COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2129 Konkoly Observatory Budapest 1982 April 26 HU ISSN 0374-0676 THE LIGHT VARIABILITY OF THE Be STAR HD 58050 (OT Gem) HD 58050 is a Be star (Hubert A.M. et al., 1979) whose variability has been suspected by Hoffmeister (1934). Recently, members of European Group GEOS visually observed a remarkable increase in its brightness (Ballereau et al., 1981 and Figer, 1981a, 1981b), to which some spectral changes have been correlated (Hubert A.M. et al., 1981). Recently HD 58050 has been named OT Gem (Kholopov et al., 1981). In his remarks, Hoffmeister also supposed a variability on short timescale, comparing HD 58050 with HD 59059. This possibility has been also suggested by Figer (1981a, 1981b): he proposed a period of 0.1250 or 0.1429 days on the basis of visual estimates. In order to establish the reliability of this periodicity, some photoelectric observations have been carried out in the nights of 1982 January, 30 and March, 15 and 16 at Merate Observatory. HD 59059 (V=6.18, B-V=-0.03, A0) has been used as comparison star and HD 60107 (V=5.25, B-V=+0.05, A1V) as check star. During each night no appreciable variation has been detected, as Table I and Table II show. Each DeltaV (or DeltaB) is the mean of several (4 or 5) measures; sigma is the standard error. On the other hand, small changes in brightness are present in the night-to-night mean magnitudes. This variability on large time-scale is also proved by photographic observations (Berthold, 1982). Consequently, HD 58050 is a gamma Cas variable only. Mean DeltaV values of each night are, respectively: -0.185, -0.190, -0.198; no variation is found in the colour index B-V. An additional remark must be made about HD 60107, the check star: it has been suspected to be a variable star on the basis of the photoelectric observations collected by Blanco et al. (1968), but with a great deal of prudence (FitzGerald, 1973). Eggen (1963) notes a variability in the radial velocity, too, However, HD 59059-HD 60107 differences have been constant during my Table I ------------------------------------------------------- Hel. J.D. DeltaV sigma Hel. J.D. DeltaV sigma 2440000 + 2440000 + ------------------------------------------------------- 5000.451 - 0.185 0.002 5044.318 - 0.188 0.002 .455 - 0.186 0.001 .329 - 0.189 0.007 .460 - 0.188 0.003 .341 - 0.195 0.003 .480 - 0.186 0.005 .358 - 0.189 0.004 .495 - 0.187 0.002 .369 - 0.192 0.003 .529 - 0.186 0.005 .541 - 0.185 0.003 5045.278 - 0.199 0.002 .571 - 0.184 0.003 .285 - 0.199 0.001 .576 - 0.180 0.001 .295 - 0.194 0.005 .309 - 0.199 0.002 .315 - 0.200 0.005 5044.277 - 0.195 0.003 .314 - 0.195 0.004 .286 - 0.190 0.005 .300 - 0.184 0.004 V observations of HD 58050. DeltaV are in the sense HD 59059 minus HD 58050 Table II --------------------------------------------------- Hel. J.D. DeltaB sigma --------------------------------------------------- 2440000 + 5000.482 - 0.060 0.002 B observations of .513 - 0.060 0.001 HD 58050. DeltaB are in .531 - 0.062 0.003 the sense HD 59059 .540 - 0.062 0.002 minus HD 58050. 5045.328 - 0.073 0.005 Table III -------------------------------------------------------- Hel. J.D. DeltaV sigma Hel. J.D. DeltaV sigma -------------------------------------------------------- 2440000 + 2440000 + 5000.468 + 0.972 0.001 5044.335 + 0.957 0.005 .514 + 0.959 0.005 .353 + 0.959 0.001 .555 + 0.959 0.006 5045.291 + 0.960 0.003 5044.285 + 0.964 0.004 .304 + 0.958 0.002 .299 + 0.966 0.004 .321 + 0.966 0.004 .314 + 0.953 0.004 .342 + 0.964 0.004 V observations of HD 60107. DeltaV are in the sense HD 59059 minus HD 60107. observations, as Table III shows: FitzGerald's hypothesis about incorrect data seems to be plausible. Anyhow, further measures are desirable. E. PORETTI Osservatorio Astronomico di Brera Via E. Bianchi, 46 22055 Merate Italy References: Ballereau D., Hubert A.M., 1981, IAUC 3565 [BIBCODE 1981IAUC.3565....1B ] Berthold Th., 1982, private communication Blanco V.M., Demers S., Douglass G.G., FitzGerald M.P., 1968, Publication of the USNO, Second Series, Vol. XXI Eggen O.J., 1963, A.J., 68, 697 [BIBCODE 1963AJ.....68..697E ] Figer A., 1981a, GEOS Circular SA 1 Figer A., 1981b, Workshop on Pulsating B stars, Nice, 237-246 [BIBCODE 1981pbs..work..237F ] FitzGerald M.P., 1973, A.&A. Suppl., 9, 297-311 [BIBCODE 1973A&AS....9..297F ] Hoffmeister C., 1934, AN, 253,195 [BIBCODE 1934AN....253..195H ] Hubert A.M., Hubert H., 1979, An atlas of Be stars Hubert A.M., Hubert H., Ballereau D., Chambon M.Th., 1981, Be stars, Munich, 195-199 [BIBCODE 1982IAUS...98..195H ] Kholopov P.N., Samus N.N., Kukarkina N.P., Medvedeva G.I., Perova N.B., 1981, I.B.V.S. No. 2042