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Spectral flux density. In spectroscopy, spectral flux density is the quantity that describes the rate at which energy is transferred by electromagnetic radiation through a real or virtual surface, per unit surface area and per unit wavelength (or, equivalently, per unit frequency). It is a radiometric rather than a photometric measure.
The jansky (symbol Jy, plural janskys) is a non- SI unit of spectral flux density, [1] or spectral irradiance, used especially in radio astronomy. It is equivalent to 10 −26 watts per square metre per hertz. The flux density or monochromatic flux, S, of a source is the integral of the spectral radiance, B, over the source solid angle:
Flux as flow rate per unit area. In transport phenomena (heat transfer, mass transfer and fluid dynamics), flux is defined as the rate of flow of a property per unit area, which has the dimensions [quantity]· [time] −1 · [area] −1. [6] The area is of the surface the property is flowing "through" or "across".
Spectral index. In astronomy, the spectral index of a source is a measure of the dependence of radiative flux density (that is, radiative flux per unit of frequency) on frequency. Given frequency in Hz and radiative flux density in Jy, the spectral index is given implicitly by Note that if flux does not follow a power law in frequency, the ...
Radiant flux: Φ e [nb 2] watt: W = J/s M⋅L 2 ⋅T −3: Radiant energy emitted, reflected, transmitted or received, per unit time. This is sometimes also called "radiant power", and called luminosity in Astronomy. Spectral flux: Φ e,ν [nb 3] watt per hertz: W/Hz: M⋅L 2 ⋅T −2: Radiant flux per unit frequency or wavelength. The latter ...
The monochromatic AB magnitude is defined as the logarithm of a spectral flux density with the usual scaling of astronomical magnitudes and a zero-point of about 3 631 janskys (symbol Jy), [1] where 1 Jy = 10−26 W Hz−1 m−2 = 10−23 erg s−1 Hz−1 cm−2 ("about" because the true definition of the zero point is based on magnitudes as ...
The equivalent width of a spectral line is a measure of the area of the line on a plot of intensity versus wavelength in relation to underlying continuum level. It is found by forming a rectangle with a height equal to that of continuum emission, and finding the width such that the area of the rectangle is equal to the area in the spectral line ...
Radiative flux. Radiative flux, also known as radiative flux density or radiation flux (or sometimes power flux density[1]), is the amount of power radiated through a given area, in the form of photons or other elementary particles, typically measured in W/m 2. [2] It is used in astronomy to determine the magnitude and spectral class of a star ...