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Abstract

The discovery of the first disintegrating exoplanet opened a new door in the field of exoplanets. The rocky exoplanet K2-22b is just the third known disintegrating exoplanet, and it orbits an M dwarf with a period of just 9 hr. It was discovered by NASA's K2 mission in 2014. Sanchis- Ojeda et al. (2015) presented the analysis of the K2 observations that were obtained between May and August 2014 and 15 ground-based follow-up light curves obtained between January and March 2015. From these data, Sanchis-Ojeda et al. (2015) measured rapidly variable transit depths for K2-22b ranging from 0% to 1.3%. A wavelength-dependent transit light curve shape was also measured during one particularly deep transit, supporting dust scattering during the transit. In addition, K2-22b appears to have both a leading and trailing dust tail. The star itself also exhibits photometric variability at the 1% level with a rotation period of 15 days. We will present results from 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 since 2015. In these new observations we recover the transit at multiple epochs and measure a typical depth of <1.5%. We find that our measured transit depths are comparable to depths measured in observations from 2014 and 2015. However, our observations are suggestive of a decrease in the transit depth over the timescale of our observing campaign. 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. In addition, we find no strong evidence of wavelength-dependent transit depths for epochs where we have simultaneous coverage at multiple wavelengths. We will discuss opportunities for 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. In particular, we will use recent observations of the inflated low-mass exoplanet KELT-11b with the Hubble Space Telescope as a benchmark for future high-precision observations of exoplanets like K2-22b.