Rahul Gupta, S Gupta, T Chattopadhyay, V Lipunov, A J Castro-Tirado, D Bhattacharya, S B Pandey, S R Oates, Amit Kumar, Y-D Hu, A F Valeev, P Yu Minaev, H Kumar, J Vinko, Dimple Dimple, V Sharma, A Aryan, A Castellón, A Gabovich, A Moskvitin, A Ordasi, A Pál, A Pozanenko, B-B Zhang, B Kumar, D Svinkin, D Saraogi, D Vlasenko, E Fernández-García, E Gorbovskoy, G C Anupama, K Misra, K Sárneczky, L Kriskovics, M Á Castro-Tirado, M D Caballero-García, N Tiurina, P Balanutsa, R R Lopez, R Sánchez-Ramírez, R Szakáts, S Belkin, S Guziy, S Iyyani, S N Tiwari, Santosh V Vadawale, T Sun, V Bhalerao, V Kornilov, V V Sokolov, Ministerio de Ciencia e Innovación (España), European Commission, National Natural Science Foundation of China, and National Key Research and Development Program (China)
Full list of authors: Gupta, Rahul; Gupta, S.; Chattopadhyay, T.; Lipunov, V.; Castro-Tirado, A. J.; Bhattacharya, D.; Pandey, S. B.; Oates, S. R.; Kumar, Amit; Hu, Y. -D.; Valeev, A. F.; Minaev, P. Yu; Kumar, H.; Vinko, J.; Dimple; Sharma, V.; Aryan, A.; Castellón, A.; Gabovich, A.; Moskvitin, A.; Ordasi, A.; Pál, A.; Pozanenko, A.; Zhang, B. -B.; Kumar, B.; Svinkin, D.; Saraogi, D.; Vlasenko, D.; Fernández-García, E.; Gorbovskoy, E.; Anupama, G. C.; Misra, K.; Sárneczky, K.; Kriskovics, L.; Castro-Tirado, M. Á.; Caballero-García, M. D.; Tiurina, N.; Balanutsa, P.; Lopez, R. R.; Sánchez-Ramírez, R.; Szakáts, R.; Belkin, S.; Guziy, S.; Iyyani, S.; Tiwari, S. N.; Vadawale, Santosh V.; Sun, T.; Bhalerao, V.; Kornilov, V.; Sokolov, V. V., 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 (αpt) 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, αpt 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 n0 ∼ 7.41, kinetic energy EK ∼ 7.24 × 1054 erg, and radiated gamma-ray energy Eγ,iso ∼ 6.05 × 1054 erg. © 2022 The Author(s)., RG, DB, SBP, KM, and VB acknowledge BRICS grant DST/IMRCD/BRICS/PilotCall1/ProFCheap/2017(G) for the financial support. This publication uses data from the AstroSat mission of the Indian Space Research Organisation (ISRO), archived at the Indian Space Science Data Centre (ISSDC). CZT-Imager is built by a consortium of institutes across India, including the Tata Institute of Fundamental Research (TIFR), Mumbai, the Vikram Sarabhai Space Centre, Thiruvananthapuram, ISRO Satellite Centre (ISAC), Bengaluru, Inter University Centre for Astronomy and Astro-physics, Pune, Physical Research Laboratory, Ahmedabad, and Space Application Centre, Ahmedabad. This research also has used data obtained through the HEASARC Online Service, provided by the NASA-GSFC, in support of NASA High Energy Astrophysics Programmes. This work is based on data from the OSN Public Archive at IAA (IAA-CSIC) and the CAHA Archive at CAB (INTA-CSIC). The MASTER equipment is supported by Lomonosov MSU Development Programme. VL and VK are supported by RFBR 19-29-11011 grant. The research group of JV is supported by the project ‘Transient Astrophysical Objects’ GINOP 2.3.2-15-2016-00033 of the National Research, Development and Innovation Office (NKFIH), Hungary, funded by the European Union. AA acknowledges funds and assistance provided by the Council of Scientific and Industrial Research (CSIR), India with file number 09/948(0003)/2020-EMR-I. AP, SB, and PM acknowledge a support of the RSCF grant 18-12-00378. The GROWTH India Telescope (GIT) is a 70 cm telescope with a 0.7 deg field of view, set up by the Indian Institute of Astrophysics and the Indian Institute of Technology Bombay with support from the Indo-US Science and Technology Forum (IUSSTF) and the Science and Engineering Research Board (SERB) of the Department of Science and Technology (DST), Government of India (https://sites.google.com/view/growthindia/). It is located at the IAO (Hanle), operated by the Indian Institute of Astrophysics (IIA). MCG acknowledges support from the Ramón y Cajal Fellowship RYC2019-026465-I. YDH acknowledges support under the additional funding from the RYC2019-026465-I. BBZ acknowledges support by the National Key Research and Development Programme of China (2018YFA0404204), the National Natural Science Foundation of China (grant numbers 11833003, U2038105, and 12121003), the science research grants from the China Manned Space Project with NO.CMS-CSST-2021-B11, and the Programme for Innovative Talents, Entrepreneur in Jiangsu. RSM acknowledges support under the CSIC-MURALES project with reference 20215AT009., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.