| Authors : | Suman Bala (IIT Bombay)
Sujay Mate (TIFR Mumbai),
Parth Sastry (IIT Bombay ),
Advait Mehla (IIT Bombay),
Divita Saraogi (IIT Bombay),
Mithun NPS (PRL Ahmedabad),
Sourav Palit (ICSP Kolkata),
Gaurav Waratkar (IIT Bombay),
Varun Bhalerao (IIT Bombay),
Shriharsh Tendulkar (TIFR Mumbai),
Santosh Vadawale (PRL Ahmedabad) |
| Abstract : | Gamma-Ray Bursts (GRBs) are the strongest explosions to probe the extreme nature of the Universe. Extensive studies of GRBs over a few decades have led to a broad understanding of the phenomenon and the central engine driving it. However, the details remain murky: in particular, there are many open questions about the physics of emission in the prompt phase of the GRB. Spectral and temporal properties of this prompt emission are consistent with multiple models like the synchrotron model (ordered and random), Compton drag model, Photospheric model, etc. New observations are necessary to break this deadlock between models. One such observable is the polarisation of high-energy photons: these models predict different ranges of polarisation fractions for GRBs. Polarisation measurements of a large number of GRBs will allow us to establish the underlying model of GRB prompt emission conclusively. However, high-energy polarisation measurements are extremely challenging, and only a few instruments have been able to undertake such a study to date.
The proposed Daksha mission has excellent capabilities to accurately measure polarisation of GRBs. Daksha utilises CZT detectors to measure polarisation, building upon the legacy of AstroSat CZTI. The all-sky coverage of Daksha ensures that bright GRBs will not be missed. The hemispherical design implies that many detector packages can measure polarisation with different angles of incidence, giving control over systematics. Over five years of observations, Daksha will be able to single-handedly measure polarisation of 40-50 bursts, enough to conclusively distinguish between the models above. In this talk, I will introduce the proposed Indian mission Daksha, discuss details of the polarisation measurement using Compton scattering of incoming photons, and discuss how it will help us probe the physical processes associated with GRBs. |
