Quiescent X-ray emission from the M9 dwarf LHS 2065

TL;DR

This study reports the detection of quiescent X-ray emission from the ultracool M9 dwarf LHS 2065, indicating the presence of a corona in one of the coolest stars observed in X-rays.

Contribution

First detection of quasi-quiescent X-ray emission from an M9 dwarf, demonstrating coronal activity in the coolest stars emitting X-rays.

Findings

Detected X-ray emission with L_x = 2.2 +/- 0.7 x 10^26 erg/s

Star shows activity level of log L_x/L_bol = -3.7

Evidence of minor variability and spectral changes

Abstract

We investigate an archival XMM-Newton observation of LHS 2065, an ultracool dwarf with spectral type M9. We clearly detect LHS 2065 at soft X-ray energies in less than 1 h effective exposure time above the 3 sigma 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 derive an X-ray luminosity of L_x = 2.2 +/- 0.7 x 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. 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.