COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 1616

                                   Konkoly Observatory
                                   Budapest
                                   1979 May 31



        FLARE STARS IN THE COMA CLUSTER REGION




    In accordance with the program of flare star investigation
in stellar agregates accomplished at Byurakan Observatory, we
have continued the observations of the Coma cluster region 
initiated by G. Haro (1).
    Our plates centered at RA=12h18.5m, D=+26d24' (1950.0) were
obtained from April 1969 to March 1975. They present several
series of multiple exposure patrol plates, which have been taken
both Schmidt telescopes (21"/21" and 40"/52") of Byurakan 
Observatory.
    The total effective observational time was about 153h. Some
of the plates (about 10h of effective patrol time) have been put
in our disposal by I. Jankovics from Konkoly Observatory.
    Usually we used Orwo ZU2 or Kodak 103 aO photographic 
emulsions with ultraviolet filter Schott UG 1 on the 40"/52" 
telescope.
    Data for new flare stars and new flare events on previously
known flare stars are presented in chronological order in the
Table.

                        Table 1

N          RA       D          m     Deltam    UT

T3      12h24.5m  +27d18'    16.7pg   3.7   19.03.71   5x10   76
B1*        17.0    25 30     (21 pg  >4.8   22.03.71   2x10
B2         15.7    27 06     18.1pg   3.3   28.04.71  18x10
B3         16.8    27 30     16.6pg   1.2   15.04.72   3x10
B4         22.7    23 53     19.6pg   4.9   30.05.72   5x10
T3         24.5    27 18     16.7pg   2.0   31.05.72   5x10   76
T1         22.0    26 01     16.7 U   1.6   27.03.74   3x10   69
B5         29.4    25 26     16.6 U   1.3   27.03.74   3x10
B6*        23.9    26 10     (21 pg  >5.5   14.05.74   2x 5
B7         22.2    27 04     18.5 U   3.9   12.02.75   3x10   70
B7         22.2    27 04     18.5 U   2.6   16.02.75   2x10   70

*: There is a very week star on the red copy of the POSS chart.

It contains the following data: serial number of flare stars
discovered at Byurakan (B) or Tonantzintla (T) Observatories,
position for 1950.0, approximate photographic or ultraviolet
magnitude at minimum light, amplitude of flare event in the
corresponding light, the date of observation and duration of
each flare. The serial number of the star according to Sanduleak's
(2) list is added in the last column. Taking into account the
results of the papers (1), (3) and (4) the total number of known
flare stars in the Coma cluster region is 14 and the number of
flare-ups is 21. The total effective coverage is 337h45m. Our
data support G. Haro's conclusion (1) about the relatively low
flare activity in the direction of the Coma cluster.
   But it is necessary to remark that the observed number of
flare stars, if they all are members of this cluster, already
contradicts to the conclusion that the main sequence of the
cluster is very poor and even terminates at about V=11m (5).
    It is already known that not all flare stars are members
of the Coma cluster. For instance, the T3 star is, according to
its proper motion, doubtless a foreground star. The same can
be said about FP Com (6). According to V. Ambartsumian's formula
(7) the total number of flare stars in this region should be
greater than 40.
    On the other side, if we suppose that most of them are
general field stars, then the number of flare stars in this
particular direction is greater than in any other direction of
the Galaxy.
    In this connection it is interesting to note the coincidence
of three flare stars with the stars from Sanduleak's list, of
which 34 stars are situated in our region. It is known that this
list was compiled by Sanduleak for detailed investigation of
very red dwarfs near NGP, where their real excess - according to
( 2 ) - seems to be shown.                  
    I wish to thank akad.V.A. Ambartsumian for helpful 
discussion.


                         L.K. ERASTOVA
                         Byurakan Astrophysical
                         Observatory


References:
1. Haro, G., Flare Stars, Stars and Stellar Systems, vol. VII, 141, 1968 [BIBCODE 1968SSS.....7..141H ]
2. Sanduleak, N., A.J., 81, 350, 1976 [BIBCODE 1976AJ.....81..350S ]
3. Sedjakina, A.N., VS, 18, 218, 1971
4. Luyten, W.J., Erickson, R.R., PASP, 77, 472, 1965 [BIBCODE 1965PASP...77..472L ]
5. Argue, A.N., Kenworthy, C.M., M.N. 146, 479, 1969 [BIBCODE 1969MNRAS.146..479A ]
6. Argue, A.N., Kenworthy, C.M. Observatory, 88, 109, 1968 [BIBCODE 1968Obs....88..109A ]
7. Ambartsumian, V.A., Stars, Nebulae, Galaxies, 283, Yerevan, 1969