Recent detection of sub-TeV emission from gamma-ray bursts (GRBs) represents a breakthrough in the GRB study. The multi-wavelength data of the afterglows of GRB 190114C support the synchrotron self-Compton (SSC) origin for its sub-TeV emission. We present a comparative analysis on the SSC emission of GRB afterglows in the homogeneous and wind environment in the framework of the forward shock model. The $γγ$ absorption of very high-energy photons due to pair production within the source and the Klein-Nishina effect on the inverse-Compton scattering are considered. Generally a higher SSC flux is expected for a larger circum-burst density due to a larger Compton parameter, but meanwhile the internal $γγ$ absorption is more severer for sub-TeV emission. The flux ratio between the SSC component and the synchrotron component decreases more quickly with time in the wind medium case than that in the homogenous-density medium case. The light curves of the SSC emission are also different for the two types of media. We also calculate the cascade emission resulted from the absorbed high-energy photons. In the ISM environment with $n> 1\,\rm cm^{-3}$, the cascade synchrotron emission could be comparable to the synchrotron emission of the primary electrons in the optical band, which may flatten the optical afterglow light curve at early time ($t<1$ h). In the wind medium with $A_{\ast}> 0.1$, the cascade emission in the eV-GeV band is comparable or even larger than the emission of the primary electrons at early time.
The free decay of non-helical relativistic magnetohydrodynamic turbulence is studied numerically, and found to exhibit cascading of magnetic energy toward large scales. Evolution of the magnetic energy spectrum $P_M(k,t)$ is self-similar in time and well modeled by a broken power law with sub-inertial and inertial range indices very close to $7/2$ and $-2$ respectively. The magnetic coherence scale is found to grow in time as $t^{2/5}$, much too slow to account for optical polarization of gamma-ray burst afterglow emission if magnetic energy is to be supplied only at microphysical length scale…
The new and extreme population of GRBs detected by Fermi-LAT shows several new features in high energy gamma-rays that are providing interesting and unexpected clues into GRB prompt and afterglow emission mechanisms. Over the last 6 years, it has been Swift that has provided the robust dataset of UV/optical and X-ray afterglow observations that opened many windows into components of GRB emission structure. The relationship between the LAT detected GRBs and the well studied, fainter, less energetic GRBs detected by Swift-BAT is only beginning to be explored by multi-wavelength studies. We explo…
The Hall effect is an important nonlinear mechanism affecting the evolution of magnetic fields in neutron stars. Studies of the governing equation, both theoretical and numerical, have shown that the Hall effect proceeds in a turbulent cascade of energy from large to small scales. We investigate the small-scale Hall instability conjectured to exist from the linear stability analysis of Rheinhardt and Geppert. Identical linear stability analyses are performed to find a suitable background field to model Rheinhardt and Geppert's ideas. The nonlinear evolution of this field is then modelled using…
We present an analysis of 123 Gamma-ray bursts (GRBs) with known redshifts possessing an afterglow plateau phase. We reveal that $L_a-T^{*}_a$ correlation between the X-ray luminosity $L_a$ at the end of the plateau phase and the plateau duration, $T^*_a$, in the GRB rest frame has a power law slope different, within more than 2 $σ$, from the slope of the prompt $L_{f}-T^{*}_{f}$ correlation between the isotropic pulse peak luminosity, $L_{f}$, and the pulse duration, $T^{*}_{f}$, from the time since the GRB ejection. Analogously, we show differences between the prompt and plateau phases in th…
Modeling the Multi-Wavelength Afterglow of Short Gamma-Ray Bursts with a Plateau Phase
Nanjing University（南京大学）；Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education（现代天文学与天体物理学教育部重点实验室（南京大学））；Xinjiang Astronomical Observatory, Chinese Academy of Sciences（中国科学院新疆天文台）；Xinjiang Key Laboratory of Radio Astrophysics（新疆射电天文重点实验室）；State Key Laboratory of Radio Astronomy and Technology（射电天文与技术国家重点实验室）；Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台）；Institute of Space Weather, Nanjing University of Information Science and Technology（南京信息工程大学空间天气研究所）；Guangxi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, Guangxi University（广西大学物理科学与技术学院相对论天体物理学重点实验室）；Institute of Fundamental Physics and Quantum Technology, Ningbo University（宁波大学基础物理与量子技术研究所）
The X-ray afterglow plateau emission observed in many Gamma-ray Bursts (GRBs) has been interpreted as either being fueled by fallback onto a newly formed black hole, or by the spin-down luminosity of an ultra-magnetized millisecond neutron star. If the latter model is assumed, GRB X-ray afterglow light curves can be analytically reproduced. We fit a sample of GRB X-ray plateaus, interestingly yielding a distribution in the magnetic field versus spin period (B-P) diagram consistent with $B\propto P^{7/6}$. This is expected from the well-established physics of the spin-up line minimum period for…
In this work we study the distribution of temporal power-law decay indices, $α$, in the Gamma Ray Burst (GRB) afterglow phase, fitted for $176$ GRBs (139 long GRBs, 12 short GRBs {\it with extended emission} and 25 X-Ray Flashes (XRFs)) with known redshifts. These indices are compared with the temporal decay index, $α_W$, derived with the light curve fitting using the \cite{willingale07} model. This model fitting yields similar distributions of $α_W$ to the fitted $α$, but for individual bursts a difference can be significant. Analysis of ($α$, $L_a$) distribution, where $L_a$ is the character…
We present synthetic radio images of the GRB170817A afterglow, computed from moving-mesh hydrodynamic simulations of binary neutron star merger outflows. Having expanded for nearly a year, the merger remnant is expected to subtend roughly 5 milli-arcseconds (mas) on the sky, potentially resolvable by very long baseline radio imaging techniques. Any observations revealing the radio centroid to be offset from the line-of-site to the merger would be the smoking gun of a jetted outflow. However, our results indicate that a measurement of the centroid position alone cannot independently determine w…
We explore the possibility that radio loud gamma-ray bursts (GRBs) result from the collapse of massive stars in interacting binary systems, while radio quiet GRBs are produced by the collapse of single massive stars. A binary collapsar system can have the necessary angular momentum and energy budget to explain the longer prompt gamma-ray durations and higher isotropic energies seen in the the radio loud sub-sample of long GRBs. Additionally binary systems can lead to rich and extended circumstellar environments that allow for the presence of the long-lived radio afterglows seen in the radio lo…
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。
We analyze the additional effect on planetary atmospheres of recently detected gamma-ray burst afterglow photons in the range up to 1 TeV. For an Earth-like atmosphere we find that there is a small additional depletion in ozone versus that modeled for only prompt emission. We also find a small enhancement of muon flux at the planet surface. Overall, we conclude that the additional afterglow emission, even with TeV photons, does not result in a significantly larger impact over that found in past studies.
With this paper we introduce the concept of apparent structure of a GRB jet, as opposed to its intrinsic structure. The latter is customarily defined specifying the functions epsilon(theta) (the energy emitted per jet unit solid angle) and Gamma(theta) (the Lorentz factor of the emitting material); the apparent structure is instead defined by us as the isotropic equivalent energy E_iso(theta_v) as a function of the viewing angle theta_v. We show how to predict the apparent structure of a jet given its intrinsic structure. We find that a Gaussian intrinsic structure yields a power law apparent …
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 $10\text{--}150 \, \mathrm{M}_\odot$ with $Δ\mathrm{M}=10 \, \mathrm{M}_\odot$ and rotation rate $v/v_{\rm{crit}}=0$ to $0.6$ with a velocity resolution $Δv/v_{\rm{crit}} =0.1$. 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 associa…
Dense gas linked to star-forming regions photoionised by embedded gamma-ray bursts
Istituto di Astrofisica e Planetologia Spaziali, INAF（太空天体物理学与行星学研究所，意大利国家天体物理研究所）；Osservatorio Astronomico di Roma, INAF（罗马天文台，意大利国家天体物理研究所）；Physics Department, University of Calabria（卡拉布里亚大学物理系）；Osservatorio di Astrofisica e Scienza dello Spazio, INAF（空间天体物理学与科学观测站，意大利国家天体物理研究所）；Laboratori Nazionali di Frascati, INFN（弗拉斯卡蒂国家实验室，意大利国家核物理研究所）；Instituto de Astronomía, Universidad Nacional Autónoma de México（墨西哥国立自治大学天文学研究所）；Department of Physics, University of Western Australia（西澳大利亚大学物理系）；College of Science and Mathematics, University of the Virgin Islands（维尔京群岛大学科学与数学学院）
Recently (May-November 2013) highest energy neutrino events have been presented by ICECUBE. Most (21) of all these (28) events are cascades shower whose flux exhibits a sharp hardening respect other lower energy atmospheric neutrino component, events suggesting an injection of extraterrestrial neutrino, mostly nu e, nu tau, making cascades. ICECUBE claimed that a component (10:6+5:0 3:6), a third, of these events must be a trace of expected downward muons and-or atmospheric neutrinos (muon track dominated): The probability that this scenario occurs is very poor, about 0.1- 0.5%. The paradox mi…
The brightest long gamma-ray burst detected so far by the Swift-BAT and Fermi-GBM telescopes, GRB~221009A, provides an unprecedented opportunity for understanding the high-energy processes in extreme transient phenomena. We find that the conventional leptonic models, synchrotron and synchrotron-self-Compton, for the afterglow emission from this source have difficulties explaining the observation of $\gtrsim 10$ TeV $γ$ rays, by the LHAASO detector, and extending up to 18 TeV energies. We model $γ$-ray spectrum estimated in the energy range 0.1-1 GeV by the Fermi-LAT detector. The flux predicte…
Gamma-ray Bursts (GRBs) are flashes of gamma-rays thought to originate from rare forms of massive star collapse (long GRBs), or from mergers of compact binaries (short GRBs) containing at least one neutron star (NS). The nature of the post-explosion / post-merger remnant (NS versus black hole, BH) remains highly debated. In ~50% of both long and short GRBs, the temporal evolution of the X-ray afterglow that follows the flash of gamma-rays is observed to "plateau" on timescales of 100-10000 s since explosion, possibly signaling the presence of energy injection from a long-lived, highly magnetiz…
The gamma ray burst apparent average isotropic power versus their red-shift of all known GRB (Sept.2009) is reported. It calls for an unrealistic Gamma Ray Burst Evolution around us or it just probe the need of a very thin gamma precession-jet model. These precessing and spinning jet are originated by Inverse Compton and-or Synchrotron Radiation at pulsars or micro-quasars sources, by ultra-relativistic electrons. These Jets are most powerful at Supernova birth, blazing, once on axis, to us and flashing GRB detector. The trembling of the thin jet (spinning, precessing, bent by magnetic fields)…
