COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 2066

                                 Konkoly Observatory
                                 Budapest
                                 1982 January 5

                                 HU ISSN 0374-0676




 VARIABLE STARS IN THE GENERAL CATALOGUE OF TRIGONOMETRIC
                       PARALLAXES



  In preparation for W. van Altena's forthcoming revision of
the General Catalogue of Trigonometric Parallaxes, I have checked
the earlier version and its supplement (Jenkins 1952, 1963) for
variable stars. The 1958 edition of the GCVS and its 1960 
supplement has 194 stars in common with the parallax catalogues.
However, only two thirds of these (134 stars) are noted as variable 
in the parallax catalogues. Subsequently, of course, large
numbers of new variables have been discovered. Now at least 458
of the nearly 6400 parallax stars are named variables (Kukarkin
1969-77, Kholopov 1977-81). A great many others are given in the
catalogues of suspected variables (Kukarkin 1951, 1965) but they
are not included in this survey.
  The distribution of the parallaxes of the named variables is
shown in the Figure. These represent nearly all types of 
variability, from supernovae down to stars of nearly negligible 
variability. 55 are eclipsing variables, 9 are of dubious 
variability, classified as "cst", and the types of variability are
still lacking for 83. Only 27 of the variables have parallaxes
over .100". Of these 18 are of the UV Ceti type and 3 are BY Dra
stars (a group that may be related to the UV Cet). One (RT Lac)
is an eclipsing binary, while the remaining 5 are of undetermined
type. There are 10 additional UV Cet stars, all with parallaxes
over .045". The lower part of the Figure shows the distribution 
of the parallaxes of the UV Cet and BY Dra stars. In 1958 the
GCVS listed 11 stars as UV Cet type, of which 8 are included in
the parallax catalogues, but only one being noted as variable,
with no type assigned. These parallax stars had been chosen for
parallax determination on the basis of their proper motions,
not because of their peculiar variability.

                         [FIGURE 1]

  The available apparent magnitudes of the UV Ceti stars as
given in the GCVS are on heterogeneous system, ranging from
v, p, V, B through U. Older visual magnitudes in the parallax
catalogue are often grossly in error, especially for the fainter
stars (see, for example, Hoffleit 1970 for a comparison of 
photographic estimates, indicating differences with a probable error
of over a whole magnitude. Provisional estimates of visual magnitude 
of faint stars are often no better). A crude reduction of
the parallaxes to absolute magnitude, using the published visual
magnitudes of the UV Ceti stars, gives an unweighted mean
M_v= 11.7 +- .4, the individual values ranging from 8.5 to 16.5.
  Parallaxes less than .030". are rarely significant. Among the
72 stars with parallaxes larger than .030". in addition to the
UV Ceti stars, there are 13 eclipsing variables and 9 Delta
Scuti stars. Other types are represented by less than five stars
each. In all, the parallax catalogues contain 33 known Delta
Scuti stars. The 9 with parallaxes exceeding 030". indicate a
mean absolute magnitude, M_v = 2.1 +- .1, the values ranging from
0.4 to 4.2. For no other types is there a sufficient number of
significant parallaxes to warrant an estimate of the mean absolute
magnitude.
  The new catalogue of trigonometric parallaxes will contain
not only revisions of the currently known parallaxes, and in
many cases up-dated photometric data, but a few thousand 
additional stars, undoubtedly including many more variable stars.
As it will be some time before this compilation is completed,
the list of variables among the stars in the 1952 catalogue and
its 1963 supplement will be furnished to interested users upon
request.





                  DORRIT HOFFLEIT
                  Yale University Observatory
                  Box 6666, New Haven
                  Conn. 06511, U.S.A.

References:

Hoffleit, D., 1970, Trans. Yale Univ. Obs. 30, (25).
Jenkins, L., 1952, General Catalogue of Trigonometric Stellar
         Parallaxes, New Haven.
         1963, Supplement to the General Catalogue of
         Trigonometric Stellar Parallaxes, New Haven. [BIBCODE 1952gcsr.book.....J ]
Kukarkin et al., 1951, Catalogue of Stars Suspected of Variability,
         Moscow [BIBCODE 1951CSV...C......0K ]
         1965, Second Catalogue of Suspected Variable Stars,
         Moscow [BIBCODE 1965CSV...C......0K ]
         1969-71, General Catalogue of Variable Stars,
         Vols. I - III, Moscow [BIBCODE 1969gcvs.book.....K ]
         1971, First Supplement to GCVS [BIBCODE 1971fstt.book.....K ]
         1974, Second Supplement to GCVS [BIBCODE 1974sstt.book.....K ]
         1976, Third Supplement to GCVS, Moscow [BIBCODE 1976tstt.book.....K ]
         1977, 62nd Name-List of Variable Stars, IBVS No. 1248
Kholopov et al., 1977, 63rd Name-List of Variable Stars,
         IBVS No. 1414
         1979, 64th Name-List of Variable Stars, IBVS No. 1581
         1981, 65th Name-List of Variable Stars, IBVS No. 1921