129 lines
5.5 KiB
Python
129 lines
5.5 KiB
Python
from ..target.ATarget import ATarget
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from ..SpectralQty import SpectralQty
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import astropy.units as u
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from astropy.modeling.models import BlackBody
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from astropy.constants import c, k_B
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from ...lib.logger import logger
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from ..Entry import Entry
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from typing import Union
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import numpy as np
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class BlackBodyTarget(ATarget):
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"""
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This class models the spectral flux density of a star of given magnitude using as black body radiator
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"""
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# Bands from Handbook of Space Astronomy and Astrophysics p. 139
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_band = dict(U=dict(wl=365 * u.nm, sfd=4.27e-11 * u.W / (u.m ** 2 * u.nm)),
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B=dict(wl=440 * u.nm, sfd=6.61e-11 * u.W / (u.m ** 2 * u.nm)),
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V=dict(wl=550 * u.nm, sfd=3.64e-11 * u.W / (u.m ** 2 * u.nm)),
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R=dict(wl=700 * u.nm, sfd=1.74e-11 * u.W / (u.m ** 2 * u.nm)),
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I=dict(wl=900 * u.nm, sfd=8.32e-12 * u.W / (u.m ** 2 * u.nm)),
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J=dict(wl=1250 * u.nm, sfd=3.18e-12 * u.W / (u.m ** 2 * u.nm)),
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H=dict(wl=1650 * u.nm, sfd=1.18e-12 * u.W / (u.m ** 2 * u.nm)),
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K=dict(wl=2200 * u.nm, sfd=4.17e-13 * u.W / (u.m ** 2 * u.nm)),
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L=dict(wl=3600 * u.nm, sfd=6.23e-14 * u.W / (u.m ** 2 * u.nm)),
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M=dict(wl=4800 * u.nm, sfd=2.07e-14 * u.W / (u.m ** 2 * u.nm)),
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N=dict(wl=10200 * u.nm, sfd=1.23e-15 * u.W / (u.m ** 2 * u.nm)))
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@u.quantity_input(wl_bins='length', temp=[u.Kelvin, u.Celsius], mag=[u.mag, u.mag / u.sr])
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def __init__(self, wl_bins: u.Quantity, temp: u.Quantity = 5778 * u.K, mag: u.Quantity = None,
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band: str = "V", law: str = "Planck"):
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"""
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Initialize a new black body point source
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Parameters
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----------
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wl_bins : length-Quantity
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Wavelengths used for binning
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temp : Quantity in Kelvin / Celsius
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Temperature of the black body
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mag : Quantity in mag or mag / sr
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Desired apparent magnitude of the black body source. If the magnitude is given in mag / sr or an equivalent
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unit, an extended source will be assumed.
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band : str
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Band used for fitting the planck curve to a star of 0th magnitude. Can be one of [U, B, V, R, I, J, H, K].
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law : str
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Which law to use for the calculation of the flux values. Can be either 'Planck' for using Planck's law or
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'RJ' to use the Rayleigh-Jeans approximation.
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Returns
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-------
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"""
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if band.upper() not in self._band.keys():
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logger.error("Band has to be one of '[" + ", ".join(list(self._band.keys())) + "]'")
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# Create blackbody model with given temperature
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bb = None
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if law.lower() == "planck":
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bb = BlackBody(temperature=temp, scale=1 * u.W / (u.m ** 2 * u.nm * u.sr))
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elif law.upper() == "RJ":
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bb = self.__rayleigh_jeans_factory(temp)
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else:
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logger.error("Unknown law '" + law + "' for target type BlackBody.")
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if mag is not None:
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# Calculate the correction factor for a star of 0th magnitude using the spectral flux density
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# for the central wavelength of the given band
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if mag.unit.is_equivalent(u.mag / u.sr):
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solid_angle_unit = (u.mag / mag.unit)
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mag = mag * solid_angle_unit
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factor = self._band[band.upper()]["sfd"] / (bb(self._band[band.upper()]["wl"]) * (
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solid_angle_unit.to(u.sr) * u.sr))
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else:
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factor = self._band[band.upper()]["sfd"] / (bb(self._band[band.upper()]["wl"]) * u.sr) * u.sr
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# Calculate spectral flux density for the given wavelengths and scale it for a star of the given magnitude
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sfd = bb(wl_bins) * factor * 10 ** (- 2 / 5 * mag / u.mag) # / 1.195 * 1.16 # scaling for AETC validation
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else:
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sfd = bb(wl_bins)
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# Initialize super class
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super().__init__(SpectralQty(wl_bins, sfd), wl_bins)
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@staticmethod
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@u.quantity_input(temp=[u.Kelvin, u.Celsius])
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def __rayleigh_jeans_factory(temp: u.Quantity):
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"""
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Create a lambda function for the Rayleigh-Jeans law
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Parameters
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----------
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temp : u.Quantity
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The temperature in Kelvins
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Returns
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-------
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res : lambda
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A lambda function for the Rayleigh-Jeans law with the variable lambda wavelength
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"""
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return lambda wl: (2 * c * k_B * temp / wl ** 4 / u.sr).to(u.W / (u.m ** 2 * u.nm * u.sr))
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@staticmethod
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def check_config(conf: Entry) -> Union[None, str]:
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"""
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Check the configuration for this class
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Parameters
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----------
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conf : Entry
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The configuration entry to be checked.
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Returns
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-------
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mes : Union[None, str]
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The error message of the check. This will be None if the check was successful.
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"""
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mes = conf.check_quantity("temp", u.K)
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if mes is not None:
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return mes
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if hasattr(conf, "mag"):
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mes = conf.check_quantity("mag", u.mag)
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if mes is not None:
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mes = conf.check_quantity("mag", u.mag / u.sr)
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if mes is not None:
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return mes
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mes = conf.check_selection("band", ["U", "B", "V", "R", "I", "J", "H", "K", "L", "M", "N"])
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if mes is not None:
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return mes
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if hasattr(conf, "law"):
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mes = conf.check_selection("law", ["Planck", "RJ"])
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if mes is not None:
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return mes
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