Abstract. New extensive multicolour photoelectric photometry, performed since 1994, is presented. 17 moreor-less complete light curves were obtained and analyzed. The Wilson-Devinney code applied to the BVRI light curves without the maculation effect together with published spectroscopic mass ratio and semi-major axis yielded new absolute parameters of the eclipsing pair: m1 = 1.10 M , m2 = 0.66 M , R1 = 1.16 R , R2 = 0.63 R , a = 3.107 R and the orbital inclination i = 80.9• . The observed orbital period changes are conclusively explained by the mutual action of the third body in the system (P3 = 30 years) and the maculation effects. Simultaneous analysis of the period changes and the visual brightness excludes the possibility of their explanation by Applegate's mechanism. The differences in the maxima heights caused by the maculation exhibit variations with the period of 709± 10 days. The distance to the system d = 86± 5 pc determined from the absolute dimensions and luminosities of the components is larger than the Hipparcos astrometric value d = 66 ± 6 pc.

We present Hubble Space Telescope (HST) imaging, a Very Large Array (VLA) radio map (4.74 GHz), optical high‐resolution (echelle) spectroscopy and UBV photoelectric photometry of the symbiotic star CH Cyg obtained during its 1998–2000 active phase. The HST imaging, taken during eclipse, shows the central stars are embedded in a nebula extending to 620 ± 150 au for a distance of 270 ± 66 pc. The inner nebula is strongly influenced by the onset of activity and associated outflow in 1998. The surface brightness contours of the contemporaneous radio VLA observation agree well with HST images. Photometric observations of the broad 1999 U‐minimum suggest that it is due to the eclipse of the active hot component by the giant on the long‐period (14.5 yr) outer orbit. We also find that the onset of the 1998 and the 1992 active periods occur at the same orbital phase of the inner binary. Spectroscopic observations reveal two types of outflow from the active star: a high‐velocity (>1200 km s−1) hot star wind sporadically alternating with a more massive outflow indicated by P‐Cygni‐like profiles. We present evidence connecting the extended nebulosity with the high‐velocity shocked outflow, and hence the activity in the central binary.

Abstract. We analysed photometric and spectroscopic optical observations of the eclipsing symbiotic binary AX Persei. For the first time, we present and discuss its historical, 1887-1999, photographic/B-band and visual light curve (LC). The red giant in AX Per losses mass via the wind at a rate ofṀ = 7.4 ± 1.7 10 −7 M yr −1 . The terminal velocity of the wind is v∞ = 32 ± 6 km s −1 . We estimated an effective radius of the H ii nebula during the post-outburst stage (to JD 2450000) to be of Rn = 192 ± 25 R and its average electron concentratioñ ne = (2.9 − 3.6) ± 0.7 10 9 cm −3 for the electron temperature Te = 1-1.5 10 in AX Per is rather dense, having the electron concentration ne([O iii]) ≈ 3 107 cm −3 for Te = 1-1.5 10 4 K. Spectroscopic observations made in the middle of the 1992.8 and 1994.7 eclipses showed that a significant part of flux emitted in the H i, He ii and nebular [O iii] lines originates in the vicinity of the hot component. Transition of AX Per to its nebular phase occurred at/around JD 2450000. A small ∼0.6 mag brightening at that time and consequently very broad wave-like variation in the LC developed. This event was caused by dilution of a shell around the hot star, during which about of 1.5 10 50 particles (∼1.3 10 −7 M ) were injected into the ionized region.

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High‐resolution, time‐resolved spectroscopic observations of Z CMa carried out on 1997 January 14–17 are presented. Large night‐to‐night and hour‐to‐hour variations in Hα, Hβ and Na i D P Cygni absorptions, as well as an Hβ emission peak, were observed. Variations in the red wings of the hydrogen emission lines were also detected. The high‐velocity wide‐emission component on the blue side of Hα appeared on January 17. The observations are discussed in the framework of current wind models.