Multi-wavelength study of the luminous GRB 210619B observed with Fermi and ASIM

Publication date: 
Main author: 
Caballero-García, M. D.
IAA authors: 
Caballero-García, M. D.;Hu, Y. -D.;Castro-Tirado, A. J.;Sánchez-Ramírez, R.;Castro-Tirado, M. A.;Fernández-García, E.;Pérez-García, I.;Sun, T. R.
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.
Monthly Notices of the Royal Astronomical Society
Publication type: 
We report on detailed multi-wavelength observations and analysis of the very bright and long GRB 210619B, detected by the Atmosphere-Space Interactions Monitor (ASIM) installed on the International Space Station (ISS) 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 indices (α<SUB>pt</SUB>) 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 α<SUB>pt</SUB> exhibit the flux tracking pattern. The late time broadband photometric dataset can be explained within the framework of the external forward shock model with ν<SUB>m</SUB> &lt;ν<SUB>c</SUB> &lt;ν<SUB>x</SUB> (where ν<SUB>m</SUB>, ν<SUB>c</SUB>, and ν<SUB>x</SUB> are the synchrotron peak, cooling-break, and X-ray frequencies, respectively) spectral regime supporting a rarely observed hard electron energy index (p &lt; 2). We find moderate values of host extinction of E(B-V) = 0.14 ± 0.01 mag for the Small Magellanic Cloud (SMC) extinction law. In addition, we also report late-time optical observations with the 10.4 m GTC placing deep upper limits for the host galaxy (z=1.937), favouring a faint, dwarf host for the burst.
ADS Bibcode: 
gamma-ray burst: general;gamma-ray burst: individual: GRB 210619B;methods: data analysis;Astrophysics - High Energy Astrophysical Phenomena