Agenda de Lagrange

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Octobre 2020

Vacances de la Toussaint – pas de séminaire
 mardi 20 octobre 2020
Vacances de la Toussaint – pas de séminaire
 mardi 27 octobre 2020

Novembre 2020

Séminaire Lagrange
Multi-messenger studies with GRANDMA
 mardi 3 novembre 2020, 10h30, Remote
Sarah Antier, APC
Multi-messenger studies have been vitalized by GW170817 in which diverse messengers - photons and gravitational waves - provide a new picture of the collision of two neutron stars. In this talk,
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    I will first review briefly how coherent analysis of the messengers can not only better constrain the astrophysical scenarios at play, but also further knowledge on the cosmology and nuclear physics side. In a second half, I will present the Global Rapid Advanced Network Devoted to the Multi-messenger Addicts (GRANDMA, PI Sarah Antier), which aims to identify and characterize the electromagnetic counterparts of gravitational-wave sources. I will detail the consortium, its characteristics and public tools provided for time-domain astronomy. I will finish with a summary of our scientific achievements and future prospects for GRANDMA.
The challenge of robust orbital measurements of directly-imaged exoplanets and brown dwarfs
 mardi 17 novembre 2020
Anne-Lise Maire, Université de Liège
Orbital monitoring of circumstellar systems is complementary to the spectrometry of the atmospheres as it allows for analyzing their architecture, dynamical state and evolution, and formation. It is required to derive
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    the orbital parameters and robust model-independent mass measurements. Measuring these parameters for imaged exoplanets and brown dwarfs can lead to degeneracies and biases because a small fraction of the orbit is typically sampled (<20%). I will discuss these issues and methods that I developed to mitigate them in my studies. Precise and robust measurements of the position of the companions over time are critical. I showed the good and stable astrometric calibration of VLT/SPHERE since it has been made available to the community in 2015. This has allowed for precise position measurements down to ~1–3 mas, whereas the precision reached in pre-SPHERE studies was ~10 mas. My work has served as a reference for various studies carried out in the guaranteed-time survey and in open-time programs: the discovery of a handful of exoplanets and brown dwarfs, the rejection of companion candidates as background objects, the measurement of the position and orbit of a few tens of (sub)stellar companions, the analysis of companion-disk dynamical interactions and of the motion of disk features. I will also discuss the lessons learned from the astrometric study of SPHERE for the development of the high-contrast imaging instruments on the ELT.
Séminaire Lagrange
The X-ray Integral Field Unit on board the ESA’s Athena space X-ray observatory: current status and the initiative of reducing the travel carbon footprint of the project
 mardi 24 novembre 2020, 10h30, Remote seminar:
Didier BARRET - IRAP, France

Décembre 2020

Séminaire Lagrange
 mardi 1er décembre 2020, 10h30, Remote via zoom
Steven Longmore, Liverpool
Séminaire Lagrange
Sagittarius A* - the massive black hole at the centre of the Milky Way
 mardi 15 décembre 2020, 10h30, Remote via zoom
Rainer Schoedel, IAA Granada
High angular resolution near-infrared observations have not only accumulated evidence beyond doubt that there is a massive black hole at the centre of the Milky Way, but have also allowed us
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    to measure its properties with high precision and start to confirm detailed predictions of General Relativity. I will review the observational techniques and evidence that have been applied in this research and will provide some insider perspective on this year’s Nobel prize for Reinhard Genzel and Andrea Ghez’s work.

Mise à jour : 20/10/20 19:32