6,688 research outputs found
Toward a homogeneous set of transiting planet parameters
With 40 or more transiting exoplanets now known, the time is ripe to seek
patterns and correlations among their observed properties, which may give
important insights into planet formation, structure, and evolution. This task
is made difficult by the widely different methodologies that have been applied
to measure their properties in individual cases. Furthermore, in many systems
our knowledge of the planet properties is limited by the knowledge of the
properties of the parent stars. To address these difficulties we have
undertaken the first comprehensive analysis of the data for 23 transiting
planets using a uniform methodology. We revisit several of the recently
proposed correlations, and find new ones involving the metallicity of the
parent stars.Comment: 4 pages including figures. To appear in Proceedings of IAU Symposium
253, "Transiting Planets", May 2008, Cambridge, M
Sodium Absorption From the Exoplanetary Atmosphere of HD189733b Detected in the Optical Transmission Spectrum
We present the first ground-based detection of sodium absorption in the
transmission spectrum of an extrasolar planet. Absorption due to the atmosphere
of the extrasolar planet HD189733b is detected in both lines of the NaI
doublet. High spectral resolution observations were taken of eleven transits
with the High Resolution Spectrograph (HRS) on the 9.2 meter Hobby-Eberly
Telescope (HET). The NaI absorption in the transmission spectrum due to
HD189733b is (-67.2 +/- 20.7) x 10^-5 deeper in the ``narrow'' spectral band
that encompasses both lines relative to adjacent bands. The 1-sigma error
includes both random and systematic errors, and the detection is >3-sigma. This
amount of relative absorption in NaI for HD189733b is ~3x larger than detected
for HD209458b by Charbonneau et al. (2002), and indicates these two
hot-Jupiters may have significantly different atmospheric properties.Comment: 12 pages, 2 figures; Accepted for publication in ApJ Letter
Orbital Orientations of Exoplanets: HAT-P-4b is Prograde and HAT-P-14b is Retrograde
We present observations of the Rossiter-McLaughlin effect for two
exoplanetary systems, revealing the orientations of their orbits relative to
the rotation axes of their parent stars. HAT-P-4b is prograde, with a
sky-projected spin-orbit angle of lambda = -4.9 +/- 11.9 degrees. In contrast,
HAT-P-14b is retrograde, with lambda = 189.1 +/- 5.1 degrees. These results
conform with a previously noted pattern among the stellar hosts of close-in
giant planets: hotter stars have a wide range of obliquities and cooler stars
have low obliquities. This, in turn, suggests that three-body dynamics and
tidal dissipation are responsible for the short-period orbits of many
exoplanets. In addition, our data revealed a third body in the HAT-P-4 system,
which could be a second planet or a companion star.Comment: AJ, in press [8 pages
Resolving the Surfaces of Extrasolar Planets With Secondary Eclipse Light Curves
We present a method that employs the secondary eclipse light curves of
transiting extrasolar planets to probe the spatial variation of their thermal
emission. This technique permits an observer to resolve the surface of the
planet without the need to spatially resolve its central star. We evaluate the
feasibility of this technique for the HD 209458 system [..]. We consider two
representations of the planetary thermal emission; a simple model parameterized
by a sinusoidal dependence on longitude and latitude, as well as the results of
a three-dimensional dynamical simulation of the planetary atmosphere previously
published by Cooper & Showman. We find that observations of the secondary
eclipse light curve are most sensitive to a longitudinal offset in the
geometric and photometric centroids of the hemisphere of the planet visible
near opposition. To quantify this signal, we define a new parameter, the
``uniform time offset,'' which measures the time lag between the observed
secondary eclipse and that predicted by a planet with a uniform surface flux
distribution. We compare the predicted amplitude of this parameter for HD
209458 with the precision with which it could be measured with IRAC. We find
that IRAC observations at 3.6um a single secondary eclipse should permit
sufficient precision to confirm or reject the Cooper & Showman model of the
surface flux distribution for this planet. We quantify the signal-to-noise
ratio for this offset in the remaining IRAC bands (4.5um, 5.8um, and 8.0um),
and find that a modest improvement in photometric precision (as might be
realized through observations of several eclipse events) should permit a
similarly robust detection.Comment: AASTeX 5.2, 24 pages, 5 figures, accepted for publication in ApJ; v2:
clarifications, updated to version accepted by ApJ; v3: try to reduce spacin
Twenty-One New Light Curves of OGLE-TR-56b: New System Parameters and Limits on Timing Variations
Although OGLE-TR-56b was the second transiting exoplanet discovered, only one
light curve, observed in 2006, has been published besides the discovery data.
We present twenty-one light curves of nineteen different transits observed
between July 2003 and July 2009 with the Magellan Telescopes and Gemini South.
The combined analysis of the new light curves confirms a slightly inflated
planetary radius relative to model predictions, with R_p = 1.378 +/- 0.090 R_J.
However, the values found for the transit duration, semimajor axis, and
inclination values differ significantly from the previous result, likely due to
systematic errors. The new semimajor axis and inclination, a = 0.01942 +/-
0.00015 AU and i = 73.72 +/- 0.18 degrees, are smaller than previously
reported, while the total duration, T_14 = 7931 +/- 38 s, is 18 minutes longer.
The transit midtimes have errors from 23 s to several minutes, and no evidence
is seen for transit midtime or duration variations. Similarly, no change is
seen in the orbital period, implying a nominal stellar tidal decay factor of
Q_* = 10^7, with a three-sigma lower limit of 10^5.7.Comment: 14 pages, 5 figures, accepted to Ap
HATS-1b: The First Transiting Planet Discovered by the HATSouth Survey
We report the discovery of HATS-1b, a transiting extrasolar planet orbiting
the moderately bright V=12.05 G dwarf star GSC 6652-00186, and the first planet
discovered by HATSouth, a global network of autonomous wide-field telescopes.
HATS-1b has a period P~3.4465 d, mass Mp~1.86MJ, and radius Rp~1.30RJ. The host
star has a mass of 0.99Msun, and radius of 1.04Rsun. The discovery light curve
of HATS-1b has near continuous coverage over several multi-day periods,
demonstrating the power of using a global network of telescopes to discover
transiting planets.Comment: Submitted to AJ 10 pages, 5 figures, 6 table
A Prograde, Low-Inclination Orbit for the Very Hot Jupiter WASP-3b
We present new spectroscopic and photometric observations of the transiting
exoplanetary system WASP-3. Spectra obtained during two separate transits
exhibit the Rossiter-McLaughlin (RM) effect and allow us to estimate the
sky-projected angle between the planetary orbital axis and the stellar rotation
axis, lambda = 3.3^{+2.5}_{-4.4} degrees. This alignment between the axes
suggests that WASP-3b has a low orbital inclination relative to the equatorial
plane of its parent star. During our first night of spectroscopic measurements,
we observed an unexpected redshift briefly exceeding the expected sum of the
orbital and RM velocities by 140 m/s. This anomaly could represent the
occultation of material erupting from the stellar photosphere, although it is
more likely to be an artifact caused by moonlight scattered into the
spectrograph.Comment: 23 pages, 4 figures, Accepted for publication in The Astrophysical
Journal, Replacement includes revised citation
The Apparently Decaying Orbit of WASP-12
We present new transit and occultation times for the hot Jupiter WASP-12b.
The data are compatible with a constant period derivative:
ms yr and Myr. However, it is difficult to tell whether
we have observed orbital decay, or a portion of a 14-year apsidal precession
cycle. If interpreted as decay, the star's tidal quality parameter is
about . If interpreted as precession, the planet's Love number is
. Orbital decay appears to be the more parsimonious model: it is
favored by despite having two fewer free parameters than the
precession model. The decay model implies that WASP-12 was discovered within
the final 0.2% of its existence, which is an unlikely coincidence but
harmonizes with independent evidence that the planet is nearing disruption.
Precession does not invoke any temporal coincidence, but does require some
mechanism to maintain an eccentricity of 0.002 in the face of rapid
tidal circularization. To distinguish unequivocally between decay and
precession will probably require a few more years of monitoring. Particularly
helpful will be occultation timing in 2019 and thereafter.Comment: 10 pages [AAS journals, in press, note added in proof
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