Astronomers detect the first heartbeat of a newborn star

Gamma Ray Bursts: Unveiling the Hidden Heartbeat of a Millisecond Magnetar

Gamma ray bursts (GRBs) are the most luminous explosions in the universe, briefly outshining entire galaxies with a violent flash of high-energy radiation. These astronomical detonations release more energy in a few seconds than our Sun will produce over its entire ten billion year lifetime, sending jets of gamma rays racing through space. Despite their incredible brightness, gamma ray bursts are fleeting events, lasting anywhere from milliseconds to several minutes before fading away.

On March 7th, 2023, satellites detected one of these extraordinary bursts, designated GRB 230307A. It was the second brightest burst ever recorded and originated from the collision and merger of two compact stars—most likely neutron stars—located in a distant galaxy.

What made this event particularly curious was its unusually long duration of one minute. According to prevailing theories, a merger of this type should produce a burst lasting less than two seconds. Intrigued by this anomaly, an international team of researchers from the University of Hong Kong, Nanjing University, and the Chinese Academy of Sciences decided to investigate further.

The team sifted through more than 600,000 datasets collected by China’s GECAM satellites and NASA’s Fermi satellite, searching for hidden patterns within the burst. What they discovered was remarkable: a repeating signal maintaining a very consistent rhythm over time. This revealed that the star was spinning at an incredible rate of 909 times per second.

This rapid pulsation marks the first direct detection of a periodic signal from a millisecond magnetar inside a gamma ray burst. As Professor Bing Zhang, Chair Professor of the Department of Physics at HKU and co-corresponding author of the study, explained, “By uncovering its hidden heartbeat, we can finally say with confidence that some GRBs are powered not by black holes, but by newborn magnetars.”

One surprising aspect of the discovery was understanding why the signal was so brief. The team theorizes that the magnetar’s rapid spin imprints a periodic signal onto the gamma ray jet through its magnetic field. However, because the jet evolves quickly, this “heartbeat” becomes visible only when the emission briefly becomes asymmetric. For just 160 milliseconds, the periodic pulse was detectable before the jet’s symmetry concealed it once again.

This breakthrough transforms our understanding of the most extreme explosions in the universe, demonstrating that newly born magnetars can survive compact star mergers. The research opens exciting new avenues in astronomy, linking gamma rays, gravitational waves, and the physics of compact stars under the most extreme conditions imaginable.
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