AI 中文总结
本研究验证了低分辨率SpeX/IRTF Y+J光谱结合贝叶斯全光谱拟合方法，可可靠测得与光学参考标度一致的造父变星金属丰度，为扩展至更远样本提供了基础。
AI 中文摘要
经典造父变星的金属丰度可追踪近期化学增丰情况，有助于评估基于造父变星的距离测量中的系统误差。这类丰度主要通过高分辨率光学光谱推导，其提供了基准丰度标度，但测量仅局限于近邻天体系统。要将此类研究扩展至更远距离的造父变星，需借助互补的低分辨率近红外方法并谨慎处理模型与数据的残差。我们测试低分辨率SpeX/IRTF Y+J波段光谱能否产出与均匀化光学丰度一致的金属丰度。我们分析了14颗周期约13至69天的银道面经典造父变星，补充了IRTF光谱库中的2颗短周期恒星。采用基于MARCS/TURBOSPECTRUM光谱的贝叶斯全光谱拟合及正则化协方差似然，我们推导了[M/H]并将其与均匀化光学[Fe/H]对比。对于主要的14颗恒星样本，推导的金属丰度重现了光学参考标度，平均偏移为-0.05 dex，离散度为0.09 dex，稳健离散度为0.12 dex；后验不确定度的中位数为0.22 dex。纳入额外2颗恒星仅使这些数值发生微小变化。与对角似然相比，协方差感知处理降低了平均偏移并提升了不确定度校准的稳定性。因此，当明确处理短程相关残差和局域化建模缺陷时，低分辨率Y+J光谱包含经典造父变星可用的金属丰度信息。所得近红外金属丰度标度为将造父变星金属丰度研究扩展至更大、更远的样本提供了实用基础。
英文摘要
Classical Cepheid metallicities trace recent chemical enrichment and help assess systematics in Cepheid-based distance measurements. They are derived mainly from high-resolution optical spectroscopy, which provides the benchmark abundance scale but limits measurements to nearby systems. Extending such studies to more distant Cepheids with extremely large telescopes requires complementary low-resolution near-infrared methods and careful treatment of model--data residuals. We test whether low-resolution SpeX/IRTF Y+J-band spectra can yield metallicities compatible with homogenised optical abundances. We analyse 14 Galactic classical Cepheids with periods of approximately 13--69 d, supplemented by two shorter-period stars from the IRTF Spectral Library. Using Bayesian full-spectrum fitting based on MARCS/TURBOSPECTRUM spectra and a regularised covariance likelihood, we infer [M/H] and compare it with homogenised optical [Fe/H]. For the primary 14-star sample, the inferred metallicities reproduce the optical reference scale with a mean offset of -0.05 dex, a scatter of 0.09 dex, and a robust scatter of 0.12 dex; the median posterior uncertainty is 0.22 dex. Including the two additional stars changes these values only slightly. Compared with a diagonal likelihood, the covariance-aware treatment reduces the mean offset and improves the stability of the uncertainty calibration. Low-resolution Y+J spectra therefore contain usable metallicity information for classical Cepheids when short-range correlated residuals and localised modelling imperfections are treated explicitly. The resulting near-infrared metallicity scale provides a practical foundation for extending Cepheid metallicity work to larger and more distant samples.
Comments19 pages, 6 figures, accepted for publication in Astronomy & Astrophysics
