<p>How could I determine semiamplitude from these data for NGC300 X-1 without fitting, only with data of phase and JD? This is a common problem for exoplanets, X-ray binaries and other general binary sistems. So, I am interested in general techniques (if any) beyond fitting (a list of software for data fitting for RV plots would be also welcome in the answer)
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CC BY-SA 4.0
2024-02-19T22:32:00.893Z
What do you mean by "without fitting"?  Surely finding the semi-amplitude **is** fitting a sine curve to the graph.  Least Squares has a good tradition (I get a least squares fit with an amplitude of 256.6.
James K
CC BY-SA 4.0
2024-02-19T23:31:47.620Z
I was tempted to guess an approximation to K making K=(v_r(max)-(v_r(min))/2. Indeed, ... k(guess)=(456.6-(-68.3)(/2=262.5km/s, not far from the given value. I presume the issue is the phase and a trigonometric condition.
riemannium
<exoplanet><data-analysis><x-ray>
How to determine semiamplitude from Julian Date data?
riemannium
# How to determine semiamplitude from Julian Date data?

(Asked by: username_0 on 2024-02-19)

How could I determine semiamplitude from these data for NGC300 X-1 without fitting, only with data of phase and JD? This is a common problem for exoplanets, X-ray binaries and other general binary sistems. So, I am interested in general techniques (if any) beyond fitting (a list of software for data fitting for RV plots would be also welcome in the answer)
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**Tags:** exoplanet, data-analysis, x-ray
> **Comments:**
> **username_1**: What do you mean by "without fitting"?  Surely finding the semi-amplitude **is** fitting a sine curve to the graph.  Least Squares has a good tradition (I get a least squares fit with an amplitude of 256.6.  
> **username_0**: I was tempted to guess an approximation to K making K=(v_r(max)-(v_r(min))/2. Indeed, ... k(guess)=(456.6-(-68.3)(/2=262.5km/s, not far from the given value. I presume the issue is the phase and a trigonometric condition.  

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