164 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
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.
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 size
SGAS 143845.1+145407: A Big, Cool Starburst at Redshift 0.816
We present the discovery and a detailed multi-wavelength study of a
strongly-lensed luminous infrared galaxy at z=0.816. Unlike most known lensed
galaxies discovered at optical or near-infrared wavelengths this lensed source
is red, r-Ks = 3.9 [AB], which the data presented here demonstrate is due to
ongoing dusty star formation. The overall lensing magnification (a factor of
17) facilitates observations from the blue optical through to 500micron, fully
capturing both the stellar photospheric emission as well as the re-processed
thermal dust emission. We also present optical and near-IR spectroscopy. These
extensive data show that this lensed galaxy is in many ways typical of
IR-detected sources at z~1, with both a total luminosity and size in accordance
with other (albeit much less detailed) measurements in samples of galaxies
observed in deep fields with the Spitzer telescope. Its far-infrared spectral
energy distribution is well-fit by local templates that are an order of
magnitude less luminous than the lensed galaxy; local templates of comparable
luminosity are too hot to fit. Its size (D~7kpc) is much larger than local
luminous infrared galaxies, but in line with sizes observed for such galaxies
at z~1. The star formation appears uniform across this spatial scale. In this
source, the luminosity of which is typical of sources that dominate the cosmic
infrared background, we find that star formation is spatially extended and well
organised, quite unlike the compact merger-driven starbursts which are typical
for sources of this luminosity at z~0.Comment: 18 pages, 10 figure
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