Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), a research team led by Dr. WANG Shuangqiang from the pulsar research group at the Xinjiang Astronomical Observatory（XAO) of the Chinese Academy of Sciences discovered plasma lensing phenomenon in a black widow pulsar PSR J1720-0533.
Black widow pulsar systems have a low-mass companion star in a compact orbit with a millisecond pulsar. They are characterized by ablating the companion by emission from pulsar. Black widow pulsars get their name from the “black widow”spiders that the female eats the male after mating. Black widow pulsars offer valuable opportunities to investigate the characteristics of the companion stars under intense irradiation.
In this study, the researchers found that the emission of PSR J1720-0533 during the ingress of the eclipse shows quasi-periodic modulations, which could be caused by plasma lensing.
By analyzing the lensing phenomenon, the researchers obtained that the maximum magnification for the lens is 1.6 and the corresponding lens size is a few tens of kilometers. The discovery of the plasma lensing phenomenon in PSR J1720-0533 demonstrates a link between the dispersion measure and lensing.
Moreover, the researchers analyzed the polarization profiles near the eclipse of PSR J1720-0533, and found that the linear polarization of the emission disappeared before the dispersion measure showed significant changes. This phenomenon provides a strong evidence that there is a significant magnetic field in the companion.
This results suggested that the magnetic field plays an important role in the eclipse mechanism of balck widow pulsars.
In addition the researchers also estimated the mass-loss rate of the companion to be 10 -12M⊙/yr and speculated that the companion will be destroyed completely in 1010yr.
Fig. The upper panel shows the total intensity of pulse emission vs. pulsar spin and orbital phases with the sub-integration of 1 s of PSR J1720-0533. Enlargements of the ingress and egress of the pulsar are shown in the middle left and middle right panels, respectively. The bottom panels show the pulse flux density variations near the eclipse.
Contact:
WANG Shuangqiang
Xinjiang Astronomical Observatory, Chinese Academy of Sciences
Email: wangshuangqiang@xao.ac.cn
Web: https://doi.org/10.3847/2041-8213/ac365c
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