COMMISSION 27 OF THE I. A. U.
                   INFORMATION BULLETIN ON VARIABLE STARS
                               Number 3514

                                                         Konkoly Observatory
                                                         Budapest
                                                         5 September 1990

                                                         HU ISSN 0374 - 0676


      PHOTOMETRY OF THE NEW ECLIPSING BINARY DHK 16 = SAO 80992

Kaiser (1990) discovered that the 9th-magnitude star SAO 80992 = BD +26d1996
is an eclipsing binary, which he designated DHK 16 in his discovery list. The
spectral type is G0, the position RA: 09h41m22s, Dec: +25d35.1' (1950).
   Regular visual monitoring by Baldwin soon detected additional minima. A.
discrete Fourier transform analysis of these visual observations by Kaiser
produced several possible periods, the most promising being 0.69 day.
   Williams observed the star photoelectrically with an Optec SSP-3 photometer
and 28-cm Schmidt-Cassegrain. Most observations were made in the R band because
of the variable's faintness with a 28-cm aperture and the photodiode's greater
sensitivity at longer wavelengths. These observations (Figure 1) show that the
0.69-day DFT period is the half-period of an Algol-type eclipsing binary with
nearly equal minima. A least-squares period solution using the discovery photo
(HJD 2447968.691), one photoelectric minimum (the initial epoch of Equation 1),
and six times of minima estimated from visual observations results in the
preliminary light elements:

            Min. I = HJD 2447999.617 + 1.3742d E                  (1)
                              +-.002  +-.0002

  The comparison star was SAO 80978 (7.26 V, +1.10 B-V, K1III). Williams
measured the comparison star and the variable at maximum in the V and R bands
relative to several nearby stars from the Arizona-Tonantzintla Catalogue
(Iriarte et al. 1965) and obtained the following results:

          Comparison = SAO 80978 = 7.26 V, +0.80 V-R
          Var (max)  = SAO 80992 = 9.22 V, +0.54 V-R


                                 [FIGURE 1]

 Figure 1. R-band differential photometry of DHK 16 = SAO 80992 phased
 according to Equation (1).


   The eclipses appear to be partial, with duration of eclipse close to 0.10 P
= 3.3 hours. Due to incomplete phase coverage and increased scatter when the
variable was faint, the amplitudes of the two minima remain somewhat uncertain.
However, available observations indicate that the primary minimum is 0m.70 R
deep and the secondary minimum is within 0.1m of the primary.


      DAVID B. WILLIAMS         MARVIN E. BALDWIN        DANIEL H. KAISER
      9270-A Racquetball Way    Route 1                  2631 Washington Street
      Indianapolis, IN 46260    Butlerville, IN 47223    Columbus, IN 47201
      USA                       USA                      USA



REFERENCES

Iriarte, B., Johnson, H. L., Mitchell, R. I., Wisniewski, W. K., 1965,
   Sky & Telescope, 30, 21. [BIBCODE 1965S&T....30...21I ]
Kaiser, D. H., 1990, Inform. Bull. Var. Stars No. 3480.