Prochaska 2008 GRB 080607的宿主星系的分子气体

主要内容:
第一个看到分子气体的伽玛暴宿主星系

精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· Electronic Refereed Journal Article (HTML)

· Full Refereed Journal Article (PDF/Postscript)

· arXiv e-print (arXiv:0901.0556)

· References in the article

· Also-Read Articles (Reads History)

·

· Translate This Page

Title:		The First Positive Detection of Molecular Gas in a GRB Host Galaxy
Authors:		Prochaska, J. X.; Sheffer, Y.; Perley, D. A.; Bloom, J. S.; Lopez, L. A.; Dessauges-Zavadsky, M.; Chen, H.-W.; Filippenko, A. V.; Ganeshalingam, M.; Li, W.; Miller, A. A.; Starr, D.
Publication:		The Astrophysical Journal Letters, Volume 691, Issue 1, pp. L27-L32 (2009). (ApJ Homepage)
Publication Date:		01/2009
Origin:		IOP
Keywords:		gamma rays: bursts, ISM: molecules
DOI:		10.1088/0004-637X/691/1/L27
Bibliographic Code:		2009ApJ...691L..27P

Abstract

We report on strong H₂ and CO absorption from gas within the host galaxy of gamma-ray burst (GRB) 080607. Analysis of our Keck/LRIS afterglow spectrum reveals a very large H I column density (N_H\,\\scriptsize {\sc i}= 10^{22.70 \pm 0.15} \,cm^{-2}) and strong metal-line absorption at z _GRB = 3.0363 with a roughly solar metallicity. We detect a series of A – X bandheads from CO and estimate N(CO) = 10^16.5±0.3 cm^–2 and T ^CO _ex > 100 K. We argue that the high excitation temperature results from UV pumping of the CO gas by the GRB afterglow. Similarly, we observe H₂ absorption via the Lyman-Werner bands and estimate N_H_2= 10^{21.2 \pm 0.2} \,cm^{-2} with T_ex^H_2 = 10-300 K. The afterglow photometry suggests an extinction law with R_V ≈ 4 and A_V ≈ 3.2 mag and requires the presence of a modest 2175 Å bump. Additionally, modeling of the Swift XRT X-ray spectrum confirms a large column density with N _H = 10^22.58±0.04 cm^-2. Remarkably, this molecular gas has extinction properties, metallicity, and a CO/H₂ ratio comparable to those of translucent molecular clouds of the Milky Way, suggesting that star formation at high z proceeds in similar environments as today. However, the integrated dust-to-metals ratio is sub-Galactic, suggesting the dust is primarily associated with the molecular phase while the atomic gas has a much lower dust-to-gas ratio. Sightlines like GRB 080607 serve as powerful probes of nucleosynthesis and star-forming regions in the young universe and contribute to the population of "dark" GRB afterglows.

---

Bibtex entry for this abstract Preferred format for this abstract (see Preferences)

Genet 2008 用多个pulse的高纬辐射来解释X射线余辉的陡降

主要内容:


精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0901.0680)

· References in the Article

·

· Translate This Page

Title:		Is the Rapid Decay Phase from High Latitude Emission?
Authors:		Genet, F.; Granot, J.
Publication:		eprint arXiv:0901.0680
Publication Date:		01/2009
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		3 pages, submitted to the proceedings of the Sixth Huntsville gamma-ray bursts symposium
Bibliographic Code:		2009arXiv0901.0680G

Abstract

There is good observationnal evidence that the Steep Decay Phase (SDP) that is observed in most Swift GRBs is the tail of the prompt emission. The most popular model to explain the SDP is Hight Latitude Emission (HLE). Many models for the prompt emission give rise to HLE, like the popular internal shocks (IS) model, but some models do not, such as sporadic magnetic reconnection events. Knowing if the SDP is consistent with HLE would thus help distinguish between different prompt emission models. In order to test this, we model the prompt emission (and its tail) as the sum of independent pulses (and their tails). A single pulse is modeled as emission arising from an ultra-relativistic thin spherical expanding shell. We obtain analytic expressions for the flux in the IS model with a Band function spectrum. We find that in this framework the observed spectrum is also a Band function, and naturally softens with time. The decay of the SDP is initially dominated by the tail of the last pulse, but other pulses can dominate later. Modeling several overlapping pulses as a single broader pulse would overestimates the SDP flux. One should thus be careful when testing the HLE.

---

Bibtex entry for this abstract Preferred format for this abstract (see Preferences)

Ukwatta 2008 原初黑洞产生伽玛暴的spectral lag

主要内容:


精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0901.0542)

· References in the Article

·

· Translate This Page

Title:		Spectral Lags of Gamma-Ray Bursts from Primordial Black Hole (PBH) Evaporations
Authors:		Ukwatta, T. N.; MacGibbon, J. H.; Parke, W. C.; Dhuga, K. S.; Eskandarian, A.; Gehrels, N.; Maximon, L.; Morris, D. C.
Publication:		eprint arXiv:0901.0542
Publication Date:		01/2009
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		3 pages; Submitted to proc. of Huntsville 2008 symposium on GRBs
Bibliographic Code:		2009arXiv0901.0542U

Abstract

Primordial Black Holes (PBHs), which may have been created in the early Universe, are predicted to be detectable by their Hawking radiation. PBHs with an initial mass of 5.0 * 10^14 g should be expiring today with a burst of high energy particles. Evaporating PBHs in the solar neighborhood are candidate Gamma-Ray Bursts (GRBs) progenitors. We propose spectral lag, which is the temporal delay between the high energy photon pulse and the low energy photon pulse, as a possible method to detect PBH evaporation events with the Fermi Gamma-ray Space Telescope Observatory.

---

Bibtex entry for this abstract Preferred format for this abstract (see Preferences)

Maeda 2008 从对超新星的Ni56限制而限制伽玛暴喷出物

主要内容:


精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0901.0410)

· References in the Article

·

· Translate This Page

Title:		Nucleosynthesis of 56Ni in wind-driven Supernova Explosions and Constraints on the Central Engine of Gamma-Ray Bursts
Authors:		Maeda, Keiichi; Tominaga, Nozomu
Publication:		eprint arXiv:0901.0410
Publication Date:		01/2009
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		10 pages, 5 figures. Accepted for publication in Monthly Notices of the Royal Astronomical Society. The resolution of figures is lower than the original, accepted version
Bibliographic Code:		2009arXiv0901.0410M

Abstract

Theoretically expected natures of a supernova driven by a wind/jet are discussed. Approximate analytical formulations are derived to clarify basic physical processes involved in the wind/jet-driven explosions, and it is shown that the explosion properties are characterized by the energy injection rate (Edot_iso) and the mass injection rate (Mdot_iso). To explain observations of SN 1998bw associated with Gamma-Ray Burst (GRB) 980425, the following conditions are required: Edot_iso Mdot_iso > ~ 10^{51} erg M_sun s^{-2} and Edot_iso > ~ 2 x 10^{52} erg s^{-1} (if the wind Lorentz factor Gamma_w ~ 1) or Edot_iso > ~ 7 x 10^{52} erg s^{-1} (if Gamma_w >> 1). In SN 1998bw, 56Ni (~ 0.4M_sun) is probably produced in the shocked stellar mantle, not in the wind. The expected natures of SNe, e.g., ejected 56Ni masses and ejecta masses, vary depending on Edot_iso and Mdot_iso. The sequence of the SN properties from high Edot_iso and Mdot_iso to low Edot_iso and Mdot_iso is the following: SN 1998bw-like -- intermediate case -- low mass ejecta (< ~ 1M_sun$) where 56Ni is from the wind -- whole collapse. This diversity may explain the diversity of supernovae associated with GRBs. Our result can be used to constrain natures of the wind/jet, which is linked to the central engine of GRBs, by studying properties of the associated supernovae.

---

Bibtex entry for this abstract Preferred format for this abstract (see Preferences)

Zhang 2008 中子星的超吸积

主要内容:


精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0901.0431)

· References in the Article

·

· Translate This Page

Title:		Hyperaccreting Neutron-Star Disks and Neutrino Annihilation
Authors:		Zhang, Dong; Dai, Z. G.
Publication:		eprint arXiv:0901.0431
Publication Date:		01/2009
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		37 pages, 10 figures, submitted to ApJ
Bibliographic Code:		2009arXiv0901.0431Z

Abstract

Newborn neutron stars surrounded by hyperaccreting and neutrino-cooled disks may exist in some gamma-ray bursts (GRBs) and/or supernovae (SNe). In this paper we further study the structure of such a neutron-star disk based on the two-region (i.e., inner & outer) disk scenario following our previous work, and calculate the neutrino annihilation luminosity from the disk in various cases. We investigate the effects of the viscosity parameter $\alpha$, energy parameter $\epsilon$ (measuring the neutrino cooling efficiency of the inner disk) and outflow strength on the structure of the entire disk as well as the effect of emission from the neutron star surface boundary emission on the total neutrino annihilation rate. The inner disk satisfies the entropy-conservation self-similar structure for the viscosity parameter $\epsilon\simeq 1$ and the advection-dominated structure for $\epsilon<1$.> Bibtex entry for this abstract Preferred format for this abstract (see Preferences)

Curran 2008 用Swift暴拟合参数

主要内容:


精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0901.0519)

· References in the Article

·

· Translate This Page

Title:		Swift GRBs and the blast wave model
Authors:		Curran, P. A.; van der Horst, A. J.; Starling, R. L. C.; Wijers, R. A. M. J.
Publication:		eprint arXiv:0901.0519
Publication Date:		01/2009
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		6 pages, submitted to the proceedings of the 6th Huntsville GRB Symposium (2008)
Bibliographic Code:		2009arXiv0901.0519C

Abstract

The complex structure of the light curves of Swift GRBs has made their interpretation and that of the blast wave caused by the burst, more difficult than in the pre-Swift era. We aim to constrain the blast wave parameters: electron energy distribution, p, density profile of the circumburst medium, k, and the continued energy injection index, q. We do so by comparing the observed multi-wavelength light curves and X-ray spectra of a Swift sample to the predictions of the blast wave model. We can successfully interpret all of the bursts in our sample of 10, except two, within the framework of the blast wave model, and we can estimate with confidence the electron energy distribution index for 6 of the sample. Furthermore we identify jet breaks in half of the bursts. A statistical analysis of the distribution of p reveals that, even in the most conservative case of least scatter, the values are not consistent with a single, universal value. The values of k suggest that the circumburst density profiles are not drawn from only one of the constant density or wind-like media populations.

---

Bibtex entry for this abstract Preferred format for this abstract (see Preferences)

Stratta 2008 慢下降阶段时标和红移的反相关

主要内容:
红移越大, shallow decay的时标越短.

不过样本不全, 有很多没放上来(是不是有选择效应). 按照这么说那没有shallow decay的都是很高红移的! 但事实上不是.
另外关系不致密.

精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0901.0257)

· References in the Article

·

· Translate This Page

Title:		Evidence for an anticorrelation between the duration of the shallow decay phase of GRB X-ray afterglows and redshift
Authors:		Stratta, G.; Guetta, D.; D'Elia, V.; Perri, M.; Covino, S.; Stella, L.
Publication:		eprint arXiv:0901.0257
Publication Date:		01/2009
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		4 pages, 2 figures, 1 table, accepted as a Letter to A&A
Bibliographic Code:		2009arXiv0901.0257S

Abstract

One of the most intriguing features discovered by Swift is a plateau phase in the X-ray flux decay of about 70% of the afterglows of gamma-ray bursts (GRBs). The physical origin of this feature is still being debated. We constrain the proposed interpretations, based on the intrinsic temporal properties of the plateau phase. We selected and analyzed all the Swift/XRT GRB afterglows at known redshift observed between March 2005 and June 2008 featuring a shallow decay phase in their X-ray lightcurves. For our sample of 21 GRBs we find an anticorrelation of the logarithm of the duration of the shallow phase with re dshift, with a Spearman rank-order correlation coefficient of r=-0.4 and a null hypothesis probability of 5%. When we correct the durations for cosmological dilation, the anticorrelation strenghtens, with r=-0.6 and a null hypothesis probability of 0.4%. Considering only those GRBs in our sample that have a well-measured burst peak energy (8 out of 21), we find an anticorrelation between the energy of the burst and the shallow phase duration, with r=-0.80 and a null hypothesis probability of 1.8%. If the burst energy anticorrelation with the shallow phase duration is real, then the dependence of the shallow phase on redshift could be the result of a selection effect, since on average high-redshift bursts with lower energies and longer plateaus would be missed. A burst energy anticorrelation with the shallow phase duration would be expected if the end of the plateau arises from a collimated outflow. Alternative scenarios are briefly discussed involving a possible cosmological evolution of the mechanism responsible for the X-ray shallow decay.

---

Bibtex entry for this abstract Preferred format for this abstract (see Preferences)

Bagoly 2008 不同的卫星有不同的红移分布

主要内容:


精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· Electronic On-line Article (HTML)

· arXiv e-print (arXiv:0901.0103)

· Table of Contents

· References in the Article

· Also-Read Articles (Reads History)

·

· Translate This Page

Title:		Different satellites-different GRB redshift distributions?
Authors:		Bagoly, Z.; Balázs, L. G.; Horváth, I.; Kelemen, J.; Mészáros, A.; Veres, P.; Tusnády, G.
Publication:		2008 NANJING GAMMA-RAY BURST CONFERENCE. AIP Conference Proceedings, Volume 1065, pp. 119-122 (2008). (AIPC Homepage)
Publication Date:		10/2008
Origin:		AIP
Keywords:		gamma-ray sources (astronomical), red shift, telescopes
Abstract Copyright:		(c) 2008: American Institute of Physics
DOI:		10.1063/1.3027895
Bibliographic Code:		2008AIPC.1065..119B

Abstract

The measured redshifts of gamma-ray bursts (GRBs), which were first detected by the Swift satellite, seem to be bigger on average than the redshifts of GRBs detected by other satellites. We analyzed the redshift distribution of GRBs triggered and observed by different satellites (Swift[1], HETE2[2], BeppoSax, Ulyssses). After considering the possible biases significant difference was found at the p = 95.70% level in the redshift distributions of GRBs measured by HETE and the Swift.

---

Bibtex entry for this abstract Preferred format for this abstract (see Preferences)

Medvedev 2008 PIC模拟看能否产生Fermi能观测到的高能光子

主要内容:


精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0901.0051)

· References in the Article

·

· Translate This Page

Title:		GRB physics with Fermi
Authors:		Medvedev, Mikhail V.
Publication:		eprint arXiv:0901.0051
Publication Date:		12/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		6 pages; submitted to proc. of Huntsville 2008 symposium on GRBs
Bibliographic Code:		2009arXiv0901.0051M

Abstract

Radiation from GRBs in the prompt phase, flares and an afterglow is thought to be produced by accelerated electrons in magnetic fields. Such emission may be produced at collisionless shocks of baryonic outflows or at reconnection sites (at least for the prompt and flares) of the magnetically dominated (Poynting flux driven) outflows, where no shocks presumably form at all. An astonishing recent discovery is that during reconnection strong small-scale magnetic fields are produced via the Weibel instability, very much like they are produced at relativistic shocks. The relevant physics has been successfully and extensively studied with the PIC simulations in 2D and, to some extent, in 3D for the past few years. We discuss how these simulations predict the existence of MeV-range synchrotron/jitter emission in some GRBs, which can be observed with Fermi. Recent results on modeling of the spectral variability and spectral correlations of the GRB prompt emission in the Weibel-jitter paradigm applicable to both baryonic and magnetic-dominated outflows is reviewed with the emphasis on observational predictions.

---

Bibtex entry for this abstract Preferred format for this abstract (see Preferences)

Grindlay 2008 Nature关于Racusin2008, GRB 080319B的news and views

主要内容:


精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· Electronic Refereed Journal Article (HTML)

· arXiv e-print (arXiv:0901.0041)

· References in the article

· Also-Read Articles (Reads History)

·

· Translate This Page

Title:		Gamma-ray bursts: Light on the distant Universe
Authors:		Grindlay, Jonathan
Affiliation:		AA(Jonathan Grindlay is at the Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA. josh@head.cfa.harvard.edu)
Publication:		Nature, Volume 455, Issue 7210, pp. 177-178 (2008). (Nature Homepage)
Publication Date:		09/2008
Origin:		NATURE
Abstract Copyright:		(c) 2008: Nature
DOI:		10.1038/455177a
Bibliographic Code:		2008Natur.455..177G

Abstract

Observations of a long-lasting γ-ray burst, one that has the brightest optical counterpart yet discovered, challenge theoretical understanding of these bursts but may enhance their usefulness as cosmic probes.

---

Bibtex entry for this abstract Preferred format for this abstract (see Preferences)