The Gaia alerted fading of the FUor-type star Gaia21elv

Nagy, Zsófia and Park, Sunkyung and Ábrahám, Péter and Kóspál, Ágnes and Fernando, Cruz-Saenz de Miera and Kun, Mária and Siwak, Michal and Szilágyi, Máté and Fiorellino, Elenonora and Marton, Gábor and Szabados, László (2023) The Gaia alerted fading of the FUor-type star Gaia21elv. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 524 (3). pp. 3344-3356. ISSN 0035-8711

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Abstract

FU Orionis objects (FUors) are eruptive young stars, which exhibit outbursts that last from decades to a century. Due to the duration of their outbursts, and to the fact that only about two dozens of such sources are known, information on the end of their outbursts is limited. Here we analyse follow-up photometry and spectroscopy of Gaia21elv, a young stellar object, which had a several decades long outburst. It was reported as a Gaia science alert due to its recent fading by more than a magnitude. To study the fading of the source and look for signatures characteristic of FUors, we have obtained follow-up near infrared (NIR) spectra using Gemini South/IGRINS, and both optical and NIR spectra using VLT/X-SHOOTER. The spectra at both epochs show typical FUor signatures, such as a triangular shaped H-band continuum, absorption-line dominated spectrum, and P Cygni profiles. In addition to the typical FUor signatures, [O I], [Fe II], and [S ii] were detected, suggesting the presence of a jet or disk wind. Fitting the spectral energy distributions with an accretion disc model suggests a decrease of the accretion rate between the brightest and faintest states. The rapid fading of the source in 2021 was most likely dominated by an increase of circumstellar extinction. The spectroscopy presented here confirms that Gaia21elv is a classical FUor, the third such object discovered among theGaiascience alerts.

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