B型快速自转星轩辕十四的光球层丰度研究
On the photospheric abundances of the B-type fast rotator Regulus
AI总结：
本文通过光谱拟合结合非局部热动平衡效应，测定B型快转星轩辕十四的14种元素丰度，发现其碳丰度显著不足且无法用现有简单机制解释，需后续研究。
AI中文摘要：
本文对轩辕十四（late B型快速自转恒星）开展光谱研究，旨在探究其光球层的化学元素丰度（尤其是轻元素）；由于这类极快速自转恒星（自转速度>~300 km/s）的丰度测定难度极大，相关研究此前鲜有开展。基于光谱能量分布确定其大气参数为有效温度T_eff=12345K、表面重力log g=3.58，微湍流速度v_t=0.5 km/s。采用光谱拟合技术推导了14种元素（氦He、碳C、氮N、氧O、氖Ne、镁Mg、硅Si、硫S、钙Ca、钛Ti、铬Cr、锰Mn、铁Fe、镍Ni）的丰度，其中对氦至钙的较轻元素考虑了非局部热动平衡（non-LTE）效应。得到的相对于太阳的丰度[X/H]呈现出显著趋势：多数元素的丰度接近太阳丰度（偏差在±<~0.3 dex以内），仅碳呈现明显的丰度不足（[C/H]~-1.4），这一现象难以解释。例如，由CN循环产物混合（如快速自转或双星质量转移导致）引发碳丰度不足的简单场景并不成立，因为未观测到任何氮的丰度增丰。该问题仍有待进一步研究。
英文摘要：
A spectroscopic study of Regulus (late B-type rapidly-rotating star) was conducted with an aim of investigating its photospheric chemical abundances (especially for light elements), which has barely been challenged so far because of the considerable difficulty of abundance determination for such a very fast rotator (>~300 km/s). The atmospheric parameters were determined to be T_eff = 12345K (effective temperature) and log g = 3.58 (surface gravity) based on the spectral energy distribution, while the microturbulence was estimated as v_t = 0.5 km/s. The abundances of 14 elements (He, C, N, O, Ne, Mg, Si, S, Ca, Ti, Cr, Mn, Fe, and Ni) were derived by applying the spectrum-fitting technique, where the non-LTE effect was taken into account for lighter elements from He to Ca. The resulting relative-to-the-Sun abundances ([X/H]) revealed a remarkable trend that, while most elements indicate near-solar abundances (within +/-<~0.3dex), only C shows a marked deficiency ([C/H]~ -1.4) which is hard to explain. For example, a simple scenario of C underabundance caused by mixing of CN-cycled product (e.g., due to rapid rotation or binary mass transfer) is unlikely because any N enrichment is not observed. This problem remains yet to be further investigated.
