Linder 2009 完全用吸积盘解释X射线余辉的快下将和平降阶段

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Title:		Collapsar Accretion and the Gamma-Ray Burst X-Ray Light Curve
Authors:		Lindner, Christopher C.; Milosavljevic, Milos; Couch, Sean M.; Kumar, Pawan
Publication:		eprint arXiv:0910.4989
Publication Date:		10/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics
Comment:		16 pages, 10 figures
Bibliographic Code:		2009arXiv0910.4989L

Abstract

We present axisymmetric hydrodynamical simulations of the long-term accretion of a rotating GRB progenitor star, a "collapsar," onto the central compact object. The simulations were carried out with the adaptive mesh refinement code FLASH in two spatial dimensions and with an explicit shear viscosity. The evolution of the central accretion rate exhibits phases reminiscent of the long GRB gamma-ray and X-ray light curve, which lends support to the proposal that the luminosity is modulated by the central accretion rate. After a few tens of seconds, an accretion shock sweeps outward through the star. The formation and outward expansion of the accretion shock is accompanied with a sudden and rapid power-law decline in the central accretion rate Mdot ~ t^{-2.8}, which resembles the L_X ~ t^{-3} decline observed in the X-ray light curves. The collapsed, shock-heated stellar envelope settles into a thick, low-mass equatorial disk embedded within a massive, pressure-supported atmosphere. After a few hundred seconds, the inflow of low-angular-momentum material in the axial funnel reverses into an outflow from the surface of the thick disk. Meanwhile, the rapid decline of the accretion rate slows down, or even settles a in steady state with Mdot ~ 5x10^{-5} Msun/s, which resembles the "plateau" phase in the X-ray light curve. While the duration of the "prompt" phase depends on the resolution in our simulations, we provide an analytical model taking into account neutrino losses that estimates the duration to be ~20 s. The model suggests that the steep decline in GRB X-ray light curves is triggered by the circularization of the infalling stellar envelope at radii where the virial temperature is below ~10^{10} K, such that neutrino cooling shuts off and an outward expansion of the accretion shock becomes imminent.

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Re: 测试一下用邮件发blogger加图片

再次测试. 貌似显示起来比较困难.

2009/10/27 Yuan-Chuan Zou <yuanchuan@gmail.com>

添加的时候貌似没什么问题, 就看是否能在blogger那边显示了.

测试一下用邮件发blogger加图片

添加的时候貌似没什么问题, 就看是否能在blogger那边显示了.

Xiao 2009 加权估计长暴的红移

用多种方法估计红移, 然后给每个方法一个权重, 得到加权平均值. (不觉得这样就可以得到更好的估计值) ・ Find Similar Abstracts (with default settings below)

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Title:		Estimating Redshifts for Long Gamma-Ray Bursts
Authors:		Xiao, Limin; Schaefer, Bradley E.
Publication:		eprint arXiv:0910.4945
Publication Date:		10/2009
Origin:		ARXIV
Keywords:		Astrophysics - Cosmology and Extragalactic Astrophysics
Comment:		The Astrophysical Journal accepted
Bibliographic Code:		2009arXiv0910.4945X

Abstract

We are constructing a program to estimate the redshifts for GRBs from the original Swift light curves and spectra, aiming to get redshifts for the Swift bursts \textit{without} spectroscopic or photometric redshifts. We derive the luminosity indicators from the light curves and spectra of each burst, including the lag time between low and high photon energy light curves, the variability of the light curve, the peak energy of the spectrum, the number of peaks in the light curve, and the minimum rise time of the peaks. These luminosity indicators can each be related directly to the luminosity, and we combine their independent luminosities into one weighted average. Then with our combined luminosity value, the observed burst peak brightness, and the concordance redshift-distance relation, we can derive the redshift for each burst. In this paper, we test the accuracy of our method on 107 bursts with known spectroscopic redshift. The reduced $\chi^2$ of our best redshifts ($z_{best}$) compared with known spectroscopic redshifts ($z_{spec}$) is 0.86, and the average value of $log_{10}(z_{best}/z_{spec})$ is 0.01, with this indicating that our error bars are good and our estimates are not biased. The RMS scatter of $log_{10}(z_{best}/z_{spec})$ is 0.26. For Swift bursts measured over a relatively narrow energy band, the uncertainty in determining the peak energy is one of the main restrictions on our accuracy. Although the accuracy of our $z_{best}$ values are not as good as that of spectroscopic redshifts, it is very useful for demographic studies, as our sample is nearly complete and the redshifts do not have the severe selection effects associated with optical spectroscopy.

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2009.9.14-9.18 威尼斯shocking universe会议

会议网址: http://www.brera.inaf.it/sanservolo2009/index.html

他们说要提供ppt的, 不知道为什么也没上网.

以下是会议日程. 大致第一天Swift相关；第二天Fermi相关；第三天半天, 比较杂；第四天比较关注宇宙方面的如宿主星系, 高红移；第五天的也比较杂.

(时间表拷贝自网站上)

Sunday - September 13th
18:00 - 20:00	Registration & Welcome Cocktail
Monday - September 14th
07:45 - 08:45	Registration
	Chairman	M. Feroci
08:45 - 09:00	G. Chincarini	Welcome 此人很像偷天陷阱里的男主角老头. 附剧照 http://posters.imdb.cn/jz/46852
09:00 - 09:35	M. Lyutikov	GRB: observational progress and theoretical problems 主要内容大致有(这里以及以下都包含严重的偏见和记忆误差): 1. 一共有8个想080513这样的, 可能是短暴加一个tail; 2. 暴本身阶段的低频端的硬谱可能来自电子的分布; 3.说080916C的同步辐射模型是不行的
09:35 - 09:50	I. Steele	Optical polarization measurements of GRB060418 and GRB090102 他们利物浦的望远镜加了偏振片, 这是两个观测. 其中060418的小于8%, 最令人惊讶的是090102的有10%, 而且致信度还很高!
09:50 - 10:05	C. Guidorzi	The controversial link between prompt optical and gammarays: temporal study of GRB 080319B 说这个暴的光变里有3.3s的周期现象. 下图是time lag
10:05 - 10:30	Coffee Break
10:30 - 10:55	S. Barthelmy	GRB Prompt Emission and Swift-BAT 图左显示了三个仪器的分布和E_p的分布 1. 统计上, pulse的宽度 W~E_p^-0.4~z^0.4 2. 谱形上, cutoff power law的比Band的还多 3. 观测上, Swift的高红移的暴并没有更软 (这个可能说明E_p比较大, 即使红移比较高, 还是没看到peak的地方； 或者谱整个是一个比较好的幂律, 这样也不会看到变软； 或者, 当然最直接的解释应该是高红移的暴本身比较硬.) 4. 他们Swift在准备 sub-threshold, 就是不要那么强的伽玛光子信号就触发. 这样可以看到更多弱暴, 虽然会有很多误触发.
10:55 - 11:20	S. Kobayashi	Magnetized Fireballs and Early Afterglows
11:20 - 11:45	A. Pe'er	Observations, theory and implications of thermal emission from gamma-ray bursts 他主要还是说他的Themal component
11:45 - 12:05	L. Amati	Spectrum-energy correlation in GRB: status and perspectives 会议上有两个报告说Amati关系不对, 让他很郁闷. 在Tsvi的报告提问阶段都快结束后强烈要求发言, 终于给他机会, 说了很大一通. 最后说你们不能这样, 搞的让大家以为我这个关系真的就是错的样. Tsvi听了半天, 然后回了一句话, 闪人. 没听大明白, 大意是它是错的就是错的.
12:05 - 12:30	J. Racusin	Jet Breaks and Energetics of Swift GRB X-ray Afterglows
12:30 - 12:45	D. Burrows	Chandra Searches for Jet Breaks 几类光变所占的比例.
12:45 - 13:00	P. Evans	Confronting GRB afterglow models with a complete set of XRT light curves and hardness ratios
13.00 - 14.20	Lunch
	Chairman	S. Barthelmy
14:20 - 14:45	A. MacFadyen	GRB Afterglow Lightcurves from Multi-Dimensional Simulations
14:45 - 15:10	R. Margutti	GRB temporal structure: flares and short term variability
15:10 - 15:30	R. Yamazaki	Prior Emission Model for the Plateau Phase in the X-ray Afterglow
15:30 - 15:55	E. Del Monte	The observation of Gamma Ray Bursts with AGILE
15:55 - 16:10	R. Klebesadel	The Discovery of Cosmic Gamma-Ray Bursts 此人算是伽玛暴的开山鼻祖, 1973?年发表了第一篇观测到伽玛暴的文章. 不知道会议组怎么这么有能耐, 居然能请到他来. 讲完后以及提问完后迎来了会上最长时间的掌声, 起码有一分钟. 具体内容不是很有意思, 提问还是蛮有意思的. Kouveliotou问他为什么那么晚才发文章, 他解释说忙, 还有因为计算机故障还是什么. 据说还有另外的版本, 说是因为军事机密问题, 不能发. (参见伽玛暴的发现的相关内容) 由于Vela是军事卫星, 主要目的是看前苏联有没有搞秘密核试验. 所以有人就问那你们到底看到了没有, 他坚决不泄密.
16:10 - 16:35	Coffee Break
16:35 - 17:00	F. Daigne	The prompt emission of gamma-ray bursts in the internal shock model
17:00 - 17:15	S. Sugita	Timing and spectral analysis of Short GRB and Multi-spiked Long GRB
17:15 - 17:30	E. Liang	Single Power-Law Decaying XRT lightcurves and Implications for the Unified Origin of the X-rays
17:30 - 17:45	P. Roming	A Large Homogenous Sample of Optical GRB Afterglow Light Curves
17:45 - 18:00	M. De Pasquale	Chromatic evolution in GRB afterglows
18:00 - 18:20	S. Covino	Optical observations of GRB afterglows
18:20 - 18:35	J. Nousek	Status of the Swift Mission
Tuesday - September 15th
	Chairman	P. Michelson
09:00 - 09:25	N. Omodei	Gamma-Ray Burst at HighEnergy: the Fermi LAT first observation of the shocking Universe
09:25 - 09:45	N. Kawai	Pulse structures of GRB 080916C observed with Fermi LAT/GBM
09:45 - 10:05	S. Guiriec	GRB 090510, a short and hard burst detected by Fermi
10:05 - 10:25	F. De Palma	GRB 090902B, a long GRB with High Energy emission detected with Fermi
10:25 - 11:00	Coffee Break
11:00 - 11:20	E. Bissaldi	GRB 090323 and GRB 090328: two ksec long high-energy GammaRay Bursts detected with Fermi
11:20 - 11:45	B. Paciesas	Fermi GBM results
11:45 - 12:10	M. Briggs	Spectral Evolution of Three Short GRBs on Fine Timescales
12:10 - 12:30	V. Connaughton	High-Energy Spectral signatures of LAT-detected short gamma-ray bursts
12:30 - 12:55	J. Granot	Some Implications of Fermi High-Energy GRB Observations
12.55 - 14.20	Lunch
	Chairman	R. Bellazzini
14:20 - 14:45	K. Asano	Theoretical Interpretation for Fermi LAT-detected Gamma-ray Bursts
14:45 - 15:10	C. Dermer	Evidence for Ultra-High Energy Cosmic Ray Acceleration from Fermi Observations of GRBs
15:10 - 15:35	P. Michelson	Fermi LAT results
15:35 - 16:00	B. Atwood	Fermi-LAT Analysis to Maximize GRB Science
16:00 - 16:30	Coffee Break
16:30 - 16:50	D. Kocevski	LAT Upper Limits to GRBs
16:50 - 17:05	T. Aune	Constraints on GeV-TeV Emission from the "nakedeye" GRB 080319B
17:05 - 17:30	Y. Fan	Interpretation and implication of the non-detection of GeV spectrum excess by Fermi gamma-ray Space Telescope in most GRBs
17:30 - 17:45	A. Melandri	The Rise and Fall of GRBs - Lorentz Factors and Fireball Shock Physics
17:45 - 18:10	R. Barniol-Duran	High energy photons from Fermi GRBs: Who would have thought that they were produced in the external shock?
19:15	Visit at the S. Marco Basilica
Wednesday - September 16th
	Chairman	P. Roming
09:00 - 09:30	E. Berger	The Host Galaxies of Short GRBs: Implications for the Progenitors and Comparison to Long GRB Hosts
09:30 - 09:45	F. Virgili	Are all short GRBs of compact star merger origin?
09:45 - 10:00	P. D'Avanzo	Optical spectroscopy of short GRB afterglows
10:00 - 10:20	W. Lee	The role of winds and tidal tails from post merger disks in the production of outflows and late time flares in SGRBs
10:20 - 10:40	Poster competition
10:40 - 11:10	Coffee Break
11:10 - 11:40	C. Fryer	Neutrinos and Gravitational Waves from Long Duration GRBs
11:40 - 12:05	P. Vreeswijk	GRB optical afterglow spectroscopy and host galaxies: an unbiased approach
12:05 - 12:20	D. Perley	The Environments of Dark Gamma-Ray Bursts
12:20 - 12:35	A. De Ugarte Postigo	GRB 090313: X-shooter's first glimpse of a GRB
12:35 - 13:15	K. Hamaguchi	News on Eta-Carinae
13:15	Lunch
13:45	Free Afternoon - Social Trip to S. Francesco del Deserto island
Thursday - September 17th
	Chairman	J. Osborne
09:00 - 09:25	S. Savaglio	Gamma-Ray Burst Host Galaxies and the High Redshift Universe
09:25 - 09:50	A. Fruchter	Environments, Hosts, and their Implications for the Physics and Progenitors of GRBs
09:50 - 10:05	E. Levesque	Modeling the Host Galaxies of Long-Duration Gamma-Ray Bursts
10:05 - 10:20	P. Schady	Dust Extinction Properties within GRB Host Galaxies
10:20 - 10:35	K. Svensson	The host galaxies of core-collapse supernovae and gamma ray bursts
10:35 - 11:00	Coffee Break
11:00 - 11:30	A. Soderberg	A Holistic View of the GRB-SN Connection
11:30 - 11:55	M. Della Valle	GRB-SN Connection: observational outcomes
11:55 - 12:15	S. Nagataki	GRB-SN Connection: Central Engine of Long GRBs and Explosive Nucleosynthesis
12:15 - 12:30	A. Kamble	XRF080109/SN2008D : an investigation at radio frequencies
12:30 - 12:45	R. Shen	The late jet in GRBs and its interactions with a supernova ejecta and a cocoon
12:45 - 13:00	F. De Colle	Bipolar Supernova Explosions: Nucleosynthesis and the Role of Magnetic Fields
13.00 - 14.30	Lunch
	Chairman	N. Kawai
14:30 - 15:00	P. Kumar	The Physics of GRB Prompt Emission
15:00 - 15:30	B. Zhang	GRB prompt emission models: from low sigma to high sigma
15:30 - 16:00	T. Piran	TBA
16:00 - 16:30	Coffee Break
16:30 - 16:45	E. Nakar	Introduction for a debate
16:45 - 17:20		Debate: where do we stand?
17:20 - 17:35	A. Levan	Illuminating the dark ages with GRB 090423
17:35 - 17:50	R. Salvaterra	GRB 090423 reveals an exploding star at the epoch of reionization
17:50 - 18:05	D. Frail	Discovery of the Radio Afterglow from GRB 090423
18:05 - 18:20	A. Cucchiara	GRB 090429B as the second "extreme redshift" gamma-ray burst
18:20 - 18:45	T. Totani	GRBs and High Redshift Universe: High Redshift Galaxies, Pop III Stars, and Reionization
20:30	Social Dinner
Friday - September 18th
	Chairman	K. Hurley
08:45 - 09:10	C. Kouveliotou	Magnetar Observations with Fermi/GBM
09:10 - 09:25	S. Dall'Osso	Magnetars at birth as strong sources of Gravitation Wave Radiation
09:25 - 09:40	Y. Nakagawa	Suzaku Observations of Short Bursts from SGR 0501+4516
09:40 - 10:10	E. Ramirez-Ruiz	Compact Objects in The Era of Celestial Cinematography
10:10 - 10:40	Coffee Break
10:40 - 11:05	V. D'Elia	UVES-VLT High Resolution Spectroscopy of Gamma-Ray Burst afterglows: host galaxies and intervening absorbers
11:05 - 11:20	S. Vergani	Statistics and characteristics of MgII absorbers along GRB lines of sight observed with VLT-UVES
11:20 - 11:35	S. Campana	Circumburst ambient surrounding GRBs in the X-ray band
11:35 - 11:50	C. Thoene	GRB 090426 - a new class or a strange environment?
11:50 - 12:00	I. Horvath	GRB groups observed by BATSE, BeppoSAX and Swift
12:00 - 12:15	D. Lopez-Camara	Quiescence and late time activity in collapsars due to critical angular momentum distributions
12:15 - 12:30	G. Beskin	Discovery of the "central engine" manifestation in the Naked-Eye Burst prompt optical emission
12.30 - 14.00	Lunch
	Chairman	D. Burrows
14:00 - 14:25	K. Yamaoka	Suzaku observations of GRB prompt emissions and X-ray afterglows
14:25 - 14:55	C. Bianco	The extended afterglow luminosity evolution over the equitemporal surfaces
14:55 - 15:10	F. Genet	Steep decay phase and prompt emission models
15:10 - 15:25	V. Mangano	Modeling the spectral evolution in the decaying tails of Swift GRBs
15:25 - 15:45	S. Inoue	Probing UV radiation fields and magnetic fields in the era of first star formation through GeV γ-rays from very high-z GRBs
15:45 - 16:00	P. Romano	Supergiant Fast X-ray Transients: the Swift monitoring program
16:00 - 16:45	N. Gehrels	Concluding Remarks

van Leeuwen, Joeri 2009 LOFAR的射电巡天

主要内容:
将要投入使用的射电阵, 可能可以探测到孤儿射电余辉.

精彩摘抄:


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Title:		Neutron Stars and Gamma Ray Bursts with LOFAR
Authors:		van Leeuwen, Joeri; LOFAR Transients Key Science Project, The
Publication:		eprint arXiv:0909.3212
Publication Date:		09/2009
Origin:		ARXIV
Keywords:		Astrophysics - Instrumentation and Methods for Astrophysics
Comment:		Proceedings of the "Frontiers of Space Astrophysics: Gamma Ray Bursts & Neutron Stars" meeting in Cairo/Alexandria, Egypt, April 2009. 4 Pages
Bibliographic Code:		2009arXiv0909.3212V

Abstract

LOFAR, the Low Frequency Array, is an innovative new radio telescope currently under construction in the Netherlands. With its continuous monitoring of the radio sky we expect LOFAR will detect many new transient events, including GRB afterglows and pulsating/single-burst neutron stars. We here describe all-sky surveys ranging from a time resolution of microseconds to a cadence span of years.

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Lee, William H. 2009 数值模拟中子星-黑洞并合产生短暴

主要内容:


精彩摘抄:


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Title:		Short gamma-ray bursts from tidal capture and collisions of compact stars in globular clusters
Authors:		Lee, William H.; Ramirez-Ruiz, Enrico; van de Ven, Glenn
Publication:		eprint arXiv:0909.2884
Publication Date:		09/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		Submitted to ApJ
Bibliographic Code:		2009arXiv0909.2884L

Abstract

A new mechanism is proposed by which short gamma-ray burst (SGRB) production can be achieved. In this new paradigm, it is supposed that the compact objects contained within a globular cluster (GC) interact through close encounters, rather than being driven together by pure gravitational wave emission in existing binaries. Here we perform a careful assessment of the relevant processes and stellar dynamics within GCs as these undergo core collapse over cosmic time. We show that such events are frequent enough in their cores to be consistent both with current observational rate demands for SGRB production and with the widening range of observed redshifts of the associated hosts. Precise modeling of the hydrodynamics allows for a detailed description of the encounter, and our calculations show that there is in principle no problem in accounting for the global energy budget of a typical SGRB. The particulars of each collision, are variable in several aspects, and can lead to interesting diversity. First, the characteristics of the encounter are highly dependent on the impact parameter. This is in contrast to the merger scenario, where the masses of the compact objects dictate a typical length and luminosity scale for SGRB activity. Second, the nature of the compact star itself can produce very different outcomes. Finally, the presence of tidal tails in which material will fall back onto the central object at a later time is a robust feature of the present set of calculations. The mass involved in these structures is considerably larger than for binary mergers. It is thus possible, in principle, to account generically in this scenario for a prompt episode of energy release as well as for activity many dynamical time scales later. (abridged)

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Bissaldi 2009 GRB 090902B的观测

主要内容:


精彩摘抄:
原始光变


处理后的高能光变, 有比较好的幂律形式, 很像外激波. (和另外一个暴090510很像)
谱, 高能有一个excess.

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Title:		Fermi Observations of GRB 090902B: A Distinct Spectral Component in the Prompt and Delayed Emission
Authors:		The Fermi/GBM collaboration; The Fermi/LAT Collaborations; The Swift Team
Publication:		eprint arXiv:0909.2470
Publication Date:		09/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		Submitted to ApJ Letters. Contact Authors: Elisabetta Bissaldi (ebs@mpe.mpg.de), James Chiang (jchiang@slac.stanford.edu), Francesco de Palma (francesco.depalma@ba.infn.it), Sheila McBreen (smcbreen@mep.mpg.de)
Bibliographic Code:		2009arXiv0909.2470T

Abstract

We report on the observation of the bright, long gamma-ray burst, GRB 090902B, by the Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) instruments on-board the Fermi observatory. This was one of the brightest GRBs to have been observed by the LAT, which detected several hundred photons during the prompt phase. With a redshift of z = 1.822, this burst is among the most luminous detected by Fermi. Time-resolved spectral analysis reveals a significant power-law component in the LAT data that is distinct from the usual Band model emission that is seen in the sub-MeV energy range. This power-law component appears to extrapolate from the GeV range to the lowest energies and is more intense than the Band component both below $\sim$ 50 keV and above 100 MeV. The Band component undergoes substantial spectral evolution over the entire course of the burst, while the photon index of the power-law component remains constant for most of the prompt phase, then hardens significantly towards the end. After the prompt phase, power-law emission persists in the LAT data as late as 1 ks post-trigger, with its flux declining as $t^{-1.5}$. The LAT detected a photon with the highest energy so far measured from a GRB, $33.4_{-3.5}^{+2.7}$ GeV. This event arrived 82 seconds after the GBM trigger and $\sim$ 50 seconds after the prompt phase emission had ended in the GBM band. We discuss the implications of these results for models of GRB emission and for constraints on models of the Extragalactic Background Light.

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