Precision distance to Galactic Cepheid variables with infrared observation

通过红外观测到银河造父变星的精确距离

• 批准号: 10640225
• 负责人: SEKIGUCHI Maki
• 金额: $ 2.56万
• 依托单位: Institute for Cosmic Ray Research, University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10640225/
• 关键词: Cepheid variables; distance determination; セフアイド変光星

We have installed an existing 40cm telescope tube onto the purchased mount resulting in fully automatic observation, No other system exists for infrared observing of stellar-clusters with Cepheid variables, We installed an existing IR-camera to the telescope. We improved the camera's cooling capacity for longer automatic observation. After observing several clusters, we found that singal-to-noise ratio of that camera is five times worse than expected. This noise problem allows us to observe clusters only within 1 Kpc. We therefore focused our analysis on M25 and NGC1647 and found that the error contribution from dust absorption was reduced by a factor of four compared to previous observation in visible wavelength. Parallel to the observation, we put emphasis on the improvement of isochrone and on importance of metallicity. We found the existing B-V transformation contains large uncertainty. Using the modern updated database and metallicity-dependence, we derived better revised B-V transformation (AJ in press). As far the metallicity, we derived a new formula to estimate metallicity from UBV photometory (in preparation).

我们已将现有的 40 厘米望远镜管安装到购买的支架上，从而实现全自动观测，没有其他系统可用于对具有造父变星的恒星团进行红外观测，我们在望远镜上安装了现有的红外相机。我们改进了相机的冷却能力，以实现更长时间的自动观察。在观察了几个集群后，我们发现该相机的信噪比比预期差五倍。这个噪声问题使得我们只能观察到 1 Kpc 以内的簇。因此，我们将分析重点放在 M25 和 NGC1647 上，发现与之前在可见光波长下的观察相比，灰尘吸收造成的误差贡献减少了四倍。与观察平行，我们强调等时线的改进和金属丰度的重要性。我们发现现有的B-V变换存在很大的不确定性。使用现代更新的数据库和金属丰度依赖性，我们得出了更好的修正 B-V 变换（AJ 正在出版）。至于金属丰度，我们从UBV光度法（准备中）导出了一个新的公式来估算金属丰度。

项目成果

M. SEKIGUCHI: "A Study of the B-V colour temperature relation"Astronomical Journal. (印刷中8月号予定). (2000)

M. SEKIGUCHI：“B-V 色温关系的研究”天文学杂志（8 月号，目前正在印刷）（2000 年）。

M. SEKIGUCHI: "A study of the B-V color temperature relation"Astronomical Journal. (in print). (2000)

M. SEKIGUCHI：“B-V 色温关系的研究”天文学杂志。