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unbind - find unbound stars to a stellar system


unbind in=snapshot_in out=snapshot_out [parameter=value]


unbind tries to find stars that are unbound to a stellar system. It simply calculates the binding energy (per unit mass) and flags the stars for which this is larger than a specified cutoff energy (ecutoff) are flagged as ’escaped’. The program outputs the stars which are either bound or unbind to the system.

The Key field (an integer) in the snapshot(5NEMO) data is also copied accordingly; when it is not present it will be initialized to the order of particles present in the input file, 0 being the first one, and nbody-1 the last one.


The following parameters are recognized in order; they may be given in any order if the keyword is also given. Use --help to confirm this man page is up to date.
input file, in snapshot(5NEMO) format. If potentials are not present in the snapshot, an (expansive) exact N-squared energy calculation is forced. [no default]
output file, in snapshot(5NEMO) format, containing the masses and phasespace coordinates of the (un)bound particles [no default].
Logical determining if you want force an exact N-squared calculation, in case potentials were found to be present in the snapshot [default: f].
Softening parameter used in energy calculations in case an exact N-squared energy calculation is done. [default: 0.025]
Cutoff of binding energy (per unit mass), above which the stars will be removed from the snapshot [default: 0].
Logical determining if the bound (t) or unbound (f) stars should be written to file [default: t, i.e. bound stars are written to file].
Logical determining if you want a map displayed by star number of the stars bound and unbound to the system. This is handy to compare maps of the same system under slightly different conditions.
Which times to process, by default all.


In a multi-time snapshot series when stars around unbound, some programs only allocate space for a snapshot in the beginning, thus if there are snapshots with more particles than in the first one, the program may crash.

See Also

snapmask(1NEMO) , skid(1TIPSY)


Peter Teuben


~/src/pjt/nbody       unbind.c unbind.1

Update History

12-Nov-87    V1.0 created              Peter Teuben
15-Nov-87    V1.2 cutoff and output added     PJT
19-nov-87    V1.3 bind keyword added    PJT
9-Mar-88    V1.4 memory allocation better    PJT
xx-apr-88    V1.6 added map option PJT
6-jun-88    V1.7 new filestruct - keywords changed    PJT
24-oct-88    V1.8 added Key copy    PJT

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