COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3600 Konkoly Observatory Budapest 8 May 1991 HU ISSN 0374 - 0676 SEVEN YEARS OF PHOTOMETRY FOR HR 8752 = V509 Cas The hypergiant HR 8752 = V509 Cas has been observed photometrically at the Corralitos Observatory for the past seven observing seasons. Some of this work has been previously published (Halbedel 1985,1986,1988). This communication reports on the observations obtained since the last of these papers. HR 8752 has been previously known to be variable in both spectrum and magnitude. Observed spectral types have ranged from F6 (observed in 1985 by Mantegazza 1988) to K2-5 Ia (Lambert & Luck 1978). Photometrically, the star seems to vary semi-regularly: Percy & Welch (1981) suggest a period of about a year, Ferro (1985) 385 days, and Sheffer & Lambert (1987) 415 days. The most recently published data show that while the star does undergo these semi-periodic changes, the maxima are getting progressively fainter and the star bluer (Halbedel 1988). HR 8752 has been observed photometrically at the Corralitos Observatory for the past 7 observing seasons with its 0.6-m. telescope and uncooled EMI 9924A tube-based photon-counting photometer. Comparison stars utilized were HR 8761 (V=6.20; B-V=+1.50) and HR 8778 (V=6.43; B-V=+0.90). Over the time period of observation, these two stars were stable to within 0.015 in V and 0.016 in B-V. The thusfar unpublished Corralitos magnitudes appear in Table 1 and graphically in Figure 1. It may be seen that the trend towards fainter maxima and bluer color has continued. [FIGURE 1] FIGURE 1: MAGNITUDES AND COLORS FOR HR 8752. THE TOP DIAGRAM SHOWS V MAGNITUDE, THE BOTTOM B-V. The star is fainter now than at any time in the past 7 years. It is also possible that there has been a reduction in the range of each individual cycle, though this may be an effect of time incompleteness of observation. A period search over all 7 years of data utilizing the Minimum Phase TABLE 1: MAGNITUDES FOR HR 8752 JD JD (2440000+) V B-V (2440000+) V B-V 7320.93260 5.009 +1.225 7806.77917 4.971 +1.100 7411.84791 5.000 1.166 7810.74028 4.967 1.145 7412.77708 5.006 1.144 7818.73472 4.989 1.128 7435.82986 5.035 1.184 7827.73819 4.986 1.126 7436.74236 5.006 1.229 7835.69891 4.991 1.111 7437.70763 5.028 1.161 7859.64861 5.021 1.121 7440.73888 5.053 1.173 7878.62638 4.990 1.151 7441.71388 5.044 1.187 7880.58889 5.039 1.133 7470.67777 5.062 1.196 7896.59583 5.046 1.142 7472.68124 5.014 1.186 7915.59236 5.044 1.131 7475.64374 5.041 1.193 7917.58889 5.057 1.130 7477.62847 5.046 1.179 8041.92777 5.036 1.136 7501.66181 5.023 1.158 8122.77986 5.030 1.106 7516.59236 5.015 1.164 8133.82083 5.031 1.109 7525.60972 4.988 1.178 8159.74236 5.028 1.099 7526.58472 5.002 1.129 8176.67778 5.000 1.119 7527.59236 4.962 1.162 8178.71181 5.039 1.101 7540.57777 4.984 1.135 8201.67083 5.068 1.112 7703.91181 5.086 1.191 8204.60833 5.075 1.116 7788.76874 4.991 1.136 8225.61667 5.099 1.136 7790.74028 5.015 1.122 8228.63819 5.120 1.151 7793.80694 4.950 1.133 8244.61806 5.101 1.134 Dispersion Technique of Stellingwerf (1978) finds a best overall period of 409 days, in keeping with previous determinations. In view of the interesting behavior of this star and the possibility of long-term variations upon which the >1 year long cycles are superimposed, it will continue to be observed at the Corralitos Observatory in the future. E.M. HALBEDEL Corralitos Observatory P.O. Box 16314 Las Cruces, NM 88004-6314 U.S.A. REFERENCES Ferro, A. 1985, MNRAS, 216, 571 [BIBCODE 1985MNRAS.216..571A ] Halbedel, E.M. 1985, IBVS No. 2718 Halbedel, E.M. 1986, IBVS No. 2876 Halbedel, E.M. 1988, IBVS No. 3170 Lambert, D.L. & Luck, R.E. 1978, MNRAS, 184, 405 [BIBCODE 1978MNRAS.184..405L ] Mantegazza, L. 1988, IBVS No. 3269 Percy, J.R. & Welch, D.L. 1981, PASP, 93, 367 [BIBCODE 1981PASP...93..367P ] Sheffer, Y. & Lambert, D.L. 1987, PASP, 99, 1277 [BIBCODE 1987PASP...99.1277S ] Stellingwerf, R.P. 1978, ApJ, 224, 953 [BIBCODE 1978ApJ...224..953S ]