X-Ray Eclipse Time Delays in 4U2129+47

Abstract

4U 2129+47 was discovered in the early 80's and classified as an accretion disk corona source due to its broad and partial X-ray eclipses. The 5.24 hr binary orbital period was inferred from the X-ray and optical light curve modulation, implying a late K or M spectral type companion star. The source entered a low state in 1983, during which the optical modulation disappeared and an F8 IV star was revealed, suggesting that 4U 2129+47 might be part of a triple system. The nature of 4U 2129+47 has since been investigated, but no definitive conclusion has been reached. Here, we present timing and spectral analyses of two XMM-Newton observations of this source, carried out in May and June, 2005. We find evidence for a delay between two mid-eclipse epochs measured ~22 days apart, and we show that this delay can be naturally explained as being due to the orbital motion of the binary 4U 2129+47 around the center of mass of a triple system. This result thus provides further support in favor of the triple nature of 4U 2129+47.

6 pages, 5 figures, accepted by A&A

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Cited by in corpus (10)

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• Black Holes in Short Period X-ray Binaries and the Transition to Radiatively Inefficient Accretion
• A possible solution of the puzzling variation of the orbital period of MXB 1659-298
• IGR J17451-3022: a dipping and eclipsing low mass X-ray binary
• Exploring X-ray variability with unsupervised machine learning I. Self-organizing maps applied to XMM-Newton data
• The relation between outburst rate and orbital period in low-mass X-ray binary transients
• A Further Drop into Quiescence by the Eclipsing Neutron Star 4U 2129+47
• On the triple nature of the X-ray source 4U2129+47 (= V1727 Cyg)