Discovery of a new Galactic bona fide luminous blue variable with Spitzer

TL;DR

This paper reports the discovery of a new Galactic luminous blue variable star, Wray 16-137, identified through its infrared shell and spectral variability, confirming its classification as a bona fide LBV.

Contribution

The study presents the first identification of Wray 16-137 as a Galactic LBV using infrared imaging and spectroscopic follow-up, demonstrating its S Dor-like outburst behavior.

Findings

Discovery of a mid-infrared shell around Wray 16-137

Spectroscopic evidence of LBV-like emission spectrum

Photometric variability indicating an S Dor-like outburst

Abstract

We report the discovery of a circular mid-infrared shell around the emission-line star Wray 16-137 using archival data of the Spitzer Space Telescope. Follow-up optical spectroscopy of Wray 16-137 with the Southern African Large Telescope revealed a rich emission spectrum typical of the classical luminous blue variables (LBVs) like P Cygni. Subsequent spectroscopic and photometric observations showed drastic changes in the spectrum and brightness during the last three years, meaning that Wray 16-137 currently undergoes an S Dor-like outburst. Namely, we found that the star has brightened by \approx 1 mag in the V and I_c bands, while its spectrum became dominated by Fe ii lines. Taken together, our observations unambiguously show that Wray 16-137 is a new member of the family of Galactic bona fide LBVs.