S. Bowyer and J. Clarke, University of California at Berkeley; and P. Henry, Harvard-Smithsonian Center for Astrophysics, write: "We obtained a CCD direct image of the field of the x-ray burst source 4U 1916-05 on June 26 with the 4-m Mayall telescope at Kitt Peak. The limiting magnitude is R ~ 23, and at R ~ 23 there appears a faint, point-source object within +/- 1" of the position indicated on IAUC 3620. Two other stars appear on the edge of the error circle, one 3" east and one 3" northwest; however, spectroscopy of these stars with the 3-m Shane telescope at Lick shows both to have late-type-star continua without high-excitation emission lines. We therefore consider the R ~ 23 object to be the likely optical counterpart of the x-ray source. The resulting value of Lx/Lopt ~ 2 X 10**4, placing the source at the upper extreme of measured x-ray to optical luminosities for x-ray bursters."
International Astronomical Union Circular
- Pub Date:
- September 1981