The Bright Star in the globular cluster 47 Tucanae (NGC 104) is a post-AGB star of spectral type B8 III. The ultraviolet spectra of late-B stars exhibit a myriad of absorption features, many due to species unobservable from the ground. The Bright Star thus represents a unique window into the chemistry of 47 Tuc. We have analyzed observations obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE), the Cosmic Origins Spectrograph (COS) aboard the Hubble Space Telescope, and the MIKE Spectrograph on the Magellan Telescope. By fitting these data with synthetic spectra, we determine various stellar parameters (T_eff = 10,850 +/- 250 K, log g = 2.20 +/- 0.13) and the photospheric abundances of 26 elements, including Ne, P, Cl, Ga, Pd, In, Sn, Hg, and Pb, which have not previously been published for this cluster. Abundances of intermediate-mass elements (Mg through Ga) generally scale with Fe, while the heaviest elements (Pd through Pb) have roughly solar abundances. Its low C/O ratio indicates that the star did not undergo third dredge-up and suggests that its heavy elements were made by a previous generation of stars. If so, this pattern should be present throughout the cluster, not just in this star. Stellar-evolution models suggest that the Bright Star is powered by a He-burning shell, having left the AGB during or immediately after a thermal pulse. Its mass (0.54 +/- 0.16 M_sun) implies that single stars in 47 Tuc lose 0.1--0.2 M_sun on the AGB, only slightly less than they lose on the RGB.
We use Hubble Space Telescope multicolour photometry of the globular cluster 47 Tucanae to uncover a population of 24 objects with no previous classification that are outliers from the single-star model tracks in the colour-magnitude diagram and yet are likely cluster members. By comparing those sources with evolutionary models and X-ray source catalogues, we were able to show that the majority of those sources are likely binary systems that do not have any X-ray source detected nearby, most possibly formed by a white dwarf and a main-sequence star and a small number of possible double-degener…
Using parallaxes from Gaia DR2, we estimate the distance to the globular clusters 47 Tuc and NGC 362, taking advantage of the background stars in the Small Magellanic Cloud and quasars to account for various parallax systematics. We found the parallax to be dependent on the Gaia DR2 G apparent magnitude for stars with $13<\textrm{G}<18$ , where brighter stars have a lower parallax zero point than fainter stars. The distance to 47 Tuc was found to be $4.45\pm0.01\pm0.12$ kpc, and for NGC 362 $8.54\pm0.20\pm0.44$ kpc with random and systematic errors listed respectively. This is the first time a…
We have developed a technique to restore scientific usage in compromised (publicly-available) images collected with the James Webb Space Telescope (JWST) of the Galactic globular cluster NGC 104 (47 Tucanae). In spite of the degradation and limited data, we were able to recover photometry and astrometry for the coolest stellar objects ever observed within a globular cluster, possibly unveiling the brightest part of the brown dwarf (BD) sequence. This is supported by: (i) proper motion membership, derived by the comparison with positions obtained from Hubble Space Telescope archival early epoch…
We report the first detection of circumstellar CO in a globular cluster. Observations with ALMA have detected the CO J=3-2 and SiO v=1 J=8-7 transitions at 345 and 344 GHz, respectively, around V3 in 47 Tucanae (NGC 104; [Fe/H] = -0.72 dex), a star on the asymptotic giant branch. The CO line is detected at 7 sigma at a rest velocity v_LSR = -40.6 km/s and expansion velocity of 3.2 +/- ~0.4 km/s. The brighter, asymmetric SiO line may indicate a circumstellar maser. The stellar wind is slow compared to similar Galactic stars, but the dust opacity remains similar to Galactic comparisons. We sugge…
ALMA observations show a non-detection of carbon monoxide around the four most luminous asymptotic giant branch (AGB) stars in the globular cluster 47 Tucanae. Stellar evolution models and star counts show that the mass-loss rates from these stars should be ~1.2-3.5 x 10^-7 solar masses per year. We would naively expect such stars to be detectable at this distance (4.5 kpc). By modelling the ultraviolet radiation field from post-AGB stars and white dwarfs in 47 Tuc, we conclude CO should be dissociated abnormally close to the stars. We estimate that the CO envelopes will be truncated at a few …
We present new large field-of-view ($\sim$1°$\times$1°) Ca-CN photometry of the prototypical metal-rich globular cluster 47 Tucanae (NGC 104). Our results are the following. (1) The populational number ratios of the red giant branch (RGB) and red horizontal branch (RHB) are in excellent agreement: n(CN-w):n(CN-s) = 30:70 ($\pm$1--2), where the CN-w and CN-s stand for the CN-weak and CN-strong populations, respectively. Both the CN-s RGB and RHB populations are more centrally concentrated than those of CN-w populations are. (2) Our photometric metallicities of individual RGB stars in each popul…
Based on over 5400 BV images of 47 Tuc collected between 1998 and 2010 we obtained light curves of 65 variables, 21 of which are newly detected objects. New variables are located mostly just outside of the core in a region poorly studied by earlier surveys of the cluster. Among them there are four detached eclipsing binaries and five likely optical counterparts of X-ray sources. Two detached systems are promising targets for follow-up observations. We briefly discuss properties of the most interesting new variables.
47 Tucanae is one of the most interesting and well observed and theoretically studied globular clusters. This allows us to study the reliability of our understanding of white dwarf cooling sequences, to confront different methods to determine its age, and to assess other important characteristics, like its star formation history. Here we present a population synthesis study of the cooling sequence of the globular cluster 47 Tucanae. In particular, we study the distribution of effective temperatures, the shape of the color-magnitude diagram, and the corresponding magnitude and color distributio…
We present Hubble Space Telescope observations of the upper part (T_eff> 10 000 K) of the white dwarf cooling sequence in the globular cluster 47 Tucanae and measure a luminosity function of hot white dwarfs. Comparison with previous determinations from large scale field surveys indicates that the previously determined plateau at high effective temperatures is likely a selection effect, as no such feature is seen in this sample. Comparison with theoretical models suggests that the current estimates of white dwarf neutrino emission (primarily by the plasmon channel) are accurate, and variations…
Dust production among post-main-sequence stars is investigated in the Galactic globular cluster 47 Tucanae (NGC 104) based on infrared photometry and spectroscopy. We identify metallic iron grains as the probable dominant opacity source in these winds. Typical evolutionary timescales of AGB stars suggest the mass-loss rates we report are too high. We suggest that this is because the iron grains are small or elongated and/or that iron condenses more efficiently than at solar metallicity. Comparison to other works suggests metallic iron is observed to be more prevalent towards lower metallicitie…
The light elements Li, O, Na, Al, and Mg are known to show star to star variations in the globular clusters 47 Tuc and NGC 6752. Such variations are interpreted as due to processing in a previous generation of stars. In this paper we investigate the abundances of the alpha-element sulphur, for which no previous measurements exist. In fact this element has not been investigated in any Galactic globular cluster so far. The only globular cluster for which such measurements are available is Terzan 7, which belongs to the Sgr dSph. We use high resolution spectra of the S I Mult. 1, acquired with th…
We use near-infrared observations obtained as part of the {\sl Visible and Infrared Survey Telescope for Astronomy} (VISTA) Survey of the Magellanic Clouds (VMC), as well as two complementary {\sl Hubble Space Telescope} ({\sl HST}) data sets, to study the luminosity and mass functions as a function of clustercentric radius of the main-sequence stars in the Galactic globular cluster 47 Tucanae. The {\sl HST} observations indicate a relative deficit in the numbers of faint stars in the central region of the cluster compared with its periphery, for $18.75\leq m_{\rm F606W}\leq 20.9$ mag (corresp…
We used ultra-deep UV observations obtained with the Hubble Space Telescope to search for optical companions to binary millisecond pulsars (MSPs) in the globular cluster 47 Tucanae. We identified four new counterparts (to MSPs 47TucQ, 47TucS, 47TucT and 47TucY) and confirmed those already known (to MSPs 47TucU and 47TucW). In the color magnitude diagram, the detected companions are located in a region between the main sequence and the CO white dwarf cooling sequences, consistent with the cooling tracks of He white dwarfs of mass between 0.15 Msun and 0.20 Msun. For each identified companion, m…
Fundamental parameters and time-evolution of mass loss are investigated for post-main-sequence stars in the Galactic globular cluster 47 Tucanae (NGC 104). This is accomplished by fitting spectral energy distributions (SEDs) to existing optical and infrared photometry and spectroscopy, to produce a true Hertzsprung--Russell diagram. We confirm the cluster's distance as 4611 (+213, -200) pc and age as 12 +/- 1 Gyr. Horizontal branch models appear to confirm that no more RGB mass loss occurs in 47 Tuc than in the more-metal-poor omega Centauri, though difficulties arise due to inconsistencies be…
We report the discovery of the likely white dwarf companions to radio millisecond pulsars 47 Tuc Q and 47 Tuc S in the globular cluster 47 Tucanae. These blue stars were found in near-ultraviolet images from the Hubble Space Telescope for which we derived accurate absolute astrometry, and are located at positions consistent with the radio coordinates to within 0.016 arcsec (0.2sigma). We present near-ultraviolet and optical colours for the previously identified companion to millisecond pulsar 47 Tuc U, and we unambiguously confirm the tentative prior identifications of the optical counterparts…
It is generally accepted today that Galactic globular clusters (GGCs) consist of at least two generations of stars that are different in their chemical composition and perhaps age. However, knowledge about the kinematical properties of these stellar generations, which may provide important information for constraining evolutionary scenarios of the GGCs, is still limited. We therefore study the connections between chemical and kinematical properties of different stellar generations in the Galactic globular cluster 47 Tuc. To achieve this goal, we used abundances of Li, O, and Na determined in 1…
We present results of deep radio continuum observations of two galactic globular clusters 47 Tucanae (47 Tuc) and Omega Centauri (Omega Cen) with Australia Telescope Compact Array (ATCA). No statistically significant evidence for radio emission was found from the central region for the two clusters. However, both clusters show a 2.5-sigma detection near the center that may be confirmed by future deeper radio observations. The 3-sigma upper limits of the radio observations is 20 and 40 microJy/beam for Omega Cen and 47 Tuc, respectively. By using the fundamental plane of accreting black holes w…
We investigate possible relations between the abundances of zinc and the light elements sodium, magnesium, and potassium in the atmospheres ofred giant branch (RGB) stars of the Galactic globular cluster 47~Tuc and study connections between the chemical composition and dynamical properties of the cluster RGB stars. The abundance of zinc was determined in 27 RGB stars of 47~Tuc using 1D local thermal equilibrium (LTE) synthetic line profile fitting to the high-resolution 2dF spectra obtained with the Anglo-Australian Telescope (AAT). Synthetic spectra used in the fitting procedure were computed…
Globular clusters are known to host peculiar objects, named Blue Straggler Stars (BSSs), significantly heavier than the normal stellar population. While these stars can be easily identified during their core hydrogen-burning phase, they are photometrically indistinguishable from their low-mass sisters in advanced stages of the subsequent evolution. A clear-cut identification of these objects would require the direct measurement of the stellar mass. We used the detailed comparison between chemical abundances derived from neutral and from ionized spectral lines as a powerful stellar "weighing de…
High-resolution Hubble Space Telescope optical observations have been used to analyze the stellar population and the structure of the poorly investigated bulge globular cluster NGC 6316. We constructed the first high-resolution reddening map in the cluster direction, which allowed us to correct the evolutionary sequences in the color magnitude diagram (CMD) for the effects of differential reddening. A comparison between the CMDs of NGC 6316 and 47 Tucanae revealed strikingly similar stellar populations, with the two systems basically sharing the same turn-off, sub-giant branch, and horizontal …
We present 22 new (+3 confirmed) cataclysmic variables (CVs) in the non core-collapsed globular cluster 47 Tucanae (47 Tuc). The total number of CVs in the cluster is now 43, the largest sample in any globular cluster so far. For the identifications we used near-ultraviolet (NUV) and optical images from the Hubble Space Telescope, in combination with X-ray results from the Chandra X-ray Observatory. This allowed us to build the deepest NUV CV luminosity function of the cluster to date. We found that the CVs in 47 Tuc are more concentrated towards the cluster center than the main sequence turno…
We present a deep near-infrared color--magnitude diagram of the Galactic globular cluster 47 Tucanae, obtained with the Visible and Infrared Survey Telescope for Astronomy (VISTA) as part of the VISTA near-infrared Y, J, K_s survey of the Magellanic System (VMC). The cluster stars comprising both the subgiant and red-giant branches exhibit apparent, continuous variations in color--magnitude space as a function of radius. Subgiant-branch stars at larger radii are systematically brighter than their counterparts closer to the cluster core; similarly, red-giant-branch stars in the cluster's periph…
Intermediate mass black holes play a critical role in understanding the evolutionary connection between stellar mass and super-massive black holes. However, to date the existence of these species of black holes remains ambiguous and their formation process is therefore unknown. It has been long suspected that black holes with masses $10^{2}-10^{4}M_{\odot}$ should form and reside in dense stellar systems. Therefore, dedicated observational campaigns have targeted globular cluster for many decades searching for signatures of these elusive objects. All candidates found in these targeted searches…
We investigate near-ultraviolet (NUV) variability in the Galactic globular cluster (GC) 47 Tucanae (47 Tuc). This work was undertaken within the GC sub-project of the Transient UV Objects project, a programme which aims to find and study transient and strongly variable UV sources. Globular clusters are ideal targets for transient searches because of their high stellar densities and large populations of variable systems. Using all archival observations of 47 Tuc obtained with the UV/optical telescope (UVOT) aboard the Neil Gehrels Swift observatory with the uvm2 filter, we searched for UV varia…
We use deep multi-epoch PSF photometry taken with the Visible and Infrared Survey Telescope for Astronomy (VISTA) to measure and analyze the proper motions of stars within the Galactic globular cluster 47 Tucanae (47 Tuc, NGC 104). The observations are part of the ongoing near-infrared VISTA survey of the Magellanic Cloud system (VMC). The data analyzed here corresponds to one VMC tile and covers a total sky area of 1.77 deg^2. Absolute proper motions with respect to ~9070 background galaxies are calculated from a linear regression model applied to the stellar positions in 11 epochs in the Ks …
We explore the possibility of searching for extratidal features around the Galactic globular cluster NGC362 using the Gaia DR2 together with a modified version of a classical statistical decontamination algorithm. Our results suggest that an important stellar component is associated with this globular cluster, which is perfectly distinguishable from the populations in the Small Magellanic Cloud and that of the nearby NGC104 (47 Tucanae). We thus confirm once again the power of Gaia to disentangle different stellar components along the same line-of-sight.
A recent analysis comparing the [Na/Fe] distributions of red giant branch (RGB) and asymptotic giant branch (AGB) stars in the Galactic globular cluster NGC 6752 found that the ratio of Na-poor to Na-rich stars changes from 30:70 on the RGB to 100:0 on the AGB. The surprising paucity of Na-rich stars on the AGB in NGC 6752 warrants additional investigations to determine if the failure of a significant fraction of stars to ascend the AGB is an attribute common to all globular clusters. Therefore, we present radial velocities, [Fe/H], and [Na/Fe] abundances for 35 AGB stars in the Galactic globu…
We have constructed the Spectral Energy Distributions (SEDs) of a sample of Blue Straggler Stars (BSSs) in the core of the globular cluster 47 Tucanae, taking advantage of the large set of high resolution images, ranging from the ultraviolet to the near infrared, obtained with the ACS/HRC camera of the Hubble Space Telescope. Our final BSS sample consists of 22 objects, spanning the whole color and magnitude extension of the BSS sequence in 47 Tucanae. We fitted the BSS broadband SEDs with models to derive temperature, surface gravity, radius, luminosity and mass. We show that BSSs indeed defi…
47 Tuc is an ideal target to study chemical evolution and GC formation in massive more metal-rich GCs since is the closest, massive GC. We present chemical abundances for O, Na, Al, Si, Ca, Ti, Fe, Ni, La, and Eu in 164 red giant branch (RGB) stars in the massive globular cluster 47 Tuc using spectra obtained with both the Hydra multi-fiber spectrograph at the Blanco 4-m telescope and the FLAMES multi-object spectrograph at the Very Large Telescope. We find an average [Fe/H]=--0.79$\pm$0.09 dex, consistent with literature values, as well as over-abundances of alpha-elements ($[α/\mbox{Fe}]\sim…
Globular clusters trace the formation history of the spheroidal components of both our Galaxy and others, which represent the bulk of star formation over the history of the universe. They also exhibit a range of metallicities, with metal-poor clusters dominating the stellar halo of the Galaxy, and higher metallicity clusters found within the inner Galaxy, associated with the stellar bulge, or the thick disk. Age differences between these clusters can indicate the sequence in which the components of the Galaxy formed, and in particular which clusters were formed outside the Galaxy and later swa…
We used high-resolution spectra acquired with the multifiber facility FLAMES at the Very Large Telescope of the European Southern Observatory to investigate the chemical and kinematical properties of a sample of 22 Blue Straggler Stars (BSSs) and 26 red giant branch stars in the nearby globular cluster NGC 6752. We measured radial and rotational velocities and Fe, O and C abundances. According to radial velocities, metallicity and proper motions we identified 18 BSSs as likely cluster members. We found that all the BSSs rotate slowly (less than 40 km/s), similar to the findings in 47 Tucanae, …
We combined Chandra ACIS observations of the globular cluster 47 Tucanae (hereafter, 47 Tuc) from 2000, 2002, and 2014-15 to create a deeper X-ray source list, and study some of the faint radio millisecond pulsars (MSPs) present in this cluster. We have detected 370 X-ray sources within the half-mass radius (2$'$.79) of the cluster, 81 of which are newly identified, by including new data and using improved source detection techniques. The majority of the newly identified sources are in the crowded core region, indicating cluster membership. We associate five of the new X-ray sources with chrom…
Aims. We present a new technique to estimate the relative ages of multiple stellar populations hosted by five globular clusters: NGC 104 (47 Tuc), NGC 6121 (M4), NGC 6352, NGC 6362 and NGC 6723. Methods. We used the catalogs of the database "HST UV Globular cluster Survey (HUGS)" to create color-magnitude and two-color diagrams of the Globular Clusters. We identified the multiple populations within each globular cluster, and we divided them into two main stellar populations: POPa or first generation (1G) and POPb, composed of all the successive generations of stars. The new technique allows us…
We present DECam imaging for the peculiar Galactic globular clusters NGC1851, NGC1904 (M79), NGC2298 and NGC2808. Our deep photometry reveals that all the clusters have an important contribution of stars beyond their King tidal radii and present tails with different morphologies. We have also explored the surroundings of the clusters where the presence of the Canis Major overdensity and/or the low Galactic latitude Monoceros ring at d~8kpc is evident. A second stellar system is found at d~17kpc and spans at least 18deg x 15deg in the sky. As one of the possible scenarios to explain that featur…
We derived Potassium abundances in red giant branch stars in the Galactic globular clusters NGC104 (144 stars), NGC6752 (134 stars) and NGC6809 (151 stars) using high-resolution spectra collected with FLAMES at the ESO - Very Large Telescope. In the considered samples we do not find significant intrinsic spreads in [K/Fe] (confirming the previous findings by Carretta et al.), at variance with the cases of the massive clusters NGC2419 and NGC2808. Additionally, marginally significant [K/Fe]-[O/Fe] anti-correlations are found in NGC104 and NGC6809, and [K/Fe]-[Na/Fe] correlations are found in NG…
In these proceedings we present initial results of a spectroscopic analysis of a small sample of evolved K-giants in the globular cluster 47 Tucanae. We derive the effective temperature, surface gravity and microturbulence of all targets using standard methods. Further we derive LTE abundances of [Fe/H] and [O/Fe] as well as the abundance of sodium, using NLTE corrections. We find a mean metallicity for the cluster of [Fe/H]$=-0.75\pm0.10$, in excellent agreement with several other studies. Also, we confirm the sodium-oxygen anticorrelation previously reported by a number of other authors. Fin…
The series of events, which occurred at high redshift and originated multiple stellar populations in Globular Clusters (GCs) are still poorly understood. Theoretical work suggests that the present-day dynamics of stars in nearby GCs, including the rotation and velocity dispersion, may retain important clues on the formation of multiple populations. So far, the dynamics of multiple populations have been investigated either from radial velocities of a relatively-small sample of stars, or from relative proper motions of stars in the small field of view provided by the Hubble Space Telescope. In t…
Recently, Kundu et al (2019) reported that the globular cluster NGC 5024 (M53) possesses five extra-tidal RR Lyrae. In fact, four of them were instead known members of a nearby globular cluster NGC 5053. The status of the remaining extra-tidal RR Lyrae is controversial depending on the adopted tidal radius of NGC 5024. We have also searched for additional extra-tidal RR Lyrae within an area of $\sim8$~deg$^2$ covering both globular clusters. This includes other known RR Lyrae within the search area, as well as stars that fall within the expected range of magnitudes and colors for RR Lyrae (and…
NGC 2419 is a massive outer halo Galactic globular cluster whose stars have previously been shown to have somewhat peculiar abundance patterns. We have observed seven luminous giants that are members of NGC 2419 with Keck/HIRES at reasonable SNR. One of these giants is very peculiar, with an extremely low [Mg/Fe] and high [K/Fe] but normal abundances of most other elements. The abundance pattern does not match the nucleosynthetic yields of any supernova model. The other six stars show abundance ratios typical of inner halo Galactic globular clusters, represented here by a sample of giants in t…
In this paper we present photometric CCD observations of the globular cluster NGC 6093 (M80) in filters B, V , R and I. We produce the colour-magnitude diagrams for this object and obtain values for its metallicity [Fe/H], reddening E(V-B), E(V-I) and distance modulus (m - M)_0.
We present metallicities for red giant stars in the globular cluster NGC 6273 based on intermediate resolution GMOS-S spectra of the calcium triplet region. For the 42 radial velocity members with reliable calcium triplet line strength measurements, we obtain metallicities, [Fe/H], using calibrations established from standard globular clusters. We confirm the presence of an intrinsic abundance dispersion identified by Johnson et al. (2015). The total range in [Fe/H] is ~1.0 dex and after taking into account the measurement errors, the intrinsic abundance dispersion is σ[Fe/H] = 0.17 dex. Among…
We have used archival Hubble Space Telescope observations obtained with the Advanced Camera for Surveys to study the Hα emission properties of main sequence stars in the globular cluster 47 Tucanae. Using a combination of multi-band observations in the F606W, F814W and F658N bands, we search for stars showing Hα excess emission. An accurate photometric measurement of their Hα equivalent width allows us to identify objects with large Hα emission, which we attribute to mass accretion rather than enhanced chromospheric activity. The spatial position of some of these stars is coincident with that …
We determined abundances of Mg and K in the atmospheres of 53 (Mg) and 75 (K) turn-off (TO) stars of the Galactic globular cluster 47 Tuc. The obtained abundances, together with those of Li, O, and Na, were used to search for possible relations between the abundances of K and other light elements, Li, O, Na, and Mg, as well as the connections between the chemical composition of TO stars and their kinematical properties. Abundances of Mg and K were determined using archival VLT FLAMES/GIRAFFE spectra, in combination with the 1D NLTE spectral synthesis methodology. Spectral line profiles were co…
We present radial velocities and chemical abundances for red giant branch stars in the Galactic bulge globular clusters NGC 6342 and NGC 6366. The velocities and abundances are based on measurements of high resolution (R > 20,000) spectra obtained with the MMT-Hectochelle and WIYN-Hydra spectrographs. We find that NGC 6342 has a heliocentric radial velocity of +112.5 km/s (sigma = 8.6 km/s), NGC 6366 has a heliocentric radial velocity of -122.3 km/s (sigma = 1.5 km/s), and that both clusters have nearly identical metallicities ([Fe/H] ~ -0.55). NGC 6366 shows evidence of a moderately extended …
The phenomenon of multiple populations in globular clusters is still far from understood, with several proposed mechanisms to explain the observed behaviour. The study of elemental and isotopic abundance patterns are crucial for investigating the differences among candidate pollution mechanisms. We derive magnesium isotopic ratios for 13 stars in the globular cluster 47 Tucanae (NGC 104) to provide new, detailed information about the nucleosynthesis that has occurred within the cluster. For the first time, the impact of 3D model stellar atmospheres on the derived Mg isotopic ratios is investig…
By examining the diffusion of young white dwarfs through the core of the globular cluster 47 Tucanae, we estimate the time when the progenitor star lost the bulk of its mass to become a white dwarf. According to stellar evolution models of the white-dwarf progenitors in 47 Tucanae, we find this epoch to coincide approximately with the star ascending the asymptotic giant branch ($3.0 \pm 8.1$ Myr before the tip of the AGB) and more than ninety million years after the helium flash (with ninety-percent confidence). From the diffusion of the young white dwarfs we can exclude the hypothesis that th…
We study the abundances of Na, Mg, and K in the atmospheres of 32 RGB stars in the Galactic globular cluster (GGC) 47 Tuc, with the goal to investigate the possible existence of Na-K and Mg-K correlations/anti-correlations, similar to those that were recently discovered in two other GGCs, NGC 2419 and 2808. The abundances of K, Na, and Mg were determined using high-resolution 2df spectra obtained with the AAT. The 1D NLTE abundance estimates were obtained using 1D hydrostatic ATLAS9 model atmospheres and spectral line profiles synthesized with the MULTI package. We also used 3D hydrodynamical …
Context: The study of chemical abundance patterns in globular clusters is of key importance to constrain the different candidates for intra-cluster pollution of light elements. Aims: We aim at deriving accurate abundances for a large range of elements in the globular cluster 47 Tucanae (NGC 104) to add new constraints to the pollution scenarios for this particular cluster, expanding the range of previously derived element abundances. Methods: Using tailored 1D LTE atmospheric models together with a combination of equivalent width measurements, LTE, and NLTE synthesis we derive stellar paramete…
Short period, massive planets, known as hot Jupiters (HJs), have been discovered around $\sim 1$ percent of local field stars. The inward migration necessary to produce HJs may be `low eccentricity', due to torques in the primordial disc, or `high eccentricity' (HEM). The latter involves exciting high orbital eccentricity, allowing sufficiently close passages with the host star to raise circularising tides in the planet. We present an analytic framework for quantifying the role of dynamical encounters in high density environments during HEM. We show that encounters can enhance or suppress HEM,…
We present the iron abundance of 24 asymptotic giant branch (AGB) stars members of the globular cluster 47 Tucanae, obtained with high-resolution spectra collected with the FEROS spectrograph at the MPG/ESO-2.2m Telescope. We find that the iron abundances derived from neutral lines (with mean value [Fe I/H] = -0.94 +/- 0.01, σ = 0.08 dex) are systematically lower than those derived from single ionized lines ([Fe II/H] = -0.83 +/- 0.01, σ = 0.05 dex). Only the latter are in agreement with those obtained for a sample of red giant branch (RGB) cluster stars, for which Fe I and Fe II lines provide…
We derive relative proper motions of stars in the fields of globular clusters M4, M12, M22, NGC 3201, NGC 6362 and NGC 6752 based on a uniform data set collected between 1997 and 2008. We assign a membership class for each star with a measured proper motion, and show that these membership classes can be successfully used to eliminate field stars from color-magnitude diagrams of the clusters. They also allow for the efficient selection of rare objects such as blue/yellow/red stragglers and stars from the asymptotic giant branch. Tables with proper motions and photometry of over 87000 stars are …
We have measured the absolute proper motions of globular clusters NGC 6397, NGC 6626 (M 22) and NGC 6656 (M 28) as part of our ongoing Southern Proper-Motion Program. The reference system is the ICRS via Hipparcos stars for these three low galactic latitude clusters. Formal errors range between ~0.3 and 0.7 mas/yr. Notable is the result for NGC 6397 which differs by 2.5 mas/yr from two HST determinations, while agreeing with previous ground-based ones. We determine orbits for all three clusters in an axisymmetric and barred model of the Galaxy and discuss these in the context of globular-clust…
