Calendar
Stanza Google Meet: meet.google.com/sxz-cctp-tsc
Speaker: Gabriele Cozzo (UniPA)
Titolo: “Study of the accretion phenomena of T Tauri stars with the GRAVITY instrument”
Abstract
Accretion through circumstellar disks plays a fundamental role in the process of star formation. Characterising how accretion works in the context of young stellar objects will also help us to constrain the properties of the regions in which planets form and migrate. The accretion mechanism in low-mass pre-main-sequence stars (T Tauri Stars) is driven by the stellar magnetic field, which disrupts the disk at the magnetospheric radius, generally located at scales of order a few stellar radii. Almost bipolar field lines channel the material from the disk to the star, which ends with shocking at the stellar surface at near free-fall velocities. From decades, the technological improvement has driven the development of new ways to probe faint and distant objects as Classical T Tauri stars are and disentangle the multifarious physical processes involved in sustaining the stars’ evolution. The state-of-the-art in interferometry science has indeed attained unprecedented capabilities in terms of angular resolutions. This new potentiality, coupled with the purpose to understand the innermost regions of CTTSs, deserves a new approach to interpret data and manipulate information. This work addresses the ambition to lay the foundation of a new framework of observational data interpretation that sheds light on the capabilities of new-class interferometric instruments, like the Very Large Telescope Interferometer, in sampling and disentangling the physical conditions in which a star is born.
Stanza Google meet: https://meet.google.com/sxz-cctp-tsc
Speaker: Ruggero Biondo (UniPA)
Titolo: Tracing the ICME plasma with a MHD simulation
Abstract:
The determination of the chemical composition of Interplanetary Coronal Mass Ejection (ICME) plasma is an open issue. More specifically, it is not yet fully understood how remote sensing observations of the solar corona plasma during solar disturbances evolve in plasma properties measured in-situ away from the Sun. The ambient conditions of the background interplanetary plasma are important for space weather because they influence the evolutions, arrival times and geo-effectiveness of the disturbances. The Reverse In-situ and MHD APproach (RIMAP) is a technique to reconstruct the heliosphere on the ecliptic plane (including the magnetic Parker spiral) directly from in situ measurements acquired at 1 AU. It combines analytical and numerical approaches, preserving the small-scale longitudinal variability of the wind flow-lines. In this work, we use RIMAP to test the interaction of an ICME with the interplanetary medium. We model the propagation of a homogeneous non-magnetized (i.e., with no internal flux rope) cloud starting at 800 km/s at 0.1 AU out to 1.1 AU. Our 3D MHD simulation made with the PLUTO MHD code shows the formation of a compression front ahead of the ICME, continuously driven by the cloud expansion. Using a passive tracer, we find that the initial ICME material does not fragment behind the front during its propagation, and we quantify the mixing of the propagating plasma cloud with the ambient solar wind plasma, which can be detected at 1 AU.
Speaker: Valerio Fardella (UNIPA)
Titolo: L’analisi delle atmosfere degli esopianeti. Come e perché.
relazione di Laurea triennale,
indirizzo Google Meet: meet.google.com/sxz-cctp-tsc
Abstract:
La composizione chimica dell’atmosfera di un esopianeta può aiutare a capire quale siano la composizione e, a volte, l’evoluzione passata dell’esopianeta. L’atmosfera, se è presente, può essere osservata quando il pianeta transita davanti la sua stella. Lo spettro in trasmissione che si osserva in tal modo contiene informazioni sulle abbondanze presenti nell’atmosfera. Tuttavia, alcuni fenomeni fisici e chimici possono ostacolare significativamente la rilevazione di queste abbondanze. In questa presentazione vengono mostrati alcuni aspetti dell’osservazione ed analisi di uno spettro in trasmissione di un’atmosfera esoplanetaria e alcune delle informazioni che è possibile trarre da esso.
Ripetizione di tesi magistrale
Laureanda: Stefania Benanti
Titolo: Studio dell’emissione UV di un CME solare – Possibili estrapolazioni per la ricerca di CME stellari
Stanza Google meet: https://meet.google.com/sxz-cctp-tsc
Abstract: I CME stellari sono notoriamente difficili da osservare, tanto che a oggi non ci sono CME stellari effettivamente confermati ma solo una decina di candidati CME. Mentre identificazione, osservazione e studio dei CME solari è possibile grazie alla risoluzione spaziale, in mancanza di quest’ultima è necessario ricorrere a tecniche indirette per la ricerca dei CME stellari. In particolare si ricorre a tecniche basate sulla ricerca di componenti blueshiftate negli spettri stellari. Tale ricerca è attualmente effettuata prevalentemente in banda ottica, tuttavia potrebbe essere la banda UV quella più promettente. In questa tesi ho quindi scelto un particolare CME solare con lo scopo di studiarne le caratteristiche fisiche e determinare l’emissione totale in tutta la banda UV. Avendo infatti lo spettro totale atteso per il CME, quanto ricavato in questa tesi può essere riscalato per fare previsioni di quale dovrebbe essere l’emissione UV di un CME stellare in termini di spettro, luminosità e durata.
Relatrice: Costanza Argiroffi
Seminario in modalita` ibrida
link Google meet https://meet.google.com/sxz-cctp-tsc
Speaker: Giacomo Permunian (Universita` di Ferrara)
Titolo : La chimica e mineralogia della condrite ordinaria 6A.
Abstract: Ordinary chondrites (OCs), costituiscono la classe di meteoriti più abbondante tra quelle viste cadere (falls) e trovate (finds). Sulla base delle loro differenze chimiche, isotopiche, mineralogiche e tessiturali (petrografiche) sono suddivise in tre gruppi (H, L, LL). La possibilità di studiare questi materiali con sempre più dettaglio ha permesso di ampliare la nostra conoscenza sulla varietà dei materiali nel Sistema Solare e di comprendere meglio le condizioni chimico-fisiche della nebulosa solare.
Presenterò lo studio in corso della meteorite COs 6A, di tipo H, trovata nella provincia di Tata in Marocco, di cui ho studiato principalmente la petrografia (tessitura della roccia) e la composizione mineralogica dei principali costituenti (olivina, Ca-poor pyroxenes e feldspati). Olivine e pirosseni sono i fondamentali costituenti anche del mantello terrestre (e suoi analoghi del sistema solare), e sono tra i costituenti più comuni delle polveri del mezzo inter e circumstellare. Nell’ambito del tirocinio presso l’INAF di Palermo abbiamo usato questi materiali come analoghi di polvere inter e circumstellare.
Seminario in forma ibrida,
indirizzo Google meet: https://meet.google.com/sxz-cctp-tsc
Speaker: Salvatore Sciortino (INAF)
Titolo: The Athena predicted PSF and ELSP and their effects on X-ray (stellar) studies
Abtract:
In the past 12-18 months improved descriptions of the predicted Athena PSF
(Point Spread Function) and of the predicted Athena/XIFU ELSF (Extended Line
Spread Function) have become available and their effects has been investigated by more detailed simulations of WFI and XIFU based studies. I will discuss and illustrate the most relevant outcomes of this investigations and their possible effect on (stellar) X-ray studies and more in general the currently predicted
capability (and related limit) of future Athena observations.
Speaker: Víctor Almendros Abad (CENTRA, Faculdade de Ciências da Universidade de Lisboa; European Southern Observatory)
Title: Milky Way’s young substellar population
indirizzo google meet: https://meet.google.com/sxz-cctp-tsc
Abstract:
Young clusters and star forming regions are home to a large number of substellar objects with masses below the hydrogen-burning limit at ~0.075 MSun. Most of our knowledge about their populations comes from nearby regions (d < 400 pc), where we find consistent formation rates of 2-5 young brown dwarfs per 10 newborn stars. Brown dwarf theories, on the other hand, predict that high gas or stellar densities, as well as the presence of massive OB stars, may be factors that boost the incidence of newly formed brown dwarfs with respect to stars. The next frontier in substellar studies, therefore, is the exploration of massive star clusters, characterized by significantly different star-forming environments than those found in our immediate vicinity. In this contribution I will present our deep NIR imaging using the AO-supported instrument HAWK-I/VLT in Galactic massive clusters RCW 38 and NGC 2244, complemented by the spectroscopic follow-up using KMOS/VLT. We report the most complete substellar IMFs in the two clusters, along with the first bona-fide brown dwarfs beyond 1 kpc, providing an ideal dataset for a comparison with nearby star forming regions. Finally, I will present our future plans with two approved JWST programs, which include the first substellar IMF in a starburst cluster, and spectroscopic confirmation of first single Jupiter-mass objects in a nearby star forming region.
SPEAKER: Julien Gressot, Doctorant FNS – Histoire des techniques et de l’innovation, Institut d’histoire
AFFILIATION: Université de Neuchâtel (Switzerland)
TITLE: The Photographic Zenith tube (PZT) of the Neuchâtel Observatory: Achievement of time determination or failure of innovation?
ABSTRACT: Throughout its existence, the Neuchâtel Observatory has sought to be at the forefront of astronomical time determination. In the mid-20th century, a technological innovation began to spread in observatories with PZTs (Photographic Zenith Tube). The Neuchâtel Observatory was one of the first to obtain this instrument, the purpose of which was to eliminate the human factor by automating the time determination and certain other instrumental errors. PZTs were presented as the most accurate instruments of their time, but their development was soon halted. In this paper, we will examine the technical evolution of PZTs, the reasons why they became the must-have instrument, and the explanations for their rapid abandonment.
Google Meet room: https://meet.google.com/sxz-cctp-tsc
Speaker: Quentin Changeat (UCL)
Title: Atmospheric retrievals in the era of next generation telescopes.
Abstract: With the recent launch of the NASA/ESA/CSA-JWST telescope and the upcoming ESA-Ariel, we are now entering a new era of exoplanet characterisation. These next-generation telescopes will revolutionise our understanding of exoplanet atmospheres, but the analysis of their observations will be very challenging.