Physics

Dr Nachiketa Chakraborty
Max-Planck Institute, Heidelberg, Germany

Abstract :
The most explosive and transient phenomena in the universe harbour the 
most powerful, natural particle accelerators like active galactic nuclei 
(AGNs), gamma-ray bursts (GRBs), X-ray binaries (XRBs) etc. These 
phenomena serve as laboratories for studying extreme physical 
environments, possible sources of ultra high energy cosmic rays, 
neutrinos and gravitational waves and for cosmology. Despite extensive 
research, some fundamental properties of individual transients like 
origin of accelerated particles and radiation, unifying properties of 
jets, flaring behaviour, etc are open questions. Complexity of 
environments and processes often make it hard to disentangle different 
effects. This suggests complementing conventional observables like the 
broadband spectra with statistical observables extracted from
lightcurves (power spectrum and flux distribution), polarization
etc.  As a population too, characteristic patterns in variability from 
quasi-periodicity to Lorentz-violating time-delays, contribution to
cosmological backgrounds, etc., are subjects of ongoing research. Such 
observables probed with methods of data science like statistics and 
machine learning serve as 
crucial cross checks to neutrino and gravitational wave observations
in the multi-messenger era. In this presentation, I demonstrate the
potential of temporal observables in particular as probes of 
microphysics of extreme environments in individual transients as well as 
their role as a population.