主辦單位
ASROC
協辦單位
ASIAA
贊助單位
MOST
會徽Logo
名稱Title
2020天文年會
中研院天文所 國際會議廳

論文摘要

The Polarization Performance of the Compton Telescopes - The Compton Spectrometer and Imager(COSI) and the Compton Polarimeter(Compol)

[ Oral ]

Chien-Ying Yang (NTHU); Hsiang-Kuang Chang (NTHU); COSI collaborations; Compol collaborations

Polarization measurements offer a unique method to determine the emission mechanisms and source geometries (e.g. magnetic field, accretion disk, and jet). Determining the polarization characteristics will provide crucial clues about the extreme environments in different astrophysical sources such as pulsars, AGNs, Galactic BHs, and Gamma-ray bursts(GRBs).\\ Gamma-ray polarization can be determined by Compton scattering. In this work, we use Monte Carlo simulations with a Geant4-based MEGAlib package to study the polarimetric performance of two Compton telescopes: the Compton Spectrometer and Imager (COSI) and Compton Polarimeter (Compol).\\ COSI is a compact Compton telescope which is inherently sensitive to gamma-ray polarization in the energy range of 0.2–2.0 MeV. A long duration gamma-ray burst, GRB 160530A, was detected by COSI during its 2016 COSI’s balloon flight. In order to determine COSI’s polarization response and to identify systematic deviations from an ideal sinusoidal modulation, the polarization performance of COSI was validated in the laboratory prior to the 2016. We took the measurements used to validate COSI’s polarimetric performance. Based on these results, COSI has a high probability to determine the polarization of GRBs. \\ Compol is the instrument to observe gamma-ray polarization from Cygnus X-1 using a small Compton polarimeter on board a 3U CubeSat. Silicon detectors and cerium bromide scintillators were employed in the instrument models that we discuss in this study. We found that, with a 10 Ms on- axis, zenith-direction observation in a low-inclination, low-altitude, Earth-orbit radiation background environment, the minimum detectable polarization degree can be down to about 10$\%$ in 160–250 keV, 20$\%$ in 250–400 keV, and 65$\%$ in 400–2000 keV. A 3U CubeSat dedicated to observing Cygnus X-1 can therefore yield useful information on the polarization state of gamma-ray emissions from the brightest persistent X-ray black hole binary in the sky.\\