COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                        Number 3697

                                              Konkoly Observatory
                                              Budapest
                                              28 February 1992

                                              HU ISSN 0374 - 0676


                The latest ascending branch
           in the long-term light curve of MV Lyrae


In continuation of our programme for study of low-state cataclysmic binaries
(Kraicheva (1988), Kraicheva, Antov, Genkov (1987, 1989), Popov, Kraicheva
(1991)) some photometric data for MV Lyrae were obtained during 1988-1991. We
observed the star on 58 plates of the Rozhen 50/70 Schmidt telescope and one
plate of the Rozhen 2m RCC telescope. The B system of comparison star
magnitudes of Andronov and Shugarov (1982) was used. Photometric measurement
of the plates was carried out on the automatic iris photometer Ascoris (Carl
Zeiss, Jena) at NAO "Rozhen". On plates not good enough for measurements,
estimates were made by the Nijland-Blazhko method. In Table 1 and in Fig. 1 the
results of our observations are presented; colons denote values of less
weight. The underlined magnitude is that from plate of 2m telescope. Our
observations include the ascending branch of the long-term light curve and
complete the curve of Wenzel and Fuhrmann (1989), Fuhrmann and Wenzel (1990).


                             [FIGURE 1]


    It should be noted that:

1. The amplitudes of brightness changes may reach 1.5m - 2.0m in low and
intermediate state which is essentially larger than the values of 0.1- 0.5m
obtained for the active state.

2. The decrease in the brightness of MV Lyrae from 12.5 to 18.0m according to
Romano and Rosino (1980) occur for about a month. The absent, however,
corresponding to our observations and those of Wenzel and Fuhrmann (1989) 
lasts considerably longer about 1-1.5 years.

                     Table 1

            Photographic Observations in B of MV Lyrae
HJD 2440000+   B     HJD 2440000+  B      HJD 2440000+  B
 7320.431    17.20   7765.465    14.63     8125.426   12.65
 7348.440    16.21:  7765.492    14.25:    8128.371   12.65
 7379.416    17.35:  7766.454    14.60     8128.390   12.80
 7382.447    16.50   7766.480    14.45     8128.408   12.80
 7386.348    17.50   7824.406    13.00     8130.387   12.75
 7417.360    17.30   7825.292    12.95     8130.435   12.75
 7417.386    17.40   7825.311    12.85     8131.396   12.70
 7417.486    17.20   7826.266    13.00     8131.414   12.60
 7418.397    17.16   8064.524    12.70     8132.412   12.45
 7418.427    17.15   8064.546    13.00     8150.406   12.87
 7441.459    16.01   8066.432    12.80     8150.429   12.75
 7444.296    17.15   8066.523    12.80     8151.469   12.90
 7444.326    17.14   8102.440    12.65     8154.353   12.80
 7445.316    17.45   8102.459    12.70     8154.377   12.95
 7445.342    16.90   8103.483    12.70     8155.401   12.90
 7447.309    16.90   8103.507    12.60     8155.425   13.00
 7448.294    16.65   8104.471    12.45     8156.321   12.80
 7739.422    13.95   8104.488    12.55     8156.345   13.00
 7739.447    13.95   8104.520    12.60     8422.330   12.53
 7740.464    13.45   8125.384    12.50

Besides photographic estimates of the brightness, in July 1991, we started
photoelectric observations of the star with the 60cm telescope of Belogradchik
Astronomical Observatory. The photometer used and the data processing have
been described by Antov et al. ( 1991 ).

Star "B" (see Walker, 1954) served as comparison star. The integration time was
10 sec. Magnitude estimates in a standard UBV system are presented in Table 2.

                     Table 2

Photoelectric UBV Observations of MV Lyrae
  HJD 2440000+   V    B-V     U-B
  8449.478   12.178  -0.114  -1.069
  8449.517   12.722  -0.236  -0.933
  8950.389   12.611  -0.201  -1.030


                               [FIGURE 2]


In addition, a patrol with a duration of 1.5 hours was carried out in the "u"
region on the night of July 12/13. Patrol observations (Fig. 2) revealed the
existence of rapid variations in light with an amplitude up to 0.4m within 5
minutes.


                            Z. KRAICHEVA, V. GENKOV
                            Department of Astronomy
                            Bulgarian Academy of Sciences
                            72 Trakia Blvd.
                            1784 Sofia, Bulgaria

References

Andronov, I. L., Shugarov, S. Yu., 1982, Astron. Tsirk., No 1218, 3 [BIBCODE 1982ATsir1218....3A ]
Antov, A. P., Genkov, V. V., Konstantinova-Antova, R., Kirov, N. K., 1991, 
   Inf. Bull. Var. Stars, No 3577
Fuhrmann, B., Wenzel, W., 1990, Inf. Bull. Variable Stars, No 3513
Kraicheva, Z., 1988, Inf. Bull. Variable Stars, No 3210
Kraicheva, Z., Antov, A., Genkov, V., 1987, Inf. Bull. Variable Stars, No 3093
Kraicheva, Z., Antov, A., Genkov, V., 1989, Commun. Konkoly Obs. Hung. Acad. Sci., 10, No 93, 243
									[BIBCODE 1989CoKon..93..243K ]
Popov, V., Kraicheva, Z., 1991, Contr. Astr. Obs. Skalnate Pleso, No 20, 63 [BIBCODE 1990CoSka..20...63P ]
Romano, G., Rosino, L., 1980, Inf. Bull. Variable Stars, No 1776
Walker, M., 1954, PASP, 66, 71 [BIBCODE 1954PASP...66...71W ]
Wenzel, W., Fuhrmann, B., 1989, Inf. Bull. Variable Stars, No 3391