"Stellar Formation and Evolution" at 2nd semester of academic year 2021

material for the course "Stellar Formation and Evolution" at NCU at the 2nd semester of academic year 2021

For the session on 03/May/2022, we need Python, Numpy, Scipy, and Matplotlib. If you do not have these software installed on your computer, try to install them.

Things you need for this hands-on session:

• a computer
• Python
• Numpy, Scipy, and Matplotlib
• your favourite web browser to access to https://github.com/
• your favourite text editor to modify codes
• your favourite terminal emulator to execute Python scripts

usage of simple.py

The script "simple.py" is for solving the equation dy/dx=-ky. Try following.

% ./simple.py

or you may try following.

% python3.9 simple.py

If your pytyhon executable is "python3.8", then try following.

% python3.8 simple.py

If your python executable is "python" instead of "python3.9" or "python3.8", then try following.

% python simple.py

You will find a file "simple.png" after successful execution of the script. Display the file "simple.png"

% feh -dF simple.png

usage of eqmotion.py

The script "eqmotion.py" is for solving the equation of motion. This script simulate the orbital motion of a planet around a star. Try following.

% ./eqmotion.py -vy0 1.3 -t 30 -o planet

Then, you find may PNG files generated by this script. Next, make a MP4 movie file using ffmpeg command.

% ffmpeg5 -f image2 -start_number 0 -framerate 30 -i planet_%08d.png -an -vcodec libx264 -pix_fmt yuv420p -threads 12 planet.mp4

If your ffmpeg command is "ffmpeg" instead of "ffmpeg5", then try following.

% ffmpeg -f image2 -start_number 0 -framerate 30 -i planet_%08d.png -an -vcodec libx264 -pix_fmt yuv420p -threads 12 planet.mp4

Play the file "planet.mp4"

% mplayer planet.mp4

If you would like to add an audio track to your video file, then try following

% ffmpeg -i planet.mp4 -i audiofile.f251.webm -c:v copy planet_with_audio.mp4

usage of laneemden.py and plot_polytrope.py

The script "laneemden.py" is for solving Lane-Emden equation, and the script "plot_polytrope.py" is for plotting results. Try following.

% ./laneemden.py -n 0.0 -o laneemden_n00.data
% ./laneemden.py -n 0.5 -o laneemden_n05.data
% ./laneemden.py -n 1.0 -o laneemden_n10.data
% ./laneemden.py -n 1.5 -o laneemden_n15.data
% ./laneemden.py -n 2.0 -o laneemden_n20.data
% ./laneemden.py -n 2.5 -o laneemden_n25.data
% ./laneemden.py -n 3.0 -o laneemden_n30.data
% ./laneemden.py -n 3.5 -o laneemden_n35.data
% ./laneemden.py -n 4.0 -o laneemden_n40.data
% ./laneemden.py -n 4.5 -o laneemden_n45.data

Then, try following to generate plots.

% ./plot_polytrope.py laneemden_n*.data

Display plots.

% feh -dF polytrope*.png