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Calculate stellar evolution

Evolutionary calculations (How-to)

Goal

Compute a star’s rotation and activity evolution tracks, then (a) plot a quantity, (b) query values at specific ages, and (c) save the result for reuse.

Prerequisites

Make sure the package and stellar evolution data are installed:

pip install fwl-mors
mors download all

Units: Age is in Myr, Prot is in days, and Omega is in units of the current solar rotation rate (Ξ©β˜‰).

Step 1: Create a Star

Pick one of these common ways:

A) Set initial rotation using Ξ© (at ~1 Myr)

import mors
star = mors.Star(Mstar=1.0, Omega=10.0)

B) Set initial rotation using rotation period (days)

import mors
star = mors.Star(Mstar=1.0, Prot=2.7)

C) Fit a track through a point (Age, Ξ©)

import mors
star = mors.Star(Mstar=1.0, Age=100.0, Omega=50.0)

Use (C) only at ages where rotation tracks have not strongly converged for that mass; otherwise the fit may be ill-posed or fail if the requested rotation rate is unrealistic.

Step 2: Inspect available tracks and units

star.PrintAvailableTracks()
print(star.Units['Lx'])

Step 3: Plot an evolutionary track

Tracks are stored in star.Tracks and also exposed as <Quantity>Track arrays.

import matplotlib.pyplot as plt

plt.plot(star.Tracks['Age'], star.Tracks['Lx'])
# or: plt.plot(star.AgeTrack, star.LxTrack)
plt.xlabel(f"Age [{star.Units['Age']}]")
plt.ylabel(f"Lx [{star.Units['Lx']}]")
plt.show()

Step 4: Find a value at a given age

print(star.Value(150.0, 'Lx'))
# or:
print(star.Value(Age=150.0, Quantity='Lx'))
# or (preferred when available):
print(star.Lx(150.0))

Step 5: Save and reload

star.Save(filename="star.pickle")
star2 = mors.Load("star.pickle")

Common pitfalls

  • Age is in Myr (not years).
  • Omega is in Ξ©β˜‰ (not rad/s).
  • Fitting with Age=... + Omega=... may fail at late ages or for extreme rotation rates.