# NGC 300 ULX1: spin evolution, super-Eddington accretion and outflows

## TL;DR

NGC 300 ULX1, an ultra-luminous X-ray pulsar, exhibits rapid spin evolution and steady accretion despite flux drops, likely due to outflows or disk precession, revealing new insights into super-Eddington accretion processes.

## Contribution

This study provides the first detailed monitoring of NGC 300 ULX1's spin evolution and flux behavior, highlighting the role of outflows and disk precession in super-Eddington accretion.

## Key findings

- Spin period decreased from 126 s to <20 s in 4 years
- Flux dropped by over 20 times while spin-up remained steady
- Absorption likely caused by outflows or precessing disk

## Abstract

NGC300 ULX1 is an ultra-luminous X-ray pulsar, showing an unprecedented spin evolution, from about 126 s to less than 20 s in only 4 years, consistent with steady mass accretion rate. Following its discovery we have been monitoring the system with Swift/XRT and NICER to further study its properties. We found that even though the observed flux of the system dropped by a factor of $\gtrsim$20, the spin-up rate remained almost constant. A possible explanation is that the decrease in the observed flux is a result of increased absorption of obscuring material due to outflows or a precessing accretion disk.