Title: Unraveling the chemistry of planet-forming disks in the ALMA era
Speaker: Dr. Romane Le Gal (CNES post-doctoral researcher, IRAP)
Abstract: Over the past decades, questions on the origins and prevalence of life on planets have shifted from metaphysical questions to hot research topics in astrophysics. The latest generation of high-sensitivity telescopes has provided access to the cradles of star and planet formation at unprecedented spatial and spectral resolutions, making it possible to study the chemical evolution of interstellar matter from molecular clouds to forming planetary systems. A key question in this context is to assess how much of the pre-stellar molecular composition survives and becomes incorporated into planets. Or, conversely, how much nascent planets are affected by chemical reprocessing that occurs in their birth environments, i.e. in planet-forming disks around young stars. Indeed, these disks are exposed to energetic radiations and undergo strong dynamical phenomena such as planet formation, which may substantially alter their chemical inventory. In this talk I will present how my research combines observations and astrochemical modeling fed by theoretical and experimental studies to 1) better understand and characterize the chemistry of these disks, 2) start disentangling between chemical inheritance and chemical reprocessing in planet-forming disks, and 3) identify chemical signatures of planet formation.
Title: Exploration of the Jovian Outer Magnetosphere with Juno
Speaker: Vincent Hue (Research Scientist – Southwest Research Institute)
Abstract: Jupiter’s magnificent auroral lightshow is a direct manifestation of its strong magnetic field, which couples its magnetospheric plasma and ionosphere. In the ultraviolet spectral range, the Jovian auroras are highly structured, and reflect the numerous processes occurring throughout the magnetosphere. Since July 2016, NASA’s New Frontiers mission Juno performs in-situ and remote sensing measurements from within the Jovian magnetosphere. In this talk, we discuss the main auroral regions with a particular emphasis on the polar auroral regions, linked to the outermost region of Jupiter’s magnetosphere and possibly the solar wind. These are the most highly dynamic components of the Jovian auroras, often exhibiting flares evolving over short timescales. We present a new type of auroral feature recently discovered by the Ultraviolet Spectrograph on Juno (Juno-UVS), which consists in circular expanding UV-emission, and discuss their potential origin.
Title: Non-thermal cosmic ray desorption of ices mantles and complex organic molecules
Speaker: Emmanuel Dartois (Institut des Sciences Moléculaires d’Orsay (ISMO))
Abstract:
Title: Molecular diversity of early-stage high-mass protostars: evidence for a deeply embedded hot corino phase?
Speaker: Laure Bouscasse (IRAM)
Abstract:During star formation the molecular gas undergoes significant chemical evolution leading to a molecular richness at the emergence of hot cores. The chemical formation pathways even for simpler molecules are debated. Using a spectral survey between 159GHz and 374GHz with the APEX telescope, we investigated a sample of 6 massive clumps dominated by a single collapsing massive object down to 400au scales. In all 6 sources of the sample, on average 40 species were found. Through LTE modeling we could constrain the physical origin of these species within the envelope. While some objects exhibit a clear structure with a well-defined warm gas phase, some remain mostly cold with warm gas traced only by methanol and methyl cyanide. The molecular composition of the sample is remarkably similar: their molecular content is composed of the simplest molecules and the most complex ones in the cold component of envelope for all our objects. However, some differences in the molecular emission are found in the deuterated molecules, S-bearing molecules, and the COMs. Towards the warm component, the comparison of the relative molecular abundances shows an emerging warm gas phase with high molecular abundances for dimethyl ether, methyl formate, formamide, and the cyanides. Finally in our objects, we found similar relative abundances for O-bearing molecules relative to CH3OCH3 while cyanides exhibit remarkably higher abundances relative to CH3CN compared to hot corinos. Altogether we could characterize a phase preceeding the emergence of bright hot cores resembling in many aspects a deeply embedded hot corino phase in the emergence of high-mass protostars.
Title: What are the magnetic switchbacks observed by the mission Parker Solar Probe ?
Speaker: Naïs Fargette (Institut de Recherche en Astrophysique et Planetologie)
Abstract:
Near the Sun, the solar wind magnetic field is dominated by Alfvénic structures that undergo reversals of the radial magnetic field while keeping a constant strahl and constant magnetic field amplitude as well. They are called magnetic switchbacks and are interpreted as accelerated folds on the magnetic field in the solar wind. They were observed by numerous missions (Wind, Ulysses, Solar Orbiter) and were most striking in Parker Solar Probe data, below 0.3 AU. Their origin is still debated and scenarii include interchange reconnection at the Sun’s surface, propagation of alfvenic waves and a turbulence driven phenomenon. In this talk I will present some characteristics of the switchback structures, give an overview of the existing formation theories and describe the latest results on the topic.
Title: The bimodal A(Li) distribution of Milky Way’s thin disk dwarf stars and the Galactic scale events
Speaker: Santi Roca-Fàbrega (Universidad Complutense de Madrid)
Abstract: The lithium abundance, A(Li), in stellar atmospheres suffers from various enhancement and depletion processes during the star’s lifetime. While several studies have demonstrated that these processes are linked to the physics of stellar formation and evolution, the role that Galactic-scale events play in the galactic A(Li) evolution is not yet well understood. In this talk I will show that the observed A(Li) bi-modal distribution, in particular in the FGK-dwarf population of field stars, is not a statistical artefact but it is a consequence of a particular Milky Way star formation history profile combined with the stellar evolution’s 7Lii depletion mechanisms. I will show that A(Li) evolution can be used as an additional proxy for the star formation history of our Galaxy.
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Title: Cosmology (& astrophysics) with the Lyman alpha forest
Speaker: Ignasi Pérez-Ràfols (Sorbonne Université, Laboratoire de Physique Nucléaire et de Hautes Energies)
Abstract: The acceleration of the expansion rate of the Universe is yet to be explained. Several models, including LCDM, try to explain this acceleration. LCDM bases its explanation on a mysterious dark energy, adding up to ~75% of the total energy density of the Universe. Other models present modified theories of gravity to explain this effect. But which one is correct? The expansion history of the Universe is a great observable to discriminate between these models. I will talk about measurements of this expansion history at redshift greater than 2 using BAO with the Lyman alpha forest. I will talk about the most recent results from eBOSS, and also from the next generation of surveys that is currently starting: DESI and WEAVE. I will talk about how improving our knowledge of the Lyman alpha forest can help us not only with answering our cosmological questions, but also with our understanding on galaxy evolution.
Title: How do stars get their mass? Understanding the origin of the IMF from the mass distribution of cores
Speaker: Dr. Thomas Nony (UNAM)
Abstract:
Title: Shaping Extrasolar Systems with Giant Planets
Speaker: Laetitia Rodet (Department of Astronomy, Cornell University )
Abstract:
In the last decades, exoplanet surveys have revealed the presence of giant planets (Jupiter-sized or larger) orbiting at least 5 % of Sun-like stars. This percentage will likely increase in the near future, in particular with the coming data releases of the Gaia mission. Due to their mass, giant planets have a significant impact on the dynamics of the entire planetary system. First insights on their architecture show larger eccentricities and inclinations than the smaller planets, and orbital periods ranging from hours (hot Jupiters) to years (cold Jupiters), and even thousands of years.
In this talk, I will present how giant planets shape the architecture of extrasolar systems, in particular the orbits of fellow giant planet companions, inner super Earths, moons and planetesimals. I will compare analytical expectations, N-body simulations, and actual observations, focusing especially on directly imaged-systems. Giant planets can directly perturb their environment through secular interactions, scattering or resonances. Moreover, cold Jupiters are sensitive to the close flybys of neighboring stars. The occasional kicks that those flybys induce can significantly change a giant planet orbit, which will then impact the rest of the planetary system. This phenomenon could be linked to the formation of hot Jupiters, the misalignment of inner super Earths or the asymmetries in debris disks.
Title: Disks around evolved binaries: do they form second-generation planets?
Speaker: Jaques Kluska (KU Leuven)
Abstract:
Title: Circumbinary envelope and wind mass transfer: from cool evolved stars to high-mass X-ray binaries
Speaker: Ileyk el Mellah (IPAG)
Abstract:
Stellar multiplicity has been recognized as a ubiquitous feature: stars seldom live an effectively single life. In the late stellar evolutionary stages, mass loss plays a major role while interaction with an orbiting companion can leave remarkable imprints in the circumbinary envelope and influence the final fate of the system. In binaries, whether the outflows are line-driven from a blue supergiant or dust-driven from a red giant, the flow morphology shares common features which shed light on the launching mechanism. High spatial and spectral resolution instruments have identified arcs and spirals around cool evolved stars which suggest the presence of underlying (sub-)stellar companions. On the other hand, in high-mass X-ray binaries, time-resolved spectroscopy over multiple orbits reveals how the clumpy wind is disrupted and accreted by the compact object.
In this talk, I will present simulations of mass transfer mediated by dust and line-driven winds in binaries. With the mesh-based radiative magneto-hydrodynamics code MPI-AMRVAC, we designed a versatile 3D setup suitable to capture the wind dynamics. In high mass X-ray binaries, we can follow the wind over several orders of magnitude as it is accreted onto the compact object. I will show how the compact object can also be used as an orbiting X-ray backlight whose shimmering betrays the structure of the foreground absorbing material. Around cool evolved stars, these simulations are extended up to several 10 orbital separations at an affordable computational cost, thanks to adaptive mesh refinement. For different dust chemical content, they can reproduce the morpho-kinematics properties we extracted from ALMA’s multi-channel molecular line emission maps. In both cases, I will describe how mass transfer redistributes angular momentum and can lead to orbital inspiral.