UVIT-HST-Gaia-VISTA study of KRON 3 in the Small Magellanic Cloud: A
  cluster with an extended red clump in UV
  We have demonstrated the advantage of combining multi-wavelength
observations, from the ultraviolet (UV) to near-infrared, to study Kron 3, a
massive star cluster in the Small Magellanic Cloud. We have estimated the
radius of the cluster Kron 3 to be 2.'0 and for the first time, we report the
identification of NUV-bright red clump (RC) stars and the extension of the RCin
colour and magnitude in the NUV vs (NUV-optical) colour-magnitude diagram
(CMD). We found that extension of the RC is an intrinsic property of the
cluster and it is not due to contamination of field stars or differential
reddening across the field. We studied the spectral energy distribution of the
RC stars and estimated a small range in temperature ~5000 - 5500K, luminosity
~60 - 90 Land radius ~8.0 - 11.0 Supporting their RC nature. The range of UV
magnitudes amongst the RC stars (~23.3 to 24.8 mag) is likely caused by the
combined effect of variable mass loss, variation in initial helium abundance
(Y_ini=0.23 to 0.28), and a small variation in age (6.5-7.5 Gyr) and
metallicity ([Fe/H]=-1.5 to -1.3). Spectroscopic follow-up observations of RC
stars in Kron 3 are necessary to confirm the cause of the extended RC.
