Search for Optical Counterpart of GX3 + 1

Abstract

AN accurate determination of the position of the X-ray source GX3 + 1 has been reported by Janes et al.¹, who used the results of lunar occupations of the source during two rocket flights. The intersecting positions of the lunar limb, as seen from the rocket, occur near the centre of the previous best position of the source determined by Schnopper et al.². Slitless spectra of stars in the spectral range 5600 to 8000 Å in the field of the occultation position were obtained by Kunkel et al.³ who found no emission features in an angular field of 7.5 × 2 arc min. Following a comparison of the occultation position with a Royal Observatory, Cape Town, direct photographic plate, Janes et al. concluded that either GX3 + 1 is star 14 of Kunkel et al., or it is optically fainter than 18 mag. and lies between stars 14 and 15, or it is fainter than 21 mag, and lies in the occultation error box.