利用法布里-珀罗标准具提高天文高分辨光谱仪的波长定标精度

Improvement of Wavelength Calibration Accuracy of Astronomical High-Resolution Spectrometers with Fabry-Perot Etalons

用于天文高分辨光谱波长定标的法布里-珀罗标准具(FPE)具有宽波长覆盖与密集透过峰序列的光谱,有望实现比传统定标源更高的波长定标精度。然而FPE透过峰波长是未知的,这为定标带来了挑战。本研究在不借助额外精密测量设备(如傅里叶变换光谱仪)情况下,使用天文高分辨光谱仪常规定标源钍氩灯(ThAr)为FPE提供波长信息,再利用FPE密集的透过峰序列以及电介质反射膜穿透深度与波长关系的平滑性质,修正波长信息中的误差,得到FPE透过峰精确的波长并完成波长定标。在兴隆2.16 m望远镜高分辨光纤光谱仪上的定标测试显示,FPE的波长定标精度达到0.053 pm,相比单独使用ThAr的波长定标精度(0.290 pm)有显著的提高。

Due to the wide wavelength coverage and dense transmission peak sequence of its spectrum, the Fabry-Perot etalon(FPE) for wavelength calibration of astronomical high-resolution spectra is expected to achieve higher calibration accuracy than traditional calibration sources. However, the unknown wavelengths of FPE transmission peaks pose a challenge for calibration. In this study, without precision measurement devices(such as Fourier transform spectrometers), the thorium-argon(ThAr) lamp, a conventional calibration source equipped on astronomical high-resolution spectrometers, was used to provide the FPE with wavelengths. Then, the errors in the ThAr wavelengths were corrected by using the dense transmission peak sequence of the FPE and the smooth relationship between the penetration depth of the dielectric reflective coating and the wavelength. Accurate wavelengths of the FPE transmission peaks were thus obtained, and wavelength calibration was performed. The calibration test on the fiber-fed high-resolution spectrometer of the Xinglong 2.16-m telescope showed that the wavelength calibration accuracy of the FPE reached 0.053 pm, which was significantly higher than that(0.290 pm) in the case of the ThAr being used alone.