Chincarini 2007 Swift暴的X射线耀发总结

主要内容:
一共69个。

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astro-ph/0702371 [abs, ps, pdf, other] :

Title: The First Survey of X-ray Flares from Gamma Ray Bursts Observed by Swift: Temporal Properties and Morphology
Authors: G. Chincarini, A. Moretti, P. Romano, A.D. Falcone, D. Morris, J. Racusin, S. Campana, C. Guidorzi, G. Tagliaferri, D.N. Burrows, C. Pagani, M. Stroh, D. Grupe, M. Capalbi, G. Cusumano, N. Gehrels, P. Giommi, V. La Parola, V. Mangano, T. Mineo, J.A. Nousek, P.T. O'Brien, K.L. Page, M. Perri, E. Troja, R. Willingale, B. Zhang
Comments: submitted to ApJ

We present the first systematic investigation of the morphological and timing properties of flares in GRBs observed by Swift/XRT. We consider a large sample drawn from all GRBs detected by Swift, INTEGRAL and HETE-2 prior to 2006 Jan 31, which had an XRT follow-up and which showed significant flaring. Our sample of 33 GRBs includes long and short, at low and high redshift, and a total of 69 flares. The strongest flares occur in the early phases, with a clear anti-correlation between the flare peak intensity and the flare time of occurrence. Fitting each X-ray flare with a Gaussian model, we find that the mean ratio of the width and peak time is = 0.13+/-0.10, albeit with a large scatter. Late flares at times > 2000 seconds have long durations, Delta t>300 s, and can be very energetic compared to the underlying continuum. We further investigated if there is a clear link between the number of pulses detected in the prompt phase by BAT and the number of X-ray flares detected by XRT, finding no correlation. However, we find that the distribution of intensity ratios between successive BAT prompt pulses and that between successive XRT flares is the same, an indication of a common origin for gamma-ray pulses and X-ray flares. All evidence indicates that flares are indeed related to the workings of the central engine and, within the standard fireball scenario, originate from internal shocks rather than external shocks. While all flares can be explained by long-lasting engine activity, 29/69 flares may also be explained by refreshed shocks. However, 10 can only be explained by prolonged activity of the central engine.

Naoz 2007 高红移伽玛暴的诞生率

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astro-ph/0702357 [abs, ps, pdf, other] :

Title: An Observational Limit on the Earliest GRBs
Authors: Smadar Naoz, Omer Bromberg
Comments: 6 Pages, 3 figures, submitted to MNRAS

We predict the redshift of the first observable (i.e., in our past light cone) Gamma Ray Burst (GRB) and calculate the GRB-rate redshift distribution of the Population III stars at very early times (z=20-60). Using the last 2 years of data from Swift we place an upper limit on the efficiency (\eta_{GRB}) of GRB production per solar mass from the first generation of stars. We find that the first observable GRB is most likely to have formed at redshift 60. The observed rate of extremely high redshift GRBs (XRGs) is a subset of a group of 15 long GRBs per year, with no associated redshift and no optical afterglow counterparts, detected by Swift. Taking this maximal rate we get that \eta_{GRB}<1.1~10^{-4} GRBs per solar mass in stars. A more realistic evaluation, e.g., taking a subgroup of 5% of the total sample of Swift gives an upper limit of \eta_{GRB}<3.2~10^{-5} GRBs per solar mass.

Ghirlanda 2007 Swift暴的E_p-E_gamma和E_p-E_iso-t_jet关系

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astro-ph/0702352 [abs, ps, pdf, other] :

Title: Confirming the gamma-ray burst spectral-energy correlations in the era of multiple time breaks
Authors: G. Ghirlanda (1), L. Nava (1,2), G. Ghisellini (1), C. Firmani (1,3) ((1)INAF-Osservatorio Astronomico di Brera; (2)Univ. Insubria; (3)U.N.A.M. - Mexico)
Comments: 12 pages, 1 table, 8 figures. Accepted for publication in A&A

We test the spectral-energy correlation including the new bursts detected (mostly) by Swift with firm measurements of their redshifts and peak energy. The problem of identifying the jet breaks is discussed in the complex and multibreak/flaring X-ray light curves observed by Swift. We use the optical data as the most reliable source for the identification of the jet break, since the X-ray flux may be produced by a mechanism different from the external shocks between the fireball and the circumburst medium, which are responsible for the optical afterglow. We show that the presence of an underlying SN event in XRF 050416A requires a break to occur in the afterglow optical light curve at around the expected jet break time. The possible presence of a jet break in the optical light curve of GRB 050401 is also discussed. We point out that, for measuring the jet break, it is mandatory that the optical light curve extends after the epoch where the jet break is expected. The interpretation of the early optical breaks in GRB 050922C and GRB 060206 as jet breaks is controversial because they might instead correspond to the flat-to-steep decay transition common in the early X-ray light curves. All the 16 bursts coming from Swift are consistent with the E_p-E_gamma and E_p-E_iso-t_jet correlation. No outlier is found to date. Moreover, the small dispersion of these correlations, confirmed also by the Swift bursts, strengthens the case of using GRBs as standard candles.

Fryer 2007 伽玛暴和Ib/c型超新星的成协

主要内容:
结论：长暴并不总来自单星，也可能是双星。

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astro-ph/0702338 [abs, ps, pdf, other] :

Title: Constraints on Type Ib/c and GRB Progenitors
Authors: C.L. Fryer, P.A. Mazzali, J. Prochaska, E. Cappellaro, A. Panaitescu, E. Berger, M. van Putten, E.P.J. van den Heuvel, P. Young, A. Hungerford, G. Rockefeller, S.-C. Yoon, P. Podsiadlowski, K. Nomoto, R. Chevalier, B. Schmidt, S. Kulkarni
Comments: 36 pages, 6 figures

Although there is strong support for the collapsar engine as the power source of long-duration gamma-ray bursts (GRBs), we still do not definitively know the progenitor of these explosions. Here we review the current set of progenitor scenarios for long-duration GRBs and the observational constraints on these scenarios. Examining these, we find that single-star models cannot be the only progenitor for long-duration GRBs. Several binary progenitors can match the solid observational constraints and also have the potential to match the trends we are currently seeing in the observations. Type Ib/c supernovae are also likely to be produced primarily in binaries; we discuss the relationship between the progenitors of these explosions and those of the long-duration GRBs.

Publications of the Astronomical Society of the Pacific
November 2007, Vol. 119, No. 861: pp. 1211-1232

Kumar 2007 伽玛暴外流的辐射模型

主要内容:
认为内激波，外激波等都不能解释伽玛暴本身的辐射。电磁模型倒是可能。

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astro-ph/0702319 [abs, ps, pdf, other] :

Title: The nature of the outflow in gamma-ray bursts
Authors: P. Kumar, E. McMahon (University of Texas, Austin), A. Panaitescu (LANL), R. Willingale, P. O'Brien (Leicester), D. Burrows (Penn State), J. Cummings, N. Gehrels, S. Holland (NASA GSFC), S. B. Pandey (Mullard), D. Vanden Berk (Penn State), S. Zane (Mullard)
Comments: Accepted to MNRAS Letters. 6 pages, 2 figures, & 2 tables

The Swift satellite has enabled us to follow the evolution of gamma-ray burst (GRB) fireballs from the prompt gamma-ray emission to the afterglow phase. The early x-ray and optical data obtained by telescopes aboard the Swift satellite show that the source for prompt gamma-ray emission, the emission that heralds these bursts, is short lived and that its source is distinct from that of the ensuing, long-lived afterglow. Using these data, we determine the distance of the gamma-ray source from the center of the explosion. We find this distance to be 1e15-1e16 cm for most bursts and we show that this is within a factor of ten of the radius of the shock-heated circumstellar medium (CSM) producing the x-ray photons. Furthermore, using the early gamma-ray, x-ray and optical data, we show that the prompt gamma-ray emission cannot be produced in internal shocks, nor can it be produced in the external shock; in a more general sense gamma-ray generation mechanisms based on shock physics have problems explaining the GRB data for the ten Swift bursts analyzed in this work. A magnetic field dominated outflow model for GRBs has some attractive features, although the evidence in its favor is inconclusive. Finally, the x-ray and optical data allow us to provide an upper limit on the density of the CSM of about 10 protons per cubic cm at a distance of about 5e16 cm from the center of explosion.

Akerlof 2007 GLAST LAT对伽玛暴定位的误差估计

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astro-ph/0702295 [abs, pdf] :

Title: Statistical Estimates of Coordinate Error Circles for LAT-detected GRBs
Authors: Carl W. Akerlof, Fang Yuan
Comments: 4 pages, 8 figures, poster paper presented at the First GLAST Symposium, February 5-8, 2007

The GLAST mission to be launched in November 2007 will provide unique information about high energy photon fluxes from gamma-ray bursts. These data will be most useful when combined with multiwavelength observations that provide more complete characterizations of such events. To assist this process, we have estimated the GLAST Large Area Telescope (LAT) angular resolution for the coordinates of ensembles of photons from GRBs as a function of burst spectral index and fluence. This information may be useful in guiding the development of more effective GRB optical afterglow observation programs.

Achterberg 2007 用IceCube搜寻伽玛暴引起的中微子

主要内容:
没有发现信号。

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astro-ph/0702265 [abs, ps, pdf, other] :

Title: Search for neutrino-induced cascades from gamma-ray bursts with AMANDA
Authors: IceCube Collaboration: A. Achterberg, et al
Comments: 38 pages. 16 postscript figures

Using the neutrino telescope AMANDA-II, we have conducted two analyses searching for neutrino-induced cascades from gamma-ray bursts. No evidence of astrophysical neutrinos was found, and limits are presented for several models. We also present neutrino effective areas which allow the calculation of limits for any neutrino production model. The first analysis looked for a statistical excess of events within a sliding window of 1 or 100 seconds (for short and long burst classes, respectively) during the years 2001-2003. The resulting upper limit on the diffuse flux normalization times E^2 for the Waxman-Bahcall model at 1 PeV is 1.6 x 10^-6 GeV cm^-2 s^-1 sr^-1. For this search 90% of the neutrinos would fall in the energy range 50 TeV to 7 PeV. The second analysis looked for neutrino-induced cascades in coincidence with 73 bursts detected by BATSE in the year 2000. The resulting upper limit on the diffuse flux normalization times E^2, also at 1 PeV, is 1.5 x 10^-6 GeV cm^-2 s^-1 sr^-1 for the same energy range. The neutrino-induced cascade channel is complementary to the up-going muon channel. We comment on its advantages for searches of neutrinos from GRBs and its future use with IceCube.

Godet 2007 GRB 050822的观测

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astro-ph/0702262 [abs, ps, pdf, other] :

Title: GRB 050822: Detailed analysis of an XRF observed by Swift
Authors: O. Godet, K.L. Page, J. Osborne, B. Zhang, D.N. Burrows, P.T. O'Brien, J. E. Hill, J. Racusin, A.P. Beardmore, M.R. Goad, A. Falcone, D.C. Morris, H. Ziaeepour
Comments: 26 pages (referee format), 8 figures, submitted to A&A

We report on the temporal and spectral characteristics of the early X-ray emission from the GRB 050822 as observed by Swift. This burst is likely to be an XRF showing major X-ray flares in its XRT light-curve. The quality of the data allows a detailed spectral analysis of the early afterglow in the X-ray band. During the X-ray flares, a positive correlation between the count rate and the spectral hardness (i.e. higher the count rate is and harder the spectrum is) is clearly seen for the X-ray flares. This behaviour similar to that seen for Gamma-ray pulses indicates that the energy peak of the spectrum is in the XRT energy band and it moves at lower energy with time. We show evidence for the possible detection of the emergence of the forward-shock emission produced at a radius larger than 4 x 10^{16} cm (a forming region clearly different to that producing the prompt emission). Finally, we show that the null detection of a jet break up to T_0+4 x 10^6s in the X-ray light curve of this XRF can be understood: i) if the jet seen on-axis is uniform with a large opening angle (theta > 20 deg); or ii) if the jet is a structured Gaussian-like jet with the line-of-sight outside the bright Gaussian core.

Zhang 2007 不同尺度天体的相似性 3

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astro-ph/0702246 [abs, ps, pdf, other] :

Title: Similar phenomena at different scales: Black Holes, the Sun, Gamma-ray Bursts, Supernovae, Galaxies and Galaxy Clusters
Authors: Shuang Nan Zhang
Comments: 22 pages, 13 figures, invited discourse for the 26th IAU GA, Prague, Czech Republic, Aug. 2006, to be published in Vol. 14 IAU Highlights of Astronomy, Ed. K.A. van der Hucht. Revised slightly to match the final submitted version, after incorporating comments and suggestions from several colleagues. A full-resolution version is available on request from the author at zhangsn@tsinghua.edu.cn

Many similar phenomena occur in astrophysical systems with spatial and mass scales different by many orders of magnitudes. For examples, collimated outflows are produced from the Sun, proto-stellar systems, gamma-ray bursts, neutron star and black hole X-ray binaries, and supermassive black holes; various kinds of flares occur from the Sun, stellar coronae, X-ray binaries and active galactic nuclei; shocks and particle acceleration exist in supernova remnants, gamma-ray bursts, clusters of galaxies, etc. In this report I summarize briefly these phenomena and possible physical mechanisms responsible for them. I emphasize the importance of using the Sun as an astrophysical laboratory in studying these physical processes, especially the roles magnetic fields play in them; it is quite likely that magnetic activities dominate the fundamental physical processes in all of these systems.
As a case study, I show that X-ray lightcurves from solar flares, black hole binaries and gamma-ray bursts exhibit a common scaling law of non-linear dynamical properties, over a dynamical range of several orders of magnitudes in intensities, implying that many basic X-ray emission nodes or elements are inter-connected over multi-scales. A future high timing and imaging resolution solar X-ray instrument, aimed at isolating and resolving the fundamental elements of solar X-ray lightcurves, may shed new lights onto the fundamental physical mechanisms, which are common in astrophysical systems with vastly different mass and spatial scales. Using the Sun as an astrophysical laboratory, "Applied Solar Astrophysics" will deepen our understanding of many important astrophysical problems.

Margutti 2007 GRB031203宿主星系的谱

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astro-ph/0702225 [abs, ps, pdf, other] :

Title: Spectroscopical Study of the Host Galaxy of GRB031203
Authors: R. Margutti, G. Chincarini, D. Fugazza
Comments: 2 pages; 2 figures; Proceeding of the "Swift and GRBs: Unveiling the Relativistic Universe" meeting,Venice, June 5-9,2006, to be published by "Il Nuovo Cimento"

We revisit the host galaxy of GRB031203 using a set of spectra obtained with VLT. Assuming a Galactic color excess E(B-V)=0.72 (mag)in the direction of the burst,we derive an internal extinction of about 0.4 (mag). After correcting for reddening, we find an electronic density of 156 cm^{-3} and a temperature of 12443(K). With an ISM dominated by photo-ionization, we estimate a metallicity of 12+Log[O/H]=8.12 and a star formation rate of 12.3 (M_{o}yr^{-1}). This galaxy does not host a clearly detectable population of WR stars.

Troja 2007 GRB070110的观测

主要内容:
有极亮的X射线余辉

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文章信息:

astro-ph/0702220 [abs, ps, pdf, other] :

Title: Swift observations of GRB 070110: an extraordinary X-ray afterglow powered by the central engine
Authors: E. Troja, G. Cusumano, P. O'Brien, B. Zhang, B. Sbarufatti, V. Mangano, R. Willingale, G. Chincarini, J. P. Osborne, F. E. Marshall, D. N. Burrows, S. Campana, N. Gehrels, C. Guidorzi, H. A. Krimm, V. La Parola, E. W. Liang, T. Mineo, A. Moretti, K. L. Page, P. Romano, G. Tagliaferri, B. B. Zhang
Comments: 10 pages, 5 figures, submitted to ApJ

We present a detailed analysis of Swift multi-wavelength observations of GRB 070110 and its remarkable afterglow. The early X-ray light curve, interpreted as the tail of the prompt emission, displays a spectral evolution already seen in other gamma-ray bursts. The optical afterglow shows a shallow decay up to ~2 d after the burst, which is not consistent with standard afterglow models. The most intriguing feature is a very steep decay in the X-ray flux at ~20 ks after the burst, ending an apparent plateau. The abrupt drop of the X-ray light curve rules out an external shock as the origin of the plateau in this burst and implies long-lasting activity of the central engine. The temporal and spectral properties of the plateau phase point towards a continuous central engine emission rather than the episodic emission of X-ray flares. We suggest that the observed X-ray plateau is powered by a spinning down central engine, possibly a millisecond pulsar, which dissipates energy at an internal radius before depositing energy into the external shock.

Ghirlanda 2007 有关谱的统计关系在宇宙学中的应用

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astro-ph/0702212 [abs, ps, pdf, other] :

Title: GRBs spectral correlations and their cosmological use
Authors: G. Ghirlanda (INAF-Osservatorio Astronomico di Brera)
Comments: 10 pages, 6 figures. To appear in Phil. Trans. Roy. Soc. A. Proc. of the Royal Society Discussion meeting on Gamma-ray Bursts, September 18-20, 2006

Jelínek 2007 GRB060117早期极亮光学辐射的正反激波模型

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astro-ph/0702197 [abs, ps, pdf, other] :

Title: GRB 060117: Reverse + forward shock solution
Authors: Martin Jelínek, Michael Prouza, Petr Kubánek, René Hudec, Martin F. Nekola, Jan Ridky, Jiri Grygar
Comments: 2 pages, 1 figure; Proceedings of "SWIFT and GRBs: Unveiling the Relativistic Universe" June 5-9, 2006 Venice (Italy)

We present a discovery and observation of an extraordinarily bright prompt optical emission of the GRB 060117 obtained by a wide-field camera atop the robotic telescope FRAM of the Pierre Auger Observatory from 2 to 10 minutes after the GRB.
We found rapid average temporal flux decay of alpha = -1.7 +/- 0.1 and a peak brightness R = 10.1 mag.
We interpret the shape of the lightcurve as a transition between reverse and forward shock emission.

Endo 2007 GRB030329宿主星系的CO辐射

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astro-ph/0702191 [abs, ps, pdf, other] :

Title: A Revised Estimate of the CO (J=1-0) Emission from the Host Galaxy of GRB 030329 Using the Nobeyama Millimeter Array
Authors: Akira Endo, Kotaro Kohno, Bunyo Hatsukade, Kouji Ohta, Nobuyuki Kawai, Yoshiaki Sofue, Kouichiro Nakanishi, Tomoka Tosaki, Baltasar Vila-Vilaro, Nario Kuno, Takeshi Okuda, Kazuyuki Muraoka
Comments: 8 pages, 3 figures, accepted for publication in ApJ

A sensitive observation of the CO (J=1-0) molecular line emission in the host galaxy of GRB 030329 (z =0.1685) has been performed using the Nobeyama Millimeter Array in order to detect molecular gas and hidden star formation. No sign of CO emission was detected, which invalidates our previous report on the presence of molecular gas. The 3sigma upperlimit on the CO line luminosity (L'_CO) of the host galaxy is 6.9 x 10^8 K km s^-1 pc^2. The lowerlimit of the host galaxy's metallicity is estimated to be 12+log(O/H) ~ 7.9, which yields a CO line luminosity to H_2 conversion factor of alpha_CO = 40 Msun (K km s^-1 pc^2)^-1. Assuming this alpha_CO factor, the 3sigma upperlimit on the molecular gas mass of the host galaxy is 2.8 x 10^10 Msun. Based on the Schmidt law, the 3sigma upperlimit of the total star formation rate (SFR) of the host galaxy is estimated to be 38 Msun yr^-1. These results independently confirm the inferences of previous observations in the optical, submillimeter, and X-ray band, which regard this host galaxy as a compact dwarf galaxy, and not a massive, aggressively star forming galaxy.

Balazs 2007 长短暴的物理区别 2

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astro-ph/0702152 [abs, ps, pdf, other] :

Title: Physical Difference between the short and long GRBs
Authors: L. G. Balazs, Z. Bagoly, I. Horvath, A. Meszaros, P. Meszaros
Comments: 2 figures
Journal-ref: Baltic Astron. 12 (2004) 207-210

We provided separate bivariate log-normal distribution fits to the BATSE short and long burst samples using the durations and fluences. We show that these fits present an evidence for a power-law dependence between the fluence and the duration, with a statistically significant different index for the long and short groups. We argue that the effect is probably real, and the two subgroups are different physical phenomena. This may provide a potentially useful constraint for models of long and short bursts.

Schady 2007 本地环境对伽玛暴余辉的消光 2

主要内容:
可能可解释1/3的swift暴没有观测到余辉。

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astro-ph/0702122 [abs, ps, pdf, other] :

Title: Dust and Gas in the Local Environments of Gamma-Ray Bursts
Authors: P.Schady, K.O.Mason, M.J.Page, M.De Pasquale, D.C.Morris, P.Romano, P.W.A.Roming, S.Immler, D.E.Vanden Berk
Comments: 13 pages, 8 figures, accepted by MNRAS

Using a sample of gamma-ray burst (GRB) afterglows detected by both the X-Ray and the UV/Optical Telescopes (XRT and UVOT) on Swift, we modelled the spectral energy distributions (SEDs) to determine gas column densities and dust extinction in the GRB local environment. In six out of seven cases we find an X-ray absorber associated with the GRB host galaxy with column density (assuming solar abundances) ranging from (0.8 - 7.7)x10^{21}cm^{-2}. We determine the rest-frame visual extinction A_V using the SMC, LMC and Galactic extinction curves to model the dust in the GRB host galaxy, and this ranges from A_V = 0.12\pm 0.04 to A_V = 0.65^{+0.08}_{-0.07}. The afterglow SEDs were typically best fit by a model with an SMC extinction curve. In only one case was the GRB afterglow better modelled by a Galactic extinction curve, which has a prominent absorption feature at 2175angstrom. We investigate the selection effects present in our sample and how these might distort the true distribution of A_V in GRB host galaxies. We estimate that GRBs with no afterglow detected blueward of 5500angstrom have average rest-frame visual extinctions almost eight times those observed in the optically bright population of GRBs. This may help account for the ~1/3 of GRBs observed by Swift that have no afterglow detected by UVOT.

Wei 2007 早期高能辐射的同步自康普顿模型 3

主要内容:
以目前shallow decay为提示，假设在能量注入情况下，计算同步自康普顿辐射，可以解释早期的持续高能辐射。并解释了GRB94017

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astro-ph/0702106 [abs, ps, pdf, other] :

Title: The synchrotron-self-Compton radiation accompanying shallow decaying X-ray afterglow: the case of GRB 940217
Authors: Da-Ming Wei (PMO), Yi-Zhong Fan (HU and PMO)
Comments: 11 pages, including 1 figure and 1 table

High energy emission (> tens MeV) of Gamma-Ray Bursts (GRBs) provides an important clue to understand the physical processes involved in GRBs, which may be correlated with the GRB early afterglow. A shallow decline phase has been well detected in about half {\it Swift} Gamma-ray Burst X-ray afterglows. The widely considered interpretation involves a significant energy injection and possibly time-evolving shock parameter(s). This work we calculate the synchrotron-self-Compton (SSC) radiation of such an external forward shock and show that it could explain the well-known long term high energy (i.e., tens MeV to GeV) afterglow of GRB 940217. We propose that the cooperation of Swift and GLAST will help to reveal the nature of GRBs.

Macquart 2007 伽玛暴prompt阶段的射电辐射探测率

主要内容:
从伽玛暴源出来的伽玛光子与ISM作用，发生康普顿和拉曼散射，产生射电辐射。

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astro-ph/0702098 [abs, ps, pdf, other] :

Title: On the Detectability of Prompt Coherent GRB Radio Emission
Authors: J.-P. Macquart
Comments: ApJ Lett accepted

Both induced Compton scattering and induced Raman scattering strongly limit the observability of the extremely bright (<<> 10^3 (D/100 Mpc), or if the intrinsic opening angle of the emission is extremely small. Thus the presence or absence of such radio emission provides an excellent constraint on the Lorentz factor of the GRB outflow during the very early stages of its outburst. Induced Raman scattering imposes an even more stringent limit independent of the emission opening angle, but only effective if GRB emission must propagate through a dense progenitor wind within ~ 10^{15} cm from the blast center.

Stephens 2007 短暴的超重磁中子星模型

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astro-ph/0702080 [abs, ps, pdf, other] :

Title: Magnetized Hypermassive Neutron Star Collapse: a candidate central engine for short-hard GRBs
Authors: Branson C. Stephens, Matthew D. Duez, Yuk Tung Liu, Stuart L. Shapiro, Masaru Shibta
Comments: 3 pages, 1 figure, submitted to the MG11 proceedings

Hypermassive neutron stars (HMNSs) are equilibrium configurations supported against collapse by rapid differential rotation and likely form as transient remnants of binary neutron star mergers. Though HMNSs are dynamically stable, secular effects such as viscosity or magnetic fields tend to bring HMNSs into uniform rotation and thus lead to collapse. We simulate the evolution of magnetized HMNSs in axisymmetry using codes which solve the Einstein-Maxwell-MHD system of equations. We find that magnetic braking and the magnetorotational instability (MRI) both contribute to the eventual collapse of HMNSs to rotating black holes surrounded by massive, hot accretion tori and collimated magnetic fields. Such hot tori radiate strongly in neutrinos, and the resulting neutrino-antineutrino annihilation could power short-hard GRBs.

van Eijndhoven 2007 伽玛暴高能中微子的观测

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astro-ph/0702029 [abs, ps, pdf, other] :

Title: On the observability of high-energy neutrinos from gamma ray bursts
Authors: Nick van Eijndhoven
Comments: 8 pages, 7 figures

A method is presented for the identification of high-energy neutrinos from gamma ray bursts by means of a large-scale neutrino telescope. The procedure makes use of a time profile stacking technique of observed neutrino induced signals in correlation with satellite observations. By selecting a rather wide time window, a possible difference between the arrival times of the gamma and neutrino signals may also be identified. This might provide insight in the particle production processes at the source. By means of a toy model it will be demonstrated that a statistically significant signal can be obtained with a km^3 scale neutrino telescope on a sample of 500 gamma ray bursts for a signal rate as low as 1 detectable neutrino for 3% of the bursts.

Hafizi 2007 谱时延关系和Amati关系不兼容

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astro-ph/0702028 [abs, ps, pdf, other] :

Title: Is the time lag-luminosity relation of GRBs a consequence of the Amati relation?
Authors: Mimoza Hafizi, Robert Mochkovitch
Comments: Accepted for publication in Astronomy & Astrophysics, 5 pages, 3 figures

The lag-luminosity relation (LLR) provides a way of estimating GRB luminosity by measuring the spectral lags between different energy bands. We want to understand the origin of the LLR and test its validity. This appears especially important if the LLR is to be used as a distance indicator. We perform a linear analysis of the lag between two spectral bands. The lag is obtained as the time interval between the maxima of a given pulse in the two bands. We get a simple expression for the lag, which shows in a very simple way how it is related to the spectral evolution of the burst via the variation of the peak energy and spectral indices. When this expression is coupled to the Amati relation, it leads to a LLR that agrees with the observational results only if the burst's spectral evolution is limited to a decrease in peak energy during pulse decay. However, when the variation of the spectral indices is also taken into account, the predicted LLR differs from the observed one. We briefly discuss some ways to solve this problem, such as a possible correlation between pulse spikiness and burst luminosity.

Fan 2007 伽玛暴余辉的偏振限定量子引力模型

主要内容:
用伽玛暴的偏振限定量子引力模型。

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astro-ph/0702006 [abs, ps, pdf, other] :

Title: Gamma-ray Burst UV/optical afterglow polarimetry as a probe of Quantum Gravity
Authors: Yi-Zhong Fan, Da-Ming Wei, Dong Xu
Comments: 4 pages including 3 eps figures, accepted for publication in MNRAS

A possible birefringence effect that arises in quantum gravity leads to a frequency-dependent rotation of the polarization angle of linearly polarized emission from distant sources. Here we use the UV/optical polarization data of the afterglows of GRB 020813 and GRB 021004 to constrain this effect. We find an upper limit on the Gambini & Pulin birefringence parameter $| \eta | <2\times>

Ghirlanda 2007 GRB060218的Ep-Eiso关系

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文章信息:

astro-ph/0702004 [abs, ps, pdf, other] :

Title: GRB 060218 and the outliers with respect to the Ep-Eiso correlation
Authors: G. Ghirlanda, G. Ghisellini (INAF-Osservatorio Astronomico di Brera)
Comments: To appear in the conference proceeding of the IV workshop on "Science with the new generation of high energy Gamma-Ray Experiment", 20-22 June 2006, Isola d'Elba