Greiner 2008 GRB 080129 的早期光学辐射

主要内容:


精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0811.4291)

·

· Translate This Page

Title:		A strong optical flare before the rising afterglow of GRB 080129
Authors:		Greiner, J.; Krühler, T.; McBreen, S.; Ajello, M.; Giannos, D.; Schwarz, R.; Savaglio, S.; Küpcü Yoldas, A.; Clemens, C.; Stefanescu, A.; Sala, G.; Bertoldi, F.; Szokoly, G.; Klose, S.
Publication:		eprint arXiv:0811.4291
Publication Date:		11/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		accepted for publ. in ApJ, 5 Figs
Bibliographic Code:		2008arXiv0811.4291G

Abstract

We report on GROND observations of a 40 sec duration (rest-frame) optical flare from GRB 080129 at redshift 4.349. The rise- and decay time follow a power law with indices +12 and -8, respectively, inconsistent with a reverse shock and a factor 10$^5$ faster than variability caused by ISM interaction. While optical flares have been seen in the past (e.g. GRB 990123, 041219B, 060111B and 080319B), for the first time, our observations not only resolve the optical flare into sub-components, but also provide a spectral energy distribution from the optical to the near-infrared once every minute. The delay of the flare relative to the GRB, its spectral energy distribution as well as the ratio of pulse widths suggest it to arise from residual collisions in GRB outflows \cite{liw08}.If this interpretation is correct and can be supported by more detailed modelling or observation in further GRBs, the delay measurement provides an independent, determination of the Lorentz factor of the outflow.

---

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

Ryde 2008 暴本身的黑体成份

主要内容:


精彩摘抄:
用双成份拟合BATSE的暴的谱

BB成份的温度随时间以幂律形式降低

黑体流量也随时间呈幂律变化, 拐折时间和温度的相同

推算出来的半径, 随时间增大.

文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0811.4135)

·

· Translate This Page

Title:		Quasi-blackbody component and radiative efficiency of the prompt emission of gamma-ray bursts
Authors:		Ryde, Felix; Pe'er, Asaf
Publication:		eprint arXiv:0811.4135
Publication Date:		11/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		38 pages, submitted to the Astrophysical Journal
Bibliographic Code:		2008arXiv0811.4135R

Abstract

We identify the spectral peak in the prompt emission of gamma-ray bursts (GRBs) with a quasi blackbody component. We show that thermal photons carry a significant fraction (~30 % to more than 50 %) of the prompt emission energy, thereby significantly contributing to the high radiative efficiency. We study a sample of 56 long bursts, all strong enough to allow time-resolved spectroscopy and show that it is possible to model the spectra with a Planck function combined with a single power-law, with the latter describing the non-thermal component in the observed 20-2000 keV range. We analyze the evolution of both the temperature and flux of the thermal component in 49 individual time-resolved pulses, for which the temporal coverage is sufficient, and find a recurring broken power-law behavior: the temperature is nearly constant during the first few seconds, after which it decays as a power law with a sample-averaged index of -0.68. The thermal flux first rises with an averaged index of 0.63 after which it decays with an averaged index of -2. The break times are the same to within errors. The ratio of the observed to the emergent flux typically exhibits a monotoneous power-law increase during the entire pulse and during complex bursts. We show here that the thermal emission can be used to study the properties of the photosphere, hence the physical parameters of the GRB fireball.

---

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

Zhang 2008 3D 相对论流体的MHD数值模拟Kelvin-Helmholtz不稳定性

主要内容:


精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0811.3638)

· References in the Article

·

· Translate This Page

Title:		Three-Dimensional Relativistic MHD Simulations of the Kelvin-Helmholtz Instability: Magnetic Field Amplification by a Turbulent Dynamo
Authors:		Zhang, Weiqun; MacFadyen, Andrew; Wang, Peng
Publication:		eprint arXiv:0811.3638
Publication Date:		11/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		submitted to ApJL, high-resolution version available at http://cosmo.nyu.edu/~wqzhang/publications/kh.pdf, movies of simulations available at http://cosmo.nyu.edu/~wqzhang/movies/
Bibliographic Code:		2008arXiv0811.3638Z

Abstract

Magnetic field strengths inferred for relativistic outflows including gamma-ray bursts (GRB) and active galactic nuclei (AGN) are larger than naively expected by orders of magnitude. We present three-dimensional relativistic magnetohydrodynamics (MHD) simulations demonstrating amplification and saturation of magnetic field by a macroscopic turbulent dynamo triggered by the Kelvin-Helmholtz shear instability. We find rapid growth of electromagnetic energy due to the stretching and folding of field lines in the turbulent velocity field resulting from non-linear development of the instability. Using conditions relevant for GRB internal shocks and late phases of GRB afterglow, we obtain amplification of the electromagnetic energy fraction to $\epsilon_B \sim 5 \times 10^{-3}$. This value decays slowly after the shear is dissipated and appears to be largely independent of the initial field strength. The conditions required for operation of the dynamo are the presence of velocity shear and some seed magnetization both of which are expected to be commonplace. We also find that the turbulent kinetic energy spectrum for the case studied obeys Kolmogorov's 5/3 law and that the electromagnetic energy spectrum is essentially flat with the bulk of the electromagnetic energy at small scales.

---

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

Fynbo 2008 GRB作为大质量星的探针

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:0811.3897)

· Table of Contents

· References in the Article

· Also-Read Articles (Reads History)

·

· Translate This Page

Title:		GRBs as Probes of Massive Stars Near and Far
Authors:		Fynbo, Johan P. U.; Malesani, Daniele
Affiliation:		AA(Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen O, Denmark jfynbo@dark-cosmology.dk), AB(Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen O, Denmark jfynbo@dark-cosmology.dk)
Publication:		Massive Stars as Cosmic Engines, Proceedings of the International Astronomical Union, IAU Symposium, Volume 250, p. 443-456
Publication Date:		00/2008
Origin:		CUP
Keywords:		gamma rays: bursts, galaxies: distances and redshifts
Abstract Copyright:		(c) 2008: Copyright © International Astronomical Union 2008
DOI:		10.1017/S1743921308020814
Bibliographic Code:		2008IAUS..250..443F

Abstract

Long-duration gamma-ray bursts are the manifestations of massive stellar death. Due to the immense energy release they are detectable from most of the observable universe. In this way they allow us to study the deaths of single (or binary) massive stars possibly throughout the full timespan massive stars have existed in the Universe. GRBs provide a means to infer information about the environments and typical galaxies in which massive stars are formed. Two main obstacles remain to be crossed before the full potential of GRBs as probes of massive stars can be harvested: i) we need to build more complete and well understood samples in order not to be fooled by biases, and ii) we need to understand to which extent GRBs may be intrinsically biased in the sense that they are only formed by a limited subset of massive stars defined by most likely a restricted metallicity interval. I describe the status of an ongoing effort to build a more complete sample of long-duration GRBs with measured redshifts. Already now we can conclude that the environments of GRB progenitors are very diverse with metallicities ranging from solar to a hundredth solar and extinction ranging from none to A_V > 5 mag. We have also identified a sightline with significant escape of Lyman continuum photons and another with a clear 2175 Å extinction bump.

---

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

Coward 2008 余辉响应时间对红移测量的偏差

主要内容:
趋势就是光学余辉被观测的时间越长, 越能确定高红移的暴.
注意这里的响应时间是整个观测的duration, 而不是第一次follow的反应时间.

精彩摘抄:
响应时间和红移的统计关系.

可是如果响应时间在100分钟左右的就没有红移大于2的, 这也太夸张了吧. 难道就不能通过宿主星系来确定一下红移? 同样大于1000分钟的就没有红移比较小的暴. 我怀疑这不是选择效应, 而是一个真实的趋势了

文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0811.3443)

· References in the Article

·

· Translate This Page

Title:		GRB optical afterglow and redshift selection effects: The learning curve effect at work
Authors:		Coward, D. M.
Publication:		eprint arXiv:0811.3443
Publication Date:		11/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		5 pages, 4 figures, MNRAS Letter (accepted)
Bibliographic Code:		2008arXiv0811.3443C

Abstract

We show how the observed gamma ray burst (GRB) optical afterglow (OA) and redshift distributions are changing in time from selection effects. For a subset of {\it Swift} triggered long duration bursts, we show that the mean time taken to acquire spectroscopic redshifts for a GRB OA has evolved to shorter times. We identify a strong correlation between the mean time taken to acquire a spectroscopic redshift and the measured redshift. This correlation reveals that shorter response times favour smaller redshift bursts. This is compelling evidence for a selection effect that biases longer response times with relatively brighter high redshift bursts. Conversely, for shorter response times, optically fainter bursts that are relatively closer are bright enough for spectroscopic redshifts to be acquired. This selection effect could explain why the average redshift, $\approx2.8$ measured in 2005, has evolved to $\approx2$, by mid 2008. Understanding these selection effects provides an important tool for separating the contributions of intrinsically faint bursts, those obscured by host galaxy dust and bursts not seen in the optical because their OAs are observed at late times. The study highlights the importance of rapid response telescopes capable of spectroscopy, and identifies a new redshift selection effect that has not been considered previously, namely the response time to measure the redshift.

---

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

Granot 2008 解析推导余辉辐射面的光度分布

主要内容:


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:0811.3248)

· References in the article

· Also-Read Articles (Reads History)

·

· Translate This Page

Title:		Analytic expressions for the surface brightness profile of gamma-ray burst afterglow images
Authors:		Granot, Jonathan
Affiliation:		Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield, Herts AL10 9AB;
Publication:		Monthly Notices of the Royal Astronomical Society: Letters, Volume 390, Issue 1, pp. L46-L50. (MNRAS Homepage)
Publication Date:		10/2008
Origin:		MNRAS
MNRAS Keywords:		radiation mechanisms: non-thermal , relativity , shock waves , gamma-rays: bursts
Abstract Copyright:		(c) Journal compilation © 2008 RAS
DOI:		10.1111/j.1745-3933.2008.00533.x
Bibliographic Code:		2008MNRAS.390L..46G

Abstract

The exact profile of a gamma-ray burst afterglow image on the plane of the sky can provide important constraints on the underlying physics. In particular, it can test whether the magnetic field in the emitting shocked external medium decreases significantly with the distance behind the shock front, or remains roughly constant. Moreover, it enables more accurate measurements of the afterglow image size and the expected scintillation properties. In this work, analytic expressions are derived for the afterglow image in power-law segments (PLSs) of the afterglow synchrotron spectrum in which the emission originates from a very thin layer just behind the shock, while simple semi-analytic expressions are derived for the remaining PLSs in which the emission arises from the bulk of the shocked fluid. In all cases, the expressions are for a general power-law external density profile, and are convenient to use in afterglow studies.

---

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

Sakmoto 2008 估计E_p的值

主要内容:
log E_p = 3.3-0.8\Gamma
其中\Gamma是光子谱指数

精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0811.3401)

· References in the Article

·

· Translate This Page

Title:		Epeak estimator for Gamma-Ray Bursts Observed by the Swift Burst Alert Telescope
Authors:		Sakamoto, T.; Sato, G.; Barbier, L.; Barthelmy, S. D.; Cummings, J. R.; Fenimore, E. E.; Gehrels, N.; Hullinger, D.; Krimm, H. A.; Lamb, D. Q.; Markwardt, C. B.; Palmer, D. M.; Parsons, A. M.; Stamatikos, M.; Tueller, J.; Ukwatta, T. N.
Publication:		eprint arXiv:0811.3401
Publication Date:		11/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		27 pages, 31 figures, accepted for publication in ApJ
Bibliographic Code:		2008arXiv0811.3401S

Abstract

We report a correlation based on a spectral simulation study of the prompt emission spectra of gamma-ray bursts (GRBs) detected by the Swift Burst Alert Telescope (BAT). The correlation is between the Epeak energy, which is the peak energy in the \nu F_\nu spectrum, and the photon index (\Gamma) derived from a simple power-law model. The Epeak - \Gamma relation, assuming the typical smoothly broken power-law spectrum of GRBs, is \log Epeak = 3.258 - 0.829\Gamma (1.3 < \Gamma <> Bibtex entry for this abstract Preferred format for this abstract (see Preferences)

Pélangeon 2008 HETE-2的暴看local的暴的诞生率

主要内容:
有所有HETE-II E_p, T_90
等的数据

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:0811.3304)

· References in the article

· Also-Read Articles (Reads History)

·

· Translate This Page

Title:		Intrinsic properties of a complete sample of HETE-2 gamma-ray bursts. A measure of the GRB rate in the Local Universe
Authors:		Pélangeon, A.; Atteia, J.-L.; Nakagawa, Y. E.; Hurley, K.; Yoshida, A.; Vanderspek, R.; Suzuki, M.; Kawai, N.; Pizzichini, G.; Boër, M.; Braga, J.; Crew, G.; Donaghy, T. Q.; Dezalay, J. P.; Doty, J.; Fenimore, E. E.; Galassi, M.; Graziani, C.; Jernigan, J. G.; Lamb, D. Q.; Levine, A.; Manchanda, J.; Martel, F.; Matsuoka, M.; Olive, J.-F.; Prigozhin, G.; Ricker, G. R.; Sakamoto, T.; Shirasaki, Y.; Sugita, S.; Takagishi, K.; Tamagawa, T.; Villasenor, J.; Woosley, S. E.; Yamauchi, M.
Publication:		Astronomy and Astrophysics, Volume 491, Issue 1, 2008, pp.157-171 (A&A Homepage)
Publication Date:		11/2008
Origin:		EDP
Keywords:		gamma rays: bursts, X-rays: bursts
DOI:		10.1051/0004-6361:200809709
Bibliographic Code:		2008A&A...491..157P

Abstract

Context: As a result of the numerous missions dedicated to the detection of Gamma-ray bursts (GRBs), the observed properties of these events are now well known. However, studying their parameters in the source frame is not simple since it requires having measurements of both the bursts' parameters and of their distances. Aims: Taking advantage of the forthcoming Catalog of the High Energy Transient Explorer 2 (HETE-2) mission, the aim of this paper is to evaluate the main properties of HETE-2 GRBs - the peak energy (E_peak), the duration (T₉₀) and the isotropic energy (E_iso) - in their source frames and to derive their unbiased distribution. Methods: We first construct a complete sample containing all the bursts localized by the Wide-Field X-ray Monitor (WXM) on-board HETE-2, which are selected with a uniform criterion and whose observed parameters can be constrained. We then derive the intrinsic E_peak, T₉₀ and E_iso distributions using their redshift when it is available, or their pseudo-redshift otherwise. We finally compute the “volume of detectability” V_max of each GRB, i.e. the volume of the universe in which the burst is bright enough to be part of our sample, and the corresponding number of GRB within their visibility volume N_Vmax, in order to derive a weight for each detected burst accounting both for the detection significance and the star formation history of the universe. Results: We obtain unbiased distributions of three intrinsic properties of HETE-2 GRBs: E_peak^intr, T₉₀^intr and the isotropic energy of the burst. These distributions clearly show the predominence of X-ray flashes (XRFs) in the global GRB population. We also derive the rate of local GRBs: R₀^H2 ⪆ 11 Gpc^-3 yr^-1, which is intermediate between the local rate obtained by considering only the “high-luminosity” bursts (~1 Gpc^-3 yr^-1) and that obtained by including the “low-luminosity” bursts (⪆200 Gpc^-3 yr^-1). Conclusions: This study shows that the XRFs are predominent in the GRB population and are closely linked to the “classical” GRBs. We show that HETE-2 detected no low-luminosity GRB like GRB 980425 or XRF 060218, due to the small size of its detectors, excluding this type of burst from our statistical analysis. The comparison of the GRB rate derived in this study with the known rate of type Ib/c supernovae clearly shows that the progenitors of SNe Ib/c must have some special characteristics in order to produce a gamma-ray burst or an X-ray flash.

Tables [see full textsee full text] and [see full textsee full text] are only available in electronic form at http://www.aanda.org

---

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

Zou 2008 GRB 080319B及其他几个暴的高能辐射

主要内容:
高能的辐射如果只考虑逆康普顿散射的话, 可能存在:
1. 内激波IC. 如果光学和伽玛射线来源不同的话, 可能有光学光子被伽玛区的电子IC； 伽玛光子被光学区的电子IC. 但二者自己的SSC的可能性不大, 光学区的能量太低, 2nd IC可能性更小； 伽玛区的直接到了KN区而被抑制.
2. 正反激波阶段的EIC. 主要可能是prompt阶段的光学光子被正向激波电子IC； 和伽玛光子被反向激波的电子IC. 二者内部的SSC可能性比较小, 不过也有可能.
3. 外激波的SSC.

精彩摘抄:


文章信息:

· arXiv e-print (arXiv:0811.2997)

· References in the Article

·

· Translate This Page

Title:		Expected high energy emission from GRB 080319B and origins of the GeV emission of GRBs 080514B, 080916C and 081024B
Authors:		Zou, Yuan-Chuan; Fan, Yi-Zhong; Piran, Tsvi
Publication:		eprint arXiv:0811.2997
Publication Date:		11/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		8 pages, including 3 figures and 1 table
Bibliographic Code:		2008arXiv0811.2997Z

Abstract

We calculate the high energy (sub-GeV to TeV) prompt and afterglow emission of GRB 080319B that was distinguished by a naked-eye optical flash and by an unusual strong early X-ray afterglow. There are three possible sources for high energy emission: the prompt optical and $\gamma$-ray photons IC scattered by the internal shock electrons, the prompt photons IC scattered by the early external reverse-forward shock electrons, and the higher band of the synchrotron and the synchrotron self-Compton emission of the external shock. There should have been in total $\sim 500$ high energy photons detectable for the Large Area Telescope (LAT) onboard the Fermi satellite, and $> 30$ photons of those with energy $> 10$ GeV. The $> 10$ GeV emission had a duration about twice that of the soft $\gamma$-rays. AGILE could have observed these energetic signals if it was not occulted by the Earth at that moment. The physical origins of the high energy emission detected in GRB 080514B, GRB 080916C and GRB 081024B are also discussed. These observations can be reasonably interpreted by available high energy emission models based on our current understanding of GRBs and afterglows.

---

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

Bietenholz 2008 VLBI Observations of SN 2008D

主要内容:
简单地说就是一正常超新星. 速度的upper limit是0.75 c.
和一般超新星的膨胀速度小于30, 000 km s−1也是一致的.

精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0811.3173)

· References in the Article

·

· Translate This Page

Title:		VLBI Observations of SN 2008D
Authors:		Bietenholz, M. F.; Soderberg, A. M.; Bartel, N.
Publication:		eprint arXiv:0811.3173
Publication Date:		11/2008
Origin:		ARXIV
Keywords:		Astrophysics
Bibliographic Code:		2008arXiv0811.3173B

Abstract

We report on two epochs of VLBI observations of the Type Ib/c supernova SN 2008D, which was associated with the X-ray outburst XRF 080109, At our first epoch, at t=30 days after the explosion, we observed at 22 and 8.4 GHz, and at our second, at t=133 days, at 8.4 and 5.0 GHz. The VLBI observations allow us to accurately measure the source's size and position at each epoch, and thus constrain its expansion velocity and proper motion. We find the source at best marginally resolved at both epochs, allowing us to place a 3sigma upper limit of ~0.75c on the expansion velocity of a circular source. For an elongated source, our measurements are compatible with mildly relativistic expansion. However, our 3sigma upper limit on the proper motion is 4 micro-arcsec/day, corresponding to an apparent velocity of <0.6c,>c. Taken together, our measurements argue against the presence of any long-lived relativistic outflow in SN 2008D. On the other hand, our measurements are consistent with the non-relativistic expansion velocities of <30,000> Bibtex entry for this abstract Preferred format for this abstract (see Preferences)

Bosnjak 2008 数值计算内激波的高能辐射

主要内容:
数值计算和解析结果比较, 发现相差很大, 解析结果估计过高

精彩摘抄:


文章信息:

· Find Similar Abstracts (with default settings below)

· arXiv e-print (arXiv:0811.2956)

· References in the Article

·

· Translate This Page

Title:		Prompt high-energy emission from gamma-ray bursts in the internal shock model
Authors:		Bosnjak, Z.; Daigne, F.; Dubus, G.
Publication:		eprint arXiv:0811.2956
Publication Date:		11/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		27 pages, 20 figures, submitted to A&A
Bibliographic Code:		2008arXiv0811.2956B

Abstract

The prompt GRB emission is thought to arise from electrons accelerated in internal shocks propagating within a highly relativistic outflow. The launch of Fermi offers the prospect of observations with unprecedented sensitivity in high-energy (>100 MeV) gamma-rays. The aim is to explore the predictions for HE emission from internal shocks, taking into account both dynamical and radiative aspects, and to deduce how HE observations constrain the properties of the relativistic outflow. The emission is modeled by combining a time-dependent radiative code with a dynamical code giving the evolution of the physical conditions in the shocked regions.Synthetic lightcurves and spectra are compared to observations. The HE emission deviates significantly from analytical estimates, which tend to overpredict the IC component, when the time dependence and full cross-sections are included. The exploration of the parameter space favors the case where the dominant process in the BATSE range is synchrotron emission. The HE component becomes stronger for weaker magnetic fields. The HE lightcurve can display a prolonged pulse duration due to IC emission, or even a delayed peak compared to the BATSE range.Alternatively, having dominant IC emission in the BATSE range requires most electrons to be accelerated into a steep power-law distribution and implies strong 2nd order IC scattering. In this case, the BATSE and HE lightcurves are very similar. The combined dynamical and radiative approach allows a firm appraisal of GRB HE prompt emission. A diagnostic procedure is presented to identify from observations the dominant emission process and derive constrains on the bulk Lorentz factor, particle density and magnetic field of the outflow.

---

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

Kocevski 2008 考察伽玛暴pulses的曲率效应

主要内容:
如果是锥状喷流, 则应该有时间上的curvature效应. 分析发现pulses的上升和下降指数分别大约为 1.5和2.5. (前者貌似应该是1, 后者是2+beta~3) 不过作者说大多数下降都比curvature的陡.

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:astro-ph/0303556)

· References in the article

· Citations to the Article (44) (Citation History)

· Refereed Citations to the Article

· SIMBAD Objects (65)

· NED Objects (51)

· Also-Read Articles (Reads History)

· HEP/Spires Information

·

· Translate This Page

Title:		Search for Relativistic Curvature Effects in Gamma-Ray Burst Pulses
Authors:		Kocevski, Dan; Ryde, Felix; Liang, Edison
Affiliation:		AA(Department of Space Physics and Astronomy, Rice University, MS 108, 6100 South Main, Houston, TX 77005; kocevski@rice.edu, felix@ahoor.stanford.edu, liang@spacsun.rice.edu.), AB(Department of Space Physics and Astronomy, Rice University, MS 108, 6100 South Main, Houston, TX 77005; kocevski@rice.edu, felix@ahoor.stanford.edu, liang@spacsun.rice.edu.; Center for Space Science and Astrophysics, Stanford University, Stanford, CA 94305.; Current address: Stockholm Observatory, AlbaNova, SE-106 91 Stockholm, Sweden.), AC(Department of Space Physics and Astronomy, Rice University, MS 108, 6100 South Main, Houston, TX 77005; kocevski@rice.edu, felix@ahoor.stanford.edu, liang@spacsun.rice.edu.)
Publication:		The Astrophysical Journal, Volume 596, Issue 1, pp. 389-400. (ApJ Homepage)
Publication Date:		10/2003
Origin:		UCP
ApJ Keywords:		Gamma Rays: Bursts, Gamma Rays: Theory, Relativity
Abstract Copyright:		(c) 2003: The American Astronomical Society
DOI:		10.1086/377707
Bibliographic Code:		2003ApJ...596..389K

Abstract

We analyze the time profiles of individual gamma-ray burst (GRB) pulses that are longer than 2 s by modeling them with analytical functions that are based on physical first principles and well-established empirical descriptions of GRB spectral evolution. These analytical profiles are independent of the emission mechanism and can be used to model both the rise and decay profiles, allowing for the study of the entire pulse light curve. Using this method, we have studied a sample of 77 individual GRB pulses, allowing us to examine the fluence, pulse width, asymmetry, and rise and decay power-law distributions. We find that the rise phase is best modeled with a power law of average index r=1.48+/-0.07 and that the average decay phase has an index of d=2.44+/-0.12. We also find that the ratio between the rise and decay times (the pulse asymmetry) exhibited by the GRB pulse shape has an average value of 0.47, which varies little from pulse to pulse and is independent of pulse duration or intensity. Although this asymmetry is largely uncorrelated to other pulse properties, a statistically significant trend is observed between the pulse asymmetry and the decay power-law index, possibly hinting at the underlying physics. We compare these parameters with those predicted to occur if individual pulse shapes are created purely by relativistic curvature effects in the context of the fireball model, a process that makes specific predictions about the shape of GRB pulses. The decay index distribution obtained from our sample shows that the average GRB pulse fades faster than the value predicted by curvature effects, with only 39% of our sample being consistent with the curvature model. We discuss several refinements of the relativistic curvature scenario that could naturally account for these observed deviations, such as symmetry breaking and varying relative timescales within individual pulses.

---

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