Publication details

Gaia21bty: An EXor light curve exhibiting a FUor spectrum

Authors

SIWAK Michal HILLENBRAND Lynne A KOSPAL Agnes ABRAHAM Peter GIANNINI Teresa DE Kishalay MOOR Attila SZILAGYI Mate JANÍK Jan KOEN Chris PARK Sunkyung NAGY Zsofia CRUZ-SAENZ de Miera Fernando FIORELLINO Eleonora MARTON Gabor KUN Maria LUCAS Philip W UDALSKI Andrzej SZABO Zsofia Marianna

Year of publication 2023
Type Article in Periodical
Magazine / Source Monthly Notices of the Royal Astronomical Society
MU Faculty or unit

Faculty of Science

Citation
Web
Doi http://dx.doi.org/10.1093/mnras/stad2135
Keywords accretion; accretion discs; stars: formation; stars: pre-main-sequence; stars: variables: T Tauri; Herbig Ae/Be
Description Gaia21bty, a pre-main-sequence star that previously had shown aperiodic dips in its light curve, underwent a considerable Delta G approximate to 2.9 mag brightening that occurred over a few months between 2020 October and 2021 February. The Gaia light curve shows that the star remained near maximum brightness for about 4-6 months, and then started slowly fading over the next 2 yr, with at least three superimposed similar to 1 mag sudden rebrightening events. Whereas the amplitude and duration of the maximum is typical for EX Lupi-type stars, optical and near-infrared spectra obtained at the maximum are dominated by features which are typical for FU Ori-type stars (FUors). Modelling of the accretion disc at the maximum indicates that the disc bolometric luminosity is 43 L-circle dot and the mass accretion rate is 2.5 x 10(-5) M-circle dot yr(-1), which are typical values for FUors even considering the large uncertainty in the distance (1.7(-0.4)(+0.8) kpc). Further monitoring is necessary to understand the cause of the quick brightness decline, the rebrightening, and the other post-outburst light changes, as our multicolour photometric data suggest that they could be caused by a long and discontinuous obscuration event. We speculate that the outburst might have induced large-scale inhomogeneous dust condensations in the line of sight leading to such phenomena, whilst the FUor outburst continues behind the opaque screen.

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