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.