COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                        Number 2736

                                             Konkoly Observatory
                                             Budapest
                                             28 May 1985

                                             HU ISSN 0374 - 0676



      GAMMA Cae: A BINARY WITH A SUSPECTED VARIABLE SECONDARY

   Gam Cae [5h00m48.5s,-35deg37'11"; 1900] is on the University of Virginia
parallax program at Mt. Stromlo as part of an effort to measure parallax
for a sample of southern giants (Ianna and Culver 1985).
   While inspecting a number of our plates, it was noted that the
secondary was not always apparent. Close examination of all the accumulated 
plates shows that this cannot be accounted for purely as a result
of variable seeing conditions at the time of exposure.

   Gam Cae (=HR 1652 = HD32831) is a K3 III for which Eggen (1973)
gives V = 4.55, B-V = +1.20, (R-I) = 0.46. The secondary is located at
a distance of 3" in a position angle of about 310 degrees. In the Innes
catalogue (Cape Annals) the magnitude of the primary and secondary are
given as 4.7 and 9.6; Eggen and Stokes (1970) not a companion to HR 1652
of magnitude 8; the Index Catalog of Double starts lists m(A) = 4.7,
m(B) = 8.2. Thus the published magnitude differences range between about
3.5 and 5.
   We have scanned several of our plates having the best images of the
secondary with the PDS microdensitometer at Mt. Stromlo. The secondary
is still weak and not cleanly separated from the primary. These are
IIa-O plates explosed unfiltered with the 66 cm Yale-Columbia refractor
having a plate scale of 18.85 arcsec/mm and approximate a B magnitude.
Double peak Gaussian functions are fit to marginal distributions derived
from the scan map topography. From these fits magnitude and position
data can be extracted. The following results were found:

   Plate #    # images     sep      P.A.     Deltam        date
   4391         3         3.15      324      1.4       16 Feb 1983
   4856         3         3.11      327      1.7        3 Jan 1984

The fitting routines failed to converge for 6 other plates where the
secondary image is weaker. In these cases we estimate a Deltam of about 2.0
or more. The programs have been checked using pairs of simulated stars



and seem to work well in the range of separation and magnitude difference
found in the present case. On several plates the companion is not visible
at all, and, although the seeing is not very good on these plates, it does
not appear to be poor enough to account for the non-appearance of the
secondary.

   There seems a fair probability that the secondary in the Gam Cae
system is variable. A hotter companion could account for a somewhat
reduced magnitude difference in the blue, however there seems no very
likely object that could be two magnitudes brighter in the blue and
two to four magnitudes fainter than the primary simultaneously. Of
course the observed visual magnitude differences also may not completely
characterize any variations. The evidence suggests additional observations 
of the secondary would be useful to clarify the nature of this
object.


               ROGER B. CULVER
             Department of Physics
            Colorado State University
           Ft. Collins, Colorado 80523
                   U.S.A.


                     and


               PHILIP A. IANNA
            Department of Astronomy
           The University of Virginia
        Charlottesville, Virginia 22903-0818
                    U.S.A.


References:
Eggen, O.J. 1973. Publ. Astron. Soc. Pacific 85, 542. [BIBCODE 1973PASP...85..542E ]
Eggen, O.J. and Stokes, N.R. 1970. Astrophys. J. 161, 199. [BIBCODE 1970ApJ...161..199E ]
Ianna, P.A. and Culver, R.B. 1985. Astron. J., in press. [BIBCODE 1985AJ.....90.1870I ]