While many observed debris discs are thought to have gaps suggestive of the presence of planets, direct imaging surveys do not find many high-mass planets in these systems. We investigate if divergent migration is a viable mechanism for forming gaps in young debris discs with planets of low enough mass to currently elude detection. We perform numerical integrations of planet pairs embedded in planetesimal discs to assess the conditions for which divergent, planetesimal-driven migration occurs and gaps form within the disc. Gap widths and the migration rate of planets within a pair depend on both disc mass and the degree to which the planets share disc material. We find that planet pairs with planets more massive than Neptune can produce gaps with widths similar to their orbit distance within 10 Myr at orbit separations probed by direct imaging campaigns. Pairs of migrating super-Earths likely cannot form observable gaps on the same time and distance scales, however. Inferring the responsible planet masses from these gaps while neglecting migration could overestimate the mass of planets by more than an order of magnitude.

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This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2018 Royal Astronomical Society. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.


Asteroids: general, Celestial mechanics, Circumstellar matter, Methods: miscellaneous, Minor planets, Planet-disc interactions, Planetary systems

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Monthly Notices of the Royal Astronomical Society