GRB 160625B: Evidence for a Gaussian-shaped Jet

Cunningham, Virginia; Cenko, S. Bradley; Ryan, Geoffrey; Vogel, S. N.; Corsi, A.; Cucchiara, Antonino; Fruchter, A.; Horesh, A.; Kangas, T.; Kocevski, D.; Perley, D.; Racusin, J. L.

doi:10.3847/1538-4357/abc2cd

Cited by 21 publications

(15 citation statements)

References 92 publications

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“…10 3 -. This efficiency is much lower than the typical estimates for other GRBs in the literature (Fan & Piran 2006;Zhang et al 2007;Wygoda et al 2016;Beniamini et al 2016), even though we note that a recently published study (Cunningham et al 2020) of GRB 160625B also found a low efficiency when leaving the χ e parameter free to vary. The prompt emission efficiency we find is compatible with that expected in the case of internal shocks within the jet (Rees & Meszaros 1994) with a moderate Lorentz factor contrast (Kumar 1999).…”

Section: = -+contrasting

confidence: 67%

Multiwavelength View of the Close-by GRB 190829A Sheds Light on Gamma-Ray Burst Physics

Salafia

Ravasio

Yang

et al. 2022

ApJL

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We monitored the position of the close-by (about 370 Mpc) gamma-ray burst GRB 190829A, which originated from a massive star collapse, through very long baseline interferometry (VLBI) observations with the European VLBI Network and the Very Long Baseline Array, carrying out a total of nine observations between 9 and 117 days after the gamma-ray burst at 5 and 15 GHz, with a typical resolution of a few milliarcseconds. From a state-of-the art analysis of these data, we obtained valuable limits on the source size and expansion rate. The limits are in agreement with the size evolution entailed by a detailed modeling of the multiwavelength light curves with a forward-plus-reverse shock model, which agrees with the observations across almost 18 orders of magnitude in frequency (including the HESS data at TeV photon energies) and more than 4 orders of magnitude in time. Thanks to the multiwavelength, high-cadence coverage of the afterglow, inherent degeneracies in the afterglow model are broken to a large extent, allowing us to capture some unique physical insights; we find a low prompt emission efficiency of ≲10−3, a low fraction of relativistic electrons in the forward shock downstream χ e < 13% (90% credible level), and a rapid decay of the magnetic field in the reverse shock downstream after the shock crossing. While our model assumes an on-axis jet, our VLBI astrometry is not sufficiently tight as to exclude any off-axis viewing angle, but we can exclude the line of sight to have been more than ∼2° away from the border of the gamma-ray-producing region based on compactness arguments.

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Section: = -+contrasting

confidence: 67%

Multiwavelength View of the Close-by GRB 190829A Sheds Light on Gamma-Ray Burst Physics

Salafia

Ravasio

Yang

et al. 2022

ApJL

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“…Descriptions of the MCMC implementation may be found in Refs. 176,177 and the nested sampling implementation in Ref. 20 .…”

Section: Modelingmentioning

confidence: 99%

Discovery and confirmation of the shortest gamma-ray burst from a collapsar

et al. 2021

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Gamma-ray bursts (GRBs) are among the brightest and most energetic events in the universe.The duration and hardness distribution of GRBs has two clusters 1 , now understood to reflect (at least) two different progenitors 2 . Short-hard GRBs (SGRBs; T 90 <2 s) arise from compact binary mergers, while long-soft GRBs (LGRBs; T 90 >2 s) have been attributed to the collapse of peculiar massive stars (collapsars) 3 . The discovery of SN 1998bw/GRB 980425 4 marked the first association of a LGRB with a collapsar and AT 2017gfo 5 /GRB 170817A/GW170817 6 marked the first association of a SGRB with a binary neutron star merger, producing also gravitational wave (GW). Here, we present the discovery of ZTF20abwysqy (AT2020scz), a fast-fading optical transient in the Fermi Satellite and the InterPlanetary Network (IPN) localization regions of GRB 200826A; X-ray and radio emission further confirm that this is the afterglow. Follow-up imaging (at rest-frame 16.5 days) reveals excess emission above the afterglow that cannot be explained as an underlying kilonova (KN), but is consistent with being the supernova (SN). Despite the GRB duration being short (rest-frame T 90 of 0.65 s), our panchromatic follow-up data confirms a collapsar origin. GRB 200826A is the shortestLGRB found with an associated collapsar; it appears to sit on the brink between a successful and a failed collapsar. Our discovery is consistent with the hypothesis that most collapsars fail to produce ultra-relativistic jets.

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“…We perform a comparison of the models applied in this work using their WAIC scores, described in Section 3.1 (see also Troja et al 2020;Cunningham et al 2020). We note that the WAIC analysis is not applicable to individual modes within the models, and that we only compare the overall model fits presented in Table A1.…”

Section: Model Comparisonmentioning

confidence: 99%

OUP accepted manuscript

2021

MNRAS

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We present a detailed multiwavelength analysis of two short gamma-ray bursts (sGRBs) detected by the Neil Gehrels Swift Observatory: GRB 160624A at z = 0.483 and GRB 200522A at z = 0.554. These sGRBs demonstrate very different properties in their observed emission and environment. GRB 160624A is associated with a late-type galaxy with an old stellar population (≈3 Gyr) and moderate ongoing star formation (≈1 M yr −1 ). Hubble and Gemini limits on optical/near-infrared emission from GRB 160624A are among the most stringent for sGRBs, leading to tight constraints on the allowed kilonova properties. In particular, we rule out any kilonova brighter than AT2017gfo, disfavouring large masses of wind ejecta ( 0.03 M ). In contrast, observations of GRB 200522A uncovered a luminous (L F125W ≈ 10 42 erg s −1 at 2.3 d) and red (r − H ≈ 1.3 mag) counterpart. The red colour can be explained either by bright kilonova emission powered by the radioactive decay of a large amount of wind ejecta (0.03 M M 0.1 M ) or moderate extinction, E(B − V) ≈ 0.1−0.2 mag, along the line of sight. The location of this sGRB in the inner regions of a young (≈0.1 Gyr) star-forming (≈2−6 M yr −1 ) galaxy and the limited sampling of its counterpart do not allow us to rule out dust effects as contributing, at least in part, to the red colour.

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GRB 160625B: Evidence for a Gaussian-shaped Jet

Cited by 21 publications

References 92 publications

Multiwavelength View of the Close-by GRB 190829A Sheds Light on Gamma-Ray Burst Physics

Multiwavelength View of the Close-by GRB 190829A Sheds Light on Gamma-Ray Burst Physics

Discovery and confirmation of the shortest gamma-ray burst from a collapsar

OUP accepted manuscript

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