Magnitude conversions¶
Translate absolute magnitude to power scale¶
- PyAstronomy.pyasl.absMagToPower(am, absMagSun=4.75, absLumSun=3.846e+33)¶
Convert absolute magnitude to power scale
The default values for the absolute magnitude and luminosity of the Sun are adopted from Harmanec and Prsa 2011 (2011PASP..123..976H).
- Parameters
- amfloat
Absolute magnitude.
- absMagSunfloat, optional
Absolute magnitude of the Sun.
- absLumSunfloat, optional
Absolute luminosity of the Sun. The default is given in units of erg/s.
- Returns
- Powerfloat
Total emitted power. Same units as absLumSun; the default corresponds to erg/s.
Example¶
from __future__ import print_function, division
from PyAstronomy import pyasl
absMagSun = 4.75
print("Absolute bolometric magnitude of the Sun: ", absMagSun)
print(" Absolute luminosity [erg/s]: ", pyasl.absMagToPower(absMagSun))
Translate distance module into distance¶
- PyAstronomy.pyasl.absModuleToDist(magApp, magAbs)¶
Convert apparent and absolute magnitude into distance.
- Parameters
- magAppfloat
Apparent magnitude of object.
- magAbsfloat
Absolute magnitude of object.
- Returns
- Distancefloat
The distance resulting from the difference in apparent and absolute magnitude [pc].
Example¶
from __future__ import print_function, division
from PyAstronomy import pyasl
# Apparent magnitude
appMag = 11.37
# Absolute (bolometric) magnitude of Sun
absMagSun = 4.75
print("Distance of a sun-like star with apparent bolometric ", end=' ')
print("brightness of 11.37 mag: %5.2f pc" % (pyasl.absModuleToDist(appMag, absMagSun)))
Convert magnitude into flux density¶
- PyAstronomy.pyasl.magToFluxDensity_bessel98(band, mag, mode='nu')¶
Convert magnitude into flux density according to Bessel et al. 1998
The conversion implemented here is based on the data given in Table A2 of Bessel et al. 1998, A&A 333, 231-250, which gives “Effective wavelengths (for an A0 star), absolute fluxes (corresponding to zero magnitude) and zeropoint magnitudes for the UBVRI- JHKL Cousins-Glass-Johnson system”. Note that zp(f_nu) and zp(f_lam) are exchanged in the original table.
- Parameters
- bandstring
Any of U, B, V, R, I, J, H, K, Kp, L, and L*
- magfloat, array
The magnitude value to be converted
- modestring, {nu, mod}
Determines whether f_nu or f_lam will be calculated.
- Returns
- f_nu/lamfloat
The corresponding flux density in units if erg/cm**2/s/Hz in the case of mode ‘nu’ and erg/cm**2/s/A in the case of ‘lam’.
- lam_efffloat
Effective filter wavelength in Angstrom
Example¶
from __future__ import print_function
from PyAstronomy import pyasl
import numpy as np
mag_R = 15.5
fd_nu, le = pyasl.magToFluxDensity_bessel98("R", mag_R, "nu")
fd_lam, _ = pyasl.magToFluxDensity_bessel98("R", mag_R, "lam")
print("R-band magnitude: ", mag_R)
print("R-band flux density [erg/cm**2/s/Hz]: ", fd_nu)
print("R-band flux density [erg/cm**2/s/A]: ", fd_lam)
print("Effective wavelength of filter [A]: ", le)
print("Convert f_nu into f_lam [erg/cm**2/s/A] by multiplication with (c/lam**2): ",
fd_nu * (299792458e2/(le/1e8)**2) / 1e8)