Blue Stragglers, Young White Dwarfs and UV-excess stars in the core of 47 Tuc

Abstract

We used a set of archived HST/WFPC2 images to probe the stellar population in the core of the nearby Galactic Globular Cluster (GGC) 47 Tuc. From the ultraviolet (UV) Color Magnitude Diagrams (CMDs) obtained for ~4,000 stars detected within the Planetary Camera (PC) field of view we have pinpointed a number of interesting objects: (i) 43 blue stragglers stars (BSSs) including 20 new candidates; (ii) 12 bright (young) cooling white dwarfs (WDs) at the extreme blue region of the UV-CMD; (iii) a large population of UV-excess (UVE) stars, lying between the BSS and the WD sequences. The WD candidates identified here define a clean pattern in the CMD, which define the WD cooling sequence. Moreover, both the location on the UV-CMDs and the number of WDs are in excellent agreement with the theoretical expectations. The UVE stars discovered here represent the largest population of anomalous blue objects ever observed in a globular cluster -- if the existence of such a large population is confirmed, we have finally found the long-searched population of interacting binaries predicted by the theory. Finally, we have investigated the feasibility of the optical identification of the companions of the binary X-ray sources recently detected by CHANDRA and of binary millisecond pulsars (MSPs) residing in the core of 47 Tuc. Unfortunately, the extreme faintness expected for the MSP companions together with the huge stellar crowding in the cluster center prevent statistically reliable identifications based only on positional coincidences.

27 pages, LaTex, 4 Postscript figures. Astrophysical Journal, in press

References in corpus (2)

• High Resolution X-ray Imaging of a Globular Cluster Core: Compact Binaries in 47Tuc
• Timing the millisecond pulsars in 47 Tucanae

Cited by in corpus (73)

• Legacy ExtraGalactic UV Survey (LEGUS) with The Hubble Space Telescope. I. Survey Description
• A Deep Chandra Survey of the Globular Cluster 47 Tucanae: Catalog of Point Sources
• Relativistic Binaries in Globular Clusters
• Star formation histories of early-type galaxies. I: Higher order Balmer lines as age indicators
• Monte Carlo Simulations of Globular Cluster Evolution. III. Primordial Binary Interactions
• The Ital-FLAMES survey of the Sagittarius dwarf Spheroidal galaxy. I. Chemical abundances of bright RGB stars
• Blue Straggler Stars: a direct comparison of Star counts and population ratios in six Galactic Globular Clusters
• An Extensive Census of HST Counterparts to Chandra X-ray Sources in the Globular Cluster 47 Tucanae. I. Astrometry and Photometry
• The peculiar Horizontal Branch of NGC 2808
• The pure non-collisional Blue Straggler population in the giant stellar system omega Centauri
• Discovery of another peculiar radial distribution of Blue Stragglers in Globular Clusters: The case of 47 Tuc
• The puzzling dynamical status of the core of the globular cluster NGC 6752
• Implications for the Formation of Blue Straggler Stars from HST Ultraviolet Observations of NGC 188
• Blue Straggler Stars in the Unusual Globular Cluster NGC 6388
• A Panchromatic Study of the Globular Cluster NGC 1904. I: The Blue Straggler Population
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters - XV. The dynamical clock: reading cluster dynamical evolution from the segregation level of blue straggler stars
• VLT spectroscopy of NGC3115 globular clusters
• A Far-Ultraviolet Survey of 47 Tucanae. I. Imaging
• Mergers of close primordial binaries
• The Blue Straggler Population of the Globular Cluster M5
• Blue Straggler masses from pulsation properties. I. The case of NGC6541
• The small Blue Straggler star population in the dense Galactic Globular Cluster NGC 6752
• Stellar Exotica in 47 Tucanae
• Discovery of three new millisecond pulsars in Terzan 5
• The Helium White Dwarf orbiting the Millisecond Pulsar in the halo of the Globular Cluster NGC 6752
• Wide Field Photometry of the Galactic Globular Cluster M22
• The surprising external upturn of the Blue Straggler radial distribution in M55
• UV Properties of Galactic Globular Clusters with GALEX II. Integrated colors
• No evidence of mass segregation in the low mass Galactic globular cluster NGC 6101
• A Chandra X-ray Study of the Globular Cluster M80
• UV Properties of Galactic Globular Clusters with GALEX I. The Color-Magnitude Diagrams
• The dynamical state and blue straggler population of the globular cluster NGC 6266 (M62)
• The optical companion to the binary millisecond pulsar J1824-2452H in the globular cluster M28
• Population Synthesis in the Blue I. Synthesis of the Integrated Spectrum of 47 Tucanae from its Color-Magnitude Diagram
• The "UV-route" to search for Blue Straggler Stars in Globular Clusters: first results from the HST UV Legacy Survey
• Multiwavelength photometry in the Globular Cluster M2
• Radio timing and optical photometry of the black widow system PSR J1518+0204C in the globular cluster M5
• Ultra-deep GEMINI near-infrared observations of the bulge globular cluster NGC 6624
• Optical Identification of He White Dwarfs Orbiting Four Millisecond Pulsars in the Globular Cluster 47 Tucanae
• The Swift UVOT Stars Survey: I. Methods and Test Clusters
• The "dynamical clock": dating the internal dynamical evolution of star clusters with Blue Straggler Stars
• An extremely low-mass He white dwarf orbiting the millisecond pulsar J1342+2822B in the globular cluster M3
• Proper motions and structural parameters of the Galactic globular cluster M71
• A population of binaries in the Asymptotic Giant Branch of 47 Tucanae?
• Helium-Core White Dwarfs in Globular Clusters
• Radio Timing and Optical Photometry of the Black Widow System PSR J1953+1846A in the Globular Cluster M71
• Spectral Energy Distribution of Blue Stragglers in the core of 47 Tucanae
• Slowly cooling white dwarfs in M13 from stable hydrogen burning
• Weighing stars: the identification of an Evolved Blue Straggler Star in the globular cluster 47 Tucanae
• Spinning like a Blue Straggler: the population of fast rotating Blue Straggler stars in Omega Centauri
• Hα photometry of low mass stars in 47 Tucanae: chromospheric activity and exotica
• Probing the role of dynamical friction in shaping the BSS radial distribution. I - Semi-analytical models and preliminary N-body simulations
• GlobULeS-IV. UVIT/AstroSat detection of extremely low mass white dwarf companions to blue straggler stars in NGC 362
• Relativistic Binaries in Globular Clusters
• Constraining the true nature of an exotic binary in the core of NGC 6624
• A Blue Straggler Binary System with at least Three Progenitors in the Core of a Globular Cluster?
• Slowly cooling white dwarfs in NGC 6752
• A young white dwarf orbiting PSR J1835-3259B in the bulge globular cluster NGC 6652
• The radial distribution of Blue stragglers in Galactic Globular Cluster NGC 6656 $-$ Clues on the dynamical status
• Quantum effects and stability of chameleon cosmology
• The temperature distribution of horizontal branch stars: methods and first results
• Far-Ultraviolet Surveys of Globular Clusters: Hunting for the Products of Stellar Collisions and Near Misses
• The dynamical age of the LMC globular cluster NGC 1835 using the "dynamical clock"
• Rotational velocities of Blue Straggler Stars in the Globular Cluster M55
• Relativistic dynamical friction in stellar systems
• Discovery of an extended Horizontal Branch in the Large Magellanic Cloud globular cluster NGC1835
• The "canonical" White Dwarf Cooling Sequence of M5
• Constraining the optical emission from the double pulsar system J0737-3039
• Stellar populations of the globular cluster NGC 5053 investigated using AstroSat-Ultra Violet Imaging Telescope
• Structural parameters, chronological age and dynamical age of the LMC globular cluster NGC 1754
• Exotic populations in Globular Clusters: Blue Stragglers as tracers of the internal dynamical evolution of stellar systems
• The ESO-VLT MIKiS survey reloaded: velocity dispersion profile and rotation curve of NGC 1904
• Study of dynamical status of the globular cluster NGC 1851 using Ultraviolet Imaging Telescope