Herein, meteoritic isotopic data can provide strong constraints for the source components that describe the s and r process, respectively, i.e. AGB stars, massive stars, and neutron star mergers.

Traces of radioactive material in samples from the early solar system provide an additional source of information, as they include the temporal signatures of radioactive decay, and thus the ingestion history of material into the mix of early solar system matter (Lugaro et al, 2022). In total 19 isotopic species have been analyzed with respect to their relative enrichment, comparing to abundance fractions as expected from the variety of nucleosynthesis processes (Davis, 2022). Thus, a clear enrichment of 26Al by about a factor 10 over the large-scale interstellar abundance is interpreted as a late ingestion of some specific nucleosynthesis ashes. Candidates could be a nearby AGB or Wolf-Rayet star (Wasserburg et al, 1977; Boss and Keiser, 2010; Dwarkadas et al, 2017; Vescovi et al, 2018), being prominent sources of 26Al, and presumably less destructive to a protostellar system than a supernova might be. But among the many scenarios discussed, it remains difficult to weigh the different plausibilities for ingestion of fresh nucleosynthesis ejecta into a protostellar system (Lugaro et al, 2022). Another example is the constraint on a candidate source of r-process ejecta in the vicinity of the solar system near its formation time, derived from the combined 129I and 247Cm isotopic abundances inferred for the early solar system (Cˆot´e et al, 2021).

4.4 Constraining stellar matter in compact stars

The characteristics of nuclear binding and nucleon interactions shape the macroscopic behavior of matter, which is observed in particular in compact stars that are not stabilized by the above-discussed release of nuclear energy through fusion reactions. This shapes astronomical phenomena from such stars, which in turn can be exploited to constrain nuclear binding at a macroscopic level.

Gravitational waves have come available as an astronomical tool in the last two decades, with LIGO and VIRGO experiments in the US and Italy, respectively. The discovery of the kilonova AT2017gfo (Smartt et al, 2017) associated with gravitationalwave event GW170817 (Abbott et al, 2017a) and with gamma-ray burst GRB170817A (Abbott et al, 2017b) provides one of the great recent successes in nuclear astrophysics. It confirms earlier predictions (Li and Paczy´nski, 1998; Rosswog, 2005; Metzger et al, 2010) of such an event to exist, and also confirms its expected signatures to first order in an unprecedented broad range of astronomical messengers, now also including gravitational waves. Gravitational waves have revealed characteristic signals within the Hz to kHz regime (Abbott et al, 2017a) as expected from neutron star collisions (Bauswein and Janka, 2012), as well as from neutron star / black-hole collisions. From these signals, constraints have been derived on the elasticity of neutron star matter (Lattimer, 2021), as one of the neutron stars is tidally destroyed in the late phase of the inspiral (or early phase of the collision). The Japanese KAGRA interferometer joined LIGO and VIRGO in 2021 for collaborative measurements in the ’O4’ run, and is the first detector for gravitational waves installed underground for better noise suppression (Akutsu et al, 2021). Space-based interferometer instrumentation will enhance the range of period that can be measured in gravitational waves beyond the sub-second periods of ground-based instruments from tens of seconds to years, thus

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