Mass ejection by the symbiotic binary Z And during its 2000–2002 outburst

Abstract

Abstract. Broad-band UBV JHKLM data have been obtained at the time of the quiescent orbital photometric maximum of the classical symbiotic binary system Z And and at some epochs of its 2000-2002 active phase. The data of the active phase are related to the time of the optical maximum and after it when the star was returning to quiescence. Broad-band quiescent RI photometry from the literature was also used to obtain the parameters of the cool component of this binary. All of these data suggest that the hot compact component has undergone a major expansion and the emission measure of the circumbinary nebula has also increased. Some mechanisms for interpretation of the outburst are reviewed.

Discovery of the eclipse in the symbiotic binary Z Andromedae

“…Figure 2 shows the result, which suggests that radii of both the eclipsing and the eclipsed object are relatively large and comparable each to other. Based on fundamental parameters published by NV89, MK96, and Tomov et al (2003), we derived the range of the giant's radius as R g ∼ (0.17−0.32) A and limited the size of Letter to the Editor the eclipsed object by its Roche lobe radius, R L ecl , as R ecl < R L ecl ∼ (0.26−0.32) A (A stands for the separation between the centers of mass of the binary components). First we tried to match the eclipse profile for a spherical shape of the hot object by using a code of Kvačkay (1994).…”

“…We use this ephemeris further in this letter. The binary of Z And composes of a late-type, M4.5 III, giant (Mürset & Schmid 1999) with M g ∼ 2 M , R g ∼ 85−140 R and L g ∼ 880 L (Nussbaumer & Vogel 1989, hereafter NV89;MK96;Tomov et al 2003). The hot component is probably a magnetic accreting white dwarf (Sokoloski & Bildsten 1999) with M h ∼ 0.5−1 M , L h ≈ 900−2500 L , and T eff ∼ 10 5 K, surrounded by an ionized nebula (MK96; FC95).…”

Broad-band multicolour observations of the symbiotic binary Z And during quiescence and its activity at the end of 2002

“…Several phases of activity (after 1915, 1939, 1960, 1984 and 2000) of Z And Based on observations collected at the Crimean Station of the Sternberg Astronomical Institute, Ukraine and the National Astronomical Observatory Rozhen, Bulgaria. were observed up to now, characterized by repeated brightenings with amplitudes up to 2−3 mag. The results of the observations during almost all of the active phases show energy redistribution in the continuum of the hot component caused by expansion of an optically thick shell (Swings & Struve 1941;Boyarchuk 1967;Fernandez-Castro et al 1995;Tomov et al 2003a, hereafter Paper I).…”

Symbiotic stars with similar line profiles during activity

“…In this way an optically thick disc-like shell forms in the orbital plane, which plays the role of the observed photosphere. This shell occults the hot compact object and since the shell has a lower effective temperature [8,13,14] it is responsible for redistribution of the continuum energy and a growth of the optical flux of the star. The observed P Cyg absorption is related to this shell (see Fig.…”