Short-Lived Radioisotopic enrichment from AGB interlopers in low-mass star-forming regions

Abstract

The decay of Short-Lived Radioisotopes (SLRs) can be a significant source of heating early in protoplanetary systems, though how a protoplanetary disk becomes enriched with these SLRs far above the galactic background level remains an open question. Observational evidence suggests that this enrichment occurs during the period from when the disk forms to when it progresses into a protoplanetary system, and is homogenous throughout the resultant planetary system. Whilst SLRs such as 26Al and 60Fe can be injected into disks through interaction with Wolf-Rayet winds and supernovae, these outflows can disrupt disks, and in the case of low-mass star-forming regions high-mass stars may not form at all. Recent research has determined the existence of AGB ``interlopers'', Asymptotic Giant Branch stars that pass close to or through star-forming regions that could be an alternative source of SLR enrichment to WR winds and supernovae. In this paper we study the effect of AGB interlopers on star-forming regions from a dynamical perspective, determining the enrichment amount of 26Al and 60Fe in disks within small clusters via numerous N-body simulations via a parameter space exploration. We find that enrichment is widespread from AGB stars, with efficient enrichment dependent on the time at which the interloper intersects the star-forming region. Velocity is a factor, though interlopers travelling at 30 km/s are capable of enriching many disks in a star-forming region assuming they encounter a disk when the interloper is more evolved.