2,016 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
Evaluating kernels on Xeon Phi to accelerate Gysela application
This work describes the challenges presented by porting parts ofthe Gysela
code to the Intel Xeon Phi coprocessor, as well as techniques used for
optimization, vectorization and tuning that can be applied to other
applications. We evaluate the performance of somegeneric micro-benchmark on Phi
versus Intel Sandy Bridge. Several interpolation kernels useful for the Gysela
application are analyzed and the performance are shown. Some memory-bound and
compute-bound kernels are accelerated by a factor 2 on the Phi device compared
to Sandy architecture. Nevertheless, it is hard, if not impossible, to reach a
large fraction of the peek performance on the Phi device,especially for
real-life applications as Gysela. A collateral benefit of this optimization and
tuning work is that the execution time of Gysela (using 4D advections) has
decreased on a standard architecture such as Intel Sandy Bridge.Comment: submitted to ESAIM proceedings for CEMRACS 2014 summer school version
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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
Operations on integral lifts of K(n)
This very rough sketch is a sequel to arXiv:1808.08587; it presents evidence
that operations on lifts of the functors K(n) to cohomology theories with
values in modules over valuation rings of local number fields, indexed by
Lubin-Tate groups of such fields, are extensions of the groups of automorphisms
of the indexing group laws, by the exterior algebras on the normal bundle to
the orbits of the group laws in the space of lifts.Comment: \S 2.0 hopefully less cryptic. To appear in the proceedings of the
2015 Nagoya conference honoring T Ohkawa. Comments very welcome
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