干涉测量校准器的角直径估算. VLTI-AMBER校准器lambda Gruis示例
Angular diameter estimation of interferometric calibrators - Example of lambda Gruis, calibrator for VLTI-AMBER
摘要：
上下文精确的长基线干涉测量需要用参考星仔细校准。具有高角直径精度的小型校准器可确保真实可见度不确定性由测量误差主导。目标。我们回顾了一些间接的方法来估计角直径，使用各种类型的输入数据。每一个直径估计，获得了测试案例校准星lambda Gru，与2002年出版的Bordé校准器目录中发现的值2.71 mas进行比较。方法.根据光谱类型、光谱指数、带内星等、宽波段光度学和分光光度学对角直径进行的角大小估计，给出了接近的角直径估计值，但不确定性略有变化。光度学和分光光度学的拟合需要具有“合理”恒星参数的物理大气模型。角直径的不确定性估计的残差自举置信区间。本文中提出的所有数值结果和图形输出都是使用PV-WAVE下开发的例程获得的，该例程构成模块化软件套件SPIDAST，用于校准和校准光谱和干涉测量，特别是使用VLTI-AMBER获得的测量。结果在Teff = 4250 K，log（g）= 2.0，z = 0.0dex，M = 1.0Msun，xiturb = 2.0km/s的条件下，用MARCS模型拟合ISO-SWS 2.38-27.5 μ m光谱，得到λ Gru的最终角直径估计为2.70mas，置信区间为2.65- 2.81mas（68%）。
英文摘要：
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 Bordé 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.
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