D'Elia, V. VLT/X-shooter对GRB 090926A的光学余辉谱的观测

主要内容:
这里的谱主要是发射线和吸收线。从而分析暴周环境。

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Title:		VLT/X-shooter spectroscopy of the GRB 090926A afterglow
Authors:		D'Elia, V.; Fynbo, J. P. U.; Covino, S.; Goldoni, P.; Jakobsson, P.; Matteucci, F.; Piranomonte, S.; Sollerman, J.; Thoene, C. C.; Vergani, S. D.; Vreeswijk, P. M.; Watson, D. J.; Wiersema, K.; Zafar, T.; de Ugarte Postigo, A.; Flores, H.; Hjorth, J.; Kaper, L.; Levan, A. J.; Malesani, D.; Milvang-Jensen, B.; Pian, E.; Tagliaferri, G.; Tanvir, N. R.
Publication:		eprint arXiv:1007.5357
Publication Date:		07/2010
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		12 pages, 8 .ps figures, accepted for publication in A&A. Abstract reduced due to space constraints
Bibliographic Code:		2010arXiv1007.5357D

Abstract

The aim of this paper is to study the environment and intervening absorbers of the gamma-ray burst GRB 090926A through analysis of optical spectra of its afterglow. We analyze medium resolution spectroscopic observations (R=10 000, corresponding to 30 km/s, S/N=15 - 30 and wavelength range 3000-25000) of the optical afterglow of GRB 090926A, taken with X-shooter at the VLT ~ 22 hr after the GRB trigger. The spectrum shows that the ISM in the GRB host galaxy at z = 2.1071 is rich in absorption features, with two components contributing to the line profiles. In addition to the ground state lines, we detect C II, O I, Si II, Fe II and Ni II excited absorption features. No host galaxy emission lines, molecular absorption features nor diffuse interstellar bands are detected in the spectrum. The Hydrogen column density associated to GRB 090926A is log N_H/cm^{-2} = 21.60 +/- 0.07, and the metallicity of the host galaxy is in the range [X/H] =3.2X10^{-3}-1.2X10^{-2} with respect to the solar values, i.e., among the lowest values ever observed for a GRB host galaxy. A comparison with galactic chemical evolution models has suggested that the host of GRB090926A is likely to be a dwarf irregular galaxy. We put an upper limit to the Hydrogen molecular fraction of the host galaxy ISM, which is f < 7X10^{-7}. We derive information on the distance between the host absorbing gas and the site of the GRB explosion. The distance of component I is found to be 2.40 +/- 0.15 kpc, while component II is located far away from the GRB, possibly at ~ 5 kpc. These values are compatible with that found for other GRBs.

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Takahashi 2010 用高红移的伽马暴的pair echos来探测当地的星系磁场

主要内容:
高红移的伽马暴的伽马光子可能CMB光子发生碰撞，产生正负电子对，用将来的Cherenkov望远镜整列可能对这些电子对观测，并从而限制当地（或者路上？）磁场。

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Title:		Probing Early Cosmic Magnetic Fields through Pair Echos from High-Redshift GRBs
Authors:		Takahashi, Keitaro; Inoue, Susumu; Ichiki, Kiyotomo; Nakamura, Takashi
Publication:		eprint arXiv:1007.5363
Publication Date:		07/2010
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		22 pages, 7 figures
Bibliographic Code:		2010arXiv1007.5363T

Abstract

We discuss the expected properties of pair echo emission from gamma-ray bursts (GRBs) at high redshifts ($z \gtrsim 5$), their detectability, and the consequent implications for probing intergalactic magnetic fields (IGMFs) at early epochs. Pair echos comprise inverse Compton emission by secondary electron-positron pairs produced via interactions between primary gamma-rays from the GRB and low-energy photons of the diffuse intergalactic radiation, arriving with a time delay that depends on the nature of the intervening IGMFs. At sufficiently high $z$, the IGMFs are unlikely to have been significantly contaminated by astrophysical outflows, and the relevant intergalactic radiation may be dominated by the well-understood cosmic microwave background (CMB). Pair echoes from luminous GRBs at $z \sim 5-10$ may be detectable by future facilities such as the Cherenkov Telescope Array or the Advanced Gamma-ray Imaging System, as long as the GRB primary emission extends to multi-TeV energies, the comoving IGMFs at these redshifts are $B \sim 10^{-16}-10^{-15}~{\rm Gauss}$, and the non-CMB component of the diffuse intergalactic radiation is relatively low. Observations of pair echos from high-$z$ GRBs can provide a unique, in-situ probe of weak IGMFs during the epochs of early structure formation and cosmic reionization.

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Sakamoto 2010 短暴GRB 050925的观测

主要内容:
也可能是一个软伽马重复暴。

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Title:		Probing the Nature of Short Swift Bursts via Deep INTEGRAL Monitoring of GRB 050925
Authors:		Sakamoto, T.; Barbier, L.; Barthelmy, S. D.; Cummings, J. R.; Fenimore, E. E.; Gehrels, N.; Krimm, H. A.; Markwardt, C. B.; Palmer, D. M.; Parsons, A. M.; Sato, G.; Stamatikos, M.; Tueller, J.
Publication:		eprint arXiv:1008.0226
Publication Date:		08/2010
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		13 pages, 13 figures, accepted for publication in ASR special issue on Neutron Stars and Gamma Ray Bursts, full resolution of Fig 5 is available at http://asd.gsfc.nasa.gov/Takanori.Sakamoto/GRB050925/integral_ibis_images.eps
Bibliographic Code:		2010arXiv1008.0226S

Abstract

We present results from Swift, XMM-Newton, and deep INTEGRAL monitoring in the region of GRB 050925. This short Swift burst is a candidate for a newly discovered soft gamma-ray repeater (SGR) with the following observational burst properties: 1) galactic plane (b=-0.1 deg) localization, 2) 150 msec duration, and 3) a blackbody rather than a simple power-law spectral shape (with a significance level of 97%). We found two possible X-ray counterparts of GRB 050925 by comparing the X-ray images from Swift XRT and XMM-Newton. Both X-ray sources show the transient behavior with a power-law decay index shallower than -1. We found no hard X-ray emission nor any additional burst from the location of GRB 050925 in ~5 Ms of INTEGRAL data. We discuss about the three BATSE short bursts which might be associated with GRB 050925, based on their location and the duration. Assuming GRB 050925 is associated with the H II regions (W 58) at the galactic longitude of l=70 deg, we also discuss the source frame properties of GRB 050925.

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Xu 2010 用环状喷流解释伽马暴早期余辉的变平

主要内容:
如标题。

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Title:		Early Rebrightenings of X-ray Afterglows from Ring-Shaped GRB Jets
Authors:		Xu, M.; Huang, Y. -F.
Publication:		eprint arXiv:1008.1686
Publication Date:		08/2010
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		11 pages, 5 figures, Accepted for publication in Astronomy and Astrophysics
Bibliographic Code:		2010arXiv1008.1686X

Abstract

Early rebrightenings at a post-burst time of 10^2 - 10^4 s have been observed in the afterglows of some gamma-ray bursts (GRBs). Unlike X-ray flares, these rebrightenings usually last for a relatively long period. The continuous energy injection mechanism usually can only produce a plateau in the afterglow light curve, but not a rebrightening. Also, a sudden energy injection can give birth to a rebrightening, but the rebrightening is a bit too rapid. Here we argued that the early rebrightenings can be produced by the ring-shaped jet model. In this scenario, the GRB outflow is not a full cone, but a centrally hollowed ring. Assuming that the line of sight is on the central symmetry axis of the hollow cone, we calculate the overall dynamical evolution of the outflows and educe the multiband afterglow light curves. It is found that the early rebrightenings observed in the afterglows of a few GRBs, such as GRBs 051016B, 060109, 070103 and 070208 etc, can be well explained in this framework. It is suggested that these long-lasted early rebrightenings in GRB afterglows should be resulted from ring-shaped jets.

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Thielemann 2010 大质量恒星及其超新星

主要内容:
书中的一章。主要考虑化学演化和星风。

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Title:		Massive Stars and their Supernovae
Authors:		Thielemann, Friedrich-Karl; Hirschi, Raphael; Liebendörfer, Matthias; Diehl, Roland
Publication:		eprint arXiv:1008.2144
Publication Date:		08/2010
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		79 pages; Chapter of "Astronomy with Radioactivities", a book in Springer's 'lecture notes in physics series, Vol. 812, Eds. Roland Diehl, Dieter H. Hartmann, and Nikos Prantzos, to appear in summer 2010; doi:10.1007/978-3-642-12698-7_4
Bibliographic Code:		2010arXiv1008.2144T

Abstract

Massive stars and their supernovae are prominent sources of radioactive isotopes, the observations of which thus can help to improve our astrophysical models of those. Our understanding of stellar evolution and the final explosive endpoints such as supernovae or hypernovae or gamma-ray bursts relies on the combination of magneto-hydrodynamics, energy generation due to nuclear reactions accompanying composition changes, radiation transport, and thermodynamic properties (such as the equation of state of stellar matter). Nuclear energy production includes all nuclear reactions triggered during stellar evolution and explosive end stages, also among unstable isotopes produced on the way. Radiation transport covers atomic physics (e.g. opacities) for photon transport, but also nuclear physics and neutrino nucleon/nucleus interactions in late phases and core collapse. Here we want to focus on the astrophysical aspects, i.e. a description of the evolution of massive stars and their endpoints, with a special emphasis on the composition of their ejecta (in form of stellar winds during the evolution or of explosive ejecta). Low and intermediate mass stars end their evolution as a white dwarf with an unburned C and O composition. Massive stars evolve beyond this point and experience all stellar burning stages from H over He, C, Ne, O and Si-burning up to core collapse and explosive endstages. In this chapter we discuss the nucleosynthesis processes involved and the production of radioactive nuclei in more detail.

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Couch 2010 数值模拟SN 2008D的非对称shock breakout

主要内容:


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初始的密度分布

shock的演化


































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Title:		Aspherical Supernova Shock Breakout and the Observations of Supernova 2008D
Authors:		Couch, Sean M.; Pooley, David; Wheeler, J. Craig; Milosavljevic, Milos
Publication:		eprint arXiv:1007.3693
Publication Date:		07/2010
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		17 page, 27 figures. Submitted to ApJ
Bibliographic Code:		2010arXiv1007.3693C

Abstract

Shock breakout is the earliest, readily-observable emission from a core-collapse supernova explosion. Observing supernova shock breakout may yield information about the nature of the supernova shock prior to exiting the progenitor and, in turn, about the core-collapse supernova mechanism itself. X-ray Outburst 080109, later associated with SN 2008D, is a very well-observed example of shock breakout from a core-collapse supernova. Despite excellent observational coverage and detailed modeling, fundamental information about the shock breakout, such as the radius of breakout and driver of the light curve time scale, is still uncertain. The models constructed for explaining the shock breakout emission from SN 2008D all assume spherical symmetry. We present a study of the observational characteristics of {\it aspherical} shock breakout from stripped-envelope core-collapse supernovae. We conduct two-dimensional, jet-driven supernova simulations from stripped-envelope progenitors and calculate the resulting shock breakout X-ray spectra and light curves. The X-ray spectra evolve significantly in time as the shocks expand outward and are not well-fit by single-temperature and radius black bodies. The time scale of the X-ray burst light curve of the shock breakout is related to the shock crossing time of the progenitor, not the much shorter light crossing time that sets the light curve time scale in spherical breakouts. This could explain the long shock breakout light curve time scale observed for XRO 080109/SN 2008D.

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Pannarale 2010 数值模拟黑洞+中子星的一个玩具模型

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Title:		Black hole-neutron star mergers and short GRBs: a relativistic toy model to estimate the mass of the torus
Authors:		Pannarale, Francesco; Tonita, Aaryn; Rezzolla, Luciano
Publication:		eprint arXiv:1007.4160
Publication Date:		07/2010
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology
Comment:		12 pages, 4 figures, 1 table
Bibliographic Code:		2010arXiv1007.4160P

Abstract

The merger of a binary system composed of a black hole and a neutron star may leave behind a torus of hot, dense matter orbiting around the black hole. While numerical-relativity simulations are necessary to simulate this process accurately, they are also computationally expensive and unable at present to cover the large space of possible parameters, which include the relative mass ratio, the stellar compactness and the black hole spin. To mitigate this and provide a first reasonable coverage of the space of parameters, we have developed a method for estimating the mass of the remnant torus from black hole-neutron star mergers. The toy model makes use of the relativistic affine model to describe the tidal deformations of an extended tri-axial ellipsoid orbiting around a Kerr black hole and measures the mass of the remnant torus by considering which of the fluid particles composing the star are on bound orbits at the time of the tidal disruption. We tune the toy model by using the results of fully general-relativistic simulations obtaining relative precisions of few a percent and use it to investigate the space of parameters extensively. In this way we find that the torus mass is largest for systems with highly spinning black holes, small stellar compactnesses and large mass ratios. As an example, tori as massive as $M_{b,\text{tor}} \simeq 1.33\,M_{\odot}$ can be produced for a very extended star with compactness $C\simeq 0.1$ inspiralling around a black hole with dimensionless spin $a=0.85$ and mass ratio $q\simeq 0.3$. However, for a more astrophysically reasonable mass ratio $q \simeq 0.14$ and a canonical value of the stellar compactness $C\simeq 0.145$, the toy model sets a considerably smaller upper limit of $M_{b,\text{tor}} \lesssim 0.34\,M_{\odot}$.

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Veres 2010 想将暴本身和余辉的光变连起来

主要内容:
做法貌似是通过谱指数将辐射流量换算到同一个能断。

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Title:		Gamma-Ray Bursts: Connecting the Prompt Emission with the Afterglow
Authors:		Veres, P.; Bagoly, Z.
Affiliation:		AA(Department of Physics of Complex Systems, Eötvös University, H-1117 Budapest, Pázmany P. s. 1/A, Hungary; veresp@elte.hu; Department of Physics, Bolyai Military University, H-1581 Budapest, POB 15, Hungary), AB(Department of Physics of Complex Systems, Eötvös University, H-1117 Budapest, Pázmany P. s. 1/A, Hungary; zsolt.bagoly@elte.hu)
Publication:		Baltic Astronomy, Vol. 18, p. 284-288
Publication Date:		00/2009
Origin:		BALTA
Keywords:		gamma rays: bursts
Bibliographic Code:		2009BaltA..18..284V

Abstract

With the early afterglow localizations of gamma-ray burst positions made by Swift, the clear delimitation of the prompt phase and the afterglow is not so obvious anymore. It is important to see weather the two phases have the same origin or they stem from different parts of the progenitor system. We will combine the two kinds of gamma-ray burst data from the Swift-XRT instrument (windowed timing and photon counting modes) and from BAT. A thorough desription of the applied procedure is given. We apply various binning techniques to the different data: Bayes blocks, exponential binning and signal-to-noise type of binning. We present a handful of flux curves and their possible applications.

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Dermer 2010 Fermi 暴的一个小综述

主要内容:
包括一部分甚高能的内容。

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几个高能暴的能量分布。

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Title:		First Light on GRBs with Fermi
Authors:		Dermer, Charles D.
Publication:		eprint arXiv:1008.0854
Publication Date:		08/2010
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		9 pages, 2 figures, in Deciphering the Ancient Universe with GRBs, Kyoto, Japan, April 19-23, 2010
Bibliographic Code:		2010arXiv1008.0854D

Abstract

Fermi LAT (Large Area Telescope) and GBM (Gamma ray Burst Monitor) observations of GRBs are briefly reviewed, keeping in mind EGRET expectations. Using gamma\gamma constraints on outflow Lorentz factors, leptonic models are pitted against hadronic models, and found to be energetically favored. Interpretation of the Fermi data on GRBs helps establish whether GRBs accelerate cosmic rays, including those reaching $\approx 10^{20}$ eV.

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Toma, Kenji 2010 Pop III伽马暴的余辉

主要内容:
第三类伽马暴，实际上是z>20的第三类恒星坍缩形成的。文章考虑这种类型的暴的余辉。三个主要特点可能是：总能量大，时标长，外部介质密。

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Title:		Population III GRB Afterglows: Constraints on Stellar Masses and External Medium Densities
Authors:		Toma, Kenji; Sakamoto, Takanori; Meszaros, Peter
Publication:		eprint arXiv:1008.1269
Publication Date:		08/2010
Origin:		ARXIV
Keywords:		Astrophysics - Cosmology and Extragalactic Astrophysics
Comment:		16 pages, 7 figures
Bibliographic Code:		2010arXiv1008.1269T

Abstract

Population III stars are theoretically expected to be prominent around redshifts z ~ 20, consisting of mainly very massive stars with M_* >~ 10 M_sun$, but there is no direct observational evidence for these objects. They may produce collapsar gamma-ray bursts (GRBs), with jets driven by magnetohydrodynamic processes, whose total isotropic-equivalent energy could be as high as E_iso >~ 10^{57} erg over a cosmological-rest-frame duration of t_d >~ 10^4 s, depending on the progenitor mass. Here we calculate the afterglow spectra of such Pop. III GRBs based on the standard external shock model, and show that they will be detectable with the Swift BAT/XRT and Fermi LAT instruments. We find that in some cases a spectral break due to electron-positron pair creation will be observable in the LAT energy range, which can put constraints on the ambient density of the pre-collapse Pop. III star. Thus, high redshift GRB afterglow observations could be unique and powerful probes of the properties of Pop. III stars and their environments. We examine the detection threshold of the BAT instrument in detail, focusing on the image trigger system, and show that the prompt emission of Pop. III GRBs could also be detected by BAT. Finally we briefly show that the late-time radio afterglows of Pop. III GRBs for typical parameters, despite the large distances, can be very bright: ~ 140 mJy at 1 GHz, which may lead to a constraint on the Pop. III GRB rate from the current radio survey data, and ~2.4 mJy at 70 MHz, which implies that Pop. III GRB radio afterglows could be interesting background source candidates for 21 cm absorption line detections.

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