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http://hdl.handle.net/20.500.12386/29643
Title: | NuSTAR J095551+6940.8: a highly magnetised neutron star with super-Eddington mass accretion | Authors: | Simone Dall'Osso Rosalba Perna STELLA, Luigi |
Issue Date: | 2015 | Journal: | MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | Number: | 449 | Issue: | 2 | First Page: | 2144 | Abstract: | The identification of the Ultraluminous X-ray source (ULX) X-2 in M82 as an accreting pulsar has shed new light on the nature of a subset of ULXs, while rising new questions on the nature of the super-Eddington accretion. Here, by numerically solving the torque equation of the accreting pulsar within the framework of the magnetically threaded-disk scenario, we show that three classes of solutions, corresponding to different values of the magnetic field, are mathematically allowed. We argue that the highest magnetic field one, corresponding to B $\sim 10^{13}$ G, is favoured based on physical considerations and the observed properties of the source. In particular, that is the only solution which can account for the observed variations in $\dot{P}$ (over four time intervals) without requiring major changes in $\dot{M}$, which would be at odds with the approximately constant X-ray emission of the source during the same time. For this solution, we find that the source can only accomodate a moderate amount of beaming, 0.5 $\lesssim b < 1$. Last, we show that the upper limit on the luminosity, L$_X < 2.5 \times 10^{38}$ erg s$^{-1}$ from archival observations, is consistent with a highly-magnetized neutron star being in the propeller phase at that time. | URI: | http://hdl.handle.net/20.500.12386/29643 | URL: | https://academic.oup.com/mnras/article/449/2/2144/1064867 | ISSN: | 0035-8711 | DOI: | 10.1093/mnras/stv170 | Bibcode ADS: | 2015MNRAS.449.2144D | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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