Our aim is to confirm the nature of the long period radial velocity measurements for β Gem first found by Hatzes & Cochran (1993). We present precise stellar radial velocity measurements for the K giant star β Gem spanning over 25 years. An examination of the Ca II K emission, spectral line shapes from high resolution data (R = 210,000), and Hipparcos photometry was also made to discern the tru...

An undersampled point spread function may interact with the microstructure of a solid-state detector such that the total flux detected can depend sensitively on where the PSF center falls within a pixel. Such intra-pixel sensitivity variations will not be corrected by flat field calibration and may limit the accuracy of stellar photometry conducted with undersampled images, as are typical for H...

We consider the procedure of isochrone fitting and its application to the study of red giant branch (RGB) photometry in old stellar populations. This is extended to consider the problems introduced by the inclusion of lower-magnitude regions of the Colour Magnitude Diagram (CMD). We refer especially to our previous paper Frayn & Gilmore (2002), where the details of our isochrone interpolation a...

We investigate the properties of two stellar concentrations in a low-absorption disk zone in Centaurus, located respectively at l = 306.47◦, b = −0.61◦, and l = 307.01◦, b = −0.74◦. The present analysis is based mostly on 2MASS photometry, as well as optical photometry. Based on colour-magnitude diagrams and stellar radial density profiles, we show that these concentrations are not open star cl...

J , H , K, and L photometry for the stars in the central ∼ 2 (∼ 5 pc) of the Galaxy are presented. Using the observed J − H , H −K, and K − L colors and assumed intrinsic colors, we determine the interstellar extinction at 2.2 μm (AK) for approximately 1100 individual stars. The mean AK (= 3.3 mag) is similar to previous results, but we find that the reddening is highly variable and some stars ...

Spectra of galaxies contain an enormous amount of information about the relative mixture of ages and metallicities of constituent stars. We present a comprehensive study designed to extract the maximum information from spectra of data quality typical in large galaxy surveys. These techniques are not intended for detailed stellar population studies that use high quality spectra. We test techniqu...

Context. In recent years, increasing evidence for chemical complexity and multiple stellar populations in massive globular clusters (GCs) has emerged, including extreme horizontal branches (EHBs) and UV excess. Aims. Our goal is to improve our understanding of UV excess in compact stellar systems, covering the regime of both ultra-compact dwarf galaxies (UCDs) and massive GCs. Methods. We use d...