TNG XXII的GAPS方案。解释恒星活动的HD189733 b扩展氦大气的GIARPS观点
The GAPS programme at TNG XXII. The GIARPS view of the extended helium atmosphere of HD189733 b accounting for stellar activity
摘要：
太阳系外行星的轨道非常接近他们的主恒星是强烈的辐射。这可能导致上层大气层膨胀并蒸发到太空中。在1083.3nm处的亚稳态氦（HeI）三重态最近被证明是探测扩展和逃逸的系外行星大气的有力诊断。我们进行高分辨率透射光谱的过境热木星HD 189733 b的GIARPS（GIANO-B + HARPS-N）观测模式的国家伽利略望远镜，利用同时光学+近红外光谱覆盖范围来检测氦在行星的扩展大气和测量恒星的磁活动对行星吸收信号的影响。在HD 189733 b的5次运输事件期间进行了观察。通过比较在和出的过境GIANO-B的观测，我们计算高分辨率的透射光谱，我们进行等效宽度测量和光变曲线分析，以衡量过量的在途吸收HeI三重态。我们在所有五次凌日中都探测到了吸收信号。平均在途吸收深度为0.75+/-0.03%。我们检测到夜间的氦吸收信号的变化可能是由于过境事件发生在恒星表面的不均匀性。我们评估的影响恒星活动的伪信号上的真正的行星吸收使用的HeI和H $α$线的比较分析。我们解释的时间序列的氦吸收线在三个晚上不受恒星污染-表现出平均在途吸收深度为0.77+/-0.04%-使用3-d大气代码。我们的模拟表明，氦层只填充部分洛希瓣。观测结果可以解释为热层加热到$\sim$ 12000 K，膨胀到$\sim$ 1.2行星半径，并损失$\sim$ 1 g/s的亚稳态氦。
英文摘要：
Exoplanets orbiting very close to their host star are strongly irradiated. This can lead the upper atmospheric layers to expand and evaporate into space. The metastable helium (HeI) triplet at 1083.3nm has recently been shown to be a powerful diagnostic to probe extended and escaping exoplanetary atmosphere. We perform high-resolution transmission spectroscopy of the transiting hot Jupiter HD189733b with the GIARPS (GIANO-B + HARPS-N) observing mode of the Telescopio Nazionale Galileo, taking advantage of the simultaneous optical+near infrared spectral coverage to detect HeI in the planet's extended atmosphere and to gauge the impact of stellar magnetic activity on the planetary absorption signal. Observations were performed during five transit events of HD189733b. By comparison of the in- and out-of-transit GIANO-B observations we compute high-resolution transmission spectra, on which we perform equivalent width measurements and light-curves analyses to gauge the excess in-transit absorption in the HeI triplet. We detect an absorption signal during all five transits. The mean in-transit absorption depth amounts to 0.75+/-0.03%. We detect night-to-night variations in the HeI absorption signal likely due to the transit events occurring in presence of stellar surface inhomogeneities. We evaluate the impact of stellar-activity pseudo-signals on the true planetary absorption using a comparative analysis of the HeI and the H$α$ lines. We interpret the time-series of the HeI absorption lines in the three nights not affected by stellar contamination -exhibiting a mean in-transit absorption depth of 0.77+/-0.04%- using a 3-d atmospheric code. Our simulations suggest that the helium layers only fill part of the Roche lobe. Observations can be explained with a thermosphere heated to $\sim$12000 K, expanding up to $\sim$1.2 planetary radii, and losing $\sim$1 g/s of metastable helium.
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