LTT 1445 Ab是一个海洋世界还是一个冰冷的哈伯世界？探索Twinkle的潜力以揭示其本质
Is LTT 1445 Ab a Hycean World or a cold Haber World? Exploring the Potential of Twinkle to Unveil Its Nature
摘要：
我们探讨了Twinkle确定附近类地行星LTT 1445 Ab的大气成分的前景，包括检测潜在生物特征氨（NH $_{3}$）的可能性。在6.9 pc的距离，这个系统是第二个最近的已知凌日系统，将通过透射光谱与即将到来的闪烁任务进行观测。Twinkle配备0.45米望远镜，同时覆盖0.5 - 4.5 $μ$米的光谱波长范围，分辨率在50 - 70之间，旨在研究系外行星、明亮恒星和太阳系天体。我们调查了该任务研究LTT 1445 Ab的潜力，发现Twinkle数据可以区分冷的哈伯世界（N $_2$ -H $_2$主导的大气）和Hycean世界，H $_2$ O-H $_2$主导的大气，$χ_ν^{2}$ = 3.01。内部成分分析支持LTT 1445 Ab的哈伯世界假设，这表明该行星可能缺乏大量的水层。我们使用petitRADTRANS和Twinkle模拟器来模拟更可能的冷哈伯世界的情况下，NH $_{3}$被认为是一个生物签名的传输光谱。我们研究了不同的情况下的可探测性：不同的氢含量，氨的浓度，和云覆盖。我们发现，氨可以在$\sim$ 3 $σ$水平检测到最佳（无云）条件下，25次过境和4.0 ppm NH $_{3}$的体积混合比。我们提供了检索分析的例子，以限制潜在的NH $_{3}$和H $_{2}$ O在大气中。我们的研究说明了Twinkle在表征潜在宜居系外行星大气层方面的潜力。
英文摘要：
We explore the prospects for Twinkle to determine the atmospheric composition of the nearby terrestrial-like planet LTT 1445 Ab, including the possibility of detecting the potential biosignature ammonia (NH$_{3}$). At a distance of 6.9 pc, this system is the second closest known transiting system and will be observed through transmission spectroscopy with the upcoming Twinkle mission. Twinkle is equipped with a 0.45 m telescope, covers a spectral wavelength range of 0.5 - 4.5 $μ$m simultaneously with a resolving power between 50 - 70, and is designed to study exoplanets, bright stars, and solar system objects. We investigate the mission's potential to study LTT 1445 Ab and find that Twinkle data can distinguish between a cold Haber World (N$_2$-H$_2$-dominated atmosphere) and a Hycean World with a H$_2$O-H$_2$-dominated atmosphere, with a $χ_ν^{2}$ = 3.01. Interior composition analysis favors a Haber World scenario for LTT 1445 Ab, which suggests that the planet probably lacks a substantial water layer. We use petitRADTRANS and a Twinkle simulator to simulate transmission spectra for the more likely scenario of a cold Haber World for which NH$_{3}$ is considered to be a biosignature. We study the detectability under different scenarios: varying hydrogen fraction, concentration of ammonia, and cloud coverage. We find that ammonia can be detected at a $\sim$ 3$σ$ level for optimal (non-cloudy) conditions with 25 transits and a volume mixing ration of 4.0 ppm of NH$_{3}$. We provide examples of retrieval analysis to constrain potential NH$_{3}$ and H$_{2}$O in the atmosphere. Our study illustrates the potential of Twinkle to characterize atmospheres of potentially habitable exoplanets.
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