367 citations · 6.1k across the 116 of their papers we have counts for
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Blue Stragglers After the Main Sequence
Alison Sills, Amanda Karakas, John Lattanzio
We study the post-main sequence evolution of products of collisions between main sequence stars (blue stragglers), with particular interest paid to the horizontal branch and asympt…
The Dynamical Implications of Multiple Stellar Formation Events in Galactic Globular Clusters
Jonathan M. B. Downing, Alison Sills
Various galactic globular clusters display abundance anomalies that affect the morphology of their colour-magnitude diagrams. In this paper we consider the possibility of helium en…
Where the Blue Stragglers Roam: Searching for a Link Between Formation and Environment
Nathan Leigh, Alison Sills, Christian Knigge
The formation of blue stragglers is still not completely understood, particularly the relationship between formation environment and mechanism. We use a large, homogeneous sample o…
Discovery of Carbon/Oxygen depleted Blue Straggler Stars in 47 Tucanae: the chemical signature of a mass-transfer formation process
F. R. Ferraro, E. Sabbi, R. Gratton +10
We use high-resolution spectra obtained with the ESO Very Large Telescope to measure surface abundance patterns of 43 Blue Stragglers stars (BSS) in 47 Tuc. We discovered that a su…
The Chemical Evolution of Helium in Globular Clusters: Implications for the Self-Pollution Scenario
Amanda Karakas, Yeshe Fenner, Alison Sills +2
We investigate the suggestion that there are stellar populations in some globular clusters with enhanced helium (Y from 0.28 to 0.40) compared to the primordial value. We assume th…
Tracing the Dynamical History of the Globular Cluster 47 Tucanae
Eric Monkman, Alison Sills, Justin Howell +3
We use two stellar populations in the globular cluster 47 Tucanae to trace its dynamical history: blue stragglers and low mass main sequence stars. We assumed that the blue straggl…
Structure and Evolution of Nearby Stars with Planets II. Physical Properties of ~1000 Cool Stars from the SPOCS Catalog
Genya Takeda, Eric B. Ford, Alison Sills +3
We derive detailed theoretical models for 1074 nearby stars from the SPOCS (Spectroscopic Properties of Cool Stars) Catalog. The California and Carnegie Planet Search has obtained…
Helium enhancements in globular cluster stars from Asymptotic Giant Branch star pollution
Amanda Karakas, Yeshe Fenner, Alison Sills +2
Using a chemical evolution model we investigate the intriguing suggestion that there are populations of stars in some globular clusters (e.g. NGC 2808, omega Centauri) with enhance…
A comparison of hydrodynamics techniques for modelling collisions between main sequence stars
Hy Trac, Alison Sills, Ue-Li Pen
An Eulerian TVD code and a Lagrangian SPH code are used to simulate the off-axis collision of equal-mass main sequence stars in order to address the question of whether stellar mer…
Constraining global properties of the Draco dwarf spheroidal galaxy
Sergey Mashchenko, Alison Sills, H. M. P. Couchman
By fitting a flexible stellar anisotropy model to the observed surface brightness and line-of-sight velocity dispersion profiles of Draco we derive a sequence of cosmologically pla…
Formation of mini-galaxies in defunct cosmological HII regions
Sergey Mashchenko, H. M. P. Couchman, Alison Sills
Using a large set of high resolution numerical simulations incorporating non-equilibrium molecular hydrogen chemistry and a constant source of external radiation, we study gas coll…
The Effect of Pre-Main Sequence Stars on Star Cluster Dynamics
R. Wiersma, A. Sills, S. Portegies Zwart
We investigate the effects of the addition of pre-main sequence evolution to star cluster simulations. We allowed stars to follow pre-main sequence tracks that begin at the deuteri…
Simulations of Stellar Collisions Involving Pre-Main Sequence Stars
Daniel Laycock, Alison Sills
In this paper, we present the results of smoothed particle hydrodynamic (SPH) simulations of collisions between pre-main sequence stars and a variety of other kinds of stars. Simul…
Lithium enhancement in X-ray binaries due to stellar rotation
T. J. Maccarone, P. G. Jonker, A. I. Sills
We discuss the high lithium abundances in the secondary stars of X-ray binaries. We show that no lithium production in these stars is necessary, and that the abundances can be expl…
Modeling star formation in dwarf spheroidal galaxies: a case for extended dark matter halos
Sergey Mashchenko, H. M. P. Couchman, Alison Sills
We propose a simple model for the formation of dwarf spheroidal galaxies, in which stars are assumed to have formed from isothermal gas in hydrostatic equilibrium inside extended d…
Globular Clusters with Dark Matter Halos. II. Evolution in Tidal Field
Sergey Mashchenko, Alison Sills
In this second paper in our series, we continue to test primordial scenarios of globular cluster formation which predict that globular clusters formed in the early universe in the…
Globular Clusters with Dark Matter Halos. I. Initial Relaxation
Sergey Mashchenko, Alison Sills
In a series of two papers, we test the primordial scenario of globular cluster formation using results of high-resolutions N-body simulations. In this first paper we study the init…
The small Blue Straggler star population in the dense Galactic Globular Cluster NGC 6752
E. Sabbi, F. R. Ferraro, A. Sills +1
We have used high resolution WFPC2-HST and wide field ground-based observations to construct a catalog of blue straggler stars (BSS) which spans the entire radial extent of the glo…
The Universality of Initial Conditions for Globular Cluster Formation
Sergey Mashchenko, Alison Sills
We investigate a simple model for globular cluster (GC) formation. We simulate the violent relaxation of initially homogeneous isothermal stellar spheres and show that it leads to…
The contribution of primordial binaries to the blue straggler population in 47 Tucanae
M. Mapelli, S. Sigurdsson, M. Colpi +5
The recent observation (Ferraro et al. 2003b) of the blue straggler population in 47 Tucanae gives the first detailed characterization of their spatial distribution in the cluster…
Discovery of another peculiar radial distribution of Blue Stragglers in Globular Clusters: The case of 47 Tuc
Francesco R. Ferraro, Giacomo Beccari, Robert T. Rood +3
We have used high resolution WFPC2-HST and wide field ground-based observations to construct a catalog of blue straggler stars (BSS) in the globular cluster 47 Tuc spanning the ent…
Theoretical Examination of the Lithium Depletion Boundary
Christopher J. Burke, Marc H. Pinsonneault, Alison Sills
We explore the sensitivity in open cluster ages obtained by the lithium depletion boundary (LDB) technique to the stellar model input physics. The LDB age technique is limited to o…
Blue Straggler Stars: a direct comparison of Star counts and population ratios in six Galactic Globular Clusters
Francesco R. Ferraro, Alison Sills, Robert T. Rood +2
The central regions of six Galactic Globular Clusters (GGCs) (M3, M80, M10, M13, M92 and NGC 288) have been imaged using HST-WFPC2 and the ultraviolet (UV) filters (F255W, F336W).…
Rotation and activity in the solar-metallicity open cluster NGC2516
Donald M. Terndrup, Marc Pinsonneault, Robin D. Jeffries +3
We report new measures of radial velocities and rotation rates (v sin i) for 51 F and early-G stars in the open cluster NGC2516, and combine these with previously published data. F…