Detailed abundances of planet-hosting wide binaries. I. Did planet formation imprint chemical signatures in the atmospheres of HD 20782/81?

Journal Article · Sun Jun 01 04:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/787/2/98· OSTI ID:22356803

Mack, III, Claude E.; Stassun, Keivan G. ^[1]; Schuler, Simon C. ^[2]; Norris, John ^[3]

---

1. Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States)
2. University of Tampa, Tampa, FL 33606 (United States)
3. Research School of Astronomy and Astrophysics, The Australian National University, Weston, ACT 2611 (Australia)

Using high-resolution, high signal-to-noise echelle spectra obtained with Magellan/MIKE, we present a detailed chemical abundance analysis of both stars in the planet-hosting wide binary system HD 20782 + HD 20781. Both stars are G dwarfs, and presumably coeval, forming in the same molecular cloud. Therefore we expect that they should possess the same bulk metallicities. Furthermore, both stars also host giant planets on eccentric orbits with pericenters ≲0.2 AU. Here, we investigate if planets with such orbits could lead to the host stars ingesting material, which in turn may leave similar chemical imprints in their atmospheric abundances. We derived abundances of 15 elements spanning a range of condensation temperature, T {sub C} ≈ 40-1660 K. The two stars are found to have a mean element-to-element abundance difference of 0.04 ± 0.07 dex, which is consistent with both stars having identical bulk metallicities. In addition, for both stars, the refractory elements (T {sub C} >900 K) exhibit a positive correlation between abundance (relative to solar) and T {sub C}, with similar slopes of ≈1×10{sup –4} dex K{sup –1}. The measured positive correlations are not perfect; both stars exhibit a scatter of ≈5×10{sup –5} dex K{sup –1} about the mean trend, and certain elements (Na, Al, Sc) are similarly deviant in both stars. These findings are discussed in the context of models for giant planet migration that predict the accretion of H-depleted rocky material by the host star. We show that a simple simulation of a solar-type star accreting material with Earth-like composition predicts a positive—but imperfect—correlation between refractory elemental abundances and T {sub C}. Our measured slopes are consistent with what is predicted for the ingestion of 10-20 Earths by each star in the system. In addition, the specific element-by-element scatter might be used to distinguish between planetary accretion and Galactic chemical evolution scenarios.

• OSTI ID: 22356803
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 787; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CORRELATIONS
ELEMENT ABUNDANCE
EVOLUTION
INGESTION
METALLICITY
MIGRATION
NOISE
ORBITS
PLANETS
REFRACTORIES
RESOLUTION
SIMULATION
SPECTRA
STARS
STELLAR ATMOSPHERES