  White dwarfs with emission lines from gaseous debris discs are among the
rarest examples of planetary remnant hosts, but at the same time they are key
objects for studying the final evolutionary stage of planetary systems. Making
use of the large number of white dwarfs identified in Gaia DR2, we are
conducting a survey of planetary remnants and here we present the first results
of our search: six white dwarfs with gaseous debris discs. This first
publication focuses on the main observational properties of these objects and
highlights their most unique features. Three systems in particular stand out:
WDJ084602.47+570328.64 displays an exceptionally strong infrared excess which
defies the standard model of a geometrically-thin, optically-thick dusty debris
disc; WDJ213350.72+242805.93 is the hottest gaseous debris disc host known with
Teff=29282 K; and WDJ052914.32-340108.11, in which we identify a record number
of 51 emission lines from five elements. These discoveries shed light on the
underlying diversity in gaseous debris disc systems and bring the total number
of these objects to 21. With these numbers we can now start looking at the
properties of these systems as a class of objects rather than on a case-by-case
basis.

Solar and Stellar Astrophysics