This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: An international team of astronomers, including researchers from the Department of Physics and the Hong Kong Institute for Astronomy and Astrophysics (HKIAA) at The University of Hong Kong (HKU), has discovered a previously hidden phase of high-energy activity following the merger of compact stars. This fleeting cosmic explosion, known as EP250704a in X-rays and GRB 250704B in gamma rays, was jointly captured by the China-led Einstein Probe (EP), the Space Variable Objects Monitor (SVOM) and the Insight-Hard X-ray Modulation Telescope (HXMT).
EP's wide-field X-ray telescope detected the event from its onset and continued to observe several episodes of soft X-ray emission after the gamma-ray signal disappeared. While the gamma-ray burst lasted only about 0.4 seconds, the source continued to shine in soft X-rays for nearly 10 minutes, revealing a phase of activity that conventional gamma-ray observations would likely have missed. These findings have been published as a cover article in Science Bulletin.
Short gamma-ray bursts are commonly associated with the merger of compact objects such as neutron stars. As the two objects spiral together and collide, they release an intense burst of high-energy radiation. Traditionally, astronomers have identified these events mainly through gamma rays.
Most X-ray telescopes can only turn to a burst after a gamma-ray detector has first located it, meaning the earliest X-ray emission may already be over by the time observations begin. Einstein Probe changes this picture by continuously monitoring a wide area of the sky at soft X-ray energies. In this case, it revealed that what appeared to be a brief gamma-ray event was accompanied by much longer-lasting X-ray activity.
Yi-Han Iris Yin, a Ph.D. student at HKU's Department of Physics and the Hong Kong Institute for Astronomy and Astrophysics (HKIAA), is a co-corresponding author of the study. She led the analysis of the high-energy prompt emission and contributed to the physical interpretation of the event. Yin's analysis of the X-ray signal revealed key insights into the merger's aftermath: Working with an international team led by An Li of Beijing Normal University (BNU) and Bin-Bin Zhang of Nanjing University (NJU), the researchers found that similar soft X-ray emission may have been present in previous short gamma-ray bursts but remained undetected because it was too soft and faint for conventional gamma-ray instruments.
"Einstein Probe is allowing us to uncover a part of compact star mergers that was hidden from previous gamma-ray observations," said Yin. "The short gamma-ray flash may represent only the beginning of the high-energy activity. By observing the universe at soft X-ray energies, we can now follow these systems for much longer and obtain a more complete view of what happens during and after the merger." Discover the latest in science, tech, and space with over 100,000 subscribers who rely on Phys.org for daily insights. d research that matter—daily or weekly.
Extract — continue reading at the source.
