EAS Publications Series
Volume 17, 2005Element Stratification in Stars: 40 Years of Atomic Diffusion
|Page(s)||143 - 148|
|Published online||13 January 2006|
G. Alecian, O. Richard and S. Vauclair (eds)
EAS Publications Series, 17 (2005) 143-148
The DB gap and pulsations of white dwarfs
Department of Astronomy, University of Tokyo, Tokyo 113-0033, Japan
Corresponding author: firstname.lastname@example.org
The ratio of DA to DB white dwarfs is temperature sensitive. No DBs are found between 45 000 K and 30 000 K, and this exclusion zone is known as the “DB gap”. A working hypothesis to explain the DB gap is proposed. Since the temperatures of the upper and the lower bounds of the DB gap coincide with the effective temperatures where the He II/III and He I/II convection zones show up respectively, convective mixing is suspected to be the cause of the appearance of DBs outside the DB gap. Inversely, chemical separation due to gravitational settling in the convectively stable atmosphere is suspected to be the cause of the presence of the DB gap. According to this scenario, the white dwarfs which will turn back to DBs after the DB gap phase are expected to have a superadiabatic layer which is nonetheless convectively stable due to chemical separation, when they are located near the lower bound of the DB gap. Such white dwarfs are expected to be pulsationally unstable.
© EAS, EDP Sciences, 2005
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.