AI 中文总结
研究网罟座球状星团中的RR型变星，通过近红外观测和光变曲线模板得出其周期-光度关系等，导出精确距离模数，与LMC几何距离吻合，有望校准第二星族距离阶梯。
AI 中文摘要
网罟座是大麦哲伦星系（LMC）外围一个古老、贫金属且恒星分布稀疏的球状星团，拥有丰富的天琴座RR型变星。它尽可能接近单一恒星族群，金属丰度差异可忽略且红化程度低，是测试恒星脉动模型和校准第二星族距离指标的理想实验室。我们展示了用8.1米双子座南望远镜上的Flamingos-2成像仪获得的网罟座RR型变星的多时期近红外（NIR，JHKs）均匀观测结果。利用NIR光变曲线模板，我们得出了32颗RR型变星的精确强度平均星等和峰峰值振幅，包括22颗基模（RRab）、4颗第一泛音（RRc）和6颗混合模（RRd）脉动变星。网罟座RR型变星的经验JHKs周期-光度（PL）关系非常紧密，其色散（约0.05星等）与银河系球状星团中观测到的相当。导出的PL斜率比银河系星团变量报道的更浅。采用基于银河系球状星团和脉动模型的最新经验和理论周期-光度-金属丰度（PLZ）校准，我们得出网罟座的真实距离模数为μ0 = 18.472±0.035星等。该星团距离与LMC的精确几何距离非常吻合，使网罟座接近LMC的质心距离。特征明确的RR型变星族群和精确距离使网罟座成为校准第二星族距离阶梯的潜在锚点。
英文摘要
Reticulum is an old, metal-poor, and sparsely populated globular cluster in the outer regions of the Large Magellanic Cloud (LMC) and hosts a rich population of RR Lyrae stars. Being as close as possible to a single stellar population with negligible metallicity spread and low reddening, Reticulum is an ideal laboratory for testing stellar pulsation models and calibrating population II distance indicators. We present homogeneous multi-epoch near-infrared (NIR, JHKs) observations of RR Lyrae variables in Reticulum obtained with the Flamingos-2 imager on the 8.1-m Gemini South Telescope. Using NIR light-curve templates, we derive accurate intensity-averaged magnitudes and peak-to-peak amplitudes for 32 RR Lyrae stars, including 22 fundamental-mode (RRab), 4 first-overtone (RRc), and 6 mixed-mode (RRd) pulsators. The empirical JHKs period-luminosity (PL) relations of Reticulum RR Lyrae are very tight, exhibiting dispersions (~0.05 mag) comparable to those observed in Galactic globular clusters. The derived PL slopes are shallower than those reported for Galactic cluster variables. Adopting recent empirical and theoretical period-luminosity-metallicity (PLZ) calibrations based on Galactic globular clusters and pulsation models, we derive a true distance modulus of $μ_0 = 18.472 \pm 0.035$ mag to Reticulum. This cluster distance is in excellent agreement with the precise geometric distance to the LMC and places Reticulum close to the LMC barycentric distance. The well-characterized RR Lyrae population and a precise distance make Reticulum a potential anchor for calibrating Population II distance ladder.
CommentsAccepted for publication in The Astronomical Journal
