热木星HD209458b大气光谱中的TiO和VO宽带吸收特征
TiO and VO broad band absorption features in the optical spectrum of the atmosphere of the hot-Jupiter HD209458b
摘要：
在热木星HD209458 b的大气中寻找氧化钛（TiO）和氧化钒（VO）气相物种的存在。我们将行星透射光谱的模型与Sing等人（2008 a）使用存档的HST-STIS时间序列光谱获得的多波长食深度测量（从3000到10000埃）进行了比较。我们利用这些观测结果来寻找6000至8000埃之间行星大气中额外吸收体的光谱特征。随着钠耗尽和瑞利散射最近公布的这颗系外行星的大气，一个额外的吸收剂的来源不确定，红的钠线，居住在大气中的行星。此外，这颗行星有一个平流层，它正在经历一个由位于高空的吸收器捕获光学恒星通量引起的逆温。最近的模型预测，HD209458 b大气中TiO和VO的存在可能是造成这种温度反演的原因。虽然没有具体的TiO和VO光谱带头签名已被确定明确在所观察到的光谱，我们建议在这里，这些分子的不透明度是可能的候选人，以解释其余的连续宽带吸收之间观察到6200和8000埃。为了合理地匹配数据，TiO和VO分子的丰度被评估为低于太阳的10到1000倍。这一上限结果与由于诸如冷凝之类的损耗效应而引起的随高度的预期变化一致。
英文摘要：
The presence of titanium oxide (TiO) and vanadium oxide (VO) gas phase species is searched for in the atmosphere of the hot Jupiter HD209458b. We compared a model for the planets transmitted spectrum to multi-wavelength eclipse-depth measurements (from 3000 to 10000 Angstrom), obtained by Sing et al. (2008a) using archived HST-STIS time series spectra. We make use of these observations to search for spectral signatures from extra absorbers in the planet atmosphere between 6000 and 8000 Angstrom. Along with sodium depletion and Rayleigh scattering recently published for this exoplanet atmosphere, an extra absorber of uncertain origin, redward of the sodium lines, resides in the atmosphere of the planet. Furthermore, this planet has a stratosphere experiencing a thermal inversion caused by the capture of optical stellar flux by absorbers that resides at altitude. Recent models have predicted that the presence of TiO and VO in the atmosphere of HD209458b may be responsible for this temperature inversion. Although no specific TiO and VO spectral band head signatures have been identified unambiguously in the observed spectrum, we suggest here that the opacities of those molecules are possible candidates to explain the remaining continuous broad band absorption observed between 6200 and 8000 Angstrom. To match reasonably well the data, the abundances of TiO and VO molecules are evaluated from ten to one thousand times below solar. This upper limit result is in agreement with expected variations with altitude due to depletion effects such as condensation.
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