HAPPY BIRTHDAY SWIFT: ULTRA-LONG GRB 141121A AND ITS BROADBAND AFTERGLOW

• Published in: The Astrophysical journal Vol. 812; no. 2; pp. 122 - 134
• Main Authors: Cucchiara, A., Veres, P., Corsi, A., Cenko, S. B., Perley, D. A., Lien, A., Marshall, F. E., 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., González, J., Román-Zúñiga, C. G., Gehrels, N., Moseley, H.
• Format: Journal Article
• Language: English
• Published: United States The American Astronomical Society 20.10.2015
• Subjects: AFTERGLOW; Afterglows; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Broadband; Bursting; COSMIC GAMMA BURSTS; COSMIC RADIO SOURCES; DIAGRAMS; Explosions; Gamma ray bursts; gamma-ray burst: general; gamma-ray burst: individual (GRB 141121A); Radio; RED SHIFT; VISIBLE RADIATION; X-rays
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.1088/0004-637X/812/2/122

ABSTRACT We present our extensive observational campaign on the Swift-discovered GRB 141121A, almost 10 years after its launch. Our observations cover radio through X-rays and extend 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 Eγ,iso = 8.0 × 1052 erg. Due to the long prompt duration, GRB 141121A falls into the recently discovered class of ultra-long GRBs (UL-GRBs). Peculiar features of this burst are (1) a flat early-time optical light curve and (2) a radio-to-X-ray rebrightening around three 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 days) 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 gamma-ray burst explosions, and future missions (like SVOM, XTiDE, or ISS-Lobster) will provide many more of such objects.