On the Instantaneous Spectrum of Gamma-Ray Bursts

Ruffini, Remo; Bianco, C. L.; Xue, She‐Sheng; Chardonnet, Pascal; Fraschetti, Federico; Gurzadyan, V. G.

doi:10.1142/s0218271804004980

Cited by 62 publications

(156 citation statements)

References 17 publications

Supporting

Mentioning

149

Contrasting

Order By: Relevance

“…This allows us to assume, to a first approximation, a modeling of thin spherical shells for the CBM distribution and consequently only consider their radial dependence (Ruffini et al 2002). The emission process is assumed to be thermal in the comoving frame of the shell (Ruffini et al 2004). The observed GRB non-thermal spectral shape is produced by the convolution of a very large number of thermal spectra with different temperatures and different Lorentz and Doppler factors.…”

Section: The Fireshell Modelmentioning

confidence: 99%

On the nature of GRB 050509b: a disguised short GRB

Barros¹,

Amati²,

Bernardini³

et al. 2011

A&A

View full text Add to dashboard Cite

Context. GRB 050509b, detected by the Swift satellite, is the first case where an X-ray afterglow has been observed associated with a short gamma-ray burst (GRB). Within the fireshell model, the canonical GRB light curve presents two different components: the proper-GRB (P-GRB) and the extended afterglow. Their relative intensity is a function of the fireshell baryon loading parameter B and of the CircumBurst Medium (CBM) density (n CBM ). In particular, the traditionally called short GRBs can be either "genuine" short GRBs (with B 10 −5 , where the P-GRB is energetically predominant) or "disguised" short GRBs (with B 3.0 × 10 −4 and n CBM 1, where the extended afterglow is energetically predominant). Aims. We verify whether GRB 050509b can be classified as a "genuine" short or a "disguised" short GRB, in the fireshell model. Methods. We investigate two alternative scenarios. In the first, we start from the assumption that this GRB is a "genuine" short burst.In the second attempt, we assume that this GRB is a "disguised" burst. Results. If GRB 050509b were a genuine short GRB, there should initially be very hard emission, which is ruled out by the observations. The analysis that assumes that this is a disguised short GRB is compatible with the observations. The theoretical model predicts a value of the extended afterglow energy peak that is consistent with the Amati relation. Conclusions. GRB 050509b cannot be classified as a "genuine" short GRB. The observational data are consistent with a "disguised" short GRB classification, i.e., a long burst with a weak extended afterglow "deflated" by the low density of the CBM. We expect that all short GRBs with measured redshifts are disguised short GRBs because of a selection effect: if there is enough energy in the afterglow to measure the redshift, then the proper GRB must be less energetic than the afterglow. The Amati relation is found to be fulfilled only by the extended afterglow excluding the P-GRB.

show abstract

Section: The Fireshell Modelmentioning

confidence: 99%

On the nature of GRB 050509b: a disguised short GRB

Barros¹,

Amati²,

Bernardini³

et al. 2011

A&A

View full text Add to dashboard Cite

show abstract

“…Within the fireshell model (Ruffini et al 2002(Ruffini et al , 2004(Ruffini et al , 2005(Ruffini et al , 2009Bianco et al 2005a,b), all GRBs originate from an optically thick e ± plasma of total energy E e ± tot in the range 10 49 -10 54 erg and a temperature T in the range 1-4 MeV. After an early expansion, the e ± -photon plasma reaches thermal equilibrium with the engulfed baryonic matter M B described by the dimensionless parameter B = M B c 2 /E e ± tot , which must be B < 10 −2 to allow the fireshell to expand further.…”

Section: Brief Summary Of the Fireshell Modelmentioning

confidence: 99%

“…This second parameter takes into account the CBM filamentary structure (Ruffini et al 2004) and the possible occurrence of fragmentation in the shell (Dainotti et al 2007). The emission from the baryonic matter shell is spherically symmetric.…”

Section: Brief Summary Of the Fireshell Modelmentioning

confidence: 99%

“…This allows us to assume, to first approximation, a modeling of thin spherical shells for the CBM distribution and consequently consider just their radial dependence (Ruffini et al 2002). The emission process is assumed to be thermal in the comoving frame of the shell (Ruffini et al 2004). The observed GRB non-thermal spectral shape is produced by the convolution of a very large number of thermal spectra with different temperatures and different Lorentz and Doppler factors.…”

Section: Brief Summary Of the Fireshell Modelmentioning

confidence: 99%

See 1 more Smart Citation

GRB 071227: an additional case of adisguisedshort burst

Caito¹,

Amati

Bernardini

et al. 2010

A&A

View full text Add to dashboard Cite

Context. Observations of gamma-ray bursts (GRBs) have shown an hybridization between the two classes of long and short bursts. In the context of the fireshell model, the GRB light curves are formed by two different components: the proper GRB (P-GRB) and the extended afterglow. Their relative intensity is linked to the fireshell baryon loading B. The GRBs with P-GRB predominance are the short ones, the remainders are long. A new family of disguised short bursts has been identified: long bursts with a protracted low instantaneous luminosity due to a low density CircumBurst Medium (CBM). In the 15-150 keV energy band GRB 071227 exhibits a short duration (about 1.8 s) spike-like emission followed by a very soft extended tail up to one hundred seconds after the trigger. It is a faint (E iso = 5.8 × 10 50 ) nearby GRB (z = 0.383) that does not have an associated type Ib/c bright supernova (SN). For these reasons, GRB 071227 has been classified as a short burst not fulfilling the Amati relation holding for long burst. Aims. We check the classification of GRB 071227 provided by the fireshell model. In particular, we test whether this burst is another example of a disguised short burst, after GRB 970228 and GRB 060614, and, for this reason, whether it fulfills the Amati relation. Methods. We simulate GRB 071227 light curves in the Swift BAT 15-50 keV bandpass and in the XRT (0.3-10 keV) energy band within the fireshell model. Results. We perform simulations of the tail in the 15-50 keV bandpass, as well as of the first part of the X-ray afterglow. This infers that: E e ± tot = 5.04 × 10 51 erg, B = 2.0 × 10 −4 , E P−GRB /E aft ∼ 0.25, and n cbm = 3.33 particles cm −3 . These values are consistent with those of "long duration" GRBs. We interpret the observed energy of the first hard emission by identifying it with the P-GRB emission. The remaining long soft tail indeed fulfills the Amati relation. Conclusions. Previously classified as a short burst, GRB 071227 on the basis of our analysis performed in the context of the fireshell scenario represents another example of a disguised short burst, after GRB 970228 and GRB 060614. Further confirmation of this result is that the soft tail of GRB 071227 fulfills the Amati relation.

show abstract

“…Ruffini et al 2001Ruffini et al , 2009, and references therein) has led to identifying a canonical GRB structure described by two parameters: the total energy E e ± tot of the initially optically thick electronpositron plasma and its baryon load B = M B c 2 /E e ± tot . To this information characterizing the source is added the information on the density and filamentary distribution of the circumburst medium (CBM) (Ruffini et al 2004b(Ruffini et al , 2005Patricelli et al 2010Patricelli et al , 2011.…”

Section: Introductionmentioning

confidence: 99%

Evidence for a proto-black hole and a double astrophysical component in GRB 101023

Penacchioni

Ruffini

Izzo

et al. 2012

A&A

View full text Add to dashboard Cite

Context. It has been recently shown that GRB 090618, observed by AGILE, Coronas Photon, Fermi, Konus, Suzaku, and Swift, is composed of two very different components: episode 1, lasting 50 s, shows a thermal plus power-law spectrum with a characteristic temperature evolving in time as a power law; episode 2 (the remaining 100 s) is a canonical long GRB. We have associated episode 1 to the progenitor of a collapsing bare core leading to the formation of a black hole: what was defined as a "proto black hole" Aims. In precise analogy with GRB 090618 we aim to analyze the 89 s of the emission of GRB 101023, observed by Fermi, Gemini, Konus and Swift, to see if there are two different episodes: the first one presenting a characteristic black-body temperature evolving in time as a broken power law, and the second one consistent with a canonical GRB. Methods. To obtain information on the spectra, we analyzed the data provided by the GBM detector onboard the Fermi satellite, and we used the heasoft package XSPEC and RMFIT to obtain their spectral distribution. We also used the numerical code GRBsim to simulate the emission in the context of the fireshell scenario for episode 2. Results. We confirm that the first episode can be well fit by a black body plus power-law spectral model. The temperature changes with time following a broken power law, and the photon index of the power-law component presents a soft-to-hard evolution. We estimate that the radius of this source increases with time with a velocity of 1.5 × 10 4 km s −1 . The second episode appears to be a canonical GRB. By using the Amati and the Atteia relations, we determined the cosmological redshift, z ∼ 0.9±0.084(stat.)±0.2(sys.). The results of GRB 090618 are compared and contrasted with the results of GRB 101023. Particularly striking is the scaling law of the soft X-ray component of the afterglow. Conclusions. We identify GRB 090618 and GRB 101023 with a new family of GRBs related to a single core collapse and presenting two astrophysical components: a first one related to the proto-black hole prior to the process of gravitational collapse (episode 1), and a second one, which is the canonical GRB (episode 2) emitted during the formation of the black hole. For the first time we are witnessing the process of a black hole formation from the instants preceding the gravitational collapse up to the GRB emission. This analysis indicates progress towards developing a GRB distance indicator based on understanding the P-GRB and the prompt emission, as well as the soft X-ray behavior of the late afterglow.

show abstract

On the Instantaneous Spectrum of Gamma-Ray Bursts

Cited by 62 publications

References 17 publications

On the nature of GRB 050509b: a disguised short GRB

On the nature of GRB 050509b: a disguised short GRB

GRB 071227: an additional case of adisguisedshort burst

Evidence for a proto-black hole and a double astrophysical component in GRB 101023

Contact Info

Product

Resources

About