2 research outputs found
An Unusual Transmission Spectrum for the Sub-Saturn KELT-11b Suggestive of a Sub-Solar Water Abundance
We present an optical-to-infrared transmission spectrum of the inflated
sub-Saturn KELT-11b measured with the Transiting Exoplanet Survey Satellite
(TESS), the Hubble Space Telescope (HST) Wide Field Camera 3 G141 spectroscopic
grism, and the Spitzer Space Telescope (Spitzer) at 3.6 m, in addition to
a Spitzer 4.5 m secondary eclipse. The precise HST transmission spectrum
notably reveals a low-amplitude water feature with an unusual shape. Based on
free retrieval analyses with varying molecular abundances, we find strong
evidence for water absorption. Depending on model assumptions, we also find
tentative evidence for other absorbers (HCN, TiO, and AlO). The retrieved water
abundance is generally solar (0.001--0.7 solar
over a range of model assumptions), several orders of magnitude lower than
expected from planet formation models based on the solar system metallicity
trend. We also consider chemical equilibrium and self-consistent 1D
radiative-convective equilibrium model fits and find they too prefer low
metallicities (, consistent with the free retrieval
results). However, all the retrievals should be interpreted with some caution
since they either require additional absorbers that are far out of chemical
equilibrium to explain the shape of the spectrum or are simply poor fits to the
data. Finally, we find the Spitzer secondary eclipse is indicative of full heat
redistribution from KELT-11b's dayside to nightside, assuming a clear dayside.
These potentially unusual results for KELT-11b's composition are suggestive of
new challenges on the horizon for atmosphere and formation models in the face
of increasingly precise measurements of exoplanet spectra.Comment: Accepted to The Astronomical Journal. 31 pages, 20 figures, 7 table
The KELT Follow-up Network and Transit False-positive Catalog: Pre-vetted False Positives for TESS
The Kilodegree Extremely Little Telescope (KELT) project has been conducting
a photometric survey for transiting planets orbiting bright stars for over ten
years. The KELT images have a pixel scale of ~23"/pixel---very similar to that
of NASA's Transiting Exoplanet Survey Satellite (TESS)---as well as a large
point spread function, and the KELT reduction pipeline uses a weighted
photometric aperture with radius 3'. At this angular scale, multiple stars are
typically blended in the photometric apertures. In order to identify false
positives and confirm transiting exoplanets, we have assembled a follow-up
network (KELT-FUN) to conduct imaging with higher spatial resolution, cadence,
and photometric precision than the KELT telescopes, as well as spectroscopic
observations of the candidate host stars. The KELT-FUN team has followed-up
over 1,600 planet candidates since 2011, resulting in more than 20 planet
discoveries. Excluding ~450 false alarms of non-astrophysical origin (i.e.,
instrumental noise or systematics), we present an all-sky catalog of the 1,128
bright stars (6<V<10) that show transit-like features in the KELT light curves,
but which were subsequently determined to be astrophysical false positives
(FPs) after photometric and/or spectroscopic follow-up observations. The
KELT-FUN team continues to pursue KELT and other planet candidates and will
eventually follow up certain classes of TESS candidates. The KELT FP catalog
will help minimize the duplication of follow-up observations by current and
future transit surveys such as TESS.Comment: Accepted for publication in AJ, 21 pages, 12 figures, 7 table