COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                      Number 3379

                                       Konkoly Observatory
                                       Budapest
                                       5 October 1989

                                       HU ISSN 0374 - 0676


          UBV OBSERVATIONS OF II Peg IN 1988-1989


II Peg (=BD+27d4662 = HD 224085 = SAO 91578) is a bright RS CVn-type
single-line spectroscopic system (K2 IV-V). This very interesting spotted
binary has been one of the most observed in the northern hemisphere (see Rodono
et al., 1986: Strassmeier et al. 1988 and references therein) and has shown
highly variable light curve with peak-to-peak V-band amplitude up to 0.5
magnitude (Byrne 1986, Cutispoto et al. 1987).

We present UBV photometry obtained at Mt. Hopkins in 1988-89 by the Phoenix
Automatic Photoelectric Telescope (APT) and BV data obtained middle 1989 at the
mountain station of Catania Observatory on Mt. Etna. The observations were
corrected for atmospheric extinction and nightly mean standard differential
magnitudes (variable-comparison star) were computed.

The UBV APT data were obtained during 30 nights in the period October 1988 -
January 1989 with an uncooled UBV photometer fed by a 0.25-m cassegrain
telescope. Our comparison star was HD 244016 (V=8.52, B-V=0.776, U-B=0.49)
while HD 223462 was used as check star. No significant variations between
comparison and check star were observed.

The Catania BV observations were made during 7 nights in June-July 1989 with an
uncooled simultaneous UBV photometer fed by a 0.61-m quasi-cassegrain
telescope. Our principal comparison star was HD 224084 (V=8.245, B-V=1.281,
U-B=1.356), while HD 224016 and BD+27d4648 were used as check stars and were
observed several times on each night. No significant variations between
comparison and check stars were observed.

The V light and color curves of II Peg are shown in Figures 1 and 2 where the
phases are reckoned from the spectroscopic ephemeris by Raveendran et al.
(1981):

HJD = 2443030.396+6.724464 * E

Typical nightly standard deviations for V, B-V and U-B data are 0.005, 0.01
and 0.01 mag. respectively. A listing of the individual data will be provided
upon request to the first author.


                             [FIGURE 1]

 Fig.1.: V-light, U-B and B-V color curves of II Peg in October 1988 -
         January 1989. Phases are reckoned from the ephemeris: 
         HJD = 2443030.396 + 6.724464 x E (Raveendran et al. 1981).


In both observing periods the V light curve is single-peaked with the rising
branch steeper than the descending one and has an estimated amplitude of about
0.43 mag. Small color variations show the star to be bluer at light maximum,
in agreement with the cool spot hypothesis. The APT data show that the light
curve has remained considerably stable for more than 14 star rotations. In
mid-1989 the star was fainter than in late 1988 - early 1989, indicating a
global increase of II Peg's degree of spottedness.


                               [FIGURE 2]

 Fig.2.: V-light and B-V color curves of II Peg in June - July 1989.
         Phases are reckoned from the ephemeris: 
         HJD = 2443030.396 + 6.724464 x E (Raveendran et al. 1981).
         

In Figure 3 a collection of the published photometry of II Peg is reported,
with the vertical bars indicating the peak-to-peak V amplitude of the light
curve. There is a clear systematic decrease of the II Peg luminosity at light
maximum and of its mean light level from 1974 to 1984, which is followed by a
definite increase after 1984. This systematic trend could be suggestive of a
spot cycle and once again stresses the importance of long-term systematic
photometry of spotted stars.

We wish to thank Prof. Marcello Rodono for suggesting us to carry out the
present observations and for making available to us the APT data.


                               [FIGURE 3]

 Fig.3.: Collection of the published photometry of II Peg. Vertical
         bars indicate the peak-to-peak amplitude in the V light curve.



G. CUTISPOTO (1), G. LETO (2), I. PAGANO (2)
(1) Catania Astrophysical Observatory
(2) Institute of Astronomy Catania University
V.le A. Doria, 6
I-95125, Catania
Italy

References:

Byrne, B.P.: 1986, Inf. Bull. Var. Stars, No. 2951.
Cutispoto, G. et al.: 1987, Inf. Bull. Var. Stars, No. 3034.
Raveendran, A.V., Mohin, S., Mekkaden, M.V.: 1981, Mon. Not. Roy. Astron.
   Soc. 196, 289. [BIBCODE 1981MNRAS.196..289R ]
Rodono, M. et al.: 1986, Astron. Astrophys. 165, 135. [BIBCODE 1986A&A...165..135R ]
Strassmeier, K.G. et al.: 1988, Astron. Astrophys. Suppl. Ser. 72, 291. [BIBCODE 1988A&AS...72..291S ]