A New Luminous blue variable in the outskirt of the Andromeda Galaxy

TL;DR

This paper reports the discovery of a new luminous blue variable star in the outskirts of the Andromeda galaxy, characterized by significant brightness variation and spectral changes, expanding understanding of LBV distribution.

Contribution

The discovery of LAMOST J0037+4016 as a new LBV in M31's outskirts, with detailed spectral and photometric analysis, provides new insights into LBV properties and their spatial distribution.

Findings

LAMOST J0037+4016 shows 1.2 mag variability in V band.

Spectral data indicate transitions between A-type and B-type supergiant phases.

The star's luminosity and mass suggest it is a less luminous LBV.

Abstract

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 south-western corner (a possible faint spiral arm) of M31 with an unexpectedly large projection distance of $\sim$ 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 epoch close to the outburst phase and a hot B-type supergiant with weak [Fe II] emission lines at epoch of much dimmer brightness. The near-infrared color-color diagram further shows 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 ($4.42 \pm 1.64$)$\times 10^5$ $L_{\odot}$ and an initial mass $\sim 30$ $M_{\odot}$, indicating its nature of less luminosity class of LBV.