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Equation 20 · Part 11 · A Neutron Star Is a Redshift Standard

subscript

ΔE/E≈veq/c=2πνR/c≈1.3×10−1(ν/500 Hz)(R/12 km)\Delta E/E \approx v_{eq}/c = 2\pi\nu R/c \approx 1.3\times10^{-1}(\nu/500\,\text{Hz})(R/12\,\text{km})
subscript

What this part means

The lower label selects a particular version, component, or indexed member of the quantity. For example, x₀ and xₜ can be values at different positions.

Its job in the formula

A subscript distinguishes a version, component, step, or member of a quantity. It does not automatically mean multiplication.

The passage around this formula

The mechanism behind that contradiction is simple enough to state in one line, and the paper’s authors compute it carefully because the commonly quoted version understates it by an order of magnitude. Surface rotation Doppler-broadens any spectral line by a fraction of its energy equal to the star’s equatorial velocity over the speed of light, Δ\Delta E/E ≈\approx veqv_{eq}/c = 2π\piν\nu R/c ≈\approx 1.3×\times10^{-1}(ν\nu/500\,Hz\text{Hz})(R/12\,km\text{km}) , where ν\nu is the star’s spin frequency and R its radius.

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Learn the underlying idea

A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.

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Sources cited in the article section

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