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 NUVversus (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 ∼5000–5500 K, luminosity ∼60–90 L⊙, and radius ∼8.0–11.0 R⊙ supporting their RC nature. The range of UV magnitudes amongst the RC stars (∼23.3–24.8 mag) is likely caused by the combined effects of variable mass-loss, variation in initial helium abundance (Yini = 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.

中文翻译：

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UVIT-HST-Gaia-VISTA 对小麦哲伦星云中 Kron 3 的研究：在紫外线中具有扩展的红色团块的星团

我们已经证明了结合从紫外 (UV) 到近红外的多波长观测来研究小麦哲伦云中的一个巨大星团 Kron 3 的优势。我们估计 Kron 3 星团的半径为 2.0 arcmin，并且我们首次报告了 NUV 亮红团（RC）星的识别以及 NUV 对（NUV-光学）颜色-幅度图（CMD）。我们发现 RC 的扩展是星团的固有特性，它不是由于场星的污染或整个场的差异变红。我们研究了 RC 恒星的光谱能量分布，并估计了一个小范围的温度 ~5000-5500 K、光度 ~60-90 L⊙、半径 ~8.0-11.0 R⊙ 支持它们的 RC 特性。RC 恒星的紫外星等范围（~23.3-24.8 等）可能是由可变质量损失、初始氦丰度变化（Yini = 0.23-0.28）和年龄小变化（6.5 –7.5 Gyr）和金属丰度（[Fe/H] = -1.5 至 -1.3）。对 Kron 3 中 RC 星的光谱后续观测对于确认扩展 RC 的原因是必要的。