Testing pulsational instabilities & beginner's questions

[xiaweiwang]

Dear all,

I'm trying to study the pulsational instabilities of ZAMS models. I'm very new to MESA and GYRE. So please forgive me for my naive questions!

1. I created ZAMS models with MESA and fed them to GYRE adiabatic code, but I got no modes for the l=0 case. The results shown in terminal is the following:

Root bracketing
Time elapsed : 1.176 s

Root Solving
l n_pg n_p n_g Re(omega) Im(omega) chi n_iter n
Time elapsed : 0.000 s
Root Solving
l n_pg n_p n_g Re(omega) Im(omega) chi n_iter n
Time elapsed : 0.000 s

However, the l=1,2,3... cases all worked out well. I wonder what was going on with adiabatic l=0? I have attached a particular model profile and in list.

m50_z0.04.data.GYRE

model

(511.37 KiB) Downloaded 237 times

gyre_nad.in

inlist

(1.76 KiB) Downloaded 169 times

2. Could you please explain a bit about the physical intuition of the output parameters n_p, n_g and n_pg? Does l=0 correspond to the fundamental mode, l=1 to the 1st overtone and etc.?

3. I tried a dozen of ZAMS models (including some models with very high metallicity and mass), but none of them has imaginary omega. Is it possible at all to get some imaginary omegas with the adiabatic code?

4. Then I tried to calculate the non-adiabatic pulsation modes for ZAMS models. Sometimes GYRE says "too many iterations" after several steps even though I set n_iter_max = 1.0d5. What is the problem? Please see the attached file.

m60_z0.10.data.GYRE

model

(508.48 KiB) Downloaded 240 times

gyre_nad.in

inlist

(1.76 KiB) Downloaded 175 times

5. After running the non-adiabatic code, is it possible to tell if a star is made unstable by the pulsational instabilities?

Thank you very much for your time!

All my best,
Xiawei

[rhtownsend]

Hi Xiawei --

Lots of good questions here. Let me start with the first one:

Dear all,

I'm trying to study the pulsational instabilities of ZAMS models. I'm very new to MESA and GYRE. So please forgive me for my naive questions!

1. I created ZAMS models with MESA and fed them to GYRE adiabatic code, but I got no modes for the l=0 case. The results shown in terminal is the following:

Root bracketing
Time elapsed : 1.176 s

Root Solving
l n_pg n_p n_g Re(omega) Im(omega) chi n_iter n
Time elapsed : 0.000 s
Root Solving
l n_pg n_p n_g Re(omega) Im(omega) chi n_iter n
Time elapsed : 0.000 s

However, the l=1,2,3... cases all worked out well. I wonder what was going on with adiabatic l=0? I have attached a particular model profile and in list.

m50_z0.04.data.GYRE

gyre_nad.in

The problem here is the frequency range specified in your input file is too low -- radial modes are typically found at dimensionless frequencies above 1.

Try changing freq_min to 1 and freq_max to 10 -- that should yield radial modes.

cheers,

Rich

[xiaweiwang]

Hi Rich,

Thanks for the help! Now the l=0 modes are working.

Best,
Xiawei