星期二, 九月 30, 2008
星期一, 九月 29, 2008
De Pasquale 2008 Two-Component jet to explain the shallow decays phase
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· Find Similar Abstracts (with default settings below) - · arXiv e-print (arXiv:0809.4688)
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| Title: | Jet breaks at the end of the slow decline phase of Swift GRB lightcurves | |
| Authors: | De Pasquale, M.; Evans, P.; Oates, S.; Page, M.; Zane, S.; Schady, P.; Breeveld, A.; Holland, S.; Kuin, P.; Still, M.; Roming, P.; Ward, P. | |
| Publication: | eprint arXiv:0809.4688 | |
| Publication Date: | 09/2008 | |
| Origin: | ARXIV | |
| Keywords: | Astrophysics | |
| Comment: | 19 pages, 3 figures | |
| Bibliographic Code: | 2008arXiv0809.4688D |
Abstract
The Swift mission has discovered an intriguing feature of Gamma-Ray Burst (GRBs) afterglows, a phase of shallow decline of the flux in the X-ray and optical lightcurves. This behaviour is typically attributed to energy injection into the burst ejecta. At some point this phase ends, resulting in a break in the lightcurve, which is commonly interpreted as the cessation of the energy injection. In a few cases, however, while breaks in the X-ray lightcurve are observed, optical emission continues its slow flux decline. This behaviour suggests a more complex scenario. In this paper, we present a model that invokes a double component outflow, in which narrowly collimated ejecta are responsible for the X-ray emission while a broad outflow is responsible for the optical emission. The narrow component can produce a jet break in the X-ray lightcurve at relatively early times, while the optical emission does not break due to its lower degree of collimation. In our model both components are subject to energy injection for the whole duration of the follow-up observations. We apply this model to GRBs with chromatic breaks, and we show how it might change the interpretation of the GRBs canonical lightcurve. We also study our model from a theoretical point of view, investigating the possible configurations of frequencies and the values of GRB physical parameters allowed in our model.Bibtex entry for this abstract Preferred format for this abstract (see Preferences)
星期日, 九月 28, 2008
Special topics
I think I should add another category, which collect the papers for special topics. This is useful for works. When I am working on a special topic, the relevant papers can be collected in this label.
星期五, 九月 26, 2008
GRB movies
GRB movies
星期四, 九月 25, 2008
Castro-Tirado 2008 SWIFT J195509+261406可能是SGR，有光学观测
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· Find Similar Abstracts (with default settings below) - · arXiv e-print (arXiv:0809.4231)
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| Title: | Optical and infrared flares from a transient Galactic soft gamma-ray repeater | |
| Authors: | Castro-Tirado, A. J.; de Ugarte Postigo, A.; Gorosabel, J.; Jelinek, M.; Fatkhullin, T. A.; Sokolov, V. V.; Ferrero, P.; Kann, D. A.; Klose, S.; Sluse, D.; Bremer, M.; Winters, J. M.; Nuernberger, D.; Perez-Ramirez, D.; Guerrero, M. A.; French, J.; Melady, G.; Hanlon, L.; McBreen, B.; Aceituno, F. J.; Cunniffe, R.; Kubanek, P.; Vitek, S.; Schulze, S.; Wilson, A. C.; Hudec, R.; Gonzalez-Perez, J. M.; Shahbaz, T.; Guziy, S.; Pandey, S. B.; Pavlenko, L.; Sonbas, E.; Trushkin, S. A.; Bursov, N. N.; Nizhelskij, N. A.; Sabau-Graziati, L. | |
| Publication: | eprint arXiv:0809.4231 | |
| Publication Date: | 09/2008 | |
| Origin: | ARXIV | |
| Keywords: | Astrophysics | |
| Comment: | Version submitted to Nature on 31 Jan 2008. A substantially revised version of this work has been published in Nature, vol. 455 issue 7212 pp 506-509 under the title "Flares from a Galactic magnetar suggest a missing link to dim isolated neutron stars"; Nature, 25 September 2008 vol 455 issue 7212 pp506-509; doi:10.1038/nature07328 | |
| Bibliographic Code: | 2008arXiv0809.4231C |
Abstract
Soft gamma-ray repeaters (SGRs) are a rare type of gamma-ray transient sources that are ocasionally detected as bursts in the high-energy sky. They are thought to be produced by magnetars, young neutron stars with very strong magnetic fields of the order of 10^(14-15) G. Only three such objects are known in our Galaxy, and a fourth one is associated with the supernova remnant N49 in the Large Magellanic Cloud. In none of these cases has an optical counterpart to either the gamma-ray flares or the quiescent source been identified. Here we present multi-wavelength observations of a puzzling source, SWIFT J195509+261406, for which we detected more than 40 flaring episodes in the optical band over a time span of 3 days, plus a faint infrared flare 11 days later, after which it returned to quiescence. We propose that SWIFT J195509+261406 is a member of a subgroup of SGRs for which the long-term X-ray emission is transient in nature. Furthermore, it is the first SGR for which bursts have been detected in the optical and near-infrared bands and maybe the link between the "persistent" SGRs and the dim isolated neutron stars.Bibtex entry for this abstract Preferred format for this abstract (see Preferences)
星期三, 九月 24, 2008
Cuoco 2008 Auger data显示超高能宇宙射线更可能来自AGN而不是GRB
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| Title: | A global autocorrelation analysis of the Auger data | |
| Authors: | Cuoco, A.; Hannestad, S.; Haugboelle, T.; Kachelriess, M.; Serpico, P. D. | |
| Publication: | eprint arXiv:0809.4003 | |
| Publication Date: | 09/2008 | |
| Origin: | ARXIV | |
| Keywords: | Astrophysics | |
| Comment: | 7 pages, 3 figures | |
| Bibliographic Code: | 2008arXiv0809.4003C |
Abstract
We perform a global autocorrelation analysis of the Auger data with the aim to constrain the number density $n_s$ of ultrahigh energy cosmic ray (UHECR) sources, estimating at the same time the effect of the bias of UHECR sources and of the systematic energy scale uncertainty on $n_s$. The data show no significant small-scale clustering which may be explained by magnetic deflections over scales of a few degrees. The case of continuous, uniformly distributed sources is disfavored at 99% C.L. and the fit improves if the sources follow the large-scale structure of matter in the universe. The observed clustering starts to restrict the potential mechanisms accelerating UHECRs: Gamma-ray bursts as main UHECR sources are disfavored not only by energy considerations, but also because they require pervasive nG extragalactic magnetic fields to be consistent with the observed clustering, while active galactic nuclei fits well the deduced number density and luminosities.Bibtex entry for this abstract Preferred format for this abstract (see Preferences)
Roming 2008 第一个UVOT的catalog
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大部分从100-100,000s都是单一幂律下降，指数是-1.
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· Find Similar Abstracts (with default settings below) - · arXiv e-print (arXiv:0809.4193)
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| Title: | The First Swift Ultra-Violet/Optical Telescope GRB Afterglow Catalog | |
| Authors: | Roming, P. W. A.; Koch, T. S.; Oates, S. R.; Porterfield, B. L.; Vanden Berk, D. E.; Boyd, P. T.; Holland, S. T.; Hoversten, E. A.; Immler, S.; Marshall, F. E.; Page, M. J.; Racusin, J. L.; Schneider, D. P.; Breeveld, A. A.; Brown, P. J.; Chester, M. M.; Cucchiara, A.; De Pasquale, M.; Gronwall, C.; Hunsberger, S. D.; Kuin, N. P. M.; Landsman, W. B.; Schady, P.; Still, M. | |
| Publication: | eprint arXiv:0809.4193 | |
| Publication Date: | 09/2008 | |
| Origin: | ARXIV | |
| Keywords: | Astrophysics | |
| Comment: | 60 pages, 17 figures, 8 tables, accepted for publication by the Astrophysical Journal | |
| Bibliographic Code: | 2008arXiv0809.4193R |
Abstract
We present the first Swift Ultra-Violet/Optical Telescope (UVOT) gamma-ray burst (GRB) afterglow catalog. The catalog contains data from over 64,000 independent UVOT image observations of 229 GRBs first detected by Swift, the High Energy Transient Explorer 2 (HETE2), the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL), and the Interplanetary Network (IPN). The catalog covers GRBs occurring during the period from 2005 Jan 17 to 2007 Jun 16 and includes ~86% of the bursts detected by the Swift Burst Alert Telescope (BAT). The catalog provides detailed burst positional, temporal, and photometric information extracted from each of the UVOT images. Positions for bursts detected at the 3-sigma-level are provided with a nominal accuracy, relative to the USNO-B1 catalog, of ~0.25 arcseconds. Photometry for each burst is given in three UV bands, three optical bands, and a 'white' or open filter. Upper limits for magnitudes are reported for sources detected below 3-sigma. General properties of the burst sample and light curves, including the filter-dependent temporal slopes, are also provided. The majority of the UVOT light curves, for bursts detected at the 3-sigma-level, can be fit by a single power-law, with a median temporal slope (alpha) of 0.96, beginning several hundred seconds after the burst trigger and ending at ~1x10^5 s. The median UVOT v-band (~5500 Angstroms) magnitude at 2000 s for a sample of "well" detected bursts is 18.02. The UVOT flux interpolated to 2000 s after the burst, shows relatively strong correlations with both the prompt Swift BAT fluence, and the Swift X-ray flux at 11 hours after the trigger.Bibtex entry for this abstract Preferred format for this abstract (see Preferences)
Stefanescu 2008 长得像伽玛暴的光学辐射SWIFT J195509.6+261406.
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虽然光变像伽玛暴，不过不是瞬时爆发，间断性的持续时间很长，像SGR。说可能是磁星。
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| Title: | Very fast optical flaring from a possible new Galactic magnetar | |
| Authors: | Stefanescu, A.; Kanbach, G.; Słowikowska, A.; Greiner, J.; McBreen, S.; Sala, G. | |
| Publication: | eprint arXiv:0809.4043 | |
| Publication Date: | 09/2008 | |
| Origin: | ARXIV | |
| Keywords: | Astrophysics | |
| Comment: | 8 pages, 3 figures. A substantially revised version of this manuscript was published in Nature. Due to license issues, the accepted manuscript will only be put on astro-ph as v2 6 months after this version; Nature 455 (2008) pp503-505; doi:10.1038/nature07308 | |
| Bibliographic Code: | 2008arXiv0809.4043S |
Abstract
Highly luminous rapid flares are characteristic of processes around compact objects like white dwarfs, neutron stars or black holes. In the high energy regime of X- and gamma-rays, outbursts with variability time-scales of seconds and faster are routinely observed, e.g. in gamma-ray bursts or Soft Gamma Repeaters. In the optical, flaring activity on such time-scales has never been observed outside the prompt phase of GRBs. This is mostly due to the fact that outbursts with strong, fast flaring usually are discovered in the high-energy regime. Most optical follow-up observations of such transients employ instruments with integration times exceeding tens of seconds, which are therefore unable to resolve fast variability. Here we show the observation of extremely bright and rapid optical flaring in the galactic transient SWIFT J195509.6+261406. Flaring of this kind has never previously been reported. Our optical light-curves are phenomenologically similar to high energy light-curves of Soft Gamma Repeaters and Anomalous X-ray Pulsars, which are thought to be neutron stars with extremely high magnetic fields (magnetars). This suggests similar emission processes may be at work, but in contrast to the other known magnetars with strong emission in the optical.Bibtex entry for this abstract Preferred format for this abstract (see Preferences)
Marisaldi 2008 AGILE上的MCAL
主要内容:
可探测伽玛暴
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Abstract
The Mini-Calorimeter (MCAL) instrument on-board the AGILE satellite is a non-imaging gamma-ray scintillation detector sensitive in the 300keV-100MeV energy range with a total on-axis geometrical area of 1400cm^2. Gamma-Ray Bursts (GRBs) are one of the main scientific targets of the AGILE mission and the MCAL design as an independent self-triggering detector makes it a valuable all-sky monitor for GRBs. Furthermore MCAL is one of the very few operative instruments with microsecond timing capabilities in the MeV range. In this paper the results of GRB detections with MCAL after one year of operation in space are presented and discussed. A flexible trigger logic implemented in the AGILE payload data-handling unit allows the on-board detection of GRBs. For triggered events, energy and timing information are sent to telemetry on a photon-by-photon basis, so that energy and time binning are limited by counting statistics only. When the trigger logic is not active, GRBs can be detected offline in ratemeter data, although with worse energy and time resolution. Between the end of June 2007 and June 2008 MCAL detected 51 GRBs, with a detection rate of about 1 GRB/week, plus several other events at a few milliseconds timescales. Since February 2008 the on-board trigger logic has been fully active. Comparison of MCAL detected events and data provided by other space instruments confirms the sensitivity and effective area estimations. MCAL also joined the 3rd Inter-Planetary Network, to contribute to GRB localization by means of triangulation.Bibtex entry for this abstract Preferred format for this abstract (see Preferences)
Dermer 2008 伽玛暴和Fermi望远镜
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| Title: | Gamma Ray Bursts and the Fermi Gamma Ray Space Telescope: Notes to the La Plata Lectures | |
| Authors: | Dermer, Charles D.; Fryer, Chris L. | |
| Publication: | eprint arXiv:0809.3959 | |
| Publication Date: | 09/2008 | |
| Origin: | ARXIV | |
| Keywords: | Astrophysics | |
| Comment: | 33 pages; notes to a series of 5 one-hour lectures given at the First La Plata School in Astrophysics and Geophysics, La Plata, Argentina, March 10 - 14, 2008 | |
| Bibliographic Code: | 2008arXiv0809.3959D |
Abstract
Gamma-ray bursts (GRBs) are a mixed class of sources consisting of, at least, the long duration and short-hard subclasses, the X-ray flashes, and the low-luminosity GRBs. In all cases, the release of enormous amounts of energy on a short timescale makes an energetic, relativistic or mildly relativistic fireball that expands until it reaches a coasting Lorentz factor determined by the amount of baryons mixed into the fireball. Radiation is produced when the blast wave interacts with the surrounding medium at an external shock, or when shell collisions dissipate kinetic energy at internal shocks. This series of notes is organized as follows: (1) The observational situation of GRBs is summarized; (2) Progenitor models of GRBs are described; (3) An overview of the the blast-wave physics used to model leptonic emissions is given; (4) GRB physics is applied to hadronic acceleration and ultra-high energy cosmic ray production; (5) Prospects for GRB physics and gamma-ray astronomy with the Fermi Gamma-ray Space Telescope (FGST, formerly GLAST), and space-based and ground-based observatories are considered. Also included are exercises and problems.Bibtex entry for this abstract Preferred format for this abstract (see Preferences)
星期一, 九月 22, 2008
Peng 2008 Ep在pulse各时段的演化
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基本上峰值的时候Ep高一些。
（我同意对伽玛暴pulse个体的分析比对整个duration的分析要靠谱些。）
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| Title: | Spectral hardness evolution characteristics of tracking Gamma-ray Burst pulses | |
| Authors: | Peng, Z. Y.; Lu, R. J.; Fang, L. M.; Bao, Y. Y.; Yin, Y. | |
| Publication: | eprint arXiv:0809.3620 | |
| Publication Date: | 09/2008 | |
| Origin: | ARXIV | |
| Keywords: | Astrophysics | |
| Comment: | 32 pages, 26 figures, 2 tables, accepted for publication in New Astronomy | |
| Bibliographic Code: | 2008arXiv0809.3620P |
Abstract
Employing a sample presented by Kaneko et al. (2006) and Kocevski et al. (2003), we select 42 individual tracking pulses (here we defined tracking as the cases in which the hardness follows the same pattern as the flux or count rate time profile) within 36 Gamma-ray Bursts (GRBs) containing 527 time-resolved spectra and investigate the spectral hardness, $E_{peak}$ (where $E_{peak}$ is the maximum of the $\nu F_{\nu}$ spectrum), evolutionary characteristics. The evolution of these pulses follow soft-to-hard-to-soft (the phase of soft-to-hard and hard-to-soft are denoted by rise phase and decay phase, respectively) with time. It is found that the overall characteristics of $E_{peak}$ of our selected sample are: 1) the $E_{peak}$ evolution in the rise phase always start on the high state (the values of $E_{peak}$ are always higher than 50 keV); 2) the spectra of rise phase clearly start at higher energy (the median of $E_{peak}$ are about 300 keV), whereas the spectra of decay phase end at much lower energy (the median of $E_{peak}$ are about 200 keV); 3) the spectra of rise phase are harder than that of the decay phase and the duration of rise phase are much shorter than that of decay phase as well. In other words, for a complete pulse the initial $E_{peak}$ is higher than the final $E_{peak}$ and the duration of initial phase (rise phase) are much shorter than the final phase (decay phase). This results are in good agreement with the predictions of Lu et al. (2007) and current popular view on the production of GRBs. We argue that the spectral evolution of tracking pulses may be relate to both of kinematic and dynamic process even if we currently can not provide further evidences to distinguish which one is dominant. Moreover, our statistical results give some witnesses to constrain the current GRB model.Bibtex entry for this abstract Preferred format for this abstract (see Preferences)
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