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

Deadline for manuscript submissions: closed (20 April 2022) | Viewed by 64397

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Special Issue Editors

Dr. Elena Moretti

E-Mail Website
Guest Editor

Institut de Fisica d'Altes Energies (IFAE), The Barcelona Institute of Science and Technology (BIST), E-08193 Barcelona, Spain
Interests: gamma-ray bursts; transients; high energy and very high energy astrophysics

Prof. Francesco Longo

E-Mail Website
Guest Editor

Dipartimento di Fisica, Università degli Studi di Trieste and INFN, Sezione di Trieste, Via Valerio 2, I-34127 Trieste, Italy
Interests: gamma-ray bursts; solar flares; high energy and very high energy astrophysics

Special Issue Information

Dear Colleagues,

The study of Gamma-Ray Bursts (GRBs) has been a very active field since their discovery by the Vela satellites about fifty years ago.

Recent years have witnessed exciting breakthroughs that further stimulated the interest of the scientific community in the GRB field. The recent identification of a spectral component beyond synchrotron emission in the afterglow phase increased the debate about particle acceleration and emission processes at place in a GRB. The ubiquity of the extra spectral component and the environmental conditions under which it is produced are still under debate. Moreover whether this component is also present in the earlier prompt phase or not is another open question.

The recent advancements in the GRB field were achieved thanks to the multi-wavelength and multi-messenger approach. Being able to simultaneously collect data on a burst with different instruments is the key for a deep and complete understanding of the phenomena under study. Indeed, the multi-messenger and multi-wavelength observation of just one neutron-star-neutron-star merging event (detected both electromagnetically and via gravitational waves) yields a step forward in the comprehension of GRB jet dynamics and morphology—an aspect of the GRB phenomena that has been poorly probed by the observations so far.

These observations on the environment, emission processes, and jet dynamics are key tools to unveil the nature of the progenitors of GRB of short and long duration and the connection of GRB to other astrophysical questions, such as the origin of the heavy elements or the high redshift universe stellar population.

If from one side the discoveries increased the curiosity of the community, on the other side the next generation of instruments will be ready in the coming years to provide the tools for continuing the exploration. Future missions will provide a more complete picture of the phenomena by measuring the polarization of the bulk of prompt emission and by providing detection of high redshift GRBs.

The purpose of this Special Issue of Galaxies is to give an overview of the main challenges and problems that the GRB field is currently confronted with, to propose some possible solutions, and to explore the tools that the community will have in their hands in the near future. We are convinced that this Special Issue will become a reference that pictures the current state-of-the- art findings in the GRB field and envisions it in the future.

Dr. Elena Moretti
Prof. Francesco Longo
Guest Editors

Galaxies 2020 Best Paper Award for Special Issue “Gamma-Ray Burst Science in 2030” (500 CHF)

Winner announcement date: 30 June 2022
download description

Dear colleagues,

To award the excellence of the papers in Special Issue: Gamma-Ray Burst Science in 2030, we are pleased to launch our new Best Paper Award. One review or research article will receive this award. The paper will be selected after thorough evaluation by the journal Award Committee, led by the EiC, Prof. Dr. Emilio Elizalde.

Eligibility for the award:
– Open to all career levels;
– ONLY submissions in “Gamma-Ray Burst Science in 2030”, excluding feature papers invited by the Guest Editor.

Selection criteria:
The paper will be selected by the journal Award Committee according to the following criteria (data source: Web of Science (Clarivate Analytics)):
– Scientific merit and broadness of impact;
– Relevance to the journal’s field;
– Originality of research objectives and/or presented ideas;
– Creativity of the study design or uniqueness of approaches and concepts;
– Clarity of presentation;
– Citation and download rates by 28 April 2022;
– Authorship (first author, teamwork, and collaboration with other institutions).

Announcement:

The editorial team would like to congratulate the winner of the Galaxies 2020 Best Paper Award for Special Issue “Gamma-Ray Burst Science in 2030”, who was chosen by a Selection Committee chaired by the journal’s Editors-in-Chief, Dr. Margo Aller and Dr. Jose L. Gómez. Following a review process by the Award Evaluation Committee, the winner was selected.

Two Classes of Gamma-ray Bursts Distinguished within the First Second of Their Prompt Emission
By Lána Salmon, Lorraine Hanlon and Antonio Martin-Carrillo
Galaxies 2022, 10(4), 78; doi:10.3390/galaxies10040078

Please join us in congratulating the winner of the Galaxies 2020 Best Paper Award for Special Issue “Gamma-Ray Burst Science in 2030”. We would also like to take this opportunity to thank all of our authors for their continued support of Galaxies.

Kind regards,
Galaxies Editorial Office

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Galaxies is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

gamma-ray bursts
instruments for astrophysics
emission processes
jet dynamics
multi-wavelength
multi-messenger
high redshift

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Published Papers (18 papers)

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Jump to: Review

22 pages, 4351 KiB

Open AccessArticle

Two Classes of Gamma-ray Bursts Distinguished within the First Second of Their Prompt Emission

by Lána Salmon, Lorraine Hanlon and Antonio Martin-Carrillo

Galaxies 2022, 10(4), 78; https://doi.org/10.3390/galaxies10040078 - 26 Jun 2022

Cited by 6 | Viewed by 3692

Abstract

Studies of Gamma-Ray Burst (GRB) properties, such as duration and spectral hardness, have found evidence for additional classes, beyond the short/hard and long/soft prototypes, using model-dependent methods. In this paper, a model-independent approach was used to analyse the gamma-ray light curves of large samples of GRBs detected by BATSE, Swift/BAT and Fermi/GBM. All the features were extracted from the GRB time profiles in four energy bands using the Stationary Wavelet Transform and Principal Component Analysis. t-distributed Stochastic Neighbourhood Embedding (t-SNE) visualisation of the features revealed two distinct groups of Swift/BAT bursts using the T₁₀₀ interval with 64 ms resolution data. When the same analysis was applied to 4 ms resolution data, two groups were seen to emerge within the first second (T₁) post-trigger. These two groups primarily consisted of short/hard (Group 1) and long/soft (Group 2) bursts, and were 95% consistent with the groups identified using the T₁₀₀ 64 ms resolution data. Kilonova candidates, arising from compact object mergers, were found to belong to Group 1, while those events with associated supernovae fell into Group 2. Differences in cumulative counts between the two groups in the first second, and in the minimum variability timescale, identifiable only with the 4 ms resolution data, may account for this result. Short GRBs have particular significance for multi-messenger science as a distinctive EM signature of a binary merger, which may be discovered by its gravitational wave emissions. Incorporating the T₁ interval into classification algorithms may support the rapid classification of GRBs, allowing for an improved prioritisation of targets for follow-up observations. Full article

(This article belongs to the Special Issue Gamma-Ray Burst Science in 2030)

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17 pages, 766 KiB

Open AccessArticle

Two Dimensional Clustering of Swift/BAT and Fermi/GBM Gamma-ray Bursts

by Lána Salmon, Lorraine Hanlon and Antonio Martin-Carrillo

Galaxies 2022, 10(4), 77; https://doi.org/10.3390/galaxies10040077 - 25 Jun 2022

Cited by 6 | Viewed by 2727

Abstract

Studies of Gamma-ray Burst (GRB) properties, such as duration and spectral hardness, have found evidence for additional classes beyond the short-hard (merger) and long-soft (collapsar) prototypes. Several clustering analyses of the duration-hardness plane identified a third, intermediate duration, class. In this work, Gaussian Mixture Model-based (GMM) clustering is applied to the Swift/BAT and Fermi/GBM samples of GRBs. The results obtained by the hierarchical combination of Gaussian components (or clusters) based on an entropy criterion are presented. This method counteracts possible overfitting arising from the application of Gaussian models to non-Gaussian underlying data. While the initial GMM clustering of the hardness-duration plane identifies three components (short/intermediate/long) for the Swift/BAT and Fermi/GBM samples, only two components (short/long) remain once the entropy criterion is applied. The analysis presented here suggests that the intermediate duration class may be the result of overfitting, rather than evidence of a distinct underlying population. Full article

(This article belongs to the Special Issue Gamma-Ray Burst Science in 2030)

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65 pages, 11248 KiB

Open AccessArticle

Gamma-Ray Bursts Afterglow Physics and the VHE Domain

by Davide Miceli and Lara Nava

Galaxies 2022, 10(3), 66; https://doi.org/10.3390/galaxies10030066 - 5 May 2022

Cited by 25 | Viewed by 4805

Abstract

Afterglow radiation in gamma-ray bursts (GRB), extending from the radio band to GeV energies, is produced as a result of the interaction between the relativistic jet and the ambient medium. Although in general the origin of the emission is robustly identified as synchrotron radiation from the shock-accelerated electrons, many aspects remain poorly constrained, such as the role of inverse Compton emission, the particle acceleration mechanism, the properties of the environment and of the GRB jet itself. The extension of the afterglow emission into the TeV band has been discussed and theorized for years, but has eluded for a long time the observations. Recently, the Cherenkov telescopes, MAGIC and H.E.S.S., have unequivocally proven that afterglow radiation is also produced above 100 GeV, up to at least a few TeV. The accessibility of the TeV spectral window will largely improve with the upcoming facility CTA (the Cherenkov Telescope Array). In this review article, we first revise the current model for afterglow emission in GRBs, its limitations and open issues. Then, we describe the recent detections of very high energy emission from GRBs and the origin of this radiation. Implications on the understanding of afterglow radiation and constraints on the physics of the involved processes will be deeply investigated, demonstrating how future observations, especially by the CTA Observatory, are expected to give a key contribution in improving our comprehension of such elusive sources. Full article

(This article belongs to the Special Issue Gamma-Ray Burst Science in 2030)

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12 pages, 2764 KiB

Open AccessArticle

Breakthrough Multi-Messenger Astrophysics with the THESEUS Space Mission

by Giulia Stratta, Lorenzo Amati, Marica Branchesi, Riccardo Ciolfi, Nial Tanvir, Enrico Bozzo, Diego Götz, Paul O’Brien and Andrea Santangelo

Galaxies 2022, 10(3), 60; https://doi.org/10.3390/galaxies10030060 - 21 Apr 2022

Cited by 5 | Viewed by 2897

Abstract

The mission concept THESEUS (Transient High Energy Sky and Early Universe Surveyor) aims at exploiting Gamma-Ray Bursts (GRB) to explore the early Universe, as well as becoming a cornerstone of multi-messenger and time-domain astrophysics. To achieve these goals, a key feature is the capability to survey the soft X-ray transient sky and to detect the faint and soft GRB population so far poorly explored. Among the expected transients there will be high-redshift GRBs, nearby low-luminosity, X-ray Flashes and short GRBs. Our understanding of the physics governing the GRB prompt emission will benefit from the 0.3 keV–10 MeV simultaneous observations for an unprecedented large number of hundreds of events per year. In particular the mission will provide the identification, accurate sky localisation and characterization of electromagnetic counterparts to sources of gravitational wave and neutrino sources, which will be routinely detected during the 2030s by the upgraded second generation and third generation Gravitational Wave (GW) interferometers and next generation neutrino detectors. Full article

(This article belongs to the Special Issue Gamma-Ray Burst Science in 2030)

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41 pages, 1971 KiB

Open AccessArticle

On the Evolution of the Hubble Constant with the SNe Ia Pantheon Sample and Baryon Acoustic Oscillations: A Feasibility Study for GRB-Cosmology in 2030

by Maria Giovanna Dainotti, Biagio De Simone, Tiziano Schiavone, Giovanni Montani, Enrico Rinaldi, Gaetano Lambiase, Malgorzata Bogdan and Sahil Ugale

Galaxies 2022, 10(1), 24; https://doi.org/10.3390/galaxies10010024 - 29 Jan 2022

Cited by 159 | Viewed by 5580

Abstract

The difference from 4 to 6

σ

in the Hubble constant (

H_{0}

) between the values observed with the local (Cepheids and Supernovae Ia, SNe Ia) and the high-z probes (Cosmic Microwave Background obtained by the Planck data) still challenges the [...] Read more.

The difference from 4 to 6

σ

in the Hubble constant (

H_{0}

) between the values observed with the local (Cepheids and Supernovae Ia, SNe Ia) and the high-z probes (Cosmic Microwave Background obtained by the Planck data) still challenges the astrophysics and cosmology community. Previous analysis has shown that there is an evolution in the Hubble constant that scales as

f (z) = H_{0} / {(1 + z)}^{η}

, where

H_{0}

H_{0} (z = 0)

and

η

is the evolutionary parameter. Here, we investigate if this evolution still holds by using the SNe Ia gathered in the Pantheon sample and the Baryon Acoustic Oscillations. We assume

H_{0} = 70 {km s}^{- 1} {Mpc}^{- 1}

as the local value and divide the Pantheon into three bins ordered in increasing values of redshift. Similar to our previous analysis but varying two cosmological parameters contemporaneously (

H_{0}

Ω_{0 m}

in the

Λ

CDM model and

H_{0}

w_{a}

in the

w_{0} w_{a}

CDM model), for each bin we implement a Markov-Chain Monte Carlo analysis (MCMC) obtaining the value of

H_{0}

assuming Gaussian priors to restrict the parameters spaces to values we expect from our prior knowledge of the current cosmological models and to avoid phantom Dark Energy models with

w < - 1

. Subsequently, the values of

H_{0}

are fitted with the model

f (z)

. Our results show that a decreasing trend with

η \sim 10^{- 2}

is still visible in this sample. The

η

coefficient reaches zero in 2.0

σ

for the

Λ

CDM model up to 5.8

σ

for

w_{0} w_{a}

CDM model. This trend, if not due to statistical fluctuations, could be explained through a hidden astrophysical bias, such as the effect of stretch evolution, or it requires new theoretical models, a possible proposition is the modified gravity theories,

f (R)

. This analysis is meant to further cast light on the evolution of

H_{0}

and it does not specifically focus on constraining the other parameters. This work is also a preparatory to understand how the combined probes still show an evolution of the

H_{0}

by redshift and what is the current status of simulations on GRB cosmology to obtain the uncertainties on the

Ω_{0 m}

comparable with the ones achieved through SNe Ia. Full article

(This article belongs to the Special Issue Gamma-Ray Burst Science in 2030)

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12 pages, 1931 KiB

Open AccessArticle

Distributed Architectures and Constellations for γ-ray Burst Science

by Fabrizio Fiore, Norbert Werner and Ehud Behar

Galaxies 2021, 9(4), 120; https://doi.org/10.3390/galaxies9040120 - 16 Dec 2021

Cited by 7 | Viewed by 2413

Abstract

The gravitational wave/γ-ray burst GW/GRB170817 event marked the beginning of the era of multi-messenger astrophysics, in which new observations of Gravitational Waves (GW) are combined with traditional electromagnetic observations from the very same astrophysical source. In the next few years, Advanced LIGO/VIRGO and KAGRA in Japan and LIGO-India will reach their nominal/ultimate sensitivity. In the electromagnetic domain, the Vera C. Rubin Observatory and the Cherenkov Telescope Array (CTA) will come online in the next few years, and they will revolutionize the investigation of transient and variable cosmic sources in the optical and TeV bands. The operation of an efficient X-ray/γ-ray all-sky monitor with good localisation capabilities will play a pivotal role in providing the high-energy counterparts of the GW interferometers and Rubin Observatory, bringing multi-messenger astrophysics to maturity. To reach the required precision in localisation and timeliness for an unpredictable physical event in time and space requires a sensor distribution covering the whole sky. We discuss the potential of large-scale, small-platform-distributed architectures and constellations to build a sensitive X-ray/γ-ray all-sky monitor and the programmatic implications of this, including the set-up of an efficient assembly line for both hardware development and data analysis. We also discuss the potential of a constellation of small platforms operating at other wavelengths (UV/IR) that are capable of repointing quickly to follow-up high-energy transients. Full article

(This article belongs to the Special Issue Gamma-Ray Burst Science in 2030)

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13 pages, 579 KiB

Open AccessArticle

Accounting for Selection Bias and Redshift Evolution in GRB Radio Afterglow Data

by Maria Dainotti, Delina Levine, Nissim Fraija and Poonam Chandra

Galaxies 2021, 9(4), 95; https://doi.org/10.3390/galaxies9040095 - 7 Nov 2021

Cited by 23 | Viewed by 3076

Abstract

Gamma-ray Bursts (GRBs) are highly energetic events that can be observed at extremely high redshift. However, inherent bias in GRB data due to selection effects and redshift evolution can significantly skew any subsequent analysis. We correct for important variables related to the GRB [...] Read more.

T_{90}^{*}

, the prompt isotropic energy,

E_{iso}

, the rest-frame end time of the plateau emission,

T_{a, radio}^{*}

, and its correspondent luminosity

L_{a, radio}

, for radio afterglow. In particular, we use the Efron–Petrosian method presented in 1992 for the correction of our variables of interest. Specifically, we correct

E_{iso}

and

T_{90}^{*}

for 80 GRBs, and

L_{a, radio}

and

T_{a, radio}^{*}

for a subsample of 18 GRBs that present a plateau-like flattening in their light curve. Upon application of this method, we find strong evolution with redshift in most variables, particularly in

L_{a, radio}

, with values similar to those found in past and current literature in radio, X-ray and optical wavelengths, indicating that these variables are susceptible to observational bias. This analysis emphasizes the necessity of correcting observational data for evolutionary effects to obtain the intrinsic behavior of correlations to use them as discriminators among the most plausible theoretical models and as reliable cosmological tools. Full article

(This article belongs to the Special Issue Gamma-Ray Burst Science in 2030)

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15 pages, 553 KiB

Open AccessArticle

Progenitors of Long-Duration Gamma-ray Bursts

by Arpita Roy

Galaxies 2021, 9(4), 79; https://doi.org/10.3390/galaxies9040079 - 19 Oct 2021

Cited by 8 | Viewed by 2486

Abstract

We review the current scenario of long-duration Gamma-ray burst (LGRB) progenitors, and in addition, present models of massive stars for a mass range of

10 - 150 M_{⊙}

with

Δ M = 10 M_{⊙}

and rotation rate [...] Read more.

We review the current scenario of long-duration Gamma-ray burst (LGRB) progenitors, and in addition, present models of massive stars for a mass range of

10 - 150 M_{⊙}

with

Δ M = 10 M_{⊙}

and rotation rate

v / v_{crit} = 0

0.6

with a velocity resolution

Δ v / v_{crit} = 0.1

. We further discuss possible metallicity and rotation rate distribution from our models that might be preferable for the creation of successful LGRB candidates given the observed LGRB rates and their metallicity evolution. In the current understanding, LGRBs are associated with Type-Ic supernovae (SNe). To establish LGRB-SN correlation, we discuss three observational paths: (i) space-time coincidence, (ii) evidence from photometric light curves of LGRB afterglows and SN Type-Ic, (iii) spectroscopic study of both LGRB afterglow and SN. Superluminous SNe are also believed to have the same origin as LGRBs. Therefore, we discuss constraints on the progenitor parameters that can possibly dissociate these two events from a theoretical perspective. We further discuss the scenario of single star versus binary star as a more probable pathway to create LGRBs. Given the limited parameter space in the mass, mass ratio and separation between the two components in a binary, binary channel is less likely to create LGRBs to match the observed LGRB rate. Despite effectively-single massive stars are fewer in number compared to interacting binaries, their chemically homogeneous evolution (CHE) might be the major channel for LGRB production. Full article

(This article belongs to the Special Issue Gamma-Ray Burst Science in 2030)

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53 pages, 1091 KiB

Open AccessArticle

A Roadmap to Gamma-Ray Bursts: New Developments and Applications to Cosmology

by Orlando Luongo and Marco Muccino

Galaxies 2021, 9(4), 77; https://doi.org/10.3390/galaxies9040077 - 12 Oct 2021

Cited by 45 | Viewed by 3484

Abstract

Gamma-ray bursts are the most powerful explosions in the universe and are mainly placed at very large redshifts, up to

z ≃ 9

. In this short review, we first discuss gamma-ray burst classification and morphological properties. We then report the likely relations [...] Read more.

Gamma-ray bursts are the most powerful explosions in the universe and are mainly placed at very large redshifts, up to

z ≃ 9

. In this short review, we first discuss gamma-ray burst classification and morphological properties. We then report the likely relations between gamma-ray bursts and other astronomical objects, such as black holes, supernovae, neutron stars, etc., discussing in detail gamma-ray burst progenitors. We classify long and short gamma-ray bursts, working out their timescales, and introduce the standard fireball model. Afterwards, we focus on direct applications of gamma-ray bursts to cosmology and underline under which conditions such sources would act as perfect standard candles if correlations between photometric and spectroscopic properties were not jeopardized by the circularity problem. In this respect, we underline how the shortage of low-z gamma-ray bursts prevents anchor gamma-ray bursts with primary distance indicators. Moreover, we analyze in detail the most adopted gamma-ray burst correlations, highlighting their main differences. We therefore show calibration techniques, comparing such treatments with non-calibration scenarios. For completeness, we discuss the physical properties of the correlation scatters and systematics occurring during experimental computations. Finally, we develop the most recent statistical methods, star formation rate, and high-redshift gamma-ray burst excess and show the most recent constraints obtained from experimental analyses. Full article

(This article belongs to the Special Issue Gamma-Ray Burst Science in 2030)

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14 pages, 640 KiB

Open AccessArticle

Stable Up-Down Quark Matter Nuggets, Quark Star Crusts, and a New Family of White Dwarfs

by Lang Wang, Jian Hu, Cheng-Jun Xia, Jian-Feng Xu, Guang-Xiong Peng and Ren-Xin Xu

Galaxies 2021, 9(4), 70; https://doi.org/10.3390/galaxies9040070 - 28 Sep 2021

Cited by 14 | Viewed by 2495

Abstract

The possible existence of stable up-down quark matter (

u d

QM) was recently proposed, and it was shown that the properties of

u d

QM stars are consistent with various pulsar observations. In this work we investigate the stability of

u d

[...] Read more.

The possible existence of stable up-down quark matter (

u d

QM) was recently proposed, and it was shown that the properties of

u d

QM stars are consistent with various pulsar observations. In this work we investigate the stability of

u d

QM nuggets and found at certain size those objects are more stable than others if a large symmetry energy and a small surface tension were adopted. In such cases, a crust made of

u d

QM nuggets exists in quark stars. A new family of white dwarfs comprised entirely of

u d

QM nuggets and electrons were also obtained, where the maximum mass approaches to the Chandrasekhar limit. Full article

(This article belongs to the Special Issue Gamma-Ray Burst Science in 2030)

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14 pages, 490 KiB

Open AccessArticle

The Low-Energy Spectral Index of Gamma-ray Burst Prompt Emission from Internal Shocks

by Kai Wang and Zi-Gao Dai

Galaxies 2021, 9(3), 68; https://doi.org/10.3390/galaxies9030068 - 15 Sep 2021

Cited by 6 | Viewed by 2196

Abstract

The prompt emission of most gamma-ray bursts (GRBs) typically exhibits a non-thermal Band component. The synchrotron radiation in the popular internal shock model is generally put forward to explain such a non-thermal component. However, the low-energy photon index

α \sim - 1.5

predicted [...] Read more.

α \sim - 1.5

predicted by the synchrotron radiation is inconsistent with the observed value

α \sim - 1

. Here, we investigate the evolution of a magnetic field during propagation of internal shocks within an ultrarelativistic outflow, and revisit the fast cooling of shock-accelerated electrons via synchrotron radiation for this evolutional magnetic field. We find that the magnetic field is first nearly constant and then decays as

B^{'} \propto t^{- 1}

, which leads to a reasonable range of the low-energy photon index,

- 3 / 2 < α < - 2 / 3

. In addition, if a rising electron injection rate during a GRB is introduced, we find that

α

reaches

- 2 / 3

more easily. We thus fit the prompt emission spectra of GRB 080916c and GRB 080825c. Full article

(This article belongs to the Special Issue Gamma-Ray Burst Science in 2030)

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Review

Jump to: Research

38 pages, 5725 KiB

Open AccessReview

The Structure of Gamma Ray Burst Jets

by Om Sharan Salafia and Giancarlo Ghirlanda

Galaxies 2022, 10(5), 93; https://doi.org/10.3390/galaxies10050093 - 30 Aug 2022

Cited by 27 | Viewed by 3845

Abstract

Due to relativistic bulk motion, the structure and orientation of gamma-ray burst (GRB) jets have a fundamental role in determining how they appear. The recent discovery of the GW170817 binary neutron star merger and the associated GRB boosted the interest in the modeling and search for signatures of the presence of a (possibly quasi-universal) jet structure in long and short GRBs. In this review, following a pedagogical approach, we summarize the history of GRB jet structure research over the last two decades, from the inception of the idea of a universal jet structure to the current understanding of the complex processes that shape the structure, which involves the central engine that powers the jet and the interaction of the latter with the progenitor vestige. We put some emphasis on the observable imprints of jet structure on prompt and afterglow emission and on the luminosity function, favoring intuitive reasoning over technical explanations. Full article

(This article belongs to the Special Issue Gamma-Ray Burst Science in 2030)

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24 pages, 2624 KiB

Open AccessReview

The Detection of GRBs at VHE: A Challenge Lasting for More than Two Decades, What Is Next?

by Alessio Berti and Alessandro Carosi

Galaxies 2022, 10(3), 67; https://doi.org/10.3390/galaxies10030067 - 10 May 2022

Cited by 8 | Viewed by 2989

Abstract

Unveiling the mystery of gamma-ray bursts (GRBs) has been the target of many multi-waveband observational and theoretical efforts during the last decades. The results collected by current and past space-based instruments have provided important insights into the mechanisms at the origin of their prompt and afterglow phases. On the other hand, many questions, such as the the origin of the multi-GeV signal observed in a large number of events, remained unanswered. Within this framework, the first firm detections of a very-high-energy (VHE,

E ≳ 100

GeV) emission component by MAGIC and H.E.S.S. collaborations represented an important, long-awaited result for the VHE astrophysics community. However, while such discoveries opened a new era in the study of GRBs, they also provided an unexpected complexity due to the differences between the phenomenology of the observed events. This revealed that we still have an incomplete comprehension of GRB physics. In the nearby future, observations by the Cherenkov Telescope Array Observatory (CTAO), with unprecedented sensitivity in the VHE band, will have a key role in the study of these enigmatic objects and their interactions with the surrounding environment. In this review we will cover the recent GRB history, highlighting the efforts of follow-up campaigns by the VHE community that led to the first VHE GRB detection, and outlining what we can expect from future facilities in the next decades. Full article

(This article belongs to the Special Issue Gamma-Ray Burst Science in 2030)

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20 pages, 739 KiB

Open AccessReview

The GRB Prompt Emission: An Unsolved Puzzle

by Željka Bošnjak, Rodolfo Barniol Duran and Asaf Pe’er

Galaxies 2022, 10(2), 38; https://doi.org/10.3390/galaxies10020038 - 22 Feb 2022

Cited by 12 | Viewed by 4011

Abstract

The recent multi-messenger and multi-wavelength observations of gamma-ray bursts (GRBs) have encouraged renewed interest in these energetic events. In spite of the substantial amount of data accumulated during the past few decades, the nature of the prompt emission remains an unsolved puzzle. We [...] Read more.

(This article belongs to the Special Issue Gamma-Ray Burst Science in 2030)

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5 pages, 1138 KiB

Open AccessReview

The SVOM Mission

by Maria Grazia Bernardini, Bertrand Cordier and Jianyan Wei

Galaxies 2021, 9(4), 113; https://doi.org/10.3390/galaxies9040113 - 4 Dec 2021

Cited by 14 | Viewed by 2775

Abstract

SVOM (Space-based multiband astronomical Variable Objects Monitor) is a sino-french mission that is dedicated to Gamma-Ray Burst (GRB) science, expected to be launched in mid 2023. The mission includes four space-based and three ground-based instruments that, working together, will discover GRBs and provide rapid multi-wavelength follow-up in order to obtain a complete coverage of the GRB emission over seven decades in energy, from the trigger up to the very late phases of the afterglow. Thanks to its characteristics, SVOM will play a crucial role in time-domain and multi-messenger astronomy. Full article

(This article belongs to the Special Issue Gamma-Ray Burst Science in 2030)

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13 pages, 999 KiB

Open AccessReview

Electromagnetic Precursors of Short Gamma-Ray Bursts as Counterparts of Gravitational Waves

by Jieshuang Wang and Liangduan Liu

Galaxies 2021, 9(4), 104; https://doi.org/10.3390/galaxies9040104 - 15 Nov 2021

Cited by 6 | Viewed by 2475

Abstract

Precursor emissions are found in some short gamma-ray bursts (SGRBs). In this paper, we review the theories and observations of the SGRB precursor and discuss its prospect as an electromagnetic counterpart of the gravitational wave event produced by neutron star (NS) mergers. The observed luminosity, spectrum, and duration of precursors are explained by the magnetospheric interaction model during the inspiral or the cocoon/jet shock breakout model during the jet propagation. In general, these two models predict that the precursor will be weaker than the main GRB, but will be of a larger opening angle, which makes it an advantageous gamma-ray counterpart for NS mergers in the local Universe, especially for NS - black hole mergers with very low mass ratios, in which the main GRBs are not expected. The joint observation of the precursor, SGRB, and gravitational wave will help to reveal the jet launch mechanism and post-merger remnant. Full article

(This article belongs to the Special Issue Gamma-Ray Burst Science in 2030)

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13 pages, 594 KiB

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Probing Gamma-Ray Burst VHE Emission with the Southern Wide-Field-of-View Gamma-Ray Observatory

by Giovanni La Mura, Ulisses Barres de Almeida, Ruben Conceição, Alessandro De Angelis, Francesco Longo, Mário Pimenta, Bernardo Tomé and Davide Miceli

Galaxies 2021, 9(4), 98; https://doi.org/10.3390/galaxies9040098 - 8 Nov 2021

Cited by 2 | Viewed by 2575

Abstract

Recent observations have confirmed that Gamma-Ray Burst (GRB) afterglows produce Very High-Energy radiation (VHE,

E > 100

GeV). This highly anticipated discovery opens new scenarios in the interpretation of GRBs and in their role as probes of Extragalactic Background Light (EBL) and Lorentz [...] Read more.

Recent observations have confirmed that Gamma-Ray Burst (GRB) afterglows produce Very High-Energy radiation (VHE,

E > 100

GeV). This highly anticipated discovery opens new scenarios in the interpretation of GRBs and in their role as probes of Extragalactic Background Light (EBL) and Lorentz Invariance Violation (LIV). However, some fundamental questions about the actual nature of VHE emission in GRBs and its evolution during the burst are still unsolved. These questions will be difficult to address, even with future imaging Cherenkov telescopes, such as the Cherenkov Telescope Array (CTA). Here we investigate the prospects of gamma-ray sky monitoring with Extensive Air Showers arrays (EAS) to address these problems. We discuss the theoretical aspects connected with VHE radiation emission and the implications that its temporal evolution properties have on the interpretation of GRBs. By revisiting the high-energy properties of some Fermi-LAT detected GRBs, we estimate the typical fluxes expected in the VHE band and compare them with a range of foreseeable instrument performances, based on the Southern Wide Field-of-view Gamma-ray Observatory concept (SWGO). We focus our analysis on how different instrument capabilities affect the chances to explore the burst onset and early evolution in VHE, providing invaluable complementary information with respect to Cherenkov telescope observations. We show that under the assumption of conditions already observed in historical events, the next-generation ground monitoring detectors can actually contribute to answer several key questions. Full article

(This article belongs to the Special Issue Gamma-Ray Burst Science in 2030)

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64 pages, 6533 KiB

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GRB Polarization: A Unique Probe of GRB Physics

by Ramandeep Gill, Merlin Kole and Jonathan Granot

Galaxies 2021, 9(4), 82; https://doi.org/10.3390/galaxies9040082 - 27 Oct 2021

Cited by 34 | Viewed by 5591

Abstract

Over half a century from the discovery of gamma-ray bursts (GRBs), the dominant radiation mechanism responsible for their bright and highly variable prompt emission remains poorly understood. Spectral information alone has proven insufficient for understanding the composition and main energy dissipation mechanism in GRB jets. High-sensitivity polarimetric observations from upcoming instruments in this decade may help answer such key questions in GRB physics. This article reviews the current status of prompt GRB polarization measurements and provides comprehensive predictions from theoretical models. A concise overview of the fundamental questions in prompt GRB physics is provided. Important developments in gamma-ray polarimetry including a critical overview of different past instruments are presented. Theoretical predictions for different radiation mechanisms and jet structures are confronted with time-integrated and time-resolved measurements. The current status and capabilities of upcoming instruments regarding the prompt emission are presented. The very complimentary information that can be obtained from polarimetry of X-ray flares as well as reverse-shock and early to late forward-shock (afterglow) emissions are highlighted. Finally, promising directions for overcoming the inherent difficulties in obtaining statistically significant prompt-GRB polarization measurements are discussed, along with prospects for improvements in the theoretical modeling, which may lead to significant advances in the field. Full article

(This article belongs to the Special Issue Gamma-Ray Burst Science in 2030)

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