Photometric filter transmission curves

Broad-band photometry is an important tool to study variability and band transmission curves are, e.g., required to derive photometric fluxes from spectra. The TransmissionCurves() class provides access to photometric transmission curves.

Further information on photometric bands:

Band	Destination
Bessel	Bessel 1990, PASP 102, 1181B (helpful link)
Johnson	Johnson and Morgan 1951, ApJ 114, 522 (helpful link)
Spitzer IRAC	Transmission curves for Spitzer IRAC instrument Call addSpitzerIRACPassbands to add to passband inventory.
Kepler	Kepler passband (high resolution) Call addKeplerPassband to add passband to inventory.
TESS	Transmission curve for TESS mission (futher information) Call addTESSPassband to add passband to inventory.
Gaia (DR3)	Transmission curves (G, G_BP, G_RP) for the Kepler mission (DR3) (further information)

Example of usage

from __future__ import print_function
from PyAstronomy import pyasl
import numpy as np
import matplotlib.pylab as plt
# Import six for Python 2/3 compatibility
import six

# Get transmission curve object
tcs = pyasl.TransmissionCurves()

# Add passbands from Spitzer IRAC
tcs.addSpitzerIRACPassbands()

print("Available bands: ", tcs.availableBands())

# Wavelength axis
wvl = np.linspace(3000, 10000, 10000)

# Plot transmission curves for Bessel b, v, and r bands
for (b, c) in six.iteritems({"b": "b", "v": "k", "r": "r"}):
    tc = tcs.getTransCurve("Bessel " + b)
    trans = tc(wvl)
    plt.plot(wvl, trans, c+'-', label="Bessel " + b)

# Plot transmission curves for Johnson U, B, and V bands
for (b, c) in six.iteritems({"U": "m", "B": "b", "V": "k"}):
    tc = tcs.getTransCurve("Johnson " + b)
    trans = tc(wvl)
    plt.plot(wvl, trans, c+'--', label="Johnson " + b)

plt.legend()
plt.xlabel("Wavelength [$\AA$]")
plt.ylabel("Transmission")
plt.show()


# Create Planck spectrum ...
wvl = np.arange(3000., 10000., 1.0)
spec = pyasl.planck(T=5777., lam=wvl*1e-10)
# ... and convolve with Johnson V band
vbs = tcs.convolveWith(wvl, spec, "Johnson V")

plt.plot(wvl, spec, 'b-', label='Input spectrum')
plt.plot(wvl, vbs, 'r--', label='Convolution with Johnson V band')
plt.legend()
plt.show()

API

class PyAstronomy.pyasl.TransmissionCurves(fn='default')

Photometric transmission curves for various photometric bands.

A list of supported bands can be obtained by calling availableBands.

Parameters

fnstring, optional

The filename of the data file. Default is ‘default’, which means that the shipped data file will be used.

Methods

addKeplerPassband([forceDownload, verbose])	Adds Kepler mission passband.
addPassband(name, wvl, trans[, snc])	Add a new passband to the inventory.
addSpitzerIRACPassbands([forceDownload, verbose])	Adds Spitzer IRAC passbands.
addTESSPassband([forceDownload, verbose])	Adds TESS mission passband.
availableBands()	Band names of available transmission curves.
convolveWith(wvl, spec, bn[, ik])	Convolve spectrum with transmission curve.
getTransCurve(bn[, ik])	Get a transmission curve.
getTransCurveData(bn)	Get data specifying the transmission curve.

addKeplerPassband(forceDownload=False, verbose=True)

Adds Kepler mission passband.

Kepler high-resolution passband is downloaded from: https://keplergo.github.io/KeplerScienceWebsite/data/kepler_response_hires1.txt

and added as ‘Kepler_HR’.

Parameters

forceDownloadboolean, optional

If True, a re-download of the passband files is triggered. Default is False.

verboseboolean, optional

If True (default), download process will print information on progress.

addPassband(name, wvl, trans, snc=False)

Add a new passband to the inventory.

Parameters

namestring

The name of the passband.

wvlarray

Wavelength in A.

transarray

Transmission of the passband.

sncboolean, optional

A Skip Name Check flag. If False (default), an exception is raised if the passband name is already present in the inventory of passbands. Otherwise the old passband is replaced by the new specification.

addSpitzerIRACPassbands(forceDownload=False, verbose=True)

Adds Spitzer IRAC passbands.

On first call, the passband files are downloaded. The files are downloaded from:

http://irsa.ipac.caltech.edu/data/SPITZER/docs/irac/calibrationfiles/spectralresponse/

Parameters

forceDownloadboolean, optional

If True, a re-download of the passband files is triggered. Default is False.

verboseboolean, optional

If True (default), download process will print information on progress.

addTESSPassband(forceDownload=False, verbose=True)

Adds TESS mission passband.

TESS passband is downloaded from: https://heasarc.gsfc.nasa.gov/docs/tess/data/tess-response-function-v1.0.csv

and added as ‘TESS’.

Parameters

forceDownloadboolean, optional

If True, a re-download of the passband files is triggered. Default is False.

verboseboolean, optional

If True (default), download process will print information on progress.

availableBands()

Band names of available transmission curves.

Returns

Available nameslist of strings

All bands for which data are available.

convolveWith(wvl, spec, bn, ik='linear')

Convolve spectrum with transmission curve.

Parameters

wvl, specarrays

Wavelength axis [A] and spectral data.

bnstring

Name of the band.

ikstring, optional

The type of interpolation. Accepts all values also accepted by the kind keyword of scipy’s interp1d routine. Default is ‘linear’.

Returns

Convolved spectrumarray

Input spectrum multiplied with transmission curve of the specified band.

getTransCurve(bn, ik='linear')

Get a transmission curve.

Parameters

bnstring

Name of the band.

ikstring, optional

The type of interpolation. Accepts all values also accepted by the kind keyword of scipy’s interp1d routine. Default is ‘linear’.

Returns

Transmission curvecallable

An object (scipy.interpolate.interp1d) that can be called with wavelength (float or array in [A]) as argument and returns the transmission.

getTransCurveData(bn)

Get data specifying the transmission curve.

Returns

Transmission table2d array

A table (array) with wavelength [A] in first column and transmission (0-1) in the second column.