Study on the magnetic field strength of NGC 300 ULX1

TL;DR

This study estimates the magnetic field of NGC 300 ULX1 as an accreting magnetar with potential evolution into a millisecond pulsar, providing insights into magnetar evolution and PULX characteristics.

Contribution

It presents the first inferred magnetic field strength of NGC 300 ULX1 and suggests it is an accreting magnetar, proposing a new class of PULXs and their evolutionary pathways.

Findings

Magnetic field of NGC 300 ULX1 is approximately 3.0×10^{14} G.

NGC 300 ULX1 may evolve into a recycled or millisecond pulsar.

Other PULXs might also host accreting magnetars.

Abstract

NGC 300 ULX1 is a pulsating ultraluminous X-ray source (PULX) with the longest spin period of $P\simeq31.6\,\rm s$ and a high spin-up rate of $\dot P\simeq5.56\times10^{-7}\,\rm s\,s^{-1}$ that is ever seen in the confirmed PULXs. In this paper, the inferred magnetic field of NGC 300 ULX1 is $\sim3.0\times10^{14}\,\rm G$ using the recent observed parameters after its first detection of pulsations. According to the evolved simulation of the magnetic field and the spin period, it will become a recycled pulsar or a millisecond pulsar under the conditions of the companion mass and the accretion rate limitation. We suggest that NGC 300 ULX1 is an accreting magnetar accounting for its super Eddington luminosity. We also propose that there might be other accreting magnetars in the confirmed PULXs. Such PULXs will be helpful for understanding the magnetar evolution and the millisecond pulsar formation whose magnetic field is stronger than $\sim10^{9}\,\rm G$.