COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 1364

                                   Konkoly Observatory
                                   Budapest
                                   1977 November 21



      HR 239 AND HR 8676 : TWO delta Sct - TYPE VARIABLES




    During an observing run at the 50 cm ESO-telescope at La
Silla (Chile), HR239 (HD 4849, -44d216) was observed as a 
program star and HR 8676 (HD 215874, 70 Aqr) as a comparison star.
Both stars are classified as F0. For HR 239 this classification
was verified in essence by a coude-spectrogram obtained at the
1.5 m ESO telescope by Mr. F. Spite. The standard ESO photometer
with an EMI 6256, cooled by Peltier elements to -20d relative
to ambient temperature, was used for the observations. Diaphragms
of 21" and 30" were used. B and V colours have been measured for
HR 239 in the night of Sept. 6/7, 1977 and UBV for HR 8676 in the
night of Sept. 28/29, 1977. In addition, Mrs. B.E. Helt from 
Copenhagen University Observatory covered one cycle of HR 239 in
the night of Sept. 24/25, 1977 with a simultaneous 4-colour 
photometer in the Stromgren system at the 50 cm Danish telescope
at La Silla.
   A sophisticated telescope control system and a convenient
preliminary on-line reduction system, developed by J. Fluxa and
D. Hofstadt enabled the writer to switch rapidly from one star
to the other and check for constant brightness and colour. The
latter was done by using mean extinction and a zero-point for
the colour transformation which was determined at the beginning
of every night. Both have proven to be sufficient for a preliminary 
check of the magnitudes on-line.
   HR 239 as a program star was observed in the sequence:
comparison 1 (HD 5042), program star, comparison 2 (HD 5062),
comparison 1, program star, etc. The magnitude difference in V
between the two comparison stars was constant to within sigma=0.003m
for a total of 33 measurements. This value corresponds also to
the internal accuracy with which the light curve for HR 239 has
been determined in V. The V light curve using extinction corrected 
and colour transformed magnitudes is shown in Figure 1. The
colour difference (B-V) for the variable was constant during
the nearly 3 hrs of observations to within 0.0034 mag. For the
comparison star a sigma of 0.0037 mag was determined, this being
essentially the same as for the variable.
   A raw estimate for the amplitude range of the V light curve
is 0.015 mag with a period of about 80 min. The measurements in
y obtained 18 days later by B.E. Helt confirmed the first results
concerning the shape of the light curve, the amplitude and the
period. However, the scatter of her measurements has been almost
twice as much as for the Johnson colours.
   HR 8676 was observed during a night of very poor seeing.
The first 9 measurements have been obtained with a 21" diaphragm,
but then it was necessary to change to a 30" diaphragm. The 
comparison stars have been HD 216494 (74 Aqr), originally a program
star, and HD 215874 (75 Aqr). The correction for changing the          
diaphragm in V was obtained by averaging the first 9 measurements
of 74 Aqr which resulted in V=5.80m (sigma=0.0044 mag) and averaging
the following 9 measurements, which have been obtained already
with the 30" diaphragm. The latter observations gave a mean
V=5.78m (sigma=0.0021 mag). Thus, a correction of -0.020 mag was 
applied to the first 9 measurements of HR 8676 in V. The resulting
light-curve using on-line reduced magnitudes can be seen in 
Figure 2. Although the seeing was poor during this night, the 
relative photometric accuracy was slightly better than in the
night of Sept. 6/7 1977. A first inspection of the light curve
results in an amplitude in V of 0.025 mag and a period of about
125 min.
   Considering the rather late spectral type which is published 
for these stars and which is confirmed by their Stromgren
indices, one is tempted to classify HR 239 and HR 8676 as delta Sct
type variables. This might be less evident for HR 8676, if one
uses the Period - Spectral type diagram for Dwarf Cepheids and
delta Sct type stars, as published By M.S. Frolov (1976). However,
both stars are located in the M_v - Sp diagram very close to the
ZAMS and the cool limit of the instability strip (Breger et al.,
1975). Thus fundamental mode pulsation should be expected. It is
evident, that more and better observations, especially spectra,
are needed to clarify this point.

                      [FIGURE 1]

Figure 1. V-magnitudes for HR 239 and the comparison (HR 245).

                      [FIGURE 2]

Figure 2. Raw V-magnitudes for HR 8676 and the comparison (74 Aqr).

Acknowledgements:
This observations have been collected at the European Southern
Observatory, La Silla, Chile. The writer is indebted to the Gen.
Director, Prof. L. Woltjer, for the kind hospitality at La Silla
and for making telescope time available. He also has to thank
Mr's Fluxa, Hofstadt Suter and Vidal for their continuous help
during the observing run. The writer gratefully acknowledges
that Mrs. B.E. Helt spent nearly two hours of her telescope time
on HR 239 and that Mr. F. Spite friendly took a spectrogram of
this star. This work is part of the project No. 2339, supported
by the Austrian "Fonds zur Forderung der wissenschaftlichen 
Forschung".



                           WERNER W. WEISS
                      University Observatory, FOA,
                           Vienna, Austria

References:
Breger, M., Bregman, J.N. 1975, Astrophys. J. 200, 343 [BIBCODE 1975ApJ...200..343B ]
Frolov, M.S. 1976, IBVS No. 1096



                    [Note printed in IBVS 1400]

Note to I.B.V.S. No. 1364: In Figure 1, increasing magnitudes in
V were plotted in positive direction.