HD66051, an eclipsing binary hosting a highly peculiar, HgMn-related star

TL;DR

HD66051 is an eclipsing binary with a peculiar HgMn-like primary star showing surface inhomogeneities and unique chemical composition, providing insights into stellar atmospheres and chemical anomalies.

Contribution

This study presents the detailed chemical analysis and variability of HD66051, revealing a HgMn-related star with surface inhomogeneities, a rare configuration for such systems.

Findings

Primary star is a peculiar HgMn-like late B-type with overabundant heavy elements.

Secondary star is a slowly rotating A-type star with typical temperature.

Surface inhomogeneities cause long-term photometric variability.

Abstract

HD66051 is an eclipsing system with an orbital period of about 4.75 d that exhibits out-of-eclipse variability with the same period. New multicolour photometric observations confirm the longevity of the secondary variations, which we interpret as a signature of surface inhomogeneities on one of the components. Using archival and newly acquired high-resolution spectra, we have performed a detailed abundance analysis. The primary component is a slowly rotating late B-type star ($T_{\rm eff} = 12500\pm200$ K; $\log g = 4.0$, $v\sin i = 27\pm2$ km s$^{-1}$) with a highly peculiar composition reminiscent of the singular HgMn-related star HD 65949, which seems to be its closest analogue. Some light elements as He, C, Mg, Al are depleted, while Si and P are enhanced. Except for Ni, all the iron-group elements, as well as most of the heavy elements, and in particular the REE elements, are overabundant. The secondary component was estimated to be a slowly rotating A-type star ($T_{\rm eff} \sim 8000$ K; $\log g = 4.0$, $v\sin i \sim 18$ km s$^{-1}$). The unique configuration of HD\,66051 opens up intriguing possibilities for future research, which might eventually and significantly contribute to the understanding of such diverse phenomena as atmospheric structure, mass transfer, magnetic fields, photometric variability and the origin of chemical anomalies observed in HgMn stars and related objects.