58 lines
2.8 KiB
Python
58 lines
2.8 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 ...lib.helpers import error
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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=4.17e-13 * u.W / (u.m ** 2 * u.nm)),
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M=dict(wl=4800 * u.nm, sfd=4.17e-13 * u.W / (u.m ** 2 * u.nm)),
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N=dict(wl=10200 * u.nm, sfd=4.17e-13 * 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)
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def __init__(self, wl_bins: u.Quantity, temp: u.Quantity = 5778 * u.K,
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mag: u.Quantity = 0 * u.mag, band: str = "V"):
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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
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Desired apparent magnitude of the point source
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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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Returns
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-------
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"""
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if band not in self._band.keys():
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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 = BlackBody(temperature=temp, scale=1 * u.W / (u.m ** 2 * u.nm * u.sr))
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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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factor = self._band[band]["sfd"] / (bb(self._band[band]["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)
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# Initialize super class
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super().__init__(SpectralQty(wl_bins, sfd), wl_bins)
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