High-precision photometric and high-resolution spectroscopic characterisation of HD 180347

TL;DR

This study combines space-based photometry and high-resolution spectroscopy to characterize HD 180347, identifying it as a rotational variable with chemical peculiarities typical of Am stars, and providing detailed atmospheric and abundance parameters.

Contribution

The paper presents a comprehensive analysis of HD 180347 using TESS photometry and HERMES spectroscopy, revealing its rotational period and chemical peculiarities for the first time.

Findings

HD 180347 is a rotational variable with a period of about 4.1 days.

The star shows chemical peculiarities consistent with an Am classification.

NLTE analysis confirms depletion of Ca and Sc and enhancement of heavy elements.

Abstract

We report the analysis of high-precision space-based photometric and high-resolution spectroscopic observations of HD 180347. The high-quality light curves from the Transiting Exoplanet Survey Satellite (TESS) under sectors 14, 15, and 26 were used. By visual inspection of the light curves and the Fourier transforms, only low-frequency signals (less than 1 d$^{-1}$) were detected. After using wavelet, autocorrelation, and composite spectrum analyses, HD 180347 is classified as a rotational variable with a period of about 4.1 $\pm$ 0.2 days. In reference to the observation limit of TESS, no pulsations were detected. For the spectroscopic analysis, we used data collected with the High Efficiency and Resolution Mercator \'{E}chelle Spectrograph (HERMES). We determined the spectral type of this star and obtained atmospheric parameters such as the effective temperature, the surface gravity, and the projected rotational, microturbulent, and radial velocities. We performed a detailed chemical abundance analysis. The LTE abundances were derived for 25 chemical elements. For 13 of them, including Ca, Sc, Sr, Zr, and Ba, which are important for the characterisation of chemical peculiarity, we also present the non-local thermodynamic equilibrium (NLTE) abundances. NLTE improves the accuracy of the derived abundances and confirms that Ca and Sc are depleted in HD 180347 relative to their solar abundances, while the heavy elements beyond Sr are enhanced, by more than 0.7 dex. Based on the spectral class and the element abundance pattern, we classify this star as Am (kA1hA8mA8).