51 research outputs found
Study of Io's sodium jets with the TRAPPIST telescopes
Io is the most volcanically active body in the Solar System. This volcanic
activity results in the ejection of material into Io's atmosphere, which may
then escape from the atmosphere to form various structures in the jovian
magnetosphere, including the plasma torus and clouds of neutral particles. The
physical processes involved in the escape of particles - for example, how the
volcanoes of Io provide material to the plasma torus - are not yet fully
understood. In particular, it is not clear to what extent the sodium jet, one
of the sodium neutral clouds related to Io, is a proxy of processes that
populate the various reservoirs of plasma in Jupiter's magnetosphere. Here, we
report on observations carried out over 17 nights in 2014-2015, 30 nights in
2021, and 23 nights in 2022-2023 with the TRAPPIST telescopes, in which
particular attention was paid to the sodium jet and the quantification of their
physical properties (length, brightness). It was found that these properties
can vary greatly from one jet to another and independently of the position of
Io in its orbit. No clear link was found between the presence of jets and
global brightening of the plasma torus and extended sodium nebula, indicating
that jets do not contribute straightforwardly to their population. This work
also demonstrates the advantage of regular and long-term monitoring to
understanding the variability of the sodium jet and presents a large corpus of
jet detections against which work in related fields may compare.Comment: Alexander de Becker and Linus Head contributed equally to this work
and share first authorshi
The impact and rotational lightcurves of Comet 9P/Tempel 1
UVES and HIRES high-resolution spectra of comet 9P/Tempel 1 are used to
investigate the impact and rotational light curves of various species with a
view toward building a simple model of the distribution and activity of the
sources. The emission by OH, NH, CN, C3, CH, C2, NH2 and OI, are analyzed, as
well as the light scattered by the dust. It is found that a simple model
reproduces fairly well the impact lightcurves of all species combining the
production of the observed molecules and the expansion of the material
throughout the slit. The rotational light curve for each species is explained
in terms of a single model with three sources.Comment: 34 pages, 11 figures Accepted for publication in the special issue of
Icarus associated with the Deep Impact mission to Comet 9P/Tempel
Spitzer Transits of the Super-Earth GJ1214b and Implications for its Atmosphere
We observed the transiting super-Earth exoplanet GJ1214b using warm Spitzer at 4.5 μm wavelength during a 20 day quasi-continuous sequence in 2011 May. The goals of our long observation were to accurately define the infrared transit radius of this nearby super-Earth, to search for the secondary eclipse, and to search for other transiting planets in the habitable zone of GJ1214. We here report results from the transit monitoring of GJ1214b, including a reanalysis of previous transit observations by Désert et al. In total, we analyze 14 transits of GJ1214b at 4.5 μm, 3 transits at 3.6 μm, and 7 new ground-based transits in the I+z band. Our new Spitzer data by themselves eliminate cloudless solar composition atmospheres for GJ1214b, and methane-rich models from Howe & Burrows. Using our new Spitzer measurements to anchor the observed transit radii of GJ1214b at long wavelengths, and adding new measurements in I+z, we evaluate models from Benneke & Seager and Howe & Burrows using a χ^2 analysis. We find that the best-fit model exhibits an increase in transit radius at short wavelengths due to Rayleigh scattering. Pure water atmospheres are also possible. However, a flat line (no atmosphere detected) remains among the best of the statistically acceptable models, and better than pure water atmospheres. We explore the effect of systematic differences among results from different observational groups, and we find that the Howe & Burrows tholin-haze model remains the best fit, even when systematic differences among observers are considered
Temperate Earth-sized planets transiting a nearby ultracool dwarf star.
Star-like objects with effective temperatures of less than 2,700 kelvin are referred to as 'ultracool dwarfs'. This heterogeneous group includes stars of extremely low mass as well as brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion), and represents about 15 per cent of the population of astronomical objects near the Sun. Core-accretion theory predicts that, given the small masses of these ultracool dwarfs, and the small sizes of their protoplanetary disks, there should be a large but hitherto undetected population of terrestrial planets orbiting them--ranging from metal-rich Mercury-sized planets to more hospitable volatile-rich Earth-sized planets. Here we report observations of three short-period Earth-sized planets transiting an ultracool dwarf star only 12 parsecs away. The inner two planets receive four times and two times the irradiation of Earth, respectively, placing them close to the inner edge of the habitable zone of the star. Our data suggest that 11 orbits remain possible for the third planet, the most likely resulting in irradiation significantly less than that received by Earth. The infrared brightness of the host star, combined with its Jupiter-like size, offers the possibility of thoroughly characterizing the components of this nearby planetary system
Peculiar architectures for the WASP-53 and WASP-81 planet-hosting systems
We report the detection of two new systems containing transiting planets. Both were identified by WASP as worthy transiting planet candidates. Radial velocity observations quickly verified that the photometric signals were indeed produced by two transiting hot Jupiters. Our observations also show the presence of additional Doppler signals. In addition to short-period hot Jupiters, we find that the WASP-53 and WASP-81 systems also host brown dwarfs, on fairly eccentric orbits with semimajor axes of a few astronomical units. WASP-53c is over 16 MJupsin ic and WASP-81c is 57 MJupsin ic. The presence of these tight, massive companions restricts theories of how the inner planets were assembled. We propose two alternative interpretations: the formation of the hot Jupiters within the snow line or the late dynamical arrival of the brown dwarfs after disc dispersal. We also attempted to measure the Rossiter–McLaughlin effect for both hot Jupiters. In the case of WASP-81b, we fail to detect a signal. For WASP-53b, we find that the planet is aligned with respect to the stellar spin axis. In addition we explore the prospect of transit-timing variations, and of using Gaia's astrometry to measure the true masses of both brown dwarfs and also their relative inclination with respect to the inner transiting hot Jupiters.Publisher PDFPeer reviewe
The EBLM project : III. A Saturn-size low-mass star at the hydrogen-burning limit
This work was partially supported by a grant from the Simons Foundation (PI Queloz, grant number 327127).We report the discovery of an eclipsing binary system with mass-ratio q ∼ 0.07. After identifying a periodic photometric signal received by WASP, we obtained CORALIE spectroscopic radial velocities and follow-up light curves with the Euler and TRAPPIST telescopes. From a joint fit of these data we determine that EBLM J0555-57 consists of a sun-like primary star that is eclipsed by a low-mass companion, on a weakly eccentric 7.8-day orbit. Using a mass estimate for the primary star derived from stellar models, we determine a companion mass of 85 ± 4 MJup (0.081 M⊙) and a radius of 0.84+ 0.14 -0.04RJup (0.084 R⊙) that is comparable to that of Saturn. EBLM J0555-57Ab has a surface gravity log g2 =5.50+ 0.03 -0.13 and is one of the densest non-stellar-remnant objects currently known. These measurements are consistent with models of low-mass stars.PostprintPeer reviewe
The remarkable surface homogeneity of the Dawn mission target (1) Ceres
Dwarf-planet (1) Ceres is one of the two targets, along with (4) Vesta, that
will be studied by the NASA Dawn spacecraft via imaging, visible and
near-infrared spectroscopy, and gamma-ray and neutron spectroscopy. While
Ceres' visible and near-infrared disk-integrated spectra have been well
characterized, little has been done about quantifying spectral variations over
the surface. Any spectral variation would give us insights on the geographical
variation of the composition and/or the surface age. The only work so far was
that of Rivkin & Volquardsen (2010, Icarus 206, 327) who reported
rotationally-resolved spectroscopic (disk-integrated) observations in the
2.2-4.0 {\mu}m range; their observations showed evidence for a relatively
uniform surface. Here, we report disk-resolved observations of Ceres with
SINFONI (ESO VLT) in the 1.17-1.32 {\mu}m and 1.45-2.35 {\mu}m wavelength
ranges. The observations were made under excellent seeing conditions (0.6"),
allowing us to reach a spatial resolution of ~75 km on Ceres' surface. We do
not find any spectral variation above a 3% level, suggesting a homogeneous
surface at our spatial resolution. Slight variations (about 2%) of the spectral
slope are detected, geographically correlated with the albedo markings reported
from the analysis of the HST and Keck disk-resolved images of Ceres (Li et al.,
2006, Icarus 182, 143; Carry et al., 2008, A&A 478, 235). Given the lack of
constraints on the surface composition of Ceres, however, we cannot assert the
causes of these variations.Comment: 8 pages, 5 figures, 2 tables, accepted for publication in Icaru
The EBLM Project : IV. Spectroscopic orbits of over 100 eclipsing M dwarfs masquerading as transiting hot-Jupiters
We present 2271 radial velocity measurements taken on 118 single-line binary stars, taken over eight years with the CORALIE spectrograph. The binaries consist of F/G/K primaries and M dwarf secondaries. They were initially discovered photometricallyby the WASP planet survey, as their shallow eclipses mimic a hot Jupiter transit. The observations we present permit a precise characterisation of the binary orbital elements and mass function. With modelling of the primary star, this mass function is converted to a mass of the secondary star. In the future, this spectroscopic work will be combined with precise photometric eclipses to draw anempirical mass/radius relation for the bottom of the mass sequence. This has applications in both stellar astrophysics and the growing number of exoplanet surveys around M dwarfs. In particular, we have discovered 34 systems with a secondary mass below 0.2M⊙ and so we will ultimately double the number of known very low-mass stars with well-characterised masses and radii.The quality of our data combined with the amplitude of the Doppler variations mean that we are able to detect eccentricities as small as 0.001 and orbital periods to sub-second precision. Our sample can revisit some earlier work on the tidal evolution of close binaries, extending it to low mass ratios. We find some exceptional binary systems that are eccentric at orbital periods below three days, while our longest circular orbit has a period of 10.4 days. Amongst our systems, we note one remarkable architecture in J1146-42 that boasts three stars within one astronomical unit. By collating the EBLM binaries with published WASP planets and brown dwarfs, we derive a mass spectrum with twice the resolutionof previous work. We compare the WASP/EBLM sample of tightly bound orbits with work in the literature on more distant companionsup to 10 AU. We note that the brown dwarf desert appears wider, as it carves into the planetary domain for our short-period orbits.This would mean that a significantly reduced abundance of planets begins at ∼3MJup, well before the deuterium-burning limit. This may shed light on the formation and migration history of massive gas giants.PostprintPeer reviewe
A combined transmission spectrum of the Earth-sized exoplanets TRAPPIST-1 b and c
Three Earth-sized exoplanets were recently discovered close to the habitable
zone of the nearby ultracool dwarf star TRAPPIST-1. The nature of these planets
has yet to be determined, since their masses remain unmeasured and no
observational constraint is available for the planetary population surrounding
ultracool dwarfs, of which the TRAPPIST-1 planets are the first transiting
example. Theoretical predictions span the entire atmospheric range from
depleted to extended hydrogen-dominated atmospheres. Here, we report a
space-based measurement of the combined transmission spectrum of the two inner
planets made possible by a favorable alignment resulting in their simultaneous
transits on 04 May 2016. The lack of features in the combined spectrum rules
out cloud-free hydrogen-dominated atmospheres for each planet at 10-
levels; TRAPPIST-1 b and c are hence unlikely to harbor an extended gas
envelope as they lie in a region of parameter space where high-altitude
cloud/haze formation is not expected to be significant for hydrogen-dominated
atmospheres. Many denser atmospheres remain consistent with the featureless
transmission spectrum---from a cloud-free water vapour atmosphere to a
Venus-like atmosphere.Comment: Early release to inform further the upcoming review of HST's Cycle 24
proposal
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