Search for giant planets in M67 IV: survey results

We present the results of a seven-year-long radial velocity survey of a sample of 88 main-sequence and evolved stars to reveal signatures of Jupiter-mass planets in the solar-age and solar-metallicity open cluster M67. We aim at studying the frequency of giant planets in this cluster with respect to the field stars. In addition, our sample is also ideal to perform a long-term study to compare the chemical composition of stars with and without giant planets in detail. We analyzed precise radial velocity (RV) measurements obtained with five different instruments. We conducted Monte Carlo simulations to estimate the occurrence rate of giant planets in our radial velocity survey. All the planets previously announced in this RV campaign with their properties are summarized here: 3 hot Jupiters around the main-sequence stars YBP1194, YBP1514, and YBP401, and 1 giant planet around the evolved star S364. Two additional planet candidates around the stars YBP778 and S978 are also analyzed in the present work. We discuss stars that exhibit large RV variability or trends individually. For 2 additional stars, long-term trends are compatible with new binary candidates or substellar objects, which increases the total number of binary candidates detected in our campaign to 14. Based on the Doppler-detected planets discovered in this survey, we find an occurrence of giant planets of ~18.0%(+12.0/-8.0%) in the selected period-mass range. This frequency is slightly higher but consistent within the errors with the estimate for the field stars, which leads to the general conclusion that open cluster and field statistics agree. However, we find that the rate of hot Jupiters in the cluster (~5.7%(+5.5/-3.0%)) is substantially higher than in the field.Comment: Accepted by A&

The M4 Core Project with HST - IV. Internal Kinematics from Accurate Radial Velocities of 2771 Cluster Members

We present a detailed study of the internal kinematics of the Galactic Globular Cluster M 4 (NGC 6121), by deriving the radial velocities from 7250 spectra for 2771 stars distributed from the upper part of the Red Giant Branch down to the Main Sequence. We describe new approaches to determine the wavelength solution from day-time calibrations and to determine the radial velocity drifts that can occur between calibration and science observations when observing with the GIRAFFE spectrograph at VLT. Two techniques to determine the radial velocity are compared, after a qualitative description of their advantages with respect to other commonly used algorithm, and a new approach to remove the sky contribution from the spectra obtained with fibre-fed spectrograph and further improve the radial velocity precision is presented. The average radial velocity of the cluster is $\langle v \rangle = 71.08 \pm 0.08$ km s$^{-1}$ with an average dispersion of $\mu_{v_c} = 3.97$ km s$^{-1}$. Using the same dataset and the same statistical approach of previous analyses, 20 additional binary candidates are found, for a total of 87 candidates. A new determination of the internal radial velocity dispersion as a function of cluster distance is presented, resulting in a dispersion of $4.5$ km s$^{-1}$ within 2$^{\prime}$ from the center of cluster and steadily decreasing outward. We statistically confirm the small amplitude of the cluster rotation, as suggested in the past by several authors. This new analysis represents a significant improvement with respect to previous results in literature and provides a fundamental observational input for the modeling of the cluster dynamics.Comment: 17 pages, 17 figures. Accepted for publication in MNRAS on September 15, 201

Absolute proper motion of the Galactic open cluster M67

We derived the absolute proper motion (PM) of the old, solar-metallicity Galactic open cluster M67 using observations collected with CFHT (1997) and with LBT (2007). About 50 galaxies with relatively sharp nuclei allow us to determine the absolute PM of the cluster. We find (mu_alpha cos(delta),mu_delta)_J2000.0 = (-9.6+/-1.1,-3.7+/-0.8) mas/yr. By adopting a line-of-sight velocity of 33.8+/-0.2 km/s, and assuming a distance of 815+/-50 pc, we explore the influence of the Galactic potential, with and without the bar and/or spiral arms, on the galactic orbit of the cluster.Comment: 7 pages, 5 figures, and 3 tables. Published in Astronomy and Astrophysics, Volume 513, id.A51

The Y dwarf population with HST : unlocking the secrets of our coolest neighbours – I. Overview and first astrometric results

In this paper, we present our project that aims at determining accurate distances and proper motions for the Y brown dwarf population using the Hubble Space Telescope. We validate the program with our first results, using a single new epoch of observations of the Y0pec dwarf WISE J163940.83−684738.6. These new data allowed us to refine its proper motion and improve the accuracy of its parallax by a factor of three compared to previous determinations, now constrained to ϖ = 211.11 ± 0.56 mas. This newly derived absolute parallax corresponds to a distance of 4.737 ± 0.013 pc, an exquisite and unprecedented precision for faint ultracool Y dwarfs

Deep near-IR observations of the Globular Cluster M4: Hunting for Brown Dwarfs

We present an analysis of deep HST/WFC3 near-IR (NIR) imaging data of the globular cluster M4. The best-photometry NIR colour-magnitude diagram (CMD) clearly shows the main sequence extending towards the expected end of the Hydrogen-burning limit and going beyond this point towards fainter sources. The white dwarf sequence can be identified. As such, this is the deepest NIR CMD of a globular cluster to date. Archival HST optical data were used for proper-motion cleaning of the CMD and for distinguishing the white dwarfs (WDs) from brown dwarf (BD) candidates. Detection limits in the NIR are around F110W approx 26.5 mag and F160W approx27 mag, and in the optical around F775W approx 28 mag. Comparing our observed CMDs with theoretical models, we conclude that we have reached beyond the H-burning limit in our NIR CMD and are probably just above or around this limit in our optical-NIR CMDs. Thus, any faint NIR sources that have no optical counterpart are potential BD candidates, since the optical data are not deep enough to detect them. We visually inspected the positions of NIR sources which are fainter than the H-burning limit in F110W and for which the optical photometry did not return a counterpart. We found in total five sources for which we did not get an optical measurement. For four of these five sources, a faint optical counterpart could be visually identified, and an upper optical magnitude was estimated. Based on these upper optical magnitude limits, we conclude that one source is likely a WD, one source could either be a WD or BD candidate, and the remaining two sources agree with being BD candidates. For only one source no optical counterpart could be detected, which makes this source a good BD candidate. We conclude that we found in total four good BD candidates.Comment: ApJ accepted, 28 pages including 16 figure

Ontological evaluation in the knowledge based system

In the last few years, several studies have emphasized the use of ontologies as an alternative to organization of the information. The notion of ontology has become popular in fields such as intelligent information integration, information retrieval on the Internet, and knowledge management. Different groups use different approaches to develop and verify de effectiveness of ontologies. This diversity can be a factor that makes the formularization difficult of formal methodologies of evaluation. This paper intends to provide a way to identify the effectiveness of knowledge representation based on ontology that was developed through Knowledge Based System tools. The reason is that all processing and storage of gathered information and knowledge base organization is performed using this structure. Our evaluation is based on case studies of the KMAI system, involving real world ontology for the money laundry domain. Our results indicate that modification of ontology structure can effectively reveal faults, as long as they adversely affect the program state.Applications in Artificial Intelligence - Knowledge EngineeringRed de Universidades con Carreras en Informática (RedUNCI

The Chemical Evolution of Helium in Globular Clusters: Implications for the Self-Pollution Scenario

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 that a previous generation of massive Asymptotic Giant Branch (AGB) stars have polluted the cluster. Two independent sets of AGB yields are used to follow the evolution of helium and CNO using a Salpeter initial mass function (IMF) and two top-heavy IMFs. In no case are we able to produce the postulated large Y ~ 0.35 without violating the observational constraint that the CNO content is nearly constant.Comment: accepted for publication in Ap

MCAO near-IR photometry of the Globular Cluster NGC 6388: MAD observations in crowded fields

Deep photometry of crowded fields, such as Galactic Globular Clusters, is severely limited by the actual resolution of ground-based telescopes. On the other hand, the Hubble Space Telescope does not provide the near-infrared (NIR) filters needed to allow large color baselines. In this work we aim at demonstrating how ground based observations can reach the required resolution when using Multi-Conjugated Adaptive Optic (MCAO) devices in the NIR, such as the experimental infrared camera (MAD) available on the VLT. This is particularly important since these corrections are planned to be available on all ground--based telescopes in the near future. We do this by combining the infrared photometry obtained by MAD/VLT with ACS/HST optical photometry of our scientific target, the bulge globular cluster NGC 6388, in which we imaged two fields. In particular, we constructed color-magnitude diagrams with an extremely wide color baseline in order to investigate the presence of multiple stellar populations in this cluster. From the analysis of the external field, observed with better seeing conditions, we derived the deepest optical-NIR CMD of NGC 6388 to date. The high-precision photometry reveals that two distinct sub-giant branches are clearly present in this cluster. We also use the CMD from the central region to estimate the distance ((m-M)=15.33) and the reddening (E(B-V)=0.38) for this cluster. We estimate the age to be ~11.5+/- 1.5 Gyr. The large relative-age error reflects the bimodal distribution of the SGB stars. This study clearly demonstrates how MCAO correction in the NIR bands implemented on ground based telescopes can complement the high-resolution optical data from HST.Comment: 9 pages, 10 figures. Accepted for publication on A. &

Biochemical and Fatty Acids Composition of Water Buffalo (Bubalus Bubalis) Follicular Fluid

Aim of this study was to characterize the biochemical and fatty acids composition of follicular fluid collected from follicles of different sizes and in different phases of ovarian cycle in water buffalo farmed in Italy. Ovaries were collected at slaughterhouse during the breeding season; follicular fluid was aspirated dividing samples in small and large follicles (< 6 mm and > 6 mm respectively) and in luteal and follicular phase. Biochemical analysis and gas-chromatography were performed. Biochemical and fatty acids composition were greatly influenced by both follicular dimension and phase of ovarian cycle. Biochemical composition and its variations were in agreement with previously study conducted in buffalo and other species. This is the first report of the fatty acids composition of buffalo follicular fluid. Twenty-two fatty acids were identified in follicular fluid; nine were saturated fatty acids, six monounsatured fatty acids and seven polyunsatured fatty acids. The most dominant fatty acids were linoleic acid, oleic acid, palmitic acid, stearic acid and arachidonic acid. All the identified fatty acids concentrations vary at least because of follicle dimension or phase, with the exception of γ-linoleic acid and arachidonic acid which concentrations remain stable in all classes