The Chemical Homogeneity of Sun-like Stars in the Solar Neighborhood

Abstract

The compositions of stars are a critical diagnostic tool for many topics in astronomy such as the evolution of our Galaxy, the formation of planets, and the uniqueness of the Sun. Previous spectroscopic measurements indicate a large intrinsic variation in the elemental abundance patterns of stars with similar overall metal content. However, systematic errors arising from inaccuracies in stellar models are known to be a limiting factor in such studies, and thus it is uncertain to what extent the observed diversity of stellar abundance patterns is real. Here we report the abundances of 30 elements with precisions of 2% for 79 Sun-like stars within 100 parsecs. Systematic errors are minimized in this study by focusing on solar twin stars and performing a line-by-line differential analysis using high-resolution, high-signal-to-noise spectra. We resolve [X/Fe] abundance trends in galactic chemical evolution at precisions of 10 −3 dex Gyr −1 and reveal that stars with similar ages and metallicities have nearly identical abundance patterns. Contrary to previous results, we find that the ratios of carbon-tooxygen and magnesium-to-silicon in solar metallicity stars are homogeneous to within 10% throughout the solar neighborhood, implying that exoplanets may exhibit much less compositional diversity than previously thought. Finally, we demonstrate that the Sun has a subtle deficiency in refractory material relative to >80% of solar twins (at 2σ confidence), suggesting a possible signpost for planetary systems like our own.

Differential abundance analysis of Procyon and θ Sculptoris: Comparison with abundance patterns of solar‐like pairs

“…Moreover, local substructure of the plot for the elements Ca-Zn and neutron-addition elements is similar to that which can be found for solar twins. Our PDA versus Z plot structural shows similarity to plots that can be made from the extensive work of Bedell et al (2018). That PDA structure and substructure is clearly a function of age.…”

“…A primary advantage of the historical work, near independence from gf ‐values, is retained. The stars are chosen to have identical or nearly identical spectral types, and presumably closely comparable structures and abundances–to be “twins.” The precision of the method has revealed significant differences which may arise as a result of star formation and Galactic chemical evolution (GCE) (Bedell et al , henceforth BD18).…”

High-resolution Spectroscopic Study of Dwarf Stars in the Northern Sky: Lithium, Carbon, and Oxygen Abundances

“…They found that 100 % of their sample of stars with detected planets has C/O< 0.8. Meanwhile, in a spectroscopic study of Sun-like stars, Bedell et al (2018) found that the ratios of C/O in solar metallicity stars are homogeneous to within 10 % throughout the solar neighborhood, implying that exoplanets may exhibit much less diversity in their composition than previously thought. The recent work by Pavlenko et al (2019) determined carbon and oxygen abundances in atmospheres of the supersolar metallicity stars with and without detected planets and confirmed that metal-rich dwarf stars with planets are more carbon-rich in comparison with nonplanet host stars, with a statistical significance of 96 %.…”

“…The past decade induced the theoretical and observational studies of carbon and oxygen abundances in stars in the context of determining a composition of extrasolar terrestrial planets, assuming that the composition of the host star and its protoplanetary disk is interrelated (see, e.g., Bond et al 2010;Petigura & Marcy 2011;Nissen et al 2014;Delgado Mena et al 2015;Madhusudhan et al 2016;Bedell et al 2018, and references therein). C and O and their elemental number rations C/O 1 could also be used to derive information related to the starplanet connection as in the case of lithium depletion.…”

The Chemical Signatures of Planetary Engulfment Events in Binary Systems

“…Twin stars are objects with atmospheric parameters very similar to each other (e.g., ∆T eff 300 K and ∆log g 0.2 dex). It has been shown that a strictly differential line-by-line analysis of twin stars permits us to obtain differential abundances at the highest precision possible (e.g., Meléndez et al 2009;Bedell et al 2014Bedell et al , 2018Liu et al 2014;Spina et al 2018). In fact, when studying samples of twin stars, most of the systematic uncertainties that plague chemical abundance analyses are so similar among stars in the same binary pair that a strict differential line-by-line analysis cancels them out.…”