Poster Presentation
Structure jet of Gamma-Ray Bursts
Presenter: Wei Ju Chen (NCU)
We investigate the double jet components through multi-wavelength observation of GRB 160623A. GRB 160623A was detected by Fermi-LAT and its X-ray afterglow was identified by Neil Gehrels Swift observatory. The Fermi-LAT observations exhibited more than 15 photons above 1 GeV in the prompt phase. Based on optical observation, the redshift of this event is determined as z = 0.367. We executed submilimeter follow-up observations using Submilimeter Array(SMA) at the 230 GHz band and successfully identified the bright(~15 mJy) afterglow. The continuous monitoring was also performed until 21 days after the burst. We perform multi-wavelength analysis using Fermi, CALET, Swift, SMA, and AMI. The analysis indicates the post jet-break model describes the X-ray afterglows with the jet-opening angle smaller than 2.4 degrees.
When we assume the origin of the radio afterglow is the same synchrotron with X-ray, the both spectrum and temporal evolutions in radio cannot be explained. By performing relativistic hydrodynamic jet simulation, the radio afterglow is described by the standard forward shock model with the jet-opening angle of ~27 degrees, which is significantly wider than the X-ray jet. Hence, these multi-wavelength analysis indicate existence of double-jets or structured jet. Since numerical jet simulation of collapser indicates that the maximum angle of jet is depending on initial Lorentz factor (~12 degree), the origin of the wide jet may be related with cocoon radiation.
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