The occurrence of a planet transiting in front of its host star offers the opportunity to observe the planet’s atmosphere filtering starlight. The fraction of occulted stellar flux is roughly proportional to the optically thick area of the planet, the extent of which depends on the opacity of the planet’s gaseous envelope at the observed wavelengths. Chemical species, haze, and clouds are now routinely detected in exoplanet atmospheres through rather small features in transmission spectra, i.e., collections of planet-to-star area ratios across multiple spectral bins and/or photometric bands. Technological advances have led to a shrinking of the error bars down to a few tens of parts per million (ppm) per spectral point for the brightest targets. The upcoming James Webb Space Telescope (JWST) is anticipated to deliver transmission spectra with precision down to 10 ppm. The increasing precision of measurements requires a reassessment of the approximations hitherto adopted in astrophysical models, including transit light-curve models. Recently, it has been shown that neglecting the planet’s thermal emission can introduce significant biases in the transit depth measured with the JWST/Mid-InfraRed Instrument, integrated between 5 and 12 μm. In this paper, we take a step forward by analyzing the effects of the approximation on transmission spectra over the 0.6–12 μm wavelength range covered by various JWST instruments. We present open-source software to predict the spectral bias, showing that, if not corrected, it may affect the inferred molecular abundances and thermal structure of some exoplanet atmospheres.

行星在其主恒星前方过渡的发生为观察行星的大气层过滤星光提供了机会。隐性恒星通量的比例大致与行星的光学厚度区域成正比，其程度取决于行星气态包壳在观察到的波长下的不透明度。现在，通常在系外行星大气中通过透射光谱中相当小的特征来检测化学物种，霾和云，即跨多个光谱区和/或光度学带的行星与恒星面积比的集合。技术上的进步导致误差条缩小到最亮目标的每个光谱点每百万分之几十（ppm）。即将面世的詹姆斯·韦伯太空望远镜（JWST）有望以低至10 ppm的精度提供透射光谱。测量精度的提高要求对天体物理模型（包括过渡光曲线模型）迄今采用的近似值进行重新评估。最近，有研究表明，忽略地球的热辐射会导致使用JWST /中红外仪（集成在5和12之间）测量的传输深度产生明显的偏差。μ微米。在本文中，我们向前迈出一步通过分析在0.6-12透射光谱近似的效果μ通过各种JWST文书涵盖米的波长范围。我们目前使用开源软件来预测光谱偏差，表明如果不进行校正，它可能会影响推断的某些系外行星大气的分子丰度和热结构。