Quiescent X-ray emission from the M9 dwarf LHS 2065

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 3$σ$ 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 $L_ X = 2.2 ± 0.7 × 10^26$ erg/s in the 0.3-0.8 keV band, the corresponding activity level of log $L_ X$/ $L_ bol≈ -3.7$ 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.