Atul Chhotray was awarded the 2017 Physics Department Graduate Research Award.
A native of India, Atul joined OSU in 2014 as a transfer student from North Carolina State University.
Atul has since performed his research in the computational astrophysics group of Dr. Davide Lazzati.
Atul’s thesis research is an effort to better understand the radiation properties and acceleration mechanism of baryonic jets from gamma-ray bursts (GRBs) and blazars. Both these sources produce extremely fast and energetic outflows from central engines believed to be powered by black holes, where gravity reaches it maximum strength. The origin of the GRB prompt emission has been a very debated topic in the last few decades. In his thesis work, Atul studied (with Monte Carlo techniques) the photon-lepton interactions that lead to the acceleration of the outflow and, ultimately, to the release of non-thermal radiation. A paper containing the results from the code has been published in The Astrophysical Journal (Chhotray et al. 2015, ApJ, 802, 132) and one has been recently submitted for publication.
Atul’s work studies previously unexplored regimes of radiatively-driven acceleration, discovering the existence of significant acceleration after the photons decouple from the leptons of the outflow, and deriving approximations of his numerical results. His study of radiation shows that non-thermal photon spectra can be observed because of partial thermalization of photon and lepton populations that are initially at different temperatures. His conclusions dispel the long-held tenet that the observation of non-thermal radiation implies the presence of non-thermal electrons.
Atul also spent the summer of 2015 at the Osservatorio Astronomico of Brera, in Italy, where he performed research on Blazar jets under the supervision of Prof. Gabriele Ghisellini. While in Brera, Atul developed a radiation feedback code to study radiation viscosity in blazar jets with polar stratification (a fast spine surrounded by a slower sheath). Atul’s work showed that radiation provides friction between sections of a jet moving at different speeds and prevents the existence of steep stratification. His results give theoretical foundations to phenomenological models that explain the simultaneous observation of radiation in a broad frequency range from individual Blazar jets.