Recent Talks

HARISSA is the acronym of ESO/VLT/SPHERE large program of high angular-resolution imaging survey of asteroids. The program was granted by 152hours of observations for five semesters, between 2017 and 2019. Its objective was the survey of a representative sample of large asteroids (diameter larger than 100km) for ~35 objects throughout their rotation. The presentation will point some results of highlighted science produced and published of this program.

GroundBIRD is a millimeter-wave telescope to observe the polarization patterns of the cosmic microwave background (CMB). The telescope scans at a high rotation speed (20 revolutions per minute), and observes ~40% full sky with suppressed atmospheric 1/f noise. High-sensitivity detector arrays of MKIDs (microwave kinetic inductance detectors) are utilized to obtain the fast time response of >1kHz. The cryogenic system keeps the detectors at 250mK for over 24 hours with 20rpm rotation. The data acquisition system is implemented using field-programmable gate arrays (FPGAs), which realizes flexibly changing frequencies, multiplexing, powers, and also sampling rate for each MKID array. Communication between the detector and other angular readout systems was also established for timing synchronization where the sub-millisecond resolution with 120°/sec rotation is required. The telescope was developed in Japan, and installed at Teide Observatory in September 2019. We have demonstrated that all systems are working correctly by observing the moon.

We should find life beyond the solar system ("exolife") within a decade. This will require optical instruments that can perform exoplanet direct imaging.  There are good reasons to expect that telescopes from the ground will lead this search. Unfortunately, none of the currently envisioned large telescopes are optimal for detecting and measuring the emitted or reflected starlight from life-bearing exoplanets. This talk will describe what a 20-100m-class optical telescope would look like and could do if it were designed to solve exoplanet imaging problems. Such a telescope could be initiated today using technologies that are either currently available or under vigorous development.

Time-domain space missions have revolutionized our understanding of stellar physics and stellar populations. Virtually all evolved stars can be detected as oscillators in missions such as Kepler, K2, TESS and PLATO.  Asteroseismology, or the study of stellar oscillations, can be combined with spectroscopy to infer masses, radii and ages for very large samples of stars.  This asteroseismic data can also be used to train machine learning tools to infer ages for even larger stellar population studies, sampling a large fraction of the volume of the Milky Way galaxy. In this talk I demonstrate that asteroseismic radii are in excellent agreement with those inferred using Gaia and spectroscopic data; this demonstrates that the current asteroseismic data is precise and accurate at the 1-2% level.  Major new catalogs for Kepler and K2 data are nearing completion, and I present initial results from both. We find unexpected age patterns in stars though to be chemically old, illustrating the power of age information for Galactic archeology.  Prospects for future progress in the TESS era will also be discussed.

Los funcionarios y sacerdotes del antiguo Egipto formaban una clase social muy jerarquizada en la que sus integrantes tenían múltiples y muy dispares funciones. Algunos de ellos se dedicaban a la observación de la bóveda celeste, y es a estos a los que identificamos comúnmente como astrónomos egipcios. Este seminario estará dedicado al estudio de los términos con los que eran designados los astrónomos, la combinación de estos términos con otros títulos o cargos, y el análisis de los documentos en los que son mencionados a lo largo de la extensa historia de la civilización egipcia. Ello nos permitirá identificar mejor a aquellos antiguos observadores de la bóveda celeste, a sus funciones y su evolución en el tiempo desde el reino Antiguo hasta la Época Romana, centrándonos en algunos de los más singulares. 

Our view of the gas and its physical conditions in the central region of AGN has been enriched by the discover of fast and massive outflows of HI and molecular gas. These outflows can be driven by radiation/winds but also by the interaction of the radio plasma with the ISM. Understanding the origin and quantifying their impact requires to trace their location and derive their physical conditions (density of the gas, mass, mass outflow rate and kinetic energy of the outflow etc.). Particularly interesting has been the finding that in the first phase of their life, jet in radio galaxies can be particularly effective in driving such outflows. This crucial phase is at the heart of the idea of feedback, therefore particularly relevant for studying feedback in action.

In this talk, I will present some of the results we have obtained to trace jet-driven HI and molecular gas outflows down to scales ranging from hundred to tens of pc. The impact of low-power radio jets will be discussed and the comparison with the predictions from numerical simulations will also be presented.

Outflows of up to few hundred Msun/yr have been found in molecular gas using ALMA while the HI observed with VLBI is showing that the outflowing gas is clumpy as also predicted from numerical simulations. I will describe the kinematics of the gas and its conditions and the relevance they may have for feedback.    

Traditional Searches for Extraterrestrial Intelligence (SETI) use large radio telescopes to look for artificial signals from specific stars. In the era of large astronomical surveys, it is now possible to efficiently search for objects having certain predicted signatures of astro-engineering. In this talk, I present an international, cross-disciplinary project between astronomers and researchers in machine learning, the "Vanishing and Appearing Sources during a Century of Observations" (VASCO) project, where we scan the sky for objects that have physically disappeared from (or appeared on) the sky during the last decades. Some of the contaminants we expect are variable astrophysical objects with decade-long time scales. We compare the USNO to PanStarrs catalogues using several epochs of observations. Here, I present the updates about the candidate from the pilot paper (Villarroel+ 2016) and the discovery of ~100 transients (~1/3rd with amplitudes larger than 5 mags). The final goal of the project is to identify interesting astrophysical targets for follow-up analysis with extreme, exotic or bizarre patterns of variability.

We review some ideas and facts and disputes related to the research about the stellar density distribution in the Galactic bulge in the last decades: the discovery of the bulge triaxiality, boxiness, the long-bar as an extra component or as an extension of the own bulge (1st dispute), or the proposal of its X-shape form that has been criticized as an artifact due to an inappropriate use of red clumps as standard candles (2nd dispute).

Most of what we know about the masses and radii of stars comes from the studies of eclipsing binary stars (EBs). As the physical principles that govern the motion are well understood, modelling EB data represents a tractable geometrical problem. The attained accuracy of fundamental parameters is ~2-3% in the best possible cases (Torres et al. 2010), which plays a paramount role in stellar astrophysics: these results are used to calibrate the mass-radius relationship, critically test stellar evolution models, provide fundamental parameters (temperature, luminosity, mass and radius) for stellar and substellar objects across the main sequence, and anchor the distance scale. Given that so much in stellar astrophysics hinges critically on the values derived from EBs, we naturally wonder whether there are any circumstances that would allow us to beat down the uncertainties by another order of magnitude, say to a ~0.2-0.3% level, and thus achieve a 10-fold increase in calibration and gauge reliability. This could be done if the correlations between parameters were somehow reduced, and solution degeneracy somehow broken. If, for example, we had a third star in the system that happens to eclipse the binary, then the shapes of extraneous eclipses in a light curve would constrain the orbital inclination and stellar radii much more than the binary eclipses alone.
In this talk, I will discuss these and similar considerations and show what Kepler, K2 and TESS missions brought to the table.