COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                        Number 925

                                     Konkoly Observatory
                                     Budapest
                                     1974 September 19


           VARIABLE STARS AMONG THE FOUR-COLOUR
                  (uvby) STANDARD STARS

    From 1971 to 1973 four-colour (uvby) observations were made in
the southern sky by Mr. Bent Gronbech, Dr. Bengt Stromgren and the
author with a four-channel spectrograph-photometer attached to the
Danish 50 cm reflector on Cerro La Silla (ESO), Chile. Among the
133 four-colour standards (Crawford and Barnes, 1970) measured 
regularly, five were noted as being variable. Of these, HR 2707  and
7152 were previously known (V571 Mon and epsilon CrA), while HR 373 and
3084 do not appear in the General Catalogue of Variable Stars (GCVS,
3.ed) and HR 4133 appears in the Special Supplement to GCVS (1972)
as a suspected variable. However, HR 373 has been noted as variable
by Cousins (1962), who found a range of 0m.12 in V from five 
observations.
                             Table 1

                  HR 373     HR 3084     HR 4133

          V       5m.407      4m.500      3m.860
    scatter       0m.051      0m.016      0m.015
    weight        55.5       82.0        32.0
    no. of nights 24         41          16

    The y observations have been transformed to the standard V 
magnitudes of the UBV system. In Table 1 the mean V magnitudes are
given; the weight is the number of observations, some of them having
only half weight. The internal r.m.s. error of one V value determined
from 7094 standard star observations is 0m.008  (including HR 2707,
3084 and 4133, but excluding HR 373 and 7152).
    The spectral type of HR 373 is gG5, and the star is probably a
yellow semi-regular variable (SRd). If this is true, it must be one
of the brightest members of its class since only o^1 Cen and V441 Her
(89 Her) are brighter. The amplitude is probably not very much larger
than 0m.2 and the star may resemble IS Gem and VW Dra (HR 2512 and
6448) with respect to amplitude, period and spectral type. It shows
no variation in b-y or m_1 but the scatter in c_1 is 0.014 while  the
r.m.s. error of one c_1 value computed from the standard star 
observations is 0m.005.

   HR 3084 is a spectroscopic binary with variable radial velocity,
spectral type B3V (Catalogue of Bright Stars) or B3IV (Cousins and
Stoy, 1963). The variations have an amplitude of about 0m.07 and could
be due to pulsations (beta Canis Majoris type variable) or to ellipsoidal
variations. The four-colour indices show no variations.
   HR 4133 is an early type supergiant (B1Ib) and the variations have
an amplitude of about 0m.07. They are possibly intrinsic, due to 
pulsations (Abt, 1957). The four-colour indices show no variations.


1974, September 5.

                                      ERIK HEYN OLSEN
                            Copenhagen University Observatory
                                    Brorfelde, Denmark.

References:

Abt, H.A. 1957, Ap.J. 126, 138. [BIBCODE 1957ApJ...126..138A ]
Cousins, A.W.J. 1962, MNASSA 21, 20.  [BIBCODE 1962MNSSA..21...20C ]
Cousins, A.W.J. and Stoy, R.H. 1963, Roy.Obs.Bull. No. 64. [BIBCODE 1963pmcs.book.....C ]
Crawford, D.L. and Barnes, J.V. 1970, A.J. 75, 978. [BIBCODE 1970AJ.....75..978C ]