Low abundances of TiO and VO on the dayside of KELT-9 b: Insights from ground-based photometric observations

IF 2.2 4区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS
Yuya Hayashi, Norio Narita, Akihiko Fukui, Quentin Changeat, Kiyoe Kawauchi, Kai Ikuta, Enric Palle, Felipe Murgas, Hannu Parviainen, Emma Esparza-Borges, Alberto Peláez-Torres, Pedro Pablo Meni Gallardo, Giuseppe Morello, Gareb Fernández-Rodríguez, Néstor Abreu García, Sara Muñoz Torres, Yéssica Calatayud Borrás, Pilar Montañés Rodríguez, John H Livingston, Noriharu Watanabe, Jerome P de Leon, Yugo Kawai, Keisuke Isogai, Mayuko Mori
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引用次数: 0

Abstract

We present ground-based photometric observations of secondary eclipses of the hottest known planet KELT-9 b using MuSCAT2 and Sinistro. We detect secondary eclipse signals in i and $z_{\rm s}$ with eclipse depths of $373^{+74}_{-75}$ and $638^{+199}_{-178}$ parts per million, respectively. We perform an atmospheric retrieval on the emission spectrum combined with the data from HST/WFC3, Spitzer, TESS, and CHEOPS to obtain the temperature profile and chemical abundances, including TiO and VO, which have been thought to produce temperature inversion structures in the dayside of ultra-hot Jupiters. While we confirm a strong temperature inversion structure, we find low abundances of TiO and VO with mixing ratios of $\rm {log(TiO)}=-7.80^{+0.15}_{-0.30}$ and $\rm {log(VO)}=-9.60^{+0.64}_{-0.57}$, respectively. The low abundances of TiO and VO are consistent with theoretical predictions for such an ultra-hot atmosphere. In such low abundances, TiO and VO have little effect on the temperature structure of the atmosphere. The abundance of ${\rm e}^{-}$, which serves as a proxy for ${\rm H}^{-}$ ions in this study, is found to be high, with $\rm {log(e^-)}=-4.89\pm {0.06}$. These results indicate that the temperature inversion in KELT-9 b’s dayside atmosphere is likely not caused by ${\rm TiO/VO}$, but rather by the significant abundance of ${\rm H}^{-}$ ions. The best-fitting model cannot fully explain the observed spectrum, and chemical species not included in the retrieval may introduce modeling biases. Future observations with broader wavelength coverage and higher spectral resolution are expected to provide more accurate diagnostics on the presence and abundances of ${\rm TiO/VO}$. These advanced observations will overcome the limitations of current data from HST and photometric facilities, which are constrained by narrow wavelength coverage and instrumental systematics.
KELT-9 b日面的氧化钛和氧化亚氮丰度较低:地面光度观测的启示
我们利用 MuSCAT2 和 Sinistro 对已知最热行星 KELT-9 b 的二次食进行了地基光度观测。我们探测到了 i 和 $z_{\rm s}$ 的二次食信号,食深分别为百万分之 373^{+74}_{-75}$ 和百万分之 638^{+199}_{-178}$ 。我们结合来自 HST/WFC3、Spitzer、TESS 和 CHEOPS 的数据,对发射光谱进行了大气检索,以获得温度曲线和化学丰度,包括 TiO 和 VO。虽然我们证实了强烈的温度反转结构,但我们发现TiO和VO的丰度很低,混合比分别为$\rm {log(TiO)}=-7.80^{+0.15}_{-0.30}$ 和$\rm {log(VO)}=-9.60^{+0.64}_{-0.57}$ 。TiO和VO的低丰度符合对这种超热大气的理论预测。在如此低的丰度下,TiO 和 VO 对大气的温度结构几乎没有影响。在本研究中,作为 ${rm H}^{-}$ 离子替代物的 ${rm e}^{-}$ 的丰度很高,为 $\rm {log(e^-)}=-4.89\pm {0.06}$。这些结果表明,KELT-9 b日侧大气的温度反转很可能不是由${rm TiO/VO}$引起的,而是由大量的${rm H}^{-}$离子引起的。最佳拟合模型并不能完全解释观测到的光谱,而且未包含在检索中的化学物种可能会带来建模偏差。预计未来波长覆盖范围更广、光谱分辨率更高的观测将为 ${rm TiO/VO}$ 的存在和丰度提供更准确的诊断。这些先进的观测将克服目前来自 HST 和测光设施的数据的局限性,这些数据受到波长覆盖范围窄和仪器系统性的限制。
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来源期刊
Publications of the Astronomical Society of Japan
Publications of the Astronomical Society of Japan 地学天文-天文与天体物理
CiteScore
4.10
自引率
13.00%
发文量
98
审稿时长
4-8 weeks
期刊介绍: Publications of the Astronomical Society of Japan (PASJ) publishes the results of original research in all aspects of astronomy, astrophysics, and fields closely related to them.
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