A new class of disk-accreting white dwarfs\: diagnosing boundary layers

SU Lyn is a purely accretionpowered symbiotic star revealed for us from Xrays.Its weak highexciting emission lines rendered it invisible to optical surveys.While indicating that the already significant total estimated Galacticpopulation of symbiotics (virgul3x10^5) is biased and thus underestimated, thisdiscovery opens a new window on accretion and evolution of symbiotics. Here wepropose XMMNewton observations of two targets to go deeper in the subject\\: (i)SU Lyn, to better understand the response of the accretion disk and boundarylayer to changes in accretion rate, and (ii) IGR J171643803, in an exploratoryeffort to validate it as a member of the class. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]