Abinash Das.Physics · Georgia Institute of Technology
Research

Research.

I am a Ph.D. student in the School of Physics at Georgia Tech and a member of the Center for Relativistic Astrophysics, co-advised by David R. Ballantyne and Tamara Bogdanović. See the interactive orbit figure ↗

Current project

01 — Summer 2026–Present
In progress

Radio Modeling of Dual Active Galactic Nuclei

Role
Graduate Researcher, Center for Relativistic Astrophysics, Georgia Institute of Technology
Advisors
David R. Ballantyne (PI) and Tamara Bogdanović (Co-PI)
Funding
NSF AST-2407658, “The Population and Evolution of Dual AGNs at Radio Wavelengths: Predictions for the ngVLA”

When galaxies merge, each can bring a supermassive black hole into the remnant. If both are accreting, the system appears as a dual AGN, and finding such pairs is one route to studying how SMBHs pair up and evolve. This project asks what those pairs should look like at radio wavelengths.

  • Develop a theoretical and computational framework for predicting radio emission from dual AGNs in post-merger galaxies, with applications to searches for SMBH pairs.
  • Connect host-galaxy and SMBH properties from IllustrisTNG with pre-existing orbital-evolution calculations to model the evolving accretion and radio-emission properties of the pair.
  • Model accretion from magnetized gas and relativistic jet power, considering the dependence on the black holes’ motion and the surrounding galactic environment.
  • Calculate radio synchrotron spectra, including synchrotron self-absorption, to predict the fluxes and spectral properties of the two AGN cores.
  • Investigate how radio detectability depends on projected separation, redshift, host-galaxy properties, and observing frequency, toward predictions for next-generation Very Large Array (ngVLA) surveys.

The project is part of the NSF-funded program led by David R. Ballantyne (PI) and Tamara Bogdanović (Co-PI). The host-galaxy properties come from the IllustrisTNG simulations, and the orbital-evolution calculations predate this work; my part is building the radio-emission framework that connects them. The work is in progress, and results will appear here once they are published.

Schematic synchrotron spectra of two radio coresIllustration in arbitrary units. Each curve rises steeply at low frequency, where the source is optically thick (flux density proportional to frequency to the 5/2 power), turns over, and then falls as a power law where it is optically thin. The second core turns over at a higher frequency.
IllustrationTextbook spectra of compact synchrotron sources with self-absorption, in arbitrary units: optically thick (S ∝ ν5/2) below the turnover and optically thin (S ∝ ν−α) above it. Included to explain the physics being modeled. Not a result of this project.

Earlier research

02 — 2021–2026
May 2025–May 2026

Ultrafast Optics and Pulse Characterization

Graduate Researcher
School of Physics, Georgia Institute of Technology
Advisor: Rick Trebino

Quantitative characterization of ultrashort pulse-shape instability using two-dimensional runs analysis of second-harmonic-generation frequency-resolved optical gating (SHG FROG) traces.

The group studied how to quantify pulse-shape instability in a train of ultrashort pulses from the pattern of residuals between measured and retrieved SHG FROG traces.

My contributions

  • Co-wrote the peer-reviewed paper.
  • Wrote and implemented the computational code for computing runs in the differences between measured and retrieved FROG traces, used for the statistical characterization of pulse-train instability.
  • Worked on the mathematical and analytical proofs in the paper, including Appendix A on the invariance of the weighted runs statistic under time–bandwidth-preserving rescaling.

Related publication: Optics (2026)

September 2023–January 2024

Gamma-Ray Bursts as Standard Candles

Undergraduate Researcher
Theoretical Cosmology, University of Arizona
Advisor: Fulvio Melia

Using gamma-ray bursts as standard candles to extend the Hubble diagram beyond the redshift range of conventional distance indicators.

  • Investigated the use of gamma-ray bursts as standard candles for extending the Hubble diagram beyond the redshift range accessible to conventional distance indicators.
  • Incorporated the Platinum and LGRB95 gamma-ray-burst data sets into the analysis.
April 2022–January 2024

Intrinsic Alignments and Weak Lensing

Undergraduate Researcher
Arizona Cosmology Lab, University of Arizona
Advisor: Tim Eifler

Intrinsic galaxy alignments in the tidal alignment and tidal torquing (TATT) model, in the context of weak gravitational lensing.

  • Investigated intrinsic galaxy alignments using the tidal alignment and tidal torquing (TATT) model in the context of weak gravitational lensing.
  • Implemented algorithms to generate synthetic data for predictions of Large Synoptic Survey Telescope (LSST) observations.
  • Examined model parameters through statistical analysis and visualization, assessing their effects on cosmic shear and galaxy–galaxy lensing signals.
June–July 2021

Mission Concepts for Venus and Deimos

Summer Researcher
Asteroids Laboratory, University of Arizona
Advisor: Jekan Thanga

A CubeSat mission concept for the atmosphere of Venus and a hybrid power-system concept for a proposed scientific base on Deimos.

  • Developed a CubeSat mission concept targeting the atmosphere of Venus, including instrument selection and mission-feasibility assessment.
  • Designed a hybrid power-system concept for a proposed scientific base on Deimos, considering energy supply for an extraterrestrial environment.

Selected Academic Projects

03 — 2022–2025
Fall 2025 · Course project

From the CMB to the first particles: cosmological initial conditions

Course
PHYS 7127: Cosmology & Galaxies, Georgia Institute of Technology
Instructor
John Wise

A two-part computational term project: from the cosmic microwave background and the matter power spectrum to the initial conditions of a cosmological simulation.

Part A · CMB and matter power spectra

Used the Boltzmann solver CAMB with the Planck 2018 cosmological parameters to compute the CMB temperature and linear matter power spectra, located the first acoustic peak (ℓ ≈ 220) and compared its scale with the sound horizon at last scattering, and explored how the spectra respond to the baryon fraction, spatial curvature (ΩΛ = 0), a low dark-matter density, early reionization (z = 30) and massive neutrinos.

Figures The temperature spectra show a higher baryon density raising the first peak, the open model pushing the peaks to higher multipoles, a low dark-matter density strengthening the peaks, and early reionization damping the whole spectrum. The matter power spectra show the turnover moving and small-scale power changing with the same parameters.

Part B · Zel'dovich initial conditions

Wrote Python code that turns the CAMB matter power spectrum into initial conditions for a cosmological simulation at z = 99 in a (20 comoving Mpc)³ volume on a 64³ grid: a Gaussian random density field built with fast Fourier transforms, and dark-matter particle displacements and velocities from the Zel'dovich approximation, for Planck 2018 and an open universe without dark energy.

Figures Slices through the density and velocity fields for both cosmologies, the power spectrum measured on the grid set against the CAMB input, and a slice of particle positions after the Zel'dovich displacement.

Earlier course projects

University of Arizona, listed with their collaborators.

Photometric Analysis of the Eclipsing Binary GALEX J19444+5459

December 2022

ASTR 302, University of Arizona

Collaborators: R. Basant and A. Olson

  • Obtained V-band observations with the Kuiper 61-inch telescope and reduced the imaging data using IRAF, including noise and cosmic-ray correction and photometry.
  • Constructed light curves, determined the orbital period and primary and secondary eclipse depths, and estimated component radii for the brown dwarf and subdwarf B star.

Numerical Solution of the Two-Dimensional Schrödinger Equation

May 2023

PHYS 305, University of Arizona

  • Applied finite-difference methods and eigenvalue calculations to solve the two-dimensional Schrödinger equation for different potentials.
  • Analyzed energy levels and wave functions and visualized the resulting quantum states.

ATMO 436A, University of Arizona

Collaborator: G. Fabian

  • Examined the cyclone’s formation, intensity, and contributing meteorological factors, alongside its effects on human life, the environment, and agriculture.
  • Project report: doi:10.13140/RG.2.2.32826.98242.