Qi 2008 SN Ia 和GRB一起限制暗能量参数

主要内容:


精彩摘抄:


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

主要内容:


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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

主要内容:


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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

主要内容:


精彩摘抄:


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

主要内容:


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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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Matteucc 2008 大质量恒星对星系化学演化的贡献

主要内容:
其中提到了Ibc型超新星和伽玛暴的诞生率的比例，后者只有前者的0.1-1% （但应该没有考虑伽玛暴的喷流效应）.

精彩摘抄:


文章信息:

· arXiv e-print (arXiv:0803.3016)

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Title:		The role of massive stars in galactic chemical evolution
Authors:		Matteucci, Francesca
Publication:		eprint arXiv:0803.3016
Publication Date:		03/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		12 pages, 6 Figures. To appear on the Proceedings of the IAUS 250
Bibliographic Code:		2008arXiv0803.3016M

Abstract

I will review the role of massive stars in galactic evolution both from the nucleosynthesis and energetics point of view. In particular, I will highlight some important observational facts explained by means of massive stars in galaxies of different morphological type: the Milky Way, ellipticals and dwarf spheroidals. I will describe first the time-delay model and its interpretation in terms of abundance ratios in galaxies, then I will discuss the importance of mass loss in massive stars to reproduce the data in the Galactic bulge and disk. I will discuss also how massive stars can be important producers of primary nitrogen if rotation in stellar models is taken into account. Concerning elliptical galaxies, I will show that to reproduce the observed [Mg/Fe] versus Mass relation in these galaxies it is necessary to assume a more important role of massive stars in more massive galaxies and that this can be achieved by means of downsizing in star formation. I will discuss how massive stars are responsible in triggering galactic winds both in ellipticals and dwarf spheroidals. These latter systems show a low overabundance of alpha-elements relative to Fe with respect to Galactic stars of the same [Fe/H]: this is interpreted as due to a slow star formation coupled with very efficient galactic winds. Finally, I will show a comparison between the predicted Type Ib/c rates in galaxies and the observed GRB rate and how we can impose constraints on the mechanism of galaxy formation by studying the GRB rate at high redshift.

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Savaglio 2008 伽玛暴宿主星系统计

主要内容:
89% of the hosts are at z < 1.6.
There is no compelling evidence that GRB hosts are peculiar galaxies.

精彩摘抄:


文章信息:

arXiv:0803.2718 [pdf, other]

Title: The Galaxy Population Hosting Gamma-Ray Bursts

Authors: S. Savaglio (MPE), K. Glazebrook (Swinburne University), D. Le Borgne (CEA/Saclay)

Comments: 34 pages, 19 figures, 11 tables, submitted to ApJ, revised version after first referee report

Subjects: Astrophysics (astro-ph)

We present the most extensive and complete study of the properties for the largest sample (46 objects) of gamma-ray burst (GRB) host galaxies. The redshift interval and the mean redshift of the sample are 0 lt z lt 6.3 z="0.96" a_v="0.5.">

GRB 080319B--注定不平凡的暴

GCN collections:
http://gcn.gsfc.nasa.gov/other/080319.gcn3

http://isdc.unige.ch/Soft/ibas/results/triggers/spiacs/2008-03/2008-03-19T06-12-46.8589-06429-00007-0.png
BAT data, here is more
http://gcn.gsfc.nasa.gov/notices_s/306757/BA/

XRT (normal)



Optical comparison

Optical live image, by pi-of-the-sky
http://grb.fuw.edu.pl/pi/index.html


Optical prompt and afterglow light curves, by pi-of-the-sky.


Another prompt optical observation
http://vo.astronet.ru/~karpov/grb080319b_lc_10.gif
Karpov
Special Astrophysical Observatory of Russian Academy of Sciences, Russia
GCN 7502

Live optical image before and after the burst trigger. from
http://vo.astronet.ru/~karpov


Pre-burst optical data by SDSS:
http://mizar.as.arizona.edu/~grb/public/GRB080319B/
or GCN7465

XRT, UVOT image
http://swift.gsfc.nasa.gov/docs/swift/results/releases/images/080319B/

一个红移达到0.937这么远的暴，居然光学瞬时辐射有6个星等！

van Putten 2008 黑洞相对论效应产生高能非热辐射

主要内容:


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文章信息:

· arXiv e-print (arXiv:0803.2067)

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Title:		Non-thermal high-energy emissions from black holes by a relativistic capillary effect
Authors:		van Putten, Maurice H. P. M.
Publication:		eprint arXiv:0803.2067
Publication Date:		03/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		1 figure
Bibliographic Code:		2008arXiv0803.2067V

Abstract

Gravitational spin-orbit interactions induce a relativistic capillary effect along open magnetic flux-tubes, that join the event horizon of a spinning black hole to infinity. It launches a leptonic outflow from electron-positron pairs created near the black hole, which terminates in an ultra-relativistic Alfv\'en wave. Upstream to infinity, it maintains a clean linear accelerator for baryons picked-up from an ionized ambient environment. We apply it to the origin of UHECRs and to spectral energy correlations in cosmological gamma-ray bursts. The former is identified with the Fermi-level of the black hole event horizon, the latter with a correlation $E_pT_{90}^{1/2}\simeq E_\gamma$ in HETE-II and Swift data.

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搬家的一个困难：blogger貌似还不能拷贝图片到自己服务器上

下面这个图片就不是在blogger的服务器上，而是一个网页链接

Nomoto 2008 伽玛暴和极端贫金属星的关联

主要内容:
作为早期宇宙核合成的探针

精彩摘抄:


文章信息:

· arXiv e-print (arXiv:0803.1964)

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Title:		The Connection between Gamma-Ray Bursts and Extremely Metal-Poor Stars as Nucleosynthetic Probes of the Early Universe
Authors:		Nomoto, K.; Tominaga, N.; Tanaka, M.; Maeda, K.; Umeda, H.
Publication:		eprint arXiv:0803.1964
Publication Date:		03/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		8 pages, 6 figures. To appear in "Massive Stars as Cosmic Engines", Proceedings of IAU Symposium 250 (December 2007, Kauai), eds. F. Bresolin, P.A. Crowther, & J. Puls (Cambridge Univ. Press)
Bibliographic Code:		2008arXiv0803.1964N

Abstract

The connection between the long GRBs and Type Ic Supernovae (SNe) has revealed the interesting diversity: (i) GRB-SNe, (ii) Non-GRB Hypernovae (HNe), (iii) X-Ray Flash (XRF)-SNe, and (iv) Non-SN GRBs (or dark HNe). We show that nucleosynthetic properties found in the above diversity are connected to the variation of the abundance patterns of extremely-metal-poor (EMP) stars, such as the excess of C, Co, Zn relative to Fe. We explain such a connection in a unified manner as nucleosynthesis of hyper-aspherical (jet-induced) explosions Pop III core-collapse SNe. We show that (1) the explosions with large energy deposition rate, $\dot{E}_{\rm dep}$, are observed as GRB-HNe and their yields can explain the abundances of normal EMP stars, and (2) the explosions with small $\dot{E}_{\rm dep}$ are observed as GRBs without bright SNe and can be responsible for the formation of the C-rich EMP (CEMP) and the hyper metal-poor (HMP) stars. We thus propose that GRB-HNe and the Non-SN GRBs (dark HNe) belong to a continuous series of BH-forming stellar deaths with the relativistic jets of different $\dot{E}_{\rm dep}$.

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Panaitescu 2008 Swift的光学余辉统计

主要内容:
把光学余辉统计起来，分了四类：早期快上升的，早期慢上升的，有平台的和直接下降的。但没解决什么问题。有提出了一个统计关系：peak flux – peak epoch relation。

精彩摘抄:
光学余辉的三类：含上升的，纯下降，平台

文章信息:

· arXiv e-print (arXiv:0803.1872)

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Title:		Taxonomy of GRB optical light-curves: identification of a salient class of early afterglows
Authors:		Panaitescu, A.; Vestrand, W. T.
Publication:		eprint arXiv:0803.1872
Publication Date:		03/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		8 pages, submitted to MNRAS
Bibliographic Code:		2008arXiv0803.1872P

Abstract

The temporal behaviour of the early optical emission from Gamma-Ray Burst afterglows can be divided in four classes: fast-rising with an early peak, slow-rising with a late peak, flat plateaus, and rapid decays since first measurement. The fast-rising optical afterglows display correlations among peak flux, peak epoch, and post-peak power-law decay index that can be explained with a structured outflow seen off-axis, but the shock origin (reverse or forward) of the optical emission cannot be determined. The afterglows with plateaus and slow-rises may be accommodated by the same model, if observer location offsets are larger than for the fast-rising afterglows, or could be due to a long-lived injection of energy and/or ejecta in the blast-wave. If better calibrated with more afterglows, the peak flux-peak epoch relation exhibited by the fast and slow-rising optical light-curves could provide a way to use this type of afterglows as standard candles.

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McBreen 2008 Spectral lag of GRB 060505

主要内容:
GRB 060614 almost has no spectral time lag, so it can be classified into short burst. But this work find GRB 060505 has lag about 0.36 s, maybe in long bursts category (but without SN component).

精彩摘抄:
可以看到GRB060614 GRB 060505的time lag在不同的区域

文章信息:

· arXiv e-print (arXiv:0803.1919)

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Title:		The Spectral Lag of GRB060505: A Likely Member of the Long Duration Class
Authors:		McBreen, S.; Foley, S.; Watson, D.; Hanlon, L.; Malesani, D.; Fynbo, J. P. U.; Kann, D. A.; Gehrels, N.; McGlynn, S.; Palmer, D.
Publication:		eprint arXiv:0803.1919
Publication Date:		03/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		Accepted by ApJL, 5 pages, 3 Figures
Bibliographic Code:		2008arXiv0803.1919M

Abstract

Two long gamma-ray bursts, GRB 060505 and GRB 060614, occurred in nearby galaxies at redshifts of 0.089 and 0.125 respectively. Due to their proximity and durations, deep follow-up campaigns to search for supernovae (SNe) were initiated. However none were found in either case, to limits more than two orders of magnitude fainter than the prototypical GRB-associated SN, 1998bw. It was suggested that the bursts, in spite of their durations (4 and 102 s), belonged to the population of short GRBs which has been shown to be unrelated to SNe. In the case of GRB 060614 this argument was based on a number of indicators, including the negligible spectral lag, which is consistent with that of short bursts. GRB 060505 has a shorter duration, but no spectral lag was measured. We present the spectral lag measurements of GRB 060505 using Suzakus Wide Area Monitor and the Swift Burst Alert Telescope. We find that the lag is 0.36+/- 0.05 s, inconsistent with the lags of short bursts and consistent with the properties of long bursts and SN-GRBs. These results support the association of GRB 060505 with other low-luminosity GRBs also found in star-forming galaxies and indicates that at least some massive stars may die without bright SNe.

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Burrows 2008 XRT Observation statistics

主要内容:


精彩摘抄:


文章信息:

· arXiv e-print (arXiv:0803.1844)

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Title:		The Swift X-Ray Telescope: Status and Performance
Authors:		Burrows, David N.; Kennea, J. A.; Abbey, A. F.; Beardmore, A.; Campana, S.; Capalbi, M.; Chincarini, G.; Cusumano, G.; Evans, P. A.; Hill, J. E.; Giommi, P.; Goad, M.; Godet, O.; Moretti, A.; Morris, D. C.; Osborne, J. P.; Pagani, C.; Page, K. L.; Perri, M.; Racusin, J.; Romano, P.; Starling, R. L. C.; Tagliaferri, G.; Tamburelli, F.; Tyler, L. G.; Willingale, R.
Publication:		eprint arXiv:0803.1844
Publication Date:		03/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		9 pages, 14 figures; Proc. SPIE, ed. O. H. W. Siegmund, Vol. 6686, p. 668607-1 to 668607-9, (2007)
Bibliographic Code:		2008arXiv0803.1844B

Abstract

We present science highlights and performance from the Swift X-ray Telescope (XRT), which was launched on November 20, 2004. The XRT covers the 0.2-10 keV band, and spends most of its time observing gamma-ray burst (GRB)afterglows, though it has also performed observations of many other objects. By mid-August 2007, the XRT had observed over 220 GRB afterglows, detecting about 96% of them. The XRT positions enable followup ground-based optical observations, with roughly 60% of the afterglows detected at optical or near IR wavelengths. Redshifts are measured for 33% of X-ray afterglows. Science highlights include the discovery of flaring behavior at quite late times, with implications for GRB central engines; localization of short GRBs, leading to observational support for compact merger progenitors for this class of bursts; a mysterious plateau phase to GRB afterglows; as well as many other interesting observations such as X-ray emission from comets, novae, galactic transients, and other objects.

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Foley 2008 INTEGRAL暴的一些统计

主要内容:
包含了大量的数据！
统计主要是谱上的，还有L_p, E_p, spectral lag, redshift等

精彩摘抄:
各个卫星所观测到的暴和余辉的个数

文章信息:

· arXiv e-print (arXiv:0803.1821)

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Title:		Global characteristics of GRBs observed with INTEGRAL and the inferred large population of low-luminosity GRBs
Authors:		Foley, S.; McGlynn, S.; Hanlon, L.; McBreen, S.; McBreen, B.
Publication:		eprint arXiv:0803.1821
Publication Date:		03/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		22 pages, 13 figures and appendix, accepted for publication in A&A
Bibliographic Code:		2008arXiv0803.1821F

Abstract

INTEGRAL has two sensitive gamma-ray instruments that have detected 46 gamma-ray bursts (GRBs) up to July 2007. We present the spectral, spatial, and temporal properties of the bursts in the INTEGRAL GRB catalogue using data from the imager, IBIS, and spectrometer, SPI. Spectral properties of the GRBs are determined using power-law, Band model and quasithermal model fits to the prompt emission. Spectral lags, i.e. the time delay in the arrival of low-energy gamma-rays with respect to high-energy gamma-rays, are measured for 31 of the GRBs. The photon index distribution of power-law fits to the prompt emission spectra is consistent with that obtained by Swift. The peak flux distribution shows that INTEGRAL detects proportionally more weak GRBs than Swift because of its higher sensitivity in a smaller field of view. The all-sky rate of GRBs above ~0.15 ph cm^-2 s^-1 is ~1400 yr^-1 in the fully coded field of view of IBIS. Two groups are identified in the spectral lag distribution, one with short lags <0.75>0.75 s. Most of the long-lag GRBs are inferred to have low redshifts because of their long spectral lags, their tendency to have low peak energies and their faint optical and X-ray afterglows. They are mainly observed in the direction of the supergalactic plane with a quadrupole moment of Q=-0.225+/-0.090 and hence reflect the local large-scale structure of the Universe. The rate of long-lag GRBs with inferred low luminosity is ~25% of Type Ib/c supernovae. Some of these bursts could be produced by the collapse of a massive star without a supernova or by a different progenitor, such as the merger of two white dwarfs or a white dwarf with a neutron star or black hole, possibly in the cluster environment without a host galaxy.

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Hakkila 2008 time lag, 峰值光度和时标之间的统计关系

主要内容:
time lag, 峰值光度和时标之间有比较好的统计关系。基本上，spectral time lag越短，峰值亮度越大，duration越长(我担心duration越长从而谱时延越短是因为pulse的时标长了，时延不清楚，从而以为比较短的，也就是这个关系不是内禀的)。

精彩摘抄:
L_peak vs Pulse duration

文章信息:

· arXiv e-print (arXiv:0803.1655)

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Title:		Correlations Between Lag, Luminosity, and Duration in Gamma-ray Burst Pulses
Authors:		Hakkila, Jon; Giblin, Timothy W.; Norris, Jay P.; Fragile, P. Chris; Bonnell, Jerry T.
Publication:		eprint arXiv:0803.1655
Publication Date:		03/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		14 pages, 4 figures, 1 table; accepted for publication in Astrophysical Journal Letters
Bibliographic Code:		2008arXiv0803.1655H

Abstract

We derive a new peak lag vs. peak luminosity relation in gamma-ray burst (GRB) pulses. We demonstrate conclusively that GRB spectral lags are pulse rather than burst properties and show how the lag vs. luminosity relation determined from CCF measurements of burst properties is essentially just a rough measure of this newly derived relation for individual pulses. We further show that most GRB pulses have correlated properties: short-lag pulses have shorter durations, are more luminous, and are harder within a burst than long-lag pulses. We also uncover a new pulse duration vs. pulse peak luminosity relation, and indicate that long-lag pulses often precede short-lag pulses. Although most pulse behaviors are supportive of internal shocks (including long-lag pulses), we identify some pulse shapes that could result from external shocks.

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Swift卫星的漂亮照片

来自NASA网址，http://www.nasa.gov/vision/universe/watchtheskies/swift_multimedia.html
看起来好假，虽然很漂亮。但网站上没说这是艺术家的图片。不过从这个网页出现的时间上来说应该是在卫星发射之前，所以应该是想像的。

Gruzinov 2008 企图第一性原理数值计算出伽玛暴中磁场产生

主要内容:
给出了大致方法，应该是还没有结果。认为2D的模拟肯定产生不了磁场，必须3D.

精彩摘抄:


文章信息:

· arXiv e-print (arXiv:0803.1182)

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Title:		GRB: magnetic fields, cosmic rays, and emission from first principles?
Authors:		Gruzinov, Andrei
Publication:		eprint arXiv:0803.1182
Publication Date:		03/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		5 pages
Bibliographic Code:		2008arXiv0803.1182G

Abstract

We describe a scenario for large-scale magnetic field generation and particle acceleration in a collisionless collision of cold plasma clouds. A first-principle (i.e. using particles) numerical simulation of this process might be possible. Our scenario is essentially 3D. We argue that {\it large-scale} magnetic fields are not generated in 2D, even in collisionless plasma. We calculate and numerically simulate magnetic field generation by relativistic collisionless Kelvin-Helmholtz instability in 2D. Collisionless tangential discontinuity might be more important than collisionless shock, because tangential discontinuity remains unstable even in the hydro limit, when the shock stabilizes.

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Graefener 2008 Mass loss from late-type WN stars

主要内容:


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文章信息:

· arXiv e-print (arXiv:0803.0866)

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Title:		Mass loss from late-type WN stars and its Z-dependence: very massive stars approaching the Eddington limit
Authors:		Graefener, G.; Hamann, W. -R.
Publication:		eprint arXiv:0803.0866
Publication Date:		03/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		16 pages, 10 figures, accepted by A&A
Bibliographic Code:		2008arXiv0803.0866G

Abstract

The mass loss from Wolf-Rayet (WR) stars is of fundamental importance for the final fate of massive stars and their chemical yields. Its Z-dependence is discussed in relation to the formation of long-duration Gamma Ray Bursts (GRBs) and the yields from early stellar generations. However, the mechanism of formation of WR-type stellar winds is still under debate. We present the first fully self-consistent atmosphere/wind models for late-type WN stars. We investigate the mechanisms leading to their strong mass loss, and examine the dependence on stellar parameters, in particular on the metallicity Z. We identify WNL stars as very massive stars close to the Eddington limit, potentially still in the phase of central H-burning. Due to their high L/M ratios, these stars develop optically thick, radiatively driven winds. These winds show qualitatively different properties than the thin winds of OB stars. The resultant mass loss depends strongly on Z, but also on the Eddington factor, and the stellar temperature. We combine our results in a parametrized mass loss recipe for WNL stars. According to our present model computations, stars close to the Eddington limit tend to form strong WR-type winds, even at very low Z. Our models thus predict an efficient mass loss mechanism for low metallicity stars. For extremely metal-poor stars, we find that the self-enrichment with primary nitrogen can drive WR-type mass loss. These first WN stars might play an important role in the enrichment of the early ISM with freshly produced nitrogen.

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Komatsu 2008 WMAP 5年观测结果

主要内容:
利用5年的数据重新定了一遍omega_m, omega_lambda, omega_k, 等宇宙学参数的值。

精彩摘抄:


文章信息:

arXiv:0803.0547 [ps, pdf, other]

Title: Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation

Authors: E. Komatsu, J. Dunkley, M. R. Nolta, C. L. Bennett, B. Gold, G. Hinshaw, N. Jarosik, D. Larson, M. Limon, L. Page, D. N. Spergel, M. Halpern, R. S. Hill, A. Kogut, S. S. Meyer, G. S. Tucker, J. L. Weiland, E. Wollack, E. L. Wright

Comments: 49 pages, 20 figures, submitted to ApJS

Subjects: Astrophysics (astro-ph)

(Abridged) The WMAP 5-year data strongly limit deviations from the minimal LCDM model. We constrain the physics of inflation via Gaussianity, adiabaticity, the power spectrum shape, gravitational waves, and spatial curvature. We also constrain the properties of dark energy, parity-violation, and neutrinos. We detect no convincing deviations from the minimal model. The parameters of the LCDM model, derived from WMAP combined with the distance measurements from the Type Ia supernovae (SN) and the Baryon Acoustic Oscillations (BAO), are: Omega_b=0.0462+-0.0015, Omega_c=0.233+-0.013, Omega_Lambda=0.721+-0.015, H_0=70.1+-1.3 km/s/Mpc, n_s=0.960+0.014-0.013, tau=0.084+-0.016, and sigma_8=0.817+-0.026. With WMAP+BAO+SN, we find the tensor-to-scalar ratio r<0.20>1 is disfavored regardless of r. We obtain tight, simultaneous limits on the (constant) equation of state of dark energy and curvature. We provide a set of "WMAP distance priors," to test a variety of dark energy models. We test a time-dependent w with a present value constrained as -0.38<1+w_0<0.14>

Klotz 2008 GRB 060904B and GRB 070420的早期光学余辉

主要内容:


精彩摘抄:
GRB 060904B 光学和X射线
GRB 070420 光学和X射线 光变曲线

文章信息:

· arXiv e-print (arXiv:0803.0505)

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Title:		Early emission of rising optical afterglows: The case of GRB 060904B and GRB 070420
Authors:		Klotz, A.; Gendre, B.; Stratta, G.; Galli, A.; Corsi, A.; Preger, B.; Cutini, S.; Pelangeon, A.; Atteia, J. L.; Boer, M.; Piro, L.
Publication:		eprint arXiv:0803.0505
Publication Date:		03/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		11 pages, 5 color figues, 2 b&w figures, accepted for publication by Astronomy and Astrophysics
Bibliographic Code:		2008arXiv0803.0505K

Abstract

We present the time-resolved optical emission of gamma-ray bursts GRB 060904B and GRB 070420 during their prompt and early afterglow phases. We used time resolved photometry from optical data taken by the TAROT telescope and time resolved spectroscopy at high energies from the Swift spacecraft instrument. The optical emissions of both GRBs are found to increase from the end of the prompt phase, passing to a maximum of brightness at t_{peak}=9.2 min and 3.3 min for GRB 060904B and GRB 070420 respectively and then decrease. GRB 060904B presents a large optical plateau and a very large X-ray flare. We argue that the very large X-flare occurring near t_{peak} is produced by an extended internal engine activity and is only a coincidence with the optical emission. GRB 070420 observations would support this idea because there was no X-flare during the optical peak. The nature of the optical plateau of GRB 060904B is less clear and might be related to the late energy injection.

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