26 research outputs found
The Hubble PanCET program: The near-ultraviolet transmission spectrum of WASP-79b
We present Hubble Space Telescope (HST) transit observations of the
Hot-Jupiter WASP-79b acquired with the Space Telescope Imaging Spectrograph
(STIS) in the near ultraviolet (NUV). Two transit observations, part of the
PanCET program, are used to obtain the transmission spectra of the planet
between 2280 and 3070{\AA}. We correct for systematic effects in the raw data
using the jitter engineering parameters and polynomial modelling to fit the
white light curves of the two transits. We observe an increase in the
planet-to-star radius ratio at short wavelengths, but no spectrally resolved
absorption lines. The difference between the radius ratios at 2400 and
3000{\AA} reaches (4.5). Although the NUV
transmission spectrum does not show evidence of hydrodynamical escape, the
strong atmospheric features are likely due to species at very high altitudes.
We performed a 1D simulation of the temperature and composition of WASP-79b
using Exo-REM. The temperature pressure profile crosses condensation curves of
radiatively active clouds, particularly MnS, MgSiO, Fe, and
AlO. Still, none of these species produces the level of observed
absorption at short wavelengths and can explain the observed increase in the
planet's radius. WASP-79b's transit depth reaches 23 scale height, making it
one of the largest spectral features observed in an exoplanet at this
temperature (1700 K). The comparison of WASP-79b's transmission spectrum
with three warmer hot Jupiters shows a similar level of absorption to WASP-178b
and WASP-121b between 0.2 and 0.3m, while HAT-P-41b's spectrum is flat.
The features could be explained by SiO absorption.Comment: Accepted for publication January 31, 2023 in the Journal Astronomy &
Astrophysic
JWST/NIRCam Transmission Spectroscopy of the Nearby Sub-Earth GJ 341b
We present a JWST/NIRCam transmission spectrum from m of the
recently-validated sub-Earth GJ 341b (
, K) orbiting a nearby bright M1
star ( pc, ). We use three independent
pipelines to reduce the data from the three JWST visits and perform several
tests to check for the significance of an atmosphere. Overall, our analysis
does not uncover evidence of an atmosphere. Our null hypothesis tests find that
none of our pipelines' transmission spectra can rule out a flat line, although
there is weak evidence for a Gaussian feature in two spectra from different
pipelines (at 2.3 and ). However, the candidate features are seen at
different wavelengths (4.3 m vs 4.7 m), and our retrieval analysis
finds that different gas species can explain these features in the two
reductions (CO at compared to O at ), suggesting
that they are not real astrophysical signals. Our forward model analysis rules
out a low mean molecular weight atmosphere ( solar metallicity) to
at least , and disfavors CH-dominated atmospheres at ,
depending on the reduction. Instead, the forward models find our transmission
spectra are consistent with no atmosphere, a hazy atmosphere, or an atmosphere
containing a species that does not have prominent molecular bands across the
NIRCam/F444W bandpass, such as a water-dominated atmosphere. Our results
demonstrate the unequivocal need for two or more transit observations analyzed
with multiple reduction pipelines, alongside rigorous statistical tests, to
determine the robustness of molecular detections for small exoplanet
atmospheres.Comment: 25 pages, 18 figures, 6 tables. Accepted for publication in A
Double Trouble: Two Transits of the Super-Earth GJ 1132 b Observed with JWST NIRSpec G395H
The search for rocky planet atmospheres with JWST has focused on planets
transiting M dwarfs. Such planets have favorable planet-to-star size ratios,
enhancing the amplitude of atmospheric features. Since the expected signal
strength of atmospheric features is similar to the single-transit performance
of JWST, multiple observations are required to confirm any detection. Here, we
present two transit observations of the rocky planet GJ 1132 b with JWST
NIRSpec G395H, covering 2.8-5.2 m. Previous HST WFC3 observations of GJ
1132 b were inconclusive, with evidence reported for either an atmosphere or a
featureless spectrum based on analyses of the same dataset. Our JWST data
exhibit substantial differences between the two visits. One transit is
consistent with either a HO-dominated atmosphere containing ~1% CH and
trace NO ( = 1.13) or stellar contamination from unocculted
starspots ( = 1.36). However, the second transit is consistent
with a featureless spectrum. Neither visit is consistent with a previous report
of HCN. Atmospheric variability is unlikely to explain the scale of the
observed differences between the visits. Similarly, our out-of-transit stellar
spectra show no evidence of changing stellar inhomogeneity between the two
visits - observed 8 days apart, only 6.5% of the stellar rotation rate. We
further find no evidence of differing instrumental systematic effects between
visits. The most plausible explanation is an unlucky random noise draw leading
to two significantly discrepant transmission spectra. Our results highlight the
importance of multi-visit repeatability with JWST prior to claiming atmospheric
detections for these small, enigmatic planets.Comment: 22 pages, 10 figures, 2 tables. Accepted for publication in ApJ
Letters. Co-First Authors. Bonus materials and spectral data:
https://doi.org/10.5281/zenodo.1000208
JWST-TST DREAMS: Quartz Clouds in the Atmosphere of WASP-17b
Clouds are prevalent in many of the exoplanet atmospheres that have been
observed to date. For transiting exoplanets, we know if clouds are present
because they mute spectral features and cause wavelength-dependent scattering.
While the exact composition of these clouds is largely unknown, this
information is vital to understanding the chemistry and energy budget of
planetary atmospheres. In this work, we observe one transit of the hot Jupiter
WASP-17b with JWST's MIRI LRS and generate a transmission spectrum from 5-12
m. These wavelengths allow us to probe absorption due to the
vibrational modes of various predicted cloud species. Our transmission spectrum
shows additional opacity centered at 8.6 m, and detailed atmospheric
modeling and retrievals identify this feature as SiO(s) (quartz) clouds.
The SiO(s) clouds model is preferred at 3.5-4.2 versus a cloud-free
model and at 2.6 versus a generic aerosol prescription. We find the
SiO(s) clouds are comprised of small m particles,
which extend to high altitudes in the atmosphere. The atmosphere also shows a
depletion of HO, a finding consistent with the formation of
high-temperature aerosols from oxygen-rich species. This work is part of a
series of studies by our JWST Telescope Scientist Team (JWST-TST), in which we
will use Guaranteed Time Observations to perform Deep Reconnaissance of
Exoplanet Atmospheres through Multi-instrument Spectroscopy (DREAMS).Comment: 19 pages, 7 figures, accepted for publication in ApJ
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
Transmission Spectroscopy of WASP-79b from 0.6 to 5.0 ÎŒm
As part of the Panchromatic Exoplanet Treasury program, we have conducted a spectroscopic study of WASP-79b, an inflated hot Jupiter orbiting an F-type star in Eridanus with a period of 3.66 days. Building on the original WASP and TRAPPIST photometry of Smalley et al., we examine Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) (1.125-1.650 ÎŒm), Magellan/Low Dispersion Survey Spectrograph (LDSS)-3C (0.6-1 ÎŒm) data, and Spitzer data (3.6 and 4.5 ÎŒm). Using data from all three instruments, we constrain the water abundance to be -2.20 †log(HO) †-1.55. We present these results along with the results of an atmospheric retrieval analysis, which favor inclusion of FeH and H in the atmospheric model. We also provide an updated ephemeris based on the Smalley, HST/WFC3, LDSS-3C, Spitzer, and Transiting Exoplanet Survey Satellite (TESS) transit times. With the detectable water feature and its occupation of the clear/cloudy transition region of the temperature/gravity phase space, WASP-79b is a target of interest for the approved James Webb Space Telescope (JWST) Director's Discretionary Early Release Science (ERS) program, with ERS observations planned to be the first to execute in Cycle 1. Transiting exoplanets have been approved for 78.1 hr of data collection, and with the delay in the JWST launch, WASP-79b is now a target for the Panchromatic Transmission program. This program will observe WASP-79b for 42 hr in four different instrument modes, providing substantially more data by which to investigate this hot Jupiter.With funding from the Spanish government through the "MarĂa de Maeztu Unit of Excellence" accreditation (MDM-2017-0737
Transmission Spectroscopy of WASP-79b from 0.6 to 5.0 ÎŒm
As part of the PanCET program, we have conducted a spectroscopic study of
WASP-79b, an inflated hot Jupiter orbiting an F-type star in Eridanus with a
period of 3.66 days. Building on the original WASP and TRAPPIST photometry of
Smalley et al (2012), we examine HST/WFC3 (1.125 - 1.650 m),
Magellan/LDSS-3C (0.6 - 1 m) data, and Spitzer data (3.6 and 4.5 m).
Using data from all three instruments, we constrain the water abundance to be
--2.20 log(HO) --1.55. We present these results along with
the results of an atmospheric retrieval analysis, which favor inclusion of FeH
and H in the atmospheric model. We also provide an updated ephemeris based
on the Smalley, HST/WFC3, LDSS-3C, Spitzer, and TESS transit times. With the
detectable water feature and its occupation of the clear/cloudy transition
region of the temperature/gravity phase space, WASP-79b is a target of interest
for the approved JWST Director's Discretionary Early Release Science (DD ERS)
program, with ERS observations planned to be the first to execute in Cycle 1.
Transiting exoplanets have been approved for 78.1 hours of data collection, and
with the delay in the JWST launch, WASP-79b is now a target for the
Panchromatic Transmission program. This program will observe WASP-79b for 42
hours in 4 different instrument modes, providing substantially more data by
which to investigate this hot Jupiter
Dragonfly: In Situ Exploration of Titan's Organic Chemistry and Habitability
International audienceTitan quadcopter / Samples complex organics / How does life begin
Dragonfly: In Situ Exploration of Titan's Organic Chemistry and Habitability
International audienceDragonfly explores / Life's chemical origins / Titan's mysteries
Dragonfly: In Situ Exploration of Titan's Organic Chemistry and Habitability
International audienceDragonfly explores / Life's chemical origins / Titan's mysteries