Two Distinct Red Giant Branches in the Globular Cluster NGC 288
  We report the presence of two distinct red giant branches (RGBs) in the
globular cluster NGC 288 from the narrow-band calcium and Str\"{o}mgren b & y
photometry obtained at the CTIO 4m Blanco telescope. The RGB of NGC 288 is
clearly split into two in the hk [=(Ca - b) - (b - y)] index, while the split
is not shown in the b - y color. Unlike other globular clusters with multiple
populations reported thus far, the horizontal branch of NGC 288 is only mildly
extended. Our stellar population models show that this and the presence of two
distinct RGBs in NGC 288 can be reproduced if slightly metal-rich (\Delta [m/H]
$\approx$ 0.16) second generation stars are also enhanced in helium by small
amount (\Delta Y $\approx$ 0.03) and younger by ~ 1.5 Gyrs. The RGB split in hk
index is most likely indicating that the second generation stars were affected
by supernovae enrichment, together with the pollutions of lighter elements by
intermediate-mass asymptotic giant branch stars or fast-rotating massive stars.
In order to confirm this, however, spectroscopy of stars in the two distinct
RGB groups is urgently required.
