[AstroPy] Blackbody fit and Wien's displacement law

[Rudolf Baer]

Hi Derek
thank you very much !  I have learned something.
Cheers
Rudolf

On Mon, Jul 26, 2021 at 4:04 PM Derek Homeier <
derek at astro.physik.uni-goettingen.de> wrote:

> Hi Rudolf,
>
>
> Where does the  *500 (micron * K) *come from?
>
> What would be the correct way to determine the position of  lambda Wien
> for my plot?
>
> the 5099 micron * K result from substituting the (energy) value of the
> B_lambda maximum, 4.965 k_B T,
> in hc / E_max [hc / 4.965 k_B = 2898 micron * K] with the corresponding
> one for B_nu, 2.821 k_B T:
> hc / 2.821 k_B ~ 5099 micron * K
>
> To find the equivalent in (lambda B_lambda) ~~ (nu B_nu), you’d have to
> solve for the derivative of that function
> analogously to the derivation of Wien’s law for the other two functional
> forms, e.g. in
>
> https://en.wikipedia.org/wiki/Wien%27s_displacement_law#Derivation_from_Planck's_law
>
> If I am not mistaken the numerical value is also given in
> https://en.wikipedia.org/wiki/Planck%27s_law#Percentiles
> for the 41.8 percentile (maximum in logarithmic spectral axis), i.e. 3670
> (μm·K).
>
> Cheers,
> Derek
>
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