The radiative subpulse modulation and spectral features of PSR B1929+10 with the whole pulse phase emission

¹ Guangxi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, Guangxi University, Nanning 530004, China
² National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China
³ Guizhou Radio Astronomical Observatory, Guiyang 550025, China
⁴ School of Astronomy and Space Science, University of Chinese Academy of Sciences, Beijing 100049, China
⁵ Department of Astronomy, School of Physics, Peking University, Beijing 100871, China
⁶ Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China
⁷ Department of Astronomy, School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China

^⋆ Corresponding authors: lujig@nao.cas.cn, lew@gxu.edu.cn, r.x.xu@pku.edu.cn

Received: 17 March 2025
Accepted: 29 June 2025

Abstract

Context. The emission mechanism of pulsars is still not well understood. Observations of their intrinsic radio emission and polarization could shed light on the physical processes of the pulsars, such as the acceleration of the charged particles and the radio wave propagation in the pulsar magnetosphere, the location of the radio emission, and the geometry of emission.

Aims. To measure the radio emission characteristics and polarization behaviors of the normal and bright pulsar PSR B1929+10, we carried out a long-term observation to track this pulsar. Features of its intrinsic emission helped us understand the emission mechanism.

Methods. In this work, we report on a long-term observation of the nearby pulsar PSR B1929+10 using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The total time of the observation is 110 minutes. A high-precision polarization calibration signal source was required, and it was implemented in this observation.

Results. We find, for the first time, two new emission components with an extremely weak observed flux density of about 10⁻⁴ of the magnitude of the peak radio emission of PSR B1929+10. Our results show that the intrinsic radio emission of PSR B1929+10 covers the 360° of longitude, demonstrating that this pulsar is a whole 360° of longitude emission pulsar. We find at least 15 components of pulse emission in the average pulse profile. Additionally, we identified five modes of subpulse modulation in different emission regions, which differ from the pulse components. Moreover, the narrowband emission feature and the frequent jumps in the observed linear polarization position angle (PPA) were also detected in the single pulse of this pulsar. To understand the magnetosphere of this pulsar, we analyzed the observed PPA variations across the whole 360° of longitude and fit them using the classical rotating vector model. For the best-fit model, the inclination angle, α, and the impact angle, β, of this pulsar are 55°.62 and 53°.47, respectively. Using the rotating magnetosphere approximation of the magnetic dipole field, we investigated the 3D pulsar magnetosphere and the sparking pattern on the polar cap surface. Our analysis indicates that the extremely narrow zone of the polar cap, which is associated with a high-altitude magnetospheric region, is responsible for the weak emission window. This pulsar has extremely high-altitude magnetospheric radio emissions.