Speaker
Description
Daksha, a proposed Indian mission, will be the most sensitive all-sky high-energy time domain telescope in the world. Daksha will detect and characterise about ten electromagnetic counterparts of the gravitational wave (EMGW) events per year and about thousand classical GRBs (especially high redshift GRBs) per year. For bright transients, Daksha will be able to measure hard X-ray polarisation, a key to understanding the geometry and physical process of the emission mechanism. The mission will consist of two identical satellites monitoring the entire sky in the energy range of 1 – 1000 keV and with all-sky median effective area of ~1300 cm$^2$ for a single satellite and an effective fluence sensitivity of 4 $\times$ $10^{–8}$ erg/cm$^2$ (for a 1 second duration transient). Daksha will have 340 pixelated Cadmium Zinc Telluride (CZT) detectors on each satellite arranged in a quasi-hemispherical configuration and without any field of view collimation (open detectors). These CZT detectors form an excellent polarimeter capable of measuring photon polarisation in the energy range 100 – 400 keV. The CZTI instrument aboard AstroSat has successfully measured the polarisation of the Crab pulsar and 11 GRBs using these detectors. In this talk, I will introduce the Daksha mission concept, discuss details of the polarisation measurement method using the CZT detectors, and show results of simulations carried out using the mass model to estimate polarisation measurement sensitivity of the Daksha mission.