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Probing into emission mechanisms of GRB 190530A using time-resolved spectra and polarization studies: synchrotron origin?

Gupta, Rahul and Gupta, S. and Chattopadhyay, T. and Lipunov, V. and Castro-Tirado, A. J. and Vinkó, József and Pál, András and Sárneczky, Krisztián and Kriskovics, Levente and Szakáts, Róbert (2022) Probing into emission mechanisms of GRB 190530A using time-resolved spectra and polarization studies: synchrotron origin? MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 511 (2). pp. 1694-1713. ISSN 0035-8711

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Abstract

Multipulsed GRB 190530A, detected by the Gamma-ray Burst Monitor (GBM) and Large Area Telescope onboard Fermi, is the sixth most fluent GBM burst detected so far. This paper presents the timing, spectral, and polarimetric analysis of the prompt emission observed using AstroSat and Fermi to provide insight into the prompt emission radiation mechanisms. The time-integrated spectrum shows conclusive proof of two breaks due to peak energy and a second lower energy break. Time-integrated (55.43 +/- 21.30 per cent) as well as time-resolved polarization measurements, made by the Cadmium Zinc Telluride Imager (CZTI) onboard AstroSat, show a hint of high degree of polarization. The presence of a hint of high degree of polarization and the values of low energy spectral index (alpha(pt)) do not run over the synchrotron limit for the first two pulses, supporting the synchrotron origin in an ordered magnetic field. However, during the third pulse, alpha(pt) exceeds the synchrotron line of death in few bins, and a thermal signature along with the synchrotron component in the time-resolved spectra is observed. Furthermore, we also report the earliest optical observations constraining afterglow polarization using the MASTER (P < 1.3 per cent) and the redshift measurement (z = 0.9386) obtained with the 10.4 m GTC (Gran Telescopio Canarias) telescopes. The broad-band afterglow can be described with a forward shock model for an ISM (interstellar medium)-like medium with a wide jet opening angle. We determine a circumburst density of n(0) similar to 7.41, kinetic energy E-K similar to 7.24 x 10(54) erg, and radiated gamma-ray energy E-gamma,E-iso similar to 6.05 x 10(54) erg.

Item Type: Article
Uncontrolled Keywords: gamma-ray burst: general; gamma-ray burst: individual: GRB 190530A; polarization; methods: data analysis; telescopes;
Subjects: Q Science / természettudomány > QB Astronomy, Astrophysics / csillagászat, asztrofizika
SWORD Depositor: MTMT SWORD
Depositing User: MTMT SWORD
Date Deposited: 27 Sep 2022 12:08
Last Modified: 27 Sep 2022 12:08
URI: http://real.mtak.hu/id/eprint/150059

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