Recent Talks

Traditionally, astronomers study stars and planets by telescope. But we can also learn about them by using a microscope – through studying meteorites. From meteorites, we can learn about the processes and materials that shaped the Solar System and our planet. Tiny grains within meteorites have come from other stars, giving information about the stellar neighbourhood in which the Sun was born.

Meteorites are fragments of ancient material, natural objects that survive their fall to Earth from space. Some are metallic, but most are made of stone. They are the oldest objects that we have for study. Almost all meteorites are fragments from asteroids, and were formed at the birth of the Solar System, approximately 4570 million years ago. They show a compositional variation that spans a whole range of planetary materials, from completely unmelted and unfractionated stony chondrites to highly fractionated and differentiated iron meteorites. Meteorites, and components within them, carry records of all stages of Solar System history. There are also meteorites from the Moon and from Mars that give us insights to how these bodies have formed and evolved.

In her lecture, Monica will describe how the microscope is another tool that can be employed to trace stellar and planetary processes.

The visible survey spectrometers, VIMOS and FLAMES, have need in successful operation for nearly a decade. and within the next few weeks these will be joined by KMOS and near IR mulit-IFU spectrometer. There are also two new instruments in their early design stages, MOONS a near IR Fibre fed spectrometer and 4MOST a visible fibre fed spectrometer. This talk will present these instruments and the observing opportunity that these will provide.

The origin and structure of the Earth's crust is still a major question. Current measurements of the nearby crust are based largely on seismic, gravimetric and electrical  techniques. In this talk, we introduce a novel method based on cosmic-ray muons to create a direct snapshot of the density profile within a volcano (and/or other geological features).  By measuring the muon
absorption along the different paths through an object (volcano, mountain, a fault, ...), one can deduce the density profile within the object. The major feature of this
technique makes possible for us to perform a tomographic measurement by placing two or more cosmic ray detection
systems around the object. Another strong point of this technique is the possibility to carry out fulltime monitoring, since  muons are incessantly arriving, recalling they are
the most numerous energetic charged particles at sea level.

The basis of stellar population modeling was established around 40 years ago somehow
optimized to the technical facilities and observational data available at that epoch. Since then,
it has been used extensively in astronomy and there has been great improvements relating
their associated ingredients in concordance with the development of more powerful computational
and observational facilities.
However, there has been no similar improvements in the understanding about what is
actually modeling neither in improve the modeling itself to include the current technical advances
to obtain more accurate result in the physical inferences obtained from them.
In this talk I present some advances in the subject of stellar
population modeling and how to take advantage of current facilities to obtain more robust
and accurate inferences from stellar systems at different scales
covering the continuum between fully resolved populations to fully unresolved ones in a unified framework.

CARMENES (Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs) is a next-generation instrument being built for the 3.5m telescope at the Calar Alto Observatory by a consortium of German and Spanish institutions. It consists of two separated spectrographs covering the wavelength ranges from 0.5 to 1.0 mum and from 1.0 to 1.7 mum with spectral resolutions R = 82,000, each of which shall perform high-accuracy radial-velocity measurements (~1 m/s) with long-term stability. The fundamental science objective of CARMENES is to carry out a survey of ~300 late-type main-sequence stars with the goal of detecting low-mass planets in their habitable zones. We aim at being able to detect 2 MEarth planets in the habitable zone of M5V stars. The CARMENES first light is expected to occur in Spring 2014.

We report on the discovery of a fourth component in the HD 221356 star system, previously known to be formed by an F8V, slightly metal-poor primary ([Fe/H]= -0.26), and a distant M8V+L3V pair. In our ongoing common proper motion search based on VISTA Hemisphere Survey (VHS) and 2MASS catalogues, we have detected a faint (J = 13.76 ± 0.04 mag) co-moving companion of the F8 star located at a projected distance of ~312 AU. Near-infrared spectroscopy of the new companion indicates an L1±1 spectral type. Using evolutionary models the mass of the new companion is estimated at ~0.08 solar masses, which places the object close to the stellar-substellar borderline. This multiple system provides an interesting example of objects with masses slightly above and below the hydrogen burning mass limit.

Type-Ia supernovae (SNIa) are believed to be thermonuclear explosions of accreting carbon-oxygen white dwarfs that reach the Chandrasekhar mass limit of about 1.39 solar masses. However, the nature of the companion star is still under debate, i.e. to be either a dwarf, a sub giant, or a giant star (single-degenerate channel), or another white dwarf (double-degenerate channel). Both channels have been proposed but their relative frequency remains unclear. We have been exploring regions close to the center of supernova remnants of Galactic SNe to search for the companion of these type-Ia SNe. I will show the very recent results we have found in two Galactic type-Ia SNe.

The coronal heating problem has been with us for almost 70 years now. Among the different proposed explanations, wave-based heating mechanisms are recurrently invoked. In the last decade, a wealth of high resolution observations have shown that wave-like dynamics is present at almost all layers of the solar atmosphere. As a consequence, a renewed interest has grown on their role in plasma heating mechanisms. We will discuss a series of aspects related to the current status of MHD wave heating of the solar corona. The talk will focus on the following ones: a) recent observational discoveries of waves and their relevance to the heating problem; b) our theoretical understanding on their nature and properties; c) our current level of comprehension of the sequence of physical processes that link oscillations with dissipation and heat conversion; and d) the merits and faults of current theories, including suggestions for the way forward in both theory and observations.

For the first time, we present the low-mass function of the entire young star cluster Sigma Orionis (3 Myr, 352 pc, no internal extinction) from 0.25 Msun through the brown dwarf regime down to 3-4 Mjup in the planetary-mass domain. We have used VISTA Orion data (ZYJHKs) in the magnitude interval J= 13 - 21 mag (completeness at J = 21.0 mag, Z = 22.6 mag, and 10 Mjup). Combined with Spitzer/IRAC (3.6 and 4.5 micron) and optical images (Iz-band) from our archives has allowed us to identify over 200 cluster low-mass member candidates in an area of 0.79 deg2, i.e., uncovering most of the cluster area. All of these objects have colors compatible with spectral types M, L, and T, i.e., Teff = 3000-1000 K. 23 of them are new planetary mass candidates in the Sigma Orionis cluster, thus doubling the number of cluster planetary mass objects known so far. By considering the Mayrit catalog, we have "extended" our mass function from 0.25 Msun up to the high-mass stars (O-type) of the cluster, covering four orders of magnitude in mass.

The status of instrumentation at the ORM/OT telescopes will be reviewed. A short introduction regarding the different ways to access telescope time (normal call for proposals, service nights and DDT) will also be given. The aim of this talk is to help preparing observing proposals for the coming semester 13A. Questions/comments are welcome.