EDP Sciences
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Volume 382, Number 3, February II 2002
Page(s) L9 - L12
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20011295

A&A 382, L9-L12 (2002)
DOI: 10.1051/0004-6361:20011295


X-ray emission from the ultracool dwarf LHS 2065

J. H. M. M. Schmitt and C. Liefke

Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
    e-mail: cliefke@hs.uni-hamburg.de

(Received 30 July 2001 / Accepted 15 September 2001 )

We report the results of a 68 ks long X-ray observation of the M9V ultracool dwarf star LHS 2065 with the ROSAT high resolution imager (HRI). During the observations a major X-ray flare occurred with a peak X-ray luminosity of $4 \times 10^{27}$ erg/s and a total soft energy release of $2 \times 10^{31}$ erg. In addition, another flare with smaller peak X-ray luminosity and energy release occurred. The X-ray observations were carried out half a year apart. In the first half of the observations no significant X-ray emission from LHS 2065 could be detected, while in the second half in addition to flares also quiescent X-ray emission at a level of $2.3 \times 10^{26}$ erg/s was seen. LHS 2065 belongs to the coolest hydrogen burning stars known. The ROSAT observations show that coronal emission may be quite common even among such very late-type stars.

Key words: stars: activity -- stars: coronae -- stars: late type -- stars: flare -- X-rays: stars

Offprint request: J. H. M. M. Schmitt, jschmitt@hs.uni-hamburg.de

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