Origin of the p-process radionuclides 92Nb and 146Sm in the early Solar System and inferences on the birth of the Sun

TL;DR

This study investigates the origins of early Solar System radionuclides 92Nb and 146Sm, exploring stellar production scenarios and their implications for the Sun's birth environment, suggesting a complex nucleosynthesis history and a star-forming region with many stellar siblings.

Contribution

It provides a detailed analysis of the stellar sources of 92Nb and 146Sm, proposing that multiple nucleosynthesis sites are needed and inferring the Sun's formation in a massive star-forming region.

Findings

A consistent model for 92Nb and 53Mn production is challenging within current uncertainties.

A longer isolation time (~10 Myr) before Sun formation is supported by radionuclide data.

Multiple stellar sources, including supernovae, are likely responsible for radionuclide abundances.

Abstract

The abundances of 92Nb and 146Sm in the early Solar System are determined from meteoritic analysis and their stellar production is attributed to the p process. We investigate if their origin from thermonuclear supernovae deriving from the explosion of white dwarfs with mass above the Chandrasekhar limit is in agreement with the abundance of 53Mn, another radionuclide present in the early Solar System and produced in the same events. A consistent solution for 92Nb and 53Mn cannot be found within the current uncertainties and requires that the 92Nb/92Mo ratio in the early Solar System is at least 50% lower than the current nominal value, which is outside its present error bars. A different solution is to invoke another production site for 92Nb, which we find in the alpha-rich freezeout during core-collapse supernovae from massive stars. Whichever scenario we consider, we find that a relatively long time interval of at least ~10 Myr must have elapsed from when the star-forming region where the Sun was born was isolated from the interstellar medium and the birth of the Sun. This is in agreement with results obtained from radionuclides heavier than iron produced by neutron captures and lends further support to the idea that the Sun was born in a massive star-forming region together with many thousands of stellar siblings.