stellarSpecModel

This is a simple package to interpolate the stellar spectral grid. Users provide stellar parameters (Teff, FeH, logg), the package will return the corresponding stellar spectrum.

Installation

You can install the package by using pip:

pip install git+https://github.com/zzxihep/stellarSpecModel.git

Some system may raise an error error: externally-managed-environment, you can try to add --break-system-packages to the command above.

pip install git+https://github.com/zzxihep/stellarSpecModel.git --break-system-packages

or clone the repository and install it:

git clone https://github.com/zzxihep/stellarSpecModel.git
cd stellarSpecModel
python setup.py install --user

Dependencies

The package depends on the following packages:

• numpy
• scipy
• astropy
• selenium (optional, for downloading the grid)

The package need to download the stellar spectral grid from website, so you need to install selenium to download the grids. Otherwise, you can download the grids manually and put them in the ~/.stellarSpecModel/grid_data/ folder. The URL of the grid files are:

• https://www.jianguoyun.com/p/DZmcNoUQ2ZfcCBjW-5cFIAA
• https://www.jianguoyun.com/p/Def5fgsQ2ZfcCBiYmpgFIAA

see more details in config.py

Usage

The package currently provides two classes: MARCS_Model and BTCond_Model for the MARCS and BT-Cond grid respectively. The usage of the two classes are the same. MARCS grid has a wavelength coverage of 3800-9700 Angstrom with high sampling, while BT-Cond grid has a wavelength coverage of 300-3E5 Angstrom with low sampling. You can also use your own grid by inheriting the StellarSpecModel class.

Here we show an example of using the package:

from stellarSpecModel import MARCS_Model, BTCond_Model
import matplotlib.pyplot as plt

btcond_model = BTCond_Model()
marcs_model = MARCS_Model()
print('MARCS wavelength unit =', marcs_model.wavelength_units)
print('MARCS flux units =', marcs_model.flux_units)
print('min and max Teff of MARCS grid =', marcs_model.min_teff, marcs_model.max_teff)
print('min and max FeH of MARCS grid =', marcs_model.min_feh, marcs_model.max_feh)
print('min and max logg of MARCS grid =', marcs_model.min_logg, marcs_model.max_logg)
print('Teff grid of MARCS =', marcs_model.teff_grid)
print('FeH grid of MARCS =', marcs_model.feh_grid)
print('logg grid of MARCS =', marcs_model.logg_grid)
print('\n')

print('BTCond wavelength unit =', btcond_model.wavelength_units)
print('BTCond flux units =', btcond_model.flux_units)
print('min and max Teff of BTCond grid =', btcond_model.min_teff, btcond_model.max_teff)
print('min and max FeH of BTCond grid =', btcond_model.min_feh, btcond_model.max_feh)
print('min and max logg of BTCond grid =', btcond_model.min_logg, btcond_model.max_logg)
print('Teff grid of BTCond =', btcond_model.teff_grid)
print('FeH grid of BTCond =', btcond_model.feh_grid)
print('logg grid of BTCond =', btcond_model.logg_grid)

teff = 5700
feh = 0
logg = 4.5
marcs_flux = marcs_model.get_flux(teff, feh, logg)
btcond_flux = btcond_model.get_flux(teff, feh, logg)
plt.plot(marcs_model.wavelength, marcs_flux, label='MARCS')
plt.plot(btcond_model.wavelength, btcond_flux, label='BTCond')
plt.legend()
plt.xlabel('Wavelength ({})'.format(marcs_model.wavelength_units))
plt.ylabel('Flux ({})'.format(marcs_model.flux_units))
plt.xlim(2750, 10000)
plt.ylim(0, 1.1 * max(marcs_flux))
plt.show()

The output of the above code is:

MARCS wavelength unit = Angstrom
MARCS flux units = erg / (Angstrom cm2 s)
min and max Teff of MARCS grid = 2700.0 8000.0
min and max FeH of MARCS grid = -4.0 1.0
min and max logg of MARCS grid = 2.0 5.0
Teff grid of MARCS = [2700. 2800. 2900. 3000. 3100. 3200. 3300. 3400. 3500. 3600. 3700. 3800.
 3900. 4000. 4250. 4500. 4750. 5000. 5250. 5500. 5750. 6000. 6250. 6500.
 6750. 7000. 7250. 7500. 7750. 8000.]
FeH grid of MARCS = [-4.   -3.   -2.5  -2.   -1.5  -1.   -0.75 -0.5  -0.25  0.    0.25  0.5
  0.75  1.  ]
logg grid of MARCS = [2.  2.5 3.  3.5 4.  4.5 5. ]


BTCond wavelength unit = Angstrom
BTCond flux units = erg / (Angstrom cm2 s)
min and max Teff of BTCond grid = 3500.0 8000.0
min and max FeH of BTCond grid = -4.0 0.5
min and max logg of BTCond grid = 1.0 5.0
Teff grid of BTCond = [3500. 3600. 3700. 3800. 3900. 4000. 4100. 4200. 4300. 4400. 4500. 4600.
 4700. 4800. 4900. 5000. 5100. 5200. 5300. 5400. 5500. 5600. 5700. 5800.
 5900. 6000. 6100. 6200. 6300. 6400. 6500. 6600. 6700. 6800. 6900. 7000.
 7200. 7400. 7600. 7800. 8000.]
FeH grid of BTCond = [-4.  -3.5 -3.  -2.5 -2.  -1.5 -1.  -0.5  0.   0.3  0.5]
logg grid of BTCond = [1.  1.5 2.  2.5 3.  3.5 4.  4.5 5. ]

Note

The flux of the grid spectrum corresponds to the flux received by an observer located at the surface of a star. Therefore, assuming that the radius of a star is equal to $1 R_\odot$, and the observer's position is at a distance of 100 parsecs, the received flux will be nflux = flux * (cs.R_sun / (100*u.pc)).to('').value**2.