THE 4.5 μm FULL-ORBIT PHASE CURVE OF THE HOT JUPITER HD 209458b
THE 4.5 μm FULL-ORBIT PHASE CURVE OF THE HOT JUPITER HD 209458b
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热木星 HD 209458b 的 4.5μm 全轨道相位曲线
DOI：
10.1088/0004-637x/790/1/53
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
J. Langton
中科院分区：
文献类型：
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作者：
R. Zellem;N. Lewis;H. Knutson;C. Griffith;A. Showman;J. Fortney;N. Cowan;E. Agol;A. Burrows;D. Charbonneau;D. Deming;G. Laughlin;J. Langton
炽热的木星 HD 209458b 特别适合详细研究，因为它是目前已知的最亮的凌日系外行星系统之一（V 星等 = 7.65；K 星等 = 6.308），并且具有较大的行星与恒星对比度。 HD 209458b预计将围绕其主星同步旋转，其热点因超级自转赤道风而向恒星下点向东移动。在这里，我们展示了 HD 209458b 的首次全轨道观测，其中它的 4.5μm 发射是用 Spitzer/IRAC 记录的。我们的研究将之前 HD 209458b 次生日食发射的 4.5μm 测量结果修正了约 35%，从而改变了我们对其白天大气特性的解释。我们发现行星日侧的热点向星下点向东移动了 40.°9 ± 6.°0，这与预测赤道超自转的环流模型一致。 HD 209458b的日面（Tbright = 1499 ± 15 K）和夜面（Tbright = 972 ± 44 K）发射表明昼夜亮度温度对比度小于在更高辐射的系外行星上观察到的亮度温度对比度，这表明昼夜温度对比度可能部分是入射恒星辐射的函数。观察到的相曲线形状与全球环流模型预测略有偏差，这可能是由于这些模型中使用的当前热 CH4 线列表中的不平衡化学或缺陷所致。需要在其他波长下观测相位曲线，以确定日面逆温的可能存在和空间范围，并提高我们对这颗行星大气环流的整体了解。
The hot Jupiter HD 209458b is particularly amenable to detailed study as it is among the brightest transiting exoplanet systems currently known (V-mag = 7.65; K-mag = 6.308) and has a large planet-to-star contrast ratio. HD 209458b is predicted to be in synchronous rotation about its host star with a hot spot that is shifted eastward of the substellar point by superrotating equatorial winds. Here we present the first full-orbit observations of HD 209458b, in which its 4.5 μm emission was recorded with Spitzer/IRAC. Our study revises the previous 4.5 μm measurement of HD 209458b's secondary eclipse emission downward by ∼35% to , changing our interpretation of the properties of its dayside atmosphere. We find that the hot spot on the planet's dayside is shifted eastward of the substellar point by 40.°9 ± 6.°0, in agreement with circulation models predicting equatorial superrotation. HD 209458b's dayside (Tbright = 1499 ± 15 K) and nightside (Tbright = 972 ± 44 K) emission indicate a day-to-night brightness temperature contrast smaller than that observed for more highly irradiated exoplanets, suggesting that the day-to-night temperature contrast may be partially a function of the incident stellar radiation. The observed phase curve shape deviates modestly from global circulation model predictions potentially due to disequilibrium chemistry or deficiencies in the current hot CH4 line lists used in these models. Observations of the phase curve at additional wavelengths are needed in order to determine the possible presence and spatial extent of a dayside temperature inversion, as well as to improve our overall understanding of this planet's atmospheric circulation.