COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS NUMBER 352 Konkoly Observatory Budapest 1969 June 2 THE FLARE STAR YZ CMi Members of the Variable Star Section, Royal Astronomical Society of New Zealand, monitored YZ CMi during the periods 1969 Jan.11-25; Feb.10-24 for a total of 65 hours. The first period was for the international observing session; the second was chosen as the star selected by the I.A.U. Working Group for that period - AD Leo - is not well placed for N. Z. observers. All observations were visual except Feb.19 1230-1337 and Feb.22 1137-1302 (U.T.), when Andrews and Rowe monitored YZ CMi with photoelectric photometer at the West Melton Observatory (Christchurch). A summary of the hours of coverage and times of 31 suspected flares are given below. 1969 U.T. OBSERVERS Jan.10 1037-1121 Bt 11 1105-1206 Jn 12 1006-1101; 1119-1202; 1235-1315 Bt 13 1135-1244 Jn 16 1001-1124 Bt 17 1345-1600 Jn 18 0945-1200; 1230-1340; 1424-1615 Bt; Hv; Mt. 19 0912-1345 Jn; MA; Wk. 20 0854-0910; 0931-1031; 1050-1317 Ce; Fe; Hv; Mt. 22 0852-0934; 1345-1615 MA; Jn. 24 0848-0936; 0950-1505 MA; Wk. Feb.12 0912-1400 Bt; En. 13 0952-1200; 1242-1424 Bt 18 0815-1202; 1204-1300 Bt; MA; MJ; Wk. 19 0808-1337 Bt; Ce; En; MA. 20 0922-0927; 1025-1130; 1141-1300 Bt; Ce. 21 0819-1200; 1214-1245 Ce; Ci; Fe; Hv; MJ. 22 0900-1357; 1401-1430 Ce; Cs; En; Fe. 23 0826-1012; 1018-1102 MA; Wk. Total Coverage: - 65 hrs 4 mins. (Visual observers: - F.M. Bateson (Bt); G.W. Christie (Ci); S. Clements (Ce); R.W. Cross (Cs); R.W. Evans (En); D.C. Fisher (Fe); S.R. Hovell (Hv); M.V. Jones (Jn); B.F. Marino (MA); G. McCallum (MJ); V.L. Matchett (Mt); W.S.G. Walker (Wk). Photo-electric observers (p.e.) F. Andrews and C. Rowe. SUSPECTED FLARES 1969 U.T. Deltam_vis DURATION OBSERVER REMARKS (mins) Jan.16 10h04.5m 0.3 1.5 Bt 10 11.5 0.4 ) 12.5 Bt 10 13.0 0.4 ) 18 10 23.5 0.3 2.5 Bt 13 30.25 0.3 3.5 Bt 14 37 0.3 4 Mt 15 02 0.3 2 Mt 20 10 28.25 0.3 1 Fe 13 24.3 0.3 ~ 4 Mt ) Suspect a period 13 29.6 0.3 ~ 1 1/2 Mt ) of prolonged 13 37.4 0.3 ~ 1 Mt ) activity. 13 38.6 0.3 ~ 1 Mt ) Feb.12 13 11.0 0.4 ) 13.5 Bt 13 18.5 0.3 ) Bt 13 51.8 0.3 1 Bt 13 10 27.0 0.6 3 Bt 10 35.0 0.3 3 Bt 10 49.0 0.3 15.5 Bt 11 26.5 0.3 1 Bt 11 30.0 0.6 6 Bt 12 56.0 0.3 3 Bt 13 17.5 0.3 2 Bt 13 22.5 0.3 1.5 Bt 13 40.0 0.3 ) 4 Bt 13 42.2 0.3 ) Bt 13 52.5 0.4 5 Bt 19 09 57.0 0.3 4 En and MA. Independently observed at same time from separate sites. 20 12 24.5 0.3 1.5 Bt 12 40.5 0.3 1 Bt 21 10 44.6 0.3 2 Fe 22 09 55.5 0.2 2.5 Ce ) Same flare? Observed 09 56.3 0.3 0.3 Fe from separate sites. Chart 151 (1) was used by all observers with magnitude sequence from Circular 135 (2). A full discussion of these results appears in Circular 136 (3). Mt. John Observatory 1969 May 16 F.M. BATESON REFERENCE (1) Bateson, F.M., Jones, A.F. and Stranson, I. 1968. Charts for Southern Variables, Series 1. Published by F.M. Bateson, Lake Tekapo, N. Z. (2) Circular 135, V.S.S., RASNZ. 1968 (3) Circular 136, V.S.S., RASNZ. 1969