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Paper: Variable Emission from a Gaseous Disc around a Metal-Polluted White Dwarf
Volume: 493, 19th European Workshop on White Dwarfs
Page: 279
Authors: Wilson, D. J.; Gänsicke, B. T.; Koester, D.; Raddi, R.; Breedt, E.; Southworth, J.; Parsons, S. G.
Abstract: We present the discovery of a variable gaseous disc around the metal-polluted DA white dwarf SDSS J1617+1620. Time-series spectroscopy obtained during the period 2006-2014 has shown the appearance of very strong double-peaked Ca ii 8600Å emission lines in 2008, that subsequently faded again over several years. The white dwarf is strongly metal polluted, requiring ongoing accretion, and exhibits infrared excess emission from circumstellar dust. Our observations represent the strongest evidence yet for real-time evolution of planetary debris discs around WDs, and we discuss potential scenarios including a secondary impact of a dense planetesimal onto the dusty disc, or the periodic passage of a debris stream during the formation of the dusty disc.
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