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Jitter radiation images, spectra, and light curves from a relativistic spherical blastwave
Brian J. Morsony, Jared C. Workman, Davide Lazzati +1
We consider radiation emitted by the jitter mechanism in a Blandford-McKee self-similar blastwave. We assume the magnetic field configuration throughout the whole blastwave meets t…
The short GRB070707 afterglow and its very faint host galaxy
S. Piranomonte, P. D'Avanzo, S. Covino +18
We present the results from an ESO/VLT campaign aimed at studying the afterglow properties of the short/hard gamma ray burst GRB 070707. Observations were carried out at ten differ…
Precursors in Swift Gamma Ray Bursts with redshift
D. Burlon, G. Ghirlanda, G. Ghisellini +4
We study a sample of Gamma-Ray Bursts detected by the Swift satellite with known redshift which show a precursor in the Swift-BAT light curve. We analyze the spectra of the precurs…
X-ray flares, neutrino cooled disks, and the dynamics of late accretion in GRB engines
Davide Lazzati, Rosalba Perna, Mitchell C. Begelman
We compute the average luminosity of X-ray flares as a function of time, for a sample of 10 long-duration gamma-ray burst afterglows. The mean luminosity, averaged over a timescale…
X-ray flares and their relation to the inner engine activity of GRBs
Davide Lazzati, Brian J. Morsony, Rosalba Perna +1
Flares overlaid on the smooth power-law decay of Swift X-ray afterglows are rather common, appearing in roughly half the observed light curves. They are a manifestation of the late…
A Direct Measurement of the Dust Extinction Curve in an Intermediate-Redshift Galaxy
Kevin Heng, Davide Lazzati, Rosalba Perna +5
We present a proof-of-concept study that dust extinction curves can be extracted from the infrared (IR), optical, ultraviolet (UV) and X-ray afterglow observations of GRBs without…
The nature of HHL 73 from optical imaging and Integral Field Spectroscopy
R. Lopez, S. F. Sanchez, B. Garcia-Lorenzo +3
We present new results on the nature of the Herbig-Haro-like object 73 (HHL73, also known as [G84b] 11) based on narrow-band CCD H_alpha and [SII] images of the HHL73 field, and In…
Multicolor observations of the afterglow of the short/hard GRB 050724
D. Malesani, S. Covino, P. D'Avanzo +19
New information on short/hard gamma-ray bursts (GRBs) is being gathered thanks to the discovery of their optical and X-ray afterglows. However, some key aspects are still poorly un…
Jitter radiation as a possible mechanism for Gamma-Ray Burst afterglows. Spectra and lightcurves
Mikhail V. Medvedev, Davide Lazzati, Brian C. Morsony +1
The standard model of GRB afterglows assumes that the radiation observed as a delayed emission is of synchrotron origin, which requires the shock magnetic field to be relatively ho…
Dust Echoes from the Ambient Medium of Gamma-Ray Bursts
Kevin Heng, Davide Lazzati, Rosalba Perna
Long gamma-ray bursts (GRBs) are likely associated with the collapse of massive stars, which produce dust and are born in dusty environments. Absorption and scattering of ultraviol…
Jitter radiation in gamma-ray bursts and their afterglows: emission and self-absorption
Jared Workman, Brian Morsony, Davide Lazzati +1
Relativistic electrons moving into a highly tangled magnetic field emit jitter radiation. We present a detailed computation of the jitter radiation spectrum, including self-absorpt…
The physics of GRB jets and their interaction with the progenitor star
Davide Lazzati, Brian J. Morsony, Mitchell C. Begelman
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…
X-ray flares and the duration of engine activity in gamma-ray bursts
Davide Lazzati, Rosalba Perna
The detection of bright X-ray flares superimposed on the regular afterglow decay in Swift gamma-ray bursts has triggered theoretical speculations on their origin. We study the temp…
GRB progenitors and their environments
Davide Lazzati
The detection of supernova features in the late spectra of several gamma-ray burst afterglows has shown that at least a fraction of long-duration gamma-ray bursts are associated to…
Gamma-Ray Burst jet dynamics and their interaction with the progenitor star
Davide Lazzati, Brian J. Morsony, Mitchell C. Begelman
The association of at least some long gamma-ray bursts with type Ic supernova explosions has been established beyond reasonable doubt. Theoretically, the challenge is to explain th…
Temporal and Angular Properties of GRB Jets Emerging from Massive Stars
Brian J. Morsony, Davide Lazzati, Mitchell C. Begelman
We study the long-term evolution of relativistic jets in collapsars and examine the effects of viewing angle on the subsequent gamma ray bursts. We carry out a series of high-resol…
Time resolved spectroscopy of GRB 021004 reveals a clumpy extended wind
D. Lazzati, R. Perna, J. Flasher +2
High resolution spectroscopy of GRB 021004 revealed a wealth of absorption lines from several intermediate ionization species. The velocity structure of the absorber is complex and…
Polarization in the prompt emission of gamma-ray bursts and their afterglows
Davide Lazzati
Synchrotron is considered the dominant emission mechanism in the production of gamma-ray burst photons in the prompt as well as in the afterglow phase. Polarization is a characteri…
The X-ray afterglow of the short gamma ray burst 050724
S. Campana, G. Tagliaferri, D. Lazzati +23
Short duration (<2 s) Gamma-ray bursts (GRBs) have been a mystery since their discovery. Until May 2005 very little was known about short GRBs, but this situation has changed rapid…
Long Gamma-Ray Bursts as standard candles
D. Lazzati, G. Ghirlanda, G. Ghisellini +4
As soon as it was realized that long GRBs lie at cosmological distances, attempts have been made to use them as cosmological probes. Besides their use as lighthouses, a task that p…
Thick fireballs and the steep decay in the early X-ray afterglow of gamma-ray bursts
Davide Lazzati, Mitchell C. Begelman
We study the early afterglows of gamma-ray bursts produced by geometrically thick fireballs, following the development of the external shock as energy is continually supplied to th…
A Gamma-Ray Burst Mission to Investigate the Properties of Dark Energy
D. Q. Lamb, G. R. Ricker, D. Lazzati +26
[Abridged] Very recently, relations between the peak energy of Gamma-Ray Burst burst spectra, the isotropic-equivalent energy of the burst, and the radiated energy of the burst hav…
Extinction properties of the X-ray bright/optically faint afterglow of GRB 020405
G. Stratta, R. Perna, D. Lazzati +3
We present an optical-to-X-ray spectral analysis of the afterglow of GRB 020405. The optical spectral energy distribution not corrected for the extragalactic extinction is signific…
GRB Progenitors and Environment
Davide Lazzati
The study and knowledge of the environment of Gamma-Ray Bursts is of great interest from many points of view. For high redshift (z>0.5) events, the structure of the ambient medium…