Echelle spectra of the infrared He I λ10830 line were obtained with NIRSPEC on the Keck 2 telescope for 41 metal-deficient field giant stars including those on the red giant branch (RGB), asymptotic giant branch (AGB), and red horizontal branch (RHB). The presence of this He I line is ubiquitous in stars with Teff & 4500K and MV fainter than −1.5, and reveals the dynamics of the atmosphere. The...

For a complete 12 μm flux-limited sample of 207 IRAS sources (F12 ≥ 150 Jy, |b| ≥ 5), the majority of which are AGB stars (∼87%), we have extracted light curves in seven infrared bands between 1.25 μm − 60 μm using the database of the Diffuse Infrared Background Experiment (DIRBE) instrument on the Cosmic Background Explorer (COBE) satellite. Using previous infrared surveys, we filtered these l...

We study the dense core of the globular cluster Messier 13 (NGC 6205) using pre-refurbishment Planetary Camera-I images obtained with the Hubble Space Telescope. Short exposures (60 s) through the F555W and F785LP filters (similar to Johnson V and I, respectively) have been used to obtain V and I photometry of 2877 stars brighter than V ∼ 20 in a 1.25 arcmin region of the cluster including its ...

We detected the H2O 6.3 μm bands in more than 30 normal red giants stars from K5III to M8III as well as in some early M supergiants on the SWS spectra retrieved from the ISO Data Archive. This result, however, shows serious inconsistency with the present model photospheres which predict H2O only in the latest M (super)giant stars. Also H2O was once discovered in the early M (super)giant stars n...

We present Keck 10-meter / LRIS spectra of candidate red giants in the halo of M31, located at a projected radius of R = 19 kpc on the minor axis. These spectroscopic targets have been selected using a combination of UBRI-based and morphological screening to eliminate background galaxies. Radial velocity measurements are used to separate M31 halo giants from foreground Milky Way dwarf stars, M3...

This study confirms the results of the preliminary study (Russell, 1997) indicating that RV Tau variables in globular clusters don’t show the kind of anomalous abundances seen in RV Tau variables observed in the field. By making comparisons with red giants in the same clusters, it has been possible, for the first time, to identify precisely how each element deviates from the normal abundance ra...

I present a selection of results obtained from VLT FORS1 and ISAAC photometric monitoring of late-type giants in NGC 5128 (=Centaurus A). The combination of optical and near-IR photometry allows to probe the full metallicity range of the stars on the upper red giant branch, thanks to combined low-metallicity sensitivity of the optical and high-metallicity sensitivity of the near-IR bands. The m...

With the advent of surveys generating multi-epoch photometry and their discoveries of large numbers of variable stars, the classification of the obtained times series has to be automated. We have developed a classification algorithm for the periodic variable stars using a Bayesian classifier on a Fourier decomposition of the light curve. This algorithm is applied to ASAS (All Sky Automated Surv...

Atmospheric parameters (Teff , log g), and radial velocities are derived for twelve candidate blue horizontal branch (HB) stars in the globular clusters 47 Tuc and NGC 362, which so far have been known to contain primarily red HB stars. The spectroscopic targets were selected from the catalog of hot stars detected in these clusters at 1600 Å using the Ultraviolet Imaging Telescope (UIT). Spectr...