XMM-Newton Detection of Pulsations and a Spectral Feature in the X-ray Emission of the Isolated Neutron Star 1RXS

We report on the results of a deep XMM-Newton observation of RBS 1774, the most recent dim isolated neutron star candidate found in the ROSAT archive data. Spectral and timing analysis of the high-quality PN and MOS data confirm the association of this source with an isolated neutron star. The spectrum is thermal and blackbody-like, and there is evidence at a significance level > 4σ that the source is an X-ray pulsar, with spin period of 9.437 s. Spectral fitting reveils the presence of an absorption feature at∼ 0.7 keV, but at this level data do not have enough resolution to allow us to discriminate between an absorption line or an edge. We compare the newly measured properties of RBS 1774 with those of other known dim isolated neutron stars, and discuss possible interpretations for the absorption feature. Subject headings: stars: individual (1RXS J214303.7+065419/RBS 1774) — stars: neutron — X-rays: stars Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK; [email protected] Department of Physics, University of Padova, via Marzolo 8, 35131 Padova, Italy; [email protected] INAF-Osservatorio Astronomico di Padova, vicolo dell’Osservatorio 5, 35122, Padova, Italy; [email protected] Department of Physics and Mathematics, Universitá dell’Insubria Via Valleggio 11, 22100, Como, Italy; [email protected]; [email protected] Institut für Theoretische Physik der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland Smithsonian Astrophysical Observatory, MS 3, 60 Garden Street, Cambridge, MA 02138, USA; [email protected]