Gravitational waves reveal the pair-instability mass gap and constrain nuclear burning in massive stars Article Swipe
YOU?
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· 2025
· Open Access
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· DOI: https://doi.org/10.21203/rs.3.rs-7539007/v1
· OA: W4414262139
<title>Abstract</title> Stellar evolution theory predicts that electron–positron pair production in the cores of massive stars triggers unstable thermonuclear explosions that prevent the direct formation of black holes above about 50M?, creating a “pair-instability gap” [1]. Yet black holes have been detected above this mass with gravitational waves; such objects might be explained with uncertainties in the physics of mas28 sive stars and stellar collapse or with hierarchical mergers of black holes in stellar clusters [2–5]. Hierarchical mergers are associated with large spins as pre30 dicted by general relativity [6–8], and isotropic spin orientations [9]. Here we present strong evidence for the pair-instability mass gap in the LIGO–Virgo– KAGRA fourth transient catalog [10], with a lower edge at 45.3+6.5 -4.8 32 M?. We also obtain a measurement of the 12C(a, ?)16O reaction rate, yielding an Sfactor of 242.5+310.4 -101.5 34 keVb, a parameter critical for modeling helium burning and stellar evolution. The new data reveal two populations: a low-spin group with no black holes above the gap, consistent with direct stellar collapse, and a high-spin, isotropic group that extends across the full mass range and occupies the gap, consistent with hierarchical mergers. These findings confirm the role of pair-instability in shaping the black hole spectrum, establish a new link between gravitational-wave astronomy and nuclear astrophysics, and highlight hierarchi41 cal mergers and star cluster dynamics as key channels in the growth of black holes [11, 12].
