A search for X-Ray luminous late type stars in NIPSS data

The purpose of this project is to obtain optical identifications of x-ray luminous late type stars. Our approach consists of detecting position coincidences between unidentified x-ray sources and stars for which (V-I) > 3 mag., as obtained from the Near Infrared Photographic Sky Survey (NIPSS) database. Objects with effective temperatures below 3000 K are the most frequent counterparts found by this method at high galactic latitudes (Craine 1987). In this paper we present a derivation of the detection limits of the NIPSS relevant to the lower main sequence dwarf stars. Significantly, M8 or M9 stars with apparent V magnitudes below the detection limit may still appear on the NIPSS I band photographs, where the detection limit is extended to pre-main sequence objects of about 0.03 solar luminosity.