Photometric and Spectroscopic Study of the EXor-like Eruptive Young Star Gaia19fct

Park, Sunkyung and Kóspál, Ágnes and Ábrahám, Péter and Cruz-Sáenz de Miera, Fernando and Fiorellino, Eleonora and Siwak, Michał and Nagy, Zsófia and Giannini, Teresa and Carini, Roberta and Szabó, Zsófia Marianna and Lee, Jeong-Eun and Lee, Jae-Joon and Vitali, Fabrizio and Kun, Mária and Cseh, Borbála and Krezinger, Máté and Kriskovics, Levente and Ordasi, András and Pál, András and Szakáts, Róbert and Vida, Krisztián and Vinkó, József (2022) Photometric and Spectroscopic Study of the EXor-like Eruptive Young Star Gaia19fct. ASTROPHYSICAL JOURNAL, 941 (2). p. 165. ISSN 0004-637X

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Abstract

Gaia19fct is one of the Gaia-alerted eruptive young stars that has undergone several brightening events. We conducted monitoring observations using multifilter optical and near-infrared photometry, as well as near-infrared spectroscopy, to understand the physical properties of Gaia19fct and investigate whether it fits into the historically defined two classes. We present the analyses of light curves, color variations, spectral lines, and CO modeling. The light curves show at least five brightening events since 2015, and the multifilter color evolutions are mostly gray. The gray evolution indicates that bursts are triggered by mechanisms other than extinction. Our near-infrared spectra exhibit both absorption and emission lines and show time variability throughout our observations. We found lower rotational velocity and lower temperature from the near-infrared atomic absorption lines than from the optical lines, suggesting that Gaia19fct has a Keplerian rotating disk. The CO overtone features show a superposition of absorption and emission components, which is unlike other young stellar objects. We modeled the CO lines, and the result suggests that the emission and absorption components are formed in different regions. We found that although Gaia19fct exhibits characteristics of both types of eruptive young stars, FU Orionis-type objects and EX Lupi-type objects, it shows more similarity with EXors in general.

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