Toward Detection of Exoplanetary Rings via Transit Photometry: Methodology and a Possible Candidate

Abstract

Detection of a planetary ring of exoplanets remains as one of the most attractive but challenging goals in the field. We present a methodology of a systematic search for exoplanetary rings via transit photometry of long-period planets. The methodology relies on a precise integration scheme we develop to compute a transit light curve of a ringed planet. We apply the methodology to 89 long-period planet candidates from the Kepler data so as to estimate, and/or set upper limits on, the parameters of possible rings. While a majority of our samples do not have a sufficiently good signal-to-noise ratio for meaningful constraints on ring parameters, we find that six systems with a higher signal-to-noise ratio are inconsistent with the presence of a ring larger than 1.5 times the planetary radius assuming a grazing orbit and a tilted ring. Furthermore, we identify five preliminary candidate systems whose light curves exhibit ring-like features. After removing four false positives due to the contamination from nearby stars, we identify KIC 10403228 as a reasonable candidate for a ringed planet. A systematic parameter fit of its light curve with a ringed planet model indicates two possible solutions corresponding to a Saturn-like planet with a tilted ring. There also remain other two possible scenarios accounting for the data; a circumstellar disk and a hierarchical triple. Due to large uncertain factors, we cannot choose one specific model among the three.

Detection of a repeated transit signature in the light curve of the enigma star KIC 8462852: A possible 928-day period

“…The straight ingress and egress slopes, and the flat bottom of the light curve point toward the possibility that the transiting body can be a single body with a simple shape. Acknowledging that the Hill-spheres of a massive planet can extend to several stellar radius in size, the transit of a ring system surrounding a giant planet could explain the observed photometric event A and B, as done for the light curve of 1SWASP J140747.93-394542.6 (also named J1407), an old star in the ScoCen OB association (Kenworthy & Mamajek 2015); see also Lecavelier des Etangs et al (2017) and Aizawa et al (2017) for other case studies of exo-planetary ring systems. This scenario will be discussed in Sect.…”

“…Indeed, a ring system can be stable within half a Hill-sphere radius of a planet. Around a massive planet the Hill-sphere can extend up to several stellar radii in size ; therefore rings (Kenworthy & Mamajek 2015;Lecavelier des Etangs et al 2017;Aizawa et al 2017) or dust envelope like e.g. Fomalhaut b (Kalas et al 2008) can be large enough that the transit duration can reach up to a few days.…”

Exploring Whether Super-puffs can be Explained as Ringed Exoplanets

“…The difficulty is that such signals are subtle and difficult to discern in current data. In a few cases, potential rings or constraints on rings have been made in this way (Heising et al 2015;Aizawa et al 2017Aizawa et al , 2018, and in at least one instance it has been argued that an exoplanet has a giant ring system from a series of complex eclipses (Kenworthy & Mamajek 2015;Rieder & Kenworthy 2016). There is clearly still a lot we do not know about the rings of exoplanets.…”

Fast and precise light-curve model for transiting exoplanets with rings

“…Naturally, due to the much simpler geometry, it is significantly faster to run than ringed planets models. The speed of pyPplusS is roughly 2300 times slower than pyTransit on the same machine, while the performance quoted in Aizawa et al (2017), which we believe to be the closest comparison to pyPplusS, is 3000 times slower than pyTransit. pyPplusS is therefore somewhat faster than the algorithm by Aizawa et al (2017).…”

“…The two best candidates currently known are 1SWASP J140747.93-394542.6 (hereafter J1407b) and KIC 10403228: Over a single ∼56 day period J1407b was seen to undergo a series of deep and complex dimming events that were fitted with a comparatively complex set of no less than 37 separate rings (Mamajek et al, 2012;van Werkhoven et al, 2014). More recently the single asymmetric transitlike event of KIC 10403228 was modelled as the transit of a grazing planet with an oblique ring (Aizawa et al, 2017). Both of these cases are single events and lack confirmation from follow-up observations.…”