A new preprint (arXiv:2604.01420, not yet peer-reviewed) analyzes the mass distribution of merging black holes detected by LIGO, Virgo, and KAGRA, arguing that 'failed supernovae' — stars whose cores collapse directly into black holes without a successful explosion — create a distinct population around 10 solar masses. This connects stellar evolution theory directly to gravitational-wave observations in a way that earlier coverage has largely overlooked.

The researchers examined 153 binary black hole merger observations from the GWTC-4.0 catalog. Using statistical modeling of the primary mass distribution, they report a pronounced peak in the merger rate density of 7.36_{-3.11}^{+6.35} M_⊙^{-1} yr^{-1} Gpc^{-3} at approximately 10 solar masses. The rate then drops by roughly two orders of magnitude, becoming consistent with zero (at 90% confidence) between 12 and 16.1 solar masses, before rising again above 16 solar masses. The study explicitly treats these as a possible separate subpopulation rather than a smooth continuum.

Methodology relied on population inference techniques applied to the catalog events, accounting for detection biases and selection effects inherent to gravitational-wave observatories. Limitations are important: the sample size of 153 events, while the largest to date for this type of analysis, still yields large uncertainties in narrow mass bins. The results depend on assumptions about the underlying astrophysical model and may shift as future observing runs add hundreds more events. This is preprint work and has not undergone peer review.

Previous reporting on gravitational-wave catalogs has typically emphasized either individual spectacular mergers or the upper mass gap (around 50-120 solar masses) caused by pair-instability supernovae. What was missed was the fine-grained structure between 10-20 solar masses and its potential origin in the physics of core collapse. The compactness of the stellar core near 10 solar masses appears to favor direct collapse over explosion, reinforcing an overdensity that standard stellar evolution models alone could not fully explain.

Synthesizing this with the LIGO/Virgo GWTC-3 and GWTC-4 papers (which provide the raw event catalog and selection functions) and theoretical work on failed supernovae such as the 2019 Astrophysical Journal study by Sukhbold and Woosley on the 'compactness parameter' in massive star cores, a clearer picture emerges. The 10 solar mass peak is not merely an observational curiosity but a direct imprint of how supernova engines fail in a narrow progenitor mass window. This suggests multiple formation channels for black holes: some from standard supernovae, others from quiet direct collapses, producing the observed rate changes of multiple orders of magnitude across just a few solar masses.

The finding strengthens the dialogue between theory and observation. Stellar models have long predicted that explosion outcomes depend sensitively on core structure; gravitational waves are now showing us the population-level consequences. As detector sensitivity improves, we may resolve whether the dip between 12-16 solar masses represents a true 'mass gap' in merging systems or simply a transition between formation pathways.