40 - Polarimetry with ASTRO-H soft gamma-ray detector

Summary

ASTRO-H is a next-generation JAXA X-ray satellite to be launched in 2014. The Soft Gamma-ray Detector (SGD) onboard ASTRO-H is a semi-conductor Compton camera with a narrow field-of-view (FOV) to achieve very low background. Although the SGD is primarily a spectrometer in the 40–600 keV energy band, it is also sensitive to polarization in the 50–200 keV energy band. This paper describes instrument design, expected performance, and experimental validation of polarimetric performance of the SGD.

Introduction

ASTRO-H, the new Japanese X-ray Astronomy Satellite following Suzaku, is a combination of

• high energy-resolution soft X-ray spectroscopy (0.3–10 keV) provided by thin-foil X-ray optics (SXT, Soft X-ray Telescope) and a microcalorimeter array (SXS, Soft X-ray Spectrometer);

• soft X-ray imaging spectroscopy (0.5–12 keV) provided by SXT and a CCD (SXI, Soft X-ray Imager);

• hard X-ray imaging spectroscopy (3–80 keV) provided by multi-layer coating, focusing hard X-ray mirrors (HXT, Hard X-ray Telescope) and silicon (Si) and cadmium telluride (CdTe) cross-strip detectors (HXI, Hard X-ray Imager);

• soft gamma-ray spectroscopy (40–600 keV) provided by semiconductor Compton camera with narrow FOV (SGD, Soft Gamma-ray Detector).

The SXT-SXS and SGD systems will be developed by an international collaboration led by Japanese and US institutions.

The SXS will use a 6×6 format microcalorimeter array. The energy resolution is expected to be better than 7 eV. The FOV and the effective area will be, respectively, about 3 arc minutes and about 210 cm² combined with the ∼6 m focal-length SXT.