Search of gaseous disks in white dwarfs

L. SAKER, L. GOMEZ, L. GARCIA

La Serena

Congreso; Segunda reunión AAA-SOCHIAS; 2018

AAA-Sochias

In recent years, thanks to Spitzer and WISE, the number of white dwarfs (WDs) with IR 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 8600 a (distinctive of a gas in a Keplerian stable rotating disk). However, not all WDs with debris disk have a gas disk, and it still remains unknown why WDs of similar characteristics retain their gas disks and other do not. One manner to infer some constrains or hints to help clarify this issue is to analyze and confront significant groups of both types of objects. In this context, we have obtained GMOS/GEMINI optical spectra for a sample of 13 WDs with IR excess, selected from our sample of 29 debris disks WDs, to find the gas counterpart to the dusty disks. We combined our sample with other objects from the literature and analyze the largest available sample. We obtained a final sample composed by 2 objects with the lines in absorption, 8 WDs with the Ca II triplet in emission, and 16 stars which do not present the Ca lines. With the aim of finding key characteristics to better understand gas disks in WDs, we constructed the H-W1 vs. J-H diagram. On average, WDs with the Ca II triplet in emission do not have different H-W1 color index from WDs with Ca lines in absorption and without lines. This similarity in color suggests that dusty disks have homogenous properties in all WDs regardless the present of a gas componenent.