Determination of the orbital periods of CP Puppis and T Pyxidis.

ABSTRACT. We present preliminary results of spectroscopic observations with the 2.5-m DuPont telescope at the Las Campanas Observatory, Chile, in February 16-22, 1986. We used the 2D-Frutti Spectrograph (Shectman Qt a#. 1985, A tt Repo o he o o6 he Mo ( on d L Ganip Ob , Carnegie Institution, p. 52) and obtained 131 spectrograms of the classical nova OP Pup (1942) and 101 spectrograms of the recurrent nova T Pyx in the spectral range 3600-7200 A with are- solution of approximately 3 A. An analysis of radial velocities from the strongest emission lines (Balmer series, Be II 4686) confirms, for OP Pup, the orbital period P - 0d0614215 derived by Duerbeck (1987, M. .R.A.S., 229, 653). Our radial velocity amplitude of the primary K1 = 84.616.3 km 1 is consistent with an orbital inclination # 600 and masses 1 = 0.6 M@ and 2 = 0.15 M@ for the stellar components. We will combine our spectroscopy with simultaneous photoelectric photometry made in cooperation with the Munich Group (B. Barwig, K.-B. Mantel) in order to investigate the nature of the periodic variations. OP Pup seems to be the first classical nova with an orbital period below the period gap (2 - 3h) For T Pyx, we derive, for the first time, the orbital period of 0d1433 which is nearly twice the period of the infrared variability (Q 100 min) observed by Szkody and Feinswog (1988, Ap. 5., 334, 422). If this is taken to be the ellipsoidal variation of the secondary star the orbital inclination must be rather high. In this case, our relatively small radial velocity amplitude K1 = 29.114.9 km 1 implies that the secondary of T Pyx is slightly evolved rather than a typical main sequence star. Keq : STARS-BINARIES