Gaia20bdk – New FU Ori-type star in the Sh 2-301 star-forming region

¹ Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences, MTA Centre of Excellence, Konkoly-Thege Miklós út 15-17, 1121 Budapest, Hungary
² Mt. Suhora Astronomical Observatory, University of the National Education Commission, ul. Podchorążych 2, 30-084 Kraków, Poland
³ Institute of Physics and Astronomy, ELTE Eötvös Loránd University, Pázmány Péter sétány 1/A, H-1117 Budapest, Hungary
⁴ Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
⁵ Department of Astrophysics, Türkenschanzstraße 17, 1180 Vienna, Austria
⁶ Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Toruń, ul. Grudziądzka 5, PL-87-100 Toruń, Poland
⁷ Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
⁸ South African Astronomical Observatory, PO Box 9 Observatory, 7935 Cape Town, South Africa
⁹ Department of Physics, University of Johannesburg, PO Box 524 Auckland Park 2006, South Africa
¹⁰ Department of Physics, University of the Free State, PO Box 339 Bloemfontein 9300, South Africa
¹¹ Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
¹² INAF-Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy
¹³ Instituto de Astrofísica de Canarias, IAC, Vía Láctea s/n, 38205 La Laguna (S.C.Tenerife), Spain
¹⁴ Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna (S.C.Tenerife), Spain
¹⁵ Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, UT3-PS, OMP, CNRS, 9 av. du Colonel-Roche, 31028 Toulouse Cedex 4, France
¹⁶ Scottish Universities Physics Alliance (SUPA), School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK
¹⁷ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
¹⁸ Centre for Astrophysics, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
¹⁹ Astronomical Observatory, Jagiellonian University, ul. Orla 171, PL-30-244 Kraków, Poland

^⋆ Corresponding author; michal.siwak@csfk.org

Received: 11 June 2024
Accepted: 16 December 2024

Abstract

Context. We analyse multi-colour photometric and spectroscopic observations of the young stellar object (YSO) Gaia20bdk.

Aims. We aim to investigate the exact nature of the eruptive phenomenon that the star has been undergoing since 2018.

Methods. We used public-domain archival photometry to characterise the quiescent phase and to establish the major physical parameters of the progenitor. We used our own optical and infrared (IR) photometry and spectroscopy, along with data from the public domain, to study the outburst.

Results. Gaia20bdk is a member of the Sharpless 2-301 star-forming region, at a distance of 3.3 kpc. The progenitor is a rather massive 2.7 ± 0.5 M_⊙, G7-type Class I young star, with an effective temperature of 5300₋₃₀₀⁺⁵⁰⁰ K and bolometric luminosity of 11 ± 2 L_⊙. The optical and IR photometric and spectroscopic data obtained during the outburst reveal a variety of signatures commonly found in classical FU Ori-type stars (FUors). Our disc modelling gives a bolometric luminosity of 100 − 200 L_⊙ and mass accretion rate of 1 − 2 × 10⁻⁵ M_⊙ yr⁻¹, also confirming the object’s FUor classification. Further monitoring is necessary to track the light changes, accretion rate, and spectral variations, as well as to understand the mechanisms behind the disc flickering.