COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                         Number 998

                                      Konkoly Observatory
                                      Budapest
                                      1975 May 14


                      FLARE ACTIVITY OF YZ CMi

       The flare star YZ CMi (M_v=11.6, RA=7h43m16s delta=3deg37'12", 1974)
was monitored photoelectrically on 21 October 1974, during a period
of simultaneous observations with the ANS Satellite. The star was
observed through the U filter of the Johnson and Morgan System.The
stellar intensity was measured against the sky-back-ground only,
without observing any comparison star. During the observing interval 
22h04m UT to 23h33m UT, one flare was recorded with its maximum
at UT 23h20m28s.
       The flare light curve (Fig.1) shows that the flare is a rapid
succession of two Oskanyan type I flares. It appears that energy has
been added at various times during the development and decay of the
flare event (Bopp and Moffett 1973).
       Flare characteristics were computed using the techniques and
procedure as applied earlier (Oskanyan, 1970; Bhatt and Sinvhal, 1971)
and are given in Table I. The detailed spectral energy distribution
during active state is not exactly known and varies from flare to
flare (Moffett and Bopp, 1971). In the computations, it has been 
assumed that the spectral energy distribution in the U-band is the same
during a flare event as in the quiescent state.
       The author is thankful to Dr. S.D. Sinvhal for suggestions.
Part of this work was carried out with financial assistance with
PL-480 funds under Smithsonian Institution Project No. SFG-0-6425.


                                              B. B. SANWAL
                                  Uttar Pradesh State Observatory
                                  Manora Peak, Naini Tal-263129, India

References:
1) Bopp, B.W., Moffett, T.J., 1973, Ap.J., 185, 239 [BIBCODE 1973ApJ...185..239B ]
2) Bhatt, T.R., Sinvhal, S.D., 1971, I.A.U. Colloquium, 15, 124. [BIBCODE 1971ndnf.coll..124S ]
3) Moffett, T.J., and Bopp, B.W., 1971, Ap.J. (Letters), 168, L117. [BIBCODE 1971ApJ...168L.117M ]
4) Oskanyan, V.S., 1970, I.B.V.S. No. 488


                              Table I

          Characteristics of flare on YZ CMi (dM 4.5e)

                                                                Energy  Total
Date UT max Flare duration X_{fm+s}/ Delta{m_u} sigma/  P  F(z) released emiss.
1974       Before    After   /X_s                /X_s (min)      at    during
           max       max                                        flare   the
           tb        ta                                         max     flare
                                                                10^29   up
Oct.                                                            ergs/s 10^30ergs
21 23h20m28s 0.5m   4.2m     1.54       0.47    0.033 .615 1.15  8.9   2.14

Notes 1) Monitoring interval 22h04m UT to 23h33m UT.
      2) Photomultiplier tube used: EMI 6094S thermoelectrically cooled
         to -20degC.


                         [FIGURE 1]