[Mesa-users] Where did the mass lost from M1 go?

[Levi]

Dear Ruggero, 
Thanks for your patient and detailed explanation of my problem. As you mentioned, the root cause was that M2 is always above critical rotation after mass transfer. I greatly appreciate your help to assist with resolving this doubt.
Thank you once again for your assistance.
Sincerely,
Levi
---- Replied Message ----
| From | Ruggero Valli<ruvalli at MPA-Garching.MPG.DE> |
| Date | 4/3/2023 16:01 |
| To | Levi<lileiixx at 163.com> |
| Cc | mesa-users at lists.mesastar.org<mesa-users at lists.mesastar.org> |
| Subject | Re: [Mesa-users] Where did the mass lost from M1 go? |

Dear Levi,

When mass transfer starts, the matter that flows from the donor to the accretor will carry some angular momentum (the amount is controlled by the flag do_jdot_accretion in binary_controls) and this will spin up the accretor very quickly. While this is happening the total mass of the system is conserved (if you neglect a small amount lost due to winds). Since you have set

mass_transfer_alpha = 0.0d0
mass_transfer_beta = 0.0d0
mass_transfer_delta = 0.0d0
mass_transfer_gamma = 0.0d0

in binary_controls, all the mass lost from the donor ends up on the accretor and spins it up. However, at some point, the surface of the accretor will reach a critical velocity, which is the keplerian orbital velocity at the radius of the star. In other words, the matter at the surface of the star feels a centrifugal force equal and opposite to the gravitational force. If the star were to spin a little bit faster, the matter at the surface would be flung away. But at the same time, the star is accreting new matter that is trying to make it spin faster. Physically it is not clear what would happen at this point. What MESA assumes, is that when the star is above critical rotation, it will shed mass through powerful winds until it goes back below critical rotation. The way this happens is controlled by

max_mdot_redo_cnt = 0
min_years_dt_for_redo_mdot = 0
surf_omega_div_omega_crit_limit = 0.99d0
surf_omega_div_omega_crit_tol = 0.05d0
mdot_revise_factor = 1.1d0
implicit_mdot_boost = 0.1d0

and have a look also at

mdot_omega_power = 0.43d0
max_rotational_mdot_boost = 1d4


in the controls inlist.

So, in practice, what is happening in your systems is that after a very brief moment of conservative mass transfer, the accretor reaches critical rotation and from that point on it basically stops accreting anymore. All the mass lost from the donor is lost from the system through winds from the surface of the accretor.


I hope this helps,

Ruggero





On 4/3/23 06:12, Levi via Mesa-users wrote:





| |
Levi
|
|
lileiixx at 163.com
|

Hello everyone,




I am a MESA (version 15140) user currently working with the double_BH test suite, which looks like coming from Marchant (2016). However, I am experiencing some difficulties and would greatly appreciate your assistance in resolving them.

I have evolved this binary system from ZAMS (with initial_period_in_days = 100), but when mass transfer started from M1, M2 could not continue evolving due to its rapid rotation speed, which caused the program to stop calculating. At this point, M1 has evolved to central hydrogen exhaustion (as shown in the attachment). I have noticed that the mass of the primary star (M1=30Msun) is decreasing significantly more than the secondary star (M2=28Msun) is increasing during the mass transfer process , and it appears that the system is not losing any mass. I am unsure of where the mass of the primary star is going. 




I am very concerned with this matter and would greatly appreciate any guidance or assistance that you could provide. Thank you so much for your help.

Some information in binary_history.data has been plotted and included in the attachment, as well as the plots of M1 and M2 at the end of the program. Please let me know if you require any further information from me.




Best regards,




Levi



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