FUNDAMENTAL PERFORMANCE OF A DISPERSED FIXED DELAY INTERFEROMETER IN SEARCHING FOR PLANETS AROUND M DWARFS
FUNDAMENTAL PERFORMANCE OF A DISPERSED FIXED DELAY INTERFEROMETER IN SEARCHING FOR PLANETS AROUND M DWARFS
复制标题
DOI：
10.1088/0004-637x/738/2/132
复制
发表时间：
2011-05
期刊：
影响因子：
--
通讯作者：
Ji Wang;J. Ge;P. Jiang;Bo Zhao
中科院分区：
文献类型：
--
作者：
Ji Wang;J. Ge;P. Jiang;Bo Zhao
提出了一种新的方法来计算基本的多普勒测量极限与一个分散的固定延迟干涉仪（DFDI）在近红外（NIR）波长范围内搜索系外行星周围的M矮星在未来十年。它是基于计算的Q因子，通量归一化多普勒灵敏度的测量与DFDI创建的边缘光谱。我们计算的Q因子作为光谱分辨率R，恒星投影旋转速度Vsin i，恒星有效温度Teff，和干涉仪的光程差（OPD）的函数。我们还比较了DFDI的Q因子的流行的交叉色散阶梯光栅光谱仪的方法（直接阶梯光栅（DE）方法）。我们发现：（1）在R从5000到20,000的范围内，QDFDI是QDE的1.5 - 3倍;（2）QDFDI和QDE在很高的R（R ≤ 100,000）处收敛;（3）QDFDI随着R的增加和Vsin i的减少而增加;（4）对于给定的R，QDFDI随着Teff从3100 K下降到2400 K（M4V到M9V）而增加。我们还研究了QDFDI如何受到OPD的影响，发现对于宽范围的R，与最佳OPD的5 mm偏差不会显著影响QDFDI（10%或更少）。鉴于近红外多普勒测量很可能是探测器有限的一段时间，我们引入新的价值函数，这是直接相关的光子限制径向速度（RV）的不确定性，DFDI和DE方法来评估多普勒性能。我们发现，DFDI的波长覆盖和多目标能力的DE有限的检测器资源的强度。我们模拟的DFDI设计的基础上，被认为是下一代红外多普勒测量的红系外行星跟踪器（IRET）的性能。预测的光子限制的RV不确定性表明，如果存在的话，IRET能够在附近明亮的M矮星周围的可居住区探测到类地系外行星。本文提出了一种新的方法来定量估计大地线对RV不确定度的影响。我们的研究表明，光子限制RV不确定性可以达到99%的强度，大地线可以从测量的恒星光谱。在低到中等水平的大地线强度去除（50%-90%），最佳RV不确定性通常是光子限制RV不确定性的两到三倍。
We present a new method to calculate fundamental Doppler measurement limits with a dispersed fixed delay interferometer (DFDI) in the near-infrared (NIR) wavelength region for searching for exoplanets around M dwarfs in the coming decade. It is based on calculating the Q factor, a measure of flux-normalized Doppler sensitivity in the fringing spectra created with DFDI. We calculate the Q factor as a function of spectral resolution R, stellar-projected rotational velocity Vsin i, stellar effective temperature Teff, and optical path difference (OPD) of the interferometer. We also compare the DFDI Q factor to that for the popular cross-dispersed echelle spectrograph method (the direct echelle (DE) method). We find that (1) QDFDI is a factor of 1.5–3 higher than QDE at R ranging from 5000 to 20,000; (2) QDFDI and QDE converge at a very high R (R ⩾ 100,000); (3) QDFDI increases as R increases and Vsin i deceases; (4) for a given R, QDFDI increases as Teff drops from 3100 K to 2400 K (M4V to M9V). We also investigate how QDFDI is affected by OPD and find that a 5 mm deviation from the optimal OPD does not significantly affect QDFDI (10% or less) for a wide range of R. Given that the NIR Doppler measurement is likely to be detector-limited for a while, we introduce new merit functions, which is directly related to photon-limited radial velocity (RV) uncertainty, to evaluate Doppler performance with the DFDI and DE methods. We find that DFDI has strength in wavelength coverage and multi-object capability over the DE for a limited detector resource. We simulate the performance of the InfraRed Exoplanet Tracker (IRET) based on the DFDI design, being considered for the next generation IR Doppler measurements. The predicted photon-limited RV uncertainty suggests that IRET is capable of detecting Earth-like exoplanets in habitable zone around nearby bright M dwarfs if they exist. A new method is developed to quantitatively estimate the influence of telluric lines on RV uncertainty. Our study shows that photon-limited RV uncertainty can be reached if 99% of the strength of telluric lines can be removed from the measured stellar spectra. At low to moderate levels of telluric line strength removal (50%–90%), the optimal RV uncertainty is typically a factor of two to three times larger than photon-limited RV uncertainty.