PROBE OF THE MAGNETIC FIELD IN THE HOT SUPERGIANT ζ Per

Анотація

At the surface of ∼7% of single hot
stars stable mainly dipolar strong magnetic fields have
been detected. The main hypothesis today is that
these magnetic fields are of fossil origin. In other
words, these fields formed from the seed field in the
molecular clouds from which the stars were formed.
The recent observational and theoretical results confi-
rm this theory: the properties of the observed fields
correspond to those expected from fossil fields. Massi-
ve stars are stars whose initial mass exceeds about
8 solar masses. Massive stars play a significant role
in the chemical and dynamical evolution of galaxies.
However, much of their variability, particularly during
their evolved supergiant stage, is poorly understood.
To date magnetic field was registered only at three hot
stars of I-II luminosity types: ρ Leo (B1 Ib), ζ Ori
Aa (O9.2 Ib), and ? CMa (B1.5 II). We performed
high-accuracy spectropolarimetric observation of the
hot supergiant ζ Per (B1 Ib) over 26 nights from 1997
to 2012 with long-slit spectrograph mounted in the
coude focus of 2.6-m reflector ZTSh at the Crimean
Astrophysical Observatory. We also used circularly
polarized spectra obtained during 2 nights in 2008 wi-
th echelle spectrograph ESPADONS mounted at 3.6-
m CFHT. Effective magnetic field B e (longitudinal
component of the field integrated over visible hemi-
sphere) of ζ Per was calculated in the line He I 6678.149 A. Statistically significant longitudinal magnetic field
(B e /σ B > 3) was registered in 14 from 199 single
measurements. These significant magnetic field values
are all in the range from −145 to +148 G with the
mean error 27 G. We suppose the supergiant ζ Per can
be magnetic, but its magnetic field properties is diffi-
cult to detect likely due to the insufficient precision of
the used spectropolarimetric measurements compared
to the expected field strength.