COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1840

                                    Konkoly Observatory
                                    Budapest
                                    1980 September 8

                                    HU ISSN 0374-0676



    TIMES OF MINIMA OF SIX ALGOL-LIKE ECLIPSING BINARIES




   As a part of a two- to three-year program of monitoring primary 
eclipses of Algol-like binaries for evidence of mass-transfer 
events, we give 20 times of minima for six systems observed
from 1978 to 1980. When observations are complete, times will
follow for about eight more systems. Observations were made with
the 1.0 M Prairie Observatory, the Nos. 3 and 4 0.4 M and the
No.2 0.9 M Kitt Peak National Observatory reflectors. Single
channel pulse-counting photometers with RCA 31034A-02 photomultiplier 
tubes were used for all observations, and data were obtained 
in Stromgren-Crawford u v b y and Kron I_k standard photometric 
systems. Times of minima for each color were determined
by the method of Kwee and Van Woerden (1956), as programmed by
R.C. Crawford.
   Times of minima and mean errors are listed in Table I.
Except in three cases noted in footnotes, times in all colors
agreed to within observational errors, The first eclipse listed
for RZ Cas was slightly abnormal in shape, showing small-amplitude 
"waves" during ingress and egress, and a flat tilted 19-minute 
interval around minimum light in all colors. Other observers 
have seen similar features (Archer 1958; Szafraniec 1960;
Burke and Rolland 1966; Margrave et al. 1975). Evidently, the
time of minimum is unaffected, as the ephemeris Min I=3740.5582+
1^d.1952492 E represents all minima satisfactorily. We cannot explain 
the time quoted by Margrave (1979), 3796.7303, which is
nearly 7 min earlier than our time.

                   Table I
             Times of primary minima


   Binary HJD-2440000           Binary HJD-2440000

KO Aql 4487.7954 +- 0.0001   U CrB  3671.6922^a
                                    4313.8051+-0.0002^b
RZ Cas 3741.7533 +- 0.0001          4351.7817+-0.0001^b
       3759.6822 +- 0.0001          4382.8505+-0.0001
       3766.8536 +- 0.0000
       3796.7349 +- 0.0000   AI Dra 3659.6606+-0.0002
       4121.8432 +- 0.0002          4009.7139+-0.0001
       4127.8190 +- 0.0001          4015.7079+-0.0001
       4151.7241 +- 0.0001
       4181.6054 +- 0.0001   TT Lyr 4383.8555+-0.0001
       4273.6387 +- 0.0000
                             RW Mon 3864.7101+-0.0001
                                    3883.7710+-0.0001

a Determined graphically.
b Omitted u; in the first eclipse, u was early by 0.0017 day;
 in the second, u was late by 0.0020 day.
c Omitted u, which as late by 0,0010 day.


   The author thanks the National Science Foundation for support 
of this work, and the director of Kitt Peak National Observatory 
for observing time. R.C. Crawford assisted in making
some of the observations, and his advice is gratefully acknowledged.



                       EDWARD C. OLSON

                       Department of Astronomy
                       University of Illinois
                       Urbana, IL 61801

References:
Archer, S. 1958, J.B.A.A., 68, 266
Burke, E.W., and Rolland, W.W. 1966, Astron.J., 71, 38 [BIBCODE 1966AJ.....71...38B ]
Kwee, K.K., and Van Woerden, H. 1956, Bull.Astr.Inst,Netherl.12,327 [BIBCODE 1956BAN....12..327K ]
Margrave, T.E.,Lukes, M.A.,Doolittle, J.H.,Evenskaas, R.S.,
      MacDonald, J.W., and Murray, N.D. 1975, I.B.V.S. No. 1019
Margrave, T.E. 1979, I.B.V.S. No. 1631
Szafraniec, R. 1960, Acta Astr., 10, 99 [BIBCODE 1960AcA....10...99S ]