Structure and evolution of FK Comae corona

Space Science Department, European Space Agency – Postbus 299, 2200 AG Noordwijk, The Netherlands

Corresponding author: P. Gondoin, pgondoin@astro.estec.esa.nl

Received: 16 October 2001
Accepted: 17 December 2001

Abstract

FK Comae (HD 117555) is a rapidly rotating single G giant whose distinctive characteristics include a quasisinusoidal optical light curve and high X-ray luminosity. FK Comae was observed twice at two weeks interval in January 2001 by the XMM-Newton space observatory. Analysis results suggest a scenario where the corona of FK Comae is dominated by large magnetic structures similar in size to interconnecting loops between solar active regions but significantly hotter. The interaction of these structures themselves could explain the permanent flaring activity on large scales that is responsible for heating FK Comae plasma to high temperatures. During our observations, these flares were not randomly distributed on the star surface but were partly grouped within a large compact region of about 30 degree extent in longitude reminiscent of a large photospheric spot. We argue that the dynamo driven activity on FK Comae will disappear in the future with the effect of suppressing large scale magnetic structures in its corona.