A Large Ground-Based Observing Campaign of the Disintegrating Planet K2-22b

TL;DR

This study presents a comprehensive ground-based photometric campaign of the disintegrating planet K2-22b, revealing persistent transit variability and shallow depths, with no strong wavelength dependence, highlighting the need for ongoing monitoring.

Contribution

First extensive ground-based observational campaign of K2-22b, demonstrating transit variability and providing data to understand disintegrating planets' evolution.

Findings

Transit depths are consistent over years, indicating ongoing disintegration.

No significant wavelength dependence detected in transit depths.

Transit shape variability observed, but detailed analysis remains challenging.

Abstract

We present 45 ground-based photometric observations of the K2-22 system collected between December 2016 and May 2017, which we use to investigate the evolution of the transit of the disintegrating planet K2-22b. Last observed in early 2015, in these new observations we recover the transit at multiple epochs and measure a typical depth of <1.5%. We find that the distribution of our measured transit depths is comparable to the range of depths measured in observations from 2014 and 2015. These new observations also support ongoing variability in the K2-22b transit shape and time, although the overall shallowness of the transit makes a detailed analysis of these transit parameters difficult. We find no strong evidence of wavelength-dependent transit depths for epochs where we have simultaneous coverage at multiple wavelengths, although our stacked Las Cumbres Observatory data collected over days-to-months timescales are suggestive of a deeper transit at blue wavelengths. We encourage continued high-precision photometric and spectroscopic monitoring of this system in order to further constrain the evolution timescale and to aid comparative studies with the other few known disintegrating planets.