[Chris Belczynski, Gijs Nelemans]

I) Outline: we will run the simple model including only binary stars, and we will try to compare several properties of formed compact object binaries.
This will serve as a test that we could do some work together and get coherent results.

Both the initial conditions and evolutionary prescriptions were set as to be easily met by all our codes.
If some things are not easily modified to meet requested criteria, please let me know ASAP: belczynski@northwestern.edu.

I will collect all your comments till end of February 2003, and than update this page, so we could all start the first run in March.

II) Initial Conditions

  1. 106 binaries at ZAMS
  2. Outburst Star Formation at time=0.0 Myr
  3. primary mass: M1 [ 5 -- 100 Msun ], IMF ~ -2.5
  4. secondary mass: M2 [ 0.5 -- M1 Msun ], drawn from flat q distribution (q:=M2 / M1)
  5. separation a: [ ZAMS+ZAMS in contact -- 106 Rsun ] drawn from distribution
    flat in logarithm ( ~ 1/a )
  6. all systems circular
  7. metallicity: solar ( Z=0.02 )

III) Evolutionary Prescriptions

  1. NS kicks drawn from single Gaussian with width=290 km s-1.
    No BH kicks.
  2. Wind mass loss prescriptions -- use standard values of your code
  3. Standard Common Envelope with: alpha * lambda =1.0
  4. Mass Transfers onto compact objects (WD/NS/BH) Eddington limited, rest of material is lost with specific angular momentum of the compact accretor.
  5. Other Mass Transfers treated non-conservatively: 50% of transferred material attached to companion, the remaining 50% lost from the system with specific angular momentum of the binary.
  6. Maximum NS mass: 3 Msun
  7. Calculation of NS / BH masses:

    if (MpreSN < 6.0 Msun) you form NS
    else you form BH

    Mns=1.4 Msun (rest of mass lost in SN)
    Mbh =0.65 MpreSN (rest of mass lost in SN)

    MpreSN -- presupernova mass of exploding star.
    (note that Mns does not depend on MpreSN)

    note: lower limit for NS formation as you have in your codes

  8. Helium stars do evolve: they experience radial expansion and may initiate MT events. We try to follow these MT episodes the best way we can with our codes (unless we see that the merger is unavoidable).
  9. tidal evolution: as we have it in our codes
  10. magnetic breaking: formalism of Rappaport, Verbunt, Joss 1983, ApJ 275, 713 (see eq.36; use gamma =2.0).

IV) Output

  1. numbers (not rates!) of:
    n1: all formed NS-NS systems
    n2: all formed BH-NS systems
    n3: all formed BH-BH systems

    n4: coalescing NS-NS systems
    n5: coalescing BH-NS systems
    n6: coalescing BH-BH systems

    note: "coalescing" means that the given system will merge within 15 Gyrs (counting since the binary was formed at ZAMS) i.e. if Tevol+Tmer<15 Gyrs system is coalescing, where Tevol -- is time since ZAMS to formation of compact object binary and Tmer -- time from the formation of compact object binary to final merger of two compact objects.

  2. all compact objects: distributions of periods, merger times, masses.

    please send me a single file, which will include:

    M1[Msun]   M2[Msun]   Period[day]   Tmer[Myr]

    for all formed NS-NS, BH-NS, BH-BH systems at the time of their formation (after second SN/core collapse event).

    M1,M2 -- masses of compacted objects
    Period -- orbital period
    Tmer -- merger time (since the formation of compact object binary to final merger of two compact objects).

  3. for systems that will eventually form compact object binaries,
    get orbital periods after the first SN/core collapse event:

    please send me a single file, which will include: