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Implicit mass accretion rate can be lareger than mass transfer rate #546

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ZepeiX opened this issue Jun 2, 2023 · 0 comments
Open

Implicit mass accretion rate can be lareger than mass transfer rate #546

ZepeiX opened this issue Jun 2, 2023 · 0 comments
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@ZepeiX
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ZepeiX commented Jun 2, 2023

Describe the bug
To avoid repeat calculations of the accretor's mdot, the implicit accretion rate is calculated only in the first iteration and then both explicit and implicit accretion rate will not be updated in the following redos. However, in each redo the mass transfer rate changes and it is possible that the mass transfer rate becomes smaller than the accretion rate.

In addition, in run_binary_support.f90, there are three conditional statements

if (j == b% a_i .and. b% num_tries >0 .and. s% was_in_implicit_wind_limit)
    cycle

where s% should be b% s_accretor% as it should point to the accretor rather than star 2.

To Reproduce
Use implicit method to calculate the accretion rate considering the angular momentum transport of the accreted material and the rotation of the star.
The input files to reproduce the issue is attached. A small modification in binary_mdot.f90 is for implementing reverse mass transfer with 'Kolb' scheme, see #545.
MESA version 11701.

Discussion
Currently, the implicit accretion rate is calculated based on the mass transfer rate at the first iteration. The following update of mass transfer rate alone with the update of the donor star are not affecting the accretion rate. Mostly, the impact is not significant, while in some cases, it is noticeable like the example here where the accretion rate becomes larger. However, as discussed in #507, calculating implicit mdot for the accretor every redo can increase the computational time.

Additional context
reproduce_implicit_issue.zip

@evbauer evbauer added the binary Binary module label Jun 2, 2023
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