Radial velocities of RR Lyrae stars in and around NGC 6441
  Detailed elemental abundance patterns of metal-poor ([Fe/H] ~ -1~dex) stars
in the Galactic bulge indicate that a number of them are consistent with
globular cluster (GC) stars and may be former members of dissolved GCs. This
would indicate that a few per cent of the Galactic bulge was built up from
destruction and/or evaporation of globular clusters. Here an attempt is made to
identify such presumptive stripped stars originating from the massive, inner
Galaxy globular cluster NGC~6441 using its rich RR Lyrae variable star (RRL)
population. We present radial velocities of forty RRLs centered on the globular
cluster NGC~6441. All of the 13 RRLs observed within the cluster tidal radius
have velocities consistent with cluster membership, with an average radial
velocity of 24 +- 5~km/s and a star-to-star scatter of 11~km/s. This includes
two new RRLs that were previously not associated with the cluster. Eight RRLs
with radial velocities consistent with cluster membership but up to three time
the distance from the tidal radius are also reported. These potential
extra-tidal RRLs also have exceptionally long periods, which is a curious
characteristic of the NGC~6441 RRL population that hosts RRLs with periods
longer than seen anywhere else in the Milky Way. As expected of stripped
cluster stars, most are inline with the cluster's orbit. Therefore, either the
tidal radius of NGC~6441 is underestimated and/or we are seeing dissolving
cluster stars stemming from NGC~6441 that are building up the old spheroidal
bulge.
