[Mesa-users] Nonphysical behavior of outermost envelope of rapidly rotating stars
Larry Molnar
lmolnar at calvin.edu
Mon Jul 27 16:14:36 EDT 2020
Hi Pablo,
I have run some more cases for M = 1 solar mass to show more precisely the strange behavior.
1. I am now saving out every profile so the plots are not choppy.
2. I used smaller steps in Omega/Omega_crit initial to show the suddenness of the onset of the behavior.
3. I redid one case using the wind controls you suggested.
I attach the inlist used for the final case. M10RotExampleA.txt contains the controls used to make the nonrotating ZAMS model from which the other models start. M10RotExampleB.txt contains the controls for the main sequence evolution for a specific initial value of Omega/Omega_crit.
I attach three plots to show the behavior.
1. HighRes_HR.png: shows initial rotation ratios of 0.39, 0.40, and 0.41 differ from each other marginally while 0.42 makes a large excursion. The case labeled 0.421 is actually 0.420 again but with the wind controls turned on. These do not seem to have changed the output at all.
2. HighRes_L-age.png: shows the luminosity with age is very similar in all cases, a sign that only the outermost layer participates in the excursion.
3. HighRes_OmegaOmegaC-age.png: shows the rotation ratios at the photosphere with age. The last case not to make the excursion is OmRat_intial = 0.41. It has a maximum value of OmRat = 0.678, which is nowhere near the breakup value.
In summary, this nonlinear behavior during main sequence hydrogen burning for an intermediate rotation rate seems to me very unexpected, although I can't say what exactly is going wrong. It is far enough from breakup rotation that details of the wind do not seem relevant (which is consistent with the lack of change when those parameters are turned on). This also seems to contradict the results given by earlier versions of MESA (as seen, for example, in the HR tracks of Gossage et al. (2018, ApJ, 863, 67). Their Figure 1 (lower left corner) shows cases for OmRat_inital = 0.50 with normal behavior.
Any additional thoughts would be appreciated.
Larry
From: Larry Molnar <lmolnar at calvin.edu>
Sent: Saturday, July 25, 2020 2:56 PM
To: Pablo Marchant <pamarca at gmail.com>
Cc: mesa-users at lists.mesastar.org
Subject: Re: [Mesa-users] Nonphysical behavior of outermost envelope of rapidly rotating stars
Hi Pablo,
I did include the inlists. (They were renamed as .txt files for convenience on a Windows machine.)
I was aware of the default w_div_wcrit_max = 0.9d0, but the problem set in at the smaller value of 0.7, so it was not clear that this flag should be active.
Not every step is being output.
Larry
________________________________
From: Pablo Marchant <pamarca at gmail.com>
Sent: Saturday, July 25, 2020 3:02 AM
To: Larry Molnar <lmolnar at calvin.edu>
Cc: mesa-users at lists.mesastar.org <mesa-users at lists.mesastar.org>
Subject: Re: [Mesa-users] Nonphysical behavior of outermost envelope of rapidly rotating stars
Hi Larry,
it's usually best if you include your inlists as well. Note that although the fits are good up to Omega_Psi/Omega_cri~0.999, there's still a cap on the rotational corrections that by default is set lower than this, with the option
w_div_wcrit_max = 0.9d0
essentially all values that are a function of w are capped to this. This is just an inherent necessity from the explicit calculation of these corrections.
Now, given this cap a model can go past Omega_Psi/Omega_cri=1 because the centrifugal forces are capped in this way. The workaround we have for this is an implicit method to boost wind strength when approaching critical, that boosts it just enough so that the star remains at the edge. The test case high_rot_darkening does this, and you can turn it on with the set of options
! implicit wind scheme when critical rotation is reached
max_mdot_redo_cnt = 200
min_years_dt_for_redo_mdot = 1d-5
surf_w_div_w_crit_limit = 0.99d0
surf_w_div_w_crit_tol = 0.01d0
rotational_mdot_boost_fac = 1d10
rotational_mdot_kh_fac = 1d10
mdot_revise_factor = 1.1
implicit_mdot_boost = 0.1
in your controls. This will boost the wind in such a way the star remains at omega/omega_c<0.99.
And just a last comment, I don't know if you're outputting every step in your simulations, but your tracks look a bit choppy before the craziness ensues. This could be a sign of poor timestep resolution.
Cheers
On Fri, Jul 24, 2020 at 10:34 PM Larry Molnar <lmolnar at calvin.edu<mailto:lmolnar at calvin.edu>> wrote:
I am running the latest MESA based on the revisions described in Paxton et al. (2019): MESA R12778, SDK 20.3.2, on a Linux operating system.
I am interested in rotation of main sequence stars with intermediate mass. With the improved estimates of geometrical factors, the ratio OmRat = Omega_Psi/Omega_crit should be accurate up to 0.999. However, when we ran simple test cases with rotation turned on near ZAMS, we found spurious excursions in the H-R diagrams for OmRat_initial >= 0.4. I attach a pair of inlist files we used to get to ZAMS and then to turn on rotation from that point. We ran cases with initial mass of 1.0 and 2.0 Msun and with a range of OmRat_initial up to 0.6. I attach HR diagrams for each mass showing a set of curves for different initial OmRat. I also attach plots of luminosity vs age and OmRat of the photosphere vs. age for each mass.
For the initial mass = 2 solar masses case, the excursion in the H-R diagram occurs for initial values of OmRat > 0.4. The excursions begin at the end of hydrogen burning in the convective core, a time when the OmRat should jump up slightly. However, in the misbehaving cases OmRat jumps above unity to nonphysical values. The stellar luminosities remain normal with time, though. So it seems the only part of the stellar structure that is wacky is the outermost envelope. Once the star begins to go up the giant branch, everything is normal again.
For the initial mass = 1 solar masses case, a similar set of excursions occurs although the trigger is slightly different. There is no convective core to stop burning. The trigger instead is when the OmRat reaches ~0.7. As before, everything returns to normal again once the star begins to go up the giant branch. I include a table of values below for the case M_init = 1.0 and OmRat_init = 0.5. The errant behavior is in profile numbers 7-26.
Any ideas on what is going on in the code (or if there is something different I should do in the control file) are welcome.
Larry Molnar
Profile
age
R1
Temp.
Lum.
OmRat
#
y
Rsun
K
Lsun
0
3.98E+07
0.9203
5239
5.73E-01
0.54
1
4.47E+07
0.9339
5250
5.95E-01
0.5476
2
8.26E+07
0.9425
5252
6.07E-01
0.5534
3
3.17E+08
0.9561
5260
6.29E-01
0.5674
4
1.55E+09
0.987
5268
6.74E-01
0.5929
5
3.14E+09
1.0363
5257
7.37E-01
0.6347
6
4.60E+09
1.1119
5188
8.05E-01
0.7127
7
5.13E+09
1.5238
4457
8.23E-01
1.1583
8
5.28E+09
1.5776
4394
8.34E-01
1.2469
9
5.84E+09
1.6156
4386
8.68E-01
1.2807
10
6.12E+09
1.6364
4381
8.87E-01
1.2986
11
7.48E+09
1.7523
4350
9.88E-01
1.3919
12
8.72E+09
1.8746
4320
1.10E+00
1.4736
13
9.78E+09
1.9916
4293
1.21E+00
1.5268
14
1.03E+10
2.0571
4281
1.28E+00
1.5483
15
1.07E+10
2.1132
4271
1.34E+00
1.5672
16
1.10E+10
2.1657
4261
1.39E+00
1.5817
17
1.13E+10
2.2148
4252
1.44E+00
1.5912
18
1.15E+10
2.2598
4244
1.49E+00
1.5959
19
1.17E+10
2.3052
4236
1.54E+00
1.596
20
1.19E+10
2.3419
4229
1.58E+00
1.5928
21
1.20E+10
2.3749
4223
1.61E+00
1.5869
22
1.22E+10
2.4125
4217
1.65E+00
1.5767
23
1.27E+10
2.5281
4196
1.78E+00
1.5202
24
1.30E+10
2.6287
4181
1.90E+00
1.3909
25
1.33E+10
2.6598
4185
1.95E+00
1.1868
26
1.34E+10
2.6092
4218
1.94E+00
0.982
27
1.35E+10
1.8622
5089
2.09E+00
0.5952
28
1.35E+10
1.7896
5179
2.07E+00
0.5577
29
1.36E+10
1.7977
5175
2.08E+00
0.4921
30
1.37E+10
1.8189
5146
2.08E+00
0.4188
31
1.38E+10
1.8553
5096
2.09E+00
0.3655
32
1.38E+10
1.9031
5045
2.11E+00
0.3262
33
1.39E+10
1.9607
4999
2.16E+00
0.297
34
1.39E+10
2.028
4962
2.24E+00
0.275
35
1.40E+10
2.1052
4933
2.36E+00
0.2575
36
1.40E+10
2.1921
4910
2.51E+00
0.2431
37
1.40E+10
2.2873
4893
2.70E+00
0.2315
38
1.41E+10
2.3882
4881
2.91E+00
0.2223
39
1.41E+10
2.4941
4873
3.15E+00
0.2147
40
1.42E+10
2.6087
4865
3.42E+00
0.2078
41
1.42E+10
2.7251
4858
3.72E+00
0.202
42
1.42E+10
2.846
4851
4.03E+00
0.1968
43
1.42E+10
2.9752
4844
4.38E+00
0.192
44
1.43E+10
3.0965
4839
4.72E+00
0.1882
45
1.43E+10
3.2259
4832
5.10E+00
0.1843
46
1.43E+10
3.3599
4825
5.50E+00
0.1807
47
1.43E+10
3.4945
4817
5.91E+00
0.1775
48
1.44E+10
3.6267
4810
6.33E+00
0.1745
49
1.44E+10
3.7604
4803
6.76E+00
0.1717
50
1.44E+10
3.897
4795
7.21E+00
0.1691
51
1.44E+10
4.0306
4788
7.67E+00
0.1666
52
1.44E+10
4.1611
4780
8.12E+00
0.1644
53
1.44E+10
4.2913
4773
8.59E+00
0.1624
54
1.44E+10
4.4265
4765
9.08E+00
0.1603
55
1.44E+10
4.562
4757
9.58E+00
0.1584
56
1.44E+10
4.6921
4749
1.01E+01
0.1567
57
1.45E+10
4.8267
4742
1.06E+01
0.1549
58
1.45E+10
4.9623
4734
1.11E+01
0.1532
59
1.45E+10
5.0033
4731
1.13E+01
0.1528
Prof. Larry Molnar
Department of Physics and Astronomy
Calvin University
1734 Knollcrest Circle SE
Grand Rapids, MI 49546-4403 USA
E-mail: lmolnar at calvin.edu<mailto:lmolnar at calvin.edu>
Phone: 616-526-6341
_______________________________________________
mesa-users at lists.mesastar.org<mailto:mesa-users at lists.mesastar.org>
https://lists.mesastar.org/mailman/listinfo/mesa-users<https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.mesastar.org_mailman_listinfo_mesa-2Dusers&d=DwMFaQ&c=4rZ6NPIETe-LE5i2KBR4rw&r=rohBEfdOjnrgwB12cgkmE-lSVHI5uTtNMjZ7eHCNBFw&m=TcV9zvWM_qhAe3cKy0vLoh10y3Q8TnJfqy2u4UVgI4w&s=aopYUxFCI8sZ1wKbWCljf4UKIV4oAPGoa0z8dZIwdGk&e=>
--
Pablo Marchant Campos
M.Sc on Astrophysics, Universidad Católica de Chile
PhD on Astrophysics, Argelander-Institut für Astronomie, Universität Bonn
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