COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 2697

                                  Konkoly Observatory,
                                  Budapest
                                  27 March 1985

                                  HU ISSN 0374 - 0676



    THE SYMBIOTIC STAR AG PEGASI: UBV PHOTOMETRY DURING 1962- 1984



  AG Peg is one of the brightest and most studied symbiotic stars. It is
known that its brightness increased by 3m from 1840 to 1860 with a subsequent
slow decrease (Rigollet, 1947). It is being continued now at a rate Deltam_pg~~
0.04m/yr (Meinunger, 1983). The increase of brightness in 1946 noted by
Rigollet (1947) has been caused by light fluctuations appeared around 1935
(Meinunger, 1983).
  UBV photometry of AG Peg was resumed at the Crimean Astrophysical Observatory 
in 1980 (Belyakina, 1970). The results of our observations (dot) are
shown in the Figure together with Burchi's 1980 (Delta), Fernie's 1972 (o), and
Meinunger's 1983 (x) results.
  Evidently, the V, B, U light curves resemble each other and are in fact
undulated fluctuations, in combination with a general decrease 
(DeltaV ~~ 0.02m/yr, DeltaB ~~ 0.04m/yr, DeltaU ~~ 0.045m/yr). 
The amplitudes of these fluctuations increase
noticeably in time. But they tend to be constant in the intensity scale with
ratio I_V : I_B : I_U = 0.8 : 1.0 : 0.8. The 1984 observations were not used
for this calculation.
  Some values (800d, 827d) have been assumed or derived for the light
fluctuation, period of AG Peg (Belyakina, 1970, Meinunger, 1983). In the
last few years different values (733d, 760d) were obtained from the visual
observations of this variable (Slovak, 1982; Luthardt, 1984).
  Figure 1 shows moments of the light curve minima indicated by vertical
lines according to:

          Min. = J.D. 24 39 000 + 820d E      

This value fits the light curve apparently well. But the minimum of the V
light curve in 1983 is displaced. Possibly that was the reason why the
period values derived by Slovak (1982) and Luthardt (1984) are shorter.
  The IR photometry has demonstrated that the red component of AG Peg
binary system is constant (Glass et al., 1973; Feast et al., 1977; Mendoza,
1972).
                          [FIGURE 1]

   Probably the light fluctuations of AG Peg are caused by the orbital
motion of the components. It follows from the correlation of the light curve
and radial velocity curve of this variable star.




                           T.S. BELYAKINA
                     Crimean Astrophysical Observatory
                       334413 Nauchny, Crimea, USSR




References:

Belyakina, T.S., 1970, Astrofizika, 6, 49. [BIBCODE 1970Afz.....6...49B ]
Burchi, R., 1980, IBVS No. 1813.
Feast, M.W., Robertson, B.S.C., Catchpole, R.M., 1977, M.N. R.A.S., 179, 499. [BIBCODE 1977MNRAS.179..499F ]
Fernie, J.D., 1972, P.A.S.P., 84, 528. [BIBCODE 1972PASP...84..528F ]
Glass, I.S., Webster, B.L., 1973, M.N.R.A.S., 165, 77. [BIBCODE 1973MNRAS.165...77G ]
Luthardt, R., 1984, IBVS No. 2495.
Meinunger, L., 1983, MVS, 9, H.4, 92.
Mendoza, E., 1972, Bol. Obs. Tonantzintla y Tacubaya, 6, 211. [BIBCODE 1972BOTT....6..211M ]
Rigollet, R., 1947, Astronomie, 61, 247.
Slovak, M.H., 1982, J. AAVSO, 11, 67. [BIBCODE 1982JAVSO..11...67S ]