Related papers: Multiple stellar populations and their influence o…
Blue stragglers are thought to be formed from the merger or coalescence of two stars, but the details of their formation in clusters has been difficult to disentangle. We discuss the two main formation mechanisms for blue stragglers…
We investigate the viability of a model in which the chemical anomalies among Globular Cluster stars are due to accretion of gas onto the protostellar discs of low mass stars. This model has been suggested as a way to reduce the large…
The study of cluster populations as tracer of galaxy evolution is now quite possible with 8 m class telescopes and modern instrumentation. The cluster population can be used as a good tracer of the star forming episodes undergone by the…
Stars in globular clusters are generally believed to have all formed at the same time, early in the Galaxy's history. 'Blue stragglers' are stars massive enough that they should have evolved into white dwarfs long ago. Two possible…
Blue stragglers in globular clusters are abnormally massive stars that should have evolved off the stellar main sequence long ago. There are two known processes that can create these objects: direct stellar collisions and binary evolution.…
Almost several decades after the discovery of the first multiple populations in galactic globular clusters (GC) the debate on their formation is still extremely current and NGC2808 remains one of the best benchmark to test any scenario for…
In young dense clusters repeated collisions between massive stars may lead to the formation of a very massive star (above 100 Msun). In the past the study of the long-term evolution of merger remnants has mostly focussed on collisions…
There is increasing evidence that some massive globular clusters (GCs) host multiple stellar populations having different heavy element abundances enriched by supernovae. They usually accompany multiple red giant branches (RGBs) in the…
Theory and observations suggest that single-star evolution is not able to produce black holes (BHs) with masses in the range $3-5M_{\odot}$ and above $\sim 45M_{\odot}$, referred to as the lower mass gap (LMG) and the upper mas gap (UMG),…
Recent surveys of the blue straggler (BS) population in the galactic globular cluster M3 (NGC 5272) give the first complete characterization of the number density of BSs as a function of radius over an entire globular cluster. The BSs in M3…
We have surveyed the blue straggler star population of the Galactic globular cluster M5 using high-resolution images of the core along with wide-field ground-based images reaching to more than 19 core radii. To gauge M5's relative…
We develop a Bayesian model for globular clusters composed of multiple stellar populations, extending earlier statistical models for open clusters composed of simple (single) stellar populations (vanDyk et al. 2009, Stein et al. 2013).…
Recent work, based on data from the Hubble Space Telescope (HST) UV Legacy Survey of Galactic Globular Clusters (GCs), has revealed that all the analyzed clusters host two groups of first- (1G) and second-generation (2G) stars. In most GCs,…
The presence of young stellar populations in the Large Magellanic Cloud cluster NGC 1783 has caught significant attention, with suggestions ranging from it being a genuine secondary stellar generation to a population of blue straggler stars…
Multiple stellar populations are observed in almost all globular-clusters, but the origin of this phenomenon is still debated. We investigate the role cool supergiants may have played. To do this, we combine two investigative methods:…
When two stars collide and merge they form a new star that can stand out against the background population in a starcluster as a blue straggler. In so called collision runaways many stars can merge and may form a very massive star that…
We present preliminary results obtained from the comparison of the specific frequencies of Blue Straggler Stars (BSS) detected so far in a sample of 26 Galactic globular clusters. The number of BSS seems to increase almost linearly with…
Observations show that nearly all star clusters and stellar populations contain blue straggler stars (BSs). BSs in a cluster can significantly enhance the integrated spectrum of the host population, preferentially at short wavelengths, and…
We studied the color distribution of the main sequence of the Globular Cluster NGC 2808, based on new deep HST-WFPC2 photometry of a field in the uncrowded outskirts of the cluster. The color distribution of main sequence stars is wider…
We examine the blue straggler populations of 13 low-luminosity (M_V_t >~ -6) globular clusters and 2 old open clusters. These clusters test blue straggler formation in environments intermediate between higher luminosity (and usually higher…