10.4 m GTC observations of the nearby VHE-detected GRB 190829A/SN 2019oyw^⋆

¹ Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
e-mail: huyoudong072@hotmail.com
² Universidad de Granada, Facultad de Ciencias Campus Fuentenueva s/n, 18071 Granada, Spain
³ Departamento de Ingeniería de Sistemas y Automática, Escuela de Ingenierías, Universidad de Málaga, C. Dr. Ortiz Ramos s/n, 29071 Málaga, Spain
⁴ Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263002, India
⁵ School of Studies in Physics and Astrophysics, Pandit Ravishankar Shukla University, Chattisgarh 492 010, India
⁶ Department of Physics, Deen Dayal Upadhyaya Gorakhpur University, Gorakhpur 273009, India
⁷ Special Astrophysical Observatory of Russian Academy of Sciences, Nizhniy Arkhyz, Russia
⁸ Crimean Astrophysical Observatory, Russian Academy of Sciences, Nauchnyi 298409, Russia
⁹ Departamento de Álgebra, Geometría y Topología, Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos s/n, 29071 Málaga, Spain
¹⁰ Astronomical Institute, Academy of Sciences of the Czech Republic, Boční II 1401, 141 00 Prague, Czech Republic
¹¹ Mykolaiv National University, Astronomical Observatory, Mykolaiv, Ukraine
¹² Research Institute, Mykolaiv Astronomical Observatory, Mykolaiv, Ukraine
¹³ School of Physics, O’Brien Centre for Science North, University College Dublin, Belfield, Dublin 4, Ireland
¹⁴ School of Physics and Astronomy, University of Birmingham, B15 2TT Birmingham, UK
¹⁵ INAF, Astrophysics and Space Science Observatory, Via P. Gobetti 101, 40129 Bologna, Italy
¹⁶ INAF, Istituto di Astrofisica e Planetologia Spaziali, Via Fosso del Cavaliere 100, 00133 Rome, Italy
¹⁷ School of Astronomy and Space Science, Nanjing University, Nanjing 210093, PR China
¹⁸ Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing, PR China

Received: 6 September 2020
Accepted: 15 November 2020

Abstract

Aims. Gamma-ray burst (GRB) 190829A (z = 0.0785) was detected by Fermi and Swift and also at very high energy (VHE) by the High-Energy Stereoscopic System (H.E.S.S.) telescopes. The prompt emission displayed two emission episodes separated by a quiescent gap of ∼40 s. We present the 10.4 m Gran Telescopio Canarias (GTC) observations of the afterglow of GRB 190829A and its underlying supernova. We also compare GRB 190829A to GRB 180728A, a GRB with similar behaviour, and discuss the implications on underlying physical mechanisms producing these two GRBs.

Methods. We present multi-band photometric data along with spectroscopic follow-up observations taken with the 10.4 m GTC telescope. Together with the data from the prompt emission, the 10.4 m GTC data are used to understand the emission mechanisms and possible progenitor.

Results. A detailed analysis of the multi-band observations of the afterglow requires the cooling frequency to pass between the optical and X-ray bands at early epochs. The afterglow then transitions to the underlying supernova (SN) 2019oyw, which dominates later on.

Conclusions. Although the prompt emission temporal properties of GRB 190829A and GRB 180728A are similar, the two pulses are different in the spectral domain. We find that SN 2019oyw associated with GRB 190829A is powered by Ni decay and is a Type Ic-BL SN. The spectroscopic and photometric properties of this SN are consistent with those observed for SN 1998bw, but evolved earlier.