A search for star formation in the translucent clouds MBM7 and MBM55

The star formation capability of two molecular clouds at high galactic lati tude (\b\ > 30 degrees) is investigated. Possible pre-main sequence stars i n and around the translucent clouds MBM7 and MBM55 have been identified via their X-ray emission by inspecting ROSAT All-Sky Survey observations of th e clouds and environs and ROSAT pointed observations of the high-density co res within the clouds. Follow-up optical spectroscopy of the stellar X-ray sources with V less than or equal to 15.5 mag was conducted with the 1.5-m Fred Lawrence Whipple Observatory telescope to identify standard signatures of pre-main sequence stars (LiI lambda 6708 Angstrom absorption and H alph a emission). We found 11 stars which have lithium equivalent widths, W(Li), above our detection threshold. Three of the stars with lithium also have w eak Ho? emission. Relative ages for the stars with lithium are estimated by their position on an W(Li) vs. T-eff diagram. A calibration derived from d ata for several clusters with known ages indicates the stars are older than the translucent high-latitude clouds. This conclusion is supported by a co mparison with theoretical evolutionary tracks of the stars from our sample for which we have distance measurements from Hipparcos. We find it is unlik ely that any of the X-ray active, lithium-rich stars we identified have for med in the clouds in question. Theoretical and observational arguments supp ort this conclusion and render unlikely the possibility that low-extinction translucent clouds are the sites of star formation.