Chemically tagging the Hyades stream: Does it partly originate from the
  Hyades cluster?
  The Hyades stream has long been thought to be a dispersed vestige of the
Hyades cluster. However, recent analyses of the parallax distribution, of the
mass function, and of the action-space distribution of stream stars have shown
it to be rather composed of orbits trapped at a resonance of a density
disturbance. This resonant scenario should leave a clearly different signature
in the element abundances of stream stars than the dispersed cluster scenario,
since the Hyades cluster is chemically homogeneous. Here, we study the
metalllicty as well as the element abundances of Li, Na, Mg, Fe, Zr, Ba, La,
Ce, Nd, and Eu for a random sample of stars belonging to the Hyades stream, and
compare them with those of stars from the Hyades cluster. From this analysis:
(i) we independently confirm that the Hyades stream cannot be solely composed
of stars originating in the Hyades cluster; (ii) we show that some stars from
the Hyades stream nevertheless have abundances compatible with an origin in the
cluster; (iii) we emphasize that the use of Li as a chemical tag of the cluster
origin of main-sequence stars is very efficient in the range 5500 - 6200 K,
since the Li sequence in the Hyades cluster is very tight; (iv) we show that,
while this evaporated population has a metallicity excess of ~0.2 dex w.r.t.
the local thin disk population, identical to that of the Hyades cluster, the
remainder of the Hyades stream population has still a metallicity excess of
~0.06 to 0.15 dex, consistent with an origin in the inner Galaxy; (v) we show
that the Hyades stream can be interpreted as an inner 4:1 resonance of the
spiral pattern: this then also reproduces an orbital family compatible with the
Sirius stream, and places the origin of the Hyades stream up to 1 kpc inwards
from the solar radius, which might explain the observed metallicity excess of
the stream population.
