Rotation is one of the most important observable in stellar astrophysics driving strongly the evolution of stars. This review presents the main observational results on the rotation of Red Giant and Horizontal-Branch stars carried out along the past 50 years. The review brings, in particular, the most recent results based on very accurate measurements of rotational velocity obtained mostly along the last decade.

From recent measurements of the rotational velocities of 1100 B stars and 1700 A stars, we determined the maximum periods of binaries with fully circularized orbits. Combined with published data, we derived the relation of period (days) = 0.001 age0.42 (yr). We were able to reproduce the rotational velocities of giants from v sin i of dwarfs only if rigid body rotation applies to both. However for evolutionary expansions greater than 5 the angular momentum is conserved in shells, which is reasonable physically.

A brief overview of the available information of v sin i and stellar radii in binares is presented.

A correlation between orbital period and log(LX/Lbol) is found for a sample of B-type binary systems. We suggest that wind-wind collisions are the likely mechanism for generating the X-ray emission, and that the mass-loss rates may be enhanced in non-synchronously rotating systems due to the oscillations that are excited by the tidal forces.

66 Oph is a multiple system with a close binary orbiting the B2Ve primary Be star. The binary parameters were derived by two independent methods and spectra of components BA and BB were separated by Fourier disentangling.

We obtained high-resolution spectroscopic observations at 2.226 μm of 13 S-type symbiotic binaries using the Phoenix infrared spectrograph on Kitt Peak telescopes. from an empirical calibration we determined v sin i values for the giant components. Combined with information from a program to determine orbits, the rotational velocities have been used to estimate the sizes of these stars and the fraction of their Roche lobes that they fill.

We present an ongoing study on tidal interactions in late-type close binary stars. New results on tidal circularization are combined with existing data to test and constrain theoretical predictions of tidal circularization in the pre-main-sequence (PMS) phase and throughout the main-sequence phase of stellar evolution. Current data suggest that tidal circularization during the PMS phase sets the tidal cutoff period for binary populations younger than ~ 1 Gyr. Binary populations older than ~ 1 Gyr show increasing tidal cutoff periods with age, consistent with active main-sequence tidal circularization.

We present infrared interferometric angular size measurements for rapidly rotating stars which indicate non-circular projected disk brightness distributions. For the A7IV-V star Altair, assuming that the apparent oblateness of the photosphere is due to the star's rapid rotation, a rigorous evaluation of the observation data in the context of a rigidly rotating Roche model shows that an estimate of v sin i = 210 ± 13 km s–1 can be derived that is independent of spectroscopic techniques. Altair is the first main sequence star for which direct observations of an oblate photosphere have been reported, and the first star for which v sin i has been established from observations of the star's photospheric geometry. Future prospects for this technique are considered, and a prospective catalog of 67 rotationally oblate targets is presented.

Optical long baseline interferometry is a technique sensitive to sky projected brightness distributions, constituting a powerful tool for the study of detailed stellar surface structures. Moreover, by combining high spectral and angular resolution we obtain a technique called differential interferometry that is also sensitive to mechanisms that induce chromatic signatures, such as stellar spots and large scale mass motions (e.g. rapid rotation, non-radial pulsations, shear currents produced by hydrodynamical instabilities). We present here a study of the signatures of stellar rotation on differential interferometry observables showing that they are very sensitive to differential rotation and stellar inclination.

At the time of the last Stellar Rotation symposium in 1969, the map of known pulsators in the H-R Diagram covered a lot less territory, being confined mainly to the classical instability strip. Among the new classes of pulsators are the strongly magnetic roAp (rapidly oscillating Ap) stars whose pulsation amplitudes and phases are modulated with their rotation periods. Among the classical pulsators, the δ Scuti stars are now known to show many more eigenmodes and frequency splitting than was ever recognised three decades ago. Both are examples of the diagnostic potential and severe challenges to detect and interpret correctly rotational fine structure in the pulsational frequency spectrum. In a pulsating star, rotation can perturb the structure or dynamics, and it can split degeneracies to serve as a diagnostic of pulsational modes. One tool which should help us exploit the potential and overcome the challenges of studying the interaction between rotation and pulsation is Canada's MOST (Microvariability & Oscillations of STars) microsatellite. MOST is a small optical telescope and ultraprecise CCD photometer designed to detect and characterise acoustic (p-mode) oscillations with periods of minutes and amplitudes as low as 1 micromagnitude in bright stars. While customised to conduct asteroseismology of solar-type stars, the MOST mission will also include roAp stars as prime targets and eventuallly δ Scutis as secondary targets. I present here simulations of MOST observations of such targets with different rotation periods, in advance of the real data expected in the months after the scheduled 30 June 2003 launch.

In this contribution we review the current status of the determination of the rotational frequency in non-radially pulsating B stars, i.e. β Cep stars and slowly pulsating B stars. Considerable progress is currently being made in the understanding of the non-radial oscillations of main-sequence B stars by means of high-temporal, high-spatial resolution spectroscopic time series. This has led to the detection of frequency multiplets, which are interpreted as rotationally splitted non-radial modes and which allow an accurate determination of the surface rotational frequency in some stars. We outline how our future goal, i.e. the derivation of the internal rotation frequency, can be achieved.

We review the present status of our knowledge about observational evidence of the influence of rotation on the evolution and chemical surface enrichment of OB Main Sequence stars. We pay special attention to the CNO elements and show that luminosity class IV-V OB stars provide a good reference point for abundance analyses.

While there is clear evidence of rotationally induced mixing in OB stars, we show that fast rotation is not a guarantee of enrichment. A comparison of observed data with present evolutionary models indicates that the observed facts can be explained assuming that the stars are born with a distribution of rotational velocities, and that depending on the stellar mass the surface abundance changes will be dominated by rotation or mass loss. Only the existence of a large number of B supergiants beyond the Main Sequence cannot be explained in this scenario. We show that current evolutionary models including rotation do not adequately account for the transfer of angular momentum from the interior to the surface.

We point out that the difficulty in determining He abundances and in knowing the present or past binary status of many stars leads us to consider the above conclusions as preliminary.

We present CNO abundance determinations in 11 Magellanic Cloud O and early B supergiants based on physical parameters obtained from FUSE, HST/IUE and VLT spectroscopy, plus model atmospheres which allow for stellar winds and line blanketing. In all cases, nitrogen is substantially enhanced whilst carbon and generally oxygen are moderately depleted, indicative of rotationally induced mixing of unprocessed and CNO processed material at their stellar surfaces.

We have carried out a spectral analysis of 17 O-type stars in the Small Magellanic Cloud (SMC). We find several lines of evidence that rotation plays an important role in massive stars in this low-metallicity galaxy (Z=0.2 Z⊙): (1) strong enrichment of nitrogen in half the program stars due to rotational mixing of processed material in the core up to the surface; (2) reduction of the effective gravity by the centrifugal force; (3) apparent anomalies in cluster isochrones that imply some stars are rotating at critical velocities.

High dispersion spectra in the visible range were obtained for field Be Stars in both hemispheres. As Be Stars form a class of Main Sequence fast rotators, we are intended to test how their chemical composition can be affected by rotation.

In the present work, we propose a study performed on a pole-on Be star using its IUE and FUSE spectra that we showed only slightly affected by circumstellar emission. All our computations take into account the effects of fast rotation on the spectra (differential Doppler broadening + deformation and gravitational darkening). Using the line profiles of several well known transitions and a least squares method, we determine the abundance of light elements in the photosphere of HD 120991 and compare them to the chemical composition of the interstellar medium seen in the line of sight.

Massive young stars can be used to trace the current chemical composition of the Galactic disk and to define its metallicity gradient. However, evolutionary models of massive rotating stars predict changes of the surface abundances due to rotationally induced mixing. The abundance analysis of elements sensitive to mixing, such as CNO, can be used to test these rotating stellar models. In this study we identify those stars that show one particular signature of mixing, N-enrichment, in our sample of 70 OB stars for which we have conducted an abundance analysis. This sample is used to define radial metallicity gradients in the Milky Way and we investigate the variation of the calculated nitrogen gradient after the exclusion of these, probably mixing-induced, N-rich stars.

The abundances of red giants will be reviewed, in particular those of carbon, nitrogen, oxygen and 12C:13C. The observed abundances are compared to predictions based on recent models with stellar rotation. Three topics will be emphasized: abundances in very metal-poor stars related to a previous generation of supernova; 12C:13C in red giants and rotation induced extra mixing; CNO abundances in yellow supergiants and their connection with models computed with rotation.

Lithium abundances have been determined for 130 stars sampled on the basis that they have just about completed depletion of Li on the main sequence and have not yet begun their ascent on the red giant branch. The main goal is to study the effects of rotation on Li depletion. Analysis of the data reveals that fast rotating stars have suffered little depletion whereas slowly rotating stars have both low and high Li abundances. No one-to-one correlation appears to exist between Li abundance and the present v sini. The large observed spread in Li abundance is perhaps a consequence of an initial range in rotational velocities in stars spinning down to low values on the main sequence. An attempt is made to study the Li evolution as a function of age, mass and rotation against the backdrop of the evolutionary tracks on the HR diagram.