Investigating the structure of the accretion disc in WZ Sge from multiwaveband time-resolved spectroscopic observations – I |
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| Authors: | Warren Skidmore Elena Mason Steve B Howell David R Ciardi Stuart Littlefair V S Dhillon |
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| Institution: | School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS;Department of Physics and Astronomy, University of Wyoming, PO Box 3905, University Station, Laramie, WY 82071, USA;Astrophysics Group, Planetary Science Institute, 620 North 6th Avenue, Tucson, AZ 85705, USA;Department of Astronomy, 211 Bryant Space Science Center, PO Box 112055, University of Florida, Gainesville, FL 32611-2055, USA;Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH |
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| Abstract: | We present the first of two papers describing an in-depth study of multiwaveband phase-resolved spectroscopy of the unusual dwarf nova WZ Sge. In this paper we present an extensive set of Doppler maps of WZ Sge covering optical and infrared emission lines, and describe a new technique for studying the accretion discs of cataclysmic variables using ratioed Doppler maps. Applying the ratioed Doppler map technique to our WZ Sge data shows that the radial temperature profile of the disc is unlike that predicted for a steady state α disc. Time-averaged spectra of the accretion disc line flux (with the bright spot contribution removed) show evidence in the shapes of the line profiles for the presence of shear broadening in a quiescent non-turbulent accretion disc. From the positions of the bright spots in the Doppler maps of different lines, we conclude that the bright spot region is elongated along the ballistic stream, and that the density of the outer disc is low. The velocity of the outer edge of the accretion disc measured from the H α line is found to be 723±23 km s?1. Assuming that the accretion disc reaches to the 3:1 tidal resonance radius, we derive a value for the primary star mass of 0.82 M⊙. We discuss the implications of our results on the present theories of WZ Sge type dwarf nova outbursts. |
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| Keywords: | accretion accretion discs binaries: close stars: individual: WZ Sge novae cataclysmic variables |
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