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Up: Monitoring MWC560 V 694

1. Introduction

MWC560 is a peculiar system which became popular in the beginning of 1990 when it was caught in the strongest outburst ever recorded (Tomov 1990; Tomov et al. 1990). Now it is accepted that MWC560 is a symbiotic-like system consisting of an M4-5III cool component (Thakar & Wing 1992) and a white dwarf probably possessing a strong magnetic field (Tomov et al. 1992, 1994; Michalitsianos et al. 1993). The interaction of the matter accreted from the giant's stellar wind with the rapidly rotating magnetosphere, as well as high-velocity matter ejection along the line of sight, can account for many of the observed features in the brightness and the spectrum (Tomov et al. 1992, 1994; Shore et al. 1994; Tomov et al. 1996, hereafter Paper I).

The star brightness shows a large variety of long and short-term changes. In Paper I we presented the UBV photometric behaviour of MWC560 during 1990-1995.

Because of the unique character of the spectrum of MWC560, it is important to show its evolution in detail. In this paper we present results from our vast collection of photographic spectra in the optical region, obtained in the period 1990-1993. In Paper III we shall report on high and low resolution CCD observations of MWC560 we have obtained since 1990 at a number of different observatories.

Copyright by the European Southern Observatory (ESO)