Time resolved spectral analysis of bright gamma ray bursts

Ghirlanda, G.; Celotti, A.; Ghisellini, G.

doi:10.1051/0004-6361:20021038

Cited by 81 publications

(109 citation statements)

References 19 publications

(47 reference statements)

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“…Similar results were obtained by time-resolved spectral analysis Ghirlanda et al 2002;K06). In spite of this, the nature and emission mechanisms responsible for the prompt emission of GRBs are still a matter of debate.…”

Section: Introductionsupporting

confidence: 86%

Spectral catalogue of bright gamma-ray bursts detected with theBeppoSAX/GRBM

Guidorzi

Lacapra

Frontera

et al. 2010

A&A

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Context. The emission process responsible for the so-called "prompt" emission of gamma-ray bursts is still unknown. A number of empirical models fitting the typical spectrum still lack a satisfactory interpretation. A few GRB spectral catalogues derived from past and present experiments are known in the literature and allow to tackle the issue of spectral properties of gamma-ray bursts on a statistical ground. Aims. We extracted and studied the time-integrated photon spectra of the 200 brightest GRBs observed with the Gamma-Ray Burst Monitor which flew aboard the BeppoSAX mission (1996)(1997)(1998)(1999)(2000)(2001)(2002) to provide an independent statistical characterisation of GRB spectra. Methods. The spectra have a time-resolution of 128 s and consist of 240 energy channels covering the 40-700 keV energy band. The 200 brightest GRBs were selected from the complete catalogue of 1082 GRBs detected with the GRBM ), whose products are publicly available and can be browsed/retrieved using a dedicated web interface. The spectra were fit with three models: a simple power law, a cut-off power law or a Band model. We derived the sample distributions of the best-fitting spectral parameters and investigated possible correlations between them. For a few, typically very long GRBs, we also provide a loose (128-s) time-resolved spectroscopic analysis. Results. The typical photon spectrum of a bright GRB consists of a low-energy index around 1.0 and a peak energy of the ν F ν spectrum E p 240 keV in agreement with previous results on a sample of bright CGRO/BATSE bursts. Spectra of ∼35% of GRBs can be fit with a power law with a photon index around 2, indicative of peak energies either close to or outside the GRBM energy boundaries. We confirm the correlation between E p and fluence, in agreement with previous results, with a logarithmic dispersion of 0.13 around the power law with index 0.21 ± 0.06. This is shallower than its analogous in the GRB rest-frame, the Amati relation, between the intrinsic peak energy and the isotropic-equivalent released energy (slope of ∼0.5). The reason for this difference mainly lies in the instrumental selection effect connected with the finite energy range of the GRBM particularly at low energies. Conclusions. We confirm the statistical properties of the low-energy index and peak energy distributions found by other experiments. These properties are not yet systematically explained in the current literature with the proposed emission processes. The capability of measuring time-resolved spectra over a broadband energy range, ensuring precise measurements of parameters such as E p , will be of key importance for future experiments.

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Section: Introductionsupporting

confidence: 86%

Spectral catalogue of bright gamma-ray bursts detected with theBeppoSAX/GRBM

Guidorzi

Lacapra

Frontera

et al. 2010

A&A

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“…These processes were found to be consistent with the observational data of many GRBs (Tavani 1996;Frontera et al 2000). However, several limitations have been reported in relation with the low-energy spectral slopes of time-integrated spectra (Crider et al 1997;Preece et al 2002;Ghirlanda et al 2002Ghirlanda et al , 2003Daigne et al 2009) and timeresolved spectra (Ghirlanda et al 2003). Additional limitations on SSC have also been pointed out by Kumar & McMahon (2008a) and Piran et al (2009).…”

Section: A Brief Review Of the Fireshell And Alternative Modelssupporting

confidence: 75%

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

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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“…These two exactly compensate each other leading to independence of the observed quantities on η in this region. This remains the same for η > η p also, since here T esc = T p =const and from (124) γ =const.…”

Section: Approximate Resultsmentioning

confidence: 56%

The Blackholic energy and the canonical Gamma-Ray Burst

Ruffini¹,

Bernardini²,

Bianco³

et al. 2007

AIP Conference Proceedings

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Abstract. Gamma-Ray Bursts (GRBs) represent very likely "the" most extensive computational, theoretical and observational effort ever carried out successfully in physics and astrophysics. The extensive campaign of observation from space based X-ray and γ-ray observatory, such as the Vela, CGRO, BeppoSAX, HETE-II, INTEGRAL, Swift, R-XTE, Chandra, XMM satellites, have been matched by complementary observations in the radio wavelength (e.g. by the VLA) and in the optical band (e.g. by VLT, Keck, ROSAT). The net result is unprecedented accuracy in the received data allowing the determination of the energetics, the time variability and the spectral properties of these GRB sources. The very fortunate situation occurs that these data can be confronted with a mature theoretical development. Theoretical interpretation of the above data allows progress in three different frontiers of knowledge: a) the ultrarelativistic regimes of a macroscopic source moving at Lorentz gamma factors up to ∼ 400; b) the occurrence of vacuum polarization process verifying some of the yet untested regimes of ultrarelativistic quantum field theories; and c) the first evidence for extracting, during the process of gravitational collapse leading to the formation of a black hole, amounts of energies up to 10 55 ergs of blackholic energy -a new form of energy in physics and astrophysics. We outline how this progress leads to the confirmation of three interpretation paradigms for GRBs proposed in July 2001. Thanks mainly to the observations by Swift and the optical observations by VLT, the outcome of this analysis points to the existence of a "canonical" GRB, originating from a variety of different initial astrophysical scenarios. The communality of these GRBs appears to be that they all are emitted in the process of formation of a black hole with a negligible value of its angular momentum. The following sequence of events appears to be canonical: the vacuum polarization process in the dyadosphere with the creation of the optically thick self accelerating electron-positron plasma; the engulfment of baryonic mass during the plasma expansion; adiabatic expansion of the optically thick "fireshell" of electronpositron-baryon plasma up to the transparency; the interaction of the accelerated baryonic matter with the interstellar medium (ISM). This leads to the canonical GRB composed of a proper GRB (P-GRB), emitted at the moment of transparency, followed by an extended afterglow. The sole parameters in this scenario are the total energy of the dyadosphere E dya , the fireshell baryon loading M B defined by the dimensionless parameter B ≡ M B c 2 /E dya , and the ISM filamentary distribution around the source. In the limit B → 0 the total energy is radiated in the P-GRB with a vanishing contribution in the afterglow. In this limit, the canonical GRBs explain as well the short GRBs. In these lecture notes we systematically outline the main results of our model comparing and contrasting them with the ones in the current literature. In both cases, we have li...

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Time resolved spectral analysis of bright gamma ray bursts

Cited by 81 publications

References 19 publications

Spectral catalogue of bright gamma-ray bursts detected with theBeppoSAX/GRBM

Spectral catalogue of bright gamma-ray bursts detected with theBeppoSAX/GRBM

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

The Blackholic energy and the canonical Gamma-Ray Burst

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