Re: [mesa-users] Bug in edot mechanism in binary module

[Glenn-Michael O. <gle...@ku...>]

Hi Mesa,


A reminder that this has not yet been fixed.


So users that use the binary module and are simulating eccentric orbits with the effect of tides included should be careful for this issue.


Best regards,

Glenn-Michael Oomen

________________________________
Van: Glenn-Michael Oomen
Verzonden: dinsdag 21 maart 2017 17:56
Aan: mes...@li...
Onderwerp: Bug in edot mechanism in binary module


Dear developers,


I would like to report on a bug in the binary_edot file. It concerns the tidal mechanism from Hut (1981).


In line 129 in the code, there is multiplied by pow_cr(1-b% eccentricity**2,6.5d0) instead of divided by it, which has huge implications once the eccentricity becomes large (suppose your eccentricity is 0.9, this results in a discrepancy of almost 10 orders of magnitude!).


So basically in binary_edot.f90, line 128-129:


edot_tidal = -27.0d0*qratio*(1+qratio)*pow8(r_phot/osep) &
            * b% eccentricity*pow_cr(1-b% eccentricity**2,6.5d0)*b% Ftid_1

should be

edot_tidal = -27.0d0*qratio*(1+qratio)*pow8(r_phot/osep) &
            * b% eccentricity*pow_cr(1-b% eccentricity**2,-6.5d0)*b% Ftid_1

as it is given in Eq. 10 of Hut (1981).

Cheers,
Glenn-Michael Oomen