094335

We have detected external heavy element pollution in a cool white dwarf thathosts a fully-detached brown dwarf companion in a 1.7 h orbit. Our measuredlower limit m(Na)/m(Ca) > 900 in the accreted matter can only be plausiblyexplained by substellar wind capture the first detection of its kind. Howeverthe accretion rate inference is based solely on models with no empirical basis.Here we propose X-ray observations with XMM-Newton to determine the actualaccretion rate due to the capture of a substellar wind which in turn directlyconstrains the intrinsic substellar mass loss rate both of which will beastrophysical firsts. [truncated! Please see actual data for full text]