16907

This program will determine the line spread functions (LSFs) and spectral resolution obtained with the G160M grating at the Cosmic Origins Spectrograph.s (COS) sixth lifetime position. Well-constrained LSFs allow users to evaluate the feasibility and S-N constraints of their observations comma as well perform line profile fitting on their data. COS periodically shifts where its targets. light lands on the detector to avoid gain sag. The sixth of these d_commalifetime positionsd_comma (LPs) will become active for G160M exposures in Cycle 30. COS. LSFs and spectral resolution change with LP and with the grating and central wavelength settings used. This program will make observations to constrain the LSFs of two G160M central wavelength settings (cenwaves) comma G160M-1533 and G160M-1623 comma which encompass the range of cenwaves moving to LP6. We will acquire G160M-1533 and G160M-1623 spectra of the SMC blue supergiant star AV75 comma whose spectrum contains both narrow ISM absorption lines and complex convolved lines. We expect a S-N of 60 per resolution element at 1600 Angstroms. We will then convolve existing STIS E140M spectra of AV75 with various versions of the optically-modelled COS LP6 LSFs comma and determine which convolutions best agree with the COS spectra gathered here. These will be selected as the COS LP6 LSFs and used to determine the spectral resolution.本项目旨在测定G160M光栅在宇宙起源摄谱仪（Cosmic Origins Spectrograph，COS）第6个寿命位（lifetime position，LP）下获得的线扩散函数（line spread function，LSF）与光谱分辨率。约束良好的线扩散函数可帮助用户评估观测的可行性与信噪比（signal-to-noise ratio，S-N）限制条件，同时支持对其观测数据开展线型轮廓拟合。为避免探测器增益衰减，COS会周期性偏移目标光线在探测器上的落点，这类偏移位置即为寿命位。G160M光栅的第6个寿命位（LP6）将在第30个观测周期（Cycle 30）的G160M曝光任务中启用。COS的线扩散函数与光谱分辨率会随寿命位、光栅配置以及中心波长设置发生变化。本项目将开展观测以约束两种G160M中心波长设置下的线扩散函数，即G160M-1533与G160M-1623，二者覆盖了将迁移至LP6的全部中心波长范围。我们将获取小麦哲伦星系（Small Magellanic Cloud，SMC）蓝超巨星AV75的G160M-1533与G160M-1623光谱。该恒星的光谱同时包含窄星际介质（Interstellar Medium，ISM）吸收线与复杂的卷积线型。我们预期在1600埃波段处，每个分辨率单元的信噪比可达60。随后，我们将使用多款经光学建模得到的COS LP6线扩散函数，对AV75已有的空间望远镜成像摄谱仪（Space Telescope Imaging Spectrograph，STIS）E140M光谱进行卷积处理，并筛选出与本次获取的COS光谱匹配度最高的卷积结果。这些最优匹配的卷积模型将被确定为COS LP6线扩散函数，并用于计算对应的光谱分辨率。