COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 2430

                                      Konkoly Observatory
                                      Budapest
                                      9 November 1983

                                      HU ISSN 0374-0676



      ON THE CYCLE LENGTH OF THE CATACLYSMIC VARIABLE T LEONIS


  T Leonis has one of the shortest orbital periods (1h25m) of the cataclysmic
binaries with late type secondaries. To my knowledge, only the periods of the
long cycle dwarf novae WZ Sge and SW UMa and of the polar EF Eri are shorter
(around 1h22m). To estimate the cycle length of T Leo therefore seemed important.
Up to now only four eruptions were explicitly mentioned in the literature, 
three of them of the past century plus the one of 1967 June 2, observed
by Cragg of the AAVSO (Sky Telesc. 37, 128, Journ.It.Astron.Soc. Canada 62,
142). Five further maxima (1962 Febr. 10, 1971 May 29, 1982 Apr. 12 and June
23, 1983 March 24), detected by members of the AAVSO (Lowder et al.) and
AFOEV (Verdenet, Candela, Minois, Bruno and Hanon), remained rather unnoticed.
  A total of N = 807 suitable Sonneberg patrol blue plates were checked for
maxima of the star. The exposures have been taken since 1929.5 mainly by
P. Ahnert and H. Huth of fields centred at 12h+10d, 12h-4d, 12h0d, the 
declinations of which were chosen one after another and valid for several years each.
n = 16 plates of this material show 14 reliable eruptions. Eight of these are
represented also on overlapping neighbouring fields, or on simultaneous 
photovisual exposures on which the star is remarkably fainter in maximum than
on the blue sensitive ones. Available records on regular visual series 
obviously started at 1955 (AAVSO Quarterly Report 22). Since then four maxima
have been showing on our investigated exposures. Two of these eruptions are
common to AAVSO findings, whereas four further visually detected maxima are
not on the checked series because of moonlight or evening twilight.
  Taking into account the sun and moonlight gaps in the photographic material
of that region and the losses because of meteorological reason we estimate
that 30% of all eruptions are represented on the investigated plates. 
Therefore we get for the mean cycle length.

        c~~(1983.3 - 1929.5) / 14 * 364 * 0.3 = 420d

Another approach can be arrived at by, considering the ratio N/n in combination 
with the mean duration L of maxima. The observations yield individual
values of L lying between < 6^d and >11^d. We take L = 5...10 days and have

          C ~~ L * N/n = 250...500 days.

At present it cannot be decided whether the star exhibits two sorts of eruptions
(short ones and supermaxima). It should be mentioned that faint 14.5m
traces of the variable could occasionally be perceived on the plates. We
are inclined to interprete them as due to fluctuations in minimum brightness
and therefore we count only observations < 12.6m as belonging to real outbursts.
  A cycle length near 400 days places T Leonis well to the vicinity of
SW UMa, V 436 Cen, EK TrA and OY Car, not to speak of WZ Sge, all of them
lying in the shortest orbital period domain. The only exception from this
tendency recognizable so far is 3A 1148+719, which seems to have a mean cycle
length of several years (Wenzel, I.B.V.S. No. 2262, Mitt.Verand.Sterne
Sonneberg 9, 141) at an orbital period of 3h 55m.
  A list of the observed eruptions and some further details will be published
in Mitt.Verand.Sterne Sonneberg 10, No. 2.





                  W. WENZEL

            Sternwarte Sonneberg
            Zentralinstitut fur Astrophysik
            der Akademie der Wissenschaften
            der DDR