Calculating R'_HK

The first thing I need to do is to be able to plot the extracted spectra (fits files) produced by my IRAF reduction in Python. This is proving to be a bit more difficult than it should be (see this post). One difference between the problem in the linked post and my problem is that my fits files are plotting just fine in splot, but not in python.

Once the above problem is sorted out, here is a prescription for calculating R'HK:

(1) Calculate an S value

• defined based on the operation of the Mount Wilson spectrometers (Duncan et al. 1991)
• R and V channels are 20A wide centered on 4001.07A and 3901.07A (in the star's frame) respectively
• H and K channels are triangular with the FWHM =1.09A
• S=alpha*(H+K)/(R+V), alpha = 2.4

(2)  Calculate R_HK from S and B-V (Middelkoop 1982)

\[C=1.13(B-V)^3 - 3.91(B-V)^2 + 2.84(B-V) - 0.47\]


\[R_{HK} = 1.34\times10^{-4}\times  C \times S\]

(3) Make a photometric correction to get R'_HK

\[logR_{phot} = -4.898 + 1.918(B-V)^2 - 2.893(B-V)^3
\]


\[R'_{HK} = R_{HK} - R_{phot}\]



Now, I have had some trouble plotting my spectra in Python (the headers seem to be screwed up so that when I plot the spectra, the x-axis doesn't have the wavelength solution applied and the spectra seems to only reach the peak of the blaze profile). But maybe I can get around this:

The equivalent width tells you (in a round-about way) the flux inside some rectangle centered on the line in question. If you normalize that by the width of a rectangular bandpass to account for the continuum, you should get the same units (and the same physical measurement) as if you had calculated R'HK. There should be a straight-foward constant correction factor one could apply to transform that number into an R'HK. More to come...