Synchrotron Radiation Dominates the Extremely Bright GRB 221009A

Yang, Jun; Zhao, Xiaoxia; Yan, Zhenyu; Wang, X.; Zhang, Yanqiu; An, Zhu; Cai, C.; Li, Xinqiao; Liu, Jia-Cong; Liu, Zi-Ke; Ma, Xiang; Meng, Yan-Zhi; Peng, W. X.; Qiao, Rui; Shao, L.; Song, Liming; Tan, Wenjun; Wang, Ping; Wang, Chen-Wei; Wen, Xiang-Yang; Xiao, Shuo; Xue, W. C.; Yang, Yu-Han; Yin, Yi-Han; Zhang, Bing; Zhang, Fan; Zhang, Shuai; Zhang, Shuang‐Nan; Zheng, Chao; Zheng, S.; Xiong, S. L.; Zhang, Bin-Bin

doi:10.3847/2041-8213/acc84b

Cited by 22 publications

(24 citation statements)

References 51 publications

(47 reference statements)

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“…In the energy spectrum analysis, we found that there may be a photosphere emission component in the early phase of GRB 230307A, which is similar to that of the also very bright GRB 130427A (Preece et al 2014). However, the brightest of all time (the BOAT, GRB 221009A) is believed to be dominated by nonthermal synchrotron radiation throughout its duration (Yang et al 2023). So these bright GRBs clearly have different emission components.…”

Section: Comparison With Other Grbsmentioning

confidence: 63%

A Broken “α–intensity” Relation Caused by the Evolving Photosphere Emission and the Nature of the Extraordinarily Bright GRB 230307A

Wang¹,

Xia²,

Zheng

et al. 2023

ApJL

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GRB 230307A is one of the brightest gamma-ray bursts detected so far. With the excellent observation of GRB 230307A by the Fermi Gamma-ray Burst Monitor, we can reveal the details of prompt emission evolution. As found in high time-resolution spectral analysis, the early low-energy spectral indices (α) of this burst exceed the limit of synchrotron radiation (α = −2/3) and gradually decreases with the energy flux (F). A tight E p ∝ F 0.54 correlation holds within the whole duration of the burst, where E p is the spectral peak energy. Such an evolution pattern of α and E p with intensity is called “double tracking.” For the α–F relation, we find a log Bayes factor ∼210 in favor of a smoothly broken power-law function over a linear function in log-linear space. We call this particular α–F relation a broken “α–intensity” and interpret it as the evolution of the ratio of thermal and nonthermal components, which is also the evolution of the photosphere. GRB 230307A with a duration of ∼35 s, if indeed at a redshift of z = 0.065, is likely a neutron star merger event (i.e., it is intrinsically “short”). Intriguingly, different from GRB 060614 and GRB 211211A, this long event is not composed of a hard spike followed by a soft tail, suggesting that the properties of the prompt emission light curves are not a good tracer of the astrophysical origins of the bursts. The other possibility of z = 3.87 would point toward a very peculiar nature of both GRB 230307A and its late-time thermal-like emission.

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Section: Comparison With Other Grbsmentioning

confidence: 63%

A Broken “α–intensity” Relation Caused by the Evolving Photosphere Emission and the Nature of the Extraordinarily Bright GRB 230307A

Wang¹,

Xia²,

Zheng

et al. 2023

ApJL

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“…Then we perform spectral fitting by utilizing the Python package, MySpecFit, in accordance with the methodology outlined in Refs. 27,68 . The MySpecFit package facilitates Bayesian parameter estimation by wrapping the widely-used Fortran nested sampling implementation Multinest [69][70][71][72] .…”

Section: Spectral Analysismentioning

confidence: 99%

“…In addition, GRB 230307A poses higher total energy and harder spectra, likely indicating a more intense merger event. We also consider the scenario where the host galaxy has a redshift of 3.87 46 and notice that in this case, the isotropic energy of GRB 230307A is ∼ 10 56 erg, which is an order of magnitude larger than that of the brightest-of-all-time GRB 221009A 20,68 .…”

Section: Classificationmentioning

confidence: 99%

Magnetar emergence in a peculiar gamma-ray burst from a compact star merger

Zhang

Sun

Wang

et al. 2023

Preprint

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The central engine that powers gamma-ray bursts (GRBs), the most powerful explosions in the universe, is still not identified. Besides hyper-accreting black holes, rapidly spinning and highly magnetized neutron stars, known as millisecond magnetars, have been suggested to power both long and short GRBs1–7. The presence of a magnetar engine following compact star mergers is of particular interest as it would provide essential constraints on the poorly understood equation of state for neutron stars8, 9. Indirect indications of a magnetar engine in these merger sources have been observed in the form of plateau features present in the X-ray afterglow light curves of some short GRBs10, 11. Additionally, some X-ray transients lacking gamma-ray bursts (GRB-less) have been identified as potential magnetar candidates originating from compact star mergers6, 12, 13. Nevertheless, smoking gun evidence is still lacking for a magnetar engine in short GRBs, and the associated theoretical challenges have been addressed14. Here we present a comprehensive analysis of the broad-band prompt emission data of a peculiar, very bright GRB 230307A. Despite its apparently long duration, the prompt emission and host galaxy properties point toward a compact star merger origin, being consistent with its association with a kilonova15. More intriguingly, an extended X-ray emission component emerges as the γ-ray emission dies out, signifying the emergence of a magnetar central engine. We also identify an achromatic temporal break in the high-energy band during the prompt emission phase, which was never observed in previous bursts and reveals a narrow jet with half opening angle of approximately 3.4◦.

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“…At 13:16:59.99 UT (T 0 ) on 2022 October 9, the Fermi Gamma-ray Burst Monitor triggered and located GRB 221009A (Veres et al 2022;Lesage et al 2023), which was also detected by the Fermi Large Area Telescope (Fermi-LAT; Bissaldi et al 2022), Konus-Wind (Frederiks et al 2022), Swift-BAT-GUANO (Dichiara et al 2022), GECAM-C (Liu et al 2022;An et al 2023;Yang et al 2023), and LHAASO (LHAASO Collaboration 2023). Its redshift is reported to be z = 0.151 (de Ugarte Postigo et al 2022).…”

Section: Fermi-lat Data Analysismentioning

confidence: 99%

Constraints on the Intergalactic Magnetic Field Strength from γ-Ray Observations of GRB 221009A

Huang,

Dai,

Zhang

et al. 2023

ApJL

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Characteristics of the cascade gamma-ray signal resulting from very-high-energy gamma-ray sources, such as gamma-ray bursts, can be used to constrain the strength and structure of intergalactic magnetic fields (IGMFs). There has been a debate on whether GRB 190114C, the first gamma-ray burst with observed TeV photons, can constrain the IGMF. Recently, LHAASO detected the brightest-of-all-time GRB 221009A, which has much larger energy in the TeV band, and the spectrum extends to energy above 10 TeV, providing an unprecedented opportunity to study IGMF. We perform a Monte Carlo simulation of the cascade process with the public ELMAG code, considering the TeV data of GRB 221009A observed by LHAASO. By comparing the resulting cascade emission with the flux limit obtained from Fermi-LAT observations, we infer a limit of B ≥ 10−18.5 G for IGMF. Though this limit may not be as strong as the limit from blazars, it serves as an independent constraint on IGMF from a new class of TeV sources.

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Synchrotron Radiation Dominates the Extremely Bright GRB 221009A

Cited by 22 publications

References 51 publications

A Broken “α–intensity” Relation Caused by the Evolving Photosphere Emission and the Nature of the Extraordinarily Bright GRB 230307A

A Broken “α–intensity” Relation Caused by the Evolving Photosphere Emission and the Nature of the Extraordinarily Bright GRB 230307A

Magnetar emergence in a peculiar gamma-ray burst from a compact star merger

Constraints on the Intergalactic Magnetic Field Strength from γ-Ray Observations of GRB 221009A

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