COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                      Number 1810

                                    Konkoly Observatory
                                    Budapest
                                    1980 July 1






        ON THE LARGE-SCALE VARIATIONS OF MV LYRAE





     A deep minimum of MV Lyrae was detected by Romano and Rosino
on Asiago plates (1). I therefore inspected our homogeneous series
of sky patrol plates of the interval August 1956 to June 1980
(n=429) and the longer focus plates of the field R Lyrae, taken
with the astrographs 17/120 cm , 40/160 cm and 40/190 cm essentially 
between 1964 and 1967 and sporadically up to 1979 (n=115).
The patrol plates in general cover the time interval mentioned
above without marked seasonal gaps.

     Our findings can be summarized as follows:
1. The irregular fast changes (occurring from night to night) which
were observed by Parenago (2), Walker (3), Weber (4) and Romano and
Rosino (1) seem to be of varying intensity. For example in 1964
and 1965 we find small changes only (about 0.5 mag around mpg =
12.4m), strong variations hovewer in 1960 (from 12.1m to 13.7m).The
rapid (hourly) variations will not be discussed here.
2. The mean brightness varies (even without considering the deep
minima) in time-scales of months. For instance in 1968 the brightness 
without exception fluctuated below 12m4, in 1969, 1971 and
1972 preferably above 12m4.
3. The minimum of ref. (1) is confirmed: The brightness was only
slightly fainter than 12m4 on 1979 June 26, but 14m5 and 14m1 on
August 15 (2 consecutive plates) and never distinctly brighter
than 14m0 up to 1980 June 6.
4. A second minimum occurred 1956 to 1957 July 4 (star sometimes
invisible fainter than 14m5, ascent to 12m4 1957 August to November), 
a third one 1976 (1976 June 28 invisible fainter than
15m8, descent with fluctuations 1974 and 1975, ascent winter
1976/77).

5. Because the minima on the whole last 7 year and even longer,
the probability is small that further minima since 1956 have
remained undetected.
    Although some features of the light-curve remind one of the
HdC stars of R CrB type rather than of old novae, the spectroscopic 
findings (5) and details of the variability certainly exclude
the former suggestion and to the same degree the latter one. More
probable however is a relation to the polars of AM Her type. This
assumption was emphasized already by Vojkhanskaya et al, (6),(7)
on the basis of polarimetric observations, and now gains high importance 
because of the similarity of the light-curves of MV Lyr
and AM Her (8). X-ray observations are urgently recommended.
    Our comparison stars (see chart) were linked to the Mt.
Wilson photographic system of Selected Area 38. The brighter ones
are in good agreement with the B data of (3).



                     [FIGURE 1]

                                   W. Wenzel
                               Sternwarte Sonneberg
                            Zentralinstitut fur Astrophysik
                           Akademie der Wissenschaften der DDR

References:
(1) Romano, G., Rosino, L., IBVS No. 1776, 1980
(2) Parenago, P., VS 6, p.26, 1946
(3) Walker, M.F., PASP 66, p.71, 1954 [BIBCODE 1954PASP...66...71W ]
(4) Weber, R., J.des Obs. 44, p.275, 1961 [BIBCODE 1961JO.....44..275W ]
(5) Greenstein, J.L., PASP 66, p.79, 1954 [BIBCODE 1954PASP...66...79G ]
(6) Vojkhanskaya, N.F., et al.,Astron.Zhurn.Pis'ma 4,p.272,1978 [BIBCODE 1978SvAL....4..148V ]
(7) Vojkhanskaya, N.F.,Mitrofanov,I.G.,Astron.Zhurn Pis'ma 6,
             p.159, 1980 [BIBCODE 1980SvAL....6...87V ]
(8) Hudec, R., Meinunger, L., MVS 7, p.195 (1977)


Erratum (IBVS No. 1789)
As is quoted correctly in the text, the nebulous object lies at alpha=5h44m1 in
the field of beta Aur and not at 15h44m. Readers should delete the "1" in the
heading.