189 research outputs found
Examining the broadband emission spectrum of WASP-19b: A new z band eclipse detection
WASP-19b is one of the most irradiated hot-Jupiters known. Its secondary
eclipse is the deepest of all transiting planets, and has been measured in
multiple optical and infrared bands. We obtained a z band eclipse observation,
with measured depth of 0.080 +/- 0.029 %, using the 2m Faulkes Telescope South,
that is consistent with the results of previous observations. We combine our
measurement of the z band eclipse with previous observations to explore
atmosphere models of WASP-19b that are consistent with the its broadband
spectrum. We use the VSTAR radiative transfer code to examine the effect of
varying pressure-temperature profiles and C/O abundance ratios on the emission
spectrum of the planet. We find models with super-solar carbon enrichment best
match the observations, consistent with previous model retrieval studies. We
also include upper atmosphere haze as another dimension in the interpretation
of exoplanet emission spectra, and find that particles <0.5 micron in size are
unlikely to be present in WASP-19b.Comment: 10 pages, 8 figures, 2 tables, accepted for publication in Ap
SuperLupus: A Deep, Long Duration Transit Survey
SuperLupus is a deep transit survey monitoring a Galactic Plane field in the
Southern hemisphere. The project is building on the successful Lupus Survey,
and will double the number of images of the field from 1700 to 3400, making it
one of the longest duration deep transit surveys. The immediate motivation for
this expansion is to search for longer period transiting planets (5-8 days) and
smaller radii planets. It will also provide near complete recovery for the
shorter period planets (1-3 days). In March, April, and May 2008 we obtained
the new images and work is currently in progress reducing these new data.Comment: 3 pages, 2 figures, to appear in the Proceedings of IAU Symposium
253, 2008: Transiting Planet
Episodic disk accretion in the halo of the 'old' Pre-Main Sequence cluster Eta Chamaeleontis
We present multi-epoch medium-resolution observations of two M4.5 candidate
members in the halo of the ~8 Myr Eta Chamaeleontis open cluster. Over six
months of observations both stars exhibited variations in their H-alpha line
profiles on timescales of days to months, with at least one episode of
substantial activity attributable to accretion from a circumstellar disk. We
derive an accretion rate ~10^-8.7 Msun/yr for this event, with a rate of
~10^-10.6 Msun/yr in quiescence. Episodic accretion like that observed here
means existing surveys of accreting Weak-lined T-Tauri Stars in young clusters
are likely incomplete and that gas dissipation timescales calculated from the
fraction of accreting objects are underestimates.Comment: 5 pages, 5 figures, 1 table. Accepted for publication in MNRAS
Letter
Lupus-TR-3b: A Low-Mass Transiting Hot Jupiter in the Galactic Plane?
We present a strong case for a transiting Hot Jupiter planet identified
during a single-field transit survey towards the Lupus Galactic plane. The
object, Lupus-TR-3b, transits a V=17.4 K1V host star every 3.91405d.
Spectroscopy and stellar colors indicate a host star with effective temperature
5000 +/- 150K, with a stellar mass and radius of 0.87 +/- 0.04M_sun and 0.82
+/- 0.05R_sun, respectively. Limb-darkened transit fitting yields a companion
radius of 0.89 +/- 0.07R_J and an orbital inclination of 88.3 +1.3/-0.8 deg.
Magellan 6.5m MIKE radial velocity measurements reveal a 2.4 sigma K=114 +/-
25m/s sinusoidal variation in phase with the transit ephemeris. The resulting
mass is 0.81 +/- 0.18M_J and density 1.4 +/- 0.4g/cm^3. Y-band PANIC image
deconvolution reveal a V>=21 red neighbor 0.4'' away which, although highly
unlikely, we cannot conclusively rule out as a blended binary with current
data. However, blend simulations show that only the most unusual binary system
can reproduce our observations. This object is very likely a planet, detected
from a highly efficient observational strategy. Lupus-TR-3b constitutes the
faintest ground-based detection to date, and one of the lowest mass Hot
Jupiters known.Comment: 4 pages, 4 figures, accepted for publication in ApJ
Revisiting WASP-47 with ESPRESSO and TESS
Abstract: WASP-47 hosts a remarkable planetary system containing a hot Jupiter (WASP-47 b; P = 4.159 days) with an inner super-Earth (WASP-47 e; P = 0.7896 days), a close-orbiting outer Neptune (WASP-47 d; P = 9.031 days), and a long-period giant planet (WASP-47 c; P = 588.4 days). We use the new Transiting Exoplanet Survey Satellite (TESS) photometry to refine the orbital ephemerides of the transiting planets in the system, particularly the hot Jupiter WASP-47 b, for which we find an update equating to a 17.4 minute shift in the transit time. We report new radial-velocity measurements from the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) spectrograph for WASP-47, which we use to refine the masses of WASP-47 d and WASP-47 e, with a high-cadence observing strategy aimed to focus on the super-Earth WASP-47 e. We detect a periodic modulation in the K2 photometry that corresponds to a 32.5 ± 3.9 day stellar rotation, and find further stellar activity signals in our ESPRESSO data consistent with this rotation period. For WASP-47 e we measure a mass of 6.77 ± 0.57 M ⊕ and a bulk density of 6.29 ± 0.60 g cm−3, giving WASP-47 e the second most precisely measured density to date of any super-Earth. The mass and radius of WASP-47 e, combined with the exotic configuration of the planetary system, suggest the WASP-47 system formed through a mechanism different to systems with multiple small planets or more typical isolated hot Jupiters
Transits against Fainter Stars: The Power of Image Deconvolution
Compared to bright star searches, surveys for transiting planets against fainter (V = 12-18) stars have the advantage of much higher sky densities of dwarf star primaries, which afford easier detection of small transiting bodies. Furthermore, deep searches are capable of probing a wider range of stellar environments. On the other hand, for a given spatial resolution and transit depth, deep searches are more prone to confusion from blended eclipsing binaries. We present a powerful mitigation strategy for the blending problem that includes the use of image deconvolution and high-resolution imaging. The techniques are illustrated with Lupus-TR-3 and very recent IR imaging with PANIC on Magellan. The results are likely to have implications for the CoRoT and KEPLER missions designed to detect transiting planets of terrestrial siz
A gap in the mass distribution for warm Neptune and terrestrial planets
Structure in the planet distribution provides an insight into the processes that shape the formation and evolution of planets. The Kepler mission has led to an abundance of statistical discoveries in regards to planetary radius, but the number of observed planets with measured masses is much smaller. By incorporating results from recent mass determination programs, we have discovered a new gap emerging in the planet population for sub-Neptune-mass planets with orbital periods less than 20 days. The gap follows a slope of decreasing mass with increasing orbital period, has a width of a few M ⊕, and is potentially completely devoid of planets. Fitting Gaussian mixture models to the planet population in this region favors a bimodel distribution over a unimodel one with a reduction in Bayesian information criterion of 19.9, highlighting the gap significance. We discuss several processes that could generate such a feature in the planet distribution, including a pileup of planets above the gap region, tidal interactions with the host star, dynamical interactions with the disk, with other planets, or with accreting material during the formation process
Phase light curves for extrasolar Jupiters and Saturns
We predict how a remote observer would see the brightness variations of giant
planets similar to Jupiter and Saturn as they orbit their central stars. We
model the geometry of Jupiter, Saturn and Saturn's rings for varying orbital
and viewing parameters. Scattering properties for the planets and rings at
wavelenghts 0.6-0.7 microns follow Pioneer and Voyager observations, namely,
planets are forward scattering and rings are backward scattering. Images of the
planet with or without rings are simulated and used to calculate the
disk-averaged luminosity varying along the orbit, that is, a light curve is
generated. We find that the different scattering properties of Jupiter and
Saturn (without rings) make a substantial difference in the shape of their
light curves. Saturn-size rings increase the apparent luminosity of the planet
by a factor of 2-3 for a wide range of geometries. Rings produce asymmetric
light curves that are distinct from the light curve of the planet without
rings. If radial velocity data are available for the planet, the effect of the
ring on the light curve can be distinguished from effects due to orbital
eccentricity. Non-ringed planets on eccentric orbits produce light curves with
maxima shifted relative to the position of the maximum planet's phase. Given
radial velocity data, the amount of the shift restricts the planet's unknown
orbital inclination and therefore its mass. Combination of radial velocity data
and a light curve for a non-ringed planet on an eccentric orbit can also be
used to constrain the surface scattering properties of the planet. To summarize
our results for the detectability of exoplanets in reflected light, we present
a chart of light curve amplitudes of non-ringed planets for different
eccentricities, inclinations, and the viewing azimuthal angles of the observer.Comment: 40 pages, 13 figures, submitted to Ap.
The Lupus Transit Survey For Hot Jupiters: Results and Lessons
We present the results of a deep, wide-field transit survey targeting Hot
Jupiter planets in the Lupus region of the Galactic plane conducted over 53
nights concentrated in two epochs separated by a year. Using the Australian
National University 40-inch telescope at Siding Spring Observatory (SSO), the
survey covered a 0.66 sq. deg. region close to the Galactic Plane (b=11 deg.)
and monitored a total of 110,372 stars (15.0<V<22.0). Using difference imaging
photometry, 16,134 light curves with a photometric precision of sigma<0.025 mag
were obtained. These light curves were searched for transits, and four
candidates were detected that displayed low-amplitude variability consistent
with a transiting giant planet. Further investigations, including spectral
typing and radial velocity measurements for some candidates, revealed that of
the four, one is a true planetary companion (Lupus-TR-3), two are blended
systems (Lupus-TR-1 and 4), and one is a binary (Lupus-TR-2). The results of
this successful survey are instructive for optimizing the observational
strategy and follow-up procedure for deep searches for transiting planets,
including an upcoming survey using the SkyMapper telescope at SSO.Comment: 27 pages, 9 figures, 4 tables. Accepted for publication in A
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