Blackbody components in gamma-ray bursts spectra?

Ghirlanda, G.; Bošnjak, Ž.; Ghisellini, G.; Tavecchio, F.; Firmani, C.

doi:10.1111/j.1365-2966.2007.11890.x

Cited by 55 publications

(49 citation statements)

References 44 publications

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“…The problem with this interpretation is that one of the key assumptions of their scenario is that the value of the bulk Lorentz factor in the dissipation region must be finetuned (i.e., of the order of 1/θ j , where θ j is the opening angle of the fireball). This assumption is relaxed in the "reborn fireball" scenario ), but it remains to be explained why so few bursts have pure black body spectra (Ghirlanda et al 2003), and, even when adding a power-law component (Ryde et al 2005), its slope is too soft to explain low-energy data (in the keV band), as shown by Ghirlanda et al (2007).…”

Section: Interpretations Of the Spectral-energy Correlationsmentioning

confidence: 99%

Spectral-luminosity relation within individualFermigamma rays bursts

Ghirlanda¹,

Nava

Ghisellini³

2010

A&A

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132

151

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We study the spectra of all long gamma ray bursts (GRBs) of known redshift detected by the Fermi satellite untill the end of July 2009. Their fluxes and fluences are large enough to allow a time dependent study of their spectral characteristics in the 8 keV-1 MeV energy range. We find that the peak energy E peak of their EL(E) spectrum correlates with the luminosity in a remarkably tight way within individual bursts. This time-resolved E peak − L iso correlation is very similar for all the considered bursts and has a slope and normalisation similar to the analogous E peak − L iso correlation defined by the time-integrated spectra of different bursts detected by several different satellites. For a few of the considered GRBs, we could also study the behaviour of the E peak − L iso correlation during the rising and decaying phases of individual pulses within each burst, finding no differences. Our results indicate the presence of a similar physical mechanism, operating for the duration of different GRBs, tightly linking the burst luminosity with the peak energy of the spectrum emitted at different times. Such a physical mechanism is the same during the rise and decay phase of individual pulses composing a GRB. While calling for a robust physical interpretation, these results strongly indicate that the E peak − L iso spectral energy correlation found considering the time-integrated spectra of different bursts is real and not the result of instrumental selection effects.

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Section: Interpretations Of the Spectral-energy Correlationsmentioning

confidence: 99%

Spectral-luminosity relation within individualFermigamma rays bursts

Ghirlanda¹,

Nava

Ghisellini³

2010

A&A

Self Cite

132

151

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“…-quasi-thermal model (QT) (Ryde 2005;Thompson et al 2007;Ghirlanda et al 2007), consisting of a power law and a blackbody:…”

Section: Spectral Extractionmentioning

confidence: 99%

The updated spectral catalogue of INTEGRAL gamma-ray bursts

Vianello

Götz

Mereghetti

2009

A&A

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We present a catalogue with the properties of all the bursts detected and localized by the IBIS instrument onboard the INTEGRAL satellite from November 2002 to September 2008. The sample is composed of 56 bursts, corresponding to a rate of ∼0.8 GRB per month. Thanks to the performances of the INTEGRAL Burst Alert System, 50% of the IBIS GRBs have detected afterglows, while 5% have redshift measurements. A spectral analysis of the 43 bursts in the INTEGRAL public archive has been carried out using the most recent software and calibration, deriving an updated, homogeneous and accurate catalogue with the spectral features of the sample. When possible a time-resolved spectral analysis also has been carried out. The GRBs in the sample have 20-200 keV fluences in the range 5 × 10 −8 -2.5 × 10 −4 erg cm −2 , and peak fluxes in the range 0.11-56 ph cm −2 s −1 . While most of the spectra are well fitted by a power law with photon index ∼1.6, we found that 9 bursts are better described by a cut-off power law, resulting in E p values in the range 35-190 keV. Altough these results are comparable to those obtained with BAT onboard Swift, there is marginal evidence that ISGRI detects dimmer bursts than Swift/BAT. Using the revised spectral parameters and an updated sky exposure map that also takes into account the effects of the GRB trigger efficiency, we strengthen the evidence for a spatial correlation with the super galactic plane of the faint bursts with long spectral lag.

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“…The pulse temperatures were found to lie within 20-100 keV and were observed to evolve in a characteristic way, decaying as a broken power law in time (Ryde & Peér 2009). However, the BATSE energy range (25-1800 keV) made it difficult to fully assess these models (see, e.g., Ghirlanda et al 2007). The broader energy range (8 keV-40 MeV) of the Gamma-Ray Burst Monitor (GBM) on the Fermi Gamma-Ray Space Telescope alleviates this shortcoming.…”

Section: Introductionmentioning

confidence: 99%

Evidence for a Photospheric Component in the Prompt Emission of the Short GRB 120323a and Its Effects on the GRB Hardness-Luminosity Relation

Guiriec

Daigne

Hascoët

et al. 2013

ApJ

145

221

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The short GRB 120323A had the highest flux ever detected with the Gamma-Ray Burst Monitor on board the Fermi Gamma-Ray Space Telescope. Here we study its remarkable spectral properties and their evolution using two spectral models: (1) a single emission component scenario, where the spectrum is modeled by the empirical Band function (a broken power law), and (2) a two-component scenario, where thermal (a Planck-like function) emission is observed simultaneously with a non-thermal component (a Band function). We find that the latter model fits the integrated burst spectrum significantly better than the former, and that their respective spectral parameters are dramatically different: when fit with a Band function only, the E peak of the event is unusually soft for a short gamma-ray burst (GRB; 70 keV compared to an average of 300 keV), while adding a thermal component leads to more typical short GRB values (E peak ∼ 300 keV). Our time-resolved spectral analysis produces similar results. We argue here that the two-component model is the preferred interpretation for GRB 120323A based on (1) the values and evolution of the Band function parameters of the two component scenario, which are more typical for a short GRB, and (2) the appearance in the data of a significant hardness-intensity correlation, commonly found in GRBs, when we employee two-component model fits; the correlation is non-existent in the Band-only fits. GRB 110721A, a long burst with an intense photospheric emission, exhibits the exact same behavior. We conclude that GRB 120323A has a strong photospheric emission contribution, observed for the first time in a short GRB. Magnetic dissipation models are difficult to reconcile with these results, which instead favor photospheric thermal emission and fast cooling synchrotron radiation from internal shocks. Finally, we derive a possibly universal hardness-luminosity relation in the source frame using a larger set of GRBs (L Band i = (1.59 ± 0.84) × 10 50 (E rest peak,i ) 1.33±0.07 erg s −1 ), which could be used as a possible redshift estimator for cosmology.

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Blackbody components in gamma-ray bursts spectra?

Cited by 55 publications

References 44 publications

Spectral-luminosity relation within individualFermigamma rays bursts

Spectral-luminosity relation within individualFermigamma rays bursts

The updated spectral catalogue of INTEGRAL gamma-ray bursts

Evidence for a Photospheric Component in the Prompt Emission of the Short GRB 120323a and Its Effects on the GRB Hardness-Luminosity Relation

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