Calendar
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.
Prova tesi di Edoardo Alaimo (UNIPA), seminario in modalita` ibrida
Google meet: https://meet.google.com/sxz-cctp-tsc
Titolo: CHARACTERISATION AND MODELLING OF THE UV-VIS-IR TRANSMISSION OF MULTILAYER THIN FILM FILTERS FOR APPLICATIONS IN HIGH HIGH ENERGY ASTROPHYSICS
Abstract: TBD
Seminario in forma ibrida
Indirizzo Google meet: https://meet.google.com/sxz-cctp-tsc
Speaker: R. Giuffrida (UNIPA)
Titolo: The supernova remnant SN 1006 as a Galactic particle accelerator
Abstract:
The origin of cosmic-rays is an open issue of high-energy astrophysics. Supernova remnants are expected to be the main source of Galactic cosmic rays up to energies of about 3 PeV, provided that they transfer a significant fraction of their kinetic energy to the particles (∼ 10%). In particular, the loss of such a large fraction of energy is predicted to alter the shock dynamics by enhancing the shock compression ratio above the canonical value of 4 (shock modification). The bilateral supernova remnant SN 1006 is an ideal target to study shock modification because of its evolution in a fairly uniform environment. SN 1006 shows bright synchrotron X-ray emission from ultrarelativistic electrons accelerated at the shock front in its northeastern and southwestern limbs. If efficient hadron acceleration occurs in these regions, we should observe shock modification therein. We performed a spatially resolved spectral analysis of Chandra and XMM-Newton observations of SN 1006 by selecting narrow regions between the shock front and the contact discontinuity and measuring the density of the X-ray emitting plasma. Our results show an increase of the compression ratio from the characteristic value of 4, in thermal limb, up to ∼ 7 in nonthermal limbs, i.e. in regions where the ambient magnetic field is almost parallel to the shock velocity. We conclude that an efficient particle acceleration causes shock modification in quasi-parallel shocks in SN 1006. By comparing our results with state-of-the-art models, we find that SN 1006 is transferring a significant fraction of its kinetic energy to hadrons. The inferred values of compression ratios and cosmic ray slopes are consistent with those expected for modified shocks when the effects of the postcursor are included.