Planet Engulfment Detections are Rare According to Observations and Stellar Modeling

Abstract

Dynamical evolution within planetary systems can cause planets to be engulfed by their host stars. Following engulfment, the stellar photosphere abundance pattern will reflect accretion of rocky material from planets. Multi-star systems are excellent environments to search for such abundance trends because stellar companions form from the same natal gas cloud and are thus expected to share primordial chemical compositions to within 0.03$-$0.05 dex. Abundance measurements have occasionally yielded rocky enhancements, but few observations targeted known planetary systems. To address this gap, we carried out a Keck-HIRES survey of 36 multi-star systems where at least one star is a known planet host. We found that only HAT-P-4 exhibits an abundance pattern suggestive of engulfment, but is more likely primordial based on its large projected separation (30,000 $\pm$ 140 AU) that exceeds typical turbulence scales in molecular clouds. To understand the lack of engulfment detections among our systems, we quantified the strength and duration of refractory enrichments in stellar photospheres using MESA stellar models. We found that observable signatures from 10 $M_{\oplus }$ engulfment events last for $\sim$90 Myr in 1 $M_{\odot }$ stars. Signatures are largest and longest lived for 1.1$-$1.2 $M_{\odot }$ stars, but are no longer observable $\sim$2 Gyr post-engulfment. This indicates that engulfment will rarely be detected in systems that are several Gyr old.

15 pages, 12 figures; submitted to MNRAS

References in corpus (32)

• Array Programming with NumPy
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• The GALAH+ Survey: Third Data Release
• The frequency of planetary debris around young white dwarfs
• The Chemical Composition of an Extrasolar Minor Planet
• Precision Stellar Characterization of FGKM Stars using an Empirical Spectral Library
• The Mass of Kepler-93b and The Composition of Terrestrial Planets
• Chemical Homogeneity in Collinder 261 and Implications for Chemical Tagging
• Chemical Transport and Spontaneous Layer Formation in Fingering Convection in Astrophysics
• Stellar Chemical Abundances: In Pursuit of the Highest Achievable Precision
• Oxygen abundances in G- and F-type stars from HARPS
• Identical or fraternal twins? : The chemical homogeneity of wide binaries from Gaia DR2
• The chemical compositions of solar twins in the open cluster M67
• Compositions of Planetary Debris around Dusty White Dwarfs
• High precision abundances in the 16 Cyg binary system: a signature of the rocky core in the giant planet
• Detection of Stars within $\sim$0.8 arcseconds of Kepler Objects of Interest
• A high precision chemical abundance analysis of the HAT-P-1 stellar binary: constraints on planet formation
• Abundance Differences Between Exoplanet Binary Host Stars XO-2N and XO-2S -- Dependence on Stellar Parameters
• Detailed Abundances of Planet-Hosting Wide Binaries. I. Did Planet Formation Imprint Chemical Signatures in the Atmospheres of HD 20782/81?
• Signatures of rocky planet engulfment in HAT-P-4. Implications for chemical tagging studies
• Fingerprints of giant planets in the composition of solar twins
• Chemical evidence for planetary ingestion in a quarter of Sun-like stars
• Lessons from the curious case of the `fastest' star in Gaia DR2
• The Magellan PFS Planet Search Program: Radial Velocity and Stellar Abundance Analyses of the 360 AU, Metal-Poor Binary "Twins" HD 133131A & B
• Light Elements in the Universe
• Reconstructing fossil sub-structures of the Galactic disk: clues from abundance patterns of old open clusters and moving groups
• Detailed elemental abundances of binary stars: Searching for signatures of planet formation and atomic diffusion
• Planet Engulfment Signatures in Twin Stars
• Long-Term Lithium Abundance Signatures following Planetary Engulfment
• Discovery of Gas Accretion Onto Stars in 13 Myr old h and chi Persei
• High-precision analysis of binary stars with planets. I. Searching for condensation temperature trends in the HD 106515 system
• The influence of planetary engulfment on stellar rotation in metal-poor main-sequence stars

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• Two neighbours of the ultra-short-period Earth-sized planet K2-157 b in the warm Neptunian savanna
• Host-star and exoplanet composition: Polluted white dwarf reveals depletion of moderately refractory elements in planetary material
• Engulfment of a hot Jupiter as a possible origin of the rapid spin and internal spin misalignment of the planet-hosting red giant Kepler-56
• The GAPS Programme at TNG. LIII. New insights on the peculiar XO-2 system
• Observational imprints of tidal internal gravity wave dissipation in star-planet systems
• Evolution of the ZTF SLRN-2020 star-planet merger