Photospheric magnetic field and surface differential rotation of the FK Com star HD 199178

Petit, P., Donati, J-F., Oliveira, J.M., Aurière, M., Bagnulo, S., Landstreet , J.D., Lignières, F., Lüftinger, T., Marsden, S., Mouillet , D., Paletou, F., Strasser, S., Toqué, N., and Wade, G.A. (2004) Photospheric magnetic field and surface differential rotation of the FK Com star HD 199178. Monthly Notices of the Royal Astronomical Society, 351 (3). pp. 826-844.

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Abstract

We present spectropolarimetric observations of the FK Com star HD 199178 obtained between 1998 December and 2003 August at the Télescope Bernard Lyot (Observatoire du Pic du Midi, France). We report the detection of a photospheric magnetic field and reconstruct its distribution by means of Zeeman–Doppler imaging. We observe large regions where the magnetic field is mainly azimuthal, suggesting that the dynamo processes generating the magnetic activity of HD 199178 may be active very close to the stellar surface. We investigate the rapid evolution of surface brightness and magnetic structures from a continuous monitoring of the star over several weeks in 2002 and 2003. We report that significant changes occur in the distribution of cool-spots and magnetic regions on typical time-scales of the order of two weeks. Our spectropolarimetric observations also suggest that the surface of HD 199178 is sheared by differential rotation, with a difference in rotation rate between equatorial and polar regions of the order of 1.5 times that of the Sun.

Item ID: 16737
Item Type: Article (Refereed Research - C1)
Keywords: magnetic fields; polarization; stars: activity; stars: imaging; stars: individual: HD 199178; stars: rotation
ISSN: 1365-2966
Date Deposited: 13 Jul 2011 06:33
FoR Codes: 02 PHYSICAL SCIENCES > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970102 Expanding Knowledge in the Physical Sciences @ 100%
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