All along the line of sight: a closer look at opening angles and absorption regions in the atmospheres of transiting exoplanets
All along the line of sight: a closer look at opening angles and absorption regions in the atmospheres of transiting exoplanets
复制标题
沿着视线：仔细观察凌日系外行星大气中的开口角度和吸收区域
DOI：
10.1093/mnras/stab3432
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发表时间：
2022
影响因子：
4.8
通讯作者：
Wardenier J
中科院分区：
文献类型：
--
作者：
Wardenier J
透射光谱包含了大量关于过境系外行星大气层的信息。然而，大的热和化学梯度沿着视线可以导致有偏见的推断，在大气反演。为了确定离行星临边面多远的大气层仍然影响透射光谱，我们推导了一个新的公式来估计行星的张角。这是大气层对向的角度，有助于从行星中心沿沿着观察。我们基准我们的公式与3D蒙特卡罗辐射传输代码，我们定义了一个开放的角度适合解释JWST观测，假设10 ppm的噪声地板。我们发现，对于温度低于ca的行星，张角只有几度。500开尔文，而它可以大到25度的（超）热彗星和50度的热海王星。与以前的作品相比，我们更强大的方法导致更小的估计在很大范围的尺度高度和行星半径的张开角。最后，我们表明，超热彗星有一个开放的角度是小于行星在过境期间旋转的角度。这使得时间分辨的透射光谱观测可以在凌日的前半段和后半段探测行星边缘的独立部分。
Transmission spectra contain a wealth of information about the atmospheres of transiting exoplanets. However, large thermal and chemical gradients along the line of sight can lead to biased inferences in atmospheric retrievals. In order to determine how far from the limb plane the atmosphere still impacts the transmission spectrum, we derive a new formula to estimate the opening angle of a planet. This is the angle subtended by the atmospheric region that contributes to the observation along the line of sight, as seen from the planet centre. We benchmark our formula with a 3D Monte Carlo radiative transfer code and we define an opening angle suitable for the interpretation of JWST observations, assuming a 10-ppm noise floor. We find that the opening angle is only a few degrees for planets cooler than ca. 500 Kelvins, while it can be as large as 25 degrees for (ultra-)hot Jupiters and 50 degrees for hot Neptunes. Compared to previous works, our more robust approach leads to smaller estimates for the opening angle across a wide range scale heights and planetary radii. Finally, we show that ultra-hot Jupiters have an opening angle that is smaller than the angle over which the planet rotates during the transit. This allows for time-resolved transmission spectroscopy observations that probe independent parts of the planetary limb during the first and second half of the transit.