Transmission spectroscopy enables the characterization of exoplanet atmospheres by probing absorption features in their terminator regions. In the optical, it is particularly sensitive to metal oxides and atomic species that can strongly influence atmospheric energy balance and thermal structure. We aim to investigate the atmospheric properties of the hot Jupiter HAT-P-47b through optical transmission spectroscopy. Thirteen TESS transits were analyzed to refine the planetary ephemeris and system parameters. Two ground-based transits were observed with the Multi-Object Double Spectrograph (MODS) on the Large Binocular Telescope (LBT) and the Optical System for Imaging and Low-Intermediate-Resolution Integrated Spectroscopy+ (OSIRIS+) on the Gran Telescopio Canarias (GTC). Chromatic transit light curves were modeled to derive instrument-specific transmission spectra and multiple Bayesian spectral retrievals were performed to characterize the atmospheric properties. The MODS transmission spectrum provides moderate Bayesian evidence (Deltałn =2. 68) for TiO absorption, whereas the OSIRIS+ spectrum does not yield statistically significant evidence for any specific opacity source. Both datasets exhibit a wavelength-dependent slope indicative of enhanced aerosol scattering. The MODS and OSIRIS+ joint free-chemistry retrieval, dominated by the higher signal-to-noise MODS data, yields moderate evidence (Deltałn =3. 44) for TiO with a log mass fraction of -6. 86^ Z Z +0. 64 _ -0. 63 dex. The same model indicates an aerosol contribution to the optical scattering opacity approximately 5000 larger than pure H₂ Rayleigh scattering. HAT-P-47b appears to host a cloudy atmosphere with evidence for aerosols and tentative evidence for TiO absorption. Future high-precision observations will be essential to confirm the presence of TiO and further characterize its atmospheric structure.
Wang et al. (Mon,) studied this question.