Calculating cumulative periastron time shift from relativistic orbital decay

Join the discussion
Registration is free. Start your own thread to ask a follow-up.
2 replies · 2K views
Meerio
Messages
16
Reaction score
1
B1913+16.gif

I'm confused about how the predictions of this graph were formed.
I have this formula:
Untitled.png

But the change in frequency per second is about : 2x 10^-12 which has a problem because when you multiply this by 10 years you don't even get a change of frequency of 1/1000 of a second and in the graph it says it's around 5 seconds.
Anyone know what I'm doing wrong?

Paper: https://arxiv.org/pdf/1011.0718v1.pdf
 
Physics news on Phys.org
This is the cumulative change in time, not in frequency. You need the integral or sum.

The first measured orbit was about 7.75 hours, the next was 2.4 * 10-12 * 7.75h = 67ns shorter (integrated shift: 67 ns), the following one was 2*67 ns shorter than the first one (cumulative shift: 67+2*67 = 201 ns) and so on.

In 10 years, there were 11300 orbits, for a cumulative shift of 1/2 * 67 ns * 113002 = 4.3 seconds, in agreement with the parabola shown there.
 
  • Like
Likes   Reactions: Meerio