53 lines
2.4 KiB
Python
53 lines
2.4 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 esbo_etc.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
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# band_sfd = {"U": 1790*u.Jansky, "B": 4063*u.Jansky, "V": 3636*u.Jansky, "R": 3064*u.Jansky,
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# "I": 2416*u.Jansky, "J": 1590*u.Jansky, "H": 1020*u.Jansky, "K": 640*u.Jansky}
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band_sfd = dict(U=4.175e-11, B=6.32e-11, V=3.631e-11, R=2.177e-11, I=1.126e-11, J=3.15e-12, H=1.14e-12, K=3.96e-13)
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band_sfd = {k: v * u.W / (u.m ** 2 * u.nm) for k, v in band_sfd.items()}
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band_wl = dict(U=366 * u.nm, B=438 * u.nm, V=545 * u.nm, R=641 * u.nm, I=798 * u.nm, J=1220 * u.nm, H=1630 * u.nm,
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K=2190 * 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_wl.keys():
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error("Band has to be one of '[" + ", ".join(list(self.band_wl.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_sfd[band] / (bb(self.band_wl[band]) * 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))
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