Future Astro-H Observations of Gamma-ray Bursts

Author: Masanori Ohno

Abstract: There have been several reports of marginal detection of spectral features such as iron-K line emission, its recombination edge, and several lines due to light metals. Such spectral features are very important not only to determine the redshift of the GRBs by X-ray observation itself but also to investigate physical condition of environment of GRBs, for example, outflow velocity of ejecta and condition of circumsteller material of hypernovae. However, previous reports still controversial for limited statistics. Therefore, confirmation of those spectral features are still challenging area for X-ray afterglow observation. The high resolution X-ray calorimeter (Soft X-ray Spectrometer; SXS) and X-ray CCD camera (Soft X-ray Imager; SXI) are very powerful tool to detect such spectral features and we found that Astro-H can confirm the same spectral features as previous report with reasonable observational conditions such as a required time for slewing the spacecraft and expected number of events based on current Swift-XRT statistics. The Hard X-ray Imager (HXI) might observe interesting features like hard tail or cut-off from afterglow continuum. In addition to those focal plane instruments, Astro-H is also able to observe the prompt gamma-ray emission utilizing Soft Gamma-ray Detector (SGD). SGD is surrounded by large 25 BGO shield detectors to guard the main detector and we can use these shield detectors as a all-sky monitor. The data acquisition system of SGD shield detectors for all-sky monitor is specialized for very short transients such as short GRBs and soft gamma repeaters. In this presentation, we discuss a capability of observation of GRBs including both prompt gamma-ray emission and X-ray afterglow.