M51 ULX-7: superorbital periodicity and constraints on the neutron star magnetic field

Vasilopoulos, G., Lander, S. K., Koliopanos, F. and Bailyn, C. D. (2020) M51 ULX-7: superorbital periodicity and constraints on the neutron star magnetic field. Monthly Notices of the Royal Astronomical Society, 491 (4). pp. 4949-4959. ISSN 0035-8711

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Abstract

In this work, we explore the applicability of standard theoretical models of accretion to the observed properties of M51 ULX-7. The spin-up rate and observed X-ray luminosity are evidence of a neutron star with a surface magnetic field of 2-7 x 10(13) G, rotating near equilibrium. Analysis of the X-ray light curve of the system (Swift/XRT data) reveals the presence of a similar to 39 d superorbital period. We argue that the superorbital periodicity is due to disc precession, and that material is accreted on to the neutron star at a constant rate throughout it. Moreover, by attributing this modulation to the free precession of the neutron star we estimate a surface magnetic field strength of 3-4 x 10(13) G. The agreement of these two independent estimates provide strong constraints on the surface polar magnetic field strength of the NS.

Item Type: Article
Uncontrolled Keywords: stars: neutron,pulsars: individual: m51 ulx-7,galaxies: individual: m51,x-rays: binaries,x-ray sources,warped accretion discs,super-eddington accretion,optically thick envelopes,ngc 300 ulx1,free precession,long periods,light curves,black-holes,smc x-1
Depositing User: LivePure Connector
Date Deposited: 06 May 2020 00:06
Last Modified: 28 Aug 2020 23:54
URI: https://ueaeprints.uea.ac.uk/id/eprint/75028
DOI: 10.1093/mnras/stz3298

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