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Wind shear and turbulence on Titan: Huygens analysis
Lorenz, Ralph D.
Wind shear measured by Doppler tracking of the Huygens probe is evaluated, and found to be within the range anticipated by pre-flight assessments (namely less than two times the Brunt-Väisälä frequency). The strongest large-scale shear encountered was ∼5 m/s/km, a level associated with 'Light' turbulence in terrestrial aviation. Near-surface winds…
Schumann resonances at Mars: Effects of the day-night asymmetry and the dust-loaded ionosphere
Montmessin, F.; Toledo-Redondo, S.; Molina-Cuberos, G. J. +6 more
Schumann resonances are standing waves that oscillate in the electromagnetic cavity formed between the conducting lower ionosphere and the surface of the planet. They have been measured in situ only on Earth and Titan, although they are believed to exist on other planets like Mars. We report numerical simulations of the Martian electromagnetic cav…
AGNs with discordant optical and X-ray classification are not a physical family: diverse origin in two AGNs
Barcons, X.; Carrera, F. J.; Braito, V. +7 more
Approximately 3-17 per cent of active galactic nuclei (AGNs) without detected rest-frame UV/optical broad emission lines (type-2 AGN) do not show absorption in X-rays. The physical origin behind the apparently discordant optical/X-ray properties is not fully understood. Our study aims at providing insight into this issue by conducting a detailed a…
AKARI near-infrared background fluctuations arise from normal galaxy populations
Komatsu, E.; Helgason, K.
We show that measurements of the fluctuations in the near-infrared background (NIRB) from the AKARI satellite can be explained by faint galaxy populations at low redshifts. We demonstrate this using reconstructed images from deep galaxy catalogues (Hawk-I UDS/GOODS Survey and S-Cosmic Assembly Deep Near-Infrared Extragalactic Legacy Survey) and tw…
The Short-term Stability of a Simulated Differential Astrometric Reference Frame in the Gaia Era
Sozzetti, Alessandro; Abbas, Ummi; Bucciarelli, Beatrice +5 more
We use methods of differential astrometry to construct a small field inertial reference frame stable at the micro-arcsecond level. Such a high level of astrometric precision can be expected with the end-of-mission standard errors to be achieved with the Gaia space satellite using global astrometry. We harness Gaia measurements of field angles and …
Heights of Coronal Mass Ejections and Shocks Inferred from Metric and DH Type II Radio Bursts
Shanmugaraju, A.; Suresh, K.; Lee, Jae-Ok +2 more
A set of 27 continuous events that showed extension of metric Type-II radio bursts (m-Type IIs) into the deca-hectometric (DH) domain is considered. The coronal mass ejections (CMEs) associated with this type of continuous event supply more energy to produce space-weather effects than the CMEs that produce Type-II bursts in any one region. Since t…
Rosetta Mission: Electron Scattering Cross Sections—Data Needs and Coverage in BEAMDB Database
Mason, Nigel J.; Jevremović, Darko; Bredehöft, Jan Hendrik +2 more
The emission of [O I] lines in the coma of Comet 67P/Churyumov-Gerasimenko during the Rosetta mission have been explained by electron impact dissociation of water rather than the process of photodissociation. This is the direct evidence for the role of electron induced processing has been seen on such a body. Analysis of other emission features is…
Galactic Latitude Dependence of Near-infrared Diffuse Galactic Light: Thermal Emission or Scattered Light?
Matsuura, S.; Sano, K.
Near-infrared (IR) diffuse Galactic light (DGL) consists of scattered light and thermal emission from interstellar dust grains illuminated by the interstellar radiation field (ISRF). At 1.25 and 2.2 µ {{m}}, a recent observational study shows that intensity ratios of the DGL to interstellar 100 µ {{m}} dust emission steeply decrease to…
DDO 161 and UGCA 319: an isolated pair of nearby dwarf galaxies
Rizzi, L.; Karachentsev, I. D.; Makarova, L. N. +3 more
We report Hubble Space Telescope/Advanced Camera for Surveys observations of two nearby gas-rich dwarf galaxies: DDO 161 and UGCA 319. Their distances determined via the tip of the red giant branch are 6.03_{-0.21}^{+0.29} and 5.75 ± 0.18 Mpc, respectively. The galaxies form an isolated pair dynamically well separated from the nearest neighbours: …
Do water fountain jets really indicate the onset of the morphological metamorphosis of circumstellar envelopes?
Hsia, Chih-Hao; Yung, Bosco H. K.; Nakashima, Jun-ichi +1 more
Small-scale bipolar jets with short dynamical ages from 'water-fountain' (WF) sources are regarded as an indication of the onset of circumstellar envelope morphological metamorphosis of intermediate-mass stars. Such a process usually happens at the end of the asymptotic giant branch (AGB) phase. However, recent studies found that WFs could be AGB …