Program: GN-2016B-Q-56

In recent years, thanks to Spitzer and WISE, the number of white dwarfs (WD) with infrared excesses attributed to the presence of a debris disk, has increased significantly. Additionally, disks of gas were found in a handful of WDs with debris disks, through detection of emission lines of Ca triplet in 860 nm (distinctive of a gas in a Keplerian stable rotating disk). However, not all WDs with debris disk have gas disk. At the present time it is not known why WDs of similar characteristics retain their gas disks and other do not. One manner to infer some constrains or hits to help clarify this issue is to analyze and confront significant groups of both types of objects. In this context, we propose to obtain optical spectra of 4 WDs with infrared excess, selected from our sample of 29 debris disks WDs, to find the gas counterpart to the dusty disks. Other objects will be proposed next semester. In this manner, we expect to observe about 20 stars in 3 years. Our observations with those from the literature will allow us to find key characteristics to better understand gas disks in WDs.