COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3193 Konkoly Observatory Budapest 24 May 1988 HU ISSN 0374-0676 VARIABLE C IN M33 Variable C is a Luminous Blue Variable (LBV, see Lamers 1987). Its variability was discovered by Hubble and Sandage (1953). Photographic and UBV(R) magnitudes or light curves were published by Hubble and Sandage (1953), Humphreys (1975), Humphreys et al. (1984), Rosino and Bianchini (1973), Sharov (1973, 1981) and van den Bergh et al. (1975). As a result of the supernova search carried out in Konkoly Observatory (by M. L.) there are eighty plates of M33 which were used to estimate the magnitudes of the LBVs of this galaxy (results for Var. B and Var. 2=Y Tri will be reported later). The observations were made between 1965 and 1987 with the 60/90/180 cm Schmidt-telescope of Konkoly Observatory in Piszkesteto using Kodak 103aO plates without filters. The magnitudes, given in Table I, are eye estimates using the sequence of Hubble and Sandage (1953). The uncertainty in these values is about 0.5 mag. The light curve of Var. C is shown in Figure 1. It can be seen that the star is in its maximum phase. Previously only one bright maximum was observed by Hubble and Sandage (1953), though Rosino and Bianchini (1973) also reported a small, flat maximum in the middle 60's. Lamers (1987) divided the light curve changes of the LBVs into three classes. The observed variation of Var. C clearly belongs to the second class, i.e. the moderate variations (the photographic amplitude is ~1.5 mag). This means that the change in brightness is connected with increased Table I Photographic observations of Variable C J.D. mpg J.D. mpg J.D. mpg 2400000+ 2400000+ 2400000+ 39090.51 16.6 41714.34 16.5 44136.58 16.6 39498.38 16.3 41903.53 16.7 44167.47 16.6 39529.3 16.5 41921.55 16.7 44256.3 16.7 39711.55 16.1 42008.55 16.7 44554.47 16.6 39766.41 16.4 42066.4 16.7 44912.59 16.8 39796.44 16.5 42095.3 16.7 44989.29 16.6 39827.53 16.7 42278.44 16.7 45018.31 16.7 40073.56 16.4 42397.36 16.8 45197.53 16.8 40092.48 16.1 42473.31 16.8 45230.43 16.8 40144.49 16.6 42695.46 16.7 45261.46 16.7 40157.49 16.1 42725.47 16.8 45347.26 16.6 40183.42 16.5 42754.44 16.7 45593.5 16.0 40203.38 16.4 42756.5 16.8 45615.46 16.0 40230.24 16.4 43013.52 16.7 45647.49 15.6 40654.31 16.6 43072.49 16.7 45940.56 15.5 40798.54 16.6 43191.3 16.7 46026.43 15.4 40837.56 16.7 43344.57 16.6 46030.28 15.3 40916.47 16.7 43399.43 16.8 46321.43 15.4 41164.53 16.7 43430.5 16.6 46355.55 15.6 41183.5 16.7 43464.5 16.7 46441.35 15.3 41213.45 16.6 43489.29 16.7 46468.36 15.3 41518.55 16.4 43720.55 16.7 46677.57 15.4 41520.51 16.6 43756.43 16.7 46706.41 15.5 41625.46 16.6 43757.56 16.8 46738.5 15.7 41679.26 16.6 43787.54 16.8 46763.46 15.6 41687.38 16.5 43809.56 16.6 47060.48 15.5 41689.28 16.6 43815.28 16.6 [FIGURE 1] mass loss, while the bolometric magnitude is constant (Mbol = -9.8 mag, Humphreys et al. 1987). Using the theoretical calculations of Davidson (1987), Lamers (1987) derived various relations between temperature, magnitude and mass loss rate. For small rates the connection between the change in mass loss and change in magnitude is Delta log Mdot ~ -0.3 Delta mv Unfortunately, we have photographic amplitude instead of visual, so the values of Delta log Mdot were calculated for several values of Delta mv. Adopting the value of Mdot=3*10^-5 Msol/yr for the mass loss rate in maximum (Humphreys et al. 1987), the calculated minimum rates are given in Table II. Table II Delta mv Delta log Mdot Mdot (M_sol/yr) 1.0 -0.30 1.5 x 10^-5 1.5 -0.45 1.1 x 10^-5 2.0 -0.60 7.5 x 10^-6 M. LOVAS and E. ZSOLDOS Konkoly Observatory Budapest, P.O. Box 67 1525 Hungary References: Davidson, K. 1987, Ap.J. 317, 760 [BIBCODE 1987ApJ...317..760D ] Hubble, E., Sandage, A. 1953, Ap.J. 118, 353 [BIBCODE 1953ApJ...118..353H ] Humphreys, R.M. 1975, Ap.J. 200, 426 [BIBCODE 1975ApJ...200..426H ] Humphreys, R.M., Blaha, C., D'Odorico, S., Gull, T.R., Benvenuti, P. 1984, Ap.J. 278, 124 [BIBCODE 1984ApJ...278..124H ] Humphreys, R.M., Leitherer, C., Stahl, O., Wolf, B., Zickgraf, F.-J. 1987, B.A.A.S. 19, 1053 [BIBCODE 1987BAAS...19R1053H ] Lamers, H.J.G.L.M. 1987, in: Instabilities in Luminous Early Type Stars, eds. H.J.G.L.M. Lamers, C.W.H. de Loore, D. Reidel, p. 99 [BIBCODE 1987ASSL..136...99L ] Rosino, L., Bianchini, A. 1973, A.Ap. 22, 453 [BIBCODE 1973A&A....22..453R ] Sharov, A.S. 1973, Per.Zv. 19, 3 --- 1981, Per.Zv. 21, 485 van den Bergh, S., Herbst, E., Kowal, C.T. 1975, Ap.J.Suppl. 29, 303 [BIBCODE 1975ApJS...29..303V ]