We present the low-resolution transmission spectra of the puffy hot Jupiter HAT-P-65b (0.53 M_Jup, 1.89 R_Jup, T _eq = 1930 K), based on two transits observed using the OSIRIS spectrograph on the 10.4 m Gran Telescopio CANARIAS. The transmission spectra of the two nights are consistent, covering the wavelength range 517–938 nm and consisting of mostly 5 nm spectral bins. We perform equilibrium-chemistry spectral retrieval analyses on the jointly fitted transmission spectrum and obtain an equilibrium temperature of K and a cloud coverage of %, revealing a relatively clear planetary atmosphere. Based on free-chemistry retrieval, we report strong evidence for titanium oxide (TiO). Additional individual analyses in each night reveal weak-to-moderate evidence for TiO in both nights, but moderate evidence for Na or VO only in one of the nights. Future high-resolution Doppler spectroscopy as well as emission observations will help confirm the presence of TiO and constrain its role in shaping the vertical thermal structure of HAT-P-65b’s atmosphere.

我们基于使用 OSIRIS 光谱仪在 10.4 m Gran Telescopio CANARIAS 上观察到的两次凌日，展示了膨胀的热木星 HAT-P-65b（0.53 M _Jup，1.89 R _Jup，T _eq = 1930 K）的低分辨率透射光谱. 两晚的透射光谱一致，覆盖波长范围为 517-938 nm，主要由 5 nm 光谱仓组成。我们对联合拟合的透射光谱进行平衡-化学光谱反演分析，获得K的平衡温度和%，显示出相对清晰的行星大气。基于自由化学检索，我们报告了氧化钛 (TiO) 的有力证据。每晚的额外个别分析揭示了两个晚上 TiO 的弱到中等证据，但仅在其中一个晚上发现 Na 或 VO 的中等证据。未来的高分辨率多普勒光谱以及发射观测将有助于确认二氧化钛的存在并限制其在塑造 HAT-P-65b 大气垂直热结构中的作用。