The long-active afterglow of GRB 210204A: detection of the most delayed flares in a gamma-ray burst

Creators: Kumar, Harsh; Gupta, Rahul; Saraogi, Divita; Ahumada, Tomás; Andreoni, Igor; Anupama, G. C.; Aryan, Amar; Barway, Sudhanshu; Bhalerao, Varun; Chandra, Poonam; Coughlin, Michael W.; Dimple, [None]; Dutta, Anirban; Ghosh, Ankur; Ho, Anna Y. Q.; Kool, E. C.; Kumar, Amit; Medford, Michael S.; Misra, Kuntal; Pandey, Shashi B.; Perley, Daniel A.; Riddle, Reed; Ror, Amit Kumar; Setiadi, Jason M.; Yao, Yuhan

Abstract

We present results from extensive broadband follow-up of GRB 210204A over the period of 30 d. We detect optical flares in the afterglow at 7.6 × 10⁵ s and 1.1 × 10⁶ s after the burst: the most delayed flaring ever detected in a GRB afterglow. At the source redshift of 0.876, the rest-frame delay is 5.8 × 10⁵ s (6.71 d). We investigate possible causes for this flaring and conclude that the most likely cause is a refreshed shock in the jet. The prompt emission of the GRB is within the range of typical long bursts: it shows three disjoint emission episodes, which all follow the typical GRB correlations. This suggests that GRB 210204A might not have any special properties that caused late-time flaring, and the lack of such detections for other afterglows might be resulting from the paucity of late-time observations. Systematic late-time follow-up of a larger sample of GRBs can shed more light on such afterglow behaviour. Further analysis of the GRB 210204A shows that the late-time bump in the light curve is highly unlikely due to underlying SNe at redshift (z) = 0.876 and is more likely due to the late-time flaring activity. The cause of this variability is not clearly quantifiable due to the lack of multiband data at late-time constraints by bad weather conditions. The flare of GRB 210204A is the latest flare detected to date.

Additional Information

© 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model). Received: 14 March 2022. Revision received: 11 April 2022. Accepted: 11 April 2022. Published: 18 April 2022. This work made use of data from the GROWTH-India Telescope (GIT) set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB). It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/. This work is partially based on data obtained with the 2m Himalayan Chandra Telescope of the Indian Astronomical Observatory (IAO), operated by the Indian Institute of Astrophysics (IIA), an autonomous Institute under Department of Science and Technology, Government of India. We thank the staff at IAO and at IIA's Centre for Research and Education in Science and Technology (CREST) for their support. We thank Jesper Sollerman for his useful suggestions that helped in improving quality of this work. This research is partially based on observations (proposal number DOT-2021-C1-P62 and DOT-2021-C1-P19) obtained at the 3.6m Devasthal Optical Telescope (DOT), which is a National Facility run and managed by Aryabhatta Research Institute of Observational Sciences ( ARIES), an autonomous Institute under Department of Science and Technology, Government of India. PC acknowledges support of the Department of Atomic Energy, Government of India, under project no. 12-R&D-TFR-5.02-0700. We thank the staff of the GMRT that made these observations possible. The GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. HK thanks the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining Grant #1829740, the Brinson Foundation, and the Moore Foundation; his participation in the program has benefited this work. RG, AA, VB, KM, and SBP acknowledge BRICS grant DST/IMRCD/BRICS /PilotCall1 /ProFCheap/2017(G) for the financial support. RG, VB, and SBP also acknowledge the financial support of Indian Space Research Organisation (ISRO) under AstroSat archival Data utilization program (DS_2B-13013(2)/1/2021-Sec.2). RG is also thankful to Dr P. Veres for sharing data files presented in Fig. 4. This publication uses data from the AstroSat mission of the ISRO\, archived at the Indian Space Science Data Centre (ISSDC). This research has made use of data obtained from Himalayan Chandra Telescope under proposal number HCT-2021-C1-P02. We thank both HCT stuff for undertaking the observations. HCT observations were carried out under the ToO program. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is funded by the National Aeronautics and Space Administration and operated by the California Institute of Technology. This research has made use of data obtained from the High Energy Astrophysics Science Archive Research Center (HEASARC) and the Leicester Database and Archive Service (LEDAS), provided by NASA's Goddard Space Flight Center and the Department of Physics and Astronomy, Leicester University, UK, respectively. This research has made use of NASA's Astrophysics Data System. This research has made use of data and/or services provided by the International Astronomical Union's Minor Planet Center. This research has made use of the VizieR catalogue access tool, CDS, Strasbourg, France (DOI : 10.26093/cds/vizier). The original description of the VizieR service was published in 2000, A&AS 143, 23. DATA AVAILABILITY. All data used in this article have been included in a tabular format within the article.

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