A Strong Limit on the Very-high-energy Emission from GRB 150323A

Journal Article · Tue Apr 10 00:00:00 EDT 2018 · The Astrophysical Journal (Online)

DOI:https://doi.org/10.3847/1538-4357/aab371· OSTI ID:1544054

Abeysekara, A. U. ^[1]; Archer, A. ^[2]; Benbow, W.  ^[3]; Bird, R.  ^[4]; Brose, R. ^[5]; Buchovecky, M. ^[4]; Bugaev, V. ^[2]; Connolly, M. P. ^[6]; Cui, W.  ^[7]; Errando, M.  ^[2]; Falcone, A.; Feng, Q. ; Finley, J. P. ; Flinders, A.; Fortson, L.; Furniss, A. ; Gillanders, G. H. ; Hütten, M.; Hanna, D. ; Hervet, O. ; Holder, J.; Hughes, G.; Humensky, T. B.; Johnson, C. A. ; Kaaret, P. ; Kar, P.; Kelley-Hoskins, N.; Kertzman, M.; Kieda, D. ; Krause, M. ; Krennrich, F.; Lang, M. J. ; Lin, T. T. Y.; Maier, G. ; McArthur, S.; Moriarty, P.; Mukherjee, R. ; O’Brien, S.; Ong, R. A.; Park, N.; Perkins, J. S. ; Petrashyk, A.; Pohl, M. ; Popkow, A. ; Pueschel, E. ; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T. ; Roache, E.; Rulten, C.; Sadeh, I.; Santander, M.; Sembroski, G. H.; Shahinyan, K. ; Tyler, J.; Wakely, S. P.; Weiner, O. M.; Weinstein, A.; Wells, R. M.; Wilcox, P.; Wilhelm, A.; Williams, D. A. ; Zitzer, B.; Vurm, Indrek ; Beloborodov, Andrei

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1. Univ. of Utah, Salt Lake City, UT (United States)
2. Washington Univ., St. Louis, MO (United States)
3. Harvard Smithsonian Ctr for Astophysics, Amado, Arizona (United States)
4. Univ. of California, Los Angeles, CA (United States)
5. Univ. of Potsdam (Germany)
6. National Univ. of Ireland Galway (Ireland)
7. Purdue Univ., West Lafayette, IN (United States)

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 ~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 ~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 ~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 ≳ 3 × 10¹¹ 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.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
• Sponsoring Organization: USDOE
• Contributing Organization: VERITAS Collaboration
• OSTI ID: 1544054
• Journal Information: The Astrophysical Journal (Online), Vol. 857, Issue 1; ISSN 1538-4357
• Publisher: Institute of Physics (IOP)
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
Astronomy & Astrophysics
gamma rays
gamma-ray burst