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Galaxies
Special Issues
Gamma-Ray Bursts: Recent Theoretical Models and Observations
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Gamma-Ray Bursts: Recent Theoretical Models and Observations

A special issue of Galaxies (ISSN 2075-4434).

Deadline for manuscript submissions: closed (30 September 2016) | Viewed by 17888

Special Issue Editors

Dr. Ioannis Contopoulos

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Guest Editor
Research Center for Astronomy, Academy of Athens, Athens, Greece
Interests: magnetic fields; accretion; accretion disks; pulsars: general; MHD
Dr. Samantha Oates

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Guest Editor
Instituto de Astrofísica de Andalucía (IAA-CSIC), Granada, Spain
Interests: gamma-ray bursts

Special Issue Information

Dear Colleagues,

Gamma-ray bursts (GRBs) are cosmic flashes of gamma-rays, and consist some of the most energetic events ever detected. They are powerful beacons of the early Universe, and extreme physical laboratories. They are intrinsically linked to the lifecycle of stars and galaxies and can, therefore, provide complementary insights into their evolution. Multi-wavelength observations of these enigmatic events allow us to go deeper into their underlying physics, but 40 years after their discovery their origin remains enigmatic. A great amount of theoretical work has been invested in order to understand what are their central engine and their emission mechanism. Obviously, any discussion of potential GRB models leads us to search for their signatures in GRB observations. In the modern era of multi messenger astronomy from various space missions and ground observatories, the study of these events and their afterglows is likely to intensify as we try to piece together information from the full electromagnetic spectrum, gravitational waves, and neutrinos.

This Special Issue of Galaxies is mainly based on the contributions presented during Symposium 11 at the European Week of Astronomy and Space Science (4­–5 July, 2016, Athens, Greece) that has been organized with the aim to discuss the physics and observations of GRBs, bringing together a number of theorists and observers from the already sizeable GRB community in Europe and worldwide.

Dr. Ioannis Contopoulos
Dr. Samantha Oates
Guest Editors

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Published Papers (4 papers)

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Research

520 KiB  
Article
The Signature of the Blandford-Znajek Mechanism in GRB Light Curves
by Ioannis Contopoulos, Antonios Nathanail and Achillies Strantzalis
Galaxies 2017, 5(2), 21; https://doi.org/10.3390/galaxies5020021 - 12 Apr 2017
Cited by 2 | Viewed by 4522
Abstract
In 1977, Blandford and Znajek showed how the spin energy of a rotating black hole may be extracted electromagnetically through a magnetic field that threads the black hole horizon. A characteristic feature of this mechanism is that, under certain fairly general conditions, the [...] Read more.
In 1977, Blandford and Znajek showed how the spin energy of a rotating black hole may be extracted electromagnetically through a magnetic field that threads the black hole horizon. A characteristic feature of this mechanism is that, under certain fairly general conditions, the energy loss rate decays exponentially. We looked precisely for such behavior in the X-ray light curves of Long and Ultra Long duration Gamma-Ray Bursts (GRBs) observed with the XRT instrument on board the Swift satellite, and found that almost 30% of XRT light curves show an exponential decay before they reach the afterglow plateau. A similar behavior (Fast Rise Exponential Decay-FRED) was observed in γ -rays with the BATSE instrument aboard the CGRO satellite. We consider both of these findings as the signature of the Blandford-Znajek mechanism in action in the central engine of GRBs. Full article
(This article belongs to the Special Issue Gamma-Ray Bursts: Recent Theoretical Models and Observations)
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1769 KiB  
Article
Black Hole Accretion in Gamma Ray Bursts
by Agnieszka Janiuk, Michal Bejger, Petra Sukova and Szymon Charzynski
Galaxies 2017, 5(1), 15; https://doi.org/10.3390/galaxies5010015 - 13 Feb 2017
Cited by 6 | Viewed by 4900
Abstract
We study the structure and evolution of the hyperaccreting disks and outflows in the gamma ray bursts central engines. The torus around a stellar mass black hole is composed of free nucleons, Helium, electron-positron pairs, and is cooled by neutrino emission. Accretion of [...] Read more.
We study the structure and evolution of the hyperaccreting disks and outflows in the gamma ray bursts central engines. The torus around a stellar mass black hole is composed of free nucleons, Helium, electron-positron pairs, and is cooled by neutrino emission. Accretion of matter powers the relativistic jets, responsible for the gamma ray prompt emission. The significant number density of neutrons in the disk and outflowing material will cause subsequent formation of heavier nuclei. We study the process of nucleosynthesis and its possible observational consequences. We also apply our scenario to the recent observation of the gravitational wave signal, detected on 14 September 2015 by the two Advanced LIGO detectors, and related to an inspiral and merger of a binary black hole system. A gamma ray burst that could possibly be related with the GW150914 event was observed by the Fermi satellite. It had a duration of about 1 s and appeared about 0.4 s after the gravitational-wave signal. We propose that a collapsing massive star and a black hole in a close binary could lead to the event. The gamma ray burst was powered by a weak neutrino flux produced in the star remnant’s matter. Low spin and kick velocity of the merged black hole are reproduced in our simulations. Coincident gravitational-wave emission originates from the merger of the collapsed core and the companion black hole. Full article
(This article belongs to the Special Issue Gamma-Ray Bursts: Recent Theoretical Models and Observations)
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432 KiB  
Article
Challenging the Forward Shock Model with the 80 Ms Follow up of the X-ray Afterglow of Gamma-Ray Burst 130427A
by Massimiliano De Pasquale, Mathew Page, David Alexander Kann, Samantha R. Oates, Steve Schulze, Bing Zhang, Zach Cano, Bruce Gendre, Daniele Malesani, Andrea Rossi, Neil Gehrels, Eleonora Troja, Luigi Piro, Michel Boër and Giulia Stratta
Galaxies 2017, 5(1), 6; https://doi.org/10.3390/galaxies5010006 - 16 Jan 2017
Cited by 3 | Viewed by 4436
Abstract
GRB 130427A was the most luminous gamma-ray burst detected in the last 30 years. With an isotropic energy output of 8.5 × 10 53 erg and redshift of 0.34, it combined very high energetics with a relative proximity to Earth in an unprecedented [...] Read more.
GRB 130427A was the most luminous gamma-ray burst detected in the last 30 years. With an isotropic energy output of 8.5 × 10 53 erg and redshift of 0.34, it combined very high energetics with a relative proximity to Earth in an unprecedented way. Sensitive X-ray observatories such as XMM-Newton and Chandra have detected the afterglow of this event for a record-breaking baseline longer than 80 million seconds. The light curve displays a simple power-law over more than three decades in time. In this presentation, we explore the consequences of this result for a few models put forward so far to interpret GRB 130427A, and more in general the implication of this outcome in the context of the standard forward shock model. Full article
(This article belongs to the Special Issue Gamma-Ray Bursts: Recent Theoretical Models and Observations)
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2000 KiB  
Article
Exploring the Behaviour of Long Gamma-Ray Bursts with Intrinsic Afterglow Correlations: log L200s−α>200s
by Samantha R. Oates, Judith L. Racusin, Massimilliano De Pasquale, Daniel Kocevski, Mathew J. Page, Alberto J. Castro-Tirado, Javier Gorosabel, Philip J. Smith, Alice A. Breeveld and Paul M. Kuin
Galaxies 2017, 5(1), 4; https://doi.org/10.3390/galaxies5010004 - 10 Jan 2017
Cited by 2 | Viewed by 3536
Abstract
In these proceedings, we summarise the exploration so far of the relationship between the afterglow luminosity (measured at rest frame 200s; log L 200 s ) and average afterglow decay rate (measured from rest frame 200s onwards, α > 200 s ) of [...] Read more.
In these proceedings, we summarise the exploration so far of the relationship between the afterglow luminosity (measured at rest frame 200s; log L 200 s ) and average afterglow decay rate (measured from rest frame 200s onwards, α > 200 s ) of long duration Gamma-ray Bursts (GRBs), first reported in the optical/UV light curves of GRB afterglows. We show that this correlation is also present in the X-ray afterglows of GRBs as observed by Swift-XRT. We explore how the parameters of the correlation observed in both the X-ray and optical/UV light curves relate to each other and the prompt emission phase and whether these correlations are consistent with predictions of the standard afterglow model. We find that the observed correlations are consistent with a common underlying physical mechanism producing GRBs and their afterglows regardless of the detailed temporal behaviour. However, a basic afterglow model has difficulty explaining all the observed correlations. This leads us to briefly discuss alternative more complex models. Full article
(This article belongs to the Special Issue Gamma-Ray Bursts: Recent Theoretical Models and Observations)
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