Back to “Normal” for the Disintegrating Planet Candidate KIC 12557548 b

Abstract

KIC 12557548 b is the first of a growing class of intriguing disintegrating planet candidates, which lose mass in the form of a metal-rich vapor that condenses into dust particles. Here, we follow up on two perplexing observations of the system: (1) the transits appeared shallower than average in 2013 and 2014, and (2) the parameters derived from a high-resolution spectrum of the star differed from other results using photometry and low-resolution spectroscopy. We observe five transits of the system with the 61-inch Kuiper telescope in 2016 and show that they are consistent with photometry from the Kepler spacecraft in 2009-2013, suggesting that the dusty tail has returned to normal length and mass. We also evaluate high-resolution archival spectra from the Subaru HDS spectrograph and find them to be consistent with a main-sequence T _eff = 4440 ± 70 K star in agreement with the photometry and low-resolution spectroscopy. This disfavors the hypothesis that planet disintegration affected the analysis of prior high-resolution spectra of this star. We apply Principal Component Analysis to the Kepler long-cadence data to understand the modes of disintegration. There is a tentative 491-day periodicity of the second principal component, which corresponds to possible long-term evolution of the dust grain sizes, though the mechanism on such long timescales remains unclear.