  We demonstrate that a massive asymptotic giant branch (AGB) star is a good
candidate as the main source of short-lived radionuclides in the early solar
system. Recent identification of massive (4-8 solar masses) AGB stars in the
Galaxy, which are both lithium- and rubidium-rich, demonstrates that these
stars experience proton captures at the base of the convective envelope (hot
bottom burning), together with high-neutron density nucleosynthesis with 22Ne
as a neutron source in the He shell and efficient dredge-up of the processed
material. A model of a 6.5 solar masses star of solar metallicity can
simultaneously match the abundances of 26Al, 41Ca, 60Fe, and 107Pd inferred to
have been present in the solar nebula by using a dilution factor of 1 part of
AGB material per 300 parts of original solar nebula material, and taking into
account a time interval between injection of the short-lived nuclides and
consolidation of the first meteorites equal to 0.53 Myr. Such a polluting
source does not overproduce 53Mn, as supernova models do, and only marginally
affects isotopic ratios of stable elements. It is usually argued that it is
unlikely that the short-lived radionuclides in the early solar system came from
an AGB star because these stars are rarely found in star forming regions,
however, we think that further interdisciplinary studies are needed to address
the fundamental problem of the birth of our solar system.
