Multiwavelength Observations of the Candidate Disintegrating Sub-Mercury Kic 12557548b, ,

Abstract

We present multiwavelength photometry, high angular resolution imaging, and radial velocities, of the unique and confounding disintegrating low-mass planet candidate KIC 12557548b. Our high angular resolution imaging, which includes spacebased HST/WFC3 observations in the optical (∼0.53 µm and ∼0.77 µm), and groundbased Keck/NIRC2 observations in K'-band (∼2.12 µm), allow us to rule-out background and foreground candidates at angular separations greater than 0.2 ′′ that are bright enough to be responsible for the transits we associate with KIC 12557548. Our radial velocity limit from Keck/HIRES allows us to rule-out bound, low-mass stellar companions (∼0.2 M ⊙ ) to KIC 12557548 on orbits less than 10 years, as well as placing an upper-limit on the mass of the candidate planet of 1.2 Jupiter masses; therefore, the combination of our radial velocities, high angularresolution imaging, and photometry are able to rule-out most false positive interpretations of the transits. Our precise multiwavelength photometry includes two simultaneous detections of the transit of KIC 12557548b using CFHT/WIRCam at 2.15 µm and the Kepler space telescope at 0.6 µm, as well as simultaneous null-detections of the transit by Kepler and HST/WFC3 at 1.4 µm. Our simultaneous HST/WFC3 and Kepler null-detections, provide no evidence for radically different transit depths at these wavelengths. Our simultaneous CFHT/WIRCam detections in the near-infrared and with Kepler in the optical reveal very similar transit depths (the average ratio of the transit depths at ∼2.15 µm compared to ∼0.6 µm is: 1.02 ± 0.20). This suggests that if the transits we observe are due to scattering from single-size particles streaming from the planet in a comet-like tail, then the particles must be ∼0.5 microns in radius or larger, which would favour that KIC 12557548b is a sub-Mercury, rather than super-Mercury, mass planet.

The Ĝ Search for Extraterrestrial Civilizations With Large Energy Supplies. Iv. The Signatures and Information Content of Transiting Megastructures

“…Rappaport et al (2012) announced KIC 12557548b (KIC 1255b for short), an apparently evaporating planet with a 16 hr period discovered with the Kepler observatory. Consistent with Arnold's prediction, its transit depths vary, even between consecutive transits "from a maximum of 1.3% of the stellar flux to a minimum of 0.2% or less without a discernible rhyme or reason" (Croll et al 2014). Further, Figure 1 shows how the transit light curves "exhibit[] an obvious ingress/egress asymmetry, with a sharp ingress followed by a longer, more gradual egress" (Croll et al 2014) consistent with Forgan's model.…”

“…Croll et al (2014) observed the target in ¢ K band ( m2.15 m) at CFHT simultaneously with Kepler (in the broadband optical near 0.6 mm) and found no wavelength difference (the depth ratio between the two bands was 1.02 ±0.2).…”

“…Notable in this DTS are the two quiescent periods at the beginning and end of the DTS where the measured transit depth is nearly zero, and between those two quiescent areas where the depths are highly variable. This DTS was kindly provided by B. Croll (2015, private communication) who describes its construction in Croll et al (2014). We rejected one highly negative depth in the KIC 1255b time series as unphysical.…”

“…Figure 5 shows the PDF for the KIC 1255b DTS. The PDF on the left was generated in the same manner as the Kepler-4b DTS, with a kernel width equal to the average measurement uncertainty of the transit depths (Croll et al 2014). The smoothness of the PDF is due to the larger width of the convolving kernel, but the width of the PDF is notably much wider than for Kepler-4b and does stretch below = depth 0 owing to the quiescent periods.…”

Tables of phase functions, opacities, albedos, equilibrium temperatures, and radiative accelerations of dust grains in exoplanets

“…Rappaport et al (2012) discovered a transiting disintegrating exoplanet KIC12557548b with a comet-like dusty tail extending well beyond its Hill radius and featuring a pre-transit brightening. Recent studies have shown that pre-transit brightening is due to strong forward scattering and can be used, together with the color dependence of the transit depth, to constrain the particle size of dust grains in the comet-like tail, which was found to be of the order of 1 micron (Budaj 2013;Croll et al 2014;Bochinski et al 2015) (see also Brogi et al 2012;van Werkhoven et al 2014). Two other objects of this kind (KOI-2700b, EPIC201637175B) have been discovered already by Rappaport et al (2014) and Sanchis-Ojeda et al (2015).…”