R. Konstantinova-Antova, M. Auriere, P. Petit, C. Charbonnel, S. Tsvetkova, A. Lebre, R. Bogdanovski
We have studied the active giant V390 Aur using spectropolarimetry to obtain
direct and simultaneous measurements of the magnetic field and the activity
indicators in order to get a precise insight of its activity. We used the
spectropolarimeter NARVAL at the Bernard Lyot Telescope (Observatoire du Pic du
Midi, France) to obtain a series of Stokes I and Stokes V profiles. The Least
Square deconvolution (LSD) technique was applied to detect the Zeeman signature
of the magnetic field in each of our 13 observations and to measure its
longitudinal component. We could also monitor the CaII K & H and IR triplet, as
well as the H_alpha lines which are activity indicators. In order to
reconstruct the magnetic field geometry of V390 Aur, we applied the Zeeman
Doppler Imaging (ZDI) inversion method and present a map for the magnetic
field. Based on the obtained spectra, we also refined the fundamental
parameters of the star and the Li abundance. The ZDI revealed a structure in
the radial magnetic field consisting of a polar magnetic spot of positive
polarity and several negative spots at lower latitude. A high latitude belt is
present on the azimuthal field map, indicative of a toroidal field close to the
surface. It was found that the photometric period cannot fit the behaviour of
the activity indicators formed in the chromosphere. Their behaviour suggests
slower rotation compared to the photosphere, but our dataset is too short to be
able to estimate the exact periods for them.Accepted for publication in A&A All
these results can be explained in terms of an \alpha-\omega dynamo operation,
taking into account the stellar structure and rotation properties of V390 Aur
that we study using up to-date stellar models computed at solar metallicity.
The calculated Rossby number also points to a very efficient dynamo
View original:
http://arxiv.org/abs/1201.5042
No comments:
Post a Comment