[Mesa-users] Accounting for baryonic to gravitational mass conversion

[Farag, Ebraheem]

Hello Gianluca,

Find line ~ 591 in $MESA_DIR/binary/private/binary_mdot.f90. It should read:

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b% component_mdot(b% a_i) = (1 - b% mdot_edd_eta) * b% component_mdot(b% a_i)
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Insert a factor "b% xtra(1)":

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b% component_mdot(b% a_i) = b% xtra(1) *  (1 - b% mdot_edd_eta) * b% component_mdot(b% a_i)
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Then run:

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cd $MESA_DIR/binary
./mk
./export
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Now set the following in your binary controls inlist of your model:
xtra(1)  = 0.85d0

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Keep in mind xtra(1) defaults to 0d0, so with this factor in your inlist, you need to ensure it is set to 1d0 or 0.85d0, or else the factor will default to 0d0 and will zero out the radiation corrected transfer rate.

-EbF


________________________________
From: Mesa-users <mesa-users-bounces at lists.mesastar.org> on behalf of Gianluca Pagliaro <gianluca.pagliaro at aei.mpg.de>
Sent: Wednesday, July 9, 2025 1:08 PM
To: mesa-users at lists.mesastar.org <mesa-users at lists.mesastar.org>
Subject: [Mesa-users] Accounting for baryonic to gravitational mass conversion

Good evening,
in the context of a neutron star (point mass) accreting mass from a donor star, I would like to implement the baryonic to gravitational mass conversion for the neutron star.

I came across the ' use_radiation_corrected_transfer_rate ' flag, and I believe it's the best way to implement it. In the docs I read it works as follows:
delta_mass = (1-eta) * mass_transfer_rate * dt

where I believe eta the standard accretion efficiency: eta = 1 - alpha - beta - delta , as described in the MESA documentation.

In the simplistic assumption of a constant 15% baryonic mass being converted in gravitational binding energy, I would need to multiply the above equation by 0.85.
I see there's no hook for this function, so I wonder how can I do it.

Thank you,
Gianluca.

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