SS 433

E. W. Gottlieb and W. Liller, Center for Astrophysics, report that the blue magnitudes of SS 433, as derived from plates in the Harvard archival collection, show a significant tendency to be cyclic with a period of 161.7 +/- 0.3 days. Prior to 1929 there was little indication of periodicity; instead the star stayed near its minimum brightness at B = 17.5 +/- 0.3 with occasional flares to B < 17.0. Since 1929 the lightcurve cycle has repeated with a spread of +/- 0.3 magnitude with only three of 39 points falling more than 0.5 magnitude below the mean lightcurve. This preliminary value of the period agrees well with the 160 +/- 3 days over which spectral-line motions recur (Margon et al., IAUC 3345). E. F. Milone, University of Calgary, reports that JHKL observations of SS 433 carried out with the 150-cm Mt. Lemmon infrared telescope by T. A. Clark and himself indicate variability on a timescale of days. Compared to theta Lyr and BD +34 4213, SS 433 dimmed by average values of 0.23, 0.21, 0.12 and 0.07 magnitude in J, H, K and L, respectively, on Apr. 15.5 UT with respect to the situation on the adjacent nights of Apr. 14 and 17. There is further a suggestion of smaller variations over a shorter timescale, and the object's J-L color index is more than 1.2 magnitudes greater than that of theta Lyr.