Kostelecky 2008 罗伦兹违背的天文检测

主要内容:


精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0809.2846)

· References in the Article

·

· Translate This Page

Title:		Astrophysical Tests of Lorentz and CPT Violation with Photons
Authors:		Kostelecky, Alan; Mewes, Matthew
Publication:		eprint arXiv:0809.2846
Publication Date:		09/2008
Origin:		ARXIV
Keywords:		Astrophysics, General Relativity and Quantum Cosmology, High Energy Physics - Phenomenology
Comment:		11 pages
Bibliographic Code:		2008arXiv0809.2846K

Abstract

A general framework for tests of Lorentz invariance with electromagnetic waves is presented, allowing for operators of arbitrary mass dimension. Signatures of Lorentz violations include vacuum birefringence, vacuum dispersion, and anisotropies. Sensitive searches for violations using sources such as active galaxies, gamma-ray bursts, and the cosmic microwave background are discussed. Direction-dependent dispersion constraints are obtained on operators of dimension 6 and 8 using gamma-ray bursts and the blazar Markarian 501. Stringent constraints on operators of dimension 3 are found using 5-year data from the Wilkinson Microwave Anisotropy Probe. No evidence appears for isotropic Lorentz violation, while some support at one sigma is found for anisotropic violation.

---

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

Chen 2008 由于余辉而发现的高红移星暴矮星系

主要内容:


精彩摘抄:


文章信息:

· arXiv e-print (arXiv:0809.2608)

· References in the Article

·

· Translate This Page

Title:		High-Redshift Starbursting Dwarf Galaxies Revealed by GRB Afterglows
Authors:		Chen, Hsiao-Wen; Perley, Daniel A.; Pollack, Lindsey K.; Prochaska, J. X.; Bloom, J. S.; Dessauges-Zavadsky, M.; Pettini, M.; Lopez, S.; Dall'Aglio, A.; Becker, G. D.
Publication:		eprint arXiv:0809.2608
Publication Date:		09/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		24 emulateapj pages, 24 figures, ApJ in press; full-resolution version available at http://lambda.uchicago.edu/public/tmp/ghost.pdf
Bibliographic Code:		2008arXiv0809.2608C

Abstract

We present a study of 15 long-duration gamma-ray burst (GRB) host galaxies at z>2. The GRBs are selected with available early-time afterglow spectra in order to compare interstellar medium (ISM) absorption-line properties with stellar properties of the host galaxies. In addition to five previously studied hosts, we consider new detections for the host galaxies of GRB050820 and GRB060206 and place 2-sigma upper limits to the luminosities of the remaining unidentified hosts. We examine the nature of the host galaxy population and find that (1) the UV luminosity distribution of GRB host galaxies is consistent with expectations from a UV luminosity weighted random galaxy population with a median luminosity of =0.1 L*; (2) there exists a moderate correlation between UV luminosity and SiII 1526 absorption width, which together with the observed large line widths of W(1526)>1.5 Ang for a large fraction of the objects suggests a galactic outflow driven velocity field in the host galaxies; (3) there is tentative evidence for a trend of declining ISM metallicity with decreasing galaxy luminosity in the star-forming galaxy population at z=2-4; (4) the interstellar UV radiation field is found ~ 35-350 times higher in GRB hosts than the Galactic mean value; and (5) additional galaxies are found at <>2, and demonstrates that high spatial resolution images are necessary for an accurate identification of GRB host galaxies in the presence of strong intervening absorbers.

---

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

Aharonian 2008 HESS对GRB 060602B的观测

主要内容:


精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0809.2334)

· References in the Article

·

· Translate This Page

Title:		H.E.S.S. Observations of the Prompt and Afterglow Phases of GRB 060602B
Authors:		HESS Collaboration: F. Aharonian
Publication:		eprint arXiv:0809.2334
Publication Date:		09/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		8 pages, 4 figures, 1 table; ApJ in press
Bibliographic Code:		2008arXiv0809.2334H

Abstract

We report on the first completely simultaneous observation of a gamma-ray burst (GRB) using an array of Imaging Atmospheric Cherenkov Telescopes which is sensitive to photons in the very-high-energy (VHE) gamma-ray range (>~100 GeV). On 2006 June 2, the Swift Burst Alert Telescope (BAT) registered an unusually soft gamma-ray burst (GRB 060602B). The burst position was under observation using the High Energy Stereoscopic System (H.E.S.S.) at the time the burst occurred. Data were taken before, during, and after the burst. A total of 5 hours of observations were obtained during the night of 2006 June 2-3, and 5 additional hours were obtained over the next 3 nights. No VHE gamma-ray signal was found during the period covered by the H.E.S.S. observations. The 99% confidence level flux upper limit (>1 TeV) for the prompt phase (9s) of GRB 060602B is 2.9x10^-9 erg cm^-2 s^-1. Due to the very soft BAT spectrum of the burst compared to other Swift GRBs and its proximity to the Galactic center, the burst is likely associated with a Galactic X-ray burster, although the possibility of it being a cosmological GRB cannot be ruled out. We discuss the implications of our flux limits in the context of these two bursting scenarios.

---

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

Chincarini 2008 伽玛暴的耀发II

主要内容:
主要关于050904和050724的

精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0809.2151)

·

· Translate This Page

Title:		Flares in Gamma Ray Bursts (II)
Authors:		Chincarini, G.; Margutti, R.; Mao, J.; Pasotti, F.; Guidorzi, C.; Covino, S.; D'avanzo, P.
Publication:		eprint arXiv:0809.2151
Publication Date:		09/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		paper to be published in COSPAR conference at Montreal
Bibliographic Code:		2008arXiv0809.2151C

Abstract

We illustrate some of the preliminary results obtained with a new sample of flares and a new analysis. In these proceedings we deal mainly with the analysis related to the flare energy and describe the work in progress to measure the average flare luminosity curve. We discuss in brief GRB050904 and GRB050724 for matters relevant to this work. In particular we measure the contribution given to the flares by GRB050904 and give a new interpretation for the decaying early XRT light curve of GRB050724. We briefly illustrate the first evidence that the early decay is given by the subsequent emission of events with Width/TPeak <> Bibtex entry for this abstract Preferred format for this abstract (see Preferences)

Martayan 2008 麦哲伦云的长暴诞生率

主要内容:


精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0809.2205)

· References in the Article

·

· Translate This Page

Title:		ZAMS rotational velocities of Be/Oe stars and LGRBs progenitors in the Magellanic Clouds
Authors:		Martayan, Christophe; Zorec, Jean; Fremat, Yves
Publication:		eprint arXiv:0809.2205
Publication Date:		09/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		poster IAUS256
Bibliographic Code:		2008arXiv0809.2205M

Abstract

The Large and Small Magellanic Clouds are priviledged environments to perform tests of theoretical predictions at low metallicity on rotational velocities and stellar evolution. According to theoretical predictions, the rotational velocities of B-type stars are expected to be higher in low metallicity (LMC/SMC) than in high metallicity (MW) environments. To verify the models, we observed with the VLT-FLAMES 523 B and Be stars, which form, at the moment, the largest observed sample of these kind of objects in the MCs. We first determined the stellar fundamental parameters and we found that B and Be stars rotate faster in the MCs than in the MW. We also determined the first distribution of the average ZAMS rotational velocities versus the mass of Be stars. These results indicate that the appearance of Be stars is mass-, metallicity-, stellar evolution-, and star-formation regions-dependant. Moreover, the recent models of Long Gamma Ray Bursts progenitors foresee possible LGRBs progenitors at the SMC's metallicity. We confront these models with the observed (ZAMS rotational velocities, masses) distributions of the fastest rotators (Be and Oe stars) in our sample. Furthermore, we compare the corresponding predicted rates from our study with observed rates of LGRBs.

---

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

Stamatikos 2008 伽玛暴spectral lag和瞬时光学辐射的关系

主要内容:
从下图看，可能存在什么相关性。

精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0809.2132)

· References in the Article

·

· Translate This Page

Title:		A Correlation of Spectral Lag Evolution with Prompt Optical Emission in GRBs?
Authors:		Stamatikos, Michael; Ukwatta, Tilan N.; Sakamoto, Takanori; Dhuga, Kalvir S.
Publication:		eprint arXiv:0809.2132
Publication Date:		09/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		5 pages. Adapted from a contribution to the Proceedings of the 2008 Nanjing GRB Conference. Edited by Y. F. Huang, Z. G. Dai and B. Zhang
Bibliographic Code:		2008arXiv0809.2132S

Abstract

We report on observations of correlated behavior between the prompt gamma-ray and optical emission from GRB 080319B, which (i) strongly suggest that they occurred within the same astrophysical source region and (ii) indicate that their respective radiation mechanisms were most likely dynamically coupled. Our preliminary results, based upon a new cross-correlation function (CCF) methodology for determining the time-resolved spectral lag, are summarized as follows. First, the evolution in the arrival offset of prompt gamma-ray photon counts between Swift-BAT 15-25 keV and 50-100 keV energy bands (intrinsic gamma-ray spectral lag) appears to be anti-correlated with the arrival offset between prompt 15-350 keV gamma-rays and the optical emission observed by TORTORA (extrinsic optical/gamma-ray spectral lag), thus effectively partitioning the burst into two main episodes at ~T+28+/-2 sec. Second, prompt optical emission is nested within intervals of (a) trivial intrinsic gamma-ray spectral lag (~T+12+-2 and ~T+50+/-2 sec) with (b) discontinuities in the hard to soft evolution of the photon index for a power law fit to 15-150 keV Swift-BAT data (~T+8+/-2 and ~T+48+/-1 sec), both of which coincide with the rise (~T+10+/-1 sec) and decline (~T+50+/-1 sec) of prompt optical emission. This potential discovery, robust across heuristic permutations of BAT energy channels and varying temporal bin resolution, provides the first observational evidence for an implicit connection between spectral lag and the dynamics of shocks in the context of canonical fireball phenomenology.

---

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

Lin 2008 短暴可能在软谱段有更长时间的辐射

主要内容:


精彩摘抄:


文章信息:

arXiv:0809.1796 [ps, pdf, other]

Title: Extended Emission of Short Gamma-Ray Bursts

Authors: Lin Lin, En-Wei Liang, Bin-Bin Zhang, Shuang Nan Zhang

Comments: 2008 Nanjing GRB Conference

Subjects: Astrophysics (astro-ph)

Preliminary results of our analysis on the extended emission of short/medium duration GRBs observed with Swift/BAT are presented. The Bayesian blocks algorithm is used to analyze the burst durations and the temporal structure of the lightcurves in different energy bands. We show here the results of three bursts (GRBs 050724, 061006 and 070714B) that have a prominent soft extended emission component in our sample. The extended emission of these bursts is a continuous, flickering-liked component, lasting $\sim 100$ seconds post the GRB trigger at 15-25 keV bands. Without considering this component, the three bursts are classified as short GRBs, with $T_{90}=2\sim 3$ seconds. GRB 060614 has an emission component similar to the extended emission, but this component has pulse-liked structure, possibly indicating that this emission component is different from that observed in GRBs 050724, 061006, and 070714B. Further analysis on the spectral evolution behavior of the extended emission component is on going.

Curran 2008 用拟合余辉的办法定伽玛暴的红移

主要内容:


精彩摘抄:


文章信息:

arXiv:0809.1559 [ps, pdf, other]

Title: Robust photometric redshift determinations of gamma-ray burst afterglows at z > 2

Authors: P.A. Curran (1), R.A.M.J. Wijers (1), M.H.M. Heemskerk (1), R.L.C. Starling (2), K. Wiersema (2), A.J. van der Horst (3) ((1) U. of Amsterdam, (2) U. of Leicester, (3) NSSTC)

Comments: Accepted to A&A: 8 pages, 5 figures

Subjects: Astrophysics (astro-ph)

Theory suggests that about 10% of Swift-detected gamma-ray bursts (GRBs) will originate at redshifts greater than 5 yet a number of high redshift candidates may be left unconfirmed due to the lack of measured redshifts. Here we introduce our code, GRBz, a method of simultaneous multi-parameter fitting of GRB afterglow optical and near infrared, spectral energy distributions. It allows for early determinations of the photometric redshift, spectral index and host extinction to be made. We assume that GRB afterglow spectra are well represented by a power-law decay and model the effects of absorption due to the Lyman forest and host extinction. We use a genetic algorithm-based routine to simultaneously fit the parameters of interest, and a Monte Carlo error analysis. We use GRBs of previously determined spectroscopic redshifts to prove our method, while also introducing new near infrared data of GRB 990510 which further constrains the value of the host extinction. Our method is effective in estimating the photometric redshift of GRBs, relatively unbiased by assumptions of the afterglow spectral index or the host galaxy extinction. Monte Carlo error analysis is required as the method of error estimate based on the optimum population of the genetic algorithm underestimates errors significantly.

Dainotti 2008 Lb-Tb关系

主要内容:
文中叫a，实际上就是break time。

精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0809.1389)

· References in the Article

·

· Translate This Page

Title:		A time - luminosity correlation for Gamma Ray Bursts in the X - rays
Authors:		Dainotti, M. G.; Cardone, V. F.; Capozziello, S.
Publication:		eprint arXiv:0809.1389
Publication Date:		09/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		5 pages, 2 figures, accepted for publication on MNRAS Letters
Bibliographic Code:		2008arXiv0809.1389D

Abstract

Gamma ray bursts (GRBs) have recently attracted much attention as a possible way to extend the Hubble diagram to very high redshift. However, the large scatter in their intrinsic properties prevents directly using them as distance indicator so that the hunt is open for a relation involving an observable property to standardize GRBs in the same way as the Phillips law makes it possible to use Type Ia Supernovae (SNeIa) as standardizable candles. We use here the data on the X - ray decay curve and spectral index of a sample of GRBs observed with the Swift satellite. These data are used as input to a Bayesian statistical analysis looking for a correlation between the X - ray luminosity L_X(T_a) and the time constant T_a of the afterglow curve. We find a linear relation between \log{[L_X(T_a)]} and \log{[T_a/(1+z)]} with an intrinsic scatter sigma_{int} = 0.33 comparable to previously reported relations. Remarkably, both the slope and the intrinsic scatter are almost independent on the matter density Omega_M and the constant equation of state w of the dark energy component thus suggesting that the circularity problem is alleviated for the $L_X - T_a$ relation.

---

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

Giuliani 2008 AGILE观测到了比GRB 080514B暴本身时标更长的高能辐射

主要内容:
说EGRET也观测到了类似的现象的。
“Similar behavior was seen in the past from a few other GRBs observed with EGRET. ”

精彩摘抄:
最上面的是高能的光变，比伽玛暴本身的时标要长。

文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0809.1230)

· References in the Article

·

· Translate This Page

Title:		AGILE detection of delayed gamma-ray emission from GRB 080514B
Authors:		Giuliani, A.; Mereghetti, S.; Fornari, F.; Del Monte, E.; Feroci, M.; Marisaldi, M.; Esposito, P.; Perotti, F.; Tavani, M.; Argan, A.; Barbiellini, G.; Boffelli, F.; Bulgarelli, A.; Caraveo, P.; Cattaneo, P. W.; Chen, A. W.; Costa, E.; D'Ammando, F.; Di Cocco, G.; Donnarumma, I.; Evangelista, Y.; Fiorini, M.; Fuschino, F.; Galli, M.; Gianotti, F.; Labanti, C.; Lapshov, I.; Lazzarotto, F.; Lipari, P.; Longo, F.; Morselli, A.; Pacciani, L.; Pellizzoni, A.; Piano, G.; Picozza, P.; Prest, M.; Pucella, G.; Rapisarda, M.; Rappoldi, A.; Soffitta, P.; Trifoglio, M.; Trois, A.; Vallazza, E.; Vercellone, S.; Zanello, D.; Salotti, L.; Cutini, S.; Pittori, C.; Preger, B.; Santolamazza, P.; Verrecchia, F.; Gehrels, N.; Page, K.; Burrows, D.; Rossi, A.; Hurley, K.; Mitrofanov, I.; Boynton, W.
Publication:		eprint arXiv:0809.1230
Publication Date:		09/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		A&A letters, in press
Bibliographic Code:		2008arXiv0809.1230G

Abstract

GRB 080514B is the first gamma ray burst (GRB), since the time of EGRET, for which individual photons of energy above several tens of MeV have been detected with a pair-conversion tracker telescope. This burst was discovered with the Italian AGILE gamma-ray satellite. The GRB was localized with a cooperation by AGILE and the interplanetary network (IPN). The gamma-ray imager (GRID) estimate of the position, obtained before the SuperAGILE-IPN localization, is found to be consistent with the burst position. The hard X-ray emission observed by SuperAGILE lasted about 7 s, while there is evidence that the emission above 30 MeV extends for a longer duration (at least ~13 s). Similar behavior was seen in the past from a few other GRBs observed with EGRET. However, the latter measurements were affected, during the brightest phases, by instrumental dead time effects, resulting in only lower limits to the burst intensity. Thanks to the small dead time of the AGILE/GRID we could assess that in the case of GRB 080514B the gamma-ray to X-ray flux ratio changes significantly between the prompt and extended emission phase.

---

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