Galaxy Zoo: 'Hanny's Voorwerp', a quasar light echo?

  title={Galaxy Zoo: 'Hanny's Voorwerp', a quasar light echo?},
  author={Chris J. Lintott and Kevin Schawinski and William C. Keel and Hanny van Arkel and Nicola Bennert and Edward M. Edmondson and Daniel Thomas and Daniel J. B. Smith and Peter D. Herbert and Matt J. Jarvis and Shanil N. Virani and Daniel Andreescu and Steven Bamford and Kate R. Land and P. G. Murray and Robert C. Nichol and Jordan Raddick and An{\vz}e Slosar and Alexander S. Szalay and Jan vandenBerg},
  journal={Monthly Notices of the Royal Astronomical Society},
We report the discovery of an unusual object near the spiral galaxy IC 2497, discovered by visual inspection of the Sloan Digital Sky Survey (SDSS) as part of the Galaxy Zoo project. The object, known as Hanny’s Voorwerp, is bright in the SDSS g band due to unusually strong [O III]4959, 5007 emission lines. We present the results of the first targeted observations of the object in the optical, ultraviolet and X-ray, which show that the object contains highly ionized gas. Although the line… 
We present Hubble Space Telescope imaging and spectroscopy, along with supporting Galaxy Evolution Explorer and ground-based data, for the extended high-ionization cloud known as Hanny's Voorwerp,
Hanny's Voorwerp : Evidence of AGN activity and a nuclear starburst in the central regions of IC 2497
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The Soft X-Ray Counterpart of Hanny’s Voorwerp Near IC 2497
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Joint NuSTAR and Chandra analysis of the obscured quasar in IC 2497 - Hanny's Voorwerp system
We present new Nuclear Spectroscopic Telescope Array (NuSTAR) observations of the core of IC 2497, the galaxy associated with Hanny's Voorwerp. The combined fits of the Chandra  (0.5–8 keV) and
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We present multi-wavelength radio observations in the direction of the spiral galaxy IC 2497 and the neighbouring emission nebula known as "Hanny's Voorwerp". Our WSRT continuum observations at 1.4
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