Research

I work on binary systems made of Neutron Stars (NS) and NS/ White Dwarfs 
(WD)/Black Holes (BH), as well as double White Dwarf systems, and core-collapse of massive, rapidly rotating stars. Currently, I'm studying magnetic helicity which is robustly conserved in systems with large magnetic Reynolds numbers, including most systems of astrophysical interest. This plays a major role in suppressing the kinematic large scale dynamo and driving the large scale dynamo through the magnetic helicity flux. 

Also, I study how compact objects form, evolve, and merge, and which transient events they produce. I also work on resolving the critical conditions for deflagration and detonation shock waves.
I study turbulent nuclear burning, which can largely enhance nuclear burning rates and may serve as an additional mechanism for stellar explosions. Moreover, it may power thermonuclear and pair-instability supernovae, liberate the neutrinos in core-collapse supernovae, and synthesize r-process heavy nuclei in kilonovae and collapsars.

Hypotheses are tested using extensive hydrodynamical, thermonuclear, AMR, and multidimensional simulations coupled with detailed nuclear reaction networks (The computational requirements for these use MESA and FLASH). The results of these simulations are followed by an analysis of composition using a large-scale nucleosynthetic network – (PPN). These enable us just to calculate the detailed properties of SN’s ejecta. The results of post-processing are also used as an input for modeling the radiative transfer evolution (SuperNu), which is used to provide detailed (light curve/spectra) predictions for the observable properties arising from each theoretical model and chemical composition of SN ejecta.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CO WD 0.8M⊙ & HeCO WD 0.69M⊙: Propagation of the shock originating from the helium detonation as it moves around the primary WD. The panels show the time evolution from the time of the ignition of the helium detonation (top left panel) to the time when the shock converges in the CO core of the primary WD (bottom right panel). The black dotted and gray solid contours indicate densities of 2×10^6 g cm−3 and 10^7 g cm−3 ,  respectively.


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Z_R Snapshots of Collapsar (M~13 M⊙) show density, temperature, and He4 as well as Ni56 mass fractions in the meridional plane ( ̄ρ,z) during the first.1.7 viscous timescales. Production of He4 and Ni56  indicate significant nuclear burning that develops into a global detonation of the accretion disk and leads to the production of iron-group nuclei.  

  

Log-log plot of the dimensionless fractional turbulent enhancement in the nuclear burning rate, as a function of the RMS temperature fluctuation on length scale r, normalized to the mean temperature, in the distributed burning regime. The curves shown are for neutrino cooling via the URCA process (solid line), C12 -C12 burning (dashed), and triple-alpha reaction (dot dashed). The inset figure shows the same three curves on the same set of axes, compensated by the factor (1/[n*(n - 1)]). For weak enhancement, the compensated enhancement collapses onto a single curve, demonstrating its universal nature.

 

 

 

 

turbulent_enhancement.png