A New Candidate Luminous Blue Variable

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_⊙), 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 H I, He I, Fe II, Fe [II], Mg II, 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 ≈20 are known in the Galaxy. The key to the new classification is the fact that we compute a new distance and extinction that yield a luminosity significantly in excess of those for post-AGB PPNe, for which the initial masses are <8 M_⊙. Assuming single star evolution, we estimate an initial mass of ≈40 M_⊙.