Modeling the Observations of GRB 180720B: from Radio to Sub-TeV Gamma-Rays

Fraija, N.; Dichiara, S.; Pedreira, A. C. Caligula do E. S.; Galván-Gaméz, A.; Becerra, R. L.; Montalvo, A.; Montero, J.; Kamenetskaia, B. Betancourt; Zhang, Bin-Bin

doi:10.3847/1538-4357/ab3e4b

Cited by 53 publications

(38 citation statements)

References 60 publications

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“…The value of the initial bulk Lorentz factor inferred during the deceleration phase is similar to those reported by other burst detected by Fermi-LAT (Veres & Mészáros 2012). Since GRB 160509A exhibited one of the most energetic photons reported by Fermi-LAT in the second GRB catalog, it is expected that the value of the bulk Lorentz factor lies in the range of the brightest LAT-detected bursts (500Γ1000; Abdo et al 2009a;Ackermann 2010;Ackermann et al 2011;Ackermann 2013;Ackermann et al 2014;Fraija et al 2019bFraija et al , 2019c, as found in this work.…”

Section: The Bulk Lorentz Factorssupporting

confidence: 88%

GRB Fermi-LAT Afterglows: Explaining Flares, Breaks, and Energetic Photons

Fraija

Laskar²,

Dichiara

et al. 2020

ApJ

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The Fermi-LAT collaboration presented the second gamma-ray burst (GRB) catalog covering its first 10 years of operations. A significant fraction of afterglow-phase light curves in this catalog cannot be explained by the closure relations of the standard synchrotron forward-shock model, suggesting that there could be an important contribution from another process. In view of the above, we derive the synchrotron self-Compton (SSC) light curves from the reverse shock in the thick-and thin-shell regime for a uniform-density medium. We show that this emission could explain the GeV flares exhibited in some LAT light curves. Additionally, we demonstrate that the passage of the forward shock synchrotron cooling break through the LAT band from jets expanding in a uniformdensity environment may be responsible for the late time (≈10 2 s) steepening of LAT GRB afterglow light curves. As a particular case, we model the LAT light curve of GRB 160509A that exhibited a GeV flare together with a break in the long-lasting emission, and also two very high energy photons with energies of 51.9 and 41.5 GeV observed 76.5 and 242 s after the onset of the burst, respectively. Constraining the microphysical parameters and the circumburst density from the afterglow observations, we show that the GeV flare is consistent with an SSC reverse-shock model, the break in the long-lasting emission with the passage of the synchrotron cooling break through the Fermi-LAT band, and the very energetic photons with SSC emission from the forward shock, when the outflow carries a significant magnetic field (R B ;30) and it decelerates in a uniform-density medium with a very low density ( =-+ -n 4.554 10 cm 1.121 1.128 43 ).Unified Astronomy Thesaurus concepts: Gamma-ray bursts (629); Radiative processes (2055); Magnetic fields (994); Non-thermal radiation sources (1119); Interstellar medium (847)

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Section: The Bulk Lorentz Factorssupporting

confidence: 88%

GRB Fermi-LAT Afterglows: Explaining Flares, Breaks, and Energetic Photons

Fraija

Laskar²,

Dichiara

et al. 2020

ApJ

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“…The BAT light curve exhibited a multi-peaked structure with a duration of T 90 = 150 s [50]. Promptly, GRB 180720B was followed up by X-ray Telescope (XRT) and the Ultra-Violet/Optical Telescope (UVOT), by Fermi GMB and LAT [52,53], by Konus-Wind [54], by CALET Gamma-ray Monitor [55] and several orbiting and ground instruments in optical and radio bands [56]. The host galaxy of GRB 180720B was located to have a redshift of z = 0.654 [57].…”

Section: Grb 180720bmentioning

confidence: 99%

Search for very-high-energy photons from Gamma-ray bursts with HAWC

Fraija¹,

González²

2019

Proceedings of 36th International Cosmic Ray Conference — PoS(ICRC2019)

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Detections of very-high-energy (VHE; > 100 GeV) photons from Gamma-ray bursts (GRBs) can provide fundamental information on the involved radiative processes, physical composition of the ejecta and acceleration processes. The High Altitude Water Cherenkov (HAWC) gamma-ray observatory is the best gamma-ray instrument to study transient phenomena over a long period of time from 100 GeV to 100 TeV. Its large field of view and duty cycle (> 95%) allow it to search blindly for sources of GRBs and to follow up on external alerts from satellite instruments, such as Fermi and Swift, searching for their VHE counterpart. We present results from the ongoing GRB monitoring program and VHE upper limits of the latest interesting low-redshift and/or powerful bursts in HAWC's field of view: GRB 170206A, GRB 170817A, GRB 180720B and GRB 190114C.

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“…; Abdalla et al 2019) telescopes from high-luminosity bursts GRB 180720B and GRB 190114C, respectively. The high-energy and VHE photons detected by the Fermi Large Area Telescope (LAT), H.E.S.S., and MAGIC beyond the synchrotron limit were interpreted in the SSC forward-shock (FS) scenario (Fraija et al 2019c(Fraija et al , 2019aZhang 2019). On the other hand, llGRBs, characterized by being less energetic and having opening angles 30°, are not natural candidates to emit VHE photons.…”

Section: Introductionmentioning

confidence: 99%

On the Origin of the Multi-GeV Photons from the Closest Burst with Intermediate Luminosity: GRB 190829A

Fraija

Vereš

Beniamini

et al. 2021

ApJ

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Very high energy (VHE) emission is usually interpreted in the synchrotron self-Compton scenario and expected from the low-redshift and high-luminosity gamma-ray bursts (GRBs), such as GRB 180720B and GRB 190114C. Recently, the H.E.S.S. telescopes reported VHE emission from one of the closest bursts, GRB 190829A, which was associated with the supernova 2019oyw. In this paper, we present a temporal and spectral analysis from optical bands to the Fermi-LAT energy range over multiple observational periods beginning after the trigger time and extending for almost 3 months. We show that the X-ray and optical observations are consistent with synchrotron forward-shock emission evolving between the characteristic and cooling spectral breaks during the early and late afterglow in a uniform-density medium. Modeling the light curves together with the spectral energy distribution, we show that the outflow expanded with an initial bulk Lorentz factor of Γ ∼ 30, which is high for low-luminosity GRBs and low for high-luminosity GRBs. The values of the initial bulk Lorentz factor and the isotropic-equivalent energy suggest that GRB 190829A is an intermediate-luminosity burst; consequently, it becomes the first burst of this class to be detected in the VHE gamma-ray band by an imaging atmospheric Cherenkov telescope and, in turn, the first event to not be simultaneously observed by the Fermi-LAT instrument. Analyzing the intermediateluminosity bursts with z  0.2, such as GRB 130702A, we show that bursts with intermediate luminosities are potential candidates to be detected in VHEs.

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Modeling the Observations of GRB 180720B: from Radio to Sub-TeV Gamma-Rays

Cited by 53 publications

References 60 publications

GRB Fermi-LAT Afterglows: Explaining Flares, Breaks, and Energetic Photons

GRB Fermi-LAT Afterglows: Explaining Flares, Breaks, and Energetic Photons

Search for very-high-energy photons from Gamma-ray bursts with HAWC

On the Origin of the Multi-GeV Photons from the Closest Burst with Intermediate Luminosity: GRB 190829A

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