COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS NUMBER 423 Konkoly Observatory Budapest 1970 March 20 PHOTOELECTRIC OBSERVATIONS OF THE FLARE STAR YZ CMi In this Bulletin we give preliminary results of our photoelectric observations of the flare star YZ CMi carried out at the Catania Astrophysical Observatory during the cooperative campaign organized by the Working Group on Flare Stars for the period January 31 to February 13, 1970 (Andrews and Chugainov, 1970). The observations were performed with an EMI 6156 A photomultiplier attached to a 61 cm of aperture quasi- cassegrain reflector. As a rule, a Schott filter combination (BG 12/1 + GG 13/2) was used. Some short V measurements, which were carried out in order to determine the colour index of YZ CMi are also included. In Table 1 the effective time coverage is given. The total number of observation hours is 35.7. In Table 2 the characteristics of the 11 observed flares are reported. Figures 1,2 and 3 give the light curves of the observed flares in the relative intensity scale versus Universal Time. C. Lo Presti, G. Russo, F. Spinella and V. Stancanelli collaborated in the present work. Reference Andrews A.D., Chugainov P.F. 1970. Comm. 27 IAU Inf.Bull. Var.Stars. No. 416. [FIGURE 1] [FIGURE 2] [FIGURE 3] [FIGURE 4-5] [FIGURE 6] [FIGURE 7] [FIGURE 8] [FIGURE 9] [FIGURE 10] [FIGURE 11] Table 1 Date 1970 F COVERAGE (U.T.) m_lim -m_0 Feb. 2 B 19h58m-20h02m; 2004-2008; 2015-2016; 2017-2018; 2029-2039; 2040-2054; 2103-2108; 2303-2314; 2320-2354; +3m02 3 B 2254-2301; 2303-2314; 2320-2354; 2357-2359 +3.23 4 B 0000-0049; 0053-0137; 1823-1915; 1921-1932; 1957-2018; 2020-2039; 2041-2100; +3.23* 2109-2130; 2132-2149; 2213-2242; 2243-2252; 2258-2348; +3.54 V 1945-1946; 1947-1948; 2208-2209; 2210-2211; +4.61 5 B 0010-0020; 0022-0059; 0104-0118; 0130-0200; +3.54 1832-1928; 1955-1959; 2001-2012; 2014-2120; 2156-2241; 2256-2352; +3.89 V 0006-0007; 0008-0009; 1950-1953; 2140-2143 +4.61 6 B 0023-0050; 0052-0144; 1915-1919; 1936-2015; 2033-2116; 2118-2212; 2215-2230; +3.89* 2233-2245 +3.74 V 0018-0022 +4.70 8 B 1803-1913; 1916-1932; 1956-2059; 2100-2236; 2243-2314; 2317-2353; +3.88 V 1952-1953; 1954-1955 +4.72 9 B 0019-0116; +3.88 V 0012-0013; 0014-0015; 0138-0139; 0140-0141 +4.72 10 B 2222-2243; 2303-2350; 2359-2400; +3.58 11 B 0000-0024; 0032-0044; 0102-0132. 2021-2041; 2107-2157; 2205-2225; 2227-2244; +3.58* 2246-2304; 2305-2324; 2326-2400 +3.35 12 B 0000-0003; 1934-1936; 1938-2037; 2041-2110; 2124-2233; 2243-2333; +3.35* 2335-2400 +3.04 V 1807-1906; 1913-1932 +3.62 13 B 0000-0007; 0009-0043; 0107-0202 +3.04* 1802-1813; 1814-1852; 2359-2400 +2.82 14 B 0000-0015; 0017-0028; 0030-0045; 0106-0115; 0118-0128; 0129-0143 +2.82 F = Schott filters (B = BG 12/1 + GG 13; V = GG 14/2) M_lim - m_0 = -2.5 log (3 sigma / I_0), where sigma represents the standard deviation of the mean random noise fluctuation for a night and I_0 represents the mean intensity of the quiet star during the same night. *The underlined values of m_lim -m_0 refer to the underlined coverage. TABLE 2 no t_max d_b d_a m_lim -m_0 (m_f-m_0)_max P a b 1970 Feb min min 1 4, 19h10.8m 0.01 0.2 +3.36m +0.92 0.03 - 0 2 4, 20 15.8 0.3 1.6 +3.63 +1.92 0.11 4 0 3 4, 22 28.7 0.2 4.5 +3.45 +0.94 0.33 - 0 4 5, 19 15.3 0.05 0.5 +3.75 +2.06 0.03 1 0 5 5, 19 17.4 0.2 0.4 +3.75 +1.86 0.07 1 0 6 5, 22 05.0 0.1 0.2 +3.96 +1.20 0.02 1 0 7 6, 20 03.0 0.1 1.9 +3.73 +1.34 0.10 2 2 8 8, 18 33.5 0.7 59.0 +3.57 -1.45 16.99 3 1 9 9, 01 01.0 2.4 1.9 +3.37 +0.38 0.64 4 0 10 10, 23 28.3 0.3 3.6 +3.53 +0.67 0.38 - 1 11 13, 01.31.5 0.5 6.3 +3.70 -1.00 2.29 - 0 t_max = date and U.T. of the flare maximum; d_b = duration of the flare before maximum; d_a = duration of the flare after maximum including whatever post-maximum activity; m_lim - m_0 = -2.5 log (3 sigma / I_0) where sigma and I_0 indicate the standard noise fluctuation and the mean intensity of the quiet star near the observed flare, respectively; (m_f - m_0)_max = -2.5 log [(I_0+f - I_0)/I_0]_max, where I_0+f is the intensity deflection due to the quiet star (I_0) plus that of flare (I_f) at maximum; P= Integral ( I_0+f - I_0)/I_0 dt, integrated intensity in minutes; a = flare feature: 1 - uncertain, 2 - double, 3 - multiple, 4 - complex structure; b = sky condition with the following standard: 0 - very clear, 1 - clear, 2 - with some cirrus. S. CRISTALDI M. RODONO Citta Universitaria viale A. Doria 95123 Catania - Italy