Back to "Normal" for the Disintegrating Planet Candidate KIC 12557548 b

TL;DR

This study confirms the return to normal transiting behavior of disintegrating planet candidate KIC 12557548 b, clarifies stellar parameters, and explores potential long-term dust evolution through PCA analysis of Kepler data.

Contribution

It provides new transit observations confirming the system's return to typical behavior and analyzes stellar and dust properties with PCA to investigate long-term evolution.

Findings

Transits returned to normal length and mass after previous shallow observations.

High resolution spectra are consistent with a main-sequence star, ruling out disintegration effects on stellar analysis.

A tentative 491-day periodicity suggests possible long-term dust grain size evolution.

Abstract

KIC 12557548 b is 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 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 5 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 Teff=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.