Young stellar objects (YSOs) are still accreting material from their disc via magnetic field lines. About half of them show photometric variations on daily-weekly timescales, with an amplitude of a few times 0.1 mag. Some YSOs show brightness variations on even longer time-scales: months, years, centuries. Eruptive YSOs show brightness variations with an amplitude of a few magnitudes and remain bright on longer timescales. These outbursts are caused by a sudden increase of the mass accretion rate by a few orders of magnitude. Eruptive YSOs are commonly divided into two main classes: EX Lupi-type stars (EXors) and FU Orionis-type stars (FUors). The former show brightenings of 2-4 mag, last for less than a year and are recurrent, the latter brighten by up to 5 magnitudes and last for several decades. So far the number of confirmed FUors is limited to no more than a dozen while the number of known EXors is limited to less than 25, including candidates.
The Gaia Photometric Science Alerts System, with its large sky coverage and approximately monthly cadence, provides an efficient tool to identify new eruptive YSOs. Based on the Gaia Science alerts, our group recently published the discovery of a new FUor (Gaia18dvy) and two EXors (Gaia20eae and Gaia19fct). Our latest result is a confirmation of a known YSO ? Gaia21elv - to be a bona fide Fuor. Gaia21elv is one of those few FUors, which may have ended its long-term outburst. Our follow-up observations include photometry using 1-m class telescopes, and spectroscopy using the Telescopio Nazionale Galileo, the Nordic Optical Telescope, the Liverpool Telescope, the New Technology Telescope, the Gran Telescopio Canarias, the Large Binocular Telescope, and the Very Large Telescope.
In our poster we present some of our latest results on follow-up observations of eruptive YSOs found from Gaia alerts.