EDP Sciences
Free access
Volume 404, Number 1, June II 2003
Page(s) 355 - 364
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20030482

A&A 404, 355-364 (2003)
DOI: 10.1051/0004-6361:20030482

The corona of V390 Aurigae (HD 33798)

P. Gondoin

European Space Agency, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
(Received 3 December 2002 / Accepted 24 March 2003 )

V390 Aurigae (HD 33798) is a rapidly rotating, lithium rich, late-type giant whose distinctive characteristics include a high X-ray luminosity observed by the XMM-Newton space observatory. Series of lines of highly ionized Fe and several Lyman lines of hydrogen-like ions and triplet lines of helium-like ions are visible in the reflection grating spectra, most notably from O and Ne. X-ray emission from plasma at high temperature ( T> 107 K) indicates intense flaring activity on this star. Analysis results suggest a scenario where the corona of V390 Aurigae is dominated by large magnetic structures similar in size to interconnecting loops between solar active regions but significantly hotter. The interaction of these structures could explain the permanent flaring activity on large scales that is responsible for heating plasma to high temperatures. The intense activity on V390 Aurigae is related to its evolutionary position at the bottom of the red giant branch. It is anticipated that the rotation of the star will spin-down in the future, thus decreasing the efficiency of its  $\alpha-\Omega$ dynamo with the suppressing of large scale magnetic structures in its corona.

Key words: stars: individual: V390 Aurigae -- stars: activity -- stars: coronae -- stars: evolution -- stars: late-type -- X-ray: stars

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© ESO 2003