COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                        Number 3369

                                             Konkoly Observatory
                                             Budapest
                                             24 August 1989

                                             HU ISSN 0374-0676


        TIME OF MINIMUM DETERMINATION FOR AS CAMELOPARDALIS


AS Cam (HD 35311) is an important system in the study of relativistic apsidal
motion. It is one of only a few binary systems with observed apsidal motion
significantly less than what is predicted by general relativity and standard
classical theory (Guinan et al., 1987a). Yet more binary systems are being
found to behave in this fashion, such as V541 Cygni and V1143 Cygni as well as
DI Her, the prototype apsidal motion system (Lines et al., 1989: Guinan et
al., 1987b). This phenomenon is not yet completely understood, and may be more
common in eccentric eclipsing binary systems than was initially thought.

I observed AS Cam on several nights in January 1989, and obtained two sets of
data when the star was near the center of primary eclipse. I used the USAF
Academy 61 cm telescope with an uncooled EMI 9789 photomultiplier tube to
conduct standard ubv differential photometry. The stars HD 34463 and HD 34886
were used as comparison and check respectively, and neither one showed any sign
of variability. On 27 Jan 1989 UT, AS Cam was observed from just prior to
until approximately one hour after primary minimum. This data is plotted in
Figure 1.

The data was reduced using estimated first order extinction coefficients, and
curve fitting was accomplished using a second order polynomial fit to a
fine-mesh cubic spline. Error bars are not included for individual points on
the graph, but the maximum error for any point is 0.03 magnitude. As Figure 1
shows, the time of minimum is almost identical for all three filters, and
analysis of the fit gives the average time of primary eclipse as:

T(minimum) = HJD 2447553.6410+-0.0022d

Using the ephemeris of Guinan et al., the (O-C) = -0.0012d. Unfortunately,
all further attempts to observe AS Cam at minimum during the next two months
were fruitless due to bad weather at my location. Hopefully other observers
have obtained further timings of primary and secondary minimum, so that the
motion of this system can be further refined.


                             [FIGURE 1]


I wish to thank Dr. Raymond Bloomer Jr. and Dr. Jamie Varni for their
assistance in preparing this article.


CHRISTOPHER J. COULS
Department of Physics
USAF Academy
Colorado Springs CO 80840

References:

Guinan, E. F., Maloney, F. P., and Boyd, P. T.: 1987a, I.B.V.S. No. 3029.
Guinan, E. F., Najafi, S. I., Zamani-Noor, F., Boyd, P. T., and Carroll, S. M.:
   1987b, I.B.V.S. No. 3070.
Lines, R. D., Lines, H., Guinan, E. F., and Carroll, S. M.: 1989, 
   I.B.V.S. No. 3286.