Related papers: Red Giant Branch Bump Star Counts in Data and Stel…
Previous studies have shown that the large, diffuse galaxies NGC1052-DF2 and NGC1052-DF4 both have populations of unusually luminous globular clusters as well as a very low dark matter content. Here we present newly-obtained deep Hubble…
Differences between the local value of the Hubble constant measured via the distance ladder versus the value inferred from the cosmic microwave background with the assumption of the standard $\Lambda$CDM model have reached over 5$\sigma$…
The luminosity of the Tip of the Red Giant Branch (TRGB) provides an excellent measure of galaxy distances and is easily determined in the resolved images of nearby galaxies observed with Hubble Space Telescope. There is now a large amount…
Because of their brightness, gamma-ray burst (GRB) afterglows are viable targets for investigating the dust content in their host galaxies. Simple intrinsic spectral shapes of GRB afterglows allow us to derive the dust extinction. Recently,…
New theoretical evaluations of the Red Giant Branch Tip (TRGB) luminosity, by adopting the most updated physical inputs in computing canonical stellar models, are presented. Theoretical relations for the run of the TRGB bolometric and I…
The tip of the red giant branch has been used to measure distances to 500 nearby galaxies with the Hubble Space Telescope (HST) which are available in the Color-Magnitude Diagrams and Tip of the Red Giant Branch (CMDs/TRGB) catalog on the…
Redshift and luminosity distributions are essential for understanding the cosmic evolution of extragalactic objects and phenomena, such as galaxies, gamma-ray bursts, and fast radio bursts (FRBs). For FRBs, these distributions are primarily…
In this letter, we calculate the redshift distribution of gamma-ray bursts assuming that they trace (i) the globally averaged star formation rate or (ii) the average metallicity in the Universe. While at redshifts 5 and below, both the star…
(Abridged) We demonstrate that the amount of extra mixing required to fit the observed low C/N and 12C/13C ratios in first giant branch (FGB) stars is also sufficient to explain the C and N abundances of Galactic AGB stars. We simulate the…
We used a proper combination of high-resolution HST observations and wide-field ground based data to derive the radial star density profile of 26 Galactic globular clusters from resolved star counts (which can be all freely downloaded…
Deriving the physical properties of red supergiants (RSGs) depends upon accurate corrections for reddening by dust. We use our recent modeling of the optical spectra of RSGs to address this topic. We find: (1) Previous broad-band studies…
We present an extensive peakbagging effort on Kepler data of $\sim$50 red giant stars in the open star cluster NGC 6819. By employing sophisticated pre-processing of the time series and Markov Chain Monte Carlo techniques we extracted…
We present results from an HST/ACS imaging study of the metal-poor blue compact dwarf galaxy SBS 1415+437. It has been argued previously that this is a very young galaxy that started to form stars only less than 100 Myr ago. However, we…
Preliminary results from an ongoing project to compute a grid of post-AGB models is presented. Our preliminary results show that stellar evolution computations that include an updated treatment of the microphysics predict post-AGB…
Red clump giants in the Galactic bulge are approximate standard candles and hence they can be used as distance indicators. We compute the proper motion dispersions of RCG stars in the Galactic bulge using the proper motion catalogue from…
We show that collisions with stellar--mass black holes can partially explain the absence of bright giant stars in the Galactic Centre, first noted by Genzel et al, 1996. We show that the missing objects are low--mass giants and AGB stars in…
Long-duration Gamma Ray Bursts (GRBs) are linked to the collapse of massive stars and their hosts are exclusively identified as active, star forming galaxies. Four long GRBs observed at high spectral resolution at redshift 1.5 <z < 4…
Asymptotic giant branch (AGB) stars play a key role in the enrichment of galaxies with heavy elements. Due to their large amplitude variability, the measurement of elemental abundances is a highly challenging task that has not been solved…
We compare a large sample of galaxies between 0.5<z<2.6 with theoretical predictions for how the optical diagnostic line ratios in galaxy ensembles change as a function of cosmic time. We show that star forming galaxies at high redshift…
We exploit multi-band Hubble Space Telescope photometry to investigate multiple populations (MPs) along the red horizontal branches (HBs) and red clumps of fourteen metal-rich Globular Clusters (GCs), including twelve Milky Way GCs and the…