Optical Studies Of X-Ray Sources With The MASCOT-A Charge-Coupled Device (CCD)-Based Astronomical Instrument

The first observing run with the MASCOT (MIT Astronomical Spectrometer/Camera for Optical Telescopes) on the 1.3 m telescope at the McGraw-Hill Observatory in March 1981 demonstrated that the spectrophotometric sensitivity and stability of the instrument is consistent with the estimates made by Meyer and Ricker (1981) and Dewey and Ricker (1990), based on their calculations and laboratory calibrations. A pair of Texas Instruments virtual phse CCD's were used as the MASCOT optical detectors. In the W band (4000Å-7000Å), the MASCOT achieved a sky-limited sensitivity of +24.4 mag arc sec -2 in an 1800s integration (1 arc sec pixel size; 5σ level of significance). The ability to "flatten" pictures to a level consistent with (sky + source) photon statistics and readout noise was demonstrated. As an example of the capabilities which the MASCOT has demon-strated, we discuss our preliminary results from optical observations of four high galactic latitude Einstein x-ray sources without optical counterparts (i.e. "empty field" sources). For the four sources we observed, we established an optical counterpart for one source (1413+13), based on positional coincidence (better than 1.8 arc sec); detected four possible candidates in the error bode of anotper source (1009+35), and established sensi-tive upper limits (>22.3 mag; 4000 Å - 7000 Å, 5 upper limits) for optical counterparts in the error boxes for the other two sources (0920+39 and 0931-11).