51 lines
2.5 KiB
Python
51 lines
2.5 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 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 = {"U": 4.175e-11, "B": 6.32e-11, "V": 3.631e-11, "R": 2.177e-11,
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"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 = {"U": 366 * u.nanometer, "B": 438 * u.nanometer, "V": 545 * u.nanometer, "R": 641 * u.nanometer,
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"I": 798 * u.nanometer, "J": 1220 * u.nanometer, "H": 1630 * u.nanometer, "K": 2190 * u.nanometer}
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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
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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)
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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(self.band_wl, sfd))
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