| 1. |
- Alsubai, Khalid, et al.
(author)
-
Qatar Exoplanet Survey : Qatar-3b, Qatar-4b, and Qatar-5b
- 2017
-
In: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 153:4
-
Journal article (peer-reviewed)abstract
- We report the discovery of Qatar-3b, Qatar-4b, and Qatar-5b, three new transiting planets identified by the Qatar Exoplanet Survey. The three planets belong to the hot Jupiter family, with orbital periods of P-Q3b = 2.50792 days, P-Q4b = 1.80539 days, and P-Q5b = 2.87923 days. Follow-up spectroscopic observations reveal the masses of the planets to be M-Q3b = 4.31 +/- 0.47 M-J, M-Q4b = 6.10 +/- 0.54 M-J, and M-Q5b = 4.32 +/- 0.18 M-J, while model fits to the transit light curves yield radii of R-Q3b = 1.096 +/- 0.14 RJ, R-Q4b = 1.135 +/- 0.11 R-J, and R-Q5b = 1.107 +/- 0.064 R-J. The host stars are low-mass main sequence stars with masses and radii M-Q3 = 1.145 +/- 0.064 M circle dot, M-Q4 = 0.896 +/- 0.048 M circle dot, M-Q5 = 1.128 +/- 0.056 M circle dot and R-Q3 = 1.272 +/- 0.14 R circle dot, R-Q4 = 0.849 +/- 0.063 R circle dot, and R-Q5 = 1.076 +/- 0.051 R circle dot for Qatar-3, 4, and 5 respectively. The V magnitudes of the three host stars are V-Q3 = 12.88, V-Q4 = 13.60, and V-Q5 = 12.82. All three new planets can be classified as heavy hot Jupiters (M > 4 M-J).
|
|
| 2. |
- Bell, Taylor, et al.
(author)
-
Nightside clouds and disequilibrium chemistry on the hot Jupiter WASP-43b
- 2024
-
In: Nature Astronomy. - 2397-3366. ; In Press
-
Journal article (peer-reviewed)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.
|
|
| 3. |
- Crossfield, Ian J. M., et al.
(author)
-
197 CANDIDATES AND 104 VALIDATED PLANETS IN K2's FIRST FIVE FIELDS
- 2016
-
In: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 226:1
-
Journal article (peer-reviewed)abstract
- We present 197 planet candidates discovered using data from the first year of the NASA K2 mission (Campaigns 0-4), along with the results of an intensive program of photometric analyses, stellar spectroscopy, high-resolution imaging, and statistical validation. We distill these candidates into sets of 104 validated planets (57 in multi-planet systems), 30 false positives, and 63 remaining candidates. Our validated systems span a range of properties, with median values of R-P = 2.3 R-circle plus, P = 8.6 days, T-eff = 5300 K, and Kp = 12.7 mag. Stellar spectroscopy provides precise stellar and planetary parameters for most of these systems. We show that K2 has increased by 30% the number of small planets known to orbit moderately bright stars (1-4 R-circle plus, Kp = 9-13. mag). Of particular interest are 76 planets smaller than 2 R-circle plus, 15 orbiting stars brighter than Kp = 11.5. mag, 5 receiving Earth-like irradiation levels, and several multi-planet systems-including 4 planets orbiting the M dwarf K2-72 near mean-motion resonances. By quantifying the likelihood that each candidate is a planet we demonstrate that our candidate sample has an overall false positive rate of 15%-30%, with rates substantially lower for small candidates (<2 R-circle plus) and larger for candidates with radii >8 R-circle plus and/or with P < 3 days. Extrapolation of the current planetary yield suggests that K2 will discover between 500 and 1000 planets in its planned four-year mission, assuming sufficient follow-up resources are available. Efficient observing and analysis, together with an organized and coherent follow-up strategy, are essential for maximizing the efficacy of planet-validation efforts for K2, TESS, and future large-scale surveys.
|
|
| 4. |
- Niazmand Bilandi, Rasul, et al.
(author)
-
Comparative study of experimental and CFD results for stepped planing hulls
- 2023
-
In: Ocean Engineering. - : Elsevier BV. - 0029-8018 .- 1873-5258. ; 280, s. 114887-114887
-
Journal article (peer-reviewed)abstract
- In recent years, research has been conducted on reducing resistance by adding steps on the bottom of high-speedcraft. The most significant issue in the design of multi-stepped planing craft is the selection of an appropriate stepconfiguration, i.e., step geometry, location, and height. This requires a general knowledge of the hydrodynamicbehavior of each step configuration. Although the towing tank test is an effective method to predict accuratelythe hydrodynamic behavior of stepped planing boats, there are restrictions in studying some details. In this study,a Computational Fluid Dynamic (CFD) method is used to investigate the hydrodynamic behavior of a steppedplaning hull with eight different step configurations in detail. Comparison of the results of trim angle, resistance,sinkage, wetted surface, and ventilation length of swept-stepped planing hulls for different step configurations atvarious Froude numbers shows that a maximum average resistance reduction occurs at 1.9 < FrB < 4.0 with thestep height of 2.73% BTC located at 48.46% L from the transom. There is also a lower resistance associated with astep height of 0.91% BTC at 48.35% L distance from the transom at FrB > 4. These results can be used to improvehigh-speed planing hull performances by utilizing an appropriate step configuration.
|
|
| 5. |
- Powell, Diana, et al.
(author)
-
Sulfur dioxide in the mid-infrared transmission spectrum of WASP-39b
- 2024
-
In: Nature. - 0028-0836 .- 1476-4687. ; 626:8001, s. 979-983
-
Journal article (peer-reviewed)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.
|
|
| 6. |
- Southworth, John, et al.
(author)
-
Detection of the Atmosphere of the 1.6 M-circle plus Exoplanet GJ 1132 b
- 2017
-
In: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 153:4
-
Journal article (peer-reviewed)abstract
- Detecting the atmospheres of low-mass, low-temperature exoplanets is a high-priority goal on the path to ultimately detecting biosignatures in the atmospheres of habitable exoplanets. High-precision HST observations of several super-Earths with equilibrium temperatures below 1000 K have to date all resulted in featureless transmission spectra, which have been suggested to be due to high-altitude clouds. We report the detection of an atmospheric feature in the atmosphere of a 1.6 M-circle plus transiting exoplanet, GJ 1132 b, with an equilibrium temperature of similar to 600 K and orbiting a nearby M dwarf. We present observations of nine transits of the planet obtained simultaneously in the griz and JHK passbands. We find an average radius of 1.43 +/- 0.16 R-circle plus for the planet, averaged over all the passbands, and a radius of 0.255 +/- 0.023 R-circle dot for the star, both of which are significantly greater than previously found. The planet radius can be decomposed into a surface radius at similar to 1.375 R-circle plus overlaid by atmospheric features that increase the observed radius in the z and K bands. The z-band radius is 4 sigma higher than the continuum, suggesting a strong detection of an atmosphere. We deploy a suite of tests to verify the reliability of the transmission spectrum, which are greatly helped by the existence of repeat observations. The large z-band transit depth indicates strong opacity from H2O and/or CH4 or a hitherto-unconsidered opacity. A surface radius of 1.375 +/- 0.16 R-circle plus allows for a wide range of interior compositions ranging from a nearly Earth-like rocky interior, with similar to 70% silicate and similar to 30% Fe, to a substantially H2O-rich water world.
|
|
| 7. |
- Vitiello, Luigi, et al.
(author)
-
A comprehensive stepped planing hull systematic series : Part 1-Resistance test
- 2022
-
In: Ocean Engineering. - : Elsevier BV. - 0029-8018 .- 1873-5258. ; 266, s. 112242-
-
Journal article (peer-reviewed)abstract
- This work addresses the experimental study of a new systematic series of stepped planing hulls. Indeed, the interest in the stepped planing hulls is constantly growing, both in the industrial/commercial and academic fields. Designers and boat builders have been orienting toward the multi-stepped hulls solution to ensure good dynamic stability, reliable seakeeping and operability at high speeds. However, there is a lack of a compre-hensive stepped hull systematic series with various step configurations including a forward V-shaped step, as typically used on modern boats. For the abovementioned reasons, a systematic series of eight different models of stepped hulls have been developed and tested. The towing tank tests have been carried out at the naval basin of the Universit`a degli Studi di Napoli "Federico II" Dipartimento di Ingegneria Industriale (DII) in calm water at different speeds (Fr backward difference = 1.077-6.774) and for three different static trim conditions. All models are built with a transparent bottom to visualize the wetted surface and the eventual development of vortices generated behind the step. The eight models are defined by modifying three significant design parameters for stepped hulls (i.e. the number of steps, longitudinal step position, and step height).
|
|
