COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1690 Konkoly Observatory Budapest 1979 October 17 CONFIRMATION OF SUSPECTED VARIABILITY IN HD 86590 Our attention was drawn to HD 86590 by Bolton (1978ab), who pointed out that it is a short-period SB1 and that its light curve might show an RS CVn-type (= BY Dra-type) photometric wave and possibly also an eclipse. Therefore we obtained differential photoelectric photometry at two observatories in early 1979. There are published accounts of some earlier photoelectric photometry. Table VII of Eggen (1964) gives V_E = 7.75m, B-V = +0.88m, and U-B = +0.43m. Eggen (1978) explains that his February and May 1963 observations showed a range of 0.08m in V, that two observations in March 1978 gave V = 7.75m, and that the "visual magnitude" was 7.90m on 2 April 1978. Table II of Argue (1966), however, gives very different magnitudes and color indices: V = 8.45, B-V = +1.02, and U-B = +0.76m. At Dyer Observatory the 24-inch (60 cm) reflector was used to obtain 34 two-color (BV) observations on 11 nights between JD 2,443,944.7 and 2,440,002.7; details are given by Vaucher (1979). At the other observatory the 11-inch (28 cm) reflector was used to obtain 18 one-color (V) observations on 6 nights between JD 2,443,951.7 and 2,443,987.7. Nightly means are plotted in the Figure versus [FIGURE 1] the spectroscopically determined orbital period of P = 1.0703544d of Bolton (1978ab). The magnitudes Delta V are differential with respect to the comparison star HD 86857 and have been corrected for atmospheric extinction and transformed to the UBV system. The rms deviation of 16 differential observations of the check star HD 86818 with respect to our comparison star on 8 nights was only +-0.007m. HD 86590 is clearly variable. The light curve is nearly sinusoidal, with a full amplitude of 0.14m in V. Such an amplitude is nicely consistent with the 0.15m range indicated by Eggen's observations in 1978, assuming they were made on the same photometric system, i.e., both V or both V_E. It would be interesting to see if the 1963 observations of Eggen, which showed a range of 0.08m, give a light curve similar to ours when plotted with respect to the same orbital period. Zero phase in our figure is arbitrary, but an epoch of minimum light is JD 2,443,969.85. The one errant point at Delta V = 0.40m around phase 0.875p made us at least consider the possibility of an eclipse but, even though there was no reason at all to suspect the accuracy of that point (which is a mean of three individual observations, each one bracketed by two comparison star measures), we are very reluctant to conclude we have observed an eclipse which, if real, must have been very shallow and extremely brief. Nevertheless, the question of eclipses remains open because there are larger unobserved phase intervals in which an eclipse could be hiding. We are continuing photometry of this interesting binary, to search for possible eclipses and to establish how closely the photometric period coincides with the orbital period. Our appreciation goes to Dr. C. T. Bolton for the help he provided by private correspondence. DOUGLAS S. HALL CHRISTOPHER A. VAUCHER Dyer Observatory Vanderbilt University Nashville, Tennessee 37235 HOWARD LOUTH Louth Observatory 2199 Hathaway Road Sedro Woolley, Washington 98284 References: Argue, A. N. 1966, M.N.R.A.S. 133, 475. [BIBCODE 1966MNRAS.133..475A ] Bolton, C. T. 1978a, private communication on 4 April 1978. Bolton, C. T. 1978b, I.A.U. Commission 42 Working Group on RS CVn Binaries, Circular No. 10. Eggen, O. J. 1964, A.J. 69, 570. [BIBCODE 1964AJ.....69..570E ] Eggen, O. J. 1978, I.A.U. Commission 27, Inf. Bull. Var. Stars, No. 1426. Vaucher, C. A. 1979, Master's Thesis, Vanderbilt University, Nashville, Tennessee.