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Featured researches published by Guido Chincarini.


Monthly Notices of the Royal Astronomical Society | 2009

Methods and results of an automatic analysis of a complete sample of Swift-XRT observations of GRBs

P. A. Evans; A. P. Beardmore; Kim L. Page; J. P. Osborne; Paul T. O'Brien; R. Willingale; Rhaana L. C. Starling; D. N. Burrows; Olivier Godet; L. Vetere; Judith Lea Racusin; Mike R. Goad; K. Wiersema; L. Angelini; Milvia Capalbi; Guido Chincarini; Neil Gehrels; J. A. Kennea; Raffaella Margutti; D. C. Morris; C. J. Mountford; C. Pagani; Matteo Perri; Patrizia Romano; Nial R. Tanvir

We present a homogeneous X-ray analysis of all 318 gamma-ray bursts detected by the X-ray telescope (XRT) on the Swift satellite up to 2008 July 23; this represents the largest sample of X-ray GRB data published to date. In Sections 2-3, we detail the methods which the Swift-XRT team has developed to produce the enhanced positions, light curves, hardness ratios and spectra presented in this paper. Software using these methods continues to create such products for all new GRBs observed by the Swift-XRT. We also detail web-based tools allowing users to create these products for any object observed by the XRT, not just GRBs. In Sections 4-6, we present the results of our analysis of GRBs, including probability distribution functions of the temporal and spectral properties of the sample. We demonstrate evidence for a consistent underlying behaviour which can produce a range of light-curve morphologies, and attempt to interpret this behaviour in the framework of external forward shock emission. We find several difficulties, in particular that reconciliation of our data with the forward shock model requires energy injection to continue for days to weeks.


The Astrophysical Journal | 2005

Evidence for a canonical GRB afterglow light curve in the Swift/XRT data

Ja Nousek; Vanessa Mangano; Paul T. O'Brien; P. Giommi; Olivier Godet; S. D. Barthelmy; Mike R. Goad; Sergio Campana; G. Cusumano; J. P. Osborne; A. P. Beardmore; A. Falcone; Jonathan Granot; G. Tagliaferri; Milvia Capalbi; David N. Burrows; Patrizia Romano; C. P. Hurkett; J. A. Kennea; Guido Chincarini; Dirk Grupe; Enrico Ramirez-Ruiz; Sandy Patel; Kim L. Page; Alan A. Wells; Chryssa Kouveliotou; A. Moretti; N. Gehrels

We present new observations of the early X-ray afterglows of the first 27 gamma-ray bursts (GRBs) detected with the Swift X-ray Telescope (XRT). The early X-ray afterglows show a canonical behavior, where the light curve broadly consists of three distinct power law segments. These power law segments are separated by two corresponding break times. On top of this canonical behavior of the early X-ray light curve, many events have superimposed X-ray flares, which are most likely caused by internal shocks due to long lasting sporadx activity of the central engine, up to several hours after the GRB. We find that the initial steep decay is consistent with it being the tail of the prompt emission: from photons that are radiated at large angles relative to our line of sight. The first break in the light curve takes place when the forward shock emission becomes dominant, with the intermediate shallow flux decay likely caused by the continuous energy injection into the external shock. When this energy injection stops, a second break is then observed in the light curve. This energy injection increases the energy of the afterglow shock by at least a factor of f greater than or approx. equal to 4, and augments the already severe requirements for the efficiency of the prompt gamma-ray emission.


The Astrophysical Journal | 2006

Evidence for a canonical gamma-ray burst afterglow light curve in the Swift XRT data

John A. Nousek; C. Kouveliotou; Dirk Grupe; Kim L. Page; Jonathan Granot; Enrico Ramirez-Ruiz; Sandeep K. Patel; D. N. Burrows; Vanessa Mangano; S. D. Barthelmy; A. P. Beardmore; Sergio Campana; Milvia Capalbi; Guido Chincarini; G. Cusumano; A. Falcone; N. Gehrels; P. Giommi; Mike R. Goad; Olivier Godet; C. P. Hurkett; J. A. Kennea; A. Moretti; P. T. O’Brien; J. P. Osborne; Patrizia Romano; G. Tagliaferri; Alan A. Wells

We present new observations of the early X-ray afterglows of the first 27 gamma-ray bursts (GRBs) well observed by the Swift X-Ray Telescope (XRT). The early X-ray afterglows show a canonical behavior, where the light curve broadly consists of three distinct power-law segments: (1) an initial very steep decay (/t � � with 3P � 1 P5), followed by (2) a very shallow decay (0:5P � 2 P1:0), and finally (3) a somewhat steeper decay (1P � 3 P1:5). These power-law segments are separated by two corresponding break times, tbreak;1 P500 s and 10 3 sPtbreak;2P 10 4 s. On top of this canonical behavior, many events have superimposed X-ray flares, which are most likely caused by internal shocks due to long-lasting sporadic activity of the central engine, up to several hours after the GRB. We find that the initial steep decay is consistent with it being the tail of the prompt emission, from photons that are radiated at large angles relative to our line of sight. The first break in the light curve (tbreak;1) takes place when the forward shock emission becomes dominant, with the intermediate shallow flux decay (� 2) likely caused by the continuous energy injection into the external shock. When this energy injection stops, a second break is then observed in the light curve (tbreak;2). This energy injection increases the energy of the afterglow shock by at least a factor of f k4 and augments the already severe requirements for the efficiency of the prompt gamma-ray emission. Subject headingg gamma rays: bursts — radiation mechanisms: nonthermal


Nature | 2006

The association of GRB 060218 with a supernova and the evolution of the shock wave.

Sergio Campana; Vanessa Mangano; Alexander J. Blustin; Peter J. Brown; David N. Burrows; Guido Chincarini; J. R. Cummings; G. Cusumano; M. Della Valle; Daniele Malesani; P. Meszaros; John A. Nousek; M. J. Page; Takanori Sakamoto; Eli Waxman; Bing Zhang; Z. G. Dai; Neil Gehrels; Stefan Immler; F. E. Marshall; K. Mason; A. Moretti; Paul T. O'Brien; Julian P. Osborne; Kim L. Page; Patrizia Romano; Pwa Roming; Gianpiero Tagliaferri; L. R. Cominsky; P. Giommi

Although the link between long Gamma Ray Bursts (GRBs) and supernovae (SNe) has been established, hitherto there have been no observations of the beginning of a supernova explosion and its intimate link to a GRB. In particular, we do not know however how a GRB jet emerges from the star surface nor how a GRB progenitor explodes. Here we report on observations of the close GRB060218 and its connection to SN2006aj. In addition to the classical non-thermal emission, GRB060218 shows a thermal component in its X-ray spectrum, which cools and shifts into the optical/UV band as time passes. We interpret these features as arising from the break out of a shock driven by a mildly relativistic shell into the dense wind surrounding the progenitor. Our observations allow us for the first time to catch a SN in the act of exploding, to directly observe the shock break-out and to provide strong evidence that the GRB progenitor was a Wolf-Rayet star.Although the link between long γ-ray bursts (GRBs) and supernovae has been established, hitherto there have been no observations of the beginning of a supernova explosion and its intimate link to a GRB. In particular, we do not know how the jet that defines a γ-ray burst emerges from the stars surface, nor how a GRB progenitor explodes. Here we report observations of the relatively nearby GRB 060218 (ref. 5) and its connection to supernova SN 2006aj (ref. 6). In addition to the classical non-thermal emission, GRB 060218 shows a thermal component in its X-ray spectrum, which cools and shifts into the optical/ultraviolet band as time passes. We interpret these features as arising from the break-out of a shock wave driven by a mildly relativistic shell into the dense wind surrounding the progenitor. We have caught a supernova in the act of exploding, directly observing the shock break-out, which indicates that the GRB progenitor was a Wolf–Rayet star.


Science | 2005

Bright X-ray Flares in Gamma-Ray Burst Afterglows

David N. Burrows; Patrizia Romano; A. Falcone; Shiho Kobayashi; Bing Zhang; A. Moretti; Paul T. O'Brien; Michael R. Goad; Sergio Campana; Kim L. Page; Lorella Angelini; S. D. Barthelmy; Andrew P. Beardmore; Milvia Capalbi; Guido Chincarini; J. R. Cummings; G. Cusumano; Derek B. Fox; Paolo Giommi; J. E. Hill; J. A. Kennea; Hans A. Krimm; Vanessa Mangano; Francis E. Marshall; P. Meszaros; David C. Morris; John A. Nousek; Julian P. Osborne; Claudio Pagani; Matteo Perri

Gamma-ray burst (GRB) afterglows have provided important clues to the nature of these massive explosive events, providing direct information on the nearby environment and indirect information on the central engine that powers the burst. We report the discovery of two bright x-ray flares in GRB afterglows, including a giant flare comparable in total energy to the burst itself, each peaking minutes after the burst. These strong, rapid x-ray flares imply that the central engines of the bursts have long periods of activity, with strong internal shocks continuing for hundreds of seconds after the gamma-ray emission has ended.


Nature | 2005

A short γ-ray burst apparently associated with an elliptical galaxy at redshift z = 0.225

Neil Gehrels; Craig L. Sarazin; Paul T. O'Brien; Bing Zhang; Loius M. Barbier; S. D. Barthelmy; Alexander J. Blustin; David N. Burrows; J. Cannizzo; J. R. Cummings; Michael R. Goad; Stephen T. Holland; C. P. Hurkett; J. A. Kennea; Andrew J. Levan; Craig B. Markwardt; K. O. Mason; P. Meszaros; M. J. Page; David M. Palmer; E. Rol; Takanori Sakamoto; R. Willingale; Lorella Angelini; Andrew P. Beardmore; Patricia T. Boyd; Alice A. Breeveld; Sergio Campana; Margaret Chester; Guido Chincarini

Gamma-ray bursts (GRBs) come in two classes: long (> 2 s), soft-spectrum bursts and short, hard events. Most progress has been made on understanding the long GRBs, which are typically observed at high redshift (z ≈ 1) and found in subluminous star-forming host galaxies. They are likely to be produced in core-collapse explosions of massive stars. In contrast, no short GRB had been accurately (< 10″) and rapidly (minutes) located. Here we report the detection of the X-ray afterglow from—and the localization of—the short burst GRB 050509B. Its position on the sky is near a luminous, non-star-forming elliptical galaxy at a redshift of 0.225, which is the location one would expect if the origin of this GRB is through the merger of neutron-star or black-hole binaries. The X-ray afterglow was weak and faded below the detection limit within a few hours; no optical afterglow was detected to stringent limits, explaining the past difficulty in localizing short GRBs.


The Astrophysical Journal | 2006

The early x-ray emission from grbs

P. T. O’Brien; R. Willingale; Julian P. Osborne; Mike R. Goad; Kim L. Page; S. Vaughan; E. Rol; A. P. Beardmore; Olivier Godet; C. P. Hurkett; Alan A. Wells; Bing Zhang; Shiho Kobayashi; David N. Burrows; John A. Nousek; J. A. Kennea; A. Falcone; Dirk Grupe; Neil Gehrels; S. D. Barthelmy; John K. Cannizzo; J. R. Cummings; J. E. Hill; Hans A. Krimm; Guido Chincarini; Gianpiero Tagliaferri; Sergio Campana; A. Moretti; P. Giommi; Matteo Perri

We present observations of the early X-ray emission for a sample of 40 gamma-ray bursts (GRBs) obtained using the Swift satellite, for which the narrow-field instruments were pointed at the burst within 10 minutes of the trigger. Using data from the Burst Alert Telescope and the X-Ray Telescope, we show that the X-ray light curve can be well described by an exponential that relaxes into a power law, often with flares superimposed. The transition time between the exponential and the power law provides a physically defined timescale for the burst duration. In most bursts, the power law breaks to a shallower decay within the first hour, and a late emission hump is observed, which can last for many hours. In other GRBs the hump is weak or absent. The observed variety in the shape of the early X-ray light curve can be explained as a combination of three components: prompt emission from the central engine, afterglow, and the late hump. In this scenario, afterglow emission begins during or soon after the burst, and the observed shape of the X-ray light curve depends on the relative strengths of the emission due to the central engine and that of the afterglow. There is a strong correlation such that those GRBs with stronger afterglow components have brighter early optical emission. The late emission hump can have a total fluence equivalent to that of the prompt phase. GRBs with the strongest late humps have weak or no X-ray flares.


Nature | 2006

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

M. Della Valle; Guido Chincarini; N. Panagia; G. Tagliaferri; Daniele Malesani; Vincenzo Testa; Dino Fugazza; Sergio Campana; S. Covino; Vanessa Mangano; L. A. Antonelli; P. D’Avanzo; K. Hurley; I. F. Mirabel; L. J. Pellizza; S. Piranomonte; L. Stella

Gamma-ray bursts (GRBs) are short, intense flashes of soft γ-rays coming from the distant Universe. Long-duration GRBs (those lasting more than ∼2 s) are believed to originate from the deaths of massive stars, mainly on the basis of a handful of solid associations between GRBs and supernovae. GRB 060614, one of the closest GRBs discovered, consisted of a 5-s hard spike followed by softer, brighter emission that lasted for ∼100 s (refs 8, 9). Here we report deep optical observations of GRB 060614 showing no emerging supernova with absolute visual magnitude brighter than MV = -13.7. Any supernova associated with GRB 060614 was therefore at least 100 times fainter, at optical wavelengths, than the other supernovae associated with GRBs. This demonstrates that some long-lasting GRBs can either be associated with a very faint supernova or produced by different phenomena.


The Astrophysical Journal | 2010

THE AFTERGLOWS OF SWIFT-ERA GAMMA-RAY BURSTS. I. COMPARING PRE-SWIFT AND SWIFT-ERA LONG/SOFT (TYPE II) GRB OPTICAL AFTERGLOWS

D. A. Kann; Sylvio Klose; Bin-Bin Zhang; Daniele Malesani; Ehud Nakar; Alexei S. Pozanenko; A. C. Wilson; N. Butler; P. Jakobsson; S. Schulze; M. Andreev; L. A. Antonelli; I. Bikmaev; Vadim Biryukov; M. Böttcher; R. A. Burenin; J. M. Castro Cerón; A. J. Castro-Tirado; Guido Chincarini; Bethany Elisa Cobb; S. Covino; P. D'Avanzo; Valerio D'Elia; M. Della Valle; A. de Ugarte Postigo; Yu. S. Efimov; P. Ferrero; Dino Fugazza; J. P. U. Fynbo; M. Gålfalk

We have gathered optical photometry data from the literature on a large sample of Swift-era gamma-ray burst (GRB) afterglows including GRBs up to 2009 September, for a total of 76 GRBs, and present an additional three pre-Swift GRBs not included in an earlier sample. Furthermore, we publish 840 additional new photometry data points on a total of 42 GRB afterglows, including large data sets for GRBs 050319, 050408, 050802, 050820A, 050922C, 060418, 080413A, and 080810. We analyzed the light curves of all GRBs in the sample and derived spectral energy distributions for the sample with the best data quality, allowing us to estimate the host-galaxy extinction. We transformed the afterglow light curves into an extinction-corrected z = 1 system and compared their luminosities with a sample of pre-Swift afterglows. The results of a former study, which showed that GRB afterglows clustered and exhibited a bimodal distribution in luminosity space, are weakened by the larger sample. We found that the luminosity distribution of the two afterglow samples (Swift-era and pre-Swift) is very similar, and that a subsample for which we were not able to estimate the extinction, which is fainter than the main sample, can be explained by assuming a moderate amount of line-of-sight host extinction. We derived bolometric isotropic energies for all GRBs in our sample, and found only a tentative correlation between the prompt energy release and the optical afterglow luminosity at 1 day after the GRB in the z = 1 system. A comparative study of the optical luminosities of GRB afterglows with echelle spectra (which show a high number of foreground absorbing systems) and those without, reveals no indication that the former are statistically significantly more luminous. Furthermore, we propose the existence of an upper ceiling on afterglow luminosities and study the luminosity distribution at early times, which was not accessible before the advent of the Swift satellite. Most GRBs feature afterglows that are dominated by the forward shock from early times on. Finally, we present the first indications of a class of long GRBs, which form a bridge between the typical high-luminosity, high-redshift events and nearby low-luminosity events (which are also associated with spectroscopic supernovae) in terms of energetics and observed redshift distribution, indicating a continuous distribution overall.


The Astrophysical Journal | 2004

SN 2003lw and GRB 031203: A Bright Supernova for a Faint Gamma-Ray Burst

Daniele Malesani; Gianpiero Tagliaferri; Guido Chincarini; S. Covino; M. Della Valle; Dino Fugazza; Paolo A. Mazzali; Filippo Maria Zerbi; Paolo D'Avanzo; S. Kalogerakos; A. Simoncelli; L. A. Antonelli; L. Burderi; Sergio Campana; A. Cucchiara; F. Fiore; G. Ghirlanda; Paolo Goldoni; Diego Gotz; S. Mereghetti; I. F. Mirabel; Patrizia Romano; L. Stella; Takeo Minezaki; Yuzuru Yoshii; K. Nomoto

Optical and near-infrared observations of the gamma-ray burst GRB 031203, at z = 0.1055, are reported. A very faint afterglow is detected superposed onto the host galaxy in our first infrared JHK observations, carried out ~9 hr after the burst. Subsequently, a rebrightening is detected in all bands, peaking in the R band about 18 rest-frame days after the burst. The rebrightening closely resembles the light curve of a supernova like SN 1998bw, assuming that the GRB and the SN went off almost simultaneously, but with a somewhat slower evolution. Spectra taken close to the maximum of the rebrightening show extremely broad features as in SN 1998bw. The determination of the absolute magnitude of this SN (SN 2003lw) is difficult owing to the large and uncertain extinction, but likely this event was brighter than SN 1998bw by 0.5 mag in the VRI bands, reaching an absolute magnitude MV = -19.75 ± 0.15.

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