# Ultraslow PSR J0901-4046 with an ultrahigh magnetic field of $3.2\times10^{16}$ G

**Authors:** D. N. Sob'yanin  
**arXiv:** [2304.03702](https://arxiv.org/abs/2304.03702)  
**Date:** 2023-04-07  
**Summary page:** https://www.summarizepaper.com/en/paper/2304.03702v1/

## Key points

- PSR J0901-4046 is a radio-emitting neutron star with an ultralong spin period of 76 seconds.
- The canonical magnetic field estimated from the pulsar period and its time derivative is insufficient for it to operate in the radio band.
- A higher magnetic field can be estimated from the pulse width, but it is still lower than necessary for radio pulsars with magnetic fields exceeding the critical value.
- If the observed microstructure of single pulses reflects relativistic beaming, then the inferred surface magnetic field appears to be $3.2\times10^{16}$ G.
- Without this assumption, it is no less than $2.7\times10^{16}$ G, which explains why PSR J0901-4046 emits radio waves despite having weak or moderate magnetic fields.
- This estimation makes PSR J0901-4046 a radio pulsar with one of the strongest known magnetic fields and indicates that it slows down not by magnetic-dipole radiation but rather by an electric current of 56 MA when rotational energy is expended in accelerating charged particles over its polar cap.
- Relativistic beaming may play a crucial role in explaining why some neutron stars are active in the radio band despite having weak or moderate magnetic fields.
- This study sheds new light on our understanding of neutron stars and their complex physical processes and opens up exciting avenues for future research in this area.

## Summary

A recent discovery of a radio-emitting neutron star, PSR J0901-4046, with an ultralong spin period of 76 seconds has raised fundamental questions about how such a slowly rotating magnetized object can be active in the radio band. The canonical magnetic field estimated from the pulsar period and its time derivative is wholly insufficient for PSR J0901-4046 to operate. However, consideration of a magnetic inclination angle of 10 degrees estimated from the pulse width gives a higher magnetic field, which is still an order of magnitude lower than the necessary minimum following from the death line for radio pulsars with magnetic fields exceeding the critical value. In this study by D.N. Sob'yanin, it is shown that if the observed microstructure of single pulses reflects relativistic beaming, then the inferred surface magnetic field appears to be $3.2\times10^{16}$ G. Without this assumption, it is no less than $2.7\times10^{16}$ G, which explains why PSR J0901-4046 emits radio waves despite having weak or moderate magnetic fields. This estimation makes PSR J0901-4046 a radio pulsar with one of the strongest known magnetic fields and indicates that it slows down not by magnetic-dipole radiation but rather by an electric current of 56 MA when rotational energy is expended in accelerating charged particles over its polar cap. The findings suggest that relativistic beaming may play a crucial role in explaining why some neutron stars are active in the radio band despite having weak or moderate magnetic fields and provide insights into their underlying physical mechanisms. Overall, this study sheds new light on our understanding of neutron stars and their complex physical processes and opens up exciting avenues for future research in this area.