We report a very bright, long-duration gamma-ray burst (GRB), GRB 220426A, observed by the Fermi satellite. GRB 220426A, with a total duration of T
90 = 6 s, is composed of two main pulses and some subpeaks. The spectral analysis of this burst with a Band function reveals that both the time-integrated and the time-resolved spectra are very narrow with a high α ≳ 0.2 and low β ≲ −3.1. It is highly reminiscent of GRB 090902B, a special GRB with a photospheric emission identification. Then, we perform the spectral analysis of this burst based on nondissipated photospheric emission, which can be well modeled by a multicolor blackbody with a cutoff power-law distribution of the thermal temperature. The spectral fittings reveal that the photospheric emission can well describe the radiation spectrum of this burst. We conclude that this burst would be a second burst in the class of GRB 090902B observed by the Fermi satellite. We also discuss the physics of the photosphere and the origin of the high-energy component in GRB 220426A.
We report on a very bright, long-duration gamma-ray burst (GRB), GRB 220426A, observed by Fermi satellite. GRB 220426A with total duration of T 90 = 6 s is composed with two main pulses and some sub-peaks. The spectral analysis of this burst with Band function reveals that both the time-integrated and the time-resolved spectra are very narrow with high α 0.2 and low β −3.1. It is strong reminiscent of GRB 090902B, a special GRB with identification of the photospheric emission. Then, we perform the spectral analysis of this burst based on a non-dissipated photospheric emission, which can be well modelled as the multicolor-blackbody with a cutoff power-law distribution of the thermal temperature. The spectral fittings reveal that the photospheric emission can well describe the radiation spectrum of this burst. We conclude that this burst would be a second burst in the class of GRB 090902B observed by Fermi satellite. We also discuss the physics of photosphere and the origin of the high-energy component in GRB 220426A .
A Mini-Orange spectrometer used for in-beam measurements of internal conversion electrons, which consists of a Si(Li) detector and different sets of SmO5 permanent magnets for filtering and transporting the conversion electrons to the Si(Li) detector, has been developed at China Institute of Atomic Energy. The working principle and configuration of the Mini-Orange spectrometer are described. The performance of the setup is illustrated by measured singles conversion electron spectra using the Mini-Orange spectrometer.
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