Article (Scientific journals)
The Newly Discovered Pulsating Low Mass White Dwarfs: An Extension of the ZZ Ceti Instability Strip
Van Grootel, Valérie; Fontaine, Gilles; Brassard, Pierre et al.
2013In Astrophysical Journal, 762, p. 57
Peer Reviewed verified by ORBi
 

Files


Full Text
0004-637X_762_1_57.pdf
Publisher postprint (634.19 kB)
Request a copy

All documents in ORBi are protected by a user license.

Send to



Details



Keywords :
stars: oscillations; white dwarfs
Abstract :
[en] In light of the exciting discovery of g-mode pulsations in extremely low-mass, He-core DA white dwarfs, we report on the results of a detailed stability survey aimed at explaining the existence of these new pulsators as well as their location in the spectroscopic Hertzsprung–Russell diagram. To this aim, we calculated some 28 evolutionary sequences of DA models with various masses and chemical layering. These models are characterized by the so-called ML2/α = 1.0 convective efficiency and take into account the important feedback effect of convection on the atmospheric structure. We pulsated the models with the nonadiabatic code MAD, which incorporates a detailed treatment of time-dependent convection. On the other hand, given the failure of all nonadiabatic codes, including MAD, to account properly for the red edge of the strip, we resurrect the idea that the red edge is due to energy leakage through the atmosphere. We thus estimated the location of that edge by requiring that the thermal timescale in the driving region—located at the base of the H convection zone—be equal to the critical period beyond which l = 1 g-modes cease to exist. Using this approach, we find that our theoretical ZZ Ceti instability strip accounts remarkably well for the boundaries of the empirical strip, including the low-gravity, low-temperature regime where the three new pulsators are found. We also account for the relatively long periods observed in these stars, and thus conclude that they are true ZZ Ceti stars, but with low masses.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Van Grootel, Valérie  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Fontaine, Gilles
Brassard, Pierre
Dupret, Marc-Antoine ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Language :
English
Title :
The Newly Discovered Pulsating Low Mass White Dwarfs: An Extension of the ZZ Ceti Instability Strip
Publication date :
01 January 2013
Journal title :
Astrophysical Journal
ISSN :
0004-637X
eISSN :
1538-4357
Publisher :
University of Chicago Press, Chicago, United States - Illinois
Volume :
762
Pages :
57
Peer reviewed :
Peer Reviewed verified by ORBi
Funders :
F.R.S.-FNRS - Fonds de la Recherche Scientifique [BE]
Available on ORBi :
since 16 October 2012

Statistics


Number of views
59 (4 by ULiège)
Number of downloads
0 (0 by ULiège)

Scopus citations®
 
51
Scopus citations®
without self-citations
41
OpenCitations
 
50

Bibliography


Similar publications



Contact ORBi