COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                        NUMBER 808

                                               Konkoly Observatory
                                               Budapest
                                               1973 June 30


                 NOTE ON THREE OF G. HILL'S STARS


    In Astrophysical Journal Supplement Series Nr. 130 (1967) G. Hill
published the results of an extensive search for new variable B
stars. His findings meant a substantial widening of the region in
the H-R diagram within which beta CMa stars had been found up to then;
also overrun were the barriers set by low rotational velocity and by
the period-luminosity law. But Hill's method to derive periods is 
open to serious scepticism when it is applied to stars which have
beats and phase shifts of the maxima and minima in their lightcurves,
and this is known to be quite common among beta CMa stars. Hill's results
should therefore be checked by means of conventional long photometric
runs on each of his stars.
    The author spent several nights in observing three of them, two
beta CMa stars and one eclipsing variable, during observation campaigns
at the ESO Observatory in Chile during 1968 and 1969-70. He arrived
at the following conclusions:
    1. HD 53755, B0-V, a beta CMa star with amplitude Deltam_b=0,032 and
Deltam_U=0,031 and P=0.43389d according to Hill: neither the period nor
the amplitude could be found back. If there is any periodicity at all
discernable in the small lightfluctuations of the star, we would 
suggest 6h25m for the period length and 0,02m for the amplitude in v.
    2. HD 53794, B0, 5-IV, a beta CMa star with amplitude Delta_m = 0,027
and P = 0,12377d according to Hill: only on one occasion, namely in
the night of 20 December 1968 was a period of 3h found back for a
lightvariation of 0,01m. For the rest a period of 10h52,5m is not 
unlikely associated with lightchanges of the order of 0,01m-0,02m, and
RV changes observed on spectrograms taken in the course of one and
the same night. But the star in certainly a spectroscopic binary with
very long period; this can be concluded from our RV measurements which
reveal the RV to drop steadily from ~+50 Km/sec on 19 Nov 1969 to
~-20 Km/sec on 21 Jan. 1970.
    3. HD 53756, B2-IV, an eclipsing binary with Delta_m=0,025 and
P=4,1237d according to Hill: this star is indeed an eclipsing binary
with slightly elongated components, but the period is P=2,8d. 
A secondary minimum almost as deep as the primary but revealing a 
slightly eccentric orbit caused Hill's mistake.
    This star will be extensively reported on in a separate publication.

A. VAN HOOF
Astronomisch Instituut K.U.L.
Leuven - Belgium