[Mesa-users] Using make_o_ne_wd to prepare some white dwarf models
LAM Yi Hua
lamyihua at gmail.com
Sat Jul 21 07:44:34 EDT 2018
Dear MESA community,
Recently, I'd like to test some reactions associated with nova outbursts
using MESA-r10398 and MESA-sdk (revision 245). [Hopefully, older MESA-sdk
version won't affect the simulation.] So, most probably, the suitable white
dwarf (WD) model for testing the reactions should be ONe WD, but not CO WD.
I have some questions to ask the community.
FIRST step:
I used the "make_o_ne_wd" test_suite to prepare some simple white dwarf
models.
For the first test, the simulation of this default model stopped at
model 592
termination code: xa_central_upper_limit
Then, I commented these two lines in the &star_job of inlist_make_o_ne_wd
file:
! xa_central_upper_limit_species(1) = 'ne20'
! xa_central_upper_limit(1) = 0.35d0
I ran the simulation again, but it stopped at
model 840
stopping because of problems -- too many retries
terminated evolution: nonzero_ierr
termination code: max_number_retries
Perhaps, someone can identify the problem.
Anyway, it is not a big deal. Although the HR diagram shown in Figure 1 of
make_o_ne_wd/docs/make_o_ne_wd.pdf could not be reproduced, at least I can
confirm that my installation is successful, and a partial HR diagram was
produced from log Teff=3.9 up to 5.5 and log L/Ldot = 3.7 up to 4.5. Also,
I do not think the problem is due to older MESA-SDK version. After that, I
tested the make_o_ne_wd test_suite of MESA-r8118 with MESA-sdk (revision
245). This simulation ran successfully until it terminated with
log_L_lower_limit. The produced HR diagram make_o_ne_wd (MESA-r8118) is not
exactly the same as the partial HR diagram of MESA-r10398, in particular
there is a kink from Teff=3.9 to 4.2 in the HR diagram of make_o_ne_wd of
MESA-r8118 during the post-AGB stage. In fact, the HR diagram shown in
Figure 1 of make_o_ne_wd.pdf also has that kink.
As long as we can still produce a WD model eventually, shall we change some
settings to eliminate/reduce such kink? [Question 1]
Both HR paths produced from MESA-r10398 and MESA-r8118 show some
oscillation at the end of post-AGB stage, around Teff=5.1 to 5.4 and log
L/Ldot = 4 to 4.4. If we can still produce a WD model eventually, shall we
change some settings to eliminate/reduce such oscillation? [Question 2]
SECOND step:
I extend the list of isotopes and reactions stated in co_burn_plus.net which
is used by make_o_ne_wd. The newly extended list includes 78 isotopes (from
1H up to 40Ca) and associated 480 reactions. These 78 isotopes were also
included by Politano et al. (1995) and Weiss et al. (1990). Also, I made a
few changes to inlist_make_o_ne_wd:
**************************************************************
&star_job
eosDT_use_linear_interp_for_X = .true. < This flag does not exist in MESA-r
8118. I compare results produced by MESA-r10398 with and without this flag.
< I found that implementing this
linear interpretation increases mass loss.
< However, if I switch it to be
.true. for initiall mass 9.5 Mdot, it causes the problem of dt <
min_timestep_limit=1d-20 at model 1070.
< Perhaps, this is not the reason
causing the problem of dt < min_timestep_limit .
< There is no problem for
initial_mass=9.8 or 9.7. Maybe, there are some settings associated with the
change of initial mass.
! change_D_omega_flag = .true. < These flags do not exist in MESA-r
8118. I switch off these flags because they do not smoothen the post-AGB HR
path.
! new_D_omega_flag = .true. < Bill Paxton said he is
"experimenting a new scheme to reduce the noise in the rotational mixing
diffusion coefficients
< by doing spatial and temporal
smoothing."
< The default flags are .false.
&controls
max_number_retries = 500 < I increased it for
more attempts solving the hydro-Newton equation before termination.
max_model_number = 6000 <
! xa_central_upper_limit_species(1) = 'ne20' < I switched off these
two flags due to reason mentioned above.
! xa_central_upper_limit(1) = 0.35d0 <
min_timestep_limit=1d-20 <
log_L_lower_limit = 0 <
**************************************************************
I did not apply any "stellar engineering" (trick) during mass loss at
end-AGB stage when star mass drops from 10 Mdot to 5.5 Mdot.
With defining initial_mass= 10, the simulation stops at log_L_lower_limit =
0 and eventually, the star becomes a white dwarf with 16O and 20Ne rich
core, and log_cntr_T=8.08 (center temperature). The mass fraction of 16O is
0.545 from 0 to 1.195 Mdot, whereas the mass fraction of 12C is about 0.427
at the mass coordinate of 1.195 Mdot and drops to around 0.010 at the mass
coordinate of 1.175 Mdot. I suppose the small mass region with high
fraction of 12C is the so-called C-rich buffer zone separating the bottom
of the convective envelope from the WD surface according to some
literatures.
If I am not mistaken, to further cool the WD and to make a naked WD, we
need to remove this buffer zone first, otherwise the code cannot proceed
due to unresolved hydro-Newton equation causing termination of dt <
min_timestep_limit=1d-20. I did try to cool the WD (restart the simulation)
after the stage of log_L_lower_limit = 0 and log_cntr_T=8.08 (center
temperature). But it does not work, it keeps stopping with limit of dt <
min_timestep_limit=1d-20, even I tried to change some settings.
I think, to proceed the cooling of a WD to the desired temperature,
artificially
removing this buffer zone will be more effective than changing various
settings of simulation.
To do so, do we just simply change the mass fractions of 12C and other
isotopes in the freshly saved *.mod and *.data files to 0 after the
simulation stop? [Question 3]
Do we have to rescale the dq (fraction of total mstar in cell) column?
[Question
4]
And, how about other physical properties recorded in columns of lnd, lnT,
lnR, L, omega, etc. do we need to follow some procedure/method to change
them? [Question 5]
Besides, I did try with initial_mass=9.5d0, but the simulation stops at
model 1120 due to unresolved hydro-Newton equation and finally it reached
dt < min_timestep_limit=1d-20. There is no problem to set
initial_mass=9.8d0. Perhaps, there are some settings directly related to
the change of initial star mass. May I know the best way to overcome this
problem? [Question 6]
If we would like to use the default EOS and opacity defined in Paxton et al
MESA-steering paper [Astrophys. J. Suppl. 192 (2011) 3], do we set the EOS
and opacity as what are defined in the default inlist of make_o_ne_wd as
below? [Question 7]
eos_file_prefix = 'mesa'
kappa_file_prefix = 'gs98'
If this is not the correct way, may I know how to define the default EOS
and opacity? [Question 8]
If I am not mistaken, the default reaction library of MESA-r10398 is JINA
REACLIB, do we still need to include these few lines below in inlist
file? [Question
9]
set_rates_preference = .true.
new_rates_preference = 2
set_rate_c12ag = 'jina reaclib'
set_rate_n14pg = 'jina reaclib'
set_rate_3a = 'jina reaclib'
May I know the best option for the below reactions associated with 12C?
[Question 10]
Is there anyone would like to share her/his experience?
! + `'CF88_basic_1212'` : the single rate approximation from CF88.
! + `'CF88_multi_1212'` : combines the rates for the n, p, and a
channels.
! c12(c12,n)mg23, c12(c12,p)na23, and c12(c12,a)ne20 and
! uses neutron branching from dayras, switkowski, and woosley,
1976.
! + `'G05'` : based on Gasques, et al. Phys Review C, 72, 025806
(2005)
set_rate_1212 = ''
Thanks for your precious time...
Your responses are very appreciated...
best regards,
Yi Hua
LAM
-- CaTCh EVEry SiNGle OppORtuNItY WhEN U r StILl alIVe --
---- Success Belonged To Those Who's Willing To Strive For It ----
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