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.
Siwak, M., Hillenbrand, L.A., Kospal, A., Abraham, P., Giannini, T., De, K., et al. (2023). Gaia21bty: An EXor light curve exhibiting a FUor spectrum. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 524(4), 5548-5565 [10.1093/mnras/stad2135].
Gaia21bty: An EXor light curve exhibiting a FUor spectrum
Fiorellino E.
;
2023
Abstract
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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
