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arXiv · 2605.19413

Gaia21bja: pre-main sequence star with quasi-periodic bursts

Ádám Mátéfy·Zsófia Nagy·Ágnes Kóspál·Péter Ábrahám·Fernando Cruz-Sáenz de Miera·Máté Szilágyi·Michał Siwak·Eleonora Fiorellino·Teresa Giannini·Mária Kun·László Szabados·Gábor Marton·Patrik Németh·Brunella Nisini·Zsófia Marianna Szabó
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Abstract

Gaia21bja is a Gaia alerted young stellar object (YSO) that exhibits at least seven quasi-peridoic brightenings over a 20 year-long light curve with durations of 1.5-2 years and amplitudes up to $\sim$1.7 mag in the Gaia $G$-band. We analyze its optical and near-infrared photometry and spectra taken using the IRTF and VLT in its faint and bright states in order to characterize its physical properties. A Lomb-Scargle periodogram analysis results in a most significant period of $916\pm77$ days. We derived the stellar parameters as $R_\star= 0.78 \pm 0.04~R_\odot$, $L_\star=(4.5\pm0.3) \times 10^{-2}~L_\odot$, and $M_\star= 0.16 \pm 0.03~M_\odot$. The spectra taken during the burst are dominated by emission lines and are similar to those of EX Lupi-type eruptive young stars (EXors). We found that the accretion luminosity and mass accretion rate increased by a factor of $5.5-6$ during the burst. Based on this, and the quasi-periodic bursts, we suggest that Gaia21bja is an eruptive YSO, and is most consistent with the `Periodic' category of the Outbursting YSOs Catalogue.

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Ádám Mátéfy, Zsófia Nagy, Ágnes Kóspál, Péter Ábrahám, Fernando Cruz-Sáenz de Miera, Máté Szilágyi, Michał Siwak, Eleonora Fiorellino, Teresa Giannini, Mária Kun, László Szabados, Gábor Marton, Patrik Németh, Brunella Nisini, Zsófia Marianna Szabó. 2026-05-19. Gaia21bja: pre-main sequence star with quasi-periodic bursts. https://doi.org/10.3847/1538-4357%2Fae6a8d

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