Multiwavelength study of the luminous GRB 210619B observed with Fermi and ASIM. Issue 3 (12th December 2022)

• Record Type: Journal Article
• Authors: Caballero-García, M D; Gupta, Rahul; Pandey, S B; Oates, S R; Marisaldi, M; Ramsli, A; Hu, Y-D; Castro-Tirado, A J; Sánchez-Ramírez, R; Connell, P H; Christiansen, F; Ror, A Kumar; Aryan, A; Bai, J-M; Castro-Tirado, M A; Fan, Y-F; Fernández-García, E; Kumar, A; Lindanger, A; Mezentsev, A; Navarro-González, J; Neubert, T; Østgaard, N; Pérez-García, I; Reglero, V; Sarria, D; Sun, T R; Xiong, D-R; Yang, J; Yang, Y-H; Zhang, B-B;
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 519:Issue 3(2023)
• Page Start: 3201
• Page End: 3226
• Publication Date: 2022-12-12
• Subjects: methods: data analysis -- gamma-ray burst: general -- gamma-ray burst: individual: GRB 210619B; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac3629
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We report on detailed multiwavelength observations and analysis of the very bright and long GRB 210619B, detected by the Atmosphere-Space Interactions Monitor installed on the International Space Station and the Gamma-ray Burst Monitor (GBM) on-board the Fermi mission. Our main goal is to understand the radiation mechanisms and jet composition of GRB 210619B. With a measured redshift of z = 1.937, we find that GRB 210619B falls within the 10 most luminous bursts observed by Fermi so far. The energy-resolved prompt emission light curve of GRB 210619B exhibits an extremely bright hard emission pulse followed by softer/longer emission pulses. The low-energy photon index (αpt ) values obtained using the time-resolved spectral analysis of the burst suggest a transition between the thermal (during harder pulse) to non-thermal (during softer pulse) outflow. We examine the correlation between spectral parameters and find that both peak energy and αpt exhibit the flux tracking pattern. The late time broad-band photometric data set can be explained within the framework of the external forward shock model with ν m < ν c < ν x (where ν m, ν c, and ν x are the synchrotron peak, cooling-break, and X-ray frequencies, respectively) spectral regime supporting a rarely observed hard electron energy index ( p < 2). We find moderate values of host extinction of E ( B − V ) = 0.14 ± 0.01 mag for the small magellanic cloud extinction law. In addition, we also report late-time optical observations with the 10.4 m Gran Telescopio de Canarias placing deep upper limits for the host galaxy ( z = 1.937), favouring a faint, dwarf host for the burst.