COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1037

                                   Konkoly Observatory
                                   Budapest
                                   1975 August 22


   A REVISED PERIOD FOR ONE OF THE WESSELINK-SHUTTLEWORTH
                SMC VARIABLES



Amongst the 44 faint pulsating variables in the SMC discussed by
Wesselink and Shuttleworth (MNRAS 130, 443, 1965), five stars were
of special interest because of their periods smaller than 1 day.
Also in view of the shape of their light-curves they resemble the
RR Lyrae stars, only with that difference that their absolute
magnitudes must be brighter than -1. It has been suggested more than
once (e.a. Landi Dessy, PASP 71, 435, 1959) that these variables
are the extension towards shorter periods of the population
I Cepheids of the Magellanic Clouds.
For one of them, viz. WS 2, a period of 0.807774d was derived.
This period however did not fit photographic B and V (of the UBV
system) observations (van Genderen, BAN Suppl. 3, 221, 1969). A
slightly different period viz. 0.8327d gave a reasonable representation 
of these observations, but not for those of Wesselink and
Shuttleworth. Also in view of its large deviation in the period-
luminosity relation and the H-R diagram for nearly a hundred SMC
Cepheids (van Genderen, ibid), such a short period was suspected.
A period of several days would be more plausible.
A new investigation of both series of observations revealed a
more acceptable period viz. 4.96632d+-0.00050d (e.e.). The reciprocals 
of this period and the two shorter ones differ nearly by one.
Fig. 1. shows the light-curves: The top one represents brightness
estimates with the Argelander step method, by Wesselink and Shuttleworth 
(ibid) and the two lower ones are the photographic V (circles)
and B (crosses) observations mentioned above. Uncertain 
estimates are between brackets. Phases have been computed with the
formula:

(JD - 2433895.495) / 4.96632

                     [FIGURE 1]

A few observations seem to be standing off suspiciously from
the mean light-curves, but this is a feature present in more
light-curves shown in both papers, especially the photographic 
ones are subject to the disturbing influence of many adjacent 
stars. We therefore suggest that the new period is probably 
the right one.
I am very grateful to Dr. A. J. Wesselink for his kindness to
allow me to use his unpublished observations.



                        A.M. VAN GENDEREN
                      Leiden Southern Station
                      P.O. Box 13 Broederstroom-0240
                      South-Africa