Graze-and-Merge Collisions under External Perturbers

Abstract

Graze-and-merge collisions (GMCs) are common multi-step mergers occurring in low-velocity off-axis impacts between similar sized planetary bodies. The first impact happens at somewhat faster than the mutual escape velocity; for typical impact angles this does not result in immediate accretion, but the smaller body is slowed down so that it loops back around and collides again, ultimately accreting. The scenario changes in the presence of a third major body, i.e. planets accreting around a star, or satellites around a planet. We find that when the loop-back orbit remains inside roughly 1/3 of the Hill radius from the target, then the overall process is not strongly affected. As the loop-back orbit increases in radius, the return velocity and angle of the second collision become increasingly random, with no record of the first collision's orientation. When the loop-back orbit gets to about 3/4 of the Hill radius, the path of smaller body is disturbed up to the point that it will usually escape the target.

arXiv comment19 pages, 16 figures, 1 table, accepted for publication in ApJ

References in corpus (6)

• Collisions between Gravity-Dominated Bodies: 2. The Diversity of Impact Outcomes during the End Stage of Planet Formation
• Collisions Between Gravity-Dominated Bodies: 1. Outcome Regimes and Scaling Laws
• Formation of Terrestrial Planets from Protoplanets under a Realistic Accretion Condition
• The Formation of the Collisional Family around the Dwarf Planet Haumea
• The peculiar shapes of Saturn's small inner moons as evidence of mergers of similar-sized moonlets
• Fate of the runner in hit-and-run collisions

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• Ejection of close-in super-Earths around low-mass stars in the giant impact stage