26 research outputs found
Toi-1235 b: A keystone super-earth for testing radius valley emergence models around early m dwarfs
Small planets on close-in orbits tend to exhibit envelope mass fractions of
either effectively zero or up to a few percent depending on their size and
orbital period. Models of thermally-driven atmospheric mass loss and of
terrestrial planet formation in a gas-poor environment make distinct
predictions regarding the location of this rocky/non-rocky transition in
period-radius space. Here we present the confirmation of TOI-1235 b (
days, R), a planet whose size and
period are intermediate between the competing model predictions, thus making
the system an important test case for emergence models of the rocky/non-rocky
transition around early M dwarfs ( R,
M). We confirm the TESS planet discovery using
reconnaissance spectroscopy, ground-based photometry, high-resolution imaging,
and a set of 38 precise radial-velocities from HARPS-N and HIRES. We measure a
planet mass of M which implies an iron core
mass fraction of % in the absence of a gaseous envelope. The
bulk composition of TOI-1235 b is therefore consistent with being Earth-like
and we constrain a H/He envelope mass fraction to be % at 90% confidence.
Our results are consistent with model predictions from thermally-driven
atmospheric mass loss but not with gas-poor formation, which suggests that the
former class of processes remain efficient at sculpting close-in planets around
early M dwarfs. Our RV analysis also reveals a strong periodicity close to the
first harmonic of the photometrically-determined stellar rotation period that
we treat as stellar activity, despite other lines of evidence favoring a
planetary origin ( days,
M) that cannot be firmly ruled out by our data
Identification of carbon dioxide in an exoplanet atmosphere
Carbon dioxide (CO2) is a key chemical species that is found in a wide range of planetary atmospheres. In the context of exoplanets, CO2 is an indicator of the metal enrichment (that is, elements heavier than helium, also called ‘metallicity’)1–3, and thus the formation processes of the primary atmospheres of hot gas giants4–6. It is also one of the most promising species to detect in the secondary atmospheres of terrestrial exoplanets7–9. Previous photometric measurements of transiting planets with the Spitzer Space Telescope have given hints of the presence of CO2, but have not yielded definitive detections owing to the lack of unambiguous spectroscopic identification10–12. Here we present the detection of CO2 in the atmosphere of the gas giant exoplanet WASP-39b from transmission spectroscopy observations obtained with JWST as part of the Early Release Science programme13,14. The data used in this study span 3.0–5.5 micrometres in wavelength and show a prominent CO2 absorption feature at 4.3 micrometres (26-sigma significance). The overall spectrum is well matched by one-dimensional, ten-times solar metallicity models that assume radiative–convective–thermochemical equilibrium and have moderate cloud opacity. These models predict that the atmosphere should have water, carbon monoxide and hydrogen sulfide in addition to CO2, but little methane. Furthermore, we also tentatively detect a small absorption feature near 4.0 micrometres that is not reproduced by these models
Extrasolar enigmas: from disintegrating exoplanets to exoasteroids
Thousands of transiting exoplanets have been discovered to date, thanks in
great part to the {\em Kepler} space mission. As in all populations, and
certainly in the case of exoplanets, one finds unique objects with distinct
characteristics. Here we will describe the properties and behaviour of a small
group of `disintegrating' exoplanets discovered over the last few years (KIC
12557548b, K2-22b, and others). They evaporate, lose mass unraveling their
naked cores, produce spectacular dusty comet-like tails, and feature highly
variable asymmetric transits. Apart from these exoplanets, there is
observational evidence for even smaller `exo-'objects orbiting other stars:
exoasteroids and exocomets. Most probably, such objects are also behind the
mystery of Boyajian's star. Ongoing and upcoming space missions such as {\em
TESS} and PLATO will hopefully discover more objects of this kind, and a new
era of the exploration of small extrasolar systems bodies will be upon us.Comment: Accepted for publication in the book "Reviews in Frontiers of Modern
Astrophysics: From Space Debris to Cosmology" (eds Kabath, Jones and Skarka;
publisher Springer Nature) funded by the European Union Erasmus+ Strategic
Partnership grant "Per Aspera Ad Astra Simul" 2017-1-CZ01-KA203-03556
Early Release Science of the exoplanet WASP-39b with JWST NIRSpec G395H
This is the author accepted manuscript. The final version is available from Nature Research via the DOI in this recordData Availability:
The data used in this paper are associated with JWST program ERS 1366 (observation #4) and
are available from the Mikulski Archive for Space Telescopes (https://mast.stsci.edu). Science
data processing version (SDP_VER) 2022_2a generated the uncalibrated data that we
downloaded from MAST. We used JWST Calibration Pipeline software version (CAL_VER)
1.5.3 with modifications described in the text. We used calibration reference data from context
(CRDS_CTX) 0916, except as noted in the text. All the data and models presented in this
publication can be found at 10.5281/zenodo.7185300.Code Availability:
The codes used in this publication to extract, reduce and analyze the data are as follows;
STScI JWST Calibration pipeline45 (https://github.com/spacetelescope/jwst), Eureka!53
(https://eurekadocs.readthedocs.io/en/latest/), ExoTiC-JEDI47 (https://github.com/ExoTiC/ExoTiC-JEDI), juliet71 (https://juliet.readthedocs.io/en/latest/), Tiberius15,49,50,
transitspectroscopy51 (https://github.com/nespinoza/transitspectroscopy). In addition, these
made use of batman65 (http://lkreidberg.github.io/batman/docs/html/index.html), celerite86
(https://celerite.readthedocs.io/en/stable/), chromatic (https://zkbt.github.io/chromatic/),
Dynesty72 (https://dynesty.readthedocs.io/en/stable/index.html), emcee69
(https://emcee.readthedocs.io/en/stable/), exoplanet83 (https://docs.exoplanet.codes/en/latest/),
ExoTEP75–77, ExoTHETyS79 (https://github.com/ucl-exoplanets/ExoTETHyS), ExoTiCISM57 (https://github.com/Exo-TiC/ExoTiC-ISM), ExoTiC-LD58 (https://exoticld.readthedocs.io/en/latest/), george68 (https://george.readthedocs.io/en/latest/) JAX82
(https://jax.readthedocs.io/en/latest/), LMFIT70 (https://lmfit.github.io/lmfit-py/),
Pylightcurve78 (https://github.com/ucl-exoplanets/pylightcurve), Pymc3138
(https://docs.pymc.io/en/v3/index.html) and Starry84 (https://starry.readthedocs.io/en/latest/),
each of which use the standard python libraries astropy139,140, matplotlib141, numpy142,
pandas143, scipy64 and xarray144. The atmospheric models used to fit the data can be found at
ATMO[Tremblin2015,Drummond2016,Goyal2018,Goyal2020]88–91, PHOENIX92–94,
PICASO98,99 (https://natashabatalha.github.io/picaso/), Virga98,107
(https://natashabatalha.github.io/virga/), and gCMCRT115
(https://github.com/ELeeAstro/gCMCRT).Measuring the abundances of carbon and oxygen in exoplanet atmospheres is considered a crucial avenue for unlocking the formation and evolution of exoplanetary systems. Access to an exoplanet’s chemical inventory requires high precision observations, often inferred from individual molecular detections with low-resolution space-based and high-resolution ground-based facilities. Here we report the medium-resolution (R≈600) transmission spectrum of an exoplanet atmosphere between 3–5 μm covering multiple absorption features for the Saturn-mass exoplanet WASP-39b, obtained with JWST NIRSpec G395H. Our observations achieve 1.46×
photon precision, providing an average transit depth uncertainty of 221 ppm per spectroscopic bin, and present minimal impacts from systematic effects. We detect significant absorption from CO2 (28.5σ
) and H2O (21.5σ
), and identify SO2 as the source of absorption at 4.1 μ
m (4.8σ
). Best-fit atmospheric models range between 3×
and 10×
solar metallicity, with sub-solar to solar C/O ratios. These results, including the detection of SO2, underscore the importance of characterising the chemistry in exoplanet atmospheres, and showcase NIRSpec G395H as an excellent mode for time series observations over this critical wavelength range.Science and Technology Facilities Council (STFC)UKR
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An Unusual Transmission Spectrum for the Sub-Saturn KELT-11b Suggestive of a Subsolar Water Abundance
We present an optical-to-infrared transmission spectrum of the inflated
sub-Saturn KELT-11b measured with the Transiting Exoplanet Survey Satellite
(TESS), the Hubble Space Telescope (HST) Wide Field Camera 3 G141 spectroscopic
grism, and the Spitzer Space Telescope (Spitzer) at 3.6 m, in addition to
a Spitzer 4.5 m secondary eclipse. The precise HST transmission spectrum
notably reveals a low-amplitude water feature with an unusual shape. Based on
free retrieval analyses with varying molecular abundances, we find strong
evidence for water absorption. Depending on model assumptions, we also find
tentative evidence for other absorbers (HCN, TiO, and AlO). The retrieved water
abundance is generally solar (0.001--0.7 solar
over a range of model assumptions), several orders of magnitude lower than
expected from planet formation models based on the solar system metallicity
trend. We also consider chemical equilibrium and self-consistent 1D
radiative-convective equilibrium model fits and find they too prefer low
metallicities (, consistent with the free retrieval
results). However, all the retrievals should be interpreted with some caution
since they either require additional absorbers that are far out of chemical
equilibrium to explain the shape of the spectrum or are simply poor fits to the
data. Finally, we find the Spitzer secondary eclipse is indicative of full heat
redistribution from KELT-11b's dayside to nightside, assuming a clear dayside.
These potentially unusual results for KELT-11b's composition are suggestive of
new challenges on the horizon for atmosphere and formation models in the face
of increasingly precise measurements of exoplanet spectra
Factors Associated with HPV Vaccine Awareness in a Population-Based Sample of Hispanic Women in Puerto Rico
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Complex Modulation of Rapidly Rotating Young M Dwarfs: Adding Pieces to the Puzzle
New sets of young M dwarfs with complex, sharp-peaked, and strictly periodic
photometric modulations have recently been discovered with Kepler/K2 (scallop
shells) and TESS (complex rotators). All are part of star-forming associations,
are distinct from other variable stars, and likely belong to a unified class.
Suggested hypotheses include star spots, accreting dust disks, co-rotating
clouds of material, magnetically constrained material, spots and misaligned
disks, and pulsations. Here, we provide a comprehensive overview and add new
observational constraints with TESS and SPECULOOS Southern Observatory (SSO)
photometry. We scrutinize all hypotheses from three new angles: (1) we
investigate each scenario's occurrence rates via young star catalogs; (2) we
study the features' longevity using over one year of combined data; and (3) we
probe the expected color dependency with multi-color photometry. In this
process, we also revisit the stellar parameters accounting for activity
effects, study stellar flares as activity indicators over year-long time
scales, and develop toy models to simulate typical morphologies. We rule out
most hypotheses, and only (i) co-rotating material clouds and (ii) spots and
misaligned disks remain feasible - with caveats. For (i), co-rotating dust
might not be stable enough, while co-rotating gas alone likely cannot cause
percentage-scale features; and (ii) would require misaligned disks around most
young M dwarfs. We thus suggest a unified hypothesis, a superposition of
large-amplitude spot modulations and sharp transits of co-rotating gas clouds.
While the complex rotators' mystery remains, these new observations add
valuable pieces to the puzzle going forward
Valorisation of human excreta for recovery of energy and high-value products : a mini-review
The current approach to managing waste is one of the major reasons for ecosystem imbalances. In many parts of the world, human excreta is indiscriminately dumped in the environment, leading to the entry of high concentrations of nutrients and pathogens. In urban sanitary systems, nutrients are often not recovered, but large amounts of natural resources (e.g. water) are used for treating wastes at the expense of the environment. These practices are unsuitable and pose risks to human health and the environment, as such current efforts are geared towards providing on-site sanitation and opportunities for nutrient and resource recovery. This mini-review summarises the efforts to valorise human waste and process routes for the recovery of value-added products. These involve a review of ecological sanitation, systems that safely collect and treat human waste in situ and advanced waste-to-energy systems to convert recovered materials to fuels, heat and/or electricity. Focus is given to low-cost technological solutions that offer ecological benefits and opportunities to recover useful products. The barriers and opportunities to the adoption of on-site sanitation and appropriate technologies are discussed, considering current limitations and potential benefits. There are opportunities to recover useful products from human wastes; however, further research is needed to ascertain the value and impact of recovered products