Quiescent X-ray emission from ultracool dwarf 1RXS J115928.5-524717

We propose to perform XMMNewton observations of a very low mass star 1RXS115928.5524717. Given the sensitivity of XMMNewton over previous missions, weare confident that coronal Xray emission can now be detected in the very lowestmass stars and substellar objects known. Therefore, the objective of thisproposal is to make such detection and thereby establish the existence ofmagnetic activity at the very bottom of the main sequence and beyond. Our targetis recently discovered a previously unknown, high proper motion( approx ,1.1 ^{arcsec} ,yr ^{1} ) member of the immediate solar neighborhood:a very low mass star (Sp type M9) detected only during an Xray bright flare ofduration 1.52 hours with ROSAT AllSky Survey. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]