Seminars and Colloquia at ESO Santiago

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A fundamental concept in observational astronomy is fitting complex models to data obtained from a multitude of instrumentation installed at a variety of telescopes. Such observations are accompanied by a convoluted array of noise sources imprinted on the obtained data. This together with the fundamental Poisson noise inherent to any data, makes model comparison even more challenging. Both parametric and non-parametric approaches to full noise consideration, such as wavelets and Gaussian Processes respectively, have been proposed.  I will present an example of how the consideration of the full covariance matrix, instead of just the variances, can lead to better estimation of precision and accuracy. Finally, I will go through some basic concepts of how this formulation can be implemented in a Bayesian framework in order to obtain posterior probability distributions, from which optimal parameter values and their uncertainties are estimated, using Markov Chain Monte Carlo simulations.

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While adaptive optics is the most widespread method to compensate for atmospheric turbulence, these methods are particularly difficult to implement in the optical regime given the technical challenges imposed by the short coherence times. An alternative to reach the diffraction limit of an optical telescope is provided by speckle interferometry, where, instead of real-time corrections, observations are obtained in timescales similar to the coherence time (a few ms), and the diffraction limit is recovered via a post-hoc reduction in Fourier space. In 2019, the Gemini telescopes commissioned two speckle interferometers, Zorro and 'Alopeke, owned by NASA Ames, which have remained as "permanent visiting" instruments since then. In this talk I will present the characteristics of these instruments, to then present a number of science cases where these instruments are particularly suited, mostly leaning to my own research on RR Lyrae in binary systems, and blue stragglers in hierarchical triplets

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Studies of micrometeorites in mid-Ordovician limestones and Earth’s impact craters show that our planet witnessed a massive infall of ordinary L chondrite material ~466 million years ago that it believed to be at the origin of the first major mass extinction event (Schmitz et al. 2019). The breakup of a large asteroid in the main belt is the likely cause of this massive infall. In modern times, material originating from this breakup still dominates meteorite falls (~37% of all falls). I will present spectroscopic observations and dynamical evidence that we have identified the only plausible source of this catastrophic event and of the most abundant class of meteorites falling on Earth today.

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