COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2349 Konkoly Observatory Budapest 13 June 1983 HU ISSN 0374-0676 UNUSUAL BEHAVIOUR OF THE RECURRENT NOVA T CrB Our observations of T CrB were accomplished on the 48 cm telescope of the Byurakan Astrophysical Observatory during nine nights in March-June 1982 and one night in January 1983. The aim of these observations was to detect possible flares, expected (Palmer and Africano, 1982) about the phase 0.2 of the orbital period (Kraft, 1958). The star has been monitored in the u band. Since 02.04.1982 differential photometry in the ubv bands was accomplished as well. BD+26d2761 served as comparison star. The stars BD+26d2756 and BD+26d2763 were used as control stars. The results of monitoring are given in Table I, where: phi is the orbital Table I ----------------------------------------------------------- Date phi A t(min) sigma_T sigma_BD T(min) ----------------------------------------------------------- 04.03.1982 0.06 0.40m 4.9 0.090m 0.010m 64 13.03 0.10 0.65 4.4 0.146 0.023 77 15.03 0.11 0.49 5.9 0.085 0.032 94 30.03 0.17 0.41 4.9 0.069 0.026 81 02.04 0.19 0.63 4.9 0.122 0.025 189 08.06 0.48 - - 0.048 0.045 117 19.06 0.53 - - 0.058 0.069 63 29.06 0.57 - - 0.072 0.076 34 25.01.1983 0.50 - - 0.066 0.072 20 ----------------------------------------------------------- phase, A - the maximum amplitude of ultra-violet light variation during the night, t - average time interval between light maxima, sigma_T - standard deviation of T CrB, sigma_BD - standard deviation of the comparison star BD+26.2761d, T - the duration of each night's observation. One can see from Table I that since 8 June 1982 the observed (see as well Walker, 1956, Bianchini and Middleditch, 1976) ultra-violet light variation of T CrB has stopped. The standard deviation of T CrB (sigma_T) has decreased and become equal to the corresponding value (sigma_BD) of the comparison star. The results of differential photometry (Table II) presented in Figure 1, show that the brightness of T CrB decreased in all the observed bands (ubv) at the same time when the ultra-violet light variations stopped. Table II ----------------------------------- Date Deltau Deltab Deltav ----------------------------------- 04.03.1982 -0.46m - - 13.03 -0.96 - - 15.03 -0.22 - - 30.03 -0.89 - - 02.04 -0.70 0.17m 0.06m 08.06 0.11 0.75 - 15.06 0.23 0.73 0.53 19.06 0.05 0.71 0.55 29.06 0.06 0.72 0.49 25.01.1983 -0.59 0.40 0.28 ---------------------------------- [FIGURE 1] The average brightness decrease in different bands was: Deltau = 0.70m, Deltab = 0.56m, Deltav = 0.47m, That means that the star has reddened. The observation of T CrB in 1983 showed that the brightness had somewhat increased, yet had not reached its original value. The average increase of brightness in ubv bands was: Deltau = 0.70m, Deltab = 0.33m, Deltav = 0.24m. The star had become bluer. The ultra-violet light variation was not observable. A.V. OSKANIAN Jr. Byurakan Observatory Armenian SSR, USSR 378433 Byurakan References: Bianchini, A., Middleditch, J., 1976, I.B.V.S. No. 1151 Kraft, R.P., 1958, Astrophys. Journal 127, 625 [BIBCODE 1958ApJ...127..625K ] Palmer, L.H., Africano, J.L., 1982, I.B.V.S. No. 2069 Walker, M.F., 1956, I.A.U. Symp. No. 3, p. 46 [BIBCODE 1957IAUS....3...46W ]