COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS NUMBER 367 Konkoly Observatory Budapest 1969 July 22 REPORT ON THE OBSERVATIONS OF THE FLARE STAR AD Leo OBTAINED DURING 1969 The results obtained from our photoelectric observations of AD Leo carried out from February, 9 to May, 24 at the Catania Observatory stellar station (Serra La Nave, 1700 m above sea level), are here reported. The Cassegrain reflectors with photomultiplier + + filters combinations utilized are indicated in the following Table: Telescope Photo- Spectral Schott Light (aperture) multiplier response filters 30 cm EMI 6256 A S 13 GG 14 (2 mm) v 61 cm EMI 6256 S S 13 BG 12 (1 mm) + + GG 13 (2mm) b 91 cm EMI 6256 A S 13 BG 12 (1 mm) + + GG 13 (2 mm) b Considering only once the period of simultaneous observations at different instruments, we have gathered a total Combined coverage of 58.4 hours in 18 nights. During this period 10 flares were observed. No systematic measurements of the comparison star BD +20deg2475 were made but its luminosity was checked with BD +21deg2193. The data referring to the observations made during the international patrol planned by the Working Group on flare stars (Andrews, et al. 1968) have already been published (Cristaldi, et.al. 1969), but they were included in this report in order to give all our observed data according to the standardised one proposed by Andrews, et al. (1969). The light curves of the flares no. 1 to no. 5 are here omitted because they have been already published on the (I_0+f I_0)/I_0 scale (Cristaldi, et al. 1969). The characteristics of our observations and the obtained data are given in Tables I and II. No transformation equations to the standard UBV system were applied, therefore the b and v lights quoted in the Tables are in our instrumental system. The accompanying Figures show the light curves of the observed flares. Unfortunately, the upper part of the most intense flare (no. 10) was lost because the operator could not switch the instrumental sensitivity; therefore, the t_max, t_e, I(m)_max and P data given in the Table II, are determined from a free-hand extrapolation of the light curve (broken line). Finally, we should like to point out that in the case of a complex flare light curve (like the one indicated in the Figure as curve no. 8-9) we consider the peaks as belonging to independent flares when separated by even a small interval of time during which the (I_0+f-I_0)-I_0 value drops to zero. Catania Astrophysical Observatory, Italy. 1969, July 14 S. CRISTALDI, M. NARBONE and M. RODONO REFERENCES Andrews, A. D., Chugainov, P. F., Gershberg, R. E, and Oskanian, V. S., 1968, Comm. 27 IAU, Inf. Bull. Var. Stars, No. 175 Cristaldi, S., Narbone, M. and Rodono, M., 1969, Comm. 27 IAU, Inf. Bull. Var. Stars, No. 333 Andrews, A. D., Chugainov, P. F., Gershberg, R. E. and Oskanian, V. S. 1969, Comm.27 IAU, Inf. Bull. Var. Stars, No. 326 [FIGURE 1] [FIGURE 2] TABLE I M L T1 L Detailed Coverage (UT) TC Delta m_lim CC Feb. 09 91 b 01h31m-0255; 0258-0328; 0331-0411; 0413-0454. 195m +4.62 195m Feb. 13 " " 2008-2142; 2147-2225. 132 +3.68 132 Feb. 14 " " 1902-1948. 49 +3.72 30 v 1908-1927; 1932-1948; 1958-1959, 38 +4.05 47 Feb.15-16 91 b 2025-2035; 2037-2205; 2212-2307; 2313-0008; 0013-0044. 239 +4.25 30 v 1945-2032; 2042-2046; 2053-2231; 2238-2330; 2339-2349. 211 +4.08 292 Feb.17-18 91 b 1938-1957; 1959-2035; 2041-2056; 2104-2134; 2138-2147; 2153-2210; 2213-0040; 0045-0139 0142-0151; 0201-0220; 0224-0349. 442 +4.25 442 Feb.21-22 " " 1911-2036; 2038-2134; 2141-0129; 0140-0225; 0228-0300. 443 +4.35 443 Mar.01-02 " " 1923-2131; 2133-2218; 2220-0015; 0017-0208; 0209-0226; 0230-0344; 0347-0401. 502 +2.82 502 Mar. 11 " " 1951-2111; 2113-2128. 93 +4.48 93 18 " " 1850-2017; 2022-2057; 2105-2204. 181 +4.40 181 Mar.21-22 " " 22h56m-2319; 2324-0007; 0010-0018; 0021-0081. 104 +4.40 104 Mar.31-01 " " 2220-2249; 2251-2318; 2320-2349; 2351-0007; 0012--0055. 144 +3.08 144 Apr.02-03 " " 1944-2208; 2210-2302; 2304-2312; 2314-2333; 2335-0015; 0018-0118. 323 +3.58 323 Apr.03-04 " " 2216-2234; 223g-2317; 2322-0010; 0014-0034; 0039-0044; 0049-0116. 163 +4.56 163 May 01 " " 2004-2250. 166 +3.75 166 May 03 " " 1941-2003. 22 +3.85 22 May 16 61 " 2028-2103. 35 +3.20 35 May 18 61 " 2009-2027; 2029-2142; 2145-2221; 2223-2301; 2304-2307. 168 +3.08 168 May 24 61 " 2058-2106; 2108-2129; 2132-2133; 2135-2155. 50 +2.62 50 M = month; D = day; T1 = cm aperture of telescope; L = light; TC = total coverage per night; Delta m_lim = -2.5 log(3sigma/I_0) where sigma represents the standard deviation of the random noise fluctuations and I_0 represents the intensity of the quiet star; CC = combined coverage from different instruments. TABLE II Observed Flares M D CC No T1 L t_b t_max t_e Delta m_lim I(m)_max P sec z Feb. 13 132m 1 91 b 21h26m9 21h29m1 ? +3m7 +2m08 ? 1.205 " 14 46 2 " " 19 08.0 19 08.8 19h10m6 +3.7 +2.25 0.19min 2.164 " " " 3 " " 19 10.0 19 12.2 19 17.0 +3.7 +2.08 0.50 2.138 " 15 272 4 " " 20 54.4 20 55.2 21 10.0 +4.2 +1.62 0.57 2.184 " " " 5 " " 23 25.4 23 25.6 23 31.0 +4.2 +2.12 0.09 1.088 Mar. 01 483 6 " " 22 59.0 22 59.9 23 00.0 +3.0 +2.12 0.06 1.051 Apr. 04 158 7 " " 01 01.7 01 02.1 01 09.8 +4.4 +1.70 0.31 2.061 May 01 159 8 " " 20 44.5 20 44.7 20 45.0 +3.8 +2.00 0.02 1.184 " " " 9 " " 20 45.1 20 45.3 21 45.5 +3.8 +1.38 0.04 1.185 10 " " 21 27.9 21 29.1 22 05.0 +3.8 -1.80 18.78 1.318 M = month; D = day; CC = combined coverage from different instrument; T1 = cm aperture of telescope; L = light; t_b = UT of the beginning; t_max = UT of the maximum intensity; t_e = UT of the end; Delta m_lim = -2.5 log(3sigma/I_0), where sigma represents the standard noise fluctuation and I_0 represents the intensity of the quiet star; I(m)_max = 2.5 log [(I_0+f)/I_0]_max; P = integral(I_0+f-I_0)/I_0 dt (integrated intensity in minutes).