004-637X
SN  - 1538-4357
VL  - 821
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  -