RX J004717.4-251811: The first eclipsing X-ray binary outside the Local Group

Abstract

The X-ray source RX J004717.4-251811 in the nearby starburst galaxy NGC 253 was found to undergo changes from a low to a high state twice, during an XMM-Newton EPIC observation in December 2000 and also during a Chandra observation one year earlier. These transitions are interpreted as egresses from eclipses of a compact object in a high mass X-ray binary system (HMXB). The phase of eclipse egress during the Chandra observation is given by barycenter corrected MJD 51539.276+-0.006 and the binary period determined to p = (352.870+-0.012) d / n by the time difference between the two egresses and number n of periods in-between. Allowed periods may be further constrained by additional XMM-Newton, Chandra, ROSAT, and Einstein observations resulting in only seven acceptable periods with 1.47024 d and 3.20793 d most promising. No significant regular pulsations of the source in the range 0.3-1000 s were found. Fluctuations on time scales of 1000 s were observed together with extended intervals of low intensity. The energy spectrum during the bright state can best be described by an absorbed flat power law (NH=1.9x10^21 cm^-2, Gamma=1.7). In the bright state the source luminosity is 4x10^38 erg/s (0.5--5 keV), just compatible with the Eddington luminosity of a 1.4 M_sun neutron star. A possible optical identification is suggested. RX J004717.4-251811 parameters are compared to other eclipsing X-ray binaries (XRBs).

9 pages including 5 figures, accepted for publication in A&A

References in corpus (5)

• The European Photon Imaging Camera on XMM-Newton: The MOS Cameras
• The USNO-B Catalog
• Distances to Nearby Galaxies in Sculptor
• XMM-Newton observations of NGC 253: Resolving the emission components in the disk and nuclear area
• XMM-Newton observations of the isolated neutron star RX J0806.4-4123

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• Exploring X-ray variability with unsupervised machine learning I. Self-organizing maps applied to XMM-Newton data
• Multiwavelength study of the bright X-ray source population in the interacting galaxies NGC5774/NGC5775
• Detection of X-ray elongated emission from a ultraluminous X-ray source in the interacting pair of galaxies NGC 5953/5954