The inhomogeneous surface distribution of heavy elements is known to cause periodic light variability of magnetic chemically peculiar stars. It is unclear to what extent the same paradigm applies to mercury–manganese (HgMn) stars. We aim to model the photometric variability of the HgMn star φ Phe using abundance maps obtained from high-resolution spectroscopy and to study how this variability evolves with time. We compute a grid of atlas12 model atmospheres and the corresponding synspec synthetic spectra. Interpolating within this grid and integrating the specific intensity over the visible stellar surface at different rotational phases, we obtain theoretical light curves of the star. We predict the variability of φ Phe in the ultraviolet and in the visible spectral regions with amplitude of the order of millimagnitudes, mainly caused by absorption in lines of yttrium, chromium, and titanium. We also show how this variability is affected by changes of the distribution of the heavy elements over time. The main characteristics of the predicted light variability of φ Phe correspond roughly to the variability of the star observed with the Transiting Exoplanet Survey Satellite (TESS).

HD\,37776 (V901\,Ori, B2\,Vp), also known as Landstreet's Star, is possibly the most remarkable magnetic chemically peculiar (mCP) star known. Zeeman Doppler Imaging revealed this young, rapidly rotating star's surface magnetic field to be not only the strongest ($\sim 30$ kG) of the He-strong class of hot mCP stars but also by far the most topologically complex. In contrast to the overwhelming majority of mCP stars, which are well described by tilted dipoles, Landstreet's Star's non-axisymmetric surface magnetic field is entirely dominated by high-order spherical harmonics. It is one of the handful of stars for which rotational period change has been measured, and over the past two decades of monitoring, the object has demonstrated an unexpected acceleration in its rotation that so far defies explanation. Recently acquired TESS data have provided a photometric data set of unprecedented precision. These data have revealed a highly stable yet multi-featured light curve, making Landstreet's Star the prototype of hot mCP stars whose light curves are difficult to reproduce using the standard model of chemical/photometric spots modulated by solid-body rotation.

The A2 V star σ Scl was suspected of being a low-amplitude rotating variable of the Ap-type star by several authors. Aiming to decide whether the star is a variable chemically peculiar (CP) star, we searched for the photometric and spectroscopic variability, and determined chemical abundances of σ Scl. The possible variability was tested using several types of periodograms applied to the photometry from Long-Term Photometry of Variables project (LTPV) and Hipparcos. Sixty spectrograms of high signal-to-noise (S/N) were obtained and used for chemical analysis of the stellar atmosphere and for looking for spectral variability that is symptomatic for the CP stars. We did not find any signs of the light variability or prominent chemical peculiarity, that is specific for the CP stars. The only exception is the abundance of scandium, which is significantly lower than the solar one and yttrium and barium, which are strongly overabundant. As a by-product of the analysis, and with the addition of 29 further spectra, we found that σ Scl is a single-lined spectroscopic binary with orbital period of 46.877(8) d. We argue that σ Scl is not an Ap star, but rather a marginal Am star in SB1 system. The spectral energy distribution of the binary reveals infrared excess due to circumstellar material.

The particular field of research of the group of hot stars at our department involves mainly the study of spherically symmetric line-driven stellar winds and outflows, asymmetric stellar environment (outflowing disks of B-type stars), and chemically peculiar (CP) stars. We carry out a range of activities within our team and its wider cooperation, from photometric and spectroscopic observations and processing of the data to calculation of theoretical models of stellar and interstellar processes which are connected with studied objects. We have also developed several types of astrophysical computational codes that particularly fit to multidimensional simulations of the specific studied problems. We describe basically the main types of hot stars with winds or outflowing disks and introduce some of main results of our recent research. These include namely the basic features of one-dimensional models disks of critically or sub-critically rotating B-type stars, two-dimensional self-consistent models of the disk density and temperature structure, two-dimensional introductory self-consistent models of the disk with aligned and co-rotating compact companion, as well as examples of models of CP stars and models of interaction of exploding supernova (SN) envelope with asymmetric circumstellar environment.

We used in seasons 2011 and 2012 (7+7 nights) ´ Echelle spectroscop FEROS at La Silla observatory to obtain high dispersion spectra of chemically peculiar stars. The lecture will describe the observed stars, their selection, but also practical experience with the observation of this instrument.

The variability of the chemically peculiar stars is commonly believed to be a result of inhomogeneous distribution of heavier elements, spectral energy redistribution, and rotation. However, this phenomenon is still not completely understood. HD114365 is a Si-rich chemically peculiar star, which is variable with a period of 1.272 days. We use the technique of Doppler imaging to perform an abundance analysis of the star using spectroscopic observations made with the 2.2m telescope and the FEROS spectrograph at La Silla, Chile. We present abundance maps of HD114365 for several chemical elements.