Gaseous disks in white dwarfs: properties of the current sample

In recent years, the number of white dwarfs (WDs) showing infrared (IR) excesses, attributed to circumstellar dust disks, has grown significantly. Gaseous disks have also been detected in some WDs with dust. We obtained optical spectra with Gemini/GMOS for thirteen WDs exhibiting IR excesses to search for gaseous components. No Ca II emission was detected, suggesting the gas phase may be short-lived compared to the dusty stage. Combining our data with literature, we compiled the largest sample of WDs with and without gas disks. We find no significant differences in stellar properties between the two groups, although disks with gas may be, on average, brighter. The detection rate of Ca II emission supports the idea that the gas phase persists for only a fraction of the total disk lifetime. A more definitive assessment will likely require dedicated searches for both gas and dust across large WD samples.