7 research outputs found
Exploring the Ability of HST WFC3 G141 to Uncover Trends in Populations of Exoplanet Atmospheres Through a Homogeneous Transmission Survey of 70 Gaseous Planets
We present the analysis of the atmospheres of 70 gaseous extrasolar planets
via transit spectroscopy with Hubble's Wide Field Camera 3 (WFC3). For over
half of these, we statistically detect spectral modulation which our retrievals
attribute to molecular species. Among these, we use Bayesian Hierarchical
Modelling to search for chemical trends with bulk parameters. We use the
extracted water abundance to infer the atmospheric metallicity and compare it
to the planet's mass. We also run chemical equilibrium retrievals, fitting for
the atmospheric metallicity directly. However, although previous studies have
found evidence of a mass-metallicity trend, we find no such relation within our
data. For the hotter planets within our sample, we find evidence for thermal
dissociation of dihydrogen and water via the H opacity. We suggest that the
general lack of trends seen across this population study could be due to i) the
insufficient spectral coverage offered by HST WFC3 G141, ii) the lack of a
simple trend across the whole population, iii) the essentially random nature of
the target selection for this study or iv) a combination of all the above. We
set out how we can learn from this vast dataset going forward in an attempt to
ensure comparative planetology can be undertaken in the future with facilities
such as JWST, Twinkle and Ariel. We conclude that a wider simultaneous spectral
coverage is required as well as a more structured approach to target selection.Comment: Accepted for publication in ApJ
Exploring the Ability of Hubble Space Telescope WFC3 G141 to Uncover Trends in Populations of Exoplanet Atmospheres through a Homogeneous Transmission Survey of 70 Gaseous Planets
We present analysis of the atmospheres of 70 gaseous extrasolar planets via transit spectroscopy with Hubble’s Wide Field Camera 3 (WFC3). For over half of these, we statistically detect spectral modulation that our retrievals attribute to molecular species. Among these, we use Bayesian hierarchical modeling to search for chemical trends with bulk parameters. We use the extracted water abundance to infer the atmospheric metallicity and compare it to the planet’s mass. We also run chemical equilibrium retrievals, fitting for the atmospheric metallicity directly. However, although previous studies have found evidence of a mass–metallicity trend, we find no such relation within our data. For the hotter planets within our sample, we find evidence for thermal dissociation of dihydrogen and water via the H− opacity. We suggest that the general lack of trends seen across this population study could be due to (i) the insufficient spectral coverage offered by the Hubble Space Telescope’s WFC3 G141 band, (ii) the lack of a simple trend across the whole population, (iii) the essentially random nature of the target selection for this study, or (iv) a combination of all the above. We set out how we can learn from this vast data set going forward in an attempt to ensure comparative planetology can be undertaken in the future with facilities such as the JWST, Twinkle, and Ariel. We conclude that a wider simultaneous spectral coverage is required as well as a more structured approach to target selection
Five key exoplanet questions answered via the analysis of 25 hot Jupiter atmospheres in eclipse
Population studies of exoplanets are key to unlocking their statistical
properties. So far the inferred properties have been mostly limited to
planetary, orbital and stellar parameters extracted from, e.g., Kepler, radial
velocity, and GAIA data. More recently an increasing number of exoplanet
atmospheres have been observed in detail from space and the ground. Generally,
however, these atmospheric studies have focused on individual planets, with the
exception of a couple of works which have detected the presence of water vapor
and clouds in populations of gaseous planets via transmission spectroscopy.
Here, using a suite of retrieval tools, we analyse spectroscopic and
photometric data of 25 hot Jupiters, obtained with the Hubble and Spitzer Space
Telescopes via the eclipse technique. By applying the tools uniformly across
the entire set of 25 planets, we extract robust trends in the thermal structure
and chemical properties of hot Jupiters not obtained in past studies. With the
recent launch of JWST and the upcoming missions Twinkle, and Ariel, population
based studies of exoplanet atmospheres, such as the one presented here, will be
a key approach to understanding planet characteristics, formation, and
evolution in our galaxy.Comment: 66 pages, 23 figures, 7 tables. Published in The Astrophysical
Journal Supplement Serie
Exploring the Ability of Hubble Space Telescope WFC3 G141 to Uncover Trends in Populations of Exoplanet Atmospheres through a Homogeneous Transmission Survey of 70 Gaseous Planets
International audienceWe present analysis of the atmospheres of 70 gaseous extrasolar planets via transit spectroscopy with Hubble's Wide Field Camera 3 (WFC3). For over half of these, we statistically detect spectral modulation that our retrievals attribute to molecular species. Among these, we use Bayesian hierarchical modeling to search for chemical trends with bulk parameters. We use the extracted water abundance to infer the atmospheric metallicity and compare it to the planet's mass. We also run chemical equilibrium retrievals, fitting for the atmospheric metallicity directly. However, although previous studies have found evidence of a mass-metallicity trend, we find no such relation within our data. For the hotter planets within our sample, we find evidence for thermal dissociation of dihydrogen and water via the H − opacity. We suggest that the general lack of trends seen across this population study could be due to (i) the insufficient spectral coverage offered by the Hubble Space Telescope's WFC3 G141 band, (ii) the lack of a simple trend across the whole population, (iii) the essentially random nature of the target selection for this study, or (iv) a combination of all the above. We set out how we can learn from this vast data set going forward in an attempt to ensure comparative planetology can be undertaken in the future with facilities such as the JWST, Twinkle, and Ariel. We conclude that a wider simultaneous spectral coverage is required as well as a more structured approach to target selection
ARES. II. Characterizing the Hot Jupiters WASP-127 b, WASP-79 b, and WASP-62b with the Hubble Space Telescope
This paper presents the atmospheric characterization of three large, gaseous planets: WASP-127 b, WASP-79 b, and WASP-62 b. We analyzed spectroscopic data obtained with the G141 grism (1.088-1.68 μm) of the Wide Field Camera 3 on board the Hubble Space Telescope using the Iraclis pipeline and the TauREx3 retrieval code, both of which are publicly available. For WASP-127 b, which is the least dense planet discovered so far and is located in the short-period Neptune desert, our retrieval results found strong water absorption corresponding to an abundance of log(H2O) = -2.71 +0.78−1.05 and absorption compatible with an iron hydride abundance of log(FeH) = −5.25+0.88−1.10, with an extended cloudy atmosphere. We also detected water vapor in the atmospheres of WASP-79 b and WASP-62 b, with best-fit models indicating the presence of iron hydride, too. We used the Atmospheric Detectability Index as well as Bayesian log evidence to quantify the strength of the detection and compared our results to the hot Jupiter population study by Tsiaras et al. While all the planets studied here are suitable targets for characterization with upcoming facilities such as the James Webb Space Telescope and Ariel, WASP-127 b is of particular interest due to its low density, and a thorough atmospheric study would develop our understanding of planet formation and migration. * ARES: Ariel Retrieval of Exoplanets School