Karan Akbari
karanakbari14@gmail.com · github.com/WizardEternal · orcid.org/0009-0005-0550-4018
Education
Master's degree in Astrophysics
St. Xavier's College, Mumbai · Final grade: 8.08 CGPA out of 10
Bachelor's degree in Physics
Central University of Rajasthan · Final grade: 7.89 CGPA out of 10
Diploma in Programming
Indian Institute of Technology Madras · IITM BS programme
Advanced Certificate in Machine Learning and Data Science
Indian Institute of Technology Madras · IITM BS programme
Publications
Refereed
- Akbari, K., “A Cross-Band (X-ray × Optical) Periodicity Search for Supermassive Black Hole Binaries: A Null Result and the First Completeness-Corrected Constraint”, ApJ 1009, 184 (2026). doi:10.3847/1538-4357/ae9d7c, arXiv:2608.16787 · project page
- Akbari, K., Patel, C., Bhattacharya, S., Bhattacharyya, S., & Choudhury, M., “Probing heartbeat oscillations from the black hole X-ray binary GRS 1915+105 using spectral-timing analysis”, ApJ 1007, 64 (2026). doi:10.3847/1538-4357/ae877d · project page
- Patel, C., Bhattacharya, S., Akbari, K., Nadar, R., Bhattacharyya, S., & Choudhury, M., “Circumstellar Disc and X-ray Variability in the Be/X-ray Binary SXP 5.05 During its 2024 Outburst”, JHEAP, 100758 (2026). doi:10.1016/j.jheap.2026.100758
Preprints and submitted
- Akbari, K., “Misspecification in amortized X-ray spectral inference: a detection benchmark, a gain shift three schemes cannot see, and marginalizing it out”. arXiv:2606.17098 · project page
- Akbari, K., “A Calibration Audit of a Gaia XP White-Dwarf Main-Sequence Binary Catalog: How Much the BP-Band Residual Contaminates at Its Bound and Above”. arXiv:2607.08856 · project page
- Patel, C., Bhattacharya, S., Akbari, K., Bhattacharyya, S., & Choudhury, M., “A continuous transition from Type-C Quasi Periodic Oscillations to the Heartbeat state in the Black hole X-ray binary 4U 1630-47”, under review at MNRAS. arXiv:2511.01883
Research experience
Identifiability in joint spectral-timing analysis of X-ray data
Short paper in preparation, TIFR
Methods collaboration with Prof. Sudip Bhattacharyya at TIFR: two X-ray instruments with complementary energy and time resolution observe the same window, and the question is which timing observables the pair determines and which the data leave free at any exposure. Computing the attainable sets exactly shows which observables no exposure can pin down, and which ones only need more counts.
XRISM/Resolve forecast for phase-resolved wind spectroscopy of heartbeat states
Manuscript in preparation, sole author, TIFR
Monte-Carlo forecast of what Resolve at 4.5 eV would recover from the disk wind across the heartbeat cycle of GRS 1915+105 and IGR J17091-3624, on an instrument model tied to two real sources. An equilibrium wind reaches a 3σ detection probability of at most 0.07, so a modulation detected at 3σ is itself evidence of a dynamic wind; the dynamic track is rejected against a constant wind with probability 0.84 to 0.98 at 3σ in 162 ks. A 3σ detection at full amplitude needs 130 to 180 ks net, which brackets the standing 150 ks award.
Machine learning and simulation-based inference: when a learned posterior can be trusted
Two papers, sole author, Independent
Two sole-author methods papers on the reliability of amortized neural inference. Three independent misspecification checks are all blind to a 3% detector gain shift that still biases the photon index by +0.02, and marginalizing the gain during training leaves that bias in place; a Gaia XP catalog audit finds its BP-band residual weakly contaminates the selection, at a spurious rate of 0.09±0.02 against a 0.053 baseline.
Cross-band (X-ray × optical) periodicity search for SMBHBs
Published in ApJ, sole author, Independent
Sole-author search over 1194 Swift-BAT hard X-ray AGN and 175 4XMM-DR14 AGN, against ZTF and ASAS-SN optical. Requiring the same period in both bands makes the joint false-alarm rate the product of the independent single-band rates. No source survives, and the null becomes the first completeness-corrected constraint on the co-periodic fraction: under 3% at hard X-ray fractional modulation above 0.3, over periods of 100 to 900 days. The limiting factor is the X-ray monitoring cadence.
SMBHB merger population and detectability in IllustrisTNG
Manuscript in preparation, TIFR
With Dr. Sayantan Bhattacharya: forward-modeled the IllustrisTNG black hole merger catalog into a multi-messenger detectability budget spanning PTA and LISA bands and electromagnetic survey windows, including periodicity recovery fractions. Built on the TNG population, inspiral simulator, and Stripe 82 search pipelines listed under Projects.
Broadband spectral and timing studies of X-ray binaries
One paper published, one under review, TIFR
Projects with Mr. Chintan Patel, Dr. Sayantan Bhattacharya and Prof. Sudip Bhattacharyya: the heartbeat state of 4U 1630-47 and its transition from Type-C QPOs (under review at MNRAS), and the 2024 outburst of the Be/X-ray pulsar SXP 5.05 (published in JHEAP). Statistical analysis on both papers, with contributions across the spectral and timing work.
Spectral and Temporal X-ray Analysis of Microquasar GRS 1915+105
Published in ApJ, TIFR
Started as my MSc thesis under Prof. Sudip Bhattacharyya (August 2024 to May 2025), then I kept working on it at TIFR until it became a first-author ApJ paper. Spectral and temporal X-ray analysis of the ρ-class heartbeat of GRS 1915+105 from Swift and AstroSat data, heavily automated.
Technical skills
Programming
Python, Bash, Fortran, SQL, C++ (Basic)
Software
HEAsoft, CIAO, SAS, CASA, CARTA, MESA, Gnuplot, SAODS9
Missions
RXTE, NICER, Swift, NuSTAR, XMM-Newton, Chandra, AstroSat (LAXPC/SXT), eROSITA; Gaia, ZTF, ASAS-SN, SDSS/Stripe 82; LISA, NANOGrav; IllustrisTNG
ML & inference
PyTorch, TensorFlow, Scikit-Learn, transformers, CNNs and ViTs, gradient boosting; simulation-based inference (sbi), normalizing flows, nested sampling (ultranest), MCMC, hierarchical Bayesian modelling, simulation-based calibration, conformal prediction
HPC & Cloud
SLURM, MPI, Dask, AWS (S3, EC2, Lambda)
Conferences and workshops
IAU Symposium 413
Contributed talk (accepted) at IAU Symposium 413, “AGN Jets from Gamsberg to the Multi-Messenger Frontier,” Windhoek, Namibia (18–22 January 2027). Talk title: A Cross-Band (X-ray × Optical) Coincident-Periodicity Search in Jet-Dominated AGN: A Null Result and the Case of PG 1553+113
AstroSat Decade Conference
Presented a poster at the International Conference on “A Decade of AstroSat Observations: Science Outcomes and Future Prospects,” organized by URSC/ISRO, Bengaluru. Poster title: Phase-Resolved Spectral and Timing Study of ρ-Class Variability in GRS 1915+105
Chandra CIAO Workshop
Chandra/CIAO data analysis training at the Harvard-Smithsonian Center for Astrophysics, including astrostatistics with Dr. Vinay Kashyap
XPoSat Workshop
Presented at the National Workshop on Hands-on Data Analysis of XSPECT on-board XPoSat, organized by ISRO at URSC, Bengaluru. Identified and corrected bugs in official XPoSat analysis pipeline. Improved pipeline performance through multiprocessing implementation. Co-author on the workshop white paper (arXiv:2607.21365)
Machine learning and software projects
Supermassive black hole binaries, gravitational waves & multi-messenger
TNG SMBHB Population Pipeline
Turns the IllustrisTNG black hole merger catalog into a multi-messenger detectability funnel across PTA, LISA and EM survey windows; found and fixed a catalog bug that forced q = 1.
Stripe 82 SMBHB Periodicity Search
Searches the MacLeod et al. Stripe 82 quasar catalog with per-object damped-random-walk false-alarm nulls, controlling the red noise that fakes periods in Lomb-Scargle searches: 44 candidates at 99% significance, 10 at 99.9%.
LISA Gap Imputer
Transformer pipeline for imputing gaps in LISA strain from antenna repointing and micrometeorite hits, trained on colored-noise realizations with injected SMBHB chirps and galactic binaries. Benchmarked against spline and Gaussian-process baselines.
Post-Newtonian Inspiral Simulator
Simulates SMBHB inspirals from 105 to 1010 M☉ against NANOGrav and LISA sensitivity curves, with EM detectability for Stripe 82, PTF and LSST.
ZTF Kilonova Vetting Pipeline
Reproduces the human-vetting decisions from the Kasliwal et al. 2020 ZTF O3 gravitational-wave follow-up campaign with a feature-based classifier. It also catalogues where such pipelines fail on sparse real-time photometry.
X-ray & high-energy astrophysics
SBI Calibration Benchmark
Calibration and misspecification tests for amortized neural posterior estimation in X-ray spectral fitting: misspecification detection across three schemes, a gain-marginalized retrain, and an exact nested-sampling cross-check. PyTorch, sbi, ultranest.
XRB Luminosity Function Forward Model
Completeness-folded likelihood and hierarchical stacking for X-ray binary luminosity functions; removes the slope bias of detection-naive fits and sharpens the slope by 2.4×.
Galactic X-ray Source Classifier
Calibrated gradient-boosted classifier (STAR/CV/XRB/AGN) for eROSITA Galactic-plane sources with Gaia counterparts, with leakage-free calibration, a label-circularity audit, and out-of-distribution flagging. Assigns confident labels to 93% of ~20,750 unlabeled inner-plane sources.
AutoRXTE: Automated RXTE Analysis Pipeline
End-to-end RXTE analysis toolkit, from automated HEASARC data acquisition through GTI filtering, event extraction, power spectra, automated XSPEC fitting, and color-color diagrams.
Automated AstroSat Data Download Tool
Built Selenium-based system for batch-downloading observations with filtering by source name, date range, and instrument configuration (website only allows single downloads)
Other projects
Gaia XP WD-MS Calibration Audit
Injection-recovery audit of the Li et al. 2025 Gaia XP white-dwarf/main-sequence catalog (~30k sources), testing whether the BP-band calibration residual manufactures spurious contamination at its published bound.
Galaxy Morphology, CNNs vs Vision Transformers
Five CNN and vision-transformer architectures on Galaxy10 DECaLS, after catching SMOTE leakage, a wrong loss-target encoding and ImageNet normalization on galaxy pixels in the first version.
Automated Voigt Profile Fitting and Wiener Deconvolution
Automated optical–NIR spectral-line pipeline: FFT-based Wiener deconvolution for instrumental PSF removal, Voigt profile fitting, redshift correction, and line identification against NIST catalogs. Developed on ePESSTO+ supernova spectra.
Binary Star Mass Transfer using MESA
Simulated conservative and non-conservative mass transfer in binary systems. Tracked accretor rejuvenation, metallicity evolution, and contact binary formation over stellar evolutionary timescales
Seismic and Nuclear Blast Wave Differentiation using FFT
Applied Fourier analysis to distinguish earthquakes from nuclear detonations using simulated blast wave data from US DOE archives
Radio Astronomy using Horn Antenna
Observed galactic center emissions using horn antenna to detect 21cm hydrogen line and map radio sources
Molecular spectral line analysis of SiS for IRC+10216 using CASA
Analyzed circumstellar molecular emission from carbon star using radio interferometry data
References
Available on request.