[Mesa-users] Neutron star wind model: Tau Factor

Pero, Jason jsp5218 at mavs.uta.edu
Wed Oct 26 18:06:14 UTC 2022

Hello MESA users,

MESA version r22.05.1
inlists attached

I'm having trouble simulating the hydrodynamic phase of a neutron star x-ray burst. During the hydrostatic rise the tau_factor is set to a value similar to what is in the ns_he test suite:

set_initial_tau_factor = .true.
set_to_this_tau_factor = 100

During the wind phase I switch from the hydrostatic to the hydrodynamic solver at which time a change the tau_factor to capture regions closer to the photosphere:

relax_initial_tau_factor = .true.
relax_tau_factor = .true.
relax_to_this_tau_factor = 1

Running the hydrodynamic phase then produces the following error:

stopping because of problems dt < min_timestep_limit

 failed in relax tau factor

 star_relax_tau_factor ierr          -1

I've tried different tau factors ranging from 1-99 and still no luck. Based on the debug information it looks like there is an issue with the density becoming unrealistic. I then tried adjusting the control options "min_timestep_limit" and "hydro_mtx_max_allowed_logRho", but still can't get the model to relax to the new tau factor.

Any help/advice would be greatly appreciated.

Jason Pero

Graduate Research Assistant

University of Texas at Arlington​
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