Watson 2010 用X射线余辉的谱来估算暴周物质的金属柱密度

主要内容:
附近金属由于被电离，只能在X射线才能看到谱。

通过金属丰度还可以知道前身星。如果太高，PopIII就不可能了。

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Title:		The metallicity of gamma-ray burst environments from high energy observations
Authors:		Watson, D.; Laursen, P.
Publication:		eprint arXiv:1011.1009
Publication Date:		11/2010
Origin:		ARXIV
Keywords:		Astrophysics - Cosmology and Extragalactic Astrophysics
Comment:		4 pages, 4 figures, submitted to A&A letters
Bibliographic Code:		2010arXiv1011.1009W

Abstract

Gamma-ray bursts (GRBs) and their early afterglows ionise their circumburst material. Only high-energy spectroscopy therefore, allows examination of the matter close to the burst itself. Soft X-ray absorption allows an estimate to be made of the total column density in metals. The detection of the X-ray afterglow can also be used to place a limit on the total gas column along the line of sight based on the Compton scattering opacity. Such a limit would enable, for the first time, the determination of lower limits on the metallicity in the circumburst environments of GRBs. In this paper, we determine the limits that can be placed on the total gas column density in the vicinities of GRBs based on the Compton scattering. We simulate the effects of Compton scattering on a collimated beam of high energy photons passing through a shell of high column density material to determine the expected lightcurves, luminosities, and spectra. We compare these predictions to observations, and determine what limits can realistically be placed on the total gas column density. The smearing out of pulses in the lightcurve from Compton scattering is not likely to be observable, and its absence does not place strong constraints on the Compton depth for GRBs. However, the distribution of observed luminosities of bursts allows us to place statistical, model-dependent limits that are typically <~1e25 cm^{-2} for less luminous bursts, and as low as ~1e24 cm$^{-2} for the most luminous. Using the shape of the high-energy broadband spectrum, however, in some favourable cases, limits as low as ~5e24 cm^{-2} can placed on individual bursts, implying metallicity lower limits from X- and gamma-rays alone from 0 up to 0.01 Z/Zsun. At extremely high redshifts, this limit would be at least 0.02 Z/Z_sun, enough to discriminate population III from non-primordial GRBs.

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Zhang 2010 内部磁扰动产生伽马射线辐射

主要内容:
一个新的模型，企图解决內激波模型的困难。

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Title:		The Internal-Collision-Induced Magnetic Reconnection and Turbulence (ICMART) Model of Gamma-Ray Bursts
Authors:		Zhang, Bing; Yan, Huirong
Publication:		eprint arXiv:1011.1197
Publication Date:		11/2010
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		ApJ, in press (submitted on May 6, 2010). 27 emulateapj pages, 4 figures
Bibliographic Code:		2010arXiv1011.1197Z

Abstract

The recent Fermi observation of GRB 080916C shows that the bright photosphere emission associated with a putative fireball is missing, which suggests a Poynting-flux-dominated outflow. We propose a model of gamma-ray burst (GRB) prompt emission in the Poynting-flux-dominated regime, namely, the Internal-Collision-induced MAgnetic Reconnection and Turbulence (ICMART) model. It is envisaged that the GRB central engine launches an intermittent, magnetically-dominated wind, and that in the GRB emission region, the ejecta is still moderately magnetized. Similar to the internal shock (IS) model, the mini-shells interact internally at the traditional internal shock radius. Most of these early collision have little energy dissipation, but serve to distort the ordered magnetic field lines. At a certain point, the distortion of magnetic field configuration reaches the critical condition to allow fast reconnection seeds to occur, which induce relativistic MHD turbulence in the interaction regions. The turbulence further distorts field lines easing additional magnetic reconnections, resulting in a runway release of the stored magnetic field energy (an ICMART event). Particles accelerated in the ICMART region radiate synchrotron photons that power the observed gamma-rays. Each ICMART event corresponds to a broad pulse in the GRB lightcurve, and a GRB is composed of multiple ICMART events. This model retains the merits of the IS and other models, but may overcome several difficulties/issues faced by the IS model (e.g. low efficiency, fast cooling, electron number excess, Amati/Yonetoku relation inconsistency, and missing bright photosphere). It predicts two-component variability time scales, and a decreasing Ep and polarization degree during each ICMART event. The model may be applied to most Fermi LAT GRBs that have time-resolved, featureless Band-function spectra (abridged).

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Murase 2010 晚期内激波来解释X射线余辉的平降及其相应的高能辐射

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Title:		On the Implications of Late Internal Dissipation for Shallow-Decay Afterglow Emission and Associated High-Energy Gamma-Ray Signals
Authors:		Murase, Kohta; Toma, Kenji; Yamazaki, Ryo; Meszaros, Peter
Publication:		eprint arXiv:1011.0988
Publication Date:		11/2010
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Extragalactic Astrophysics
Comment:		15 pages, 14 figures
Bibliographic Code:		2010arXiv1011.0988M

Abstract

The origin of the shallow-decay emission during early X-ray afterglows has been an open issue since the launch of the Swift satellite. One of the appealing models is the late internal dissipation model, where X-ray emission during the shallow-decay phase is attributed to internal dissipation, analogous to the prompt gamma-ray emission. We discuss possible scenarios of the late prompt emission, such as late internal shocks, magnetic reconnection, and photospheric dissipation. We also consider the consequences of late dissipation and a two-component (early and late) jet model for the high-energy (GeV-TeV) emission. We study not only synchrotron self-Compton (SSC) emission from the early and late jets but also external inverse-Compton (EIC) emission, which is naturally predicted in the late dissipation model. For the latter, we perform numerical calculations taking into account the equal-arrival-time surface of EIC photons, and show that the EIC component typically has a peak at ~1-100 GeV which may dominate over the SSC components. We demonstrate that very-high-energy gamma rays from both these components are detectable for nearby and/or energetic GRBs, with current and future Cherenkov detectors such as MAGIC, VERITAS, CTA and HAWC, and possibly Fermi. Although the expected event rate would not be large, detections should be useful as a test of the model. Multi-wavelength observations using both the ground-based telescopes and the Swift and/or Fermi satellites are also important to constrain the models.

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Marchenko 2010 PopI WR星的星风

主要内容:
这个应该给暴周环境提供一些限制。

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Title:		Population I Wolf-Rayet Runaway Stars: The Case of WR124 and its Expanding Nebula M1-67
Authors:		Marchenko, S. V.; Moffat, A. F. J.; Crowther, P. A.
Affiliation:		AA(Science Systems and Applications, Inc., 10210 Greenbelt Road, Suite 600, Lanham, MD 20706, USA sergey.marchenko@ssaihq.com), AB(Département de Physique and Observatoire du Mont Mégantic, Université de Montréal, CP 6128, Succursale Centre-Ville, Montréal, QC H3C 3J7, Canada moffat@astro.umontreal.ca), AC(Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Rd, Sheffield, S3 7RH, UK Paul.Crowther@sheffield.ac.uk)
Publication:		The Astrophysical Journal Letters, Volume 724, Issue 1, pp. L90-L94 (2010). (ApJL Homepage)
Publication Date:		11/2010
Origin:		IOP
ApJ Keywords:		gamma-ray burst: general, stars: distances, stars: individual: WR 124, stars: Wolf-Rayet, supernovae: general
DOI:		10.1088/2041-8205/724/1/L90
Bibliographic Code:		2010ApJ...724L..90M

Abstract

In 1997 and 2008 we used the WFPC2 camera on board the Hubble Space Telescope to obtain two sets of narrow-band Hα images of the runaway Wolf-Rayet (WR) star WR 124 surrounded by its nebula M1-67. This two-epoch imaging provides an expansion parallax and thus a practically assumption-free geometric distance to the nebula, d = 3.35 ± 0.67 kpc. Combined with the global velocity distribution in the ejected nebula, this confirms the extreme runaway status of WR 124. WR stars embedded within such ejection nebulae at the point of core collapse would produce different supernova characteristics from those expected for stars surrounded by wind-filled cavities. In galaxies with extremely low ambient metallicity, Z <= 10^–3 Z _sun, γ-ray bursts originating from fast-moving runaway WR stars may produce afterglows which appear to be coming from regions with a relatively homogeneous circumburst medium.

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Christensen 2010 60个长暴余辉的谱线

主要内容:

对60个长暴，分析了它们的谱线。找到了一些原子的发射线和吸收线。

暗暴有比较强的吸收线（暗示暗暴周围的物质比较密集，可能是吸收导致的暗暴）。

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Title:		A High Signal-to-Noise Ratio Composite Spectrum of Gamma-ray Burst Afterglows
Authors:		Christensen, L.; Fynbo, J. P. U.; Prochaska, J. X.; Thoene, C. C.; de Ugarte Postigo, A.; Jakobsson, P.
Publication:		eprint arXiv:1011.0734
Publication Date:		11/2010
Origin:		ARXIV
Keywords:		Astrophysics - Cosmology and Extragalactic Astrophysics
Comment:		Accepted for publication in ApJ, 24 pages
Bibliographic Code:		2010arXiv1011.0734C

Abstract

We present a composite spectrum of 60 long duration gamma-ray burst (GRB) afterglows with redshifts in the range 0.35

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Greiner 2010 暗暴的来源

主要内容:
可能主要来自两个方面：暴周的吸收；红移较高。
没说本征比较暗。

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Title:		The nature of ``dark'' gamma-ray bursts
Authors:		Greiner, J.; Krühler, T.; Klose, S.; Afonso, P.; Clemens, C.; Filgas, R.; Yoldaş, A. Küpcü; Nardini, M.; Olivares, F.; Rau, A.; Rossi, A.; Schady, P.; Updike, A.
Affiliation:		AA(Max-Planck-Inst. für extraterrestrische Physik, Giessenbachstr. 1
Publication:		DECIPHERING THE ANCIENT UNIVERSE WITH GAMMA-RAY BURSTS. AIP Conference Proceedings, Volume 1279, pp. 144-151 (2010). (AIPC Homepage)
Publication Date:		10/2010
Origin:		AIP
Keywords:		gamma-ray sources (astronomical), cosmology, photometry, X-ray spectra
PACS Keywords:		gamma-ray sources; gamma-ray bursts, Particle-theory and field-theory models of the early Universe, Photometric, polarimetric, and spectroscopic instrumentation, X-ray
Abstract Copyright:		(c) 2010: American Institute of Physics
DOI:		10.1063/1.3509253
Bibliographic Code:		2010AIPC.1279..144G

Abstract

More than 13 years after the discovery of the first afterglows, the nature of dark gamma-ray bursts (GRB) has still eluded explanation: while each long-duration GRB typically has an X-ray afterglow, optical/NIR emission is only seen for 40-60% of those. Here we use the afterglow detection statistics of the systematic follow-up observations performed with GROND since mid-2007 in order to derive the fraction of ``dark bursts''. We find that the faint optical afterglow emission of ``dark bursts'' is due to a combination of two components: (i) moderate intrinsic extinction at moderate redshifts, and (ii) about 25% of bursts at redshift >5.

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Afonso 2010 GRB 050502b的光学余辉

主要内容:
有个拐折

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Title:		GRB 050502B optical afterglow: a jet break at high redshift
Authors:		Afonso, P.; Greiner, J.; Pian, E.; Covino, S.; Malesani, D.; Küpcü Yoldaş, A.; Krühler, T.; Clemens, C.; McBreen, S.; Rau, A.; Giannios, D.; Hjorth, J.
Publication:		eprint arXiv:1011.0113
Publication Date:		10/2010
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Bibliographic Code:		2010arXiv1011.0113A

Abstract

Aims: GRB 050502B is well known for the very bright flare displayed in its X-ray light curve. Despite extensive studies, however, the optical light curve has never been discussed and its redshift is unconstrained. Possible correlations between optical and X-ray data are analysed. Methods: Photometric data from TNG in the R and I bands were used to compare the optical afterglow with the X-ray light curve. The HyperZ package and a late time VLT host observation were used to derive redshift estimates. Results: The I-band afterglow decay followed a power-law of index {\alpha} = 2.1 $\pm$ 0.6, after a late break at ~ $1.3 \times 10^5$ s. The R - I color is remarkably red and the broadband spectral index {\beta}_OX = $0.9 \pm 0.1$ is consistent with the X-ray spectral slope {\beta}_X. Although a photometric redshift of z > 4 is the most conservative result to consider, a photometric redshift of z = 5.2 $\pm$ 0.3 is suggested with no extinction in the host, based on which an isotropic energy E_{\gamma},iso = $(3.8 \pm 0.7) \times 10^52$ erg and a jet opening angle {\theta} ~ $3.7^{\circ}$ are subsequently derived. Conclusions: The combined X-ray and optical data suggest an achromatic break, which we interpret as a jet break. The post jet break slope obeys roughly the closure relation for the jet slow cooling model. Because of the afterglow's very red color, in order for the redshift to be low (z < 1), extinction, if present in the host, must be significantly high. Since the optical-to-X-ray index is consistent with the X-ray spectrum, and there is no XRT evidence for excess N_H, GRB 050502B was likely at high redshift.

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Michelson 2010 Fermi第一年的结果

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Title:		Fermi Gamma-ray Space Telescope: high-energy results from the first year
Authors:		Michelson, P. F.; Atwood, W. B.; Ritz, S.
Affiliation:		AA(Department of Physics, Kavli Institute for Particle Astrophysics and Cosmology, and W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94304, USA peterm@stanford.edu), AB(Santa Cruz Institute for Particle Physics, Department of Physics, University of California at Santa Cruz, Santa Cruz, CA 95064, USA atwood@scipp.ucsc.edu), AC(Santa Cruz Institute for Particle Physics, Department of Physics, University of California at Santa Cruz, Santa Cruz, CA 95064, USA ritz@scipp.ucsc.edu)
Publication:		Reports on Progress in Physics, Volume 73, Issue 7, pp. 074901 (2010).
Publication Date:		07/2010
Origin:		IOP
DOI:		10.1088/0034-4885/73/7/074901
Bibliographic Code:		2010RPPh...73g4901M

Abstract

The Fermi Gamma-ray Space Telescope (Fermi) was launched on 11 June 2008 and began its first year sky survey on 11 August 2008. The Large Area Telescope (LAT), a wide field-of-view pair-conversion telescope covering the energy range from 20 MeV to more than 300 GeV, is the primary instrument on Fermi. While this review focuses on results obtained with the LAT, the Gamma-ray Burst Monitor (GBM) complements the LAT in its observations of transient sources and is sensitive to x-rays and γ-rays with energies between 8 keV and 40 MeV. During the first year in orbit, the Fermi LAT has observed a large number of sources that include active galaxies, pulsars, compact binaries, globular clusters, supernova remnants as well as the Sun, the Moon and the Earth. The GBM and LAT together have uncovered surprising characteristics in the high-energy emission of gamma-ray bursts that have been used to set significant new limits on violations of Lorentz invariance. The Fermi LAT has also made important new measurements of the Galactic diffuse radiation and has made precise measurements of the spectrum of cosmic-ray electrons and positrons from 20 GeV to 1 TeV.

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Oates 2010 对Swift的UVOT和XRT观测的统计

主要内容:
比较它们的光变曲线。说500秒以前不同，500秒以后很像，都可以用外籍波来解释。

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Title:		A Statistical Comparison of the Optical/UV and X-ray Afterglows of Gamma-Ray Bursts using the Swift Ultra-violet Optical and X-ray Telescopes
Authors:		Oates, S. R.; Page, M. J.; Schady, P.; De Pasquale, M.; Evans, P. A.; Page, K. L.; Chester, M. M.; Curran, P. A.; Koch, T. S.; Kuin, N. P. M.; Roming, P. W. A.; Siegel, M. H.; Zane, S.; Nousek, J. A.
Publication:		eprint arXiv:1010.6212
Publication Date:		10/2010
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		20 pages, 5 figures and 4 tables. Accepted for publication by MNRAS
Bibliographic Code:		2010arXiv1010.6212O

Abstract

We present the systematic analysis of the UVOT and XRT light curves for a sample of 26 Swift Gamma-Ray Bursts (GRBs). By comparing the optical/UV and X-ray light curves, we found that they are remarkably different during the first 500s after the BAT trigger, while they become more similar during the middle phase of the afterglow, i.e. between 2000s and 20000s. If we take literally the average properties of the sample, we find that the mean temporal indices observed in the optical/UV and X-rays after 500s are consistent with a forward-shock scenario, under the assumptions that electrons are in the slow cooling regime, the external medium is of constant density and the synchrotron cooling frequency is situated between the optical/UV and X-ray observing bands. While this scenario describes well the averaged observed properties, some individual GRB afterglows require different or additional assumptions, such as the presence of late energy injection. We show that a chromatic break (a break in the X-ray light curve that is not seen in the optical) is present in the afterglows of 3 GRBs and demonstrate evidence for chromatic breaks in a further 4 GRBs. The average properties of these breaks cannot be explained in terms of the passage of the synchrotron cooling frequency through the observed bands, nor a simple change in the external density. It is difficult to reconcile chromatic breaks in terms of a single component outflow and instead, more complex jet structure or additional emission components are required.

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Ozel 2010 一个质量为2个太阳质量的脉冲星

主要内容:
给并合的中子星的理论提出了新的挑战。

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Title:		The Massive Pulsar PSR J1614-2230: Linking Quantum Chromodynamics, Gamma-ray Bursts, and Gravitational Wave Astronomy
Authors:		Ozel, Feryal; Psaltis, Dimitrios; Ransom, Scott; Demorest, Paul; Alford, Mark
Publication:		eprint arXiv:1010.5790
Publication Date:		10/2010
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena, General Relativity and Quantum Cosmology, Nuclear Theory
Comment:		Accepted for publication in ApJL
Bibliographic Code:		2010arXiv1010.5790O

Abstract

The recent measurement of the Shapiro delay in the radio pulsar PSR J1614-2230 yielded a mass of 1.97 +/- 0.04 M_sun, making it the most massive pulsar known to date. Its mass is high enough that, even without an accompanying measurement of the stellar radius, it has a strong impact on our understanding of nuclear matter, gamma-ray bursts, and the generation of gravitational waves from coalescing neutron stars. This single high mass value indicates that a transition to quark matter in neutron-star cores can occur at densities comparable to the nuclear saturation density only if the quarks are strongly interacting and are color superconducting. We further show that a high maximum neutron-star mass is required if short duration gamma-ray bursts are powered by coalescing neutron stars and, therefore, this mechanism becomes viable in the light of the recent measurement. Finally, we argue that the low-frequency (<= 500 Hz) gravitational waves emitted during the final stages of neutron-star coalescence encode the properties of the equation of state because neutron stars consistent with this measurement cannot be centrally condensed. This will facilitate the measurement of the neutron star equation of state with Advanced LIGO/Virgo.

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