Barniol 2008 早期快降的绝热膨胀解释

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· arXiv e-print (arXiv:0806.1226)

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Title:		Adiabatic expansion, early x-ray data and the central engine in GRBs
Authors:		Barniol Duran, R.; Kumar, P.
Publication:		eprint arXiv:0806.1226
Publication Date:		06/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		6 pages, 2 figures, submitted for publication on MNRAS
Bibliographic Code:		2008arXiv0806.1226B

Abstract

The Swift satellite early x-ray data shows a very steep decay in most of the Gamma-Ray Bursts light curves. This decay is either produced by the rapidly declining continuation of the central engine activity or by some left-over radiation starting right after the central engine shuts off. The latter scenario consists of the emission from an "ember" that cools via adiabatic expansion and, if the jet angle is larger than the inverse of the source Lorentz factor, the large angle emission. In this work, we calculate the temporal and spectral properties of the emission from such a cooling ember, providing a new treatment for the micro-physics of the adiabatic expansion. We compare the theoretical expectations of the adiabatic expansion (and the large angle emission) with the current observations of the early x-ray data and find that only about 20% of our sample of 107 bursts is potentially consistent with this model. This leads us to believe that, for most bursts, the central engine does not turn off completely during the steep decay of the x-ray light curve; therefore, this phase is produced by the continued rapidly declining activity of the central engine.

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Zhang 2008 Relationship between pulse width and energy in GRB 060124

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Electronic Refereed Journal Article (HTML)

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· arXiv e-print (arXiv:0806.1279)

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Title:		Relationship between pulse width and energy in GRB 060124: from X-ray to γ-ray bands
Authors:		Zhang, Fu-Wen; Qin, Yi-Ping
Affiliation:		AA(National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, P.O. Box 110, Kunming, Yunnan 650011, China; The Graduate School of the Chinese Academy of Sciences, P.O. Box 3908, Beijing 100039, China), AB(Center for Astrophysics, Guangzhou University, Guangzhou 510006, China; Physics Department, Guangxi University, Nanning, Guangxi 530004, China)
Publication:		New Astronomy, Volume 13, Issue 7, p. 485-490. (NewA Homepage)
Publication Date:		10/2008
Origin:		ELSEVIER
Keywords:		95.85.Pw, 95.85.Nv
Abstract Copyright:		Elsevier B.V.
DOI:		10.1016/j.newast.2008.01.005
Bibliographic Code:		2008NewA...13..485Z

Abstract

GRB 060124 is the first event that both prompt and afterglow emission were observed simultaneously by the three Swift instruments. Its main peak also triggered Konus-Wind and HETE-II. Therefore, investigation on both the temporal and spectral properties of the prompt emission can be extended to X-ray bands. We perform a detailed analysis on the two well identified pulses of this burst, and find that the pulses are narrower at higher energies, and both X-rays and γ-rays follow the same w–E relation for an individual pulse. However, there is no a universal power-law index of the w–E relation among pulses. We find also that the rise-to-decay ratio r/d seems not to evolve with E and the r/d values are well consistent with that observed in typical GRBs. The broadband spectral energy distribution also suggests that the X-rays are consistent with the spectral behavior of the γ-rays. These results indicate that the X-ray emission tracks the γ-ray emission and the emissions in the two energy bands are likely to be originated from the same physical mechanism.

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Zhang 2008 980425和060218光变

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· arXiv e-print (arXiv:0806.1278)

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Title:		Broadband lightcurve characteristics of GRBs 980425 and 060218 and comparison with long-lag, wide-pulse GRBs
Authors:		Zhang, Fu-Wen
Publication:		eprint arXiv:0806.1278
Publication Date:		06/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		26 pages, 10 figures, 3 tables, accepted for publication in ApJ
Bibliographic Code:		2008arXiv0806.1278Z

Abstract

It has been recently argued that low-luminosity gamma-ray bursts (LL-GRBs) are likely a unique GRB population. Here, we present systematic analysis of the lightcurve characteristics from X-ray to gamma-ray energy bands for the two prototypical LL-GRBs 980425 and 060218. It is found that both the pulse width ($w$) and the ratio of the rising width to the decaying width ($r/d$) of theses two bursts are energy-dependent over a broad energy band. There exists a significant trend that the pulses tend to be narrower and more symmetry with respect to the higher energy bands for the two events. Both the X-rays and the gamma-rays follow the same $w - E$ and $r/d - E$ relations. These facts may indicate that the X-ray emission tracks the gamma-ray emission and both are likely to be originated from the same physical mechanism. Their light curves show significant spectral lags. We calculate the three types of lags with the pulse peaking time ($t_{peak}$), the pulse centroid time ($t_{cen}$), and the cross-correlation function (CCF). The derived $t_{peak}$ and $t_{cen}$ are a power-law function of energy. The lag calculated by CCF is strongly correlated with that derived from $t_{peak}$. But the lag derived from $t_{cen}$ is less correlated with that derived from $t_{peak}$ and CCF. The energy dependence of the lags is shallower at higher energy bands. These characteristics are well consistent with that observed in typical long-lag, wide-pulse GRBs, suggesting that GRBs 980425 and 060218 may share the similar radiation physics with them.

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Yu 2008 GRB 080319B 内激波的正反激波模型

主要内容:
伽玛射线来自相对论性的反向激波，光学辐射来自非相对论性的正向激波。

（大家都是从中心引擎出来的shell，为什么反向激波和正向激波不是等价的？）

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· arXiv e-print (arXiv:0806.2010)

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Title:		GRB 080319B: optical and gamma-ray emissions from internal forward-reverse shocks
Authors:		Yu, Y. W.; Wang, X. Y.; Dai, Z. G.
Publication:		eprint arXiv:0806.2010
Publication Date:		06/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		11 pages, submitted to ApJ Letters
Bibliographic Code:		2008arXiv0806.2010Y

Abstract

The temporal coincidence between the prompt $\gamma$-ray and optical emissions of gamma-ray burst (GRB) 080319B suggests that they may originate from a same emitting region or two regions sharing the same dynamical behavior. Meanwhile, the significant excess of the optical flux over the extrapolation of the $\gamma$-ray spectrum to the optical band indicates two different emission components. We here consider the popular internal shock model where a forward and a reverse shock are generated simultaneously during a collision of two relativistic shells. In the case that the Lorentz factors of these two shocks are very different, the synchrotron emission driven by them could peak at two different energy bands. We show that such a two-component synchrotron scenario can account for the prompt optical and $\gamma$-ray emissions of GRB 080319B under some unique conditions. In addition, the luminosity of an inverse-Compton sub-GeV or GeV component predicted in this scenario is not higher than that of synchrotron MeV gamma-rays, which could be tested by the {\em Gamma-ray Large Area Space Telescope} (GLAST).

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Thoene 2008 GRB 060526的余辉和宿主星系观测

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· arXiv e-print (arXiv:0806.1182)

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Title:		Photometry and Spectroscopy of GRB 060526: A detailed study of the afterglow and host of a high-redshift gamma-ray burst
Authors:		Thoene, C. C.; Kann, D. A.; Johannesson, G.; Selj, J. H.; Jaunsen, A.; Fynbo, J. P. U.; Baliyan, K. S.; Bartolini, C.; Bikmaev, I. F.; Bloom, J. S.; Burenin, R. A.; Cobb, B. E.; Covino, S.; Curran, P. A.; Dahle, H.; French, J.; Ganesh, S.; Greco, G.; Guarnieri, A.; Hanlon, L.; Hjorth, J.; Ibrahimov, M.; Israel, G. L.; Jakobsson, P.; Jensen, B. L.; Jorgensen, U. G.; Khamitov, I. M.; Malesani, D.; Masetti, N.; Naranen, J.; Pakstiene, E.; Pavlinsky, M. N.; Perley, D. A.; Piccioni, A.; Pizzichini, G.; Pozanenko, A.; Nanni, D.; Rumyantsev, V.; Sharapov, D.; Starr, D.; Sunyaev, R. A.; Terra, F.; Vreeswijk, P. M.; Wilson, A. C.
Publication:		eprint arXiv:0806.1182
Publication Date:		06/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		15 pages, 8 figures, submitted to A&A
Bibliographic Code:		2008arXiv0806.1182T

Abstract

With this paper we want to investigate the highly variable afterglow light curve and environment of Gamma-Ray Burst (GRB) 060526 at z=3.221. We present one of the largest photometric datasets ever obtained for a GRB afterglow, consisting of multi-color photometric data from the optical to the NIR. The data set contains 218 data points in total to which we add additional data from the literature. Furthermore, we present low-resolution high signal-to-noise spectra of the afterglow. The afterglow light curve is modeled with both an analytical model using broken power-law fits and with a broadband numerical energy injection model. The absorption lines detected in the spectra are used to derive column densities using a multi-ion single-component curve-of-growth analysis from which we derive the metallicity of the host of GRB 060526. The overall light curve follows a broken power-law with a break at t = 2.401 +- 0.061 days. It shows deviations from the smooth power-law that can be explained by additional energy injections from the central engine. The broadband SED of the afterglow shows little extinction along the line of sight. The metallicity derived from S II and Fe II is relatively high for a galaxy at that redshift but comparable to the metallicity of other GRB hosts at similar redshifts. There is a candidate host galaxy at a relatively large offset of 7.7 kpc from the afterglow position with R =26.4 mag which would imply a rather luminous host.

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Capozziello 2008 伽玛暴定宇宙学参数

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数据和关系都是原来的，貌似方法有所不同。

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· arXiv e-print (arXiv:0806.1120)

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Title:		Cosmography by GRBs
Authors:		Capozziello, S.; Izzo, L.
Publication:		eprint arXiv:0806.1120
Publication Date:		06/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		4 pages, 4 figures
Bibliographic Code:		2008arXiv0806.1120C

Abstract

Relations connecting GRB quantities can be used to constrain cosmographic parameters of the Hubble law at medium-high redshifts. We consider a sample of 64 GRBs to construct the luminosity distance - redshift relation and derive the values of the parameters q_0$, j_0 and s_0. The results, calibrated by SNeIa data, agree with the $\Lambda$CDM model.

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Romano 2008 SAX J0840.7+2248可能不是X射线双星而是GRB 980429

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· arXiv e-print (arXiv:0806.0925)

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Title:		Swift uncovers that SAX J0840.7+2248 is not an X-ray Binary, but BeppoSAX X-ray Rich GRB 980429
Authors:		Romano, P.; Guidorzi, C.; Sidoli, L.; Montanari, E.; Capitanio, F.; Amati, L.; Cucchiara, A.; Frontera, F.; Masetti, N.; Mereghetti, S.; Rossi, F.
Publication:		eprint arXiv:0806.0925
Publication Date:		06/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		GAMMA-RAY BURSTS 2007: Proceedings of the Santa Fe Conference, 4 pages, 2 figures. Higher definition version of figure 1 at http://www.ifc.inaf.it/~romano/sax0840/romanop_sf_figA.eps
Bibliographic Code:		2008arXiv0806.0925R

Abstract

During our Swift/XRT program to obtain X-ray positions at arcsecond level for a sample of Galactic X-ray binaries, we discovered that SAX J0840.7+2248 is not a binary, but rather BeppoSAX/WFC+GRBM X-ray Rich GRB 980429. Here we report on this discovery and on the properties of this long, X-ray rich gamma-ray burst, from prompt to (very) late followup.

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Prochaska 2008 余辉中NV（氮5）的吸收线

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· arXiv e-print (arXiv:0806.0399)

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Title:		A Survey for NV Absorption at z~z_GRB in GRB Afterglow Spectra: Clues to Gas Near the Progenitor Star
Authors:		Prochaska, Jason X.; Dessauges-Zavadsky, Miroslava; Ramirez-Ruiz, Enrico; Chen, Hsiao-Wen
Publication:		eprint arXiv:0806.0399
Publication Date:		06/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		Accepted to ApJ, 12 pages, 4 color figures
Bibliographic Code:		2008arXiv0806.0399P

Abstract

We survey NV absorption in the afterglow spectra of long-duration gamma-ray bursts (GRBs) with the intent to study highly ionized gas in the galaxies hosting these events. We identify a high incidence (6/7) of spectra exhibiting NV gas with z~z_GRB and the majority show large column densities NV > 10^14 cm^-2. With one exception, the observed line-profiles are kinematically `cold', i.e. they are narrow and have small velocity offset (Dv <> 10^3 cm^-3) environments, typical of molecular clouds. The observations, therefore, primarily constrain the physical conditions -- metallicity, density, velocity fields -- of the gas within the (former) molecular cloud region surrounding the GRB.

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Chevalier 2008 XRF 080109/SN 2008D的shock breakout 模型

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arXiv:0806.0371 [ps, pdf, other]

Title: Shock Breakout Emission from a Type Ib/c Supernova: XRF 080109/SN 2008D

Authors: Roger A. Chevalier, Claes Fransson

Comments: 11 pages, 1 figure, submitted to ApJL 4/30/08

Subjects: Astrophysics (astro-ph)

The X-ray flash 080109, associated with SN 2008D, can be attributed to the shock breakout emission from a normal Type Ib/c supernova. If the observed emission is interpreted as blackbody emission, the temperature and radiated energy are close to expectations, considering that scattering dominates absorption processes so that spectrum formation occurs deep within the photosphere. The X-ray emission observed at ~10 days is attributed to inverse Compton scattering of photospheric photons with relativistic electrons produced in the interaction of the supernova with the progenitor wind. A simple model for the optical/ultraviolet emission from shock breakout is developed and applied to SN 1987A, SN 1999ex, SN 2008D, and SN 2006aj, all of which have optical emission observed at t~1 day. The emission from the first three can plausibly be attributed to shock breakout emission. The photospheric temperature is most sensitive to the radius of the progenitor star core and the radii in these cases are in line with expectations from stellar evolution. The early optical/ultraviolet observations of SN 2006aj cannot be accommodated by a shock breakout model in a straightforward way.

Casandjian 2008 Compton EGRET 高能源的catalogue的修正版

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有188个源，比3rd catalogue的源减少了100来个，发现不是的。

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arXiv:0806.0113 [ps, pdf, other]

Title: A revised catalogue of EGRET gamma-ray sources

Authors: Jean-Marc Casandjian, Isabelle A. Grenier

Comments: Accepted in A&A Full resolution figures and ASCII tables can be downloaded from: this http URL

Subjects: Astrophysics (astro-ph)

We present a catalog of point gamma-ray sources detected by the EGRET detector aboard the Compton Gamma Ray Observatory. We have used the whole gamma-ray dataset of reprocessed photons at energies above 100 MeV together with new Galactic interstellar emission models based on recent CO, HI, dark gas, and interstellar radiation field data. Two different assumptions have been used for the cosmic-ray distribution in the Galaxy to explore the resulting systematic uncertainties in source detection and characterization. We have used the same 2-dimensional maximum-likelihood detection method as for the 3rd EGRET catalogue. The revised catalogue lists 188 sources, 14 of which are marked as confused, compared to the 271 entries of the 3rd EGRET (3EG) catalogue. 107 former sources have not been confirmed because of the additional structure in the interstellar background. The vast majority of them were unidentified and marked as possibly extended or confused in the 3EG catalogue. In particular, we do not confirm most of the 3EG sources associated with the local clouds of the Gould Belt. Alternatively, we find 30 new sources with no 3EG counterpart. The new error circles for the confirmed 3EG sources largely overlap the previous ones, but several counterparts of particular interest that had been discussed in the litterature, such as Sgr A*, radiogalaxies and several microquasars are now found outside the error circles. We have cross-correlated the source positions with a large number of radio pulsars, pulsar wind nebulae, supernova remnants, OB associations, blazars and flat radiosources and we find a surprising large number of sources (87) at all latitudes with no counterpart among the potential gamma-ray emitters.

Nakagawa 2008 SGR 1900+14最近几年爆发的X射线余辉观测

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arXiv:0806.0099 [ps, pdf, other]

Title: The Swift Discovery of X-ray Afterglows Accompanying Short Bursts from SGR 1900+14

Authors: Y. E. Nakagawa, T. Sakamoto, G. Sato, N. Gehrels, K. Hurley, D. M. Palmer

Comments: 12 pages, 3 figures, 3 tables, accepted for publication in ApJL

Subjects: Astrophysics (astro-ph)

The discovery of X-ray afterglows accompanying two short bursts from SGR 1900+14 is presented. The afterglow luminosities at the end of each observation are lower by 30-50% than their initial luminosities, and decay with power law indices p ~ 0.2-0.4. Their initial bolometric luminosities are L ~ 10^34-10^35 erg s^-1. We discuss analogies and differences between the X-ray afterglows of SGR short bursts and short gamma-ray bursts.

Campana 2008 大质量星怎样产生伽玛暴

主要内容:
只有1%的Ic型超新星有伽玛暴（这个结果怎么来的？）。

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Only ~1% of core collapse SNe are able to produce a highly relativistic collimated outflow, and hence a GRB.

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· arXiv e-print (arXiv:0805.4698)

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Title:		Outliers from the mainstream: how a massive star can produce a gamma-ray burst
Authors:		Campana, S.; Panagia, N.; Lazzati, D.; Beardmore, A. P.; Cusumano, G.; Godet, O.; Chincarini, G.; Covino, S.; Della Valle, M.; Guidorzi, C.; Malesani, D.; Moretti, A.; Perna, R.; Romano, P.; Tagliaferri, G.
Publication:		eprint arXiv:0805.4698
Publication Date:		05/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		ApJL in press 4 pages 2 figures
Bibliographic Code:		2008arXiv0805.4698C

Abstract

It is now recognized that long-duration Gamma-Ray Bursts (GRBs) are linked to the collapse of massive stars, based on the association between (low-redshift) GRBs and (type Ic) core-collapse supernovae (SNe). The census of massive stars and GRBs reveals, however, that not all massive stars do produce a GRB. Only ~1% of core collapse SNe are able to produce a highly relativistic collimated outflow, and hence a GRB. The extra crucial parameter has long been suspected to be metallicity and/or rotation. We find observational evidence strongly supporting that both ingredients are necessary in order to make a GRB out of a core-collapsing star. A detailed study of the absorption pattern in the X-ray spectrum of GRB060218 reveals evidence of material highly enriched in low atomic number metals ejected before the SN/GRB explosion. We find that, within the current scenarios of stellar evolution, only a progenitor star characterized by a fast stellar rotation and sub-solar initial metallicity could produce such a metal enrichment in its close surrounding.

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