Division D: High Energy Phenomena and Fundamental Physics

August 9 and 12, 2024, Cape Town, Division D workshop 

Polarimetry of high-energy sources

Innovative technologies have allowed great progress in high-energy polarimetry in the last few years. Space instruments like INTEGRAL, AstroSat, IXPE, and Polar have successfully detected polarised emission from a large variety of high-energy objects including supernova remnants, pulsars, accreting black holes and neutron stars, gamma-ray bursts and different types of AGN. X-ray and gamma-ray polarimetric measurements provide unique insights into particle acceleration and radiation mechanisms as well as into the magnetic-field orientation and particle-flow geometry in the environment of compact objects. They complement imaging and spectroscopic observations, enhancing our understanding of the physical processes at work in these extreme astrophysical environments.

In accreting systems around a neutron star, stellar black hole or supermassive black hole, polarimetry helps to understand the orientation of the accretion disc and the geometry and degree of magnetisation of the disc corona and of the accretion column. General relativity effects on the polarised emission from the thermal disc provide insight into the black-hole spin and inclination. In relativistic jets powered by compact objects, polarimetric data can constrain the magnetic-field structure along the jet as well as the jet composition and emission mechanisms, in particular the lepton-to-hadron ratio among the highest-energy jet particles. Polarimetry can shed light on the emission and dissipation mechanisms during intense flares from gamma-ray bursts and magnetars. It contributes to the understanding of the magnetic-field configuration around neutron stars, inside the co-rotating magnetosphere and beyond, where the field lines unfold and transfer energy to a powerful relativistic wind. For magnetars, polarimetry also provides a path to demonstrating the birefringence of the magnetised quantum vacuum, a fundamental physics objective that is presently beyond the reach of terrestrial experiments.  Polarimetry also provides information about the magnetic-field structure in supernova remnants to help the study of cosmic-ray acceleration processes and the nature of magnetohydrodynamic turbulence.

The success of recent polarimetric observations have dramatically expanded our views on the exploitation of polarimetric information. The goal of this workshop is to take advantage of the General Assembly to familiarise the community with the science potential and recent achievements of high-energy polarimetry, to link with polarimetric experts at other wavelengths, and to discuss future prospects for instrumental developments that will further deepen our knowledge.


The research topics listed above are not exhaustive. To build an exciting and enlightening program, we welcome ideas and contributions on polarimetric observations and diagnostics at all wavelengths about high-energy sources. Abstracts are due on the General Assembly 2024 website before March 1st, 2024: https://astronomy2024.org/abstracts-grants/

Participants in this workshop will receive admission to all scientific activities of the IAU General Assembly, including the Focus Meetings on “The High-Energy Gamma-ray Universe: Results and perspectives with wide-field ground-based facilities” and on “Bridging the final stages of massive stars to supernovae and transients” and the IAU symposium on “Gravitational Wave Astrophysics”.

Meeting SOC  (Division D steering committee): 

Isabelle Grenier (France, chair), Matthew G. Baring (United States, co-chair), Aya Bamba (Japan), Dipankar Bhattacharya (India), Andreja Gomboc (Slovenia), Christine Jones (United States), Elena Pian (Italy), Nanda Rea (Spain), Gustavo Esteban Romero (Argentina), Peter Sven Shawhan (United States), Silvia Zane (United Kingdom).

You can learn more about the work of this Division at this website https://iau.org/science/scientific_bodies/divisions/D/