Inhomogeneous distribution of mercury on the surfaces of rapidly rotating HgMn stars

Abstract

Starspots are usually associated with the action of magnetic fields at the stellar surfaces. However, recently an inhomogeneous chemical distribution of mercury was found for the mercury-manganese (HgMn) star alpha And -- a well-established member of a non-magnetic subclass of the chemically peculiar stars of the upper main sequence. In this study we present first results of the high-resolution survey of the HgII 3984 resonance line in the spectra of rapidly rotating HgMn stars with atmospheric parameters similar to those of alpha And. We use spectrum synthesis modelling and take advantage of the Doppler resolution of the stellar surfaces to probe horizontal structure of mercury distribution. Clear signatures of spots are found in the HgII 3984 line profiles of HR 1185 and HR 8723. Two observations of the latter star separated by two days give evidence for the line profile variability. We conclude that inhomogeneous distribution of Hg is a common phenomenon for the rapidly rotating HgMn stars in the 13000--13800 K effective temperature range independently of the stellar evolutionary stage. These results establish existence of a new class of spectrum variable spotted B-type stars. It is suggested that the observed Hg inhomogeneities arise from dynamical instabilities in the chemical diffusion processes and are unrelated to magnetic phenomena.

arXiv comment6 pages, 3 figures, accepted by Astronomy & Astrophysics

References in corpus (2)

• SB9: The Ninth Catalogue of Spectroscopic Binary Orbits
• B Star Rotational Velocities in h and chi Persei: A Probe of Initial Conditions During the Star-Formation Process

Cited by in corpus (21)

• Weather in stellar atmosphere: the dynamics of mercury clouds in alpha Andromedae
• The search for magnetic fields in mercury-manganese stars
• No detection of large-scale magnetic fields at the surfaces of Am and HgMn stars
• MOBSTER - II. Identification of rotationally variable A stars observed with \emph{TESS} in Sectors 1 to 4
• A search for magnetic fields in the variable HgMn star $\alpha$ Andromedae
• TESS survey of rotational and pulsational variability of mercury-manganese stars
• Magnetic field, chemical composition and line profile variability of the peculiar eclipsing binary star AR Aur
• Dynamical evolution of titanium, strontium, and yttrium spots on the surface of the HgMn star HD 11753
• Are there tangled magnetic fields on HgMn stars?
• Chemical spots in the absence of magnetic field in the binary HgMn star 66 Eridani
• Magnetism, chemical spots, and stratification in the HgMn star phi Phoenicis
• HD66051: the first eclipsing binary hosting an early-type magnetic star
• Looking for pulsations in HgMn stars through CoRoT lightcurves
• Time-dependent atomic diffusion in the atmospheres of CP stars. A big step forward: introducing numerical models including a stellar mass loss
• A search for pulsations in the HgMn star HD 45975 with CoRoT photometry and ground-based spectroscopy
• No magnetic field in the spotted HgMn star mu Leporis
• A spectroscopic test of the rotational modulation origin of periodic \emph{Kepler} photometric variability of A-type stars
• Abundances and search for vertical stratification in the atmospheres of four HgMn stars
• Interferometry of chemically peculiar stars: theoretical predictions vs. modern observing facilities
• The spots on Ap stars
• HD 42477: coupled r modes, g modes and a p mode in an A0Vnne star