Robust r-process Nucleosynthesis beyond Lanthanides in the Common Envelop Jet Supernovae

Abstract The common envelop jet supernovae (CEJSNe) r -process scenario has been proposed as an r -process nucleosynthesis site in the past decade. Jets launched by a neutron star that spirals in inside the core of a red supergiant star in a common envelope evolution supply the proper conditions for forming elements heavier than iron through the rapid neutron-capture process. The present work initially unveils the r -process abundance patterns that result from the density profile in the relatively long-lived jets. The results indicate that the expansion profile unique to the CEJSN scenario can produce the largest ratio of the third r -process peak elements to lanthanides among current r -process scenarios and, in addition, can form quite an amount of lanthanides, about 1% of matters above the first peak, in a single event. The comparison of the ratio of the third-peak elements to the lanthanides with several observed r-enhanced metal-poor stars and with other r -process scenarios suggests that a high mass of third-peak elements is anticorrelated with a high fraction of lanthanides, both in observations and theory. The CEJSN-like scenario plays a significant role in this conclusion since it reproduces the observational features of some particular r-enhanced metal-poor stars where other r -process scenarios encounter problems. Due to the formation of extremely heavy elements, the CEJSN also offers a credible estimation of the age of the most actinide-boosted star by cosmochronometry.