PT - JOURNAL ARTICLE AU - Israel, Gian Luca AU - Belfiore, Andrea AU - Stella, Luigi AU - Esposito, Paolo AU - Casella, Piergiorgio AU - De Luca, Andrea AU - Marelli, Martino AU - Papitto, Alessandro AU - Perri, Matteo AU - Puccetti, Simonetta AU - Castillo, Guillermo A. Rodríguez AU - Salvetti, David AU - Tiengo, Andrea AU - Zampieri, Luca AU - D’Agostino, Daniele AU - Greiner, Jochen AU - Haberl, Frank AU - Novara, Giovanni AU - Salvaterra, Ruben AU - Turolla, Roberto AU - Watson, Mike AU - Wilms, Joern AU - Wolter, Anna TI - An accreting pulsar with extreme properties drives an ultraluminous x-ray source in NGC 5907 AID - 10.1126/science.aai8635 DP - 2017 Feb 24 TA - Science PG - 817--819 VI - 355 IP - 6327 4099 - http://science.sciencemag.org/content/355/6327/817.short 4100 - http://science.sciencemag.org/content/355/6327/817.full SO - Science2017 Feb 24; 355 AB - Ultraluminous x-ray sources (ULXs) are strange objects in other galaxies that cannot be explained by conventional accretion onto stellar-mass objects. This has led to exotic interpretations, such as the long-sought intermediate-mass black holes. Israel et al. observed a ULX in the nearby galaxy NGC 5907 and found that it is instead a neutron star. The spinning neutron star is accreting material so fast that its spin period is quickly accelerating. The only way that it can consume enough material to explain these properties is if it has a strong multipolar magnetic field.Science, this issue p. 817Ultraluminous x-ray sources (ULXs) in nearby galaxies shine brighter than any x-ray source in our Galaxy. ULXs are usually modeled as stellar-mass black holes (BHs) accreting at very high rates or intermediate-mass BHs. We present observations showing that NGC 5907 ULX is instead an x-ray accreting neutron star (NS) with a spin period evolving from 1.43 seconds in 2003 to 1.13 seconds in 2014. It has an isotropic peak luminosity of ~1000 times the Eddington limit for a NS at 17.1 megaparsec. Standard accretion models fail to explain its luminosity, even assuming beamed emission, but a strong multipolar magnetic field can describe its properties. These findings suggest that other extreme ULXs (x-ray luminosity ≥ 1041 erg second−1) might harbor NSs.