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Abeysekara, AU,Archer, A,Benbow, W,Bird, R,Brose, R,Buchovecky, M,Bugaev, V,Connolly, MP,Cui, W,Errando, M,Falcone, A,Feng, Q,Finley, JP,Flinders, A,Fortson, L,Furniss, A,Gillanders, GH,Hutten, M,Hanna, D,Hervet, O,Holder, J,Hughes, G,Humensky, TB,Johnson, CA,Kaaret, P,Kar, P,Kelley-Hoskins, N,Kertzman, M,Kieda, D,Krause, M,Krennrich, F,Lang, MJ,Lin, TTY,Maier, G,McArthur, S,Moriarty, P,Mukherjee, R,O'Brien, S,Ong, RA,Park, N,Perkins, JS,Petrashyk, A,Pohl, M,Popkow, A,Pueschel, E,Quinn, J,Ragan, K,Reynolds, PT,Richards, GT,Roache, E,Rulten, C,Sadeh, I,Santander, M,Sembroski, GH,Shahinyan, K,Tyler, J,Wakely, SP,Weiner, OM,Weinstein, A,Wells, RM,Wilcox, P,Wilhelm, A,Williams, DA,Zitzer, B,Vurm, I,Beloborodov, A,VERITAS Collaboration
2018
April
Astrophysical Journal
A Strong Limit on the Very-high-energy Emission from GRB 150323A
Published
Optional Fields
gamma rays: general gamma-ray burst: general gamma-ray burst: individual (GRB 150323A) GAMMA-RAY BURSTS EXTRAGALACTIC BACKGROUND LIGHT RADIATION EVOLUTION REDSHIFT 130427A
857
On 2015 March 23, the Very Energetic Radiation Imaging Telescope Array System (VERITAS) responded to a Swift-Burst Alert Telescope (BAT) detection of a gamma-ray burst, with observations beginning 270 s after the onset of BAT emission, and only 135 s after the main BAT emission peak. No statistically significant signal is detected above 140 GeV. The VERITAS upper limit on the fluence in a 40-minute integration corresponds to about 1% of the prompt fluence. Our limit is particularly significant because the very-high-energy (VHE) observation started only similar to 2 minutes after the prompt emission peaked, and Fermi-Large Area Telescope observations of numerous other bursts have revealed that the high-energy emission is typically delayed relative to the prompt radiation and lasts significantly longer. Also, the proximity of GRB 150323A (z = 0.593) limits the attenuation by the extragalactic background light to similar to 50% at 100-200 GeV. We conclude that GRB 150323A had an intrinsically very weak high-energy afterglow, or that the GeV spectrum had a turnover below similar to 100 GeV. If the GRB exploded into the stellar wind of a massive progenitor, the VHE non-detection constrains the wind density parameter to be A greater than or similar to 3 x 10(11) g . cm(-1), consistent with a standard Wolf-Rayet progenitor. Alternatively, the VHE emission from the blast wave would be weak in a very tenuous medium such as the interstellar medium, which therefore cannot be ruled out as the environment of GRB 150323A.
10.3847/1538-4357/aab371
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