INFORMATION BULLETIN ON VARIABLE STARS
22 May 1989
HU ISSN 0374 - 0676
1988-89 OBSERVATIONS OF II Peg
R. CASAS (1,2) J.M. GOMEZ-FORRELLAD (1) Ll. TOMAS (2)
(1) Grup d'Estudis Astronomics, Apdo. 9481, 08080 Barcelona, Spain
(2)Instituto de Astrofisica de Canarias, 38200-La Laguna (Tenerife), Spain
In 1988/9 we have pursued our observations of the RS CVn star II Peg, which were begun in 1986.
The present observations were made between November 14 and December 15 1988 (Figure 1) and between January 13 and February 9 1989 using the 0.5m Mons reflector in the Instituto de Astrofisica de Canarias's Teide Observatory, with a solid-state photometer and Johnson B, V, R, I filters. From January 8 to February 10 observations were also taken with a solid-state photometer and also an uncooled 1P21 photomultiplier in the B and V bands using GEA's (Grup d'Estudis Astronomics) 0.4m telescope in Mollet Observatory. A total of 118 points were taken, 37 in B, 43 in V, 19 in R and 19 in I. SAO 091577 (Teide Observatory) and SAO 091503 (Mollet Observatory) were used as comparisons, these having been used previously both by us and by other observers.
Unlike in 1987/8 when the amplitude of variation of the star was one of the lowest recorded in the last years, 0.15 magnitudes in V (Cano et al., 1987 and our additional unpublished data) during this period the amplitude is about 0.5 magnitudes in V and appeared to increase towards the end of the observations (see Figure 2).
The orbital phases in Figures 1 and 2 were calculated according to the ephemeris (Vogt, 1981):
It must be mentioned that the maximum magnitude registered was approximately 7.25 in U, one of the highest measured since Chugainov (1976) and about 0.05-0.1 magnitudes brighter than normally accepted for the spotless stellar disc (Vogt, 1981; Poe end Eaton, 1985). The high brightness at maximum does not appear to be attributable to scaling errors, given that it was obtained independently with distinct instruments with different comparison stars.
Cano, J.A., Casas, R., Gallart, C., Gomez, J.M., Jariod, E., Peracaula, M.: 1987, Inf.Bull.Var.Stars, No. 3107.
Chugainov, P.F.: 1976, Izv.Krymskoj.Astrop.Obs., 54, 89
Pos, C.H., Eaton, J.A.: 1985, Ap.J., 289, 644
Vogt, S.S.: 1981, A.J., 247, 975.