Mercury-manganese stars in the observations of TESS satellite

Mercury-manganese (HgMn) stars have spectral types from B7 to B9 and luminosity classes III-V. They are classified by a strong line of Hg II at 398.39 nm and several lines of Mn II visible in the blue part of the spectrum. Abundance anomalies found in HgMn stars are due to atomic diffusion processes, which are very sensitive to mixing motions. Hence, it is not surprising that HgMn stars are slow rotators (projected rotation velocities less than about 75 km/s) and often dwell in binary systems. It is assumed that HgMn stars are non-magnetic chemically peculiar stars, however weak magnetic fields have been detected for some of them (e.g. Mathys and Hubrig 1995). In addition, periodic variability was discovered in the spectra of some HgMn stars, which may indicate inhomogeneous distribution of chemical elements on the surface and indirectly the presence of magnetic fields. However, investigations of the photometric variability of HgMn stars are still unexpectedly rare considering available data, both ground-based and satellite. Here we present the results of TESS photometry analysis for more than 100 known HgMn stars. Most stars in our sample appear to be variables, both known and new-found ones. Binarity, rotational modulation and internal pulsations are discussed as possible causes of variability