The Large Magellanic Cloud (LMC) star cluster NGC 2249 has been found to exhibit an extended main-sequence turn-off (eMSTO) in the color-magnitude diagram (CMD) derived from the data of the Hubble Space Telescope (HST). Such CMDs can potentially be explained via a spread of stellar age or rotation rate of single-aged stars, leading to a confusion of its stellar population type. In this work, we use different combinations of age spread (A), rotation (R), and binarity (B) to study the stellar population of this cluster, via a deep HST CMD. Because binaries are commonly observed in star clusters, three models of this study take binaries into account. We finally derive the best-fit stellar population parameters, i.e., metallicity (Z = 0.008), age (0.7–1.0 Gyr), reddening ($E(B-I)$ = 0.52–0.55 mag), distance modulus (18.54–18.57 mag), binary fraction (50%), rotating star fraction (0–50%), and star formation history mode for NGC 2249. We find that both age spread (A + B or A + R + B) and rotating stars (R + B) can reproduce the main CMD features well, while rotation alone does not reproduce the detailed eMSTO morphology. This suggests that an age spread of 200 Myrs is needed to form the eMSTO of cluster NGC 2249, even if stellar rotation is taken into account. Dynamical simulation could be useful for revealing the origin of the eMSTO.

大麦哲伦星云（LMC）星团NGC 2249在从哈勃太空望远镜（HST）的数据推导的色度图（CMD）中表现出扩展的主序列关闭（eMSTO ）。此类CMD可能通过恒星年龄的分布或单年龄恒星的自转率来解释，从而导致其恒星种群类型的混乱。在这项工作中，我们使用年龄分布（A），旋转（R）和二元性（B）的不同组合，通过深度HST CMD研究该星团的恒星种群。由于双星通常在星团中观察到，因此本研究的三个模型都将双星考虑在内。我们最终得出最合适的恒星总体参数，即金属性（Z = 0.008），年龄（0.7-1.0 Gyr），发红（$Ë（乙--\mathrm{一世}）$ = 0.52–0.55 mag），距离模量（18.54–18.57 mag），双星分数（50％），旋转星体分数（0–50％）和NGC 2249的星体形成历史模式。我们发现这两个年龄都扩散了（A + B或A + R + B）和旋转的恒星（R + B）可以很好地重现CMD的主要特征，而单独旋转则不能重现详细的eMSTO形态。这表明即使考虑了恒星旋转，也需要200 Myrs的年龄扩散来形成星团NGC 2249的eMSTO。动态仿真对于揭示eMSTO的起源可能很有用。