COMMISSION 27 OF THE I.A.U.
              INFORMATION BULLETIN ON VARIABLE STARS
                           Number 1263

                                                    Konkoly Observatory
                                                    Budapest
                                                    1977 April 12


STATISTICS ON FLARE OBSERVATIONS OF UV Cet, YZ CMi AND AD Leo AT
        THE UTTAR PRADESH STATE OBSERVATORY

The flare stars UV Ceti, YZ CMi and AD Leo were photoelectrically 
monitored between 27 Dec. 1970 and 10 Dec. 1975. The 
instrumental details, the individual flare characteristics along
with the light curves and actual monitoring intervals have been
published variously (Ref. 1-11). A consolidated summary of the
results obtained so far is given in Table I.
   The observed flare events show a large range in total energy, 
flare magnitude, rise and decay rates, duration etc. But the
following significant conclusions can be drawn:

  I. The mean energy per flare increases with increasing intrinsic
     quiescent luminosity of the parent star.
 II. Intrinsically brighter flare stars have more energetic but
     less frequent flares.
III. The rise times become more rapid as the quiscent energy of
     the parent star decreases.
 IV. Most of the flare light curves are either combinations of
     spike and slow flares or else successive flare events are
     overlapped, supporting the view that energy can be added at various
     times during the development and decay of a flare event rather
     than its just being an abrupt rise to a maximum followed by slow
     and exponential decay.
  V. Flares with greater energy release occasionally last longer.
     It is not clear whether all of the energy lost during an event
     is lost by a few strong events or numerous weaker events. 
     Observations with better time resolution can perhaps answer this 
     question.

   In addition to the above stars EV Lac (dM4.5e; mv=10.25)
too was monitored for a total of 16.6 hours, during which only
two flares were recorded. Due to the paucity of flares of this
star it would not be correct to base any conclusions on statistics 
pertaining to this star.


                               Table I

                                Total    Total    No. of     Mean    Energy
                               nights monitoring   flares    interval range
                                of               detected            of flare
                             observing  interval             between  events
                                        (hours)             flares    10E30
                                                           (hours)    ergs
Star     spectral  mv    Filter
          type

UV Ceti  dM5.5e  12.95    B       5      11.6       17       0.7      1.2-.07
YZ CMi   dM4.5e  11.24    B      36     103.8       20       5.2     22.0-0.8
AD Leo   dM3.5e  9.43     B      39      90.2       13       6.9     70.6-1.0
         Total:                  80     205.6       50


            Quiescent     Mean     Mean    Mean
                         energy    flare   rise
            energy       per    duration   time
            10E28       flare             (min)
            ergs/sec  10E30ergs  (min)

UV Ceti      0.73        0.26     5.6      0.5
YZ CMi      20.6         8.2      9.5      0.8
AD Leo      82.0        14.0     10.6      1.9

   Part of this work was carried out under Smithsonian Institution 
Project No. SFG-0-6425, which project now stands completed.


                                S.D. SINVHAL
                                B.B. SANWAL

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



References:

1. Bhatt, T.R., Sinvhal, S.D., 1971, I.B.V.S. No. 557
2. Bhatt, T.R., Sinvhal, S.D., 1971, I.A.U. Coll. 15, 124 [BIBCODE 1971ndnf.coll..124S ]
3. Kapoor, R.C., Sinvhal, S.D., 1972, I.B.V.S. No. 750
4. Kapoor, R.C. 1973, ibid. 758 [IBVS 758]
5. Kapoor, R.C., Sanwal, B.B., Sinvhal, S.D., 1973, ibid. 810 [IBVS 810]
6. Kapoor, R.C., 1973, ibid. 848 [IBVS 848]
7. Kapoor, R.C., Sinvhal, S.D., 1974, ibid. 901 [IBVS 901]
8. Sanwal, B.B., 1974, ibid. 932 [IBVS 932]
9. Sanwal, B.B., 1975, ibid. 998 [IBVS 998]
10. Sanwal, B.B., 1976, ibid. 1180 [IBVS 1180]
11. Sanwal, B.B., 1976, ibid. 1210 [IBVS 1210]