COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                      Number 2706


                                      Konkoly Observatory
                                      Budapest
                                      15 April 1985

                                      HU ISSN 0374 - 0676



          COMPARISON STARS FOR SOME ECLIPSING BINARIES



   As part of a continuing photometric program of mostly long-period
interacting eclipsing binaries, comparison and check stars have been observed
for constancy. Observations were made with u,v,b,y, and I intermediate-band
filters, and transformed to the standard Stromgren-Crawford and Kron
systems. Most observations were made with the 1-m Prairie reflector located
at the Mount Laguna Observatory. All were made with a pulse-counting
photometer with refrigerated RCA 31034A-02 photomultiplier.




                      TABLE I


         Constant Comparison and Check Stars
Binary   Comparison Star    Check Star       n
AQ Cas   + 61deg 223         +62deg 229      6
RS Cep   + 80deg 156         +79deg 159     12
RZ Cnc   + 31deg 1848        +31deg 1857     7
KU Cyg   + 46deg 2879          1            26
RX Gem   + 33deg 1417        +33deg 1421     6
AU Mon   - 01deg 1413        -01deg 1446     7
RZ Oph   + 06deg 3917        +06deg 3918    24
DN Ori   + 10deg 973         +09deg 1016     3
RW Per   + 42deg 938         +41deg 844     21
RZ Sct   - 08deg 4606        -08deg 4605    10
RW Tau   + 27deg 628         +27deg 618      3


  1 Star 'd', Popper (1964)





                  TABLE II


               Non-Constant Stars
           Binary        Star
           AQ Cas       +61deg 240
           RS Cep       +80deg 159
           RZ Cnc       +32deg 1776





                    TABLE III


                                Comparison Star Colors
Comparison to:   (V-I)                     (b-y)         (v-y)           (u-b)           n
AQ Cas           0.294 +/- 0.005    0.279 +/- 0.004   0.688 +/- 0.004  1.313 +/- 0.005   1
RS Cep           -0.130 +/- 0.007   0.047 +/- 0.003   0.242 +/- 0.005  1.462 +/- 0.014   4
RZ Cnc           1.052 +/- 0.013    0.777 +/- 0.003   2.149 +/- 0.006  3.206 +/- 0.009   6
KU Cyg           1.008 +/- 0.017    0.729 +/- 0.005   1.823 +/- 0.016  2.730 +/- 0.020   5
RX Gem           -0.234 +/- .023    0.000 +/- 0.002   0.123 +/- 0.003  0.964 +/- 0.005   3
AU Mon           -0.143 +/- 0.005   0.027 +/- 0.008   0.181 +/- 0.008  1.269 +/- 0.008   2
RZ Oph           0.520 +/- 0.006    0.415 +/- 0.004   1.034 +/- 0.005  1.700 +/- 0.008   11
DN Ori           0.014 +/- 0.010    0.095 +/- 0.017   0.396 +/- 0.012  1.629 +/-  .012   1
RW Per           0.348 +/- 0.005    0.315 +/- 0.006   0.773 +/- 0.009  1.437 +/- 0.012   3
RZ Sct               (:)            0.184 +/- 0.004   0.442 +/- 0.011  1.678 +/- 0.005   2
RW Tau          -0.067(:)           0.088 +/- 0.026   0.310 +/- 0.024  1.484 +/- 0.027   3





   Those binaries whose comparison and check stars were constant at all
observed wavelengths to better than 0.01 mag. are listed in Table I. The last
column gives the number of nights on which comparison/check star observations
were made. Table II lists other stars, close to three binaries, which are
variable with amplitude > 0.01 mag.

   Colors of the constant comparison stars of Table I were found for those
nights on which more than a dozen standard stars were observed. These results
are given in Table III. Transformation equations for (v-y) and (u-b) are
(Olson, 1981):


      (v-y) = P + I' C (cl) + RC (vy)


      (u-b) = L' + J" C (cl) + M' C (ub).




   The author thanks the U.S. National Science Foundation for continuing
support of his program on interacting binaries, and the Director and Staff of
the Mount Laguna Observatory for support and assistance.





                 EDWARD C. OLSON
                 Department of Astronomy, University of Illinois
                 1011 W. Springfield
                 Urbana, IL 61801-3000





References:



Olson, E. C. 1981, Publ. Astron. Soc. Pacific 93, 783. [BIBCODE 1981PASP...93..783O ]
Popper, D. M. 1964, Astroph. J. 139, 143. [BIBCODE 1964ApJ...139..143P ]