The first spectroscopic verification of an extragalactic classical chemically peculiar star

TL;DR

This study provides the first spectroscopic confirmation of a chemically peculiar star in the Large Magellanic Cloud, validating photometric detection methods and expanding understanding of such stars beyond the Milky Way.

Contribution

It is the first spectroscopic verification of an extragalactic CP star, confirming the effectiveness of the Delta a photometric system in identifying these objects outside the Milky Way.

Findings

Confirmed a classical B8 Si star in the LMC

Detected an early B-type emission-line star

Validated photometric detection of extragalactic CP stars

Abstract

We present the first spectroscopic verification of a bona fide chemically peculiar (CP) star in the Large Magellanic Cloud. CP stars reside on the upper main sequence and are characterized by strong global stellar magnetic fields with a predominant dipole component oriented at random with respect to the stellar rotation axis and displaced from the star's centre. Overabundances with respect to the Sun for heavy elements such as silicon, chromium, strontium and europium are also a common phenomenon. These objects are excellent astrophysical laboratories by which to investigate many of the processes connected with star formation and evolution. Several studies comparing the incidence of CP stars in the Large Magellanic Cloud with that of the Milky Way have been published. These investigations are based on the photometric detection of CP stars via the Delta a system which has been tested and calibrated for objects in the Milky Way. From our spectroscopic observations made at Las Campanas Observatory, we are able to confirm one classical B8 Si star among the photometric sample, as well as one early B-type emission-line star which was also initially detected by its significantly deviating Delta a value. We conclude that classical extragalactic CP stars do exist and that the photometric Delta a system is able to detect them in an efficient way.