The "Square Kilometre Array" (SKA) is a large radio telescope project characterized, as suggested by its name, by a total collecting area of approximately one square kilometre, and consisting of several interferometric arrays to observe metric and centimetric wavelengths. The construction of its first phase (SKA1, about 10% of the final array) is expected to start in 2021. SKA will be one of the most formidable instruments for astrophysics and fundamental physics of the next decades. It will allow to address a wide domain of topics, including the cosmic dawn, galaxy evolution, cosmological magnetic fields, transient sources, fundamental physics (mostly through pulsars) and cradle of life.
The project is currently being led by a project office (SKA Organization, SKAO), responsible of the design of the Observatory, which CNRS recently joined on behalf of a public-private partnership named "Maison SKA-France".
In April 2019, a big international science meeting will be held at the SKAO Headquarters (https://indico.skatelescope.org/event/467), which will focus on ongoing research with the SKA pathfinders and precursors, as well as on the preparation of future SKA key science projects. The meeting is also intended to inform the community about SKA-related data challenges that are going to be organized by the SKA Organization.
In this framework, and in view of the INSU perspective work of 2019 and of the next revision of the national roadmap for large research infrastructures, the AS SKA-LOFAR and Maison SKA-France wish to organize a series of small one-day workshops in order to capitalize on the success of the publication of the French SKA White Book in October 2017 (https://ska-france.oca.eu/images/SKA-France-Media/FWB_051017.pdf) by increasing the mobilization of the French community around the SKA.
In spring 2019, we plan to organize one workshop in Paris related to PNHE topics around the topic of transients radio sources, which are usually associated with emission along the whole electromagnetic spectrum. This includes accreting binaries (black holes, neutrons stars, CVs), Ultra-Luminous X-ray Sources (ULX), Gamma-Ray Bursts (GRB), gravitational wave events. Special care will be dedicated to the synergy with the forthcoming high energy missions (SVOM, CTA, ATHENA, …) and new multi-messengers facilities.
The format of the workshop will include about 15-20 talks, among which at least one from an invited international expert of the field (possibly one of the chair of the SKA Science Working Groups). The presentations will be intended to boost discussions about the interest and participation of French astronomers to the definition of the SKA Key Science Projects.
The Universe is a violent and dynamic environment, in which the explosions of massive stars can outshine an entire galaxy, supermassive black holes swallow stars whole, merging neutron stars cause ripples in the fabric of spacetime and bursts of ultra-high energy radiation which can be detected at vast distances, and particles are accelerated to energies far surpassing anything possible in laboratories on the Earth. The extremes of physics – density, temperature, pressure, velocity gravitational and magnetic fields – experienced in these environments provide a unique glimpse at the laws of physics operating in extraordinary regimes. Such ‘extreme astrophysics’, is a high priority for global research in the 21st century.
Our current understanding of the population of radio transients implies that we should detect thousands, or even millions, of such events with ‘next generation’ radio facilities such as The Low-Frequency Array (LOFAR), The South African Karoo Array Telescope (MeerKAT) and The Australian SKA Pathfinder (ASKAP), and ultimately
the Square Kilometre Array (SKA). As well as drawing our attention to the extremes of astrophysics, these sources are potentially observable to vast distances (possibly as far as the Epoch of Reionisation at redshift z > 6) and will turn out to be amongst our most valuable probes of the intergalactic and intercluster medium on large scales. They may furthermore, in some cases, turn out to be the electromagnetic signatures of events which produce detectable gravitational waves, which would be a breakthrough connection.