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Following the standard procedures of taking account of the scattered light, removal of cosmic particle traces and extraction of the spectra from the images, the spectra were normalized to the continuum and reduced to the scale of laboratory wavelengths. The dispersion curves were plotted separately for each order immediately from emission lines of the object. In so doing lines were selected which yielded radial velocities close to the symbiotic velocity of MWC 560 (+35 km/s). The averaging of the overlapping spectrum orders was performed on the wavelength scale.
The visible spectrum of MWC 560 is poor in absorption lines especially near
the brightness maximum. In our atlas are visible only the blue-shifted
components of ,
, NaI and FeII(42),
interstellar lines NaI, a few diffuse interstellar bands (DIB) and telluric
lines of
and
and, at length, traces of the spectra of
the M giant. To reveal these traces, the spectrum of
Peg M2.5 II-III
obtained with the same resolution as the spectrum of MWC 560 and the list of
absorption lines identified in it (Davis, 1947) were taken.
Principal attention was given to the identification of the emission spectrum. The following elements and ionization stages (species): HI, CI, NI, [NI], [OI], NaI, MgI, SiII, CaI, CaII, ScII, TiI, TiII, VII, CrI, CrII, MnII, FeI, FeII, [FeII], YII, ZrII, BaII, LaII, CeII, PrII, NdII have been revealed, which are mostly present in the blue part of the spectrum of MWC 560 (Kolev and Tomov, 1993) too.
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The identification was performed in two steps. At first the whole set of
lines within the boundaries of the atlas with the wavelengths and oscillator
strength accessible to us was compared alternatively for each of the species
listed. For instance, for FeI the table of Nave et al. (1994) was used, for
FeII the data of Johansson (1978) and Boyarchuk and Savanov (1986), while for
[FeII] the data of Quinet et al. (1996). The closeness of the tabulated and
observed values not only for the wavelength but also for the relative
intensity of a line was considered a condition for reliable identification.
About one-third of all emission lines were used in measuring radial
velocities and plotting dispersion curves. For these the departure of the
measured wavelengths from the tabulated ones does not exceed
Å. In the rest of the cases the wavelengths were estimated from
the atlas, and discrepancies as large as
Å were permissible.
The relationships between the tabulated gf values and the observed residual
intensities, r, were presented in a diagram form. As is seen in Fig. 1, where
an example of r(lggf) dependence for FeI is given, allowance for the
excitation potential makes the relationships clear enough, which makes it
possible to correctly refer a line to a given species.
Subsequently our spectra were compared with the like and well
described spectra of real objects to check that the identification was
correct. As a whole, the spectrum of MWC 560 is close to the spectra of the
symbiotic stars XX Oph (Merrill, 1951) and PU Vul (Belyakina et al., 1985;
Iijima and Ortolani, 1984) as well as to the spectrum of the solar
chromosphere (Pierce, 1968; Kastner, 1995). Its individual species are well
represented in the spectra of T Tauri stars (Appenzeller et al., 1986) and
Car (Thackeray, 1967).