rotins 1.0.0

A Python package for rotational and instrumental broadening of stellar spectra

rotins

A Python package for rotational and instrumental broadening of stellar spectra. This is a Python translation of the FORTRAN program used in TLUSTY by Ivan Hubeny et al.

Installation

pip install rotins

Features

• Rotational broadening with configurable limb darkening coefficient
• Instrumental broadening using Gaussian profiles
• Support for both FWHM and spectral resolution parameters
• Both object-oriented and functional programming interfaces
• Support for normalized and non-normalized spectra
• Efficient convolution with proper edge handling

Quick Start

import numpy as np
from rotins import RotIns, rotins

# Load your spectrum (wavelength and flux arrays)
wl = np.loadtxt("spectrum_wl.txt")
flux = np.loadtxt("spectrum_flux.txt")

# Using the class-based interface
broadener = RotIns(vsini=50.0, fwhm=0.1)  # vsini in km/s, fwhm in wavelength units
conv_wl, conv_flux = broadener.broaden(wl, flux)

# Using the functional interface
broaden = rotins(vsini=50.0, fwhm=0.1)
conv_wl, conv_flux = broaden(wl, flux)

Documentation

Class-based Interface

from rotins import RotIns

broadener = RotIns(
    vsini=50.0,           # Rotational velocity in km/s
    fwhm=0.1,            # FWHM in wavelength units
    fwhm_type="fwhm",    # Either "fwhm" or "res"
    limb_coeff=0.6,      # Limb darkening coefficient
    base_flux=1.0,       # Base flux level
)

# Broaden the spectrum
conv_wl, conv_flux = broadener.broaden(
    wl,                  # Wavelength array
    flux,               # Flux array
    lim=(4000, 5000),   # Optional wavelength limits
)

Functional Interface

from rotins import rotins

# Create a broadening function
broaden = rotins(
    vsini=50.0,           # Rotational velocity in km/s
    fwhm=0.1,            # FWHM in wavelength units
    fwhm_type="fwhm",    # Either "fwhm" or "res"
    limb_coeff=0.6,      # Limb darkening coefficient
    base_flux=1.0,       # Base flux level
)

# Apply broadening to multiple spectra
conv_wl1, conv_flux1 = broaden(wl1, flux1)
conv_wl2, conv_flux2 = broaden(wl2, flux2, lim=(4000, 5000))

Parameters

• vsini: Rotational velocity in km/s. If None or 0.0, no rotational broadening is applied.
• fwhm: Full Width at Half Maximum in wavelength units (if fwhm_type="fwhm") or resolving power (if fwhm_type="res"). If None or 0.0, no instrumental broadening is applied.
• fwhm_type: Type of the FWHM parameter. Either "fwhm" for direct wavelength units or "res" for spectral resolution.
• limb_coeff: Limb darkening coefficient. Default is 0.6 (from SYNSPEC).
• base_flux: Base flux level. Use 1.0 for normalized spectra, 0.0 for non-normalized spectra.
• lim: Optional tuple of (min_wavelength, max_wavelength) to limit the broadening range.

Scientific Details

The calculations follow the formulas from:

Gray, D.F., 2008, The Observation and Analysis of Stellar Photospheres, Cambridge University Press, Cambridge, 3rd edition.

Rotational Broadening

The rotational broadening kernel is given by:

G(\Delta\lambda) = \frac{2(1-\epsilon)[1-(\Delta\lambda/\Delta\lambda_0)^2]^{1/2}+(\pi\epsilon/2)[1-(\Delta\lambda/\Delta\lambda_0)^2]}{\pi\Delta\lambda_0(1-\epsilon/3)}

where:

• \epsilon is the limb darkening coefficient
• \Delta\lambda_0 = \frac{\lambda v \sin i}{c}
• c is the speed of light

Instrumental Broadening

Instrumental broadening uses a Gaussian kernel with:

\sigma = \frac{\textrm{FWHM}}{2\sqrt{2\ln 2}}

Contributing

Pull requests are welcome. Please ensure that tests pass and add new tests for new features.

License

MIT License - see the LICENSE file for details.

Citation

If you use this package in your research, please cite:

@software{rotins,
  author = {Krishna, Sriram},
  title = {rotins: A Python package for stellar spectral broadening},
  year = {2022},
  url = {https://github.com/k-sriram/rotins}
}