Find stellar rotation and activity quantities

Compute high-energy emission quantities (X-ray, EUV, Ly-\(\alpha\)) from stellar mass, age, and rotation rate, optionally add variability scatter, and retrieve detailed model diagnostics via ExtendedQuantities.

Prerequisites

Make sure the package and stellar evolution data are installed:

pip install fwl-mors
mors download all

Step 1: Get the full XUV dictionary

Use mors.Lxuv with either Omega (Ω☉) or Prot (days) to specify the surface rotation:

import mors

# using rotation rate
xuv = mors.Lxuv(Mstar=1.0, Age=5000.0, Omega=1.0)

# using rotation period
xuv = mors.Lxuv(Mstar=1.0, Age=5000.0, Prot=25.4)

The returned dictionary contains:

print(sorted(xuv.keys()))
print(f"Lx = {xuv['Lx']:.3e} erg/s")

Step 2: Retrieve a single quantity directly

Convenience functions exist for X-ray, EUV, and Ly-\(\alpha\) luminosities:

import mors

Lx  = mors.Lx(Mstar=1.0, Age=5000.0, Omega=1.0)
Lly = mors.Lly(Mstar=1.0, Age=5000.0, Omega=1.0)

mors.Leuv supports a band argument to select the wavelength range:

Leuv_total = mors.Leuv(Mstar=1.0, Age=5000.0, Omega=1.0, band=0)  # 10–92 nm
Leuv1      = mors.Leuv(Mstar=1.0, Age=5000.0, Omega=1.0, band=1)  # 10–36 nm
Leuv2      = mors.Leuv(Mstar=1.0, Age=5000.0, Omega=1.0, band=2)  # 36–92 nm

Step 3: Add variability scatter (optional)

MORS provides scatter functions that sample a log-normal distribution to represent stellar variability around the mean emission.

X-ray scatter

Pass the mean value (any of Lx, Fx, or Rx) and receive a delta to add:

import mors

Lx  = mors.Lx(Mstar=1.0, Age=5000.0, Omega=1.0)
dLx = mors.XrayScatter(Lx)
Lx_scattered = Lx + dLx

Full XUV scatter

XUVScatter takes the dictionary from Lxuv and returns a dictionary of deltas with the same keys, with correlated offsets across all bands:

import mors

xuv  = mors.Lxuv(Mstar=1.0, Age=5000.0, Omega=1.0)
dxuv = mors.XUVScatter(xuv)

xuv_scattered = {k: xuv[k] + dxuv[k] for k in xuv}

Controlling the scatter width

The scatter width is set by sigmaXray (default 0.359 dex). Pass a custom parameter dictionary to both the emission and scatter functions to change it:

import mors

my_params = mors.NewParams(sigmaXray=0.3)

Lx  = mors.Lx(Mstar=1.0, Age=5000.0, Omega=1.0, params=my_params)
dLx = mors.XrayScatter(Lx, params=my_params)
Lx_scattered = Lx + dLx

Step 4: Get detailed model diagnostics (ExtendedQuantities)

ExtendedQuantities returns a large dictionary of model internals including stellar structure properties, wind quantities, magnetic field strengths, and torques. It requires both the envelope and core rotation rates:

import mors

q = mors.ExtendedQuantities(Mstar=1.0, Age=5000.0, OmegaEnv=1.0, OmegaCore=1.0)
print(list(q.keys()))

For a coupled core–envelope system at early ages, OmegaEnv and OmegaCore will generally differ. For a fully spun-down star, they can be set equal.

Common pitfalls

• Do not set both Omega and Prot in the same call — only one rotation representation can be used at a time.
• Scatter functions are stochastic — results differ each call unless you set a NumPy random seed.
• ExtendedQuantities requires both OmegaEnv and OmegaCore; unlike Lxuv, it does not accept Omega as a shorthand.