SpringerLink
Forum Springer Astron. Astrophys.
Forum Whats New Search Orders


Astron. Astrophys. 330, 685-695 (1998)

Next Section Table of Contents

Doppler imaging of stellar surface structure

VI. HD 129333 = EK Draconis: a stellar analog of the active young Sun

K.G. Strassmeier * 1 and J.B. Rice [FORMULA] 2

1 Institut für Astronomie, Universität Wien, Türkenschanzstraße 17, A-1180 Wien, Austria (strassmeier@astro.ast.univie.ac.at)
2 Department of Physics, Brandon University, Brandon, Manitoba R7A 6A9, Canada (rice@BrandonU.ca)

Received 3 September 1997 / Accepted 29 September 1997

Abstract

We present the first Doppler images of the single G1.5V-star EK Draconis from high-resolution CFHT spectra obtained in 1995. EK Dra is an important target for investigating the evolution of stellar magnetism because it resembles the rapidly-rotating young Sun. From the inversion of a total of 12 spectral lines we reconstruct several cool spots at low and medium latitudes but the dominating feature is located consistently at a latitude of [FORMULA] 70-80o , thus, at far higher latitudes than where our Sun shows spots. In fact, our data indicate that this feature could be an appendage of a larger polar cap-like spot as seen on other rapidly-rotating stars, however, due to the small [FORMULA] of just 17.3 [FORMULA] 0.4 km s-1 the cap's existence remains inconclusive. Spot temperatures between [FORMULA] 1200 K and 400 K are recovered. We have used the non-parametrized convective-flux description of Canuto & Mazzitelli for our input model atmospheres and found good agreement with local line profiles computed from standard mixing-length atmospheres.

New phase-resolved UBVRI data spanning the 1996/97 observing season indicate a surprisingly short photometric period of 2.599 [FORMULA] 0.001 days, which is different by 7% from the longest seasonal period found so far but in good agreement with the long-term photometric period of 2.605 days. We interpret these differences as being due to differential surface rotation and adopt the long-term photometric period to be the rotation period of EK Dra. Our data also confirms the continuing decline of the mean brightness seen since 1994 and we suspect the high-latitude feature to be the cause.

Key words: stars: activity of – stars: imaging – stars: individual: EK Dra – stars: late-type – starspots

* Visiting Astronomer, Canada-France-Hawaii Telescope, operated by the National Research Council of Canada, the Centre National de la Recherche Scientifique de France, and the University of Hawaii

SIMBAD Objects

Contents

Next Section Table of Contents

© European Southern Observatory (ESO) 1998

Online publication: January 16, 1998
helpdesk.link@springer.de