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D. Rizzuto C. Guidorzi P. Romano S. Covino S. Campana M. Capalbi G. Chincarini G. Cusumano D. Fugazza V. Mangano A. Moretti M. Perri G. Tagliaferri 《Monthly notices of the Royal Astronomical Society》2007,379(2):619-628
We test the gamma-ray burst (GRB) correlation between temporal variability and peak luminosity of the γ-ray profile on a homogeneous sample of 36 Swift /Burst Alert Telescope (BAT) GRBs with firm redshift determination. This is the first time that this correlation can be tested on a homogeneous data sample. The correlation is confirmed, as long as the six GRBs with low luminosity ( <5 × 1050 erg s−1 in the rest-frame 100–1000 keV energy band) are ignored. We confirm that the considerable scatter of the correlation already known is not due to the combination of data from different instruments with different energy bands, but it is intrinsic to the correlation itself. Thanks to the unprecedented sensitivity of Swift /BAT, the variability/peak luminosity correlation is tested on low-luminosity GRBs. Our results show that these GRBs are definite outliers. 相似文献
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S. R. Oates C. G. Mundell S. Piranomonte K. L. Page M. De Pasquale A. Monfardini A. Melandri S. Zane C. Guidorzi D. Malesani A. Gomboc N. Bannister A. J. Blustin M. Capalbi D. Carter P. D'Avanzo S. Kobayashi H. A. Krimm P. T. O'Brien M. J. Page R. J. Smith I. A. Steele N. Tanvir 《Monthly notices of the Royal Astronomical Society》2006,372(1):327-337
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Ghirlanda G. Salvaterra R. Toffano M. Ronchini S. Guidorzi C. Oganesyan G. Ascenzi S. Bernardini M. G. Camisasca A. E. Mereghetti S. Nava L. Ravasio M. E. Branchesi M. Castro-Tirado A. Amati L. Blain A. Bozzo E. O’Brien P. Götz D. Le Floch E. Osborne J. P. Rosati P. Stratta G. Tanvir N. Bogomazov A. I. D’Avanzo P. Hafizi M. Mandhai S. Melandri A. Peer A. Topinka M. Vergani S. D. Zane S. 《Experimental Astronomy》2021,52(3):277-308
Gamma-ray Bursts (GRBs) are the most powerful transients in the Universe, over–shining for a few seconds all other γ-ray sky sources. Their emission is produced within narrowly collimated relativistic jets launched after the core–collapse of massive stars or the merger of compact binaries. THESEUS will open a new window for the use of GRBs as cosmological tools by securing a statistically significant sample of high-z GRBs, as well as by providing a large number of GRBs at low–intermediate redshifts extending the current samples to low luminosities. The wide energy band and unprecedented sensitivity of the Soft X-ray Imager (SXI) and X-Gamma rays Imaging Spectrometer (XGIS) instruments provide us a new route to unveil the nature of the prompt emission. For the first time, a full characterisation of the prompt emission spectrum from 0.3 keV to 10 MeV with unprecedented large count statistics will be possible revealing the signatures of synchrotron emission. SXI spectra, extending down to 0.3 keV, will constrain the local metal absorption and, for the brightest events, the progenitors’ ejecta composition. Investigation of the nature of the internal energy dissipation mechanisms will be obtained through the systematic study with XGIS of the sub-second variability unexplored so far over such a wide energy range. THESEUS will follow the spectral evolution of the prompt emission down to the soft X–ray band during the early steep decay and through the plateau phase with the unique ability of extending above 10 keV the spectral study of these early afterglow emission phases.
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A. Melandri C. Guidorzi S. Kobayashi D. Bersier C. G. Mundell P. Milne A. Pozanenko W. Li A. V. Filippenko Y. Urata M. Ibrahimov I. A. Steele A. Gomboc R. J. Smith N. R. Tanvir E. Rol K. Huang 《Monthly notices of the Royal Astronomical Society》2009,395(4):1941-1949
We present a comprehensive multiwavelength temporal and spectral analysis of the 'fast rise exponential decay' GRB 070419A. The early-time emission in the γ-ray and X-ray bands can be explained by a central engine active for at least 250 s, while at late times the X-ray light curve displays a simple power-law decay. In contrast, the observed behaviour in the optical band is complex (from 102 up to 106 s). We investigate the light-curve behaviour in the context of the standard forward/reverse shock model; associating the peak in the optical light curve at ∼450 s with the fireball deceleration time results in a Lorenz factor Γ≈ 350 at this time. In contrast, the shallow optical decay between 450 and 1500 s remains problematic, requiring a reverse shock component whose typical frequency is above the optical band at the optical peak time for it to be explained within the standard model. This predicts an increasing flux density for the forward shock component until t ∼ 4 × 106 s , inconsistent with the observed decay of the optical emission from t ∼ 104 s . A highly magnetized fireball is also ruled out due to unrealistic microphysic parameters and predicted light-curve behaviour that is not observed. We conclude that a long-lived central engine with a finely tuned energy injection rate and a sudden cessation of the injection is required to create the observed light curves, consistent with the same conditions that are invoked to explain the plateau phase of canonical X-ray light curves of γ-ray bursts. 相似文献
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F. Rossi C. Guidorzi L. Amati F. Frontera P. Romano S. Campana G. Chincarini E. Montanari A. Moretti G. Tagliaferri 《Monthly notices of the Royal Astronomical Society》2008,388(3):1284-1292
Using a sample of 14 BeppoSAX and 74 Swift GRBs with measured redshift we tested the correlation between the intrinsic peak energy of the time-integrated spectrum, E p, i , the isotropic-equivalent peak luminosity, L p,iso , and the duration of the most intense parts of the GRB computed as T 0.45 ('Firmani correlation'). For 41 out of 88 GRBs we could estimate all of the three required properties. Apart from 980425, which appears to be a definite outlier and notoriously peculiar in many respects, we used 40 GRBs to fit the correlation with the maximum likelihood method discussed by D'Agostini, suitable to account for the extrinsic scatter in addition to the intrinsic uncertainties affecting every single GRB. We confirm the correlation. However, unlike the results by Firmani et al., we found that the correlation does have a logarithmic scatter comparable with that of the E p, i – E iso ('Amati') correlation. We also find that the slope of the product L p,iso T 0.45 is equal to ∼0.5, which is consistent with the hypothesis that the E p, i – L p,iso – T 0.45 correlation is equivalent to the E p, i – E iso correlation (slope ∼0.5). We conclude that, based on presently available data, there is no clear evidence that the E p, i – L p,iso – T 0.45 correlation is different (both in terms of slope and dispersion) from the E p, i – E iso correlation. 相似文献
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R. Salvaterra C. Guidorzi S. Campana G. Chincarini G. Tagliaferri 《Monthly notices of the Royal Astronomical Society》2009,396(1):299-303
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 Burst and Transient Source Experiment (BATSE) in two different scenarios: (i) the GRB luminosity evolves with redshift and (ii) GRBs form preferentially in low-metallicity environments. In both cases, model predictions are consistent with the Swift number counts and with the number of detections at z > 2.5 and >3.5. To discriminate between the two evolutionary scenarios, we compare the model results with the number of luminous bursts (i.e. with isotropic peak luminosity in excess of 1053 erg s−1 ) detected by Swift in its first 3 yr of mission. Our sample conservatively contains only bursts with good redshift determination and measured peak energy. We find that pure luminosity evolution models can account for the number of sure identifications. In the case of a pure density evolution scenario, models with Z th > 0.3 Z⊙ are ruled out with high confidence. For lower metallicity thresholds, the model results are still statistically consistent with available lower limits. However, many factors can increase the discrepancy between model results and data, indicating that some luminosity evolution in the GRB LF may be needed also for such low values of Z th . Finally, using these new constraints, we derive robust upper limits on the bright end of the GRB LF, showing that this cannot be steeper than ∼2.6. 相似文献