Dynamical evolution of titanium, strontium, and yttrium spots on the surface of the HgMn star HD 11753

TL;DR

This study investigates the surface inhomogeneities and chemical spot evolution on HgMn stars, using spectral analysis and Doppler imaging to reveal rapid changes in element distributions over time.

Contribution

It provides the first detailed Doppler imaging maps showing dynamic chemical spot evolution on HgMn stars, highlighting physical processes causing these changes.

Findings

Detected spectral line profile variability for multiple elements.

Derived rotation periods for three HgMn stars.

Revealed noticeable changes in surface element distributions over ~65 days.

Abstract

Aims. We gathered about 100 high-resolution spectra of three typical HgMn (mercury-manganese) stars, HD 11753, HD 53244, and HD 221507, to search for slowly pulsating B-like pulsations and surface inhomogeneous distribution of various chemical elements. Methods. Classical frequency analysis methods were used to detect line profile variability and to determine the variation period. Doppler imaging reconstruction was performed to obtain abundance maps of chemical elements on the stellar surface. Results. For HD 11753, which is the star with the most pronounced variability, distinct spectral line profile changes were detected for Ti, Sr, Y, Zr, and Hg, whereas for HD 53244 and HD 221507 the most variable line profiles belong to the elements Hg and Y, respectively. We derived rotation periods for all three stars from the variations of radial velocities and equivalent widths of spectral lines belonging to inhomogeneously distributed elements: P_rot (HD 11753)=9.54 d, P_rot (HD 53244)=6.16 d, and P_rot (HD 221507)=1.93 d. For HD 11753 the Doppler imaging technique was applied to derive the distribution of the most variable elements Ti, Sr, and Y using two datasets separated by ~65 days. Results of Doppler imaging reconstruction revealed noticeable changes in the surface distributions of TiII, SrII, and YII between the datasets, indicating the hitherto not well understood physical processes in stars with radiative envelopes that cause a rather fast dynamical chemical spot evolution.