Discovery of a 0.42-s pulsar in the ultraluminous X-ray source NGC 7793 P13

Journal
Date Issued
2017
Author(s)
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Esposito, P.
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Belfiore, A.
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Tiengo, A.
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Haberl, F.
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Greiner, J.
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Lisini, G.
DOI
Abstract
NGC 7793 P13 is a variable (luminosity range ∼100) ultraluminous X-ray source proposed to host a stellar-mass black hole of less than 15 M☉ in a binary system with orbital period of 64 d and a 18-23 M☉ B9Ia companion. Within the EXTraS (Exploring the X-ray Transient and variable Sky) project, we discovered pulsations at a period of ∼0.42 s in two XMM-Newton observations of NGC 7793 P13, during which the source was detected at LX ∼ 2.1 × 1039 and 5 × 1039 erg s-1 (0.3-10 keV band). These findings unambiguously demonstrate that the compact object in NGC 7793 P13 is a neutron star accreting at super-Eddington rates. While standard accretion models face difficulties accounting for the pulsar X-ray luminosity, the presence of a multipolar magnetic field with B ∼ few × 1013 G close to the base of the accretion column appears to be in agreement with the properties of the system.
Volume
466
Issue
1
Start page
L48
Uri
Url
Issn Identifier
0035-8711
Ads BibCode
2017MNRAS.466L..48I
Rights
open.access
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