Astronomers have studied the pulsar PSR J2129+4119. This neutron star exhibits several patterns of behavior at once. Scientists are trying to unravel its secrets.
Pulsar with strange behavior
Using the Five-hundred-meter Aperture Spherical Radio Telescope (FAST), astronomers from the Chinese Academy of Sciences (CAS) and other institutions observed a nearby pulsar known as PSR J2129+4119.
Radio emissions from pulsars exhibit a variety of phenomena, including subpulse drift, signal disappearance, or mode change. In the case of subpulse drift, the radio emission from the pulsar appears to drift in phase within the main pulse profile. When it comes to signal disappearance, the emission from the pulsar suddenly stops for several or hundreds of pulse periods before resuming.
Discovered in 2017, PSR J2129+4119 is an old and nearby pulsar located approximately 7,500 light-years away. Its pulse period is 1.69 seconds, its dispersion measure is 31 cm/pc³, and its characteristic age is 342.8 million years. The pulsar lies below the so-called “death line” — a theoretical boundary on the period-derivative diagram below which coherent radio emission is maintained.
Pulsar’s pulses beyond the “death limit”
Now, a team of astronomers led by Habtamu Menberu Tedila of CAS has studied PSR J2129+4119 using highly sensitive FAST observations, which have revealed a variety of radiation phenomena from this pulsar. Scientists say that despite being located well below the traditional “death line,” the pulsar exhibits long-lasting and diverse radiation behavior, including pauses, weak pulses, regular emission, and single bright pulses.
In particular, observations show that PSR J2129+4119 exhibits stable and multimodal emission behavior, including three different modes: pauses, weak pulses, and regular pulses. Occasionally, it also emits bright pulses, quasi-periodic microstructure, and shows clear signs of subpulse modulation. The pause fraction was measured to be approximately 8.13%.
Features of pulsar radio emission
In addition, observations have shown that both regular and weak pulses from PSR J2129+4119 exhibit high linear polarization. The collected data indicate a small incidence angle (approximately -3 degrees), which is consistent with an almost tangential line of observation. It appears that after the break, the regular pulses of the pulsar demonstrate enhanced rear components relative to the pulses before the break. According to the authors of the article, this indicates a gradual reactivation of the magnetosphere rather than a purely geometric origin.
The data also show that the microstructure is present in approximately 64% of the pulsar’s regular pulses, with an average period of 4.57 milliseconds and an average width of 4.3 milliseconds.
Thus, all new results indicate that PSR J2129+4119 remains magnetospherically active and emits coherently, despite its low energy loss.
“The pulsar’s diverse observational behavior, including beat-like modulation, emission asymmetries near nulls, and quasi-periodic microstructure, suggests that its magnetosphere operates near the threshold for coherent emission, providing valuable constraints on the physical conditions that enable or suppress pulsar radio emission,” the researchers conclude.
According to phys.org
