COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                      Number 3406

                                       Konkoly Observatory
                                       Budapest
                                       18 December 1989

                                       HU ISSN 0374 - 0676



   REVISED ELEMENTS AND LIGHT CURVE FOR LS DELPHINI

The small amplitude W UMa type eclipsing binary LS Del (=
BD+19d4574, HD 199497, SAO 106694) was discovered by Bond (1976)
on spectroscopic and photoelectric observations. According to
Kholopov et al. (1981) the visual magnitude varies from 8.61 to
8.76.
The period given by Bond (1976), 0.3638 days, was improved by
Ruyou et al. (1987). Based on photoelectric observations of 4
nights these authors of the Beijing Astronomical Observatory noted
the period to be 0.3639207 days.


To test the new elements, we did an observing run on LS Delphini
in the years 1987 and 1989. The telescope used was a 0.34 m
Cassegrain, equipped with a 1P21 phototube. All measurements were
done in V colour.

As a result the ephemeris given by Ruyou et al. (1987) fails to
represent our observations and the quoted period turned out to be
spurious.
Indeed the true period is 7.2 seconds shorter, so the O-C against
the ephemeris of Ruyou et al. (1987) will add up to 0.5 cycles
within about 2 years. Therefore the quoted ephemeris will seem
roughly correct in an even year, but will clear up as erroneous in
odd years. Unfortunately all yet published observations were done
in even years. Subsequently primary and secondary minima will be
mixed up.

Table: Times of photoelectric minima of LS Delphini.
O-C values are calculated against the elements
of this paper.
JD hel.      E          O-C     Observer        Reference
42687.418    -13992.5   +.002   Bond            IBVS   1214
46668.1609   -3051.5    -.006   Ruyou et al.    IBVS   2982
46670.1686   -3046      +.001   Ruyou et al.    IBVS   2982
46671.0744   -3043.5    -.003   Ruyou et al.    IBVS   2982
47028.362    -2061.5    -.004   Wunder              this paper
47729.486    -134.5     +.004   Wieck               this paper
47737.490    -112.5     +.004   Wieck/Wunder        this paper
47778.421    0          +.003   Wieck/Wunder/       this paper
                                Skaberna
47790.423    33         -.002   Wunder              this paper


                          [FIGURE 1]


 On base of the data shown in the table we calculated the new
 ephemeris, namely:


        JDhel. MinI = 2447778.4180 + 0.36383792 * E
                             +/-16        +/-16

The time of minimum published by Bond (1976) is not, as Ruyou et
al. (1987) stated, a primary but a secondary minimum. Finally, a
minimum published by Diethelm (1987) turned out to be incorrect
and is therefore omitted.

A light curve in V colour of LS Delphini was made from selected
data in 1989 and is illustrated in the figure.


                          M. WIECK
                          E. WUNDER

                          Nurnberg Observatory
                          Regiomontanusweg 1
                          8500 Nurnberg 20, F.R.G.


References:

Bond, H.E., 1976, Inf. Bull. Var. Stars, No. 1214.
Diethelm, R., 1987, BBSAG-Bulletin, No. 84.
Kholopov, P.N., Samus, N.N., Kukarkina, N.P., Medvedeva, G.I.,
   Perova, N.B., 1981, Inf. Bull. Var. Stars, No. 1921.
Royou, W., Wenxian, L., Qingyuan, F., 1987, Inf. Bull. Var. Stars, No. 2982.