Forming Circumbinary Planets: N-body Simulations of Kepler-34

Observations of circumbinary planets orbiting very close to the central stars have shown that planet formation may occur in a very hostile environment, where the gravitational pull from the binary should be very strong on the primordial protoplanetary disk. Elevated impact velocities and orbit crossings from eccentricity oscillations are the primary contributors towards high energy, potentially destructive collisions that inhibit the growth of aspiring planets. In this work, we conduct high resolution, inter-particle gravity enabled N-body simulations to investigate the feasibility of planetesimal growth in the Kepler-34 system. We improve upon previous work by including planetesimal disk self-gravity and an extensive collision model to accurately handle inter-planetesimal interactions. We find that super-catastrophic erosion events are the dominant mechanism up to and including the orbital radius of Kepler-34(AB)b, making in-situ growth unlikely. It is more plausible that Kepler-34(AB)b migrated from a region beyond 1.5 AU. Based on the conclusions that we have made for Kepler-34 it seems likely that all of the currently known circumbinary planets have also migrated significantly from their formation location with the possible exception of Kepler-47(AB)c.Comment: 6 pages, 5 figures, accepted for publication in ApJ

A Self-Consistent Model of the Circumstellar Debris Created by a Giant Hypervelocity Impact in the HD172555 System

Spectral modeling of the large infrared excess in the Spitzer IRS spectra of HD 172555 suggests that there is more than 10^19 kg of sub-micron dust in the system. Using physical arguments and constraints from observations, we rule out the possibility of the infrared excess being created by a magma ocean planet or a circumplanetary disk or torus. We show that the infrared excess is consistent with a circumstellar debris disk or torus, located at approximately 6 AU, that was created by a planetary scale hypervelocity impact. We find that radiation pressure should remove submicron dust from the debris disk in less than one year. However, the system's mid-infrared photometric flux, dominated by submicron grains, has been stable within 4 percent over the last 27 years, from IRAS (1983) to WISE (2010). Our new spectral modeling work and calculations of the radiation pressure on fine dust in HD 172555 provide a self-consistent explanation for this apparent contradiction. We also explore the unconfirmed claim that 10^47 molecules of SiO vapor are needed to explain an emission feature at 8 um in the Spitzer IRS spectrum of HD 172555. We find that unless there are 10^48 atoms or 0.05 Earth masses of atomic Si and O vapor in the system, SiO vapor should be destroyed by photo-dissociation in less than 0.2 years. We argue that a second plausible explanation for the 8 um feature can be emission from solid SiO, which naturally occurs in submicron silicate "smokes" created by quickly condensing vaporized silicate.Comment: Accepted to the Astrophysical Journa

Study of the microstructure resulting from brazed aluminium materials used in heat exchangers

Re-solidification of AA4343 cladding after brazing as well as the related precipitation in the modified AA3003 core material have been investigated. Analysis of the re-solidified material showed that partial dissolution of the core alloy occurs in both the brazing joints and away of them. Far from the brazing joints, the dissolution is, however, limited and diffusion of silicon from the liquid into the core material leads to solid-state precipitation in the so-called “band of dense precipitates” (BDP). On the contrary, the dissolution is enhanced in the brazing joint to such an extent that no BDP could be observed. The intermetallic phases present in the resolidified areas as well as in the core material have been analyzed and found to be mainly cubic alpha-Al(Mn,Fe)Si. These results were then compared to predictions made with available phase diagram information

Planet formation in Binaries

Spurred by the discovery of numerous exoplanets in multiple systems, binaries have become in recent years one of the main topics in planet formation research. Numerous studies have investigated to what extent the presence of a stellar companion can affect the planet formation process. Such studies have implications that can reach beyond the sole context of binaries, as they allow to test certain aspects of the planet formation scenario by submitting them to extreme environments. We review here the current understanding on this complex problem. We show in particular how each of the different stages of the planet-formation process is affected differently by binary perturbations. We focus especially on the intermediate stage of kilometre-sized planetesimal accretion, which has proven to be the most sensitive to binarity and for which the presence of some exoplanets observed in tight binaries is difficult to explain by in-situ formation following the "standard" planet-formation scenario. Some tentative solutions to this apparent paradox are presented. The last part of our review presents a thorough description of the problem of planet habitability, for which the binary environment creates a complex situation because of the presence of two irradation sources of varying distance.Comment: Review chapter to appear in "Planetary Exploration and Science: Recent Advances and Applications", eds. S. Jin, N. Haghighipour, W.-H. Ip, Springer (v2, numerous typos corrected

Spitzer Evidence for a Late Heavy Bombardment and the Formation of Urelites in {eta}Corvi at Approximately 1 Gyr

We have analyzed Spitzer and NASA/IRTF 2 - 35 micrometer spectra of the warm, ~350 K circumstellar dust around the nearby MS star eta Corvi (F2V, 1.4 plus or minus 0.3 Gyr). The spectra show clear evidence for warm, water- and carbon-rich dust at ~3 AU from the central star, in the system's Terrestrial Habitability Zone. Spectral features due to ultra-primitive cometary material were found, in addition to features due to impact produced silica and high temperature carbonaceous phases. At least 9 x 10(exp 18) kg of 0.1 - 100 micrometer warm dust is present in a collisional equilibrium distribution with dn/da ~ a(exp -3.5), the equivalent of a 130 km radius KBO of 1.0 grams per cubic centimeter density and similar to recent estimates of the mass delivered to the Earth at 0.6 - 0.8 Gyr during the Late Heavy Bombardment. We conclude that the parent body was a Kuiper-Belt body or bodies which captured a large amount of early primitive material in the first Myrs of the system's lifetime and preserved it in deep freeze at approximately 150 AU. At approximately 1.4 Gyr they were prompted by dynamical stirring of their parent Kuiper Belt into spiraling into the inner system, eventually colliding at 5-10 kilometers per second with a rocky planetary body of mass less than or equal to M(sub Earth at approximately 3 AU, delivering large amounts of water (greater than 0.1 % of M(sub Earth's Oceans)) and carbon-rich material. The Spitzer spectrum also closely matches spectra reported for the Ureilite meteorites of the Sudan Almahata Sitta fall in 2008, suggesting that one of the Ureilite parent bodies was a KBO

Dynamical analysis and constraints for the HD 196885 system

The HD\,196885 system is composed of a binary star and a planet orbiting the primary. The orbit of the binary is fully constrained by astrometry, but for the planet the inclination with respect to the plane of the sky and the longitude of the node are unknown. Here we perform a full analysis of the HD\,196885 system by exploring the two free parameters of the planet and choosing different sets of angular variables. We find that the most likely configurations for the planet is either nearly coplanar orbits (prograde and retrograde), or highly inclined orbits near the Lidov-Kozai equilibrium points, i = 44^{\circ} or i = 137^{\circ} . Among coplanar orbits, the retrograde ones appear to be less chaotic, while for the orbits near the Lidov-Kozai equilibria, those around \omega= 270^{\circ} are more reliable, where \omega_k is the argument of pericenter of the planet's orbit with respect to the binary's orbit. From the observer's point of view (plane of the sky) stable areas are restricted to (I1, \Omega_1) \sim (65^{\circ}, 80^{\circ}), (65^{\circ},260^{\circ}), (115^{\circ},80^{\circ}), and (115^{\circ},260^{\circ}), where I1 is the inclination of the planet and \Omega_1 is the longitude of ascending node.Comment: 10 pages, 7 figures. A&A Accepte

On the dynamics and collisional growth of planetesimals in misaligned binary systems

Context. Abridged. Many stars are members of binary systems. During early phases when the stars are surrounded by discs, the binary orbit and disc midplane may be mutually inclined. The discs around T Tauri stars will become mildly warped and undergo solid body precession around the angular momentum vector of the binary system. It is unclear how planetesimals in such a disc will evolve and affect planet formation. Aims. We investigate the dynamics of planetesimals embedded in discs that are perturbed by a binary companion on a circular, inclined orbit. We examine collisional velocities of the planetesimals to determine when they can grow through accretion. We vary the binary inclination, binary separation, D, disc mass, and planetesimal radius. Our standard model has D=60 AU, inclination=45 deg, and a disc mass equivalent to the MMSN. Methods. We use a 3D hydrodynamics code to model the disc. Planetesimals are test particles which experience gas drag, the gravitational force of the disc, the companion star gravity. Planetesimal orbit crossing events are detected and used to estimate collisional velocities. Results. For binary systems with modest inclination (25 deg), disc gravity prevents planetesimal orbits from undergoing strong differential nodal precession (which occurs in absence of the disc), and forces planetesimals to precess with the disc on average. For bodies of different size the orbit planes become modestly mutually inclined, leading to collisional velocities that inhibit growth. For larger inclinations (45 degrees), the Kozai effect operates, leading to destructively large relative velocities. Conclusions. Planet formation via planetesimal accretion is difficult in an inclined binary system with parameters similar to those considered in this paper. For systems in which the Kozai mechanism operates, the prospects for forming planets are very remote.Comment: 24 pages, 16 figures, recently published in Astronomy and Astrophysic

Differential role of TRP channels in prostate cancer

Abstract A major clinical problem with PC (prostate cancer) is the cell's ability to survive and proliferate upon androgen withdrawal. Indeed, deregulated cell differentiation and proliferation, together with the suppression of apoptosis, provides the condition for abnormal tissue growth. Here, we examine the differential role of TRP (transient receptor potential) channels in the control of Ca 2+ homoeostasis and growth of PC cells

DELIVERABLE: D5.1 MONITORING AND VALIDATION STRATEGIES

This deliverable report will present the strategies developed for monitoring the case study demonstrations to be undertaken as part of WP4. The strategies presented will include both methods for quantitative validation, including data capture and relevant KPIs, and those catering for more qualitative evaluation using aspects such as contextual interviews, self-observations, and/or questionnaires.This work is part of the DR BOB Project. The DR-BOB Collaborative Project (Grant Agreement No. 696114) is co-funded by the European Commission, Information Society and Media Directorate-General, under the Horizon 2020 Programme (H2020)