60 research outputs found
The size and shape of the oblong dwarf planet Haumea
We use thermal radiometry and visible photometry to constrain the size,
shape, and albedo of the large Kuiper belt object Haumea. The correlation
between the visible and thermal photometry demonstrates that Haumea's high
amplitude and quickly varying optical light curve is indeed due to Haumea's
extreme shape, rather than large scale albedo variations. However, the
well-sampled high precision visible data we present does require longitudinal
surface heterogeneity to account for the shape of lightcurve. The thermal
emission from Haumea is consistent with the expected Jacobi ellipsoid shape of
a rapidly rotating body in hydrostatic equilibrium. The best Jacobi ellipsoid
fit to the visible photometry implies a triaxial ellipsoid with axes of length
1920 x 1540 x 990 km and density 2.6 g cm^-3$, as found by Lellouch et
al(2010). While the thermal and visible data cannot uniquely constrain the full
non-spherical shape of Haumea, the match between the predicted and measured
thermal flux for a dense Jacobi ellipsoid suggests that Haumea is indeed one of
the densest objects in the Kuiper belt.Comment: 21 pages, 2 figures, 2 tables -- Accepted for publication in Earth,
Moon and Planet
Simulating the Multi-Epoch Direct Detection Technique to Isolate the Thermal Emission of the Non-Transiting Hot Jupiter HD187123B
We report the 6.5 detection of water from the hot Jupiter HD187123b
with a Keplerian orbital velocity of 53 13 km/s. This high
confidence detection is made using a multi-epoch, high resolution, cross
correlation technique, and corresponds to a planetary mass of
1.4 and an orbital inclination of 21 5.
The technique works by treating the planet/star system as a spectroscopic
binary and obtaining high signal-to-noise, high resolution observations at
multiple points across the planet's orbit to constrain the system's binary
dynamical motion. All together, seven epochs of Keck/NIRSPEC -band
observations were obtained, with five before the instrument upgrade and two
after. Using high resolution SCARLET planetary and PHOENIX stellar spectral
models, along with a line-by-line telluric absorption model, we were able to
drastically increase the confidence of the detection by running simulations
that could reproduce, and thus remove, the non-random structured noise in the
final likelihood space well. The ability to predict multi-epoch results will be
extremely useful for furthering the technique. Here, we use these simulations
to compare three different approaches to combining the cross correlations of
high resolution spectra and find that the Zucker 2003 log(L) approach is least
affected by unwanted planet/star correlation for our HD187123 data set.
Furthermore, we find that the same total S/N spread across an orbit in many,
lower S/N epochs rather than fewer, higher S/N epochs could provide a more
efficient detection. This work provides a necessary validation of multi-epoch
simulations which can be used to guide future observations and will be key to
studying the atmospheres of further separated, non-transiting exoplanets.Comment: Accepted to AJ, 14 pages, 10 figure
Detection of Water Vapor in the Thermal Spectrum of the Non-Transiting Hot Jupiter upsilon Andromedae b
The upsilon Andromedae system was the first multi-planet system discovered
orbiting a main sequence star. We describe the detection of water vapor in the
atmosphere of the innermost non-transiting gas giant ups~And~b by treating the
star-planet system as a spectroscopic binary with high-resolution, ground-based
spectroscopy. We resolve the signal of the planet's motion and break the
mass-inclination degeneracy for this non-transiting planet via deep combined
flux observations of the star and the planet. In total, seven epochs of Keck
NIRSPEC band observations, three epochs of Keck NIRSPEC short wavelength
band observations, and three epochs of Keck NIRSPEC long wavelength
band observations of the ups~And~system were obtained. We perform a multi-epoch
cross correlation of the full data set with an atmospheric model. We measure
the radial projection of the Keplerian velocity ( = 55 9 km/s), true
mass ( = 1.7 ), and orbital inclination \big(
= 24 4\big), and determine that the planet's opacity structure
is dominated by water vapor at the probed wavelengths. Dynamical simulations of
the planets in the ups~And~system with these orbital elements for ups~And~b
show that stable, long-term (100 Myr) orbital configurations exist. These
measurements will inform future studies of the stability and evolution of the
ups~And~system, as well as the atmospheric structure and composition of the hot
Jupiter.Comment: Accepted to A
Ground- and Space-based Detection of the Thermal Emission Spectrum of the Transiting Hot Jupiter KELT-2Ab
We describe the detection of water vapor in the atmosphere of the transiting
hot Jupiter KELT-2Ab by treating the star-planet system as a spectroscopic
binary with high-resolution, ground-based spectroscopy. We resolve the signal
of the planet's motion with deep combined flux observations of the star and the
planet. In total, six epochs of Keck NIRSPEC -band observations were
obtained, and the full data set was subjected to a cross correlation analysis
with a grid of self-consistent atmospheric models. We measure a radial
projection of the Keplerian velocity, , of 148 7 km s,
consistent with transit measurements, and detect water vapor at 3.8. We
combine NIRSPEC -band data with IRAC secondary eclipse data to
further probe the metallicity and carbon-to-oxygen ratio of KELT-2Ab's
atmosphere. While the NIRSPEC analysis provides few extra constraints on the
data, it does provide roughly the same constraints on metallicity and
carbon-to-oxygen ratio. This bodes well for future investigations of the
atmospheres of non-transiting hot Jupiters.Comment: accepted to A
Contrast and Temperature Dependence of Multi-Epoch High-Resolution Cross-Correlation Exoplanet Spectroscopy
While high-resolution cross-correlation spectroscopy (HRCCS) techniques have proven effective at characterizing the atmospheres of transiting and non-transiting hot Jupiters, the limitations of these techniques are not well understood. We present a series of simulations of one HRCCS technique, which combines the cross-correlation functions from multiple epochs, to place temperature and contrast limits on the accessible exoplanet population for the first time. We find that planets approximately Saturn-size and larger within ∼0.2 AU of a Sun-like star are likely to be detectable with current instrumentation in the L-band, a significant expansion compared with the previously-studied population. Cooler (T_(eq) ≤ 1000 K) exoplanets are more detectable than suggested by their photometric contrast alone as a result of chemical changes which increase spectroscopic contrast. The L-band CH₄ spectrum of cooler exoplanets enables robust constraints on the atmospheric C/O ratio at T_(eq)∼900K, which have proven difficult to obtain for hot Jupiters. These results suggest that the multi-epoch approach to HRCCS can detect and characterize exoplanet atmospheres throughout the inner regions of Sun-like systems with existing high-resolution spectrographs. We find that many epochs of modest signal-to-noise (S/N_(epoch)∼1500) yield the clearest detections and constraints on C/O, emphasizing the need for high-precision near-infrared telluric correction with short integration times
Evidence for the Direct Detection of the Thermal Spectrum of the Non-Transiting Hot Gas Giant HD 88133 b
We target the thermal emission spectrum of the non-transiting gas giant HD
88133 b with high-resolution near-infrared spectroscopy, by treating the planet
and its host star as a spectroscopic binary. For sufficiently deep summed flux
observations of the star and planet across multiple epochs, it is possible to
resolve the signal of the hot gas giant's atmosphere compared to the brighter
stellar spectrum, at a level consistent with the aggregate shot noise of the
full data set. To do this, we first perform a principal component analysis to
remove the contribution of the Earth's atmosphere to the observed spectra.
Then, we use a cross-correlation analysis to tease out the spectra of the host
star and HD 88133 b to determine its orbit and identify key sources of
atmospheric opacity. In total, six epochs of Keck NIRSPEC L band observations
and three epochs of Keck NIRSPEC K band observations of the HD 88133 system
were obtained. Based on an analysis of the maximum likelihood curves calculated
from the multi-epoch cross correlation of the full data set with two
atmospheric models, we report the direct detection of the emission spectrum of
the non-transiting exoplanet HD 88133 b and measure a radial projection of the
Keplerian orbital velocity of 40 15 km/s, a true mass of
1.02, a nearly face-on orbital inclination of
15, and an atmosphere opacity structure at high
dispersion dominated by water vapor. This, combined with eleven years of radial
velocity measurements of the system, provides the most up-to-date ephemeris for
HD 88133.Comment: 9 pages, 6 figures; accepted for publication in Ap
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