[Paper Review] Accurate abundance patterns of solar twins and analogs ? Does the anomalous solar chemical composition come from planet formation?

M. Asplund|arXiv (Cornell University)|Jan 1, 2009

Stellar, planetary, and galactic studies7 citations

TL;DR

This study analyzes high-resolution, high-S/N spectra of 64 solar twins and analogs to investigate elemental abundance patterns, finding that the Sun exhibits a 0.08 dex depletion in low-condensation temperature (TC) elements relative to high-TC elements compared to most solar twins. The observed trend correlates with TC and suggests that the Sun's anomalous composition may stem from planet formation, potentially enabling identification of Sun-like planetary systems via detailed chemical analysis.

ABSTRACT

We derive the abundance of 19 elements in a sample of 64 stars with fundamental parameters very similar to solar, which minimizes the impact of systematic errors in our spectroscopic 1D-LTE differential analysis, using high-resolution ( R'60; 000), high signalto-noise ratio (S= N '200) spectra. The estimated errors in the elemental abundances relative to solar are as small as'0: 025 dex. The abundance ratios [X/Fe] as a function of [Fe= H] agree closely with previously established patterns of Galactic thin-disk chemical evolution. Interestingly, the majority of our stars show a s ignificant correlation between [X /Fe] and condensation temperature (TC). In the sample of 22 stars with parameters closest to solar, we find that, on average, low TC elements are depleted with respect to high TC elements in the solar twins relative to the Sun by about 0.08 dex ('20 %). An increasing trend is observed for the abundances as a function of TC for 900< TC< 1800 K, while abundances of lower TC elements appear to be roughly constant. We speculate that this is a signature of the planet formation that occurred around t he Sun but not in the majority of solar twins. If this hypothesis is correct, stars with planetary systems like ours, although rare (freq uency of'15 %), may be identified through a very detailed inspection of the chemical compositions of their host stars.

Motivation & Objective

• To determine if the Sun's anomalous chemical composition relative to solar twins is due to planet formation.
• To minimize systematic errors in abundance analysis by selecting stars with solar-like fundamental parameters.
• To investigate whether elemental abundance ratios correlate with condensation temperature (TC) in solar twins and analogs.
• To assess whether the observed abundance trends in the Sun are consistent with planetary system formation processes.
• To explore the potential for identifying stars with planetary systems through detailed chemical composition analysis.

Proposed method

• High-resolution (R ≥ 60,000) and high signal-to-noise ratio (S/N ≥ 200) spectroscopy was used to analyze 64 stars with solar-like parameters.
• A 1D-LTE differential spectroscopic analysis was applied to minimize systematic errors in abundance determination.
• Elemental abundances were measured relative to the Sun, with errors as low as ±0.025 dex.
• Abundance ratios [X/Fe] were plotted against [Fe/H] and condensation temperature (TC) to identify trends.
• Stars with parameters closest to the Sun (n=22) were analyzed in detail to isolate the TC-dependent abundance trend.
• The correlation between [X/Fe] and TC was quantified to assess its significance and potential origin.

Experimental results

Research questions

• RQ1 Is the Sun's anomalous elemental abundance pattern, particularly the depletion of low-TC elements, a result of planet formation?
• RQ2 Do solar twins and analogs without planetary systems exhibit the same TC-dependent abundance trends as the Sun?
• RQ3 Can the observed correlation between [X/Fe] and condensation temperature be used as a chemical signature of planetary system formation?
• RQ4 What is the magnitude of the abundance difference between low-TC and high-TC elements in solar twins compared to the Sun?
• RQ5 Is the frequency of stars with planetary systems detectable through chemical composition analysis?

Key findings

• The majority of solar twins and analogs show a significant correlation between [X/Fe] and condensation temperature (TC), indicating a systematic trend in elemental abundances.
• In the 22 stars with parameters closest to the Sun, low-TC elements are depleted by approximately 0.08 dex relative to high-TC elements compared to the Sun.
• An increasing trend in [X/Fe] with TC is observed for elements with TC between 900 K and 1800 K, while abundances of lower-TC elements remain roughly constant.
• The observed abundance pattern is consistent with the hypothesis that the Sun's chemical anomaly results from planet formation processes.
• Stars with planetary systems may be identifiable through detailed chemical analysis, as such systems could leave a detectable imprint on host star composition.
• The frequency of stars with planetary systems like the Sun is estimated at around 15%, based on the observed abundance trends.