Recent Talks

Lecture 1:
- Timescales across the HR diagram
- Key (optical) properties of compact objects
- Compact binary systems & accretion variability

Lecture 1: ULTRACAM
- High time-resolution astrophysics (HTRA) - what is it and why study it?
- The detection of light - an introduction to CCDs
- Instrumentation for high-speed photometry I: ULTRACAM
- ULTRACAM: science highlights

Lecture 1: HTRA: history across all wavelengths, with emphasis on space science technology
- From optical photographic to photoelectric photometry at ground-based observatories
- First discoveries in space at X-ray wavelengths, with rockets, then satellite surveys
- Fast timing capabiities of Uhuru, OAO-C, SAS-3, HEAO-1 - all with proportional counters
- X-ray pulsars, bursters
- use of fast timing to provide spatial resolution
- Larger collecting areas of EXOSAT, Ginga revealed QPOs, and (RXTE) MSXPs
- Early detectors for HST, EUVE

Lecture 1: Introduction to compact objects:  The sources of power
- Rotation (pulsars)
- Magnetic fields (Magnetars)
- Gravitation (basics of accretion in binary system with a compact star/BH)
- mass transfer
- accretion flows (hot vs cold) and interaction with compact star
(magnetised vs unmagnetised, hard surface vs no surface)
- Jet launching
- Thermo-nuclear (Novae/X-ray bursters)

ALMA, the Atacama Large Millimeter Array, was formally dedicated on March 13, 2013. After an overview of the highlights of ALMA: Science drivers, characteristic parameters and observing modes, I will discuss some of the of the tools available to obtain images and spectra from the observations  --those you might propose and those already in the data archive. I will present a real-time demonstration of a quite generic reduction of an actual ALMA dataset obtained from the public archive, starting from the (ASDM) raw data to produce good quality, publishable images with a dynamic range that reaches ~1800 (on the strongest calibrator); although still limited by systematic effects.

Planetary nebulae (PNe) are excellent tracers to study the chemistry, kinematics, and stellar populations of galaxies.  They can be used to
constrain the properties of galactic substructures and peer into the past tidal interactions.  In this talk, I present our successful GTC observations of PNe in the Northern Spur and the Giant Stream, two
most prominent substructures of M31.  The deep spectroscopy enabled detection of the weak [O III] 4363 temperature-diagnostic line in all target PNe and as a consequence, reliable determination of elemental abundances. Our PN sample have homogeneous oxygen abundances, although
slight difference between the two substructures are marginally noticed. The study of abundances and the spatial and kinematical properties of our sample leads to the tempting conclusions: 1) their progenitors might
belong to the same stellar population, and 2) the Northern Spur and the Giant Stream may have the same origin and may be explained by the stellar orbit proposed by Merrett et al.
The dwarf satellite M32 might be responsible for the two substructures. Deep spectroscopy of PNe in M32 will help to assess this hypothesis.

The initial mass function describes the distribution of masses for a population of stars and substellar objects when they are born. It defines the evolution of a population of stars and provides constrains on the star formation theory. The determination of the initial mass function in the substellar regime is still an open question in Astrophysics. Brown dwarfs do not have enough mass to sustain hydrogen fusion. As a consequence, mass and age are degenerate for these objects. An older high mass object may be indistinguishable from a younger low mass object. In my PhD thesis, through the characterization of brown dwarfs using several observational methods, I work towards solving the general problem of constraining the substellar initial mass function.

In my first project, I calculated trigonometric parallaxes of a sample of six cool brown dwarfs. I determined the luminosity for our objects and I found that one of them might be a brown dwarf binary. In my second project, I confirmed the youth of seven brown dwarfs (ages between 1 and 150 Myr) using spectroscopic data.In the last project of this PhD thesis, I aimed to refine the brown dwarf binary fraction using spectroscopic data in the optical and in the near infrared for 22 brown dwarfs. I found six new brown dwarf binary candidates, two of them were previously known.

The determination of distances, ages and the refinement of the brown dwarf binary fraction in this PhD thesis contribute to the determination of the initial mass function. In the next years, the Gaia satellite, the James Webb Space Telescope and the E-ELT will provide new data, allowing the discovery of new brown dwarf binaries, the constraining of atmospheric and evolutionary models, and the refinement of the initial mass function.

CARMENES may find the first uncontrovertible exoearth in the habitable zone of a star in the solar neighbourhood. Its acronym, 'Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs', is long but self-explanatory. After six years of hard design and construction, CARMENES is currently being commissioned at the German-Spanish 3.5 m Calar Alto telescope in Almería. Well in advance of its American, Japanese and Canadian-French competitors, it will be in January 2016 the first and only ultra-stable high-resolution spectrograph covering the red optical and near-infrared. As its co-project manager, I will give a summary of the homonymous CARMENES instrument, the international consortium that has built it, the on-going on-sky commissioning, and the science project that will be carried with it during guaranteed time observations.

Models of galaxy formation predict that gas accretion from the cosmic web is a primary driver of star formation over cosmic history. Except in very dense environments where galaxy mergers are also important, model galaxies feed from cold streams of gas from the web that penetrate their dark matter haloes. Although these predictions are unambiguous, the observational support has been indirect so far. I will report spectroscopic evidence for this process in extremely metal-poor galaxies (XMPs) of the local Universe, taking the form of localized starbursts associated with gas having low metallicity. Because gas mixes azimuthally in a rotation timescale (a few hundred Myr),  the observed metallicity inhomogeneities are only possible if the metal-poor gas producing stars fell onto the disk recently. I will analyze several possibilities for the origin of the metal-poor gas, favoring the metal-poor gas infall predicted by numerical models. In addition, I will show model galaxies in cosmological numerical simulations with starbursts of low metallicity like to the star-forming regions in XMPs.