COMMISSION 27 OF THE I. A. U
         INFORMATION BULLETIN ON VARIABLE STARS
                      NUMBER 264

                                      Konkoly Observatory
                                      Budapest
                                      1968 March 28


                 FLARE ACTIVITY OF YZ CMi


The flare star YZ CMi (M_v=11.^m6, RA=7^h42.^m9, D=3d39' (1968)) has been
monitored at the Boyden Observatory during the dark moon-periods between 1968,
Jan. 23/Febr. 5 and 1968, Febr. 21/March 7. The star was observed in
Johnson's spectral region B with the 16" Harvard Nasa Cassegrain reflector; the
star-intensity was measured against the sky-back-ground only, without observing
comparison stars. A total period of 67^h15^m was covered. The table contains
information about the time intervals of coverage and all 10 flares occured.
The figure shows the three most prominent flares and one minor, but complex
event with more detail.

                                   Time of   *  delta    Duration of flare
Date       Observing    Cover-     flare          m
(1968)    time (U.T.)    age       (max.)              before   after
                                   (U.T.)               max.     max.  Total
1. 23/24  19^h50-22^h42          21^h29.^m6  1  >1.^m65 0.^m8  ~21^m  ~22^m
          23 00 - 0  24  4^h16^m 22  09.0    2   0.39   0.4      3.3    3.7
                                 23  23.6    3   0.43   0.2      0.4    0.6
   24/25  19 32 -20  58  1  26
   25/26  18 37 -20  26
          23 31 - 1  02  3  20
   28/29  18 20 - 1  03  6  27    0  29.7     4  0.36:  0.8      2.5    3.7
   29/30  20 20 -23  24  3  04   20  29.7     5  0.50   1.0:     1.5    2.5
                                 21  39.7     6  1.50   0.4    ~24    ~24
   30/31  18 55 -20  14  1  19
1  31/2.1 21 41 - 0  20  2  39
2.  1/ 2  18 25 - 0  41  6  06
    2/ 3  18 24 -23  08  4  36   19  14.3     7  0.35:  0.3      0.5    0.8
    5/ 6  18 25 -19  58
          21 33 -22  30  2  30
                  TOTAL:35^h43^m

2. 21/22  18 25 - 0  05  4  40   20  40.8     8  0.70   0.8      1.7    2.5
   22/23  17 56 -18  39
          21 37 -23  45  2  51
   25/26  18 12 - 0  05  5  53   18  41.3     9  0.40   0.2      0.9    1.1
                                 21  50.4    10  1.20   0.8    ~11    ~12
   27/28  18 00 -23  58  5  58
   28/29  18 00 -23  50  5  50
2. 29/3.1 18 05 -22  00  3  55
3.  7/ 8  21 35 - 0  00  2  25
                  TOTAL:31^h32^m

* Flare Nr.
: uncertain values

The other 6 flares show the normal simple appearance: a steep increase before
and an exponential decrease of intensity after reaching the maximum. The
measurements of flare Nr. 7 and - to a smaller degree - also of Nr. 4 are not
very reliable; these flares are to be checked with other observations.


                          [FIGURE 1]


                                       J.P. EKSTEEN, Th. SCHMIDT
Boyden Observatory,
Bloemfontein,
Rep. of SOUTH AFRICA