Liu 2009 结构化喷流的早期正反激波

主要内容:
首先是理论, 然后是应用到早期X射线余辉的shallow decay

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Title:		Early afterglows from radially structured outflows and the application to X-ray shallow decays
Authors:		Liu, Xue-Wen; Wu, Xue-Feng; Zou, Yuan-Chuan; Lu, Tan
Publication:		eprint arXiv:0908.4511
Publication Date:		08/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		Research in Astron. Astrophys., 2009, Vol. 9, No. 8, 911-920
Bibliographic Code:		2009arXiv0908.4511L

Abstract

In the fireball model, it is more physically realistic that gamma-ray burst (GRB) ejecta have a range of bulk Lorentz factors (assuming $M\propto \Gamma^{-s}$). The low Lorentz factor part of the ejecta will catch up with the high Lorentz factor part when the latter is decelerated by the surrounding medium to a comparable Lorentz factor. Such a process will develop a long-lasting weak reverse shock until the whole ejecta are shocked. Meanwhile, the forward shocked materials are gradually supplied with energy from the ejecta that are catching-up, and thus the temporal decay of the forward shock emission will be slower than that without an energy supply. However, the reverse shock may be strong. Here, we extend the standard reverse-forward shock model to the case of radially nonuniform ejecta. We show that this process can be classified into two cases: the thick shell case and the thin shell case. In the thin shell case, the reverse shock is weak and the temporal scaling law of the afterglow is the same as that in Sari & Mesz (2000). However, in the thick shell case, the reverse shock is strong and thus its emission dominates the afterglow in the high energy band. Our results also show slower decaying behavior of the afterglow due to the energy supply by low Lorentz factor materials, which may help the understanding of the plateau observed in the early optical and X-ray afterglows.

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Zou 2009 早期外激波的辐射限制罗仑兹因子

主要内容:
另外还和其它方法进行了比较. 不是很一致.

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Title:		Lorentz Factor Constraint from the very early external shock of the gamma-ray burst ejecta
Authors:		Zou, Yuan-Chuan; Piran, Tsvi
Publication:		eprint arXiv:0908.4418
Publication Date:		08/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Extragalactic Astrophysics
Comment:		9 pages, 2 figures. Submitted to MNRAS
Bibliographic Code:		2009arXiv0908.4418Z

Abstract

While it is generally agreed that the emitting regions in Gamma-Ray Bursts (GRBs) move ultra relativistically towards the observer, different estimates of the initial Lorentz factors, $\Gamma_0$, lead to different, at times conflicting estimates. We show here that the quiet periods in which the signals goes down below the instrumental thresholds, put strong upper limits on the values of $\Gamma_0$. According to the standard internal-external shocks model an external shock should develop during the prompt stage. This external shock radiates in the hard X-rays to soft gamma-rays bands and this emission should be seen as a smooth background signal. The observed deep minima indicate that this contribution is negligible. This limits, in turn, $\Gamma_0$. We obtain upper limits on $\Gamma_0$ for several bursts with typical values around hundreds. We compare these values with those obtained by the other methods, which typically yield lower limits. The results are marginally consistent leaving only a narrow range of allowed values for $\Gamma_0$.

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Gao 2009 GRB 080916C and GRB 090510:高能辐射的模型

主要内容:
这两个暴都有延迟的高能现象. 他们认为瞬时阶段的高能不能来自内激波, 余辉的高能可能来自synchrotron的谱的延伸.

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Title:		GRB 080916C and GRB 090510: the high energy emission and the afterglow
Authors:		Gao, Wei-Hong; Mao, Ji-Rong; Xu, Dong; Fan, Yi-Zhong
Publication:		eprint arXiv:0908.3975
Publication Date:		08/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		11 pages including 1 figure
Bibliographic Code:		2009arXiv0908.3975G

Abstract

We constrain the physical composition of the outflows of GRBs 080916C and 090510 with the prompt emission data and find that the former is likely magnetic while the latter may be baryonic. The X-ray and optical afterglow emission of both GRBs can be reasonably fitted using the standard external shock model but the density profiles of the circum-burst medium are different. We also propose a simple method to estimate the number of the seed photons suppose the GeV afterglow photons are due to the inverse Compton radiation of external forward shock electrons. The seed photons needed in the modeling are too many to be realistic for both events. The synchrotron radiation of the forward shock seems able to account for the GeV afterglow data.

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Abbott 2009 LIGO run 5 和 Virgo Run 1都没有观测到伽玛暴的引力波

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Title:		Search for gravitational-wave bursts associated with gamma-ray bursts using data from LIGO Science Run 5 and Virgo Science Run 1
Authors:		...
Publication:		eprint arXiv:0908.3824
Publication Date:		08/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		15 pages, 3 figures
Bibliographic Code:		2009arXiv0908.3824L

Abstract

We present the results of a search for gravitational-wave bursts associated with 137 gamma-ray bursts (GRBs) that were detected by satellite-based gamma-ray experiments during the fifth LIGO science run and first Virgo science run. The data used in this analysis were collected from 2005 November 4 to 2007 October 1, and most of the GRB triggers were from the Swift satellite. The search uses a coherent network analysis method that takes into account the different locations and orientations of the interferometers at the three LIGO-Virgo sites. We find no evidence for gravitational-wave burst signals associated with this sample of GRBs. Using simulated short-duration (<1>

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Lyons 2009 Spin down magetar解释X射线余辉光变

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Title:		Can X-ray emission powered by a spinning-down magnetar explain some GRB light curve features?
Authors:		Lyons, N.; O'Brien, P. T.; Zhang, B.; Willingale, R.; Troja, E.; Starling, R. L. C.
Publication:		eprint arXiv:0908.3798
Publication Date:		08/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		10 pages, 5 figures, accepted by MNRAS
Bibliographic Code:		2009arXiv0908.3798L

Abstract

Long duration gamma-ray bursts (GRBs) are thought to be produced by the core-collapse of a rapidly-rotating massive star. This event generates a highly relativistic jet and prompt gamma-ray and X-ray emission arises from internal shocks in the jet or magnetised outflows. If the stellar core does not immediately collapse to a black hole, it may form an unstable, highly magnetised millisecond pulsar, or magnetar. As it spins down, the magnetar would inject energy into the jet causing a distinctive bump in the GRB light curve where the emission becomes fairly constant followed by a steep decay when the magnetar collapses. We assume that the collapse of a massive star to a magnetar can launch the initial jet. By automatically fitting the X-ray lightcurves of all GRBs observed by the Swift satellite we identified a subset of bursts which have a feature in their light curves which we call an internal plateau -- unusually constant emission followed by a steep decay -- which may be powered by a magnetar. We use the duration and luminosity of this internal plateau to place limits on the magnetar spin period and magnetic field strength and find that they are consistent with the most extreme predicted values for magnetars.

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Sironi, Lorenzo 2009 PIC模拟同步辐射

主要内容:
企图解释伽玛暴低能段的谱指数.

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Title:		Synthetic Spectra from PIC Simulations of Relativistic Collisionless Shocks
Authors:		Sironi, Lorenzo; Spitkovsky, Anatoly
Publication:		eprint arXiv:0908.3193
Publication Date:		08/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		5 pages, 3 figures, submitted to ApJ Letters
Bibliographic Code:		2009arXiv0908.3193S

Abstract

We extract synthetic photon spectra from first-principles particle-in-cell simulations of relativistic shocks propagating in unmagnetized pair plasmas. The two basic ingredients for the radiation, namely accelerated particles and magnetic fields, are produced self-consistently as part of the shock evolution. We use the method of Hededal & Nordlund (2005) and compute the photon spectrum via Fourier transform of the electric far-field from a large number of particles, sampled directly from the simulation. We find that the spectrum from relativistic collisionless shocks is entirely consistent with synchrotron radiation in the magnetic fields generated by Weibel instability. We can recover the so-called "jitter'' regime only if we artificially reduce the strength of the electromagnetic fields, such that the wiggler parameter K = qB lambda/mc^2 becomes much smaller than unity ("B" and "lambda" are the strength and scale of the magnetic turbulence, respectively). These findings may place constraints on the origin of non-thermal emission in astrophysics, especially for the interpretation of the hard (harder than synchrotron) low-frequency spectrum of Gamma-Ray Bursts.

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Falcone, A. D. 2009 JANUS: 一个X-ray flash探测器

主要内容:
NASA的一个小项目. 准备2013年上天.
两个望远镜: The X-Ray Flash Monitor (XRFM) and the Near-IR Telescope (NIRT). X-ray仪器的能段: 1-20keV.
sensitivity:240 mCrab.
(Note: 1 Crab unit of the 35 – 200 keV flux = 1 × 10-3 photons cm-2 s-1 keV-1.)

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Title:		The JANUS X-Ray Flash Monitor
Authors:		Falcone, A. D.; Burrows, D. N.; Barthelmy, S.; Chang, W.; Fredley, J.; Kelly, M.; Klar, R.; Palmer, D.; Persyn, S.; Reichard, K.; Roming, P.; Seifert, E.; Smith, R. W. M.; Wood, P.; Zugger, M.
Publication:		eprint arXiv:0908.3005
Publication Date:		08/2009
Origin:		ARXIV
Keywords:		Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Cosmology and Extragalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Comment:		submitted to Proc. SPIE, Vol. 7435 (2009), 7 pages, 8 figures
Bibliographic Code:		2009arXiv0908.3005F

Abstract

JANUS is a NASA small explorer class mission which just completed phase A and was intended for a 2013 launch date. The primary science goals of JANUS are to use high redshift (6.lt. z.lt.12).gt.6 XRFs/GRBs, which can be further studied by other instruments. XRFM would use a coded mask aperture design with hybrid CMOS Si detectors. It would be sensitive to XRFs/GRBs with flux in excess of approximately 240 mCrab. The spacecraft is designed to rapidly slew to source positions following a GRB trigger from XRFM. XRFM instrument design parameters and science goals are presented in this paper.

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Levesque, E. M. 2009 SN2009BB的环境

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Title:		The High-Metallicity Explosion Environment of the Relativistic Supernova 2009bb
Authors:		Levesque, E. M.; Soderberg, A. M.; Foley, R. J.; Berger, E.; Kewley, L. J.; Chakraborti, S.; Ray, A.; Torres, M. A. P.; Challis, P.; Kirshner, R. P.; Barthelmy, S. D.; Bietenholz, M. F.; Chandra, P.; Chaplin, V.; Chevalier, R. A.; Chugai, N.; Connaughton, V.; Copete, A.; Fox, O.; Fransson, C.; Grindlay, J. E.; Hamuy, M. A.; Milne, P. A.; Pignata, G.; Stritzinger, M. D.; Wieringa, M. H.
Publication:		eprint arXiv:0908.2818
Publication Date:		08/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		6 pages, 3 figures, 1 table; submitted to ApJ Letters
Bibliographic Code:		2009arXiv0908.2818L

Abstract

We investigate the environment of the nearby (d ~ 40Mpc) broad-lined Type Ic supernova SN 2009bb. This event was observed to produce a relativistic outflow likely powered by a central accreting compact object. While such a phenomenon was previously observed only in long-duration gamma-ray bursts (LGRBs), no LGRB was detected in association with SN 2009bb. Using an optical spectrum of the SN 2009bb explosion site, we determine a variety of ISM properties for the host environment, including metallicity, young stellar population age, and star formation rate. We compare the SN explosion site properties to observations of LGRB and broad-lined SN Ic host environments on optical emission line ratio diagnostic diagrams. Based on these analyses, we find that the SN 2009bb explosion site has a very high metallicity of ~2x solar, in agreement with other broad-lined SN Ic host environments and at odds with the low-redshift LGRB host environments and recently proposed maximum metallicity limits for relativistic explosions. We consider the implications of these findings and the impact that SN 2009bb's unusual explosive properties and environment have on our understanding of the key physical ingredient that enables some SNe to produce a relativistic outflow.

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Ghirlanda, G. 2009 Fermi暴的E_p-L_iso统计关系

主要内容:
说是也有比较好的这个关系

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Title:		Spectral-Luminosity relation within individual Fermi GRBs
Authors:		Ghirlanda, G.; Nava, L.; Ghisellini, G.
Publication:		eprint arXiv:0908.2807
Publication Date:		08/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		11 pages, 5 figures, 3 tables. Submitted to Astronomy and Astrophysics
Bibliographic Code:		2009arXiv0908.2807G

Abstract

We study the spectra of all long Gamma Ray Bursts (GRBs) of known redshift detected by the Fermi satellite. Their fluxes and fluences are large enough to allow a time dependent study of their spectral characteristics in the 8 keV-1 MeV energy range. We find that the peak energy Ep of their EL(E) spectrum correlates with the luminosity in a remarkable tight way within individual bursts. This time resolved Ep-Liso correlation is very similar for all the considered bursts, and has a slope and normalisation similar to the analogous Ep-Liso correlation defined by the time integrated spectra of different bursts detected by several different satellites. For a few of the considered GRBs, we could also study the behaviour of the Ep-Liso correlation during the rising and decaying phases of individual pulses within each burst, finding no differences. Our results indicate the presence of a similar physical mechanism, operating for the duration of different GRBs, linking tightly the burst luminosity with the peak energy of the spectrum emitted at different times. Such a physical mechanism is the same during the rise and decay phase of individual pulses composing a GRB. These results, while calling for a robust physical interpretation, strongly indicate that the Ep-Liso spectral energy correlation found considering the time integrated spectra of different bursts is real, and not the result of instrumental selection effects.

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Dado, Shlomo 2009 Cannon ball 模型解释 GRB 090812的x射线耀发

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Title:		X-Ray Flares In GRB090812 - Case Study
Authors:		Dado, Shlomo; Dar, Arnon
Publication:		eprint arXiv:0908.2849
Publication Date:		08/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Bibliographic Code:		2009arXiv0908.2849D

Abstract

The master formulae of the CB model of long durations gamma ray bursts (GRBs) which reproduce very well the light curves and spectral evolution of their prompt emission pulses and their smooth afterglows, also reproduce very well the lightcurves and spectral evolution of their X-ray and optical flares. Here we demonstrate that for GRB090812

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Kong, S. W. 2009 数值拟合GRB 980703的余辉

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Title:		Modeling the radio and optical/NIR afterglows of GRB 980703: a numerical study
Authors:		Kong, S. W.; Huang, Y. F.; Cheng, K. S.; Lu, T.
Publication:		eprint arXiv:0908.2850
Publication Date:		08/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		10 pages, 3 figures, PDF version only, accepted for publication in: Science in China Series G: Physics, Mechanics and Astronomy
Bibliographic Code:		2009arXiv0908.2850K

Abstract

Extensive multi-band afterglow data are available for GRB 980703. Especially, its radio afterglow was very bright and was monitored until more than 1000 days after the trigger time. Additionally, there is no obvious special feature, i.e., no rebrightenings, no plateau, and no special steep decay or slow decay in the multi-band afterglow light curves. All these conditions make GRB 980703 a precious sample in gamma-ray burst research. Here we use the observational data of GRB 980703 to test the standard fireball model in depth. It is found that the model can give a satisfactory explanation to the multi-band and overall afterglow light curves. The beaming angle of GRB 980703 is derived as ~0.23 radian, and the circum-burst medium density is ~ 27 cm-3. The total isotropic equivalent kinetic energy of the ejecta is ~ 3.8E52 ergs. A rest-frame extinction of Av ~ 2.5 mag in the host galaxy is also derived.

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Gilmore, Rudy C. 2009 预测Fermi等高能的观测率等

主要内容:
从仪器的角度

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Title:		Modeling gamma-ray burst observations by Fermi and MAGIC including attenuation due to diffuse background light
Authors:		Gilmore, Rudy C.; Prada, Francisco; Primack, Joel R.
Publication:		eprint arXiv:0908.2830
Publication Date:		08/2009
Origin:		ARXIV
Keywords:		Astrophysics - Cosmology and Extragalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Comment:		13 pages, 10 figures, 3 tables, submitted to MNRAS
Bibliographic Code:		2009arXiv0908.2830G

Abstract

Gamma rays from extragalactic sources are attenuated by pair-production interactions with diffuse photons of the extragalactic background light (EBL). Gamma-ray bursts (GRBs) are a source of high-redshift photons above 10 GeV, and could be therefore useful as a probe of the evolving UV background radiation. In this paper, we develop a simple phenomenological model for the number and redshift distribution of gamma-ray bursts that can be seen at GeV energies with the Fermi satellite and MAGIC atmospheric Cherenkov telescope. We estimate the observed number of gamma rays per year, and show how this result is modified by considering interactions with different realizations of the evolving EBL. We also discuss the bright Fermi GRB 080916C in the context of this model. We find that the LAT on Fermi can be expected to see a small number of photons above 10 GeV each year from distant GRBs. Annual results for ground-based instruments like MAGIC are highly variable due to the low duty cycle and sky coverage of the telescope. However, successfully viewing a bright or intermediate GRB from the ground could provide hundreds of photons from high redshift, which would almost certainly be extremely useful in constraining both GRB physics and the high-redshift EBL.

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Soderberg, A. M. 2009 SN2009bb的观测

主要内容:
有相对论性的喷流. (可能是个偏轴的伽玛暴或者失败的伽玛暴.)

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Title:		Discovery of a Relativistic Supernova Without a Gamma-ray Trigger
Authors:		Soderberg, A. M.; Chakraborti, S.; Pignata, G.; Chevalier, R. A.; Chandra, P.; Ray, A.; Wieringa, M. H.; Copete, A.; Chaplin, V.; Connaughton, V.; Barthelmy, S. D.; Bietenholz, M. F.; Chugai, N.; Stritzinger, M. D.; Hamuy, M.; Fransson, C.; Fox, O.; Levesque, E. M.; Grindlay, J. E.; Challis, P.; Foley, R. J.; Kirshner, R. P.; Milne, P. A.; Torres, M. A. P.
Publication:		eprint arXiv:0908.2817
Publication Date:		08/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Extragalactic Astrophysics
Comment:		Submitted to Nature. Embargoed for discussion in the press (24 pages, Manuscript and Suppl. Info.)
Bibliographic Code:		2009arXiv0908.2817S

Abstract

Type Ibc supernovae (SNe Ibc) mark the gravitational collapse of some massive stars (M > 20 Msun) propelling several solar masses of material to typical velocities of ~10,000 km/s. The closely-related but exceedingly rare class of long-duration gamma-ray bursts (GRBs) produce, in addition, a relativistic outflow powered by a central engine (accreting black hole or neutron star) and have been found exclusively through their gamma-ray signal. Here we report the discovery of luminous radio emission from the seemingly ordinary Type Ibc SN 2009bb which outshines that of all other SNe Ibc observed on a comparable timescale. These observations require a substantial mildly-relativistic outflow and indicate that the explosion was powered by a central engine, thus representing the first such event discovered without the aid of a gamma-ray trigger. A comparison with our extensive radio survey of SNe Ibc reveals that the fraction of such events is low (roughly 1 percent), measured independently from, and yet consistent with, the inferred rate of nearby GRBs. This discovery marks the observational realization that long-wavelength surveys will soon rival gamma-ray satellites in pinpointing nearby engine-driven explosions.

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Crowther, Paul A 2009 通过SGR来限制短暴

主要内容:
因为应该说有一部分BATSE的短暴可能是SGR的giant flare

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Title:		Contamination of short GRBs by giant magnetar flares: Significance of downward revision in distance to SGR 1806-20
Authors:		Crowther, Paul A; Bibby, Joanne L; Furness, James P; Clark, J Simon
Publication:		eprint arXiv:0908.2773
Publication Date:		08/2009
Origin:		ARXIV
Keywords:		Astrophysics - Solar and Stellar Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Comment:		5 pages, 4 figures, contributed talk from `Neutron Stars and Gamma Ray Bursts' (eds A. Ibrahim & J. Grindlay, AIP Conf Proc)
Bibliographic Code:		2009arXiv0908.2773C

Abstract

We highlight how the downward revision in the distance to the star cluster associated with SGR1806-20 by Bibby et al. reconciles the apparent low contamination of BATSE short GRBs by intense flares from extragalactic magnetars without recourse to modifying the frequency of one such flare per 30 years per Milky Way galaxy. We also discuss the variety in progenitor initial masses of magnetars based upon cluster ages, ranging from ~50 Msun for SGR 1806-20 and 1E 1647-455 in Westerlund 1 to ~15 Msun for SGR 1900+14 and presumably 1E 1841-045 if it originated from one of the massive RSG clusters #2 or #3.

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