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GWTC-4.0: Population Properties of Merging Compact Binaries
A. G. Abac et al 2026 The Astrophysical Journal Letters 1005 .
Caption: Figure 11.
The inferred peak (top) and width (middle) of the χeff distribution as a function of mass ratio for the (q, χeff) LINEAR model (blue) and SPLINE model (orange). The shaded regions in these panels give the 90% credible intervals. The bottom panel gives the posterior distribution for the gradient of the χeff distribution’s peak (δμeff∣q) and natural log width (﹩\delta {\mathrm{ln}}{\sigma }_{{{\rm{eff}}}| q}﹩) dependent on mass ratio. From dark to light, the shaded regions represent the 50%, 90%, and 99% credible intervals. Again, blue gives the result of the LINEAR model, while orange shows the result of the SPLINE model sliced through q = 0.6 (the approximate point at which the gradients are largest). It appears that mass ratio and χeff exhibit some kind of correlation, but the exact nature is unclear.
© 2026. The Author(s). Published by the American Astronomical Society.