COMMISSION 27 OF THE I. A. U.
          INFORMATION BULLETIN ON VARIABLE STARS
                      Number 1636

                                    Konkoly Observatory
                                    Budapest
                                    1979 July 3





       Z ANDROMEDAE: LONG TIME SCALE VARIATION OF Halpha
               DURING QUIESCENT PHASE




     The light history of the symbiotic star Z Andromedae during
the last half century is characterized by active phases with 
recurrent nova-like variations, followed by long periods during
which the star is at minimum luminosity (Mattei 1978). The mean
repetition time between the light maxima according to Mattei is
632 days, but the single time intervals largely differ from their
mean. Merrill (1944) suggested a periodic variation of the radial
velocity of the emission lines with a similar period, but Boyarchuk
(1968) pointed out that these variations seem to be primarily due
to variations in the physical conditions of emitting envelope,
rather than to a real orbital motion. Strong spectral variations
have been largely reported in the literature (e.g. Swings and
Struve 1941, Bloch et al. 1969), but at our knowledge no systematic 
observations of the spectrum of Z And during its quiescent
phase have been so far published.
     Since 1973 Z And is in a quiescent phase, and this is a
good opportunity to look deep in the system, disregarding all
those phenomena that are related to the outbursts. We have monitored 
the spectrum of the star with the Schmidt telescope of Campo
Imperatore from October 1977 to May 1979, to look for any long
time scale variation, and to derive a better spectral classification 
of the cool spectrum. Several objective prism plates were
collected on IIaO, IIIaJ, IIaF and IN Kodak emulsions. Low and
high resolution ultraviolet spectra were obtained during the same
period of time with the IUE satellite (Baratta et al. 1978, 1979).
The visual magnitude remained constant with V=10.8+-0.1 (Observations 
of Variable Stars Report, No. 32 Groningen, and Feijth,
private communication).
    The objective prism plates show that the cool spectrum is
the main contributor to the continuum of Z And longwards of
4100-4300 A.
    Several TiO absorption bands were identified, and their
strength is in agreement with a spectral type of M 6.5. From a
careful comparison with the spectra of nearby stars, we found
that the continuum of Z And does not show significant variations
during the whole period of our observations. In particular the
near infrared continuum was constant within +-0.1. This value is
much smaller than the upper limit for the luminosity variation
of the cool component derived by Boyarchuk (1968). This result
leads one to reject the hypothesis that the cool star is mainly
responsible for the large variations of Z And.
    On the other hand the Balmer emission lines markedly varied
with respect to the stellar continuum. Halpha increased its intensity
by a factor of about 3 between October 1977 and August 1978, and
decreased again in 1979 to nearly the same intensity as in 1977.

                         [FIGURE 1]

Such a variation was not displayed by the emission lines of the
other ions. In particular the He II 4686 line remained nearly
at constant intensity during the period 1977-79.
    This long time scale variation of Halpha and of the other Balmer
lines has some resemblance with the luminosity variations of
Z And during the active phases, and the epoch of maximum H_alpha
emission seems to be in phase with the last reported light maxima
(Mattei, 1978). This however does not imply the same origin for
the two phenomena, principally because of the large variation of
the time interval between the light maxima. Radial velocity and
line profile measurements of Halpha over a long period of time would
be of great help in the study of the nature of Z And.
   We are grateful to H. Feijth for providing us with the 1978
magnitudes of Z And.




                       A. ALTAMORE

                       Istituto Osservatorio Astronomico;
                       Universita di Roma

                       G.B. BARATTA

                       Osservatorio Astronomico, Roma

                       R. VIOTTI

                       Laboratorio di Astrofisica
                       Spaziale, Frascati


References:

Baratta, G.B., Altamore, A., Cassatella, A., Viotti, R. 1978,
      I.B.V.S. No. 1493
Baratta, G.B., Altamore, A., Cassatella, A., Giangrande, A.,
      Ricciardi, O., Viotti, R., 1979, IAU Circ. No. 3335 [BIBCODE 1979IAUC.3335....3B ]
Bloch, M., Jounsten, N., Swings, J.P., 1969, Bull.Soc.R.Sci.Liege,
      38e annee, no 5-6, 245  [BIBCODE 1969BSRSL..38..245B ]
Boyarchuk, A.A., 1968, Soviet A.J., 11, 818 [BIBCODE 1968SvA....11..818B ]
Mattei, J.A., 1978, J.Roy.Astron.Soc.Can., 72, 61 [BIBCODE 1978JRASC..72...61M ]
Merrill, P.W., 1944, Ap.J., 99, 481 [BIBCODE 1944ApJ....99...15M ]
Swings, P., Struve, O. 1941, Ap.J. 93, 356 [BIBCODE 1941ApJ....93..356S ]