COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                   Number 2177

                                Konkoly Observatory
                                Budapest
                                1982 July 16

                                HU ISSN 0374-0676





              1981 UBVR PHOTOMETRY OF II Peg



   Our long-term program of photometry of RS CVn stars includes the 
noneclipsing system II Peg (27d4642. HD224085), whose large light variations
began in 1945 (Hartmann, Londono and Phillips, 1979). The primary star is
K2 IV-V; the secondary is not yet known.
   Our observations were made in October-December 1981 with the 61-cm
telescope at Capilla Peak Observatory. The photometer, which is computer
controlled, is a single-channel, photon-counting design with a cooled
(-20dC) EMR 641A tube. 'The comparison star was +27d4649 for all observations.
Phases were calculated from Rucinski's (1979) epoch and period of MJD =
43033.10 + 6.724183E. Figures 1-4 give the magnitude differences (comparison-
source) in the UBVR instrumental system. The data has been folded to show
phases 0.0 and 0.5 clearly.
   From the V-band curve, we note that the minimum in the distortion wave
occurs at. about phase 0.3 and that the wave amplitude (peak to peak) is
approximately 0.2 mag. Compared to the 1977 data reported by Vogt (1981),
the distortion wave has decreased in size (from 0.43 mag) and increase in
phase (0.0). Even more curious, the light curve no longer shows the two
maxima (at phases 0.45 and 0.85) visible in the 1979 observations of Nations
and Ramsey (1981). By 1980 Raveendran et al. (1981) noted only one peak
(0.15 mag) at phase 0.6.
 
                             [FIGURE 1]
                             [FIGURE 2]
                             [FIGURE 3]
                             [FIGURE 4]

   It is clear that II Peg must be observed annually to track these dramatic
changes in its distortion wave. Also, coordinated efforts of different 
observatories are needed, as changes occur in only a few cycles. This is seen
in the V-band curve at phase ~0.8, where observations 20 days apart show a
difference of 0.05 mag.




      M. ZEILIK, R. ELSTON, G. HENSON, P. SCHMOLKE, & P. SMITH

                      Capilla Peak Observatory
                 Department of Physics and Astronomy
                     The University of New Mexico
                         Albuquerque, NM 87131
                               U.S.A.





References:

Hartmann, L., Londono, C. Phillips, M.J., 1979, Astrophys. J. 229,
   183 [BIBCODE 1979ApJ...229..183H ]
Nations, H.L. and Ramsey, L.W., 1981, Astron. J. 86, 433 [BIBCODE 1981AJ.....86..433N ]
Raveendran, A.V., Mohin, S. and Mekkaden, M.V., 1981, MNRAS 196,
   289 [BIBCODE 1981MNRAS.196..289R ]
Rucinski, S.M., 1977, PASP, 89, 280 [BIBCODE 1977PASP...89..280R ]
Vogt, S.S., 1981, Astrophys. J. 247, 975 [BIBCODE 1981ApJ...247..975V ]