COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 942 Konkoly Observatory Budapest 1974 October 30 PHOTOELECTRIC OBSERVATIONS OF THE Ap STAR HD 27309 = 56 Tau In his catalogue, Osawa (Ann. Tokyo AO, Ser. II. 9. 123, 1965) pointed out the Si (lambda 3955, lambda 4200) spectral peculiarity of the star HD 27309 (5m.32). The first photoelectric observations of the star were made by Hildebrant (Dissertation, AdW der DDR, Berlin, 1972) in the UBV system. In spite of the small number of observations, which did not permit the precise determination of the light curve from, a period of 2d.69 could be determined for the light variation. Within the range of a program of investigation of Ap-stars in ten different regions of the spectrum in the interval between 3000 and 8000 A (Nikolov, Dissertation, AdW der DDR, Berlin, 1974) the author observed HD 27309 = 56 Tau photoelectrically with the 35 cm reflector of the Academy of Sciences of the GDR at Shemaha Astrophysical Observatory (Azerbaijan SSR) from January 19 to February 18, 1973 (J.D. 2441702-732). Every observation usually consists of five symmetric blocks each of which has the following form: background, comparison star, twice variable, comparison star, background. HD 27176 (A5; 5m.56) was used as a comparison star. The observations are given in the Table in which the headings are selfexplanatory. The differences in magnitude are in the sense comparison HD 27176 minus variable. The phases are calculated by the elements J.D. (min. light)= 2440979.153+ +2d.69.E. Table I J.D. Ph Delta{m} Delta{m} Delta{m} Delta{m} Delta{m} 2440000+ 3450 A 3750 A 4050 A 4620 A 5160 A 1702,274 0,82 1,247 1,056 0,842 0,504 0,322 1705,298 0,94 1,297 - 0,856 0,518 0,359 1707,239 0,66 1,219 1,020 0,820 0,460 0,288 1711,223 0,14 1,335 1,112 0,870 0,528 0,350 1712,261 0,53 1,262 1,059 0,838 0,507 0,324 1713,202 0,88 1,295 1,061 0,845 0,516 0,342 1718,228 0,75 1,232 1,032 0,835 0,482 0,319 1720,276 0,50 1,303 1,100 0,843 0,515 0,329 Table I (continued) J.D. Ph Delta{m} Delta{m} Delta{m} Delta{m} Delta{m} 2440000+ 3450 A 3750 A 4050 A 4620 A 5160 A 1721,223 0,86 1,271 1,056 0,844 0,510 0,336 1724,207 0,97 1,302 1,073 0,853 0,512 0,326 1725,225 0,35 1,370 1,141 - 0,554 0,400 1728,268 0,48 1,366 1,130 0,865 0,536 0,348 1729,190 0,83 1,252 1,047 0,833 0,495 0,323 1732,199 0,94 1,289 1,072 0,848 0,522 0,352 Table I (continued) J.D. Ph Delta{m} Delta{m} Delta{m} Delta{m} Delta{m} 2440000+ 5420 A 6000 A 6470 A 7150 A 8100 A 1702,274 0,82 0,266 0,140 0,076 -0,067 -0,158 1705,298 0,94 0,280 0,154 - -0,029 - 1707,239 0,56 0,220 0,087 - -0,096 -0,199 1711,223 0,14 0,311 0,175 0,085 -0,021 -0,099 1712,261 0,53 0,267 0,138 0,044 -0,072 -0,148 1713,202 0,88 0,280 0,143 0,047 -0,051 -0,135 1718,228 0,75 0,249 0,120 0,031 -0,095 -0,163 1720,276 0,50 0,279 0,166 0,075 -0,044 -0,128 1721,223 0,86 0,275 0,143 0,036 -0,053 -0,140 1724,207 0,97 0,270 0,132 0,047 -0,064 -0,122 1725,225 0,35 0,352 0,195 0,122 - -0,086 1728,268 0,48 0,295 0,154 0,080 -0,038 -0,120 1729,190 0,82 0,265 0,122 0,039 -0,082 -0,154 1732,199 0,94 0,277 0,124 0,053 -0,051 -0,122 University of Sofia Bulgaria A.S. NIKOLOV