Gomboc 2006 Swift早期光学余辉回顾

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astro-ph/0612762 [abs, ps, pdf, other] :

Title: A Review of Early-Time Optical Follow-ups with 2-m Robotic Telescopes
Authors: A. Gomboc (1,2), C. Guidorzi (2,3), C.G. Mundell (2), A. Melandri (2), A. Monfardini (2), D. Bersier (2), M.F. Bode (2), D. Carter (2), S. Kobayashi (2), C.J. Mottram (2), R.J. Smith (2), I.A. Steele (2) (on behalf of the RoboNet-1.0 collaboration) ((1) University of Ljubljana, Slovenia, (2) Liverpool JMU, UK, (3) INAF - Osservatorio Astronomico di Brera, Merate, Italy)
Comments: 4 pages, 2 figures, Proceedings of the conference Swift and GRBs: Unveiling the Relativistic Universe - Venice, 5-9 June 2006 - To appear in "Il Nuovo Cimento"

We summarise recent deep, rapid GRB follow-up observations using the RoboNet-1.0 network which comprises three fully-robotic 2-m telescopes, the Liverpool Telescope and the Faulkes Telescopes North and South. Observations begin automatically within minutes of receipt of a GRB alert and may continue for hours or days to provide well-sampled multi-colour light curves or deep upper limits. Our light curves show a variety of early afterglow behaviour, from smooth, simple or broken power laws to 'bumpy', for a wide range of optical brightness (from the unprecedented faint detections of GRB 060108 and GRB 060510B to classical bright ones). We discuss GRB 051111 as an example of how the combination of optical and X-ray light curves can provide insight into the circumburst environment, in particular the role played by intrinsic extinction soon after the burst.

Chevalier 2006 射电波段的超新星和伽玛暴的成协

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astro-ph/0612734 [abs, ps, pdf, other] :

Title: Circumstellar Interaction Around Type Ib/c Supernovae and the GRB Connection
Authors: R. A. Chevalier
Comments: 8 pages, to appear in Circumstellar Media and Late Stages of Massive Stellar Evolution, RevMexAA

Radio observations of Type Ib/c supernovae suggest that circumstellar interaction takes place with a wide range of wind densities, comparable to that seen in Galactic Wolf-Rayet stars. Efficient production of magnetic field in the shocked region is needed. The X-ray emission observed from some Type Ib/c supernovae is higher than would be expected by the thermal or inverse Compton mechanisms; a synchrotron interpretation requires a flattening of the electron energy spectrum at high energies, as might occur in a cosmic ray dominated shock wave. The wind density variations that are indicated in two supernovae may be due to a binary companion, although variable mass loss from a single star remains a possibility. Other than the optical supernova radiation, the emission from the nearby SN 2006aj/GRB 060218 appears to be powered by a central engine, while that from SN 1998bw/GRB 980425 could be powered by either a central engine or the outer supernova ejecta.

温度－红移的对应？

为什么我们能看到3K的背景辐射? 为什么一定是3K的“黑体辐射”？（这意味着宇宙空间的温度是3K） 而不是表现为一种温度，但强度不是黑体辐射的强度的。

比方： 原本是一个3K的平衡态在体积V的盒子里边，盒子全反射，并且外边有一个更大的盒子，现在放开小盒子，让辐射在一个更大的盒子里游荡，通过测量，我们应该得到谱形和3K的相同，但是强度比3K黑体谱弱的谱。

我觉得现在的微波背景辐射就应该是这种“不饱和”的黑体辐射，也就是拿一个3K的物体放在宇宙空间，它会因为辐射而降低温度。但实际好像它就是这个温度。宇宙膨胀为什么一定就得到3K的黑体呢？

用暴本身的光变定喷流张角 3

首先假设是锥状喷流，根据曲率效应，时间指数和谱指数应该满足\alpha=\beta＋2（大概），但是如果在喷流边缘截至了，尾巴辐射就结束了，这个截至的时间就对应着喷流张角。

不过实际过程中至少要注意两点：
一、如果张角较大，上面的指数关系是不满足的，所以要用精确公式数值解；
二、时间零点效应要充分考虑，实际上也就对应着辐射所处的半径，这里可能需要假定。考虑到零点问题，时间指数比上面的要大，也即光变要陡。

（应该值得一试）

今天的astro－ph关于伽玛暴的文章真多

有七篇。好像是最多的一次了吧

Nature也出现狂多关于GRB060614的文章，在这一期Volume 444 Number 7122 971-1104

Goad 2006 GRB051117A的多波段观测

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astro-ph/0612661 [abs, ps, pdf, other] :

Title: Swift multi-wavelength observations of the bright flaring burst GRB051117A
Authors: M. R. Goad (1), K. L. Page (1), O. Godet (1), A. Beardmore (1), J.P. Osborne (1), P.T. O'Brien (1), R. Starling (1), S. Holland (2), D. Band (2), N. Gehrels (2), A. Falcone (3), D.N. Burrows (3), J.A. Nousek (3), P.W.A. Roming (3), A. Moretti (4), M. Perri (5) ((1) University of Leicester, (2) NASA Goddard Space Flight Center, (3) Penn State University, (4) INAF - Osservatorio Astronomica de Brera, (5) ASI Science Data Center)
Comments: Submitted to A&A Dec 5th 2006

We report on the temporal and spectral characteristics of the early X-ray emission from the Gamma Ray Burst 051117A as observed by Swift. The superb quality of the early X-ray light-curve and spectra of this source, one of the brightest seen by the X-ray Telescope at such early times, allows an unprecedented look at the spectral and temporal evolution of the prompt and early afterglow emission for this GRB and allows us to place stringent limits on the detection of lines. The X-ray light-curve at early times is characteristic of a shot-noise process, with individual shots well-modelled by a fast-rise and exponential decay spanning a broad range in rise-times and decay rates. A temporal spectral analysis of the early light-curve shows that the photon index and source intensity are highly correlated with the spectrum being significantly harder when brighter, consistent with the movement of the peak of the Band function to lower energies following individual flares. The high quality spectrum obtained from the first orbit of WT mode data, enables us to place a 3 sigma upper limit on the strength of any emission line features of EW .lt. 15 eV, assuming a narrow emission-line of 100 eV at the peak of the effective area (abridged).

D'Avanzo 2006 XRF 040812的光学余辉观测

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astro-ph/0612644 [abs, ps, pdf, other] :

Title: Discovery of the optical afterglow of XRF 040812: VLT and Chandra observations
Authors: P. D'Avanzo, D. Malesani, S. Campana, S. Covino, A. Moretti, G. Tagliaferri, G. Chincarini
Comments: To be published in the proceedings of the conference "SWIFT and GRBs: Unveiling the Relativistic Universe", Venice, June 5-9, 2006. To appear in "Il Nuovo Cimento"

We present Chandra and VLT observations of the X-Ray Flash XRF 040812. The X-ray analysis reveals with high precision the position of a hard, fading source. A careful analysis of our I-band VLT images taken starting 17 hours after the burst led to the discovery of the optical afterglow superimposed to a bright (I=21.5) host galaxy. The optical afterglow is seen decaying with an index of 1.1. We do not detect any jet break and supernova rebrightening in the optical light curve. The bright apparent luminosity of the host galaxy allows us to get a rough estimate of the redshift, comparing with a set of GRB/XRF host galaxies with known luminosity and redshift. Such comparison suggests a redshift of XRF 040812 in the range 0.3 .lt. z .lt. 0.7.>

Covino 2006 Swift暴的全色拐折

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astro-ph/0612643 [abs, ps, pdf, other] :

Title: Achromatic Breaks for Swift GRBs: Any Evidence?
Authors: S. Covino (INAF/OABr), D. Malesani (NBI-Dark, SISSA), G. Tagliaferri (INAF/OABr), S.D. Vergani (DIAS and DCU), G. Chincarini (Bicocca Univ., INAF/OABr), D.A. Kann (TLS Tautenburg), A.Moretti (INAF/OABr), L. Stella (INAF/OAR)
Comments: Proceedings of the international conference Swift and GRBs: Unveiling the Relativistic Universe - Venice, 5-9 June 2006 - To appear in "Il Nuovo Cimento"

The availability of multi-wavelength high-quality data of gamma-ray burst afterglows in the Swift era, contrary to the expectations, did not allow us to fully confirm yet one of the most fundamental features of the standard afterglow picture: the presence of an achromatic break in the decaying light curve. We briefly review the most interesting cases identified so far.

Urata 2006 GRB041006早期余辉观测

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astro-ph/0612623 [abs, ps, pdf, other] :

Title: Very early multi-color observations of the plateau phase of GRB 041006 afterglow
Authors: Y. Urata, K.Y. Huang, Y.L. Qiu, J. Hu, P.H. Kuo, T. Tamagawa, W.H. Ip, D. Kinoshita, H. Fukushi, M. Isogai, T. Miyata, Y. Nakada, T. Aoki, T. Soyano, K. Tarusawa, H. Mito, K. Onda, M. Ibrahimov, A. Pozanenko, K. Makishima
Comments: 11 pages, 2 figures, Accepted to ApJ Letters

Observations of the optical afterglow of GRB 041006 with the Kiso Observatory 1.05 m Schmidt telescope, the Lulin Observatory 1.0 m telescope and the Xinglong Observatory 0.6 m telescope. Three-bands (B, V and R) of photometric data points were obtained on 2004 October 6, 0.025-0.329 days after the burst. These very early multi band light curves imply the existence of a color dependent plateau phase. The B-band light curve shows a clear plateau at around 0.03 days after the burst. The R band light curve shows the hint of a plateau, or a possible slope change, at around 0.1 days after the burst. The overall behavior of these multi-band light curves may be interpreted in terms of the sum of two separate components, one showing a monotonic decay the other exhibiting a rising and a falling phase, as described by the standard afterglow model.

Kocevski 2006 SN2006aj的红外观测

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astro-ph/0612621 [abs, ps, pdf, other] :

Title: Multicolor Infrared Observations of SN 2006aj, the Supernova Associated with XRF 060218 - Paper I
Authors: Daniel Kocevski, Maryam Modjaz, Joshua S. Bloom, Ryan Foley, Daniel Starr, Cullen H. Blake, Michael Wood-Vasey, Emilio E. Falco, Nathaniel R. Butler, Mike Skrutskie, Andrew Szentgyorgyi
Comments: 25 pages, 7 figures (6 color, 1 bw), 3 tables

We report simultaneous multicolor near-infrared (NIR) observations of the supernova associated with x-ray Flash 060218 during the first 16 days after the high energy event. We find that the light curve rises and peaks relatively fast compared to other SN Ic, with the characteristic broad NIR peak seen in all three bands. We find that the rise profile before the peak is largely independent of NIR wavelength, each band appearing to transition into a plateau phase around day 10--13. Since the light curve is in the plateau phase when our observations end at day 16, we can only place limits on the peak absolute magnitudes, but we estimate that SN 2006aj is one of the lowest NIR luminosity XRF/GRB associated SNe observed to date. The broad peaks observed in the {\em JHK$_s$} bands point to a large increase in the NIR contribution of the total flux output from days 10--16. This evolution can be seen in the broad color and SED diagrams constructed using {\em UBVRIJHK$_s$} monochromatic flux measurements for the first 16 days of the event. Ultimately, a 10-day rise time would make SN 2006aj an extremely fast rise SN Ic event, faster than SN 1998bw and SN 2003dh, which combined with its underluminous nature, indicates a lower amount of $^{56}$Ni ejected by the progenitor compared to other XRF/GRB-SNe. Furthermore, the lack of significant color change during the rise portion of the burst points to little or no spectral evolution over the first 10 days of activity in the NIR.

Zhang 2006 伽玛暴可能重新分类

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为Volume 444 Number 7122 971-1104写的一篇news and views，这一期上有4篇关于无超新星成协的暴GRB060614的文章。

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astro-ph/0612614 [abs, pdf] :

Title: Astrophysics: A burst of new ideas
Authors: Bing Zhang (UNLV)
Comments: 7 pages, published in Nature News & Views, Vol 444, 1010-1011

Gigantic cosmological gamma-ray bursts have fallen into a dichotomy of long and short bursts, each with a very different origin. The discovery of an oddball burst calls for a rethink of that classification.

Nature 444, 1010-1011 (21 December 2006)

当天的编辑摘要

Editor's Summary

21 December 2006

The long and the short of it

---

The tidy classification system that divided -ray bursts (GRBs) into long-duration busts (lasting more than two seconds) and short may have had its day. The final nail in its coffin may be GRB 060614. Discovered on 14 June 2006 by the Burst Alert Telescope on-board the Swift satellite, this burst was long, at 102 seconds, but as reported in a clutch of papers in this issue, it has a number of properties, including the absence of an accompanying supernova, that were previously considered diagnostic of a 'short' GRB. The hunt is now on for a classification system to take account of the diversity now apparent in GRBs. In the accompanying News & Views, Bing Zhang suggests that the answer may be to adopt a Type I/Type II classification similar to that used for supernovae.

News and Views: Astrophysics: A burst of new ideas

Gigantic cosmological -ray bursts have fallen into a dichotomy of long and short bursts, each with a very different origin. The discovery of an oddball burst calls for a rethink of that classification.

Bing Zhang

doi:10.1038/4441010a

Full Text | PDF (173K)

Letter: A new -ray burst classification scheme from GRB 060614

N. Gehrels, J. P. Norris, S. D. Barthelmy, J. Granot, Y. Kaneko, C. Kouveliotou, C. B. Markwardt, P. Mészáros, E. Nakar, J. A. Nousek, P. T. O'Brien, M. Page, D. M. Palmer, A. M. Parsons, P. W. A. Roming, T. Sakamoto, C. L. Sarazin, P. Schady, M. Stamatikos and S. E. Woosley

doi:10.1038/nature05376

First paragraph | Full Text | PDF (383K)

Letter: No supernovae associated with two long-duration -ray bursts

Johan P. U. Fynbo, Darach Watson, Christina C. Thöne, Jesper Sollerman, Joshua S. Bloom, Tamara M. Davis, Jens Hjorth, Páll Jakobsson, Uffe G. Jørgensen, John F. Graham, Andrew S. Fruchter, David Bersier, Lisa Kewley, Arnaud Cassan, José María Castro Cerón, Suzanne Foley, Javier Gorosabel, Tobias C. Hinse, Keith D. Horne, Brian L. Jensen, Sylvio Klose, Daniel Kocevski, Jean-Baptiste Marquette, Daniel Perley, Enrico Ramirez-Ruiz, Maximilian D. Stritzinger, Paul M. Vreeswijk, Ralph A. M. Wijers, Kristian G. Woller, Dong Xu and Marta Zub

doi:10.1038/nature05375

First paragraph | Full Text | PDF (163K) | Supplementary information

Letter: An enigmatic long-lasting -ray burst not accompanied by a bright supernova

M. Della Valle, G. Chincarini, N. Panagia, G. Tagliaferri, D. Malesani, V. Testa, D. Fugazza, S. Campana, S. Covino, V. Mangano, L. A. Antonelli, P. D'Avanzo, K. Hurley, I. F. Mirabel, L. J. Pellizza, S. Piranomonte and L. Stella

doi:10.1038/nature05374

First paragraph | Full Text | PDF (205K) | Supplementary information

Letter: A novel explosive process is required for the -ray burst GRB 060614

A. Gal-Yam, D. B. Fox, P. A. Price, E. O. Ofek, M. R. Davis, D. C. Leonard, A. M. Soderberg, B. P. Schmidt, K. M. Lewis, B. A. Peterson, S. R. Kulkarni, E. Berger, S. B. Cenko, R. Sari, K. Sharon, D. Frail, D.-S. Moon, P. J. Brown, A. Cucchiara, F. Harrison, T. Piran, S. E. Persson, P. J. McCarthy, B. E. Penprase, R. A. Chevalier and A. I. MacFadyen

doi:10.1038/nature05373

First paragraph | Full Text | PDF (237K) | Supplementary information

Molinari 2006 用红外余辉定伽玛暴火球的膨胀速度

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astro-ph/0612607 [abs, ps, pdf, other] :

Title: A direct measurement of the relativistic expansion velocity of gamma-ray burst fireballs
Authors: E. Molinari, S.D. Vergani, D. Malesani, S. Covino, P. D'Avanzo, G. Chincarini, F.M. Zerbi, L.A. Antonelli, P. Conconi, V. Testa, G. Tosti, F. Vitali, F. D'Alessio, G. Malaspina, L. Nicastro, E. Palazzi, D. Guetta, S. Campana, P. Goldoni, N. Masetti, E.J.A. Meurs, A. Monfardini, L. Norci, E. Pian, S. Piranomonte, D. Rizzuto, M. Stefanon, L. Stella, G. Tagliaferri, P.A. Ward, G. Ihle, L. Gonzalez, A. Pizarro, P. Sinclair, J. Valenzuela
Comments: 14 pages, 2 color figures

Gamma-ray bursts are among the most powerful and remote events in the universe. It is commonly thought that these explosions originate inside fireballs expanding ultra-relativistically. Here we report a direct measurement of the relativistic expansion velocity of the fireball. Using the robotic telescope REM located in Chile we were able to catch the infrared afterglow of two gamma-ray bursts before the early maximum. By measuring the delay between the burst onset and the peak of the afterglow light curve, we determine the fireball initial Lorentz factor to be about 400, corresponding to a velocity >99.999% of the light speed.

Rosswog 2006 致密双星产生短暴或磁星

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astro-ph/0612572 [abs, ps, pdf, other] :

Title: Last moments in the life of a compact binary system: gravitational waves, gamma-ray bursts and magnetar formation
Authors: S. Rosswog
Comments: 24 pages, 18 figures, Revista Mexicana de Astronomia y Astrofisica in press higher resolution figures can be found at this http URL

The first detections of afterglows from short gamma-ray bursts (GRBs) have confirmed the previous suspicion that they are triggered by a different central engine than long bursts. In particular, the recent detections of short GRBs in galaxies without star formation lends support to the idea that an old stellar population is involved. Most prominent are mergers of either double neutron stars or of a neutron star with a stellar-mass black hole companion. Since the final identification of the central engine will only come from an integral view of several properties, we review the observable signatures that can be expected from both double neutron stars and neutron star black hole systems. We discuss the gravitational wave emission, the structure of the neutrino-cooled accretion disks, the resulting neutrino signal and possible mechanisms to launch a GRB. In addition, we address the speculative idea that in some cases a magnetar-like object may be the final outcome of a double neutron star merger. We also discuss possibilities to explain the late-time X-ray activity that has been observed in several bursts.

Butler 2006 从X射线谱演化看中心引擎的持续活动

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astro-ph/0612564 [abs, ps, pdf, other] :

Title: The Curvaceous Early Spectra of Swift X-ray Afterglows: Late Time GRB Activity Without N_H Variations
Authors: Nathaniel R. Butler, Daniel Kocevski
Comments: 23 pages plus 18 figures and 3 tables, submitted to ApJ

We demonstrate that the X-ray and Gamma-ray spectra of Swift GRBs and their afterglows are dominated by emission characteristic of an expanding, relativistic fireball. The classical afterglow due to the impact of the fireball on the external medium is often not observed until one to several hours after the GRB. Focusing on GRBs 061121, 060614, and 060124, but generalizing to the full (>50 Msec XRT exposure) Swift sample up to and including GRB061210, we show that the emission in >90% of early afterglows has a characteristic nu*F_nu spectral energy E_peak which likely evolves from the Gamma-rays through the soft X-ray band on timescales of 10^2-10^4s after the GRB. The observed spectra are strongly curved and have often been incorrectly fitted in other studies with a time-varying soft X-ray absorption. The spectral evolution inferred from fitting instead models used to fit GRBs demonstrates a common evolution--a powerlaw hardness intensity correlation and hard to soft evolution--for GRBs and the early X-ray afterglows and X-ray flares. Combined with studies of short timescale variability, our findings indicate a central engine active for longer than previously suspected. The GRB spectra are observed to become very soft at late times due to an intrinsic spectral evolution and due to the surprising faintness of some afterglows. We re-interpret early afterglow studies prior to Swift and also discuss models for the early X-ray emission.

Albert 2006 MAGIC对Swift暴高能辐射的上限限制

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astro-ph/0612548 [abs, ps, pdf, other] :

Title: MAGIC upper limits on the high energy emission from GRBs
Authors: J. Albert, E. Aliu, H. Anderhub, P. Antoranz, A. Armada, C. Baixeras, J. A. Barrio, H. Bartko, D. Bastieri, J. Becker, W. Bednarek, K. Berger, C. Bigongiari, A. Biland, R. K. Bock, P. Bordas, V. Bosch-Ramon, T. Bretz, I. Britvitch, M. Camara, E. Carmona, A. Chilingarian, S. Ciprini, J. A. Coarasa, S. Commichau, J. L. Contreras, J. Cortina, M.T. Costado, V. Curtef, V. Danielyan, F. Dazzi, A. De Angelis, C. Delgado, R. de los Reyes, B. De Lotto, E. Domingo-Santamaria, D. Dorner, M. Doro, M. Errando, M. Fagiolini, D. Ferenc, E. Fernandez, R. Firpo, J. Flix, M. V. Fonseca, L. Font, M. Fuchs, N. Galante, R. Garcia-Lopez, M. Garczarczyk, M. Gaug, M. Giller, F. Goebel, D. Hakobyan, M. Hayashida, T. Hengstebeck, A. Herrero, D. Hohne, J. Hose, C. C. Hsu, et al. (MAGIC Collaboration: 84 additional authors not shown)
Comments: 23 pages, 11 figures, submitted to ApJ

The fast repositioning system of the MAGIC Telescope has allowed during its first data cycle, between 2005 and the beginning of year 2006, observing nine different GRBs as possible sources of very high energy gammas. These observations were triggered by alerts from Swift, HETE-II, and Integral; they started as fast as possible after the alerts and lasted for several minutes, with an energy threshold varying between 80 and 200 GeV, depending upon the zenith angle of the burst. No evidence for gamma signals was found, and upper limits for the flux were derived for all events, using the standard analysis chain of MAGIC. For the bursts with measured redshift, the upper limits are compatible with a power law extrapolation, when the intrinsic fluxes are evaluated taking into account the attenuation due to the scattering in the Metagalactic Radiation Field (MRF).

de Ugarte Postigo 2006 GRB 050408的多波段观测

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astro-ph/0612545 [abs, ps, pdf, other] :

Title: Extensive multiband study of the X-ray rich GRB 050408. A likely off-axis event with an intense energy injection
Authors: A de Ugarte Postigo, T.A. Fatkhullin, G. Johannesson, J. Gorosabel, V.V. Sokolov, A.J. Castro-Tirado, Yu.Yu. Balega, O.I. Spiridonova, M. Jelinek, S. Guziy, D. Perez-Ramirez, J. Hjorth, P. Laursen, D. Bersier, S.B. Pandey, M. Bremer, A. Monfardini, K.Y. Huang, Y. Urata, W.H. Ip, T. Tamagawa, D. Kinoshita, T. Mizuno, Y. Arai, H. Yamagishi, T. Soyano, F. Usui, M. Tashiro, K. Abe, K. Onda, Z. Aslan, I. Khamitov, T. Ozisik, U. Kiziloglu, I. Bikmaev, N. Sakhibullin, R. Burenin, M. Pavlinsky, R. Sunyaev, D. Bhattacharya, A.P. Kamble, C.H. Ishwara Chandra, S.A. Trushkin
Comments: 9 pages, 4 figures, Accepted for publication in A&A Letters

Aims. Understand the shape and implications of the multiband light curve of GRB 050408, an X-ray rich (XRR) burst. Methods. We present a multiband optical light curve, covering the time from the onset of the gamma-ray event to several months after, when we only detect the host galaxy. Together with X-ray, millimetre and radio observations we compile what, to our knowledge, is the most complete multiband coverage of an XRR burst afterglow to date. Results. The optical and X-ray light curve is characterised by an early flattening and an intense bump peaking around 6 days after the burst onset. We explain the former by an off-axis viewed jet, in agreement with the predictions made for XRR by some models, and the latter with an energy injection equivalent in intensity to the initial shock. The analysis of the spectral flux distribution reveals an extinction compatible with a low chemical enrichment surrounding the burst. Together with the detection of an underlying starburst host galaxy we can strengthen the link between XRR and classical long-duration bursts.

Mereghetti 2006 暴周环境对X射线的散射

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astro-ph/0612543 [abs, ps, pdf, other] :

Title: Dust scattering X-ray expanding rings around gamma-ray bursts
Authors: S.Mereghetti, A.Tiengo, G.Vianello
Comments: Proceedings of the international conference Swift and GRBs: Unveiling the Relativistic Universe - Venice, 5-9 June 2006 - To appear in "Il Nuovo Cimento"

Scattering by dust grains in our Galaxy can produce X-ray halos, visible as expanding rings, around GRBs. This has been observed in three GRBs to date, allowing to derive accurate distances for the dust clouds as well as some constraints on the prompt GRB X-ray emission that was not directly observed. We developed a new analysis method to study dust scattering expanding rings and have applied it to all the XMM-Newton and Swift/XRT follow-up observations of GRBs.

Granot 2006 Swift暴早期余辉的变平的几种解释

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astro-ph/0612516 [abs, ps, pdf, other] :

Title: The flat decay phase in the early X-ray afterglows of Swift GRBs
Authors: Jonathan Granot
Comments: To be published in the proceedings of the conference "SWIFT and GRBs: Unveiling the Relativistic Universe", Venice, June 5-9, 2006. To appear in "Il Nuovo Cimento"

Many Swift GRBs show an early phase of shallow decay in their X-ray afterglows, lasting from $t \sim 10^{2.5} $s to $\sim 10^4 $s after the GRB, where the flux decays as $\sim t^{-0.2}-t^{-0.8}$. This is perhaps the most mysterious of the new features discovered by Swift in the early X-ray afterglow, since it is still not clear what causes it. I discuss different possible explanations for this surprising new discovery, as well as their potential implications for the gamma-ray efficiency, the afterglow kinetic energy, and perhaps even for the physics of collisionless relativistic shocks.

Panaitescu 2006 GRB990123光学和伽玛射线辐射的统一模型

主要内容:
prompt阶段的光学辐射是同步，伽玛是逆康普顿。

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文章信息:

astro-ph/0612504 [abs, ps, pdf, other] :

Title: A unified picture for the gamma-ray and prompt optical emissions of GRB 990123
Authors: A. Panaitescu, P. Kumar
Comments: 9 pages, accepted for publication by MNRAS

The prompt optical emission of GRB 990123 was uncorrelated to the gamma-ray light-curve and exhibited temporal properties similar to those of the steeply-decaying, early X-ray emission observed by Swift at the end of many bursts. These facts suggest that the optical counterpart of GRB 990123 was the large-angle emission released during (the second pulse of) the burst. If the optical and gamma-ray emissions of GRB 990123 have, indeed, the same origin then their properties require that (i) the optical counterpart was synchrotron emission and the gamma-rays arose from inverse-Compton scatterings ("synchrotron self-Compton model"), (ii) the peak-energy of the optical-synchrotron component was at ~20 eV, and (iii) the burst emission was produced by a relativistic outflow moving at Lorentz factor > 450 and at a radius > 10^{15} cm, which is comparable to the outflow deceleration radius. Because the spectrum of GRB 990123 was optically thin above 2 keV, the magnetic field behind the shock must have decayed on a length-scale of <1%>

Romano 2006 GRB060124的全方位观测

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astro-ph/0612494 [abs, ps, pdf, other] :

Title: Panchromatic study of GRB 060124: from precursor to afterglow
Authors: P. Romano, S. Campana, G. Chincarini (INAF-OAB), J. Cummings (GSFC), G. Cusumano (INAF-IASF-Pa), S. T. Holland (GSFC), V. Mangano, T. Mineo (INAF-IASF-Pa), K. L. Page (U Leicester), V. Pal'shin (Ioffe PTI), E. Rol (U Leicester), T. Sakamoto (GSFC), B. Zhang (U Nevada), et al
Comments: 4 pages, 2 figures. Proceedings of `SWIFT and GRBs: Unveiling the Relativistic Universe', June 5-9, 2006 Venice (Italy), to appear in Il Nuovo Cimento

We present observations of GRB 060124, the first event for which both the prompt and the afterglow emission could be observed simultaneously and in their entirety by the three Swift instruments and by Konus-Wind. Thanks to these exceptional circumstances, the temporal and spectral properties of the prompt emission could be studied in the optical, X-ray and gamma-ray ranges (up to 2 MeV). While the X-ray emission (0.2-10 keV) clearly tracks the gamma-ray burst, the optical component follows a different pattern, likely indicating a different origin, possibly the onset of external shocks. The prompt GRB spectrum shows significant spectral evolution, with both the peak energy and the spectral index varying. As observed in several long GRBs, significant lags are measured between the hard- and low-energy components, showing that this behaviour extends over 3 decades in energy. The GRB peaks are also much broader at soft energies. This is related to the temporal evolution of the spectrum, and can be accounted for by the softening of the electron spectral index with time. The burst energy (E_iso~5x10^{53} erg at z=2.297) and average peak energy (E_p~300 keV) make GRB 060124 consistent with the Amati relation. The X-ray afterglow is characterized by a decay which presents a break at t_b~10^5s.

Hao 2006 GRB060206的铁镁吸收线

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astro-ph/0612409 [abs, ps, pdf, other] :

Title: Strongly Variable z=1.48 MgII and FeII Absorption in the Spectra of z=4.05 GRB 060206
Authors: H. Hao, K. Z. Stanek, A. Dobrzycki, T. Matheson, M. C. Bentz, J. Kuraszkiewicz, P. M. Garnavich, J. C. Howk, M. L. Calkins, G. Worthey, M. Modjaz, J. Serven
Comments: 14 pages, 4 figures, 1 table; ApJ Letters, submitted

We report on the discovery of strongly variable MgII and FeII absorption lines seen at z=1.48 in the spectra of the z=4.05 GRB 060206 obtained between 4.13 to 7.63 hours after the burst. In particular, the FeII line equivalent width (EW) decayed rapidly from 1.72+-0.25 AA to 0.28+-0.21 AA, only to increase to 0.96+-0.21 AA in a later date spectrum. The MgII doublet shows even more complicated evolution: the weaker line of the doublet drops from 2.05+-0.25 AA to 0.92+-0.32 AA, but then more than doubles to 2.47+-0.41 AA in later data. The ratio of the EWs for the MgII doublet is also variable, being closer to 1:1 (saturated regime) when the lines are stronger and becoming closer to 2:1 (unsaturated regime) when the lines are weaker, consistent with expectations based on atomic physics. We have investigated and rejected the possibility of any instrumental or atmospheric effects causing the observed strong variations. The possibility of variable intervening absorption in GRB spectra was recently predicted by Frank et al. (astro-ph/0605676). Our discovery of clearly variable intervening FeII and MgII lines lends very strong support to their scenario, in which the characteristic size of intervening patches of MgII ``clouds'' is comparable to the GRB beam size, i.e, about 10^16 cm. We discuss various implications of this discovery, including the nature of the MgII absorbers, the physics of GRBs, and measurements of chemical abundances from GRB and quasar absorption lines.

Fan 2006 Swift暴的X射线余辉

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astro-ph/0612375 [abs, ps, pdf, other] :

Title: The interpretation of the Swift GRB X-ray afterglows
Authors: Yi-Zhong Fan
Comments: 5 pages including 1 figure, to appear in "Il Nuovo Cimento"

We discuss the current interpretations of the {\it Swift} GRB X-ray afterglows, mainly focusing on the sharp decline at the prompt tail emission, and the shallow decay afterward, which is then followed by the conventional pre-\emph{Swift} decay behavior, and the possible X-ray flares during the latter two stages. We emphasize the role of the central engine in interpreting the GRB afterglows.

Aoki 2006 GRB050904的宿主星系

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astro-ph/0612367 [abs, ps, pdf, other] :

Title: Search for the host galaxy of GRB 050904 at z=6.3
Authors: K. Aoki, H. Furusawa, K. Ohta, T. Yamada, N. Kawai
Comments: To be published in the proceedings of the conference "SWIFT and GRBs: Unveiling the Relativistic Universe", Venice, June 5-9, 2006. To appear in "Il Nuovo Cimento"

We present the results of deep imaging of the field of GRB 050904 with Suprime-Cam on the Subaru 8.2m telescope. We have obtained a narrow-band (130 A) image centered at 9200 A (NB921) and an i'-band image with total integration times of 56700 and 24060 s, respectively. The host galaxy was not detected within 1'' of the afterglow position. An object was found at 1.5'' NE from the position of the afterglow, but clear detection of this object in the i'-band image rules out its association with the burst. We obtained a limit of > 26.4 AB magnitude (2'' diameter, 3 sigma) in the NB921 image for the host galaxy, corresponding to a flux of 6.0 x 10^{28} erg/s/Hz at rest 1500 A assuming a flat spectrum of the host galaxy. The star formation rate should be less than 7.5 (M_{solar}/yr) based on the conversion rate by Madau et al (1998). This upper limit for the host of GRB 050904 is consistent with the star formation rate of other gamma-ray burst host galaxies around redshift of 2 or less.

Castro Cerón 2006 伽玛暴宿主星系的恒星形成率

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astro-ph/0612355 [abs, ps, pdf, other] :

Title: Star formation rates and stellar masses in z ~ 1 gamma ray burst hosts
Authors: J. M. Castro Cerón, M. J. Michałowski, J. Hjorth, D. Watson, J. P. U. Fynbo, J. Gorosabel
Comments: 4 pages by emulateApJ, 1 table and 2 colour figures; published in ApJ Letters
Journal-ref: ApJ Letters, 653: L85-L88, 20 DEC 2006

We analyse 4.5, 8 and 24 um band Spitzer images of six gamma ray burst host galaxies at redshifts close to 1. We constrain their star formation rates (SFR) based on the entire available spectral energy distribution rather than the 24 um band only. Further, we estimate their stellar masses (M*) based on rest frame K band luminosities. Our sample spans a wide range of galaxy properties: derived SFRs range from less than 10 to a few hundred solar masses per year; values of M* range from 10^9 to 10^10 Mo with a median of 5.6 x 10^9 Mo. Comparing the specific star formation rate (PHI = SFR/M*) of our sample as a function of M* to other representative types of galaxies (distant red galaxies, Ly-alpha emitters, Lyman break galaxies, submillimeter galaxies and z ~ 2 galaxies from the Great Observatories Origins Deep Survey-North field), we find that gamma ray burst hosts are among those with the highest PHI.

Lazzati 2006 前身星对伽玛暴喷流性质的影响

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astro-ph/0612320 [abs, ps, pdf, other] :

Title: The physics of GRB jets and their interaction with the progenitor star
Authors: Davide Lazzati, Brian J. Morsony, Mitchell C. Begelman (JILA, Univ. of Colorado)
Comments: To be published in the proceedings of the conference "SWIFT and GRBs: Unveiling the Relativistic Universe", Venice, June 5-9, 2006. To appear in "Il Nuovo Cimento"

It is now generally accepted that long gamma-ray bursts are associated with the final evolutionary stages of massive stars. As a consequence, their jets must propagate through the stellar progenitor and break out on their surface, before they can reach the photospheric radius and produce the gamma-ray photons. We investigate the role of the progenitor star in shaping the jet properties. We show that even a jet powered by a steady engine can develop a rich phenomenology at the stellar surface. We present special-relativistic simulations and compare the results to analytic considerations. We show that the jet is complex in the time as well as in the angular domain, so that observers located along different lines of sight detect significantly different bursts.

Fargion 2006 GRB和SGR的进动模型

主要内容:
Fargion做了很多这方面的工作。

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文章信息:

astro-ph/0612319 [abs, ps, pdf, other] :

Title: Solving GRBs and SGRs puzzles by precessing Jets
Authors: D.Fargion, O.Lanciano, P.Oliva
Comments: 10 pages, 16 figures

A persistent, thin, micro-nano sr. beamed gamma jet, may be ejected from BH and Pulsars, powered by ultra-relativistic electron pairs. These jet while precessing and spinning are originated by Inverse Compton and-or Synchrotron Radiation at pulsars or micro-quasars sources. They are most powerful at Supernova birth, blazing, once on axis, to us and flashing GRB detector. The trembling of thin jets explains naturally the observed erratic multi-explosive structure of different GRBs. The jets are precessing and decaying on time scales of a few hours surviving as long as thousands of years, linking huge GRB-SN jet apparent Luminosity to more modest SGR relic Jets. Therefore long-life SGR may be repeating and if they are around our galaxy they might be observed again as the few known ones and a few rarer extragalactic XRFs. The orientation of the beam respect to the line of sight plays a key role in differentiating the wide GRB morphology. The relativistic cone is as small as the inverse of the electron progenitor Lorentz factor. The hardest and brightest gamma spectra are hidden inside the inner gamma jet axis. To observe the inner beamed GRB events one needs the widest SN sample and largest cosmic volumes. The most beamed are hardest.The nearest ones, within tens Mpc distances, are mostly observable on cone jet periphery leading to longest SN-GRB duration, with lowest fluency and the softest spectra, as in earliest GRB98425 and recent GRB 060218 signature. Conical shape of few nebulae describe in space the model signature. Recent X-ray precursor, like in GRB060124, ten minutes before the GRB event, or in SGR1806-20 two minutes before the main giant burst cannot be understood otherwise.

Frederiks 2006 SGR1806－20的月亮反射

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astro-ph/0612289 [abs, ps, pdf, other] :

Title: Giant Flare in SGR 1806-20 and Its Compton Reflection from the Moon
Authors: D.D.Frederiks, S.V.Golenetskii, V.D.Palshin, R.L.Aptekar, V.N.Ilyinskii, F.P.Oleinik, E.P.Mazets, T.L.Cline
Comments: 29 pages including 18 figures; to appear in Astronomy Letters, 2007, 33, p 1-18

We analyze the data obtained when the Konus-Wind gamma-ray spectrometer detected a giant flare in SGR 1806-20 on December 27, 2004. The flare is similar in appearance to the two known flares in SGR 0526-66 and SGR 1900+14 while exceeding them significantly in intensity. The enormous X-ray and gamma-ray flux in the narrow initial pulse of the flare leads to almost instantaneous deep saturation of the gamma-ray detectors, ruling out the possibility of directly measuring the intensity, time profile, and energy spectrum of the initial pulse. In this situation, the detection of an attenuated signal of Compton back-scattering of the initial pulse emission by the Moon with the Helicon gamma-ray spectrometer onboard the Coronas-F satellite was an extremely favorable circumstance. Analysis of this signal has yielded the most reliable temporal, energy, and spectral characteristics of the pulse. The temporal and spectral characteristics of the pulsating flare tail have been determined from Konus-Wind data. Its soft spectra have been found to contain also a hard power-law component extending to 10 MeV. A weak afterglow of SGR 1806-20 decaying over several hours is traceable up to 1 MeV. We also consider the overall picture of activity of SGR 1806-20 in the emission of recurrent bursts before and after the giant flare.

Schmidt 1988 用V／V_max定伽玛暴的距离分布 3

主要内容:
这本来是一个普遍用于天文定源的分布的方法，该文章特用于伽玛暴。好处是只需要得到观测的峰值，就可以统计大致的径向分布。缺点是只有统计分布，没有准确的位置。

方法是：给出观测值C_p,C_lim，分别是峰值流量的计数和极限计数。如果设处于r处的伽玛暴最远放到r_max处还能被看到，应该满足
r_max/r=(C_p/C_lim)^{1/2} (前提：在欧几里得空间)
对应的体积：
V/V_max=(C_p/C_lim)^{-3/2}

注意左边是定义的量，右边是观测量。因此并不需要知道某个源的确切位置，就可以知道暴的分布。

假若暴是均匀分布的，那么对多个暴的V/V_max应该均匀分布（这里有问题？？？），可以先假设暴都是一样的，即V_max都相同作为简化情形来考虑。这样如果平均值＝1／2就说明暴是空间均匀分布的，如果小于1／2，说明暴的分布近距离的多一些，如果大于1／2，远距离的多一些。如极端情况，暴都分布在刚刚能看到的地方，C_p=C_max，于是V／V_max＝1。

这里自己的疑问是如果暴在空间均匀分布，那么V／V_max不应该是1／2，因为对于同一类型的暴, 即V_max相同的暴，如果它们均匀分布，在观测者看，应该是相同半径处分布的暴的个数随半径增大而增大（dV=4\pi r^2 dr），因此V／V_max应该大于1／2。

2006.12.30:
确实应该是1/2, 推导如下，还是假设在一个相同的体积下目标均匀分布，则
《V／V_max》＝(\int_0^R V/V_max 4 pi r^2 dr)
/ (\int_0^R 4 pi r^2 dr)
= 1/2
where, V=4 pi r^3/3.


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文章信息:
Tittle: Application of the V/V_max test to gamma-ray bursts
Authors: M. Schmidt, J. C. Higdon and G. Hueter
Ref: ApJ, 329, L85, 1988

Schaefer 2006 包含69个暴的哈勃图

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astro-ph/0612285 [abs, ps, pdf, other] :

Title: The Hubble Diagram to Redshift >6 from 69 Gamma-Ray Bursts
Authors: Bradley E. Schaefer
Comments: ApJ in press, 88 pages, 15 figures

One of the few ways to measure the properties of Dark Energy is to extend the Hubble daigram (HD) to higher redshifts with Gamma-Ray Bursts (GRBs). GRBs have at least five properties (their spectral lag, variability, spectral peak photon energy, time of the jet break, and the minimum rise time) which have correlations to the luminosity of varying quality. In this paper, I construct a GRB HD with 69 GRBs over a redshift range of 0.17 to >6, with half the bursts having a redshift larger than 1.7. This paper uses over 3.6 times as many GRBs and 12.7 times as many luminosity indicators as any previous GRB HD work. For the gravitational lensing and Malmquist biases, I find that the biases are small, with an average of 0.03 mag and an RMS scatter of 0.14 mag in the distance modulus. The GRB HD is well-behaved and nicely delineates the shape of the HD. The reduced chi-square for the fit to the concordance model is 1.05 and the RMS scatter about the concordance model is 0.65 mag. This accuracy is just a factor of 2.0 times that gotten for the same measure from all the big supernova surveys. I fit the GRB HD to a variety of models, including where the Dark Energy has its equation of state parameter varying as w(z)=w_0 + w_a z/(1+z). I find that the concordance model is consistent with the data. That is, the Dark Energy can be described well as a Cosmological Constant that does not change with time. (abridged)

Salvaterra2006 Swift长暴的光度函数统计

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astro-ph/0612278 [abs, ps, pdf, other] :

Title: The Gamma Ray Burst Luminosity Function in the Light of the Swift 2-year Data
Authors: R. Salvaterra, C. Chincarini
Comments: 9 pages, 3 figures, submitted to ApJ Letter

We compute the luminosity function (LF) and the formation rate of long gamma ray bursts (GRBs) by fitting the observed differential peak flux distribution obtained by the BATSE satellite in three different scenarios: i) GRBs follow the cosmic star formation and their LF is constant in time; ii) GRBs follow the cosmic star formation but the LF varies with redshift; iii) GRBs form preferentially in low-metallicity environments. We find that the differential peak flux number counts obtained by BATSE and by Swift can be reproduced using the same LF and GRB formation rate, indicating that the two satellites are observing the same GRB population. We then check the resulting redshift distributions in the light of Swift 2-year data, focusing in particular on the relatively large sample of GRBs detected at z>2.5. We show that models in which GRBs trace the cosmic star formation and are described by a constant LF are ruled out by the number of high-z Swift detections. This conclusion does not depend on the redshift distribution of bursts that lack of optical identification, nor on the existence of a decline in star formation rate at z>2, nor on the adopted faint-end of the GRB LF. Swift observations can be explained by assuming that the LF varies with time and/or that GRB formation is limited to low-metallicity environments.

Gou 2006 用反向激波的逆康普顿散射解释GRB050904 3

主要内容:
认为光学来自反向激波的同步，X和伽玛射线来自反向激波的同步自康普顿。而耀发是来自于内激波。

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文章信息

astro-ph/0612256 [abs, ps, pdf, other] :

Title: Modeling GRB 050904: Autopsy of a Massive Stellar Explosion at z=6.29
Authors: L. J. Gou, D. B. Fox, P. Meszaros
Comments: 41 pages, 6 figures, ApJ submitted

GRB 050904 at redshift z=6.29, discovered and observed by Swift and with spectroscopic redshift from the Subaru telescope, is the first gamma-ray burst to be identified from beyond the epoch of reionization. Since the progenitors of long gamma-ray bursts have been identified as massive stars, this event offers a unique opportunity to investigate star formation environments at this epoch. Apart from its record redshift, the burst is remarkable in two respects: first, it exhibits fast-evolving X-ray and optical flares that peak simultaneously at t~470 s in the observer frame, and may thus originate in the same emission region; and second, its afterglow exhibits an accelerated decay in the near-infrared (NIR) from t~10^4 s to t~3 10^4 s after the burst, coincident with repeated and energetic X-ray flaring activity. We make a complete analysis of available X-ray, NIR, and radio observations, utilizing afterglow models that incorporate a range of physical effects not previously considered for this or any other GRB afterglow, and quantifying our model uncertainties in detail via Markov Chain Monte Carlo analysis. In the process, we explore the possibility that the early optical and X-ray flare is due to synchrotron and inverse Compton emission from the reverse shock regions of the outflow. We suggest that the period of accelerated decay in the NIR may be due to suppression of synchrotron radiation by inverse Compton interaction of X-ray flare photons with electrons in the forward shock; a subsequent interval of slow decay would then be due to a progressive decline in this suppression. The range of acceptable models demonstrates that the kinetic energy and circumburst density of GRB 050904 are well above the typical values found for low-redshift GRBs.

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Zhang 2006 用"内激波余辉"和曲率效应联合解释早期X余辉的陡降阶段

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astro-ph/0612246 [abs, ps, pdf, other] :

Title: Spectral Evolution of GRB Tails: Central Engine and Internal Shock Afterglows?
Authors: Bin-Bin Zhang, En-Wei Liang, Bing Zhang
Comments: 11 pages,2 figures

A steep decay segment tens to hundreds of seconds after the gamma-ray burst (GRB) prompt emission is commonly observed in the {\em Swift} XRT light curves, which is regarded as the tail emission of the prompt gamma-rays. The most straightforward interpretation is the curvature effect due to delay of propagation of photons from larger angles with respect to the line of sight. Prompted by the observed strong spectral evolution in the tails of GRB 060218 and GRB 060614, we present a systematic time-resolved spectral analysis of 17 bright GRB tails observed by XRT. While 7 tails in our sample have no spectral evolution and can be explained with the curvature effect, the other 10 tails all show significant hard-to-soft spectral evolution. A toy model that combines the curvature effect with an underlying putative central engine afterglow component can roughly explain the observed light curves and spectral evolutions for 7 of them. The suggested central engine afterglow is typically soft ($\beta=2.5\sim 6.4$) and decays as normal GRB afterglows (typically $\alpha=0.8\sim 1.5$), similar to the late afterglow of GRB 060218. There are 3 cases (GRB 050724, GRB 060218, and GRB 060614) that cannot be described by this model. We suggest that these tails may be interpreted as an internal shock afterglow due to cooling of the shock-heated region. More detailed physical models are called for to understand these two possibly new types of afterglows.

Zhang2006 GRB060614可能就是一个短暴

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astro-ph/0612238 [abs, ps, pdf, other] :

Title: Making a Short Gamma-Ray Burst from a Long one: Implications for the Nature of GRB 060614
Authors: Bing Zhang, Bin-Bin Zhang, En-Wei Liang, Neil Gehrels, David N. Burrows, Peter Meszaros
Comments: 7 pages, 3 figures, to appear in ApJ Letters

The absence of a supernova accompanying the nearby long GRB 060614 poses a great puzzle about the progenitor of this event and challenges the current GRB classification scheme. This burst displays a short-hard emission episode followed by extended soft emission with strong spectral evolution. Noticing that this burst has an isotropic gamma-ray energy only ~8 times that of GRB 050724, a good candidate of merger-type short GRBs, we generate a ``pseudo'' burst that is ~8 times less energetic than GRB 060614 based on the spectral properties of GRB 060614 and the Ep ~ Eiso^{1/2} (Amati) relation. We find that this pseudo-burst would have been detected by BATSE as a marginal short-duration GRB, and would have properties in the Swift BAT and XRT bands similar to GRB 050724. This suggests that GRB 060614 is likely a more intense event in the traditional short-hard GRB category as would be detected by BATSE. Events like GRB 060614 that seem to defy the traditional short vs. long classification of GRBs may require modification of our classification terminology for GRBs. By analogy with supernova classifications, we suggest that GRBs be classified into Type I (typically short and associated with old populations) and Type II (typically long and associated with young populations). We propose that GRB 060614 belongs to Type I, and predict that similar events will be detected in elliptical galaxies.

Guetta 2006 伽玛暴和Ib／c型的诞生率比较

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astro-ph/0612194 [abs, ps, pdf, other] :

Title: On the Rates of Gamma Ray Bursts and Type Ib/c Supernovae
Authors: Dafne Guetta, Massimo Della Valle
Comments: 13 pages, 2 figures, ApJ Letters in press

We measure the local rates of ``low-luminosity'' (LL-GRBs, i.e. L<10^{48--49}erg/sec) n0="100--1800" n0="100--550">

GRB061007的长时间无拐折余辉

见astro－ph／0611089，我觉得可能是一个柱状喷流所造成的效果。像在AGN中就可以看到很长的非常窄的喷流。

主要好处是柱状喷流扫过的物质少，从而可能持续那么长的时间，要是锥状喷流，可能很快就进入非相对论阶段了。在时间指数和谱指数上也基本吻合：X射线，alpha＝1.54，beta～0.8，参考黄老师MNRAS,325,599(2001)，nu>(nu_m,nu_c)时， alpha=(p+1)/2, beta=p/2，当p＝2时，二者基本可以满足。

Gendre 2006 swift X射线闪

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astro-ph/0612178 [abs, ps, pdf, other] :

Title: On the nature of X-Ray Flashes in the SWIFT era
Authors: B. Gendre (1, 2), A. Galli (1, 3), L. Piro (1) ((1) IASF-Roma/INAF; (2) University Bicocca Milano; (3) INFN-Trieste)
Comments: 4 pages, 3 color figures. Submitted to Astronomy and Astrophysics Letters

X-Ray Flashes (XRFs) are soft gamma-ray bursts whose nature is not clear. Their soft spectrum can be due to cosmological effects (high redshift), an off-axis view of the jet or can be intrinsic to the source. We use SWIFT observations to investigate different scenarios proposed to explain their origin.We have made a systematic analysis of the afterglows of XRFs with known redshift observed by SWIFT. We derive their redshift and luminosity distributions, and compare their properties with a sample of normal GRBs observed by the same instrument. The high distance hypothesis is ruled out by the redshift distribution of our sample of XRFs, indicating that, at least for our sample, the off-axis and sub-energetic hypotheses are preferred. Of course, this does not exclude that some XRFs without known redshift could be at high distance. However we find that taking into account the sensitivity of the BAT instrument, SWIFT XRFs cannot be detected beyond redshift ~ 3. The luminosity distribution of XRFs is similar to the GRB one. This would rule out most off-axis models, but for the homogeneous jet model. However this model predicts a GRB rate uncomfortably near the observed rate of supernovae. This may imply that XRFs, at least those of our sample, could be intrinsically soft.

Panaitescu 2006 正向激波解释swift余辉

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文章信息:

astro-ph/0612170 [abs, ps, pdf, other] :

Title: Swift GRB Afterglows and the Forward-Shock Model
Authors: A. Panaitescu
Comments: 10 pages, submitted to MNRAS

The X-ray light-curves of the GRB afterglows monitored by Swift display one to four phases of power-law decay. In chronological order they are: the burst tail, the "hump", the standard decay, and the post jet-break decay.
More than half of GRB tails can be identified with the large-angle emission produced during the burst, but arriving at observer later. Several afterglows exhibit a slow, unbroken power-law decay from burst end until 1 day, showing that the forward shock emission is, sometimes, present from the earliest afterglow observations. In fact, the decay of most GRB tails is also consistent with that of the forward-shock emission from a narrow jet (half-angle less than 1 degree).
The X-ray light-curve hump may be due to an increase of the kinetic energy per solid angle of the forward-shock region visible to the observer, caused by either the transfer of energy from some incoming ejecta to the forward shock or by the emergence of the emission from an outflow seen from a location outside the outflow's opening. However, the correlations among the hump timing, flux, and decay index expected in the latter model are not confirmed by observations.
We identify several afterglows whose X-ray light-curves show a second steepening at 0.1-3 day that is consistent with a jet-break. Optical observations for four of them indicate that the X-ray break is achromatic, further strengthening their interpretation as jet-breaks. The decay of 75% of the X-ray afterglows monitored for more than a few days do not exhibit a steepening, implying jet half-angles larger than several degrees.

Chincarini 2006 Swift的X射线耀发

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astro-ph/0612121 [abs, pdf] :

Title: Gamma Ray Bursts Flares detected and observed by the Swift Satellite
Authors: Guido Chincarini, Alberto Moretti, Patrizia Romano, Sergio Campana, Stefano Covino, Gianpiero Tagliaferri, Abraham D. Falcone, David N. Burrows, Neil Gehrels, Vanessa Mangano, Giancarlo Cusumano, Matteo Perri, Paolo Giommi, Milvia Capalbi
Comments: Proceedings of the Beijing COSPAR Assembly 2006; submitted Nov 2, 2006

The detection of flares with the Swift satellite triggered a lot of bservational and theoretical interest in these phenomena. As a consequence a large analysis effort started within the community to characterize the phenomenon and at the same time a variety of theoretical speculations have been proposed to explain it. In this presentation we discuss part of the results we obtained analyzing a first statistical sample of GRBs observed with Swift. The first goal of this research is very simple: derive those observational properties that could distinguish between internal and external shock and between an ever active central engine and delayed shocks (refreshing) related to a very small initial Lorentz bulk factor. We discuss first the method of analysis and the morphology evidencing the similarities such flares have with the prompt emission pulses. We conclude that GRB flares are due to internal shocks and leave still open the question of whether or not the central engine is active for a time of the order of 105 seconds after the prompt emission.