12 research outputs found
Revision of Earth-sized Kepler Planet Candidate Properties with High Resolution Imaging by Hubble Space Telescope
We present the results of our Hubble Space Telescope program and describe how
our analysis methods were used to re-evaluate the habitability of some of the
most interesting Kepler planet candidates. Our program observed 22 Kepler
Object of Interest (KOI) host stars, several of which were found to be multiple
star systems unresolved by Kepler. We use our high-resolution imaging to
spatially resolve the stellar multiplicity of Kepler-296, KOI-2626, and
KOI-3049, and develop a conversion to the Kepler photometry (Kp) from the F555W
and F775W filters on WFC3/UVIS. The binary system Kepler-296 (5 planets) has a
projected separation of 0.217" (80AU); KOI-2626 (1 planet candidate) is a
triple star system with a projected separation of 0.201" (70AU) between the
primary and secondary components and 0.161" (55AU) between the primary and
tertiary; and the binary system KOI-3049 (1 planet candidate) has a projected
separation of 0.464" (225AU). We use our measured photometry to fit the
separated stellar components to the latest Victoria-Regina Stellar Models with
synthetic photometry to conclude that the systems are coeval. The components of
the three systems range from mid-K dwarf to mid-M dwarf spectral types. We
solved for the planetary properties of each system analytically and via an MCMC
algorithm using our independent stellar parameters. The planets range from
~1.6R_Earth to ~4.2R_Earth, mostly Super Earths and mini-Neptunes. As a result
of the stellar multiplicity, some planets previously in the Habitable Zone are,
in fact, not, and other planets may be habitable depending on their assumed
stellar host.Comment: 16 pages, 10 figures, ApJ, 804, 9
Hubble Space Telescope High Resolution Imaging of Kepler Small and Cool Exoplanet Host Stars
High resolution imaging is an important tool for follow-up study of exoplanet
candidates found via transit detection with the Kepler Mission. We discuss here
HST imaging with the WFC3 of 23 stars that host particularly interesting Kepler
planet candidates based on their small size and cool equilibrium temperature
estimates. Results include detections, exclusion of background stars that could
be a source of false positives for the transits, and detection of
physically-associated companions in a number of cases providing dilution
measures necessary for planet parameter refinement. For six KOIs, we find that
there is ambiguity in which star hosts the transiting planet(s), with
potentially strong implications for planetary characteristics. Our sample is
evenly distributed in G, K, and M spectral types. Albeit with a small sample
size, we find that physically-associated binaries are more common than expected
at each spectral type, reaching a factor of 10 frequency excess at M. We
document the program detection sensitivities, detections, and deliverables to
the Kepler follow-up program archive.Comment: Accepted for the Astronomical Journal; 13 pages with 9 figure
Near-infrared Emission Spectrum of WASP-103b Using Hubble Space Telescope/Wide Field Camera 3
We present here our observations and analysis of the dayside emission spectrum of the hot Jupiter WASP-103b. We observed WASP-103b during secondary eclipse using two visits of the Hubble Space Telescope with the G141 grism on Wide Field Camera 3 in spatial scan mode. We generated secondary eclipse light curves of the planet in both blended white-light and spectrally binned wavechannels from 1.1-1.7 µm and corrected the light curves for flux contamination from a nearby companion star. We modeled the detector systematics and secondary eclipse spectrum using Gaussian process regression and found that the near-IR emission spectrum of WASP-103b is featureless across the observed near-IR region to down to a sensitivity of 175 ppm, and shows a shallow slope toward the red. The atmosphere has a single brightness temperature of T_B = 2890 K across this wavelength range. This region of the spectrum is indistinguishable from isothermal, but may not manifest from a physically isothermal system, i.e., pseudo-isothermal. A solar-metallicity profile with a thermal inversion layer at 10^(−2) bar fits the spectrum of WASP-103b with high confidence, as do an isothermal profile with solar metallicity and a monotonically decreasing atmosphere with C/O > 1. The data rule out a monotonically decreasing atmospheric profile with solar composition, and we rule out a low-metallicity decreasing profile as unphysical for this system. The pseudo-isothermal profile could be explained by a thermal inversion layer just above the layer probed by our observations, or by clouds or haze in the upper atmosphere. Transmission spectra at optical wavelengths would allow us to better distinguish between potential atmospheric models
Early Universe Dynamics in Semi-Classical Loop Quantum Cosmology
Within the framework of loop quantum cosmology, there exists a semi-classical
regime where spacetime may be approximated in terms of a continuous manifold,
but where the standard Friedmann equations of classical Einstein gravity
receive non-perturbative quantum corrections. An approximate, analytical
approach to studying cosmic dynamics in this regime is developed for both
spatially flat and positively-curved isotropic universes sourced by a
self-interacting scalar field. In the former case, a direct correspondence
between the classical and semi-classical field equations can be established
together with a scale factor duality that directly relates different expanding
and contracting universes. Some examples of non-singular, bouncing cosmologies
are presented together with a scaling, power-law solution.Comment: 14 pages, In Press, JCA
Near-infrared Emission Spectrum of WASP-103b Using Hubble Space Telescope/Wide Field Camera 3
We present here our observations and analysis of the dayside emission spectrum of the hot Jupiter WASP-103b. We observed WASP-103b during secondary eclipse using two visits of the Hubble Space Telescope with the G141 grism on Wide Field Camera 3 in spatial scan mode. We generated secondary eclipse light curves of the planet in both blended white-light and spectrally binned wavechannels from 1.1-1.7 µm and corrected the light curves for flux contamination from a nearby companion star. We modeled the detector systematics and secondary eclipse spectrum using Gaussian process regression and found that the near-IR emission spectrum of WASP-103b is featureless across the observed near-IR region to down to a sensitivity of 175 ppm, and shows a shallow slope toward the red. The atmosphere has a single brightness temperature of T_B = 2890 K across this wavelength range. This region of the spectrum is indistinguishable from isothermal, but may not manifest from a physically isothermal system, i.e., pseudo-isothermal. A solar-metallicity profile with a thermal inversion layer at 10^(−2) bar fits the spectrum of WASP-103b with high confidence, as do an isothermal profile with solar metallicity and a monotonically decreasing atmosphere with C/O > 1. The data rule out a monotonically decreasing atmospheric profile with solar composition, and we rule out a low-metallicity decreasing profile as unphysical for this system. The pseudo-isothermal profile could be explained by a thermal inversion layer just above the layer probed by our observations, or by clouds or haze in the upper atmosphere. Transmission spectra at optical wavelengths would allow us to better distinguish between potential atmospheric models
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