[Mesa-users] Is it possible to fake a he wd with an envelope?

[Josiah Schwab]

Hi Chen,

I didn't quite understand your email.  But in addition to what Evan said, I
would add that if you want to make a somewhat more realistic He WD, you are
probably better off doing something other that using make_he_wd.  That test
case takes a very "stellar engineering" approach to effectively make a very
low mass (0.15Msun) degenerate He ball and has no H envelope.

You could do a real NS + MS evolution (e.g.,
https://ui.adsabs.harvard.edu/abs/2016A%26A...595A..35I/abstract).  But as
an easier alternative, you can mock up the binary evolution.  For example,
take a 1Msun star at ZAMS and put it in a fixed-size "Roche lobe".   I
tried just tried that with the wind options

      rlo_scaling_factor = 1
      rlo_wind_roche_lobe_radius = 10d0
      rlo_wind_base_mdot = 1d-5
      rlo_wind_scale_height = 1d0

and after about 5000 steps (and a surface H flash or two) I had a 0.25-ish
Msun He WD with a 1e-3-ish Msun H layer.  You can fiddle with the mass by
either further relaxing that model, changing the Roche radius, etc.

Josiah
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