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arXiv · 1609.06538

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

G. L. Israel·A. Papitto·P. Esposito·L. Stella·L. Zampieri·A. Belfiore·G. A. Rodríguez Castillo·A. De Luca·A. Tiengo·F. Haberl·J. Greiner·R. Salvaterra·S. Sandrelli·G. Lisini
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Abstract

NGC 7793 P13 is a variable (luminosity range ~100) ultraluminous X-ray source (ULX) proposed to host a stellar-mass black hole of less than 15 M$_{\odot}$ in a binary system with orbital period of 64 d and a 18-23 M$_{\odot}$ B9Ia companion. Within the EXTraS 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 $L_{\mathrm{X}}\sim2.1\times10^{39}$ and $5\times10^{39}$ 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 $\times$ 10$^{13}$ G close to the base of the accretion column appears to be in agreement with the properties of the system.

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G. L. Israel, A. Papitto, P. Esposito, L. Stella, L. Zampieri, A. Belfiore, G. A. Rodríguez Castillo, A. De Luca, A. Tiengo, F. Haberl, J. Greiner, R. Salvaterra, S. Sandrelli, G. Lisini. 2016-09-21. Discovery of a 0.42-s pulsar in the ultraluminous X-ray source NGC 7793 P13. https://doi.org/10.1093/mnrasl%2Fslw218

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