Calendar

Classical T Tauri stars are bright in the soft X-ray and far UV bands, because of large amounts of plasma at T~10⁵-10⁶ K, associated with the accretion-shock regions. Inspecting the emission from the shock region is important since it can potentially reveal fundamental properties of the accretion-stream material (i.e. geometry/density/velocity/abundances). However, the precise location of these hot plasmas (pre-shock? post-shock? different shock regions with different temperatures?) is still unclear. To constrain location and properties of these accretion-related hot plasmas, X-rays and UV observations are needed. The next XMM call (deadline 6 October 2017) offers the possibility to investigate this issue. I would like to discuss with you the opportunity to propose a joint XMM+HST program, focused on TW Hya, to perform time-resolved high-resolution spectroscopy on time scales down to 15 ks, simultaneously in the X-ray and UV bands. Correlated or uncorrelated variability of plasmas at 10⁵ and 10⁶ K will indicate whether or not they are located in the same accretion-shock regions. That will provide important constraints on the physical properties of the accretion streams in CTTS.

Abstract: For decades the Solar System has been our sole example of a planetary system, resulting in the classical view of planetary formation as a local, orderly process producing stable planetary systems. The ever growing sample of known exoplanets, however, has shown us the major role played by orbital migration and chaos in determining the evolution of planetary systems in our galaxy. This brought to questioning our very understanding of the history of the Solar System and to suggesting that it also could have undergone a more violent evolution than previously thought. In this talk I will describe how the compositional information on the planetary bodies of the Solar System can be used to shed new light on its past, illustrating the past and current investigations performed in the framework of the NASA missions Dawn and Juno, and I’ll discuss how the same principles, if not the same techniques, can be used to investigate of histories of extrasolar planets.

Abstract:
With significant new observing capabilities, centimeter-wavelength radio astronomy is currently in a renaissance leading up to the advent of the Square Kilometre Array (SKA). The sensitivity upgrades of both the NRAO Very Large Array (VLA) and the Very Long Baseline Array (VLBA) have begun to provide us with a much improved perspective on stellar centimeter radio emission, particularly concerning young stellar objects (YSOs) and ultracool dwarfs. For the first time we now have systematic access to the radio time domain. I will mainly present a deep VLA and VLBA radio survey of the Orion Nebula Cluster (ONC), where we have found hundreds of compact radio sources, a sevenfold increase over previous studies, and intricate detail on the radio emission of proplyds. We can now better disentangle thermal and nonthermal radio emission by assessing spectral indices, polarization, variability, and brightness temperatures (VLBA). With simultaneous radio-X-ray time domain information (Chandra), this project is providing first constraints on YSO radio flares and their relation with X-ray flares, as well as improved constraints on the overall high-energy irradiation of their surroundings, including protoplanetary disks. Starting with Orion, I will additionally discuss the use of the VLBA for precision stellar astrometry in the Gaia era, highlighting how VLBI astrometry is allowing us to extend the Gaia sample of YSOs and ultracool dwarfs by including embedded objects, distant obscured sources in the Galactic plane, and faint ultracool dwarfs, while providing important opportunities for astrometric cross-calibration.