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Title: Phenomenology of reverse-shock emission in the optical afterglows of gamma-ray bursts

We use a parent sample of 118 gamma-ray burst (GRB) afterglows, with known redshift and host galaxy extinction, to separate afterglows with and without signatures of dominant reverse-shock (RS) emission and to determine which physical conditions lead to a prominent reverse-shock emission. We identify 10 GRBs with reverse-shock signatures: 990123, 021004, 021211, 060908, 061126, 080319B, 081007, 090102, 090424, and 130427A. By modeling their optical afterglows with reverse- and forward-shock analytic light curves and using Monte Carlo simulations, we estimate the parameter space of the physical quantities describing the ejecta and circumburst medium. We find that physical properties cover a wide parameter space and do not seem to cluster around any preferential values. Comparing the rest-frame optical, X-ray, and high-energy properties of the larger sample of non-RS-dominated GRBs, we show that the early-time (<1 ks) optical spectral luminosity, X-ray afterglow luminosity, and γ-ray energy output of our reverse-shock dominated sample do not differ significantly from the general population at early times. However, the GRBs with dominant reverse-shock emission have fainter than average optical forward-shock emission at late times (>10 ks). We find that GRBs with an identifiable reverse-shock component show a high magnetization parameter R {sub B} = ε{sub B,r}/ε{sub B,f}more » ∼ 2-10{sup 4}. Our results are in agreement with the mildly magnetized baryonic jet model of GRBs.« less
Authors:
; ;  [1] ; ; ; ;  [2] ;  [3] ;  [4]
  1. Faculty of Mathematics and Physics, University of Ljubljana, Jadranska ulica 19, SI-1000 Ljubljana (Slovenia)
  2. Astrophysics Research Institute, Liverpool John Moores University, Liverpool, L3 5RF (United Kingdom)
  3. Physics Departments, University of Ferrara, via Saragat 1, I-44122, Ferrara (Italy)
  4. INAF Osservatorio Astronomico di Brera, via E. Bianchi 46, I-23807 Merate (Italy)
Publication Date:
OSTI Identifier:
22357130
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 785; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AFTERGLOW; COMPUTERIZED SIMULATION; COSMIC GAMMA BURSTS; EMISSION; GALAXIES; JET MODEL; LUMINOSITY; MAGNETIZATION; MONTE CARLO METHOD; RED SHIFT; SPACE; VISIBLE RADIATION; X RADIATION