| 1. |
- Kanai, M, et al.
(författare)
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- 2023
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swepub:Mat__t
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| 2. |
- Niemi, MEK, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 3. |
- Aad, G, et al.
(författare)
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- 2015
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swepub:Mat__t
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| 4. |
- Schael, S, et al.
(författare)
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Precision electroweak measurements on the Z resonance
- 2006
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Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454
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Forskningsöversikt (refereegranskat)abstract
- We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17 million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLID experiment using a polarised beam at SLC. The measurements include cross-sections, forward-backward asymmetries and polarised asymmetries. The mass and width of the Z boson, m(Z) and Gamma(Z), and its couplings to fermions, for example the p parameter and the effective electroweak mixing angle for leptons, are precisely measured: m(Z) = 91.1875 +/- 0.0021 GeV, Gamma(Z) = 2.4952 +/- 0.0023 GeV, rho(l) = 1.0050 +/- 0.0010, sin(2)theta(eff)(lept) = 0.23153 +/- 0.00016. The number of light neutrino species is determined to be 2.9840 +/- 0.0082, in agreement with the three observed generations of fundamental fermions. The results are compared to the predictions of the Standard Model (SM). At the Z-pole, electroweak radiative corrections beyond the running of the QED and QCD coupling constants are observed with a significance of five standard deviations, and in agreement with the Standard Model. Of the many Z-pole measurements, the forward-backward asymmetry in b-quark production shows the largest difference with respect to its SM expectation, at the level of 2.8 standard deviations. Through radiative corrections evaluated in the framework of the Standard Model, the Z-pole data are also used to predict the mass of the top quark, m(t) = 173(+10)(+13) GeV, and the mass of the W boson, m(W) = 80.363 +/- 0.032 GeV. These indirect constraints are compared to the direct measurements, providing a stringent test of the SM. Using in addition the direct measurements of m(t) and m(W), the mass of the as yet unobserved SM Higgs boson is predicted with a relative uncertainty of about 50% and found to be less than 285 GeV at 95% confidence level. (c) 2006 Elsevier B.V. All rights reserved.
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| 5. |
- Luque, R., et al.
(författare)
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A resonant sextuplet of sub-Neptunes transiting the bright star HD 110067
- 2023
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Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 623:7989, s. 932-937
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Tidskriftsartikel (refereegranskat)abstract
- Planets with radii between that of the Earth and Neptune (hereafter referred to as ‘sub-Neptunes’) are found in close-in orbits around more than half of all Sun-like stars 1,2. However, their composition, formation and evolution remain poorly understood 3. The study of multiplanetary systems offers an opportunity to investigate the outcomes of planet formation and evolution while controlling for initial conditions and environment. Those in resonance (with their orbital periods related by a ratio of small integers) are particularly valuable because they imply a system architecture practically unchanged since its birth. Here we present the observations of six transiting planets around the bright nearby star HD 110067. We find that the planets follow a chain of resonant orbits. A dynamical study of the innermost planet triplet allowed the prediction and later confirmation of the orbits of the rest of the planets in the system. The six planets are found to be sub-Neptunes with radii ranging from 1.94R ⊕ to 2.85R ⊕. Three of the planets have measured masses, yielding low bulk densities that suggest the presence of large hydrogen-dominated atmospheres.
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| 6. |
- Carter, Aarynn L., et al.
(författare)
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A benchmark JWST near-infrared spectrum for the exoplanet WASP-39 b
- 2024
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Ingår i: Nature Astronomy. - 2397-3366. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- A combined analysis of datasets across four JWST instrument modes provides a benchmark transmission spectrum for the Saturn-mass WASP-39 b. The broad wavelength range and high resolution constrain orbital and stellar parameters to below 1%.
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| 7. |
- Bonfanti, A., et al.
(författare)
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Characterising TOI-732 b and c: New insights into the M-dwarf radius and density valley ★,★★
- 2024
-
Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 682
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Tidskriftsartikel (refereegranskat)abstract
- TOI-732 is an M dwarf hosting two transiting planets that are located on the two opposite sides of the radius valley. Inferring a reliable demographics for this type of systems is key to understanding their formation and evolution mechanisms. Aims. By doubling the number of available space-based observations and increasing the number of radial velocity (RV) measurements, we aim at refining the parameters of TOI-732 b and c. We also use the results to study the slope of the radius valley and the density valley for a well-characterised sample of M-dwarf exoplanets. Methods. We performed a global Markov chain Monte Carlo analysis by jointly modelling ground-based light curves and CHEOPS and TESS observations, along with RV time series both taken from the literature and obtained with the MAROON-X spectrograph. The slopes of the M-dwarf valleys were quantified via a support vector machine (SVM) procedure. Results. TOI-732 b is an ultrashort-period planet (P = 0.76837931−+000000004200000039 days) with a radius Rb = 1.325+−00057058 R☉, a mass Mb = 2.46 ± 0.19 M☉, and thus a mean density ρb = 5.8+−1008 g cm−3, while the outer planet at P = 12.252284 ± 0.000013 days has Rc = 2.39+−001011 R☉, Mc = 8.04+−005048 M☉, and thus ρc = 3.24+−005543 g cm−3. Even with respect to the most recently reported values, this work yields uncertainties on the transit depths and on the RV semi-amplitudes that are smaller up to a factor of ∼1.6 and ∼2.4 for TOI-732 b and c, respectively. Our calculations for the interior structure and the location of the planets in the mass-radius diagram lead us to classify TOI-732 b as a super-Earth and TOI-732 c as a mini-Neptune. Following the SVM approach, we quantified d log Rp,valley/d log P = −0.065+−00024013, which is flatter than for Sun-like stars. In line with former analyses, we note that the radius valley for M-dwarf planets is more densely populated, and we further quantify the slope of the density valley as d log ρ̂valley/d log P = −0.02+−001204. Conclusions. Compared to FGK stars, the weaker dependence of the position of the radius valley on the orbital period might indicate that the formation shapes the radius valley around M dwarfs more strongly than the evolution mechanisms.
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| 8. |
- Bell, Taylor, et al.
(författare)
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Nightside clouds and disequilibrium chemistry on the hot Jupiter WASP-43b
- 2024
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Ingår i: Nature Astronomy. - 2397-3366. ; 8:7, s. 879-898
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- Esparza-Borges, E., et al.
(författare)
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Detection of Carbon Monoxide in the Atmosphere of WASP-39b Applying Standard Cross-correlation Techniques to JWST NIRSpec G395H Data
- 2023
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Ingår i: Astrophysical Journal Letters. - 2041-8213 .- 2041-8205. ; 955:1
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Tidskriftsartikel (refereegranskat)abstract
- 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 μm, 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 6.6σ when using a template with only 12C16O lines. The CCF significance of the CO signal increases to 7.5σ when including in the template lines from additional CO isotopologues, with the largest contribution being from 13C16O. 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.
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| 10. |
- Powell, Diana, et al.
(författare)
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Sulfur dioxide in the mid-infrared transmission spectrum of WASP-39b
- 2024
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Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 626:8001, s. 979-983
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Tidskriftsartikel (refereegranskat)abstract
- The recent inference of sulfur dioxide (SO2) in the atmosphere of the hot (approximately 1,100 K), Saturn-mass exoplanet WASP-39b from near-infrared JWST observations1–3 suggests that photochemistry is a key process in high-temperature exoplanet atmospheres4. This is because of the low (<1 ppb) abundance of SO2 under thermochemical equilibrium compared with that produced from the photochemistry of H2O and H2S (1–10 ppm)4–9. However, the SO2 inference was made from a single, small molecular feature in the transmission spectrum of WASP-39b at 4.05 μm and, therefore, the detection of other SO2 absorption bands at different wavelengths is needed to better constrain the SO2 abundance. Here we report the detection of SO2 spectral features at 7.7 and 8.5 μm in the 5–12-μm transmission spectrum of WASP-39b measured by the JWST Mid-Infrared Instrument (MIRI) Low Resolution Spectrometer (LRS)10. Our observations suggest an abundance of SO2 of 0.5–25 ppm (1σ range), consistent with previous findings4. As well as SO2, we find broad water-vapour absorption features, as well as an unexplained decrease in the transit depth at wavelengths longer than 10 μm. Fitting the spectrum with a grid of atmospheric forward models, we derive an atmospheric heavy-element content (metallicity) for WASP-39b of approximately 7.1–8.0 times solar and demonstrate that photochemistry shapes the spectra of WASP-39b across a broad wavelength range.
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| 11. |
- Hammond, Mark, et al.
(författare)
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Two-dimensional Eclipse Mapping of the Hot-Jupiter WASP-43b with JWST MIRI/LRS
- 2024
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Ingår i: Astronomical Journal. - 1538-3881 .- 0004-6256. ; 168:1
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Tidskriftsartikel (refereegranskat)abstract
- We present eclipse maps of the two-dimensional thermal emission from the dayside of the hot-Jupiter WASP-43b, derived from an observation of a phase curve with the JWST MIRI/LRS instrument. The observed eclipse shapes deviate significantly from those expected for a planet emitting uniformly over its surface. We fit a map to this deviation, constructed from spherical harmonics up to order ℓ max = 2 , alongside the planetary, orbital, stellar, and systematic parameters. This yields a map with a meridionally averaged eastward hot-spot shift of (7.75 ± 0.36)°, with no significant degeneracy between the map and the additional parameters. We show the latitudinal and longitudinal contributions of the dayside emission structure to the eclipse shape, finding a latitudinal signal of ∼200 ppm and a longitudinal signal of ∼250 ppm. To investigate the sensitivity of the map to the method, we fix the parameters not used for mapping and derive an “eigenmap” fitted with an optimized number of orthogonal phase curves, which yields a similar map to the ℓ max = 2 map. We also fit a map up to ℓ max = 3 , which shows a smaller hot-spot shift, with a larger uncertainty. These maps are similar to those produced by atmospheric simulations. We conclude that there is a significant mapping signal which constrains the spherical harmonic components of our model up to ℓ max = 2 . Alternative mapping models may derive different structures with smaller-scale features; we suggest that further observations of WASP-43b and other planets will drive the development of more robust methods and more accurate maps.
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| 12. |
- Ade, Peter, et al.
(författare)
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The Simons Observatory : science goals and forecasts
- 2019
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Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :2
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Tidskriftsartikel (refereegranskat)abstract
- The Simons Observatory (SO) is a new cosmic microwave background experiment being built on Cerro Toco in Chile, due to begin observations in the early 2020s. We describe the scientific goals of the experiment, motivate the design, and forecast its performance. SO will measure the temperature and polarization anisotropy of the cosmic microwave background in six frequency bands centered at: 27, 39, 93, 145, 225 and 280 GHz. The initial con figuration of SO will have three small-aperture 0.5-m telescopes and one large-aperture 6-m telescope, with a total of 60,000 cryogenic bolometers. Our key science goals are to characterize the primordial perturbations, measure the number of relativistic species and the mass of neutrinos, test for deviations from a cosmological constant, improve our understanding of galaxy evolution, and constrain the duration of reionization. The small aperture telescopes will target the largest angular scales observable from Chile, mapping approximate to 10% of the sky to a white noise level of 2 mu K-arcmin in combined 93 and 145 GHz bands, to measure the primordial tensor-to-scalar ratio, r, at a target level of sigma(r) = 0.003. The large aperture telescope will map approximate to 40% of the sky at arcminute angular resolution to an expected white noise level of 6 mu K-arcmin in combined 93 and 145 GHz bands, overlapping with the majority of the Large Synoptic Survey Telescope sky region and partially with the Dark Energy Spectroscopic Instrument. With up to an order of magnitude lower polarization noise than maps from the Planck satellite, the high-resolution sky maps will constrain cosmological parameters derived from the damping tail, gravitational lensing of the microwave background, the primordial bispectrum, and the thermal and kinematic Sunyaev-Zel'dovich effects, and will aid in delensing the large-angle polarization signal to measure the tensor-to-scalar ratio. The survey will also provide a legacy catalog of 16,000 galaxy clusters and more than 20,000 extragalactic sources.
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| 13. |
- Benedict, G. Fritz, et al.
(författare)
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Distance scale zero points from galactic RR Lyrae star parallaxes
- 2011
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Ingår i: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 142:6, s. 187-
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Tidskriftsartikel (refereegranskat)abstract
- We present new absolute trigonometric parallaxes and proper motions for seven Population II variable stars-five RR Lyr variables: RZ Cep, XZ Cyg, SU Dra, RR Lyr, and UV Oct; and two type 2 Cepheids: VY Pyx and kappa Pav. We obtained these results with astrometric data from Fine Guidance Sensors, white-light interferometers on Hubble Space Telescope. We find absolute parallaxes in milliseconds of arc: RZ Cep, 2.12 +/- 0.16 mas; XZ Cyg, 1.67 +/- 0.17 mas; SU Dra, 1.42 +/- 0.16 mas; RR Lyr, 3.77 +/- 0.13 mas; UV Oct, 1.71 +/- 0.10 mas; VY Pyx, 6.44 +/- 0.23 mas; and. Pav, 5.57 +/- 0.28 mas; an average sigma(pi)/pi = 5.4%. With these parallaxes, we compute absolute magnitudes in V and K bandpasses corrected for interstellar extinction and Lutz-Kelker-Hanson bias. Using these RR Lyrae variable star absolute magnitudes, we then derive zero points for M(V)-[Fe/H] and M(K)-[Fe/H]-log P relations. The technique of reduced parallaxes corroborates these results. We employ our new results to determine distances and ages of several Galactic globular clusters and the distance of the Large Magellanic Cloud. The latter is close to that previously derived from Classical Cepheids uncorrected for any metallicity effect, indicating that any such effect is small. We also discuss the somewhat puzzling results obtained for our two type 2 Cepheids.
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| 14. |
- Flagg, Laura, et al.
(författare)
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Debris Disks Can Contaminate Mid-infrared Exoplanet Spectra: Evidence for a Circumstellar Debris Disk around Exoplanet Host WASP-39
- 2024
-
Ingår i: Astrophysical Journal Letters. - 2041-8213 .- 2041-8205. ; 969:1
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Tidskriftsartikel (refereegranskat)abstract
- The signal from a transiting planet can be diluted by astrophysical contamination. In the case of circumstellar debris disks, this contamination could start in the mid-infrared and vary as a function of wavelength, which would then change the observed transmission spectrum for any planet in the system. The MIRI/Low Resolution Spectrometer WASP-39b transmission spectrum shows an unexplained dip starting at ∼10 μm that could be caused by astrophysical contamination. The spectral energy distribution displays excess flux at similar levels to that which are needed to create the dip in the transmission spectrum. In this Letter, we show that this dip is consistent with the presence of a bright circumstellar debris disk, at a distance of >2 au. We discuss how a circumstellar debris disk like that could affect the atmosphere of WASP-39b. We also show that even faint debris disks can be a source of contamination in MIRI exoplanet spectra.
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| 15. |
- Bean, Jacob L., et al.
(författare)
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The CRIRES search for planets around the lowest-mass stars. I. High-precision near-infrared radial velocities with an ammonia gas cell
- 2010
-
Ingår i: Astrophysical Journal. - 0004-637X. ; 713:1, s. 410-422
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Tidskriftsartikel (refereegranskat)abstract
- Radial velocities measured from near-infrared (NIR) spectra are a potentially powerful tool to search for planets around cool stars and sub-stellar objects. However, no technique currently exists that yields NIR radial velocity precision comparable to that routinely obtained in the visible. We are carrying out an NIR radial velocity planet search program targeting a sample of the lowest-mass M dwarfs using the CRIRES instrument on the Very Large Telescope. In this first paper in a planned series about the project, we describe a method for measuring high-precision relative radial velocities of these stars from K-band spectra. The method makes use of a glass cell filled with ammonia gas to calibrate the spectrograph response similar to the "iodine cell" technique that has been used very successfully in the visible. Stellar spectra are obtained through the ammonia cell and modeled as the product of a Doppler-shifted template spectrum of the object and a spectrum of the cell, convolved with a variable instrumental profile (IP) model. A complicating factor is that a significant number of telluric absorption lines are present in the spectral regions containing useful stellar and ammonia lines. The telluric lines are modeled simultaneously as well using spectrum synthesis with a time-resolved model of the atmosphere over the observatory. The free parameters in the complete model are the wavelength scale of the spectrum, the IP, adjustments to the water and methane abundances in the atmospheric model, telluric spectrum Doppler shift, and stellar Doppler shift. Tests of the method based on the analysis of hundreds of spectra obtained for late-M dwarfs over 6 months demonstrate that precisions of similar to 5 m s(-1) are obtainable over long timescales, and precisions of better than 3 m s(-1) can be obtained over timescales up to a week. The obtained precision is comparable to the predicted photon-limited errors, but primarily limited over long timescales by the imperfect modeling of the telluric lines.
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| 16. |
- Bean, Jacob L., et al.
(författare)
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The crires search for planets around the lowest-mass stars. I. High-precision near-infrared radial velocities with an ammonia gas cell
- 2010
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 713:1, s. 410-422
-
Tidskriftsartikel (refereegranskat)abstract
- Radial velocities measured from near-infrared (NIR) spectra are a potentially powerful tool to search for planets around cool stars and sub-stellar objects. However, no technique currently exists that yields NIR radial velocity precision comparable to that routinely obtained in the visible. We are carrying out an NIR radial velocity planet search program targeting a sample of the lowest-mass M dwarfs using the CRIRES instrument on the Very Large Telescope. In this first paper in a planned series about the project, we describe a method for measuring high-precision relative radial velocities of these stars from K-band spectra. The method makes use of a glass cell filled with ammonia gas to calibrate the spectrograph response similar to the "iodine cell" technique that has been used very successfully in the visible. Stellar spectra are obtained through the ammonia cell and modeled as the product of a Doppler-shifted template spectrum of the object and a spectrum of the cell, convolved with a variable instrumental profile (IP) model. A complicating factor is that a significant number of telluric absorption lines are present in the spectral regions containing useful stellar and ammonia lines. The telluric lines are modeled simultaneously as well using spectrum synthesis with a time-resolved model of the atmosphere over the observatory. The free parameters in the complete model are the wavelength scale of the spectrum, the IP, adjustments to the water and methane abundances in the atmospheric model, telluric spectrum Doppler shift, and stellar Doppler shift. Tests of the method based on the analysis of hundreds of spectra obtained for late-M dwarfs over 6 months demonstrate that precisions of ∼ 5 m s−1 are obtainable over long timescales, and precisions of better than 3 m s−1 can be obtained over timescales up to a week. The obtained precision is comparable to the predicted photon-limited errors, but primarily limited over long timescales by the imperfect modeling of the telluric lines.
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| 17. |
- Bean, Jacob L., et al.
(författare)
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The proposed giant planet orbiting VB 10 does not exist
- 2010
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Ingår i: Astrophysical Journal Letters. - 2041-8213. ; 711:1, s. 19-23
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Tidskriftsartikel (refereegranskat)abstract
- We present high-precision relative radial velocities of the very low mass star VB 10 that were obtained over a time span of 0.61 years as part of an ongoing search for planets around stars at the end of the main sequence. The radial velocities were measured from high-resolution near-infrared spectra obtained using the CRIRES instrument on the Very Large Telescope with an ammonia gas cell. The typical internal precision of the measurements is 10 m s(-1). These data do not exhibit significant variability and are essentially constant at a level consistent with the measurement uncertainties. Therefore, we do not detect the radial velocity variations of VB 10 expected due to the presence of an orbiting giant planet similar to that recently proposed by Pravdo & Shaklan based on apparent astrometric perturbations. In addition, we do not confirm the similar to 1 km s(-1) radial velocity variability of the star tentatively detected by Zapatero Osorio and colleagues with lower precision measurements. Our measurements rule out planets with M-p > 3 M-Jup and the orbital period and inclination suggested by Pravdo & Shaklan at better than 5 sigma confidence. We conclude that the planet detection claimed by Pravdo & Shaklan is spurious on the basis of this result. Although the outcome of this work is a non-detection, it illustrates the potential of using ammonia cell radial velocities to detect planets around very low mass stars.
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| 18. |
- Bean, Jacob L., et al.
(författare)
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The proposed giant planet orbiting VB 10 does not exist
- 2010
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 711:1, s. L19-L23
-
Tidskriftsartikel (refereegranskat)abstract
- We present high-precision relative radial velocities of the very low mass star VB 10 that were obtained over a time span of 0.61 years as part of an ongoing search for planets around stars at the end of the main sequence. The radial velocities were measured from high-resolution near-infrared spectra obtained using the CRIRES instrument on the Very Large Telescope with an ammonia gas cell. The typical internal precision of the measurements is 10 m s−1. These data do not exhibit significant variability and are essentially constant at a level consistent with the measurement uncertainties. Therefore, we do not detect the radial velocity variations of VB 10 expected due to the presence of an orbiting giant planet similar to that recently proposed by Pravdo & Shaklan based on apparent astrometric perturbations. In addition, we do not confirm the ∼1 km s−1 radial velocity variability of the star tentatively detected by Zapatero Osorio and colleagues with lower precision measurements. Our measurements rule out planets with Mp > 3 MJup and the orbital period and inclination suggested by Pravdo & Shaklan at better than 5σ confidence. We conclude that the planet detection claimed by Pravdo & Shaklan is spurious on the basis of this result. Although the outcome of this work is a non-detection, it illustrates the potential of using ammonia cell radial velocities to detect planets around very low mass stars.
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| 19. |
- Bedell, Megan, et al.
(författare)
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Kepler-11 is a Solar Twin : Revising the Masses and Radii of Benchmark Planets via Precise Stellar Characterization
- 2017
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 839:2
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Tidskriftsartikel (refereegranskat)abstract
- The six planets of the Kepler-11 system are the archetypal example of a population of surprisingly low-density transiting planets revealed by the Kepler mission. We have determined the fundamental parameters and chemical composition of the Kepler-11 host star to unprecedented precision using an extremely high-quality spectrum from Keck-HIRES (R ≃ 67,000, S/N per pixel at 600 nm). Contrary to previously published results, our spectroscopic constraints indicate that Kepler-11 is a young main-sequence solar twin. The revised stellar parameters and new analysis raise the densities of the Kepler-11 planets by between 20% and 95% per planet, making them more typical of the emerging class of "puffy" close-in exoplanets. We obtain photospheric abundances of 22 elements and find that Kepler-11 has an abundance pattern similar to that of the Sun with a slightly higher overall metallicity. We additionally analyze the Kepler light curves using a photodynamical model and discuss the tension between spectroscopic and transit/TTV-based estimates of stellar density.
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| 20. |
- Pelletier, Stefan, et al.
(författare)
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Vanadium oxide and a sharp onset of cold-trapping on a giant exoplanet
- 2023
-
Ingår i: Nature. - 0028-0836. ; 619:7970, s. 491-494
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Tidskriftsartikel (refereegranskat)abstract
- The abundance of refractory elements in giant planets can provide key insights into their formation histories1. Owing to the low temperatures of the Solar System giants, refractory elements condense below the cloud deck, limiting sensing capabilities to only highly volatile elements2. Recently, ultra-hot giant exoplanets have allowed for some refractory elements to be measured, showing abundances broadly consistent with the solar nebula with titanium probably condensed out of the photosphere3,4. Here we report precise abundance constraints of 14 major refractory elements on the ultra-hot giant planet WASP-76b that show distinct deviations from proto-solar and a sharp onset in condensation temperature. In particular, we find nickel to be enriched, a possible sign of the accretion of the core of a differentiated object during the evolution of the planet. Elements with condensation temperatures below 1,550 K otherwise closely match those of the Sun5 before sharply transitioning to being strongly depleted above 1,550 K, which is well explained by nightside cold-trapping. We further unambiguously detect vanadium oxide on WASP-76b, a molecule long suggested to drive atmospheric thermal inversions6, and also observe a global east–west asymmetry7 in its absorption signals. Overall, our findings indicate that giant planets have a mostly stellar-like refractory elemental content and suggest that temperature sequences of hot Jupiter spectra can show abrupt transitions wherein a mineral species is either present or completely absent if a cold trap exists below its condensation temperature8.
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