Related papers: Red Giant Branch Bump Star Counts in Data and Stel…
We present high-resolution (R~60,000) optical spectra of a carefully selected sample of heavily obscured and presumably massive O-rich Asymptotic Giant Branch (AGB) stars in the Magellanic Clouds (MCs). We report the discovery of strong Rb…
We examine the reliability of the tip of the red giant branch (TRGB) as a distance indicator for stellar populations with different star formation histories (SFHs) when photometric errors and completeness corrections at the TRGB are small.…
Although red clump (RC) stars are easy to identify due to their stability of luminosity and color, about 20-50% are actually red giant branch (RGB) stars in the same location on the HR diagram. In this paper, a sample of 210,504 spectra for…
Low-mass stars in the He-core-burning phase (HeCB) play a major role in stellar, galactic, and extragalactic astrophysics. The ability to predict accurately the properties of these stars, however, depends on our understanding of convection,…
The high-frequency resolution of the four-year $\textit{Kepler}$ time series allows detailed study of seismic modes in luminous giants. Seismic observables help infer interior structures via comparisons with stellar models. We aim to…
We conduct a series of comparisons between spectroscopic and photometric observations of globular clusters and stellar models to examine their predictive power. Data from medium-to-high resolution spectroscopic surveys of lithium allow us…
A grid of evolutionary sequences of stars in the mass range $1.2$-$7$ M$_{\odot}$, with solar-like initial composition is presented. We focus on this mass range in order to estimate the masses and calculate the CNO surface abundances of a…
We use the BD2 sample of gamma-ray bursts (GRBs) based on 5.9 years of BATSE DISCLA data with a variety of models of the luminosity function to derive characteristic GRB luminosities, space densities and redshift distributions. Previously…
Globular Cluster (GC) Color-Magnitude Diagrams (CMDs) are reasonably well understood in terms of standard stellar-evolution. However, there are still some open issues, such as fully accounting for the Horizontal Branch (HB) morphology in…
Gamma-Ray Bursts (GRBs), due to their high luminosities are detected up to redshift 10, and thus have the potential to be vital cosmological probes of early processes in the universe. Fulfilling this potential requires a large sample of…
We present the most extensive and complete study of the properties for the largest sample (46 objects) of gamma-ray burst (GRB) host galaxies. The redshift interval and the mean redshift of the sample are 0<z<6.3 and z=0.96 (look-back time:…
The rate of long-duration gamma ray bursts (GRBs) has been identified as a potential proxy for the star formation rate (SFR) across redshift, but the exact relationship depends on GRB progenitor models (single versus binary). The…
The color-magnitude diagrams of $\sim 7 \times 10^5$ stars obtained for 12 fields across the Galactic bulge with the OGLE project reveal a well-defined population of bulge red clump giants. We find that the distributions of the apparent…
The study of the inner region of the Milky Way's bulge is hampered by high interstellar extinction and extreme source crowding. Sensitive high angular resolution near-infrared imaging is needed to study stellar populations in such a complex…
The tip of the red giant branch (TRGB) is an important standard candle for determining luminosity distances. Although several $10^5$ small amplitude red giant stars (SARGs) have been discovered, variability was previously considered…
We present grids of massive star evolution models at four different metallicities (Z=0.004, 0.002, 0.001, 0.00001). The effects of rotation on the stellar structure and the transport of angular momentum and chemical elements through the…
Context: We present a newly discovered class of low-luminosity, dusty, evolved objects in the Magellanic Clouds. These objects have dust excesses, stellar parameters, and spectral energy distributions similar to those of dusty…
We present observations with the Hubble Space Telescope Wide Field Planetary Camera 2 of three fields centered on super-metal-rich globular clusters in the bulge of M31. Our (I,V-I) color-magnitude diagrams reach as faint as I ~ 26.5 mag…
We constrain the stellar population properties of a sample of 52 massive galaxies, with stellar mass log Ms>10.5, over the redshift range 0.5<z<2 by use of observer-frame optical and near-infrared slitless spectra from HST's ACS and WFC3…
Standard stellar evolution theory poorly predicts the surface abundances of chemical species in low-mass, red giant branch (RGB) stars. Observations show an enhancement of p-p chain and CNO cycle products in red giant envelopes, which…