Evidence for TiO in the atmosphere of the hot Jupiter HAT-P-65 b

TL;DR

This study presents transmission spectra of hot Jupiter HAT-P-65b, revealing strong evidence for TiO in its atmosphere through spectral retrieval analyses, and highlights the potential for future high-resolution observations to confirm this finding.

Contribution

First detection of TiO in the atmosphere of HAT-P-65b using low-resolution transmission spectroscopy and spectral retrieval methods.

Findings

Evidence for TiO in the atmosphere of HAT-P-65b

Atmospheric temperature estimated at 1645 K with partial cloud coverage

Weak to moderate evidence for Na or VO in individual nights

Abstract

We present the low-resolution transmission spectra of the puffy hot Jupiter HAT-P-65b (0.53 M$_\mathrm{Jup}$, 1.89 R$_\mathrm{Jup}$, $T_\mathrm{eq}=1930$ K), based on two transits observed using the OSIRIS spectrograph on the 10.4 m Gran Telescopio CANARIAS (GTC). 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 $1645^{+255}_{-244}$ K and a cloud coverage of $36^{+23}_{-17}$%, revealing a relatively clear planetary atmosphere. Based on free-chemistry retrieval, we report strong evidence for 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.