Prediction of Multiple Features in the Black Hole Mass Function due to Pulsational Pair-Instability Supernovae

Understand

Using high-resolution simulations of black hole formation from the direct collapse of massive stars undergoing pulsational pair-instability supernovae (PPISN), we find a new phenomenon which significantly affects the explosion and leads to two peaks in the resulting black hole mass function (BHMF).

• Lighter stars experiencing the pair-instability can form a narrow shell in which alpha ladder reactions take place, exacerbating the effect of the PPISN.
• The shell temperature in higher mass stars ($>62 {\rm M}_\odot $ at the onset of helium burning for population-III stars with metallicity $Z=10^{-5}$) is too low for this to occur.
• As a result, the spectrum of black holes $M_{\rm BH} (M_i)$ exhibits a shoulder feature whereby a large range of initial masses result in near-identical black hole masses.