Bio

I am a researcher working in high-energy and computational astrophysics. I work with numerical tools to gain insights into the high-energy astrophysical sources (including Gamma-ray Bursts (GRBs) and Active Galactic Nuclei (AGNs)) we observe in the sky.

I obtained my PhD working in Prof. Janiuk's group in December 2023. Before joining the astrophysics group in Warsaw, I worked as a physics lecturer in India during two academic years. (Please see my LinkedIn profile for a more detailed outline of my studies and career path.)

Education

• Ph.D. in Physics (2019 - 2023)
  from Center for Theoretical Physics, Polish Academy of Sciences,
  Warsaw, Poland.

• M.Sc. in Physics (2013 - 2015)
  from Central University of Kerala,
  Kasaragod, India.

• B.Sc. in Physics (2010 - 2013)
  at St. Thomas College Pala, from Mahatma Gandhi University,
  Kottayam, India.




Research Highlights

Variability of Magnetically Dominated Jets from Accreting Black Holes

Observational studies point to correlations between the jet variability and the Lorentz factor (Γ), covering both GRB and blazar samples. This project explored the connections between the jet energetics and temporal variability taking into account the disk magnetization and the black hole spin. The study was conducted by ideal GRMHD simulations and probing the jet energetics and time variability at different points along the line of sight. The results were quantified by computing the minimum variability time scale (MTS), and the jet Lorentz factors and the MTS-Γ anti-correlation is qualitatively verified in our models. The black hole spin can be attributed as the main driving parameter of the engine, which is reflected in the jet Lorentz factors.

Time variability of the jet-energetics (μ-parameter), at a chosen location along the jet direction, with the magnetorotatioanl (MRI) timescale associated with the system marked on it (Janiuk, James and Palit, 2021).

Modelling the GRB jet properties with 3D GRMHD simulations of magnetically arrested accretion flows

This study focused on the jet properties of gamma-ray bursts by considering a magnetically arrested disk (MAD) as the central engine. The work explored the possible dependence of the jet structure and temporal variability of the GRB jets on the MAD state. The simulations were done in 3D with a non-axisymmetric time evolution, introduced by random perturbations in the gas internal energy. The models probed in this work reached a MAD state and self-consistently produced structured jets with very fast variability in time. The models from this work were then applied to particular cases of short and long GRB systems and the results were analyzed in comparison with the observations.

3D jet structure, depicted in terms of the total jet energetics, from one of our models for the GRB central engines at an evolved time of the simulation (James, Janiuk and Nouri, 2022).

Black hole outflows driven by accretion of a large-scale magnetic field

In this project, we explored the outflows driven by large-scale magnetic fields in the vicinity of a black hole. This work examined the competing effects of inflows and outflows driven by a large-scale asymptotically uniform magnetic field in the Kerr geometry, starting from a spherically symmetric inflow. This in turn resulted in the magnetic field lines being accreted with the plasma while intermittent outflows develop mainly in the equatorial region. The outflows developed were attributed mainly to the magnetic reconnection and also possibly to the Meissner-like expulsion of magnetic field lines by a highly spinning black hole. This work provides a general insight into the effects of magnetized accretion onto rotating black holes and the associated outflows.

The equatorial mass outflow rate with time at 10 gravitational radii, after the magnetic field is turned on, for the (2D) models with maximum β = 0.1 and with different spin values (James, Janiuk and Karas, 2024).

Publications

Here, I list the recent peer-reviewed articles in which I have been a part of;
please follow one of the following links for a complete list of my publications.

Contact

Please fill out the contact form to reach me. I will get back to you as soon as possible.