C. A. Vaucher

Five years of photometry of? geminorum

Five years of photoelectric photometry of this bright K1 III RS CVn binary has been obtained at thirteen different observatories. Except for one year, the light curve has shown two minima, separated by roughly a half cycle. At the epoch of discovery (1977.2) one minimum was shallower but as of 1980.2 the two became comparable in depth. During the 1979–80 season the light curve changed shape rapidly, the shallower minimum becoming as deep as the other within about 80 days or perhaps less. Times of both minima can be fit with a photometric period of 19d.423, which is 0.9% shorter than the 19d.603 orbital period. The overall brightness range during the five years has been 4m.13

SS Bootis - A totally eclipsing binary of the RS CVn type

Photoelectric photometry gathered for SS Bootis over the 1976-1981 period shows a distortion wave amplitude variation from 0.05 to 0.20 mag, with no apparent pattern. From the rectified light curve, a new time of midprimary eclipse was found to be 2444332.0335 + or - 0.0005 days. Solutions of the primary eclipse data, rectified for star spots as well as for ellipticity and reflection, are presented.

54 Cam - A new variable star

Differential photometry of the RS CVn-type binary 54 Cam in 1978, 1979, and 1980 shows its light to be variable with a period of 10.d163±0.d009 and an amplitude inV (max. to min.) which increased from 0.m03 to 0.m06 between 1979.19 and 1980.82. An epoch of light minimum was JD 2444529.7. The 9% difference betweenP(phtm.)=10.d163 andP(orb.)=11.d0764,a much larger difference than is characteristic of other RS CVn binaries, is suggested as an explanation for the radio emission.

PHOTOELECTRIC OBSERVATIONS OF RZ CASSIOPEIAE.

Photoelectric observations for a single night are presented, resulting in a well-observed time of primary minimum light for the eclipsing binary RZ Cas. Key words: eclipsing binary - time of minimum - photometry

Four years of photometry of DK draconis=HR 4665

Differential BV photometry of the K0III+K0III long-period RS CVn-type binary DK Dra=HR 4665 in 1977, 1978, 1979, and 1980 at eight different observatories is presented. A least squares fit to times of maximum and minimum light yields the ephemeris JD=2 443 219.5+63.d75E for times of minimum. This photometric period is 1% shorter than the spectroscopically determined orbital period 64.d44. The light curve was symmetrical and roughly sinusoidal in 1979 and 1980 but was asymmetrical in 1977 and 1978, with a faster rise to maximum. During these four years DK Dra varied between V=6.m07 and 6.m35.