Abstract

This spring, teams from the APC, LUX, and LPNHE will organize the biannual symposium of the Cherenkov Telescope Array Observatory (CTAO) international collaboration. Most of the meeting will take place on the Université Paris Cité campus (lecture hall), with a welcome reception at the Paris Observatory (Cassini Room).

Scientific justification

The Cherenkov Telescope Array Observatory (CTAO, https://www.ctao.org) represents the next generation of instruments in the field of very high-energy gamma-ray astronomy. It will consist of several dozen Cherenkov telescopes spread across two sites (the northern site in the Canary Islands and the southern site in Chile). The first telescope is already operational at the northern site, and the first telescopes at the southern site will begin operations as early as 2027.

CTAO’s international collaboration currently includes 1,500 members from more than 150 institutes in 25 countries, including several laboratories in the Île-de-France region. The Observatory participates in CTAO through a scientific team at LUX and a team of engineers at UNIDIA. CTAO organizes symposia for its members twice a year: one in the spring focused on preparing for the Observatory’s scientific operations, and one in the fall focused on the construction and technical preparation of the Observatory.

The CTAO teams from three laboratories in the Île-de-France region (APC, LUX, LPNHE) have joined forces to organize the scientific conference in the spring of 2026 in Paris. Based on previous years, we expect approximately 150 in-person participants, in addition to remote participants. The scientific sessions will take place in lecture halls on the Université Paris Cité campus and will be managed by the APC team.

Preliminary program

The scientific program will consist of presentations by members of the various CTAO working groups, which specialize in the physics of galactic sources (supernova remnants, pulsar wind nebulae, pulsars, star clusters, molecular clouds, etc.), extragalactic sources (active galaxies, gamma-ray bursts, and other transients...), cosmic-ray physics, and fundamental physics (dark matter, the search for axion-like particles, etc.).

Given that CTAO will begin partial operations as early as 2027 (the “early science” phase), followed by the “Key Science Projects” phase around 2030, the presentations and discussions at the 2026 symposium will be crucial for defining the objectives of the initial observations and planning the programs that will be proposed as “key” observations.