COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS NUMBER 616 Konkoly Observatory Budapest 1972 January 22 PHOTOELECTRIC OBSERVATIONS OF THE FLARE STAR EV Lac The continuous photoelectric monitoring of the flare star EV Lac was carried out at the Crimean Astrophysical Observatory in the period of the international patrol, September 11-27, 1971. The observations were made with the 64-cm meniscus telescope in the photometric system B. The coverage, characteristics of the observed flares and their curves are given below. No reductions were made to exclude the light of the optical companion of EV Lac. The explanation of designations and symbols can be found in Ref. 1. stars were presented by different authors. In order to study EV Lac from this point of view we made comparisons of it with the stars BD +43deg4304 (a) and BD +43deg4303 (b). The observations accumulated for three seasons, 1969-1971, show that the range of secondary variations is about 0.^m03 (in the B light). Observations obtained in June-September 1971 give some indication of a period of about 5 days in the changes of the undisturbed star brightness. But a periodicity is not confirmed from the observations obtained in October 1971. The mean differences in the B magnitudes of EV Lac and the comparison star BD +43deg4303 for 4 nights in the period of cooperative observations are: 1971 Sep. 11/12: +0.113, 22/23: +0.115, 26/27: +0.125, 27/28: +0.110. In order to show how this mean differences were obtained we give Figure 1 where the individual measurements of the magnitude difference are shown as points and the straight lines show the mean difference for each of 4 nights. P.F. CHUGAINOV A.N. KULAPOVA N.I. SHAKHOVSKAYA Crimean Astrophysical Observatory Reference: (1) A.D. Andrews, P.F. Chugainov, R.E. Gershberg, V.S. Oskanian, Comm. 27 I.A.U. Inf. Bull. Var. Stars, No. 326, 1969. Date, 1971 Coverage (U.T.) Oct. 11 17^h35^m-17^h47^m,1750-1814,1820-1842,1847-1908,1910-1932, 1934-2011, 2016-2044, 2047-2210, 2214-2243, 2247-2257, 2301-2313, 2316-2340, 2343-2400 12 0000-0001, 0004-0048, 0051-0125, 1730-1752, 1753-1807, 1812-1835, 1838-1847, 1853-1904, 1920-1926, 1928-1955, 1959-2005, 2103-2123, 2129-2142, 2210-2234, 2238-2304, 2312-2344, 2349-2400 13 0000-0001, 0002-0027, 0032-0044, 0046-0049, 0056-0104, 0109-0111 15 1741-1749, 1812-1928 17 1725-1759, 1805-1858, 1908-2023, 2027-2029 18 1749-1806, 1827-1921, 1925-1947, 1952-2022, 2025-2111, 22 1719-1739, 1754-1836, 1840-1854, 1858-1951, 1955-2014, 2017-2034, 2037-2053, 2056-2116, 2119-2209, 2212-2322, 2331-2400 23 0000-0044, 0048-0105, 1715-1727, 1730-1750, 1752-1816, 1819-1835, 1837-1854, 1901-1925, 1929-2003, 2005-2024, 2029-2048 26 1645-1701, 1703-1722, 1724-1753, 1755-1810, 1838-1908, 1914-1935, 1940-2000, 2007-2031, 2035-2100, 2105-2142, 2149-2207, 2211-2226, 2228-2250, 2254-2255, 2257-2258, 2301-2302, 2307-2338, 2340-2400 27 0004-0005, 0008-0009, 0012-0013, 0016-0031, 0033-0037, 0040-0101, 0103-0105, 1648-1717, 1722-1751, 1754-1849, 1852-1949, 1955-2033, 2037-2119, 2124-2136, 2140-2141, 2145-2146, 2149-2150, 2153-2217, 2221-2222, 2225-2226, 2229-2230, 2234-2302, 2305-2321, 2325-2345, 2347-2400 28 0006-0030, 0033-0053, 0055-0111, 0114-0117 [FIGURE 1] Characteristics of the flares observed Date U.T. t_b t_a (I_f-I_0)/I_0 sigma/I_0 P_B Notes 1971 maximum minutes maximum minutes Sept. 11 20 04.8 0.5 4.1 0.09 +-0.010 0.14 11 21 05.0 1.6 44.7 0.82 0.015 5.56 1 11 23 28.2 1.3 30.2 0.43 0.007 1.92 12 22 51.7 0.9 10.1 0.14 - 0.77 2 16 18 52.8 0.6: 14.2: 0.4: - 1.0: 3 22 19 06.3 0.5 27.9 0.36 0.015 1.86 22 22 56.9 3.8 63.1 1.59 0.010 10.16 26 20 21.3 1.6 7.9 0.08 0.015 0.40 26 23 34.8 0.9 2.0 0.10 0.013 0.26 27 17 43.5 1.0 7.5 0.30 0.014 0.47 27 18 29.3 4.0 20.7 0.31 0.020 3.26 4 27 20 04.3 0.8 8.2 0.21 0.013 0.55 Notes: 1. Secondary maximum at 21 07.7. 2, Interference of clouds; the light curve is not presented. 3. Complex event in the interval 18 52-19 07; interference of clouds; the light curve is not presented. 4. Secondary maximum at 18 35.8. [FIGURE 2] [FIGURE 3] [From IBVS 0632] Errata Please add to the Tables "Coverage" published in IBVS No. 615 and 616 respectively, the following (read in the Coverage-Table of No. 616 Sept. instead of Oct.): Coverage Sept.16 (17 17-19 14, 19 18-20 57, 21 06-21 12, 21 17-22 04, 22 07-22 19, 22 24-23 01, 23 05-23 34, 23 37-24 00) 17 (00 00-00 03, 00 09-00 32, 00 40-01 06, 01 25-01 46) Oct. 15 19 01-19 08, 19 09-19 36, 19 42-20 40, 20 42-21 41, 21 42-21 58, 22 00-22 09, 22 11-22 40, 22 42-23 21, 23 26-23 44, 23 46-24 00 16 00 00-00 02, 00 03-00 23, 00 24-00 30