UVIT-HST-GAIA view of NGC 288: A census of hot stellar population and
  their properties from UV
  A complete census of Blue Horizontal Branch (BHB) and Blue Straggler Star
(BSS) population within the 10$'$ radius from the center of the Globular
Cluster, NGC 288 is presented, based on the images from the Ultraviolet Imaging
Telescope (UVIT). The UV and UV$-$optical Colour-Magnitude Diagrams (CMDs) are
constructed by combining the UVIT, HST-ACS and ground data and compared with
the BaSTI isochrones generated for UVIT filters. We used stellar proper motions
data from GAIA DR2 to select the cluster members. Our estimations of the
temperature distribution of 110 BHB stars reveal two peaks with the main peak
at $T_{eff}\sim$ 10,300 K with the distribution extending up to $T_{eff}\sim$
18,000 K. We identify the well known photometric gaps including the G-jump in
the BHB distribution which are located between the peaks. We detect a plateau
in the FUV magnitude for stars hotter than $T_{eff}\sim$ 11,500 K (G-jump),
which could be due to the effect of atomic diffusion. We detect 2 Extreme HB
(EHB) candidates with temperatures ranging from 29,000 to 32,000 K. The radial
distribution of 68 BSSs suggests that the bright BSSs are more centrally
concentrated than the faint BSS and the BHB distribution. We find that the BSSs
have a mass range of 0.86 - 1.25 M$_{\odot}$ and an age range of 2 - 10 Gyr
with a peak at 1 M$_{\odot}$ and 4 Gyr respectively. This study showcases the
importance of combining UVIT with HST, ground, and GAIA data in deriving HB and
BSS properties.
