Observational constraints on the X-ray Bright supergiant B[e] stars LHA 115-S18 \& LHA 120-S 134

TL;DR

This study reports spectroscopic observations of the supergiant B[e] stars LHA 115-S 18 and LHA 120-S 134, analyzing their variability and searching for periodicities to better understand their nature.

Contribution

It provides new spectroscopic data on S18's variability state and a pilot study of S 134, contributing to the understanding of supergiant B[e] stars in the Magellanic Clouds.

Findings

S18 remained in an intermediate spectral state between hot and cool from 2012-2015.

Spectroscopic variability and potential periodicities are being investigated.

Preliminary results of a pilot study on LHA 120-S 134 are presented.

Abstract

We present the preliminary results of an ongoing series of spectroscopic observations of the Small Magellanic Cloud star LHA 115-S 18 (S18), which has demonstrated extreme photospheric and spectroscopic variability that, in some respects, is reminiscent of Luminous Blue Variables (LBVs). In contrast to our previously published results, between 2012-2015 S18 remained in an spectral state intermediate between S18's "hot" and "cool" extremes. In conjunction with contemporaneous OGLE-IV photometric monitoring of S18, these data will be used to determine the characteristic timescale of the variability and search for periodicities, in particular binary modulated periodicity. We also present the results of a pilot study of the LMC star LHA 120-S 134.