Stellar Physics

This research line of the Astereosismology Group aims at testing the details of the internal stellar structure using different observational approaches: Exploitation of seismic data from space satellites, ground support and follow-up of these space missions and also the study of binary stars in other galaxies.

To do this several theoretical tools have been developed, among them, numerical codes of stellar structures, numerical codes for non-adiabatic stellar pulsations and numerical codes for stellar rotation. We have also developed precise time series analysis to extract pulsation frequencies for truncated time series. This
experience is being used to participate in the French-European mission COROT, in the USA (NASA) mission Kepler, in the European ESA mission PLATO, and in the BRITE nanosatellite. It is important to note that our group is also co-leading the high resolution infrared spectrograph CARMENES for the 3.5m CAHA telescope.

Particularly the main objective is to study in detail the internal structure of stars using either their membership to a binary system or their oscillations. Many theoretical stellar structures are possible with the usual external observables: effective temperature, gravity, surface abundance. The most obvious example is that of pulsating
pre-main sequence stars occupying the same position in the HR diagram as main sequence classical pulsators. The detail of how stars transport energy and momentum from its deep core is not yet understood. Our group is completely autonomous to carry out the modelling of any type of stellar structure test: the data coming from space mission and supported by simultaneous ground based additional observations are analysed and compared with theoretical predictions.
The feedback generated by this test bench is in the basis of our objectives. A non-exhaustive list of items to be addressed by these techniques are:

  • Overshooting
  • Mixing length
  • Internal Rotation
  • Meridional circulation

The Robotic Astronomy and High-Energy Astrophysics (ARAE) group activities at IAA-CSIC are multifold, dealing with scientific and technological issues. The two main research fields are: i) Compact Objects in the Galaxy and ii) Cosmic GRBs. In the former field, the group has identified in the optical band two black hole candidates supporting the mass transfer model and determining the mass function in one case. They also discovered the high-energy source GRS 1915 +105 and concluded that is a low-mass X-ray binary, with this source later becoming the prototype of Galactic microquasars. They also studied the puzzling source SWIFT J195509+261406, very likely a neutron star during its transition from young magnetar to dim isolated neutron star. Regarding cosmic gamma-ray bursts (GRBs), the group performed the first multi-wavelength study of a GRB counterpart from mm (radio) to IR (ISO spacecraft) and optical (Hubble Space Telescope), for GRB 970508, supporting the standard fireball model. They performed a detailed study of GRB 990213 which implied a collimated jet, with important implications on the energy release. They also first suggested the existence of an underlying supernova for any given GRB (GRB 980326) which was later supported for GRB 991208 (optical lightcurve) and confirmed (by spectroscopy) for GRB 030329. They also participated in the detection of GRB 090423 at z = 8.2, the most distant object of the known Universe (for the time being). In parallel, the group members have been conducting technological developments in European space science missions carrying X-ray instrumentation aboard like JEM-X on ESA’s INTEGRAL observatory and are participating in the current UFFO-p experiment aboard the Lomonosov international mission. They are pioneering the field of robotic astronomy in Spain and developed the BOOTES world-wide network of rapid-slewing optical/near-infrared 0.6m telescopes robotic telescopes and ultra sensitive all-sky cameras (leading to several patents).