Related papers: The binary fraction in the globular cluster NGC 63…

We have used the Wide Field Planetary Camera 2 aboard the Hubble Space Telescope to image the compact star cluster nuclei of the nearby, late-type, low-luminosity spiral galaxies NGC 4395, NGC 4242, and ESO 359-029. We also analyze archival…

This is the first of two papers presenting a detailed examination of Fokker-Planck models for the globular cluster NGC 6397. I show that these models provide a good match to observations of the surface density profile, mass functions at…

We search for mass segregation in the intermediate-aged open cluster NGC 6819 within a carefully identified sample of probable cluster members. Using photometry from the Gaia, 2MASS, and Pan-STARRS surveys as inputs for a Bayesian…

We present (V,V-I) VLT-FORS1 observations of the Galactic Globular Cluster NGC 6397. We derive accurate color--magnitude diagrams and luminosity functions (LFs) of the cluster Main Sequence (MS) for two fields extending from a region near…

Globular clusters (GCs) display much lower binary fractions than found among main-sequence stars in the solar neighborhood. The physical cause of this difference is debatable: does it reflect different star formation outcomes at low…

We have performed a series of direct N-body simulations that study the evolution of the Galactic globular cluster NGC 6397 under the combined influence of two-body relaxation, stellar evolution and the Milky Way's tidal field. Our…

We analyze proper motions from the Hubble Space Telescope (HST) and the second Gaia data release along with line-of-sight velocities from the MUSE spectrograph to detect imprints of an intermediate-mass black hole (IMBH) in the center of…

We report on new WFPC2 observations of the globular cluster NGC 288, focusing our attention on peculiar stars. A very pronounced binary sequence, paralleling the ordinary Main Sequence (MS) is clearly observed in the Color Magnitude Diagram…

We carried out a radial velocity survey for spectroscopic binaries in the low density globular cluster NGC5053. Our sample contains a total of 77 cluster member giant and subgiant stars with visual magnitudes of 14.5-18.6. Of these 77…

In an attempt to determine how many planetary nebulae derive from binary interactions, we have started a project to measure their unbiased binary fraction. This number, when compared to the binary fraction of the presumed parent population…

It is generally assumed that a large fraction of stars are initially born in clusters. However, a large fraction of these disrupt on short timescales and the stars end up belonging to the field. Understanding this process is of paramount…

We describe images of the center of the dense globular cluster M15 (NGC 7078) obtained with the Hubble Space Telescope Wide Field and Planetary Camera 2 (WFPC2). Data taken in the F336W, F439W, and F555W filters (approximately U, B, and V)…

We examine the theoretical implications of a population of low-mass helium-core white dwarfs in globular clusters. In particular, we focus on the observed population in the core of NGC 6397, where several low-mass white dwarf canditates…

Binary stars play a vital role in astrophysical research, as a good fraction of stars are in binaries. Binary fraction (BF) is known to change with stellar mass in the Galactic field, but such studies in clusters require binary…

The determination of the Ba abundance in globular cluster (GC) stars is a very powerful test to address several issues in the framework of multiple population scenarios. We measured the Ba content for a sample of more than 1200 stars in 15…

Using the Planetary Camera on board the Hubble Space Telescope we have measured the projected separation of the binary components in the nucleus of the planetary nebula Abell 35 to be larger than 0.08 arcsecs but less than 0.14 arcsecs. The…

Using archival Hubble Space Telescope observations, we report the discovery of four variable low-mass white dwarfs ($0.18 \, M_\odot \leq M \leq 0.5 \,M_\odot$) in the globular cluster NGC 6397. One source exhibits a periodic optical…

Searches for planetary transits carried out in open and globular clusters have yielded to date only a handful of weak, unconfirmed candidates. These results have been interpreted either as being insignificant, or as evidence that the…

We present results constraining the multiplicity of the very low mass stars and sub-stellar objects in the Orion Nebula Cluster (ONC). Our sample covers primary masses 0.012-0.1M$_{\odot}$ using archival Hubble Space Telescope data obtained…

We report the discovery of a peculiar horizontal branch (HB) in NGC 6440 and NGC 6569, two massive and metal-rich Galactic globular clusters (GGCs) located in the Galactic bulge, within 4 kpc from the Galactic Center. In both clusters, two…