Accretion from debris disks onto white dwarfs : Fingering (thermohaline) instability and derived accretion rates

Context. Recent observations of a large number of DA and DB white dwarfs show evidence of debris disks, which are the remnants of old planetary systems. The infrared excess detected with <i>Spitzer</i> and the lines of heavy elements observed in their atmospheres with high-resolution spe...

Descripción completa

Guardado en:

Detalles Bibliográficos
Autores principales:	Deal, M., Deheuvels, S., Vauclair, G., Vauclair, S., Wachlin, Felipe Carlos
Formato:	Articulo Comunicacion
Lenguaje:	Inglés
Publicado:	2013
Materias:	Ciencias Astronómicas Accretion accretion disks Convection Diffusion Hydrodynamics Planetary systems White dwarfs
Acceso en línea:	http://sedici.unlp.edu.ar/handle/10915/85482
Aporte de:	SEDICI (UNLP) de Universidad Nacional de La Plata

id	I19-R120-10915-85482
record_format	dspace
institution	Universidad Nacional de La Plata
institution_str	I-19
repository_str	R-120
collection	SEDICI (UNLP)
language	Inglés
topic	Ciencias Astronómicas Accretion accretion disks Convection Diffusion Hydrodynamics Planetary systems White dwarfs
spellingShingle	Ciencias Astronómicas Accretion accretion disks Convection Diffusion Hydrodynamics Planetary systems White dwarfs Deal, M. Deheuvels, S. Vauclair, G. Vauclair, S. Wachlin, Felipe Carlos Accretion from debris disks onto white dwarfs : Fingering (thermohaline) instability and derived accretion rates
topic_facet	Ciencias Astronómicas Accretion accretion disks Convection Diffusion Hydrodynamics Planetary systems White dwarfs
description	Context. Recent observations of a large number of DA and DB white dwarfs show evidence of debris disks, which are the remnants of old planetary systems. The infrared excess detected with <i>Spitzer</i> and the lines of heavy elements observed in their atmospheres with high-resolution spectroscopy converge on the idea that planetary material accretes onto these stars. Accretion rates have been derived by several authors with the assumption of a steady state between accretion and gravitational settling. The results are unrealistically different for DA and DB white dwarfs. Aims. When heavy matter is accreted onto stars, it induces an inverse μ-gradient that leads to fingering (thermohaline) convection. The aim of this letter is to study the impact of this specific process on the derived accretion rates in white dwarfs and on the difference between DA and DB. Methods. We solve the diffusion equation for the accreted heavy elements with a time-dependent method. The models we use have been obtained both with the IRAP code, which computes static models, and the La Plata code, which computes evolutionary sequences. Computations with pure gravitational settling are compared with computations that include fingering convection. Results. The most important result is that fingering convection has very important effects on DAs but is inefficient in DBs. When only gravitational settling is taken into account, the time-dependent computations lead to a steady state, as postulated by previous authors. When fingering convection is added, this steady state occurs much later. Conclusions. The surprising difference found in the past for the accretion rates derived for DA and DB white dwarfs disappears. The derived accretion rates for DAs are increased when fingering convection is taken into account, whereas those for DBs are not modified. More precise and developed results will be given in a forthcoming paper.
format	Articulo Comunicacion
author	Deal, M. Deheuvels, S. Vauclair, G. Vauclair, S. Wachlin, Felipe Carlos
author_facet	Deal, M. Deheuvels, S. Vauclair, G. Vauclair, S. Wachlin, Felipe Carlos
author_sort	Deal, M.
title	Accretion from debris disks onto white dwarfs : Fingering (thermohaline) instability and derived accretion rates
title_short	Accretion from debris disks onto white dwarfs : Fingering (thermohaline) instability and derived accretion rates
title_full	Accretion from debris disks onto white dwarfs : Fingering (thermohaline) instability and derived accretion rates
title_fullStr	Accretion from debris disks onto white dwarfs : Fingering (thermohaline) instability and derived accretion rates
title_full_unstemmed	Accretion from debris disks onto white dwarfs : Fingering (thermohaline) instability and derived accretion rates
title_sort	accretion from debris disks onto white dwarfs : fingering (thermohaline) instability and derived accretion rates
publishDate	2013
url	http://sedici.unlp.edu.ar/handle/10915/85482
work_keys_str_mv	AT dealm accretionfromdebrisdisksontowhitedwarfsfingeringthermohalineinstabilityandderivedaccretionrates AT deheuvelss accretionfromdebrisdisksontowhitedwarfsfingeringthermohalineinstabilityandderivedaccretionrates AT vauclairg accretionfromdebrisdisksontowhitedwarfsfingeringthermohalineinstabilityandderivedaccretionrates AT vauclairs accretionfromdebrisdisksontowhitedwarfsfingeringthermohalineinstabilityandderivedaccretionrates AT wachlinfelipecarlos accretionfromdebrisdisksontowhitedwarfsfingeringthermohalineinstabilityandderivedaccretionrates
bdutipo_str	Repositorios
_version_	1764820489441640448

Accretion from debris disks onto white dwarfs : Fingering (thermohaline) instability and derived accretion rates

Ejemplares similares