标题： 干涉仪校准源的角直径估计 - VLTI-AMBER的校准源lambda Gruis示例 显示英文标题

标题： Angular diameter estimation of interferometric calibrators - Example of lambda Gruis, calibrator for VLTI-AMBER

摘要： 上下文。 准确的长基线干涉测量需要使用参考星进行仔细校准。小校准星具有高角直径精度，确保真实的可见度不确定性主要由测量误差主导。 目标。 我们回顾了一些间接方法，用于估计角直径，使用各种类型输入数据。对于测试案例校准星lambda Gru获得的每个直径估计值，都与2002年发布的Bordé校准星目录中找到的2.71 mas值进行比较。 方法。 从光谱类型、光谱指数、带内星等、宽带光度和光谱光度得到的角尺寸估计值给出了接近的角直径估计值，具有略有变化的不确定度。对光度和光谱光度的拟合需要具有“合理”恒星参数的物理大气模型。 角直径的不确定度通过残差引导置信区间来估计。本文中呈现的所有数值结果和图形输出都是使用在PV-WAVE下开发的例程获得的，这些例程组成了模块化软件套件SPIDAST，该套件用于校准和解释光谱和干涉测量数据，特别是从VLTI-AMBER获得的数据。 结果。 通过在ISO-SWS 2.38-27.5微米光谱上对MARCS模型进行拟合，得到lambda Gru的最终角直径估计值为2.70 mas，68%置信区间为2.65-2.81 mas，恒星参数为T_eff = 4 250 K，log(g) = 2.0，z = 0.0 dex，M = 1.0 M_sun，xi_turb = 2.0 km/s。 显示英文摘要

摘要： Context. Accurate long-baseline interferometric measurements require careful calibration with reference stars. Small calibrators with high angular diameter accuracy ensure the true visibility uncertainty to be dominated by the measurement errors. Aims. We review some indirect methods for estimating angular diameter, using various types of input data. Each diameter estimate, obtained for the test-case calibrator star lambda Gru, is compared with the value 2.71 mas found in the Bord\'e calibrator catalogue published in 2002. Methods. Angular size estimations from spectral type, spectral index, in-band magnitude, broadband photometry, and spectrophotometry give close estimates of the angular diameter, with slightly variable uncertainties. Fits on photometry and spectrophotometry need physical atmosphere models with "plausible" stellar parameters. Angular diameter uncertainties were estimated by means of residual bootstrapping confidence intervals. All numerical results and graphical outputs presented in this paper were obtained using the routines developed under PV-WAVE, which compose the modular software suite SPIDAST, created to calibrate and interprete spectroscopic and interferometric measurements, particularly those obtained with VLTI-AMBER. Results. The final angular diameter estimate 2.70 mas of lambda Gru, with 68% confidence interval 2.65-2.81 mas, is obtained by fit of the MARCS model on the ISO-SWS 2.38-27.5 mum spectrum, with the stellar parameters T_eff = 4 250 K, log(g) = 2.0, z = 0.0 dex, M = 1.0 M_sun, and xi_turb = 2.0 km/s.