Compton echoes from nearby gamma-ray bursts

Beniamini, Paz; Giannios, Dimitrios; Younes, George; Horst, A. J. van der; Kouveliotou, C.

doi:10.1093/mnras/sty616

Cited by 6 publications

(6 citation statements)

References 54 publications

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“…For such higher velocities, more recent GRBs are more relevant for radio observations, and potentially lower n values can also be probed. It will also be interesting to consider the detectability of long-term X-ray emission from the same interaction between the dynamical/wind ejecta and the circum-merger medium (Beniamini et al 2018). The discovery of radio remnants would confirm the BNS origin of a GRB, would provide valuable information on the BNS merger rate, the structure of the relativistic outflows, the properties of kilonova ejecta, and the density of the circum-merger medium.…”

Section: Resultsmentioning

confidence: 99%

Radio forensics could unmask nearby off-axis gamma-ray bursts

Bartos

Lee

Corsi

et al. 2019

Monthly Notices of the Royal Astronomical Society

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The multi-messenger observation of gamma-ray burst (GRB) 170817A from the nearby binary neutron-star merger GW170817 demonstrated that low-energy γ-ray emission can be observed at relatively large angles from GRB jet axes. If such structured emission is typical, then the currently known sample of short GRBs with no distance measurements may contain multiple nearby off-axis events whose delayed afterglows could have gone undetected. These nearby neutron star mergers may produce telltale radio flares peaking years after the prompt GRB emission that could still be observable. Here, we show that several short GRBs observed by the Burst Alert Telescope (BAT) on the Neil Gehrels Swift satellite, with no identified afterglow and no distance measurement, could potentially be associated with radio flares detectable by sensitive cm-wavelength radio facilities such as the Karl G. Jansky Very Large Array. We also examine optical follow-up observations that have been carried out for these events, and find that a nearby GW170817-like kilonova is ruled out for only a third of them.

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Section: Resultsmentioning

confidence: 99%

Radio forensics could unmask nearby off-axis gamma-ray bursts

Bartos

Lee

Corsi

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…An alternative explanation for the excess in X-rays (as compared to the radio) observed in GW170817 might be the possibility of a Compton echo of the X-rays from the prompt emission of GRB 170817A, scattering off surrounding dust (Beniamini et al 2018). Given currently large uncertainties in the X-ray result, hereafter we focus on the constraints that the lack of a radio excess set on kilonova ejecta models.…”

Section: Discussionmentioning

confidence: 99%

Continued Radio Observations of GW170817 3.5 yr Post-merger

Balasubramanian

Corsi

Mooley

et al. 2021

ApJL

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We present new radio observations of the binary neutron star merger GW170817 carried out with the Karl G. Jansky Very large Array (VLA) more than 3 yr after the merger. Our combined data set is derived by coadding more than ≈32 hr of VLA time on-source, and as such provides the deepest combined observation (rms sensitivity ≈0.99 μJy) of the GW170817 field obtained to date at 3 GHz. We find no evidence for a late-time radio rebrightening at a mean epoch of t ≈ 1200 days since merger, in contrast to a ≈2.1σ excess observed at X-ray wavelengths at the same mean epoch. Our measurements agree with expectations from the post-peak decay of the radio afterglow of the GW170817 structured jet. Using these results, we constrain the parameter space of models that predict a late-time radio rebrightening possibly arising from the high-velocity tail of the GW170817 kilonova ejecta, which would dominate the radio and X-ray emission years after the merger (once the structured jet afterglow fades below detection level). Our results point to a steep energy-speed distribution of the kilonova ejecta (with energy-velocity power-law index α  5). We suggest possible implications of our radio analysis, when combined with the recent tentative evidence for a late-time rebrightening in the X-rays, and highlight the need for continued radio-to-X-ray monitoring to test different scenarios. Unified Astronomy Thesaurus concepts: Radio continuum emission (1340); Radio transient sources (2008); X-ray transient sources (1852)

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“…These results may also be used to inform understanding of future VIRGO / LIGO detected GRBs. clearly GRBs associated with GW detections could allow us to observe orders of magnitude fainter signals coming from GRBs, which would otherwise be undetected for cosmological events (see also Beniamini et al 2018,…”

Section: Discussionmentioning

confidence: 99%

Observational constraints on the structure of gamma-ray burst jets

Beniamini

Nakar

2018

Monthly Notices of the Royal Astronomical Society

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Motivated by GW170817 we examine constraints that observations put on the angular structure of long gamma-ray burst (GRB) jets. First, the relatively narrow observed distribution of E X /E γ (the isotropic equivalent early X-ray afterglow to prompt γ-ray energy ratio) implies that at any angle that γ-rays are emitted the Lorentz factor must be high. Specifically, the Lorentz factor of γ-ray emitting material cannot drop rapidly with angle, and must be Γ(θ) ∼ > 50 even if there are angles for which the gamma-ray received energy is lower by three orders of magnitude compared to the jet core. Second, jets with an angular structure of the γray emission that over-produce events with a γ-ray luminosity below the peak of the observed luminosity function are ruled-out. This eliminates models in which the γ-ray energy angular distribution isn't sufficiently steep and the Lorentz factor distribution isn't sufficiently shallow. Finally, models with a steep structure (e.g. Gaussian) which are detected away from the jet core generate afterglow light-curves that were never observed. We conclude that even if the jet kinetic energy distribution drops continuously with latitude, efficient γ-ray emission seems to be restricted to material with Γ ∼ > 50 and is most likely confined to a narrow region around the core. While our study is confined to long GRBs, where the observed sample is larger and more complete, there are indications that similar conclusions may be applicable also to short GRBs. We discuss the possible implications to the γ-rays observed in GRB 170817A.

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Compton echoes from nearby gamma-ray bursts

Cited by 6 publications

References 54 publications

Radio forensics could unmask nearby off-axis gamma-ray bursts

Radio forensics could unmask nearby off-axis gamma-ray bursts

Continued Radio Observations of GW170817 3.5 yr Post-merger

Observational constraints on the structure of gamma-ray burst jets

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