COMMISSIONS 27 AND 42 OF THE IAU
             INFORMATION BULLETIN ON VARIABLE STARS
                         Number 3979

                                                   Konkoly Observatory
                                                   Budapest
                                                   20 January 1994

                                                   HU ISSN 0374 - 0676


                   UBV OBSERVATIONS OF SU INDI



  The southern eclipsing binary system SU Ind (= HD198827, SAO 230428) has received
relatively little attention hitherto. It was included in the short period EB-type list in
Budding (1981) with the G5 spectral classification carried over from the Finding list of
Wood et al., (1980). That catalogue also gave the secondary minimum, at 0.2 mag, to
be half the depth of the primary - which presumably derives from the old photographic
light curve of Hoffmeister (1956), on which the secondary minimum is quite incomplete.
  Giuricin et al. (1983), give the binary an `a' type classification, suggesting thereby
some incipient evolutionary activity - mass exchange or Algol-like characteristics. This
might also go with the appreciable squared term in the ephemeris equation of Wood and
Forbes (1963), though those authors listed SU Ind in a group prone to relatively large
errors on this specification, due to insufficient time of minima data. In fact, the prima
facie evidence of the recent light curves shown below, for which Hoffmeister's old period
0.986323 d was used, indicates any change in this value over a thirty year interval to be
fairly small.
  The GCVS of Kholopov (1985) lists SU Ind with an F5-6 spectral type, which certainly
accords better with the b - y = 0.314 value of Wolf and Kern (1983) than did the earlier
G5. The earlier type implies that the star is more distant than originally considered (~100
pc) by Dworak (1976).
  SU Ind was observed from the Black Birch outstation of Carter Observatory for some
nights in 1983, 1989 and again in 1993, but the near unity day period value hindered rapid
collection of complete light curves. It was placed also on the target list of the recently
commissioned automatic photometric telescope (APT) of the Kotipu Place Observatory
(Hudson et al. 1992), and observed on 12 good nights during a period from August
to October 1993, using UBV filters as provided with the commercial SSP 5 photometer
manufactured by Optec Inc.
  The data have been reduced on PCs using in-house software (cf. Budding, 1993), and
are presented in Figure 1 as essentially raw results. These light curves are almost complete
from the APT, though a little contemporaneous data from Black Birch has been added to
properly locate the bottoms of the primary minima, which were not completely observed
by the APT. Observations of standard stars with this instrument indicate the V filter to
be quite close to the Johnson standard (e = 0.02), though the B filter is slightly longward
of standard (mu =1.14). The less reliably determined U calibration also indicates that U
is close to the standard specification (psi = 0.98).
  The light curves of Figure 1 are the first worked through set obtained with our SSP 5
photometer, and give a good indication of the APT's performance as a 0.36m telescope

                               [FIGURE 1]

             Figure 1.  SU Ind - Delta Mag against Phase

on a ~ 9.5 mag star in the dark suburban environment of Kotipu Place. They show the
two minima to be of essentially equal depth, and a noticeable, though not pronounced,
level of `beta-Lyrae type' proximity effect interaction between the components. These are
probably a pair of very nearly equal, dwarf, F-type stars. Further processing and detailed
analysis, including the backlog of Black Birch data, can be expected to follow this initial
report.


            E. BUDDING, G. HUDSON, R. HUDSON and J. PRIESTLEY
            Carter and Kotipu Place Observatories, Wellington, New Zealand



References

Budding, E., 1981, in Investigating the Universe, ed. F. D. Kahn, Reidel, p 271. [BIBCODE 1981ASSL...91..271B ]
Budding, E., 1993, An Introduction to Astronomical Photometry, Cambridge Univ. Press,
 Cambridge. [BIBCODE 1993iap..book.....B ]
Dworak, T. Z., 1976, IBVS No 1136.
Giuricin, G., Mardirossian, F. and Mezzetti, M., 1983, Astron. Astrophys. Suppl. Ser.,
 54, 211. [BIBCODE 1983A&AS...54..211G ]
Hoffmeister, C., 1956, Veroff. Stern. Sonneberg 3, 1. [BIBCODE 1956VeSon...3....1H ]
Hudson, G., Hudson, R. and Budding, E., 1992, Proc. IAU Coll. 136, ed. I. S. Elliott,
 (in press). [BIBCODE 1993ppsp.conf..107H ]
Kholopov, P. N., 1985 General Catalogue of Variable Stars (GCVS), II, Nauka Publ.
 House, Moscow.
Wolf, G. W. and Kern, J. T., 1983, Astrophys. J. Suppl. Ser., 52, 429. [BIBCODE 1983ApJS...52..429W ]
Wood, D. B and Forbes, J. E., 1963, Astron. J., 68, 257. [BIBCODE 1963AJ.....68..257W ]
Wood, F. B., Oliver, J. P., Florkowski, D. R. and Koch, R. H., 1980, Publ. Univ. Penn.
  Astron. Ser., 12, 1.