학술논문
A Radio Flare in the Long-Lived Afterglow of the Distant Short GRB 210726A: Energy Injection or a Reverse Shock from Shell Collisions?
Document Type
Working Paper
Author
Schroeder, Genevieve; Rhodes, Lauren; Laskar, Tanmoy; Nugent, Anya; Escorial, Alicia Rouco; Rastinejad, Jillian C.; Fong, Wen-fai; van der Horst, Alexander J.; Veres, Péter; Alexander, Kate D.; Andersson, Alex; Berger, Edo; Blanchard, Peter K.; Chastain, Sarah; Christensen, Lise; Fender, Rob; Green, David A.; Groot, Paul; Heywood, Ian; Horesh, Assaf; Izzo, Luca; Kilpatrick, Charles D.; Körding, Elmar; Lien, Amy; Malesani, Daniele B.; McBride, Vanessa; Mooley, Kunal; Rowlinson, Antonia; Sears, Huei; Stappers, Ben; Tanvir, Nial; Vergani, Susanna D.; Wijers, Ralph A. M. J.; Williams-Baldwin, David; Woudt, Patrick
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Subject
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Abstract
We present the discovery of the radio afterglow of the short $\gamma$-ray burst (GRB) 210726A, localized to a galaxy at a photometric redshift of $z\sim 2.4$. While radio observations commenced $\lesssim 1~$day after the burst, no radio emission was detected until $\sim11$~days. The radio afterglow subsequently brightened by a factor of $\sim 3$ in the span of a week, followed by a rapid decay (a ``radio flare''). We find that a forward shock afterglow model cannot self-consistently describe the multi-wavelength X-ray and radio data, and underpredicts the flux of the radio flare by a factor of $\approx 5$. We find that the addition of substantial energy injection, which increases the isotropic kinetic energy of the burst by a factor of $\approx 4$, or a reverse shock from a shell collision are viable solutions to match the broad-band behavior. At $z\sim 2.4$, GRB\,210726A is among the highest redshift short GRBs discovered to date as well as the most luminous in radio and X-rays. Combining and comparing all previous radio afterglow observations of short GRBs, we find that the majority of published radio searches conclude by $\lesssim 10~$days after the burst, potentially missing these late rising, luminous radio afterglows.
Comment: 28 pages, 10 figures, submitted to ApJ
Comment: 28 pages, 10 figures, submitted to ApJ