subtraction

The passage around this formula

The way you weigh a neutron star from a radio telescope, with no direct access to the star at all, is to time its pulses with enough precision to catch general relativity bending them. In a binary system seen close to edge-on, radio pulses from the neutron star are delayed by a few extra microseconds each orbit as they pass close to the companion star, because the companion’s gravity curves the spacetime the pulse crosses. The delay as a function of orbital phase $\phi$ is standardly written $\Delta_S(\phi) = -2r\,\ln\!\left[1 - s\sin\phi\right]$. where the “range” parameter r is set directly by the companion’s mass and the “shape” parameter s by the orbit’s inclination. Because r and s are measured independently of the pulsar’s…

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