scholarly journals Investigation of Similarity in the Spectra between Short- and Long-Duration Gamma-ray Bursts

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 106
Author(s):  
Takanori Sakamoto ◽  
Yuuki Yoshida ◽  
Motoko Serino
Keyword(s):  
Spectral Properties ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Synchrotron Emission ◽  
Energy Photon ◽  
Long Duration ◽  
Photon Index ◽  
Monitor Data ◽  
Short Grbs ◽  
Prompt Emission

We investigated the spectral properties of the prompt emission for short- and long-duration gamma-ray bursts (GRBs) using the Fermi Gamma-ray Burst Monitor data. In particular, we focused on comparing the spectral properties of short GRBs and the initial 2 s of long GRBs, motivated by the previous study of Ghirlanda et al. (2009). We confirmed the similarity in the low energy photon index α between short GRBs and the initial 2 s of long GRBs. Since about a quarter of our spectra of both short GRBs and the initial 2 s of long GRBs show α to be shallower than - 2 / 3 , it is difficult to understand in the context standard synchrotron emission.

scholarly journals The properties of prompt emission in short gamma-ray bursts with extended emission observed by Fermi/GBM

2020 ◽  
Vol 492 (3) ◽  
pp. 3622-3630
Author(s):  
Lin Lan ◽  
Rui-Jingi Lu ◽  
Hou-Jun Lü ◽  
Jun Shen ◽  
Jared Rice ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Large Scatter ◽  
Intrinsic Properties ◽  
Temporal Properties ◽  
Peak Energy ◽  
Peak Flux ◽  
Short Grbs ◽  
Prompt Emission ◽  
Extended Emission

ABSTRACT Short gamma-ray bursts (GRB) with extended emission (EE) that are composed of an initial short hard spike followed by a long-lasting EE are thought to comprise a sucategory of short GRBs. The narrow energy band available during the Swift era, combined with a lack of spectral information, prevented the discovery of the intrinsic properties of these events. In this paper, we perform a systematic search of short GRBs with EE using all available Fermi/GBM data. The search identified 26 GBM-detected short GRBs with EE that are similar to GRB 060614 observed by Swift/BAT. We focus on investigating the spectral and temporal properties of both the hard spike and the EE component of all 26 GRBs, and explore differences and possible correlations between them. We find that while the peak energy (Ep) of the hard spikes is slightly harder than that of the EE, their fluences are comparable. The harder Ep seems to correspond to a larger fluence and peak flux, with a large scatter for both the hard spike and the EE component. Moreover, the Ep of both the hard spike and the EE are compared with other short GRBs. Finally, we also compare the properties of GRB 170817A with those of short GRBs with EE and find no significant statistical differences between them. We find that GRB 170817A has the lowest Ep, probably because it is off-axis.

scholarly journals Evidence of two spectral breaks in the prompt emission of gamma-ray bursts

2019 ◽  
Vol 625 ◽  
pp. A60 ◽  
Author(s):  
M. E. Ravasio ◽  
G. Ghirlanda ◽  
L. Nava ◽  
G. Ghisellini
Keyword(s):  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Low Energy ◽  
Emission Region ◽  
Peak Energy ◽  
Standard Scenario ◽  
Low Magnetic Field ◽  
Short Grbs ◽  
Prompt Emission ◽  
Good Agreement

The long-lasting tension between the observed spectra of gamma-ray bursts (GRBs) and the predicted synchrotron emission spectrum might be solved if electrons do not completely cool. Evidence of incomplete cooling was recently found in Swift GRBs with prompt observations down to 0.1 keV, and in one bright Fermi burst, GRB 160625B. Here we systematically search for evidence of incomplete cooling in the spectra of the ten brightest short and long GRBs observed by Fermi. We find that in eight out of ten long GRBs there is compelling evidence of a low-energy break (below the peak energy) and good agreement with the photon indices of the synchrotron spectrum (respectively −2/3 and −3/2 below the break and between the break and the peak energy). Interestingly, none of the ten short GRBs analysed shows a break, but the low-energy spectral slope is consistent with −2/3. In a standard scenario, these results imply a very low magnetic field in the emission region (B′∼10 G in the comoving frame), at odd with expectations.

scholarly journals Gamma-ray Bursts

2005 ◽  
Vol 192 ◽  
pp. 459-466
Author(s):  
Alberto J. Castro-Tirado
Keyword(s):  
Gamma Ray ◽  
Massive Stars ◽  
Gamma Ray Bursts ◽  
Compact Objects ◽  
X Ray ◽  
Long Duration ◽  
Multi Wavelength ◽  
New Generation ◽  
Short Grbs

SummarySince their discovery in 1967 Gamma-ray bursts (GRBs) have been puzzling to astrophysicists. With the advent of a new generation of X–ray satellites in the late 90’s, it was possible to carry out deep multi-wavelength observations of the counterparts associated with the long duration GRBs class just within a few hours of occurrence, thanks to the observation of the fading X-ray emission that follows the more energetic gamma-ray photons once the GRB event has ended. The fact that this emission (the afterglow) extends at longer wavelengths, led to the discovery of optical/IR/radio counterparts in 1997-2003, greatly improving our understanding of these sources. The classical, long duration GRBs, have been observed to originate at cosmological distances in a range of redshifts with 0.1685 ≤ z ≤ 4.50 implying energy releases of ~ 1051 ergs. The recent results on GRB 021004 and GRB 030329 confirm that the central engines that power these extraordinary events are due to be collapse of massive stars rather than the merging of compact objects as previously also suggested. Short GRBs still remain a mystery as no counterparts have been detected so far.

scholarly journals Spectral Properties of Prompt Emission of Four Short Gamma-Ray Bursts Observed by the Suzaku-WAM and the Konus-Wind

2008 ◽  
Vol 60 (sp1) ◽  
pp. S361-S373 ◽  
Author(s):  
Masanori Ohno ◽  
Yasushi Fukazawa ◽  
Takuya Takahashi ◽  
Kazutaka Yamaoka ◽  
Satoshi Sugita ◽  
...  
Keyword(s):  
Spectral Properties ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Prompt Emission

scholarly journals HIGH ENERGETIC GAMMA RAY BURSTS AND THEIR SPECTRAL PROPERTIES WITHIN THE FIRESHELL MODEL

2012 ◽  
Vol 12 ◽  
pp. 385-389
Author(s):  
B. PATRICELLI ◽  
M.G. BERNARDINI ◽  
C.L. BIANCO ◽  
L. CAITO ◽  
G. DE BARROS ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Observational Data ◽  
Spectral Properties ◽  
Gamma Ray ◽  
Emission Spectra ◽  
Gamma Ray Bursts ◽  
Low Energy ◽  
Isotropic Energy ◽  
Thermal Spectrum ◽  
Prompt Emission

The analysis of various Gamma Ray Bursts (GRBs) characterized by an isotropic energy Eiso ≲ 1053 ergs within the fireshell model has shown how that the observed N(E) spectrum of their prompt emission can be reproduced in a satisfactory way by assuming a thermal spectrum in the comoving frame of the fireshell. Nevertheless, from the study of higher energetic bursts (Eiso ≳ 1054 ergs ) such as, for example, GRB 080319B, some discrepancies between the numerical simulations and the observational data have been observed. We investigate a different spectrum of photons in the comoving frame of the fireshell in order to better reproduce the spectral properties of GRB prompt emission within the fireshell model. We introduce a phenomenologically modified comoving thermal spectrum: a spectrum characterized by a different asymptotic low energy slope with respect to the thermal one. We test this spectrum by comparing the numerical simulations with the observed prompt emission spectra of various GRBs; we present, as an exaple, the case of GRB 080319B.

scholarly journals The diversity of GRBs and their SNe: Observations from the 10.4m GTC

2017 ◽  
Vol 12 (S331) ◽  
pp. 39-44
Author(s):  
Antonio de Ugarte Postigo ◽  
Christina Thöne ◽  
Zach Cano ◽  
David Alexander Kann ◽  
Luca Izzo ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Massive Stars ◽  
Gamma Ray Bursts ◽  
Compact Objects ◽  
The Past ◽  
Photometric And Spectroscopic Observations ◽  
Long Duration ◽  
Different Types ◽  
Short Grbs

AbstractObserving the supernovae (SNe) associated to the different types of gamma-ray bursts (GRBs) is one of the few means to study their progenitors. In the past years, it has become clear that GRB-like events are more heterogeneous than previously thought. There is a marked difference between long GRBs, which are produced by the collapse of very massive stars and are normally associated with broad-lined type Ic SNe, and short bursts, which occur when two compact objects merge and that, at least in some cases, can produce an associated kilonova. Moreover, the SNe associated with different sub-types of long GRBs are also seen to differ, especially those associated with ultra-long duration GRBs. To address this issue in a systematic way we started an observing programme in 2010 at the 10.4m GTC telescope. Here we present some results of our programme, including the detection of 12 new GRB-SNe. Highlights of our sample are the discovery of the first spectroscopic SN associated with a highly energetic (Eγ, iso ~ 1054 erg) “cosmological” burst (GRB 130427A), the study of the SN associated with a shock-breakout GRB (GRB 140606B) and the SN associated with the peculiar ultra-long GRB 101225A at z = 0.85. The sample includes also the follow-up of several short GRBs in search for kilonovae emission (GRB 130603B and GRB 160821B are important examples). Amongst our latest results we present the photometric and spectroscopic observations of the SNe associated with GRB 150818A and GRB 161219B.

scholarly journals Quark-Nova Explosion inside a Collapsar: Application to Gamma Ray Bursts

2009 ◽  
Vol 2009 ◽  
pp. 1-10 ◽  
Author(s):  
Rachid Ouyed ◽  
Denis Leahy ◽  
Jan Staff ◽  
Brian Niebergal
Keyword(s):  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Prompt Gamma ◽  
Stellar Envelope ◽  
X Ray ◽  
Star Forming ◽  
Star Forming Regions ◽  
Long Duration ◽  
Model Features ◽  
Prompt Emission

If a quark-nova occurs inside a collapsar, the interaction between the quark-nova ejecta (relativistic iron-rich chunks) and the collapsar envelope leads to features indicative of those observed in Gamma Ray Bursts. The quark-nova ejecta collides with the stellar envelope creating an outward moving cap (Γ∼1–10) above the polar funnel. Prompt gamma-ray burst emission from internal shocks in relativistic jets (following accretion onto the quark star) becomes visible after the cap becomes optically thin. Model features include (i) precursor activity (optical, X-ray,γ-ray), (ii) promptγ-ray emission, and (iii) afterglow emission. We discuss SN-less long duration GRBs, short hard GRBs (including association and nonassociation with star forming regions), dark GRBs, the energetic X-ray flares detected in Swift GRBs, and the near-simultaneous optical andγ-ray prompt emission observed in GRBs in the context of our model.

scholarly journals Magnetars and Gamma Ray Bursts

2011 ◽  
Vol 7 (S279) ◽  
pp. 289-296 ◽  
Author(s):  
Niccolò Bucciantini
Keyword(s):  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Significant Fraction ◽  
Detailed Model ◽  
Engine Model ◽  
Central Engine ◽  
Long Duration ◽  
Key Aspects ◽  
Short Grbs ◽  
Extended Emission

AbstractIn the last few years, evidences for a long-lived and sustained engine in Gamma Ray Bursts (GRBs) have increased the attention to the so called millisecond-magnetar model, as a competitive alternative to the standard collapsar scenario. I will review here the key aspects of the millisecond magnetar model for Long Duration Gamma Ray Bursts (LGRBs). I will briefly describe what constraints present observations put on any engine model, both in terms of energetics, outflow properties, and the relation with the associated Supernova (SN). For each of these I will show how the millisecond magnetar model satisfies the requirements, what are the limits of the model, how can it be further tested, and what observations might be used to discriminate against it. I will also discuss numerical results that show the importance of the confinement by the progenitor star in explaining the formation of a collimated outflow, how a detailed model for the evolution of the central engine can be built, and show that a wide variety of explosive events can be explained by different magnetar parameters. I will conclude with a suggestion that magnetars might be at the origin of the Extended Emission (EE) observed in a significant fraction of Short GRBs.

scholarly journals Prevalence of Extra Power-Law Spectral Components in Short Gamma-Ray Bursts

2021 ◽  
Vol 922 (2) ◽  
pp. 255
Author(s):  
Qing-Wen Tang ◽  
Kai Wang ◽  
Liang Li ◽  
Ruo-Yu Liu
Keyword(s):  
Power Law ◽  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Spectral Feature ◽  
Gamma Ray Bursts ◽  
Spectral Energy ◽  
Spectral Components ◽  
Short Grbs ◽  
Prompt Emission ◽  
Emission Phase

Abstract A prompt extra power-law (PL) spectral component that usually dominates the spectral energy distribution below tens of keV or above ∼10 MeV has been discovered in some bright gamma-ray bursts (GRBs). However, its origin is still unclear. In this paper, we present a systematic analysis of 13 Fermi short GRBs, as of 2020 August, with contemporaneous keV–MeV and GeV detections during the prompt emission phase. We find that the extra PL component is a ubiquitous spectral feature for short GRBs, showing up in all 13 analyzed GRBs. The PL indices are mostly harder than −2.0, which may be well reproduced by considering the electromagnetic cascade induced by ultrarelativistic protons or electrons accelerated in the prompt emission phase. The average flux of these extra PL components positively correlates with that of the main spectral components, which implies they may share the same physical origin.

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