The Gaia alerted fading of the FUor-type star Gaia21elv

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, [OI], [FeII], and [SII] 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 the Gaia science alerts.Comment: Accepted to MNRA

Report on the activities of the PKiM and PFN in period 2021–2022

The Polish Fireball Network (PFN), has been undergoing continuous development. Since then, several large grants have been obtained, which were at least partly used for modernization purposes. In recent years, two more grants have been obtained, which allowed for the expansion and modification of the existing PFN infrastructure. In 2021, the PFN76 Kozienice was modernized, but also the PFN14 Zielona Góra station was reactivated and the new PFN77 Suhora station was launched in 2022. Thanks to these improvements, the tracking of meteoroids entering the Earth Atmosphere above Poland became more accurate, which facilitates the search for meteorites and increases the chances of finding new fresh meteorites in Poland. On the night of May 10, 2021, PFN stations registered an exceptionally slow bolide. The phenomenon named PF100521 Wykrot appeared over central Poland in the Mazowieckie Voivodeship at 21:32 UT and calculations showed that some meteorites may have fallen. This phenomenon was used to conduct a series of analyzes to show how observational uncertainties affect the final results. Two variants of the results are presented in this work