Details

Autor(en) / Beteiligte

• Tanvir, N. R.
• Laskar, T.
• Levan, A. J.
• Perley, D. A.
• Zabl, J.
• Fynbo, J. P. U.
• Rhoads, J.
• Cenko, S. B.
• Greiner, J.
• Wiersema, K.
• Hjorth, J.
• Cucchiara, A.
• Berger, E.
• Bremer, M. N.
• Cano, Z.
• Cobb, B. E.
• Covino, S.
• D'Elia, V.
• Fong, W.
• Fruchter, A. S.
• Goldoni, P.
• Hammer, F.
• Heintz, K. E.
• Jakobsson, P.
• Kann, D. A.
• Kaper, L.
• Klose, S.
• Knust, F.
• Krühler, T.
• Malesani, D.
• Misra, K.
• Guelbenzu, A. Nicuesa
• Pugliese, G.
• Sánchez-Ramírez, R.
• Schulze, S.
• Stanway, E. R.
• Ugarte Postigo, A. de
• Watson, D.
• Wijers, R. A. M. J.
• Xu, D.

Titel

The Properties of GRB 120923A at a Spectroscopic Redshift of z 7.8

Ist Teil von

• The Astrophysical journal, 2018-10, Vol.865 (2), p.107

Ort / Verlag

Philadelphia: The American Astronomical Society

Erscheinungsjahr

2018

Quelle

EZB Free E-Journals

Beschreibungen/Notizen

• Gamma-ray bursts (GRBs) are powerful probes of early stars and galaxies, during and potentially even before the era of reionization. Although the number of GRBs identified at z 6 remains small, they provide a unique window on typical star-forming galaxies at that time, and thus are complementary to deep field observations. We report the identification of the optical drop-out afterglow of Swift GRB 120923A in near-infrared Gemini-North imaging, and derive a redshift of from Very Large Telescope/X-shooter spectroscopy. At this redshift the peak 15-150 keV luminosity of the burst was 3.2 × 1052 erg s−1, and in this sense it was a rather typical long-duration GRB in terms of rest frame luminosity. This burst was close to the Swift/Burst Alert Telescope detection threshold, and the X-ray and near-infrared afterglow were also faint. We present ground- and space-based follow-up observations spanning from X-ray to radio, and find that a standard external shock model with a constant-density circumburst environment of density n 4 × 10−2 cm−3 gives a good fit to the data. The near-infrared light curve exhibits a sharp break at t 3.4 days in the observer frame which, if interpreted as being due to a jet, corresponds to an opening angle of . The beaming-corrected γ-ray energy is then erg, while the beaming-corrected kinetic energy is lower, erg, suggesting that GRB 120923A was a comparatively low kinetic energy event. We discuss the implications of this event for our understanding of the high-redshift population of GRBs and their identification.