Poster Presentation

Unification of Gamma-Ray Bursts: Host galaxy of the first off-axis X-ray Flash

Author(s): CHEN JHENG CYUN

Presenter: Jheng-Cyun Chen (NCU)

We investigate the unification of Gamma-Ray Burst (GRBs) and X-ray Flashes (XRFs) by confirming the burst site environment properties. Observing the GRB properties require an ultra-relativistic collimation and a jet structure. Off-axis jet events occur as a natural consequence of GRB jet production and XRF could be same origin. The expected properties of off-axis jet events include the following: (1) absence of prompt emissions in the high-energy band, (2) the afterglows are characterized by 3-component light curves with rising, peaking, and rapidly decaying phases, and (3) association with a host galaxy, whose properties are similar to those of on-axis GRBs. Based on our afterglow and prompt radiation analysis by using the most favorable XRF sample (i.e. XRF020903), we demonstrated that the off-axis model with a large viewing angle satisfyingly describes the observed properties. In this presentation, we report host galaxy properties using ALMA observations including on-axis GRB host galaxies.