The Massive Star Population in M101. III. Spectra and Photometry of the Luminous and Variable Stars

TL;DR

This study presents spectra and photometry of luminous and variable stars in M101, identifying LBV candidates and analyzing their spectral and variability characteristics to understand their nature and behavior.

Contribution

It provides new photometric data, light curves, and spectral analysis of luminous stars in M101, including the identification of new LBV candidates and insights into their variability.

Findings

V9 may be in an LBV-like maximum light state or eruption

Three known irregular blue variables are confirmed as LBV candidates

New photometry and light curves for three variables are presented

Abstract

We discuss moderate resolution spectra, multicolor photometry, and light curves of thirty-one of the most luminous stars and variables in the giant spiral M101. The majority are intermediate A to F-type supergiants. We present new photometry and light curves for three known "irregular blue variables" V2, V4 and V9) and identify a new candidate. Their spectra and variability confirm that they are LBV candidates and V9 may be in an LBV-like maximum light state or eruption.