An enhanced slope in the transmission spectrum of the hot Jupiter WASP-104b

TL;DR

This study presents a detailed optical transmission spectrum of the hot Jupiter WASP-104b, revealing an enhanced slope at shorter wavelengths and suggesting atmospheric haziness or stellar activity effects.

Contribution

It combines multiple transit observations and reanalyzes existing data to refine system parameters and characterize the planet's atmospheric features with new spectral insights.

Findings

Enhanced slope observed at wavelengths <630 nm

Evidence suggests presence of a cloud deck at longer wavelengths

Bayesian analysis favors a hazy atmosphere, but stellar spots remain a possibility

Abstract

We present the optical transmission spectrum of the hot Jupiter WASP-104b based on one transit observed by the blue and red channels of the DBSP spectrograph at the Palomar 200-inch telescope and 14 transits observed by the MuSCAT2 four-channel imager at the 1.52 m Telescopio Carlos Sanchez. We also analyse 45 additional K2 transits, after correcting for the flux contamination from a companion star. Together with the transit light curves acquired by DBSP and MuSCAT2, we are able to revise the system parameters and orbital ephemeris, confirming that no transit timing variations exist. Our DBSP and MuSCAT2 combined transmission spectrum reveals an enhanced slope at wavelengths shorter than 630 nm and suggests the presence of a cloud deck at longer wavelengths. While the Bayesian spectral retrieval analyses favour a hazy atmosphere, stellar spot contamination cannot be completely ruled out. Further evidence, from transmission spectroscopy and detailed characterisation of the host star's activity, is required to distinguish the physical origin of the enhanced slope.