Supermassive black holes (SMBHs) located at the center of galaxies and stellar-mass black holes in X-ray bright binary systems (XRBs), exhibit highly variable and often transient X-ray and gamma-ray emissions. Additionally, Tidal Disruption Events (TDEs) —which occur when a star approaches a massive black hole and is tidally disrupted— radiate mostly in the UV and soft X-rays.
A central challenge in the study of accreting black-hole (BH) systems is to unravel the complex interplay between the physical processes operating in their active regions: the accretion disk, the hot corona, and the relativistic jets. Another crucial open question is whether particle acceleration is primarily driven by hadronic or leptonic mechanisms.
Progress on these fronts increasingly relies on coordinated multi-wavelength observations and on the detection of complementary cosmic messengers, in particular high-energy neutrinos. While accretion–ejection cycles in AGN typically evolve over long periods, TDEs and XRBs offer rare opportunities to observe a full accretion episode, including potential jet formation, within humanly accessible timescales. These sources are therefore prime targets for the new SVOM and Einstein Probe space missions. Building on our group’s involvement in both missions, we propose a comprehensive study of accretion and ejection processes across the full mass spectrum of black holes, using multi-wavelength data from SVOM and Einstein Probe alongside multi-messenger datasets available within APC’s High-Energy Astrophysics group.
Launched in June 2024, SVOM carries four instruments: two narrow–field-of-view telescopes—the Visible Telescope (VT) and the Microchannel X-ray Telescope (MXT)—and two wide-field instruments, the ECLAIRs coded-mask imager and the Gamma-Ray Monitor (GRM). ECLAIRs, with its 89° × 89° field of view, delivers sky images in the 4–150 keV range with sub-degree angular resolution. It serves as the mission’s primary instrument for detecting, localizing, and monitoring variable high-energy sources, providing flux, timing, and spectroscopic measurements through data reduction pipelines developed at APC.
Although SVOM is optimized for gamma-ray burst detection, its capabilities make it an excellent observatory for monitoring flaring activity in AGN and Galactic BHs, especially when ECLAIRs data are combined with VT and MXT observations collected in the mission’s General Program (GP). These multi-wavelength GP datasets will enable robust studies of temporal and spectral variability from the earliest phases of outbursts. Moreover, SVOM Target-of-Opportunity (ToO) observations can be triggered in response to bright AGN, TDE, or XRB outbursts, supplying crucial measurements to probe accretion–ejection physics. The APC team plays a central role in both the GP and ToO programs, which will directly support the PhD candidate’s scientific work.
Einstein Probe, launched in January 2024 and led by China with substantial European participation, is dedicated to time-domain X-ray astronomy. Its Wide Field-of-View Telescope (WXT) monitors nearly 3600 deg² of the sky, while the Follow-up X-ray Telescope (FXT) provides higher-sensitivity observations that capture detailed soft X-ray spectra and long-term light curves. This powerful new facility is expected to increase the known population of BH-associated X-ray transients by an order of magnitude, opening an unprecedented window onto accretion and jet-formation processes across mass scales.
The combined SVOM and Einstein Probe datasets available within the team will offer a unique opportunity to investigate black-hole accretion and ejection from multiple angles. The PhD candidate will lead multi-wavelength and multi-messenger observing campaigns, process and analyze high-quality data from both missions, and interpret the results to constrain the physical mechanisms powering these extreme environments. Depending on source activity and personal interest, the candidate may focus on either Galactic or extragalactic BH systems.
Expected candidate profile:
The ideal candidate will hold a Master’s degree in astrophysics or astroparticle physics, with a strong foundation in high-energy astronomy and its underlying physical processes. Experience with statistical analysis and image-processing techniques (e.g., Fourier transforms, convolutions, chi2 fit, correlation methods) is highly beneficial, particularly given the substantial data-analysis work involved with coded-mask instruments.