COMMISSION 27 OF THE I.A.U.
               INFORMATION BULLETIN ON VARIABLE STARS
                            Number 1478

                                                      Konkoly Observatory
                                                      Budapest
                                                      1978 September 27


       PHOTOELECTRIC MINIMA OF SEVEN ECLIPSING BINARIES
           AND A SINGLE MAXIMUM OF BW VULPECULAE

We report herein photoelectric observations of seven eclipsing
binaries and BW Vulpeculae made in 1975 and 1976 with the 40-cm
Boller and Chivens f/18 Cassegrain telescope of the University of
Montana. This telescope, located on 1980-meter Blue Mountain about
six air miles southwest of the university campus, is equipped with
an Astro Mechanics single-channel photometer containing an unrefrigerated 
EMI 6256B PM tube. The observations were made through a Corning
3384 V-band filter. The photomultiplier signal is fed through a DC
amplifier to a voltage-to-frequency converter, whose output is integrated 
for ten seconds by an electronic counter. Three such integrations
constitute a single observation. The observations were reduced by
computer to produce extinction-corrected differential visual magnitudes
(program star-comparison star) as a function of heliocentric Julian
Date using the photometry reduction program of Walter Fitch (Steward
Observatory). The heliocentric times of the observed minima were
determined graphically by the chord bisection method. Table 1 lists
the observed times of minimum and their probable errors, the epoch
numbers E, and the O-C values. Table 2 gives the ephemerides used to
calculate the O-C values.


  Table 1. Observed Heliocentric Times of Minimum

 Star       Hel. JD - 2440000      E        O-C

KO Aql     2637.8558 +- 0.0005      262    +0d0085
44i Boo    2619.8345 +- 0.0015   10,333    +0.0025
RZ Cas     2633.7591 +- 0.0002   10,674    -0.0008
           2664.8340 +- 0.0001   10,700    -0.0023
           2670.8114 +- 0.0003   10,705    -0.0012
           3049.7003 +- 0.0008   11,022    -0.0056
TW Cas     2666.8395 +- 0.0014      461    -0.0047
           3096.7636 +- 0.0003      762    -0.0073
           3103.9140 +- 0.0004      767    +0.0014
DO Cas     2636.7778 +- 0.0003   12,722    +0.0003
           2664.8447 +- 0.0003   12,763    -0.0041
XX Cep     2663.7476 +- 0.0003     1866    +0.0062
AT Peg     2661.8070 +- 0.0006     1940    -0.0197



       Table 2. Ephemerides for Eclipsing Binaries

Star           Heliocentric JD       Period (days)   Source

KO Aql         2,441,887.4714        2.86403         SAC 49
44 iBoo        2,439,852.4903        0.2678159       Durbeck
RZ Cas         2,429,875.6902        1.1952473       Herczeg and
                                                     Frieboes-Conde
TW Cas         2,442,008.3850        1.428328        SAC 49
DO Cas         2,433,926.4573        0.68466595      SAC 49
XX Cep         2,438,302.3209        2.33731         SAC 49
AT Peg         2,440,438.383         1.146105        SAC 49

   Minima of AT Peg observed in 1974 and 1976 by Pohl and Kizilirmak
(1974; 1976) also give negative O-C's, based on the ephemeris used here,
of -0.0041 and -0.0118, respectively, suggesting a possible decrease in
the period of AT Peg of the order of 0d.00001 since 1969.
   The observed maximum of BW Vul was found to occur at

         Hel. JD (Max) = 2,443,060.6544 +- 0.0005.

   The parabolic ephemeris equation derived by Valtier (1976) applied to the
above time yields O-C = +0.0156 days, while the linear ephemeris equation
of Tunca (1978) yields O-C = -0.0014 days.


                           T.E. MARGRAVE, J.H. DOOLITTLE,
                           D. CUTILLO, and J.S. SCHERRER

                           Blue Mountain Observatory
                           University of Montana
                           Missoula, Montana 59812
                           USA



References :

Durbeck, H. W.: IBVS No. 1023, 1975.
Herczeg, T. and Frieboes-Conde, H.: Astr. and Ap., 30, 259, 1974. [BIBCODE 1974A&A....30..259H ]
Kordylewski, K.: Supplemento ad Annuario Cracoviense No. 49, Krakow 1977.
Pohl, E. and Kizilirmak, A.: IBVS No. 937, 1974; 
   IBVS No. 1163, 1976.
Tunca, Z.: IBVS No. 1386, 1978.
Valtier, J.-C: Astr. and Ap., 51, 465, 1976. [BIBCODE 1976A&A....51..465V ]