Chincarini 2007 Swift暴的X射线耀发总结

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一共69个。

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文章信息:

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

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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.