A New Luminous Blue Variable in M31

TL;DR

This paper reports the discovery and spectral evolution of a new Luminous Blue Variable in M31, illustrating its transition through different spectral types and confirming its LBV status based on photometric and spectroscopic data.

Contribution

It presents the identification and detailed spectral evolution of the fifth confirmed LBV in M31, expanding understanding of LBV variability and characteristics.

Findings

Spectral transition from hot to cool supergiant observed

Photometric data supports LBV/S Dor classification

Bolometric luminosity consistent with known LBVs

Abstract

We report the fifth confirmed Luminous Blue Variable/S Doradus variable in M31. In 2006, J004526.62+415006.3 had the spectrum of hot Fe II emission line star with strong P Cygni profiles in the Balmer lines. In 2010, its absorption line spectrum resembled an early A-type supergiant with H and Fe II emission lines with strong P Cygni profiles, and in 2013 the spectrum had fully transitioned to an F-type supergiant due to the formation of the optically thick, cool wind which characterizes LBVs at maximum light. The photometric record supports the LBV/S Dor nature of the variability. Its bolometric luminosity ~ -9.65 mag places it on the HR Diagram near the known LBVs, AE And, Var C in M33 and S Dor.