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

Barros, Gustavo; Amati, L.; Bernardini, M. G.; Bianco, C. L.; Caito, Letizia; Izzo, L.; Patricelli, B.; Ruffini, Remo

doi:10.1051/0004-6361/201116659

Cited by 23 publications

(55 citation statements)

References 39 publications

(109 reference statements)

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“…One of the main features of the GRB afterglow has been the observation of hard-to-soft spectral variation, which is generally absent in the first spike-like emission, which we have identified as the P-GRB, Bernardini et al (2007);Caito et al (2009Caito et al ( , 2010de Barros et al (2011). An explanation of the hard-to-soft spectral variation has been advanced on the grounds of two different contributions: the curvature effect and the intrinsic spectral evolution.…”

Section: The Extended Afterglowmentioning

confidence: 94%

“…The parameter R, in particular, determines the effective temperature in the comoving frame and the corresponding peak energy of the spectrum, while n cbm determines the temporal behavior of the light curve. It is found that the CBM is typically formed of "clumps" of width ∼10 15−16 cm and average density contrast 10 have been found for GRBs exploding inside star-forming region galaxies, while values on the order of 10 −3 particles/cm 3 have been found for GRBs exploding in galactic halos Caito et al 2009;de Barros et al 2011). This clumpy medium, already predicted in pioneering works of Fermi in the theoretical study of interstellar matter in our galaxy (Fermi 1949(Fermi , 1954, is by now well-established both from the GRB observations and by additional astrophysical observations, see e.g.…”

Section: The Extended Afterglowmentioning

confidence: 97%

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A double component in GRB 090618: a proto-black hole and a genuinely long gamma-ray burst

Izzo

Ruffini

Penacchioni

et al. 2012

A&A

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114

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Context. The joint X-ray and gamma-ray observations of GRB 090618 by very many satellites offer an unprecedented possibility of testing crucial aspects of theoretical models. In particular, they allow us to test (a) in the process of gravitational collapse, the formation of an optically thick e + e − -baryon plasma self-accelerating to Lorentz factors in the range 200 < Γ < 3000; (b) its transparency condition with the emission of a component of 10 53−54 baryons in the TeV region and (c) the collision of these baryons with the circumburst medium (CBM) clouds, characterized by dimensions of 10 15−16 cm. In addition, these observations offer the possibility of testing a new understanding of the thermal and power-law components in the early phase of this GRB. Aims. We test the fireshell model of GRBs in one of the closest (z = 0.54) and most energetic (E iso = 2.90 × 10 53 erg) GRBs, namely GRB 090618. It was observed at ideal conditions by several satellites, namely Fermi, Swift, Konus-WIND, AGILE, RT-2, and Suzaku, as well as from on-ground optical observatories. Methods. We analyzed the emission from GRB 090618 using several spectral models, with special attention to the thermal and powerlaw components. We determined the fundamental parameters of a canonical GRB within the context of the fireshell model, including the identification of the total energy of the e + e − plasma, E e + e − tot , the proper GRB (P-GRB), the baryon load, the density and structure of the CBM. Results. We find evidence of the existence of two different episodes in GRB 090618. The first episode lasts 50 s and is characterized by a spectrum consisting of a thermal component, which evolves between kT = 54 keV and kT = 12 keV, and a power law with an average index γ = 1.75 ± 0.04. The second episode, which lasts for ∼100 s, behaves as a canonical long GRB with a Lorentz gamma factor at transparency of Γ = 495, a temperature at transparency of 29.22 keV and with a characteristic size of the surrounding clouds of R cl ∼ 10 15−16 cm and masses of ∼10 22−24 g. Conclusions. We support the recently proposed two-component nature of GRB 090618, namely, episode 1 and episode 2, with a specific theoretical analysis. We furthermore illustrate that episode 1 cannot be considered to be either a GRB or a part of a GRB event, but it appears to be related to the progenitor of the collapsing bare core, leading to the formation of the black hole, which we call a "proto-black hole". Thus, for the first time, we are witnessing the process of formation of a black hole from the phases just preceding the gravitational collapse all the way up to the GRB emission.

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Section: The Extended Afterglowmentioning

confidence: 94%

Section: The Extended Afterglowmentioning

confidence: 97%

A double component in GRB 090618: a proto-black hole and a genuinely long gamma-ray burst

Izzo

Ruffini

Penacchioni

et al. 2012

A&A

Self Cite

114

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“…This was followed in 2002 by a further theoretical work also evidencing the relevance of an additional parameter influencing the interpretation of the above classification: the average density of the environment CBM (Ruffini et al 2002(Ruffini et al , 2004. This led to the new concept of "disguised short" GRBs (Bernardini et al 2007Caito et al 2009Caito et al , 2010de Barros et al 2011).…”

Section: The Fireshell Versus the Fireball Model And The Issue Of Thementioning

confidence: 96%

“…In parallel, the theoretical progress in the Fireshell model of GRBs (see Ruffini et al 2001aRuffini et al , 2001bRuffini et al , 2001c) has led to an alternative explanation of the Norris-Bonnell sources as "disguised short bursts" (Bernardini et al 2007Caito et al 2009Caito et al , 2010de Barros et al 2011): canonical long bursts exploding in halos of their host galaxies, with n CBM ≈ 10 −3 particles cm −3 (see Section 2.3). The aim of this article, using the data obtained by the Fermi-GBM satellite (Meegan et al 2009), is to probe the existence of a yet new class of GRBs which we define here as "genuine short GRBs," theoretically predicted by the Fireshell model (Ruffini et al 2001b(Ruffini et al , 2002.…”

Section: Introductionmentioning

confidence: 99%

GRB 090227b: The Missing Link Between the Genuine Short and Long Gamma-Ray Bursts

Muccino¹,

Ruffini²,

Bianco³

et al. 2013

ApJ

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The time-resolved spectral analysis of GRB 090227B, made possible by the Fermi-GBM data, allows us to identify in this source the missing link between the genuine short and long gamma-ray bursts (GRBs). Within the Fireshell model of the GRBs we predict genuine short GRBs: bursts with the same inner engine of the long bursts but endowed with a severely low value of the baryon load, B 5 × 10 −5 . A first energetically predominant emission occurs at the transparency of the e + e − plasma, the Proper-GRB (P-GRB), followed by a softer emission, the extended afterglow. The typical separation between the two emissions is expected to be of the order of 10 −3 -10 −2 s. We identify the P-GRB of GRB 090227B in the first 96 ms of emission, where a thermal component with the temperature kT = (517 ± 28) keV and a flux comparable with the non-thermal part of the spectrum is observed. This non-thermal component as well as the subsequent emission, where there is no evidence for a thermal spectrum, is identified with the extended afterglow. We deduce a theoretical cosmological redshift z = 1.61 ± 0.14. We then derive the total energy E tot e + e − = (2.83 ± 0.15) × 10 53 erg, the baryon load B = (4.13 ± 0.05) × 10 −5 , the Lorentz Γ factor at transparency Γ tr = (1.44 ± 0.01) × 10 4 , and the intrinsic duration Δt ∼ 0.35 s. We also determine the average density of the circumburst medium (CBM), n CBM = (1.90 ± 0.20) × 10 −5 particles cm −3 . There is no evidence of beaming in the system. In view of the energetics and of the baryon load of the source, as well as of the low interstellar medium and of the intrinsic timescale of the signal, we identify the GRB progenitor as a binary neutron star. From the recent progress in the theory of neutron stars, we obtain masses of the stars m 1 = m 2 = 1.34 M and their corresponding radii R 1 = R 2 = 12.24 km and thickness of their crusts ∼0.47 km, consistent with the above values of the baryon load, of the energetics and of the time duration of the event.

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“…This model has allowed the nature of long GRBs to be explained and two new classes of short bursts to be introduced. A first class contains the disguised short GRBs Caito et al 2009Caito et al , 2010De Barros et al 2011): just long GRBs exploding in low density CBM (n = 10 −3 part/cm 3 ), and often referred to as short GRBs in the literature (see e.g. Gehrels et al 2005).…”

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

Self Cite

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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.

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

Cited by 23 publications

References 39 publications

A double component in GRB 090618: a proto-black hole and a genuinely long gamma-ray burst

A double component in GRB 090618: a proto-black hole and a genuinely long gamma-ray burst

GRB 090227b: The Missing Link Between the Genuine Short and Long Gamma-Ray Bursts

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

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