Discovery of carbon-rich Miras in the Galactic bulge
  Only one carbon-rich (C-rich, hereinafter) Mira variable has so far been
suggested as a member of the Galactic bulge and this is in a symbiotic system.
Here we describe a method for selecting C-rich candidates from an infrared
colour-colour diagram, (J-Ks) vs ([9]-[18]). Follow-up low-resolution
spectroscopy resulted in the detection of 8 C-rich Mira variables from a sample
of36 candidates towards the Galactic bulge. Our near-infrared photometry
indicates that two of these, including the known symbiotic, are closer than the
main body of the bulge while a third is a known foreground object. Of the 5
bulge members, one shows He I and [O II] emission and is possibly another
symbiotic star. Our method is useful for identifying rare C-rich stars in the
Galactic bulge and elsewhere. The age of these C-rich stars and the
evolutionary process which produced them remain uncertain. They could be old
and the products of either binary mass transfer or mergers, i.e. the
descendants of blue stragglers, but we cannot rule out the possibility that
they belong to a small in-situ population of metal-poor intermediate age (less
than 5 Gyr) stars in the bulge or that they have been accreted from a dwarf
galaxy.
