Chemically peculiar stars on the pre-main sequence

TL;DR

This study identifies and analyzes chemically peculiar stars on the pre-main-sequence, revealing that magnetic fields play a key role in the development of chemical peculiarities early in stellar evolution.

Contribution

First identification of pre-main-sequence CP stars, including magnetic CP2 stars, using spectral energy distribution fitting and spectral analysis.

Findings

Approximately 70% of candidates are confirmed or likely CP stars.

Nine pre-main-sequence CP stars are identified, all with magnetic fields.

Discovery of a potential pre-main-sequence CP2 star not previously reported.

Abstract

Context. The chemically peculiar (CP) stars of the upper main sequence are defined by spectral peculiarities that indicate unusual elemental abundance patterns in the presence of diffusion in the calm, stellar atmospheres. Some of them have a stable local magnetic field of up to several kiloGauss. The pre-main-sequence evolution of these objects is still a mystery and contains many open questions. Aims. We identify CP stars on the pre-main sequence to determine possible mechanisms that lead to the occurrence of chemical peculiarities in the (very) early stages of stellar evolution. Methods. We identified likely pre-main-sequence stars by fitting the spectral energy distributions. The subsequent analysis using stellar spectra and photometric time series helped us to distinguish between CP and non-CP stars. Additionally, we compared our results to the literature to provide the best possible quality assessment. Results. Out of 45 candidates, about 70 % seem to be true CP stars or CP candidates. Furthermore, 9 sources appear to be CP stars on the pre-main sequence, and all are magnetic. We finally report a possible CP2 star that is also a pre-main-sequence star and was not previously in the literature. Conclusions. The evolution of the peculiarities seems to be related to the (strong) magnetic fields in these CP2 stars.