COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 1847

                                 Konkoly Observatory
                                 Budapest
                                 1980 September 24

                                 HU ISSN 0374-0676


     PHOTOELECTRIC BEHAVIOUR OF V 818 Sco AND X-Per




  The variable star V 818 Sco identified as the optical counterpart 
of Scorpius X-1 (Sandage et a1.,1966) has been extensively
studied by many photometric observers. Despite these extensive
observations including those with high time resolutions, the
nature of Sco X-1 is still uncertain. This star was observed with
the 104 cm reflector, having a thermoelectrically cooled EMI 6094 S
photomultiplier at the Uttar Pradesh State Observatory. Usual
d.c. techniques were used to record the observations on four
nights during April 1977 - May 1978. Star C (Lyutyi, 1972) was
used as the comparison star.
  Behaviour of the star through the U, B and V filters is shown
in Figures 1-3 while Figure 4 shows observations of 16 May,1978
in B filter when the star could not be observed through other
filters. In these figures the differential instrumental magnitudes 
against the universal time have been plotted. The standard
deviations in the U, B and V filters for a single observation
of the comparison star are 0.065m, 0.035m and 0.032m, respectively.
The light curves show that the active and the quiescent states
can last for hours at a time. It can also be seen that the magnitude 
of the star and shape of the light curve change from
night to night. Durations of the anomalous behaviour (Figs.1-4)
are too long in our observations as compared to the short duration 
dips reported by Sharma et al. (1979), while the magnitude
changes are comparable.
  X-Per was also observed during 1974-1977 for 6 nights and
no variability in UBV was recorded. Even a continuous monitoring 
on 28 February 1977 for three hours did not show any variability in B filter.


                         [FIGURE 1]
                         [FIGURE 2]
                         [FIGURE 3]
                         [FIGURE 4]

  The author is thankful to Dr. C.D. Kandpal for comments
and to Mr. U.S. Chaubey for participating in a few observations.






                     B. B. SANWAL
                     Uttar Pradesh State Observatory
                     Manora Peak, Naini Tal-263129,
                     India.





References:
Lyutyi, V.M. 1972, Variable Stars 18, 417 [BIBCODE 1972PZ.....18..417L ]
Sandage, A.R., Osmer, P., Giacconi, R., Gorenstein, P., Gursky,H.,
      Waters, J., Bradt, H., Garmire, G., Sreekantan, B.V.,
      Oda, M., Osawa, K. and Jugaku, J. 1966, Astrophys.J. 146,
      316 [BIBCODE 1966ApJ...146..316S ]
Sharma, D.P., Marar, T.M.K., Kasturirangan, K., Rao, U.R.,
      Bhattacharyya, J.C., and Mohini, S., 1979, Bull.astr.
      Soc. India, 7, 119 [BIBCODE 1979BASI....7R.119S ]