Fitting a SiII curve in a supernova spectra

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SUMMARY

This discussion focuses on determining the redshift of Si II in type Ia supernova spectra to calculate the photosphere's velocity. Andrew is exploring various fitting functions, including second degree polynomials, Gaussian curves, and Lorentzian curves, to improve the accuracy of his data analysis. He reports poor results from his Chi-squared tests when using polynomial fitting, indicating a need for more suitable functions. The conversation suggests considering the graphical bisection method as a potential alternative for curve fitting.

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  • Basic concepts of redshift and its calculation
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Astronomers, astrophysicists, and data analysts working with supernova spectra who seek to enhance their curve fitting methodologies and improve the accuracy of redshift calculations.

rnielsen25
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Hello guys (and girls),

I'm trying to determine the dark phase of a type Ia supernovae. In order to do that I need to calculate the photosphere's velocity.
So I'm trying to determine the redshift of the Si II in the spectra, by finding the minima in the absorption line. But what kind of function should i use for fitting my data points? Should i use a second degree polynomial, gauss curve, or is there an actual function describing this?

Here is an example of the Si II absorption "line": https://images.slideplayer.com/15/4805820/slides/slide_4.jpg

I tried fitting the curve, using a second degree polynomial. But my Chi2 test was too bad for some of my fits. So I was hoping there was a better function?
 
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You could try a Gaussian , Viogt or Lorenzian curve but it might be better to just use the old fashioned graphical bisection method.

Regards Andrew
 

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