Happy Birthday Swift: Ultra-long GRB141121A and its broad-band Afterglow

• Published in: arXiv.org 2015-10
• Main Authors: Cucchiara, A, Veres, P, Corsi, A, Cenko, S B, Perley, D A, A Lien F E Marshall, Pagani, C, Toy, V L, Capone, J I, Frail, D A, Horesh, A, Modjaz, M, Butler, N R, Littlejohns, O M, Watson, A M, Kutyrev, A S, Lee, W H, Richer, M G, Klein, C R, Fox, O D, Prochaska, J X, Bloom, J S, Troja, E, Ramirez-Ruiz, E, de Diego, J A, Georgiev, L, Gonzalez, J, Roman-Zuniga, C G, Gehrels, N, Moseley, H
• Format: Article
• Language: English
• Subjects: Explosions; Gamma ray bursts; Gamma rays; Light curve; Missions; Radio; Red shift; X-rays
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1510.00996

We present our extensive observational campaign on the Swift-discovered GRB141121A, al- most ten years after its launch. Our observations covers radio through X-rays, and extends for more than 30 days after discovery. The prompt phase of GRB 141121A lasted 1410 s and, at the derived redshift of z = 1.469, the isotropic energy is E{\gamma},iso = 8.0x10^52 erg. Due to the long prompt duration, GRB141121A falls into the recently discovered class of UL-GRBs. Peculiar features of this burst are a flat early-time optical light curve and a radio-to-X-ray rebrightening around 3 days after the burst. The latter is followed by a steep optical-to-X-ray decay and a much shallower radio fading. We analyze GRB 141121A in the context of the standard forward-reverse shock (FS,RS) scenario and we disentangle the FS and RS contributions. Finally, we comment on the puzzling early-time (t ~3 d) behavior of GRB 141121A, and suggest that its interpretation may require a two-component jet model. Overall, our analysis confirms that the class of UL-GRBs represents our best opportunity to firmly establish the prominent emission mechanisms in action during powerful GRB explosions, and future missions (like SVOM, XTiDE, or ISS-Lobster) will provide many more of such objects.