Numerical simulations of convection at the surface of a ZZ Ceti white dwarf

Details Numerical simulations of convection at the surface of a ZZ Ceti white dwarf Numerical simulations of convection at the surface of a ZZ Ceti white dwarf

Apr 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994a%26a...284..105l&link_type=abstract

Astronomy and Astrophysics (ISSN 0004-6361), vol. 284, no. 1, p. 105-117

Astronomy and Astrophysics

Astrophysics

70

Computerized Simulation, Convective Flow, Numerical Integration, Stellar Atmospheres, Stellar Models, Variable Stars, White Dwarf Stars, Equations Of State, Hydrodynamics, Mixing Length Flow Theory, Stellar Temperature

Scientific paper

We applied two-dimensional hydrodynamics and non-grey radiative transfer calculations to the surface layers of a hydrogen-rich white dwarf (spectral type DA) with Teff = 12600 K and log g = 8.0, corresponding to a position in the HR-diagram slightly cooler than the hot boundary of the ZZ Ceti instability strip. In our simulation the entire convection zone including the overshoot layers is embedded in the computational box so that we obtain a complete and detailed model of convection for this representative object. We address the important question to what extent models based on mixing length theory (MLT) are able to predict the physical properties of convection. We find a rapidly (timescale approximately equals 100 ms) evolving flow pattern with fast concentrated downdrafts surrounded by slow broad upflows of warmer material. Convection carries up to 30% of the total flux and excites internal gravity waves by dynamical processes associated with the merging of downdrafts. The mean entropy gradient is reversed with respect to MLT predictions in the deeper layers of the convection zone. Strong overshoot occurs at its upper and lower boundary. A synthetic spectrum calculated from the mean photospheric temperature stratification can be fitted satisfactorily with a MLT model adopting alpha = 1.5. At greater depth the temperature profile approaches a model with alpha = 4. The total depth of the convective layers is rather small compared to values suggested by studies of the excitation mechanism for the pulsations of DAs.

Affiliated with

Also associated with

No associations

Rating

Numerical simulations of convection at the surface of a ZZ Ceti white dwarf does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Numerical simulations of convection at the surface of a ZZ Ceti white dwarf, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Numerical simulations of convection at the surface of a ZZ Ceti white dwarf will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1254080