New paper: Discovering New B[e] Supergiants and Candidate Luminous Blue Variables in Nearby Galaxies

Although I thought at the beginning that this would be a quick paper, it took considerable time to complete! Thanks a lot to Stephan that did significant work with figures I was able to focus on the text and the discussion. This is the first work to reveal B[e] Supergiants in low-metallicity galaxies (such as WLM) and at the same time it presents a diagnostic for separating B[e] Supergiants with LBVs (using a Spitzer-Gaia Color Magnitude Diagram).

Discovering New B[e] Supergiants and Candidate Luminous Blue Variables in Nearby Galaxies

Grigoris Maravelias, Stephan de Wit, Alceste Z. Bonanos, Frank Tramper, Gonzalo Munoz-Sanchez and Evangelia Christodoulou

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 forming 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 purpose, we initiated a large observation campaign to obtain spectroscopic data for ∼1000 IR-selected sources in 27 nearby galaxies. Within this project we successfully identified seven B[e] supergiants (one candidate) and four Luminous Blue Variables of which six and two, respectively, are new discoveries. We used spectroscopic, photometric, and light curve information to better constrain the nature of the reported objects. We particularly noted the presence of B[e]SGs at metallicity environments as low as 0.14 Z.

Figure 1. Spectra of objects classified as B[e]SGs (including the B[e]SG candidate NGC7793-1). (Left)
The full spectra for all stars with small offsets for better illustration purposes. The most prominent
emission features are indicated. (Right) The region around Hα is highlighted to emphasize the relative
strength of the emission compared to the continuum.

Galaxies 2023, 11(3), 79;

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