EP-WXT Pathfinder captures first wide-field snapshots of X-ray universe – Eurasia Review

The EP-WXT Pathfinder, the trial version of a module that will eventually become part of the Wide Field X-ray Telescope (WXT) aboard the Einstein Probe (EP) astronomical satellite, released its first results on August 27 from a previous test flight. These images include 800-second X-ray imaging of the Galactic Center region, a dense region at the heart of our galaxy, the Milky Way.

These are the first publicly available wide-field X-ray snapshots of our universe to date, taken by the first focused wide-field X-ray imaging telescope ever launched into space.

The results were reported by scientists from the Chinese Academy of Sciences (CAS) at the Second China Aerospace Science Society held in Taiyuan, China.

Since the first detection of X-ray signals from the depths of the universe 60 years ago, no wide-field focused X-ray telescope was available for X-ray surveys and observations until Pathfinder.

Pathfinder was sent into orbit to check the unit’s in-orbit performance. The test flight aims to pave the way for a future in-orbit science operation for EP as it makes observations in the X-ray waveband.

The EP will explore open questions in time domain astrophysics by observing transients. The mission is sponsored by CAS in collaboration with the European Space Agency (ESA) and the Max Planck Institute for Extraterrestrial Physics and is expected to fly by the end of 2023.

The WXT test unit covers a field of view of up to 340 square degrees (18.6 degrees x 18.6 degrees), making it the first large-scale X-ray imaging telescope. It is known that X-ray imaging by bending (focusing) rays of light is difficult due to the high energy of X-ray photons; It is difficult to get clear images from a wide field of view. Thanks to the latest technology called lobster eye microporous optics, the test unit has a field of view of at least 100 times that of other focused X-ray imaging devices. The complete WXT for flight aboard the EP will consist of 12 identical modules, covering a field of view of up to 3,600 square degrees.

During the test flight, Pathfinder made a total of four days of experimental observations in orbit and obtained X-ray spectra and images based on real measurements.

Key components of Pathfinder include the X-ray imaging mirror assembly, which features an array of 36 lobster eye microplates and a focal plane detector consisting of four groups of large-format imaging sensors.

Although these results are still preliminary and extensive data processing must be carried out, the experimental flight demonstrates that even one-shot observations can cover X-ray sources from all directions within the observed patch of sky, including stellar-mass black holes and neutron stars. The observation also picked up the X-ray brightness from a binary system containing a neutron star. Data from these observations provide information about how the X-ray radiation from these celestial bodies has changed over time, as well as the X-ray spectra of these celestial bodies. The images and spectra generated by the test observations are largely consistent with the simulations.

The instrument also targeted a number of other X-ray sources, including the Large Magellanic Cloud (LMC), one of our neighboring galaxies. The results show that even one-shot observations can cover this entire galaxy, revealing multiple X-ray sources, including black holes, neutron stars and supernova remnants. The instrument’s clear imaging of a distant quasar, 3C 382, ​​at a distance of 810 million light-years, reveals its ability to detect relatively faint X-ray sources. In his future observations, the photographer is expected to actively monitor the X-ray fluctuation of celestial bodies and discover new transient sources.

According to Dr. Yuan Weimin, Principal Investigator (PI) of the EP mission and researcher at the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC), preliminary results show that the “device runs smoothly” and meets the requirements of the EP WXT module. He smiled, “It is exciting to see the effort that took a decade pay off.”

Other researchers involved in the European Army mission were also satisfied.

Dr ZHANG Chen, principal investigator of the WXT Mirror Group, said the results promise “abundant, high-quality data” after the probe’s launch.

Professor Paul O’Brien, ESA-assigned scientist for the EP mission and researcher at the University of Leicester, said the results were “really impressive”.

Said Professor Richard Willingel, Professor O Breen Fellow at the University of Leicester.

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