Scientific Context
The recent milestone detection of the nanohertz gravitational wave background by Pulsar Timing Arrays has opened an entirely new observational window into the Universe. As we move towards the most sensitive datasets ever assembled, the astrophysical interpretation of these signals is limited by two key challenges: poor models of the intervening interstellar medium (ISM), and uncertainties in pulsar distance measurements.
This workshop brings together, for the first time, leading experts in gravitational wave science, interstellar medium studies, and Very Long Baseline Interferometry (VLBI) to collaboratively identify and address these limitations. Through keynote talks, interactive tutorials, and structured breakout sessions, we aim to produce actionable research plans and observing strategies that integrate cutting-edge techniques across all three fields.
The workshop is particularly timely given significant upgrades to the European VLBI Network, the advent of next-generation radio facilities like the SKA and DSA-2000, and the forthcoming third data release of the International Pulsar Timing Array.
Characterising the nanohertz GW background from supermassive black hole binaries using Pulsar Timing Arrays. Understanding the signal's spectrum and spatial correlations to constrain SMBHB populations.
Modelling time-variable dispersion, scattering, and scintillation. Integrating ISM measurements into timing models and developing robust correction techniques for next-generation PTA datasets.
Precision parallax-based pulsar distances using VLBI. Identifying and mitigating systematic errors from ionospheric and ISM propagation effects to achieve sub-parsec distance determinations.
Programme
Keynotes, interactive tutorials, and structured breakout sessions designed to produce concrete, actionable outcomes.
Opening Day — Setting the Scene
Lorentz Centre introduction + workshop goals (Aditya Parthasarathy)
~30 participants: 1-minute introductions sharing expertise, interests, and goals for the week
The first inroads into the low-frequency gravitational-wave spectrum: Results and Challenges — Michael Keith
The interstellar medium in space and time: current state-of-the-art in scintillometry and imaging techniques — Stella Ocker
Precision astrometry on compact objects with VLBI and avenues for advancements — Adam Deller
~25 participants
PTA: Challenges & Solutions
Daniel Reardon
Prioritise topics and questions emerging from Keynote 1
Speaker to be confirmed
Finalise shortlist of breakout questions + key ideas
PTA observables → constraints → how they plug into timing
8 teams of 6–7: one PTA challenge + actionable solution
Moderator synthesis + 1 reporter per team
All participants: shortlisted topics, define success criteria
ISM: Challenges & Solutions
Advances in pulsar scintillometry techniques — Robert Main
Prioritise topics emerging from Keynote 1
High-resolution VLBI astrometry of pulsar scintillation screens — Ashley Stock
Finalise breakout questions + key ideas
ISM observables → constraints → how they plug into timing
8 teams of 6–7: one ISM challenge + actionable solution
Moderator synthesis + 1 reporter per team
All participants: shortlisted topics, define success criteria
VLBI: Challenges & Solutions
VLBI and AGN variability — Silke Britzen & Andreas Brunthaler
Prioritise topics emerging from Keynote 1
Speaker to be confirmed
Finalise breakout questions + key ideas
VLBI observables → constraints → how they plug into timing
8 teams of 6–7: one VLBI challenge + actionable solution
Moderator synthesis + 1 reporter per team
All participants: shortlisted topics, define success criteria
Synthesis & Roadmap
Participants collaboratively draft actionable research plans, grant proposals, and observing strategies based on the week's discussions.
Culminating in a community roadmap document to guide future collaborative efforts across PTA, ISM, and VLBI communities.
Participants
Experts spanning pulsar timing, ISM studies, VLBI astrometry, and instrumentation.
Scientific Organising Committee
Chair · ASTRON & University of Amsterdam
Expert in precision pulsar timing and gravitational wave science. Led key efforts in the European and International PTA collaborations. ERC Starting Grant and NWO-I Veni fellow.
Sternberg Astronomical Institute & MPIfR
Specialist in gravitational wave science and dark matter searches with PTAs. Executive committee member of the EPTA, steering committee of the IPTA.
ASTRON
Expert in VLBI astrometry and compact object studies. WISE fellow leading observing campaigns with major VLBI facilities worldwide.
MPIfR, Germany
Specialist in pulsar scintillation and novel data analysis methods. Developing theoretical models for anisotropic interstellar scattering screens.
National Astronomical Observatories of China
Precision radio astrometry using VLBI. Led the largest astrometric survey of millisecond pulsars. IAU PhD Prize honourable mention.
Workshop Coordinator: Emmy Verlek-Hage, Lorentz Center · verlek@lorentzcenter.nl · +31 71 527 5659
Practical Information
Everything you need to know about attending the workshop in Leiden.
Lorentz Center@Omega
Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
The Lorentz Center is located on the campus of Leiden University, within walking distance of Leiden Centraal station.
Van der Valk Hotel Leiden
From Leiden train station, take bus 43 to bus stop 'Haagsche Schouw', or take a taxi (~€15).
Arrival: Sunday 17 May 2026 | Departure: Friday 22 May 2026
Check-in: 15:00 | Check-out: 11:00
The reservation is guaranteed and held for late arrival. The Lorentz Center will cover 5 nights (Sun 17 May – Fri 22 May). Please note that any hotel nights in the weekends before or after the workshop week may incur extra costs that cannot be covered. Contact the workshop coordinator for questions.
We have a dedicated Mattermost channel for real-time discussions during and after the workshop. All invited participants will receive access details by email.
This is an invitation-only workshop. If you have been invited, you will receive registration details from the Lorentz Center directly. Visit the official Lorentz Center page for registration.
Lunches and coffee breaks are provided at the Lorentz Center. A welcome reception will be held on Monday evening. Details of the workshop dinner will be announced closer to the date.
Updates
March 2026
The full programme with breakout topic assignments, interactive session details, and topic cards has been posted. See the detailed programme.
March 2026
The workshop website is now live. Programme details and logistics information will be updated as we approach May.
Coming Soon
Science documents and background materials will be shared with all participants ahead of the workshop to facilitate productive discussions from day one.