Recently, Ph.D. candidate BAI Juntao from the Xinjiang Astronomical Observatory of the Chinese Academy of Sciences, under the supervision of Prof. WANG Na, conducted  observations of four magnetars and one magnetar-like pulsar using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The study revealed the "radio-quiet" characteristics of these extreme celestial objects. The results are published in The Astrophysical Journal (ApJ, 2025, 979, 122).  

Magnetars are neutron stars with ultra-strong magnetic fields, reaching up to trillions of times the strength of Earth’s magnetic field . Despite their violent activity in X-ray and gamma-ray bands, radio emissions from magnetars are extremely rare. To date, only six magnetars have been detected to be radioactive. This "selective quiet" phenomenon has puzzled astronomers.  

Leveraging FAST’s unparalleled sensitivity, the research team observed four magnetars (SGR 0501+4516, Swift J1834.9–0846, 1E 1841–045, SGR 1900+14) and the magnetar-like pulsar PSR J1846–0258. No periodic radio pulsations or single pulses were detected at 1250 MHz. The team calculated upper limits on their radio flux densities, with the lowest value reaching 8.2 μJy, significantly lower than the measured radio flux densities of known pulsars. This suggests these objects may be intrinsically "radio-quiet" or their radio beams are not aligned with Earth. The results deepen our understanding of magnetar radio emission mechanisms and provide critical references for future observations.

 The upper limits on flux density for the four magnetars and the magnetar-like pulsar are lower than measured radio flux densities (at 1.4 GHz) of pulsars.