Abstract

We have demonstrated the advantage of combining multiwavelength 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 arcmin and for the first time, we report the identification of NUV-bright red clump (RC) stars and the extension of the RC in colour and magnitude in the NUV versus (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 similar to 5000-5500 K, luminosity similar to 60-90 L-circle dot, and radius similar to 8.0-11.0 R-circle dot supporting their RC nature. The range of UV magnitudes amongst the RC stars (similar to 23.3-24.8 mag) is likely caused by the combined effects of variable mass-loss, variation in initial helium abundance (Y-ini = 0.23-0.28), 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.