This paper represents a collective effort to provide an extensive electronic database useful for the interpretation of the spectra and evolution of galaxies. A broad variety of empirical and theoretical data are discussed here, and the data are made fully available in the AAS CD-ROM Series, Vo. 7. Several empirical stellar libraries are part of this database. They cover the ultraviolet spectral range observed with IUE, optical data from different ground-based telescopes, and ground-based infrared data. Spectral type coverage depends on the wavelength, but it is mostly complete for types O and M and luminosity classes V to I. A large metallicity range is covered as well. Theoretical libraries of selected spectral indices of cool stars and of stellar continuum fluxes in the temperature range 2000 K to 50,000 K, as well as Wolf-Rayet energy distributions are presented. Several libraries of star clusters and early-type galaxies have been selected for this database. We discuss an extensive set of empirical spectra templates covering the wavelength region from 1200 - 9800 A, as well as narrow-band line indices in a large number of passbands. Bench-mark spectra of nearby galaxies for model tests are included as well. We compiled numerous evolutionary models and isochrones for stars of all mass ranges of interest, wide metallicity range, and for all evolutionary phases, including the pre-main-sequence phase. The majority of the models have been computed by the Geneva and Padova groups. Evolutionary synthesis models computed by several independent groups are made available. They can be applied to old and young systems, and are optimized with respect to different aspects of input physics. The model predictions include stellar (colors, magnitudes, absorption features) and nebular (emission-line fluxes) properties. Finally, we present models of ionized gas to be used for the interpretation of active galactic nuclei and young star-forming galaxies. The community is encouraged to make use of this electronic database and to perform a critical comparison between the individual datasets

The Liège International Astrophysical Colloquia (LIAC) started in 1949 at the initiative of Pol Swings, and they were continued with the efforts of Paul Ledoux and Marcel Migeotte. They were organized each year except for those when a General Assembly of the IAU took place. About sixty years after the first edition we are now at the 40th edition of the series. This is not the place to list all the astrophysical discoveries that were presented before publication at a Liège colloquium. Just an example: the first interpretation by Allan Sandage of the HR diagram of a globular cluster in terms of stellar evolution was presented in 1953, but not published until 1957. At that time, even for a major advance in astrophysics such as this, the rush to publish was much, much smaller than it is nowadays.For the 40th edition of the LIAC we have decided to concentrate on ageing stars. Specifically, we have focused on low-mass red giants, either ascending the red giant branch or in the red clump heliumburning phase, sdB stars and white dwarfs. This choice was justified by the increasing quality of groundbased asteroseismic data and by the enormous amount of splendid asteroseismic observations obtained over the last few years by the space missions CoRoT and Kepler.These stars have very complex internal structures. They are extremely interesting because they bear multiple signatures of their past history. For example, their time as young main sequence stars, still with a growing convective core, left unique observational signatures still visible today. These signatures mainly take the form of chemical discontinuities and anomalies in surface abundances. They are the result of physical processes that are still not fully understood such as rotation, convection, overshooting and diffusion, which are not fully properly implemented in stellar evolution codes.Fortunately we have a powerful tool: asteroseismology, a sort of scanner. When added to other tools such as photometry, spectroscopy and interferometry, asteroseismology allows us to shed some light on the interior of stars. However, in evolved stars with huge density contrasts, fast rotating cores and chemical discontinuities leading to sharp features in the Brunt-Väisälä frequency, the message sent to us through the frequency spectra is extremely difficult to understand and interpret. It is a real challenge to decipher what such stars are really telling us.A main goal of this colloquium was first to present and discuss what we know about the structure of low-mass stars at advanced phases of their evolution, and especially to point out the numerous open problems in their structure and their evolution. Asteroseismology then gives a glimpse into the deep interior of these stars. Moreover, we can determine masses, radii and ages with an unprecedented accuracy. Not forgetting all our other tools (in particular spectroscopy for obtaining stellar metallicities), a better understanding of the evolution of stars and of the structure and the chemical evolution of our Galaxy is now within ...

γ Dor stars are main sequence variable A-F stars whose long periods (between 0.35 and 3 days) correspond to high-order gravity mode pulsation. First, we present some aspects of their internal physics and evolutionary status. Second, we consider the potential of the g modes as a probe of these internal physics. In particular, we consider the effect of sharp features present near the convective core top on the g-mode period pattern. Third, we analyse the driving mechanism of the γ Dor g modes, we stress the role of Time-Dependent Convection (TDC) and for the first time we study the role played by turbulent viscosity variations in this frame. Finally, we consider the important problem of mode identification. We show that the theoretical multi-colour photometric amplitude ratios and the phase differences between the light and velocity curves predicted by TDC models much better agree with observations than Frozen Convection (FC) models. Hence, a more secure photometric mode identification is possible with TDC models.