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\IBVShead{4162}{16 February 1995}


\title{ON THE AGE OF FLARE STAR FS2 AND THE CLUSTER OF $\alpha$ PERSEI}     

\begintext


     As has been shown earlier, there is a correlation between the 
maximum flare energy (amplitude) which is likely to be emitted  by 
star of particular magnitude (mass) and its age (Parsamian,  1976, 
1995). This relationship depends upon  the evolutionary  stage  of 
the flare stars, and of the clusters   in  which  they  have  been 
observed. It follows therefore, that the age of any flare star may 
be estimated if large flare -- sufficiently intense to be regarded as 
maximal -- is observed.
 
     During flare star searches in the  $\alpha$  Persei cluster, a large 
flare of amplitude $\Delta$U $\approx$ 9\fmm\  was observed for the star  FS2  (Semkov 
et al., 1993). According to these  authors, the (V, V$-$I)  photometry 
of FS2 makes it acceptable for membership in the  cluster.  Flares 
of such large amplitudes occur  very  seldom;  it  is  therefore 
likely that the energy emitted in this particular event  is  close 
to the upper limit described above. If star FS2 is a member of the 
 $\alpha$  Persei cluster, we can then estimate the age of the star and  of the cluster in which it resides. 

     According to Semkov et al., FS2 is a faint star of  magnitude 
U $\approx$ 21.7 and of spectral class $\geq$ M5. Given a distance  
of r= 166pc for  the   $\alpha$  
Persei cluster, the absolute  magnitude  of  FS2  is 
then M(U) = 15.6, and the absolute magnitude of the flare is M$_f$   = 
6.6. According to Table 3 in Parsamian (1995) the  age  of  the  star 
would then be 3$\times$10$^7$ yr, and the age of the  cluster  at  least  as 
large. For comparison, other independent estimates of the  age  of 
this cluster  vary  from  5$\times$10$^7$ yr  to  8$\times$10$^7$ yr  (Mermilliod,  1981, 
Prosser, 1992). 
     On the other hand if FS2 is a field star, then M(U) = 15.1 (Mampaso, 1991), 
M$_f$  = 6.1 and the age would be  $\sim$ 2$\times$10$^7$  yr. 

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\beginauthors
\authorsrightcol
Elma S. PARSAMIAN
INAOE, Mexico,
E-mail: parsam@tonali.inaoep.mx
Byurakan Astrophysical 
Observatory, Armenia
\endauthors

\references

Mampaso A., 1991, PhD Thesis,  Univ.  Laguna,  Spain 

Mermilliod, J. C., 1981, {\it Astron. \& Astrophys.}, {\bf 97}, 235 

Parsamian, E. S., 1976, {\it Astrofizika}, {\bf 12}, 235 

Parsamian, E. S., 1995, {\it Astrofizika}, in press

Prosser, Ch. F., 1992, {\it Astron.J.}, {\bf 103}, 488 

Semkov, E. H., Tsvetkova, K. P., Tsvetkov, M. K., Prosser, Ch. F., 1993,
{\it IBVS}, No.\,3917 
    
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