Drake et al. (1987) detected, for the first time, radio emission from magnetic Chemically Peculiar stars. They suggested that radio emission is consistent with gyrosynchrotron emission from continuously injected, mildly, relativistic particles trapped in a magnetic equatorial belt.

Leone (1991) showed that it is possible considering that the radio emission comes from magnetic poles and is due to the electron component of the wind flowing along the open field lines. As a consequence Leone (1991) put forward the hypothesis that such emission could be periodically variable.

In order to verify the surmise of a periodic radio emission, the magnetic Chemically Peculiar stars HD 37017 and σ Ori E have been monitored with the VLA at 6 cm.

By combining our data with those obtained by Drake et al. (1987) and Philips & Lestrade (1988), we show that the radio emission from HD 37017 and σ Ori E varies with the rotational period.

A search for CP2 stars with long photometric periods during more than one decade has led to the detection of the long period variables HD 94660 and HD 116458. Furthermore, in the case of ϒ Equ, the CP star with the longest magnetic period, a monotonic change of the light output has been measured. Light curves are presented for the known long period variables HD 187474 and HD 188041. The results on the other stars in the programme are shortly discussed.

For several of the rapidly oscillating Ap stars the best luminosity estimates available come from the asteroseismological interpretation of their pulsational frequency spectra. We give a list of the 23 currently known roAp stars along with their Strömgren photometric indices, Teff estimated from the Hβ index, and luminosity estimated asteroseismologically. In one case, ϒ Equ, we have an asteroseismological luminosity and a parallax luminosity which are in good agreement. Some of the roAp stars pulsate with frequencies greater than the critical frequency calculated for standard A-star models. This plus multi-colour high-speed photometry of HR 3831 indicate that the temperature gradients in the atmospheres of these stars are substantially steeper than in standard A-star models. We advocate a fine analysis of HR 3831 to see if there is consistency with the pulsational conclusions about T-τ in this star. Further fine analyses and multi-colour pulsational analyses on other roAp stars are then called for. The pulsation mode in HR 3831 can be decomposed into primarily an axisymmetric dipole mode with small radial, quadrupole and octupole perturbations. If the magnetic field is governing the distortion of this mode from a purely dipole mode, then the pulsation can be used to infer the magnetic field geometry. Comments on our current knowledge of all 23 roAp stars are made.

The evolutionary state of CP Stars is defined using members of open clusters. It is confirmed that all CP stars belong to the main sequence, if the case of Horizontal-Branch Stars is omitted. The frequency of CP Stars as a function of age has been reconsidered: it is found constant for the CP2 stars, but significantly increasing with age for the CP1 (Am) stars.

The results of photometric observations of early type stars in regions around the Galactic poles are presented. The aim of these investigations was to search for CP2 and CP1 and to establish new and more precise frequencies for such objects including fainter stars.

A mean frequency of 24.7% was found for the CP1 stars, 23.7% for the hot CP2, and 11.7% for the cooler ones, but with large differences between the two regions investigated.

Furthermore, a substantial number of stars (20) were found to be good candidates for λ Boo stars.

Eightysix chemically peculiar stars have been observed in the near infrared with the aim to extend the comprehension of the differences between normal and peculiar stars. These stars have been checked for variability. Most of the stars are previously known light variables, although their periods were not accurate enough to phase together different kinds of observations carried out several years apart. For about 20 stars the period has been refined by combining our own uvby observations with the ones available in the literature.

Based on photographic Zeeman spectra a magnetic field has been detected for the giant star α Dra. One of the two periods derived for the magnetic changes can be interpreted as the half rotational period corresponding to a slight variation of the radial velocity of 3.57 days. The application of an eguatorially symmetric rotator model with a magnetic field dominated by the quadrupole moment leads to a good agreement with the observed magnetic variation. The orbital elements of α Dra were newly derived.

The atmospheric structures of magnetic CP2 (Ap) stars are notoriously difficult to model: line blanketing is severe, surface gravities are extremely uncertain, and the surface abundance inhomogeneities lead to different atmospheric properties as a function of position on the star. Seismology of the p-modes of rapidly oscillating Ap (roAp) stars (Kurtz 1990), which vary with periods of a few minutes and amplitudes below 0.01 mag and 1 km/s in light and velocity, has already helped constrain the luminosities – and hence, the logg values – of some cool CP2 stars (Kurtz 1992, these proceedings). We show here that the pulsations of an roAp star can also directly probe the temperature structure of a CP2 atmosphere.

When studying the distribution of stars and interstellar matter in the galactic environment, one relies upon objects which are numerous enough and also bright enough to constitute workable samples. A-type stars seem to be a natural choice, but a successful study then depends on the reliability of the spectroscopic distance determinations. Since chemical peculiarity affects a considerable fraction of the A-type main sequence stars we have found reason to investigate the reliability of luminosity estimates for stars of various types of peculiarity. The result indicates that peculiarity is a less serious problem than undetected multiplicity.

In the past several authors investigated the incidence of CP Stars among field stars of the upper main sequence, e.g. Jaschek&Jascheck (1967), Wolff (1968), Abt (1979), or in open clusters e.g. Young&Martin (1973), Hartoog (1976), North&Cramer (1981). But the published values seem not to be very precise or universal because of the use of incomplete data bases like Osawa’s list (1965) or the old version of the Bright Star Catalogue or the concentration on selected samples e.g. open clusters. Only Smith (1973) gave realistic values in the case of CP1 stars.

In the meantime two decades passed and many new observations were obtained. In 1982 a new version of the Bright Star Catalogue with better spectral classifications was issued and a supplement to the BS catalogue was published (1983). Furthermore, Renson and co-workers presented 1991 their General Catalogue of Am and Ap Stars (in the following abbreviated to GCAAS). Now the moment has come to establish new and hopefully more precise values of the incidence of CP Stars using the new version of the Bright Star Catalogue and its supplement as the data base.

From uvby and Hβ photometry, individual stellar ages for A type stars have been derived using three different evolutionary models. In this paper we evaluate the corrections for metallicity and rotation to be applied to the physical parameters of Am and their influence on the determined ages. A test based on the Hyades open cluster is also presented.

Abt published in 1979 frequencies of peculiar stars in open clusters based on published classifications for 661 stars in 14 open clusters and associations. Among others he discussed an age dependence of the frequencies of CP3 stars and found them increasing with age. Furthermore, he suggested a possible age dependence of the rotational velocity of these stars.

But the sample he used was rather small: he found eight CP3 stars in 5 open clusters. In the mean time the number of cluster CP3 stars was more than double. Therefore, the findings of Abt shall be examined on the basis of the larger sample.

The College of Charleston The Citadel, the University of Nevada, Las Vegas and Villanova University constitute the Four College Automatic Photoelectric Telescope Consortium which has a 0.75-m telescope on Mt. Hopkins, Arizona. It has been in regular operation for two years. Prior to this time we obtained some differential UBV observations with the Phoenix 10” APT of the Fairborn Observatory. We are coordinating observations of CP stars of the upper main sequence. Some initial results include evidence for significant changes in the light curve of 56 Ari, the constancy of the HgMn stars 53 Tau and HR 4072, an improved period for HD 244801, and new observations in the broad minimum of HD 9996.

From IUE archival data and visual spectrophotometric observations published by Adelman and Pyper, nearly 20 energy distributions of 56 Ari in different rotational phases were obtained. The light variations in selected spectral bands correlate with spectrum variations. The bolometric flux varies by ˜ 2.5 % over the rotation period.

The research papers on normal and chemically peculiar stars of the upper main sequence are counted in the “Astronomy and Astrophysics Abstracts” for eight sample years in the period 1970-1990.