Qi 2008 伽玛暴限制暗能量的演化

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Title:		Gamma-ray burst contributions to constraining the evolution of dark energy
Authors:		Qi, Shi; Wang, Fa-Yin; Lu, Tan
Publication:		eprint arXiv:0807.4594
Publication Date:		07/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		3 pages, 5 figures. Forthcoming in Astronomy and Astrophysics; doi:10.1051/0004-6361:200809954
Bibliographic Code:		2008arXiv0807.4594Q

Abstract

We explore the gamma-ray bursts' (GRBs') contributions in constraining the dark energy equation of state (EOS) at high ($1.8 <> Bibtex entry for this abstract Preferred format for this abstract (see Preferences)

辐射机制？

光球层的光子被逆康普顿散射。

Tavani 2008 AGILE卫星

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Title:		The AGILE space mission
Authors:		Tavani, M.; Barbiellini, G.; Argan, A.; Bulgarelli, A.; Caraveo, P.; Chen, A.; Cocco, V.; Costa, E.; de Paris, G.; Del Monte, E.; di Cocco, G.; Donnarumma, I.; Feroci, M.; Fiorini, M.; Froysland, T.; Fuschino, F.; Galli, M.; Gianotti, F.; Giuliani, A.; Evangelista, Y.; Labanti, C.; Lapshov, I.; Lazzarotto, F.; Lipari, P.; Longo, F.; Marisaldi, M.; Mastropietro, M.; Mauri, F.; Mereghetti, S.; Morelli, E.; Morselli, A.; Pacciani, L.; Pellizzoni, A.; Perotti, F.; Picozza, P.; Pontoni, C.; Porrovecchio, G.; Prest, M.; Pucella, G.; Rapisarda, M.; Rossi, E.; Rubini, A.; Soffitta, P.; Trifoglio, M.; Trois, A.; Vallazza, E.; Vercellone, S.; Zambra, A.; Zanello, D.; Giommi, P.; Antonelli, A.; Pittori, C.
Publication:		Nuclear Instruments and Methods in Physics Research Section A, Volume 588, Issue 1-2, p. 52-62.
Publication Date:		04/2008
Origin:		ELSEVIER
Abstract Copyright:		Elsevier B.V.
DOI:		10.1016/j.nima.2008.01.023
Bibliographic Code:		2008NIMPA.588...52T

Abstract

AGILE is an Italian Space Agency mission dedicated to the exploration of the gamma-ray Universe. The AGILE, very innovative instrument, combines for the first time a gamma-ray imager (sensitive in the range 30 MeV–50 GeV) and a hard X-ray imager (sensitive in the range 18–60 keV). An optimal angular resolution and very large fields of view are obtained by the use of state-of-the-art Silicon detectors integrated in a very compact instrument. AGILE was successfully launched on April 23, 2007 from the Indian base of Sriharikota and was inserted in an optimal low-particle background equatorial orbit. AGILE will provide crucial data for the study of Active Galactic Nuclei, Gamma-Ray Bursts, unidentified gamma-ray sources, galactic compact objects, supernova remnants, TeV sources, and fundamental physics by microsecond timing. The AGILE Cycle-1 pointing program started on 2007 December 1, and is open to the international community through a Guest Observer Program.

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Piran 2008 观测对SSC模型的参数限制-很紧

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Title:		Observational Limits on Inverse Compton Processes in GRBs
Authors:		Piran, Tsvi; Sari, Re'em; Zou, Yuan-Chuan
Publication:		eprint arXiv:0807.3954
Publication Date:		07/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		13 pages, 6 figures
Bibliographic Code:		2008arXiv0807.3954P

Abstract

Inverse Compton (IC) scattering is one of two viable mechanisms that can produce the prompt gamma-ray emission in Gamma-Ray Bursts. IC requires low energy seed photons and a population of relativistic electrons that upscatter them. The same electrons can upscatter the gamma-ray photons to even higher energies in the TeV range. Using the current upper limits on the prompt optical emission we show here that under general conservative assumption the IC mechanism suffers from an "energy crisis". Namely, IC will over-produce a very high energy component that would carry much more energy than the observed prompt gamma-rays. Our analysis is general and it makes no assumptions on the specific mechanism that produces the relativistic electrons population.

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Starling 2008 GRB 980703的尘埃破坏

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Title:		Examining the evidence for dust destruction in GRB 980703
Authors:		Starling, Rhaana L. C.
Publication:		eprint arXiv:0807.4144
Publication Date:		07/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		6 pages, 4 figures, accepted for publication in A&A
Bibliographic Code:		2008arXiv0807.4144S

Abstract

The effects that gamma-ray bursts have on their environments is an important and outstanding issue. Dust destruction in particular has long been predicted while observational evidence is difficult to obtain. We examine the evidence for dust destruction by GRB 980703, in which various inconsistent measurements of the host galaxy extinction have been made using the GRB afterglow emission. We construct a spectral energy distribution from nIR to X-ray to measure the extinction at early times and compare this with previous findings. We also construct nIR/optical SEDs at intermediate epochs to examine a previously reported decrease in extinction. The extinction is very high for a GRB host galaxy. The earliest extinction measurement is likely to be lower than previously estimated, and consistent with most later measurements. In a series of SEDs we do not find any evidence of variable extinction. We therefore conclude that there is no clear evidence of dust destruction in this case.

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Couch 2008 前兆里的离子加速

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Title:		Shock Vorticity Generation from Accelerated Ion Streaming in the Precursor of Ultrarelativistic Gamma-Ray Burst External Shocks
Authors:		Couch, Sean M.; Milosavljevic, Milos; Nakar, Ehud
Publication:		eprint arXiv:0807.4117
Publication Date:		07/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		8 pages, no figures
Bibliographic Code:		2008arXiv0807.4117C

Abstract

We investigate the interaction of nonthermal ions (protons and nuclei) accelerated in an ultrarelativistic blastwave with the pre-existing magnetic field of the medium into which the blastwave propagates. While particle acceleration processes such as diffusive shock acceleration can accelerate ions and electrons, the accelerated electrons suffer larger radiative losses. Under certain conditions, the ions can attain higher energies and reach farther ahead of the shock than the electrons, and so the nonthermal particles can be partially charge-separated. To compensate for the charge separation, the upstream plasma develops a return current, which, as it flows across the magnetic field, drives transverse acceleration of the upstream plasma and a growth of density contrast in the shock upstream. If the density contrast is strong by the time the fluid is shocked, vorticity is generated at the shock transition. The resulting turbulence can amplify the post-shock magnetic field to the levels inferred from gamma-ray burst afterglow spectra and light curves. Therefore, since the upstream inhomogeneities are induced by the ions accelerated in the shock, they are generic even if the blastwave propagates into a medium of uniform density. We speculate about the global structure of the shock precursor, and delineate several distinct physical regimes that are classified by an increasing distance from the shock and, correspondingly, a decreasing density of nonthermal particles that reach that distance.

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Gendre 2008 伽玛暴和粒子天体物理

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Title:		Gamma-Ray Bursts and Particle Astrophysics
Authors:		Gendre, B.
Publication:		eprint arXiv:0807.3918
Publication Date:		07/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		8 pages, 5 figures, proceeding of the XXth rencontres de Blois, may 2008
Bibliographic Code:		2008arXiv0807.3918G

Abstract

Gamma-ray bursts are violent events occurring randomly in the sky. In this review, I will present the fireball model, proposed to explain the phenomenon of gamma-ray bursts. This model has important consequences for the production and observation at Earth of gravitational waves, high energy neutrinos, cosmic rays and high energy photons, and the second part of this review will be focused on these aspects. A last section will briefly discuss the topic of the use of gamma-ray bursts as standard candles and possible cosmological studies.

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Rossi 2008 超吸积下的微观物理

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Title:		Microphysical dissipation, turbulence and magnetic fields in hyper-accreting discs
Authors:		Rossi, Elena M.; Armitage, Philip J.; Menou, Kristen
Publication:		eprint arXiv:0807.3547
Publication Date:		07/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		14 pages, 10 figures. MNRAS, submitted
Bibliographic Code:		2008arXiv0807.3547R

Abstract

Hyper-accreting discs occur in compact-object mergers and collapsars, and may power gamma-ray bursts (GRBs). We calculate the microscopic viscosity and resistivity of plasma in these discs, and discuss the implications for their global structure and evolution. In the neutrino-cooled innermost regions, the viscosity is provided mainly by mildly degenerate electrons, while the resistivity is modified from the Spitzer value due to the effects of both relativity and degeneracy. The plasma behaves as an almost ideal MHD fluid. Among the non-ideal MHD effects the Hall term is relatively the most important, while the magnetic Prandtl number, Pr (the ratio of viscosity to resistivity), is typically larger than unity: 10 <>

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Zhilyaev 2008 双致密星并合作为短暴机制

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in favor of BH-NS mergers as a scenario for the production of short gamma-ray bursts

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Title:		The last stages of evolution of close binaries composed of compact companions
Authors:		Zhilyaev, B. E.; Dubinovska, D. L.
Publication:		eprint arXiv:0807.3754
Publication Date:		07/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		8 pages, 5 figures, Contribution to the Conference "Interacting Binaries: Accretion and Synchronization", Crimean Astrophysical Observatory, June 20-26, 2008
Bibliographic Code:		2008arXiv0807.3754Z

Abstract

Gamma-ray bursts (GRB) are the most powerful transient phenomena in the Universe. Nowadays dozens of speculations on the origin of GRB were undertaken, but so far a single model for the origin of, in particular, short GRBs does not exist. The black hole (BH) - neutron star (NS) coalescence is a promising candidate source for short GRBs. Most of binary mergers numerical simulations were carried out with the purpose of investigating the emission of gravitational waves. Such a scenario consists of an inspiral, merging and ringdown phase. In this paper we present the comparison of the observational results and analytical predictions for a test particle in a quasicircular orbit around the BH. The emission of gravitational waves causes a rapid decrease of the orbital radius and a rise of a {\it chirp} of radiation. Matter orbiting the black hole would be expected to produce high-frequency oscillations (HFO). Timescales of the coalescence process are of the order of milliseconds and oscillation frequencies of hundreds Hz for a system with a solar mass BH companion. We report on the detection of HFO in two short gamma-ray bursts in this paper. The frequencies and durations of the oscillations are in agreement with the predicted values. A {\it chirp} phenomenon is identified also. We therefore argue in favor of BH-NS mergers as a scenario for the production of short gamma-ray bursts.

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Christensen 2008 GRB 980425/SN 1998bw的宿主星系

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Title:		IFU observations of the GRB 980425/SN 1998bw host galaxy: emission line ratios in GRB regions
Authors:		Christensen, L.; Vreeswijk, P. M.; Sollerman, J.; Thoene, C. C.; Le Floc'h, E.; Wiersema, K.
Publication:		eprint arXiv:0807.3554
Publication Date:		07/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		16 pages, 10 figures. Accepted for publication in A&A
Bibliographic Code:		2008arXiv0807.3554C

Abstract

The collapsar model predicts that the progenitors of Gamma-ray Bursts (GRBs) are metal poor in Fe group elements. The existence of low metallicity stellar populations could manifest itself through special characteristics of the immediate environment of the GRB site in the host galaxy. We analyse the strong emission lines from the sub-luminous host galaxy of GRB 980425, which showed the first connection with a supernova explosion (SN 1998bw). The host has a sufficient size to allow detailed resolved spectroscopy of individual HII regions and to look for regions with special properties close to the the GRB site. Using integral field spectroscopy with VIMOS we cover most of the high surface brightness part of the host including the HII region where the supernova and GRB occurred. The star formation rate, reddening, equivalent width and stellar mass in the GRB region is similar to other HII regions in the host. Extreme values arise in the only region that shows emission lines from Wolf-Rayet stars; a region that lies 800 pc in projection from the GRB site. Strong emission line diagnostics of all HII regions imply oxygen abundances between 0.3 and 0.8 solar with the lowest values arising in the WR and GRB regions. Comparing the measured emission line ratios for a sample of low redshift GRB hosts to theoretical models and to observations of field galaxies, we find that GRBs arise in a range of metallicity environments while the regions are consistently very young. The similar line ratios of GRB hosts compared to the WR region can arise in spatially unresolved galaxies with bright HII regions near the GRB location. (Abridged)

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Tsutsui 2008 用Yonetoku关系定宇宙学参数

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Title:		Constraints on $w_0$ and $w_a$ of Dark Energy from High Redshift Gamma Ray Bursts
Authors:		Tsutsui, Ryo; Nakamura, Takashi; Yonetoku, Daisuke; Murakami, Toshio; Tanabe, Sachiko; Kodama, Yoshiki; Takahashi, Keitaro
Publication:		eprint arXiv:0807.2911
Publication Date:		07/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		5 pages, 6 figures. Submitted tu MNRAS
Bibliographic Code:		2008arXiv0807.2911T

Abstract

We extend the Hubble diagram up to $z = 5.6$ using 63 gamma-ray bursts (GRBs) via peak energy-peak luminosity relation (so called Yonetoku relation), and obtain constraints on cosmological parameters including dynamical dark energy parametrized by $P/\rho\equiv w(z) = w_0 + w_a \cdot z/(1+z)$. It is found that the current GRB data are consistent with the concordance model, ($\Omega_m = 0.28, \Omega_{\Lambda} = 0.72, w_0 = -1, w_a = 0$), within two sigma level. Although constraints from GRBs themselves are not so strong, they can improve the conventional constraints from SNeIa because GRBs have much higher redshifts. Further we estimate the constraints on the dark-energy parameters expected by future observations with GLAST (Gamma-ray Large Area Space Telescope) and \swift by Monte-Carlo simulation. Constraints would improve substantially with another 150 GRBs.

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Tanaka 2008 SN2008D的大质量氦星模型

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Title:		Supernova 2008D associated with the Luminous X-ray Transient 080109: An Energetic Explosion of a Massive Helium Star
Authors:		Tanaka, Masaomi; Tominaga, Nozomu; Nomoto, Ken'ichi; Valenti, S.; Sahu, D. K.; Minezaki, T.; Yoshii, Y.; Yoshida, M.; Anupama, G. C.; Benetti, S.; Chincarini, G.; Della Valle, M.; Mazzali, P. A.; Pian, E.
Publication:		eprint arXiv:0807.1674
Publication Date:		07/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		8 pages, 8 figures, Submitted to the Astrophysical Journal
Bibliographic Code:		2008arXiv0807.1674T

Abstract

We present a theoretical model for supernova (SN) 2008D associated with the luminous X-ray transient 080109. The optical light curve and spectra of the SN are modeled based on realistic progenitor models and the explosion models are obtained from hydrodynamic/nucleosynthetic calculations. We find that SN 2008D is a more energetic explosion than normal core-collapse supernovae, with an ejecta mass of Mej = 5.3 +- 1.0 Msun and a kinetic energy of KE = 6.0 +- 2.5 x 10^{51} erg. The mass of the progenitor is estimated to be Mms = 20-25 Msun. These properties are intermediate between those of normal SNe and hypernovae associated with gamma-ray bursts. The mass of the central remnant is estimated as 1.6 - 1.8 Msun, which is near the boundary between neutron star and black hole formation.

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Mazzali 2008 SN2008D/XRF080109的观测

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包括谱

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Title:		The metamorphosis of Supernova SN2008D/XRF080109: a link between Supernovae and GRBs/Hypernovae
Authors:		Mazzali, Paolo A.; Valenti, Stefano; Della Valle, Massimo; Chincarini, Guido; Sauer, Daniel N.; Benetti, Stefano; Pian, Elena; Piran, Tsvi; D'Elia, Valerio; Elias-Rosa, Nancy; Margutti, Raffaella; Pasotti, Francesco; Antonelli, L. Angelo; Bufano, Filomena; Campana, Sergio; Cappellaro, Enrico; Covino, Stefano; D'Avanzo, Paolo; Fiore, Fabrizio; Fugazza, Dino; Gilmozzi, Roberto; Hunter, Deborah; Maguire, Kate; Maiorano, Elisabetta; Marziani, Paola; Masetti, Nicola; Mirabel, Felix; Navasardyan, Hripsime; Nomoto, Ken'ichi; Palazzi, Eliana; Pastorello, Andrea; Panagia, Nino; Pellizza, Leonardo J.; Sari, Re'em; Smartt, Stephen; Tagliaferri, Gianpiero; Tanaka, Masaomi; Taubenberger, Stefan; Tominaga, Nozomu; Trundle, Carrie; Turatto, Massimo
Publication:		eprint arXiv:0807.1695
Publication Date:		07/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		22 pages, 7 figures. Accepted for publication in Science
Bibliographic Code:		2008arXiv0807.1695M

Abstract

The only supernovae (SNe) to have shown early gamma-ray or X-ray emission thus far are overenergetic, broad-lined Type Ic SNe (Hypernovae - HNe). Recently, SN 2008D shows several novel features: (i) weak XRF, (ii) an early, narrow optical peak, (iii) disappearance of the broad lines typical of SNIc HNe, (iv) development of He lines as in SNeIb. Detailed analysis shows that SN 2008D was not a normal SN: its explosion energy (KE ~ 6*10^{51} erg) and ejected mass (~7 Msun) are intermediate between normal SNeIbc and HNe. We derive that SN 2008D was originally a ~30Msun star. When it collapsed a black hole formed and a weak, mildly relativistic jet was produced, which caused the XRF. SN 2008D is probably among the weakest explosions that produce relativistic jets. Inner engine activity appears to be present whenever massive stars collapse to black holes.

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Piranomonte 2008 短暴070707的余辉和宿主星系

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Title:		The short GRB070707 afterglow and its very faint host galaxy
Authors:		Piranomonte, S.; D'Avanzo, P.; Covino, S.; Antonelli, L. A.; Beardmore, A. P.; Campana, S.; Chincarini, G.; D'Elia, V.; Della Valle, M.; Fiore, F.; Fugazza, D.; Guetta, D.; Guidorzi, C.; Israel, G. L.; Lazzati, D.; Malesani, D.; Parsons, A. M.; Perna, R.; Stella, L.; Tagliaferri, G.; Vergani, S. D.
Publication:		eprint arXiv:0807.1348
Publication Date:		07/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		6 pages, 5 figures, A&A, submitted, typos corrected
Bibliographic Code:		2008arXiv0807.1348P

Abstract

We present the results from an ESO/VLT campaign aimed at studying the afterglow properties of the short/hard gamma ray burst GRB 070707. Observations were carried out at ten different epochs from ~0.5 to ~80 days after the event. The optical flux decayed steeply with a power-law decay index greater than 3, later levelling off at R~27.3 mag; this is likely the emission level of the host galaxy, the faintest yet detected for a short GRB. Spectroscopic observations did not reveal any line features/edges that could unambiguously pinpoint the GRB redshift, but could set a limit z <~ 2.5. In the range of allowed redshifts, the host has a low luminosity, comparable to that of long-duration GRBs. The existence of such faint host galaxies suggests caution when associating short GRBs with bright, offset galaxies, where the true host might just be too dim for detection. The steepness of the decay of the optical afterglow of GRB 070707 challenges external shock models for the optical afterglow of short/hard GRBs. We argue that this behaviour might results from prolonged activity of the central engine.

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