With further reference to the items on IAUC 3324 and 3326, D. P. Hearn informs us that F. Boley specified to him 81.05 min as one of two possible optical orbital periods (the other being ~ 86 min) for the suggested counterpart of 2A 0311-227. The x-ray data appear to be consistent with a period of 81.0 +/- 0.1 min. S. Tapia, Lunar and Planetary Laboratory, reports: "The proposed optical counterpart of 2A 0311-227 displays a short minimum of circular polarization and a linear-polarization pulse at the times given by the ephemeris (heliocentric) 1979 Jan. 21.1793 UT +/- (0.05627 +/- 0.00002)E. Polarization measurements conducted in the 6300-9000 A spectral band indicate that there is a second short minimum of circular polarization at phase 0.4 +/- 0.03, that outside the two minima the circular polarization is always positive, and that the amplitudes of the circular-polarization modulations and the linear-polarization pulses fluctuate between 6 and 9 percent."
International Astronomical Union Circular
- Pub Date:
- February 1979