We present the analysis of TESS optical photometry of WASP-121b, which reveals the phase curve of this transiting ultra-hot Jupiter. Its hotspot is located at the sub-stellar point, showing ...inefficient heat transport from the dayside (2870 ± 50 K) to the nightside (<2500 K at 3
σ
) at the altitudes probed by TESS. The TESS eclipse depth, measured at the shortest wavelength to date for WASP-121b, confirms the strong deviation from blackbody planetary emission. Our atmospheric retrieval on the complete emission spectrum supports the presence of a temperature inversion, which can be explained by the presence of VO and possibly TiO and FeH. The strong planetary emission at short wavelengths could arise from an H
−
continuum.
We describe an analytical method for computing the orbital parameters of a planet from the periodogram of a radial velocity signal. The method is very efficient and provides a good approximation of ...the orbital parameters. The accuracy is mainly limited by the accuracy of the computation of the Fourier decomposition of the signal which is sensitive to sampling and noise. Our method is complementary with more accurate (and more expensive in computer time) numerical algorithms (e.g. Levenberg-Marquardt, Markov chain Monte Carlo, genetic algorithms). Indeed, the analytical approximation can be used as an initial condition to accelerate the convergence of these numerical methods. Our method can be applied iteratively to search for multiple planets in the same system.
We present the discovery of three new transiting hot Jupiters by the WASP-South project, WASP-161 b, WASP-163 b, and WASP-170 b. Follow-up radial velocities obtained with the Euler/CORALIE ...spectrograph and transit light curves obtained with the TRAPPIST-North, TRAPPIST-South, SPECULOOS-South, NITES, and Euler telescopes have enabled us to determine the masses and radii for these transiting exoplanets. WASP-161 b completes an orbit around its V = 11.1 F6V-type host star in 5.406 days, and has a mass Mp = 2.5 0.2MJup and radius Rp = 1.14 0.06 RJup. WASP-163 b orbits around its host star (spectral type G8V and the magnitude V = 12.5) every 1.609 days, and has a mass of MP = 1.9 0.2 MJup and a radius of Rp = 1.2 0.1 RJup. WASP-170 b has a mass of 1.7 0.2 MJup and a radius of 1.14 0.09 RJup and is on a 2.344 day orbit around a G1V-type star of magnitude V = 12.8. Given their irradiations (∼109 erg s−1 cm−2) and masses, the three new planets' sizes are in good agreement with classical models of irradiated giant planets.
Context. In 2009 we started an intense radial-velocity monitoring of a few nearby, slowly-rotating and quiet solar-type stars within the dedicated HARPS-Upgrade GTO program. Aims: The goal of this ...campaign is to gather very-precise radial-velocity data with high cadence and continuity to detect tiny signatures of very-low-mass stars that are potentially present in the habitable zone of their parent stars. Methods: Ten stars were selected among the most stable stars of the original HARPS high-precision program that are uniformly spread in hour angle, such that three to four of them are observable at any time of the year. For each star we recorded 50 data points spread over the observing season. The data points consist of three nightly observations with a total integration time of 10 min each and are separated by two hours. This is an observational strategy adopted to minimize stellar pulsation and granulation noise. Results: We present the first results of this ambitious program. The radial-velocity data and the orbital parameters of five new and one confirmed low-mass planets around the stars HD 20794, HD 85512, and HD 192310 are reported and discussed, among which is a system of three super-Earths and one that harbors a 3.6 M⊕-planet at the inner edge of the habitable zone. Conclusions: This result already confirms previous indications that low-mass planets seem to be very frequent around solar-type stars and that this may occur with a frequency higher than 30%. Based on observations made with the HARPS instrument on ESO's 3.6 m telescope at the La Silla Observatory in the frame of the HARPS-Upgrade GTO program ID 086.C-0230.Tables 7-9 (RV data) are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/534/A58
Understanding the formation and evolution of giant planets (≥1 MJup) at wide orbital separation (≥5 AU) is one of the goals of direct imaging. Over the past 15 yr, many surveys have placed strong ...constraints on the occurrence rate of wide-orbit giants, mostly based on non-detections, but very few have tried to make a direct link with planet formation theories. In the present work, we combine the results of our previously published VLT/NaCo large program with the results of 12 past imaging surveys to constitute a statistical sample of 199 FGK stars within 100 pc, including three stars with sub-stellar companions. Using Monte Carlo simulations and assuming linear flat distributions for the mass and semi-major axis of planets, we estimate the sub-stellar companion frequency to be within 0.75–5.70% at the 68% confidence level (CL) within 20–300 AU and 0.5–75 MJup, which is compatible with previously published results. We also compare our results with the predictions of state-of-the-art population synthesis models based on the gravitational instability (GI) formation scenario with and without scattering. We estimate that in both the scattered and non-scattered populations, we would be able to detect more than 30% of companions in the 1–75 MJup range (95% CL). With the threesub-stellar detections in our sample, we estimate the fraction of stars that host a planetary system formed by GI to be within 1.0–8.6% (95% CL). We also conclude that even though GI is not common, it predicts a mass distribution of wide-orbit massive companions that is much closer to what is observed than what the core accretion scenario predicts. Finally, we associate the present paper with the release of the Direct Imaging Virtual Archive (DIVA), a public database that aims at gathering the results of past, present, and future direct imaging surveys.
Context. Several competing scenarios for planetary-system formation and evolution seek to explain how hot Jupiters came to be so close to their parent stars. Most planetary parameters evolve with ...time, making it hard to distinguish between models. The obliquity of an orbit with respect to the stellar rotation axis is thought to be more stable than other parameters such as eccentricity. Most planets, to date, appear aligned with the stellar rotation axis; the few misaligned planets so far detected are massive (\textgreater2 M-J). Aims. Our goal is to measure the degree of alignment between planetary orbits and stellar spin axes, to search for potential correlations with eccentricity or other planetary parameters and to measure long term radial velocity variability indicating the presence of other bodies in the system. Methods. For transiting planets, the Rossiter-McLaughlin effect allows the measurement of the sky-projected angle beta between the stellar rotation axis and a planet's orbital axis. Using the HARPS spectrograph, we observed the Rossiter-McLaughlin effect for six transiting hot Jupiters found by the WASP consortium. We combine these with long term radial velocity measurements obtained with CORALIE. We used a combined analysis of photometry and radial velocities, fitting model parameters with the Markov Chain Monte Carlo method. After obtaining beta we attempt to statistically determine the stribution of the real spin-orbit angle psi. Results. We found that three of our targets have beta above 90 degrees: WASP-2b: beta = 153 degrees(+11)(-15), WASP-15b: beta = 139.6 degrees(+5.2)(-4.3) and WASP-17b: beta = 148.5 degrees(+5.1)(-4.2); the other three (WASP-4b, WASP-5b and WASP-18b) have angles compatible with 0 degrees. We find no dependence between the misaligned angle and planet mass nor with any other planetary parameter. All six orbits are close to circular, with only one firm detection of eccentricity e = 0.00848(-0.00095)(+0.00085) in WASP-18b. No long-term radial acceleration was detected for any of the targets. Combining all previous 20 measurements of beta and our six and transforming them into a distribution of psi we find that between about 45 and 85% of hot Jupiters have psi \textgreater 30 degrees. Conclusions. Most hot Jupiters are misaligned, with a large variety of spin-orbit angles. We find observations and predictions using the Kozai mechanism match well. If these observational facts are confirmed in the future, we may then conclude that most hot Jupiters are formed from a dynamical and tidal origin without the necessity to use type I or II migration. At present, standard disc migration cannot explain the observations without invoking at least another additional process.
WASP-43b: the closest-orbiting hot Jupiter Hellier, C.; Anderson, D. R.; Collier Cameron, A. ...
Astronomy and astrophysics (Berlin),
11/2011, Letnik:
535
Journal Article, Web Resource
Recenzirano
Odprti dostop
We report the discovery of WASP-43b, a hot Jupiter transiting a K7V star every 0.81 d. At 0.6-M⊙ the host star has the lowest mass of any star currently known to host a hot Jupiter. It also shows a ...15.6-d rotation period. The planet has a mass of 1.8 MJup, a radius of 0.9 RJup, and with a semi-major axis of only 0.014 AU has the smallest orbital distance of any known hot Jupiter. The discovery of such a planet around a K7V star shows that planets with apparently short remaining lifetimes owing to tidal decay of the orbit are also found around stars with deep convection zones.
The 'hot Jupiters' that abound in lists of known extrasolar planets are thought to have formed far from their host stars, but migrate inwards through interactions with the proto-planetary disk from ...which they were born, or by an alternative mechanism such as planet-planet scattering. The hot Jupiters closest to their parent stars, at orbital distances of only ∼0.02 astronomical units, have strong tidal interactions, and systems such as OGLE-TR-56 have been suggested as tests of tidal dissipation theory. Here we report the discovery of planet WASP-18b with an orbital period of 0.94 days and a mass of ten Jupiter masses (10 MJup), resulting in a tidal interaction an order of magnitude stronger than that of planet OGLE-TR-56b. Under the assumption that the tidal-dissipation parameter Q of the host star is of the order of 106, as measured for Solar System bodies and binary stars and as often applied to extrasolar planets, WASP-18b will be spiralling inwards on a timescale less than a thousandth that of the lifetime of its host star. Therefore either WASP-18 is in a rare, exceptionally short-lived state, or the tidal dissipation in this system (and possibly other hot-Jupiter systems) must be much weaker than in the Solar System.
Little is known about the existence of extrasolar planets around ultracool dwarfs. Furthermore, binary stars with Sun-like primaries and very low-mass binaries composed of ultracool dwarfs show ...differences in the distributions of mass ratio and orbital separation that can be indicative of distinct formation mechanisms. Using FORS2/VLT optical imaging for high precision astrometry we are searching for planets and substellar objects around these dwarfs to investigate their multiplicity properties for very low companion masses. Here we report astrometric measurements with an accuracy of two tenths of a milli-arcsecond over two years that reveal orbital motion of the nearby L1.5 dwarf DENIS-P J082303.1-491201 located at 20.77 ± 0.08 pc caused by an unseen companion that revolves about its host on an eccentric orbit in 246.4 ± 1.4 days. We estimate the L1.5 dwarf to have 7.5 ± 0.7% of the Sun’s mass, which implies a companion mass of 28 ± 2 Jupiter masses. This new system has the lowest mass ratio (0.36 ± 0.02) of known very low-mass binaries with characterised orbits. With this discovery we demonstrate 200 micro-arcsecond astrometry over an arc-minute field and over several years that is sufficient for discovering sub-Jupiter mass planets around ultracool dwarfs. We also show that the achieved parallax accuracy of <0.4% makes it possible to remove distance as a dominant source of uncertainty in the modelling of ultracool dwarfs.
We present the discovery of four new long-period planets within the HARPS high-precision sample: HD 137388b (Msini = 0.22 MJ), HD 204941b (Msini = 0.27 MJ), HD 7199b (Msini = 0.29 MJ), HD 7449b ...(Msini = 1.04 MJ). A long-period companion, probably a second planet, is also found orbiting HD 7449. Planets around HD 137388, HD 204941, and HD 7199 have rather low eccentricities (less than 0.4) relative to the 0.82 eccentricity of HD 7449b. All these planets were discovered even though their hosting stars have clear signs of activity. Solar-like magnetic cycles, characterized by long-term activity variations, can be seen for HD 137388, HD 204941 and HD 7199, whereas the measurements of HD 7449 reveal a short-term activity variation, most probably induced by magnetic features on the stellar surface. We confirm that magnetic cycles induce a long-term radial velocity variation and propose a method to reduce considerably the associated noise. The procedure consists of fitting the activity index and applying the same solution to the radial velocities because a linear correlation between the activity index and the radial velocity is found. Tested on HD 137388, HD 204941, and HD 7199, this correction reduces considerably the stellar noise induced by magnetic cycles and allows us to derive precisely the orbital parameters of planetary companions. Based on observations made with the HARPS instrument on the ESO 3.6-m telescope at La Silla Observatory (Chile), under programme IDs 072.C-0488 and 183.C-0972.Radial velocities (Tables 4-7) are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/535/A55
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