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Within our Milky Way galaxy, in the direction of the constellation Vulpecula, a cosmic "lighthouse" named PSR B1937+21 spins at an astonishing rate of 642 revolutions per second. It emits electromagnetic pulses that rival the precision of atomic clocks.

For the first time, a Chinese research team has captured the complete polarization pattern of PSR B1937+21's main pulse and interpulse as they vary with frequency. The , reported in The Astrophysical Journal, provides crucial evidence for radiation mechanisms operating under extreme physical conditions.

Using the Murriyang (Parkes) 64-meter radio telescope in Australia equipped with an ultra-wideband receiver, Ph.D. student Wang Zhen from the Xinjiang Astronomical Observatory (XAO) of the Chinese Academy of Sciences (CAS), under the guidance of his supervisors, Prof. Yuan Jianping and Prof. Wen Zhigang, conducted the three years of sustained observations.

The researchers unveiled the radiation secrets of PSR B1937+21: the linear polarization degree of the main pulse decreases as frequency increases, while the interpulse shows the opposite trend; the circular polarization degree of both emission regions strengthens with rising frequency; and the main-to-interpulse intensity ratio follows a power-law spectrum with an index of 0.52±0.02.

Discovered in 1982 as one of the first millisecond pulsars, PSR B1937+21 possesses an ultra-short rotation period of 1.558 milliseconds. Its magnetic field strength is merely one-ten-thousandth that of ordinary pulsars, suggesting possible spin-up via accretion from a companion star.

The researchers used an ultra-wideband receiving system covering 704-4032 MHz, boosting the signal-to-noise ratio 20-fold by integrating multi-year data. Furthermore, flux density measurements, dispersion measure (DM) analysis, and Faraday rotation measurements were used to infer properties of the intervening interstellar medium.

The results confirmed that emission height decreases as frequency increases, which manifests as a narrowing pulse width. The results also suggest that the main pulse and interpulse likely originate from different regions within the magnetosphere. These findings provide observational support for the "relativistic beaming model."

These findings will advance the research into neutron star magnetospheric physics and plasma radiation mechanisms, while also offering more precise timing references for gravitational wave detection.