COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 979 Konkoly Observatory Budapest 1975 March 20 FURTHER OBSERVATIONS OF UV CETI Over the period 21st September - 23rd October 1974 the flare star UV Ceti [RA = 01h37m12s, declination = 18deg08' (1966.0), visual magnitude 12.9, spectral type dM5.5e] was observed at Boyden Observatory with the 41cm Nishimura Reflector. The observations were made using a standard Johnson B. filter with a solid carbon-dioxide cooled EMI 6256A photomultiplier tube. The table gives details of the observations over a total monitoring tome of 68h38m. The level of activity over the period was quite high, thirty-one definite flares being recorded. As the table indicates there were others which were uncertain due to unfavourable observing conditions. Of particular interest is the extremely intense flare peaking at 21h16m12s Universal Time on 22nd September. This is the largest flare ever recorded at the Observatory, with a (I_{0+f}-I_0)/(I_0) value of approximately 420. The flares showed the typical characteristic flash phase followed by a gradual decline of UV Ceti type flare stars. They are similar to those recorded previously from UV Ceti by Jarrett and Eksteen. A.H. JARRETT and J.B. GIBSON Boyden Observatory, Department of Astronomy, University of the Orange Free State, Bloemfontein. Republic of South Africa. References: 1. Jarrett A.H. and Eksteen J.P. 1969, I.B.V.S. No. 349 2. Jarrett A.H. and Eksteen J.P. 1969, I.B.V.S. No. 406 3. Jarrett A.H. and Eksteen J.P. 1970, I.B.V.S. No. 412 4. Jarrett A.H. and Eksteen J.P. 1970, I.B.V.S. No. 434 5. Jarrett A.H. and Eksteen J.P. 1970, MNASSA, 29, p. 115. [BIBCODE 1970MNSSA..29..115J ] FLARE SUMMARY FOR UV CETI (September-October 1974) Total U.T. Ends Comments (I_{0+f}-I_0)/(I_0) Date hours Rise max. Sept. End was 21-22 7h06m 21h41m16s 21h41m17s 21h41m20 possibly at 0.46+-0.15 1 41m40s. Spike? Noise? 21 42 01 21 42 03 21 42 14 Flare. May be 0.62+-0.15 doubtful as dark reading was rather high. 21 44 22 21 44 29 21 45 05 Small flare. 0.46+-0.15 Star drifted out of diaphragm at max, but brought back in immediately! 00 38 40 00 38 47 - Flare >=1 +-0.12 00 59 20 00 59 22 01 00 36 Small flare 0.67+-0.21 02 06 36 02 07 12 02 08 48 Flare 1.34+-0.22 Monitoring Times: 21h09m00s - 23h46m00s (UT) 23 51 30 - 00 38 48 00 56 48 - 03 02 00 Sept. 22-23 6h07m 21h14m42s 21h14m58s - Flare 1.29+-0.24 21 15 41 21 16 12 00h00m00s Enormous Flare 420 +-80 (approximately) 21 32 14 21 32 25 22 06 00 Flare 11.8 23 02 30 23 03 26 23 15 00 Slow flare >=2.2 Monitoring Times (UT): 20h48m00s - 23h42m00s 23 49 00 - 03 02 00 (dawn) Sept. 23-24 0h25m 22h02m02s 22h02m04s 22h02m50s Possibly a flare 0.56+-0.07 as observations were moonlit cloud patches Monitoring Times (UT): 21h39m06s - 22h04m12s Sept. 24-25 02h43m 21h41m45s 21h41m48s 21h43m48s Flare 1.71+-0.43 00 05 35 00 05 42 00 06 06 Flare? Observed 0.38+-0.17 through variable clouds Monitoring Times (UT): 20h59m30s - 22h17m54s 23 40 48 - 01 04 54 Sept. 25-26 2h43m No clear cut flares Monitoring Times (UT): 00h12m48s - 01h19m36s 01 29 00 - 03 00 06 Sept. 26-27 1h49m No clear cut flares Monitoring Times (UT): 01h13m48s - 03h02m30s (dawn) Oct. 2-3 0h43m 21h48m06s 21h48m48s 21h50m06s Slow flare, 1.06+-0.16 moonlit cloud, at time of observation FLARE SUMMARY FOR UV CETI (September-October 1974) (cont.) Oct. 2-3 0h43m 21h53m42s 21h53m48s 21h54m06s Small flare 0.56+-0.16 Monitoring Times (UT): 21h19m48s - 22h02m36s (all in moonlight. Signals were noisy) Oct. 6-7 5h37m 21h53m14s 21h53m29s 21h53m43s Precursor Spike 2.78+-0.15 Obscured 21 54 10 21 57 42 Flare 1.46+-0.15 by preceding- feature 5.05+-0.15 21 54 17 21 54 27 21 54 45 Spike 22 54 12 22 54 22 - Flare. Max. lost. 11.5+-0.14 - 22 54 40 23 20 00 Flare. Max. lost. 14.5+-2.4 01 08 54 01 08 56 01 10 00 Flare 0.60+-0.28 01 43 18 01 43 42 01 44 06 Flare? 0.50+-0.28 02 03 02 02 03 08 02 04 12 Flare 1.00+-0.31 02 04 40 02 04 57 02 05 12 Flare 1.44+-0.31 Monitoring Times (UT): 21h02m00s - 21h46m36s 21 52 30 - 23 40 48 23 53 18 - 02 50 42 Oct. 8-9 4h52m 21h19m54s 21h19m56s 21h21m12s Flare? varying 1.28+-0.29 clouds 23 14 29 23 14 34 23 15 00 Flare? Troublesome 0.38+-0.18 clouds. 00 17 15 00 17 19 00 19 00 Flare. 0.60+-0.19 Monitoring Times (UT): 21h09m42s - 22h39m12s 22 45 18 - 01 47 18 01 53 06 - 02 13 54 Oct. 9-10 5h01m 22h34m24s 22h34m39s 22h34m54s Flare. End uncertain 0.95+_0.22 as telescope in contact with pier 01 55 20 01 55 27 01 55 42 Flare. 1.79+-0.32 Monitoring Times (UT): 21h45m42s - 22h34m54s 22 38 12 - 02 49 42 Oct. h m 1.03+-0.27 10-11 5h43m 21h06m06s 21h06m13s 21h07m30s Flare 0.37+-0.21 22 07 46 22 07 48 22 08 06 Flare 23 30 30 23 30 36 23 31 00 Flare? Noisy 0.44+-0.21 signal 00 27 54 00 28 18 00 30 24 Flare 1.74+-0.21 00 47 49 00 47 56 00 49 30 Flare 1.45+-0.36 01 06 00 01 06 06 01 06 42 Flare? Noisy 0.38+-0.28 signal Monitoring Times (UT): 20h50m30s - 22h31m30s 22 36 00 - 02 38 18 Oct. 11-12 5h28m 21h17m21s 21h17m23s 21h18m00s Flare? Variable 0.62+-0.23 thin clouds 22 42 43 22 43 16 22 49 48 Flare 12.55+-0.21 Monitoring Times (UT): 21h00m36s - 22h27m24s 22 35 30 - 02 37 00 FLARE SUMMARY FOR UV CETI (September-October 1974) (cont.) Total U.T. Ends Comments (I_{0+f}-I_0)/(I_0) Date hours Rise max. Oct. 12-13 5h28m 21h23m42s 21h23m50s 21h26m00s Flare 1.00+-0.23 22 59 48 23 00 05 23 05 00 Flare complex 2.12+-0.24 00 15 48 00 16 07 - First spike over 1.53+-0.24 slow flare - 00 16 42 - Second Max. 1.79+-0.24 - 00 18 54 00 20 00 Third Feature, 0.47+-0.24 Noisy signal 01 32 24 01 32 33 01 35 36 Flare 1.73+-0.27 Monitoring Times (UT): 21h01m36s - 22h23m36s 22 29 54 - 02 35 36 Oct. 15-16 2h09m 01h11m30s 01h11m36s 01h13m24s Flare? Noisy 1.42+-0.30 signal. Varying thin clouds. Monitoring Times (UT): 22h58m00s - 23h25m42s 23 50 06 - 01 31 25 Oct. 16-17 3h55m 00h20m42s 00h20m52s 00h21m42s Flare. 1.00+-0.30 00 57 48 00 58 00 00 59 30 Flare? Very noisy 0.58+-0.37 signal 01 23 06 01 23 23 01 24 12 Flare 1.40+-0.24 Monitoring Times (UT): 22h34m24s - 02h29m12s Oct. 1.00+-0.28 17-18 2h22m 23h06m24s 23h06m42s 23h08m48s Flare Monitoring Times (UT): 21h19m00s - 21h41m00s 21 47 48 - 22 04 54 22 05 54 - 22 47 06 22 51 00 - 23 14 54 23 23 54 - 00 05 24 Oct. 18-19 2h26m 23h47m45s 23h47m47s 23h48m24s Flare? Noisy signal 2.00+-0.26 Monitoring Times (UT): 21h08m36s - 22h00m12s 22 05 36 - 22 21 18 22 37 48 - 23 56 36 Oct. 21-22 1h33m 22h11m17s 22h11m18s 22h11m40s Small Flare? Noisy 0.34+-0.17 signal, thin clouds and moonlight. Monitoring Times (UT): 21h24m42s - 21h48m24s 21 53 42 - 23 03 06 Oct. 22-23 2h28m Monitoring Times (UT): 21h25m18s - 21h44m24s 21 50 24 - 23 59 48 Severe scintillation. No flares apparent.