We review progress in research on the cool magnetic CP stars especially during the past four years. Studies of energy distributions and abundances are analyzed to reveal their systematics. Model atmospheres do not yet accurately describe the average energy distributions much less the variability with the rotational periods of these stars.

Using 9 Å/mm-dispersion spectra of two Ap stars (HD2453 and HD8441) from the list by Adelman (1973) and the SiCr star HD192913 the abundances of 19 elements are obtained by the model atmosphere technique. The curve-of-growth method is used to estimate the surface magnetic field from Fe, Cr, and Ti lines.

A behaviour of H lines P12 - P13 and CaII triplet of the star HD 152107 is studied in the range λλ 8400 - 8800 Å. An analysis of the obtained data enabled us to suspect the presence of a relationship between the variation of equivalent widths of the lines of the Paschen series of Hydrogen CaII lines and that of the star’s magnetic field.

The earlier attempts to detect the lines of heavy elements (Pb, U, Th and others) in the spectra of Ap-stars from the ground-based observations are briefly discussed. UV observations of Ap-stars with the ultraviolet telescope aboard ASTRON space station are described. The reduction of these data is considered. Three spectral regions containing the lines PbIIλ2203.53, UIIλ2556.19 and ThIIλ2368.05 were analyzed by the method of synthetic spectra. It has been shown that relatively cool Ap-star 73 Dra (Teff = 8l50 K) has a great overabundance (≥ 103ε⊙) of heavy elements U, Th, Pb and W.

During many recent years, from 1973, the search for short-term variations in the spectrum of Ap-stars has been carried out at the Crimean Astrophysical Observatory. Some results are presented in the poster dedicated to 53CAM observations. Spectral observations of the magnetic star 53CAM with time resolution of about I min were supplemented by the narrow-band photometrical observations within the framework of the cooperative program of the magnetic stars observations, started in 1979.

A critical rediscussion of the luminosity confirms that ε UMa is brighter than expected for a star on the main sequence, in our determination by 0m.6.

Line spectrum variations in Ap star HD 51418 were studied. The intensities of the Eu II lines wary by about three times. Radial velocity measurements show remarkable variability of the Eu II lines with an amplitude of 16 km/s, but the Sr II and Fe II lines do not show significant changes.

Combining the information from the speckle interferometric and spectroscopic binary βCrB a mass of 1.82 solar masses and an absolute visual magnitude Mv = 1m.42 is found, indicating that the star may be in that state of evolution, when the stellar core has shrinked after hydrogen exhaustion in it and the energy generation mainly comes from the envelope. The question whether all magnetic Ap stars are in that special evolutionary state is revived.

In spectra of chemically peculiar (CT) stars the weak lines originate at very different levels on the both sides of the Balmer jump (λB = 3646 A): τ ≈ 0.01 at λ > 3646 Å and τ ≈ 0.5–1.0, when λ > 3646 Å (Khokhlova, 1978)

To estimate the radial gradient of the magnetic field, we have observed two CP-stars β CrB and α2CVn. from 1979 to 1984 on the 6-meter telescope with an achromatic circular polarization analyzer (Glagolevskij et al.,1978). Compared with classical Zeeman analyzers, whose working wavelength band is only 300 Å, the achromatic analyzer covers a wide spectral region, enabling many more lines to be measured.

A combination of camera and grating was chosen so as record the 3300 - 4000 Å region all on the same plate at the 6.7 A/mm dispersion. Since the lines used to measure the field on either side of λ 3646 Å are exposed simultaneously on a single plate, one avoids many of the systematic errors arising from various positional, photometric and polarization effects, all these should influence the short and long wave ends of the spectrogramm identically.

Study of dependence of chemical abundance on conditions of excitation within the limits which could exist in the atmosphere of bright component have led to conclusion that by no modification of physical parameters a “normal” abundance of chemical elements in the atmosphere can be obtained. The variable effective magnetic field with mean value (−1350±50) Gauss is discovered.

Spectroscopic studies of normal O and early B type stars in the visual region are discussed. Present status of UV spectroscopic analyses of hot normal stars is reviewed. Discussions on a few practical problems in analyses of UV spectra are presented.

This review tries to expose some essential aspects of our current understanding of diffusion processes in magnetic CP stars. Many problems remain to be explained due to the fact that the presence of strong magnetic fields increases the number of free parameters in “diffusion models”. More observational constraints are needed before one can attempt modelling every aspects of magnetic CP stars.

Observations show that chemical anomalies are distributed inhomogeneously on Ap star surfaces. The most elaborated explanation of the observations is based on the fact that different ions and atoms are affected by radiative forces of different strengths and, hence, have different diffusion velocities. The diffusion across the magnetic field is a factor of (l + νH2/νC2)−1 slower than along the field (νH is the gyrofrequency and νC is the collision frequency of the ions). It leads to the increasing of the heavy ion number density in regions occupied by magnetic traps.

However, such an explanation meets a number of difficulties: a) the conditions holds for the most of ion species only in regions where the optical depth is less than 10−2 if the field H exceeds 105 gs. Although little is known on the depth of the region occupied by the chemical anomalies, there are some indirect indications that it is larger than 10−2; b) The observed dipole field has a value 103−104 gs and does not form traps corresponding to the observed chemical spots which have very complicated configurations; c) the magnetic trap is imperfect. The separation process in the field is assumed to be produced by the diffusion which needs a long time. However, ions can escape from the trap together with the surrounding hydrogen plasma because of various plasma instablished which take much shorter time; d) observed space distribution of rare elements and also of Fe, Cr, Ti contradicts the predictions of the magnetic separation hypothesis (cf. V. Khohlova IAU Coll. No. 90, this volume).

The literature concerning spectroscopic studies, abundances, photometry, and systematics of intermediate-temperature (9500 K < Teff < 16000 K) normal, Hg-Mn, and related stars is reviewed. The review is restricted mainly to papers published since the last international meeting on chemically peculiar stars at Liège in June 1981, and is intended to be complete to 31 December 1984.

Quantitative analyses of the Ga abundances in 27 Hg-Mn stars, 11 Si (magnetic) stars, 8 He-weak stars, and 7 normal stars are made with the resonance lines of Ga II at 1414 Å and Ga III at 1495 Å in IUE spectra. The Ga overabundances are confirmed as a genuine anomaly in many peculiar stars. Only upper limits of the Ga abundance can be obtained for some stars. However these upper limits are much lower than those inferred from visual spectra. Among the 27 Hg-Mn stars, 17 stars are distributed in the range of 2.0 – 3.8 dex of overabundances of Ga. Ten other stars show upper limits less than 2.1 dex. Fifteen stars of 20 hotter Hg-Mn stars with Teff > 11000 K show high overabundances in a narrow range of 2.6 – 3.8 dex, while, among 7 cooler Hg-Mn stars, the only star HR 7775 shows the same overabundance as in these 15 stars. Of 11 Si stars, 9 stars have Ga overabundances ranging from 1.9 to 3.2 dex. Gallium is overabundant in 5 out of 8 He-weak stars in the range of 1.7 – 3.2 dex, while in the three other stars the upper limits are less than 1.3 dex. The Ga abundances in normal stars are all upper limits which roughly correspond to the solar value.

An anomalous enhancement of the resonance line of Ga II at 1414.44 Å is observed in IUE spectra of the silicon star HD 25823. High-resolution spectrum of this star is compared to synthetic spectra calculated in the range 1406–1422 Å. The LTE abundance of gallium is evaluated to log NGa = 6.3 ± 0.5 in the scale where log NH = 12.