COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1186 Konkoly Observatory Budapest 1976 October 12 ULTRAVIOLET MONITORING OF BY Dra STARS The BY Dra stars AU Mic, AT Mic, CC Eri, HD216803 and HDE319139 were monitored photoelectrically in the period August- -September 1974, in order to study their flare activity. The observations were carried out at Cerro Tololo Interamerican Observatory, using a 60 cm telescope, in the U-band. The data were reduced following the precepts of Kunkel (1973), and are presented in Tables 1 to 9. A detailed analysis will be published else where. Tables 1 to 5 give the coverage in universal time. All breaks greater than 1 minute were considered. The flare data are listed in Tables 6 to 9. The columns contain, respectively: Julian Date of flare maximum; secant of zenith distance; U-magnitude of peak light, after subtraction of quiescent component; flare durations T_q in minutes measured at q=0.5, 0.2 and 0.1 peak light. The meaning of symbols in column labelled "obs" is as follows: D - double peak C - complex light curve L - peak intensity close to Kunkel's weak- event threshold I - incomplete record. Usually the peak was lost during a sky measure. The symbol "u" following a quantity means that it was obtained with a precision less than that given below: JD - 0.001 day (about 1 min.) U - 0.1 magnitude T_q - 20 percent. We should note that HDE319139, a dK5e star (Bidelman 1954), was formerly not known to be a flare star, but was included in the program due to its BY Dra nature. The star HD216803 (TW PsA) showed quiescent variability, but no flares were detected on it. 2 Table 1 JD Coverage AU Mic JD Coverage AU Mic 2442000.+ (U.T.) 2442000.+ (U.T.) 270.5 04h14.3m- 06h17.3m 283.5 02h12.0m- 02h38.3m 271.5 03 04.5 - 04 51.0 03 11.0 - 03 26.0 272.5 01 56.5 - 03 54.0 04 05.5 - 04 30.0 04 51.5 - 06 06.7 285.5 01 53.0 - 03 25.5 273.5 04 45.0 - 07 01.0 03 44.2 - 05 25.0 274.5 03 14.5 - 03 47.5 294.5 04 10.0 - 05 16.0 04 48.0 - 06 16.0 295.5 02 28.5 - 02 55.7 275.5 02 19.7 - 03 00.0 02 58.0 - 03 28.5 03 09.5 - 04 20.0 296.5 02 57.0 - 04 26.0 05 03.0 - 06 16.0 297.5 05 35.0 - 06 05.5 277.5 02 09.5 - 04 38.0 304.5 03 17.0 - 04 04.5 278.5 02 52.5 - 05 21.3 311.5 03 11.5 - 04 31.5 279.5 03 00.7 - 03 29.0 316.5 03 30.5 - 04 04.5 280.5 02 47.5 - 04 21.5 319.5 0 348.0 - 04 33.0 Table 2 JD Coverage HDE319139 JD Coverage HDE319139 2442000.+ (U.T.) 2442000.+ (U.T.) 270.5 01h19.0m- 02h47.3m 284.5 23h50.0m- 24h00.0m 272.5 00 30.5 - 01 20.7 285.5 00 00.0 - 00 30.5 273.5 00 39.5 - 01 14.0 00 33.0 - 01 12.5 01 17.5 - 02 12.5 294.5 02 38.5 - 02 48.0 274.5 00 14.5 - 02 06.0 295.5 00 38.5 - 01 31.2 02 18.5 - 02 25.7 296.5 01 39.0 - 02 31.0 275.5 00 00.0 - 00 27.2 297.5 01 00.0 - 02 06.2 00 33.0 - 01 20.5 304.5 01 02.0 - 02 31.0 277.5 00 25.8 - 01 27.0 316.5 01 43.5 - 01 59.0 278.5 00 10.0 - 01 50.2 02 01.5 - 02 51.2 279.5 00 09.0 - 01 25.0 319.5 00 37.3 - 03 10.5 280.5 00 07.5 - 01 52.5 320.5 01 47.0 - 02 35.0 282.5 23 52.5 - 24 00.0 02 40.3 - 03 20.0 283.5 00 00.0 - 01 06.2 Table 3 JD Coverage CC Eri JD Coverage CC Eri 2442000.+ (U.T.) 2442000.+ (U.T.) 270.3 09h13.0m- 10h03.2m 280.5 09h54.5m- 10h02m8 271.5 07 55.2 - 09 28.5 294.5 07 10.6 - 09 01.5 272.5 08 31.2 - 09 28.3 09 21.0 - 09 49.3 09 45.0 - 10 12.0 295.5 05 50.0 - 06 12.5 273.5 08 11.0 - 09 28.7 06 15.0 - 06 39.2 274.5 08 06.5 - 09 34.0 296.5 07 38.5 - 08 19.0 09 54.0 - 10 07.0 297.5 07 28.2 - 07 51.8 275.5 08 36.0 - 09 32.0 07 54.5 - 08 15.0 09 46.5 - 10 00.0 304.5 06 40.0 - 07 53.0 277.5 07 39.3 - 09 28.0 316.5 06 18.0 - 08 07.3 278.5 07 33.7 - 09 37.1 318.5 05 10.0 - 06 15.5 09 51.7 - 10 05.5 319.5 05 57.0 - 06 59.5 280.5 08 16.5 - 08 29.0 320.5 05 50.5 - 06 29.2 08 41.0 - 09 49.0 3 Table 4 JD Coverage HD216803 JD Coverage HD216803 2442000.+ (U.T.) 2442000.+ (U.T.) 270.5 06h41.5m- 08h27.8m 278.5 06h00m5- 07h29.2m 271.5 05 52.0 - 07 39.0 279.5 05 41.5- 06 12.0 272.5 06 43.0 - 08 16.8 280.5 06 38.5- 07 39.0 273.5 07 21.0 - 07 56.5 285.5 06 15.0- 07 29.5 274.5 06 47.0 - 07 55.5 294.5 05 50.0- 06 27.0 275.5 06 34.0 - 07 55.0 297.5 06 36.0- 0 651.0 277.5 06 27.3 - 07 31.0 Table 5 JD Coverage AT Mic 2442000.+ (U.T.) 295.5 03h47.0m- 04h30.5m 296.5 04 38.0 - 06 41.2 297.5 02 46.7 - 05 03.5 Table 6 Flares AU Mic JD secz U T_0.5 T_0.2 T_0.1 Obs. 2442000.+ 271.643 1.01 14.61u 21.0u D 271.683 1.00 13.25 3.8 9.2u 272.584 1.11 14.16 1.0u 272.608u 1.06 13.67 3.4 13.0 D 272.704 1.02 9.90 > 4.0 > 30.0 62.0 I 272.711 1.04 13.98 0.4u 275.600 1.05 13.93u 2.0u 275.634 1.01 11.33 0.8 6.7 13.4 275.658u 1.00 13.45 10.7 D 277.605u 1.04 13.06 16.3 28.5 C,I 278.665u 1.00 14.80 3.8u 278.697 1.03 13.32 5.3 10.9 278.711 1.05 11.41 1.5 4.4 13.3u 280.639 1.00 12.17 1.3 21.2 28.0 C 283.599 1.02 14.50u 6.4 285.632u 1.00 13.90 1.7 7.5u 285.707 1.09 12.83 0.6u 2.8 294:632 1.07 14.40u > 3.0 I 294.713 1.19 14.16u 1.0 L 296.624 1.01 12.30 > 16.0 I 296.658u 1.05 14.64u 3.3 L 296.674u 1.08 13.36 8.0 C Table 7 Flares HDE319139 JD secz U T_0.5 T_0.2 T_0.1 Obs. 2442000.+ 274.549 1.00 11.46 10.1 43.1 72.4 277.544u 1.00 15.56u 7.0u 285.493 1.02 13.50 > 0.8 > 4.5 > 8.0 I 295.543u 1.03 15.40u 2.7u L 297.549u 1.12 15.20u 7.0u 297.542 1.03 15.67u > 2.0 I 319.579 1.39 15.14 10.0 4 Table 8 Flares CC Eri JD 2442000.+ secz U T_0.5 T_0.2 T0_.1 Obs. 271.838 1.11 13.82 1.5 12.7 14.6 I 272.908 1.03 11.24 > 4.0 > 25.0 I 274.866 1.05 13.38 0.8u 275.876u 1.04 13.60 4.5u 278.819u 1.11 14.08 8.2 I 278.843 1.06 14.10 5.7 20.0u D,C 294.809u 1.05 14.73u 1.5 L 294.846 1.03 14.60u 1.8 296.827 1.03 10.51 1.2 19.5 29.2u C 316.777 1.03 15.00u 7.1u 318.717 1.09 13.33 0.5 L 319.783 1.03 14.10 5.0 11.3 D Table 9 Flares AT Mic JD secz U T_0.5 T_0.2 T_0.1 Obs. 2442000.+ 295.670 1.07 13.02 0.3u 0.5 1.7u 295.675 1.08 13.52 1.0 3.5 296.694 1.14 14.68 4.9u 296.706 1.18 13.98 1.1u 14.6u D 296.755 1.47 14.84u 1.2 296.766 1.57 14.82u 1.3 I.C. BUSKO * C.A.O. TORRES * Observatorio Nacional-Brazil * Visiting Astronomers, Cerro Tololo Interamerican Observatory (Operated by Association of Universities for Research in Astronomy, Inc, under contract with the National Science Foundation) References: Bidelman, W.P. 1954, Ap.J. Suppl. 1, 175 [BIBCODE 1954ApJS....1..175B ] Kunkel, W.E. 1973, Ap.J. Suppl. 25, 1 [BIBCODE 1973ApJS...25....1K ]