COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1342

                                  Konkoly Observatory
                                  Budapest
                                  1977 September 26



    HD 5303: A NEW SOUTHERN RS CANUM VENATICORUM BINARY




    The southern star HD5303 (BV 625), alpha = 00h51m21s and
delta =-74d56' (1950), has been observed spectrographically on the
Boller and Chivens 61cm telescope at Mt. John Observatory, Lake
Tekapo, N.Z. These observations were part of the joint program
of the University of Canterbury and Florida to systematically
study RS CVn binaries in the southern hemisphere. Seventeen
spectra were obtained with a plate factor of 60Angstrom/mm in the blue
and UV spectral region during the period 1976 Sept 01 until 1977
Aug 23. The star is listed as a late-type southern H and K emission 
line object in the objective prism survey of Bidelman and
MacConnell (1973). It is also noted as having H and K emission
by Houk and Cowley (1975), who classify the spectrum as G2/5V+F0.
HD5303 is given as a Bamberg variable star (BV 625) of unspecified 
type with amplitude Apg= 0.3m, (Strohmeier et al., 1965).
    The spectra confirmed the strong H and K emission nature
of HD5303. Large velocity shifts of these emission lines relative 
to the H and K absorption were clearly evident. Tracings
of the spectra on the Joyce-Loebl microdensitometer at the 
University of Canterbury showed no apparent variation in the 
emission intensity.
    The spectra were measured on the Gaertner linear comparator
at Canterbury so as to obtain the radial velocity changes of the
emission lines and of selected absorption lines relative to the
comparison spectrum.
    The spectra were analysed using the period analysis program
of C.J. McInally based on the Fourier method of Gray and 
Desikachary (1973). The data were found to be most compatible with
a period of P=1.840 days. Preliminary velocity curves for the
H and K emission and for the Hdelta absorption are shown. The zero
points of the velocity axes are arbitrary. The phases were 
computed relative to phase 0.0 at JD 2443022.716 using the period
given above.
   From the Michigan spectral classification, the Hdelta absorption 
must come predominantly from the F star, while the K emission 
is clearly due to the G component alone. The peak-to-peak
velocity amplitudes of these two components were both about
130km/s, and hence the mass ratio is approximately unity.
   HD5303 complies with the definition of RS CVn stars suggested 
by Hall (1975). In addition, the mass ratio found is typical
of this category of star. Photoelectric photometry is being 
carried out to determine whether the light variations characteristic
of many RS CVn stars are present in this system.

                     [FIGURE 1]


     J.B. HEARNSHAW,            J.P. OLIVER,
     Dept. of Physics,          Dept. of Physics and
     University of Canterbury   Astronomy, University of
     Christchurch, N.Z.         Florida, Gainesville,
                                Florida, U.S.A.

References:
Bidelman, W.P. and MacConnell, D.J. 1973, Astron.J. 78, 687 [BIBCODE 1973AJ.....78..687B ]
Gray, D.F. and Desikachary, K., 1973, Astrophys.J. 181, 523 [BIBCODE 1973ApJ...181..523G ]
Hall, D.S. 1975, I.A.U. Colloquium 29, Vol. I. 287 (Budapest) [BIBCODE 1976ASSL...60..287H ]
Houk, N. and Cowley, A.P. 1975, Michigan Spectral Catalogue,
      Vol. I. (University of Michigan) [BIBCODE 1975mcts.book.....H ]
Strohmeier, W., Knigge, R. and Ott, H. 1965, I.B.V.S. No. 100