We present non-LTE corrections to abundances of Fe, O, Na, and Mg derived from LTE analyses of F-K stars over a broad range of gravities and metal abundances; they were obtained using statistical equilibrium calculations and new model atoms. Line opacity was considered by means of an empirical procedure where it was attributed to a veil of weak Fe I lines; in the case of solar-type dwarfs, resu...

The observed abundance variations in globular cluster red giants indicate that these stars may be mixing helium from the hydrogen shell outward into the envelope, presumably as a result of internal rotation. We have investigated the implications of such helium mixing for both the red-giant-branch (RGB) and horizontal-branch (HB) phases by computing a number of noncanonical evolutionary sequence...

We present new interferometric observations for 74 luminous red stars, made in the near-infrared. We show that our 2.2 km uniform-disk diameters agree with other near-infrared diameter determinations (lunar occultations and interferometers) for 22 stars measured in common with ours. From our new data, we derive e†ective temperatures that are compared with our previous work and with comparable o...

Abstract Known sources of lithium (Li) in the universe include Big Bang, novae, asymptotic giant branch stars, and cosmic-ray spallation. During their longer-lived evolutionary phases, stars are not expected to add Li budget Galaxy, but largely deplete it. In this context, recent analyses data from GALAH LAMOST for field red clump (RC) have concluded that there is need a new production channel ...

In this study, we explore the evolution of lithium in giant stars based on data assembled from literature asteroseismology and Li abundances for giants. Our final sample 187 giants consists 44 red branch (RGB), 140 core He-burning (CHeB) three with an unclassified evolutionary phase. For all stars, seismic parameters $\nu\rm_{max}$ (frequency maximum oscillation power) $\Delta \nu$ (large frequ...

We present simple stellar population models based on the empirical X-shooter Spectral Library (XSL) from near-ultraviolet (NUV) to near-infrared (NIR) wavelengths. The unmatched characteristics of relatively high resolution and extended wavelength coverage (350–2480 nm, R ∼ 10 000) XSL bring us closer bridging optical NIR studies intermediate-age old populations. It is now common find good agre...

Context. Red giants are evolved stars which exhibit solar-like oscillations. Although a multitude of stars have been observed with space telescopes, only a handful of red-giant stars were targets of spectroscopic asteroseismic observing projects. Aims. We search for solar-like oscillations in the two bright red-giant stars γ Psc and θ1 Tau from time series of ground-based spectroscopy and deter...

The absolute magnitude of barium stars has been obtained from kinematical data using a new algorithm based on the maximum-likelihood principle. The method allows to separate a sample into groups characterized by different mean absolute magnitudes, kinematics and z-scale heights. It also takes into account, simultaneously, the censorship in the sample and the errors on the observables. The metho...

Abstract While solar-like oscillations in red giants have been observed at massive scales by the Kepler mission, few features of these oscillation mode frequencies, other than their global properties, exploited for stellar characterization. The signatures acoustic glitches frequencies used studying main-sequence stars, but validity applying such techniques to evolved giants, particularly pertai...

Deep UBVI photometry for a large field covering the distant globular cluster M75 (NGC 6864) is presented. We confirm a previous suggestion (Catelan et al. 1998a) that M75 possesses a bimodal horizontal branch (HB) bearing striking resemblance to the well-known case of NGC 1851. In addition, we detect a third, smaller grouping of stars on the M75 blue tail, separated from the bulk of the blue HB...