V1500 Cygni

J. C. Kemp, Department of Physics, University of Oregon, reports that observations during June 30-July 2 with the 224-cm telescope at Mauna Kea showed a mean magnitude of ~ 10.7 in unfiltered (UBV) light. Rapid light variation or flickering was detected on a timescale of the order of 1 min, with typical peak-to-peak amplitude 0.027 magnitude; the flickering was definite, checked by comparison with a field star of comparable brightness at alternate intervals of 10 min on all three nights. No periodicity was determined, although power spectra will be computed; the rapid variations were studied mainly in unfiltered light but were also seen in various filter bands and appeared stronger in the red. Variations on a timescale of 2-5 hours were also noted, the peak-to-peak amplitude being about 0.28 magnitude in unfiltered light; the time span was not long enough to establish a periodicity, but if there is regularity, the variation on this timescale appears to be sinusoidal rather than eclipsing. Assuming a sine wave, the data on the three nights are found to be consistent with periods of 3.3, 3.8 or 4.6 hours; the last period is to be preferred, but the first one agrees better with the observations by Tempesti in Sept. 1975 (IAUC 2834). A light maximum occurred on July 1.60 UT. The linear polarization in the band 4000-6000 A was 1.07 percent in p.a. 47o.3 on June 30.58 UT and 1.20 percent in p.a. 49o.8 on July 1.57 UT. E. Leibowitz, Wise Observatory, reports that observations in the B band revealed a continuous rise by 0.23 magnitude around B = 10.7 between July 5.00 and 5.03 UT and a similar rise around the same magnitude between July 5.97 and 6.02 UT. J. Bortle, Brooks Observatory, provides visual magnitude estimates as follows: June 18.15 UT, 11.4; 27.10, 11.5; July 6.1, 11.6.