Swift observations of GW Lib: a unique insight into a rare outburst |
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| Authors: | K Byckling J P Osborne P J Wheatley G A Wynn A Beardmore V Braito K Mukai R G West |
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| Institution: | Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH;Department of Physics, University of Warwick, Coventry CV4 7AL;NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA |
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| Abstract: | The second known outburst of the WZ Sge type dwarf nova GW Lib was observed in 2007 April. We have obtained unique multiwavelength data of this outburst which lasted ～26 days. The American Association of Variable Star Observers ( AAVSO ) recorded the outburst in the optical, which was also monitored by Wide Angle Search for Planets , with a peak V magnitude of ～8. The outburst was followed in the ultraviolet and X-ray wavelengths by the Swift ultraviolet/optical and X-ray telescopes. The X-ray flux at optical maximum was found to be three orders of magnitude above the pre-outburst quiescent level, whereas X-rays are normally suppressed during dwarf nova outbursts. A distinct supersoft X-ray component was also detected at optical maximum, which probably arises from an optically thick boundary layer. Follow-up Swift observations taken 1 and 2 years after the outburst show that the post-outburst quiescent X-ray flux remains an order of magnitude higher than the pre-outburst flux. The long interoutburst time-scale of GW Lib with no observed normal outbursts support the idea that the inner disc in GW Lib is evacuated or the disc viscosity is very low. |
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| Keywords: | accretion accretion discs stars: dwarf novae novae cataclysmic variables X-rays: binaries X-rays: stars |
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