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 ( \sim 12 M _ { \odot } ) , of the Herbig AeBe type .
It is located at 1.68 \pm 0.07 kpc distance , within the Cyg OB2 star-forming region , and it is highly reddened ( E _ { B - V } =1.80 \pm 0.05 ) by interstellar extinction .
In quiescence , the spectral energy distribution is dominated by the \sim 20,000 K photospheric emission from the central B1II star , and at \lambda \geq 6 \mu m by emission from circumstellar warm dust ( T \leq 400 ^ { \circ } 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 \sim 7500 K and a luminosity L \geq 860 L _ { \odot } , corresponding to a mass accretion rate \geq 1.1 \times 10 ^ { -5 } M _ { \odot } yr ^ { -1 } .
Spectroscopic signature of possible bipolar jets ( at - 700 and + 700 km s ^ { -1 } ) 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 .