Discovering new B[e] supergiants and candidate Luminous Blue Variables in nearby galaxies

TL;DR

This study identifies new B[e] supergiants and LBVs in nearby galaxies, providing insights into episodic mass loss in massive star evolution, especially at low metallicities, through extensive spectroscopic surveys.

Contribution

It reports the discovery of new B[e] supergiants and LBVs, expanding the known population and exploring their properties across different metallicity environments.

Findings

7 B[e] supergiants and 4 LBVs identified, with 6 and 2 being new discoveries.

Presence of B[e]SGs at metallicity as low as 0.14 Z$_{igodot}$.

Spectroscopic and photometric data constrain the nature of these objects.

Abstract

Mass loss is one of the key parameters that determine stellar evolution. Despite the progress we have achieved over the last decades we still cannot match the observational derived values with theoretical predictions. Even worse, there are certain phases, such as the B[e] supergiants (B[e]SGs) and the Luminous Blue Variables (LBVs), where significant mass is lost through episodic or outburst activity. This leads to various structures around them that permit dust formation, making these objects bright IR sources. The ASSESS project aims to determine the role of episodic mass in the evolution of massive stars, by examining large numbers of cool and hot objects (such as B[e]SGs/LBVs). For this, we initiated a large observing campaign to obtain spectroscopic data for $\sim$1000 IR selected sources in 27 nearby galaxies. Within this project we successfully identified 7 B[e] supergiants (one candidate) and 4 Luminous Blue Variables of which 6 and 2, respectively, are new discoveries. We used spectroscopic, photometric, and light curve information to better constrain the nature of the reported objects. We particularly note the presence of B[e]SGs at metallicity environments as low as 0.14 Z$_{\odot}$.