2019ApJ...884L...7H

The hot massive luminous blue variables (LBVs) represent an important evolutionary phase of massive stars. Here, we report the discovery of a new LBV-LAMOST J0037+4016 in the distant outskirt of the Andromeda galaxy. It is located in the southwestern corner (a possible faint spiral arm) of M31 with an unexpectedly large projection distance of ∼22 kpc from the center. The optical light curve shows a 1.2 mag variation in V band and its outburst and quiescence phases both last over several years. The observed spectra indicate an A-type supergiant at an epoch close to the outburst phase and a hot B-type supergiant with weak [Fe II] emission lines at an epoch of much dimmer brightness. The near-infrared color-color diagram further shows that it follows the distribution of Galactic and M31 LBVs rather than B[e] supergiants. All the existing data strongly show that LAMOST J0037+4016 is an LBV. By spectral energy distribution fitting, we find it has a luminosity (4.42 ± 1.64) x 10⁵ L_☉ and an initial mass ∼30 M_☉, indicating its nature of a less luminosity class of LBV.