Earth and Planetary Astrophysics Publications (50)

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Earth and Planetary Astrophysics Publications

In the outer Solar system, primordial Trojan asteroids may have remained dynamically stable for billions of years. Several thousands of them accompany Jupiter in its journey around the Sun and a similarly large population may be hosted by Neptune. In addition, recently captured or transient Jovian and Neptunian Trojans are not uncommon. Read More


In fluid dynamical simulations in astrophysics, large deformations are common and surface tracking is sometimes necessary. Smoothed Particle Hydrodynamics (SPH) method has been used in many of such simulations. Recently, however, it has been shown that SPH cannot handle contact discontinuities or free surfaces accurately. Read More


The cyclic behaviour of (O-C) residuals of eclipse timings in the sdB+M eclipsing binary NSVS 14256825 was previously attributed to one or two Jovian-type circumbinary planets. We report 83 new eclipse timings that not only fill in the gaps in those already published but also extend the time span of the (O-C) diagram by three years. Based on the archival and our new data spanning over more than 17 years we re-examined the up to date system (O-C). Read More


A habitable exoplanet is a world that can maintain stable liquid water on its surface. Techniques and approaches to characterizing such worlds are essential, as performing a census of Earth-like planets that may or may not have life will inform our understanding of how frequently life originates and is sustained on worlds other than our own. Observational techniques like high contrast imaging and transit spectroscopy can reveal key indicators of habitability for exoplanets. Read More


We analyze an ensemble of microlensing events from the 2015 Spitzer microlensing campaign, all of which were densely monitored by ground-based high-cadence survey teams. The simultaneous observations from Spitzer and the ground yield measurements of the microlensing parallax vector $\pi_{\rm E}$, from which compact constraints on the microlens properties are derived, including $\lesssim$25\% uncertainties on the lens mass and distance. With the current sample, we demonstrate that the majority of microlenses are indeed in the mass range of M dwarfs. Read More


This chapter summarizes our current understanding of the ionosphere of Saturn. We give an overview of Saturn ionospheric science from the Voyager era to the present, with a focus on the wealth of new data and discoveries enabled by Cassini, including a massive increase in the number of electron density altitude profiles. We discuss recent ground-based detection of the effect of "ring rain" on Saturn's ionosphere, and present possible model interpretations of the observations. Read More


MESSENGER magnetometer data show that Mercury's magnetic field is not only exceptionally weak but also has a unique geometry. The internal field resembles an axial dipole that is offset to the North by 20% of the planetary radius. This implies that the axial quadrupol is particularly strong while the dipole tilt is likely below 0. Read More


Observational evidence exists for the formation of gas giant planets on wide orbits around young stars by disk gravitational instability, but the roles of disk instability and core accretion for forming gas giants on shorter period orbits are less clear. The controversy extends to population synthesis models of exoplanet demographics and to hydrodynamical models of the fragmentation process. The latter refers largely to the handling of radiative transfer in three dimensional (3D) hydrodynamical models, which controls heating and cooling processes in gravitationally unstable disks, and hence dense clump formation. Read More


The distance to the planetary system OGLE-2015-BLG-0966L and the separation between the planet and its host star are ambiguous due to an ambiguity in the distance to the source star (Street et al. 2016). We attempt to break this degeneracy by measuring the systemic radial velocity of the source star measured from a spectrum taken while the source was highly magnified. Read More


We perform the first statistical study of the effects of the interaction of suprathermal electrons with narrow-band whistler mode waves in the solar wind. We show that this interaction does occur and that it is associated with enhanced widths of the so called strahl component. The latter is directed along the inter- planetary magnetic field away from the Sun. Read More


Grid-based hydrodynamics simulations of circumstellar disks are often performed in the curvilinear coordinate system, in which the center of the computational domain coincides with the motionless star. However, the center of mass may be shifted from the star due to the presence of any non-axisymmetric mass distribution. As a result, the system exerts a gravity force on the star, causing the star to move in response, which can affect the evolution of the circumstellar disk. Read More


Since the discovery of a planet transiting its host star in the year 2000, thousands of additional exoplanets and exoplanet candidates have been detected, mostly by NASA's Kepler space telescope. Some of them are almost as small as the Earth's moon. As the solar system is teeming with moons, more than a hundred of which are in orbit around the eight local planets, and with all of the local giant planets showing complex ring systems, astronomers have naturally started to search for moons and rings around exoplanets in the past few years. Read More


Small moons (moonlets) embedded in the rings of Saturn cause S-shaped density structures in their close vicinity called propellers. These structures have been predicted by Spahn and Sremcevic (2000) and Sremcevic et al. (2002). Read More


We report new global ideal MHD simulations for thin accretion disks threaded by net vertical magnetic fields. Our computations span three orders of magnitude in radius, extend all the way to the pole, and are evolved for more than one viscous time over the inner decade in radius. Static mesh refinement is used to properly resolve MRI. Read More


Basaltic asteroids (V-types) are believed to be fragments of large differentiated bodies. The majority of them are found in the inner part of the asteroid belt, and are current or past members of the Vesta family. Recently, some V-type asteroids have been discovered far from the Vesta family supporting the hypothesis of the presence of multiple basaltic asteroids in the early solar system. Read More


ImageJ is a graphical user interface (GUI) driven, public domain, Java-based, software package for general image processing traditionally used mainly in life sciences fields. The image processing capabilities of ImageJ are useful and extendable to other scientific fields. Here we present AstroImageJ (AIJ), which provides an astronomy specific image display environment and tools for astronomy specific image calibration and data reduction. Read More


The validity of the anelastic approximation has recently been questioned in the regime of rapidly-rotating compressible convection in low Prandtl number fluids (Calkins et al. 2015). Given the broad usage and the high computational efficiency of sound-proof approaches in this astrophysically relevant regime, this paper clarifies the conditions for a safe application. Read More


Searches for stellar companions to hot Jupiters (HJs) have revealed that planetary systems hosting a HJ are approximately three times more likely to have a stellar companion with a semimajor axis between 50 and 2000 AU, compared to field stars. This correlation suggests that HJ formation is affected by the stellar binary companion. A potential model is high-eccentricity migration, in which the binary companion induces high-eccentricity Lidov-Kozai (LK) oscillations in the proto-HJ orbit, triggering orbital migration driven by tides. Read More


Observationally measuring the location of the H$_{2}$O snowline is crucial for understanding the planetesimal and planet formation processes, and the origin of water on Earth. In disks around Herbig Ae stars ($T_{\mathrm{*}}\sim$ 10,000K, $M_{\mathrm{*}}\gtrsim$ 2.5$M_{\bigodot}$), the position of the H$_{2}$O snowline is further from the central star compared with that around cooler, and less massive T Tauri stars. Read More


This chapter explores the physics shared by planetary rings and the various disks that populate the Universe. It begins with an observational overview, ranging from protoplanetary disks to spiral galaxies, and then compares and contrasts these astrophysical disks with the rings of the Solar System. Emphasis is placed on fundamental physics and dynamics, and how research into the two classes of object connects. Read More


The reconstruction of the orbital evolution of the propeller structure Bl\'eriot orbiting in Saturn's A ring from recurrent observations in Cassini ISS images yielded a considerable offset motion from the expected Keplerian orbit (Tiscareno et al., 2010). This offset motion can be composed by three sinusoidal harmonics with amplitudes and periods of 1845, 152, 58 km and 11. Read More


We use a laboratory facility to study the sputtering properties of centimeter-thick porous water ice subjected to the bombardment of ions and electrons to better understand the formation of exospheres of the icy moons of Jupiter. Our ice samples are as similar as possible to the expected moon surfaces but surface charging of the samples during ion irradiation may distort the experimental results. We therefore monitor the time scales for charging and dis- charging of the samples when subjected to a beam of ions. Read More


Over two decades of exoplanetology have yielded thousands of discoveries, yet some types of systems are yet to be observed. Circumstellar planets around one star in a binary have been found, but not for tight binaries (< 5 AU). Additionally, extra-solar moons are yet to be found. Read More


We apply Monte Carlo projection to the radial velocity data set that Anglada Escude et al. (2016) use for the discovery of Proxima b. They find an upper limit to the orbital eccentricity of 0. Read More


We analyze the process of planetary scattering around M0-type stars. To do this, we carry out N-body simulations with three Jupiter-mass planets close to their instability limit together with an outer planetesimal disk. This paper focuses on the analysis of systems in which a single Jupiter-mass planet survives after the dynamical instability event. Read More


The masses, atmospheric makeups, spin-orbit alignments, and system architectures of extrasolar planets can be best studied when the planets orbit bright stars. We report the discovery of three bodies orbiting HD 106315, a bright (V = 8.97 mag) F5 dwarf targeted by our K2 survey for transiting exoplanets. Read More


Magnetic fields play an important role in the dynamics of accretion disks, however, the origin of the fields is often obscured. Here we show that magnetic fields can be generated in an initially non-magnetized accretion disks through the Biermann battery mechanism, where the radial temperature profile and the vertical density profile of these systems provide the necessarily conditions for this process to operate naturally. We consider the generation of fields in a protoplanetary disks and disks around Black Holes (BHs). Read More


The secular approximation of the hierarchical three body systems has been proven to be very useful in addressing many astrophysical systems, from planets, stars to black holes. In such a system two objects are on a tight orbit, and the tertiary is on a much wider orbit. Here we study the dynamics of a system by taking the tertiary mass to zero and solve the hierarchical three body system up to the octupole level of approximation. Read More


Two primitive near Earth asteroids, (101955) Bennu and (162173) Ryugu, will be visited by a spacecraft with the aim of returning samples back to Earth. Since these objects are believed to originate in the inner main belt primitive collisional families (Erigone, Polana, Clarissa, and Sulamitis) or in the background of asteroids outside these families, the characterization of these primitive populations will enhance the scientific return of the missions. The main goal of this work is to shed light on the composition of the Erigone collisional family by means of visible spectroscopy. Read More


The NASA TESS mission will deliver hundreds of transiting exoplanet candidates orbiting bright stars. The spectrometers SOPHIE at OHP and SPIRou at CFHT will be ideal to obtain radial velocities of these candidates, confirm their nature, and derive the planets' masses. These measurements will be crucial to deliver the best targets for atmospheric characterization with JWST. Read More


The distributions of size and chemical composition in the regolith on airless bodies provides clues to the evolution of the solar system. Recently, the regolith on asteroid (25143) Itokawa, visited by the JAXA Hayabusa spacecraft, was observed to contain millimeter to centimeter sized particles. Itokawa boulders commonly display well-rounded profiles and surface textures that appear inconsistent with mechanical fragmentation during meteorite impact; the rounded profiles have been hypothesized to arise from rolling and movement on the surface as a consequence of seismic shaking. Read More


We observed Jupiter at wavelengths near 2 cm with the Karl G. Jansky Very Large Array in February 2015. These frequencies are mostly sensitive to variations in ammonia abundance and probe between ~0. Read More


In this article, it is argued that several habitability conditions (in fact, at least seven such conditions) appear to be fulfilled automatically on the circumbinary planets of main-sequence stars (CBP-MS), whereas on the Earth these conditions are fulfilled only by chance. Therefore, it looks natural that most of the production of replicating biopolymers in the Galaxy is concentrated on CBP-MS of particular classes, and life on Earth is an outlier, in this sense. In this scenario, Lathe's (2004) mechanism for the PCR-kind (polymerase chain reaction) tidal abiogenesis on the Earth is favoured as generic for CBP-MS. Read More


We present a semi-analytical correction to the seminal solution for the secular motion of a planet's orbit under gravitational influence of an external perturber derived by Heppenheimer (1978). A comparison between analytical predictions and numerical simulations allows us to determine corrective factors for the secular frequency and forced eccentricity in the co-planar restricted three-body problem. The correction is given in the form of a polynomial function of the system's parameters that can be applied to first-order forced eccentricity and secular frequency estimates. Read More


We have obtained new images of the protoplanetary disk orbiting TW Hya in visible, total intensity light with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST), using the newly commissioned BAR5 occulter. These HST/STIS observations achieved an inner working angle $\sim$0.2\arcsec, or 11. Read More


The model of a protoplanetary disk of a star with a low-mass companion ($M_2:M_1 \le 0.1$), moving on a circular orbit, which slightly inclined to the disk plane ($\le 10^{\circ}$), is considered. The SPH-method is used to calculate gas-dynamic ows. Read More


Many topics in planetary studies demand an estimate of the collision probability of two objects moving on nearly Keplerian orbits. In the classic works of \"Opik (1951) and Wetherill (1967), the collision probability was derived by linearizing the motion near the collision points, and there is now a vast literature using their method. We present here a simpler and more physically motivated derivation for non-tangential collisions in Keplerian orbits, as well as for tangential collisions that were not previously considered. Read More


In this work, we extensively investigate the formation of near 4:2:1 mean motion resonances (MMRs) configuration by performing two sets of N-body simulations. We model the eccentricity damping, gas drag, type I and type II planetary migration of planetesimals, planetary embryos and giant planets in the first sets. For the simulations of giant planets with type II migration, the massive terrestrial planets, with a mass up to several Earth masses, are likely produced in the systems. Read More


Growing observations of brown dwarfs have provided evidence for strong atmospheric circulation on these objects. Directly imaged planets share similar observations, and can be viewed as low-gravity versions of brown dwarfs. Vigorous condensate cycles of chemical species in their atmospheres are inferred by observations and theoretical studies, and latent heating associated with condensation is expected to be important in shaping atmospheric circulation and influencing cloud patchiness. Read More


The Asteroid Belt is characterized by the radial mixing of bodies with different physical properties, a very low mass compared to Minimum Mass Solar Nebula expectations and has an excited orbital distribution. Models of the evolution of the Asteroid Belt show that the origin of its structure is strongly linked to the process of terrestrial planet formation. The Grand Tack model presents a possible solution to the conundrum of reconciling the small mass of Mars with the properties of the Asteroid Belt, including the mass depletion, radial mixing and orbital excitation. Read More


2017Jan
Affiliations: 1National Research Nuclear University MEPhI, 2INFN, Sezione di Florence and Physics Department of University of Florence, 3INFN, Sezione di Naples and Physics Department of University of Naples Federico II, 4Lebedev Physical Institute, 5INFN, Sezione di Bari Physics and Department of University of Bari, 6INFN, Sezione di Trieste, 7Ioffe Physical Technical Institute, 8INFN, Sezione di Florence and Physics Department of University of Florence, 9INFN, Sezione di Trieste, 10INFN, Sezione di Florence and Physics Department of University of Florence, 11INFN, Sezione di Bari Physics and Department of University of Bari, 12INFN, Sezione di Bari Physics and Department of University of Bari, 13INFN, Sezione di Naples and Physics Department of University of Naples Federico II, 14KTH, Department of Physics, and The Oskar Klein Centre for Cosmoparticle Physics, 15INFN, Sezione di Rome "Tor Vergata", 16INFN, IFAC, 17INFN, Sezione di Rome "Tor Vergata", 18INFN, Sezione di Rome "Tor Vergata", 19INFN, Sezione di Rome "Tor Vergata", 20INFN, Sezione di Rome "Tor Vergata", 21National Research Nuclear University MEPhI, 22National Research Nuclear University MEPhI, 23National Research Nuclear University MEPhI, 24National Research Nuclear University MEPhI, 25Ioffe Physical Technical Institute, 26Lebedev Physical Institute, 27National Research Nuclear University MEPhI, 28National Research Nuclear University MEPhI, 29National Research Nuclear University MEPhI, 30INFN, Sezione di Rome "Tor Vergata", 31INFN, Sezione di Rome "Tor Vergata", 32National Research Nuclear University MEPhI, 33Universität Siegen, Department of Physics, 34INFN, Sezione di Rome "Tor Vergata", 35INFN, Sezione di Trieste, 36INFN, Sezione di Bari Physics and Department of University of Bari, 37INFN, IFAC, 38INFN, Sezione di Trieste, 39INFN, Sezione di Naples and Physics Department of University of Naples Federico II, 40INFN, Sezione di Florence and Physics Department of University of Florence, 41INFN, Sezione di Rome "Tor Vergata", 42INFN, Sezione di Naples and Physics Department of University of Naples Federico II, 43KTH, Department of Physics, and The Oskar Klein Centre for Cosmoparticle Physics, 44INFN, Sezione di Rome "Tor Vergata", 45INFN, Laboratori Nazionali di Frascati, 46INFN, Sezione di Florence and Physics Department of University of Florence, 47National Research Nuclear University MEPhI, 48Universität Siegen, Department of Physics, 49INFN, Sezione di Rome "Tor Vergata", 50National Research Nuclear University MEPhI, 51Lebedev Physical Institute, 52INFN, Sezione di Trieste, 53INFN, Sezione di Florence and Physics Department of University of Florence, 54Ioffe Physical Technical Institute, 55National Research Nuclear University MEPhI, 56National Research Nuclear University MEPhI, 57INFN, Sezione di Trieste, 58INFN, Sezione di Trieste

We present a measurements of electron and positron fluxes below the geomagnetic cutoff rigidity in wide energy range from 50 MeV to several GeV by the PAMELA magnetic spectrometer. The instrument was launched on June 15th 2006 on-board the Resurs-DK satellite on low orbit with 70 degrees inclination and altitude between 350 and 600 km. The procedure of trajectories calculations in the geomagnetic field separates stably trapped and albedo components produced in interactions of cosmic ray protons with the residual atmosphere from galactic cosmic rays. Read More


2017Jan
Affiliations: 1Universität Bern, 2Max-Planck-Institut für Astronomie, Heidelberg, 3Eberhard Karls Universität, Tübingen, 4Universität Bern

The key aspect determining the post-formation luminosity of gas giants has long been considered to be the energetics of the accretion shock at the planetary surface. We use 1D radiation-hydrodynamical simulations to study the radiative loss efficiency and to obtain post-shock temperatures and pressures and thus entropies. The efficiency is defined as the fraction of the total incoming energy flux which escapes the system (roughly the Hill sphere), taking into account the energy recycling which occurs ahead of the shock in a radiative precursor. Read More


The asteroid (16) Psyche is of scientific interest because it contains ~ 1% of the total mass of the asteroid belt and is thought to be the remnant metallic core of a protoplanet. Radar observations have indicated the significant presence of metal on the surface with a small percentage of silicates. Prior ground-based observations showed rotational variations in the near-infrared (NIR) spectra and radar albedo of this asteroid. Read More


We present results from a Near Infrared multi-epoch spectroscopic campaign to detect a young low-mass companion to a T Tauri star. AS 205A is a late-type dwarf (~K5) of ~1 Msun that belongs to a triple system. Independent photometric surveys discovered that AS 205A has two distinct periods (P1=6. Read More


The formation of satellites is thought to be a natural by-product of planet formation in our Solar System, and thus, moons of extrasolar planets (exomoons) may be abundant in extrasolar planetary systems, as well. Exomoons have yet to be discovered. However, moons larger than 0. Read More


In recent years an increasing number of observational studies have hinted at the presence of warps in protoplanetary discs, however a general comprehensive description of observational diagnostics of warped discs was missing. We performed a series of 3D SPH hydrodynamic simulations and combined them with 3D radiative transfer calculations to study the observability of warps in circumbinary discs, whose plane is misaligned with respect to the orbital plane of the central binary. Our numerical hydrodynamic simulations confirm previous analytical results on the dependence of the warp structure on the viscosity and the initial misalignment between the binary and the disc. Read More