Koothodil Abhijith Augustine
PhD Student in High-Energy Astrophysics
About Me
I am an Astronomy PhD student specializing in high-energy astrophysics. My research involves analyzing observational data to understand the physics of extreme cosmic objects, particularly pulsars and their surrounding nebulae.
I am currently pursuing my research at National Tsing Hua University under the supervision of Prof. Hsiang-Kuang Chang. This site serves as a portfolio of my academic journey, projects, and publications.
Projects
Anti-correlation in Hard X-ray Emission from The Crab
Conducted spectral analysis of the Crab system using 18 years of Swift BAT data. Our findings show a significant anti-correlation between the X-ray flux and the spectral power-law photon index, providing strong observational evidence for the synchrotron radiation model in the Crab nebula.
View PublicationCOSI Telescope Science
As a member of the science and data analysis working groups for the upcoming COSI space telescope, my part in the team is to analyze the soft gamma-ray pulsar population upon its launch in 2027, leveraging COSI's unique capabilities in this energy band.
Learn about COSICubeSat Polarization Studies
Had an opportunity to simulate high-energy sources (cosima), analyze Compton data (revan), and determine the minimum detectable polarization (MDP) using MEGAlib. This research contributes to developing polarization measurement techniques for custom-built CubeSats.
MEGAlib ToolkitGUI for BTO Detector Testing
The Background and Transient Observer (BTO) is a student-led experiment on the COSI satellite. I am developing a graphical user interface (GUI) to streamline data acquisition (e.g., counts/keV, temperature, voltage) and real-time analysis, such as light-curve generation, during the calibration of its NaI(Tl) detectors.
About BTOEducation
PhD in Astronomy
National Tsing Hua University, Taiwan (2023 - Present)
Research Focus: High-energy astrophysical observational study of the Crab pulsar and Pulsar Wind Nebula.
Master of Science in Physics
Sant Longowal Institute of Engineering and Technology, India (2021 - 2023)
Thesis: Exploring the JWST PRIMER Catalog: An Investigation of Infrared Galaxies.
Bachelor of Science in Physics
University College, University of Kerala, India (2018 - 2021)
Thesis: Effect of aerosol absorption coefficient on solar flux.
Technical Skills
Astrophysical Analysis
- Xspec, Fermipy, Cosipy
- Spectral & Timing Analysis
- Phase-Resolved Spectroscopy
- Simulation with MEGAlib (cosima, revan, mimrec)
Programming & Data Science
- Python (Astropy, NumPy, Pandas)
- Data Visualization (Matplotlib, Seaborn)
- Linux Shell Scripting & Automation
Publications
Investigating the Anti-Correlation between Photon Index and Flux of the Crab using RXTE and NuSTAR
arXiv e-prints (Jun 2025)
We present a systematic study of the recently reported anti-correlation between X-ray flux and photon index (Γ) in the Crab Nebula, using archival RXTE/PCA (3 - 50 keV), RXTE/HEXTE (20 - 100 keV), and NuSTAR (3 - 78 keV) observations. Spectra were extracted in soft (3 - 10 keV) and hard bands (10 - 50 keV, 10 - 78 keV, 20 - 100 keV) and fitted with an absorbed power-law model. Across all instruments and energy ranges, we confirm the existence of a persistent negative correlation -- harder spectra at higher flux levels. The correlation is stronger in the hard bands compared to the soft bands. This is consistent with synchrotron emission modulated by magnetic field variations in the pulsar wind nebula.
Anti-correlation between Flux and Photon Index of Hard X-ray Emission from The Crab
The Astrophysical Journal (ApJ) - 2025
Using Swift Burst Alert Telescope event-mode data during gamma-ray burst occurrences, we conduct spectral analysis for the Crab system. From 38 good observations, which span a period of 18 yr from 2006 to 2023, we find that the Crab’s X-ray flux not only flickers but also significantly anticorrelates to its spectral power-law photon index. Since the emission contribution of the Crab pulsar in this energy range is small, this anticorrelation is mainly about the emission of the Crab nebula. We suggest that this anticorrelation provides observational supporting evidence for the long-standing notion that the nebula emission is due to synchrotron radiation of shocked pulsar winds in the nebula.