Bloom 2008 用物理起源分类伽玛暴

主要内容:
强调用物理起源而不是表象的时标长短来分类伽玛暴。

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文章信息:

· arXiv e-print (arXiv:0804.0965)

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Title:		Gamma-ray Bursts, Classified Physically
Authors:		Bloom, Joshua S.; Butler, Nathaniel R.; Perley, Daniel A.
Publication:		eprint arXiv:0804.0965
Publication Date:		04/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		6 pages, 3 figures. Slightly expanded version of solicited paper to be published in the Proceedings of ''Gamma Ray Bursts 2007,'' Santa Fe, New Mexico, November 5-9. Edited by E. E. Fenimore, M. Galassi, D. Palmer
Bibliographic Code:		2008arXiv0804.0965B

Abstract

From Galactic binary sources, to extragalactic magnetized neutron stars, to long-duration GRBs without associated supernovae, the types of sources we now believe capable of producing bursts of gamma-rays continues to grow apace. With this emergent diversity comes the recognition that the traditional (and newly formulated) high-energy observables used for identifying sub-classes does not provide an adequate one-to-one mapping to progenitors. The popular classification of some > 100 sec duration GRBs as ``short bursts'' is not only an unpalatable retronym and syntactically oxymoronic but highlights the difficultly of using what was once a purely phenomenological classification to encode our understanding of the physics that gives rise to the events. Here we propose a physically based classification scheme designed to coexist with the phenomenological system already in place and argue for its utility and necessity.

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Esquivel 2008 磁夸克星产生超高能宇宙线

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文章信息:

· arXiv e-print (arXiv:0804.0708)

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Title:		Ultra-High-Energy Cosmic Rays from a Magnetized Strange Star Central Engine for Gamma-Ray Bursts
Authors:		Esquivel, O.; Page, D.
Publication:		eprint arXiv:0804.0708
Publication Date:		04/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		9 pages, submitted to Revista Mexicana de Astronomia
Bibliographic Code:		2008arXiv0804.0708E

Abstract

Ultra-high-energy cosmic rays (UHECRs) have been tried to be related to the most varied and powerful sources known in the universe. Gamma-ray bursts (GRBs) are natural candidates. Here, we argue that cosmic rays can be accelerated by large amplitude electromagnetic waves (LAEMWs) when the MHD approximation of the field in the wind generated by the GRB's magnetized central engine breaks down. The central engine considered here is a strange star born with differential rotation from the accretion induced conversion of a neutron star into a strange star in a low-mass X-ray binary system. The LAEMWs generated this way accelerate light ions to the highest energies $E = q\eta\Delta\Phi_{max}$ with an efficiency $\eta \sim 10^{-1}$ that accounts for all plausible energy losses. Alternatively, we also consider the possibility that, once formed, the LAEMWs are unstable to creation of a relativistically strong electromagnetic turbulence due to an overturn instability. Under this assumption, a lower limit to the efficiency of acceleration is estimated to be about $\eta \sim 10^{-2.5}$. Due to their age, low mass X-ray binary systems can be located in regions of low interstellar medium density as, e.g., globular clusters or even intergalactic medium in case of high proper motion systems, and cosmic ray energy losses due to proton collisions with photons at the decelerating region are avoided, thus opening the possibility for particles to exploit the full voltage available, well beyond that currently observed.

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Dado GRB 080319B的Cannon Ball模型

主要内容:
认为GRB 080319B是一个很普通的暴。

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文章信息:

· arXiv e-print (arXiv:0804.0621)

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Title:		Is there anything special about GRB 080319B?
Authors:		Dado, Shlomo; Dar, Arnon; De Rujula, A.
Publication:		eprint arXiv:0804.0621
Publication Date:		04/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		8 pages, 4 figures
Bibliographic Code:		2008arXiv0804.0621D

Abstract

We show that the properties of gamma ray burst 080319B and its afterglow are well reproduced by the cannonball model of long gamma ray bursts (GRBs). It was an ordinary GRB, produced by a jet of highly relativistic plasmoids (CBs), ejected in a core-collapse supernova (SN) and viewed, as some others before, particularly close to the CB-emission axis. It still remains to be seen whether GRB 080319B was associated with an SN akin to SN1998bw, the SN type ordinarily associated with GRBs, or with a much more luminous SN.

Detmers 2008 潮汐作用让WR星自转加速

主要内容:
要 产生伽玛暴一定要自转很快，文章讨论前身星如何加快自转。

（为什么一定要自转快？因为集束？还是因为要提取黑洞旋转能作为伽玛暴的能量？）

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文章信息:

arXiv:0804.0014 [ps, pdf, other]

Title: Gamma-Ray Bursts from tidally spun-up Wolf-Rayet stars?

Authors: R.G. Detmers, N. Langer, Ph. Podsiadlowski, R.G. Izzard

Comments: 9 pages, 11 figures, accepted for publication in A&A

Subjects: Astrophysics (astro-ph)

The collapsar model requires rapidly rotating Wolf-Rayet stars as progenitors of long gamma-ray bursts. However, Galactic Wolf-Rayet stars rapidly lose angular momentum due to their intense stellar winds. We investigate whether the tidal interaction of a Wolf-Rayet star with a compact object in a binary system can spin up the Wolf-Rayet star enough to produce a collapsar. We compute the evolution of close Wolf-Rayet binaries, including tidal angular momentum exchange, differential rotation of the Wolf-Rayet star, internal magnetic fields, stellar wind mass loss, and mass transfer. The Wolf-Rayet companion is approximated as a point mass. We then employ a population synthesis code to infer the occurrence rates of the various relevant binary evolution channels. We find that the simple scenario -- i.e., the Wolf-Rayet star being tidally spun up and producing a collapsar -- does not occur at solar metallicity and may only occur with low probability at low metallicity. It is limited by the widening of the binary orbit induced by the strong Wolf-Rayet wind or by the radius evolution of the Wolf-Rayet star that most often leads to a binary merger. The tidal effects enhance the merger rate of Wolf-Rayet stars with black holes such that it becomes comparable to the occurrence rate of long gamma-ray bursts.

Qi 2008 SN Ia 和GRB一起限制暗能量参数

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文章信息:

arXiv:0803.4304 [ps, pdf, other]

Title: Constraining the evolution of dark energy with type Ia supernovae and gamma-ray bursts

Authors: Shi Qi, Fa-Yin Wang, Tan Lu

Comments: 7 pages, 17 figures, accepted for publication in Astronomy and Astrophysics

Subjects: Astrophysics (astro-ph)

The behavior of the dark energy equation of state (EOS) is crucial in distinguishing different cosmological models. With a model independent approach, we constrain the possible evolution of the dark energy EOS. Gamma-ray bursts (GRBs) of redshifts up to $z>6$ are used, in addition to type Ia supernovae (SNe Ia). We separate the redshifts into 4 bins and assume a constant EOS parameter for dark energy in each bin. The EOS parameters are decorrelated by diagonalizing the covariance matrix. And the evolution of dark energy is estimated out of the uncorrelated EOS parameters. By including GRB luminosity data, we significantly reduce the confidence interval of the uncorrelated EOS parameter whose contribution mostly comes from the redshift bin of $0.5 1.8$.>

Tanvir 2008 GRB 060823A的超红余辉

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文章信息:

· arXiv e-print (arXiv:0803.4100)

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Title:		The extreme, red afterglow of GRB 060923A: Distance or dust?
Authors:		Tanvir, N. R.; Levan, A. J.; Rol, E.; Starling, R. L. C.; Gorosabel, J.; Priddey, R. S.; Malesani, D.; Jakobsson, P.; O'Brien, P. T.; Jaunsen, A. O.; Hjorth, J.; Fynbo, J. P. U.; Melandri, A.; Gomboc, A.; Milvang-Jensen, B.; Fruchter, A. S.; Jarvis, M.; Fernandes, C. A. C.; Wold, T.
Publication:		eprint arXiv:0803.4100
Publication Date:		03/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		Submitted to MNRAS (revised in light of referee's comments)
Bibliographic Code:		2008arXiv0803.4100T

Abstract

Gamma-ray bursts are powerful probes of the early universe, but locating and identifying very distant GRBs remains challenging. We report here the discovery of the K-band afterglow of Swift GRB 060923A, imaged within the first hour post-burst, and the faintest so far found. It was not detected in any bluer bands to deep limits, making it a candidate very high redshift burst (z>11). However, our later-time optical imaging and spectroscopy reveal a faint galaxy coincident with the GRB position which, if it is the host, implies a more moderate redshift (most likely z<2.8)> Bibtex entry for this abstract Preferred format for this abstract (see Preferences)

Jaunsen 2008 GRB 070306的超暗余辉

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文章信息:

· arXiv e-print (arXiv:0803.4017)

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Title:		GRB 070306: A Highly Extinguished Afterglow
Authors:		Jaunsen, A. O.; Rol, E.; Watson, D. J.; Malesani, D.; Fynbo, J. P. U.; Milvang-Jensen, B.; Hjorth, J.; Vreeswijk, P. M.; Ovaldsen, J. -E.; Wiersema, K.; Tanvir, N. R.; Gorosabel, J.; Levan, A. J.; Schirmer, M.; Castro-Tirado, A. J.
Publication:		eprint arXiv:0803.4017
Publication Date:		03/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		28 pages, 6 figures, accepted for publication in ApJ
Bibliographic Code:		2008arXiv0803.4017J

Abstract

We report on the highly extinguished afterglow of GRB 070306 and the properties of the host galaxy. An optical afterglow was not detected at the location of the burst, but in near-infrared a doubling in brightness during the first night and later power-law decay in the K band provided a clear detection of the afterglow. The host galaxy is relatively bright, R ~ 22.8. An optical low resolution spectrum revealed a largely featureless host galaxy continuum with a single emission line. Higher resolution follow-up spectroscopy shows this emission to be resolved and consisting of two peaks separated by 7 AA, suggesting it to be [O II] at a redshift of z = 1.49594 +- 0.00006. The infrared color H-K = 2 directly reveals significant reddening. By modeling the optical/X-ray spectral energy distribution at t = 1.38 days with an extinguished synchrotron spectrum, we derive A_V = 5.5 +- 0.6 mag. This is among the largest values ever measured for a GRB afterglow and visual extinctions exceeding unity are rare. The importance of early NIR observations is obvious and may soon provide a clearer view into the once elusive 'dark bursts'.

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Frederiksen 2008 Stochastically Induced Gamma-Ray Burst Wakefield Processes

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文章信息:

arXiv:0803.3618 [ps, pdf, other]

Title: Stochastically Induced Gamma-Ray Burst Wakefield Processes

Authors: J. Trier Frederiksen

Comments: 4 pages, 4 figures, submitted to ApJ Letters

Subjects: Astrophysics (astro-ph)

We present a numerical study of Gamma-Ray Burst - Circumburst Medium interaction and plasma preconditioning via Compton scattering. The simulation tool employed is a unique hybrid model; it combines a highly parallelized (Vlasov) particle-in-cell approach with continuous weighting of particles and a sub-Debye Monte-Carlo binary particle interaction framework. These first results from 3D simulations with this new simulation tool, the PhotonPlasma code, suggests that magnetic fields and plasma density filaments are created in the wakefield of prompt gamma-ray bursts, and that the photon flux density gradient has a significant impact on particle acceleration in the burst head and wakefield. We discuss some possible implications of the circumburst medium preconditioning for the trailing afterglow, and also discuss which additional processes will be needed to improve future studies within this unique and powerful simulation framework.

Bloom 2008 GRB 080319B的观测

主要内容:
给出了这个暴的主要是光学和X射线的观测。

精彩摘抄:
X射线和光学的光变

详细的光学的不同波段的光变
几个高亮瞬时光学的光变

文章信息:

· arXiv e-print (arXiv:0803.3215)

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Title:		Observations of the Naked-Eye GRB 080319B: Implications of Nature's Brightest Explosion
Authors:		Bloom, J. S.; Perley, D. A.; Li, W.; Butler, N. R.; Miller, A. A.; Kocevski, D.; Foley, R. J.; Chen, H. -W.; Filippenko, A. V.; Starr, D. L.; Macomber, B.; Prochaska, J. X.; Chornock, R.; Kann, D. A.; Poznanski, D.
Publication:		eprint arXiv:0803.3215
Publication Date:		03/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		Submitted to ApJ
Bibliographic Code:		2008arXiv0803.3215B

Abstract

The first gamma ray burst (GRB) confirmed to be bright enough to be seen with the naked eye, GRB~080319, allowed for exquisite follow-up across the electromagnetic spectrum. We present our detailed optical and infrared observations of the afterglow of the event, which started 122~s after the GRB trigger in concert with our own analysis of the Swift UVOT, BAT, and XRT data. Despite high quality measurements from about 5500 images, there seems to be no evidence for a significant amount of dust extinction in the host frame. We find significant color evolution in the optical afterglow: starting at about 1000~s the index shifts blueward before apparently shifting back to the red at late times. We compare the optical light curve of GRB 080319B with the most luminous probes of the distant universe, GRB 990103 and GRB 050904, and find GRB 080319B to be the most luminous explosion ever seen. Finally, we examine the detectability of such events with current and future facilities. We find that such an event could be detected in gamma rays by BAT out to $z$ = 4.9 ($8\sigma$), while the nominal EXIST sensitivity would allow detection to $z$ = 12.2.

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Heng 2008 中等红移处星系的尘埃消光曲线

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文章信息:

· arXiv e-print (arXiv:0803.2879)

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Title:		A Direct Measurement of the Dust Extinction Curve in an Intermediate-Redshift Galaxy
Authors:		Heng, Kevin; Lazzati, Davide; Perna, Rosalba; Garnavich, Peter; Noriega-Crespo, Alberto; Bersier, David; Matheson, Thomas; Pahre, Michael
Publication:		eprint arXiv:0803.2879
Publication Date:		03/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		9 pages, 5 figures. Accepted by ApJ
Bibliographic Code:		2008arXiv0803.2879H

Abstract

We present a proof-of-concept study that dust extinction curves can be extracted from the infrared (IR), optical, ultraviolet (UV) and X-ray afterglow observations of GRBs without assuming known extinction laws. We focus on GRB 050525A (z = 0.606), for which we also present IR observations from the Spitzer Space Telescope at about 2.3 days post-burst. We construct the spectral energy distribution (SED) of the afterglow and use it to derive the dust extinction curve of the host galaxy in 7 optical/UV wavebands. By comparing our derived extinction curve to known templates, we see that the Galactic or Milky Way extinction laws are disfavored versus the Small and Large Magellanic Cloud (SMC and LMC) ones, but that we cannot rule out the presence of a LMC-like 2175 angstrom bump in our extinction curve. The dust-to-gas ratio present within the host galaxy of GRB 050525A is similar to that found in the LMC, while about 10 to 40% more dust is required if the SMC template is assumed. Our method is useful to observatories that are capable of simultaneously observing GRB afterglows in multiple wavebands from the IR to the X-ray.

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