Nicky: grid based: ~200 grids of ? models

Stable MT:

• when stable?
  • Joke: if q<q_crit - monitor q and contact during MT
  • Ashley: For mass transfer – MT rate depends on binary parameters; system loses 50% for non-degenerate accretors, Eddington-limited for deg.don.

AM

• Nicki: L2
• Ashley: lost with specific ang. mom. of accretor (also stellar winds; Hurley or Vink)
• Joke: from accretor

<math>frac{dot{J}_mathrm{orb}}{J_mathrm{orb}} = eta frac{dot{M}_mathrm{d}}{M_mathrm{bin}}</math>

• A: <math>eta = frac{M_mathrm{d}}{M_mathrm{a}}</math>
• J: <math>eta = frac{M_mathrm{a}}{M_mathrm{d}}</math>
• N: η = 1.5
• S: η = 2.5

CE:

• no accretion
• Merger?
  • S: 5x R_wd (from WD model)
  • N: R_{mass coordinate, remnant}

Can a HMXB with RLOF and q~20 have stable MT?

• maybe: strong wind, beta=0?

Bondi-Hoyle accretion:

• A: only for BH/NS binaries
• J: always on, can have a big (and stabilising) effect on AGB
• S: no

• α, λ = 1

1: 30 days:

• only run that starts with stable mass transfer
• this run shows the largest range of differences:
  • most of them go back to the assumption for β and the related AM loss:
    • Ashley and Nicki assume β=0.5, Joke and Silvia have a variable β
    • Nicki loses mass through L2, which makes his orbit shrink dramatically in the first MT phase
    • Ashley loses mass with the AM of the accretor
  • Joke alone has wind accretion
  • Nicki's final masses are somewhat lower than those of the others

S: stable MT, C: CE

{| border=“1” ! ! Ashley ! Joke ! Nicki ! Silvia

! 1: 30 d

! 2: 150d

! 3: 500d

! 4: 1700d

! 5: 2000d

! 6: 10000d, a=3985

Homework:

• Check treatment of:
  • overshooting
  • mixing length
  • core definition
  • computation of τ_th, τ_nuc
  • wind mass loss
  • mixing during accretion

• Compute:
  • M_i-M_f relation
  • single-star evolution:
    • 1.5, 5.0, 7.5 Mo
    • get R, Mc, t, M, evolutionary phase

Final goals:

• paper showing:
  • all codes give the same answer when making the same assumptions
  • explain differences due to different stellar-evolution tracks
    • e.g. use masses where Mf-Mi is agreed upon
  • list/explain what different assumptions cause the differences

• single star
• conservation of MT, AM
• stability of MT; where stable/CE

• populations:

• conservative MT or CE
• α λ = 1
• no MB, tides, wind accretion, eccentricity…
• IMF: Kroupa (Kroupa Tout & Gilmore 1993):
• q: uniform: 0.1Mo/M1 - 1.0
• a: uniform: uniform in log a, 5-10^4 Ro
• whole population, after the formation of WD1 and WD2
• (initially scatter?)/grey scale plots

Same, but non-conservative with β=0.5, η=1.0