Sun¶

class sbpy.calib.Sun(source, description=None, bibcode=None)[source]¶

Bases: SpectralStandard

Solar spectrum.

Most functionality requires synphot. The exception is retrieval of flux densities by filter name via the solar_fluxd context manager.

Parameters:

waveQuantity: Spectral wavelengths.
fluxdQuantity: Solar spectral flux density at 1 au.
descriptionstring, optional: Brief description of the source spectrum.
bibcodestring, optional: Bibliography code for sbpy.bib.register.
metadict, optional: Any additional meta data, passed on to SourceSpectrum.

Examples

Get the default solar spectrum:

>>> sun = Sun.from_default()

Create solar standard from synphot.SourceSpectrum:

>>> import astropy.constants as const
>>> import synphot
>>> source = (synphot.SourceSpectrum(synphot.BlackBody1D, temperature=5770)
...           * (3.14159 * const.R_sun**2 / const.au**2).decompose())
>>> sun = Sun(source, description='5770 K blackbody Sun')

Create solar standard from a file:

>>> sun = Sun.from_file('filename')        

Create solar standard from an array:

>>> import numpy as np
>>> import astropy.units as u
>>> import astropy.constants as const
>>> from astropy.modeling.models import BlackBody
>>> from sbpy.calib import Sun
>>> B = BlackBody(
...     temperature=5770 * u.K,
...     scale=((const.R_sun / const.au)**2
...            * u.W / u.m**2 / u.um / u.sr)
... )
>>> wave = np.logspace(-1, 2, 300) * u.um
>>> fluxd = B(wave) * np.pi * u.sr
>>> sun = Sun.from_array(wave, fluxd, description='5770 K blackbody Sun')

Interpolate to / evaluate at 0.62 μm:

>>> print(sun(0.62 * u.um))                
1611.7080046473307 W / (um m2)

Observe as through a spectrometer:

>>> import numpy as np
>>> import astropy.units as u
>>> sun = Sun.from_default()
>>> wave = np.linspace(1, 2.5) * u.um
>>> fluxd = sun.observe(wave)              

Observe as through a filter, integrating with the bandpass transmission:

>>> from sbpy.photometry import bandpass
>>> sun = Sun.from_default()
>>> v = bandpass('Johnson V')
>>> print(sun.observe(v))                  
1839.93273227  W / (um m2)

Observe through a filter, using sbpy’s filter calibration system:

>>> from sbpy.calib import solar_fluxd
>>> import sbpy.units as sbu
>>> solar_fluxd.set({
...     'V': -26.76 * sbu.VEGAmag,
...     'V(lambda eff)': 548 * u.nm,
...     'V(lambda pivot)': 551 * u.nm
... })                                     
>>> sun = Sun.from_default()
>>> print(sun.observe('V'))
-26.76 mag(VEGA)

Attributes:

wave - Wavelengths of the source spectrum.
fluxd - Source spectrum.
description - Brief description of the source spectrum.
meta - Meta data.

Attributes Summary

`description`	Description of the source spectrum.
`fluxd`	The source spectrum.
`meta`
`source`
`wave`	Wavelengths of the source spectrum.

Methods Summary

`__call__`(wave_or_freq[, unit])	Evaluate/interpolate the source spectrum.
`color_index`(wfb, unit)	Color index (magnitudes) and effective wavelengths.
`from_array`(wave, fluxd[, meta])	Create standard from arrays.
`from_builtin`(name)	Spectrum from a built-in `sbpy` source.
`from_default`()	Initialize new spectral standard from current default.
`from_file`(filename[, wave_unit, flux_unit, ...])	Load the source spectrum from a file.
`observe`(wfb[, unit, interpolate])	Observe as through filters or spectrometer.
`observe_bandpass`(bp[, unit])	Observe through a bandpass.
`observe_filter_name`(filt[, unit])	Flux density through this filter.
`observe_spectrum`(wave_or_freq[, unit])	Observe source as through a spectrometer.
`redden`(S)	Redden the spectrum.
`show_builtin`([print])	List built-in spectra.

Attributes Documentation

description¶: Description of the source spectrum.

fluxd¶: The source spectrum.

meta¶

source¶

wave¶: Wavelengths of the source spectrum.

Methods Documentation

__call__(wave_or_freq, unit=None)¶

Evaluate/interpolate the source spectrum.

Parameters:

wave_or_freqQuantity: Requested wavelengths or frequencies of the resulting spectrum.
unitstring, Unit, optional: Spectral units of the output (flux density). If None, the default depends on wave_or_freq: W/(m2 μm) for wavelengths, Jy for frequencies.

Returns:

fluxdQuantity: The spectrum evaluated/interpolated to the requested wavelengths or frequencies.

color_index(wfb, unit)¶

Color index (magnitudes) and effective wavelengths.

Parameters:

wfbQuantity, or tuple/list of SectralElement, string: Two wavelengths, frequencies, or bandpasses.
unitstring or MagUnit: Units for the calculation, e.g., astropy.units.ABmag or sbpy.units.VEGAmag.

Returns:

eff_waveQuantity: Effective wavelengths for each wfb.
ciQuantity: Color index, m_0 - m_1, where 0 and 1 are element indexes for wfb.

classmethod from_array(wave, fluxd, meta=None, **kwargs)¶

Create standard from arrays.

Parameters:

waveQuantity: The spectral wavelengths.
fluxdQuantity: The spectral flux densities.
metadict, optional: Meta data.
**kwargs: Passed to object initialization.

classmethod from_builtin(name)¶

Spectrum from a built-in sbpy source.

Parameters:

namestring: The name of the spectrum. See show_builtin() for available sources.

classmethod from_default()¶

Initialize new spectral standard from current default.

The spectrum will be None if synphot is not available.

classmethod from_file(filename, wave_unit=None, flux_unit=None, cache=True, **kwargs)¶

Load the source spectrum from a file.

NaNs are dropped.

Parameters:

filenamestring: The name of the file. See from_file for details.
wave_unit, flux_unitstr or Unit, optional: Wavelength and flux units in the file.
cachebool, optional: If True, cache the contents of URLs.
**kwargs: Passed to object initialization.

observe(wfb, unit=None, interpolate=False, **kwargs)¶

Observe as through filters or spectrometer.

Calls observe_bandpass, observe_spectrum, or self(), as appropriate.

Parameters:

wfbQuantity, SpectralElement, string: Wavelengths, frequencies, or bandpasses. Bandpasses may be a filter name (string). May also be a list of SpectralElement or strings.
unitstring, Unit, optional: Units of the output (spectral flux density).
interpolatebool, optional: For wavelengths/frequencies, set to True for interpolation instead of rebinning. Use this when the spectral resolution of the source is close to that of the requested wavelengths.
**kwargs: Additional keyword arguments for Observation, e.g., force.

Returns:

fluxdQuantity

observe_bandpass(bp, unit=None, **kwargs)¶

Observe through a bandpass.

Parameters:

bpSpectralElement, list, or tuple: Bandpass.
unitstring, Unit, optional: Spectral flux density units for the output. The default is W/(m2 μm).
**kwargs: Additional keyword arguments for Observation, e.g., force.

Returns:

lambda_effQuantity: Effective wavelength(s) of the observation(s).
fluxdQuantity: The spectrum rebinned.

observe_filter_name(filt, unit=None)¶

Flux density through this filter.

Does not use the spectrum, but instead the flux density calibration manager. If the name of the filter is BP, then the expected keys are:

BP : flux density BP(lambda eff) : effective wavelength, optional BP(lambda pivot) : pivot wavelength, optional

Parameters:

filtstring: Name of the filter.
unitstring, Unit, optional: Spectral flux density units for the output.

Returns:

lambda_eff: Quantity: Effective wavelength. None if it is not provided.
lambda_pivot: Quantity: Pivot wavelength. None if it is not provided.
fluxdQuantity: Spectral flux density.

Raises:

FilterLookupError if the filter is not defined.

observe_spectrum(wave_or_freq, unit=None, **kwargs)¶

Observe source as through a spectrometer.

Important

This method works best when the requested spectral resolution is lower than the spectral resolution of the internal data. If the requested wavelengths/frequencies are exactly the same as the internal spectrum, then the internal spectrum will be returned without binning. This special case does not work for subsets of the wavelengths.

Parameters:

wave_or_freqQuantity: Wavelengths or frequencies of the spectrum. Spectral bins will be centered at these values. The length must be larger than 1.
unitstring, Unit, optional: Spectral flux density units for the output. If None, the default is W/(m2 μm) for wavelengths, Jy for frequencies.
**kwargs: Additional keyword arguments for Observation, e.g., force.

Returns:

fluxdQuantity: The spectrum rebinned.

Raises:

SinglePointSpectrumError - If requested wavelengths or: frequencies has only one value.

Notes

Method for spectra adapted from AstroBetter post by Jessica Lu: https://www.astrobetter.com/blog/2013/08/12/python-tip-re-sampling-spectra-with-pysynphot/

redden(S)¶

Redden the spectrum.

Parameters:

SSpectralGradient: The spectral gradient to redden.

Returns:

specSpectralSource: Reddened spectrum

classmethod show_builtin(print=True)¶: List built-in spectra.

Navigation

Sun¶