Gaia 18dvy: a new FUor in the Cygnus OB3 association

TL;DR

Gaia 18dvy is a newly identified FU Orionis-type star in Cygnus OB3, exhibiting a significant outburst with spectral and photometric features characteristic of young eruptive stars, and detailed modeling reveals its circumstellar disk properties and accretion behavior.

Contribution

This paper reports the discovery and detailed analysis of Gaia 18dvy as a new FUor, including photometric, spectroscopic, and disk modeling insights that enhance understanding of FUor outbursts.

Findings

Gaia 18dvy experienced a >4 mag outburst in 2018-2019.

Spectroscopic features confirm FUor classification.

Accretion rate peaked at 6.9 x 10^{-6} M_sun/yr in mid-2019.

Abstract

We present optical-infrared photometric and spectroscopic observations of Gaia18dvy, located in the Cygnus OB3 association at a distance of 1.88 kpc. The object was noted by the Gaia alerts system when its lightcurve exhibited a $\gtrsim$4 mag rise in 2018-2019. The brightening was also observable at mid-infared wavelengths. The infrared colors of Gaia18dvy became bluer as the outburst progressed. Its optical and near-infrared spectroscopic characteristics in the outburst phase are consistent with those of bona fide FU Orionis-type young eruptive stars. The progenitor of the outburst is probably a low-mass K-type star with an optical extinction of $\sim$3 mag. A radiative transfer modeling of the circumstellar structure, based on the quiescent spectral energy distribution, indicates a disk with a mass of $4{\times}10^{-3}\,M_{\odot}$. Our simple accretion disk modeling implies that the accretion rate had been exponentially increasing for more than 3 years until mid-2019, when it reached a peak value of $6.9 \times 10^{-6}\,M_{\odot}$yr$^{-1}$. In many respects, Gaia18dvy is similar to the FU Ori-type object HBC 722