Detecting rings at "super-puff" planets.

Some of the extremely low density planets may be having their transit depths (and consequently apparent radii) propped up by circumplanetary rings. This paper explores the possibility of determining if this is the case.

Exploring Whether Super-Puffs Can Be Explained as Ringed Exoplanets
https://arxiv.org/abs/1911.09673

Quote :

An intriguing, growing class of planets are the "super-puffs," objects with exceptionally large radii for their masses and thus correspondingly low densities (≲0.3gcm−3). Planets with such extended atmospheres are challenging for current evolutionary models, since they should be susceptible to photoevaporation. Here we consider a different explanation, namely that they have large inferred radii because they are ringed. This would naturally explain why super-puffs have thus far only shown featureless transit spectra. We find that this hypothesis cannot explain all of these objects, but can explain certain super-puffs with currently available data. The close proximity of the super-puffs to their parent stars necessitates rings with a rocky rather than icy composition. This limits the radius of the rings, and makes it challenging to explain the large size of Kepler 51b, 51c, 51d, and 79d unless the ring is composed of porous material. Furthermore, the short tidal locking timescales for Kepler 18d, 223d, and 223e mean that these planets may be spinning too slowly, resulting in a small oblateness and rings that are warped by their parent star. Kepler 87c and 177c have the best chance of being explained by rings, but ~10 ppm photometry is required to test this hypothesis. Although less favored by the arguments presented here, the presence of rings around Kepler 18d, 223d, and 223e would be easier to test (~50-150 ppm photometry). We conclude with a note about the recently discovered super-puff HIP 41378f.

On the topic of HIP 43178 f, they note that current ground-based instrumentation can determine if HIP 41378 f indeed has rings, with the only real challenge being the long orbital period and transit duration, which might need telescopes distributed around the world to obtain sufficiently good coverage and photometry (~100 ppm level precision).

Saturn for example would have Jupiter depth during transit ,so it is quite often in other planetary system planets have rings large enough to affect transit depth significantly