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http://hdl.handle.net/20.500.12386/30507
Titolo: | Discovery of a 3 s Spinning Neutron Star in a 4.15 hr Orbit in the Brightest Hard X-Ray Source in M31 | Autori: | RODRIGUEZ CASTILLO, Guillermo Andres ISRAEL, Gian Luca ESPOSITO, PAOLO PAPITTO, ALESSANDRO STELLA, Luigi TIENGO, ANDREA DE LUCA, Andrea MARELLI, MARTINO |
Data pubblicazione: | 2018 | Rivista: | THE ASTROPHYSICAL JOURNAL LETTERS | Numero: | 861 | Fascicolo: | 2 | Da pagina:: | L26 | Abstract: | We report the discovery with XMM-Newton of 3 s X-ray pulsations from 3XMM J004232.1+411314, a dipping source that dominates the hard X-ray emission of M31. This finding unambiguously assesses the neutron star (NS) nature of the compact object. We also measured an orbital period of 4.15 hr and a projected semi-axis at a_X sin i = 0.6 lt-s, which implies a low-mass companion of about 0.2-0.3 M_☉ assuming an NS of 1.5 M_☉ and an orbital inclination i = 60°-80°. The barycentric orbit-corrected pulse period decreased by ∼28 ms in about 16 year, corresponding to an average spin-up rate of \dot{P}∼ -6× {10}^-11 s s^-1 pulse period variations, probably caused by X-ray luminosity changes, were observed on shorter timescales. We identify two possible extreme scenarios for the source: a mildly magnetic NS with B _p ≃ few × 10^10 G if the pulsar is far from its equilibrium period P_eq and the disk is truncated at the value of the Alfvén radius corresponding to the observed luminosity, and a relatively young, highly magnetic NS with B_eq ≃ 2 × 10^13 G if spinning close to P_eq and the disk is truncated close to the co-rotation surface. | URI: | http://hdl.handle.net/20.500.12386/30507 | URL: | https://iopscience.iop.org/article/10.3847/2041-8213/aacf40 https://arxiv.org/abs/1804.10858 |
ISSN: | 2041-8205 | DOI: | 10.3847/2041-8213/aacf40 | Bibcode ADS: | 2018ApJ...861L..26R | Fulltext: | open |
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