COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                       Number 2807

                                         Konkoly Observatory
                                         Budapest
                                         10 October 1985

                                         HU ISSN 0374 - 0676



      LIGHT VARIABILITY OF HD220140, OPTICAL COUNTERPART OF THE

                       X-RAY SOURCE H 2311 + 77


  By means of an EXOSAT imaging observation, the star HD 220 140 (SAO 010697,
G5) was indicated by Pravdo et al. (1985) as the optical counterpart of the
bright X-ray source H2311+77. Available spectra show typical features of
RS CVn variables, and it is well known that these stars are often X-ray
emitters.

   In order to confirm this identification, B and V photometry of HD220 140
was carried out with the 50 cm Marcon telescope at Merate Observatory. Differential
measurements were made with respect to SAO 010663 (8.6, G0) and SAO 010653 
(8.3, F8). As a period of about 10 days was expected (Pravdo et al., 1985),
hence HD220 140 was observed performing 8-10 measurements per night, which
were grouped into B and V normal points. The 12 points so collected from 13
August to 8 September gave a scattered light curve suggesting a short term
variability. Three 6-hour runs in B colour were carried out in the nights
10, 11, and 12 September and three segments of a sine-shaped light curve were
obtained, clearly indicating a shorter period than 1 day.
   These measurements were also grouped into normal points which were put
together with the previous observations. The resulting time-series was
analysed by means of the least squares power technique and a period of 0.5767
day was derived with a variance reduction of 76%. No other period seems to
be plausible. The application of the PDM method (Stellingwerf, 1978) gave the
same period. The B-full amplitude is about 0.04 mag., however, as for many
other RS CVn variables, it seems to be variable. The eclipsing binaries RT And
(P=0.6289d, F8V+G5 (or K0)V) and SV Cam (P=0.5930d, G2-3V+K4V) have similar
characteristics but in the case of HD220 140 no eclipse has been observed.



                  E. PORETTI, L. MANTEGAZZA and E. ANTONELLO
                    Osservatorio Astronomico di Brera
                    22055 Merate (CO), Italy

References:
Pravdo, S.H., White, N.E., and Giommi, P., 1985, M.N.R.A.S., 215, 11P. [BIBCODE 1985MNRAS.215P..11P ]
Stellingwerf, B.F., 1978, Ap.J., 224, 953. [BIBCODE 1978ApJ...224..953S ]