An international team of astronomers has achieved a groundbreaking discovery, capturing the first direct observation of a 'heartbeat' from a newly formed magnetar. This phenomenon was detected within the gamma-ray burst GRB 230307A, which occurred on March 7, 2023. The findings, published in Nature Astronomy on November 8, 2023, reveal a periodic signal lasting 160 milliseconds at a frequency of 909 Hz, providing strong evidence for the birth of a 'millisecond magnetar' – a rapidly rotating neutron star with an exceptionally powerful magnetic field.
Gamma-ray bursts (GRBs) are the universe's most energetic events. While short GRBs are typically linked to neutron star mergers and long GRBs to core-collapse supernovae forming black holes, GRB 230307A presented an anomaly. Despite its lengthy 200-second duration, its characteristics suggested a neutron star merger rather than black hole formation. This discovery was a collaborative effort involving researchers from Nanjing University, the University of Hong Kong, and the Institute of High Energy Physics of the Chinese Academy of Sciences.
The detection of the magnetar's 'heartbeat' suggests that the equation of state for neutron stars is relatively stiff, meaning the material is more resistant to compression and provides greater support against gravity. This finding also implies a moderate energy injection into the ejected material by the magnetar engine, challenging previous models that could not generate a relativistic jet from newly born magnetars. This event marks a significant milestone as the first simultaneous observation of a compact object merger in both X-rays and gamma-rays.
Magnetars are neutron stars with magnetic fields so intense they are a quadrillion times stronger than the Sun's, with their decay powering immense X-ray and gamma-ray emissions. The insights gained from GRB 230307A offer valuable information into the physics of gamma-ray bursts and magnetar formation. Future observations by instruments like the Einstein Probe, launched on January 9, 2024, equipped with a wide field of view, may lead to the detection of more such events, further illuminating the prompt emission phase of GRBs and enhancing our understanding of stellar evolution and extreme cosmic physics.
GRB 230307A, the second brightest gamma-ray burst ever observed, demonstrated the presence of heavy chemical elements, such as tellurium, indicating the synthesis of elements necessary for life as a result of neutron star mergers. Researchers used various telescopes, including the James Webb Space Telescope, the Neil Gehrels Swift Observatory, and the Fermi Gamma-ray Space Telescope, to observe this event. The discovery confirms that neutron star collisions are ideal 'pressure cookers' for creating rare elements significantly heavier than iron.