A Spectroscopic and Photometric Investigation of the Mercury-Manganese Star KIC 6128830

TL;DR

This study combines spectroscopic and photometric data to analyze the variability of the Mercury-Manganese star KIC 6128830, exploring whether its light changes are due to pulsations or rotation, with implications for understanding such stars.

Contribution

It provides the first detailed abundance analysis and investigates the variability origin in KIC 6128830 using four years of Kepler data, highlighting the potential for rotation or pulsation explanations.

Findings

Confirmed the star's abundance pattern matches its classification.

Identified a significant variability frequency at 0.2065424 d$^{-1}$.

Discussed the likelihood of rotational versus pulsational origin for the variability.

Abstract

The advent of space-based photometry provides the opportunity for the first precise characterizations of variability in Mercury-Manganese (HgMn/CP3) stars, which might advance our understanding of their internal structure. We have carried out a spectroscopic and photometric investigation of the candidate CP3 star KIC 6128830. A detailed abundance analysis based on newly-acquired high-resolution spectra was performed, which confirms that the star's abundance pattern is fully consistent with its proposed classification. Photometric variability was investigated using four years of archival Kepler data. In agreement with results from the literature, we have identified a single significant and independent frequency $f_1$=0.2065424 d$^{-1}$ with a peak-to-peak amplitude of $\sim$3.4 mmag and harmonic frequencies up to $5f_1$. Drawing on the predictions of state-of-the-art pulsation models and information on evolutionary status, we discuss the origin of the observed light changes. Our calculations predict the occurrence of g-mode pulsations at the observed variability frequency. On the other hand, the strictly mono-periodic nature of the variability strongly suggests a rotational origin. While we prefer the rotational explanation, the present data leave some uncertainty.