# The 2018 eruption and long term evolution of the new high-mass Herbig Ae/Be object Gaia-18azl = VES 263

## TL;DR

This study reveals VES 263 as a massive Herbig Ae/Be star experiencing a significant eruption in 2018-19, with detailed analysis of its evolution, accretion processes, and long-term photometric history, contributing new insights into high-mass pre-main sequence stellar behavior.

## Contribution

First detailed characterization of VES 263 as a high-mass Herbig Ae/Be star with a long-term photometric history and eruption analysis, expanding understanding of massive star evolution.

## Key findings

- VES 263 is a ~12 Msun Herbig Ae/Be star within Cyg OB2.
- The 2018-19 eruption was driven by increased accretion disk brightness.
- Spectroscopic evidence suggests bipolar jets during the eruption.

## Abstract

We have been monitoring, at high cadence, the photometric and spectroscopic evolution of VES 263 following the discovery in 2018 of a brightening labeled as event Gaia-18azl. VES 263 is so far a neglected emission-line object discovered in the 1960s on objective prism plates, tentatively classified as a semi-regular AGB cool giant by automated analysis of ASASSN lightcurves. We have discovered that VES 263 is a bonafide massive pre-Main Sequence object (~12 Msun), of the Herbig AeBe type. It is located at 1.68+/-0.07 kpc distance, within the Cyg OB2 star-forming region, and it is highly reddened (E(B-V)=1.80+/-0.05) by interstellar extinction. In quiescence, the spectral energy distribution is dominated by the 20,000 K photospheric emission from the central B1II star, and at wavelenghts >=6 micron by emission from circumstellar warm dust (Tdust up to 400 K). The 2018-19 eruption was caused by a marked brightening of the accretion disk around the B1II star as traced by the evolution with time of the integrated flux and the double-peaked profile of emission lines. At the peak of the eruption, the disk has a bulk temperature of ~7500 K and a luminosity L>=860 Lsun, corresponding to a mass accretion rate >=1.1x10(-5) Msun/yr. Spectroscopic signature of possible bipolar jets (at -700 and +700 km/s) of variable intensity are found. We have reconstructed from Harvard, Moscow and Sonneberg photographic plates the photometric history of VES 263 from 1896 to 1995, showing through 1953-1969 a state much brighter than current eruption.