P Cygni is the longest known galactic Luminous Blue Variable and one of the most-widely studied. It is an early B-type supergiant classified variously as B1eq, B0-B1, B1p (de Jager 1980) or B1Ia (Lamers et al. 1983) but its spectrum differs from that of normal B-type supergiants in the appearance of so-called P Cygni-type profiles in the lines of abundant ions (de Groot 1969). In addition, the strongest lines of hydrogen and helium show wide emission wings which are due to electron scattering in the wind (Castor et al. 1970, Bernat & Lambert 1978) or to non-LTE effects in the extended atmosphere (Hubeny & Leitherer 1989).
In recent years a number of works devoted to the identification of spectral lines in the spectrum of P Cygni have been published (Stahl et al. 1991, 1993; Markova 1994; Markova & Zamanov 1995). As a result, many new lines of different ions were identified. Most prominent among these are emission lines of [FeII], [NII], FeIII, NII, SiII and AlIII.
Stahl et al. (1991) studied the forbidden emission lines in the spectrum of P Cygni. Here we present some results concerning the permitted emission lines. We shall use the term "pure emission" lines to indicate emission lines not visibly accompanied by absorption components.
© European Southern Observatory (ESO) 1997
Online publication: April 8, 1998