DOI: 10.6084/m9.figshare.13637672
title: Punctuated chaos and the unpredictability of the Galactic center S-star orbital evolution

description: #Description of the data. <br> Raw and processed data for the manuscript "Punctuated chaos and the unpredictability of the Galactic center S-star orbital evolution" by Simon Portegies Zwart, Tjarda Boekholt, and Douglas Heggie. <br> The initial conditions for the S-stars are taken from the observed 27 stars by 2009ApJ...692.1075G. We adopted those observed initial conditions and converted them into orbital elements adopting a distance to the black hole of 8178pc and a mass of 4.154e+6 Solar masses. we adopted a current time of 1 January 2021. <br> We subsequently calculate the orbital evolution of all particles (S-stars and black hole) for 10000years. Since the system is chaotic, we adopted Brutus (see 2018CNSNS..61..160P) with a tolerance of $10^{-24}$ to perform the calculations storing snapshots every 0.1yr. The raw data contains two of these data sets for the canonical S-star Cartesian coordinates as a function of time, and one set in which one star (S5) was displaced in the positive x-direction by $10^{-10}$ relative to it's current (1 Jan 2021) x-coordinate. <br> The calculation are performed within the AMUSE framework (2013CoPhC.183..456P). <br> Main conclusions from the paper and supported by our analysis of the data. <br> -The S-star cluster around the supermassive black hole has a Lyapunv time scale of about 450 years. <br> -The S-star cluster does not resembler a "Solar system" because of the orbits have a wide range in eccentricity and inclination. <br> -Chaos in the S-star cluster is driven by close encounters between stars, which happend to be near the supermassive black hole. <br> -The close near-black-hole encounters lead to the brownian motion of the black hole, which is reflected in changes in the S-star orbits. <br> -minitious differences in initial conditions lead to slightly different close encounters, which drive differences in the details of the black hole's Brownian motion. <br> more details in README.md <br> Running the scripts requires the Astrophysical Multipurpose Software Environment (AMUSE for short). AMUSE can be downloaded from git through:https://github.com/amusecode/amuse see https://www.amusecode.org/ for a more extensive description. <br> The data is organized in files in directories. <br> Files and directories: REDME.md # this file data_raw # raw data in AMUSE hdf5 format. data_processed # processed data files, typically in python pickle binary format src # contains the script for running Brutus in AMUSE figures # processed figures in pdf format generated from the scripts plot # plotting routins for making the figures from processed data process # processing routines, take the raw data and process them <br> Subcontent: * data_raw: Contains the raw data files in AMUSE hdf5 format. The data is generated using Brutus with a tolerance of $10^{-24}$ as indicated in the filename. similar files are availabelf for $10^{-18}$ and $10^{-21}$. -Sstar_pert_dx0_eta-24.0.amuse Raw snapshots of the S-stars at 1 January 2021 for 10000yr at time intervals of 0.1 yr. -Sstar_pert_dx-10.0_eta-24.0.amuse Raw snapshots of the S-stars at 1 January 2021 for 10000yr at time intervals of 0.1 yr. This calculation was performed using the same initial realization used to generate star_pert_dx0_eta-24.0.amuse but with star S5 displaced in the positive x-coordinate by a relative distance of $dx = 1.e-10$. Resulting in an x-coordinate ofr the star S5 of $S5.x = S5.x * (1+dx)$ <br> * data_processed: processed data files are python pickle files, written by the processing routines from the "process" directory. These files are used for the plotting routines in the "plot" directory. -Sstar_dx0_eta-24_BH_NN_distance.pkl Distance to the black hole and its nearest neighbor -Sstar_dx0_eta-24_orbits.pkl orbitsal parameters of the S-stars as a function of time of the canconical solution. -Sstar_dx0_eta-24_BHdistance.pkl Distance to the black hole -Sstars_dx0_eta-24_dxv.pkl file containting the difference between the canonical and the perturbed solution in terms of positional and velocity difference. -S5_dx-10_eta-24_dxv.pkl file containting the difference between the canonical and the perturbed solution in terms of positional and velocity difference. In this case the file presents the difference between the canconical solution and the solution in which star S5 is perturbed in the x-direction by $10^{-10}$. <br> -S5_dx-10_eta-24_orbits.pkl orbitsal parameters of the S-stars as a function of time of the solution in which star S5 is perturbed in the x-direction: $S5.x = S5.x * (1+dx)$ with $dx = 10^{-10}$ <br> * src contains runscripts and helper scripts for performing the calculations. Running these may take a long time. * figures contains the pdf file figures generated with the scripts in the "plot" directory * plot plotting routines. Takes the data from the data_processed directory and makes figures of the appropriate parameters. * process contains the scripts to process the raw simulation data (AMUSE hdf5 formatted) and turns them into specific reduced data sets (in binary python picle format). <br> <br> December 2022 Simon Portegies Zwart, Leiden Observatory <br> <br> <br>