POSSIBLE DISINTEGRATING SHORT-PERIOD SUPER-MERCURY ORBITING KIC 12557548

By S. Rappaport, A. Levine, Eugene Chiang, Ileyk El Mellah, J. Jenkins, B. Kalomeni, E. Kite, Michael C. Kotson, Lorne Nelson, Laurie Rousseau-Nepton and 1 more. 2012

179 citations recorded by the source corpus.

We report on the discovery of stellar occultations, observed with Kepler, which recur periodically at 15.685 hr intervals, but which vary in depth from a maximum of 1.3% to a minimum that can be less than 0.2%. The star that is apparently being occulted is KIC 12557548, a V = 16 mag K dwarf with Teff, s ≃ 4400 K. The out-of-occultation behavior shows no evidence for ellipsoidal light variations, indicating that the mass of the orbiting object is less than ∼3 MJ (for an orbital period of 15.7 hr). Because the eclipse depths are highly variable, they cannot be due solely to transits of a single planet with a fixed size. We discuss but dismiss a scenario involving a binary giant planet whose mutual orbit plane precesses, bringing one of the planets into and out of a grazing transit. This scenario seems ruled out by the dynamical instability that would result from such a configuration. We also briefly consider an eclipsing binary, possibly containing an accretion disk, that either orbits KIC 12557548 in a hierarchical triple configuration or is nearby on the sky, but we find such a scenario inadequate to reproduce the observations. The much more likely explanation—but one which still requires more quantitative development—involves macroscopic particles escaping the atmosphere of a slowly disintegrating planet not much larger than Mercury in size. The particles could take the form of micron-sized pyroxene or aluminum oxide dust grains. The planetary surface is hot enough to sublimate and create a high-Z atmosphere; this atmosphere may be loaded with dust via cloud condensation or explosive volcanism. Atmospheric gas escapes the planet via a Parker-type thermal wind, dragging dust grains with it. We infer a mass-loss rate from the observations of order 1 M⊕ Gyr−1, with a dust-to-gas ratio possibly of order unity. For our fiducial 0.1 M⊕ planet (twice the mass of Mercury), the evaporation timescale may be ∼0.2 Gyr. Smaller mass planets are disfavored because they evaporate still more quickly, as are larger mass planets because they have surface gravities too strong to sustain outflows with the requisite mass-loss rates. The occultation profile evinces an ingress–egress asymmetry that could reflect a comet-like dust tail trailing the planet; we present simulations of such a tail.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/4253f1f5068522541b9dd65b46e724c18a4adc4c

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In Astronomy and Astrophysics

1. J. Owen
2. J. Winn
3. Y. Lithwick
4. Yanqin Wu
5. D. Lai
6. D. Fabrycky
7. S. Naoz
8. Roberto Sanchis-Ojeda

In Instrumentation

1. J. Owen
2. J. Winn
3. Y. Lithwick
4. D. Lai
5. D. Fabrycky
6. Yanqin Wu
7. J. Brewer
8. T. Boyajian

In Statistical and Nonlinear Physics

1. Y. Lithwick
2. J. Winn
3. Yanqin Wu
4. D. Lai
5. D. Fabrycky
6. H. Schwengeler
7. J. Brewer
8. Debra A. Fischer

Citations in the corpus

• Planet Hunters IX. KIC 8462852-where's the flux? (2015, background): “The light curve expected for a typical event then has a relatively fast ingress as the head of the comet passes in front of the star, but a slower egress as the tail passes (e.g. Lecavelier Des Etangs, Vidal-Madjar & Ferlet 1999; Rappaport et al. 2012).”
• DENSITY AND ECCENTRICITY OF KEPLER PLANETS (2012, background): “13 This argument means that the dusty evaporative clouds from KIC 12557548 (Rappaport et al. 2012) is hard to explain unless the surface escape velocity from the planet is very low (E. Chiang, private communication).”
• LYα TRANSIT SPECTROSCOPY AND THE NEUTRAL HYDROGEN TAIL OF THE HOT NEPTUNE GJ 436b (2014, background): “The evaporating super-Mercury exoplanet KIC 12557548b likely has a dusty comet-like tail (Rappaport et al. 2012; Budaj 2013) and the extreme hot Jupiter WASP-12b is losing sufficient mass to completely obscure its host star’s emission in the cases of the Mg II h and k lines (Haswell et al. 2012).”
• A STUDY OF THE SHORTEST-PERIOD PLANETS FOUND WITH KEPLER (2014, background): “Within the remaining systems were two special cases, KIC 12557548 and KOI-2700 (Rappaport et al. 2012, 2013b), which have asymmetric transit profiles that have been interpreted as signs that these planets are emitting dusty comet-like tails.”
• Photoevaporation and high-eccentricity migration created the sub-Jovian desert (2018, background): “…radius-period plot (upper panel), two classes of “misleading” planets appear in the desert: (1) The triangles indicate disintegrating rocky planets, (e.g. Rappaport et al. 2012; Sanchis-Ojeda et al. 2015), where the surface temperatures are large enough to allow sublimation of the planet’s surface.”