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arXiv · 1502.04612

Direct evidence for an evolving dust cloud from the exoplanet KIC 12557548 b

Jakub J. Bochinski·Carole A. Haswell·Tom R. Marsh·Vikram S. Dhillon·Stuart P. Littlefair
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Abstract

We present simultaneous multi-color optical photometry using ULTRACAM of the transiting exoplanet KIC 12557548 b (also known as KIC 1255 b). This reveals, for the first time, the color dependence of the transit depth. Our g and z transits are similar in shape to the average Kepler short-cadence profile, and constitute the highest-quality extant coverage of individual transits. Our Night 1 transit depths are 0.85 +/- 0.04% in z; 1.00 +/- 0.03% in g; and 1.1 +/- 0.3% in u. We employ a residual-permutation method to assess the impact of correlated noise on the depth difference between the z and g bands and calculate the significance of the color dependence at 3.2σ. The Night 1 depths are consistent with dust extinction as observed in the ISM, but require grain sizes comparable to the largest found in the ISM: 0.25-1μm. This provides direct evidence in favor of this object being a disrupting low-mass rocky planet, feeding a transiting dust cloud. On the remaining four nights of observations the object was in a rare shallow-transit phase. If the grain size in the transiting dust cloud changes as the transit depth changes, the extinction efficiency is expected to change in a wavelength- and composition-dependent way. Observing a change in the wavelength-dependent transit depth would offer an unprecedented opportunity to determine the composition of the disintegrating rocky body KIC 12557548 b. We detected four out-of-transit u band events consistent with stellar flares.

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Jakub J. Bochinski, Carole A. Haswell, Tom R. Marsh, Vikram S. Dhillon, Stuart P. Littlefair. 2015-02-16. Direct evidence for an evolving dust cloud from the exoplanet KIC 12557548 b. https://doi.org/10.1088/2041-8205%2F800%2F2%2Fl21

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