Seminars and Colloquia at ESO Santiago

Forbidden Emission Lines (FELs) map outflow activity i.e. jets and winds, in Classical T Tauri stars (CTTSs). It is an open question as to whether the FEL low velocity component (LVC) traces an magneto-hydrodynamic (MHD) or photoevaporative wind. This question is relevant to excess angular momentum removal in young star. If the LVC is an MHD wind, then it should be linked to the high-velocity component (HVC)/jet. Here, I present the kinematic and spectro-astrometric analysis of the different velocity components observed in the [O I] λ5577 , [O I] λ6300 and [S II] λ6731 forbidden emission lines in three epochs of spectra from the CTTS DG Tau spanning ≈ 20 years in time. DG Tau is a well studied source that has a variable jet that has been significantly decreasing in radial velocity over the ≈ 20 years that our data spans. While the low velocity component also shows some variability over this same period of time, our study reveals that it behaves differently to the HVC which hints at key information about the origin of the LVC. In this talk, I will discuss the significance of the results for DG Tau and how this approach could be applied to other sources to test what variability can reveal about the origin of the LVC.

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The FRIPON network is composed of 250 fish-eye cameras to detects fireballs, it measures their position and triangulates it to determine the bright trajectory in the atmosphere. Initially, the aim was to extend the trajectory (dark flight calculation) and thus calculate a strewn field in order to search for a possible fresh meteorite. It is also possible to extend the trajectory into the past to obtain the orbit of the object before it entered the atmosphere. We have 11,000 orbits since the start of the project for objects ranging from 1 cm to a few meters. This is the only method for detecting interplanetary matter in this size range. I'll be showing the iresults of the project, as well as related applications (light pollution measurement, polar auroras, etc.).  Finally, FRIPON is linked to the Vigie-Ciel collaborative science program, firstly to help us search for meteorites, and secondly to disseminate science.

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The fabrication of image slicers remains a key challenge in modern astronomical instrumentation [1]. Traditional techniques, such as diamond turning, are costly and time-consuming, limiting their extensive use in astronomy. Indeed, the high precision needed in both individual slice surfaces and their relative alignment further complicates production. Future large-scale projects, such as the Wide-Field Spectroscopic Telescope (https://www.wstelescope.com/), will require an unprecedented number of these devices, posing a significant challenge for existing fabrication methods.
Ultrafast Laser-Assisted Etching (ULAE) could be a powerful route to manufacture fused silica image slicers, potentially enabling the precision shaping of fused silica over multi-millimeter scales with micron-level precision. Here, we demonstrate the potential of using ULAE for manufacturing image slicers by fabricating a 20-slice prototype, where each 1 mm  15 mm slice is a segment of a 200 mm radius sphere with varying tip and tilt orientations (Figure 1). The alignment between slices is maintained within 10 μm, meeting the stringent requirements for astronomical applications. We are currently in the process of developing in parallel a CO2-laser polishing system to remove the remaining high spatial frequencies roughness left after the etching process [2].
This work highlights the potential of precision laser manufacturing as a cost-effective and scalable solution for fabricating fused silica image slicers, paving the way for their broader implementation in future astronomical instruments.

Study of astrophysical objects requires always more complex models (black hole surrounding, exoplanet atmosphere, accretion disk, galaxy formation and evolution, …) whose inputs imply always more precise measurements. On the other side, the astronomical instruments start to reach their fundamental limits (negligible sensor readout noise, precise mirror polishing, technologies harder to scale up to extremely large telescopes, …). During this lecture, I will discuss how data science applied for optimal data reduction and processing via inverse problem approaches can bridge this gap, by pushing the experimental limits without the need of further instrumental developments. After a few examples on different applications: integral field spectroscopy (SPHERE/IFS), blind deconvolution and PSF reconstruction (SPHERE/ZIMPOL) and extreme adaptative optics (GRAVITY+), we will go through an interactive session with a simple deconvolution problem.

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