23 research outputs found
SAGE: A tool to constrain impacts of stellar activity on transmission spectroscopy
Transmission spectroscopy is a proven technique to study a transiting
exoplanet's atmosphere. However, stellar surface inhomogeneities, spots and
faculae, alter the observed transmission spectra: the stellar contamination
effect. The variable nature of the stellar activity also makes it difficult to
stitch together multi-epoch observations and evaluate any potential variability
in the exoplanet's atmosphere. This paper introduces SAGE, a tool to correct
for the time-dependent impact of stellar activity on transmission spectra. It
uses a pixelation approach to model the stellar surface with spots and faculae,
while fully accounting for limb-darkening and rotational line-broadening. The
current version is designed for low to medium-resolution spectra. We used SAGE
to evaluate stellar contamination for F to M-type hosts, testing various spot
sizes and locations, and quantify the impact of limb-darkening. We find that
limb-darkening enhances the importance of the spot location on the stellar
disk, with spots close to the disk center impacting the transmission spectra
more strongly than spots near the limb. Moreover, due to the chromaticity of
limb darkening, the shape of the contamination spectrum is also altered.
Additionally, SAGE can be used to retrieve the properties and distribution of
active regions on the stellar surface from photometric monitoring. We
demonstrate this for WASP-69 using TESS data, finding that two spots at
mid-latitudes and a combined coverage fraction of 1% are favoured. SAGE
allows us to connect the photometric variability to the stellar contamination
of transmission spectra, enhancing our ability to jointly interpret
transmission spectra obtained at different epochs.Comment: Accepted for publication in A&
Why every observatory needs a disco ball
Commercial disco balls provide a safe, effective and instructive way of
observing the Sun. We explore the optics of solar projections with disco balls,
and find that while sunspot observations are challenging, the solar disk and
its changes during eclipses are easy and fun to observe. We explore the disco
ball's potential for observing the moon and other bright astronomical
phenomena.Comment: 6 pages, 7 figures. Submitted to Physics Education. Comments welcom
Detection of Carbon Monoxide in the Atmosphere of WASP-39b Applying Standard Cross-Correlation Techniques to JWST NIRSpec G395H Data
Carbon monoxide was recently reported in the atmosphere of the hot Jupiter
WASP-39b using the NIRSpec PRISM transit observation of this planet, collected
as part of the JWST Transiting Exoplanet Community Early Release Science (JTEC
ERS) Program. This detection, however, could not be confidently confirmed in
the initial analysis of the higher resolution observations with NIRSpec G395H
disperser. Here we confirm the detection of CO in the atmosphere of WASP-39b
using the NIRSpec G395H data and cross-correlation techniques. We do this by
searching for the CO signal in the unbinned transmission spectrum of the planet
between 4.6 and 5.0 m, where the contribution of CO is expected to be
higher than that of other anticipated molecules in the planet's atmosphere. Our
search results in a detection of CO with a cross-correlation function (CCF)
significance of when using a template with only lines. The CCF significance of the CO signal increases to when including in the template lines from additional CO isotopologues,
with the largest contribution being from . Our results
highlight how cross-correlation techniques can be a powerful tool for unveiling
the chemical composition of exoplanetary atmospheres from medium-resolution
transmission spectra, including the detection of isotopologues.Comment: Accepted for publication in The Astrophysical Journal Letter
Early Release Science of the Exoplanet WASP-39b with JWST NIRSpec G395H
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 (R600) transmission
spectrum of an exoplanet atmosphere between 3-5 m covering multiple
absorption features for the Saturn-mass exoplanet WASP-39b, obtained with JWST
NIRSpec G395H. Our observations achieve 1.46x 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
CO (28.5) and HO (21.5), and identify SO as the
source of absorption at 4.1 m (4.8). Best-fit atmospheric models
range between 3 and 10x solar metallicity, with sub-solar to solar C/O ratios.
These results, including the detection of SO, 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.Comment: 44 pages, 11 figures, 3 tables. Resubmitted after revision to Natur
Early Release Science of the exoplanet WASP-39b with JWST NIRCam
Measuring the metallicity and carbon-to-oxygen (C/O) ratio in exoplanet
atmospheres is a fundamental step towards constraining the dominant chemical
processes at work and, if in equilibrium, revealing planet formation histories.
Transmission spectroscopy provides the necessary means by constraining the
abundances of oxygen- and carbon-bearing species; however, this requires broad
wavelength coverage, moderate spectral resolution, and high precision that,
together, are not achievable with previous observatories. Now that JWST has
commenced science operations, we are able to observe exoplanets at previously
uncharted wavelengths and spectral resolutions. Here we report time-series
observations of the transiting exoplanet WASP-39b using JWST's Near InfraRed
Camera (NIRCam). The long-wavelength spectroscopic and short-wavelength
photometric light curves span 2.0 - 4.0 m, exhibit minimal systematics,
and reveal well-defined molecular absorption features in the planet's spectrum.
Specifically, we detect gaseous HO in the atmosphere and place an upper
limit on the abundance of CH. The otherwise prominent CO feature at 2.8
m is largely masked by HO. The best-fit chemical equilibrium models
favour an atmospheric metallicity of 1-100 solar (i.e., an enrichment
of elements heavier than helium relative to the Sun) and a sub-stellar
carbon-to-oxygen (C/O) ratio. The inferred high metallicity and low C/O ratio
may indicate significant accretion of solid materials during planet formation
or disequilibrium processes in the upper atmosphere.Comment: 35 pages, 13 figures, 3 tables, Nature, accepte
Recommended from our members
Nightside clouds and disequilibrium chemistry on the hot Jupiter WASP-43b
Hot Jupiters are among the best-studied exoplanets, but it is still poorly understood how their chemical composition and cloud properties vary with longitude. Theoretical models predict that clouds may condense on the nightside and that molecular abundances can be driven out of equilibrium by zonal winds. Here we report a phase-resolved emission spectrum of the hot Jupiter WASP-43b measured from 5 μm to 12 μm with the JWST’s Mid-Infrared Instrument. The spectra reveal a large day–night temperature contrast (with average brightness temperatures of 1,524 ± 35 K and 863 ± 23 K, respectively) and evidence for water absorption at all orbital phases. Comparisons with three-dimensional atmospheric models show that both the phase-curve shape and emission spectra strongly suggest the presence of nightside clouds that become optically thick to thermal emission at pressures greater than ~100 mbar. The dayside is consistent with a cloudless atmosphere above the mid-infrared photosphere. Contrary to expectations from equilibrium chemistry but consistent with disequilibrium kinetics models, methane is not detected on the nightside (2σ upper limit of 1–6 ppm, depending on model assumptions). Our results provide strong evidence that the atmosphere of WASP-43b is shaped by disequilibrium processes and provide new insights into the properties of the planet’s nightside clouds. However, the remaining discrepancies between our observations and our predictive atmospheric models emphasize the importance of further exploring the effects of clouds and disequilibrium chemistry in numerical models.Peer reviewe
Early Release Science of the exoplanet WASP-39b with JWST NIRISS
Transmission spectroscopy provides insight into the atmospheric properties
and consequently the formation history, physics, and chemistry of transiting
exoplanets. However, obtaining precise inferences of atmospheric properties
from transmission spectra requires simultaneously measuring the strength and
shape of multiple spectral absorption features from a wide range of chemical
species. This has been challenging given the precision and wavelength coverage
of previous observatories. Here, we present the transmission spectrum of the
Saturn-mass exoplanet WASP-39b obtained using the SOSS mode of the NIRISS
instrument on the JWST. This spectrum spans m in wavelength and
reveals multiple water absorption bands, the potassium resonance doublet, as
well as signatures of clouds. The precision and broad wavelength coverage of
NIRISS-SOSS allows us to break model degeneracies between cloud properties and
the atmospheric composition of WASP-39b, favoring a heavy element enhancement
("metallicity") of the solar value, a sub-solar
carbon-to-oxygen (C/O) ratio, and a solar-to-super-solar potassium-to-oxygen
(K/O) ratio. The observations are best explained by wavelength-dependent,
non-gray clouds with inhomogeneous coverage of the planet's terminator.Comment: 48 pages, 12 figures, 2 tables. Under review at Natur
Nightside clouds and disequilibrium chemistry on the hot Jupiter WASP-43b
Hot Jupiters are among the best-studied exoplanets, but it is still poorly understood how their chemical composition and cloud properties vary with longitude. Theoretical models predict that clouds may condense on the nightside and that molecular abundances can be driven out of equilibrium by zonal winds. Here we report a phase-resolved emission spectrum of the hot Jupiter WASP-43b measured from 5-12 μm with JWST's Mid-Infrared Instrument (MIRI). The spectra reveal a large day-night temperature contrast (with average brightness temperatures of 1524±35 and 863±23 Kelvin, respectively) and evidence for water absorption at all orbital phases. Comparisons with three-dimensional atmospheric models show that both the phase curve shape and emission spectra strongly suggest the presence of nightside clouds which become optically thick to thermal emission at pressures greater than ~100 mbar. The dayside is consistent with a cloudless atmosphere above the mid-infrared photosphere. Contrary to expectations from equilibrium chemistry but consistent with disequilibrium kinetics models, methane is not detected on the nightside (2σ upper limit of 1-6 parts per million, depending on model assumptions)
Nightside clouds and disequilibrium chemistry on the hot Jupiter WASP-43b
Hot Jupiters are among the best-studied exoplanets, but it is still poorly
understood how their chemical composition and cloud properties vary with
longitude. Theoretical models predict that clouds may condense on the nightside
and that molecular abundances can be driven out of equilibrium by zonal winds.
Here we report a phase-resolved emission spectrum of the hot Jupiter WASP-43b
measured from 5-12 m with JWST's Mid-Infrared Instrument (MIRI). The
spectra reveal a large day-night temperature contrast (with average brightness
temperatures of 152435 and 86323 Kelvin, respectively) and evidence
for water absorption at all orbital phases. Comparisons with three-dimensional
atmospheric models show that both the phase curve shape and emission spectra
strongly suggest the presence of nightside clouds which become optically thick
to thermal emission at pressures greater than ~100 mbar. The dayside is
consistent with a cloudless atmosphere above the mid-infrared photosphere.
Contrary to expectations from equilibrium chemistry but consistent with
disequilibrium kinetics models, methane is not detected on the nightside
(2 upper limit of 1-6 parts per million, depending on model
assumptions).Comment: 61 pages, 13 figures, 4 tables. This preprint has been submitted to
and accepted in principle for publication in Nature Astronomy without
significant change
Detection of Carbon Monoxide in the Atmosphere of WASP-39b Applying Standard Cross-correlation Techniques to JWST NIRSpec G395H Data
Carbon monoxide was recently reported in the atmosphere of the hot Jupiter WASP-39b using the NIRSpec PRISM transit observation of this planet, collected as part of the JWST Transiting Exoplanet Community Early Release Science Program. This detection, however, could not be confidently confirmed in the initial analysis of the higher-resolution observations with NIRSpec G395H disperser. Here we confirm the detection of CO in the atmosphere of WASP-39b using the NIRSpec G395H data and cross-correlation techniques. We do this by searching for the CO signal in the unbinned transmission spectrum of the planet between 4.6 and 5.0 μ m, where the contribution of CO is expected to be higher than that of other anticipated molecules in the planet’s atmosphere. Our search results in a detection of CO with a cross-correlation function (CCF) significance of 6.6 σ when using a template with only ^12 C ^16 O lines. The CCF significance of the CO signal increases to 7.5 σ when including in the template lines from additional CO isotopologues, with the largest contribution being from ^13 C ^16 O. Our results highlight how cross-correlation techniques can be a powerful tool for unveiling the chemical composition of exoplanetary atmospheres from medium-resolution transmission spectra, including the detection of isotopologues