COMMISSION 27 OF THE I. A. U.
                  INFORMATION BULLETIN ON VARIABLE STARS
                              Number 2461

                                                       Konkoly Observatory
                                                       Budapest
                                                       18 January 1984
                   
                                                       HU ISSN 0374-0676


                     THE LIGHT CURVE OF FG Vul IN 1983


The M5II-star FG Vul, which is one of the oldest members (log tau ~~ 9.19)  
of the old open cluster NGC 6940 (Gotz, 1981) was measured in B (ORWO ZU21+
GG13 + BG12) on 18 plates from 17 nights obtained with the 50/70/172 cm
Schmidt camera of Sonneberg Observatory covering the time interval between
7 June 1983 and 15 December 1983.
The used sequence of comparison stars in B is listed in Table I.

                    Table I
Star       m_ B      Star     m_ B
100      11.03m      161    11.98m
164      11.31       174    12.02
179      11.64       140    12.02
136      11.76        90    12.12
175      11.78       102    12.28
152      11.91        97    12.73

In Table I the star numbers are those given by Vasilevskis and Rach (1957).


                             [FIGURE 1]




The apparent magnitudes m_B were obtained by linking to the UBV sequence of
the cluster given by Walker (1958). In each individual case the magnitude
of FG Vul was determined by measuring and considering the full sequence of
comparison stars.
  The light curve of FG Vul in 1983 is given in Figure 1. There can be seen
that the small changes in brightness are characterized by well defined minima
of different amplitudes. Taking into account the photoelectric observations
of Walker (1958) (n = 13) and Eggen (1973) (n = 5) the following preliminary
elements were derived:

          Min. = J.D. 243 6095.8 + 86.0d * E

      Min.          m_B    E    O-C    Author
      J.D. 24...

      36095.8      11.13m   0    0.0d   Walker
       6173.7+     11.24    1   -8.1+   Walker
      41520        10.90   63   +6.2    Eggen 
       5558.9      11.48  110   +3.1    Gotz
       5642.2      11.28  111   +0,4    Gotz

The dates of minima which follow from the elements for the present time are
marked in Figure 1. Doubtful observations are plotted there by circles.
The individual observations of FG Vul obtained in 1983 are listed in
Table II.

                    Table II
J.D.      m_B        J.D.     m_B      J.D.     m_B
244....             244...           244....
5493.5    11.20m    5580.4   11.34m  5642.2    11.28m
5528.5    11.26     5583.4   11.10   5663.2    11.19
5555.5    11.48     5589.4   11.04   5671.2    11.04
5556.4    11.64::   5612.3   11.13   5672.2    10.95
5561.4    11.48     5621.4   11.19   5684.19   11.27
5562.4    11.42::   5641.3   11.22   5684.20   11.25

FG Vul shows an amplitude of about Delta m_B~~ 0.5 in the given series of 
observations and belongs to the group of semiregular variables.


                                W. GOTZ
                         Akademie der Wissenschaften
                         der DDR, Zentralinstitut fur
                         Astrophysik, Sternwarte
                         Sonneberg

References:
Eggen, O.J., 1973, Ap.J. 180, p. 857 [BIBCODE 1973ApJ...180..857E ]
Gotz, W., 1981, Veroff. Sternw. Sonneberg Bd. 9, 5 
Vasilevskis, S., Rach, R.A., 1957, A.J. 62, p. 175 [BIBCODE 1957AJ.....62..175V ]
Walker, M.F., 1958, Ap.J. 128, p. 562 [BIBCODE 1958ApJ...128..562W ]