Detection of Fe and Ti on the dayside of the ultrahot Jupiter MASCARA-1b with CARMENES

TL;DR

This study used high-resolution spectroscopy with CARMENES to detect Fe and Ti on MASCARA-1b's dayside, revealing a strong atmospheric inversion and consistent elemental abundances with solar values, while also measuring the planet's rotation speed.

Contribution

First detection of Fe and Ti on MASCARA-1b's dayside using high-resolution spectra, and analysis of atmospheric structure and rotation.

Findings

Detected Fe I and Ti I signals via cross-correlation.

Identified a strong atmospheric inversion layer.

Measured planetary rotation speed consistent with tidal locking.

Abstract

Ultrahot Jupiters are a type of gaseous exoplanet that orbit extremely close to their host star, resulting in significantly high equilibrium temperatures. In recent years, high-resolution emission spectroscopy has been broadly employed in observing the atmospheres of ultrahot Jupiters. We used the CARMENES spectrograph to observe the high-resolution spectra of the dayside hemisphere of MASCARA-1b in both visible and near-infrared. Through cross-correlation analysis, we detected signals of \ion{Fe}{i} and \ion{Ti}{i}. Based on these detections, we conducted an atmospheric retrieval and discovered the presence of a strong inversion layer in the planet's atmosphere. The retrieved Ti and Fe abundances are broadly consistent with solar abundances. In particular, we obtained a relative abundance of [Ti/Fe] as $-1.0 \pm 0.8$ under the free retrieval and $-0.4^{+0.5}_{-0.8}$ under the chemical equilibrium retrieval, suggesting the absence of significant titanium depletion on this planet. Furthermore, we considered the influence of planetary rotation on spectral line profiles. The resulting equatorial rotation speed was determined to be $4.4^{+1.6}_{-2.0}\,\mathrm{km\,s^{-1}}$, which agrees with the rotation speed induced by tidal locking.