Research Note

Quiescent X-ray emission from the M9 dwarf LHS 2065

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

Received: 6 May 2008
Accepted: 20 June 2008

Abstract

Aims. X-ray emission is an important diagnostics to study magnetic activity in very low mass stars that are presumably fully convective and have an effectively neutral photosphere.

Methods. We investigate an archival XMM-Newton observation of LHS 2065, an ultracool dwarf with spectral type M9.

Results. We clearly detect LHS 2065 at soft X-ray energies in less than 1 h effective exposure time above the 3σ level with the PN and MOS1 detector. No flare signatures are present and we attribute the X-ray detection to quasi-quiescent activity. From the PN data we derived an X-ray luminosity of  erg/s in the 0.3–0.8 keV band, the corresponding activity level of log L_X/ points to a rather active star. Indications for minor variability and possible accompanying spectral changes are present, however the short exposure time and poor data quality prevents a more detailed analysis.

Conclusions. LHS 2065 is one of the coolest and least massive stars that emits X-rays at detectable levels in quasi-quiescence, implying the existence of a corona.