335 research outputs found
HST hot-Jupiter transmission spectral survey: Haze in the atmosphere of WASP-6b
We report Hubble Space Telescope (HST) optical to near-infrared transmission
spectroscopy of the hot Jupiter WASP-6b, measured with the Space Telescope
Imaging Spectrograph (STIS) and Spitzer's InfraRed Array Camera (IRAC). The
resulting spectrum covers the range m. We find evidence for
modest stellar activity of WASP-6b and take it into account in the transmission
spectrum. The overall main characteristic of the spectrum is an increasing
radius as a function of decreasing wavelength corresponding to a change of
from 0.33 to m. The spectrum suggests
an effective extinction cross-section with a power law of index consistent with
Rayleigh scattering, with temperatures of K at the planetary
terminator. We compare the transmission spectrum with hot-Jupiter atmospheric
models including condensate-free and aerosol-dominated models incorporating Mie
theory. While none of the clear-atmosphere models is found to be in good
agreement with the data, we find that the complete spectrum can be described by
models that include significant opacity from aerosols including Fe-poor
MgSiO, MgSiO, KCl and NaS dust condensates. WASP-6b is the
second planet after HD189733b which has equilibrium temperatures near
K and shows prominent atmospheric scattering in the optical.Comment: 18 pages, 15 figures, 7 table
Into the UV: A Precise Transmission Spectrum of HAT-P-41b Using Hubble’s WFC3/UVIS G280 Grism
The ultraviolet–visible wavelength range holds critical spectral diagnostics for the chemistry and physics at work in planetary atmospheres. To date, time-series studies of exoplanets to characterize their atmospheres have relied on several combinations of modes on the Hubble Space Telescope's STIS/COS instruments to access this wavelength regime. Here for the first time, we apply the Hubble WFC3/UVIS G280 grism mode to obtain exoplanet spectroscopy from 200 to 800 nm in a single observation. We test the G280 grism mode on the hot Jupiter HAT-P-41b over two consecutive transits to determine its viability for the characterization of exoplanet atmospheres. We obtain a broadband transit depth precision of 29–33 ppm and a precision of on average 200 ppm in 10 nm spectroscopic bins. Spectral information from the G280 grism can be extracted from both the positive and negative first-order spectra, resulting in a 60% increase in the measurable flux. Additionally, the first Hubble Space Telescope orbit can be fully utilized in the time-series analysis. We present detailed extraction and reduction methods for use by future investigations with this mode, testing multiple techniques. We find the results to be fully consistent with STIS measurements of HAT-P-41b from 310 to 800 nm, with the G280 results representing a more observationally efficient and precise spectrum. HAT-P-41b's transmission spectrum is best fit with a model with T eq = 2091 K, high metallicity, and significant scattering and cloud opacity. With these first-of-their-kind observations, we demonstrate that WFC3/UVIS G280 is a powerful new tool to obtain UV–optical spectra of exoplanet atmospheres, adding to the UV legacy of Hubble and complementing future observations with the James Webb Space Telescope
Into the UV: A Precise Transmission Spectrum of HAT-P-41b Using Hubble’s WFC3/UVIS G280 Grism
The ultraviolet–visible wavelength range holds critical spectral diagnostics for the chemistry and physics at work in planetary atmospheres. To date, time-series studies of exoplanets to characterize their atmospheres have relied on several combinations of modes on the Hubble Space Telescope's STIS/COS instruments to access this wavelength regime. Here for the first time, we apply the Hubble WFC3/UVIS G280 grism mode to obtain exoplanet spectroscopy from 200 to 800 nm in a single observation. We test the G280 grism mode on the hot Jupiter HAT-P-41b over two consecutive transits to determine its viability for the characterization of exoplanet atmospheres. We obtain a broadband transit depth precision of 29–33 ppm and a precision of on average 200 ppm in 10 nm spectroscopic bins. Spectral information from the G280 grism can be extracted from both the positive and negative first-order spectra, resulting in a 60% increase in the measurable flux. Additionally, the first Hubble Space Telescope orbit can be fully utilized in the time-series analysis. We present detailed extraction and reduction methods for use by future investigations with this mode, testing multiple techniques. We find the results to be fully consistent with STIS measurements of HAT-P-41b from 310 to 800 nm, with the G280 results representing a more observationally efficient and precise spectrum. HAT-P-41b's transmission spectrum is best fit with a model with T eq = 2091 K, high metallicity, and significant scattering and cloud opacity. With these first-of-their-kind observations, we demonstrate that WFC3/UVIS G280 is a powerful new tool to obtain UV–optical spectra of exoplanet atmospheres, adding to the UV legacy of Hubble and complementing future observations with the James Webb Space Telescope
HST/WFC3 transmission spectroscopy of the cold rocky planet TRAPPIST-1h
TRAPPIST-1 is a nearby ultra-cool dwarf star transited by seven rocky
planets. We observed three transits of its outermost planet, TRAPPIST-1h, using
the G141 grism of the Wide Field Camera 3 instrument aboard the Hubble Space
Telescope to place constraints on its potentially cold atmosphere. In order to
deal with the effect of stellar contamination, we model TRAPPIST-1 active
regions as portions of a cooler and a hotter photosphere, and generate
multi-temperature models that we compare to the out-of-transit spectrum of the
star. Using the inferred spot parameters, we produce corrected transmission
spectra for planet h under five transit configurations and compare these data
to planetary atmospheric transmission models using the forward model CHIMERA.
Our analysis reveals that TRAPPIST-1h is unlikely to host an aerosol-free
H/He-dominated atmosphere. While the current data precision limits the
constraints we can put on the planetary atmosphere, we find that the likeliest
scenario is that of a flat, featureless transmission spectrum in the WFC3/G141
bandpass due to a high mean molecular weight atmosphere (>1000x solar), no
atmosphere, or an opaque aerosol layer, all in absence of stellar
contamination. This work outlines the limitations of modeling active
photospheric regions with theoretical stellar spectra, and those brought by our
lack of knowledge of the photospheric structure of ultracool dwarf stars.
Further characterization of the planetary atmosphere of TRAPPIST-1h would
require higher precision measurements over wider wavelengths, which will be
possible with the James Webb Space Telescope
HST hot Jupiter transmission spectral survey: evidence for aerosols and lack of TiO in the atmosphere of WASP-12b
We present HST optical transmission spectra of the transiting hot Jupiter
WASP-12b, taken with the STIS instrument. From the transmission spectra, we are
able to decisively rule out prominent absorption by TiO in the exoplanet's
atmosphere. Strong pressure-broadened Na and K absorption signatures are also
excluded, as are significant metal-hydride features. We compare our combined
broadband spectrum to a wide variety of existing aerosol-free atmospheric
models, though none are satisfactory fits. However, we do find that the full
transmission spectrum can be described by models which include significant
opacity from aerosols: including Rayleigh scattering, Mie scattering, tholin
haze, and settling dust profiles. The transmission spectrum follows an
effective extinction cross section with a power-law of index alpha, with the
slope of the transmission spectrum constraining the quantity alphaT =
-3528+/-660 K, where T is the atmospheric temperature. Rayleigh scattering
(alpha=-4) is among the best fitting models, though requires low terminator
temperatures near 900 K. Sub-micron size aerosol particles can provide equally
good fits to the entire transmission spectrum for a wide range of temperatures,
and we explore corundum as a plausible dust aerosol. The presence of
atmospheric aerosols also helps to explain the modestly bright albedo implied
by Spitzer observations, as well as the near black body nature of the emission
spectrum. Ti-bearing condensates on the cooler night-side is the most natural
explanation for the overall lack of TiO signatures in WASP-12b, indicating the
day/night cold-trap is an important effect for very hot Jupiters. These finding
indicate that aerosols can play a significant atmospheric role for the entire
wide range of hot-Jupiter atmospheres, potentially affecting their overall
spectrum and energy balance.(abridged)Comment: 19 pages, 14 figures, 5 tables. Accepted for publication in MNRA
HST PanCET program: A Cloudy Atmosphere for the promising JWST target WASP-101b
We present results from the first observations of the Hubble Space Telescope
(HST) Panchromatic Comparative Exoplanet Treasury (PanCET) program for
WASP-101b, a highly inflated hot Jupiter and one of the community targets
proposed for the James Webb Space Telescope (JWST) Early Release Science (ERS)
program. From a single HST Wide Field Camera 3 (WFC3) observation, we find that
the near-infrared transmission spectrum of WASP-101b contains no significant
HO absorption features and we rule out a clear atmosphere at 13{\sigma}.
Therefore, WASP-101b is not an optimum target for a JWST ERS program aimed at
observing strong molecular transmission features. We compare WASP-101b to the
well studied and nearly identical hot Jupiter WASP-31b. These twin planets show
similar temperature-pressure profiles and atmospheric features in the
near-infrared. We suggest exoplanets in the same parameter space as WASP-101b
and WASP-31b will also exhibit cloudy transmission spectral features. For
future HST exoplanet studies, our analysis also suggests that a lower count
limit needs to be exceeded per pixel on the detector in order to avoid unwanted
instrumental systematics.Comment: 7 pages, 4 figures, 1 table, Accepted to ApJ
Detection of H2O and evidence for TiO/VO in an ultra hot exoplanet atmosphere
This is the author accepted manuscript. The final version is available from American Astronomical Society via the DOI in this recordWe present a primary transit observation for the ultra hot (Teq 2400 K) gas giant expolanetWASP-121b, made using the Hubble Space Telescope Wide Field Camera 3 in spectroscopic mode across the 1.12{1.64 m wavelength range. The 1.4 m water absorption band is detected at high con dence (5:4 ) in the planetary atmosphere. We also reanalyze ground-based photometric lightcurves taken in the B, r0, and z0 lters. Signi cantly deeper transits are measured in these optical bandpasses relative to the near-infrared wavelengths. We conclude that scattering by high-altitude haze alone is unlikely to account for this di erence, and instead interpret it as evidence for titanium oxide and vanadium oxide absorption. Enhanced opacity is also inferred across the 1:12{1:3 m wavelength range, possibly due to iron hydride absorption. If con rmed, WASP-121b will be the rst exoplanet with titanium oxide, vanadium oxide, and iron hydride detected in transmission. The latter are important species in M/L dwarfs, and their presence is likely to have a signi cant e ect on the overall physics and chemistry of the atmosphere, including the production of a strong thermal inversionThe research leading to these results has received funding from the European Research Council under the European Union Seventh Framework Program (FP7/2007-2013) ERC grant agreement no. 336792
The construction of ‘age difference’ and the impact of age‐mixing within UK further education colleges
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
HST hot Jupiter transmission spectral survey: detection of water in HAT-P-1b from WFC3 near-IR spatial scan observations
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We present Hubble Space Telescope near-infrared transmission spectroscopy of the transiting hot-Jupiter HAT-P-1b. We observed one transit with Wide Field Camera 3 using the G141 low-resolution grism to cover the wavelength range 1.087–1.678 μm. These time series observations were taken with the newly available spatial-scan mode that increases the duty cycle by nearly a factor of 2, thus improving the resulting photometric precision of the data. We measure a planet-to-star radius ratio of Rp/R* = 0.117 09 ± 0.000 38 in the white light curve with the centre of transit occurring at 245 6114.345 ± 0.000 133 (JD). We achieve S/N levels per exposure of 1840 (0.061 per cent) at a resolution of Δλ = 19.2 nm (R ∼ 70) in the 1.1173–1.6549 μm spectral region, providing the precision necessary to probe the transmission spectrum of the planet at close to the resolution limit of the instrument. We compute the transmission spectrum using both single target and differential photometry with similar results. The resultant transmission spectrum shows a significant absorption above the 5σ level matching the 1.4 μm water absorption band. In solar composition models, the water absorption is sensitive to the ∼1 m bar pressure levels at the terminator. The detected absorption agrees with that predicted by a 1000 K isothermal model, as well as with that predicted by a planetary-averaged temperature model.Science & Technology Facilities Council (STFC)Space Telescope Science Institut
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