Home Publications Research Data Research Grants Equipment Inventions & Patents Awards Additional Research Activities Faculties & Institutions Research Areas

Discovery of a 9.67 s Pulsar in an Ultraluminous X-Ray Source in NGC 4631 with XMM-Newton

Ducci L, Mereghetti S, Pintore F, Allak S, Santangelo A, Sasaki M, Kavanagh P (2025)

---

Publication Type: Journal article

Publication year: 2025

Journal

Book Volume: 994

Article Number: L38

Journal Issue: 2

DOI: 10.3847/2041-8213/ae1c42

Abstract

Thanks to a recent observation with XMM-Newton, we discovered periodic pulsations at P = 9.6652 ± 0.0002 s in a new ultraluminous X-ray source (ULX) in the galaxy NGC 4631. This source, dubbed as X−8, shows one of the largest spin-up rates ever observed, P ̇ = ( − 9.6 ± 0.5 ) × 1 0 − 8 s s⁻¹. These findings indicate that the compact object is a neutron star, and X−8 is a new member of the pulsating ULX class. The 0.3-10 keV luminosity of X−8 is ∼3.4 × 10³⁹ erg s⁻¹, and its X-ray spectrum can be described by an absorbed disk blackbody or a cut-off power law, similar to what is observed in other pulsating ULXs. We discuss two possible causes for the large spin-up rate: Doppler shift from orbital motion of the neutron star and intrinsic spin-up due to accretion torque. This new ULX pulsar adds a key source to the small known population, and will enable future studies to better constrain the physical mechanisms responsible for their super-Eddington luminosities.

Authors with CRIS profile

Involved external institutions

How to cite

APA:

Ducci, L., Mereghetti, S., Pintore, F., Allak, S., Santangelo, A., Sasaki, M., & Kavanagh, P. (2025). Discovery of a 9.67 s Pulsar in an Ultraluminous X-Ray Source in NGC 4631 with XMM-Newton. Astrophysical Journal Letters, 994(2). https://doi.org/10.3847/2041-8213/ae1c42

MLA:

Ducci, Lorenzo, et al. "Discovery of a 9.67 s Pulsar in an Ultraluminous X-Ray Source in NGC 4631 with XMM-Newton." Astrophysical Journal Letters 994.2 (2025).

BibTeX: Download