Photometric and spectroscopic study of the burst-like brightening of two Gaia-alerted young stellar objects

Zsófia Nagy*, Péter Ábrahám, Ágnes Kóspál, Sunkyung Park, Michał Siwak, Fernando Cruz-Sáenz de Miera, Eleonora Fiorellino, David García-Álvarez, Zsófia Marianna Szabó, Simone Antoniucci, Teresa Giannini, Alessio Giunta, Levente Kriskovics, Mária Kun, Gábor Marton, Attila Moór, Brunella Nisini, Andras Pál, László Szabados, Paweł ZielińskiŁukasz Wyrzykowski

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)
1 Downloads (Pure)


Young stars show variability on different time-scales from hours to decades, with a range of amplitudes. We studied two young stars, which triggered the Gaia Science Alerts system due to brightenings on a time-scale of a year. Gaia20bwa brightened by about half a magnitude, whereas Gaia20fgx brightened by about two and half magnitudes. We analysed the Gaia light curves, additional photometry, and spectra taken with the Telescopio Nazionale Galileo and the Gran Telescopio Canarias. Several emission lines were detected towards Gaia20bwa, including hydrogen lines from H α to H δ, Pa β, Br γ, and lines of Ca ii, O i, and Na i. The H α and Br γ lines were detected towards Gaia20fgx in emission in its bright state, with additional CO lines in absorption, and the Pa β line with an inverse P Cygni profile during its fading. Based on the Br γ lines, the accretion rate was (2.4-3.1) x 10-8M⊙ yr−1 for Gaia20bwa and (4.5-6.6) x 10-8M⊙ yr−1 for Gaia20fgx during their bright state. The accretion rate of Gaia20fgx dropped by almost a factor of 10 on a time-scale of half a year. The accretion parameters of both stars were found to be similar to those of classical T Tauri stars, lower than those of young eruptive stars. However, the amplitude and time-scale of these brightenings place these stars to a region of the parameter space, which is rarely populated by young stars. This suggests a new class of young stars, which produce outbursts on a time-scale similar to young eruptive stars, but with smaller amplitudes.
Original languageEnglish
Pages (from-to)1774-1787
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Early online date12 Jul 2022
Publication statusPublished - 1 Sept 2022


  • Stars: pre-main sequence
  • Stars: variables: T Tauri, Herbig Ae/Be


Dive into the research topics of 'Photometric and spectroscopic study of the burst-like brightening of two Gaia-alerted young stellar objects'. Together they form a unique fingerprint.

Cite this