Modeling giant extrasolar ring systems in eclipse and the case of J1407b: Sculpting by exomoons?

Abstract

The light curve of 1SWASP J140747.93-394542.6, a 16 Myr old star in the Sco-Cen OB association, underwent a complex series of deep eclipses that lasted 56 days, centered on 2007 April. This light curve is interpreted as the transit of a giant ring system that is filling up a fraction of the Hill sphere of an unseen secondary companion, J1407b. We fit the light curve with a model of an azimuthally symmetric ring system, including spatial scales down to the temporal limit set by the star's diameter and relative velocity. The best ring model has 37 rings and extends out to a radius of 0.6 AU (9 × 107 km), and the rings have an estimated total mass on the order of 100 M Moon. The ring system has one clearly defined gap at 0.4 AU (6.1 × 107 km), which, we hypothesize, is being cleared out by a <0.8 M ⊕ exosatellite orbiting around J1407b. This eclipse and model imply that we are seeing a circumplanetary disk undergoing a dynamic transition to an exosatellite-sculpted ring structure, which is one of the first seen outside our solar system.