Starspots - Transit Depth Relation of the Evaporating Planet Candidate KIC 12557548b

Abstract

Violent variation of transit depths and an ingress-egress asymmetry of the transit light curve discovered in KIC 12557548 have been interpreted as evidences of a catastrophic evaporation of atmosphere with dust (M_p gtrsim 1 M_oplus/Gyr) from a close-in small planet. To explore what drives the anomalous atmospheric escape, we perform time-series analysis of the transit depth variation of Kepler archival data for ~ 3.5 yr. We find a ~ 30% periodic variation of the transit depth with P1 = 22.83 pm 0.21 days, which is within the error of the rotation period of the host star estimated using the light curve modulation, Prot = 22.91 pm 0.24 days. We interpret the results as evidence that the atmospheric escape of KIC 12557548b correlates with stellar activity. We consider possible scenarios that account for both the mass loss rate and the correlation with stellar activity. X-ray and ultraviolet (XUV)-driven evaporation is possible if one accepts a relatively high XUV flux and a high efficiency for converting the input energy to the kinetic energy of the atmosphere. Star-planet magnetic interaction is another possible scenario though huge uncertainty remains for the mass loss rate.

6 pages, 5 figures. Published in ApJ Letters. Minor typos corrected

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• The Ĝ Search for Extraterrestrial Civilizations with Large Energy Supplies. IV. The Signatures and Information Content of Transiting Megastructures
• Multiwavelength Observations of the Candidate Disintegrating sub-Mercury KIC 12557548b
• Dusty tails of evaporating exoplanets. I. Constraints on the dust composition
• Direct evidence for an evolving dust cloud from the exoplanet KIC 12557548 b
• The Relation between the Transit Depths of KIC 12557548b & the Stellar Rotation Period
• Dusty tails of evaporating exoplanets. II. Physical modelling of the KIC 12557548b light curve
• Analysis and interpretation of 15 quarters of Kepler data of the disintegrating planet KIC 12557548 b
• Mysterious eclipses in the light-curve of KIC8462852: a possible explanation
• Inferring the Composition of Disintegrating Planet Interiors from Dust Tails with Future James Webb Space Telescope Observations
• A Transient Transit Signature Associated with the Young Star RIK-210
• Disintegrating Rocky Exoplanets
• Reduced Activity And Large Particles From the Disintegrating Planet Candidate KIC 12557548b
• The Exosphere as a Boundary: Origin and Evolution of Airless Bodies in the Inner Solar System and Beyond Including Planets with Silicate Atmospheres
• A Large Ground-Based Observing Campaign of the Disintegrating Planet K2-22b
• Chaotic winds from a dying world: a one-dimensional map for evolving atmospheres
• Back to "Normal" for the Disintegrating Planet Candidate KIC 12557548 b
• Light-curve analysis of KOI 2700b: the second extrasolar planet with a comet-like tail
• Can tidal evolution lead to close-in planetary bodies around white dwarfs I: Orbital period distribution
• LBT Reveals Large Dust Particles and a High Mass Loss Rate for K2-22 b
• Can tidal evolution lead to close-in planetary bodies around white dwarfs II: volcanism and transits
• A Disintegrating Rocky World Shrouded in Dust and Gas: Mid-IR Observations of K2-22b using JWST
• Search for a circum-planetary material and orbital period variations of short-period Kepler exoplanet candidates
• Climate Change in Hell: Long-Term Variation in Transits of the Evaporating Planet K2-22b
• Extrasolar enigmas: from disintegrating exoplanets to exoasteroids