Hi, I'm Koustav

I work on the gravitational-wave astrophysics of compact binary mergers, from finding the signals to what they tell us about gravity and the Universe.

Modelled searches

Matched-filter and machine-learning based searches for compact binary mergers.

Papers: Optimised PyCBC IMBH search · Higher-harmonics IMBH search · THAMES transfer learning · CNN detection significance

Ringdown modelling

Modelling the post-merger signal of binary black holes: calibrating analytic ringdown templates for effective-one-body waveforms against numerical relativity, and black hole spectroscopy.

Papers: Inspiral-merger informed ringdown templates

Tests of General Relativity

Parameterised tests of gravity in the strong-field regime and hierarchical tests of GR.

Papers: GWTC-4.0 mixture-model tests · GW250114 multipronged analysis · Theory-agnostic parametrised model

Next-generation detectors

Science case and network design for Cosmic Explorer, the Einstein Telescope and LIGO-India: detection rates, sky localisation, and what a continuous background of mergers means for analysis. I am the lead maintainer of gwforge, a package for building mock data.

Papers: LIGO-India in the XG era · Foreground signals in XG inference · Neutron-star radii with XG detectors · gwforge

Source characterisation & inference

Measuring what the signals encode: source properties, remnant properties, individual events, and population-level cosmological and astrophysical inference built on fast likelihoods and careful statistics.

Papers: Black-hole recoil from higher-order modes · GW230529 origins and remnant · Eccentricity in disguise? GW231123 · Systematics in dark-siren cosmology

• From source properties to strong-field tests: a multipronged analysis of GW250114 with an effective-one-body model for generic orbits
  K. Chandra, R. Gamba, D. Chiaramello · 2025 · arXiv:2512.04593
• A complete measurement of a black-hole recoil through higher-order gravitational-wave modes
  J. Calderón Bustillo, S. H. W. Leong, K. Chandra · Nature Astronomy (2025) · doi
• GW231123: a binary black hole merger with total mass 190–265 M_⊙
  LIGO–Virgo–KAGRA Collaboration · Astrophys. J. Lett. (2025) · arXiv:2507.08219
• First gravitational-wave search for intermediate-mass black hole mergers with higher-order harmonics
  K. Chandra, J. Calderón Bustillo, A. Pai, I. W. Harry · Phys. Rev. D 106, 123003 (2022) · doi
• gwforge: a user-friendly package to generate gravitational-wave mock data
  K. Chandra · Class. Quantum Grav. (2025) · doi

Full list on INSPIRE.

• Oct 2025 — Moved to AEI Potsdam. German chapter begins! 🥨
• Aug 2024 — Naik & Rastogi Excellence in PhD Thesis Award, IIT Bombay. 🏆
• Oct 2023 — Started as a postdoc at the Institute for Gravitation & the Cosmos, Penn State. 🦁
• Sep 2023 — PhD defended. Dr. Chandra activated. ☕

If my work intrigues you and you'd like to chat, feel free to contact me.

• koustav.chandra@aei.mpg.de
• Max Planck Institute for Gravitational Physics
  Am Mühlenberg 1
  14476 Potsdam, Germany
• github.com/koustavchandra
• INSPIRE profile