Numerical simulations of surface convection in a late M-dwarf
(2002) In Astronomy & Astrophysics 395(1). p.99-115- Abstract
- Based on detailed 2D and 3D numerical radiation-hydrodynamics (RHD)simulations of time-dependent compressible convection, we have studiedthe dynamics and thermal structure of the convective surface layers of aprototypical late-type M-dwarf (T<SUB>eff</SUB>approx 2800 K, log g=5.0,solar chemical composition). The RHD models predict stellar granulationqualitatively similar to the familiar solar pattern. Quantitatively, thegranular cells show a convective turn-over time scale of ~100 s, and ahorizontal scale of 80 km; the relative intensity contrast of thegranular pattern amounts to 1.1%, and root-mean-square verticalvelocities reach 240 m s<SUP>-1</SUP> at maximum. Deviations fromradiative equilibrium in the higher,... (More)
- Based on detailed 2D and 3D numerical radiation-hydrodynamics (RHD)simulations of time-dependent compressible convection, we have studiedthe dynamics and thermal structure of the convective surface layers of aprototypical late-type M-dwarf (T<SUB>eff</SUB>approx 2800 K, log g=5.0,solar chemical composition). The RHD models predict stellar granulationqualitatively similar to the familiar solar pattern. Quantitatively, thegranular cells show a convective turn-over time scale of ~100 s, and ahorizontal scale of 80 km; the relative intensity contrast of thegranular pattern amounts to 1.1%, and root-mean-square verticalvelocities reach 240 m s<SUP>-1</SUP> at maximum. Deviations fromradiative equilibrium in the higher, formally convectively stableatmospheric layers are found to be insignificant allowing a reliablemodeling of the atmosphere with 1D standard model atmospheres. Amixing-length parameter of alpha<SUB>MLT = 2.1</SUB> provides the bestrepresentation of the average thermal structure of the RHD modelatmosphere while alternative values are found when fitting theasymptotic entropy encountered in deeper layers of the stellar envelope(alpha<SUB>MLT = 1.5</SUB>), or when matching the vertical velocity(alpha<SUB>MLT = 3.5</SUB>). The close correspondence between RHD andstandard model atmospheres implies that presently existing discrepanciesbetween observed and predicted stellar colors in the M-dwarf regimecannot be traced back to an inadequate treatment of convection in the 1Dstandard models. The RHD models predict a modest extension of theconvectively mixed region beyond the formal Schwarzschild stabilityboundary which provides hints for the distribution of dust grains incooler (brown dwarf) atmospheres. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/130322
- author
- Ludwig, Hans-Günter LU ; Allard, F. and Hauschildt, P. H.
- organization
- publishing date
- 2002
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- convection, hydrodynamics, radiative transfer, stars: atmospheres, stars: late-type
- in
- Astronomy & Astrophysics
- volume
- 395
- issue
- 1
- pages
- 99 - 115
- publisher
- EDP Sciences
- external identifiers
-
- wos:000179048000015
- scopus:0036851968
- ISSN
- 0004-6361
- DOI
- 10.1051/0004-6361:20021153
- language
- English
- LU publication?
- yes
- id
- 566e1efc-5822-406b-8af5-49867d5e5123 (old id 130322)
- date added to LUP
- 2016-04-01 16:51:12
- date last changed
- 2024-01-11 16:05:40
@article{566e1efc-5822-406b-8af5-49867d5e5123,
abstract = {{Based on detailed 2D and 3D numerical radiation-hydrodynamics (RHD)simulations of time-dependent compressible convection, we have studiedthe dynamics and thermal structure of the convective surface layers of aprototypical late-type M-dwarf (T<SUB>eff</SUB>approx 2800 K, log g=5.0,solar chemical composition). The RHD models predict stellar granulationqualitatively similar to the familiar solar pattern. Quantitatively, thegranular cells show a convective turn-over time scale of ~100 s, and ahorizontal scale of 80 km; the relative intensity contrast of thegranular pattern amounts to 1.1%, and root-mean-square verticalvelocities reach 240 m s<SUP>-1</SUP> at maximum. Deviations fromradiative equilibrium in the higher, formally convectively stableatmospheric layers are found to be insignificant allowing a reliablemodeling of the atmosphere with 1D standard model atmospheres. Amixing-length parameter of alpha<SUB>MLT = 2.1</SUB> provides the bestrepresentation of the average thermal structure of the RHD modelatmosphere while alternative values are found when fitting theasymptotic entropy encountered in deeper layers of the stellar envelope(alpha<SUB>MLT = 1.5</SUB>), or when matching the vertical velocity(alpha<SUB>MLT = 3.5</SUB>). The close correspondence between RHD andstandard model atmospheres implies that presently existing discrepanciesbetween observed and predicted stellar colors in the M-dwarf regimecannot be traced back to an inadequate treatment of convection in the 1Dstandard models. The RHD models predict a modest extension of theconvectively mixed region beyond the formal Schwarzschild stabilityboundary which provides hints for the distribution of dust grains incooler (brown dwarf) atmospheres.}},
author = {{Ludwig, Hans-Günter and Allard, F. and Hauschildt, P. H.}},
issn = {{0004-6361}},
keywords = {{convection; hydrodynamics; radiative transfer; stars: atmospheres; stars: late-type}},
language = {{eng}},
number = {{1}},
pages = {{99--115}},
publisher = {{EDP Sciences}},
series = {{Astronomy & Astrophysics}},
title = {{Numerical simulations of surface convection in a late M-dwarf}},
url = {{https://lup.lub.lu.se/search/files/4799637/624135.pdf}},
doi = {{10.1051/0004-6361:20021153}},
volume = {{395}},
year = {{2002}},
}