GRB 170817A: a short GRB seen off-axis

Abstract

The angular distribution of GRB jets is not yet clear. The observed luminosity of GRB 170817A is the lowest among all known short GRBs, which is best explained by the fact that our line of sight is outside of the jet opening angle, ${\theta }_{obs}$ $>$ ${\theta }_j$, where ${\theta }_{obs}$ is the angle between our line of sight and jet axis. Inferred by gravitational wave observations, as well as radio and X-ray afterglow modeling of GRB 170817A, it is likely that ${\theta }_{obs}$ $\sim$ 20${}^{\circ }$ -- 28${}^{\circ }$. In this work, we quantitatively consider two scenarios of angular energy distribution of GRB ejecta: top-hat jet, and structured jet with a power law index $s$. For top-hat jet model, we get a large ${\theta }_j$ (e.g., ${\theta }_j$$>$$10^{\circ }$), a rather high local (i.e., z$<$0.01) short GRB rate $\sim$8--15$\times 10^3$ $Gp{c}^{-3}$$y{r}^{-1}$ (estimated 90$\sim$1850 $Gp{c}^{-3}$$y{r}^{-1}$ in Fong et al. 2015) and an extremely high $E_{peak,0}$(on-axis,rest-frame)$>$7.5$\times 10^4$keV($\sim$500keV for typical short GRB). For structured jet model, we use ${\theta }_{obs}$ to give limits on $s$ and ${\theta }_j$ for a typical on-axis luminosity short GRB (e.g., $10^{49}$ erg s${}^{-1}$$\sim$$10^{51}$ erg s${}^{-1}$), and a low on-axis luminosity case (e.g., $10^{49}$ erg s${}^{-1}$) gives more reasonable values of $s$. A structured jet model is more feasible for GRB 170817A than a top-hat jet model, due to the rather high local short GRB rate and the extremely high on-axis $E_{peak,0}$ almost rules out the top-hat jet model. GRB 170817A is likely a low on-axis luminosity GRB ($10^{49}$ erg s${}^{-1}$) with a structured jet.

arXiv comment10 Pages, 3 Figures, 1 Table, RAA, in press

References in corpus (44)

• Multi-messenger Observations of a Binary Neutron Star Merger
• GW151226: Observation of Gravitational Waves from a 22-Solar-Mass Binary Black Hole Coalescence
• Discovery of the peculiar supernova 1998bw in the error box of GRB980425
• The Fermi Gamma-Ray Burst Monitor
• An Ordinary Short Gamma-Ray Burst with Extraordinary Implications: Fermi-GBM Detection of GRB 170817A
• Gamma-Ray Bursts and the Fireball Model
• Transient Events from Neutron Star Mergers
• Swope Supernova Survey 2017a (SSS17a), the Optical Counterpart to a Gravitational Wave Source
• Beaming in Gamma-Ray Bursts: Evidence for a Standard Energy Reservoir
• Short-Duration Gamma-Ray Bursts
• Short-Hard Gamma-Ray Bursts
• A "kilonova" associated with short-duration gamma-ray burst 130603B
• Binary neutron-star mergers: a review of Einstein's richest laboratory
• A Decade of Short-duration Gamma-ray Burst Broad-band Afterglows: Energetics, Circumburst Densities, and Jet Opening Angles
• Afterglow lightcurves, viewing angle and the jet structure of gamma-ray bursts
• An enigmatic long-lasting gamma-ray burst not accompanied by a bright supernova
• The Fermi GBM Gamma-Ray Burst Spectral Catalog: Four Years Of Data
• The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. V. Rising X-ray Emission from an Off-Axis Jet
• Low Luminosity Gamma-Ray Bursts as a Unique Population: Luminosity Function, Local Rate, and Beaming Factor
• A possible Macronova in the late afterglow of the `long-short' burst GRB 060614
• The 2nd Fermi GBM Gamma-Ray Burst Catalog: The First Four Years
• The 3rd Fermi GBM Gamma-Ray Burst Catalog: The First Six Years
• Relativistic outflows from remnants of compact object mergers and their viability for short gamma-ray bursts
• The Macronova in GRB 050709 and the GRB/macronova connection
• Implications for the Origin of GRB 070201 from LIGO Observations
• The lightcurve of the macronova associated with the long-short burst GRB 060614
• A unified picture for low-luminosity and long gamma-ray bursts based on the extended progenitor of llgrb 060218/SN 2006aj
• General relativistic simulations of compact binary mergers as engines of short gamma-ray bursts
• Quasi-universal Gaussian jets: a unified picture for gamma-ray bursts and X-ray flashes
• INTEGRAL upper limits on gamma-ray emission associated with the gravitational wave event GW150914
• Off-axis short GRBs from structured jets as counterparts to GW events
• Rebrightening of XRF 030723: further evidence for a two-component jet in gamma-ray burst
• A complete sample of bright Swift short Gamma-Ray Bursts
• Progenitor models of the electromagnetic transient associated with the short GRB 130603B
• The Properties of Short gamma-ray burst Jets Triggered by neutron star mergers
• Modeling Supernova-like Explosions Associated with Gamma-ray Bursts with Short Durations
• Revisiting the Long/Soft-Short/Hard Classification of Gamma-Ray Bursts in the Fermi Era
• Structure of Gamma-Ray Burst jets: intrinsic versus apparent properties
• GRB Afterglows from Anisotropic Jets
• Luminosity function and jet structure of Gamma Ray Bursts
• Implications For The Origin Of GRB 051103 From LIGO Observations
• Light curves and spectra from off-axis gamma-ray bursts
• A new analysis of the short-duration, hard-spectrum GRB 051103, a possible extragalactic SGR giant flare
• GRB 070201: A possible Soft Gamma Ray Repeater in M31

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• Late time afterglow observations reveal a collimated relativistic jet in the ejecta of the binary neutron star merger GW170817
• Interpreting GRB170817A as a giant flare from a jet-less double neutron-star merger
• Scattered Short Gamma-Ray Bursts as Electromagnetic Counterparts to Gravitational Waves and Implications of GW170817 and GRB 170817A
• A magnetically driven origin for the low luminosity GRB 170817A associated with GW170817
• How Do Nuclear Isomers Influence the Gamma-Ray Bursts in Binary Neutron Star Mergers?