A New Method of Pulse-Wise Spectral Analysis of Gamma-Ray Bursts

Basak, Rupal; Rao, A. R.

doi:10.1088/0004-637x/768/2/187

Cited by 16 publications

(25 citation statements)

References 46 publications

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“…• The time-integrated spectrum during the bright phase (from 20s to 30s since the trigger) of GRB 081221 observed with Fermi/GBM has a broad plateau in the 15-180 keV band, and is well fitted by the mBB model, yielding the kT min = 4.4 ± 0.3 keV, kT max = 57.0 +1.6 −1.4 keV, m = −0.46 +0.05 −0.06 . • As for the time-resolved spectra, although the BB model is not the best-fit model when the whole burst is divided into 40 slices, we obtain acceptable fits with the single blackbody model (without the power-law component), which is simpler compared to the 2BB plus PL model of Basak & Rao (2013). The kT of the main burst increases rapidly from ∼ 9 keV to ∼ 20 keV.…”

Section: Discussionmentioning

confidence: 80%

Multicolor Blackbody Emission in GRB 081221

Hou

Zhang

Meng

et al. 2018

ApJ

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The radiation mechanism of the prompt emission of gamma-ray bursts (GRBs) remains an open question. Although their spectra are usually well fitted with the empirical Band function, which is widely believed to be fully nonthermal and interpreted as an optically thin synchrotron emission, accumulating evidence shows that a thermal component actually exists. In this paper, a multicolor blackbody (mBB) model is proposed for the time-integrated spectrum of GRB 081221 by assuming a power-law distribution of the thermal luminosities with temperature, which manifests photospheric emissions from a different radius and/or angle. The effects of the minimum temperature kT min , the maximum temperature kT max and the power law index m of the luminosity distribution of an mBB are discussed. The fitting to the time-integrated spectrum during the bright phase (from 20s to 30s since the trigger) of GRB 081221 by the mBB model yields kT min = 4.4 ± 0.3 keV, kT max = 57.0 +1.6 −1.4 keV, and m = −0.46 +0.05 −0.06 . When the time bin is small enough, the time-resolved spectra of GRB 081221 are well fitted with a series of single-temperature blackbodies. Our results imply the prompt emission of GRB 081221 is dominated by the photosphere emission and its time-integrated spectrum is a superposition of pure blackbody components at different times, indicating that some empirical Band spectra may be interpreted as mBB if the temperature is widely distributed.

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Section: Discussionmentioning

confidence: 80%

Multicolor Blackbody Emission in GRB 081221

Hou

Zhang

Meng

et al. 2018

ApJ

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“…We have further shown that this model gives statistically better fit compared to the other models, when all the three GRBs are considered. Considering the fact that this model is also the preferred one for the bright GRBs with single/ separable pulses (Basak & Rao 2013), we can conclude that such a composite model needs to be examined for other GRBs too. This spectral description has several attractive features which can be used to constrain the GRB emission mechanism.…”

Section: Discussionmentioning

confidence: 99%

Time-resolved spectral analysis of prompt emission from long gamma-ray bursts with GeV emission

Rao

Basak

Bhattacharya

et al. 2013

Res. Astron. Astrophys.

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We make a detailed time resolved spectroscopy of bright long gamma ray bursts (GRBs) which show significant GeV emissions (GRB 080916C, GRB 090902B, and GRB 090926A). In addition to the standard Band model, we also use a model consisting of a blackbody and a power-law to fit the spectra. We find that for the latter model there are indications for an additional soft component in the spectra. While previous studies have shown that such models are required for GRB 090902B, here we find that a composite spectral model consisting of two black bodies and a power law adequately fit the data of all the three bright GRBs. We investigate the evolution of the spectral parameters and find several generic interesting features for all three GRBs, like a) temperatures of the black bodies are strongly correlated to each other, b) flux in the black body components are strongly correlated to each other, c) the temperatures of the black body trace the profile of the individual pulses of the GRBs, and d) the characteristics of the power law component like the spectral index and the delayed onset bear a close similarity to the emission characteristics in the GeV regions. We discuss the implications of these results to the possibility of identifying the radiation mechanisms during the prompt emission of GRBs.

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“…(Liang & Kargatis 1996). However, it is known that the E peak evolution can be more complicated than the simple assumption of Basak & Rao (2012b)-there may be "intensity tracking" nature in the evolution (e.g., Ford et al 1995;Liang & Kargatis 1996;Kaneko et al 2006;Lu et al 2010;Hakkila & Preece 2011;Lu et al 2012;Basak & Rao 2013a;. Hence, in the present paper we restrict ourselves only to the pulse-wise Amati correlation.…”

Section: Data Selection and Analysismentioning

confidence: 98%

Pulse-wise Amati correlation in Fermi gamma-ray bursts

Basak¹,

Rao²

2013

Monthly Notices of the Royal Astronomical Society

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We make a detailed pulse-wise study of gamma-ray bursts (GRBs) with known redshift detected by Fermi/Gamma Ray Burst Monitor (GBM). The sample contains 19 GRBs with 43 pulses. We find that the average peak energy is correlated to the radiated energy (the Amati relation) for individual pulses with a correlation coefficient of 0.86, which is slightly better than the correlation for the full GRBs. As the present correlation holds within GRBs, it is a strong evidence supporting the reliability of such a correlation. We investigate several aspects of this correlation. (i) We divide our sample into redshift bins and study the evolution of the correlation. Though there is a marginal indication of evolution of the correlation, we can conclude that the present data is consistent with no evolution. (ii) We compare the correlation in the first or single pulses of these GRBs to that of the rest of the pulses, and confirm that the correlation is unaffected by the fact that first/single pulses are generally harder than the rest. Finally, we conclude that the pulse-wise Amati correlation is more robust and it has the potential of refining the correlation so that GRB study could be used as a cosmological tool.

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A New Method of Pulse-Wise Spectral Analysis of Gamma-Ray Bursts

Cited by 16 publications

References 46 publications

Multicolor Blackbody Emission in GRB 081221

Multicolor Blackbody Emission in GRB 081221

Time-resolved spectral analysis of prompt emission from long gamma-ray bursts with GeV emission

Pulse-wise Amati correlation in Fermi gamma-ray bursts

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