论文标题
纠正恒星点对Ariel传输光谱的影响
Correcting the effect of stellar spots on ARIEL transmission spectra
论文作者
论文摘要
这项研究的目的是评估恒星点对Ariel观察到的行星传输光谱提取的影响。我们开发了一种在存在斑点的情况下，使用透射观测值来对恒星的恒星谱进行建模。它基于在恒星光谱网格上具有不同尺寸和温度的恒星光谱网格上的频谱的最小化过程。在比较在不同时期观察到的恒星光谱时，该方法还可以研究斑点的时间演变。我们还提出了一种方法，以纠正由于未培养的恒星斑点而导致的过境深度变化，并估计如果我们对恒星斑点上的交叉点进行相同的校正，我们引入的误差。该方法对Ariel在4年任务寿命中观察到的三种类型的恒星目标进行了测试。在所有探索的情况下，该方法允许从传输外观测值和非染色点可靠地恢复点参数（尺寸和温度），可以自信地恢复噪声水平内的行星大气传输频谱（平均不确定性在地球信号的平均不确定性最高）。相反，我们发现由于神秘的斑点而导致推断的行星光谱中的系统偏见，对最亮目标的可测量效果，尤其是对于更对比的斑点。
The goal of this study is to assess the impact of the stellar spots on the extraction of the planetary transmission spectra observed by ARIEL. We develop a method to model the stellar spectrum of a star in the presence of spots by using the out-of-transit observations. It is based on a chi squared minimization procedure of the out-of-transit spectrum on a grid of stellar spectra with different sizes and temperatures of the spots. The approach allows us also to study the temporal evolution of the spots when comparing stellar spectra observed at different epochs. We also present a method to correct the transit depth variations due to non-occulted stellar spots and estimate the error we introduce if we apply the same correction to crossings over the stellar spots. The method is tested on three types of stellar targets that ARIEL will observe in its 4-years mission lifetime. In all the explored cases, the approach allows to reliably recover the spot parameters (size and temperature) from out-of-transit observations and, for non-occulted spots, to confidently recover the planetary atmosphere transmission spectrum within the noise level(with average uncertainty of at most 3.3% of the planetary signal). Conversely, we find systematic biases in the inferred planetary spectra due to the occulted spots, with measurable effects for the brightest targets especially for more contrasted spots.
