Planets Around Solar Twins/Analogs (PASTA)

II. Chemical abundances, systematic offsets, and clues as to planet formation

¹ Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai 200240, China
² Department of Astronomy, Tsinghua University, Beijing 100084, China
³ Earth and Planets Laboratory, Carnegie Institution for Science, 5241 Broad Branch Road, NW, Washington, DC 20015, USA
⁴ Department of Astronomy, The Ohio State University, 1251 Wescoe Hall Dr., Columbus, OH 43210, USA
⁵ Center for Cosmology and AstroParticle Physics, The Ohio State University, 191 West Woodruff Avenue, Columbus, OH 43210, USA
⁶ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
⁷ Center for Computational Astrophysics, Flatiron Institute, 162 5th Avenue, New York, NY 10010, USA
⁸ School of Physics and Astronomy, Monash University, Melbourne, VIC 3800, Australia
⁹ ARC Centre of Excellence for Astrophysics in Three Dimensions (ASTRO-3D), Canberra, ACT 2611, Australia

^★ Corresponding author: qinghuisun@sjtu.edu.cn

Received: 5 July 2025
Accepted: 7 August 2025

Abstract

Context. Previous studies have suggested that the Sun is relatively depleted in refractory elements compared to other solar twins or analogs, potentially as a result of planet formation. However, such conclusions are often limited by inhomogeneous samples and a lack of direct comparison with stars known to host planets.

Aims. We aim to perform a homogeneous and precise abundance analysis of solar twins and analogs that host planets, to investigate possible chemical signatures associated with planet formation.

Methods. We obtained high-resolution, high-S/N Magellan/MIKE spectra for 25 solar-like stars, including 22 confirmed or candidate planet hosts and three comparison stars. Stellar parameters and elemental abundances for 23 elements (from C to Eu) were derived through a strict line-by-line differential analysis relative to the Sun.

Results. Our sample spans [Fe/H] = –0.23 to +0.18 dex and includes 20 solar analogs, six of which are solar twins. Typical abundance uncertainties range from 0.01–0.05 dex for lighter elements (e.g., Fe, Si, C, O, and Na) and up to 0.1 dex for neutron-capture elements. The Sun is consistently depleted in refractory elements relative to all solar analogs and twins, regardless of planet type. Stars that host small planets tentatively show slightly stronger refractory element depletion than those that host giant planets, though the difference is not yet statistically significant.

Conclusions. We emphasize the need for strictly differential, line-by-line analyses relative to the Sun, as well as careful consideration of systematic differences between instruments, to ensure consistency and the homogeneity required to achieve our goals.