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The nature of the X-ray transient SAX J1711.6-3808

J. J. M. in 't Zand·C. B. Markwardt·A. Bazzano·M. Cocchi·R. Cornelisse·J. Heise·E. Kuulkers·L. Natalucci·M. Santos-Lleo·J. Swank·P. Ubertini
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Abstract

SAX J1711.6-3808 is an X-ray transient in the Galactic bulge that was active from January through May of 2001 and whose maximum 1-200 keV luminosity was measured to be 5X10-9 erg/s/cm2 which is less than ~25% of the Eddington limit, if placed at a distance equal to that of the galactic center. We study the X-ray data that were taken of this moderately bright transient with instruments on BeppoSAX and RXTE. The spectrum shows two interesting features on top of a Comptonized continuum commonly observed in low-state X-ray binaries: a broad emission feature peaking at 7 keV and extending from 4 to 9 keV, and a soft excess with a color temperature below 1 keV which reveals itself only during one week of data. High time-resolution analysis of 412 ksec worth of data fails to show bursts, coherent or high-frequency quasi-periodic oscillations. Given the dynamic range of the flux measurements, this would be unusual if a neutron star were present. SAX J1711.6-3808 appears likely to contain a black hole. No quiescent optical counterpart could be identified in archival data within the 5"-radius XMM error circle, but the limits are not very constraining because of heavy extinction (Av=16).

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J. J. M. in 't Zand, C. B. Markwardt, A. Bazzano, M. Cocchi, R. Cornelisse, J. Heise, E. Kuulkers, L. Natalucci, M. Santos-Lleo, J. Swank, P. Ubertini. 2002-05-21. The nature of the X-ray transient SAX J1711.6-3808. https://doi.org/10.1051/0004-6361%3A20020762

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