COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1988      

                                    Konkoly Observatory
                                    Budapest
                                    1981 July 7

                                    HU ISSN 0374-0676


      THE ORBITAL PERIOD OF THE OLD-NOVA GK Per (1901)


Forty image-tube spectra of GK Per have been obtained with the    
Echelle spectrograph attached at the Cassegrain focus of the
182 cm reflector of the Observatory of Asiago. The spectra
cover the range lambdalambda6100-7100 A with a mean dispersion of 16.1
A/mm. The main observed feature is the Halpha emission, which shows
a broad and variable line profile. Radial velocity measurements
of Halpha have been derived from a mean of settings on the outer edges
of the emission.
The standard error for each determination is of the order of 20
km/s.
              
Using the minimum chi^2 method, our data fit an orbit having the
following elements:


      P = 1.9020d (+-0.000043)       omega = 91 (+-6)d
      a sin i = 2.22 (+-0.03)x10^7km gamma =+97 (+-8) km/s
      e = 0.44 (+-0.25)              tau= 2444249.78 (+-0.002) JD


where errors are given at the 1sigma level.
The orbital period hat we have derived for GK Per is in agreement
with those given by Kraft (1964) and Bianchini, Hamzaoglu and
Sabbadin (1981) and rejects the solution suggested by Paczynski
(1965) and assumed by most authors.
Attention must be paid to the interpretation of the observed
eccentricity and velocity amplitude. As pointed out by Smak (1970),
the hot-spot can cause a distortion of the emission profile which
produces spurious amplitudes and eccentricities.



                     A. BIANCHINI
                     F. SABBADIN
                     E. HAMZAOGLU

               Asiago Astrophysical Observatory
               36012 Asiago (VI), Italy





References:                                        
Bianchini, A., Hamzaoglu, E. and Sabbadin, F. 1981, Astron.
      Astrophys. in press [BIBCODE 1981A&A....99..392B ]
Kraft, R.P. 1964., Astrophys. J. 139, 457 [BIBCODE 1964ApJ...139..457K ]
Paczynski, B. 1965, Acta Astron. 15, 197 [BIBCODE 1965AcA....15..197P ]
Smak, J. 1970, Acta Astron. 20, 311 [BIBCODE 1970AcA....20..311S ]