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Find stellar rotation and activity quantities

Rotation and activity quantities (How-to)

Goal

Compute high-energy emission quantities (X-ray, EUV, Ly-Ξ±) from stellar mass, age, and rotation, optionally add variability/scatter, and (if needed) retrieve a larger set of model diagnostics via ExtendedQuantities.

Prerequisites

Install MORS and download the required stellar evolution data:

pip install fwl-mors
mors download all

Units: Mstar in Mβ˜‰, Age in Myr, Prot in days, Omega in Ξ©β˜‰. Luminosities are in erg s⁻¹ and surface fluxes in erg s⁻¹ cm⁻².

Step 1: Get the full XUV dictionary (Lxuv)

Use Omega (or OmegaEnv) or Prot to specify the surface rotation.

Using Ξ© (Ξ©β˜‰): 

import mors
xuv = mors.Lxuv(Mstar=1.0, Age=5000.0, Omega=10.0)

Using rotation period (days): 

import mors
xuv = mors.Lxuv(Mstar=1.0, Age=5000.0, Prot=1.0)

The returned dictionary includes luminosities, surface fluxes, and bolometric-normalized values, e.g.: - Luminosities: Lxuv, Lx, Leuv1, Leuv2, Leuv, Lly (erg s⁻¹) - Fluxes: Fxuv, Fx, Feuv1, ... (erg s⁻¹ cm⁻²) - Normalized: Rxuv, Rx, Reuv1, ... (dimensionless)

To see what keys are present: 

print(sorted(xuv.keys()))

Step 2: Retrieve a single quantity directly (Lx, Leuv, Lly)

import mors

Lx  = mors.Lx(Mstar=1.0, Age=5000.0, Omega=10.0)
Leu = mors.Leuv(Mstar=1.0, Age=5000.0, Omega=10.0)
Lly = mors.Lly(Mstar=1.0, Age=5000.0, Omega=10.0)

Choose an EUV sub-band with band

Leuv(..., band=...) supports: - band=0 β†’ 10–92 nm (total EUV) - band=1 β†’ 10–36 nm (EUV1) - band=2 β†’ 36–92 nm (EUV2)

import mors
Leuv_total = mors.Leuv(Mstar=1.0, Age=5000.0, Omega=10.0, band=0)
Leuv1      = mors.Leuv(Mstar=1.0, Age=5000.0, Omega=10.0, band=1)
Leuv2      = mors.Leuv(Mstar=1.0, Age=5000.0, Omega=10.0, band=2)

Step 3: Add variability/scatter (optional)

MORS provides random scatter terms intended to represent variability as a log-normal scatter.

X-ray scatter (XrayScatter)

You pass the mean value (e.g., Lx) and get a delta to add: 

import mors

Lx = mors.Lx(Mstar=1.0, Age=5000.0, Omega=10.0)
dLx = mors.XrayScatter(Lx)

Lx_scattered = Lx + dLx

You can also pass Fx or Rx and receive dFx / dRx.

Full XUV scatter (XUVScatter)

XUVScatter takes the dictionary from Lxuv and returns a dictionary of deltas with the same keys: 

import mors

xuv  = mors.Lxuv(Mstar=1.0, Age=5000.0, Omega=10.0)
dxuv = mors.XUVScatter(xuv)

# Example: apply deltas to get one scattered realization
xuv_scattered = {k: xuv[k] + dxuv[k] for k in xuv}

Controlling the scatter width: the X-ray scatter width is controlled by sigmaXray in the parameters file. You can override it by passing a custom params dictionary (see the parameter how-to):

import mors

params = mors.NewParams(sigmaXray=0.3)  # example value
Lx = mors.Lx(Mstar=1.0, Age=5000.0, Omega=10.0, params=params)
dLx = mors.XrayScatter(Lx, params=params) if "params" in mors.XrayScatter.__code__.co_varnames else mors.XrayScatter(Lx)
(If XrayScatter does not accept params directly, set sigmaXray via your model run parameters and use it consistently.)

Step 4: Get detailed diagnostics (ExtendedQuantities)

If you need additional model internals (stellar properties, wind quantities, magnetic fields, torques), call ExtendedQuantities with envelope and core rotation rates:

import mors

q = mors.ExtendedQuantities(Mstar=1.0, Age=5000.0, OmegaEnv=10.0, OmegaCore=10.0)
print(list(q))

Common pitfalls

  • Don’t mix Omega (Ξ©β˜‰) and Prot (days) in the same call; pick one rotation representation.
  • Scatter functions are random; results differ each run unless you control the random seed in your workflow.
  • ExtendedQuantities requires both OmegaEnv and OmegaCore.