A new candidate Luminous Blue Variable

TL;DR

This paper identifies IRAS 16115-5044 as a candidate luminous blue variable (LBV), based on its high luminosity, spectral features, and variability, suggesting it is a rare supergiant star with an initial mass of about 40 solar masses.

Contribution

The study reclassifies IRAS 16115-5044 as an LBV using new distance and extinction measurements, expanding the known population of Galactic LBVs.

Findings

IRAS 16115-5044 exhibits LBV-like spectral features and variability.

The star's luminosity exceeds that of typical post-AGB objects.

Estimated initial mass of the star is approximately 40 solar masses.

Abstract

We identify IRAS 16115-5044, which was previously classified as a protoplanetary nebula (PPN), as a candidate luminous blue variable (LBV). The star has high luminosity (>10$^{5.75}$ L_Sun), ensuring supergiant status, has a temperature similar to LBVs, is photometrically and spectroscopically variable, and is surrounded by warm dust. Its near-infrared spectrum shows the presence of several lines of HI, He I, Fe II, Fe [II], MgII, and Na I with shapes ranging from pure absorption and P Cygni profiles to full emission. These characteristics are often observed together in the relatively rare LBV class of stars, of which only $\approx$20 are known in the Galaxy. The key to the new classification is the fact that we compute a new distance and extinction that yields a luminosity significantly in excess of those for post-AGB PPNe, for which the initial masses are <8 M_Sun. Assuming single star evolution, we estimate an initial mass of $\approx$40 M_Sun.