WASP-1: A lithium- and metal-rich star with an oversized planet

TL;DR

This study provides a detailed spectroscopic analysis of WASP-1, revealing its high metallicity and lithium abundance, and compares its planetary system to HD 149026, highlighting differences in planet densities despite stellar similarities.

Contribution

First detailed spectroscopic characterization of WASP-1 and its comparison to similar systems, exploring implications for planet density variations.

Findings

WASP-1 has high metallicity and lithium abundance.

WASP-1's planet has a different density than HD 149026b.

Host star properties alone do not determine planet density.

Abstract

In this paper we present our results of a comprehensive spectroscopicanalysis of WASP-1, the host star to the exoplanet WASP-1b. We derive T_eff = 6110 +/- 45 K, log g = 4.28 +/- 0.15, and [M/H] = 0.23 +/- 0.08, and also a high abundance of lithium, log n(Li) = 2.91 +/- 0.05. These parameters suggests an age for the system of 1-3 Gyr and a stellar mass of 1.25-1.35 M_sun. This means that WASP-1 has properties very similar to those of HD 149026, the host star for the highest density planet yet detected. Moreover, their planets orbit at comparable distances and receive comparable irradiating fluxes from their host stars. However, despite the similarity of WASP-1 with HD 149026, their planets have strongly different densities. This suggests that gas-giant planet density is not a simple function of host-star metallicity or of radiation environment at ages of ~2 Gyr.