The X-ray spectrum of the unusual neutron star X-ray binary SAX J2224.9+5421

We propose a 50ks XMMNewton observation of the unusual neutron star Xraybinary SAX J2224.9+5421. Our target was discovered by BeppoSAX/WFC when itexhibited a thermonuclear Xray burst. Followup observations aiming toconstrain the persistent emission were performed virgul8 h later and detected thesource at a 0.510 keV luminosity of virgul1E33 erg/s. This is very peculiar sinceneutron star binaries are generally considered to be in quiescence atluminosities of virgul1E311E33 erg/s, while they display accretion outbursts withluminosities of virgul1E341E38 erg/s. With the proposed observation we aim for adetailed investigation of the Xray spectrum of SAX J2224.9+5421 to find cluesexplaining its unusual behavior. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]