Dr. YAO Jumei and a team of astronomers have conducted an investigation based on FAST observation that led to the discovery of the first evidence for three-dimensional (3D) spin-velocity alignment in pulsars. Pulsar, rotating neutron star, is the imploded core of a massive star produced by a supernova explosion. As current simulations of supernova explosions have difficulty producing pulsars with spin-velocity alignment, this detection indicates that human need to gain more insight on the mechanism involved in pulsar birth, for example neutrino-driven mechanism. This important finding marks the beginning of indepth pulsar research by using FAST.
Young pulsars move and rotate much faster than their progenitors (OB stars). For decades, scientists have found that there is strong observational evidence for spin-velocity alignment in young pulsars. As it is difficult to measure pulsar radial velocity, in previous study the comparison between pulsar spin axis and velocity vector has been restricted to a 2D sky plane perpendicular to our line of sight. Based on FAST observation of PSR J0538+2817 in SNR S147, Dr. YAO Jumei obtained its radial location and radial velocity for the first time, through interstellar scintillation analysis. Then the 3D velocity was obtained by combining with previous transverse velocity measures from VLBI. At the same time, the polarization analysis resulted in the direction of the 3D spin axis. Figure 1 shows the distribution of the 3D spin and velocity vector on the surface of a unit sphere, and the angle between these two vectors is smaller than 23° with 68% probability.
Completed a D.Sc. in 2017 at Xinjiang Astronomical Observatory, under the supervision of Dr. WANG Na, also took part in this project, Dr. YAO Jumei is now a post-doctoral researcher in the team led by Dr. LI Di from National Astronomical Observatories of Chinese Academy of Sciences.
FAST is currently the world’s most sensitive single aperture radio telescope. With support of Scientific Committee, Time Allocation Committee and FAST Operation Center, more measures are processing gradually, and new detections are expected to further reveal the origin of pulsar spin-kick. This work was supported by FAST FELLLOWSHIP budgeted and administrated by Center for Astronomical Mega-Science, Chinese Academy of Sciences (CAMS). The paper has been accepted for publication by Nature Astronomy.
Figure 1: The distribution of 3D spin axis and velocity vector of PSR J0538+2817 on the surface of a unit sphere. Different colors show the 3D angle distribution with 68% and 95% confidence limit for the spin and velocity vectors, in red and gray for the velocity, in dark green and light green for the spin axis obtained FAST polarization and in blue and yellow for the spin axis measured from X-ray observation.
Contact: YAO Jumei
Xinjiang Astronomical Observatory
Email: yaojumei@xao.ac.cn
Article link: https://arxiv.org/abs/2103.01839
