COMMISSION 27 AND 42 OF THE IAU
                   INFORMATION BULLETIN ON VARIABLE STARS
                               Number 3815

                                                         Konkoly Observatory
                                                         Budapest
                                                         27 November 1992

                                                         HU ISSN 0374 - 0676


       A PERIOD FOR THE ECLIPSING BINARY DHK 29 = BD +33d4070

Kaiser (1992) reported that the star BD +33d4070 = SAO 70629 is an eclipsing
binary, which he designated DHK 29 in his discovery list. His patrol photos
show the star near minimum on two nights. Following discovery, Baldwin began
regular visual monitoring. Another minimum was soon detected, and on the same
night Kaiser was able to obtain a few photoelectric measures of the final
portion of the eclipse light curve. The star varies from 8.9-9.5: V, and
the eclipses are 5 hours in duration.
   To determine the period, Kaiser examined the variable on 320 Harvard patrol
plates from the years 1918-1952 and 1968-1989 and found 16 additional minima.
Table I lists all 18 photographic minima and the estimated times of two minima
from Baldwin's visual observations.


                                 TABLE I.

HJD 2400000+     E       O-C              HJD 2400000+     E       O-C

21859.604     -14221   -0d058   H         31750.606      -9021   -0d025   H
22228.626     -14027   -0.046   H         41951.657      -3658   +0.014   H
22698.590     -13780   +0.097   H         42693.517      -3268   +0.052   H
26479.827     -11792   -0.059   H         45525.690      -1779   -0.016   H
26559.799     -11750   +0.025   H         45563.724      -1759   -0.024   H
28366.778     -10800    0.000   H         45645.573      -1716   +0.034   H
28448.554     -10757   -0.015   H         47081.596      - 961   -0.036   K
29456.711     -10227   +0.024   H         48479.683      - 226   +0.001   K
30173.805      -9850   +0.023   H         48909.547          0   -0.012   B
30605.588      -9623   +0.027   H         48924.768      +   8   -0.008   B


H - Harvard ptg., K - Kaiser ptg., B - Baldwin visual.

The following light elements result when these minima times are introduced
into a least squares solution:

           Min.- HJD 2448909.558 + 1.9021093d * E          (1)
                            +-15        +-17

   The cycle numbers and O-C residuals in Table I are calculated from Equation
1. After this ephemeris was derived, Baldwin was able to confirm it by
observing a predicted minimum (E - 8) visually.
   The interval 1.9 days between eclipses is probably half of the orbital
period. A photoelectric measure at phase 0.52 of Equation 1 shows no decrease
from maximum light. The spectral type is F8 (AGK3, 1975), so it is quite
likely that the two components of the binary system are similar in spectral
type and produce primary and secondary eclipses of nearly equal depth. Our
visual and photographic estimates are not precise enough to distinguish between
primary and secondary minima of similar depth. Photoelectric observations in B
and V are continuing and will eventually establish precise values for the
depths of the alternate minima.
   We wish to thank Dr. Martha Hazen, curator of astronomical photographs at
Harvard College Observatory, for use of the Harvard patrol plates. We are
also grateful to Dr. Dorrit Hoffleit of the Yale University Department of
Astronomy for checking the literature on this star's spectral type.


                                             DANIEL H. KAISER
                                             2631 Washington Street
                                             Columbus, IN 47201 U.S.A.

                                             MARVIN E. BALDWIN
                                             Route 1
                                             Butlerville, IN 47223 U.S.A.



References:

AGK3: 1975, Dritter Katalog der Astronomischen Gesellschaft, Hamburg-Bergedorf.
Kaiser, D. H.: 1992, IBVS No. 3814.