COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3695 Konkoly Observatory Budapest 6 February 1992 HU ISSN 0374 - 0676 PHOTOELECTRIC OBSERVATIONS OF V1285 AQL The patrol observations of V1285 Aql, carried out in 1990 and in 1991 were a part of the programme for investigation of fast (several seconds) flares and short-time scale variations on late spectral classes stars at the Department of Astronomy of the Bulgarian Academy of Sciences. They were made in U-color of the standard UBV system and in u-color of the uvby system, using two identical single channel photon-counting photoelectric photometers, attached to 60 cm Cassegrain telescopes in the National Astronomical Observatory Rozhen and in the Belogradchik Astronomical Observatory. The photometers have been described by Panov et al.(1982) and Antov et al.(1991). The altitude above the sea level is 1750 m at Rozhen and 650 m at Belogradchik. The integration time was 1 sec. BD+8 3899 was used as a comparison star for all the observations. du(mag) is the difference between the variable star and the comparison star in the instrumental system. The data processing has been made by Kirov, Antov and Genkov's program system (Kirov et al., 1991). The data about the monitoring intervals in U.T. are given in Table 1 in the following order: - monitoring intervals; - filter; - observatory, where the observations were carried out; - the standard deviation of random noise fluctuation sigma_mag. It was calculated when the intensity of the star in impulses was lessened with the sky background. Total monitoring time: 15h22m37s * - integration time 10 s; R - Rozhen; B - Belogradchik; F - filter; O - observatory. One fast flare was detected during 10h04m08s total monitoring time in 1990 and 5h18m29s total monitoring time in 1991. Data for it are given in Table 2 in the following form: - date; - U.T. of the beginning; - U.T. of the maximum; - the duration of the flare; Monitoring intervals F O sigma_mag Monitoring intervals F O sigma_mag 16/17 July 1990 22/23 September 1990 22h48m14s-23h06m29s U R 0.3 21h27m11s-21h52m52s u B 0.5 23 17 28 -23 35 58 U R 0.3 20 57 36 -22 09 52 u B 0.4 17/18 July 1990 22 10 43 -2 21 24 u B 0.6 21 15 09 -21 24 50 U R 0.09 22 22 29 -22 31 51 u B 0.7 21 25 34 -21 44 54 U R 0.07 22 37 06 -22 49 10 u B 0.4 21 50 06 -22 17 11 U R 0.09 22 50 00 -22 58 36 u B 0.7 22 20 08 -22 51 10 U R 0.09 23/24 September 1990 00 21 23 -00 23 14 U R 0.1 20 10 54 -20 19 47 u B 0.3 00 31 55 -01 09 51 U R 0.1 20 24 05 -20 35 28 u B 0.5 18/19 July 1990 14/15 June 1991 01 39 14 -02 13 16 U R 0.2 23 36 24 -00 00 38 U R 0.08 02 15 58 -02 34 21 U R 0.2 00 07 16 -00 30 39 U R 0.08 23/24 July 1990* 15/16 June 1991 22 08 53 -22 22 10 U R 0.05 23 37 27 -00 00 51 U R 0.1 22 24 50 -22 39 51 U R 0.03 00 03 33 -00 30 04 U R 0.1 22 47 41 -23 26 23 U R 0.05 00 32 14 -00 57 29 U R 0.1 23 36 34 -23 57 15 U R 0.05 14/15 July 1991 24/25 July 1990 23 03 16 -23 28 37 U R 0.1 22 20 16 -22 34 26 U R 0.1 23 36 11 -23 50 34 U R 0.1 22 36 35 -22 48 54 U R 0.1 23 54 38 -00 08 33 U R 0.1 22 54 59 -23 08 19 U R 0.1 9/10 September 1991 26/27 Aug 1990 19 24 59 -19 41 07 U B 0.2 19 45 50 -20 02 23 u B 0.35 19 45 40 -20 01 42 U B 0.2 20 08 42 -20 27 12 u B 0.4 20 12 22 -20 25 31 U B 0.2 20 37 21 -20 52 14 u B 0.5 20 29 52 -20 41 41 U B 0.2 20 56 24 -21 07 36 u B 0.5 10/11 September 1991 21 13 18 -21 25 02 u B 0.5 19 31 23 -19 41 57 U B 0.1 21 33 47 -21 43 50 u B 0.7 19 48 16 -20 00 17 U B 0.1 27/28 Aug 1990 20 04 32 -20 17 52 U B 0.2 20 45 10 -21 00 46 u B 0.35 20 20 12 -20 30 56 U B 0.2 21 06 27 -21 18 30 u B 0.4 11/12 September 1991 21 19 57 -21 31 00 u B 0.4 19 23 38 -19 39 35 U B 0.1 21/22 Sept 1990 19 40 38 -19 51 29 U B 0.1 20 18 42 -20 32 43 u B 0.5 19 55 30 -20 11 03 U B 0.2 20 36 20 -20 39 28 u B 0.7 20 12 25 -20 19 43 U B 0.15 - the amplitude of the flare delta m_u ,where m is the magnitude in u-band of the uvby system. Delta m_u was calculated regarding the quiet state phase of the star immediately before flare; - the standard deviation of random noise fluctuation sigma_mag = 2.5log(I_0+sigma)/I_0, where I_0 is the intensity in impulses of the quiet star, lessened with the sky background, and sigma is the standard deviation of random noise fluctuation in impulses. All these values were taken during the quiet state phase immediately preceding the beginning of the flare. Table 2 Date U.T._beginning U.T._max duration Delta m_u sigma_mag 26 Aug 20h 22m 13s 20h 22m 15s 15s 2.2 0.4 1990 The light curve of the observed flare is shown in Fig. 1 and 1a. In the same night when the flare was observed two fast events with durations 1s (Delta m_u = 2.8) and 2s (Delta m_u = 2.5) were detected. The question whether they have been caused by the equipment, the atmosphere or the star remains open. Further, we intend to use a part of this observational material in searches for quasi-periodic modulation in V1285 Aql. At last, we would like to thank to Dr. Chugainov from Crimean Astrophysical Observatory, USSR for directing our attention to this star. [FIGURE 1] [FIGURE 1a] R. K. Konstantinova-Antova B. B. Kourdova Bulgarian Academy of Sciences University of Sofia Department o Astronomy Department of Astronomy 72 Lenin blvd. 5 Anton Ivanov str. 1784 Sofia, BULGARIA Sofia, BULGARIA A. P. Antov Bulgarian Academy of Sciences Department of Astronomy 72 Lenin blvd. 1784 Sofia, BULGARIA References: Antov A.P., Genkov V.V., Kirov N.N., Konstantinova-Antova R.K., Staikov Yu., Nikov Ch.N., Sediankov S.S., Yaramov K., Pamukchiev I.Ch., Notev P.T., Kostev N.G., 1991: in preparation Kirov N.K., Antov A.P., Genkov V.V., 1991: Compt. Rend. Bulg. Acad. Sci. 44. Panov K.P., Pamukchiev I.Ch., Christov P.P., Petkov D.I., Notev P.T., Kostev N.G., 1982: Compt. Rend. Bulg. Acad. Sci. 35, no. 6, p. 717.