Very high energy photons from cosmological gamma-ray bursts (GRBs) are expected to interact with extragalactic background light (EBL) and produce electron-positron pairs when they propagate through intergalactic medium (IGM). These relativistic pairs will then up-scatter cosmic microwave background (CMB) photons and emit secondary GeV emission. Meanwhile, the motion of these pairs are deflected by intergalactic magnetic field (IGMF), so the secondary GeV photons arrive later than the primary emission. It has been suggested that the properties of the secondary GeV emission can be used to constrain IGMF. Recently, TeV gamma-ray emission has been detected, for the first time, from a GRB (GRB 190114C) by the MAGIC telescope and its steep ${\rm γ-ray}$ spectrum shows a clear evidence of absorption by EBL. We then constrain the IGMF with the GeV flux limit obtained from the $Fermi$-LAT observations. We find a limit of $>10^{-19.5}$ G for the coherence length of $λ\leq 1$ Mpc. Although this limit is weaker than that obtained by using blazars, it represents the first limit from ${\rm γ-ray}$ observations of GRBs, which provides an independent constraint on IGMF. We also find that, for transient ${\rm γ-ray}$ sources, one can choose a favorable time window to search for the echo emission at a particular energy.
We discuss the expected properties of pair echo emission from gamma-ray bursts (GRBs) at high redshifts ($z \gtrsim 5$), their detectability, and the consequent implications for probing intergalactic magnetic fields (IGMFs) at early epochs. Pair echos comprise inverse Compton emission by secondary electron-positron pairs produced via interactions between primary gamma-rays from the GRB and low-energy photons of the diffuse intergalactic radiation, arriving with a time delay that depends on the nature of the intervening IGMFs. At sufficiently high $z$, the IGMFs are unlikely to have been signif…
Multi-TeV $γ$-ray candidates from GRB 221009A: a downturn in the intrinsic $γ$-ray spectrum, an echo of the prompt emission phase, and intergalactic electromagnetic cascades
Institute for Nuclear Research of the Russian Academy of Sciences（俄罗斯科学院核物理研究所）；Aryabhatta Research Institute of Observational Sciences (ARIES)（阿亚巴塔观测科学研究所）；Centre for Astro-Particle Physics (CAPP) and Department of Physics, University of Johannesburg（约翰内斯堡大学天体粒子物理中心及物理系）；Gran Sasso Science Institute（格兰萨索科学研究所）；INFN/Laboratori Nazionali del Gran Sasso（意大利国家核物理研究所/格兰萨索国家实验室）；Department of Physics, Federal State Budget Educational Institution of Higher Education M.V. Lomonosov Moscow State University（莫斯科罗蒙诺索夫国立大学物理系）；Federal State Budget Educational Institution of Higher Education, M.V. Lomonosov Moscow State University, Skobeltsyn Institute of Nuclear Physics (SINP MSU)（莫斯科罗蒙诺索夫国立大学斯科别尔辛核物理研究所）
GRB 221009A的高能γ射线候选者检测揭示了内在谱的下降，可能由火球内中子的光电核相互作用产生，随后产生高能回声辐射。
The magnetic field in intergalactic space gives important information about magnetogenesis in the early universe. The properties of this field can be probed by searching for radiation of secondary e$^+ $e$^-$ pairs created by TeV photons, that produce GeV range radiation by Compton-scattering cosmic microwave background (CMB) photons. The arrival times of the GeV "echo" photons depend strongly on the magnetic field strength and coherence length. A Monte Carlo code that accurately treats pair creation is developed to simulate the spectrum and time-dependence of the echo radiation. The extrapola…
Constraints on the intergalactic magnetic field from Fermi-LAT observations of GRB 221009A
University of Hamburg（汉堡大学）；Kirchhoff-Institute for Physics, Heidelberg University（海德堡大学基尔霍夫物理研究所）；INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（博洛尼亚天文物理与空间科学国家研究所）；Universitá di Trieste（的里雅斯特大学）；Istituto Nazionale di Fisica Nucleare, Sezione di Trieste（意大利国家核物理研究所的里雅斯特分部）
通过GRB 221009A的观测，研究利用费米- LAT数据对星际磁场进行限制，得出B < 2.5 x 10^{-17} G的约束。
Impact of Observational and Modelling Assumptions on Intergalactic Magnetic Field Constraints from TeV Gamma-Ray Bursts with the Cherenkov Telescope Array Observatory
Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM（巴黎萨克雷大学，巴黎西岱大学，法国原子能委员会，法国国家科学研究中心，天体物理学与宇宙微波背景研究组）
It is known that the GRB equivalent hydrogen column density (NHX) changes with redshift and that, typically, NHX is greater than the GRB host neutral hydrogen column density. We have compiled a large sample of data for GRB NHX and metallicity [X/H]. The main aims of this paper are to generate improved NHX for our sample by using actual metallicities, dust corrected where available for detections, and for the remaining GRB, a more realistic average intrinsic metallicity using a standard adjustment from solar. Then, by approximating the GRB host intrinsic hydrogen column density using the measur…
The intrinsic X-ray emission of Gamma-Ray Bursts (GRBs) is often found to be absorbed over and above the column density through our own galaxy. The extra component is usually assumed to be due to absorbing gas lying within the host galaxy of the GRB itself. There is an apparent correlation between the equivalent column density of hydrogen, N(H,intrinsic) (assuming it to be at the GRB redshift), and redshift, z, with the few z>6 GRBs showing the greatest intrinsic column densities. We investigate the N(H,intrinsic) - z relation using a large sample of Swift GRBs, as well as active galactic nucl…
Gamma-ray bursts (GRBs) can be divided into three subclasses: X-ray flash (XRF), X-ray rich (XRR), and classical GRB (C-GRB). An X-ray flare is the rebrightening emission shown in the early X-ray afterglow of some GRBs. In this paper, we comprehensively examine the X-ray flare properties among XRF, XRR, and C-GRB subclasses. We utilize the XRF, XRR, and C-GRB subclass samples obtained from the Swift-BAT3 catalog, and the X-ray flare observational properties are collected from Falcone et al., Chincarini et al., and Yi et al. We find that XRFs and XRRs have more bright X-ray flares than C-GRBs. …
We present high signal-to-noise ratio Gemini and MMT spectroscopy of the optical afterglow of the gamma-ray burst (GRB) 130606A at redshift z=5.913, discovered by Swift. This is the first high-redshift GRB afterglow to have spectra of comparable quality to those of z~6 quasars. The data exhibit a smooth continuum at near-infrared wavelengths that is sharply cut off blueward of 8410 Angs due to absorption from Ly-alpha at redshift z~5.91, with some flux transmitted through the Ly-alpha forest between 7000-7800 Angs. We use column densities inferred from metal absorption lines to constrain the m…
The presence of weak intergalactic magnetic fields can be studied by their effect on electro-magnetic cascades induced by multi-TeV gamma-rays in the cosmic radiation background. Small deflections of secondary electrons and positrons as the cascade develops extend the apparent size of the emission region of distant TeV gamma-ray sources. These gamma-ray halos can be resolvable in imaging atmospheric Cherenkov telescopes and serve as a measure of the intergalactic magnetic field strength and coherence length. We present a method of calculating the gamma-ray halo for isotropically emitting sourc…
The origin of ultra-high-energy cosmic rays (UHECRs) remains elusive. Gamma-ray bursts (GRBs) are among the best candidates able to meet the stringent energy requirements needed for particle acceleration to such high energies. If UHECRs were accelerated by the central engine of GRB 221009A, it might be possible to detect secondary photons and neutrinos as the UHECRs travel from the source to the Earth. Here we attempt to interpret some of the early publicly available data connected to this burst. If the reported early GeV-TeV detection was produced by secondary emission from UHECRs it probably…
We present a comprehensive statistical analysis of Swift X-ray light-curves of Gamma-Ray Bursts (GRBs), with more than 650 GRBs. Two questions drive this effort: (1) Does the X-ray emission retain any kind of memory of the prompt phase? (2) Where is the dividing line between long and short GRBs? We show that short GRBs decay faster, are less luminous and less energetic than long GRBs, but are interestingly characterized by very similar intrinsic absorption. Our analysis reveal the existence of a number of relations that link the X-ray to prompt parameters in long GRBs; short GRBs are outliers …
The origin of the most energetic cosmic ray particles is one of the most important open problems in astrophysics. Despite a big experimental effort done in the past years, the sources of these very energetic particles remain unidentified. Therefore, their distribution on the Universe and even their space density are still unknown. It has been shown that different spatial configurations of the sources lead to different energy spectra and composition profiles (in the case of sources injecting heavy nuclei) at Earth. These ensemble fluctuations are more important at the highest energies because o…
GRB 121027A is un-usual with its extremely long-lasting, energetic X-ray flares. The total energy release in X-ray flares is about one order of magnitude higher than prompt gamma-rays, making it special from most long GRBs. We show that while the prompt gamma-ray emission satisfies the empirical E_{iso}-E_{p} relation of typical long GRBs, the X-ray flares, whose spectra can be fit with a cutoff-power-law model with well-constrained E_p, significantly deviate from such a relation. Nonetheless, a time-resolved spectral analysis of X-ray flares suggest that the X-ray emission is consistent with …
Gamma-ray bursts (GRB) are generally believed to be efficient particle accelerators. In the presence of energetic protons in a GRB jet, interactions between these protons and intense radiation field of the GRB are supposed to induce electromagnetic cascade. Electrons/positrons generated in the cascade will produce an additional spectrum of robust feature, which is in the form of a power-law distribution up to GeV regime with an index of $\lesssim 2$. We suggest that measurements of Fermi-LAT at GeV band can provide independent constraints on the key GRB model parameters such as the dissipation…
The Fermi Gamma-ray Space Telescope (FGST) has opened a new high-energy window in the study of Gamma-Ray Bursts (GRBs). Here we present a thorough analysis of GRB 080825C, which triggered the Fermi Gamma-ray Burst Monitor (GBM), and was the first firm detection of a GRB by the Fermi Large Area Telescope (LAT). We discuss the LAT event selections, background estimation, significance calculations, and localization for Fermi GRBs in general and GRB 080825C in particular. We show the results of temporal and time-resolved spectral analysis of the GBM and LAT data. We also present some theoretical i…
Secondary γ-rays from intergalactic cascades may contribute to observable spectra of blazars, also modifying observable angular and temporal distributions. In this paper we briefly review basic features of intergalactic electromagnetic cascade physics, suggest a new approximation for γ-ray mean free path, consider angular patterns of magnetically broadened cascade emission, and present an example of a fit to the observable blazar spectrum.
The origin and composition of ultra-high energy cosmic rays (UHECRs) remain a mystery. The common lore is that UHECRs are deflected from their primary directions by the Galactic and extragalactic magnetic fields. Here we describe an extragalactic contribution to the deflection of UHECRs that does not depend on the strength and orientation of the initial seed field. Using the IllustrisTNG simulations, we show that outflow-driven magnetic bubbles created by feedback processes during galaxy formation deflect approximately half of all $10^{20}$ eV protons by $1^{\circ}$ or more, and up to $20$-$30…
The recent observation of high-energy neutrinos from the 2017 flare of the blazar TXS~0506+056, together with counterparts across the whole electromagnetic spectrum, opens up new possibilities for investigating the properties of this class of objects as well as the traversed medium. Propagation effects such as the attenuation of the very-high-energy gamma-ray component by the extragalactic background light are well known, and usually taken into account when fitting spectral energy distributions of objects. Other effects such as those of intergalactic magnetic fields are, however, often neglect…
Gamma-ray bursts (GRBs), which are bright flashes of gamma rays from extragalactic sources followed by fading afterglow emission, are associated with stellar core collapse events. We report the detection of very-high-energy (VHE) gamma rays from the afterglow of GRB 190829A, between 4 and 56 hours after the trigger, using the High Energy Stereoscopic System (H.E.S.S.). The low luminosity and redshift of GRB 190829A reduce both internal and external absorption, allowing determination of its intrinsic energy spectrum. Between energies of 0.18 and 3.3 tera-electron volts, this spectrum is describ…
It has been reported that some X-ray spectra of gamma-ray burst (GRB) afterglows cannot be fitted by a simple power law. A blackbody component is added to precisely fit the thermal feature in these spectra. Alternatively, we propose that bremsstrahlung radiation can also be one possible mechanism to explain the thermal component of the GRB X-ray afterglow. In particular, we examine the X-ray afterglow of the ultra-long GRB 130925A in this paper. By our calculation, we find that the X-ray thermal component observed by both Swift-XRT and NuSTAR can be well explained by the bremsstrahlung radiati…
Telescope Array collaboration has reported an evidence for existence of a source of ultra-high-energy cosmic ray (UHECR) events in Perseus-Pisces supercluster. We show that the mere existence of such a source imposes an upper bound on the strength of intergalactic magnetic field (IGMF) in the Taurus void lying between the Perseus-Pisces supercluster and the Milky Way galaxy. This limit is at the level of 10^{-10} G for a field with correlation length larger than the distance of the super-cluster ~ 70 Mpc. This bound is an order-of-magnitude stronger that the previously known bound on IGMF from…
The maximum cosmic ray energy achievable by acceleration by a relativistic blast wave is derived. It is shown that forward shocks from long GRB in the interstellar medium are powerful enough to produce the Galactic cosmic-ray component up to the ankle at $4\times 10^{18}$eV, as per an earlier suggestion (Levinson and Eichler, 1993). It is further argued that, were extragalactic long GRB responsible for the component {\it above} the ankle as well, the contribution from an occasional Galactic GRB within the solar circle would yield more than the observational limits on the outward flux from the …
As indicated by the observed X-ray flares, a great amount of energy could be intermediately released from the postburst central engine of gamma-ray bursts (GRBs). As a natural consequence, the GRB external shock could be energized over and over. With such a multiple energy injection model, we explore the unique X-ray afterglow light curve of GRB 050712, which exists four apparent shallow decay plateaus. Together with three early X-ray flares, the central engine of GRB 050712 is supposed to release energy at least seven times after the burst. Furthermore we find that the energy released during …
Primary very high energy $γ$-rays from $γ$-ray bursts (GRBs) are partially absorbed on extragalactic background light (EBL) photons with subsequent formation of intergalactic electromagnetic cascades. Characteristics of the observable cascade $γ$-ray signal are sensitive to the strength and structure of the extragalactic magnetic field (EGMF). GRB 190114C was recently detected with the MAGIC imaging atmospheric Cherenkov telescopes, for the first time allowing to estimate the observable cascade intensity. We inquire whether any constraints on the EGMF strength and structure could be obtained f…
X-ray flares in gamma-ray bursts (GRBs) are believed to be generated by the late activities of central engine, and thus provide an useful tool to diagnose the properties of central objects. In this paper, we work on a GRB X-ray flare sample whose bulk Lorentz factors are constrained by two different methods and the jet opening angles are determined by the jet breaks in afterglow lightcurves. Considering a hyperaccreting stellar-mass black hole (BH) as the central engine of GRBs and the Blandford \& Znajek process (BZ) as the jet production mechanism, we constrain the parameters of central engi…
Very long and precise follow-up measurements of the X-ray afterglow of very intense gamma ray bursts (GRBs) allow a critical test of GRB theories. Here we show that the single power-law decay with time of the X-ray afterglow of GRB 130427A, the record long and most accurately measured X-ray afterglow of an intense GRB by the Swift, Chandra and XMM Newton space observatories, and of all other known intense GRBs, is that predicted by the cannonball (CB) model of GRBs from their measured spectral index, while it disagrees with that predicted by the widely accepted fireball (FB) models of GRBs.
The observations of the exceptionally bright gamma-ray burst (GRB) 130427A by the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope provide constraints on the nature of such unique astrophysical sources. GRB 130427A had the largest fluence, highest-energy photon (95 GeV), longest $γ$-ray duration (20 hours), and one of the largest isotropic energy releases ever observed from a GRB. Temporal and spectral analyses of GRB 130427A challenge the widely accepted model that the non-thermal high-energy emission in the afterglow phase of GRBs is synchrotron emission radiated by electrons …
Cosmic rays (CRs) may be used to infer properties of intervening cosmic magnetic fields. Conversely, understanding the effects of magnetic fields on the propagation of high-energy CRs is crucial to elucidate their origin. In the present work we investigate the role of intracluster magnetic fields on the propagation of CRs with energies between $10^{16}$ and $10^{18.5}$ eV. We look for possible signatures of a transition in the CR propagation regime, from diffusive to ballistic. Finally, we discuss the consequences of the confinement of high-energy CRs in clusters and superclusters for the prod…
While very often a hot intergalactic medium (IGM) is optically thin to continuum radiation, the optical depth in resonant lines can be of order unity or larger. Resonant scattering in the brightest X-ray emission lines can cause distortions in the surface brightness distribution, spurious variations in the abundance of heavy elements, changes in line spectral shapes and even polarization of line emission. The magnitude of these effects not only depends on the density, temperature and ionization state of the gas, but is also sensitive to the characteristics of the gas velocity field. This opens…
Applying our recently-developed generalized version of the high-latitude emission theory to the observations of X-ray flares in gamma-ray bursts (GRBs), we present here clear observational evidence that the X-ray flare emission region is undergoing rapid bulk acceleration as the photons are emitted. We show that both the observed X-ray flare light curves and the photon index evolution curves can be simultaneously reproduced within a simple physical model invoking synchrotron radiation in an accelerating emission region far from the GRB central engine. Such an acceleration process demands an ad…
In this paper intergalatic electromagnetic cascades are used as a probe of cosmic ray sources. This is achieved as follows. In extragalactic space cosmic rays initiate electromagnetic cascades in which gamma-ray and neutrino emission arises. We used the joint analysis of cosmic ray data, along with extragalactic gamma-ray and neutrino emission, to study particle acceleration in the vicinity of supermassive black holes. Particle injection spectra depend on processes of particle acceleration, and here we discuss models with various injection spectra. The computation of the propagation of cosmic …
The late-time high-resolution X-ray and radio observations of GRB980425/SN1998bw, the closest known gamma ray burst (GRB) associated with a supernova (SN) explosion, may have actually resolved the hyperluminal source that produced the GRB and its afterglow. Its hyperluminal speed ~350c is consistent with that expected in the cannonball (CB) model of GRBs. The observed superluminal expansion of the late-time radio image of GRB030329/SN2003dh, the GRB with the brightest and longest followed up radio afterglow to date, is also consistent with that expected in the CB model of GRBs and extrapolates…
The extended high-energy gamma-ray (>100 MeV) emission occurring after the prompt gamma-ray bursts (GRBs) is usually characterized by a single power-law spectrum, which has been explained as the afterglow synchrotron radiation. We report on the Fermi Large Area Telescope (LAT) observations of the >100 MeV emission from the very bright and nearby GRB 130427A, up to ~100 GeV. By performing time-resolved spectral fits of GRB 130427A, we found a strong evidence of an extra hard spectral component above a few GeV that exists in the extended high-energy emission of this GRB. This extra spectral comp…
X-ray absorption of $γ$-ray burst (GRB) afterglows is prevalent yet poorly understood. X-ray derived neutral hydrogen column densities ($N_{\rm H}$) of GRB X-ray afterglows show an increase with redshift, which might give a clue for the origin of this absorption. We use more than 350 X-ray afterglows with spectroscopic redshift ($z$) from the Swift XRT repository as well as over 100 Ly\,$α$ absorption measurements in $z>1.6$ sources. The observed trend of the average optical depth $τ$ at 0.5 keV is consistent with both a sharp increase of host $N_{\rm H}(z)$, and an absorbing diffuse intergala…
We jointly analyze the gamma-ray burst (GRB) data observed with BAT and XRT on board the Swift mission to present a global view on the internal energy dissipation processes in GRBs, including precursors, prompt gamma-ray emission, extended soft gamma-ray emission, and late X-ray flares. The Bayesian block method is utilized to analyze the BAT lightcurves to identify various emission episodes. Our results suggest that these emission components likely share a same physical origin, which is repeated activation of the GRB central engine. What we observe in the gamma-ray band may be the tip-of-iceb…
The fireshell model for Gamma-Ray Bursts (GRBs) naturally leads to a canonical GRB composed of a proper-GRB (P-GRB) and an afterglow. P-GRBs, introduced by us in 2001, are sometimes considered "precursors" of the main GRB event in the current literature. We show in this paper how the fireshell model leads to the understanding of the structure of GRBs, with precise estimates of the time sequence and intensities of the P-GRB and the of the afterglow. It leads as well to a natural classification of the canonical GRBs which overcomes the traditional one in short and long GRBs.
We review extragalactic $γ$-ray propagation models with emphasis on the electromagnetic (EM) cascade process in the magnetized expanding Universe. We consider cascades initiated by primary protons of ultra-high energy accelerated by blazars and show that the observable spectrum is similar to the universal spectrum of a purely EM cascade. We also present a detailed calculation of the observable angular distribution for the case of EM cascades developing from relatively nearby (<20 Mpc) sources. Finally, we calculate the point-like source differential sensitivity of a novel liquid Argon time pro…
Recently an extraordinarily bright gamma-ray burst, GRB 221009A, was observed by several facilities covering the whole electromagnetic spectrum. Gamma rays with energies up to 18 TeV were detected, as well as a possible photon with 251 TeV. Such energetic events are not expected because they would be attenuated by pair-production interactions with the extragalactic background light. This tension is, however, only apparent, and does not call for any unconventional explanation. Here I show that these observations can be interpreted as the result of ultra-high-energy cosmic rays (UHECRs) interact…
Gamma rays from distant blazars interact with the extragalactic background light, creating electron-positron pairs, and reducing the gamma-ray flux measured by ground-based atmospheric Cherenkov gamma-ray telescopes. These pairs can Compton-scatter the cosmic microwave background, creating a gamma-ray signature observable by the Fermi Large Area Telesope (LAT). The signature is also dependent on the intergalactic magnetic field (IGMF), since it can deflect the pairs from our line of sight, reducing the gamma-ray emission. We present preliminary constraints on the IGMF using Fermi-LAT and Chere…
The origin of the first magnetic fields in the Universe is a standing problem in cosmology. Intergalactic magnetic fields (IGMFs) may be an untapped window to the primeval Universe, providing further constrains on magnetogenesis. We demonstrate the feasibility of using ultra-high-energy cosmic rays (UHECRs) to constrain the helicity of IGMFs by performing simulations of cosmic-ray propagation in simple magnetic field configurations. We show that the first harmonic moments of the arrival distribution of UHECRs may be used to measure the absolute value of the helicity and its sign.
We report a measurement of intergalactic magnetic fields using combined data from Atmospheric Cherenkov Telescopes and Fermi Gamma-Ray Space Telescope, based on the spectral data alone. If blazars are assumed to produce both gamma rays and cosmic rays, the observed spectra are not sensitive to the intrinsic spectrum of the source, because, for a distant blazar, secondary photons produced in line-of-sight cosmic-ray interactions dominate the signal. In this case, we find 0.01 fG < B < 30 fG. If one excludes the cosmic-ray component, the 0.01 fG lower limit remains, but the upper limit depends o…
We present the results of Monte-Carlo simulations of three-dimensional electromagnetic cascade initiated by interactions of the multi-TeV gamma-rays with the cosmological infrared/optical photon background in the intergalactic medium. Secondary electrons in the cascade are deflected by the intergalactic magnetic fields before they scatter on CMB photons. This leads to extended 0.1-10 degree scale emission at multi-GeV and TeV energies around extragalactic sources of very-high-energy gamma-rays. The morphology of the extended emission depends, in general, on the properties of magnetic fields in…
One of the most promising ways to probe intergalactic magnetic fields (IGMFs) is through gamma rays produced in electromagnetic cascades initiated by high-energy gamma rays or cosmic rays in the intergalactic space. Because the charged component of the cascade is sensitive to magnetic fields, gamma-ray observations of distant objects such as blazars can be used to constrain IGMF properties. Ground-based and space-borne gamma-ray telescopes deliver spectral, temporal, and angular information of high-energy gamma-ray sources, which carries imprints of the intervening magnetic fields. This provid…
The extraordinarily bright gamma-ray burst GRB 221009A was observed by a large number of observatories, from radio frequencies to gamma-rays. Of particular interest are the reported observations of photon-like air showers of very high energy: an 18 TeV event in LHAASO and a 251 TeV event at Carpet-2. Gamma rays at these energies are expected to be absorbed by pair-production events on background photons when travelling intergalactic distances. Several works have sought to explain the observations of these events, assuming they originate from GRB 221009A, by invoking axion-like particles (ALPs)…
Pair echo model of CTAO/LST-1 signal from GRB 221009A
Université Paris Cité（巴黎西岱大学）；CNRS, Astroparticule et Cosmologie（法国国家科学研究中心，亚原子粒子与宇宙学）；Laboratory of Astrophysics, École Polytechnique Fédérale de Lausanne（洛桑联邦理工学院天体物理学实验室）；Institute for Cosmic Ray Research, The University of Tokyo（东京大学宇宙射线研究所）；Université Paris-Saclay（巴黎萨克雷大学）；CEA, CNRS, AIM（法国原子能委员会，法国国家科学研究中心，天体物理学与分子生物学研究所）；Gran Sasso Science Institute（格兰萨索科学研究所）；Istituto Nazionale di Fisica Nucleare (INFN), Sez. Padova（意大利国家核物理研究所，帕多瓦分部）；INAF - Osservatorio Astronomico di Brera（意大利国家天体物理研究所，布雷拉天文台）
INTEGRAL's JEM-X instrument offers a very rare opportunity to observe the full prompt X-ray emission from GRBs and the transition to the afterglow phase. A study of prompt X-ray flares in some bursts from the INTEGRAL GRB sample and the early X-ray post-GRB emission from 3-35 keV is presented here. Significant post-GRB emission above 10 keV is observed for GRB 041219A and GRB 081003A.
The origin of ultra-high energy cosmic rays (UHECRs) is one of the most mystifying issues in astroparticle physics. It has been suggested that gamma-ray bursts (GRBs) are excellent acceleration sites for cosmic rays. The propagation of UHECRs from the GRB host galaxy to the Earth should generate delayed secondary photons and neutrinos. Here we present a dedicated search for delayed UHECR and neutrino emission centered around the position of nearby GRB 980425/SN 1998bw. Located at a distance of 36.9 Mpc, GRB 980425/SN 1998bw is well within the Greisen-Zatsepin-Kuzmin (GZK) distance horizon. We …
We explore potential of current and next-generation gamma-ray telescopes for the detection of weak magnetic fields in the intergalactic medium. We demonstrate that using two complementary techniques, observation of extended emission around point sources and observation of time delays in gamma-ray flares, one would be able to probe most of the cosmologically and astrophysically interesting part of the "magnetic field strength" vs. "correlation length" parameter space. This implies that gamma-ray observations with Fermi and ground-based Cherenkov telescopes will allow to (a) strongly constrain t…
The origin of prompt emission from gamma ray bursts remains to be an open question. Correlated prompt optical and gamma-ray emission observed in a handful of GRBs strongly suggests a common emission region, but failure to adequately fit the broadband GRB spectrum prompted the hypothesis of different emission mechanisms for the low- and high-energy radiations. We demonstrate that our multi-component model for GRB gamma-ray prompt emission provides an excellent fit to GRB 110205A from optical to gamma-ray energies. Our results show that the optical and highest gamma-ray emissions have the same s…
