S stars and <i>s</i>-process in the <i>Gaia</i> era
S stars and <i>s</i>-process in the <i>Gaia</i> era
S stars are late-type giants that are transition objects between M-type stars and carbon stars on the asymptotic giant branch (AGB). They are classified into two types: intrinsic or extrinsic, based on the presence or absence of technetium (Tc). The Tc-rich or intrinsic S stars are thermally-pulsing (TP-)AGB stars internally …