A Potential Cyclotron Resonant Scattering Feature in the Ultraluminous X-Ray Source Pulsar NGC 300 ULX1 Seen by NuSTAR and XMM-Newton

D.J. Walton , M. Bachetti , F. Furst , D. Barret (1) , M. Brightman , A.C. Fabian , B.W. Grefenstette , F.A. Harrison , M. Heida , J. Kennea , P. Kosec , R.M. Lau , K.K. Madsen , M.J. Middleton , C. Pinto , J.F. Steiner , N. Webb (1)

1 IRAP - Institut de recherche en astrophysique et planétologie

Based on phase-resolved broadband spectroscopy using XMM-Newton and NuSTAR, we report on a potential cyclotron resonant scattering feature (CRSF) at E ∼ 13 keV in the pulsed spectrum of the recently discovered ultraluminous X-ray source (ULX) pulsar NGC 300 ULX1. If this interpretation is correct, the implied magnetic field of the central neutron star is B ∼ 1012 G (assuming scattering by electrons), similar to that estimated from the observed spin-up of the star, and also similar to known Galactic X-ray pulsars. We discuss the implications of this result for the connection between NGC 300 ULX1 and the other known ULX pulsars, particularly in light of the recent discovery of a likely proton cyclotron line in another ULX, M51 ULX-8.

Mots clés: X-rays: individual; stars: neutron; X-rays: binaries

Domaines: Astrophysique [astro-ph]

D.J. Walton, M. Bachetti, F. Furst, D. Barret, M. Brightman, et al.. A Potential Cyclotron Resonant Scattering Feature in the Ultraluminous X-Ray Source Pulsar NGC 300 ULX1 Seen by NuSTAR and XMM-Newton. Astrophys.J.Lett., 2018, 857 (1), pp.L3. ⟨10.3847/2041-8213/aabadc⟩. ⟨hal-01763456⟩