Ruiz-Velasco 2007 GRB 060927的余辉观测及高红移应用

主要内容:
GRB 060927 红移有5.6, 是第二高红移的暴。对余辉的观测可以对宇宙早期再电离的情形有所帮助。

精彩摘抄:


文章信息:
arXiv:0706.1257 [ps, pdf, other] : Title: Detection of GRB 060927 at z = 5.47: Implications for the Use of Gamma-Ray Bursts as Probes of the End of the Dark Ages
Authors: A. E. Ruiz-Velasco, et al
Comments: 28 pages, submitted to the Astrophysical Journal, referee's comments included

We report on follow-up observations of the GRB 060927 using the ROTSE-IIIa telescope and a suite of larger aperture ground-based telescopes. An optical afterglow was detected 20 s after the burst, the earliest rest-frame detection of optical emission from any GRB. Spectroscopy performed with the VLT about 13 hours after the trigger shows a continuum break at lambda ~ 8070 A produced by neutral hydrogen absorption at z~5.6. We also detect an absorption line at 8158 A which we interpret as SiII at z=5.467. Hence, GRB 060927 is the second most distant GRB with a spectroscopically measured redshift. The shape of the red wing of the spectral break can be fitted by a damped Lyalpha profile with a column density with log(N_HI/cm^-2) ~ 22.5. We discuss the implications of this work for the use of GRBs as probes of the end of the dark ages and draw three main conclusions: i) GRB afterglows originating from z>6 should be relatively easy to detect from the ground, but rapid NIR monitoring is necessary to ensure that they are found; ii) The presence of large HI column densities in some GRBs host galaxies at z>5 makes the use of GRBs to probe the reionization epoch via spectroscopy of the red damping wing challenging; iii) GRBs appear crucial to locate typical star-forming galaxies at z>5 and therefore the type of galaxies responsible for the reionization of the universe.

Bertou 2007 用Pierre Auger Observatory搜索伽玛暴高能辐射

主要内容:
Pierre Auger Observatory是通过二级效应观测1GeV-1TeV的高能光子的，有1200个Cherenkov 探测器，但从2005.9到2007年都没有观测到。流量上限是1.3E-5 erg cm^-2.

精彩摘抄:


文章信息:
arXiv:0706.1256 [ps, pdf, other] : Title: Search for Gamma Ray Bursts using the single particle technique at the Pierre Auger Observatory
Authors: X.Bertou, for the Pierre Auger Observatory
Comments: 4 pages, 4 figures. To be published in Proceedings of the 30th International Cosmic Ray Conference, July 3 - 11, 2007, Merida, Yucatan, Mexico

The Pierre Auger Observatory, with an array of currently more than 1200 Cherenkov detectors filled with 12 m$^3$ of water, can detect the putative high energy emission of a GRB (photons down to a few hundreds of MeV) by the so-called ``single particle technique'', through a coherent increase in the average background particle rates over the whole array, due to secondary particles in the photon-induced showers. We present a search for bursts on data collected since September 2005, as well as a search for excesses in coincidence with bursts observed by satellites.

Vachaspati 2007 暗星作为伽玛暴的前身星

主要内容:
正在塌缩成黑洞并处于史瓦西视界内的星称为暗星，作者认为碰撞的暗星可以爆发出伽玛暴。
（但是暗星的时标应该很短，谁会和它碰撞呢）

精彩摘抄:


文章信息:
arXiv:0706.1203 [ps, pdf, other] : Title: Black Stars and Gamma Ray Bursts
Authors: Tanmay Vachaspati
Comments: 2 pages, 1 figure

Stars that are collapsing toward forming a black hole but are frozen near the Schwarzschild horizon are termed ``black stars''. Collisions of black stars, in contrast to black hole collisions, may be sources of gamma ray bursts, whose basic parameters are estimated quite simply and are found to be consistent with observed gamma ray bursts. Black star gamma ray bursts should be preceded by gravitational wave emission similar to that from the coalescence of black holes.

Curran 2007 Swift余辉的多波段同时拐折

主要内容:
Swift之前大部分是同时拐折的，但Swift的暴却好像不是。作者通过对GRB 060206多波段余辉（X射线和光学）分析，发现还是同时拐折的，这样也比较符合标准激波模型。

精彩摘抄:


文章信息
arXiv:0706.1188 [ps, pdf, other] :

Title: GRB 060206 and the quandary of achromatic breaks in afterglow light curves
Authors: P.A. Curran, A.J. van der Horst, R.A.M.J. Wijers, R.L.C. Starling, A.J. Castro-Tirado, J.P.U. Fynbo, J. Gorosabel, A.S. Jarvinen, D. Malesani, E. Rol, N.R. Tanvir, K. Wiersema, M.R. Burleigh, S.L. Casewell, P.D. Dobbie, S. Guziy, P. Jakobsson, M. Jelinek, P. Laursen, A.J. Levan, C.G. Mundell, J. Naranen, S. Piranomonte
Comments: 5 pages including 1 figure; submitted for publication in MNRAS Letters

Gamma-ray burst afterglow observations in the Swift era have a perceived lack of achromatic jet breaks compared to the BeppoSAX era. We examine the effect of the fact that pre-Swift afterglow observations tend to be dominated by the optical, whereas in the Swift era most well sampled light curves are in the X-ray. We present our multi-wavelength analysis of GRB 060206 as an illustrative example to demonstrate the possible effect of this change. The results of temporal and spectral analyses are compared, and attempts are made to fit the data within the context of the standard blast wave model. We find that while the break appears more pronounced in the optical and evidence for it from the X-ray alone is weak, the data are actually consistent with an achromatic break at about 16 hours. This break and the light curves fit standard blast wave models, either as a jet break or as an injection break. The Swift and pre-Swift samples of afterglows could well be consistent in their break behaviour, but the lack of accurate models for jet breaks and the dearth of well sampled late time optical light curves for Swift bursts preclude definitive statements on the matter.

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Weiler 2004 超新星和伽玛暴的射电辐射以及SKA将能起的作用

主要内容:
综述了超新星和伽玛暴的射电辐射的一些主要特征，总体上伽玛暴的射电余辉比射电超新星的亮度要高4个量级，伽玛暴的射电余辉可以用中等相对论性的激波很好地解释。当然SKA的提高的观测能力可以为射电的细致研究做贡献。

精彩摘抄:
几个不同类型的超新星的观测性质
部分伽玛暴的射电特性，和超新星的比较一下，要大约四个量级。


SN 1993J的几个射电波段的光变
对应的质量损失率

SN 1998bw的三个射电波段的光变


SN 000301c的几个波段的光变。

文章信息:
title： Radio emission from supernovae and gamma-ray bursters and the need for the SKA
Author： Kurt W. Weiler a,*,1, Schuyler D. Van Dyk b, Richard A. Sramek c, Nino Panagia d,2
New Astronomy Reviews 48 (2004) 1377–1398

Study of radio supernovae (SNe) over the past 25 years includes two dozen detected objects and more than 100 upper limits. From this work it is possible to identify classes of radio properties, demonstrate conformance to and deviations from existing models, estimate the density and structure of the circumstellar material and, by inference, the evolution of the presupernova stellar wind, and reveal the last stages of stellar evolution before explosion. It is also possible to detect ionized hydrogen along the line of sight, to demonstrate binary properties of the stellar system, and to show clumpiness of the circumstellar material.

Since 1997 the afterglow of c-ray bursting sources (GRBs) has occasionally been detected in the radio, as well in other wavelength bands. In particular, the interesting and unusual c-ray burst GRB 980425, almost certainly related to the radio supernova SN 1998bw, and the more recent SN 2003dh/GRB 030329 are links between the two classes of objects. Analyzing the extensive radio emission data available for SN 1998bw, one can describe its time evolution within the well established framework available for the analysis of radio emission from supernovae. This then allows relatively detailed description of a number of physical properties of the object. The radio emission can best be explained as the interaction of a mildly relativistic (C
1.6) shock with a dense pre-explosion stellar wind-established circumstellar medium that is highly structured both azimuthally, in clumps or filaments, and radially, with observed density enhancements. From this we can support the conclusion that at least some members of the slow-soft class of GRBs are related to type Ib/c SNe and can be attributed to the explosion of a massive star in a dense, highly structured CSM that was presumably established by the pre-explosion stellar system.

However, due to the lack of sensitivity of current radio telescopes, most supernovae cannot be studied if they are more distant than the Virgo Cluster (
20 Mpc) or, for exceptionally luminous Type IIn supernovae, beyond
100 Mpc. While the GRBs are up to 4 orders-of-magnitude more radio luminous, they are also generally much more distant because of their small probability of detection in smaller volumes of space and most are at z
1. Those which are radio detected rarely exceed peak flux densities of
100  300 lJy. Such low flux densities mean that detailed study of their
radio ‘‘light curves’’ and, derived from those light curves, the energetics and dynamics of the explosions and the properties of their progenitors and the circumburst medium is very difficult and severely limited in scope. The increased
capability of the SKA to attack these problems will significantly advance the field.

Wang 2007 包括伽玛暴的多种对象对宇宙学参数的限制

主要内容:
综合考虑Ia型超新星、微波背景辐射各向异性、baryon acoustic oscillation (BAO) peak、the X-ray gas mass fraction in clusters、the 2dF Galaxy Redshift Survey以及伽玛暴来定宇宙学参数。文章还考虑其他宇宙学模型、减速因子以及加速开始的转变红移。

精彩摘抄:
多个对象对宇宙学参数的限制。

文章信息:
arXiv:0706.0938 [ps, pdf, other] : Title: Measuring Dark Energy with Gamma-Ray Bursts and Other Cosmological Probes
Authors: F. Y. Wang, Z. G. Dai, Zong-Hong Zhu
Comments: 28 pages including 13 figures, accepted for publication in ApJ

It has been widely shown that the cosmological parameters and dark energy can be constrained by using data from type-Ia supernovae (SNe Ia), the cosmic microwave background (CMB) anisotropy, the baryon acoustic oscillation (BAO) peak from Sloan Digital Sky Survey (SDSS), the X-ray gas mass fraction in clusters, and the linear growth rate of perturbations at z=0.15 as obtained from the 2dF Galaxy Redshift Survey. Recently, gamma-ray bursts (GRBs) have also been argued to be promising standard candles for cosmography. In this paper, we present constraints on the cosmological parameters and dark energy by combining a recent GRB sample including 69 events with the other cosmological probes. First, we find that for the LambdaCDM cosmology this combination makes the constraints stringent and the best fit is close to the flat universe. Second, we fit the flat Cardassian expansion model and find that this model is consistent with the LambdaCDM cosmology. Third, we present constraints on several two-parameter dark energy models and find that these models are also consistent with the LambdaCDM cosmology. Finally, we reconstruct the dark energy equation-of-state parameter w(z) and the deceleration parameter q(z). We see that the acceleration could have started at a redshift from z_T=0.40_{-0.08}^{+0.14} to z_T=0.65_{-0.05}^{+0.10}. This difference in the transition redshift is due to different dark energy models that we adopt. The most stringent constraint on w(z) lies in the redshift range z\sim 0.3-0.6.

Zhilyaev 2007 原初黑洞和恒星的碰撞形成伽玛暴

主要内容:


精彩摘抄:


文章信息:
arXiv:0706.0930 [ps, pdf, other] : Title: Gamma-Ray Bursts as Manifestation of Collisions of Primordial Black Holes with Stars
Authors: B.E. Zhilyaev
Comments: 8 pages, 3 figures
Journal-ref: BCrAO 103 (2007) 58-64
Using the BATSE survey data I find that quite small fraction of GRBs numbering 37 sources seems to emit the radiation similar to thermal bremsstrahlung in the range 20 to 300 keV. I suggest that these bursts may perhaps occur from collision of stars with primordial black holes (PBH). These objects are relic of a hot matter in the early Universe. PBH in the vicinity of stars may be found in consequence of incorporation processes during the formation of stars from interstellar clouds. At present they can form the gravitationally captured haloes around stars like the family of solar comets. The comet paradigm has been used to understand various aspects of PBH. Comet collisions with the Sun and planets are ordinary events in solar system history. On the analogy, one can support the view that PBH collisions with the parent star may be quite frequent events in its history, too. PBHs are the engines driving gamma-ray bursts when collide with the stars. Entering a stellar atmosphere, PBH is supposed to produce the gamma-ray burst due to accretion with duration from a few tenths of second to a few seconds. It can exhibit the main qualitative features of some GRBs. Their masses are estimated in the range from thousandths to hundredths of the solar mass. I found that these burst sources are isotropically distributed on the sky and are seen from a distance up to 50 ps. In this context one may expect that some short GRBs are observable signatures of primordial black holes in the Universe

Moiseev 2007 GLAST LAT对高能电子的观测

主要内容:
GLAST LAT不仅能观测光子，按照作者的说法，还能观测10－1000GeV的电子，而且他们还在企图把能段扩展。预计每年和观测10^7个电子。

精彩摘抄:


文章信息:
arXiv:0706.0882 [pdf] : Title: Measuring 10-1000 GeV Cosmic Ray Electrons with GLAST/LAT
Authors: Alexander A.Moiseev, Jonathan F.Ormes, Igor V.Moskalenko
Comments: 5 pages, 5 figures, 1 table

We present here the capabilities of the GLAST Large Area Telescope to detect cosmic ray high-energy (HE) electrons in the energy range from 10 GeV to 1 TeV. We also discuss the science topics that can be investigated with HE electron data and quantify the results with LAT instrument simulations. The science topics include CR propagation, calibration of the IC gamma-ray model, testing hypotheses regarding the origin of HE energy cosmic-ray electrons, searching for any signature of Kaluza Klein Dark Matter annihilation, and measuring the HE electron anisotropy. We expect to detect ~ 107 electrons above 20 GeV per year of LAT operation.

Dado 2007 3D模型对Swift X射线余辉的解释

主要内容:
还是用他们的cannonball模型，解释目前X射线的四段光变的现象。

精彩摘抄:


文章信息:
arXiv:0706.0880 [ps, pdf, other] : Title: On the X-Ray emission of Gamma Ray Bursts
Authors: Shlomo Dado, Arnon Dar, Alvaro De Rujula
Comments: 45 pages, 8 (multiple) figures

Recent data gathered and triggered by the SWIFT satellite have greatly improved our knowledge of long-duration gamma ray bursts (GRBs) and X-ray flashes (XRFs). This is particularly the case for the X-ray data at all times. We show that the entire X-ray observations are in excellent agreement with the predictions of the `cannonball' model of GRBs and XRFs, which are based on simple physics and were published long before the launch of SWIFT. Two mechanisms underlie these predictions: inverse Compton scattering and synchrotron radiation, generally dominant at early and late times, respectively. The former mechanism provides a unified description of the gamma-ray peaks, X-ray flares and even the optical `humps' seen in some favourable cases; i.e. their very different durations, fluxes and peak-times are related precisely as predicted. The observed smooth or bumpy fast decay of the X-ray light curve is correctly described case-by-case, in minute detail. The `canonical' X-ray plateau, as well as the subsequent gradual steepening of the afterglow to an asymptotic power-law decay, are as foretold. So are the chromatic and achromatic properties of the light-curves.

Thoene 2007 GRB 060505的宿主星系

主要内容:
给出了该暴宿主星系的空间分辨，得到改宿主星系为Sbc型，在一般长暴不常见；暴大致处于恒星形成区，又和4s持续时间定为短暴不一致。

精彩摘抄:


文章信息:
arXiv:0706.0674 [ps, pdf, other] : Title: The spatially resolved host of GRB 060505 and implications for the nature of the progenitor
Authors: Christina C. Thoene, Johan P. U. Fynbo
Comments: 5 pages, 1 figure. Proceedings of the Amsterdam conference, 10 years of GRB afterglows, March 19-23, 2007, to appear in New Astronomy Reviews

We present a study of the host galaxy of the Gamma-Ray Burst (GRB) of May 5 2006 (GRB 060505). The host is spatially resolved in both imaging data and in a long slit spectrum including the GRB site. We find the galaxy to be a Sbc spiral, which is unusual for a long GRB host galaxy. The site of the GRB is considerably different from the rest of the galaxy with intense star formation, low metallicity and a young age. This suggest a massive stellar progenitor rather than a merger of compact objects which has been suggested based on the the relatively short duration of T_90=4s for the prompt emission.