Optical and Near-Infrared Spectroscopy of the Black Hole Swift J1753.5-0127
We report on a multiwavelength observational campaign of the black hole (BH) X-ray binary Swift J1753.5–0127 that consists of an ESO/X-shooter spectrum supported by contemporaneous Swift/X-ray Telescope+Ultra-Violet/Optical Telescope (UVOT) and Australia Telescope Compact Array data. Interstellar medium absorption lines in the X-shooter spectrum allow us to determine E(B-V)=0.45 ± 0.02 along the line of sight to the source. We also report detection of emission signatures of He ii λ 4686, Hα, and, for the first time, H i λ 10906 and Paβ. The double-peaked morphology of these four lines is typical of the chromosphere of a rotating accretion disk. Nonetheless, the paucity of disk features points toward a low level of irradiation in the system. This is confirmed through spectral energy distribution modeling, and we find that the UVOT+X-shooter continuum mostly stems from the thermal emission of a viscous disk. We speculate that the absence of reprocessing is due to the compactness of an illumination-induced envelope that fails to reflect enough incoming hard X-ray photons back to the outer regions. The disk also marginally contributes to the Compton-dominated X-ray emission and is strongly truncated, with an inner radius about 1000 times larger than the BH's gravitational radius. A near-infrared excess is present, and we associate it with synchrotron radiation from a compact jet. However, the measured X-ray flux is significantly higher than what can be explained by the optically thin synchrotron jet component. We discuss these findings in the framework of the radio-quiet versus X-ray-bright hypothesis, favoring the presence of a residual disk, predicted by evaporation models, that contributes to the X-ray emission without enhancing the radio flux.
Additional Information© 2015 The American Astronomical Society. Received 2015 May 9; accepted 2015 August 3; published 2015 September 10. We thank the referee for very insightful and constructive comments. F.R. thanks the ESO staff who performed the service observations. J.A.T. acknowledges partial support from NASA under Swift Guest Observer grants NNX13AJ81G and NNX14AC56G. S.C. acknowledges the financial support from the UnivEarthS Labex program of Sorbonne Paris Cité (ANR-10-LABX-0023 and ANR-11-IDEX-0005-02) and from the CHAOS project ANR-12-BS05-0009 supported by the French Research National Agency. E.K. acknowledges support from the TUBITAK BIDEB 2219 program. This work was supported by the Spanish Ministerio de Economía y Competitividad (MINECO) under grant AYA2013-47447-C3-1-P (S.M.). This research has made use of data obtained from the High Energy Astrophysics Science Archive Research Center (HEASARC), provided by NASA's Goddard Space Flight Center. This publication also makes use of data products from NEOWISE, which is a project of the Jet Propulsion Laboratory/California Institute of Technology, funded by the Planetary Science Division of the National Aeronautics and Space Administration. The Australia Telescope Compact Array is part of the Australia Telescope, which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. This research has made use of NASA's Astrophysics Data System and of the SIMBAD and VizieR databases operated at CDS, Strasbourg, France. IRAF is distributed by the National Optical Astronomy Observatories, which are operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.
Published - Rahoui_2015.pdf
Submitted - 1508.02394v1.pdf