Aharonian 2009 HESS对伽玛暴从2003到2007甚高能的观测

主要内容:
没有一个事例

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文章信息:

arXiv:0901.2187 [ps, pdf, other]

Title: H.E.S.S. observations of gamma-ray bursts in 2003-2007

Authors: F. Aharonian (HESS collaboration), et al

Comments: 9 pages, 4 tables, 3 figures

Subjects: Astrophysics (astro-ph)

Very-high-energy (VHE; >~100 GeV) gamma-rays are expected from gamma-ray bursts (GRBs) in some scenarios. Exploring this photon energy regime is necessary for understanding the energetics and properties of GRBs. GRBs have been one of the prime targets for the H.E.S.S. experiment, which makes use of four Imaging Atmospheric Cherenkov Telescopes (IACTs) to detect VHE gamma-rays. Dedicated observations of 32 GRB positions were made in the years 2003-2007 and a search for VHE gamma-ray counterparts of these GRBs was made. Depending on the visibility and observing conditions, the observations mostly start minutes to hours after the burst and typically last two hours. Results from observations of 22 GRB positions are presented and evidence of a VHE signal was found neither in observations of any individual GRBs, nor from stacking data from subsets of GRBs with higher expected VHE flux according to a model-independent ranking scheme. Upper limits for the VHE gamma-ray flux from the GRB positions were derived. For those GRBs with measured redshifts, differential upper limits at the energy threshold after correcting for absorption due to extra-galactic background light are also presented.

Fan 2009 考虑GRB 080319B的中子衰变来解释光学

主要内容:
基本意思是中子衰变可以让shell晚碰撞, 导致晚期的内激波, 产生强的光学辐射

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arXiv:0901.2128 [ps, pdf, other]

Title: Naked-eye optical flash from GRB 080319B: Tracing the decaying neutrons in the outflow

Authors: Yi-Zhong Fan, Bing Zhang, Da-Ming Wei

Comments: 4 pages, accepted for publication in Phys. Rev. D as a Rapid Communication

Journal-ref: Phys. Rev. D 79, 021301(R) (2009)

Subjects: Astrophysics (astro-ph)

For an unsteady baryonic gamma-ray burst (GRB) outflow, the fast and slow proton shells collide with each other and produce energetic soft gamma-ray emission. If the outflow has a significant neutron component, the ultra-relativistic neutrons initially expand freely until decaying at a larger radius. The late time proton shells ejected from the GRB central engine, after powering the regular internal shocks, will sweep these $\beta-$decay products and give rise to very bright UV/optical emission. The naked-eye optical flash from GRB 080319B, an energetic explosion in the distant universe, can be well explained in this way.

van Putten 2009 旋转黑洞power非热辐射

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Title:		Non-thermal transient sources from rotating black holes
Authors:		van Putten, Maurice H. P. M.; Gupta, Alok C.
Publication:		eprint arXiv:0901.1674
Publication Date:		01/2009
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		Accepted by MNRAS
Bibliographic Code:		2009arXiv0901.1674V

Abstract

Rotating black holes can power the most extreme non-thermal transient sources. They have a long-duration viscous time-scale of spin-down and produce non-thermal emissions along their spin-axis, powered by a relativistic capillary effect. We report on the discovery of exponential decay in BATSE light curves of long GRBs by matched filtering, consistent with a viscous time-scale, and identify UHECRs energies about the GZK threshold in linear acceleration of ion contaminants along the black hole spin-axis, consistent with black hole masses and lifetimes of FR II AGN. We explain the absence of UHECRs from BL Lac objects due to UHECR emissions preferably at appreciable angles away from the black hole spin-axis. Black hole spin may be key to unification of GRBs and their host environments, and to AGN and their host galaxies. Our model points to long duration bursts in radio from long GRBs without supernovae and gravitational-waves from all long GRBs.

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罗仑兹变换的记忆

罗仑兹变换, 可以用矩阵形式来记忆:
Latex

$$
\left(
\begin{array}{l}
dt \\ dx
\end{array}
\right)
=
\left(
\begin{array}{ll}
\gamma & \gamma\beta \\ \gamma\beta & \gamma
\end{array}
\right)
\left(
\begin{array}{l}
dt'\\ dx'
\end{array}
\right)
$$

为了检查, 可以假设beta=0
From Shiho

Fugusto 2009 有个高能的探测到的伽玛暴可能只是噪声

主要内容:
叫做"sunset enhancement", 就是在傍晚的时候会有高能的增亮现象, 可能被伽玛暴探测器当做伽玛暴了. 文章给了两个例子. 不过要是统计一下是不是每次探测器碰到傍晚光变就增亮, 或者统计一下各个暴的探测时间, 看是不是有很大一部分暴是在"傍晚"观测到的, 就更能说明问题了.

sunset enhancement的原理没看懂.

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文章信息:

arXiv:0901.1832 [ps, pdf, other]

Title: Gamma ray burst triggers at daytime and night-time interface

Authors: C. R. A. Augusto, J. B. Dolival, C. E. Navia, K. H. Tsui

Comments: 6 pages, 9 figures

Subjects: Astrophysics (astro-ph)

There is a difference between the solar ionization concentration in the ionosphere in the daytime and at night-time. At night the E-region ion concentration peak is dramatically reduced due to chemical losses and the rapid change in the vertical polarization electric field at the time around sunset, which is due to the accelerating neutral wind dynamo and which produces a corresponding change in the zonal electric field through curl-free requirements. The result is the formation of a layer of high conductivity, at the daytime-night-time interface. This phenomenon in the South Atlantic Anomaly (SAA) area, provokes an increase in the precipitation of charge particles which is well known and is commonly termed "sunset enhancement". In the following we show that some gamma ray burst (GRB) triggers observed by spacecraft GRB detectors such as INTEGRAL, AGILE, and Fermi are probably noise triggers, produced by omni-directional particle precipitation, because they are in temporal coincidence with muon enhancement observed at ground level by the Tupi telescopes with different orientations at $\sim 21$ UT (local sunset), and located inside the SAA region.

Covino 2009 地面Cerenkov 望远镜如何与Fermi配合

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Title:		Gamma-ray burst observations with new generation imaging atmospheric Cerenkov Telescopes in the FERMI era
Authors:		Covino, S.; Garczarczyk, M.; Galante, N.; Gaug, M.; Antonelli, A.; Bastieri, D.; Campana, S.; Longo, F.; Scapin, V.
Publication:		eprint arXiv:0901.1589
Publication Date:		01/2009
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		9 pages, two figures. Proceeding for the 6th "Science with the New Generation of High Energy Gamma-Ray Experiments" workshop
Bibliographic Code:		2009arXiv0901.1589C

Abstract

After the launch and successful beginning of operations of the FERMI satellite, the topics related to high-energy observations of gamma-ray bursts have obtained a considerable attention by the scientific community. Undoubtedly, the diagnostic power of high-energy observations in constraining the emission processes and the physical conditions of gamma-ray burst is relevant. We briefly discuss how gamma-ray burst observations with ground-based imaging array Cerenkov telescopes, in the GeV-TeV range, can compete and cooperate with FERMI observations, in the MeV-GeV range, to allow researchers to obtain a more detailed and complete picture of the prompt and afterglow phases of gamma-ray bursts.

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Bianchin 2009 用Integral上的PICsIT的历史数据寻找以前可能的伽玛暴

主要内容:
能段0.2-10MeV

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Title:		GRB Observed by IBIS/PICsIT in the MeV Energy Range
Authors:		Bianchin, V.; Foschini, L.; Di Cocco, G.; Gianotti, F.; Gotz, D.; Laurent, P.; Malaguti, G.; Schiavone, F.
Publication:		eprint arXiv:0901.1532
Publication Date:		01/2009
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		6 pages, 3 figures. Poster presented at COSPAR 2008. Advaces in Space Research, accepted for publication
Bibliographic Code:		2009arXiv0901.1532B

Abstract

We present the preliminary results of a systematic search for GRB and other transients in the publicly available data for the IBIS/PICsIT (0.2-10 MeV) detector on board INTEGRAL. Lightcurves in 2-8 energy bands with time resolution from 1 to 62.5 ms have been collected and an analysis of spectral and temporal characteristics has been performed. This is the nucleus of a forthcoming first catalog of GRB observed by PICsIT.

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Ruffini 2008 fireshell模型和长短暴的划分

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Title:		The canonical Gamma-Ray Bursts: long, "fake"-"disguised" and "genuine" short bursts
Authors:		Ruffini, Remo; Aksenov, Alexey; Grazia Bernardini, Maria; Bianco, Carlo Luciano; Caito, Letizia; Giovanna Dainotti, Maria; De Barros, Gustavo; Guida, Roberto; Vereshchagin, Gregory; Xue, She-Sheng
Publication:		eprint arXiv:0901.1549
Publication Date:		01/2009
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		8 pages,4 figures, Proceedings of the 2008 Cefalu' Conference
Bibliographic Code:		2009arXiv0901.1549R

Abstract

The Gamma-Ray Bursts (GRBs) offer the unprecedented opportunity to observe for the first time the blackholic energy extracted by the vacuum polarization during the process of gravitational collapse to a black hole leading to the formation of an electron-positron plasma. The uniqueness of the Kerr-Newman black hole implies that very different processes originating from the gravitational collapse a) of a single star in a binary system induced by the companion, or b) of two neutron stars, or c) of a neutron star and a white dwarf, do lead to the same structure for the observed GRB. The recent progress of the numerical integration of the relativistic Boltzmann equations with collision integrals including 2-body and 3-body interactions between the particles offer a powerful conceptual tool in order to differentiate the traditional "fireball" picture, an expanding hot cavity considered by Cavallo and Rees, as opposed to the "fireshell" model, composed of an internally cold shell of relativistically expanding electron-positron-baryon plasma. The analysis of the fireshell naturally leads to a canonical GRB composed of a proper-GRB and an extended afterglow. By recalling the three interpretational paradigms for GRBs we show how the fireshell model leads to an understanding of the GRB structure and to an alternative classification of short and long GRBs.

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Lazar 2009 用假设shell里有很多小的eddy来产生伽玛暴的光变

主要内容:
假设shell里有一些比较小的eddy, 它们辐射光子, 罗仑兹变换后到伽玛射线. 由于它们的尺寸比较小, 光变的pulse的时标就比较小, 而伽玛暴的持续时标是R/Gamma^2c.

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Title:		GRB Light Curves in the Relativistic Turbulence Model
Authors:		Lazar, Ayah; Nakar, Ehud; Piran, Tsvi
Publication:		eprint arXiv:0901.1133
Publication Date:		01/2009
Origin:		ARXIV
Keywords:		Astrophysics
Bibliographic Code:		2009arXiv0901.1133L

Abstract

Relativistic Turbulence provides an alternative to internal shocks as a mechanism for producing GRBs' variable light curves with efficient conversion of energy to radiation. In this model the relativistic outflow is broken into small eddies moving relativistically in the outflow's rest frame. Variability arises because an observer sees an eddy only when its velocity points towards him and only a small fraction of the eddies are observed. Relativistic turbulence with a significant relativistic velocity requires converting and maintaing a large fraction of the over all energy into turbulent motion. While it is not clear how this is achieved, we explore here, using a toy model, the constraints the model parameters results in light curves comparable to the observations. We find that a tight relation between the size of the eddies and the bulk and turbulent Lorentz factors is needed and that the variability level determines the turbulent Lorentz factor. While the model successfully produces the observed variability there are several inconsistencies with other properties of the light curves. Most of which, but not all, might be resolved if the central engine is active for a long time producing a number of shells, resembling to some extent the internal shocks model.

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Ioka 2008 伽玛暴遗迹作为"未知"TeV光子的源

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Title:		Hypernova and Gamma-Ray Burst Remnants as TeV Unidentified Sources
Authors:		Ioka, Kunihito; Meszaros, Peter
Publication:		eprint arXiv:0901.0744
Publication Date:		01/2009
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		5 pages, 3 figures
Bibliographic Code:		2009arXiv0901.0744I

Abstract

We investigate hypernova (hyper-energetic supernova) and gamma-ray burst (GRB) remnants in our Galaxy as TeV gamma-ray sources, particularly in the role of potential TeV unidentified sources, which have no clear counterpart at other wavelengths. We show that the observed bright sources in the TeV sky could be dominated by GRB/hypernova remnants, even though they are fewer than supernova remnants (SNRs). If this is the case, TeV SNRs are more extended (and more numerous) than deduced from current observations. In keeping with their role as cosmic ray accelerators, we discuss hadronic gamma-ray emission from pi^0 decay, from beta decay followed by inverse Compton emission, and propose a third, novel process of TeV gamma-ray emission arising from the decay of accelerated radioactive isotopes such as 56Co entrained by relativistic or semi-relativistic jets in GRBs/hypernovae. We discuss the relevant observational signatures which could discriminate between these three mechanisms.

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