The Science White Paper for the Einstein Probe (EP) mission has been published in Science China: Physics, Mechanics & Astronomy. This mission, spearheaded by the Chinese Academy of Sciences (CAS) in collaboration with the European Space Agency (ESA), the Max Planck Institute for Extraterrestrial Physics (MPE), and the French National Centre for Space Studies (CNES), is poised to advance the field of time-domain and X-ray astronomy significantly. EP's sophisticated observational instruments aim to probe X-ray transient sources and explosive astrophysical phenomena, thereby contributing to significant advancements in astronomical research.
The EP Science White Paper details the mission's scientific capabilities, observational methodologies, and primary objectives. Central to EP's design is the Wide-Field Lobster-Eye X-ray Telescope (WXT), which operates in the 0.5–4 keV energy regime. This telescope is precisely engineered to detect sudden X-ray transients and to monitor variability in known celestial sources. The WXT's detection capabilities are significantly enhanced compared to existing wide-field instruments, allowing for a more effective approach to capturing transient phenomena. In addition to the WXT, EP is equipped with a Wolter-I type Follow-up X-ray Telescope (FXT), designed for rapid, detailed follow-up observations to validate transient events and outbursts.
A key scientific goal of the EP mission is to enhance the characterization of rare transient sources across a range of timescales. The mission will execute comprehensive surveys of fast extragalactic transients, including enigmatic gamma-ray bursts and related phenomena, supernova shock waves, and predicted X-ray emissions from binary neutron star mergers. Furthermore, EP aims to detect tidal disruption events around black holes and monitor activity from active galactic nuclei, with a focus on capturing early signs of these occurrences.
The mission's observational focus extends to compact objects such as white dwarfs, neutron stars, and black holes within the Milky Way and its neighboring galaxies, monitoring their X-ray fluctuations and outbursts. Notably, EP is designed to identify weak signals from these outbursts, which may evade detection by current observational technology. Additionally, the mission is positioned to catalog and characterize a substantial number of stellar X-ray flares—phenomena where stars rapidly release significant energy.
EP also presents substantial opportunities in multi-messenger astronomy, with the capability to identify X-ray signals associated with gravitational wave events, neutrino sources, as well as ultra-high-energy gamma rays, and cosmic ray origins. These observations will provide valuable insights into extreme astrophysical entities and the fundamental physical processes they exhibit.
Beyond its time-domain science capabilities, the performance of EP's FXT will advance various aspects of X-ray astronomy research. With its cutting-edge technology and ambitious scientific aims, EP stands ready to delve deep into the universe's mysteries.
Dr. Yuan Weimin, the lead author of the EP Science White Paper and Principal Investigator of the EP mission at the National Astronomical Observatories, commented, " The release of the EP Science White Paper provides a valuable resource for researchers worldwide who are interested in leveraging EP for cosmic exploration. The white paper is the culmination of efforts by the EP science team and a wide array of international collaborators, highlighting our dedication to fostering an open and collaborative scientific environment. Moving forward, EP is poised to actively engage with global partners to produce groundbreaking data and discoveries, thereby advancing the frontiers of our understanding of the universe."
Since its launch in January 2024, EP has already identified over 700 eruptive celestial phenomena, including stellar superflares, supernovae, black holes (including rare intermediate-mass black holes), neutron stars, white dwarfs, and gamma-ray bursts from the early universe. EP has also uncovered new eruptive phenomena, showcasing a remarkable diversity among its detection targets, which promises to enhance our comprehension of the dynamic cosmos substantially.
