A package for simulating the evolution of dense stellar systems

Version : 3.6

Author(s) : Piet Hut (IAS), Steve McMillan (Drexel U.), Jun Makino
(U. Tokyo) Simon Portegies Zwart (U. of Amsterdam)

License : starlab

Website :
http://www.sns.ias.edu/~starlab/starlab.html

Disk space required for installation is 3.07 Mb

After the package is installed it can be accessed using the command

/opt/lfa/startstarlab

A shortcut will be installed in the KDE/GNOME desktop menu system,

as an entry in the Astronomy submenu

stellar systems, and analyzing the resultant data. It is a collection

of loosely coupled programs, linked at the level of the UNIX operating

system, that share a common data structure, and can be combined in

arbitrarily complex ways to study the dynamics of star clusters and

galactic nuclei. Current improvements in both the quality and the

quantity of observational data, together with ongoing and anticipated

increases in available computational power, combine to make this

project both necessary and feasible.

All stellar-dynamical $N$-body simulations rely on sophisticated

integration schemes to follow the motion of all particles in the

system under study. It is the job of the $N$-body program to deliver

a faithful representation of the dynamical evolution of the system,

along with information on all stellar interactions of interest, to the

user, subject only to the fundamental limitations imposed by the

chaotic equations of motion and the laws of physics. It is becoming

increasingly clear that, in order to make detailed comparisons between

simulations and the high-quality data now available, $N$-body (and

perhaps also detailed Monte-Carlo) simulations are really the only

viable option.

Performing $N$-body simulations is already is a complex and demanding

task. However, generating data is only half the job. The other half

of the work of a computational theorist parallels that of the

observer, and lies in the job of data reduction. As in the

observational case, a good set of tools is essential, and unless the

tools can be used in a flexible and coherent software environment,

their usefulness will be severely limited. Three requirements are

central in handling the data flow from a full-scale globular cluster

simulation: modularity, flexibility, and compatibility. Starlab

incorporates these three requirements.

To some extent, Starlab is modeled on NEMO, a stellar dynamics

software environment developed six years ago at the Institute for

Advanced Study, in large part by Josh Barnes, with input from Peter

Teuben and Piet Hut (and subsequently maintained and extended by Peter

Teuben). Starlab differs from NEMO mainly in the following areas: it

emphasizes the use of UNIX pipes, rather than temporary files; its use

of tree structures rather than arrays to represent $N$-body systems;

and its guarantee of data conservation---data which are not understood

by a given module are simply passed on rather than filtered out.

How to perform specific common tasks using Starlab tools.

--------------------------------------------------------

Note: Most tools are just simple interfaces onto the corresponding

library functions, so the tasks listed below could in principle

also be carried out by compiled programs rather than by

pipes. However, the use of pipes is in many ways clearer and

much more flexible.

For more information on Starlab tools, see the file TOOLS in

this directory. For details on a specific tool, type

tool-name --help

* Create a linked list of 100 equal-mass nodes of unit total mass

mknode -n 100 -m 1

* Create a system of 100 nodes with a Salpeter mass spectrum with masses

in the range 0.5 to 10

mknode -n 100 | mkmass -f 1 -x -2.35 -l 0.5 -u 10

* Create a system of 100 nodes with a mass spectrum and evolve the

stars without dynamics

mknode -n 100 | mkmass -f 1 -x -2.35 -l 0.5 -u 10 | ???Simon???

* Create a 500-particle Plummer model, with numbered stars, scaled to

standard dynamical units

mkplummer -n 500 -i

* Create a 500-particle W0 = 5 King model, with numbered stars,

unscaled

mkking -n 500 -w 5 -i -u

* Create a 500-particle W0 = 5 King model with a Miller-Scalo mass

spectrum between 0.1 and 20 solar masses, then rescale to unit total

mass, total energy -0.25, and virial ratio 0.5 and display the

results graphically

mkking -n 500 -w 5 -i -u \

| mkmass -f 2 -l 0.1 -u 20 \

| scale -m 1 -e -0.25 -q 0.5 \

| xstarplot -l 5 -P .5

* Create a 500-particle W0 = 5 King model with a Miller-Scalo mass

spectrum between 0.1 and 20 solar masses, add in a 10 percent 1-10 kT

binary population, then rescale to unit total mass, total energy

(top-level nodes) -0.25, and virial ratio (top-level nodes) 0.5, and

finally verify the results by analyzing the final snapshot

mkking -n 500 -w 5 -i -u \

| mkmass -f 2 -l 0.1 -u 20 \

| mksecondary -f 0.1 -l 0.25 \

| mkbinary -l 1 -u 10 \

| scale -m 1 -e -0.25 -q 0.5 \

| sys_stats -n -s

* Evolve this model without stellar evolution for 100 dynamical times,

with log output ever dynamical time and snapshot output every 10

dynamical times, with a self-consistent tidal field, removing

escapers when they are more than two Jacobi radii from the cluster

center

mkking -n 500 -w 5 -i -u \

| mkmass -f 2 -l 0.1 -u 20 \

| mksecondary -f 0.1 -l 0.25 \

| mkbinary -l 1 -u 10 \

| scale -m 1 -e -0.25 -q 0.5 \

| dstar_kira -t 100 -d 1 -D 10 -Q -G 2

* Create a King model with a power-law mass spectrum and a binary

population, then evolve it with stellar and binary evolution

mkking -n 500 -w 5 -i -u \

| mkmass -f 1 -x -2.0 -l 0.1 -u 20 \

| mksecondary -f 0.1 -l 0.1 \

| addstar -Q 0.5 -R 5 \

| scale -M 1 -E -0.25 -Q 0.5 \

| mkbinary -f 1 -l 1 -u 1000 -o 2 \

| dstar_kira -t 100 -d 1 -D 10 -f 0.3 -n 10 -q 0.5 -Q -G 2 -S -B

* Perform a series of 100 3-body scattering experiments involving an

equal-mass circular binary and a double-mass incomer, with impact

parameter equal to the binary semimajor axis, relative velocity at

infinity half that needed for zero total energy, and all other

parameters chosen randomly, and display the results as a movie

scatter3 -m 0.5 -e 0 -M 1 -r 1 -v 0.5 -n 100 -C 5 -D 0.1 \

| xstarplot -l 4

* Compute cross-sections for interactions between a circular binary

with component masses 0.75 and 0.25 and an incoming star of mass 1

and velocity at infinity 0.1, all stars having radius 0.05 binary

semimajor axes

sigma3 -d 100 -m 0.25 -e 0 -M 1 -v 0.1 -x 0.05 -y 0.05 -z 0.05

* Create a scattering configuration involving a head-on collision

between a circular binary and a stable hierarchical triple, and

verify the result

mkscat -M 1.5 -r 0 -v 1 -t -a 1 -e 0 -p -a 1 -e 0 -p1 -a 0.1 -e 0 \

| flatten | make_tree -D 1 | pretty_print_tree

* Create a scattering configuration involving a head-on collision

between a circular binary and a stable hierarchical triple, and

integrate it forward in time

scatter -i "-M 1.5 -r 0 -v 1 -t -a 1 -e 0 -p -a 1 -e 0 -p1 -a 0.1 -e 0" \

-t 100 -d 1 -v

(etc.)

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