2008A&A...483..231L


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.13CEST22:28:22

2008A&A...483..231L - Astronomy and Astrophysics, volume 483, 231-237 (2008/5-3)

Low heat conduction in white dwarf boundary layers?

LIU F.K., MEYER F., MEYER-HOFMEISTER E. and BURWITZ V.

Abstract (from CDS):

X-ray spectra of dwarf novae in quiescence observed by Chandra and XMM-Newton provide new information on the boundary layers of their accreting white dwarfs. Comparison of observations and models allows us to extract estimates for the thermal conductivity in the accretion layer and reach conclusions on the relevant physical processes. We calculate the structure of the dense thermal boundary layer that forms under gravity and cooling at the white dwarf surface on accretion of gas from a hot tenuous ADAF-type coronal inflow. The distribution of density and temperature obtained allows us to calculate the strength and spectrum of the emitted X-ray radiation. They depend strongly on the values of thermal conductivity and mass accretion rate. We apply our model to the dwarf nova system VW Hyi and compare the spectra predicted for different values of the thermal conductivity with the observed spectrum. We find a significant deviation for all values of thermal conductivity that are a sizable fraction of the Spitzer conductivity. A good fit arises however for a conductivity of about 1% of the Spitzer value. This also seems to hold for other dwarf nova systems in quiescence. We compare this result with thermal conduction in other astrophysical situations. The highly reduced thermal conductivity in the boundary layer requires magnetic fields perpendicular to the temperature gradient. Locating their origin in the accretion of magnetic fields from the hot ADAF-type coronal flow we find that dynamical effects of these fields will lead to a spatially intermittent, localized accretion geometry at the white dwarf surface.

Abstract Copyright:

Journal keyword(s): stars: dwarf novae - accretion, accretion disks - X-rays: individual: VW Hyi - conduction - magnetic fields - galaxies: cooling flows

Simbad objects: 11

goto Full paper

goto View the reference in ADS

Number of rows : 11

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 V* WX Hyi DN* 02 09 50.8239743875 -63 18 39.830688329   10.70     13.038 ~ 192 0
2 V* VW Hyi DN* 04 09 11.3966476826 -71 17 41.555169342   12.00 12.30 14.16   ?+L0:e 613 0
3 V* U Gem DN* 07 55 05.2323858391 +22 00 05.045435077   15.3 14.54     DA 1046 0
4 V* EI UMa DN* 08 38 21.9952271575 +48 38 02.163591536   14.9 14.78     ~ 72 1
5 V* OY Car DN* 10 06 22.0792108747 -70 14 04.582997921           ~ 549 0
6 V* EX Hya DN* 12 52 24.2220533405 -29 14 56.001981146   13.51 13.49 13.55   M5-6V 647 0
7 ACO 2142 ClG 15 58 20.00 +27 14 00.3           ~ 672 0
8 V* V603 Aql No* 18 48 54.6369118792 +00 35 02.855110952 10.73 11.65 11.64     OB+e: 511 0
9 ACO 3667 ClG 20 12 33.68 -56 50 26.3           ~ 566 1
10 V* SS Cyg DN* 21 42 42.8034554117 +43 35 09.863763484 11.07 8.2 7.70     K5V 1211 1
11 NAME Galactic Ridge ? ~ ~           ~ 427 1

    Equat.    Gal    SGal    Ecl

To bookmark this query, right click on this link: simbad:objects in 2008A&A...483..231L and select 'bookmark this link' or equivalent in the popup menu


2020.07.13-22:28:22

© Université de Strasbourg/CNRS

    • Contact