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(abridged)Prompt GRB emission is often interpreted as synchrotron radiation from high-energy electrons accelerated in internal shocks. Fast synchrotron cooling predicts that the photon index below the spectral peak is alpha=-3/2. This…

High Energy Astrophysical Phenomena · Physics 2015-05-19 F. Daigne , Z. Bosnjak , Guillaume Dubus

A comprehensive study is given to short gamma-ray bursts (sGRBs) in the third Swift/BAT GRB Catalog from December 2004 to July 2019. We examine in details the temporal properties of the three components in the prompt gamma-ray emission…

High Energy Astrophysical Phenomena · Physics 2021-03-17 X. J. Li , Z. B. Zhang , X. L. Zhang , H. Y. Zhen

We study the duration and variability of late time X-ray flares following gamma-ray bursts (GRBs) observed by the narrow field X-ray telescope (XRT) aboard the {\it Swift} spacecraft. These flares are thought to be indicative of late time…

Astrophysics · Physics 2009-11-13 Daniel Kocevski , Nathaniel Butler , Joshua S. Bloom

Existing ubiquitously in the Universe with the highest luminosity, the Lyman-$\alpha$ emission line encodes abundant physical information about the gaseous medium it interacts with. Nevertheless, the resonant nature of Ly$\alpha$…

Astrophysics of Galaxies · Physics 2022-05-11 Zhihui Li , Max Gronke

The prompt-emission spectra of gamma-ray bursts (GRBs) are commonly described by the empirical Band function. The typical low-energy spectral index is $\sim -1$, which poses a challenge to standard synchrotron radiation models. We…

High Energy Astrophysical Phenomena · Physics 2026-04-23 Jia-Ming Chen , Ke-Rui Zhu , Zhao-Yang Peng , Yong-Gang Zheng , Yun-Lu Gong , Shan Chang , Shi-Ting Tian , Li Zhang

Solar flare termination shocks have been suggested as one of the promising drivers for particle acceleration in solar flares, yet observational evidence remains rare. By utilizing radio dynamic spectroscopic imaging of decimetric stochastic…

Solar and Stellar Astrophysics · Physics 2019-10-16 Bin Chen , Chengcai Shen , Katharine K. Reeves , Fan Guo , Sijie Yu

Stochastic gradient descent (SGD) has been widely used in machine learning due to its computational efficiency and favorable generalization properties. Recently, it has been empirically demonstrated that the gradient noise in several deep…

Machine Learning · Statistics 2019-06-24 Thanh Huy Nguyen , Umut Şimşekli , Mert Gürbüzbalaban , Gaël Richard

We study the temporal intensity profile, or pulse shape, of cosmic ray ground level enhancements (GLEs) by calculating the rise $(\tau_\mathrm{r})$ and decay $(\tau_\mathrm{d})$ times for a small subset of all available events. Although…

Space Physics · Physics 2017-04-12 R. D. Strauss , O. Ogunjobi , H. Moraal , K. G. McCracken , R. A. Caballero-Lopez

Timing analysis is a powerful tool with which to shed light on the still obscure emission physics and geometry of the prompt emission of GRBs. Fourier power density spectra (PDS) characterise time series as stochastic processes and can be…

High Energy Astrophysical Phenomena · Physics 2016-04-20 C. Guidorzi , S. Dichiara , L. Amati

The principal paradigm for gamma-ray bursts (GRBs) suggests that the prompt transient gamma-ray signal arises from multiple shocks internal to the relativistic expansion. This paper explores how GRB prompt emission spectra can constrain…

High Energy Astrophysical Phenomena · Physics 2009-06-25 Matthew G. Baring

Standing slow mode waves in hot flaring loops are exclusively observed in spectrometers and are used to diagnose the magnetic field strength and temperature of the loop structure. Due to the lack of spatial information, the longitudinal…

Solar and Stellar Astrophysics · Physics 2015-07-15 D. Yuan , T. Van Doorsselaere , D. Banerjee , P. Antolin

Long gamma-ray bursts (GRBs) frequently exhibit complex prompt emission structures with multiple temporally distinct episodes, such as a main emission (ME) phase followed by a weak extended emission (EE) tail. Whether these subcomponents…

High Energy Astrophysical Phenomena · Physics 2026-02-27 Liang Li , Xiao Wang , Zhi-Li Cui , Cheng-Long Xiao , Wen Li , Yu Wang , Zi-Gao Dai , Rong-Gen Cai

We study time-resolved spectra of the prompt emission of Swift Gamma-ray bursts (GRB). Our goal is to see if previous BATSE claims of the existence of a large amount of spectra with the low energy photon indices harder than 2/3 are…

High Energy Astrophysical Phenomena · Physics 2015-05-13 V. Savchenko , A. Neronov

An intriguing hypothesis, that there exists a decaying X-ray emission component before the GRB trigger, has been suggested in order to explain the shallow decay phase of the X-ray afterglow detected in many Swift GRBs. If this "prior…

High Energy Astrophysical Phenomena · Physics 2015-05-28 Tesla Birnbaum , Bing Zhang , Bin-Bin Zhang , En-Wei Liang

This paper considers the problem of finite dimensional output feedback H-infinity control for a class of nonlinear spatially distributed processes (SDPs) described by highly dissipative partial differential equations (PDEs), whose state is…

Systems and Control · Computer Science 2015-03-31 Huai-Ning Wu , Hong-Du Wang

The prompt emission phase of gamma-ray bursts (GRBs) exhibits two distinct patterns of the peak-energy ($E_p$) evolution, i.e., time-resolved spectral analyses of $\nu F_{\nu}$ spectra of broad pulses reveal (1) "hard-to-soft" and (2)…

High Energy Astrophysical Phenomena · Physics 2018-12-26 Z. Lucas Uhm , Bing Zhang , Judith Racusin

As a basic characteristic of cosmic ray (CR) propagation, the diffusive halo can advance our understanding of many CR-related studies and indirect dark matter. The method to derive the halo size usually has degeneracy problems thus affected…

High Energy Astrophysical Phenomena · Physics 2021-10-27 Yu-Hua Yao , Bing-Qiang Qiao , Wei Liu , Qiang Yuan , Hong-Bo Hu , Xiao-Jun Bi , Chao-Wen Yang , Yi-Qing Guo

We consider a relativistic spherical shell and calculate its spectral flux as received by a distant observer. Using two different methods, we derive a simple analytical expression of the observed spectral flux and show that the well-known…

High Energy Astrophysical Phenomena · Physics 2015-08-06 Z. Lucas Uhm , Bing Zhang

Almost all the X-ray afterglows of gamma-ray bursts (GRBs) observed by the Swift satellite have a shallow decay phase in the first thousands of seconds. We show that in an inhomogeneous jet (multiple-subjet or patchy-shell) model the…

Astrophysics · Physics 2009-11-13 Kenji Toma , Kunihito Ioka , Ryo Yamazaki , Takashi Nakamura

Several trends have been identified in the prompt gamma-ray burst (GRB) emission: e.g. hard-to-soft evolution, pulse width evolution with energy, time lags, hardness-intensity/-fluence correlations. Recently Fermi has significantly extended…

High Energy Astrophysical Phenomena · Physics 2015-06-19 Z. Bosnjak , F. Daigne