Noble 2007 用OpenMP编写并行程序

主要内容:
OpenMP支持c和fortran，不需要很多并行只是，即可编写多cpu的并行程序。文章介绍用OpenMP编写天文方面的程序。

精彩摘抄:


文章信息:

arXiv:0706.4048 (cross-list from cs.DC) [ps, pdf, other]

Title: Getting More From Your Multicore: Exploiting OpenMP From An Open Source Numerical Scripting Language

Authors: Michael S. Noble

Comments: 15 pages, 16 figures; working paper, in preparation

Subjects: Distributed, Parallel, and Cluster Computing (cs.DC); Astrophysics (astro-ph)

We introduce SLIRP, a module generator for the S-Lang numerical scripting language, with a focus on its vectorization capabilities. We demonstrate how both SLIRP and S-Lang were easily adapted to exploit the inherent parallelism of high-level mathematical languages with OpenMP, allowing general users to employ tightly-coupled multiprocessors in scriptable research calculations while requiring no special knowledge of parallel programming. Motivated by examples in the ISIS astrophysical modeling & analysis tool, performance figures are presented for several machine and compiler configurations, demonstrating beneficial speedups for real-world operations.

Lamon 2007 用INTEGRAL的伽玛暴做量子引力

主要内容:
采用新的办法计算spectral time lag。

精彩摘抄:


文章信息:

arXiv:0706.4039 (cross-list from gr-qc) [ps, pdf, other]

Title: Study of Quantum Gravity Effects in INTEGRAL Gamma-Ray Bursts

Authors: Raphael Lamon, Nicolas Produit, Frank Steiner

Comments: 11 pages, 24 figures, submitted to A&A

Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics (astro-ph); High Energy Physics - Theory (hep-th)

We search for possible time lags caused by quantum gravitational (QG) effects using gamma-ray bursts detected by INTEGRAL. The advantage of this satellite is that we have at our disposal the energy and arrival time of every single photon, which enhances the precision of the time resolution. We present a new method for seeking time lags in unbinned data using a maximum likelihood and support our conclusions with Monte Carlo simulations. These simulations show that today's satellites are not apt to measure effects at the order of the Planck mass. However, a naive analysis of the data shows a mass scale well below the expected one. Only by correcting for internal time lags are we able to give a lower bound on the quantum gravitation mass scale that is in accordance with predictions.

O'Shaughnessy 2007 短暴的红移分布

主要内容:
用不同的短暴模型（NS－NS，SN－BH）推断短暴的诞生率、红移分布、宿主星系来检验模型的正确性。

精彩摘抄:


文章信息:

arXiv:0706.4139 [ps, pdf, other]

Title: Short Gamma-Ray Bursts and Binary Mergers in Spiral and Elliptical Galaxies: Redshift Distribution and Hosts

Authors: R. O'Shaughnessy (1), V. Kalogera (1), K. Belczynski (2) ((1) Northwestern University, (2) New Mexico State University)

Comments: 14 figures, using bitmapped fonts (via eps2eps) to fit in archive space restrictions; better resolution figures are available from the author. Submitted to apj

Subjects: Astrophysics (astro-ph)

To test whether the short GRB rates, redshift distribution and host galaxies are consistent with current theoretical predictions, we use avery large database of population synthesis calculations to examine BH-NS and NS-NS merger rates in the universe, factoring in (i) the star formation history of the universe, (ii) a heterogeneous population of star-forming galaxies, including spirals and ellipticals, and (iii) a simple flux-limited selection model for short GRB detection. When we require our models reproduce the known short GRB rates and redshift measurements (and, for NS-NS, the merger rates extrapolated from binary pulsars in the Galaxy), a small fraction of models reproduce all observations, both when we assume a NS-NS and a BH-NS origin for bursts. Most commonly models produce mergers preferentially in spiral galaxies if short GRBs arise from NS-NS mergers alone. Model universes where present-day binary mergers occur preferentially in elliptical galaxies necessarily include a significant fraction of binaries with long delay times between birth and merger (often $O(10{\rm Gyr})$). Though long delays occur, almost all of our models predict that a higher proportion of short GRBs should occur at moderate to high redshift (e.g., $z>1$) than has presently been observed, in agreement with recent observations which suggest a selection bias towards successful follow-up of low-redshift short GRBs. Finally, if only a fraction of BH-NS mergers have the right combination of masses and spins to make GRBs, then at best only a small fraction of BH-NS models could be consistent with all {\em current} available data. (Abridged)

为什么没有侧向膨胀

如果jet break是边沿效应而不是侧向膨胀的话，那为什么没有侧向膨胀呢？

AGN的jet可以看到一个很细很长的喷流，说明侧向膨胀确实可以不重要，这是观测上。理论上，一般认为侧向膨胀是以声速，然后用v_s = c/sqrt(3)。但实际上v_s可能远没有这么大。如果认为喷流是冷的，v_s=0; 但是如果用标准余辉喷流模型，激波化的喷流是很热的，v_s接近c/sqrt(3)。因此说明（要无侧向膨胀的话）应该激波化不严重。一种可能的方式是喷出物相比ISM很密很重，于是jet物质没有被完全激波化（但是相对论的速度会把ISM深度激波化啊）。这可能还可以解释早期X射线变平，而且jet也不能被有效减速。

2008.7.23
其实基本可以看成双温分布；
对暴本身，一部分被加速，冷却，产生伽玛射线，冷却后的产生光学（还不成熟）
对余辉，早期，冷的主导动力学和光学；热的主导X射线；还可以解释它们的不同时拐折，以及早期余辉的平降阶段（基本没减速嘛）

Yu 2007 Shallow decay阶段的高能辐射

主要内容:
依然用星风泡作为能量注入方式，考虑逆康普顿散射，会产生大量的高能辐射。

精彩摘抄:


文章信息:

arXiv:0706.3741 [ps, pdf, other]

Title: Observational Signatures of High-Energy Emission during the Shallow Decay Phase of GRB X-Ray Afterglows

Authors: Y. W. Yu, X. W. Liu, Z. G. Dai

Comments: 21 pages, 7 figures

Subjects: Astrophysics (astro-ph)

The widely existing shallow decay phase of the X-ray afterglows of gamma-ray bursts (GRBs) is generally accepted to be due to long-lasting energy injection. The outflows carrying the injecting energy, based on their composition, could correspond to two types: baryon-dominated and lepton-dominated ones. The former-type outflows could be lagging materials in a wide GRB ejecta with a radial distribution of Lorentz factor, while the latter could be an electron-positron-pair wind that is driven by the post-burst central engine. We here provide a unified description for the dynamics of the two models of energy injection, and calculate the corresponding high-energy photon emission by considering the synchrotron radiation and inverse Compton scattering (including synchrotron self-Compton and combined inverse-Compton). We find that, for both models, there is a plateau (even a hump) in high-energy light curves during the X-ray shallow decay phase. In particular, a considerable fraction of the injecting energy in the leptonic-component-dominated model can be shared by the long-lasting reverse shock since it is relativistic. Furthermore, almost all of the energy of the reverse shock is carried by leptons and thus enhances the inverse-Compton emission dramatically. Therefore, this model predicts more significant high-energy afterglow emission than the baryonic-component-dominated model. We argue that these observational signatures would be used to discriminate between different energy-injection models in the upcoming {\em Gamma-ray Large Area Space Telescope} (GLAST) era.

Bietenholz 2007 SN 2001em没有成协的伽玛暴

主要内容:
曾经有人说（如Granot）SN 2001em有一个不对着我们的喷流，预言这个喷流由于近光速运动，会在几年后离中心较远（成像的图上）。此文是继前一文(Chugai 2006,ApJ 641, 1051)之后又说没有看到这个相对论性的喷流。

精彩摘抄:
光变曲线
image

文章信息:

arXiv:0706.3344 [ps, pdf, other]

Title: SN 2001em: No Jet-Driven Gamma Ray Burst Event

Authors: M. F. Bietenholz, N. Bartel

Comments: 5 pages, 2 figs, accepted for publication in ApJ Letters

Subjects: Astrophysics (astro-ph)

We report on our second-epoch VLBI and VLA observations of the Type Ib/c supernova 2001em, five years after the explosion. SN 2001em is the first Type Ib/c supernova for which VLBI observations have been carried out. It was suggested that SN 2001em might be a jet-driven gamma ray burst (GRB), with the jet oriented near the plane of the sky, which would entail relativistic expansion or motion. Our VLBI image shows that SN 2001em is still unresolved five years after the explosion. For a distance of 83 Mpc (H_0 = 70 km/s/Mpc), the nominal expansion velocity is 5800 +/- 10,000 km/s, and the proper motion is 33,000 +/- 34,000 km/s. Our values are inconsistent with either relativistic expansion or motion, but are consistent with the non-relativistic expansion speeds and small proper motions seen in other supernovae. In particular these values are consistent with radio emission from SN 2001em being due to normal, non-relativistic supernova ejecta interacting with the circumstellar medium. Our VLA observations show a power-law decay in flux density since the time of the peak in the 8.4 GHz radio lightcurve in ~2003.

Dainotti 2007 GRB 060218与Ibc型超新星的成协

主要内容:
针对GRB 060218提出模型解释他们的成协，并提出fragmentation来解释超长的持续时间。

给出超新星和伽玛暴成协可能是来自于双星的模型。

精彩摘抄:
In order to fulfill both the above requirement, we assume that the progenitor of the GRB and the SN consists of a binary system formed by a NS close to its critical mass collapsing to a black hole, and a companion star evolved out of the main sequence originating the SN.

文章信息:

arXiv:0706.3209 [ps, pdf, other]

Title: GRB060218 and GRBs associated with Supernovae Ib/c

Authors: Maria Giovanna Dainotti, Maria Grazia Bernardini, Carlo Luciano Bianco, Letizia Caito, Roberto Guida, Remo Ruffini

Comments: 4 pages, 3 figures, to appear in A&A Letters

Subjects: Astrophysics (astro-ph)

We plan to fit the complete gamma- and X-ray light curves of the long duration GRB060218, including the prompt emission, in order to clarify the nature of the progenitors and the astrophysical scenario of the class of GRBs associated to SNe Ib/c. The initial total energy of the electron-positron plasma E_{e^\pm}^{tot}=2.32\times 10^{50} erg has a particularly low value similarly to the other GRBs associated with SNe. For the first time we observe a baryon loading B=10^{-2} which coincides with the upper limit for the dynamical stability of the fireshell. The effective CircumBurst Medium (CBM) density shows a radial dependence n_{cbm} \propto r^{-\alpha} with 1.0<\alpha<1.7>

Lipunov 2007 Spinar作为伽玛暴的能源机制

主要内容:
考虑非稳态的塌缩形成高速旋转星，其爆发作为伽玛暴能源机制。

他们不久前曾经用于解释X射线的平降过程。

精彩摘抄:


文章信息:

arXiv:0706.3191 [pdf]

Title: Spinar Paradigm and Gamma Ray Bursts Central Engine

Authors: V.Lipunov (1,2,3), E.Gorbovskoy (1,2,3) (1-Sternberg Astronomical Institute,2-Dep. of Physics of Moscow State University,3-Moscow Union 'Optic')

Comments: 37 pages, 16-figures, submited to MNRAS

Subjects: Astrophysics (astro-ph)

A spinar is a quasi-equilibrium collapsing object whose equilibrium is maintained by the balance of centrifugal and gravitational forces and whose evolution is determined by its magnetic field. The spinar quasi equilibrium model recently discussed as the course for extralong X-ray plateu in GRB (Lipunov & Gorbovskoy, 2007). We propose a simple non stationary three-parameter collapse model with the determining role of rotation and magnetic field in this paper. The input parameters of the theory are the mass, angular momentum, and magnetic field of the collapsar. The model includes approximate description of the following effects: centrifugal force, relativistic effects of the Kerr metrics, pressure of nuclear matter, dissipation of angular momentum due to magnetic field, decrease of the dipole magnetic moment due to compression and general-relativity effects (the black hole has no hare), neutrino cooling, time dilatation, and gravitational redshift. The model describes the temporal behavior of the central engine and demonstrates the qualitative variety of the types of such behavior in nature. We apply our approach to explain the observed features of gamma-ray bursts of all types. In particular, the model allows the phenomena of precursors, x-ray and optical bursts, and the appearance of a plateau on time scales of several thousand seconds to be unified.

Tanaka 2007 SGR 1900+14和SGR 1806-20的1998和2004年的giant flares观测

主要内容:
给出了 SGR 1900+14和SGR 1806-20的1998和2004年的giant flares观测，提出了从短暴里分析出SGR的办法。

精彩摘抄:


文章信息:
arXiv:0706.3123 [ps, pdf, other]

Title: Comparative study of the inial spikes of SGR giant flares in 1998 and 2004 observed with GEOTAIL: Do magnetospheric instabilities trigger large scale fracturing of magnetar's crust?

Authors: Y. T. Tanaka, T. Terasawa, N. Kawai, A. Yoshida, I. Yoshikawa, Y. Saito, T. Takashima, T. Mukai

Comments: 12 pages, 3 figures, accepted by ApJL

Subjects: Astrophysics (astro-ph)

We present the unsaturated peak profile of SGR 1900+14 giant flare on 1998 August 27. This was obtained by particle counters of the Low Energy Particle instrument onboard the GEOTAIL spacecraft. The observed peak profile revealed four characteristic structures: initial steep rise, intermediate rise to the peak, exponential decay and small hump in the decay phase. From this light curve, we found that the isotropic peak luminosity was $2.3\times10^{46}$ erg s$^{-1}$ and the total energy was $4.3 \times 10^{44}$ erg s$^{-1}$ ($E\gtrsim$ 50 keV), assuming that the distance to SGR 1900+14 is 15 kpc and that the spectrum is optically thin thermal bremsstrahlung with $kT =$ 240 keV. These are consistent with the previously reported lower limits derived from Ulysses and Konus-Wind observations. A comparative study of the initial spikes of SGR 1900+14 giant flare in 1998 and SGR 1806-20 in 2004 is also presented. The timescale of the initial steep rise shows the magnetospheric origin, while the timescale of the intermediate rise to the peak indicates that it originates from the crustal fracturing. Finally, we argue that the four structures and their corresponding timescales provide a clue to identify extragalactic SGR giant flares among short

Soderberg 2007 Ib/c型超新星的射电成分

主要内容:
给出了30个Ib/c型超新星的射电观测，并和伽玛暴的射电作对比。一般伽玛暴的明显要比超新星的高，不过也有像980425，060218等和超新星差不多的。

我觉得伽玛暴的射电辐射比较高的原因可能在于它是正轴观测，如果Ibc型超新星也有伽玛暴成分，但喷流没指向观测着，由于极束效应而使射电流量降低。也许就低于超新星自身的射电辐射了，如果喷流的射电辐射碰巧高一点（光变也是先上升后下降的），可能在超新星的射电出现鼓包，called 超新星的伽玛暴成分。

精彩摘抄:

伽玛暴（上面两个）和30个Ibc型超新星的射电光变。

动能－速度图。


文章信息:

arXiv:0706.3047 [ps, pdf, other]

Title: The Radio Properties of Type Ibc Supernovae

Authors: Alicia M. Soderberg (Caltech)

Comments: 8 pages, Proceedings for "Supernova 1987A: 20 Years After: Supernovae and Gamma-Ray Bursters" AIP, New York, eds. S. Immler, K.W. Weiler, and R. McCray

Subjects: Astrophysics (astro-ph)

Over the past few years, long-duration gamma-ray bursts (GRBs), including the subclass of X-ray flashes (XRFs), have been revealed to be a rare variety of Type Ibc supernova (SN Ibc). While all these events result from the death of massive stars, the electromagnetic luminosities of GRBs and XRFs exceed those of ordinary Type Ibc SNe by many orders of magnitude. The observed diversity of stellar death corresponds to large variations in the energy, velocity, and geometry of the explosion ejecta. Using multi-wavelength (radio, optical, X-ray) observations of the nearest GRBs, XRFs, and SNe Ibc, I show that while GRBs and XRFs couple at least 10^48 erg to relativistic material, SNe Ibc typically couple less than 10^48 erg to their fastest (albeit non-relativistic) outflows. Specifically, I find that less than 3% of local SNe Ibc show any evidence for association with a GRB or XRF. Recently, a new class of GRBs and XRFs has been revealed which are under-luminous in comparison with the statistical sample of GRBs. Owing to their faint high-energy emission, these sub-energetic bursts are only detectable nearby (z <>

Burrows 2006 新的核塌缩超新星爆发机制

主要内容:
给出了他们数值模拟出来的超新星爆发。具体没看懂。应该可以从侧面看出最新的超新星爆发机制的研究进展，至少说明爆发机制还没定下来。（此Burrows, A 不是伽玛暴的Burrows, D. N.）

精彩摘抄:


文章信息:

Title:		A New Mechanism for Core-Collapse Supernova Explosions
Authors:		Burrows, A.; Livne, E.; Dessart, L.; Ott, C. D.; Murphy, J.
Affiliation:		AA(Department of Astronomy and Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721; burrows@as.arizona.edu, luc@as.arizona.edu, jmurphy@as.arizona.edu.), AB(Racah Institute of Physics, Hebrew University, Jerusalem 91904, Israel; eli@frodo.fiz.huji.ac.il.), AC(Department of Astronomy and Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721; burrows@as.arizona.edu, luc@as.arizona.edu, jmurphy@as.arizona.edu.), AD(Max-Planck-Institut für Gravitationsphysik, Albert-Einstein-Institut, Golm/Potsdam, Germany; cott@aei.mpg.de.), AE(Department of Astronomy and Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721; burrows@as.arizona.edu, luc@as.arizona.edu, jmurphy@as.arizona.edu.)
Publication:		The Astrophysical Journal, Volume 640, Issue 2, pp. 878-890. (ApJ Homepage)

Abstract

In this paper we present a new mechanism for core-collapse supernova explosions that relies on acoustic power generated in the inner core as the driver. In our simulation using an 11 M_solar progenitor, an advective-acoustic oscillation à la Foglizzo with a period of ~25-30 ms arises ~200 ms after bounce. Its growth saturates due to the generation of secondary shocks, and kinks in the resulting shock structure funnel and regulate subsequent accretion onto the inner core. However, this instability is not the primary agent of explosion. Rather, it is the acoustic power generated early on in the inner turbulent region stirred by the accretion plumes and, most importantly, but later on, by the excitation and sonic damping of core g-mode oscillations. An l=1 mode with a period of ~3 ms grows at late times to be prominent around ~500 ms after bounce. The accreting proto-neutron star is a self-excited oscillator, ``tuned'' to the most easily excited core g-mode. The associated acoustic power seen in our 11 M_solar simulation is sufficient to drive the explosion >550 ms after bounce. The angular distribution of the emitted sound is fundamentally aspherical. The sound pulses radiated from the core steepen into shock waves that merge as they propagate into the outer mantle and deposit their energy and momentum with high efficiency. The ultimate source of the acoustic power is the gravitational energy of infall, and the core oscillation acts like a transducer to convert this accretion energy into sound. An advantage of the acoustic mechanism is that acoustic power does not abate until accretion subsides, so that it is available as long as it may be needed to explode the star. This suggests a natural means by which the supernova is self-regulating.

Weiler 1988 超新星和超新星遗迹

主要内容:
主要给了超新星和遗迹的观测的总结。

精彩摘抄:

超新星的分类
超新星遗迹的观测特征

文章信息:

Title:		Supernovae and supernova remnants
Authors:		Weiler, Kurt W.; Sramek, Richard A.
Affiliation:		AA(U.S. Navy, E. O. Hulburt Center for Space Research, Washington, DC), AB(National Radio Astronomy Observatory, Socorro, NM)
Publication:		IN: Annual review of astronomy and astrophysics. Volume 26 (A89-14601 03-90). Palo Alto, CA, Annual Reviews, Inc., 1988, p. 295-341. (Annual Reviews Homepage)

Abstract

Observational data on SN and SNRs obtained during the period 1983-1987 are compiled in tables, graphs, contour maps, and sample images and reviewed, with an emphasis on new discoveries and controversial issues. Topics addressed include type I and type II optical SN, radio SN, theoretical models of SN origin, and SN rate estimates. Consideration is given to extragalactic and Galactic SNRs of the Balmer-dominated, oxygen-rich, plerionic-composite, and evolved classes; centrally influenced SNRs; SNR evolution; relations among SNR parameters; and the SN-SNR connection. A number of recently discovered plerionic-composite SNRs are listed and briefly characterized in an appendix.

Woosley 1986 超新星爆发机制

主要内容:
综述超新星的爆发机制，主要指核塌缩的模型，也有Ia型。当时还不是很注意到Ib/c型。

精彩摘抄:


文章信息:

Title:		The physics of supernova explosions
Authors:		Woosley, S. E.; Weaver, Thomas A.
Affiliation:		AA(Lick Observatory, Santa Cruz, CA), AB(California, University, Livermore)
Publication:		IN: Annual review of astronomy and astrophysics. Volume 24 (A87-26730 10-90). Palo Alto, CA, Annual Reviews, Inc., 1986, p. 205-253. (Annual Reviews Homepage)

Abstract

Recent efforts to model the processes occurring in Type I and II supernovae, and the diagnostics used to model the events, are described. Both types of events release about the same amount of energy and produce heavy elements. Features which distinguish the two types of supernovae are summarized. Prominent stages in Type II events are reviewed, including the presupernova evolution of massive stars, core collapse and bounce. Processes occurring in a delayed explosion, e.g., failure of the shock and possible formation of a 'neutrinosphere', are discussed, along with nucleosynthesis during Type II explosions and features of peculiar Type II events.

Bethe 1990 超新星机制

主要内容:
超新星爆发理论的一篇全面的综述文章。讲大质量恒星的核塌缩型超新星。包括核合成过程、中微子过程、激波条件（非相对论性的），然后重点介绍了SN1987A.

精彩摘抄:
SN 1987A的光变曲线以及数值模拟。

文章信息:

Title:		Supernova mechanisms
Authors:		Bethe, H. A.
Affiliation:		AA(Newman Laboratory of Nuclear Studies, Cornell University, Ithaca, New York 14853)
Publication:		Reviews of Modern Physics, Volume 62, Issue 4, October 1990, pp.801-866 (RvMP Homepage)
Publication Date:		00/1990

Supernovae of Type II occur at the end of the evolution of massive stars. The phenomenon begins when the iron core of the star exceeds a Chandrasekhar mass. The collapse of that core under gravity is well understood and takes a fraction of a second. To understand the phenomenon, a detailed knowledge of the equation of state at the relevant densities and temperatures is required. After collapse, the shock wave moves outward, but probably does not succeed in expelling the mass of the star. The most likely mechanism to do so is the absorption of neutrinos from the core by the material at medium distances. Observations and theory connected with SN 1987A are discussed, as are the conditions just before collapse and the emission of neutrinos by the collapsed core.

Folatelli 2006 SN 2005bf的观测，与伽玛暴成协

主要内容:
给出了对SN2005bf的光学观测，为解释光变的两个峰，认为这个爆发分为两部分：快的喷流＋慢的整体爆发，前者先被看到，显示为有高速度的吸收线，然后整体爆发被看到，出现第二个峰。而第一个峰有喷流，可能与伽玛暴成协。表现上还有从Ic型朝Ib型转化。

精彩摘抄:
超新星的位置。
光变曲线。

文章信息:
The Astrophysical Journal, 641:1039–1050, 2006 April 20
SN 2005bf: A POSSIBLE TRANSITION EVENT BETWEEN TYPE Ib/c SUPERNOVAE AND GAMMA-RAY BURSTS
Gasto´n Folatelli, et al
ABSTRACT
We present u0g0r 0i 0BV photometry and optical spectroscopy of the Type Ib/Ic SN 2005bf covering the first100 days following discovery. The u0g0BV light curves displayed an unprecedented morphology among Type Ib/Ic supernovae, with an initial maximum some 2 weeks after discovery and a second, main maximum about 25 days after that. The bolometric light curve indicates that SN 2005bf was a remarkably luminous event, radiating at least 6:3 ; 1042 ergs s ^-1 at maximum light and a total of 2:1 ; 1049 ergs during the first 75 days after the explosion. Spectroscopically, SN 2005bf underwent a unique transformation from a Type Ic-like event at early times to a typical Type Ib supernova at later phases. The initial maximum in u0g0BV was accompanied by the presence in the spectrum of high-velocity (>14,000 km s 1) absorption lines of Fe ii, Ca ii, andH i. The photospheric velocity derived fromspectra at early epochs was below 10,000 km s ^-1, which is unusually low compared with ordinary Type Ib supernovae. We describe one-dimensional computer simulations that attempt to account for these remarkable properties. The most favored model is that of a very energetic (2 ; 1051 ergs), asymmetric explosion of a massive (8.3M)Wolf-Rayet WN star that had lost most of its hydrogen envelope. We speculate that an unobserved relativistic jet was launched producing a two-component explosion consisting of (1) a polar explosion containing a small fraction of the total mass and moving at high velocity and (2) the explosion of the rest of the star. At first, only the polar explosion is observed, producing the initial maximum and the high-velocity absorption-line spectrum resembling a Type Ic event. At late times, this fast-moving component becomes optically thin, revealing the more slowly moving explosion of the rest of the star and transforming the observed spectrum to that of a typical Type Ib supernova. If this scenario is correct, then SN 2005bf is the best example to date of a transition object between normal Type Ib/Ic supernovae and gamma-ray bursts.

Ruffini 2007 伽玛暴统一模型

主要内容:
对他们提出的模型的一篇综述，黑洞附近真空极化形成正负电子对等离子体，形成火球绝热膨胀，在变透明处辐射伽玛暴(我们认为的precursor)，之后于ISM作用产生余辉（我们认为的暴本身和余辉）。如果没有重子加载，则形成短暴。

综述，163页。按专题讲，各专题之间联系不是很紧密。

精彩摘抄:


文章信息:
arXiv:0706.2572 [ps, pdf, other] : Title: The Blackholic energy and the canonical Gamma-Ray Burst
Authors: Remo Ruffini, Maria Grazia Bernardini, Carlo Luciano Bianco, Letizia Caito, Pascal Chardonnet, Maria Giovanna Dainotti, Federico Fraschetti, Roberto Guida, Michael Rotondo, Gregory Vereshchagin, Luca Vitagliano, She-Sheng Xue
Comments: 163 pages, 89 figures, to appear on the "Proceedings of the XIIth Brazilian School of Cosmology and Gravitation", M. Novello, S.E. Perez-Bergliaffa (editors), AIP, in press
Journal-ref: AIP Conf.Proc. 910 (2007) 55-217

We outline the main results of our GRB model, based on the three interpretation paradigms we proposed in July 2001, comparing and contrasting them with the ones in the current literature. Thanks to the observations by Swift and by VLT, this analysis points to a "canonical GRB" originating from markedly different astrophysical scenarios. The communality is that they are all emitted in the formation of a black hole with small or null angular momentum. The following sequence appears to be canonical: the vacuum polarization process creating an optically thick self accelerating electron-positron plasma; the engulfment of baryonic mass during the plasma expansion; the adiabatic expansion of the optically thick "fireshell" up to the transparency; the interaction of the remaining accelerated baryons with the interstellar medium (ISM). This leads to the canonical GRB composed of a proper GRB (P-GRB), emitted at the moment of transparency, followed by an extended afterglow. The parameters are the plasma total energy, the fireshell baryon loading and the ISM filamentary distribution around the source. In the limit of no baryon loading the total energy is radiated in the P-GRB. In this limit, the canonical GRBs explain as well the short GRBs.

Xie 2007 磁场和中微子主导吸积流作为伽玛暴的能源机制

主要内容:
磁场和中微子共同作用，提取吸积盘引力能。可解释伽玛暴和之后的X射线耀。

精彩摘抄:


文章信息:
arXiv:0706.2527 [ps, pdf, other] : Title: Effects of Magnetic Fields on Neutrino-dominated Accretion Model for Gamma-ray Bursts
Authors: Yi Xie, Chang-Yin Huang, Wei-Hua Lei
Comments: 10 pages, 4 figures, accepted by ChJAA

Many models of gamma-ray bursts suggest a common central engine: a black hole of several solar masses accreting matter from a disk at an accretion rate from 0.01 to 10 M_\sun / s. The inner region of the disk is cooled by neutrino emission and large amounts of its binding energy were liberated, which could trigger the fireball. We improve the neutrino-dominated accreting flows by considering the effects of the magnetic fields, and find that more than half of the liberating energy can be extracted directly by the large-scale magnetic fields on the disk. And it turns out that the temperature of the disk is a bit lower than the neutrino-dominated accreting flows without magnetic field. Therefore, The outflows are magneticallydominated rather than neutrino dominated. In our model, neutrino mechanism can fuel some GRBs (not the brightest ones), but cannot fuel X-ray flares. However, the magnetic processes (both BZ and electromagnetic luminosity from a disk) are viable mechanisms for most of GRBs and the following X-ray flares.

Bromm 2007 伽玛暴宇宙学

主要内容:
综述文章，讲用伽玛暴作为IGM，III型恒星等的探针。没提作为标准烛光定宇宙学参数。

精彩摘抄:


文章信息:
arXiv:0706.2445 [ps, pdf, other] : Title: GRB Cosmology
Authors: Volker Bromm, Abraham Loeb
Comments: 24 pages, 9 figures, review to appear in "Gamma-ray Bursts" (CUP)

Current observations are about to open up a direct window into the final frontier of cosmology: the first billion years in cosmic history when the first stars and galaxies formed. Even before the launch of the James Webb Space Telescope, it might be possible to utilize Gamma-ray Bursts (GRBs) as unique probes of cosmic star formation and the state of the intergalactic medium (IGM) up to redshifts of several tens, when the first (Population III) stars had formed. The Swift mission, or future satellites such as EXIST, might be the first observatories to detect individual Population III stars, provided that massive metal-free stars were able to trigger GRBs. Spectroscopic follow-up observations of the GRB afterglow emission would allow to probe the ionization state and metal enrichment of the IGM as a function of redshift.

Chen 2007 NGC1705-1的环境观测

主要内容:
可能能发生伽玛暴。

精彩摘抄:


文章信息:
arXiv:0706.2364 [ps, pdf, other] : Title: Super Star Cluster NGC1705-1: A Local Analogue to the Birthsite of Long-duration Gamma-ray Bursts
Authors: Hsiao-Wen Chen (University of Chicago), J. X. Prochaska (UCO/Lick Observatory), Joshua S. Bloom (UC Berkeley)
Comments: 20 pages, including 3 figurs. ApJ in press

Recent observations suggest that global properties of the host galaxies for long-duration gamma-ray bursts (GRBs) are particularly well-suited for creating the massive star progenitors of these GRBs. Motivated by the hypothesis that massive young star clusters located in metal-poor, low-metallicity galaxies are a natural birthsite for GRB progenitors, we present a comparison study of the ISM properties along the sightline toward the super star cluster, NGC1705-1, and those in distant GRB hosts. Using the same set of metal transitions in the UV and applying known ISM structures in NGC1705, we find that NGC1705-1 resembles distant GRB host galaxies in its high neutral gas column, low molecular gas fraction, low metallicity, alpha-element enhancement,and low dust depletion. The lack of molecular gas is due to the enhanced UV radiation field in the starburst environment, consistent with the expectations for GRB progenitors. In addition, the known presence of dense neutral gas clouds at r<500>

Pastorello 2007 SN 2006jc，超新星的再爆发？

主要内容:
给出了对SN 2006jc的观测，最值得注意的是两年前在相同的方位曾出现过瞬变体。二者是否有联系？如果有，那2004年的那个爆发有两种可能性：前身的WR星的爆发；双星，其中一个在2004年爆发。

精彩摘抄:


文章信息:

Nature 447, 829-832 (14 June 2007) | doi:10.1038/nature05825; Received 24 November 2006; Accepted 2 April 2007

A giant outburst two years before the core-collapse of a massive star

A. Pastorello¹, et al

The death of massive stars produces a variety of supernovae, which are linked to the structure of the exploding stars^{1, 2}. The detection of several precursor stars of type II supernovae has been reported (see, for example, ref. 3), but we do not yet have direct information on the progenitors of the hydrogen-deficient type Ib and Ic supernovae. Here we report that the peculiar type Ib supernova SN 2006jc is spatially coincident with a bright optical transient⁴ that occurred in 2004. Spectroscopic and photometric monitoring of the supernova leads us to suggest that the progenitor was a carbon-oxygen Wolf–Rayet star embedded within a helium-rich circumstellar medium. There are different possible explanations for this pre-explosion transient. It appears similar to the giant outbursts of luminous blue variable stars (LBVs) of 60–100 solar masses⁵, but the progenitor of SN 2006jc was helium- and hydrogen-deficient (unlike LBVs). An LBV-like outburst of a Wolf–Rayet star could be invoked, but this would be the first observational evidence of such a phenomenon. Alternatively, a massive binary system composed of an LBV that erupted in 2004, and a Wolf–Rayet star exploding as SN 2006jc, could explain the observations.

Burrows 1995 核塌缩超新星

主要内容:
一篇数值模拟超新星爆发的长文。

精彩摘抄:


文章信息:
On the Nature of Core Collapse Supernova Explosions

Authors: Adam Burrows, John Hayes (University of Arizona), Bruce Fryxell (Goddard SFC)

(Submitted on 8 Jun 1995)

Abstract: We investigate in this paper the core-collapse supernova explosion mechanism in both one and two dimensions. We verify the usefulness of neutrino-driven overturn (``convection'') between the shock and the neutrinosphere in igniting the supernova explosion. The 2-D simulation of the core of a 15$\mdot$ star that we present here indicates that the breaking of spherical symmetry may be central to the explosion itself and that a multitude of bent and broken fingers is a common feature of the ejecta. In 2-D, the steady-state shock radius is larger than its value in 1-D by 30\%--100\%. The critical condition for explosion is thereby relaxed. Since supernovae are driven by neutrino heating, they are coronal phenomena, akin to winds, though initially bounded by an accretion tamp. Neutrino energy is pumped into the supernova during the shock's propagation through the inner many thousands of kilometers and not instantaneously. Curiously, just after the explosion is triggered, the matter that will eventually be ejected is still bound. The high-speed fingers that emerge from the core seem a natural explanation for the nickel bullets seen in 87A and the shrapnel inferred in some supernova remnants. Within 100 ms of the explosion, a strong, neutrino-driven wind is blowing outward from the protoneutron star.

Title:		On the Nature of Core-Collapse Supernova Explosions
Authors:		Burrows, Adam; Hayes, John; Fryxell, Bruce A.
Publication:		Astrophysical Journal v.450, p.830 (ApJ Homepage)

070615, 060614一周年

昨天没有伽玛暴，今天INTEGRAL探测到一个，是060614，没有超新星成分的伽玛暴，之后一年了。这一年，我什么也没做:(

为什么恒星的主要波段在光学

恒星质量变化范围那么大，为什么辐射的频率都在光学波段呢？如果说是计算出来就是这样就太不负责任了。

Sironi 2007 磁场因子在余辉中的演化

主要内容:
从斜激波会影响流体的旋涡量出发（非相对论流体里已有，这里用在相对论流体里），然后认为磁能与旋涡的能量相当。结果是\epsilon_B \propto \Gamma^{-1}. Lorentz因子越大，磁能分量越小。（但这个结论好像和他们abstract里的说法相反啊。）

精彩摘抄:


文章信息:
arXiv:0706.1819 [ps, pdf, other] : Title: Production of magnetic energy by macroscopic turbulence in GRB afterglows
Authors: Lorenzo Sironi, Jeremy Goodman
Comments: 24 pages, 3 figures

Afterglows of gamma-ray bursts are believed to require magnetic fields much stronger than that of the compressed pre-shock medium. As an alternative to microscopic plasma instabilities, we propose amplification of the field by macroscopic turbulence excited by the interaction of the shock with a clumpy pre-shock medium, for example a stellar wind. Using a recently developed formalism for localized perturbations to an ultra-relativistic shock, we derive constraints on the lengthscale, amplitude, and volume filling factor of density clumps required to produce a given magnetic energy fraction within the expansion time of the shock, assuming that the energy in the field achieves equipartion with the turbulence. Stronger and smaller-scale inhomogeneities are required for larger shock Lorentz factors. Hence it is likely that the magnetic energy fraction evolves as the shock slows. This could be detected by monitoring the synchrotron cooling frequency if the radial density profile ahead of the shock, smoothed over clumps, is known.

Malesani 2007 GRB 060418 and GRB 060607A的早期余辉观测

主要内容:
给出了用REM对GRB 060418 and GRB 060607A的早期余辉观测，估算早期的Lorentz因子有400。而余辉的流量有暴本身的16%，对GRB 060418来说的话。

精彩摘抄:


文章信息:
arXiv:0706.1772 [ ps, pdf, other] : Title: The GRB afterglow onset observed by REM: fireball Lorentz factor and afterglow fluence
Authors: Daniele Malesani (DARK), Emilio Molinari (INAF/Brera), Susanna Vergani (DIAS and DCU), Stefano Covino (INAF/Brera), for the REM team
Comments: 4 pages, 1 figure, to appear in New Astronomy Reviews, proceedings of "070228: The Next Decade of Gamma-Ray Burst Afterglows", Amsterdam, 2007 March 19-23, eds. R.A.M.J. Wijers, L. Kaper, E. van Eerten

We report observations of the early light curves of GRB 060418 and GRB 060607A, carried out with the pink robotic telescope REM. A clear peak is detected for both events, which is interpreted as the onset of the afterglow, that is the time at which the fireball starts decelerating. This detection allows to directly measure the initial fireball Lorentz factor, which was found to be Gamma_0 ~ 400 for both events, fully confirming the ultrarelativistic nature of gamma-ray burst fireballs. Sampling the light curve before the peak also allows to compute the bolometric fluence of the afterglow, which is 16% of the prompt one in the case of GRB 060418.

Falcone 2007 Swift X射线耀发的大总结

主要内容:
总结了所有目前Swift暴的X射线耀发，包括每个暴的耀发的个数，光度，谱指数等。还有flares的E_pk- E_iso。


精彩摘抄:


文章信息:
arXiv:0706.1564 [ ps, pdf, other] : Title: The First Survey of X-ray Flares from Gamma Ray Bursts Observed by Swift: Spectral Properties and Energetics
Authors: A. D. Falcone (1), D. Morris (1), J. Racusin (1), G. Chincarini (2 and 3), A. Moretti (2), P. Romano (2 and 3), D. N. Burrows (1), C. Pagani (1), M. Stroh (1), D. Grupe (1), S. Campana (2), S. Covino (2), G. Tagliaferri (2), R. Willingale (4), N. Gehrels (5) ((1) Pennsylvania State University, (2)INAF-Osservatorio Astronomico di Brera, (3) Universita degli studi di Milano-Bicocca, (4) University of Leicester, (5) NASA/Goddard Space Flight Center)
Comments: submitted to ApJ; 37 pages with 14 figures

Observations of gamma ray bursts (GRBs) with Swift produced the initially surprising result that many bursts have large X-ray flares superimposed on the underlying afterglow. The flares were sometimes intense, had rapid rise and decay phases, and occurred late relative to the ``prompt'' phase. Some remarkable flares are observed with fluence comparable to the prompt GRB fluence. Many GRBs have several flares, which are sometimes overlapping. Short, intense, repetitive, and late flaring can be most easily understood within the context of the standard fireball model with the internal engine that powers the prompt GRB emission in an active state at late times. However, other models for flares have been proposed. Flare origin can be investigated by comparing the flare spectra to that of the afterglow and the initial prompt emission. In this work, we have analyzed all significant X-ray flares from the first 110 GRBs observed by Swift. From this sample 33 GRBs were found to have significant X-ray flares, with 77 flares that were detected above the 3$\sigma$ level. In addition to temporal analysis presented in a companion paper, a variety of spectral models have been fit to each flare. In some cases, we find that the spectral fits favor a Band function model, which is more akin to the prompt emission than to that of an afterglow. We find that the average fluence of the flares is 2.4e-7 erg/cm^2/s in the 0.2-10 keV energy band, which is approximately a factor of ten below the average prompt GRB fluence. These results, when combined with those presented in the companion paper on temporal properties of flares, supports the hypothesis that most X-ray flares are late-time activity of the internal engine that spawned the initial GRB; not an afterglow related effect.

X射线的平降阶段和外部介质分布

假设n \propto r^{-k}, 而且k>2. 这样喷流在往外运动的过程中基本不会被减速，自身也不会怎么被激波化，所以也不用计算辐射。只算正向激波的辐射，可能可以和早期平降阶段吻合。

然后也许进入ISM，成为标准余辉。

超新星的伽玛暴成分

如果伽玛暴和超新星成协的话（这几乎是肯定的），由于伽玛暴是极束的，那么有一些超新星虽然伴随有伽玛暴，但不朝着我们，可能看不到。可是余辉应该是可以看到的啊，特别是射电余辉。

但实际上是伽玛暴的射电余辉（包括于超新星成协的）比超新星自己（没看到伽玛暴的超新星）的射电高4个量级。这可能说明两个问题，要么这些超新星（也就是所有没看到伽玛暴的超新星）都不和伽玛暴成协；要么偏轴的射电比正轴的低4个量级。

我相信后者。因为说只有看到伽玛暴和超新星成协的才成协，没看到的就都不成协好像不对哦。那后者怎么解释呢？

一、偏轴由于极束效应，流量会降低，不过在晚期的射电波段，喷流的Lorentz因子已经很小了，这种降低也会很弱；
二、假设辐射区是一个薄片，在标准模型里就是作薄层近似的，那边偏轴观测者所对应的光深就要大一些了，L=L_垂直／cos\theta。 光深大了流量自然较低。不过需要两方面的验证：一是具体计算看是否真能这么底；二是射电的谱此时应该是黑体，看观测到的是不是。

如果偏轴的射电确实比超新星的射电相比差不多，那么就要想办法把它区分出来。这个区分出来的成分就可以叫做超新星的伽玛暴成分。和目前动不动就说伽玛暴的超新星成分对应，呵呵。

Rol 2007 暗暴GRB 051022的观测

主要内容:
给出了射电和X射线的观测，红外和光学分布有2.8和6个星等的消光。

精彩摘抄:


文章信息:
arXiv:0706.1518 [ps, pdf, other] : Title: GRB051022: physical parameters and extinction of a prototype dark burst
Authors: Evert Rol, Alexander van der Horst, Klaas Wiersema, Sandeep K. Patel, Andrew Levan, Melissa Nysewander, Chryssa Kouveliotou, Ralph A.M.J. Wijers, Nial Tanvir, Dan Reichart, Andrew S. Fruchter, John Graham, Rhaana L.C. Starling, Paul T. O'Brien, Jens Hjorth, Johan Fynbo, Peter Jonker, Wilbert van Ham, David N. Burrows, Jan-Erik Ovaldsen, Andreas O. Jaunsen, Richard Strom
Comments: 18 pages, 1 figure. Submitted to ApJ

GRB051022 was undetected to deep limits in early optical observations, but precise astrometry from radio and X-ray showed that it most likely originated in a galaxy at z ~ 0.8. We report radio, optical, near infra-red and X-ray observations of GRB051022. Using the available X-ray and radio data, we model the afterglow and calculate the energetics of the afterglow, finding it to be an order of magnitude lower than that of the prompt emission. The broad-band modeling also allows us to precisely define various other physical parameters and the minimum required amount of extinction, to explain the absence of an optical afterglow. Our observations suggest a high extinction, at least 2.8 magnitudes in the infrared (J) and at least 6 magnitudes in the optical (U) in the host-galaxy restframe. Such high extinctions are unusual for GRBs, and likely indicate a geometry where our line of sight to the burst passes through a dusty region in the host that is not directly co-located with the burst itself.

Wiersema 2007 GRB 040924的观测

主要内容:
给出GRB 040924和宿主星系的观测。z = 0.858 ± 0.001

精彩摘抄:
晚期好平啊，说是超新星成分。

文章信息:
arXiv:0706.1345 [ps, pdf, other] : Title: Spectroscopy and multiband photometry of the afterglow of intermediate duration gamma-ray burst 040924 and its host galaxy
Authors: K. Wiersema, A.J. van der Horst, D.A. Kann, E. Rol, R.L.C. Starling, P.A. Curran, J. Gorosabel, A.J. Levan, J.P.U. Fynbo, A. de Ugarte Postigo, R.A.M.J. Wijers, A.J. Castro-Tirado, S.S. Guziy, A. Hornstrup, J. Hjorth, M. Jelinek, B.L. Jensen, M. Kidger, F. Martin-Luis, N.R. Tanvir, P. Tristram, P.M. Vreeswijk
Comments: A&A submitted. 10 pages, 4 figures

We present optical photometry and spectroscopy of the afterglow and host galaxy of gamma-ray burst 040924. This GRB had a rather short duration of T90 ~2.4s, and a well sampled optical afterglow light curve. We aim to use this dataset to find further evidence that this burst is consistent with a massive star core-collapse progenitor. We combine the afterglow data reported here with data taken from the literature and compare the host properties with survey data. We find that the global behaviour of the optical afterglow is well fit by a broken power-law, with a break at ~0.03 days. We determine the redshift z = 0.858 +/- 0.001 from the detected emission lines in our spectrum. Using the spectrum and photometry we derive global properties of the host, showing it to have similar properties to long GRB hosts. We detect the [Ne III] emission line in the spectrum, and compare the fluxes of this line of a sample of 15 long GRB host galaxies with survey data, showing the long GRB hosts to be comparable to local metal-poor emission line galaxies in their [Ne III] emission. We fit the supernova bump accompanying this burst, and find that it is similar to other long GRB supernova bumps, but fainter. All properties of GRB 040924 are consistent with an origin in the core-collapse of a massive star: the supernova, the spectrum and SED of the host and the afterglow.

van der Horst 2007 GRB 030329的三年射电观测

主要内容:
两篇会议文章，是arXiv:0706.1321的补充吧。

精彩摘抄:


文章信息:

arXiv:0706.1323 [ps, pdf, other] :

Title: GRB 030329: 3 years of radio afterglow monitoring
Authors: A.J. van der Horst, A. Kamble, R.A.M.J. Wijers, L. Resmi, D. Bhattacharya, E. Rol, R. Strom, C. Kouveliotou, T. Oosterloo, C.H. Ishwara-Chandra
Comments: 5 pages, 2 figures, Phil. Trans. R. Soc. A, vol.365, p.1241, proceedings of the Royal Society Scientific Discussion Meeting, London, September 2006

Radio observations of gamma-ray burst (GRB) afterglows are essential for our understanding of the physics of relativistic blast waves, as they enable us to follow the evolution of GRB explosions much longer than the afterglows in any other wave band. We have performed a three-year monitoring campaign of GRB 030329 with the Westerbork Synthesis Radio Telescopes (WSRT) and the Giant Metrewave Radio Telescope (GMRT). Our observations, combined with observations at other wavelengths, have allowed us to determine the GRB blast wave physical parameters, such as the total burst energy and the ambient medium density, as well as investigate the jet nature of the relativistic outflow. Further, by modeling the late-time radio light curve of GRB 030329, we predict that the Low-Frequency Array (LOFAR, 30-240 MHz) will be able to observe afterglows of similar GRBs, and constrain the physics of the blast wave during its non-relativistic phase.

arXiv:0706.1324 [ps, pdf, other] :

Title: GRB 030329: three years of radio afterglow monitoring
Authors: A.J. van der Horst, A. Kamble, R.A.M.J. Wijers, L. Resmi, D. Bhattacharya, E. Rol, R. Strom, C. Kouveliotou, T. Oosterloo, C.H. Ishwara-Chandra
Comments: 2 pages, to appear in Nuovo Cimento B, proceedings of the Congress "Swift and GRBs: Unveiling the Relativistic Universe", Venice, June 2006

Radio observations of gamma-ray burst (GRB) afterglows are essential for our understanding of the physics of relativistic blast waves, as they enable us to follow the evolution of GRB explosions much longer than the afterglows in any other wave band. We have performed a three-year monitoring campaign of GRB 030329 with the Westerbork Synthesis Radio Telescopes (WSRT) and the Giant Metrewave Radio Telescope (GMRT). Our observations, combined with observations at other wavelengths, have allowed us to determine the GRB blast wave physical parameters, such as the total burst energy and the ambient medium density, as well as investigate the jet nature of the relativistic outflow. Further, by modeling the late-time radio light curve of GRB 030329, we predict that the Low Frequency Array (LOFAR, 30-240 MHz) will be able to observe afterglows of similar GRBs, and constrain the physics of the blast wave during its non-relativistic phase.

van der Horst 2007 GRB 030329深度非相对论的射电辐射观测

主要内容:
给出了一直到1128天的射电观测。用一般模型限制了一些参数。

精彩摘抄:


文章信息:
arXiv:0706.1321 [ps, pdf, other] : Title: Detailed study of the GRB 030329 radio afterglow deep into the non-relativistic phase
Authors: A.J. van der Horst, A. Kamble, L. Resmi, R.A.M.J. Wijers, D. Bhattacharya, B. Scheers, E. Rol, R. Strom, C. Kouveliotou, T. Oosterloo, C.H. Ishwara-Chandra
Comments: 9 pages, 2 figures, submitted to Astronomy & Astrophysics

We explore the physics behind one of the brightest radio afterglows ever, GRB 030329, at late times when the jet is non-relativistic. We determine the physical parameters of the blast wave and its surroundings, in particular the index of the electron energy distribution, the energy of the blast wave and the density (structure) of the circumburst medium; and compare our results with results from image size measurements. We observed the GRB 030329 radio afterglow with the Westerbork Synthesis Radio Telescope and the Giant Metrewave Radio Telescope at frequencies from 325 MHz to 8.4 GHz, spanning a time range of 268-1128 days after the burst. We modeled all the available radio data and derived the physical parameters. The index of the electron energy distribution is p=2.1, the circumburst medium is homogeneous, and the transition to the non-relativistic phase happens at t_NR ~ 80 days. The energy of the blast wave and density of the surrounding medium are comparable to previous findings. Our findings indicate that the blast wave is roughly spherical at t_NR, and they are in agreement with the implications from the VLBI studies of the image size evolution. It is not clear from the presented dataset whether we have seen emission from the counter jet or not. We predict that the Low Frequency Array will be able to observe the afterglow of GRB 030329 and many other radio afterglows, constraining the physics of the blast wave during its non-relativistic phase even further.

Butler 2007 Swift暴的catalog

主要内容:
从GRB 041220 到 070509一共218个暴， 其中76个有红移，给出了它们的T90,T50,T0.45,E_pk,E_iso,\alpha,\beta,等等

精彩摘抄:


Swift时代的Amati关系，灰色的小点是在一定置信度上某个暴所可能的位置。
这是什么关系？看起来蛮致密的嘛

文章信息:
arXiv:0706.1275 [ps, pdf, other] : Title: A Complete Catalog of Swift GRB Spectra and Durations: Demise of a Physical Origin for Pre-Swift High-Energy Correlations
Authors: Nathaniel R. Butler, Daniel Kocevski, Joshua S. Bloom, Jason L. Curtis
Comments: 25 pages, 7 figures, 2 tables

We calculate durations and spectral paramaters for 218 Swift bursts detected by the BAT instrument between and including GRBs 041220 and 070509, including 76 events with measured redshifts. Incorporating prior knowledge into the spectral fits, we are able to measure the characteristic $\nu F_{\nu}$ spectral peak energy $E_{\rm pk,obs}$ and the isotropic equivalent energy $E_{\rm iso}$ (1--$10^4$ keV) for all events. This complete and rather extensive catalog, analyzed with a unified methodology, allows us to address the persistence and origin of high-energy correlations suggested in pre-Swift observations. We find that the $E_{\rm pk,obs}$-$E_{\rm iso}$ correlation is present in the Swift sample, however the best-fit powerlaw relation is inconsistent from the best-fit pre-Swift relation at >5 sigma significance. Moreover, it has a factor >~ 2 larger intrinsic scatter, after accounting for large errors on $E_{\rm pk,obs}$. A large fraction of the Swift events are hard and subluminous relative to (and inconsistent with) the pre-Swift relation, in agreement with indications from BATSE GRBs without redshift. Moreover, we determine an experimental threshold for the BAT detector and show how the $E_{\rm pk,obs}$--$E_{\rm iso}$ correlation arises artificially due to partial correlation with the threshold. We show that pre-Swift correlations found by Amati et al.(2002), Yonetoku et al. (2004), Firmani et al.(2006) (and independently by others) are likely unrelated to the physical properties of GRBs and are likely useless for tests of cosmology. Also, an explanation of these correlations in terms of a detector threshold provides a natural and quantitative explanation for why short-duration GRBs and events at low redshift tend to be outliers to the correlations.

Malesani 2007 短暴GRB 050724的多波段余辉观测

主要内容:
宿主星系、光谱和多波段光变曲线

精彩摘抄:
position

light curves

文章信息:
arXiv:0706.1273 [ps, pdf, other] : Title: Multicolor observations of the afterglow of the short/hard GRB 050724
Authors: D. Malesani, S. Covino, P. D'Avanzo, V. D'Elia, D. Fugazza, S. Piranomonte, L. Ballo, S. Campana, L. Stella, G. Tagliaferri, L.A. Antonelli, G. Chincarini, M. Della Valle, P. Goldoni, C. Guidorzi, G.L. Israel, D. Lazzati, A. Melandri, P. Romano, G. Stratta, S.D. Vergani
Comments: 8 pages, 5 figures, 4 tables, submitted to A&A following referee comments

New information on short/hard gamma-ray bursts (GRBs) is being gathered thanks to the discovery of their optical and X-ray afterglows. However, some key aspects are still poorly understood, including the collimation level of the outflow, the duration of the central engine activity, and the properties of the progenitor systems. We want to constrain the physical properties of the short GRB 050724 and of its host galaxy, in turn drawing some inferences on the global short GRB population. We present optical observations of the afterglow of GRB 050724 and of its host galaxy, significantly expanding the existing dataset for this event. We compare our results with models, complementing them with available measurements in the literature. Including X-ray data, we study the afterglow light curve and spectrum. We also present observations of the host galaxy. The observed optical emission was likely related to the large flare observed in the X-ray light curve. The apparent steep decay was therefore not due to the jet effect. Available data are indeed consistent with low collimation, in turn implying a large energy release, comparable to that of long GRBs. The flare properties also constrain the internal shock mechanism, requiring a large Lorentz factor contrast between the colliding shells. This implies that the central engine was active at late times, rather than ejecting all shells simultaneously. The host galaxy has red colors and no ongoing star formation, consistent with previous findings on this GRB. However, it is not a pure elliptical, and has some faint spiral structure. GRB 050724 provides the most compelling case for association between a short burst and a galaxy with old stellar population. It thus plays a pivotal role in constraining progenitors models, which must allow long delays between birth and explosion.