COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2715 Konkoly Observatory Budapest 29 April 1985 HU ISSN 0374 - 0676 UBV PHOTOMETRY OF HR 8752 The variable G-type hypergiant HR 8752 (= HD 217476 = V509 Cas) is among the brightest stars in the Galaxy (Humphreys, 1978). Its spectrum has undergone remarkable changes recently (Lambert and Luck, 1978). We present here photoelectric UBV photometry of this star. The observations were made in 1978-81 and 1984-85 with the 60 cm telescope in Budapest and the 1 m telescope in Piszkesteto, respectively. The star used for comparison was HR 8761, with V = 6.20, B-V = 1.50 and U-B = 1.53 (Argue, 1966). The observations are given in the Table (the magnitude differences are in the sense variable minus comparison). Table J.D. DeltaV Delta(B-V) Delta(U-B) 2443739.544 -1.327 -0.029 3797.325 -1.333 -0.011 3848.210 -1.341 -0.040 4083.526 -1.399 -0.062 4113.444 -1.409 -0.138 4128.340 -1.471 -0.133 4133.562 -1.471 -0.125 -0.428 4158.431 -1.463 -0.144 -0.364 4166.508 -1.448 -0.145 -0.382 4172.296 -1.454 -0.134 -0.393 4499.565 -1.344 -0.172 -0.433 4511.437 -1.343 -0.175 4514.385 -1.349 -0.163 -0.473 4541.289 -1.343 -0.142 -0.450 4854.535 -1.317 -0.070 -0.296 5952.458 -1.372 -0.209 -0.522 5957.471 -1.386 -0.224 -0.461 5989.434 -1.365 -0.233 -0.492 5990.358 -1.367 -0.237 -0.553 5990.366 -1.369 -0.227 -0.554 [FIGURE 1] Figure: Light and colour curves of HR 8752 vs. J.D., Symbols: dots - Percy and Welch (1981), crosses - Parsons and Montemayor (1982), square - Walker (1984), circles - present paper. Table (cont.) J.D. DeltaV Delta(B-V) Delta(U-B) 5991.373 -1.366 -0.232 -0.554 5993.370 -1.353 -0.249 -0.512 6018.306 -1.321 -0.276 -0.539 6019.245 -1.279 -0.329 -0.510 6049.508 -1.294 -0.179 -0.564 6074.222 -1.288 -0.183 -0.551 The light curve contains points from five cycles from mid-1979. It is, however, evident from the Figure that neither the period (about one year, obtained by Percy and Welch, 1981), nor the amplitude of the variation remains constant. According to Lambert et al. (1981), HR 8752 has been pulsating. They compared the star with models of long-period variables. The spectrum of HR 8752 shows, however, features characteristic for stars earlier than those. Smolinski et al. (1982) found the shape of the Halpha profile to be similar to that in long-period cepheids. Similar phenomenon was observed at the beginning of this century: Adams and Joy (1919) found the spectrum of HR 8752 to be nearly the same as that of delta Cephei and zeta Geminorum. The pre-1979 behaviour of HR 8752 seems to be quite different. The 1976- 78 observations of Walker (1983) and the first three lines in the Table (which are not plotted in the Figure) apparently do not show the same type of variation. It may be in connection with the shell ejected sometime between 1973 and 1975 (Lambert et al., 1981). E. ZSOLDOS and K. OLAH Konkoly Observatory Budapest XII., P.O. Box 67 H - 1525, Hungary References: Adams, W.S., Joy, A.H., 1919, P.A.S.P. 31. 184 Argue, A.N., 1966, Mon. Not. R. astr. Soc. 133. 475 [BIBCODE 1966MNRAS.133..475A ] Humphreys, R.M., 1978, Astrophys. J. Suppl. 38. 309 [BIBCODE 1978ApJS...38..309H ] Lambert, D.L., Hinkle, K.H., Hall, D.N.B., 1981, Astrophys. J. 248. 638 [BIBCODE 1981ApJ...248..638L ] Lambert, D.L., Luck, R.E., 1978, Mon. Not. R. astr. Soc. 184. 405 [BIBCODE 1978MNRAS.184..405L ] Parsons, S.B., Montemayor, T.J., 1982, Astrophys. J. Suppl. 49. 175 [BIBCODE 1982ApJS...49..175P ] Percy, J.R., Welch, D.L., 1981, P.A.S.P. 93. 367 [BIBCODE 1981PASP...93..367P ] Smolinski, J., Climenhaga, J.L., Funakawa, H, Fletcher, J.M., 1982, I.B.V.S. No. 2229 Walker, E.N., 1983, Mon. Not. R. astr. Soc. 203. 403 [BIBCODE 1983MNRAS.203..403W ] 1984, Vistas in Astron. 27. 421 [BIBCODE 1984VA.....27..421W ]