COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                      Number 1938

                                    Konkoly Observatory
                                    Budapest
                                    1981 March 17

                                    HU ISSN 0374-0676



         TIMES OF MINIMA OF TEN ALGOL-LIKE BINARIES



  We give times of minima for 27 primary eclipses of 10 Algol-like binaries. 
Most observations were made with the 1.0 M Prairie Observatory reflector, 
with single-channel pulse-counting photometer, RCA C31034A-02 photomultiplier, 
and Stromgren-Crawford uvby and Kron I filters. Two minima were also
obtained using the 0.4 M Mt. Laguna reflector with single-channel PC integrator 
photometer, RCA 1P21 photomultiplier, and uvby filters. Times of minima
for each color were determined in most cases by the method of Kwee and Van
Woerden (1956) and programmed by R.C. Crawford.


                              TABLE I

       TIMES OF PRIMARY MINIMA SHOWING NO WAVELENGTH DEPENDENCE


Binary 	     HJD- 	       	  Binary        HJD-
           2440000 			      2440000


XZ And   3779.8763 +- 0.0001      ST Per    3821.6554 +- 0.0002
         3809.7364 +- 0.0001                3882.5664 +- 0.0001
         3847.7403 +- 0.0001                4120.9133 +- 0.0002
         4257.6387 +- 0.0001                4520.8075 +- 0.0007^c
         4542.6659 +- 0.0000
                                  U Sge     4374.8182^a
KO Aql   3737.655  +- 0.001^a
         4049.836  +- 0.001^a     RW Tau    3820.7835 +- 0.0001
         4387.7954 +- 0.0001^b              4180.7319 +- 0.0001

W Del    4438.7465 +- 0.0001      X Tri     3760.8573 +- 0.0000
         4462.7765 +- 0.0002                3831.7795 +- 0.0002
                                            4171.8186 +- 0.0001
                                            4546.8309 +- 0.0001


a: Graphical determination.
b: Correction to I.B.V.S. No. 1840.
c: y, b, v only; I, u eclipses were asymmetrical or noisy.          

                    
                             TABLE II
       TIMES OF PRIMARY MINIMA SHOWING WAVELENGTH DEPENDENCE

                           HJD - 2440000
Binary
             I           y           b          v         u

SW Cyg   4428.7625      .7631       .7634      .7640     .7647
           +-.0003    +-.0001     +-.0001    +-.0001   +-.0003

          -----     4460.7738       .7745      .7754     .7762
                      +-.0007     +-.0008    +-.0004   +-.0004

RW Mon^a 3883.7712      .7708       .7708      .7709     .7714
           +-.0001    +-.0001     +-.0001    +-.0001   +-.0001

RV Oph   4427.7251      .7251       .7251      .7254     .7255 
           +-.0002    +-.0001     +-.0001    +-.0002   +-.0002

RW Tau   4191.8080      .8076       .8074      .8072     .8085
           +-.0001    +-.0001     +-.0001    +-.0001   +-.0001

         4587.7519      .7515       .7513      .7511     .7523
           +-.0001    +-.0002     +-.0000    +-.0000   +-.0001

 a: Replaces the single time given in I.B.V.S. No.1840.



   Table I lists times and mean errors for binaries in which times were
wavelength-independent. Table II tabulates those times showing wavelength
dependence. Apparent time of mid-eclipse is always latest in the ultraviolet. 
McNamara and Feltz (1976) noted in U Sge that ultraviolet times were
delayed from yellow, blue, and violet times by ~ 43 seconds, and Crawford
(1979) remarked on ultraviolet delays in U Cep as large as 11 minutes. Among
the systems of Table II, earliest times range from infrared in SW Cyg to violet 
in RW Tau. The maximum time spread is from 35+-19 sec (RV Oph) to 190+-37
sec (SW Cyg). All of these systems apparently are affected by circumstellar
effects of mass transfer, as discussed by Crawford (1979) and Olson (1980).

   The author thanks the National Science Foundation for support of this
work, and Dr. Burt Nelson for observing time and assistance at the Mt. Laguna
Observatory. Mr. Dean Espitallier and Mr. Tom Bryant assisted with observations 
of SW Cyg and W Del at Mt. Laguna Observatory.





                       EDWARD C. OLSON

                     Astronomy Department
           University of Illinois at Urbana-Champaign
                     1011 W. Springfield
                    Urbana, IL 61801, USA



References:


Crawford, R.C. 1979, Publ. A.S.P., 91, 111. [BIBCODE 1979PASP...91..111C ]
Kwee, K.K., and Van Woerden, H. 1956, Bull. Astr. Inst. Netherlands, 12, 327. [BIBCODE 1956BAN....12..327K ]
McNamara, D.H., and Feltz, K.A. 1976, Publ. A.S.P., 88, 688. [BIBCODE 1976PASP...88..688M ]
Olson, E.C. 1980, I.B.V.S. No. 1839.