TY  - JOUR
A1  - Shenar, Tomer
A1  - Oskinova, Lida
A1  - Jaervinen, S. P.
A1  - Luckas, P.
A1  - Hainich, Rainer
A1  - Todt, Helge Tobias
A1  - Hubrig, Swetlana
A1  - Sander, Andreas Alexander Christoph
A1  - Ilyin, Ilya
A1  - Hamann, Wolf-Rainer
T1  - Constraining the weak-wind problem
T2  - Contributions Of The Astronomical Observatory Skalnate Pleso
N2  - Mass-loss rates of massive, late type main sequence stars are much weaker than currently predicted, but their true values are very difficult to measure. We suggest that confined stellar winds of magnetic stars can be exploited to constrain the true mass-loss rates M of massive main sequence stars. We acquired UV, X-ray, and optical amateur data of HD 54879 (09.7 V), one of a few O-type stars with a detected atmospheric magnetic field (B-d greater than or similar to 2 kG). We analyze these data with the Potsdam Wolf-Rayet (PoWR) and XSPEC codes. We can roughly estimate the mass-loss rate the star would have in the absence of a magnetic field as log M-B=0 approximate to -9.0 M-circle dot yr(-1). Since the wind is partially trapped within the Alfven radius rA greater than or similar to 12 R-*,, the true mass-loss rate of HD 54879 is log M less than or similar to -10.2 M-circle dot yr(-1). Moreover, we find that the microturbulent, macroturbulent, and projected rotational velocities are lower than previously suggested (< 4 km s(-1)). An initial mass of 16 M-circle dot and an age of 5 Myr are inferred. We derive a mean X-ray emitting temperature of log T-x = 6.7 K and an X-ray luminosity of log L-x = 32 erg s(-1). The latter implies a significant X-ray excess (log L-x/L-Bol approximate to - 6.0), most likely stemming from collisions at the magnetic equator. A tentative period of P approximate to 5 yr is derived from variability of the Ha line. Our study confirms that strongly magnetized stars lose little or no mass, and supplies important constraints on the weak-wind problem of massive main sequence stars.
KW  - stars: massive
KW  - stars: magnetic field
KW  - stars: mass-loss
Y1  - 2017
UR  - https://publishup.uni-potsdam.de/frontdoor/index/index/docId/54544
SN  - 1335-1842
SN  - 1336-0337
VL  - 48
IS  - 1
SP  - 139
EP  - 143
PB  - Astronomický Ústav SAV
CY  - Tatranská Lomnica
ER  -