COMMISSION 27 OF THE I. A. U.
       INFORMATION BULLETIN ON VARIABLE STARS
                   Number 1578   

                                 Konkoly Observatory
                                 Budapest
                                 1979 March 30




  NEW VARIABLE HD 219018, THE COMPARISON STAR OF SZ Psc


Introduction

     The eclipsing binary system SZ Piscium is a member
of RS CVn stars. Extensive photometric and radial velocity
observations of SZ Psc are published by Jakate et al. (1976).
     SZ Psc was observed simultaneously photometrically
(by the author) and spectroscopically (by Dorothy Fraquelli)
during October and November 1978 season from the David Dunlap
Observatory. The purpose of the present paper is to report
the photometric variability of the usual comparison star for
SZ Psc, HD 219018 (G5).


Observations

     The photometric observations through V filter were
obtained using 48 and 61 cm telescopes of the David Dunlap
Observatory. HD 219150 (F2) was on the observing program as
a check star to HD 219018. Observations of the first night
JD 2443805 itself gave some indications of the variability
of HD 219018. Therefore, during the subsequent nights SZ Psc
was also observed independently against HD 219150.




              Table 1
       HD 219018 - HD 219150
--------------------------------------
JD_Hel      DeltaV JD_Hel       DeltaV
2443800.+          2443800.+
--------------------------------------
05.638      .478   10.554        .407
  .656      .474     .589        .410
  .685      .474     .606        .407
  .711      .470     .632        .408
06.649      .465     .664        .404
  .658      .464   13.516        .476
  .666      .466     .579        .470
  .686      .458     .637        .471
  .713      .458   15.590        .456
10.543      .401
--------------------------------------





     Table 1 gives observations of HD 219018 against HD
219150, obtained on a total of five nights. HD 219018, the
usual comparison star for SZ Psc, seems to be a variable with
an overall amplitude of at least .08 mag.

                  Table 2
----------------------------------------------------
SZ Psc - HD 219018          SZ Psc - HD 219150
JD_Hel      PHASE DeltaV    JD_Hel     PHASE  DeltaV
2443800.+
----------------------------------------------------
06.578      .706  -.436      06.650     .723    .035
   645      .722  -.435        .656     .725    .033
   682      .732  -.435        .664     .727    .025
  .715      .740  -.438        .689     .733    .029
10.535      .703  -.357      10.540     .705    .039
  .559      .709  -.364        .551     .707    .043
  .595      .718  -.365        .554     .708    .040
  .611      .722  -.368        .586     .716    .033
  .658      .734  -.366        .601     .720    .039
  .671      .737  -.367        .629     .727    .035
----------------------------------------------------




      Since there was no second check star used, the observations 
of SZ Psc itself are presented as evidence towards
the variability of HD 219018 and constancy of HD 219150.
Table 2 gives two nights of observations of SZ Psc, as observed
independently against HD 219018 and HD 219150. On both of
these nights SZ Psc was going through a similar phase of outside 
eclipse. SZ Psc against HD 219018 gives difference of
about .08 mag on these two nights whereas the observations
against HD 219150 show variations less than .01 mag as expected.
      Consequences of the variability of the comparison star
of SZ Psc in connection with the properties of this system
reported in  Jakate et al. (1976) and results of the
spectroscopic (Dorothy Fraquelli) and of the other photometric 
observations of SZ Psc will be discussed in the
future paper.



                    SHYAM M. JAKATE
                    Astrophysical Institute
                    Free University of Brussels
                    Pleinlaan 2, B-1050 Brussels
                    Belgium




Reference:          

Jakate, S.M., Bakos, G.A., Fernie, J.D. and Heard, J.F. 1976,
      Astron. J. 81. 250. [BIBCODE 1976AJ.....81..250J ]