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Garcia-Melendo E.,Fundacio Privada Observatori Esteve Duran | Arregi J.,University of the Basque Country | Rojas J.F.,University of the Basque Country | Hueso R.,University of the Basque Country | And 5 more authors.
Icarus | Year: 2011

We present a study of the equatorial region of Jupiter, between latitudes ∼15°S and ∼15°N, based on Cassini ISS images obtained during the Jupiter flyby at the end of 2000, and HST images acquired in May and July 2008. We examine the structure of the zonal wind profile and report the detection of significant longitudinal variations in the intensity of the 6°N eastward jet, up to 60ms-1 in Cassini and HST observations. These longitudinal variations are, in the HST case, associated with different cloud morphology. Photometric and radiative transfer analysis of the cloud features used as tracers in HST images show that at most there is only a small height difference, no larger than ∼0.5-1 scale heights, between the slow (∼100ms-1) and fast (∼150ms-1) moving features. This suggests that speed variability at 6°N is not dominated by vertical wind shears but instead we propose that Rossby wave activity is the responsible for the zonal variability. Removing this variability, we find that Jupiter's equatorial jet is actually symmetric relative to equator with two peaks of ∼140-150ms-1 located at latitudes 6°N and 6°S and at a similar pressure level. We also study the local dynamics of particular equatorial features such as several dark projections associated with 5μm hot spots and a large, long-lived feature called the White Spot (WS) located at 6°S. Convergent flow at the dark projections appears to be a characteristic which depends on the particular morphology and has only been detected in some cases. The internal flow field in the White Spot indicates that it is a weakly rotating quasi-equatorial anticyclone relative to the ambient meridionally sheared flow. © 2010 Elsevier Inc. Source


Garcia-Melendo E.,Fundacio Privada Observatori Esteve Duran | Garcia-Melendo E.,Institute Of Ciencies Of Lespai | Lopez-Morales M.,Institute Of Ciencies Of Lespai | Lopez-Morales M.,Carnegie Institution of Washington
Monthly Notices of the Royal Astronomical Society: Letters | Year: 2011

The transit timing variations (TTVs) technique provides a powerful tool to detect additional planets in transiting exoplanetary systems. In this Letter, we show how transiting planets with significant TTVs can be systematically missed, or catalogued as false positives, by current transit search algorithms, unless they are in multitransit systems. If the period of the TTVs, PTTV, is longer than the time baseline of the observations and its amplitude, ATTV, is larger than the timing precision limit of the data, transiting planet candidates are still detected, but with incorrect ephemerides. Therefore, they will be discarded during follow-up. When PTTV is shorter than the time baseline of the observations and ATTV is sufficiently large, constant period search algorithms find an average period for the system, which results in altered transit durations and depths in the folded light curves. Those candidates can get subsequently discarded as eclipsing binaries, grazing eclipses or blends. Also, for large enough ATTV values, the transits can get fully occulted by the photometric dispersion of the light curves. These detection biases could explain the observed statistical differences between the frequency of multiple systems among planets detected via other techniques and those detected via transits. We suggest that new transit search algorithms allowing for non-constant period planets should be implemented. © 2011 The Authors. Monthly Notices of the Royal Astronomical Society © 2011 RAS. Source


Mousis O.,University of Franche Comte | Hueso R.,University of the Basque Country | Beaulieu J.-P.,French National Center for Scientific Research | Bouley S.,University Paris - Sud | And 58 more authors.
Experimental Astronomy | Year: 2014

Amateur contributions to professional publications have increased exponentially over the last decades in the field of planetary astronomy. Here we review the different domains of the field in which collaborations between professional and amateur astronomers are effective and regularly lead to scientific publications.We discuss the instruments, detectors, software and methodologies typically used by amateur astronomers to collect the scientific data in the different domains of interest. Amateur contributions to the monitoring of planets and interplanetary matter, characterization of asteroids and comets, as well as the determination of the physical properties of Kuiper Belt Objects and exoplanets are discussed. © 2014, Springer Science+Business Media Dordrecht. Source


Wade G.A.,Royal Military College of Canada | Apellaniz J.M.,Institute Astrofisica Of Andalucia Csic | Martins F.,Montpellier University | Petit V.,West Chester University | And 15 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

This paper presents a first observational investigation of the faint Of?p star NGC1624-2, yielding important new constraints on its spectral and physical characteristics, rotation, magnetic field strength, X-ray emission and magnetospheric properties. Modelling the spectrum and spectral energy distribution, we conclude that NGC1624-2 is a main-sequence star of mass M ≃ 30M ⊙, and infer an effective temperature of 35 ± 2 kK and logg = 4.0 ± 0.2. Based on an extensive time series of optical spectral observations we report significant variability of a large number of spectral lines, and infer a unique period of 157.99 ± 0.94d which we interpret as the rotational period of the star. We report the detection of a very strong (5.35 ± 0.5 kG) longitudinal magnetic field 〈B z〉, coupled with probable Zeeman splitting of the Stokes I profiles of metal lines confirming a surface field modulus 〈B〉 of 14 ± 1 kG, consistent with a surface dipole of polar strength ≳20 kG. This is the largest magnetic field ever detected in an O-type star, and the first report of Zeeman splitting of Stokes I profiles in such an object. We also report the detection of reversed Stokes V profiles associated with weak, high-excitation emission lines of Oiii, which we propose may form in the close magnetosphere of the star. We analyse archival Chandra ACIS-I X-ray data, inferring a very hard spectrum with an X-ray efficiency of logL x/L bol = -6.4, a factor of 4 larger than the canonical value for O-type stars and comparable to that of the young magnetic O-type star θ 1OriC and other Of?p stars. Finally, we examine the probable magnetospheric properties of the star, reporting in particular very strong magnetic confinement of the stellar wind, with η * ≃ 1.5 × 10 4, and a very large Alfvén radius, R Alf = 11.4 R *. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS. Source


Garcia-Melendo E.,Fundacio Privada Observatori Esteve Duran | Garcia-Melendo E.,Institute Of Ciencies Of Lespai Csic Ieec | Perez-Hoyos S.,University of the Basque Country | Sanchez-Lavega A.,University of the Basque Country | Hueso R.,University of the Basque Country
Icarus | Year: 2011

Five years of Cassini Imaging Science Subsystem images, from 2004 to 2009, are analyzed in this work to retrieve global zonal wind profiles of Saturn's northern and southern hemispheres in the methane absorbing bands at 890 and 727. nm and in their respective adjacent continuum wavelengths of 939 and 752. nm. A complete view of Saturn's global circulation, including the equator, at two pressure levels, in the tropopause (60. mbar to 250. mbar with the MT filters) and in the upper troposphere (from ~350. mbar to ~500. mbar with the CB filter set), is presented. Both zonal wind profiles (available at the Supplementary Material Section), show the same structure but with significant differences in the peak of the eastward jets and the equatorial region, including a region of positive vertical shear symmetrically located around the equator between the 10° < c < 25° where zonal velocities close to the tropopause are higher than at 500. mbar. A comparison of previously published zonal wind sets obtained by Voyager 1 and 2 (1980-1981), Hubble Space Telescope, and ground-based telescopes (1990-2004) with the present Cassini profiles (2004-2009) covering a full Saturn year shows that the shape of the zonal wind profile and intensity of the jets has remained almost unchanged except at the equator, despite the seasonal insolation cycle and the variability of Saturn's emitted power. The major wind changes occurred at equatorial latitudes, perhaps following the Great White Spot eruption in 1990. It is not evident from our study if the seasonal insolation cycle and its associated ring shadowing influence the equatorial circulation at cloud level. © 2011 Elsevier Inc. Source

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