COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                   Number 3121


                                    Konkoly Observatory
                                    Budapest
                                    17 December 1987

                                    HU ISSN 0374-0676


            MORE ABOUT FY Aql AND GRBS 790331

  There are usually no variable optical candidates in the error boxes of
gamma-ray burst sources (GRBS). One exception is the variable star FY Aql
lying inside the box of GRBS 790331 and having been previously catalogued as
a Mira variable with a period of 208 days (Ahnert-Rohlfs and Gotz, 1954).
  On the other hand, Laros et al. (1985) have discussed the possibility
that FY Aql may in fact be a dwarf nova. More recently, spectrophotometric
data published by Hartmann and Pogge (1987) suggest the variable is of M4e
III spectral type and thus support the previous classification of FY Aql as
a Mira variable star.
  In order to get also more detailed photometric data, the object was measured
on more than 400 astrographic plates taken at the Sonneberg Observatory
of the Central Institute for Astrophysics of the Academy of Sciences of GDR
and covering the time interval 1928-1985. Because FY Aql represents one 
component of an apparent double, the integral brightness of both components was
estimated and then the brightness of FY Aql was calculated using the measured
magnitude of the other component according to Hartmann and Pogge (1987).
  Our photometric data confirm the classification of FY Aql as a Mira type
variable. Preliminary results of our investigation are:

1. The mean period over the time interval investigated is 209.7 d with elements
 Maximum = 244 5155 + 209.7d x E
2. The mean amplitude of light changes is nearly 1.7 mag in B(both components) or
  >= 3 mag in B (FY Aql only).
3.The shape of maximum is symmetric and narrower or equal than that of minimum
  indicating the variable is of a subtype beta1 or beta2 according to the 
  classification by Ludendorff (1928).
4. The typical duration of maximum (brightening) of the integral (both
  components) light curve is ~100 days.

   We conclude that FY Aql is indeed a Mira type variable, the estimated
period being fully consistent with the period-spectrum relation of Mira stars
according to Keenan (1966). More details will be published elsewhere (Hudec,
1988).


                        R. HUDEC
                        Astronomical Institute
                        251 65 Ondrejov
                        Czechoslovakia

References:

Ahnert-Rohlfs, E, and Gotz, W,: 1954, Veroff.Stern.Sonneberg, 2, 52.
Hartmann D., and Pogge R.W.: 1987, Ap.J. 318, 363.  [BIBCODE 1987ApJ...318..363H ]
Hudec, R.: 1988, Bull. Astron. Inst.Czechosl., in preparation. [BIBCODE 1989BAICz..40..261H ]
Keenan, P.C,: 1966, Ap.J.Suppl.Ser. 13, 333. [BIBCODE 1966ApJS...13..333k ]
Laros, J.G. et. al.: 1985, Ap.J. 290,728, [BIBCODE 1985ApJ...290..728L ]
Ludendorff, H.: 1928, Handbuch der Astrophysik 6,99 (Springer-Verlag
     Heidelberg).