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Sample records for open cluster m67

  1. The chemical compositions of solar twins in the open cluster M67

    NASA Astrophysics Data System (ADS)

    Liu, F.; Asplund, M.; Yong, D.; Meléndez, J.; Ramírez, I.; Karakas, A. I.; Carlos, M.; Marino, A. F.

    2016-11-01

    Stars in open clusters are expected to share an identical abundance pattern. Establishing the level of chemical homogeneity in a given open cluster deserves further study as it is the basis of the concept of chemical tagging to unravel the history of the Milky Way. M67 is particularly interesting given its solar metallicity and age as well as being a dense cluster environment. We conducted a strictly line-by-line differential chemical abundance analysis of two solar twins in M67: M67-1194 and M67-1315. Stellar atmospheric parameters and elemental abundances were obtained with high precision using Keck/High Resolution Echelle Spectrometer spectra. M67-1194 is essentially identical to the Sun in terms of its stellar parameters. M67-1315 is warmer than M67-1194 by ≈150 K as well as slightly more metal-poor than M67-1194 by ≈0.05 dex. M67-1194 is also found to have identical chemical composition to the Sun, confirming its solar-twin nature. The abundance ratios [X/Fe] of M67-1315 are similar to the solar abundances for elements with atomic number Z ≤ 30, while most neutron-capture elements are enriched by ≈0.05 dex, which might be attributed to enrichment from a mixture of asymptotic giant branch ejecta and r-process material. The distinct chemical abundances for the neutron-capture elements in M67-1315 and the lower metallicity of this star compared to M67-1194, indicate that the stars in M67 are likely not chemically homogeneous. This poses a challenge for the concept of chemical tagging since it is based on the assumption of stars forming in the same star-forming aggregate.

  2. Mass effect on the lithium abundance evolution of open clusters: Hyades, NGC 752, and M 67

    NASA Astrophysics Data System (ADS)

    Castro, M.; Duarte, T.; Pace, G.; do Nascimento, J.-D.

    2016-05-01

    Lithium abundances in open clusters provide an effective way of probing mixing processes in the interior of solar-type stars and convection is not the only mixing mechanism at work. To understand which mixing mechanisms are occurring in low-mass stars, we test non-standard models, which were calibrated using the Sun, with observations of three open clusters of different ages, the Hyades, NGC 752, and M 67. We collected all available data, and for the open cluster NGC 752, we redetermine the equivalent widths and the lithium abundances. Two sets of evolutionary models were computed, one grid of only standard models with microscopic diffusion and one grid with rotation-induced mixing, at metallicity [Fe/H] = 0.13, 0.0, and 0.01 dex, respectively, using the Toulouse-Geneva evolution code. We compare observations with models in a color-magnitude diagram for each cluster to infer a cluster age and a stellar mass for each cluster member. Then, for each cluster we analyze the lithium abundance of each star as a function of mass. The data for the open clusters Hyades, NGC 752, and M 67, are compatible with lithium abundance being a function of both age and mass for stars in these clusters. Our models with meridional circulation qualitatively reproduce the general trend of lithium abundance evolution as a function of stellar mass in all three clusters. This study points out the importance of mass dependence in the evolution of lithium abundance as a function of age. Comparison between models with and without rotation-induced mixing shows that the inclusion of meridional circulation is essential to account for lithium depletion in low-mass stars. However, our results suggest that other mechanisms should be included to explain the Li-dip and the lithium dispersion in low-mass stars.

  3. Photometric variability of Sun-like stars in the old open cluster M67

    NASA Astrophysics Data System (ADS)

    Tobin, Ryan Wesley

    Few physical processes can affect the earth's climate on a global scale. The variability of the Sun is one such process. The Sun is known to vary by about 0.1% due to Sunspots and other surface activity. We do not yet know whether the Sun's variability is normal. Using the well-known properties of the old open cluster M67, we look for variations in Sun-like stars. In this thesis, we present the results of observation, calibration, correction and analysis of stars in M67. We focus on Sun-like stars and binary systems. We also determine the limits of observation using a small research-grade telescope. We find several known variable stars with comparable amplitudes of variability. Our precision is as high as 10 millimagnitudes, ranging 10-20 for Sun-like stars. Variability is detected as low as 20 millimagnitudes in amplitude. Our current precision, however, fails to detect solar-like variations.

  4. Observing the products of stellar evolution in the old open cluster M67 with APOGEE

    NASA Astrophysics Data System (ADS)

    Bertelli Motta, Clio; Salaris, Maurizio; Pasquali, Anna; Grebel, Eva K.

    2017-04-01

    Recent works have shown how the [C/N] ratio in stars after the first dredge-up (FDU) can be used as an age estimator in virtue of its dependence on stellar mass. For this purpose, precise predictions of the surface chemical composition before and after the mixing takes place in the convective envelope of subgiant stars are necessary. Stellar evolution models can provide us with such predictions, although a comparison with objects of known age is needed for calibration. Open clusters are excellent test cases, as they represent a single stellar population for which the age can be derived through, e.g. isochrone fitting. In this study, we present a detailed analysis of stars belonging to the well-known open cluster M67 observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey in the twelfth data release of the Sloan Digital Sky Survey and whose chemical properties were derived with the APOGEE Stellar Parameters and Chemical Abundances Pipeline. We find that the [C/N] abundance of subgiant branch stars is overestimated by ∼0.2 dex due to an offset in the determination of the [N/Fe] abundance. Stars on the red giant branch and red clump are shown not to be affected by this offset. We derive [C/N]FDU = -0.46 ± 0.03 dex, which poses a strong constraint on calibrations of [C/N]FDU as age indicator. We also do not find any clear signature of additional chemical mixing processes that set in after the red giant branch bump. The results obtained for M67 indicate the importance of conducting high-resolution spectroscopic studies of open clusters of different ages in order to establish an accurate age-dating method for field stars.

  5. Search for giant planets in M67. III. Excess of hot Jupiters in dense open clusters

    NASA Astrophysics Data System (ADS)

    Brucalassi, A.; Pasquini, L.; Saglia, R.; Ruiz, M. T.; Bonifacio, P.; Leão, I.; Canto Martins, B. L.; de Medeiros, J. R.; Bedin, L. R.; Biazzo, K.; Melo, C.; Lovis, C.; Randich, S.

    2016-07-01

    Since 2008 we used high-precision radial velocity (RV) measurements obtained with different telescopes to detect signatures of massive planets around main-sequence and evolved stars of the open cluster (OC) M67. We aimed to perform a long-term study on giant planet formation in open clusters and determine how this formation depends on stellar mass and chemical composition. A new hot Jupiter (HJ) around the main-sequence star YBP401 is reported in this work. An update of the RV measurements for the two HJ host-stars YBP1194 and YBP1514 is also discussed. Our sample of 66 main-sequence and turnoff stars includes 3 HJs, which indicates a high rate of HJs in this cluster (5.6% for single stars and 4.5%% for the full sample). This rate is much higher than what has been discovered in the field, either with RV surveys or by transits. High metallicity is not a cause for the excess of HJs in M67, nor can the excess be attributed to high stellar masses. When combining this rate with the non-zero eccentricity of the orbits, our results are qualitatively consistent with a HJ formation scenario dominated by strong encounters with other stars or binary companions and subsequent planet-planet scattering, as predicted by N-body simulations. Based on observations collected at the ESO 3.6 m telescope (La Silla), at the 1.93 m telescope of the Observatoire de Haute-Provence (OHP), at the Hobby Eberly Telescope (HET), at the Telescopio Nazionale Galileo (TNG, La Palma) and at the Euler Swiss Telescope.

  6. The K2 M67 Study: Revisiting Old Friends with K2 Reveals Oscillating Red Giants in the Open Cluster M67

    NASA Astrophysics Data System (ADS)

    Stello, Dennis; Vanderburg, Andrew; Casagrande, Luca; Gilliland, Ron; Silva Aguirre, Victor; Sandquist, Eric; Leiner, Emily; Mathieu, Robert; Soderblom, David R.

    2016-12-01

    Observations of stellar clusters have had a tremendous impact in forming our understanding of stellar evolution. The open cluster M67 has a particularly important role as a calibration benchmark for stellar evolution theory due to its near-solar composition and age. As a result, it has been observed extensively, including attempts to detect solar-like oscillations in its main sequence and red giant stars. However, any asteroseismic inference has so far remained elusive due to the difficulty in measuring these extremely low-amplitude oscillations. Here we report the first unambiguous detection of solar-like oscillations in the red giants of M67. We use data from the Kepler ecliptic mission, K2, to measure the global asteroseismic properties. We find a model-independent seismic-informed distance of 816 ± 11 pc, or {(m-M)}0 = 9.57+/- 0.03 mag, an average red giant mass of 1.36+/- 0.01 {M}⊙ , in agreement with the dynamical mass from an eclipsing binary near the cluster turn-off, and ages of individual stars compatible with isochrone fitting. We see no evidence of strong mass loss on the red giant branch. We also determine seismic {log}g of all the cluster giants with a typical precision of ˜ 0.01 dex. Our results generally show good agreement with independent methods and support the use of seismic scaling relations to determine global properties of red giant stars with near-solar metallicity. We further illustrate that the data are of such high quality that future work on individual mode frequencies should be possible, which would extend the scope of seismic analysis of this cluster.

  7. A near-infrared surface compositional analysis of blue straggler stars in open cluster M67.

    NASA Astrophysics Data System (ADS)

    Seifert, Richard; Gosnell, Natalie M.; Sneden, Chris

    2017-01-01

    Blue straggler stars (BSSs) are stars whose evolutions have been directly impacted by binary system interactions. By obtaining additional mass from a companion, BSSs are able to live prolonged lives on the main sequence. BSSs bring confusions to studies that rely on a standard stellar evolutionary track when modeling stellar populations, since the presence of BSSs can make a population appear younger than it actually is. It is important to have a better understanding of the mechanisms that drive BSS formation so that BSSs may be correctly accounted for in future studies.What we know about BSS formation is that they form in one of two ways. Either from a close binary system in which one star accretes mass from its companion star or from a hierarchical trinary system in which a close inner binary merges as a result of perturbations from a farther-orbiting third star. What we don’t know are the relative frequencies of these two formation mechanisms. To investigate this problem, We obtained IGRINS near-IR (H- & K-band) high resolution spectra of 6 BSSs and 12 red giant stars in open cluster M67. Using a grid of synthetic spectra obtained from the line analysis code MOOG, we identified and fit abundances for absorption lines of iron, carbon, nitrogen, and oxygen. The latter three elements can be affected by internal hydrogen fusion, mixing, and binary mass transfer. In the BSS mass accretion mechanism, there should be enhanced abundances of these elements on the surfaces of BSSs. By analyzing the abundances of these elements in our BSS spectra, we determine the formation mechanism for each member of our BSS sample.Funding for this research comes from the John W. Cox endowment for the Advanced Studies in Astronomy. For support of this work we acknowledge NSF grants AST-1211585 and AST-1616040 to CS. The successful development of the IGRINS spectrograph has resulted from the combined efforts of teams at the University of Texas at Austin and the Korea Astronomy and Space

  8. A Comprehensive Stellar Astrophysical Study of the Old Open Cluster M67 with Kepler

    NASA Astrophysics Data System (ADS)

    Mathieu, Robert D.; Vanderburg, Andrew; K2 M67 Team

    2016-06-01

    M67 is among the best studied of all star clusters. Being at an age and metallicity very near solar, at an accessible distance of 850 pc with low reddening, and rich in content (over 1000 members including main-sequence dwarfs, a well populated subgiant branch and red giant branch, white dwarfs, blue stragglers, sub-subgiants, X-ray sources and CVs), M67 is a cornerstone of stellar astrophysics.The K2 mission (Campaign 5) has obtained long-cadence observations for 2373 stars, both within an optimized central superaperture and as specified targets outside the superaperture. 1,432 of these stars are likely cluster members based on kinematic and photometric criteria.We have extracted light curves and corrected for K2 roll systematics, producing light curves with noise characteristics qualitatively similar to Kepler light curves of stars of similar magnitudes. The data quality is slightly poorer than for field stars observed by K2 due to crowding near the cluster core, but the data are of sufficient quality to detect seismic oscillations, binary star eclipses, flares, and candidate transit events. We are in the process of uploading light curves and various diagnostic files to MAST; light curves and supporting data will also be made available on ExoFOP.Importantly, several investigators within the M67 K2 team are independently doing light curve extractions and analyses for confirmation of science results. We also are adding extensive ground-based supporting data, including APOGEE near-infrared spectra, TRES and WIYN optical spectra, LCOGT photometry, and more.Our science goals encompass asteroseismology and stellar evolution, alternative stellar evolution pathways in binary stars, stellar rotation and angular momentum evolution, stellar activity, eclipsing binaries and beaming, and exoplanets. We will present early science results as available by the time of the meeting, and certainly including asteroseismology, blue stragglers and sub-subgiants, and newly discovered

  9. Color-magnitude Diagrams for the Stellar Open Cluster M 67 in theVilnius Photometric System

    NASA Astrophysics Data System (ADS)

    Boyle, Richard P.; Janusz, Robert

    2015-01-01

    Stellar photometry in the Vilnius Photometric System requires one percent quality for deriving luminosity class and spectral type subclass. We use such existing photometry of the open cluster M 67 to calibrate new CCD observations at the Vatican Advanced Technology Telescope (VATT) for correcting the flat-fielding zero-point and deriving the color-transformation in this intermediate-band, seven filter system (Boyle et al., BAAS 37 #4, 2005).Recently we have developed a "tie-in" observational practice to apply the zero-point and color transformation of the M 67 observations to neighboring starfields of interest that have no existing photometry. Sky transparency must remain constant to better than one percent during a round of short exposures in a filter between the field having calibrated photometry and the new field having no photometry as if the new field was exposed simultaneously with the master field.Proof of success for this "tie-in" method is shown with the master field being M 67 and the "tie-in" field being the nearby extended "corona" area. The distinctive color-magnitude diagrams of the old open clusterM 67 reveal the sensitivity to having constant sky transparency during the round of short exposures on M 67 and its extended area. For the extended area has the same form in its color-magnitude diagram as M 67. So variation in sky transparency shows displacement on the color-magnitude diagrams at the one percent quality.We will attempt new analysis concerning evolution of this very old open cluster (2.56 Gyr, WEBDA, http://www.univie.ac.at/webda/) and the surrounding "coronal" extent with reference to previous work by Chupina and Vereshchagin (Astron. Astrophys, 334, 552, 1998).

  10. A new solar fluorine abundance and a fluorine determination in the two open clusters M67 and NGC 6404

    SciTech Connect

    Maiorca, E.; Randich, S.; Magrini, L.; Uitenbroek, H.; Uttenthaler, S.; Busso, M.

    2014-06-20

    We present a new determination of the solar fluorine abundance together with abundance measurements of fluorine in two Galactic open clusters. We analyzed a sunspot spectrum, observed by L. Wallace and W. Livingston with the Fourier Transform Spectrometer at the McMath/Pierce Solar Telescope situated on Kitt Peak, and spectra of four giants in the old cluster M67 (∼4.5 Gyr) and three giants in the young cluster NGC 6404 (∼0.5 Gyr), obtained with the CRIRES spectrograph at the Very Large Telescope. Fluorine was measured through the synthesis of the available HF lines. We adopted the recent set of experimental molecular parameters of HF delivered by the HITRAN database, and found a new solar fluorine abundance of A(F) = 4.40 ± 0.25, in good agreement with the M67 average fluorine abundance of A(F) = 4.49 ± 0.20. The new solar abundance is in a very good agreement with the meteoritic value. The modern spectrosynthesis tools used and the agreement with the meteoritic value and with the results in open cluster M67, known to be a solar analogue, make our solar determination very robust. At the same time, the fluorine measurement in the above-mentioned open clusters is the first step toward understanding its evolution during the last ∼10 Gyr in the Galactic disk. In order to develop this project, a larger sample of open clusters is required, in order to allow us to trace the evolution of fluorine as a function of time and, in turn, to better understand its origin.

  11. Spectroscopy of a stream of G-stars in the area of the open cluster M67

    NASA Astrophysics Data System (ADS)

    Balaguer-Nuñez L.; Galadi-Enriquez, D.; Jordi, C.; Sanchez, S. F.; Muiños, J. L.

    2011-11-01

    The systematic study of selected open clusters by our team lead to the production of the best set of Strömgren photometry ever obtained of the old open cluster M67. Its analysis showed a previously unknown clump of more than 60 stars in the HR diagram, located below the cluster main sequence. The spatial distribution of these stars suggested that most of them could be cluster members and two alternative hypothesis were proposed: (1) if members, they would be binary systems composed by a white dwarf and a red dwarf, i.e. pre-cataclysmic variable systems; and (2) if non-members, they would constitute a stream of G-type stars placed behind the cluster. Medium dispersion spectra taken using the PMAS/PPAK spectrograph at 3.5 m telescope in Calar Alto lead to the conclusion that all stars are F--G main sequence stars, and therefore the first hypothesis can be discarded. We are acquiring new uvby-H_eta photometric data with the Wide Field Camera of INT and, in addition, we are carrying out an astrometric study with the Meridian Circle of San Fernando CMASF at El Leoncito (Argentina) to derive properties of stars fainter than our previous survey and covering a wider area in the cluster region. The new data will yield proper motions of the stars in the clump as well as allow to study the properties of the corona of M67.

  12. Stellar Radial Velocities in the Old Open Cluster M67 (NGC 2682). I. Memberships, Binaries, and Kinematics

    NASA Astrophysics Data System (ADS)

    Geller, Aaron M.; Latham, David W.; Mathieu, Robert D.

    2015-09-01

    We present results from 13776 radial-velocity (RV) measurements of 1278 candidate members of the old (4 Gyr) open cluster M67 (NGC 2682). The measurements are the results of a long-term survey that includes data from seven telescopes with observations for some stars spanning over 40 years. For narrow-lined stars, RVs are measured with precisions ranging from about 0.1 to 0.8 km s-1. The combined stellar sample reaches from the brightest giants in the cluster down to about 4 mag below the main-sequence turnoff (V=16.5), covering a mass range of about 1.34 {M}⊙ to 0.76 {M}⊙ . Spatially, the sample extends to a radus of 30 arcmin (7.4 pc in projection at a distance of 850 pc or 6-7 core radii). We find M67 to have a mean RV of +33.64 km s-1 (with an internal precision of ±0.03 km s-1) well separated from the mean velocity of the field. For stars with ≥slant 3 measurements, we derive RV membership probabilities and identify RV variables, finding 562 cluster members, 142 of which show significant RV variability. We use these cluster members to construct a color-magnitude diagram and identify a rich sample of stars that lie far from the standard single star isochrone, including the well-known blue stragglers, sub-subgiants and yellow giants. These exotic stars have a binary frequency of (at least) 80%, more than three times that detected for stars in the remainder of the sample. We confirm that the cluster is mass segregated, finding the binaries to be more centrally concentrated than the single stars in our sample at the 99.8% confidence level (and at the 98.7% confidence level when only considering main-sequence stars). The blue stragglers are centrally concentrated as compared to the solar-type main-sequence single stars in the cluster at the 99.7% confidence level. Accounting for measurement precision, we derive an RV dispersion in M67 of 0.80 ± 0.04 km s-1 for our sample of single main-sequence stars, subgiants and giants with V≤slant 15.5. When corrected

  13. Blue straggler stars: lessons from open clusters.

    NASA Astrophysics Data System (ADS)

    Geller, Aaron M.

    Open clusters enable a deep dive into blue straggler characteristics. Recent work shows that the binary properties (frequency, orbital elements and companion masses and evolutionary states) of the blue stragglers are the most important diagnostic for determining their origins. To date the multi-epoch radial-velocity observations necessary for characterizing these blue straggler binaries have only been carried out in open clusters. In this paper, I highlight recent results in the open clusters NGC 188, NGC 2682 (M67) and NGC 6819. The characteristics of many of the blue stragglers in these open clusters point directly to origins through mass transfer from an evolved donor star. Additionally, a handful of blue stragglers show clear signatures of past dynamical encounters. These comprehensive, diverse and detailed observations also reveal important challenges for blue straggler formation models (and particularly the mass-transfer channel), which we must overcome to fully understand the origins of blue straggler stars and other mass-transfer products.

  14. A Spectroscopic Study of Anomalous Stellar Populations in M67

    NASA Astrophysics Data System (ADS)

    McGahee, Courtney; King, Jeremy R.; Deliyannis, Constantine P.

    2015-01-01

    A population of so-called "yellow straggler" stars occupy precarious color magnitude diagram positions in the old open cluster M67 that cannot be explained by standard single star evolution theory. These stars may have been formed by Roche lobe overflow mass transfer in close binary systems. We present new radial velocities and spectroscopic abundances of M67 yellow stragglers to test this hypothesis, and find that these objects possess a high binary frequency, but no enhancements of s-process elements that might be a smoking gun signature of mass transfer. Observations were conducted using the WIYN 3.5 m telescope in conjunction with the HYDRA spectrograph at Kitt Peak National Observatory. Support for this project was provided by NSF grants AST 09-08342, AST 0607567, and AST 1211699.

  15. A spectroscopic study of the blue stragglers in M67

    NASA Astrophysics Data System (ADS)

    Liu, G. Q.; Deng, L.; Chávez, M.; Bertone, E.; Davo, A. Herrero; Mata-Chávez, M. D.

    2008-10-01

    Based on spectrophotometric observations from the Guillermo Haro Observatory (Cananea, Mexico), a study of the spectral properties of the complete sample of 24 blue straggler stars (BSs) in the old Galactic open cluster M67 (NGC 2682) is presented. All spectra, calibrated using spectral standards, were recalibrated by means of photometric magnitudes in the Beijing-Arizona-Taipei-Connecticut system, which includes fluxes in 11 bands covering ~3500-10000 Å. The set of parameters was obtained using two complementary approaches that rely on a comparison of the spectra with (i) an empirical sample of stars with well-established spectral types and (ii) a theoretical grid of optical spectra computed at both low and high resolution. The overall results indicate that the BSs in M67 span a wide range in Teff(~ 5600 -12600 K) and surface gravities that are fully compatible with those expected for main-sequence objects (log g = 3.5 -5.0 dex).

  16. A Spectroscopic Study of Blue Stragglers in M67

    NASA Astrophysics Data System (ADS)

    Liu, G. Q.; Deng, L.; Chávez, M.; Bertone, E.

    2008-10-01

    Spectrophotometric observations of the complete sample of twenty four blue stragglers (BSs) in the old galactic open cluster M67 (NGC2682) have been collected, using the Guillermo Haro Observatory in Cananea, Mexico. All the calibrated spectra were re-calibrated by the Beijing Arizona Taipei Connecticut (BATC) photometric system which includes fluxes in 11 photometric bands covering ~3600 10000 Å. The goal of the current work is to provide observational constraints on spectral properties of BSs by determining the effective temperature (Teff) and surface gravity (log g). The overall results, obtained by applying the flux fitting method, indicate that Teff and surface gravities of BSs in M67 are fully compatible with those expected for main sequence stars.

  17. A spectroscopic study of anomalous stellar populations in M67

    NASA Astrophysics Data System (ADS)

    McGahee, Courtney Elizabeth

    A population of stars exists in the old, open cluster M67, whose photometry, color magnitude diagram locations and associated evolutionary states cannot be explained by current, standard single star evolution theory. These stars are often referred to as "yellow straggler" stars. Yellow stragglers have been identified in multiple star clusters suggesting that these stars constitute a real population. Additionally, according to independent studies, at least some of the yellow straggler stars in M67 are likely cluster members. Therefore, cluster non-membership is not a sufficient explanation for the observed anomalous photometry of these stars. It is possible that the yellow stragglers occupy their precarious color magnitude diagram positions as a result of the evolution of mass transfer blue straggler stars. These are stars which have been formed by Roche Lobe overflow mass transfer in close binary systems. If this the case for the yellow stragglers, it is hypothesized that they could potentially exhibit two spectroscopic characteristics that can be indicative of this type of mass transfer system. Specifically, variable radial velocities can be used to indicate that the yellow stragglers exist in binary systems and enhancements of s-process elements in yellow stragglers can indicate Roche Lobe overflow mass transfer from a once asymptotic giant branch star which has since evolved into a white dwarf. This dissertation details the radial velocity survey and the chemical abundance analysis that have been conducted to investigate the yellow stragglers with regard to this hypothesis. The radial velocity survey revealed that eight of the ten yellow stragglers studied exhibit variable radial velocities indicating that the yellow straggler population of M67 possess a high binary frequency. However, the chemical abundance analysis revealed that none of the yellow stragglers exhibited enhancements of the s-process elements Y and Ba. Therefore, a history which involves Roche

  18. One Percent Strömvil Photometry in M 67

    NASA Astrophysics Data System (ADS)

    Philip, A. G. D.; Boyle, R. P.; Janusz, R.

    2005-05-01

    The Vatican Advanced Technology Telescope on Mt. Graham is being used in a program of CCD photometry of open and globular clusters. We are using the Ströomvil System (Straižys et al. 1996), a combination of the Strömgren and Vilnius Systems. This system allows stars to be classified as to temperature, surface gravity, metallicity and reddening from the photometric measures alone. However, to make accurate estimates of the stellar parameters the photometry should be accurate to 1 or 1.5 percent. In our initial runs on the VATT we did not achieve this accuracy. The problem turned out to be scattered light in the telescope and this has now been reduced so we can do accurate photometry. Boyle has written a routine in IRAF which allows us to correct the flats for any differences. We take rotated frames and also frames which are offset in position by one third of a frame, east-west and north-south. Measures of the offset stars give us the corrections that need to be made to the flat. Robert Janusz has written a program, the CommandLog, which allows us to paste IRAF commands in the correct order to reduce measures made on a given observing run. There is an automatic version where one can test various parameters and get a set of solutions. Now we have a set of Strömvil frames in the open cluster, M 67 and we compare our color-magnitude diagram with those of BATC (Fan et al. 1996) and Vilnius (Boyle et al. 1998). A preliminary report of the M 67 photometry will be found in Laugalys et al. (2004). Here we report on a selected set of stars in the M 67 frames, those with errors 1 percent or less.

  19. Studies on the corona of open clusters

    NASA Astrophysics Data System (ADS)

    Balaguer-Núñez, L.; Jordi, C.; Muiños, J. L.; Galadí-Enríquez, D.; Masana, E.

    2013-05-01

    High quality proper motions on an extended area of a selection of Open Clusters (OCs) will let us study their coronas with unprecedented accuracy. We are in the process of obtaining astrometry with the Meridian Circles of San Fernando CMASF at El Leoncito (Argentina) and the CTA at La Palma of an area few times the known radius (from Webda) of a selection of OCs. We will make use of Strömgren wide-field photometry to complement their characterization. We have already analysed the old open cluster M67, deriving properties for 2738 stars fainter and, in a wider area, than any previous precise survey in the cluster region. With new data from the CMASF we have covered an area of about 2°×1.4° and down to 17 magnitude in r^'. Proper motions are then used to determine the membership probabilities of stars in the region, applying parametric and non-parametric approaches to cluster/field segregation. Adding photometric criteria, we obtained a preliminary list of 665 probable member stars, up to a distance 0.96° from the cluster centre. These are preliminary results on our work that will lead us to the most complete study of its structure, dynamics and mass segregation up to date. We have already obtained proper motions for NGC 1817, NGC 2264 and NGC 2509 that are now being processed.

  20. On Using the Color-Magnitude Diagram Morphology of M67 to Test Solar Abundances

    NASA Astrophysics Data System (ADS)

    Magic, Z.; Serenelli, A.; Weiss, A.; Chaboyer, B.

    2010-08-01

    The open cluster M67 has solar metallicity and an age of about 4 Gyr. The turnoff (TO) mass is close to the minimum mass for which solar metallicity stars develop a convective core during main sequence evolution as a result of the development of hydrogen burning through the CNO cycle. The morphology of the color-magnitude diagram (CMD) of M67 around the TO shows a clear hook-like feature, a direct sign that stars close to the TO have convective cores. VandenBerg et al. investigated the possibility of using the morphology of the M67 TO to put constraints on the solar metallicity, particularly CNO elements, for which solar abundances have been revised downward by more than 30% over the last few years. Here, we extend their work, filling the gaps in their analysis. To this aim, we compute isochrones appropriate for M67 using new (low metallicity) and old (high metallicity) solar abundances and study whether the characteristic TO in the CMD of M67 can be reproduced or not. We also study the importance of other constitutive physics on determining the presence of such a hook, particularly element diffusion, overshooting and nuclear reaction rates. We find that using the new solar abundance determinations, with low CNO abundances, makes it more difficult to reproduce the characteristic CMD of M67. This result is in agreement with results by VandenBerg et al. However, changes in the constitutive physics of the models, particularly overshooting, can influence and alter this result to the extent that isochrones constructed with models using low CNO solar abundances can also reproduce the TO morphology in M67. We conclude that only if all factors affecting the TO morphology are completely under control (and this is not the case), M67 could be used to put constraints on solar abundances.

  1. The Chemical Homogeneity of Open Clusters

    NASA Astrophysics Data System (ADS)

    Bovy, Jo

    2016-01-01

    Determining the level of chemical homogeneity in open clusters is of fundamental importance in the study of the evolution of star-forming clouds and that of the Galactic disk. Yet limiting the initial abundance spread in clusters has been hampered by difficulties in obtaining consistent spectroscopic abundances for different stellar types. Without reference to any specific model of stellar photospheres, a model for a homogeneous cluster is that it forms a one-dimensional sequence, with any differences between members due to variations in stellar mass and observational uncertainties. I present a novel method for investigating the abundance spread in open clusters that tests this one-dimensional hypothesis at the level of observed stellar spectra, rather than constraining homogeneity using derived abundances as is traditionally done. Using high-resolution APOGEE spectra for 49 giants in M67, NGC 6819, and NGC 2420 I demonstrate that these spectra form one-dimensional sequences for each cluster. With detailed forward modeling of the spectra and Approximate Bayesian Computation, I derive strong limits on the initial abundance spread of 15 elements: <0.01 (0.02) {dex} for C and Fe, ≲0.015 (0.03) {dex} for N, O, Mg, Si, and Ni, ≲0.02 (0.03) {dex} for Al, Ca, and Mn, and ≲0.03 (0.05) {dex} for Na, S, K, Ti, and V (at 68% and 95% confidence, respectively). The strong limits on C and O imply that no pollution by massive core-collapse supernovae occurred during star formation in open clusters, which, thus, need to form within ≲6 {Myr}. Further development of this and related techniques will bring the power of differential abundances to stars other than solar twins in large spectroscopic surveys and will help unravel the history of star formation and chemical enrichment in the Milky Way through chemical tagging.

  2. The K2 M67 Study: An Evolved Blue Straggler in M67 from K2 Mission Asteroseismology

    NASA Astrophysics Data System (ADS)

    Leiner, Emily; Mathieu, Robert D.; Stello, Dennis; Vanderburg, Andrew; Sandquist, Eric

    2016-11-01

    Yellow straggler stars (YSSs) fall above the subgiant branch in optical color-magnitude diagrams (CMDs), between the blue stragglers and the red giants. YSSs may represent a population of evolved blue stragglers, but none have the direct and precise mass and radius measurements needed to determine their evolutionary states and formation histories. Here we report the first asteroseismic mass and radius measurements of such a star, the yellow straggler S1237 in the open cluster M67. We apply asteroseismic scaling relations to a frequency analysis of the Kepler K2 light curve and find a mass of 2.9 ± 0.2 M⊙ and a radius of 9.2 ± 0.2 R⊙. This is more than twice the mass of the main-sequence turnoff in M67, suggesting that S1237 is indeed an evolved blue straggler. S1237 is the primary in a spectroscopic binary. We update the binary orbital solution and use spectral energy distribution fitting to constrain the CMD location of the secondary star. We find that the secondary is likely an upper main-sequence star near the turnoff, but a slightly hotter blue straggler companion is also possible. We then compare the asteroseismic mass of the primary to its mass from CMD fitting, finding that the photometry implies a mass and radius more than 2σ below the asteroseismic measurement. Finally, we consider formation mechanisms for this star and suggest that S1237 may have formed from dynamical encounters resulting in stellar collisions or a binary merger. This is paper 73 in the WIYN Open Cluster Study.

  3. Tidal radius estimates for three open clusters

    NASA Astrophysics Data System (ADS)

    Danilov, V. M.; Loktin, A. V.

    2015-10-01

    A new method is developed for estimating tidal radii and masses of open star clusters (OCL) based on the sky-plane coordinates and proper motions and/or radial velocities of cluster member stars. To this end, we perform the correlation and spectral analysis of oscillations of absolute values of stellar velocity components relative to the cluster mass center along three coordinate planes and along each coordinate axis in five OCL models. Mutual correlation functions for fluctuations of absolute values of velocity field components are computed. The spatial Fourier transform of the mutual correlation functions in the case of zero time offset is used to compute wavenumber spectra of oscillations of absolute values of stellar velocity components. The oscillation spectra of these quantities contain series of local maxima at equidistant wavenumber k values. The ratio of the tidal radius of the cluster to the wavenumber difference Δ k of adjacent local maxima in the oscillation spectra of absolute values of velocity field components is found to be the same for all five OCL models. This ratio is used to estimate the tidal radii and masses of the Pleiades, Praesepe, and M67 based on the proper motions and sky-plane coordinates of the member stars of these clusters. The radial dependences of the absolute values of the tangential and radial projections of cluster star velocities computed using the proper motions relative to the cluster center are determined, along with the corresponding autocorrelation functions and wavenumber spectra of oscillations of absolute values of velocity field components. The Pleiades virial mass is estimated assuming that the cluster is either isolated or non-isolated. Also derived are the estimates of the Pleiades dynamical mass assuming that it is non-stationary and non-isolated. The inferred Pleiades tidal radii corresponding to these masses are reported.

  4. VARIABLE STARS IN THE OPEN CLUSTER NGC 7142

    SciTech Connect

    Sandquist, Eric L.; Serio, Andrew W.; Shetrone, Matthew E-mail: aserio@gemini.edu

    2011-12-15

    We present new discoveries of variable stars near the turnoff of the old open cluster NGC 7142. Contrary to previous studies, we detect eight contact or near-contact eclipsing binaries (including three near the cluster turnoff), and most of these have good probability of being cluster members. We also identified one long-period variable that resides far to the red of the cluster giant branch, and four new detached eclipsing binaries. We have re-examined the question of distance and reddening for the cluster and find that the distance is larger and the reddening lower than in most previous studies. In turn this implies that NGC 7142 is probably slightly younger than M67, and is about 3 Gyr old. With an age of this size, NGC 7142 would be one of a small group of clusters with main-sequence turnoff stars at the transition between convective and radiative cores.

  5. Chromospheric Activity in Red Giants of M67

    NASA Astrophysics Data System (ADS)

    Dupree, A. K.; Whitney, B. A.; Pasquini, L.

    1994-12-01

    Red giants in the old open cluster M67 present a well-studied, homogeneous group of 1.27Msun stars with which to determine the evolution of chromospheric activity and mass loss. Echelle spectra of the Ca II H and K line region (lambda 3950) have been obtained with the 4-m telescope at KPNO, the MMT of the F. L. Whipple Observatory (K only), and the 3.6-m ESO telescope at La Silla, Chile. Spectra of 16 red giant stars down to V ~ 11 were obtained; five of the sample are identified as clump giants. The flux of the emission reversal in the Ca II K core has been calibrated using normalization based on the narrow-band absolute spectrophotometry of Gunn &\\ Stryker (1983, ApJS, 52, 121). A new spectral synthesis of the Calcium line region for radiative models of the M67 giants based on Kurucz atmospheres provides the correction necessary to extract the chromospheric component of the flux. The Ca K emission reversals display asymmetries indicative of outward motions for giants more luminous than M_V ~ +0.5. The chromospheric emission flux in Ca II K decreases with increasing stellar luminosity. Clump giants, which are thought to be in a core-helium burning stage, show Ca II emission comparable to the stars on the red giant branch. Evidence for chromospheric variability is found from multiple observations of several objects. Implications of these results upon the evolution of chromospheres and presence of mass loss in giants will be discussed.

  6. Lithium in a short-period tidally locked binary of M67: Implications for stellar evolution, Galactic Lithium evolution, and cosmology

    NASA Technical Reports Server (NTRS)

    Deliyannis, Constantine P.; King, Jeremy R.; Boesgaard, Ann M.; Ryan, Sean G.

    1994-01-01

    In open clusters, late-F stars exhibit a Li maximum (the Li 'peak' region) at lower abundance with age, which could be due either to stellar depletion or Galactic Li enrichment (or some other cause). We have observed a short-period tidally locked binary (SPTLB) on the Li peak region in the old cluster M67 to distinguish between alternatives. SPTLBs which synchronized in the early pre-main sequence would avoid the rotational mixing which, according to Yale models, may be responsible for depleting Li with age in open cluster dwarfs. We find that both components of the M67 SPTLB have a Li abundance lying about a factor of 2 or more above any other M67 single star and about a factor of 3 or more above the mean Li peak region abundance in M67. Our results suggest that the initial Li abundance in M67 is at least as high as approximately 3.0 = 12 + log (N(sub Li)/N(sub H)). Our high M67 SPTLB Li abundance and those in other clusters support the combination of Zahn's tidal circularization and the Yale rotational mixing theories and may indicate that the halo Li plateau (analogous to the cluster Li peak region) abundance has been depleted from a higher primordial value. Implications are discussed.

  7. Stellar photometry including saturated images: Results on M67 with WFPC2

    NASA Technical Reports Server (NTRS)

    Gilliland, Ronald L.

    1994-01-01

    The Wide Field and Planetary Camera 2 (WFPC2) on Hubble Space Telescope (HST) is providing unsurpassed imaging capabilities and supporting accurate stellar photometry over large fields of view at high angular resolution. I discuss a feature of the WFPC2 CCD systems that nominally limits the dynamic range attainable with single exposures: a 12 bit analog to digital converter that does not allow sampling of the CCD full-well depth even at the low gain (14e(sup -)/DN) setting. I demonstrate that accurate stellar photometry can be performed on stellar images that are strongly saturated. Two 40 s exposures in V and I bands on the old open cluster M67 are analyzed to demonstrate photometric capabilities with a dynamic range of over 12 mag from single exposures. New photometric results for both bright and faint objects in M67 are derived from the WFPC2 data.

  8. The open cluster NGC 6716

    SciTech Connect

    Grice, N.A.; Dawson, D.W. Western Connecticut State Univ., Danbury, CT )

    1990-08-01

    NGC 6716 is a young open star cluster in Sagittarius. Lindoff (1971) obtained photoelectric photometry for 12 stars and photographic UBV photometry for 115 stars in the cluster field down to V = 13.8. This work has been expanded to include more photoelectric standards and IRIS photometry for 332 stars in the cluster field down to V = 16. A reddening E(B-V) = 0.17 mag, a distance modulus of 8.69 + or - 0.15 mag (d = 547 pc), and an age of around 100 million years for the cluster are derived. Of the stars studied, 75 were judged as likely cluster members, 63 as possible members, and 194 as probable nonmembers. 13 refs.

  9. H-alpha and H-beta Standard Stars in M 67 and NGC 752

    NASA Astrophysics Data System (ADS)

    Joner, Michael D.; Saylor, Clint A.; Hintz, Maureen; Hintz, Eric G.

    2017-01-01

    The BYU H-alpha photometric system was defined in Joner and Hintz (2015, AJ, 150, 204) using multiple years of spectroscopic observations. The spectrophotometric methods used to form the new index were also utilized to produce an H-beta index for each of the newly established H-alpha standard stars. We present H-alpha and H-beta filter photometry for stars in the open clusters M 67 and NGC 752 that has been carefully transformed to the standard systems. These stars are suitable to use as standards for transforming CCD observations to the H-alpha and H-beta photometric systems.

  10. The abundance of fluorine in the Hyades, NGC 752, and M67

    SciTech Connect

    Nault, K. A.; Pilachowski, C. A. E-mail: catyp@astro.indiana.edu

    2013-12-01

    The abundance of fluorine is determined from the 2.3358 μm feature of the molecule HF for several giants in the Hyades, NGC 752, and M67 open clusters from spectra obtained with the Phoenix IR spectrometer on the 2.1 m telescope at Kitt Peak. The abundance of fluorine in cluster giants is consistent with that observed in field stars, and may indicate that stars with super-solar metallicities and young ages may be enhanced in fluorine by perhaps 0.2-0.3 dex compared to older or lower-metallicity field stars. Multiple sources probably contribute to the fluorine abundance in the Galactic disk, although the relative contributions of possible sources remain uncertain. Fluorine production in asymptotic giant branch stars, however, is unlikely to be the dominant source.

  11. Chemical composition of the old open clusters melotte 66 and NGC 2243

    SciTech Connect

    Gratton, R.G.

    1982-06-15

    The chemical composition of the old open cluster Melotte 66 and NGC 2243 is determined by means of high-dispersion spectra of some red giants and a model atmosphere analysis. The two clusters are found to be quite metal poor ((Fe/H) = -0.7 +- 0.1 for Melotte 66 and (Fe/H) = -1.2 +- 0.1 for NGC 2243), with oxygen perhaps enhanced in NGC 2243. A reanalysis is made of the color-magnitude diagrams of the four old open clusters which have been studied with high dispersion (M67, NGC 2420, NGC 2243, and Melotte 66), and new values for the distance moduli of M67 and Melotte 66 are determined. Age estimates are 4 x 10/sup 9/ years for M67 and NGC 2420 and 6 x 10/sup 9/ years for NGC 2243 and Melotte 66. The helium content = 0.25 +- 0.03 is estimated from the magnitude of the horizontal branch and the ratio of the horizontal branch stars to red giants, and seems remarkably constant within this sample of clusters. The results suggest that the time scale of the galactic halo collapse is long (5--10 x 10/sup 9/ years), in agreement with recent models.

  12. An application of the k-th nearest neighbor method to open cluster membership determination

    NASA Astrophysics Data System (ADS)

    Gao, Xin-Hua

    2016-12-01

    We introduce a non-parametric method for open cluster membership determination in three-dimensional (3D) velocity space (proper motion and radial velocity). Clean 3D cluster members can be obtained by statistically analyzing the Euclidean distance between each star and its k-th nearest neighbor in 3D velocity space. We use 513 sample stars in the direction of open cluster M67 to construct a 3D velocity space and test our method; 291 3D cluster members are obtained. The color-magnitude diagram, proper motions, radial velocities and spatial distribution of these 3D cluster members demonstrate the effectiveness of our method. From the 291 3D cluster members, the mean radial velocity and absolute proper motion of M67 are Vr = +33.46 ± 0.05 km s-1 and (PMRA, PMDEC) = (-7.64 ± 0.07, -5.98 ± 0.07) mas yr-1, respectively. In addition, we use 640 sample stars with precise proper motions and radial velocities in the direction of open cluster NGC 188 to test our method. The test results also show that our method is effective.

  13. X-Ray source populations in old open clusters: Collinder 261

    NASA Astrophysics Data System (ADS)

    Vats, Smriti; van den Berg, Maureen; Wijnands, Rudy

    2014-09-01

    We are carrying out an X-ray survey of old open clusters with the Chandra X-ray Observatory. Single old stars, being slow rotators, are very faint in X-rays (L_X < 1×10^27 erg/s). Hence, X-rays produced by mass transfer in cataclysmic variables (CVs) or by rapid rotation of the stars in tidally locked, detached binaries (active binaries; ABs) can be detected, without contamination from single stars. By comparing the properties of various types of interacting binaries in different environments (the Galactic field, old open clusters, globular clusters), we aim to study binary evolution and how it may be affected by dynamical encounters with other cluster stars. Stellar clusters are good targets to study binaries, as age, distance, chemical composition, are well constrained. Collinder (Cr) 261 is an old open cluster (age ~ 7 Gyr), with one of the richest populations inferred of close binaries and blue stragglers of all open clusters and is therefore an obvious target to study the products of close encounters in open clusters. We will present the first results of this study, detailing the low-luminosity X-ray population of Cr 261, in conjunction with other open clusters in our survey (NGC 188, Berkeley 17, NGC 6253, M67, NGC 6791) and in comparison with populations in globular clusters.

  14. Giant Planets in Open Clusters

    NASA Astrophysics Data System (ADS)

    Quinn, S. N.; White, R. J.; Latham, D. W.

    2015-10-01

    Two decades after the discovery of 51 Peg b, more than 200 hot Jupiters have now been confirmed, but the details of their inward migration remain uncertain. While it is widely accepted that short period giant planets could not have formed in situ, several different mechanisms (e.g., Type II migration, planet-planet scattering, Kozai-Lidov cycles) may contribute to shrinking planetary orbits, and the relative importance of each is not well-constrained. Migration through the gas disk is expected to preserve circular, coplanar orbits and must occur quickly (within ˜ 10 Myr), whereas multi-body processes should initially excite eccentricities and inclinations and may take hundreds of millions of years. Subsequent evolution of the system (e.g., orbital circularization and inclination damping via tidal interaction with the host star) may obscure these differences, so observing hot Jupiters soon after migration occurs can constrain the importance of each mechanism. Fortunately, the well-characterized stars in young and adolescent open clusters (with known ages and compositions) provide natural laboratories for such studies, and recent surveys have begun to take advantage of this opportunity. We present a review of the discoveries in this emerging realm of exoplanet science, discuss the constraints they provide for giant planet formation and migration, and reflect on the future direction of the field.

  15. LITHIUM ABUNDANCES OF THE SUPER-METAL-RICH OPEN CLUSTER NGC 6253

    SciTech Connect

    Cummings, Jeffrey D.; Deliyannis, Constantine P.; Maderak, Ryan M.; Anthony-Twarog, Barbara; Twarog, Bruce E-mail: con@astro.indiana.edu E-mail: bjat@ku.edu

    2012-11-01

    High-resolution CTIO 4 m/HYDRA spectroscopy of the super-metal-rich open cluster NGC 6253 ([Fe/H] = +0.43 {+-} 0.01) has been used to study the stellar lithium (Li) abundances near the cluster's turnoff. NGC 6253 greatly expands the range of [Fe/H] for clusters that have a Li abundance analysis. This is important for studying the complicated effects of, and potential correlations with, stellar Fe abundance on surface Li abundance. Comparisons to the younger and less-metal-rich Hyades and to the similarly aged but solar-metallicity M67 show that NGC 6253's Li abundances are qualitatively consistent with the prediction, from Standard Stellar Evolution Theory, that higher-metallicity stars have a greater Li depletion. Comparison with M67 provides evidence that the more-metal-rich NGC 6253 had a higher initial Li, which is consistent with expectations from models of Galactic Li production. NGC 6253 is also compared to the intermediate-aged NGC 3680, NGC 752, and IC 4651 open clusters. Comparison of the Li-gap positions in all six clusters shows that (1) the gap's position in T{sub eff} is independent of metallicity, but (2) higher-metallicity clusters have their gaps in higher-mass stars. In addition, the Li gap's position is shown not to evolve with age, which provides an important constraint for the non-standard depletion mechanisms that may create the Li gap.

  16. M 67: a constraint on Z_⊙ and/or on diffusive processes in stellar interiors.

    NASA Astrophysics Data System (ADS)

    VandenBerg, D. A.; Gustafsson, B.; Edvardsson, B.; Eriksson, K.; Ferguson, J. W.

    The mass of the lowest mass star that has a convective core throughout the main-sequence phase is predicted to be a fairly sensitive function of Z (especially the CNO abundances). The ˜ 4 Gyr open cluster M 67 thus provides a constraint on Z_⊙ (and the solar metals mix) because (i) it has the same metallicity as the Sun according to high-resolution spectroscopy, and (ii) its turnoff stars have masses just above this lower mass limit. While isochrones computed for Z = 0.0165, assuming the Grevesse & Sauval (1998) heavy-element mixture, are able to reproduce the M 67 color-magnitude diagram satisfactorily, those for the solar abundances derived by M. Asplund et al. (implying Z_⊙ = 0.0125) do not predict a gap near the turnoff where one is observed. These results suggest either that there is a problem with the solar metal abundances derived by Asplund et al. or that the neglect of diffusive processes in the present models is responsible for this difficulty. If the latter is the correct explanation, then M 67 provides an important constraint on the rates of diffusive processes in the deep interiors of stars.

  17. Lithium in Open Cluster Red Giants Hosting Substellar Companions

    NASA Astrophysics Data System (ADS)

    Carlberg, Joleen K.; Smith, Verne V.; Cunha, Katia; Carpenter, Kenneth G.

    2016-02-01

    We have measured stellar parameters, [Fe/H], lithium abundances, rotation, and 12C/13C in a small sample of red giants (RGs) in three open clusters that are each home to a RG star that hosts a substellar companion (SSC) (NGC 2423 3, NGC 4349 127, and BD+12 1917 in M67). Our goal is to explore whether the presence of SSCs influences the Li content. Both 12C/13C and stellar rotation are measured as additional tracers of stellar mixing. One of the companion hosts, NGC 2423 3, is found to be Li-rich with A(Li){}{{NLTE}} = 1.56 dex, and this abundance is significantly higher than the A(Li) of the two comparison stars in NGC 2423. All three SSC hosts have the highest A(Li) and 12C/13C when compared to the control RGs in their respective clusters; however, except for NGC 2423 3, at least one control star has similarly high abundances within the uncertainties. Higher A(Li) could suggest that the formation or presence of planets plays a role in the degree of internal mixing on or before the RG branch. However, a multitude of factors affect A(Li) during the RG phase, and when the abundances of our sample are compared with the abundances of RGs in other open clusters available in the literature, we find that they all fall well within a much larger distribution of A(Li) and 12C/13C. Thus, even the high Li in NGC 2423 3 cannot be concretely tied to the presence of the SSC.

  18. Lithium in Open Cluster Red Giants Hosting Substellar Companions

    NASA Technical Reports Server (NTRS)

    Carlberg, Joleen K.; Smith, Verne V.; Cunha, Katia; Carpenter, Kenneth G.

    2016-01-01

    We have measured stellar parameters, [Fe/H], lithium abundances, rotation, and (12)C/13C in a small sample of red giants (RGs) in three open clusters that are each home to a RG star that hosts a substellar companion (SSC) (NGC 2423 3, NGC 4349 127, and BD+12 1917 in M67). Our goal is to explore whether the presence of SSCs influences the Li content. Both (12)C/13C and stellar rotation are measured as additional tracers of stellar mixing. One of the companion hosts, NGC 2423?3, is found to be Li-rich with A(Li)(sub NLTE) = 1.56 dex, and this abundance is significantly higher than the A(Li) of the two comparison stars in NGC 2423. All three SSC hosts have the highest A(Li) and (12)C/13C when compared to the control RGs in their respective clusters; however, except for NGC 2423?3, at least one control star has similarly high abundances within the uncertainties. Higher A(Li) could suggest that the formation or presence of planets plays a role in the degree of internal mixing on or before the RG branch. However, a multitude of factors affect A(Li) during the RG phase, and when the abundances of our sample are compared with the abundances of RGs in other open clusters available in the literature, we find that they all fall well within a much larger distribution of A(Li) and (12)C/13C. Thus, even the high Li in NGC 2423 3 cannot be concretely tied to the presence of the SSC.

  19. High-Quality Broadband BVRI Photometry of Benchmark Open Clusters

    NASA Astrophysics Data System (ADS)

    Joner, Michael D.

    Photometric techniques are often used to observe stars and it can be demonstrated that fundamental stellar properties can be observationally determined using calibrated sets of photometric data. Many of the most powerful techniques utilized to calibrate stellar photometry employ the use of stars in clusters since the individual stars are believed to have many common properties such as age, composition, and approximate distance. Broadband photometric Johnson/Cousins BVRI observations are presented for several nearby open clusters. The new photometry has been tested for consistency relative to archival work and shown to be both accurate and precise. The careful use of a regular routine when making photometric observations, along with the monitoring of instrumental systems and the use of various quality control techniques when making observations or performing data reductions, will enhance an observer's ability to produce high-quality photometric measurements. This work contains a condensed review of the history of photometry, along with a brief description of several popular photometric systems that are often utilized in the field of stellar astrophysics. Publications written by Taylor or produced during the early Taylor and Joner collaboration are deemed especially relevant to the current work. A synopsis of seven archival publications is offered, along with a review of notable reports of VRI photometric observations for the nearby Hyades open star cluster. The body of this present work consists of four publications that appeared between the years 2005 and 2008, along with a soon to be submitted manuscript for a fifth publication. Each of these papers deals specifically with high-quality broadband photometry of open clusters with new data being presented for the Hyades, Coma, NGC 752, Praesepe, and M67. It is concluded that the VRI photometry produced during the Taylor and Joner collaborative investigations forms a high-quality data set that has been: (1) stable for

  20. The SEGUE Stellar Parameter Pipeline. II. Validation with Galactic Globular and Open Clusters

    SciTech Connect

    Lee, Y.S.; Beers, T.C.; Sivarani, T.; Johnson, J.A.; An, D.; Wilhelm, R.; Prieto, C.Allende; Koesterke, L.; Re Fiorentin, P.; Bailer-Jones, C.A.L.; Norris, J.E.

    2007-10-01

    The authors validate the performance and accuracy of the current SEGUE (Sloan Extension for Galactic Understanding and Exploration) Stellar Parameter Pipeline (SSPP), which determines stellar atmospheric parameters (effective temperature, surface gravity, and metallicity) by comparing derived overall metallicities and radial velocities from selected likely members of three globular clusters (M 13, M 15, and M 2) and two open clusters (NGC 2420 and M 67) to the literature values. Spectroscopic and photometric data obtained during the course of the original Sloan Digital Sky Survey (SDSS-1) and its first extension (SDSS-II/SEGUE) are used to determine stellar radial velocities and atmospheric parameter estimates for stars in these clusters. Based on the scatter in the metallicities derived for the members of each cluster, they quantify the typical uncertainty of the SSPP values, {sigma}([Fe/H]) = 0.13 dex for stars in the range of 4500 K {le} T{sub eff} {le} 7500 K and 2.0 {le} log g {le} 5.0, at least over the metallicity interval spanned by the clusters studied (-2.3 {le} [Fe/H] < 0). The surface gravities and effective temperatures derived by the SSPP are also compared with those estimated from the comparison of the color-magnitude diagrams with stellar evolution models; they find satisfactory agreement. At present, the SSPP underestimates [Fe/H] for near-solar-metallicity stars, represented by members of M 67 in this study, by {approx} 0.3 dex.

  1. Planet host stars in open clusters

    NASA Astrophysics Data System (ADS)

    Yang, XiaoLing; Chen, YuQin; Zhao, Gang

    2015-03-01

    We have compiled a list of all planet host star candidates reported in the literature, which are likely to be cluster members, and we checked their memberships by the spatial location, radial velocity, proper motion and photometric criteria. We found that only six stars, BD-13 2130, HD 28305, Kepler-66, Kepler-67, Pr0201 and Pr0211, are planet orbiting stars in open clusters to date. Two stars, HD 70573 and HD 89744, belong to moving groups and one star, TYC 8975-2606-1, may not be a planet host star, while three stars, HD 16175, HD 46375 and HD 108874 are not members of open clusters. We note that all these six planetary systems in the stellar cluster environment are younger than ˜1 Gyr, which might indicate that the planetary system in open cluster can not survive for a long time, and we speculate that close stellar encounters between member stars in open cluster can potentially destroy, or at least strongly affect, the presence of planetary systems.

  2. Do open clusters have distinguishable chemical signatures?

    NASA Astrophysics Data System (ADS)

    Blanco-Cuaresma, S.; Soubiran, C.; Heiter, U.

    2014-07-01

    Past studies have already shown that stars in open clusters are chemically homogeneous (e.g. De Silva et al. 2006, 2007 and 2009). These results support the idea that stars born from the same giant molecular cloud should have the same chemical composition. In this context, the chemical tagging technique was proposed by Freeman et al. (2002). The principle is to recover disrupted stellar clusters by looking only to the stellar chemical composition. In order to evaluate the feasibility of this approach, it is necessary to test if we can distinguish between stars born from different molecular clouds. For this purpose, we studied the chemical composition of stars in 32 old and intermediate-age open clusters, and we applied machine learning algorithms to recover the original cluster by only considering the chemical signatures.

  3. Open clusters in Auriga OB2

    NASA Astrophysics Data System (ADS)

    Marco, Amparo; Negueruela, Ignacio

    2016-06-01

    We study the area around the H II region Sh 2-234, including the young open cluster Stock 8, to investigate the extent and definition of the association Aur OB2 and the possible role of triggering in massive cluster formation. We obtained Strömgren and J, H, KS photometry for Stock 8 and Strömgren photometry for two other cluster candidates in the area, which we confirm as young open clusters and name Alicante 11 and Alicante 12. We took spectroscopy of ˜33 early-type stars in the area, including the brightest cluster members. We calculate a common distance of 2.80^{+0.27}_{-0.24} kpc for the three open clusters and surrounding association. We derive an age 4-6 Ma for Stock 8, and do not find a significantly different age for the other clusters or the association. The star LS V +34°23, with spectral type O8 II(f), is likely the main source of ionization of Sh 2-234. We observe an important population of pre-main-sequence stars, some of them with discs, associated with the B-type members lying on the main sequence. We interpret the region as an area of recent star formation with some residual and very localized ongoing star formation. We do not find evidence for sequential star formation on a large scale. The classical definition of Aur OB2 has to be reconsidered, because its two main open clusters, Stock 8 and NGC 1893, are not at the same distance. Stock 8 is probably located in the Perseus arm, but other nearby H II regions whose distances also place them in this arm show quite different distances and radial velocities and, therefore, are not connected.

  4. THE YOUNG OPEN CLUSTER BERKELEY 55

    SciTech Connect

    Negueruela, Ignacio; Marco, Amparo E-mail: amparo.marco@ua.es

    2012-02-15

    We present UBV photometry of the highly reddened and poorly studied open cluster Berkeley 55, revealing an important population of B-type stars and several evolved stars of high luminosity. Intermediate-resolution far-red spectra of several candidate members confirm the presence of one F-type supergiant and six late supergiants or bright giants. The brightest blue stars are mid-B giants. Spectroscopic and photometric analyses indicate an age 50 {+-} 10 Myr. The cluster is located at a distance d Almost-Equal-To 4 kpc, consistent with other tracers of the Perseus Arm in this direction. Berkeley 55 is thus a moderately young open cluster with a sizable population of candidate red (super)giant members, which can provide valuable information about the evolution of intermediate-mass stars.

  5. Re-grouping stars based on the chemical tagging technique: A case study of M67 and IC4651

    NASA Astrophysics Data System (ADS)

    Blanco-Cuaresma, S.; Soubiran, C.

    2016-12-01

    The chemical tagging technique proposed by te{2002ARA&A..40..487F} is based on the idea that stars formed from the same molecular cloud should share the same chemical signature. Thus, using only the chemical composition of stars we should be able to re-group the ones that once belonged to the same stellar aggregate. In te{2015A&A...577A..47B}, we tested the technique on open cluster stars using iSpec tep{2014A&A...569A.111B}, we demonstrated their chemical homogeneity but we found that the 14 studied elements lead to chemical signatures too similar to reliably distinguish stars from different clusters. This represents a challenge to the technique and a new question was open: Could the inclusion of other elements help to better distinguish stars from different aggregates? With an updated and improved version of iSpec, we derived abundances for 28 elements using spectra from HARPS, UVES and NARVAL archives for the open clusters M67 and IC4651, and we found that the chemical signatures of both clusters are very similar.

  6. A revised moving cluster distance to the Pleiades open cluster

    NASA Astrophysics Data System (ADS)

    Galli, P. A. B.; Moraux, E.; Bouy, H.; Bouvier, J.; Olivares, J.; Teixeira, R.

    2017-01-01

    Context. The distance to the Pleiades open cluster has been extensively debated in the literature over several decades. Although different methods point to a discrepancy in the trigonometric parallaxes produced by the Hipparcos mission, the number of individual stars with known distances is still small compared to the number of cluster members to help solve this problem. Aims: We provide a new distance estimate for the Pleiades based on the moving cluster method, which will be useful to further discuss the so-called Pleiades distance controversy and compare it with the very precise parallaxes from the Gaia space mission. Methods: We apply a refurbished implementation of the convergent point search method to an updated census of Pleiades stars to calculate the convergent point position of the cluster from stellar proper motions. Then, we derive individual parallaxes for 64 cluster members using radial velocities compiled from the literature, and approximate parallaxes for another 1146 stars based on the spatial velocity of the cluster. This represents the largest sample of Pleiades stars with individual distances to date. Results: The parallaxes derived in this work are in good agreement with previous results obtained in different studies (excluding Hipparcos) for individual stars in the cluster. We report a mean parallax of 7.44 ± 0.08 mas and distance of pc that is consistent with the weighted mean of 135.0 ± 0.6 pc obtained from the non-Hipparcos results in the literature. Conclusions: Our result for the distance to the Pleiades open cluster is not consistent with the Hipparcos catalog, but favors the recent and more precise distance determination of 136.2 ± 1.2 pc obtained from Very Long Baseline Interferometry observations. It is also in good agreement with the mean distance of 133 ± 5 pc obtained from the first trigonometric parallaxes delivered by the Gaia satellite for the brightest cluster members in common with our sample. Full Table B.2 is only

  7. VizieR Online Data Catalog: Radial velocities in M67. I. 1278 candidate members (Geller+, 2015)

    NASA Astrophysics Data System (ADS)

    Geller, A. M.; Latham, D. W.; Mathieu, R. D.

    2015-10-01

    This is the first in a series of papers studying the dynamical state of the old open cluster M67 through precise radial velocities. This is also the paper LXVII of the WIYN Open Cluster Study. Our radial velocity survey of M67 began as part of the dissertation work of Mathieu (1983PhDT.........8M), taking advantage of the CfA Digital Speedometers (DS). Three nearly identical instruments were used, initially on the MMT (from HJD2445337 to HJD2450830) and 1.5m Tillinghast Reflector (from HJD2444184 to HJD2454958) at the Fred Lawrence Whipple Observatory on Mount Hopins, Arizona, and then later on the 1.5m Wyeth Reflector (from HJD2445722 to HJD2453433) at the Oak Ridge Observatory in the Town of Harvard, Massachusetts. Subsequently the M67 target samples were expanded several times. Radial velocities measurements from other programs were integrated into the database, and our observational facilities were extended to include Hydra Multi-Object Spectrograph (MOS) at the WIYN Observatory (from HJD2453386 to HJD2456709) and the new Tillinghast Reflector Echelle Spectrograph (TRES) on the Tillinghast Reflector (from HJD2455143 to HJD2456801). Details about the telescopes, observing procedures, and data reductions of spectra obtained with the CfA DS can be found in Latham (1985srv..conf...21L, 1992ASPC...32..110L). The corresponding information for spectra obtained with Hydra at the WIYN Observatory can be found in Geller et al. 2008 (cat. J/AJ/135/2264), Geller et al. 2010 (cat. J/AJ/139/1383) and Hole et al. (2009). TRES is a stabilized fiber-fed echelle spectrograph with a CCD detector and resolution of 44000. The initial CfA sample was defined in 1982. The last surviving CfA Digital Speedometer, on the 1.5m Tillinghast Reflector, was retired in the summer of 2009. Over the following five observing seasons, TRES was used to continue the radial velocity observations of targets (mostly binaries) from both the CfA and the WIYN samples. Importantly, Roger Griffin and James

  8. Prospecting for Chemical Tags among Open Clusters

    NASA Astrophysics Data System (ADS)

    Lambert, David L.; Reddy, Arumalla B. S.

    2016-11-01

    Determination of the chemical composition of red giants in a large sample of open clusters (OCs) shows that the abundances of the heavy elements La, Ce, Nd, and Sm, but not so obviously Y and Eu, vary from one cluster to another across a sample in which all the clusters have nearly solar metallicity. For La, Ce, Nd, and Sm the amplitudes of the variations at solar metallicity scale approximately with the main s-process contribution to solar system material. Consideration of published abundances of field stars suggests that such a spread in heavy-element abundances is present for the thin and thick disk stars of different metallicities. This new result provides an opportunity to chemically tag stars by their heavy elements and to reconstruct dissolved OCs from the field-star population.

  9. NGC 7789: An open cluster case study

    SciTech Connect

    Overbeek, Jamie C.; Friel, Eileen D.; Pilachowski, Catherine A.; Mészáros, Szabolcs; Jacobson, Heather R.; Johnson, Christian I.

    2015-01-01

    We have obtained high-resolution spectra of 32 giants in the open cluster NGC 7789 using the Wisconsin–Indiana–Yale–NOAO Hydra spectrograph. We explore differences in atmospheric parameters and elemental abundances caused by the use of the linelist developed for the Gaia-ESO Survey (GES) compared to one based on Arcturus used in our previous work. [Fe/H] values decrease when using the GES linelist instead of the Arcturus-based linelist; these differences are probably driven by systematically lower (∼−0.1 dex) GES surface gravities. Using the GES linelist we determine abundances for 10 elements—Fe, Mg, Si, Ca, Ti, Na, Ni, Zr, Ba, and La. We find the cluster's average metallicity [Fe/H] = 0.03 ± 0.07 dex, in good agreement with literature values, and a lower [Mg/Fe] abundance than has been reported before for this cluster (0.11 ± 0.05 dex). We also find the neutron-capture element barium to be highly enhanced—[Ba/Fe] = +0.48 ± 0.08—and disparate from cluster measurements of neutron-capture elements La and Zr (−0.08 ± 0.05 and 0.08 ± 0.08, respectively). This is in accordance with recent discoveries of supersolar Ba enhancement in young clusters along with more modest enhancement of other neutron-capture elements formed in similar environments.

  10. NGC 7789: an Open Cluster Case Study

    NASA Astrophysics Data System (ADS)

    Overbeek, Jamie C.; Friel, Eileen D.; Jacobson, Heather R.; Johnson, Christian I.; Pilachowski, Catherine A.; Mészáros, Szabolcs

    2015-01-01

    We have obtained high-resolution spectra of 32 giants in the open cluster NGC 7789 using the Wisconsin-Indiana-Yale-NOAO Hydra spectrograph. We explore differences in atmospheric parameters and elemental abundances caused by the use of the linelist developed for the Gaia-ESO Survey (GES) compared to one based on Arcturus used in our previous work. [Fe/H] values decrease when using the GES linelist instead of the Arcturus-based linelist; these differences are probably driven by systematically lower (˜-0.1 dex) GES surface gravities. Using the GES linelist we determine abundances for 10 elements—Fe, Mg, Si, Ca, Ti, Na, Ni, Zr, Ba, and La. We find the cluster's average metallicity [Fe/H] = 0.03 ± 0.07 dex, in good agreement with literature values, and a lower [Mg/Fe] abundance than has been reported before for this cluster (0.11 ± 0.05 dex). We also find the neutron-capture element barium to be highly enhanced—[Ba/Fe] = +0.48 ± 0.08—and disparate from cluster measurements of neutron-capture elements La and Zr (-0.08 ± 0.05 and 0.08 ± 0.08, respectively). This is in accordance with recent discoveries of supersolar Ba enhancement in young clusters along with more modest enhancement of other neutron-capture elements formed in similar environments.

  11. A Constraint on Zsolar from Fits of Isochrones to the Color-Magnitude Diagram of M67

    NASA Astrophysics Data System (ADS)

    VandenBerg, Don A.; Gustafsson, Bengt; Edvardsson, Bengt; Eriksson, Kjell; Ferguson, Jason

    2007-09-01

    The mass at which a transition is made between stars that have radiative or convective cores throughout the core H burning phase is a fairly sensitive function of Z (particularly, the CNO abundances). As a consequence, the ~4 Gyr, open cluster M67 provides a constraint on Zsolar (and the solar heavy-element mixture) because (1) high-resolution spectroscopy indicates that this system has virtually the same metal abundances as the Sun, and (2) its turnoff stars have masses just above the lower limit for sustained core convection on the main sequence. In this study, evolutionary tracks and isochrones using the latest MARCS model atmospheres as boundary conditions have been computed for 0.6-1.4 Msolar on the assumption of a metals mix (implying Zsolar~0.0125) based on the solar abundances derived by M. Asplund and collaborators using 3D model atmospheres. These calculations do not predict a turnoff gap where one is observed in M67. No such difficulty is found if the analysis uses isochrones for Zsolar=0.0165, assuming the Grevesse and Sauval mix of heavy elements. Our findings, like the inferences from helioseismology, indicate a problem with the abundances of Asplund and collaborators. However, it is possible that low-Z models with diffusive processes taken into account will be less problematic.

  12. On the oxygen abundances of M 67 stars from the turn-off point through the red giant branch†

    NASA Astrophysics Data System (ADS)

    Takeda, Yoichi; Honda, Satoshi

    2015-04-01

    With an aim to examine whether the surface oxygen composition suffers any appreciable change due to evolution-induced mixing of nuclear-processed material in the envelope of red giants, abundance determinations for O/Fe/Ni based on the synthetic spectrum-fitting method were performed by using the moderate-dispersion spectra in the 7770-7792 Å region (comprising O I 7771-5, Fe I 7780, and Ni I 7788 lines) for 16 stars of the old open cluster M 67 in various evolutionary stages from the turn-off point through the red giant branch. We could not find any meaningful difference in the oxygen abundances between the non-giant group (Teff > 5000 K) and the red-giant group (Teff < 5000 K), which are almost consistent with each other on average (despite that both have rather large dispersions of a few tenths dex caused by insufficient data quality), though only one giant star (S 1054) appears to show an exceptionally low O abundance and thus needs a more detailed study. This result may suggest that oxygen content in the stellar envelope is hardly affected (or any changes are insignificant) by the mixing of H-burning products in the red giant phase, as far as M 67 stars of low mass (˜ 1.3 M⊙) are concerned, which is consistent with the prediction from the conventional stellar evolution theory of first dredge-up.

  13. The Hyades open cluster is chemically inhomogeneous

    NASA Astrophysics Data System (ADS)

    Liu, F.; Yong, D.; Asplund, M.; Ramírez, I.; Meléndez, J.

    2016-04-01

    We present a high-precision differential abundance analysis of 16 solar-type stars in the Hyades open cluster based on high-resolution, high signal-to-noise ratio (S/N ≈ 350-400) spectra obtained from the McDonald 2.7-m telescope. We derived stellar parameters and differential chemical abundances for 19 elements (C, O, Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn and Ba) with uncertainties as low as ˜0.01-0.02 dex. Our main results include: (1) there is no clear chemical signature of planet formation detected among the sample stars, i.e. no correlations in abundances versus condensation temperature; (2) the observed abundance dispersions are a factor of ≈1.5-2 larger than the average measurement errors for most elements; (3) there are positive correlations, of high statistical significance, between the abundances of at least 90 per cent of pairs of elements. We demonstrate that none of these findings can be explained by errors due to the stellar parameters. Our results reveal that the Hyades is chemically inhomogeneous at the 0.02 dex level. Possible explanations for the abundance variations include (1) inhomogeneous chemical evolution in the proto-cluster environment, (2) supernova ejection in the proto-cluster cloud and (3) pollution of metal-poor gas before complete mixing of the proto-cluster cloud. Our results provide significant new constraints on the chemical composition of open clusters and a challenge to the current view of Galactic archaeology.

  14. Catalog of open clusters and associated interstellar matter

    NASA Technical Reports Server (NTRS)

    Leisawitz, David

    1988-01-01

    The Catalog of Open Clusters and Associated Interstellar Matter summarizes observations of 128 open clusters and their associated ionized, atomic, and molecular iinterstellar matter. Cluster sizes, distances, radial velocities, ages, and masses, and the radial velocities and masses of associated interstellar medium components, are given. The database contains information from approximately 400 references published in the scientific literature before 1988.

  15. WIYN Open Cluster Study: UBVRI Photometry of NGC 2158

    NASA Astrophysics Data System (ADS)

    Taverne, Luke T.; Steinhauer, Aaron J.; Deliyannis, Constantine P.

    2015-01-01

    We present WIYN 0.9m HDI UBVRI photometry of NGC 2158, a very rich, intermediate-aged, open cluster located near the galactic anti-center. We report derived values for the cluster age, distance, reddening.

  16. First CCD UBVI photometric analysis of six open cluster candidates

    NASA Astrophysics Data System (ADS)

    Piatti, A. E.; Clariá, J. J.; Ahumada, A. V.

    2011-04-01

    We have obtained CCD UBVIKC photometry down to V ˜ 22 for the open cluster candidates Haffner 3, Haffner 5, NGC 2368, Haffner 25, Hogg 3 and Hogg 4 and their surrounding fields. None of these objects have been photometrically studied so far. Our analysis shows that these stellar groups are not genuine open clusters since no clear main sequences or other meaningful features can be seen in their colour-magnitude and colour-colour diagrams. We checked for possible differential reddening across the studied fields that could be hiding the characteristics of real open clusters. However, the dust in the directions to these objects appears to be uniformly distributed. Moreover, star counts carried out within and outside the open cluster candidate fields do not support the hypothesis that these objects are real open clusters or even open cluster remnants.

  17. Searching for the birthplaces of open clusters with ages of several billion years

    NASA Astrophysics Data System (ADS)

    Acharova, I. A.; Shevtsova, E. S.

    2016-01-01

    We discuss the possibility of finding the birthplaces of open clusters (OC) with ages of several billion years. The proposed method is based on the comparison of the results of the chemical evolution modeling of the Galactic disk with the parameters of the cluster. Five OCs older than 7 Gyr are known: NGC6791, BH176, Collinder 261, Berkeley 17, and Berkeley 39. The oxygen and iron abundances in NGC6791 and the oxygen abundance in BH176 are twice the solar level, the heavy-element abundances in other clusters are close to the corresponding solar values. According to chemical evolution models, at the time of the formation of the objects considered the regions where the oxygen and iron abundances reached the corresponding levels extended out to 5 kpc from the Galactic center.At present time theOCs considered are located several kpc from the Galactic center. Some of these clusters are located extremely high, about 1 kpc above the disk midplane, i.e., they have been subject to some mechanism that has carried them into orbits uncharacteristic of this type of objects. It follows from a comparison with the results of chemical evolution that younger clusters with ages of 4-5 Gyr, e.g., NGC1193,M67, and others, may have formed in a broad range of Galactocentric distances. Their large heights above the disk midplane is sufficient to suggest that these clusters have moved away from their likely birthplaces. Clusters are carried far away from the Galactic disk until the present time: about 40 clusters with ages from 0 to 2 Gyr are observed at heights ranging from 300 to 750 pc.

  18. Detailed studies om three open clusters from Gaia ESO Survey (GES)

    NASA Astrophysics Data System (ADS)

    Balaguer-Núnez, L.; Casamiquela, L.; Jordana, N.; Massana, P.; Jordi, C.; Masana, E.

    2017-03-01

    We present results for the intermediate-age and old open clusters NGC 6633, NGC 6705 (M 11) and NGC 2682 (M 67). We have used new Str ̈omgren-Crawford photometry, proper motions from ROA observations and spectral information from Gaia-ESO Survey (GES), to study the physical parameters of the stars in the three cluster's areas. The astrometric studies cover an area of about 1°x2° and down to r' ˜ 17 while our INT-WFC CCD intermediate-band photometry covers an area of about 40'x40' down to V ˜ 19. The stars of those areas selected as cluster members from their proper motions, are classified into photometric regions and their physical parameters determined, using uvbyHβ photometry and standard relations among colour indices for each of the photometric regions of the HR diagram. That allows us to determine reddening, distances, absolute magnitudes, spectral types, effective temperatures, gravities and metallicities, thus providing an astrophysical characterization of the clusters. These results are compared with the physical parameters obtained from GES spectral data as well as radial velocities to confirm membership. All these data lead us to a comparison of photometric and spectroscopic physical parameters.

  19. Surface Abundance and Binary Properties of Alternative-Evolution Stars in Open Clusters

    NASA Astrophysics Data System (ADS)

    Milliman, Katelyn Elise

    There is a large population of stars not described by single-star stellar evolution narratives. These non-standard stars are broadly known as blue stragglers (BS), yellow giants, and subsubgiants (SSG). In this thesis I present my work on the non-standard stellar populations in open clusters focussing on the role of binaries and the information learned from surface abundance measurements, particularly for BS formation. Formation theories for BSs include mergers in hierarchical triple systems, collisions during dynamical encounters, and mass transfer from an evolved companion. Such mass transfer events can pollute the surface abundance of the BS with the nucleosynthesis products from the evolved donor. Specifically, asymptotic giant branch (AGB) mass transfer should enhance the surface abundances of s-process elements, like barium, created during the thermally-pulsing phase of AGB evolution. The products of mergers and collisions would have no such enhancements. This makes barium an excellent marker for a mass-transfer formation history with an AGB-donor. In this thesis I start with the radial velocity (RV) surveys of the open clusters NGC 6819 and NGC 7789. I then introduce my discovery of five barium enriched BSs in NGC 6819, four of which have no RV evidence of a companion. Next, I triple the number of confirmed open cluster SSGs through my discovery of four such systems in NGC 6791 and present robust orbital solutions for three of them. And finally I discuss the implications of my work in context with the extensively studied open clusters M67 and NGC 188.

  20. Absolute Spectrophotometry of 237 Open Cluster Stars

    NASA Astrophysics Data System (ADS)

    Clampitt, L.; Burstein, D.

    1994-12-01

    We present absolute spectrophotometry of 237 stars in 7 nearby open clusters: Hyades, Pleiades, Alpha Persei, Praesepe, Coma Berenices, IC 4665, and M 39. The observations were taken using the Wampler single-channel scanner (Wampler 1966) on the Crossley 0.9m telescope at Lick Observatory from July 1973 through December 1974. 21 bandpasses spanning the spectral range 3500 Angstroms to 7780 Angstroms were observed for each star, with bandwiths ranging from 32Angstroms to 64 Angstroms. Data are standardized to the Hayes--Latham (1975) system. Our measurements are compared to filter colors on the Johnson BV, Stromgren ubvy, and Geneva U V B_1 B_2 V_1 G systems, as well as to spectrophotometry of a few stars published by Gunn, Stryker & Tinsley and in the Spectrophotometric Standards Catalog (Adelman; as distributed by the NSSDC). Both internal and external comparisons to the filter systems indicate a formal statistical accuracy per bandpass of 0.01 to 0.02 mag, with apparent larger ( ~ 0.03 mag) differences in absolute calibration between this data set and existing spectrophotometry. These data will comprise part of the spectrophotometry that will be used to calibrate the Beijing-Arizona-Taipei-Connecticut Color Survey of the Sky (see separate paper by Burstein et al. at this meeting).

  1. A new open cluster binary system in the Milky Way

    NASA Astrophysics Data System (ADS)

    Piatti, A. E.; Clariá, J. J.; Ahumada, A. V.

    2011-10-01

    We have obtained CCD UBVI_{KC} photometry for the open clusters (OCs) Hogg 12 and NGC 3590. Based on photometric and morphological criteria, as well as on the stellar density in the region, our evidence is sufficient to consider them a new open cluster binary system candidate.

  2. On the metallicity of open clusters. III. Homogenised sample

    NASA Astrophysics Data System (ADS)

    Netopil, M.; Paunzen, E.; Heiter, U.; Soubiran, C.

    2016-01-01

    Context. Open clusters are known as excellent tools for various topics in Galactic research. For example, they allow accurately tracing the chemical structure of the Galactic disc. However, the metallicity is known only for a rather low percentage of the open cluster population, and these values are based on a variety of methods and data. Therefore, a large and homogeneous sample is highly desirable. Aims: In the third part of our series we compile a large sample of homogenised open cluster metallicities using a wide variety of different sources. These data and a sample of Cepheids are used to investigate the radial metallicity gradient, age effects, and to test current models. Methods: We used photometric and spectroscopic data to derive cluster metallicities. The different sources were checked and tested for possible offsets and correlations. Results: In total, metallicities for 172 open cluster were derived. We used the spectroscopic data of 100 objects for a study of the radial metallicity distribution and the age-metallicity relation. We found a possible increase of metallicity with age, which, if confirmed, would provide observational evidence for radial migration. Although a statistical significance is given, more studies are certainly needed to exclude selection effects, for example. The comparison of open clusters and Cepheids with recent Galactic models agrees well in general. However, the models do not reproduce the flat gradient of the open clusters in the outer disc. Thus, the effect of radial migration is either underestimated in the models, or an additional mechanism is at work. Conclusions: Apart from the Cepheids, open clusters are the best tracers for metallicity over large Galactocentric distances in the Milky Way. For a sound statistical analysis, a sufficiently large and homogeneous sample of cluster metallicities is needed. Our compilation is currently by far the largest and provides the basis for several basic studies such as the statistical

  3. Stellar Nucleosynthesis in the Hyades Open Cluster

    NASA Astrophysics Data System (ADS)

    Schuler, Simon C.; King, Jeremy R.; The, Lih-Sin

    2009-08-01

    We report a comprehensive light-element (Li, C, N, O, Na, Mg, and Al) abundance analysis of three solar-type main sequence (MS) dwarfs and three red giant branch (RGB) clump stars in the Hyades open cluster using high-resolution and high signal-to-noise spectroscopy. The abundances have been derived in a self-consistent fashion, and for each group (MS or RGB), the CNO abundances are found to be in excellent star-to-star agreement. Using the dwarfs to infer the initial composition of the giants, the combined abundance patterns confirm that the giants have undergone the first dredge-up and that material processed by the CN cycle has been mixed to the surface layers. The observed abundances are compared to predictions of a standard stellar model based on the Clemson-American University of Beirut (CAUB) stellar evolution code. The model reproduces the observed evolution of the N and O abundances, as well as the previously derived 12C/13C ratio, but it fails to predict by a factor of 1.5 the observed level of 12C depletion. A similar discord appears to exist in previously reported observed and modeled C abundances of giants in the Galactic disk. Random uncertainties in the mean abundances and uncertainties related to possible systematic errors in the Hyades dwarf and giant parameter scales cannot account for the discrepancy in the observed and modeled abundances. Li abundances are derived to determine if noncanonical extra mixing, like that seen in low-mass metal-poor giants, has occurred in the Hyades giants. The Li abundance of the giant γ Tau is in good accord with the predicted level of surface Li dilution, but a ~0.35 dex spread in the giant Li abundances is found and cannot be explained by the stellar model. Possible sources of the spread are discussed; however, it is apparent that the differential mechanism responsible for the Li dispersion must be unrelated to the uniformly low 12C abundances of the giants. Na, Mg, and Al abundances are derived as an additional

  4. STELLAR NUCLEOSYNTHESIS IN THE HYADES OPEN CLUSTER

    SciTech Connect

    Schuler, Simon C.; King, Jeremy R.; The, L.-S. E-mail: jking2@ces.clemson.edu

    2009-08-10

    We report a comprehensive light-element (Li, C, N, O, Na, Mg, and Al) abundance analysis of three solar-type main sequence (MS) dwarfs and three red giant branch (RGB) clump stars in the Hyades open cluster using high-resolution and high signal-to-noise spectroscopy. The abundances have been derived in a self-consistent fashion, and for each group (MS or RGB), the CNO abundances are found to be in excellent star-to-star agreement. Using the dwarfs to infer the initial composition of the giants, the combined abundance patterns confirm that the giants have undergone the first dredge-up and that material processed by the CN cycle has been mixed to the surface layers. The observed abundances are compared to predictions of a standard stellar model based on the Clemson-American University of Beirut (CAUB) stellar evolution code. The model reproduces the observed evolution of the N and O abundances, as well as the previously derived {sup 12}C/{sup 13}C ratio, but it fails to predict by a factor of 1.5 the observed level of {sup 12}C depletion. A similar discord appears to exist in previously reported observed and modeled C abundances of giants in the Galactic disk. Random uncertainties in the mean abundances and uncertainties related to possible systematic errors in the Hyades dwarf and giant parameter scales cannot account for the discrepancy in the observed and modeled abundances. Li abundances are derived to determine if noncanonical extra mixing, like that seen in low-mass metal-poor giants, has occurred in the Hyades giants. The Li abundance of the giant {gamma} Tau is in good accord with the predicted level of surface Li dilution, but a {approx}0.35 dex spread in the giant Li abundances is found and cannot be explained by the stellar model. Possible sources of the spread are discussed; however, it is apparent that the differential mechanism responsible for the Li dispersion must be unrelated to the uniformly low {sup 12}C abundances of the giants. Na, Mg, and Al

  5. Open clusters rich in red supergiants

    NASA Astrophysics Data System (ADS)

    Negueruela, Ignacio

    2015-08-01

    In the past few years, several clusters containing large numbers of red supergiants have been discovered. These clusters are amongst the most massive young clusters known in the Milky Way, with stellar masses reaching a few tens of thousands of solar masses. They have provided us, for the first time, with large homogeneous samples of red supergiants of a given age. These large populations make them, despite heavy extinction along their sightlines, powerful laboratories to understand the evolutionary status of red supergiants. While some of the clusters, such as the eponymous RSGC1, are so obscured that their members are only observable in the near-IR, at least van der Bergh-Hagen 222 is observable even in the U band, allowing for an excellent characterisation of cluster and stellar properties. The information gleaned so far from these clusters gives strong support to the idea that late-M type supergiants represent a separate class, characterised by very heavy mass loss. It also shows that the spectral-type distribution of red supergiants in the Milky Way is very strongly peaked towards M1, while providing strong hints about the possible evolutionary sequence of red supergiants. In addition, the clusters of red supergiants represent ideal tools to study metallicity in the inner regions of the Milky Way.

  6. New variable stars in open clusters. I. Methods and results for 20 open clusters

    NASA Astrophysics Data System (ADS)

    Paunzen, E.; Zwintz, K.; Maitzen, H. M.; Pintado, O. I.; Rode-Paunzen, M.

    2004-04-01

    We present high precision CCD photometry of 1791 objects in 20 open clusters with an age of 10 Myr to 1 Gyr. These observations were performed within the Δ a photometric system which is primarily used to detect chemically peculiar stars of the upper main sequence. Time bases range from 30 min up to 60 days with data from several nights. We describe the time series analysis reaching a detection limit of down to 0.006 mag for apparent variability. In total, we have detected 35 variable objects of which four are not members of their corresponding clusters. The variables cover the entire Hertzsprung-Russell diagram, hence they are interesting targets for follow-up observations. Based on observations obtained at Complejo Astronómico el Leoncito (CASLEO), operated under the agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba y San Juan; ESO-La Silla and UTSO-Las Campanas.

  7. Spin alignment of stars in old open clusters

    NASA Astrophysics Data System (ADS)

    Corsaro, Enrico; Lee, Yueh-Ning; García, Rafael A.; Hennebelle, Patrick; Mathur, Savita; Beck, Paul G.; Mathis, Stephane; Stello, Dennis; Bouvier, Jérôme

    2017-03-01

    Stellar clusters form by gravitational collapse of turbulent molecular clouds, with up to several thousand stars per cluster1. They are thought to be the birthplace of most stars and therefore play an important role in our understanding of star formation, a fundamental problem in astrophysics2,3. The initial conditions of the molecular cloud establish its dynamical history until the stellar cluster is born. However, the evolution of the cloud's angular momentum during cluster formation is not well understood4. Current observations have suggested that turbulence scrambles the angular momentum of the cluster-forming cloud, preventing spin alignment among stars within a cluster5. Here we use asteroseismology6-8 to measure the inclination angles of spin axes in 48 stars from the two old open clusters NGC 6791 and NGC 6819. The stars within each cluster show strong alignment. Three-dimensional hydrodynamical simulations of proto-cluster formation show that at least 50% of the initial proto-cluster kinetic energy has to be rotational in order to obtain strong stellar-spin alignment within a cluster. Our result indicates that the global angular momentum of the cluster-forming clouds was efficiently transferred to each star and that its imprint has survived several gigayears since the clusters formed.

  8. Value, Cost, and Sharing: Open Issues in Constrained Clustering

    NASA Technical Reports Server (NTRS)

    Wagstaff, Kiri L.

    2006-01-01

    Clustering is an important tool for data mining, since it can identify major patterns or trends without any supervision (labeled data). Over the past five years, semi-supervised (constrained) clustering methods have become very popular. These methods began with incorporating pairwise constraints and have developed into more general methods that can learn appropriate distance metrics. However, several important open questions have arisen about which constraints are most useful, how they can be actively acquired, and when and how they should be propagated to neighboring points. This position paper describes these open questions and suggests future directions for constrained clustering research.

  9. On the physical reality of overlooked open clusters

    NASA Astrophysics Data System (ADS)

    Piatti, Andrés E.

    2017-01-01

    We present UBVRI and CT1T2 photometry for fifteen catalogued open clusters of relative high brightness and compact appearance. From these unprecedented photometric data sets, covering wavelengths from the blue up to the near-infrared, we performed a thorough assessment of their reality as stellar aggregates. We statistically assigned to each observed star within the object region a probability of being a fiducial feature of that field in terms of its local luminosity function, colour distribution and stellar density. Likewise, we used accurate parallaxes and proper motions measured by the Gaia satellite to help our decision on the open cluster reality. Ten catalogued aggregates did not show any hint of being real physical systems; three of them had been assumed to be open clusters in previous studies, though. On the other hand, we estimated reliable fundamental parameters for the remaining five studied objects, which were confirmed as real open clusters. They resulted to be clusters distributed in a wide age range, 8.0 ≤ log (t yr-1) ≤ 9.4, of solar metal content and placed between 2.0 and 5.5 kpc from the Sun. Their ages and metallicities are in agreement with the presently known picture of the spatial distribution of open clusters in the Galactic disc.

  10. Membership determination of open cluster with parametric method: cross entropy

    NASA Astrophysics Data System (ADS)

    Khoirul Fitriana, Itsna; Ikbal Arifiyanto, M.

    2016-11-01

    Stellar open clusters are useful for studying the structure and evolution of Galaxy. Determination of the open cluster members can be viewed from their kinematics: proper motion and radial velocity. It is because the star cluster members will have a motion in the same direction, towards a convergent point. Parametric method with a double elliptic bivariate gaussian function which contains 11 parameters is used as a model of the proper motion distribution. The value of these parameters are determined numerically by cross entropy method. This method is a method of data fitting using the likelihood function whose value is maximized to get the proper parameters. This method solves the problem of determining the initial value that is often difficult to determine in other numerical methods. There are four open clusters which we have analysed: NGC 2244, ASCC 100, NGC 5168, and NGC 2169. The resulting of proper motion parameters of this method matches the parameters in the literature.

  11. Near-infrared Photometry of the Open Cluster NGC 2420

    NASA Astrophysics Data System (ADS)

    Hejazi, Neda; De Robertis, Michael M.; Dawson, Peter C.

    2016-01-01

    Open clusters have been used in numerous studies of stellar formation and evolution and have provided important constraints on theoretical stellar models. In this study, we carried out deep near-infrared imaging (I, J, H and Ks bands) with the 1024×1024 CFHT-IR camera at the Cassegrain focus of the Canada-France-Hawaii 3.6 m telescope of two fields in the relatively old open cluster, NGC 2420. This cluster was selected due to its relatively low metallicity, [Fe/H] ˜ -0.5, and rather high Galactic latitude (for an open cluster), b ≈ 20°, reducing the effects of reddening as well as reducing the extent of contamination by non-members of the cluster. The empirical data were calibrated using 2MASS and Stetson standards in the field. Non-cluster stars were removed using a field-cluster decontamination algorithm. By fitting available theoretical isochrones to the observed color-magnitude diagrams, we have been able to estimate the age, metallicity and distance of the cluster which are compared to previous studies.

  12. Highly dynamically evolved intermediate-age open clusters

    NASA Astrophysics Data System (ADS)

    Piatti, Andrés E.; Dias, Wilton S.; Sampedro, Laura M.

    2017-04-01

    We present a comprehensive UBVRI and Washington CT1T2 photometric analysis of seven catalogued open clusters, namely: Ruprecht 3, 9, 37, 74, 150, ESO 324-15 and 436-2. The multiband photometric data sets in combination with 2MASS photometry and Gaia astrometry for the brighter stars were used to estimate their structural parameters and fundamental astrophysical properties. We found that Ruprecht 3 and ESO 436-2 do not show self-consistent evidence of being physical systems. The remained studied objects are open clusters of intermediate age (9.0 ≤ log(t yr-1) ≤ 9.6), of relatively small size (rcls ∼ 0.4-1.3 pc) and placed between 0.6 and 2.9 kpc from the Sun. We analysed the relationships between core, half-mass, tidal and Jacoby radii as well as half-mass relaxation times to conclude that the studied clusters are in an evolved dynamical stage. The total cluster masses obtained by summing those of the observed cluster stars resulted to be ∼10-15 per cent of the masses of open clusters of similar age located closer than 2 kpc from the Sun. We found that cluster stars occupy volumes as large as those for tidally filled clusters.

  13. Deep Observations of the Open Cluster NGC 6253

    NASA Astrophysics Data System (ADS)

    Jeffery, E. J.

    2015-06-01

    We have obtained deep observations of the metal-rich open cluster NGC 6253 with GMOS on the Gemini-South telescope, with the goal of observing the cluster white dwarfs for the first time. These observations are an important piece and further test of the variously proposed scenarios to explain the formation of the strange white dwarfs in the metal rich open cluster NGC 6791. We will use the new observations of NGC 6253 to measure the cluster's white dwarf age and search for any anomalies in the white dwarf luminosity function. The high metallicity of this cluster will allow us to explore and better understand the formation of white dwarfs in such a high metallicity environment. These observations are an important piece in the continuing puzzle that has important implications on mass loss, white dwarf cooling, and stellar evolution as a whole.

  14. Map-based trigonometric parallaxes of open clusters: Coma

    NASA Technical Reports Server (NTRS)

    Gatewood, George

    1995-01-01

    This is the fourth study in a series to determine the direct trigonometric parallaxes of four of the nearest open star clusters, the Hyades, the Pleiades, the Praesepe, and the nearby cluster in Coma (Gatewood et al. 1990; Gatewood et al. 1992); Gatewood & Kiewiet de Jonge 1994). The results for the open star cluster in Coma are compared with those of the other three clusters, and the members are found to be significantly subluminous. The trigonometric parallax of the cluster is estimated from that of three members studied with the Multichannel Astrometric Photometer (MAP) at the Thaw Refractor of the University of Pittsburgh's Allegheny Observatory. The weighted mean parallax of the cluster is +13.53 +/- 0.54 mass (0.00054 min), corresponding to a distance modulus of 4.34 +/- 0.09 mag. The U-B excess of the Coma cluster members may be used to adjust the observed absolute magnitudes and the B-V measurements as suggested by Sandage & Eggen (1959). The agreement obtained in this manner suggests that, like subdwarf stars, the stars of the Coma cluster appear subluminous because of line blanketing. One of the three members observed in this study was recognized as a member by its parallax and is the faintest known member of the cluster.

  15. Integrated spectral properties of 7 galactic open clusters

    NASA Astrophysics Data System (ADS)

    Ahumada, A. V.; Clariá, J. J.; Bica, E.; Piatti, A. E.

    2000-01-01

    This paper presents flux-calibrated integrated spectra in the range 3600-9000 Ä for 7 concentrated, relatively populous Galactic open clusters. We perform simultaneous estimates of age and foreground interstellar reddening by comparing the continuum distribution and line strengths of the cluster spectra with those of template cluster spectra with known parameters. For five clusters these two parameters have been determined for the first time (Ruprecht 144, BH 132, Pismis 21, Lyng\\aa 11 and BH 217), while the results here derived for the remaining two clusters (Hogg 15 and Melotte 105) show very good agreement with previous studies based mainly on colour-magnitude diagrams. We also provide metallicity estimates for six clusters from the equivalent widths of CaII triplet and TiO features. The present cluster sample improves the age resolution around solar metal content in the cluster spectral library for population synthesis. We compare the properties of the present sample with those of clusters in similar directions. Hogg 15 and Pismis 21 are among the most reddened clusters in sectors centered at l = 270o and l = 0o, respectively. Besides, the present results would favour an important dissolution rate of star clusters in these zones. Based on observations made at Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba and San Juan, Argentina.

  16. Study of Intermediate Age (~10-30 Myr) Open Clusters

    NASA Astrophysics Data System (ADS)

    Olguin, Lorenzo; Michel, Raul; Contreras, Maria; Hernandez, Jesus; Schuster, William; Chavarria-Kleinhenn, Carlos

    2013-07-01

    We present the study of a sample of intermediate age open clusters (age ~ 10-30 Myr) using optical (UBVRI) and infrared photometric data. Optical photometry was obtained as part of the San Pedro Martir Open Clusters Project (SPM-OCP, Schuster et al. 2007; Michel et al. 2013). Infrared photometry was retrieved from 2MASS public data archive and WISE database. Open clusters included in the SPM-OCP were selected from catalogues presented by Dias et al. (2002) and Froebrich, Scholz & Raftery (2007). One of the main goals of the SPM-OCP is to compile a self-consistent and homogeneous set of cluster fundamental parameters such as reddening, distance, age, and metallicity whenever possible. In this work, we have analyzed a set of 25 clusters from the SPM-OCP with estimated ages between 10 and 30 Myr. Derived fundamental parameters for each cluster in the sample as well as an example of typical color-color and color-magnitude diagrams are presented. Kinematic membership was established by using proper motion data taken from the literature. Based on infrared photometry, we have searched for candidate stars to posses a circumstellar disk within each clusters. For those selected candidates a follow-up spectroscpic study is being carried out. This work was partially supported by UNAM-PAPIIT grant IN-109311.

  17. Search for variables in six Galactic open clusters

    NASA Astrophysics Data System (ADS)

    Paunzen, Ernst; Handler, Gerald; Lendl, Monika; Baumann, Bernhard; Rab, Christian; Meingast, Stefan; Rode-Paunzen, Monika; Netopil, Martin; Antoci, Victoria; Zhu, Liying; Zejda, Miloslav; Božić, Hrvoje

    2017-04-01

    Variables in open cluster (known distance, age, and metallicity) fields play an important role in stellar astrophysics because they allow to investigate the interior of stars. Therefore, six Galactic open clusters were selected to search for new variables and to complement data for already known variables. As five of these clusters are younger than 40 Myr, we aim at finding variable high-mass stars such as β Cephei and Slowly Pulsating B-type stars as well as classical pulsating stars within the instability strip. About 26 000 images (312 h) photometric images were taken at the 0.8 m (Vienna, Austria) and 1.0 m (Hvar, Croatia) telescope using V and I filters. The differential light curves were analyzed with standard time series analysis methods. In total, 11 variables were found in all investigated clusters. For nine of them, we were able to determine their nature and period. In addition, the membership probabilities from the literature were analyzed.

  18. Toward open-shell nuclei with coupled-cluster theory

    SciTech Connect

    Jansen, G. R.; Hjorth-Jensen, M.; Hagen, G.; Papenbrock, T.

    2011-05-15

    We develop a method based on equation-of-motion coupled-cluster theory to describe properties of open-shell nuclei with A{+-}2 nucleons outside a closed shell. We perform proof-of-principle calculations for the ground states of the helium isotopes {sup 3-6}He and the first excited 2{sup +} state in {sup 6}He. The comparison with exact results from matrix diagonalization in small model spaces demonstrates the accuracy of the coupled-cluster methods. Three-particle-one-hole excitations of {sup 4}He play an important role for the accurate description of {sup 6}He. For the open-shell nucleus {sup 6}He, the computational cost of the method is comparable with the coupled-cluster singles-and-doubles approximation while its accuracy is similar to the coupled-cluster with singles, doubles, and triples excitations.

  19. Stellar Multiplicity of the Open Cluster ASCC 113

    NASA Astrophysics Data System (ADS)

    Guerrero, C. A.; Orlov, V. G.

    2015-10-01

    We present a high angular resolution survey of binary stars and multiple systems in the galactic open cluster ASCC 113. Combining our speckle-interferometric observations with data taken from the literature, we estimated a ratio of 27:7 (single to binaries) for the the most probable members, so the multiplicity fraction for this cluster is 20.6% ± 3%. For field stars, we estimated a ratio of multiplicities to be 125:27:4:1:0:0:0:1 (between one and eight companions), which is equivalent to a multiplicity fraction of 20.9% ± 1%. We concluded that the multiplicity fraction in the cluster and in the field are statistically indistinguishable from each other; we also concluded that the multiplicity frequency in this open cluster is rather small, ˜ 20%, in agreement with high angular resolution surveys in the Pleiades, Hyades, alpha \\ Per and Praesepe.

  20. Open clusters and associations in the Gaia era

    NASA Astrophysics Data System (ADS)

    Moraux, E.

    2016-11-01

    Open clusters and associations are groups of young stars, respectively bound and unbound, that share the same origin and disperse over time into the galactic field. As such, their formation and evolution are the key to understand the origin and properties of galactic stellar populations. Moreover, since their members have about the same age, they are ideal laboratories to study the properties of young stars and constrain stellar evolution theories. In this contribution, I present our current knowledge on open clusters and associations. I focus on the methods used to derive the statistical properties (IMF, spatial distribution, IMF) of young stars and briefly discuss how they depend on the environment. I then describe how open clusters can be used as probes to investigate the structure, dynamics and chemical composition of the Milky Way. I conclude by presenting the Gaia mission and discuss how it will revolutionize this field of research.

  1. NGC 1252: a high altitude, metal poor open cluster remnant

    NASA Astrophysics Data System (ADS)

    de la Fuente Marcos, R.; de la Fuente Marcos, C.; Moni Bidin, C.; Carraro, G.; Costa, E.

    2013-09-01

    If stars form in clusters but most stars belong to the field, understanding the details of the transition from the former to the latter is imperative to explain the observational properties of the field. Aging open clusters are one of the sources of field stars. The disruption rate of open clusters slows down with age but, as an object gets older, the distinction between the remaining cluster or open cluster remnant (OCR) and the surrounding field becomes less and less obvious. As a result, finding good OCR candidates or confirming the OCR nature of some of the best candidates still remain elusive. One of these objects is NGC 1252, a scattered group of about 20 stars in Horologium. Here we use new wide-field photometry in the UBVI passbands, proper motions from the Yale/San Juan SPM 4.0 catalogue and high-resolution spectroscopy concurrently with results from N-body simulations to decipher NGC 1252's enigmatic character. Spectroscopy shows that most of the brightest stars in the studied area are chemically, kinematically and spatially unrelated to each other. However, after analysing proper motions, we find one relevant kinematic group. This sparse object is relatively close (˜1 kpc), metal poor and is probably not only one of the oldest clusters (3 Gyr) within 1.5 kpc from the Sun but also one of the clusters located farthest from the disc, at an altitude of nearly -900 pc. That makes NGC 1252 the first open cluster that can be truly considered a high Galactic altitude OCR: an unusual object that may hint at a star formation event induced on a high Galactic altitude gas cloud. We also conclude that the variable TW Horologii and the blue straggler candidate HD 20286 are unlikely to be part of NGC 1252. NGC 1252 17 is identified as an unrelated, Population II cannonball star moving at about 400 km s-1.

  2. Multicolor CCD Photometry of the Open Cluster IC361

    DTIC Science & Technology

    2010-01-01

    journal Volume 19 Numbers 1/2 2010 Contents V. Straizys, A. Kazlauskas. Young stars in the Camelopardalis dust and molecular clouds. VI. YSOs...Vilnius + I system for 7250 stars down to 1= 19.6 mag has been obtained in the 20’ x 26’ field of the open cluster IC 361 in Camelopardalis . The catalog...1= 19.6 mag has been obtained in the 20’ x 26’ field of the open cluster IC 361 in Camelopardalis . The catalog of 1420 stars down to V ~ 18.5 mag

  3. THE MEMBERSHIP AND DISTANCE OF THE OPEN CLUSTER COLLINDER 419

    SciTech Connect

    Roberts, Lewis C.; Gies, Douglas R.; Parks, J. Robert; Grundstrom, Erika D.; McSwain, M. Virginia; Berger, David H.; Mason, Brian D.; Ten Brummelaar, Theo A.; Turner, Nils H. E-mail: gies@chara.gsu.ed E-mail: erika.grundstrom@vanderbilt.ed E-mail: dberger@sysplan.co E-mail: theo@chara-array.or

    2010-09-15

    The young open cluster Collinder 419 surrounds the massive O star, HD 193322, that is itself a remarkable multiple star system containing at least four components. Here we present a discussion of the cluster distance based upon new spectral classifications of the brighter members, UBV photometry, and an analysis of astrometric and photometric data from the third U. S. Naval Observatory CCD Astrograph Catalog and Two Micron All Sky Survey Catalog. We determine an average cluster reddening of E(B - V) = 0.37 {+-} 0.05 mag and a cluster distance of 741 {+-} 36 pc. The cluster probably contains some very young stars that may include a reddened M3 III star, IRAS 20161+4035.

  4. The Membership and Distance of the Open Cluster Collinder 419

    NASA Technical Reports Server (NTRS)

    Roberts, Lewis C., Jr.; Gies, Douglas R.; Parks, J. Robert; Grundstrom, Erika D.; McSwain, M. Virginia; Berger, David H.; Mason, Brian D.; tenBrummelaar, Theo A.; Turner, Nils H.

    2010-01-01

    The young open cluster Collinder 419 surrounds the massive O star, HD 193322, that is itself a remarkable multiple star system containing at least four components. Here we present a discussion of the cluster distance based upon new spectral classifications of the brighter members, UBV photometry, and an analysis of astrometric and photometric data from the third U. S. Naval Observatory CCD Astrograph Catalog and Two Micron All Sky Survey Catalog. We determine an average cluster reddening of E(B - V) = 0.37 +/-.05 mag and a cluster distance of 741 plus or minus 36 pc. The cluster probably contains some very young stars that may include a reddened M3 III star, IRAS 20161+4035.

  5. A Multisite Cluster Randomized Field Trial of Open Court Reading

    ERIC Educational Resources Information Center

    Borman, Geoffrey D.; Dowling, N. Maritza; Schneck, Carrie

    2008-01-01

    In this article, the authors report achievement outcomes of a multisite cluster randomized field trial of Open Court Reading 2005 (OCR), a K-6 literacy curriculum published by SRA/McGraw-Hill. The participants are 49 first-grade through fifth-grade classrooms from predominantly minority and poor contexts across the nation. Blocking by grade level…

  6. First photometric analysis of six open cluster candidates

    NASA Astrophysics Data System (ADS)

    Piatti, A. E.; Clariá, J. J.; Ahumada, A. V.

    2011-10-01

    In this study we try to clarify the nature of six catalogued open cluster (OC) candidates using CCD UBVI_{KC} photometry down to V = 22. The objects are Haffner 3, Haffner 5, NGC 2368, Haffner 25, Hogg 3 and Hogg 4. None of them was found to be a real OC.

  7. Search for variables in the open cluster King 12

    NASA Astrophysics Data System (ADS)

    Paunzen, E.; Netopil, M.; Rode-Paunzen, M.; Bozic, H.

    2015-06-01

    We present the time series analysis of CCD photometry from the 1 m telescope at the Hvar Observatory (Croatia) for 54 stars in the area of the young open clusters King 12. We found no new variable but list upper detection limits.

  8. Morphology of open clusters NGC 1857 and Czernik 20 using clustering algorithms

    NASA Astrophysics Data System (ADS)

    Bhattacharya, S.; Mahulkar, V.; Pandaokar, S.; Singh, P. K.

    2017-01-01

    The morphology and cluster membership of the Galactic open clusters-Czernik 20 and NGC 1857 were analyzed using two different clustering algorithms. We present the maiden use of density-based spatial clustering of applications with noise (DBSCAN) to determine open cluster morphology from spatial distribution. The region of analysis has also been spatially classified using a statistical membership determination algorithm. We utilized near infrared (NIR) data for a suitably large region around the clusters from the United Kingdom Infrared Deep Sky Survey Galactic Plane Survey star catalogue database, and also from the Two Micron All Sky Survey star catalogue database. The densest regions of the cluster morphologies (1 for Czernik 20 and 2 for NGC 1857) thus identified were analyzed with a K-band extinction map and color-magnitude diagrams (CMDs). To address significant discrepancy in known distance and reddening parameters, we carried out field decontamination of these CMDs and subsequent isochrone fitting of the cleaned CMDs to obtain reliable distance and reddening parameters for the clusters (Czernik 20: D = 2900 pc; E(J- K) = 0 . 33; NGC 1857: D = 2400 pc; E(J- K) =0.18-0.19). The isochrones were also used to convert the luminosity functions for the densest regions of Czernik 20 and NGC 1857 into mass function, to derive their slopes. Additionally, a previously unknown over-density consistent with that of a star cluster is identified in the region of analysis.

  9. Old open clusters in the outer Galactic disk

    NASA Astrophysics Data System (ADS)

    Carraro, G.; Geisler, D.; Villanova, S.; Frinchaboy, P. M.; Majewski, S. R.

    2007-12-01

    Context: The outer parts of the Milky Way disk are believed to be one of the main arenas where the accretion of external material in the form of dwarf galaxies and subsequent formation of streams is taking place. The Monoceros stream and the Canis Major and Argo over-densities are notorious examples. Understanding whether what we detect is the signature of accretion or, more conservatively, simply the intrinsic nature of the disk, represents one of the major goals of modern Galactic astronomy. Aims: We try to shed more light on the properties of the outer disk by exploring the properties of distant anti-center old open clusters. We want to verify whether distant clusters follow the chemical and dynamical behavior of the solar vicinity disk, or whether their properties can be better explained in terms of an extra-galactic population. Methods: VLT high resolution spectra have been acquired for five distant open clusters: Ruprecht 4, Ruprecht 7, Berkeley 25, Berkeley 73 and Berkeley 75. We derive accurate radial velocities to distinguish field interlopers and cluster members. For the latter we perform a detailed abundance analysis and derive the iron abundance [Fe/H] and the abundance ratios of several α elements. Results: Our analysis confirms previous indications that the radial abundance gradient in the outer Galactic disk does not follow the expectations extrapolated from the solar vicinity, but exhibits a shallower slope. By combining the metallicity of the five program clusters with eight more clusters for which high resolution spectroscopy is available, we find that the mean metallicity in the outer disk between 12 and 21 kpc from the Galactic center is [Fe/H] ≈ -0.35, with only marginal indications for a radial variation. In addition, all the program clusters exhibit solar scaled or slightly enhanced α elements, similar to open clusters in the solar vicinity and thin disk stars. Conclusions: We investigate whether this outer disk cluster sample might

  10. The open cluster NGC 2818 and its associated planetary nebula

    SciTech Connect

    Pedreros, M. )

    1989-12-01

    New CCD UBV photometry of the open cluster NGC 2818 central region indicates that previously derived values of distance and reddening for the cluster have been considerably overestimated, leading to erroneous values for the physical parameters of its associated planetary nebula (PK 261 + 8.1 deg). The analysis of the new data yields E(B-V) = 0.18 + or - 0.03 and V(0)-M(v) = 11.80 + or - 0.2 (2.3 + or - 0.2 kpc) for the cluster's color excess and distance modulus, respectively. If cluster membership is assumed for the planetary nebula, the above estimates result in physical parameters that compare better with those of a typical planetary nebula in the Galaxy and the Magellanic Clouds. 26 refs.

  11. PROPERTIES OF THE OLD OPEN CLUSTER CZERNIK 30

    SciTech Connect

    Hayes, Christian R.; Friel, Eileen D.; Slack, Taleah J.; Boberg, Owen M. E-mail: efriel@indiana.edu

    2015-12-15

    We present new photometric and spectroscopic data of the old open cluster Czernik 30. Wide field BVI photometry allows us to correct for the high field contamination by statistical subtraction to produce a color–magnitude diagram (CMD) that clearly reveals the cluster sequence. From spectra of stars in the cluster field obtained with the Hydra spectrograph on the Wisconsin-Indiana-Yale-NOAO 3.5 m telescope we determine a mean cluster velocity of +79.9 ± 1.5 km s{sup −1} and provide membership information that helps further define the cluster giant branch and red clump. Stellar abundances for the brighter giants in the cluster indicate a mean metallicity of [Fe/H] = −0.2 ± 0.15. Fitting theoretical isochrones to the CMD we determine the following properties of Czernik 30: age = 2.8 ± 0.3 Gyr, (m − M){sub v} = 14.8 ± 0.1, E(B − V) = 0.24 ± 0.06, and E(V − I) = 0.36 ± 0.04. Czernik 30 is an old, sub-solar metallicity cluster located at a Galactocentric radius of R{sub gc}  ∼ 13.3 kpc. Given its age and position just beyond the transition to a flat abundance gradient seen in the open cluster population, Czernik 30 provides an interesting target for future observations.

  12. 2MASS analytical study of four open cluster candidates

    NASA Astrophysics Data System (ADS)

    Bisht, D.; Yadav, R. K. S.; Durgapal, A. K.

    2017-04-01

    The astrophysical parameters of four poorly studied open star clusters namely Teutsch 126, Teutsch 54, Teutsch 61 and Czernik 3, have been estimated using the Two Micron All Sky Survey (2MASS) database. The stellar density distributions and color-magnitude diagrams are used to determine their structural parameters (cluster center, cluster radius, core radius, tidal radius, Galactocenteric coordinates and the distance from the Galactic plane). We have also derived age, color excesses, total mass, relaxation time, luminosity and mass function for each clusters. The mass function slopes for these clusters are derived as 1.59 ± 0.62, 1.31 ± 0.60, 1.22 ± 0.75 and 1.62 ± 0.56 for Teutsch 126, Teutsch 54, Teutsch 61 and Czernik 3 respectively. These values are very close with the Salpeter value (x = 1.35) within the errors. The effect of mass-segregation are observed in the clusters Teutsch 126 and Teutsch 61. Estimated values of dynamical relaxation time are less than age of the clusters under study. This concludes that these objects are dynamically relaxed. The possible reason for relaxation may be due to the dynamical evolution or imprint of star formation or both.

  13. CCD UBV photometry of the open cluster NGC 6819

    NASA Astrophysics Data System (ADS)

    Ak, T.; Bostancı, Z. F.; Yontan, T.; Bilir, S.; Güver, T.; Ak, S.; Ürgüp, H.; Paunzen, E.

    2016-04-01

    We present the results of CCD UBV observations of the open cluster NGC 6819. We calculated the stellar density profile in the cluster's field to determine the structural parameters of NGC 6819. Using the existing astrometric data, we calculated the probabilities of the stars being physical members of the cluster, and used these objects in the determination of the astrophysical parameters of NGC 6819. We inferred the reddening and metallicity of the cluster as E(B-V)=0.130±0.035 mag and [Fe/H]=+0.051± 0.020 dex, respectively, using the U-B vs B-V two-colour diagram and UV excesses of the F-G type main-sequence stars. We fit the colour-magnitude diagrams of NGC 6819 with the PARSEC isochrones and derived the distance modula, distance and age of the cluster as μV=12.22± 0.10 mag, d=2309±106 pc and t=2.4±0.2 Gyr, respectively. The parameters of the galactic orbit estimated for NGC 6819 indicate that the cluster is orbiting in a slightly eccentric orbit of e=0.06 with a period of P_{orb}= 142 Myr. The slope of the mass function estimated for the cluster is close to the one found for the stars in the solar neighbourhood.

  14. Dynamics of the coronas of open star clusters

    NASA Astrophysics Data System (ADS)

    Danilov, V. M.; Putkov, S. I.; Seleznev, A. F.

    2014-12-01

    A method for distinguishing coronas in models of open star clusters is proposed. The method uses trajectories of stars that do not leave the coronas over time intervals t comparable to the mean lifetime τ of the clusters. Corona models are constructed for six numerical cluster models, and the direction and character of the dynamical evolution of the coronas are determined. Retrograde stellar motions are dominant in the coronas. In spite of some signs of dynamical instability of the coronas (small densities compared to the critical density and accelerated expansion of the coronas), the formation of close-toequilibrium density and phase-density distributions at distances from one to three cluster tidal radii from the cluster center can be seen. Approximations are constructed for the corona and cluster phase density using distributions that depend on three parameters (the parameters of the stellar motion in the Lindblad rotating coordinate system). This temporary equilibrium of the corona is due to balance in the number of starsmoving from the central areas of the cluster to the corona, and from the corona to the corona periphery or beyond. Evidence that corona stars can be gravitationally bound at distances out to four tidal radii from the cluster center is found: the presence of nearly periodic retrograde mean motions of a large number of corona stars in the Galactic plane; 91-99% of corona stars satisfy the gravitational binding criterion of Ross, Mennim and Heggie over time intervals that are close to the mean cluster lifetime. The escape rate from the corona is estimated for t ≥ τ, and found to be from 0.03 to 0.23 of the number of corona stars per violent relaxation time.

  15. A search for new open clusters hosting cepheids

    NASA Astrophysics Data System (ADS)

    Glushkova, E. V.; Zabolotskikh, M. V.; Rastorguev, A. S.; Grudskaya, A. V.; Koposov, S. E.

    We analyze yet-unknown genetic links between open star clusters (OSC) and galactic Cepheids and report the results of the new search for Cepheids -- probable OSC members. A sample of 25% of the stars from a new catalog by Berdnikov (published in Melnik et al. 2015) which lists 674 Cepheids with reliable parameters was investigated. Based on photometric and kinematic data, we selected 17 Cepheids that are likely to be related to star clusters, four of which being new OSCs discovered by us.

  16. Map-based trigonometric parallaxes of open clusters: The Praesepe

    NASA Technical Reports Server (NTRS)

    Gatewood, George; De Jonge, Joost Kiewiet

    1994-01-01

    Trigonometric parallaxes for stars in the Praesepe open star cluster are deduced from data collected with the Multichannel Astrometric Photometer (MAP) at the Thaw Refractor of the University of Pittsburgh's Allegheny Observatory. The weighted mean parallax of five cluster members is +5.21 +/- 0.79 mas (0.00079 arcsec), corresponding to a distance modulus of 6.42 +/- 0.33 mag. We briefly compare this result with that derived earlier for the Hyades and note agreement with the distance found by main-sequence fitting. We also discuss briefly an improvement in the weighting scheme of the centroiding algorithm used in this series.

  17. Tidal disruption of open clusters in their parent molecular clouds

    NASA Technical Reports Server (NTRS)

    Long, Kevin

    1989-01-01

    A simple model of tidal encounters has been applied to the problem of an open cluster in a clumpy molecular cloud. The parameters of the clumps are taken from the Blitz, Stark, and Long (1988) catalog of clumps in the Rosette molecular cloud. Encounters are modeled as impulsive, rectilinear collisions between Plummer spheres, but the tidal approximation is not invoked. Mass and binding energy changes during an encounter are computed by considering the velocity impulses given to individual stars in a random realization of a Plummer sphere. Mean rates of mass and binding energy loss are then computed by integrating over many encounters. Self-similar evolutionary calculations using these rates indicate that the disruption process is most sensitive to the cluster radius and relatively insensitive to cluster mass. The calculations indicate that clusters which are born in a cloud similar to the Rosette with a cluster radius greater than about 2.5 pc will not survive long enough to leave the cloud. The majority of clusters, however, have smaller radii and will survive the passage through their parent cloud.

  18. Open clusters in the Kepler field. II. NGC 6866

    SciTech Connect

    Janes, Kenneth; Hoq, Sadia; Barnes, Sydney A.; Meibom, Søren

    2014-06-01

    We have developed a maximum-likelihood procedure to fit theoretical isochrones to the observed cluster color-magnitude diagrams of NGC 6866, an open cluster in the Kepler spacecraft field of view. The Markov chain Monte Carlo algorithm permits exploration of the entire parameter space of a set of isochrones to find both the best solution and the statistical uncertainties. For clusters in the age range of NGC 6866 with few, if any, red giant members, a purely photometric determination of the cluster properties is not well-constrained. Nevertheless, based on our UBVRI photometry alone, we have derived the distance, reddening, age, and metallicity of the cluster and established estimates for the binary nature and membership probability of individual stars. We derive the following values for the cluster properties: (m – M) {sub V} = 10.98 ± 0.24, E(B – V) = 0.16 ± 0.04 (so the distance = 1250 pc), age =705 ± 170 Myr, and Z = 0.014 ± 0.005.

  19. A Photometric Study of Five Open Clusters in the SDSS

    NASA Astrophysics Data System (ADS)

    Ryu, Jinhyuk; Lee, Myung Gyoon

    2011-10-01

    We present a photometric study of five open clusters (Czernik 5, Alessi 53, Berkeley 49, Berkeley 84, and Pfleiderer 3) in the Sloan Digital Sky Survey. The position and size of these clusters are determined using the radial number density profiles of the stars, and the member stars of the clusters are selected using the proper motion data in the literature. We estimate the reddening, distance and age of the clusters based on the isochrone fitting in the color-magnitude diagram. The foreground reddenings for these clusters are estimated to be E(B-V)=0.71-1.55 mag. The distances to these clusters are derived to be 2.0-4.4 kpc, and their distances from the Galactic center range from 7.57 kpc to 12.35 kpc. Their ages are in the range from 250 Myr to 1 Gyr. Berkeley 49 and Berkeley 84 are located in the Orion spur, Czernik 5 is in the Perseus arm, and Pfleiderer 3 and Alessi 53 are located beyond the Perseus arm.

  20. Rotation periods of open-cluster stars, 3

    NASA Technical Reports Server (NTRS)

    Prosser, Charles F.; Shetrone, Matthew D.; Dasgupta, Amil; Backman, Dana E.; Laaksonen, Bentley D.; Baker, Shawn W.; Marschall, Laurence A.; Whitney, Barbara A.; Kuijken, Konrad; Stauffer, John R.

    1995-01-01

    We present the results from a photometric monitoring program of 15 open cluster stars and one weak-lined T Tauri star during late 1993/early 1994. Several show rotators which are members of the Alpha Persei, Pleiades, and Hyades open clusters have been monitored and period estimates derived. Using all available Pleiades stars with photometric periods together with current X-ray flux measurements, we illustrate the X-ray activity/rotation relation among Pleiades late-G/K dwarfs. The data show a clear break in the rotation-activity relation around P approximately 6-7 days -- in general accordance with previous results using more heterogeneous samples of G/K stars.

  1. Chemical abundances of solar-type dwarfs in open clusters

    NASA Astrophysics Data System (ADS)

    Schuler, Simon C.

    Open clusters have proven continuously to be invaluable tools to the studies of stellar physics and Galactic evolution. Until recently, however, the chemical abundances of the populous and astrophysically important late-F, G, and K open cluster dwarfs have gone largely unanalyzed. In this thesis I report on the study of the chemical abundances derived from high-resolution, moderate-to-high signal-to-noise echelle spectra obtained with the 10-m Keck I, 9.2-m Hobby- Eberly, 8.2-m VLT, 4.0-m KPNO, 2.7-m Harlan J. Smith, and the 2.1-m Otto Struve telescopes of cool dwarfs in the Pleiades, Hyades, and M34 open clusters. The main result of the study is the identification of excitation-related abundance trends found among cool open cluster dwarfs ( T eff <= 5500 K), as well as an overionization of Fe- abundances derived from singly ionized lines are greater than those derived from neutral lines- among the cool Hyades dwarfs; the trends are such that abundances derived from high-excitation (h >= 4.0 eV) spectral lines and using atmospheric models assuming local thermodynamic equilibrium (LTE) increase with decreasing T eff . Particular attention is given to the high-excitation (h = 9.15 eV) near-IR ll7774 O I triplet, a line used often in the derivation of stellar O abundances and known to be susceptible to non-LTE (NLTE) effects. The O I triplet-based abundances show a dramatic increase with decreasing T eff in all three clusters, behavior that is in stark contrast to expectations from canonical NLTE calculations. Other elements with lines of various excitation potentials are also analyzed and are found to exhibit abundance trends that are qualitatively similar to those of the O I triplet. Possible explanations for the observed cool open cluster dwarf abundance anomalies are investigated, and photospheric surface temperature inhomogeneities possibly due to spots, faculae, and/or plages are found to be a plausible culprit. Indeed, multi-component LTE model atmospheres are

  2. Rotation periods of open-cluster stars, 2

    NASA Technical Reports Server (NTRS)

    Prosser, Charles F.; Shetrone, Matthew D.; Marilli, Ettore; Catalano, Santo; Williams, Scott D.; Backman, Dana E.; Laaksonen, Bentley D.; Adige, Vikram; Marschall, Laurence A.; Stauffer, John R.

    1993-01-01

    We present the results from a photometric monitoring program of 21 stars observed during 1992 in the Pleiades and Alpha Persei open clusters. Period determinations for 16 stars are given, 13 of which are the first periods reported for these stars. Brightness variations for an additional five cluster stars are also given. One K dwarf member of the alpha Per cluster is observed to have a period of rotation of only 4.39 hr. perhaps the shortest period currently known among BY Draconis variables. The individual photometric measurements have been deposited with the NSSDC. Combining current X-ray flux determinations with known photometric periods, we illustrate the X-ray activity/rotation relation among Pleiades K dwarfs based on available data.

  3. Numerical experiments on galaxy clustering in open universes

    NASA Technical Reports Server (NTRS)

    Miller, R. H.

    1984-01-01

    Numerical studies were performed on the dynamical effects on the evolution of clumps, filaments, voids, and galaxy clusters by various final Omega values. The final Omega values examined ranged from 0.03-1, and attention was given to defining observations of superclusters which would aid in determining an actual value for Omega. The numerical trials consisted of n-body integration programs governed by the total expansion and final Omega value and included comparisons between results for open and closed universes. All runs started from the same initial conditions. The dispersion trajectories of particles and the final galactic cluster forms were found to be equivalent, regardless of the final Omega value. The possibility of deriving a value for Omega from velocity data on galaxies which have not yet joined clusters is discussed.

  4. OPEN CLUSTERS AS PROBES OF THE GALACTIC MAGNETIC FIELD. I. CLUSTER PROPERTIES

    SciTech Connect

    Hoq, Sadia; Clemens, D. P. E-mail: clemens@bu.edu

    2015-10-15

    Stars in open clusters are powerful probes of the intervening Galactic magnetic field via background starlight polarimetry because they provide constraints on the magnetic field distances. We use 2MASS photometric data for a sample of 31 clusters in the outer Galaxy for which near-IR polarimetric data were obtained to determine the cluster distances, ages, and reddenings via fitting theoretical isochrones to cluster color–magnitude diagrams. The fitting approach uses an objective χ{sup 2} minimization technique to derive the cluster properties and their uncertainties. We found the ages, distances, and reddenings for 24 of the clusters, and the distances and reddenings for 6 additional clusters that were either sparse or faint in the near-IR. The derived ranges of log(age), distance, and E(B−V) were 7.25–9.63, ∼670–6160 pc, and 0.02–1.46 mag, respectively. The distance uncertainties ranged from ∼8% to 20%. The derived parameters were compared to previous studies, and most cluster parameters agree within our uncertainties. To test the accuracy of the fitting technique, synthetic clusters with 50, 100, or 200 cluster members and a wide range of ages were fit. These tests recovered the input parameters within their uncertainties for more than 90% of the individual synthetic cluster parameters. These results indicate that the fitting technique likely provides reliable estimates of cluster properties. The distances derived will be used in an upcoming study of the Galactic magnetic field in the outer Galaxy.

  5. An updated maximum likelihood approach to open cluster distance determination

    NASA Astrophysics Data System (ADS)

    Palmer, M.; Arenou, F.; Luri, X.; Masana, E.

    2014-04-01

    Aims: An improved method for estimating distances to open clusters is presented and applied to Hipparcos data for the Pleiades and the Hyades. The method is applied in the context of the historic Pleiades distance problem, with a discussion of previous criticisms of Hipparcos parallaxes. This is followed by an outlook for Gaia, where the improved method could be especially useful. Methods: Based on maximum likelihood estimation, the method combines parallax, position, apparent magnitude, colour, proper motion, and radial velocity information to estimate the parameters describing an open cluster precisely and without bias. Results: We find the distance to the Pleiades to be 120.3 ± 1.5 pc, in accordance with previously published work using the same dataset. We find that error correlations cannot be responsible for the still present discrepancy between Hipparcos and photometric methods. Additionally, the three-dimensional space velocity and physical structure of Pleiades is parametrised, where we find strong evidence of mass segregation. The distance to the Hyades is found to be 46.35 ± 0.35 pc, also in accordance with previous results. Through the use of simulations, we confirm that the method is unbiased, so will be useful for accurate open cluster parameter estimation with Gaia at distances up to several thousand parsec. Appendices are available in electronic form at http://www.aanda.org

  6. Peculiarities of α-element abundances in Galactic open clusters

    NASA Astrophysics Data System (ADS)

    Marsakov, V. A.; Gozha, M. L.; Koval', V. V.; Shpigel', L. V.

    2016-01-01

    A catalog compiling the parameters of 346 open clusters, including their metallicities, positions, ages, and velocities has been composed. The elements of the Galactic orbits for 272 of the clusters have been calculated. Spectroscopic determinations of the relative abundances, [el/Fe], for 14 elements synthesized in various nuclear processes averaged over data from 109 publications are presented for 90 clusters. The compiled data indicate that the relative abundances of primary α elements (oxygen and magnesium) exhibit different dependences on metallicity, age, Galactocentric distance, and the elements of the Galactic orbits in clusters with high, elongated orbits satisfying the criterion ( Z max 2 + 4 e 2)1/2 > 0.40 and in field stars of the Galactic thin disk ( Z max is the maximum distance of the orbit from the Galactic plane in kiloparsec and e is the eccentricity of the Galactic orbit). Since no systematic effects distorting the relative abundances of the studied elements in these clusters have been found, these difference suggest real differences between clusters with high, elongated orbits and field stars. In particular, this supports the earlier conclusion, based on an analysis of the elements of the Galactic orbits, that some clusters formed as a result of interactions between high-velocity,metal-poor clouds and the interstellar mediumof theGalactic thin disk. On average, clusters with high, elongated orbits and metallicities [Fe/H] < -0.1 display lower relative abundances of the primary a elements than do field stars. The low [O, Mg/Fe] ratios of these clusters can be understood if the high-velocity clouds that gave rise to them were formed of interstellar material from regions where the star-formation rate and/or the masses of Type II supernovae were lower than near the Galactic plane. It is also shown that, on average, the relative abundances of the primary a elements are higher in relatively metal-rich clusters with high, elongated orbits than in

  7. A spectroscopic study of the open cluster NGC 6250

    NASA Astrophysics Data System (ADS)

    Martin, A. J.; Stift, M. J.; Fossati, L.; Bagnulo, S.; Scalia, C.; Leone, F.; Smalley, B.

    2017-04-01

    We present the chemical abundance analysis of 19 upper main-sequence stars of the young open cluster NGC 6250 (log t ∼ 7.42 yr). This work is part of a project aimed at setting observational constraints on the theory of atomic diffusion in stellar photospheres, by means of a systematic study of the abundances of the chemical elements of early F-, A- and late B-type stars of well-determined age. Our data set consists of low-, medium- and high-resolution spectra obtained with the Fibre Large Array Multi Element Spectrograph (FLAMES) instrument of the ESO Very Large Telescope (VLT). To perform our analysis, we have developed a new suite of software tools for the chemical abundance analysis of stellar photospheres in local thermodynamical equilibrium. Together with the chemical composition of the stellar photospheres, we have provided new estimates of the cluster mean radial velocity, proper motion, refined the cluster membership, and we have given the stellar parameters including masses and fractional age. We find no evidence of statistically significant correlation between any of the parameters, including abundance and cluster age, except perhaps for an increase in Ba abundance with cluster age. We have proven that our new software tool may be successfully used for the chemical abundance analysis of large data sets of stellar spectra.

  8. Towards a comprehensive knowledge of the open cluster Haffner 9

    NASA Astrophysics Data System (ADS)

    Piatti, Andrés E.

    2017-03-01

    We turn our attention to Haffner 9, a Milky Way open cluster whose previous fundamental parameter estimates are far from being in agreement. In order to provide with accurate estimates, we present high-quality Washington CT1 and Johnson BVI photometry of the cluster field. We put particular care in statistically cleaning the colour-magnitude diagrams (CMDs) from field star contamination, which was found a common source in previous works for the discordant fundamental parameter estimates. The resulting cluster CMD fiducial features were confirmed from a proper motion membership analysis. Haffner 9 is a moderately young object (age ∼350 Myr), placed in the Perseus arm - at a heliocentric distance of ∼3.2 kpc - , with a lower limit for its present mass of ∼160 M⊙ and of nearly metal solar content. The combination of the cluster structural and fundamental parameters suggest that it is in an advanced stage of internal dynamical evolution, possibly in the phase typical of those with mass segregation in their core regions. However, the cluster still keeps its mass function close to that of the Salpeter's law.

  9. Nine new open clusters within 500 pc from the Sun

    NASA Astrophysics Data System (ADS)

    Röser, Siegfried; Schilbach, Elena; Goldman, Bertrand

    2016-10-01

    Aims: One of the results of the Milky Way Star Clusters (MWSC) survey was the detection of a slight under-density of old (ca. 1 Gyr) clusters within the nearest kilo-parsec from the Sun. This under-density may be due to an ineffectiveness in the detection of larger structures with lower surface brightness. We report on our attempts to reveal such clusters. Methods: We derived proper motions from a combination of Tycho-2 with URAT1, and obtained a mean precision of about 1.4 mas/yr per co-ordinate for 1.3 million stars north of -20° declination. We cut the sky into narrow proper motion slices and searched for spatial over-densities of stars in each slice. We then examined stars from over-densities in optical and near-infrared colour-magnitude diagrams to determine if they are compatible with isochrones of a cluster. We estimated the field star contamination using our data and the Besançon Galactic model. Results: We detected nine hitherto unknown open clusters in the vicinity of the Sun with ages between 70 Myr and 1 Gyr, and distances between 200 and 500 pc.

  10. Fundamental Parameters of the Open Cluster Kronberger 1

    NASA Astrophysics Data System (ADS)

    Sujatha, S.; Krishna Kumar, K.; Komala, S.

    2016-09-01

    In this paper, we present the fundamental physical parameters and the present-day mass function of the open cluster Kronberger 1. The cluster radius is estimated to be 3' and the interstellar extinction E(B-V) in the line-of-sight of the cluster is found to be 0.45±0.05 mag. This cluster is located in the direction of Auriga constellation at a distance of 2.5±0.2 kpc. From the appropriate theoretical isochrones, the log(age) of the cluster is found to be 7.65. The mass function slope for Kronberger 1 is derived for the first time and it is estimated to be α = 2.72±0.2 which is in agreement with the slope of α = 2.35 given by Salpeter. Similar results are obtained from a near infrared study performed using data from the Two Micron All Sky Survey thus substantiating the results obtained from the optical analysis. These results indicate that Kronberger 1 is a suitable object for mapping the spiral arm structure of our Galaxy and for understanding the behavior of mass function in the Galactic disk.

  11. A Bayesian Analysis of the Ages of Four Open Clusters

    NASA Astrophysics Data System (ADS)

    Jeffery, Elizabeth J.; von Hippel, Ted; van Dyk, David A.; Stenning, David C.; Robinson, Elliot; Stein, Nathan; Jefferys, William H.

    2016-09-01

    In this paper we apply a Bayesian technique to determine the best fit of stellar evolution models to find the main sequence turn-off age and other cluster parameters of four intermediate-age open clusters: NGC 2360, NGC 2477, NGC 2660, and NGC 3960. Our algorithm utilizes a Markov chain Monte Carlo technique to fit these various parameters, objectively finding the best-fit isochrone for each cluster. The result is a high-precision isochrone fit. We compare these results with the those of traditional “by-eye” isochrone fitting methods. By applying this Bayesian technique to NGC 2360, NGC 2477, NGC 2660, and NGC 3960, we determine the ages of these clusters to be 1.35 ± 0.05, 1.02 ± 0.02, 1.64 ± 0.04, and 0.860 ± 0.04 Gyr, respectively. The results of this paper continue our effort to determine cluster ages to a higher precision than that offered by these traditional methods of isochrone fitting.

  12. 3D cluster members and near-infrared distance of open cluster NGC 6819

    NASA Astrophysics Data System (ADS)

    Gao, Xin-Hua; Xu, Shou-Kun; Chen, Li

    2015-12-01

    In order to obtain clean members of the open cluster NGC 6819, the proper motions and radial velocities of 1691 stars are used to construct a three-dimensional (3D) velocity space. Based on the DBSCAN clustering algorithm, 537 3D cluster members are obtained. From the 537 3D cluster members, the average radial velocity and absolute proper motion of the cluster are Vr = +2.30 ± 0.04 km s-1 and (PMRA, PMDec) = (-2.5 ± 0.5, -4.3 ± 0.5) mas yr-1, respectively. The proper motions, radial velocities, spatial positions and color-magnitude diagram of the 537 3D members indicate that our membership determination is effective. Among the 537 3D cluster members, 15 red clump giants can be easily identified by eye and are used as reliable standard candles for the distance estimate of the cluster. The distance modulus of the cluster is determined to be (m - M)0 = 11.86 ± 0.05 mag (2355 ± 54 pc), which is quite consistent with published values. The uncertainty of our distance modulus is dominated by the intrinsic dispersion in the luminosities of red clump giants (˜ 0.04 mag).

  13. Investigation of the open star cluster NGC 6800

    NASA Astrophysics Data System (ADS)

    Ananjevskaja, Yu. K.; Frolov, V. N.; Polyakov, E. V.

    2015-07-01

    The results of a comprehensive study of the Galactic open cluster NGC 6800 are presented. The positions of stars to a limiting magnitude B ≃ 16{./ m }5 in an 80' × 80' field centered at the cluster were measured on eight plates from the Pulkovo normal astrograph with a maximum epoch difference of 57 years. The measurements were performed with the Pulkovo "Fantasy" automated measuring system. The corresponding field from the 2MASS catalogue was used as an additional plate. As a result, the relative proper motions of stars were obtained with a root-mean-square error of 3.0 mas yr-1. A catalogue of BV and JHK magnitudes for objects in the investigated region was compiled from available published resources. The astrometric selection of cluster members was made by the maximum likelihood method. An individual cluster membership probability of a star P ≥ 60% served as the first selection criterion. The position of a star on the photometric color-magnitude ( V ~ B - V, J ~ J - K s ) diagrams was considered as the second selection criterion. On the basis of these criteria, it was established that 109 stars are members of NGC 6800, These data were used to refine the physical parameters of the cluster: the mean reddening E( B - V) = 0 m . 40, the true distance modulus ( V - M V )0 = 10{./ m }05, and the cluster age ~250 Myr. The luminosity and mass functions were constructed. The position of the center of the cluster NGC 6800 was improved: α = 19h27m11{./s}2 and δ = +25°07'24〃(2000). The catalogue of relative proper motions for stars in the field is available in electronic form only.

  14. Photometry and spectroscopy in the open cluster alpha Persei, 2.

    NASA Technical Reports Server (NTRS)

    Prosser, Charles F.

    1994-01-01

    Results from a combination of new spectroscopic and photometric observations in the lower main sequence and pre-main sequence of the open cluster alpha Persei are presented. New echelle spectroscopy has provided radial and rotational velocity information for thirteen candidate members, three of which are nonmembers based on radial velocity, absence of a Li 6707 A feature, and absence of H alpha emission. A set of revised rotational velocity estimates for several slowly rotating candidates identified earlier is given, yielding rotational velocities as low as 7 km/s for two apparent cluster members. VI photometry for several pre-main-sequence members is given; the new (V, V-I(sub K) photometry yields a more clearly defined pre-main sequence. A list of approximately 30 new faint candidate members based on the (V, V-I(sub K)), charge coupled device (CCD) photometry is presented in an effort to identify additional cluster members at very low masses. Low-dispersion spectra obtained for several of these candidates provide in some cases supporting evidence for cluster membership. The single brown dwarf candidate in this cluster is for the first time placed in a color-magnitude diagram with other cluster members, providing a better means for establishing its true status. Stars from among the list of new photometric candidates may provide the means for establishing a sequence of cluster members down to very faint magnitudes (V approximately 21) and consequently very low masses. New coordinate determinations for previous candidate members and finding charts for the new photometric candidates are provided in Appendices.

  15. Photometry and spectroscopy in the open cluster Alpha Persei, 2

    NASA Technical Reports Server (NTRS)

    Prosser, Charles F.

    1993-01-01

    Results from a combination of new spectroscopic and photometric observations in the lower main-sequence and pre-main sequence of the open cluster alpha Persei are presented. New echelle spectroscopy has provided radial and rotational velocity information for thirteen candidate members, three of which are nonmembers based on radial velocity, absence of a Li 6707A feature, and absence of H-alpha emission. A set of revised rotational velocity estimates for several slowly rotating candidates identified earlier is given, yielding rotational velocities as low as 7 km/s for two apparent cluster members. VRI photometry for several pre-main sequence members is given; the new (V,V-I(sub K)) photometry yields a more clearly defined pre-main sequence. A list of approximately 43 new faint candidate members based on the (V,V-I(sub K)) CCD photometry is presented in an effort to identify additional cluster members at very low masses. Low-dispersion spectra obtained for several of these candidates provide in some cases supporting evidence for cluster membership. The single brown dwarf candidate in this cluster is for the first time placed in a color-magnitude diagram with other cluster members, providing a better means for establishing its true status. Stars from among the list of new photometric candidates may provide the means for establishing a sequence of cluster members down to very faint magnitudes (V approximately 21) and consequently very low masses. New coordinate determinations for previous candidate members and finding charts for the new photometric candidates are provided in appendices.

  16. Abundances and kinematics for ten anticentre open clusters

    NASA Astrophysics Data System (ADS)

    Cantat-Gaudin, T.; Donati, P.; Vallenari, A.; Sordo, R.; Bragaglia, A.; Magrini, L.

    2016-04-01

    Context. Open clusters are distributed all across the Galactic disk and are convenient tracers of its properties. In particular, outer disk clusters bear a key role in the investigation of the chemical evolution of the Galactic disk. Aims: The goal of this study is to derive homogeneous elemental abundances for a sample of ten outer disk open clusters, and investigate possible links with disk structures such as the Galactic anticentre stellar structure. Methods: We analysed high-resolution spectra of red giants, obtained from the Keck-HIRES and VLT-UVES archives. We derived elemental abundances and stellar atmosphere parameters by means of the classical equivalent width method. We also performed orbit integrations using proper motions. Results: The Fe abundances we derive trace a shallow negative radial metallicity gradient of slope -0.027 ± 0.007 dex kpc-1 in the outer 12 kpc of the disk. The [α/Fe] gradient appears flat, with a slope of 0.006 ± 0.007 dex kpc-1. The two outermost clusters (Be 29 and Sau 1) appear to follow elliptical orbits. The cluster Be 20 also exhibits a peculiar orbit with a large excursion above the plane. Conclusions: The irregular orbits of the three most metal poor clusters (two of which are located at the edge of the Galactic disk), are compatible with an inside-out formation scenario for the Milky Way in which extragalactic material is accreted onto the outer disk. This is the case if the irregular orbits of these clusters are confirmed by more robust astrometric measurements such as those of the Gaia mission. We cannot determine whether Be 20, Be 29, and Sau 1 are of extragalactic origin, as they may be old, genuine Galactic clusters whose orbits were perturbed by accretion events or minor mergers in the past 5 Gyr, or they may be representants of the thick disk population. The nature of these objects is intriguing and deserves further investigation in the near future. The measured equivalent widths are only available at the CDS via

  17. Testing the chemical tagging technique with open clusters

    NASA Astrophysics Data System (ADS)

    Blanco-Cuaresma, S.; Soubiran, C.; Heiter, U.; Asplund, M.; Carraro, G.; Costado, M. T.; Feltzing, S.; González-Hernández, J. I.; Jiménez-Esteban, F.; Korn, A. J.; Marino, A. F.; Montes, D.; San Roman, I.; Tabernero, H. M.; Tautvaišienė, G.

    2015-05-01

    Context. Stars are born together from giant molecular clouds and, if we assume that the priors were chemically homogeneous and well-mixed, we expect them to share the same chemical composition. Most of the stellar aggregates are disrupted while orbiting the Galaxy and most of the dynamic information is lost, thus the only possibility of reconstructing the stellar formation history is to analyze the chemical abundances that we observe today. Aims: The chemical tagging technique aims to recover disrupted stellar clusters based merely on their chemical composition. We evaluate the viability of this technique to recover co-natal stars that are no longer gravitationally bound. Methods: Open clusters are co-natal aggregates that have managed to survive together. We compiled stellar spectra from 31 old and intermediate-age open clusters, homogeneously derived atmospheric parameters, and 17 abundance species, and applied machine learning algorithms to group the stars based on their chemical composition. This approach allows us to evaluate the viability and efficiency of the chemical tagging technique. Results: We found that stars at different evolutionary stages have distinct chemical patterns that may be due to NLTE effects, atomic diffusion, mixing, and biases. When separating stars into dwarfs and giants, we observed that a few open clusters show distinct chemical signatures while the majority show a high degree of overlap. This limits the recovery of co-natal aggregates by applying the chemical tagging technique. Nevertheless, there is room for improvement if more elements are included and models are improved. Based on observations obtained at the Telescope Bernard Lyot (USR5026) operated by the Observatoire Midi-Pyrénées, Université de Toulouse (Paul Sabatier), Centre National de la Recherche Scientifique of France, and on public data obtained from the ESO Science Archive Facility under requests number 81252 and 81618.

  18. TWO BARIUM STARS IN THE OPEN CLUSTER NGC 5822

    SciTech Connect

    Katime Santrich, O. J.; Pereira, C. B.; De Castro, D. B. E-mail: claudio@on.br

    2013-08-01

    Open clusters are very useful examples to explain the constraint of the nucleosynthesis process with the luminosities of stars because the distances of the clusters are better known than those of field stars. We carried out a detailed spectroscopic analysis to derive the chemical composition of two red giants in the young open cluster NGC 5822, NGC 5822-2, and NGC 5822-201. We obtained abundances of C, N, O, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, and Nd. The atmospheric parameters of the studied stars and their chemical abundances were determined using high-resolution optical spectroscopy. We employed the local thermodynamic equilibrium model atmospheres of Kurucz and the spectral analysis code MOOG. The abundances of the light elements were derived using the spectral synthesis technique. We found that NGC 5822-2 and -201 have, respectively, a mean overabundance of the elements created by the s-process, ''s'', with the notation [s/Fe] of 0.77 {+-} 0.12 and 0.83 {+-} 0.05. These values are higher than those for field giants of similar metallicity. We also found that NGC 5822-2 and -201 have, respectively, luminosities of 140 L{sub Sun} and 76 L{sub Sun }, which are much lower than the luminosity of an asymptotic giant branch star. We conclude that NGC 5822-2 and NGC 5822-201 are two new barium stars first identified in the open cluster NGC 5822. The mass transfer hypothesis is the best scenario to explain the observed overabundances.

  19. Strengthening the open cluster distance scale via VVV photometry

    NASA Astrophysics Data System (ADS)

    Majaess, D.; Turner, D.; Moni Bidin, C.; Geisler, D.; Borissova, J.; Minniti, D.; Bonatto, C.; Gieren, W.; Carraro, G.; Kurtev, R.; Mauro, F.; Chené, A.-N.; Forbes, D.; Lucas, P.; Dékány, I.; Saito, R. K.; Soto, M.

    2012-01-01

    Approximately 14% of known Galactic open clusters possess absolute errors ≤ 20% as evaluated from n ≥ 3 independent distance estimates, and the statistics for age estimates are markedly worse. That impedes such diverse efforts as calibrating standard candles and constraining masses for substellar companions. New data from the VVV survey may be employed to establish precise cluster distances with comparatively reduced uncertainties ( ≤ 10%). This is illustrated by deriving parameters for Pismis 19 and NGC 4349, two pertinent open clusters which hitherto feature sizable uncertainties (60%). Fundamental parameters determined for Pismis 19 from new VVV JHKs photometry are d = 2.40 ± 0.15 kpc, ⟨EJ - H⟩ = 0.34 ± 0.04, and log τ = 9.05 ± 0.10, whereas for NGC 4349 the analysis yielded d = 1.63 ± 0.13 kpc, EJ - H = 0.09 ± 0.02, log τ = 8.55 ± 0.10. The results exhibit a significant ( ≥ 5 × ) reduction in uncertainties, and indicate that: i) existing parameters for the substellar object NGC 4349 127b require revision, in part because the new cluster parameters imply that the host is 20% less-massive (ℳ∗/ℳ⊙ ~ 3.1); ii) R Cru is not a member of NGC 4349 and should be excluded from period-Wesenheit calibrations that anchor the distance scale; iii) and results for Pismis 19 underscore the advantages gleaned from employing deep VVV JHKs data to examine obscured (AV ~ 4) and differentially reddened intermediate-age clusters. Based on observations taken within the ESO VISTA Public Survey VVV, Programme ID 179.B-2002.

  20. Time-Series Monitoring of Open Star Clusters

    NASA Astrophysics Data System (ADS)

    Hojaev, A. S.; Semakov, D. G.

    2006-08-01

    Star clusters especially a compact ones (with diameter of few to ten arcmin) are suitable targets to search of light variability for orchestera of stars by means of ordinary Casegrain telescope plus CCD system. A special patroling with short time-fixed exposures and mmag accuracy could be used also to study of stellar oscillation for group of stars simultaneously. The last can be carried out both separately from one site and within international campaigns. Detection and study of optical variability of X-ray sources including X-ray binaries with compact objects might be as a result of a long-term monitoring of such clusters as well. We present the program of open star clusters monitoring with Zeiss 1 meter RCC telescope of Maidanak observatory has been recently automated. In combination with quite good seeing at this observatory (see, e.g., Sarazin, M. 1999, URL http://www.eso.org/gen-fac/pubs/astclim/) the automatic telescope equipped with large-format (2KX2K) CCD camera AP-10 available will allow to collect homogenious time-series for analysis. We already started this program in 2001 and had a set of patrol observations with Zeiss 0.6 meter telescope and AP-10 camera in 2003. 7 compact open clusters in the Milky Way (NGC 7801, King1, King 13, King18, King20, Berkeley 55, IC 4996) have been monitored for stellar variability and some results of photometry will be presented. A few interesting variables were discovered and dozens were suspected for variability to the moment in these clusters for the first time. We have made steps to join the Whole-Earth Telescope effort in its future campaigns.

  1. NGC 6067: A young and populous open cluster

    NASA Astrophysics Data System (ADS)

    Alonso-Santiago, J.; Negueruela, I.; Marco, A.; Tabernero, H. M.; González-Fernández, C.; Castro, N.

    2017-03-01

    NGC 6067 is a young open cluster hosting the largest population of evolved stars among known Milky Way clusters in the 50 – 100 Ma age range. It thus represents the best laboratory in our Galaxy to constrain the evolutionary tracks of 5-7 M_{⊙} stars. We have used high-resolution spectra of a large sample of bright cluster members (45), combined with archival photometry, to obtain accurate parameters for the cluster as well as stellar atmospheric parameters. We derive a distance of 1.78±0.12 kpc, an age of 90±20 My and a tidal radius of 14.8^{6.8}_{3.2} arcmin. We estimate an initial mass above 5700 M_{⊙}, for a present-day evolved population of two Cepheids, two A supergiants and 12 red giants with masses ≈ 6 M_{⊙}. We also determine chemical abundances of Li, O, Na, Mg, Si, Ca, Ti, Ni, Rb, Y, and Ba for the clump stars. We find a supersolar metallicity, [Fe/H]=+0.19±0.05, and a homogeneous chemical composition, consistent with the Galactic metallicity gradient. The presence of a Li-rich red giant, star 276, is also detected. An over-abundance of Ba is found, supporting the enhanced s-process. The mass of V340 Nor, a Cepheid that seems younger than the cluster itself, suggests that it has been a mass gainer in an interacting binary. The ratio of blue to red giants is smaller than one, in agreement with models with moderate overshooting, but the properties of the cluster Cepheids do not seem consistent with current Padova models for supersolar metallicity.

  2. The old, metal-poor, anticentre open cluster Trumpler 5

    NASA Astrophysics Data System (ADS)

    Donati, P.; Cocozza, G.; Bragaglia, A.; Pancino, E.; Cantat-Gaudin, T.; Carrera, R.; Tosi, M.

    2015-01-01

    As part of a long-term programme, we analyse the evolutionary status and properties of the old and populous open cluster Trumpler 5 (Tr 5), located in the Galactic anticentre direction, almost on the Galactic plane. Tr 5 was observed with Wide Field Imager@MPG/ESO Telescope using the Bessel U, B, and V filters. The cluster parameters have been obtained using the synthetic colour-magnitude diagram (CMD) method, i.e. the direct comparison of the observational CMD with a library of synthetic CMDs generated with different stellar evolution sets (Padova, FRANEC, and FST). Age, reddening, and distance are derived through the synthetic CMD method using stellar evolutionary models with subsolar metallicity (Z = 0.004 or Z = 0.006). Additional spectroscopic observations with Ultraviolet VLT Echelle Spectrograph@Very Large Telescope of three red clump stars of the cluster were used to determine more robustly the chemical properties of the cluster. Our analysis shows that Tr 5 has subsolar metallicity, with [Fe/H] = -0.403 ± 0.006 dex (derived from spectroscopy), age between 2.9 and 4 Gyr (the lower age is found using stellar models without core overshooting), reddening E(B - V) in the range 0.60-0.66 mag complicated by a differential pattern (of the order of ˜±0.1 mag), and distance modulus (m - M)0 = 12.4 ± 0.1 mag.

  3. The open cluster Havlen-Moffat No. 1 revisited

    NASA Astrophysics Data System (ADS)

    Vázquez, R. A.; Baume, G.

    2001-06-01

    A deep CCD UBVRI photometric survey combined with UBVRI polarimetric observations of 21 bright stars was carried out in the region of the open cluster Havlen-Moffat No. 1. Our data reveal that the extinction law in this cluster is variable and that six cluster stars show very high polarisation values (>4%), probably because of the presence of a nearby small dust cloud. The cluster is at a distance of d = 3300 pc, it is 2-4 Myr old and the initial mass function of its most massive stars (M > 3 Msun ) has a flat slope of x~ 0.7. As an additional result, it was possible to reconcile the absolute magnitudes of the two WN7-type members using the R-values valid in the regions where they are located. Based on observations collected at the University of Toronto Southern Observatory, Las Campanas, Chile, and the Complejo Astronómico El Leoncito, (CASLEO), Argentina, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba and San Juan. Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/371/908.

  4. WIYN open cluster study. LIX. Radial velocity membership of the evolved population of the old open cluster NGC 6791

    SciTech Connect

    Tofflemire, Benjamin M.; Gosnell, Natalie M.; Mathieu, Robert D.; Platais, Imants E-mail: imants@pha.jhu.edu

    2014-10-01

    The open cluster NGC 6791 has been the focus of much recent study due to its intriguing combination of old age and high metallicity (∼8 Gyr, [Fe/H] = +0.30), as well as its location within the Kepler field. As part of the WIYN Open Cluster Study, we present precise (σ = 0.38 km s{sup –1}) radial velocities for proper motion candidate members of NGC 6791 from Platais et al. Our survey, extending down to g' ∼ 16.8, is comprised of the evolved cluster population, including blue stragglers, giants, and horizontal branch stars. Of the 280 proper-motion-selected stars above our magnitude limit, 93% have at least one radial velocity measurement and 79% have three measurements over the course of at least 200 days, sufficient for secure radial-velocity-determined membership of non-velocity-variable stars. The Platais et al. proper motion catalog includes 12 anomalous horizontal branch candidates blueward of the red clump, of which we find only 4 to be cluster members. Three fall slightly blueward of the red clump and the fourth is consistent with being a blue straggler. The cleaned color-magnitude diagram shows a richly populated red giant branch and a blue straggler population. Half of the blue stragglers are in binaries. From our radial velocity measurement distribution, we find the cluster's radial velocity dispersion to be σ {sub c} = 0.62 ± 0.10 km s{sup –1}. This corresponds to a dynamical mass of ∼4600 M {sub ☉}.

  5. Blue stragglers in open clusters. III. NGC 7789

    NASA Astrophysics Data System (ADS)

    Schönberner, D.; Andrievsky, S. M.; Drilling, J. S.

    2001-02-01

    We performed for the first time a detailed LTE spectroscopic study of a sample of blue straggler stars in the moderately old open cluster NGC 7789. For eight stars the parameters and abundances of several elements were determined. The cluster members show a remarkable surface magnesium deficiency which is quite unusual for late B - early A stars. Iron and titanium abundances are in agreement with other photometric and spectroscopic estimates of the NGC 7789 metallicity. All the confirmed blue stragglers have rather low projected rotational velocities (with one exception for K88, vsin i = 80 km s-1). Based on the spectra collected at Kitt Peak National Observatory, operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation, and at the German-Spanish Astronomical Center, Calar Alto, operated by the Max-Plank Institute for Astronomy, Heidelberg, jointly with the Spanish National Commission for Astronomy.}

  6. Two Intermediate Age Open Clusters - NGC752 and NGC3680

    NASA Astrophysics Data System (ADS)

    Carraro, G.; Bertelli, G.; Bressan, A.; Chiosi, C.

    1993-10-01

    In this paper, with the aid of synthetic color-magnitude diagram (CMD) technique we study two scarcely populated and slightly metal-poor intermediate age open clusters, namely NGC 752 and NGC 3680. The analysis is made using both standard and overshoot models calculated by the Padova group (Fagotto 1990; Alongi et al. 1991, 1993). The advantage with the synthetic CMD technique is that it allows for quantitative predictions for the star counts and luminosity functions. Adopting the metallicity indicated for each cluster by current determinations, we seek to determine the color excess, distance modulus, and age at the same time. Looking at the fit of the whole CMD, the behaviour of the main sequence stars LF, and two suitable ratios of star counts we try to discriminate between the two evolutionary schemes. We suggest that models with convective overshoot ought to be preferred to the classical ones.

  7. Late-Type Membership of the Open Cluster NGC 2232

    NASA Technical Reports Server (NTRS)

    Orban, Chris; Patten, Brian

    2004-01-01

    NGC 2232 is one of the nearest open clusters (approx.360 pc) with an age of approx.25 Myr. This places it in the unique position to study the transition from T Tauri activity to the Zero Age Main Sequence. In order for those studies to begin, late-type members must be identified for the cluster. X-ray observations combined with ground-based photometry and spectroscopy offers the best way to accomplish this goal. We present photometry in the VRI bands, 2MASS near-infrared measurements in the J, H , Ks bands and spectra for the suspected optical counterparts to the X-ray sources in the field of NGC 2232. 46 candidate members were identified through these efforts ranging from F5 to M5.

  8. On the physical nature of six galactic open cluster candidates

    NASA Astrophysics Data System (ADS)

    Piatti, A. E.; Clariá, J. J.; Ahumada, A. V.

    We present CCD UBVI_(KC) photometry in the fields of the unstudied open cluster (OC) candidates Haffner 3, Haffner 5, NGC 2368, Haffner 25, Hogg 3 and Hogg 4. Our analysis shows that none of these objects are genuine OCs since no clear main sequences or other typical features can be seen in their colour-magnitude and colour-colour diagrams. Star counts performed within and outside the OC candidate fields not only support these results but also suggest that these objects are not OC remnants. A detailed version of this work can be seen in New Astronomy, 16, 161 (2011).

  9. The OPD photometric survey of open clusters II. robust determination of the fundamental parameters of 24 open clusters

    NASA Astrophysics Data System (ADS)

    Monteiro, H.; Dias, W. S.; Hickel, G. R.; Caetano, T. C.

    2017-02-01

    In the second paper of the series we continue the investigation of open cluster fundamental parameters using a robust global optimization method to fit model isochrones to photometric data. We present optical UBVRI CCD photometry (Johnsons-Cousins system) observations for 24 neglected open clusters, of which 14 have high quality data in the visible obtained for the first time, as a part of our ongoing survey being carried out in the 0.6 m telescope of the Pico dos Dias Observatory in Brazil. All objects were then analyzed with a global optimization tool developed by our group which estimates the membership likelihood of the observed stars and fits an isochrone from which a distance, age, reddening, total to selective extinction ratio RV (included in this work as a new free parameter) and metallicity are estimated. Based on those estimates and their associated errors we analyzed the status of each object as real clusters or not, finding that two are likely to be asterisms. We also identify important discrepancies between our results and previous ones obtained in the literature which were determined using 2MASS photometry.

  10. Open Clusters as Tracers of the Galactic Disk

    NASA Astrophysics Data System (ADS)

    Cantat-Gaudin, Tristan

    2015-01-01

    Open clusters (OCs) are routinely used as reliable tracers of the properties and evolution of the galactic disk, as they can be found at all galactocentric distances and span a wide range of ages. More than 3000 OCs are listed in catalogues, although few have been studied in details. The goal of this work is to study the properties of open clusters. This work was conducted in the framework of the Gaia-ESO Survey (GES). GES is an observational campaign targeting more than 100,000 stars in all major components of the Milky Way, including stars in a hundred open clusters. It uses the FLAMES instrument at the VLT to produce high and medium-resolution spectra, which provide accurate radial velocities and individual elemental abundances. In this framework, the goals of the Thesis are: * to study the properties of OCs and of their stars from photometry and spectroscopy to derive their age, the extinction and the chemical composition of the stars, to begin to build a homogeneous data base. Looking at literature data it is clear that different authors derive substantially different chemical compositions, and in general OC parameters. * the study of OCs and their chemical homogeneity (or inhomogeneity) can cast light on what is still an open issue: the presence of multiple populations in clusters. While multiple generations of stars are now ubiquitously found in globular clusters in the Milky Way and in the Magellanic Clouds, they have not been yet detected in open clusters. What is the main driver of the self-pollution process? * to study the cluster formation process. All, or at least a significant fraction of stars form in clusters. Young clusters (a few Myr) can retain some of the properties of the molecular cloud they originate from and give us insight about the cluster assembly process. The first GES data release contains data for the young OC Gamma Velorum, in which two (dynamically different) subpopulations have been identified. This cluster can serve as a test case

  11. Polarimetry of an intermediate-age open cluster: NGC 5617

    NASA Astrophysics Data System (ADS)

    Orsatti, A. M.; Feinstein, C.; Vergne, M. M.; Martínez, R. E.; Vega, E. I.

    2010-04-01

    Aims: We present polarimetric observations in the UBVRI bands of 72 stars located in the direction of the medium age open cluster NGC 5617. Our intention is to use polarimetry as a tool in membership identification, by building on previous investigations intended mainly to determine the cluster's general characteristics rather than provide membership suitable for studies such as stellar content and metallicity, as well as study the characteristics of the dust lying between the Sun and the cluster. Methods: The obsevations were carried out using the five-channel photopolarimeter of the Torino Astronomical Observatory attached to the 2.15 m telescope at the Complejo Astronómico El Leoncito (CASLEO; Argentina). Results: We are able to add 32 stars to the list of members of NGC 5617, and review the situation for others listed in the literature. In particular, we find that five blue straggler stars in the region of the cluster are located behind the same dust as the member stars are and we confirm the membership of two red giants. The proposed polarimetric memberships are compared with those derived by photometric and kinematical methods, with excellent results. Among the observed stars, we identify 10 with intrinsic polarization in their light. NGC 5617 can be polarimetrically characterized with Pmax = 4.40 % and θv = 73.1 deg. The spread in polarization values for the stars observed in the direction of the cluster seems to be caused by the uneven distribution of dust in front of the cluster's face. Finally, we find that in the direction of the cluster, the interstellar medium is apparently free of dust, from the Sun's position up to the Carina-Sagittarius arm, where NGC 5617 seems to be located at its farthest border. Based on observations obtained at Complejo Astronómico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the Universities of La Plata, Córdoba, and San Juan.

  12. The Old, Super-Metal-Rich Open Cluster, NGC 6791

    NASA Astrophysics Data System (ADS)

    Boesgaard, Ann Merchant; Lum, Michael G. G.; Deliyannis, Constantine P.

    2015-08-01

    Stellar evolution and Galactic evolution have both been greatly advanced by the study of star clusters. In addition the elemental abundance results from clusters have revealed information about Galactic chemical evolution and nucleosynthesis. The cluster, NGC 6791, has a number of bizarre properties that make it especially interesting for comparative cluster studies. It is old (8.3 Gyr) yet metal-rich ([Fe/H] = +0.30). It has a heliocentric distance of 4 kpc and a galactic latitude of +11 degrees which makes it 1 kpc above the galactic plane. Its boxy orbit has a high eccentricity (~0.5) with a perigalactic distance of 3 kpc and an apogalactic distance of 10 kpc. The orbital period of ~130 Myr indicates that it has crossed the Galactic plane several times yet has remained as an intact cluster. We have determined abundances from high-resolution (R = 46,000) Keck/HIRES spectra of turn-off stars in this open cluster NGC 6791. We have a solid determination of [Fe/H] = +0.30 +/-0.02 from measurements of some 40 unblended, unsaturated lines of both Fe I and Fe II in eight turn-off stars. Our O abundances come from the O I triplet near 7774 Å and are corrected for small nLTE effects. We find consistent ratios of [O/Fe]n with a mean of -0.06 +/-0.02, indicating a single population of stars. Our results for the alpha elements [Mg/Fe], [Si/Fe], [Ca/Fe] and [Ti/Fe] are near solar and compare well with those of old, metal-rich field stars. The Fe-peak elements, Cr and Ni, have values of [Cr/Fe] = +0.05 +/-0.02 and [Ni/Fe] = +0.04 +/-0.01. Determinations of upper limits were found for Li by spectrum synthesis; this is consistent with the upper limits in this temperature range for turn-off/subgiant stars in the relatively old, super-metal-rich cluster NGC 6253. We speculate that no stars in NGC 6791 have retained the Li with which they formed.

  13. TX Cnc AS A MEMBER OF THE PRAESEPE OPEN CLUSTER

    SciTech Connect

    Zhang, X. B.; Deng, L.; Lu, P.

    2009-08-15

    We present B-, V-, and I-band CCD photometry of the W UMa-type binary system TX Cnc, which is a member star of the Praesepe open cluster. Based on the observations, new ephemeris and a revised photometric solution of the binary system were derived. Combined with the results of the radial velocity solution contributed by Pribulla et al., the absolute parameters of the system were determined. The mass, radius, and luminosity of the primary component are derived to be 1.35 {+-} 0.02 M {sub sun}, 1.27 {+-} 0.04 R {sub sun}, and 2.13 {+-} 0.11 L {sub sun}. Those for the secondary star are computed as 0.61 {+-} 0.01 M {sub sun}, 0.89 {+-} 0.03 R {sub sun}, and 1.26 {+-} 0.07 L {sub sun}, respectively. Based on these results, a distance modulus of (m - M) {sub V} = 6.34 {+-} 0.05 is determined for the star. It confirms the membership of TX Cnc to the Praesepe open cluster. The evolutionary status and the physical nature of the binary system are discussed compared with the theoretical model.

  14. Stellar rotational periods in the planet hosting open cluster Praesepe

    NASA Astrophysics Data System (ADS)

    Kovács, Géza; Hartman, Joel D.; Bakos, Gáspár Á.; Quinn, Samuel N.; Penev, Kaloyan; Latham, David W.; Bhatti, Waqas; Csubry, Zoltán; de Val-Borro, Miguel

    2014-08-01

    By using the dense coverage of the extrasolar planet survey project HATNet (Hungarian-made Automated Telescope Network), we Fourier analyse 381 high-probability members of the nearby open cluster Praesepe (Beehive/M44/NGC 2632). In addition to the detection of 10 variables (of δ Scuti and other types), we identify 180 rotational variables (including the two known planet hosts). This sample increases the number of known rotational variables in this cluster for spectral classes earlier than M by more than a factor of 3. These stars closely follow a colour/magnitude-period relation from early F to late K stars. We approximate this relation by polynomials for an easier reference to the rotational characteristics in different colours. The total (peak-to-peak) amplitudes of the large majority (94 per cent) of these variables span the range of 0.005-0.04 mag. The periods cover a range from 2.5 to 15 d. These data strongly confirm that Praesepe and the Hyades have the same gyrochronological ages. Regarding the two planet hosts, Pr0211 (the one with the shorter orbital period) has a rotational period that is ˜2 d shorter than the one expected from the main rotational pattern in this cluster. This, together with other examples discussed in the paper, may hint that star-planet interaction via tidal dissipation can be significant in some cases in the rotational evolution of stars hosting hot Jupiters.

  15. DEBRIS DISKS OF MEMBERS OF THE BLANCO 1 OPEN CLUSTER

    SciTech Connect

    Stauffer, John R.; Noriega-Crespo, Alberto; Rebull, Luisa M.; James, David; Strom, Steven; Wolk, Scott; Carpenter, John M.; Barrado y Navascues, David; Backman, Dana; Cargile, P. A.

    2010-08-20

    We have used the Spitzer Space Telescope to obtain Multiband Imaging Photometer for Spitzer (MIPS) 24 {mu}m photometry for 37 members of the {approx}100 Myr old open cluster Blanco 1. For the brightest 25 of these stars (where we have 3{sigma} uncertainties less than 15%), we find significant mid-IR excesses for eight stars, corresponding to a debris disk detection frequency of about 32%. The stars with excesses include two A stars, four F dwarfs, and two G dwarfs. The most significant linkage between 24 {mu}m excess and any other stellar property for our Blanco 1 sample of stars is with binarity. Blanco 1 members that are photometric binaries show few or no detected 24 {mu}m excesses whereas a quarter of the apparently single Blanco 1 members do have excesses. We have examined the MIPS data for two other clusters of similar age to Blanco 1-NGC 2547 and the Pleiades. The AFGK photometric binary star members of both of these clusters also show a much lower frequency of 24 {mu}m excesses compared to stars that lie near the single-star main sequence. We provide a new determination of the relation between the V - K {sub s} color and K {sub s} - [24] color for main sequence photospheres based on Hyades members observed with MIPS. As a result of our analysis of the Hyades data, we identify three low mass Hyades members as candidates for having debris disks near the MIPS detection limit.

  16. Photometric study of the young open cluster NGC 3293

    NASA Astrophysics Data System (ADS)

    Baume, G.; Vázquez, R. A.; Carraro, G.; Feinstein, A.

    2003-05-01

    Deep and extensive CCD photometric observations at UBV(RI)_CHalpha were carried out in the area of the open cluster NGC 3293. The new data set allows to see the entire cluster sequence down to MV ~ +4.5, revealing that stars with MV < -2 are evolving off the main sequence; stars with -2 < MV < +2 are located on the main sequence and stars with MV > +2 are placed above it. According to our analysis, the cluster distance is d = 2750 +/- 250 pc (V0-MV = 12.2 +/- 0.2) and its nuclear age is 8 +/- 1 Myr. NGC 3293 contains an important fraction of pre-main sequence (PMS) stars distributed along a parallel band to the ZAMS with masses from 1 to 2.5 cal Msun and a mean contraction age of 10 Myr. This last value does not differ too much from the nuclear age estimate. If we take into account the many factors that may affect the PMS star positions on the colour-magnitude diagram, both ages can be perfectly reconciled. The star formation rate, on the other hand, suggests that NGC 3293 stars formed surely in one single event, therefore favouring a coeval process of star formation. Using the Halpha data, we detected nineteen stars with signs of Halpha emission in the region of NGC 3293, another indication that the star formation process is still active in the region. The computed initial mass function for the cluster has a slope of x = 1.2 +/- 0.2, a bit flatter than the typical slope for field stars and similar to the values found for other young open clusters. Based on observations collected at UTSO, ESO (Dutch 0.9 m telescope) and CASLEO. The CCD and data acquisition system at CASLEO has been partly financed by R.M. Rich through U.S. NSF Grant AST-90-15827. Full Table 1 is only available in electronic form at the CDS via an anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/402/549

  17. X-Ray Activity in the Open Cluster IC 4665

    NASA Technical Reports Server (NTRS)

    Giamapapa, Mark S.; Prosser, Charles F.; Fleming, Thomas A.

    1997-01-01

    We present the results of a joint ROSAT High Resolution Imager (HRI) and optical investigation of the open cluster IC 4665. The ROSAT data contains detections for 28 stellar sources in the field, including 22 cluster members and candidate members spanning the color range -0.18 less than or equal to (B - V(sub o)) less than or equal to +1.63 (approx. B3 - M3). Upper limits are given for the remaining members (or candidate members) in the HRI field. Keck HIRES spectra have been obtained that yield radial and rotational velocity measures, respectively, for faint, low mass candidate members located within the field of the ROSAT HRI observation. In addition, photometry of possible optical counterparts to previously uncatalogued X-ray sources in the HRI field is presented. The trends in X-ray properties with (B - V) color in IC 4665 are found to be quite similar to that for other, more nearby young clusters such as the Pleiades and alpha Persei. In particular, a maximum in normalized X-ray luminosity of log (L(sub x)/L(sub bol)) approx. equal 3 is observed, beginning in the color range of (B - V)(sub o) = 0.7 - 0.8. This is similar to the corresponding color range among Pleiades members, in agreement with the earlier estimate, that the age of IC 4665 is similar to the age of the Pleiades. The correlation of rotation and X-ray emission levels is consistent with that in other young clusters. Among the high mass stars in IC 4665, five B stars are detected as X-ray sources. Of these, one is a spectroscopic binary while the remaining objects are apparently single staxs. The level of intrinsic X-ray emission observed in the rapidly rotating (v sini greater than 200 km/ s), single B stars is consistent with an origin due to shock heating of the ambient medium by radiatively driven, rotationally enhanced winds. On the basis of these observations and the results for other clusters, we argue that observed levels of X-ray emission in high mass stars of log (L(sub x)/L(sub bol

  18. Revisiting the region of the open cluster NGC 5606

    NASA Astrophysics Data System (ADS)

    Orsatti, A. M.; Feinstein, C.; Vega, E. I.; Vergne, M. M.

    2007-08-01

    We present polarimetric observations in the UBVRI bands corresponding to 54 stars located in the direction of NGC 5606. Our intention is to analyze the dust characteristics between the Sun and the cluster, as well as to confirm doubtful memberships using polarimetric tools. We also want to determine if a group of 11 B and A stars identified in the past by Vázquez & Feinstein (1991, A&AS, 87, 383) in front of NGC 5606 has any physical entity. From polarimetric data we have found at least two dust layers along the line of sight to the open cluster. The observations show that both dust layers have their local magnetic field with an orientation which is close to the direction of the Galactic Plane (θ = 70.0 °), but the direction of the polarimetric vector for the members of the cluster seems to be lower than this value. NGC 5606 can be polarimetrically characterized with P_max = 2.97% and θv = 63.5 °. The internal dispersion of the polarization values for the members of NGC 5606 seems to be compatible with intracluster dust. We were able to add four possible new members to the list of stars in NGC 5606, and to reject others accepted as members in past investigations; and we identified 17 (out of the 54 observed stars) with intrinsic polarization in their light. The group of late B- and A-type stars could be physically related, with characteristics of an open cluster of intermediate age (between 0.79 and 1. × 108 yr). For this group we obtained representative values of P = 2.12% and θv = 70.0 °. The new cluster, which we have provisionally named Anon (La Plata 1), extends from NE to SW across the face of NGC 5606 covering about 10'. The fitting procedure of Schmidt-Kaler's ZAMS (1982, in Landolt/Bornstein, Neue Series VI/2b) was used to derive the distance to the group, obtaining a distance modulus of Vo - Mv = 9.90 (649 pc from the Sun). The mean color excess associated with the small group is EB-V = 0.27 ± 0.08 mag and the dust distribution shows great

  19. A populous intermediate-age open cluster and evidence of an embedded cluster among the FSR globular cluster candidates

    NASA Astrophysics Data System (ADS)

    Bica, E.; Bonatto, C.

    2008-03-01

    We study the nature of the globular cluster (GC) candidates FSR 1603 and FSR1755 selected from the catalogue of Froebrich, Scholz & Raftery. Their properties are investigated with Two-Micron All-Sky Survey field-star decontaminated photometry, which is used to build colour-magnitude diagrams (CMDs) and stellar radial density profiles. FSR1603 has the open cluster Ruprecht 101 as optical counterpart, and we show it to be a massive intermediate-age cluster. Relevant parameters of FSR1603 are the age ~1Gyr, distance from the Sun dsolar ~ 2.7kpc, Galactocentric distance RGC ~ 6.4kpc, core radius RC ~ 1.1pc, mass function slope χ ~ 1.8, observed stellar mass (for stars with mass in the range 1.27 <= m <= 2.03Msolar) Mobs ~ 500Msolar and a total (extrapolated to m = 0.08Msolar) stellar mass Mtot ~ 2300Msolar. FSR1755, on the other hand, is not a populous cluster. It may be a sparse young cluster embedded in the HII region Sh2-3, subject to an absorption AV ~ 4.1, located at dsolar ~ 1.3kpc. Important field-star contamination, spatially variable heavy dust obscuration, even in Ks, and gas emission characterize its field. A nearly vertical, sparse blue stellar sequence shows up in the CMDs.

  20. Red giants in the vicinity of open clusters. Field stars

    NASA Astrophysics Data System (ADS)

    Pakhomov, Yu. V.; Antipova, L. I.; Boyarchuk, A. A.; Zhao, G.; Liang, Ya.

    2009-08-01

    We present a comparative analysis of the atmospheric abundances of red giants in the vicinity of open clusters. The atmospheric parameters, atmospheric abundances, masses, ages, Galactic velocities, and elements of the Galactic orbits are derived for all the studied stars. We have discovered high metal abundances (close to 0.3dex) for five stars, which we classify as super-metal-rich stars. Several stars have lower [Na/Fe] than normal red giants with similar atmospheric parameters. The kinematic characteristics of these stars are somewhat different from those for objects in the Galactic thin disk. We suggest that the observed effect can be explained by inhomogeneity of the chemical composition of gas-dust clouds, which could be due to different rates of SNe II supernovae in different regions of the Galaxy.

  1. The OCCASO Survey: Open Clusters Chemical Abundances from Spanish Observatories

    NASA Astrophysics Data System (ADS)

    Casamiquela, L.; Carrera, R.; Jordi, C.; Balaguer-Núñez, L.

    2014-07-01

    Stellar clusters are crucial in the study of a variety of topics including the star formation process, stellar nucleosynthesis and evolution, dynamical interaction among stars, or the assembly and evolution of galaxies. In particular, Open Clusters (OCs) have been widely used to constrain the formation and evolution of the Milky Way disc. They provide information about the chemical patterns and the existence of radial and vertical gradients or an age-metallicity relation. However, all these investigations are hampered by the fact that only a small fraction of clusters have been studied homogeneously. Galactic surveys performed from the ground such as the Apache Point Observatory Galactic Evolution Experiment (APOGEE), the Gaia-ESO Survey (GES), or the GALactic Archaeology with HERMES (GALAH) include OCs among their targets. OCs are also sampled from the space by the Gaia and Kepler missions. The OCCASO goal is to derive abundances for more than 20 chemical species in at least 6 Red Clump stars in ˜30 Northern hemisphere OCs. In order to ensure the reliability of the derived chemical abundances, these are derived using different analysis techniques similar to what is being performed by GES. One of the OCCASO requirements is the homogeneity between instruments, methods and model atmospheres used, and in the same scale than the GES-UVES abundances. For this reason we are performing different tests checking internal and external consistency. Derived stellar atmosphere parameters and Fe abundances will be published in the first data release scheduled for the first semester of 2015. The online pdf of the poster with first results is available at https://gaia.ub.edu/Twiki/pub/GREATITNFC/ProgramFinalconference/poster_OCCASO.pdf.

  2. Searching for Be stars in the open cluster NGC 663

    SciTech Connect

    Yu, P. C.; Lin, C. C.; Chen, W. P.; Lee, C. D.; Ip, W. H.; Ngeow, C. C.; Laher, Russ; Surace, Jason

    2015-02-01

    We present Be star candidates in the open cluster NGC 663, identified by Hα imaging photometry with the Palomar Transient Factory Survey, as a pilot program to investigate how the Be star phenomena, the emission spectra, extended circumstellar envelopes, and fast rotation, correlate with massive stellar evolution. Stellar membership of the candidates was verified by 2MASS magnitudes and colors and by proper motions (PMs). We discover four new Be stars and exclude one known Be star from being a member due to its inconsistent PMs. The fraction of Be stars to member stars [N(Be)/N(members)] in NGC 663 is 3.5%. The spectral type of the 34 Be stars in NGC 663 shows bimodal peaks at B0–B2 and B5–B7, which is consistent with the statistics in most star clusters. Additionally, we also discover 23 emission-line stars of different types, including non-member Be stars, dwarfs, and giants.

  3. WIYN OPEN CLUSTER STUDY LII: WIDE-FIELD CCD PHOTOMETRY OF THE OLD OPEN CLUSTER NGC 6819

    SciTech Connect

    Yang, Soung-Chul; Kim, Sang Chul; Kyeong, Jaemann; Sarajedini, Ata; Deliyannis, Constantine P.; Sarrazine, Angela R. E-mail: ata@astro.ufl.edu E-mail: asarrazi@bellsouth.net

    2013-01-01

    We present a comprehensive photometric study of the old open cluster, NGC 6819, using 1 Degree-Sign Multiplication-Sign 1 Degree-Sign field VI MOSAIC CCD imaging taken with the WIYN 0.9 m telescope. The resultant color-magnitude diagram (CMD) shows a well-developed main sequence (MS) extending from V {approx} 14.5 mag down to our photometric limit of V {approx} 21 mag. Fitting theoretical isochrones with the adopted values of the reddening and metallicity (E(B - V) = 0.14, [Fe/H] = +0.09 dex) to the observed CMD yields a distance modulus of (m - M){sub 0} = 11.93 {+-} 0.10 and an age of {approx}2.6 Gyr for NGC 6819. Our wide-field imaging reveals that NGC 6819 is larger in areal extent (R = 13') than previously thought. The wide field also benefits our estimate of the degree of field star contamination, and ultimately yields improved measurements of the structural parameters (r{sub c} = 2.'80, r{sub t} = 38.'2, and r{sub h} = 7') and tidal mass of the cluster (M {sub tid} = 3542.4 M {sub Sun }). The flattened luminosity and mass functions indicate that NGC 6819 has experienced mass segregation as a result of its dynamical evolution. Our variability study of the cluster blue straggler star (BSS) population using the Welch-Stetson variability index (I {sub WS}) has revealed a number of variable BSS candidates.

  4. VizieR Online Data Catalog: M67 variable stars photometry (Nardiello+, 2016)

    NASA Astrophysics Data System (ADS)

    Nardiello, D.; Libralato, M.; Bedin, L. R.; Piotto, G.; Ochner, P.; Cunial, A.; Borsato, L.; Granata, V.

    2016-07-01

    All images of the OC M 67 [(RA,DE)=(08:51:18,+11:48:00)] were collected with the Asiago 67/92cm Schmidt Telescope located on Mount Ekar (longitude 11.5710°E, latitude 45.8430°N, altitude 1370m), that belongs to the Astronomical Observatory of Padova (OAPD), which is part of the Istituto Nazionale di Astrofisica (INAF). At the focus of the Schmidt telescope there is a SBIG STL-11000M camera, equipped with a Kodak KAI-11000M detector (4050x2672 pixel, field of view: 58x38-arcmin2, pixel scale: 862.5mas/pixel). In the first observing season (2012) M 67 data were collected in white light (hereafter indicated with filter N, where N stands for 'None'), with exposure time of 120s, and 60s (during the almost-full moon nights); during the second (2013) and the third season (2014) we collected 180s+15s R-filter and 180s B-filter images. Finally, during the fourth season (2015), the observations were carried out in I band (240s+15s) and V band (240s). A catalogue for variable stars in M 67 field is presented. (1 data file).

  5. Peakbagging in the open cluster NGC 6819: Opening a treasure chest or Pandora's box?

    NASA Astrophysics Data System (ADS)

    Handberg, R.; Miglio, A.; Brogaard, K.; Bossini, D.; Elsworth, Y. P.

    2016-09-01

    Here we report on an extensive peakbagging effort on the evolved red giant stars of the open cluster NGC 6819. This consists of around 50 stars spanning all the way up the red giant branch (RGB) and down to and including the red clump (RC). These stars represent a unique sample because of their common distance, metallicity and age. By employing sophisticated pre-processing of the time series and Markov Chain Monte Carlo (MCMC) techniques, we have extracted individual frequencies, heights, and line widths for hundreds of individual oscillation modes in the sample of stars. We show that average asteroseismic parameters derived from these can be used to distinguish the stellar evolutionary state between RGB and RC stars without having to measure the often difficult dipole modes. Furthermore, we show how the fitting of some of these dipole modes can improve the detectability of acoustic glitches arising from the helium II ionization zone and how this can potentially be used to constrain the helium content in the cluster. We also discuss some of the difficulties facing similar studies in the future, where it seems that detailed studies of star clusters are facing some difficult times ahead.

  6. jClustering, an Open Framework for the Development of 4D Clustering Algorithms

    PubMed Central

    Mateos-Pérez, José María; García-Villalba, Carmen; Pascau, Javier; Desco, Manuel; Vaquero, Juan J.

    2013-01-01

    We present jClustering, an open framework for the design of clustering algorithms in dynamic medical imaging. We developed this tool because of the difficulty involved in manually segmenting dynamic PET images and the lack of availability of source code for published segmentation algorithms. Providing an easily extensible open tool encourages publication of source code to facilitate the process of comparing algorithms and provide interested third parties with the opportunity to review code. The internal structure of the framework allows an external developer to implement new algorithms easily and quickly, focusing only on the particulars of the method being implemented and not on image data handling and preprocessing. This tool has been coded in Java and is presented as an ImageJ plugin in order to take advantage of all the functionalities offered by this imaging analysis platform. Both binary packages and source code have been published, the latter under a free software license (GNU General Public License) to allow modification if necessary. PMID:23990913

  7. jClustering, an open framework for the development of 4D clustering algorithms.

    PubMed

    Mateos-Pérez, José María; García-Villalba, Carmen; Pascau, Javier; Desco, Manuel; Vaquero, Juan J

    2013-01-01

    We present jClustering, an open framework for the design of clustering algorithms in dynamic medical imaging. We developed this tool because of the difficulty involved in manually segmenting dynamic PET images and the lack of availability of source code for published segmentation algorithms. Providing an easily extensible open tool encourages publication of source code to facilitate the process of comparing algorithms and provide interested third parties with the opportunity to review code. The internal structure of the framework allows an external developer to implement new algorithms easily and quickly, focusing only on the particulars of the method being implemented and not on image data handling and preprocessing. This tool has been coded in Java and is presented as an ImageJ plugin in order to take advantage of all the functionalities offered by this imaging analysis platform. Both binary packages and source code have been published, the latter under a free software license (GNU General Public License) to allow modification if necessary.

  8. Spectrophotometry of 237 Stars in 7 Open Clusters

    NASA Astrophysics Data System (ADS)

    Clampitt, Lori; Burstein, David

    1997-08-01

    Spectrophotometry is presented for 237 stars in 7 nearby open clusters: Hyades, Pleiades, Alpha Persei, Praesepe, Coma Berenices, IC 4665, and M39. The observations were taken by Lee McDonald and David Burstein using the Wampler single-channel scanner on the Crossley 0.9m telescope at Lick Observatory from July 1973 through December 1974. Sixteen bandpasses spanning the spectral range 3500 Angstroms to 7780 Angstroms were observed for each star, with bandwidths 32Angstroms, 48 Angstroms or 64 Angstroms. Data are standardized to the Hayes-Latham system to mutual accuracy of 0.016 mag per passband. The accuracy of the spectrophotometry is assessed in three ways on a star-by-star basis. First, comparisons are made with previously published spectrophotometry for 19 stars observed in common. Second, (B-V) colors and uvby colors are compared for 236 stars and 221 stars, respectively. Finally, comparsions are made for 200 main sequence stars to the spectral synthesis models of Kurucz, fixing log g = 4.0 and [Fe/H] = 0.0, and only varying effective temperature. The accuracy of tests using uvby colors and the Kurucz models are shown to track each other closely, yielding an accuracy estimate (1 sigma ) of 0.01 mag for the 13 colors formed from bandpasses longward of the Balmer jump, and 0.02 mag for the 3 colors formed from the three bandpasses below the Balmer jump. In contrast, larger scatter is found relative to the previously published spectrophotometry of Bohm-Vitense & Johnson (16 stars in common) and Gunn & Stryker (3 stars). We also show that the scatter in the fits of the spectrophotometric colors and the uvby filter colors is a reasonable way to identify the observations of which specific stars are accurate to 1 sigma , 2 sigma , .... As such, the residuals from both the filter color fits and the Kurucz model fits are tabulated for each star where it was possible to make a comparison, so users of these data can choose stars according to the accuracy of the data

  9. The Blue Straggler RS Canum Venaticorum Star S1082 in M67: A Detailed Light Curve and the Possibility of a Triple

    NASA Astrophysics Data System (ADS)

    Sandquist, Eric L.; Latham, David W.; Shetrone, Matthew D.; Milone, Alejandra A. E.

    2003-02-01

    Using both photometric and spectroscopic data, we present a picture of the very unusual blue straggler S1082 in the old open cluster M67 whose light is the sum of a close binary (P=1.0677978 days) and another cluster member. The primary of the close binary and the third star are both blue stragglers in their own rights. Using relative photometry with millimagnitude accuracy, we provide a complete V-band light curve for the system and show a number of unusual features: brightness variations at the 0.01-0.03 mag level from month to month at all phases, a narrow primary and broad secondary eclipse, brightness differences between phases 0.25 and 0.75, and short duration (~1 hr) drops in brightness. Much of the light-curve variation appears to be because of spot activity on the cooler, fainter, nearly synchronized component of the close binary. We use spectra from several sources to constrain the temperatures of the three known components, the relative flux contributions, rotational velocities, and radial velocities. The data clearly show that the brightest star (narrow-line component) seen in the spectrum is on an orbit with period P=1189+/-7 days and eccentricity e=0.57+/-0.08, although we cannot prove that there is a dynamical link between it and the close binary. The systematic velocities of all of the stars indicate that they are members of the cluster. Our models of the system indicate that the cooler component of the close binary lies on the main sequence near the cluster turnoff, while the hotter component lies near an extension of the main sequence blueward of the turnoff, and thus qualifies as a blue straggler by itself. The reduction of the masses of the stars in the close binary compared with previous models indicates that it is possible that the more massive component of the close binary formed from a merger of just two turnoff-mass stars. Based in part on observations obtained with the Hobby-Eberly Telescope (HET), which is a joint project of the

  10. A SPITZER VIEW OF THE YOUNG OPEN CLUSTER NGC 2264

    SciTech Connect

    Sung, Hwankyung; Stauffer, John R.; Bessell, Michael S. E-mail: stauffer@ipac.caltech.edu

    2009-10-15

    We have performed mid-IR photometry of the young open cluster NGC 2264 using the images obtained with the Spitzer Space Telescope Infrared Array Camera and Multiband Imaging Photometer for Spitzer instruments and presented a normalized classification scheme of young stellar objects in various color-color diagrams to make full use of the information from multicolor photometry. These results are compared with the classification scheme based on the slope of the spectral energy distribution (SED). From the spatial distributions of Class I and II stars, we have identified two subclusterings of Class I objects in the CONE region of Sung et al. The disked stars in the other star-forming region S Mon are mostly Class II objects. These three regions show a distinct difference in the fractional distribution of SED slopes as well as the mean value of SED slopes. The fraction of stars with primordial disks is nearly flat between log m = 0.2 and -0.5 and that of transition disks is very high for solar mass stars. In addition, we have derived a somewhat higher value of the primordial disk fraction for NGC 2264 members located below the main pre-main-sequence locus (so-called BMS stars). This result supports the idea that BMS stars are young stars with nearly edge-on disks. We have also found that the fraction of primordial disks is very low near the most massive star S Mon and increases with distance from S Mon.

  11. Do open star clusters evolve towards energy equipartition?

    NASA Astrophysics Data System (ADS)

    Spera, Mario; Mapelli, Michela; Jeffries, Robin D.

    2016-07-01

    We investigate whether open clusters (OCs) tend to energy equipartition, by means of direct N-body simulations with a broken power-law mass function. We find that the simulated OCs become strongly mass segregated, but the local velocity dispersion does not depend on the stellar mass for most of the mass range: the curve of the velocity dispersion as a function of mass is nearly flat even after several half-mass relaxation times, regardless of the adopted stellar evolution recipes and Galactic tidal field model. This result holds both if we start from virialized King models and if we use clumpy sub-virial initial conditions. The velocity dispersion of the most massive stars and stellar remnants tends to be higher than the velocity dispersion of the lighter stars. This trend is particularly evident in simulations without stellar evolution. We interpret this result as a consequence of the strong mass segregation, which leads to Spitzer's instability. Stellar winds delay the onset of the instability. Our simulations strongly support the result that OCs do not attain equipartition, for a wide range of initial conditions.

  12. Sub-subgiants in Old Open Cluster NGC 6791

    NASA Astrophysics Data System (ADS)

    Milliman, Katelyn E.; Leiner, Emily; Mathieu, Robert D.; Tofflemire, Benjamin M.; Platais, Imants

    2016-01-01

    In an optical color-magnitude diagram sub-subgiants (SSGs) lie red of the main-sequence and fainter than the red giant branch in a region not easily populated by standard stellar evolution theory. We present radial-velocity follow-up to five SSG candidates in the old open cluster NGC 6791 (8 Gyr, [Fe/H]= +0.3). Our observations began in 2014 July with the Hydra multi-object spectrograph on the WIYN 3.5 m telescope. We find four SSGs to be three-dimensional kinematic members of NGC 6791, with three also being short-period binary systems. The existence of these newly discovered SSGs in NGC 6791 strengthens the case that SSGs are a new class of non-standard stellar products, and that a physical mechanism must be found that explains the unusual evolutionary path of these stars. We gratefully acknowledge funding from the National Science Foundation under grant AST- 0908082 and the Wisconsin Space Grant Consortium.

  13. Interstellar Extinction toward the Young Open Cluster NGC 1502

    NASA Astrophysics Data System (ADS)

    Topasna, Gregory A.; Kaltcheva, Nadia

    2017-01-01

    We present new multi-wavelength polarization measurements of 20 stars in the direction of the open cluster NGC 1502. Polarimetric results are combined with uvbyβ photometric data to obtain precise estimates of the total-to-selective extinction and distance for each star. NGC 1502 is located at the periphery of the Cam OB1 association and probably within the Orion Spur, with published distance estimates varying between 0.7 and 1.5 kpc. Our analysis suggests that the stars studied here form two concentrations along the line of sight. If a value of 3.2 for the total-to-selective extinction is assumed, the stars group at 0.8 ± 0.02 kpc and 1.1 ± 0.05 kpc. However, using the wavelength of maximum polarization to calculate the total-to-selective extinction for each star yields 0.9 ± 0.03 kpc and 1.3 ± 0.04 kpc, respectively. This approach indicates that combining polarimetric and uvbyβ data provides a more detailed stellar distribution of this region. Acknowledgments: Part of this work was supported by NSF grant AST-1516932.

  14. Lithium abundances and extra mixing processes in evolved stars of M 67

    NASA Astrophysics Data System (ADS)

    Canto Martins, B. L.; Lèbre, A.; Palacios, A.; de Laverny, P.; Richard, O.; Melo, C. H. F.; Do Nascimento, J. D., Jr.; de Medeiros, J. R.

    2011-03-01

    Aims: We present a spectroscopic analysis of a sample of evolved stars in M 67 (turn-off, subgiant and giant stars) in order to bring observational constraints to evolutionary models taking into account non-standard transport processes. Methods: We determined the stellar parameters (Teff, log g, [Fe/H]), microturbulent and rotational velocities and, lithium abundances (ALi) for 27 evolved stars of M 67 with the spectral synthesis method based on MARCS model atmospheres. We also computed non-standard stellar evolution models, taking into account atomic diffusion and rotation-induced transport of angular momentum and chemicals that were compared with this set of homogeneous data. Results: The lithium abundances that we derive for the 27 stars in our sample follow a clear evolutionary pattern ranging from the turn-off to the Red Giant Branch. Our abundance determination confirms the well known decrease of lithium content for evolved stars. For the first time, we provide a consistent interpretation of both the surface rotation velocity and of the lithium abundance patterns observed in an homogeneous sample of TO and evolved stars of M 67. We show that the lithium evolution is determined by the evolution of the angular momentum through rotation-induced mixing in low-mass stars, in particular for those with initial masses larger than 1.30 M⊙ when at solar metallicity. Based on observations collected at ESO, Paranal, Chile (VLT/FLAMES program ID 072.D-0309 and 074.D-0179).Table 6 is only available in electronic form at http://www.aanda.org

  15. Intermediate and old age Open Clusters science case for high resolution spectroscopy

    NASA Astrophysics Data System (ADS)

    Jordi, C.; Carrera, R.; Balaguer-Núnez, L.; Casamiquela, L.

    2017-03-01

    Open Clusters are dynamically-bound groups of stars that formed from the same giant molecular cloud, having a similar age and bulk chemical composition. Open Clusters are key objects for studying the formation and evolution of the Galactic disk. They are targets in on-going large spectroscopic surveys like Gaia-ESO and OCCASO surveys. We discuss the science case of the intermediate age and old Open Clusters for WEAVE, the upcoming multifiber spectroscopic facility in the WHT. In particular we do an overview of the target selection and the survey strategy. Additionally, the impact of the discovery of new clusters by Gaia space mission is discussed.

  16. VizieR Online Data Catalog: Abundances in Galactic open clusters (Marsakov+, 2016)

    NASA Astrophysics Data System (ADS)

    Marsakov, V. A.; Gozha, M. L.; Koval', V. V.; Shpigel', L. V.

    2016-07-01

    Spectroscopic determinations of the relative abundances of alpha-elements (O, Mg, Si, Ca, and Ti), slow neutron capture elements (Y, Ba, La, Ce, Nd, and Zr), rapid neutron capture element (Eu), and elements with an odd number of protons (Na, Al) are collected for 90 open clusters of the Galaxy. Metallicities are presented for 346 clusters. In addition catalog contains positions, ages, velocities, elements of Galactic orbits for open clusters. (2 data files).

  17. NEWS ON THE s PROCESS FROM YOUNG OPEN CLUSTERS

    SciTech Connect

    Maiorca, Enrico; Busso, Maurizio; Palmerini, Sara; Trippella, Oscar; Magrini, Laura; Randich, Sofia

    2012-03-01

    Recent spectroscopic measurements in open clusters younger than the Sun with [Fe/H] {approx}> 0 showed that the abundances of neutron-rich elements have continued to increase in the Galaxy after the formation of the Sun, roughly maintaining a solar-like distribution. This growth requires neutron fluences larger than those so far assumed, as these would have too few neutrons per iron seed. We suggest that the observed enhancements can be produced by nucleosynthesis in asymptotic giant branch (AGB) stars of low mass (M < 1.5 M{sub Sun }) if they release neutrons from the {sup 13}C({alpha},n){sup 16}O reaction in reservoirs larger by a factor of four than assumed in more massive AGB stars (M > 1.5 M{sub Sun }). Adopting such a stronger neutron source as a contributor to the abundances at the time of formation of the Sun, we show that this also affects the solar s-process distribution, so that its main component is well reproduced, without the need to assume ad hoc primary sources for the synthesis of s elements up to A {approx} 130, contrary to suggestions from other works. The changes in the expected abundances that we find are primarily due to the following reasons. (1) Enhancing the neutron source increases the efficiency of the s process, so that the ensuing stellar yields now mimic the solar distribution at a metallicity higher than before ([Fe/H ] {approx}> -0.1). (2) The age-metallicity relation is rather flat for several Gyr in that metallicity regime, so that those conditions remain stable and the enhanced nuclear yields, which are necessary to maintain a solar-like abundance pattern, can dominate the composition of the interstellar medium from which subsequent stars are formed.

  18. Nucleophilic ring opening of bridging thietanes in open triosmium cluster complexes

    SciTech Connect

    Adams, R.D.; Belinski, J.A.

    1992-07-01

    The complexes Os{sub 3}(CO){sub 9}({mu}{sub 3}-S)[{mu}-SCH{sub 2}CMe{sub 2}CMe{sub 2}CH{sub 2}] (1) and Os{sub 3}(CO){sub 9}({mu}{sub 3}-S)[{mu}-SCH{sub 2}CH{sub 2}CH{sub 2}] (2) were obtained from the reactions of Os{sub 3}(CO){sub 10}({mu}{sub 3}-S) with 3,3-dimethylthietane (DMT) and thietane, respectively, at -42 {degree}C in the presence of Me{sub 3}NO. Compound 1 was characterized by a single-crystal X-ray diffraction analysis and was found to contain a DMT group bridging two of the nonbonded metal atoms in the open cluster of three metal atoms by using both lone pairs of electrons on the sulfur atom. Compound 1 reacted with bis(triphenylphosphine)nitrogen(1+) chloride ([PPN]Cl) at 25 {degrees}C to yield the salt [PPN][Os{sub 3}-(CO){sub 9}({mu}-SCH{sub 2}CMe{sub 2}CH{sub 2}Cl)({mu}{sub 3}-S)] (3; 76%), in which the chloride ion was added to one of the methylene groups of the DMT ring in a process that caused the ring to open by cleavage of one of the carbon-sulfur bonds. A 4-chloro-3,3-dimethylpropanethiolate ligand bridges the open edge of the anionic triosmium cluster. Compound 3 was converted to the neutral complex Os{sub 3}(CO){sub 9}[{mu}-SCH{sub 2}CMe{sub 2}CMe{sub 2}CH{sub 2}Cl]({mu}{sub 3}-S)({mu}-H) (4) by reaction with HCl at 25 {degrees}C. Compound 4 is structurally similar to 3, except that is contains a hydride ligand bridging one of the two metal-metal bonds. Compounds 1 and 2 react with HCl in CH{sub 2}Cl{sub 2} solvent to yield the neutral compounds 4 and Os{sub 3}(CO){sub 9}[{mu}-SCH{sub 2}CH{sub 2}CH{sub 2}Cl]({mu}{sub 3}-S)({mu}-H) (5) in 89% and 90% yields, respectively, in one step. 11 refs., 3 figs., 10 tabs.

  19. Open Clusters as Laboratories: The Angular Momentum Evolution of Young Stars

    NASA Technical Reports Server (NTRS)

    Stauffer, John R.

    1998-01-01

    The core group concentrated on three primary research topics: (1) ROSAT observation of the coronal activity of low mass stars in young open clusters; (2) the determination of stellar ages and the determination of the timescale for dissipation of circumstellar disks around young stars; and (3) the determination of rotation velocities of low mass stars in young open cluster and the inferred angular momentum evolution of low mass stars. With accurate ages for the clusters, we can then derive an independent estimate of the timescale for debris disks to dissipate. As the second half of that project, we are using the Caltech/UC/NASA Keck telescopes to obtain spectra of brown dwarf candidates in a number of nearby, young open clusters, from which we can determine new and accurate cluster ages. The final primary program that we have addressed was the determination of rotational velocities for low mass stars in our target open clusters. Our group has obtained rotational velocities for a large number of stars in several open clusters during this LTSA program, and we have published the results in several papers. One particularly time-consuming aspect of our program was the development of a database of the photometry and rotational velocities for nearby open clusters, which we have made available to the community.

  20. On the Survival of High-altitude Open Clusters within the Milky Way Galaxy Tides

    NASA Astrophysics Data System (ADS)

    Martinez-Medina, L. A.; Pichardo, B.; Peimbert, A.; Moreno, E.

    2017-01-01

    It is a common assumption that high-altitude open clusters live longer compared to clusters moving close to the Galactic plane. This is because, at high altitudes, open clusters are far from the disruptive effects of in-plane substructures, such as spiral arms, molecular clouds, and the bar. However, an important aspect to consider in this scenario is that orbits of high-altitude open clusters will eventually cross the Galactic plane, where the vertical tidal field of the disk is strong. In this work, we simulate the interaction of open clusters with the tidal field of a detailed Milky Way Galactic model at different average altitudes and galactocentric radii. We find that the life expectancy of clusters decreases as the maximum orbital altitude increases and reaches a minimum at altitudes of approximately 600 pc. Clusters near the Galactic plane live longer because they do not experience strong vertical tidal shocks from the Galactic disk; then, for orbital altitudes higher than 600 pc, clusters again start to live longer due to the decrease in the number of encounters with the disk. With our study, we find that the compressive nature of the tides in the arms region and the bar play an important role in the survival of small clusters by protecting them from disruption: clusters inside the arms can live up to twice as long as those outside the arms at similar galactocentric distances.

  1. The same frequency of planets inside and outside open clusters of stars.

    PubMed

    Meibom, Søren; Torres, Guillermo; Fressin, Francois; Latham, David W; Rowe, Jason F; Ciardi, David R; Bryson, Steven T; Rogers, Leslie A; Henze, Christopher E; Janes, Kenneth; Barnes, Sydney A; Marcy, Geoffrey W; Isaacson, Howard; Fischer, Debra A; Howell, Steve B; Horch, Elliott P; Jenkins, Jon M; Schuler, Simon C; Crepp, Justin

    2013-07-04

    Most stars and their planets form in open clusters. Over 95 per cent of such clusters have stellar densities too low (less than a hundred stars per cubic parsec) to withstand internal and external dynamical stresses and fall apart within a few hundred million years. Older open clusters have survived by virtue of being richer and denser in stars (1,000 to 10,000 per cubic parsec) when they formed. Such clusters represent a stellar environment very different from the birthplace of the Sun and other planet-hosting field stars. So far more than 800 planets have been found around Sun-like stars in the field. The field planets are usually the size of Neptune or smaller. In contrast, only four planets have been found orbiting stars in open clusters, all with masses similar to or greater than that of Jupiter. Here we report observations of the transits of two Sun-like stars by planets smaller than Neptune in the billion-year-old open cluster NGC6811. This demonstrates that small planets can form and survive in a dense cluster environment, and implies that the frequency and properties of planets in open clusters are consistent with those of planets around field stars in the Galaxy.

  2. OpenCluster: A Flexible Distributed Computing Framework for Astronomical Data Processing

    NASA Astrophysics Data System (ADS)

    Wei, Shoulin; Wang, Feng; Deng, Hui; Liu, Cuiyin; Dai, Wei; Liang, Bo; Mei, Ying; Shi, Congming; Liu, Yingbo; Wu, Jingping

    2017-02-01

    The volume of data generated by modern astronomical telescopes is extremely large and rapidly growing. However, current high-performance data processing architectures/frameworks are not well suited for astronomers because of their limitations and programming difficulties. In this paper, we therefore present OpenCluster, an open-source distributed computing framework to support rapidly developing high-performance processing pipelines of astronomical big data. We first detail the OpenCluster design principles and implementations and present the APIs facilitated by the framework. We then demonstrate a case in which OpenCluster is used to resolve complex data processing problems for developing a pipeline for the Mingantu Ultrawide Spectral Radioheliograph. Finally, we present our OpenCluster performance evaluation. Overall, OpenCluster provides not only high fault tolerance and simple programming interfaces, but also a flexible means of scaling up the number of interacting entities. OpenCluster thereby provides an easily integrated distributed computing framework for quickly developing a high-performance data processing system of astronomical telescopes and for significantly reducing software development expenses.

  3. 2MASS photometry and kinematical studies of open cluster NGC 188

    NASA Astrophysics Data System (ADS)

    Elsanhoury, W. H.; Haroon, A. A.; Chupina, N. V.; Vereshchagin, S. V.; Sariya, Devesh P.; Yadav, R. K. S.; Jiang, Ing-Guey

    2016-11-01

    In this paper, we present our results for the photometric and kinematical studies of old open cluster NGC 188. We determined various astrophysical parameters like limited radius, core and tidal radii, distance, luminosity and mass functions, total mass, relaxation time etc. for the cluster using 2MASS catalog. We obtained the cluster's distance from the Sun as 1721 ± 41 pc and log (age)= 9.85 ± 0.05 at Solar metallicity. The relaxation time of the cluster is smaller than the estimated cluster age which suggests that the cluster is dynamically relaxed. Our results agree with the values mentioned in the literature. We also determined the clusters apex coordinates as (281°.88, -44∘ .76) using AD-diagram method. Other kinematical parameters like space velocity components, cluster center and elements of Solar motion etc. have also been computed.

  4. The Shape Evolution of Galactic Open Clusters from Observations Under Galactic External Forces

    NASA Astrophysics Data System (ADS)

    Zhai, Meng; Abt, Helmut; Zhao, Gang; Li, Chengdong

    2017-02-01

    We present the Galactic characteristics of 154 open clusters using the stellar statistics method with data from the WEBDA database. We find that all clusters in our sample are elongated in shape, which indicates that the spherical clusters are stretched out to be ellipsoid as a function of age ({log}({age}/{year})=6.64{--}9.7). By dividing a cluster into a central core and an outer part, we have computed the apparent ellipticities of these two parts respectively. The scale relations between ellipticities and age indicate that the outer parts of open clusters become more elliptical while the central cores remain circular. We suppose that the outer parts become more elliptical because they are more subjected to the external forces, e.g., Galactic differential rotation, while the central cores form a circular shape under the domination of stellar dynamics. We have also performed an analysis of the crucial influence of cluster mass and location on its shape.

  5. Open clusters as laboratories: The angular momentum evolution of young stars

    NASA Technical Reports Server (NTRS)

    Stauffer, John R.

    1994-01-01

    This is the annual status report for the third year of our LTSA grant 'Open Clusters as Laboratories.' Because we have now had a few years to work on the project, we have started to produce and publish a large number of papers. We have been extremely successful in obtaining ROSAT observations of open clusters. With the demise of the PSPC on ROSAT, our main data source has come to an end and we will be able to concentrate on analyzing those data.

  6. Global survey of star clusters in the Milky Way. IV. 63 new open clusters detected by proper motions

    NASA Astrophysics Data System (ADS)

    Scholz, R.-D.; Kharchenko, N. V.; Piskunov, A. E.; Röser, S.; Schilbach, E.

    2015-09-01

    Context. The global Milky Way Star Clusters (MWSC) survey provided new cluster membership lists and mean cluster parameters for nearly 80% of all previously known Galactic clusters. The MWSC data reduction pipeline involved the catalogue of positions and proper motions (PPMXL) on the International Celestial Reference System (ICRS) and near-infrared photometry from the Two Micron All Sky Survey (2MASS). Aims: In the first extension to the MWSC, photometric filters were applied to the 2MASS catalogue to find new cluster candidates that were subsequently confirmed or rejected by the MWSC pipeline. To further extend the MWSC census, particularly of nearby clusters, we aimed at discovering new clusters by conducting an almost global search in proper motion catalogues as a starting point. Methods: We first selected high-quality samples from the PPMXL and the Fourth US Naval Observatory CCD Astrograph Catalog (UCAC4) for comparison and verification of the proper motions. For 441 circular proper motion bins (radius 15 mas/yr) within ±50 mas/yr, the sky outside a thin Galactic plane zone (| b | < 5°) was binned in small areas ("sky pixels") of 0.25 × 0.25 deg2. Sky pixels with enhanced numbers of stars with a certain common proper motion in both catalogues were considered as cluster candidates. After visual inspection of the sky images, we built an automated procedure that combined these representations of the sky for neighbouring proper motion subsamples after a background correction. The 692 compact cluster candidates detected above a threshold that was equivalent to a minimum of 12 to 130 cluster stars in dependence on the Galactic latitude were then cross-checked with known star clusters and clusters of galaxies. New candidates served as input for the MWSC pipeline. Results: About half of our candidates overlapped with known clusters (46 globular and 68 open clusters in the Galaxy, about 150 known clusters of galaxies) or the Magellanic Clouds. About 10% of our

  7. N-Body Numerical Simulations for Orbits of Old Open Clusters

    NASA Astrophysics Data System (ADS)

    Hsu, L.; Noriega-Crespo, A.; Friel, E. D.

    1996-12-01

    Analysis on age distributions of open clusters has shown that the average time it takes for a cluster to be completely disrupted is a few hundred million years. However, the ages of the old open clusters are on the order of one to ten billion years. The purpose of this project was to model the clusters as n-body systems and find relations between orbital kinematics and survivability. This work builds off of an earlier project which modeled the orbits using just a center of mass, or "one-body" model (1). Data were available for the complete orbital parameters of seven old open clusters. These seven, along with too purely theoretical open clusters were placed in the simulations. The clusters consisted of one hundred bodies (each of one solar mass) which were placed in a model galactic potential (2). Internal interactions were taken into account, but a relatively large softening parameter was used so that binary interactions would not dominate. The results show that there is a correlation between radial distance from the galactic center and survivability. For example, the cluster ngc6791 was found to contain approximately 55% of its original mass after one gyr. The closest radial approach for ngc6791 is 4.6 kpcs. However, ngc752, which has a distance of closest radial approach of 8.7 kpcs, retained 80% of its original mass. Model clusters were identical except for center of mass positions and velocities. These results support the observation that almost all old open clusters are found at large radial distances from the center of the galaxy (usually greater than 8kpcs). Currently, data analysis is still being carried out to find trends in mass loss verses time. [1] Finlay, Friel, Noriega-Crespo & Cudworth, 1995. [2] Allen & Santillan 1991, RevMxAA.

  8. The Open Cluster Chemical Abundances and Mapping (OCCAM) Survey: Overview and Membership Methods

    NASA Astrophysics Data System (ADS)

    Donor, John; Frinchaboy, Peter M.; O'Connell, Julia; Cunha, Katia M. L.; Thompson, Benjamin A.; Melendez, Matthew; Shetrone, Matthew D.; Majewski, Steven R.; Zasowski, Gail; Allende-Prieto, Carlos; Pinsonneault, Marc H.; Roman-Lopes, Alexandre; Schultheis, Mathias; Stassun, Keivan G.; Apogee Team

    2017-01-01

    The Open Cluster Chemical Analysis and Mapping (OCCAM) survey aims to produce a comprehensive, uniform, infrared-based data set for hundreds of open clusters, and constrain key Galactic dynamical and chemical parameters using the SDSS/APOGEE survey. We present the sample and methods being used by the survey to determine membership for the few-star sampling for most clusters as observed by the SDSS/APOGEE. We present verification of the membership method using the DR13 sample, and show an extension of the method by incorporation of proper motion and parallax data from the ESA Gaia mission.This work is supported by an NSF AAG grant AST-1311835.

  9. piRNA clusters and open chromatin structure

    PubMed Central

    2014-01-01

    Transposable elements (TEs) are major structural components of eukaryotic genomes; however, mobilization of TEs generally has negative effects on the host genome. To counteract this threat, host cells have evolved genetic and epigenetic mechanisms that keep TEs silenced. One such mechanism involves the Piwi-piRNA complex, which represses TEs in animal gonads either by cleaving TE transcripts in the cytoplasm or by directing specific chromatin modifications at TE loci in the nucleus. Most Piwi-interacting RNAs (piRNAs) are derived from genomic piRNA clusters. There has been remarkable progress in our understanding of the mechanisms underlying piRNA biogenesis. However, little is known about how a specific locus in the genome is converted into a piRNA-producing site. In this review, we will discuss a possible link between chromatin boundaries and piRNA cluster formation. PMID:25126116

  10. Lithium Abundances in the Young Open Cluster IC 2602

    NASA Technical Reports Server (NTRS)

    Randich, S.; Aharpour, N.; Pallavicini, R.; Prosser, C. F.; Stauffer, J. R.

    1997-01-01

    We have obtained high-resolution spectra for 28 candidate late-type stars in the 30 Myr old cluster IC 2602. NLTE Li abundances have been derived from measured equivalent widths. The log n(Li) - T(sub eff) and log n(Li) - mass distributions for our sample stars have been compared with those of the Pleiades and alpha Persei. Our data show that F stars in the three clusters have the same lithium content, which corresponds to the initial content for Pop. I stars. G and early-K IC 2602 stars are, on average, somewhat more Li-rich than their counterparts in the two slightly older clusters. Finally, the latest-type IC 2602 stars are heavily Li depleted, with their Li content being as low as the lowest measured among the Pleiades. As in the Pleiades and alpha Per, a star-to-star scatter in lithium is observed among 30 Myr old late-K/early-K dwarfs in IC 2602, indicating that this spread develops in the pre-main sequence phases.

  11. Reddening and age for 13 southern Galactic open clusters determined from integrated spectra

    NASA Astrophysics Data System (ADS)

    Ahumada, A. V.; Clariá, J. J.; Bica, E.; Dutra, C. M.; Torres, M. C.

    2001-10-01

    In this study we present flux-calibrated integrated spectra in the range 3800-6800 Å for 13 concentrated open clusters with Galactic longitudes between 219deg and 316deg, nine of which have not been previously studied. Using the equivalent widths of the Balmer lines and comparing the cluster spectra with template spectra of Magellanic Clouds and Galactic star clusters with known parameters, we derive both foreground interstellar reddening values and age. For nine clusters these two parameters have been determined for the first time, while for the rest of the sample the results show good agreement with previous studies. The present analysis indicates four very young (Hogg 11, NGC 5606, vdB-RN 80 and Pismis 17), seven moderately young (ESO 429-SC13, Hogg 3, Hogg 12, Haffner 7, BH 87, NGC 2368 and Bochum 12) and two intermediate-age (Berkeley 75 and NGC 2635) open clusters. The derived foreground interstellar reddening values are in the range 0.00 <= E(B-V) <= 0.38. The age and reddening distributions of the present sample of relatively faint open clusters match those of open clusters with known parameters in a 90deg sector centered at l = 270deg. Based on observations made at Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba and San Juan, Argentina.

  12. Hogg 12 and NGC 3590: A New Open Cluster Binary System Candidate

    NASA Astrophysics Data System (ADS)

    Piatti, Andrés E.; Clariá, Juan J.; Ahumada, Andrea V.

    2010-05-01

    We have obtained CCD UBVIKC photometry down to V ∼ 22.0 for the open clusters Hogg 12 and NGC 3590 and the fields surrounding them. Based on photometric and morphological criteria, as well as on the stellar density in the region, our evidence is sufficient to confirm that Hogg 12 is a genuine open cluster. NGC 3590 was used as a control cluster. The color-magnitude diagrams of Hogg 12, cleaned from field star contamination, reveal that this is a solar metal content cluster, affected by E(B - V) = 0.40 ± 0.05, located at a heliocentric distance d = 2.0 ± 0.5 kpc, and of an age similar to that of NGC 3590 (t = 30 Myr). Both clusters are surprisingly small objects whose radii are barely ∼1 pc, andthey are separated in the sky by scarcely 3.6 pc. These facts, added to their similar ages, reddenings, and metallicities, allow us to consider them a new open cluster binary system candidate. Of the ∼180 open cluster binary systems estimated to exist in the Galaxy, of which 27 are actually well known, Hogg 12 and NGC 3590 appear to be one of the two closest pairs.

  13. ON THE ORIGIN OF HIGH-ALTITUDE OPEN CLUSTERS IN THE MILKY WAY

    SciTech Connect

    Martinez-Medina, L. A.; Pichardo, B.; Moreno, E.; Peimbert, A.; Velazquez, H.

    2016-01-20

    We present a dynamical study of the effect of the bar and spiral arms on the simulated orbits of open clusters in the Galaxy. Specifically, this work is devoted to the puzzling presence of high-altitude open clusters in the Galaxy. For this purpose we employ a very detailed observationally motivated potential model for the Milky Way and a careful set of initial conditions representing the newly born open clusters in the thin disk. We find that the spiral arms are able to raise an important percentage of open clusters (about one-sixth of the total employed in our simulations, depending on the structural parameters of the arms) above the Galactic plane to heights beyond 200 pc, producing a bulge-shaped structure toward the center of the Galaxy. Contrary to what was expected, the spiral arms produce a much greater vertical effect on the clusters than the bar, both in quantity and height; this is due to the sharper concentration of the mass on the spiral arms, when compared to the bar. When a bar and spiral arms are included, spiral arms are still capable of raising an important percentage of the simulated open clusters through chaotic diffusion (as tested from classification analysis of the resultant high-z orbits), but the bar seems to restrain them, diminishing the elevation above the plane by a factor of about two.

  14. The Open Cluster Chemical Abundances and Mapping (OCCAM) Survey: Optical Extension for Neutron Capture Elements

    NASA Astrophysics Data System (ADS)

    Melendez, Matthew; O'Connell, Julia; Frinchaboy, Peter M.; Donor, John; Cunha, Katia M. L.; Shetrone, Matthew D.; Majewski, Steven R.; Zasowski, Gail; Pinsonneault, Marc H.; Roman-Lopes, Alexandre; Stassun, Keivan G.; APOGEE Team

    2017-01-01

    The Open Cluster Chemical Abundance & Mapping (OCCAM) survey is a systematic survey of Galactic open clusters using data primarily from the SDSS-III/APOGEE-1 survey. However, neutron capture elements are very limited in the IR region covered by APOGEE. In an effort to fully study detailed Galactic chemical evolution, we are conducting a high resolution (R~60,000) spectroscopic abundance analysis of neutron capture elements for OCCAM clusters in the optical regime to complement the APOGEE results. As part of this effort, we present Ba II, La II, Ce II and Eu II results for a few open clusters without previous abundance measurements using data obtained at McDonald Observatory with the 2.1m Otto Struve telescope and Sandiford Echelle Spectrograph.This work is supported by an NSF AAG grant AST-1311835.

  15. A DEEP UBVRI CCD PHOTOMETRY OF SIX OPEN STAR CLUSTERS IN THE GALACTIC ANTICENTER REGION

    SciTech Connect

    Lata, Sneh; Pandey, Anil K.; Kumar, Brijesh; Bhatt, Himali; Pace, Giancarlo; Sharma, Saurabh

    2010-02-15

    We present deep UBVRI CCD photometry of six open star clusters situated in the Galactic anticenter region (l{approx} 120-200 deg.). The sample includes three unstudied (Be 6, Be 77, King 17) and three partly studied open clusters (Be 9, NGC 2186, and NGC 2304). The fundamental parameters have been determined by comparing color-color and color-magnitude diagrams with the theoretical models. The structural parameters and morphology of the clusters were discussed on the basis of radial density profiles and isodensity contours, respectively. The isodensity contours show that all the clusters have asymmetric shapes. An investigation of structural parameters indicates that the evolution of core and corona of the clusters is mainly controlled by internal relaxation processes.

  16. The Initial Mass Function of Young Open Clusters in the Galaxy: A Preliminary Result

    NASA Astrophysics Data System (ADS)

    Lim, Beomdu; Sung, Hwankyung; Hur, Hyeonoh; Park, Byeong-Gon

    2017-03-01

    The initial mass function (IMF) is an essential tool with which to study star formation processes. We have initiated the photometric survey of young open clusters in the Galaxy, from which the stellar IMFs are obtained in a homogeneous way. A total of 16 famous young open clusters have preferentially been studied up to now. These clusters have a wide range of surface densities (log σ = -1 to 3 [stars pc-2] for stars with mass larger than 5M ⊙) and cluster masses (M cl = 165 to 50, 000M ⊙), and also are distributed in five different spiral arms in the Galaxy. It is possible to test the dependence of star formation processes on the global properties of individual clusters or environmental conditions. We present a preliminary result on the variation of the IMF in this paper.

  17. S-P coupling induced unusual open-shell metal clusters.

    PubMed

    Cheng, Shi-Bo; Berkdemir, Cuneyt; Melko, Joshua J; Castleman, A W

    2014-04-02

    Metal clusters featuring closed supershells or aromatic character usually exhibit remarkably enhanced stability in their cluster series. However, not all stable clusters are subject to these fundamental constraints. Here, by employing photoelectron imaging spectroscopy and ab initio calculations, we present experimental and theoretical evidence on the existence of unexpectedly stable open-shell clusters, which are more stable than their closed-shell and aromatic counterparts. The stabilization of these open-shell Al-Mg clusters is proposed to originate from the S-P molecular orbital coupling, leading to highly stable species with increased HOMO-LUMO gaps, akin to s-p hybridization in an organic carbon atom that is beneficial to form stable species. Introduction of the coupling effect highlighted here not only shows the limitations of the conventional closed-shell model and aromaticity but also provides the possibility to design valuable building blocks.

  18. Experiences using OpenMP based on Computer Directed Software DSM on a PC Cluster

    NASA Technical Reports Server (NTRS)

    Hess, Matthias; Jost, Gabriele; Mueller, Matthias; Ruehle, Roland

    2003-01-01

    In this work we report on our experiences running OpenMP programs on a commodity cluster of PCs running a software distributed shared memory (DSM) system. We describe our test environment and report on the performance of a subset of the NAS Parallel Benchmarks that have been automaticaly parallelized for OpenMP. We compare the performance of the OpenMP implementations with that of their message passing counterparts and discuss performance differences.

  19. Experiences Using OpenMP Based on Compiler Directed Software DSM on a PC Cluster

    NASA Technical Reports Server (NTRS)

    Hess, Matthias; Jost, Gabriele; Mueller, Matthias; Ruehle, Roland; Biegel, Bryan (Technical Monitor)

    2002-01-01

    In this work we report on our experiences running OpenMP (message passing) programs on a commodity cluster of PCs (personal computers) running a software distributed shared memory (DSM) system. We describe our test environment and report on the performance of a subset of the NAS (NASA Advanced Supercomputing) Parallel Benchmarks that have been automatically parallelized for OpenMP. We compare the performance of the OpenMP implementations with that of their message passing counterparts and discuss performance differences.

  20. γ-ray production in young open clusters: Berk 87, Cyg OB2 and Westerlund 2

    NASA Astrophysics Data System (ADS)

    Bednarek, W.

    2007-11-01

    Young open clusters are sites of cosmic ray acceleration as indicated by recent detections of the TeV γ-ray sources in the directions of two open clusters (Cyg OB2 and Westerlund 2). In fact, up to now a few different scenarios for acceleration of particles inside open clusters have been considered, i.e. shocks in massive star winds, pulsars and their nebulae, supernova shocks, massive compact binaries. Here we consider in detail the radiation processes due to both electrons and hadrons accelerated inside the open cluster. As a specific scenario, we apply the acceleration process at the shocks arising in the winds of Wolf-Rayet (WR) type stars. Particles diffuse through the medium of the open cluster during the activity time of the acceleration scenario defined by the age of the WR star. They interact with the matter and radiation, at first inside the open cluster and, later in the dense surrounding clouds. We calculate the broad-band spectrum in different processes for three exemplary open clusters (Berk 87, Cyg OB2, Westerlund 2) for which the best observational constraints on the spectra are at present available. It is assumed that the high-energy phenomena, observed from the X-ray up to the GeV-TeV γ-ray energies, are related to each other. We conclude that the most likely description of the radiation processes in these objects is achieved in the hybrid (leptonic-hadronic) model in which leptons are responsible for the observed X-ray and GeV γ-ray emission and hadrons are responsible for the TeV γ-ray emission.

  1. A Chandra X-ray census of the interacting binaries in old open clusters - NGC 188

    NASA Astrophysics Data System (ADS)

    Vats, Smriti; Van Den Berg, Maureen

    2017-01-01

    We present a new X-ray study of NGC 188, one of the oldest open clusters known in the Milky Way (7 Gyr). Our X-ray observation using the Chandra X-ray Observatory is aimed at uncovering the population of close interacting binaries in the cluster. We detect 84 X-ray sources with a limiting X-ray luminosity, LX ~ 4×1029 erg s-1 (0.3-7 keV), of which 28 are within the half-mass radius. Of these, 13 are proper-motion or radial-velocity cluster members, wherein we identify a mix of active binaries (ABs) and blue straggler stars (BSSs). We also identify one tentative cataclysmic variable (CV) candidate which is a known short-period photometric variable, but whose membership to NGC 188 is unknown. We have compared the X-ray luminosity per unit of cluster mass (i.e. the X-ray emissivity) of NGC 188 with those of other old Galactic open clusters and dense globular clusters (47 Tuc, NGC 6397). Our findings confirm the earlier result that old open clusters have higher X-ray emissivities than the globular clusters (LX ≥1×1030 erg s-1). This may be explained by dynamical encounters in globulars, which could have a net effect of destroying binaries, or the typically higher metallicities of open clusters. We find one intriguing X-ray source in NGC 188 that is a BSS and cluster member, whose X-ray luminosity cannot be explained by its currently understood binary configuration. Its X-ray detection invokes the need for a third companion in the system.

  2. Massive open star clusters using the VVV survey. V. Young clusters with an OB stellar population

    NASA Astrophysics Data System (ADS)

    Ramírez Alegría, S.; Borissova, J.; Chené, A.-N.; Bonatto, C.; Kurtev, R.; Amigo, P.; Kuhn, M.; Gromadzki, M.; Carballo-Bello, J. A.

    2016-04-01

    Context. The ESO public survey VISTA Variables in the Vía Láctea (VVV) has contributed with deep multi-epoch photometry of the Galactic bulge and the adjacent part of the disk over 526 sq. deg. More than a hundred cluster candidates have been reported thanks to this survey. Aims: We present the fifth article in a series of papers focused on young and massive clusters discovered in the VVV survey. In this paper, we present the physical characterization of five clusters with a spectroscopically confirmed OB-type stellar population. Methods: To characterize the clusters, we used near-infrared photometry (J, H, and KS) from the VVV survey and near-infrared K-band spectroscopy from ISAAC at VLT, following the methodology presented in the previous articles of the series. Results: All clusters in our sample are very young (ages between 1-20 Myr), and their total mass are between (1.07+0.40-0.30)×102 M⊙ and (4.17+4.15-2.08)×103 M⊙. We observed a relation between the clusters total mass Mecl and the mass of their most massive stellar member mmax, for clusters with an age <10 Myr. Based on observations taken within the ESO VISTA Public Survey VVV (programme ID 179.B-2002), and with ISAAC/VLT (programme 087.D-0341(A)).

  3. Investigation of open clusters based on IPHAS and APASS survey data

    NASA Astrophysics Data System (ADS)

    Dambis, A. K.; Glushkova, E. V.; Berdnikov, L. N.; Joshi, Y. C.; Pandey, A. K.

    2017-02-01

    We adapt the classical Q-method based on a reddening-free parameter constructed from three passband magnitudes to the filter set of Isaac Newton Telescope Photometric Hα Survey and combine it with the maximum-likelihood-based cluster parameter estimator by Naylor & Jeffries (2006) to determine the extinction, heliocentric distances, and ages of young open clusters using Hαri data. The method is also adapted for the case of significant variations of extinction across the cluster field. Our technique is validated by comparing the colour excesses, distances, and ages determined in this study with the most bona fide values reported for the 18 well-studied young open clusters in the past and a fairly good agreement is found between our extinction and distance estimates and earlier published results, although our age estimates are not very consistent with those published by other authors. We also show that individual extinction values can be determined rather accurately for stars with (r - i) > 0.1. Our results open up a prospect for determining a uniform set of parameters for northern clusters based on homogeneous photometric data, and for searching for new, hitherto undiscovered open clusters.

  4. Chemical abundance gradients from open clusters in the Milky Way disk: Results from the APOGEE survey

    NASA Astrophysics Data System (ADS)

    Cunha, K.; Frinchaboy, P. M.; Souto, D.; Thompson, B.; Zasowski, G.; Allende Prieto, C.; Carrera, R.; Chiappini, C.; Donor, J.; García-Hernández, D. A.; García Pérez, A. E.; Hayden, M. R.; Holtzman, J.; Jackson, K. M.; Johnson, J. A.; Majewski, S. R.; Mészáros, S.; Meyer, B.; Nidever, D. L.; O'Connell, J.; Schiavon, R. P.; Schultheis, M.; Shetrone, M.; Simmons, A.; Smith, V. V.; et al.

    2016-09-01

    Metallicity gradients provide strong constraints for understanding the chemical evolution of the Galaxy. We report on radial abundance gradients of Fe, Ni, Ca, Si, and Mg obtained from a sample of 304 red-giant members of 29 disk open clusters, mostly concentrated at galactocentric distances between ˜ 8-15 kpc, but including two open clusters in the outer disk. The observations are from the APOGEE survey. The chemical abundances were derived automatically by the ASPCAP pipeline and these are part of the SDSS III Data Release 12. The gradients, obtained from least squares fits to the data, are relatively flat, with slopes ranging from -0.026 to -0.033 dex kpc-1 for the α-elements [O/H], [Ca/H], [Si/H], and [Mg/H], and -0.035 dex kpc-1 and -0.040 dex kpc-1 for [Fe/H] and [Ni/H], respectively. Our results are not at odds with the possibility that metallicity ([Fe/H]) gradients are steeper in the inner disk ({R_GC˜ 7}-12 kpc) and flatter towards the outer disk. The open cluster sample studied spans a significant range in age. When breaking the sample into age bins, there is some indication that the younger open cluster population in our sample (log age < 8.7) has a flatter metallicity gradient when compared with the gradients obtained from older open clusters.

  5. WIYN Open Cluster Study. LXXII. A uvbyCaHβ CCD Analysis of the Metal-deficient Open Cluster NGC 2506

    NASA Astrophysics Data System (ADS)

    Anthony-Twarog, Barbara J.; Deliyannis, Constantine P.; Twarog, Bruce A.

    2016-12-01

    Precision uvbyCaHβ photometry of the metal-deficient, old open cluster NGC 2506 is presented. The survey covers an area of 20\\prime × 20\\prime and extends to V˜ 18 for b - y and Hβ and to V˜ 17.0 for c 1 and hk. For V brighter than 16.0, photometric scatter among the indices leads to the recovery of six known variables within the cluster core and five new variables in the outer 5\\prime of the survey field. Proper motions, radial velocities, and precise multicolor indices are used to isolate a highly probable sample of cluster members from the very rich color-magnitude diagram. From 257 highly probable members at the cluster turnoff, we derive a reddening estimate of E(b-y)=0.042+/- 0.001 (E(B-V)=0.058+/- 0.001), where the errors refer to the internal standard errors of the mean. [Fe/H] is derived from the A/F dwarf members using both m 1 and hk, leading to [Fe/H] = -0.296 ± 0.011 (sem) and -0.317 ± 0.004 (sem), respectively. The weighted average, heavily dominated by hk, is [Fe/H] = -0.316 ± 0.033. Based on red giant members, we place an upper limit of ±0.010 on the variation in the reddening across the face of the cluster. We also identify two dozen potential red giant cluster members outside the cluster core. Victoria-Regina isochrones on the Strömgren system produce an excellent match to the cluster for an apparent modulus of (m-M)=12.75+/- 0.1 and an age of 1.85 ± 0.05 Gyr.

  6. CCD UBV photometry and kinematics of the open cluster NGC 225

    NASA Astrophysics Data System (ADS)

    Bilir, Selçuk; Bostancı, Z. Funda; Yontan, Talar; Güver, Tolga; Bakış, Volkan; Ak, Tansel; Ak, Serap; Paunzen, Ernst; Eker, Zeki

    2016-11-01

    We present the results of CCD UBV photometric and spectroscopic observations of the open cluster NGC 225. In order to determine the structural parameters of NGC 225, we calculated the stellar density profile in the cluster's field. We estimated the probabilities of the stars being physical members of the cluster using the existing astrometric data. The most likely members of the cluster were used in the determination of the astrophysical parameters of the cluster. We calculated the mean radial velocity of the cluster as Vr = - 8.3 ± 5.0 km s-1 from the optical spectra of eight stars in the cluster's field. Using the U - B vs B - V two-colour diagram and UV excesses of the F-G type main-sequence stars, the reddening and metallicity of NGC 225 were inferred as E (B - V) = 0.151 ± 0.047 mag and [Fe /H ] = - 0.11 ± 0.01 dex, respectively. We fitted the colour-magnitude diagrams of NGC 225 with the PARSEC isochrones and derived the distance modulus, distance and age of the cluster as μV = 9.3 ± 0.07 mag, d = 585 ± 20 pc and t = 900 ± 100 Myr, respectively. We also estimated the galactic orbital parameters and space velocity components of the cluster and found that the cluster has a slightly eccentric orbit of e = 0.07 ± 0.01 and an orbital period of Porb = 255 ± 5 Myr.

  7. Two 'b's in the Beehive: The Discovery of the First Hot Jupiters in an Open Cluster

    NASA Astrophysics Data System (ADS)

    Latham, David W.; Quinn, S. N.; White, R. J.

    2012-10-01

    We report the discovery of two giant planets orbiting stars in Praesepe (also known as the Beehive Cluster), the first known hot Jupiters in an open cluster. Pr0201b orbits a V=10.52 late F dwarf with a period of 4.4264 days and has a minimum mass of 0.540 Mjup, while Pr0211b orbits a V=12.06 late G dwarf with a period of 2.1451 days and has a minimum mass of 1.844 Mjup. Because they reside in a cluster, the ages of these planets are amongst the best-determined of any planet outside our own solar system. As we endeavor to learn more about the frequency and characteristics of planets, the environment in which most stars form -- open clusters like Praesepe -- may provide essential clues.

  8. The Palomar-Las Campanas Observatory-NOAO (PLCON) Open Cluster Survey

    NASA Astrophysics Data System (ADS)

    Phelps, R. L.; Tollefson, J.; Reafsnyder, S.; Frinchaboy, P.; Craig, Aidan; Postlethwaite, J.; Marshall, T.

    2000-12-01

    The Palomar-Las Campanas Observatory-NOAO (PLCON) Open Cluster Survey is a long-term survey intended to provide CCD derived, VI color-magnitude diagrams for the majority of the Milky Way's open clusters, most of which have been poorly studied in the past, or never studied at all. From these data, systematic estimates of cluster reddenings, distances and ages can be derived using a limited number of telescopes, CCDs and filter sets. These data will be useful for systematic studies of Galactic structure in the disk, the properties of unique/interesting stars within clusters, stellar evolution theory, and a host of other timely astrophysical questions. This paper will report on recent results from the Survey. This work is supported, in part, by grants from the National Science Foundation and the California State University, Sacramento Research and Creative Activity Awards Program.

  9. Neutron Capture Elements in the Open Cluster Chemical Abundance & Mapping (OCCAM) Survey

    NASA Astrophysics Data System (ADS)

    O'Connell, Julia; Frinchaboy, Peter M.; Shetrone, Matthew D.; Hearty, Fred R.; Majewski, Steven R.; Zasowski, Gail; Sdss /Apogee-1, III

    2015-01-01

    The Open Cluster Chemical Abundance & Mapping (OCCAM) survey is a systematic survey of Galactic open clusters using data primarily from the SDSS-III/APOGEE-1 survey. The high-resolution (R=22,500), near-infrared (H-band) APOGEE-1 survey allows for cluster membership probability determination and analysis of light and iron-peak elements. Neutron capture elements, however, prove to be elusive in the IR region covered by APOGEE. In an effort to fully study detailed Galactic chemical evolution, we conducted a high resolution (R~60,000) spectroscopic abundance analysis of neutron capture elements for OCCAM clusters in the optical regime to complement the APOGEE results. We present results based on prominent resonance lines for Eu, La, Ba, and Ce in the ~5400-6750 AA range using data obtained at McDonald Observatory with the 2.1m Otto Struve telescope and Sandiford Echelle Spectrograph.

  10. Photometry Using Kepler "Superstamps" of Open Clusters NGC 6791 & NGC 6819

    NASA Astrophysics Data System (ADS)

    Kuehn, Charles A.; Drury, Jason A.; Bellamy, Beau R.; Stello, Dennis; Bedding, Timothy R.; Reed, Mike; Quick, Breanna

    2015-09-01

    The Kepler space telescope has proven to be a gold mine for the study of variable stars. Usually, Kepler only reads out a handful of pixels around each pre-selected target star, omitting a large number of stars in the Kepler field. Fortunately, for the open clusters NGC 6791 and NGC 6819, Kepler also read out larger "superstamps" which contained complete images of the central region of each cluster. These cluster images can be used to study additional stars in the open clusters that were not originally on Kepler's target list. We discuss our work on using two photometric techniques to analyze these superstamps and present sample results from this project to demonstrate the value of this technique for a wide variety of variable stars.

  11. On the subject of the Ba overabundance in the open clusters stars

    NASA Astrophysics Data System (ADS)

    Mishenina, T. V.; Korotin, S. A.; Carraro, G.; Kovtyukh, V. V.; Yegorova, I. A.

    2016-01-01

    For eight distant open clusters, namely Ruprecht 4, Ruprecht 7, Berkeley 25, Berkeley 73, Berkeley 75, NGC 6192, NGC 6404, and NGC 6583, we determined the yttrium and barium abundances using the UVES, VLT spectra (ESO, Chile). The stars of one young cluster (Ruprecht 7) demonstrate significant barium overabundance(∼0.55 dex) that can not be due to the determination error. We have considered the Ba abundance determination errors due to LTE approach, saturation of the lines, synthetic and observed barium line fitting, and the causes of the Ba overabundance associated with the Galactic disc enrichment or the origin of open clusters. Possible explanation for this overabundance can be the origin of n-capture elements enrichment of the clusters (galactic or extragalactic) or additional sources of the Ba production.

  12. CCD photometry of Andromeda IV - Dwarf irregular galaxy or M31 open cluster?

    NASA Technical Reports Server (NTRS)

    Jones, Joseph H.

    1993-01-01

    CCD photometry of Andromeda IV was obtained during discretionary time in August of 1989 at the Canada-France-Hawaii Telescope on Mauna Kea and the data were reduced at CFHT during the summer of 1991. And IV has been catalogued both as a dwarf galaxy and as an open star cluster in M31. The color-magnitude diagrams presented indicate that this object has a young population of stars with a narrow age range, consistent with the characteristics of an open star cluster or stellar association. A radial velocity measurement taken from the literature and analyzed with respect to the rotation curve of M31 indicates this object resides in the disk of the Andromeda Galaxy, strengthening the conclusion that it is indeed a very large open star cluster or a densely populated stellar association rather than a dwarf irregular galaxy.

  13. Open-Source Sequence Clustering Methods Improve the State Of the Art.

    PubMed

    Kopylova, Evguenia; Navas-Molina, Jose A; Mercier, Céline; Xu, Zhenjiang Zech; Mahé, Frédéric; He, Yan; Zhou, Hong-Wei; Rognes, Torbjørn; Caporaso, J Gregory; Knight, Rob

    2016-01-01

    Sequence clustering is a common early step in amplicon-based microbial community analysis, when raw sequencing reads are clustered into operational taxonomic units (OTUs) to reduce the run time of subsequent analysis steps. Here, we evaluated the performance of recently released state-of-the-art open-source clustering software products, namely, OTUCLUST, Swarm, SUMACLUST, and SortMeRNA, against current principal options (UCLUST and USEARCH) in QIIME, hierarchical clustering methods in mothur, and USEARCH's most recent clustering algorithm, UPARSE. All the latest open-source tools showed promising results, reporting up to 60% fewer spurious OTUs than UCLUST, indicating that the underlying clustering algorithm can vastly reduce the number of these derived OTUs. Furthermore, we observed that stringent quality filtering, such as is done in UPARSE, can cause a significant underestimation of species abundance and diversity, leading to incorrect biological results. Swarm, SUMACLUST, and SortMeRNA have been included in the QIIME 1.9.0 release. IMPORTANCE Massive collections of next-generation sequencing data call for fast, accurate, and easily accessible bioinformatics algorithms to perform sequence clustering. A comprehensive benchmark is presented, including open-source tools and the popular USEARCH suite. Simulated, mock, and environmental communities were used to analyze sensitivity, selectivity, species diversity (alpha and beta), and taxonomic composition. The results demonstrate that recent clustering algorithms can significantly improve accuracy and preserve estimated diversity without the application of aggressive filtering. Moreover, these tools are all open source, apply multiple levels of multithreading, and scale to the demands of modern next-generation sequencing data, which is essential for the analysis of massive multidisciplinary studies such as the Earth Microbiome Project (EMP) (J. A. Gilbert, J. K. Jansson, and R. Knight, BMC Biol 12:69, 2014, http

  14. TWO 'b's IN THE BEEHIVE: THE DISCOVERY OF THE FIRST HOT JUPITERS IN AN OPEN CLUSTER

    SciTech Connect

    Quinn, Samuel N.; White, Russel J.; Cantrell, Justin R.; Latham, David W.; Furesz, Gabor; Szentgyorgyi, Andrew H.; Geary, John C.; Torres, Guillermo; Bieryla, Allyson; Berlind, Perry; Calkins, Michael C.; Esquerdo, Gilbert A.; Stefanik, Robert P.; Buchhave, Lars A.; Dahm, Scott E.

    2012-09-10

    We report the discovery of two giant planets orbiting stars in Praesepe (also known as the Beehive Cluster). These are the first known hot Jupiters in an open cluster and the only planets known to orbit Sun-like, main-sequence stars in a cluster. The planets are detected from Doppler-shifted radial velocities; line bisector spans and activity indices show no correlation with orbital phase, confirming the variations are caused by planetary companions. Pr0201b orbits a V = 10.52 late F dwarf with a period of 4.4264 {+-} 0.0070 days and has a minimum mass of 0.540 {+-} 0.039 M{sub Jup}, and Pr0211b orbits a V = 12.06 late G dwarf with a period of 2.1451 {+-} 0.0012 days and has a minimum mass of 1.844 {+-} 0.064 M{sub Jup}. The detection of two planets among 53 single members surveyed establishes a lower limit of 3.8{sup +5.0}{sub -2.4}% on the hot Jupiter frequency in this metal-rich open cluster. Given the precisely known age of the cluster, this discovery also demonstrates that, in at least two cases, giant planet migration occurred within 600 Myr after formation. As we endeavor to learn more about the frequency and formation history of planets, environments with well-determined properties-such as open clusters like Praesepe-may provide essential clues to this end.

  15. Blue straggler stars in Galactic open clusters and the effect of field star contamination

    NASA Astrophysics Data System (ADS)

    Carraro, G.; Vázquez, R. A.; Moitinho, A.

    2008-05-01

    Context: We investigate the distribution of blue straggler stars in the field of three open star clusters. Aims: The main purpose is to highlight the crucial role played by general Galactic disk fore-/back-ground field stars, which are often located in the same region of the color magnitude diagram as blue straggler stars. Methods: We analyze photometry taken from the literature of 3 open clusters of intermediate/old age rich in blue straggler stars, which are projected in the direction of the Perseus arm, and study their spatial distribution and the color magnitude diagram. Results: As expected, we find that a large portion of the blue straggler population in these clusters are simply young field stars belonging to the spiral arm. This result has important consequences on the theories of the formation and statistics of blue straggler stars in different population environments: open clusters, globular clusters, or dwarf galaxies. Conclusions: As previously emphasized by many authors, a detailed membership analysis is mandatory before comparing the blue straggler population in star clusters to theoretical models. Moreover, these sequences of young field stars (blue plumes) are potentially powerful tracers of Galactic structure and they require further consideration.

  16. CCD UBV(RI)C and 2MASS photometry of seven open clusters

    NASA Astrophysics Data System (ADS)

    Akkaya Oralhan, {İ.; Michel, R.

    Fundamental astrophysical parameters have been derived for Be 45, Be 55, Di 07, Feib 01, Ki 02, NGC 457 and NGC 1548 open clusters (OCs) using CCD U BV (RI)_C photometric data and PPMXL database. CCD U BV (RI)_C photometric data observed with the 84 cm telescope at the San Pedro Mártir National Astronomical Observatory (SPMO), México. The cluster members and field stars in the cluster regions have separated through their Proper Motion (PM) vector point diagrams. We have used JH{Ks} photometry of 2MASS data taken from PPMXL catalogue to have stellar Radial Density Profile (RDP) and determine limit radius of these seven clusters. Five different Color-Magnitude diagrams ane one color-color diagram have been used together with Padova isochrones and intrinsic-colour calibrations to obtain reddenings, metallicities, distance moduli, and ages for these seven clusters.

  17. White Dwarfs in the Metal-Rich Open Cluster NGC 6253

    NASA Astrophysics Data System (ADS)

    Jeffery, E. J.; Campos, F.; Romero, A.; Kepler, S. O.

    2017-03-01

    We have obtained 53 images with the g filter and 19 images with the i filter, each with 600-second exposures of the super metal rich open cluster NGC 6253 with the Gemini-South telescope to create deep images of the cluster to observe the cluster white dwarfs for the first time. We will analyze the white dwarf luminosity function to measure the cluster's white dwarf age, search for any anomalous features (as has been seen in the similarly metal rich cluster NGC 6791), and constrain the initial-final mass relation at high metallicities. We present an update on these observations and our program to study the formation of white dwarfs in super high metallicity environments.

  18. A comprehensive photometric study of dynamically evolved small van den Bergh-Hagen open clusters

    NASA Astrophysics Data System (ADS)

    Piatti, Andrés E.

    2016-12-01

    We present results from Johnson UBV, Kron-Cousins RI and Washington CT1T2 photometries for seven van den Bergh-Hagen (vdBH) open clusters, namely, vdBH 1, 10, 31, 72, 87, 92, and 118. The high-quality, multiband photometric data sets were used to trace the cluster stellar density radial profiles and to build colour-magnitude diagrams and colour-colour diagrams from which we estimated their structural parameters and fundamental astrophysical properties. The clusters in our sample cover a wide age range, from ˜60 Myr up to 2.8 Gyr, are of relatively small size (˜1-6 pc) and are placed at distances from the Sun which vary between 1.8 and 6.3 kpc, respectively. We also estimated lower limits for the cluster present-day masses as well as half-mass relaxation times (tr). The resulting values in combination with the structural parameter values suggest that the studied clusters are in advanced stages of their internal dynamical evolution (age/tr ˜ 20-320), possibly in the typical phase of those tidally filled with mass segregation in their core regions. Compared to open clusters in the solar neighbourhood, the seven vdBH clusters are within more massive (˜80-380 M⊙), with higher concentration parameter values (c ˜ 0.75-1.15) and dynamically evolved ones.

  19. The Open Cluster Chemical Abundances and Mapping (OCCAM) Survey: Galactic Gradients using SDSS-IV/DR13 and Gaia

    NASA Astrophysics Data System (ADS)

    Frinchaboy, Peter M.; Donor, John; O'Connell, Julia; Cunha, Katia M. L.; Thompson, Benjamin A.; Melendez, Matthew; Shetrone, Matthew D.; Majewski, Steven R.; Zasowski, Gail; Allende-Prieto, Carlos; Carrera, Ricardo; García Pérez, Ana; Hayden, Michael R.; Hearty, Fred R.; Holtzman, Jon A.; Johnson, Jennifer; Meszaros, Szabolcs; Nidever, David L.; Pinsonneault, Marc H.; Roman-Lopes, Alexandre; Schiavon, Ricardo P.; Schultheis, Mathias; Smith, Verne V.; Sobeck, Jennifer; Stassun, Keivan G.; APOGEE Team

    2017-01-01

    The Open Cluster Chemical Analysis and Mapping (OCCAM) survey aims to produce a comprehensive, uniform, infrared-based data set forhundreds of open clusters, and constrain key Galactic dynamical and chemical parameters using the SDSS/APOGEE survey. We report on multi-element radial abundance gradients obtained from a sample of over 30 disk open clusters. The chemical abundances were derived automatically by the ASPCAP pipeline and these are part of the SDSS IV Data Release 13. The open cluster sample studied spans a significant range in age allowing exploration of the evolution of the Galactic abundance gradient.This work is supported by an NSF AAG grant AST-1311835.

  20. OPEN CLUSTERS IN THE MILKY WAY OUTER DISK: NEWLY DISCOVERED AND UNSTUDIED CLUSTERS IN THE SPITZER GLIMPSE-360, CYG-X, AND SMOG SURVEYS

    SciTech Connect

    Zasowski, G.; Beaton, R. L.; Hamm, K. K.; Majewski, S. R.; Patterson, R. J.; Babler, B.; Churchwell, E.; Meade, M.; Whitney, B. A.; Benjamin, R. A.; Watson, C.

    2013-09-15

    Open stellar clusters are extremely valuable probes of Galactic structure, star formation, kinematics, and chemical abundance patterns. Near-infrared (NIR) data have enabled the detection of hundreds of clusters hidden from optical surveys, and mid-infrared (MIR) data are poised to offer an even clearer view into the most heavily obscured parts of the Milky Way. We use new MIR images from the Spitzer GLIMPSE-360, Cyg-X, and SMOG surveys to visually identify a large number of open cluster candidates in the outer disk of the Milky Way (65 Degree-Sign < l < 265 Degree-Sign ). Using NIR color-magnitude diagrams, stellar isochrones, and stellar reddening estimates, we derive cluster parameters (metallicity, distance, reddening) for those objects without previous identification and/or parameters in the literature. In total, we present coordinates and sizes of 20 previously unknown open cluster candidates; for 7 of these we also present metallicity, distance, and reddening values. In addition, we provide the first estimates of these values for nine clusters that had been previously cataloged. We compare our cluster sizes and other derived parameters to those in the open cluster catalog of Dias et al. and find strong similarities except for a higher mean reddening for our objects, which signifies our increased detection sensitivity in regions of high extinction. The results of this cluster search and analysis demonstrate the ability of MIR imaging and photometry to augment significantly the current census of open clusters in the Galaxy.

  1. First CCD UBVI photometric analysis of four moderately young open clusters in the third galactic quadrant

    NASA Astrophysics Data System (ADS)

    Piatti, Andrés E.; Clariá, Juan J.; Ahumada, Andrea V.

    2010-10-01

    We present CCD photometry in the Johnson UBV and Kron-Cousins I systems down to V ~ 22.0 for the open clusters NGC2311, Trumpler6, NGC2432 and BH54 and their surrounding fields. Trumpler6 and BH54 have never been studied before and so we provide, for the first time, estimates of their fundamental parameters. We obtained colour-magnitude diagrams (CMDs) and colour-colour diagrams cleaned from field star contamination by statistically subtracting stars in terms of spatial density, magnitude and colour distributions. Cluster angular radii were estimated from star counts in appropriate-sized boxes distributed throughout the entire observed fields. Using the cleaned CMDs and colour-colour diagrams, we applied sound photometric membership criteria to discriminate cluster members from interloper field stars. The interstellar extinction across the cluster fields derived from the 100-μm dust emission full-sky maps can be considered uniform within the quoted uncertainties. The E(B - V) and E(V - I) colour excesses and the apparent distance moduli of the clusters were estimated from the fit of the zero-age main-sequence to the colour-colour diagrams and CMDs, respectively. Cluster ages were determined from the comparison of the four clusters' CMDs with solar metallicity theoretical isochrones of the Geneva group. All the clusters were found to be moderately young objects, their ages ranging between 60 and 250Myr.

  2. Neutron Capture Elements in the Open Cluster Chemical Abundance & Mapping (OCCAM) Survey

    NASA Astrophysics Data System (ADS)

    O'Connell, Julia; Frinchaboy, Peter M.; Shetrone, Matthew D.; Majewski, Steven R.; Zasowski, Gail; Hearty, Fred R.

    2016-01-01

    The Open Cluster Chemical Abundance & Mapping (OCCAM) survey is a systematic survey of Galactic open clusters using data primarily from the SDSS-III/APOGEE-1 survey. The high-resolution (R=22,500), near-infrared (H-band) APOGEE-1 survey allows for cluster membership probability determination and analysis of light and iron-peak elements. Neutron capture elements, however, prove to be elusive in the IR region covered by APOGEE. In an effort to fully study detailed Galactic chemical evolution, we conducted a high resolution (R~60,000) spectroscopic abundance analysis of neutron capture elements for OCCAM clusters in the optical regime to complement the APOGEE results. We present results for ten open clusters using data obtained at McDonald Observatory with the 2.1m Otto Struve telescope and Sandiford Echelle Spectrograph. We see abundance trends for Ba II, La II and Eu II that are consistent with Galactic abundance patterns for these elements. Ce II appears to be slightly enhanced in all program stars with a median value of ~0.1 dex and a spread of 0.5 dex for the entire sample.

  3. PULSATING B-TYPE STARS IN THE OPEN CLUSTER NGC 884: FREQUENCIES, MODE IDENTIFICATION, AND ASTEROSEISMOLOGY

    SciTech Connect

    Saesen, S.; Briquet, M.; Aerts, C.; Carrier, F.; Miglio, A.

    2013-10-01

    Recent progress in the seismic interpretation of field β Cep stars has resulted in improvements of the physical description in the stellar structure and evolution model computations of massive stars. Further asteroseismic constraints can be obtained from studying ensembles of stars in a young open cluster, which all have similar age, distance, and chemical composition. We present an observational asteroseismology study based on the discovery of numerous multi-periodic and mono-periodic B stars in the open cluster NGC 884. We describe a thorough investigation of the pulsational properties of all B-type stars in the cluster. Overall, our detailed frequency analysis resulted in 115 detected frequencies in 65 stars. We found 36 mono-periodic, 16 bi-periodic, 10 tri-periodic, and 2 quadru-periodic stars and one star with nine independent frequencies. We also derived the amplitudes and phases of all detected frequencies in the U, B, V, and I filter, if available. We achieved unambiguous identifications of the mode degree for 12 of the detected frequencies in nine of the pulsators. Imposing the identified degrees and measured frequencies of the radial, dipole, and quadrupole modes of five pulsators led to a seismic cluster age estimate of log (age/yr) = 7.12-7.28 from a comparison with stellar models. Our study is a proof-of-concept for and illustrates the current status of ensemble asteroseismology of a young open cluster.

  4. Spectral analysis of A and F dwarf members of the open cluster M6: preliminary results

    NASA Astrophysics Data System (ADS)

    Kılıçoǧlu, T.; Monier, R.; Fossati, L.

    2010-12-01

    We present the first abundance analysis of CD-32 13109 (NGC 6405 47), member of the M6 open cluster. The photospheric abundances of 14 chemical elements were determined by comparing synthetic spectra and observed spectra of the star. Findings show that this star should be an Am star.

  5. Open clusters in the log Age vs. M_V plane

    NASA Astrophysics Data System (ADS)

    Bellazzini, M.; Perina, S.; Galleti, S.; Federici, L.; Buzzoni, A.; Fusi Pecci, F.

    In the log Age vs. integrated absolute magnitude (M_V) plane, the open clusters of the Milky Way form a well-defined band parallel to theoretical sequences decribing the passive evolution of Simple Stellar Populations and display a pretty sharp upper threshold in mass (M˜ 2× 104 M⊙) over a 4 dex range of ages.

  6. Recent Advances in Open-Shell Perturbation Theory and Coupled-Cluster Theory

    NASA Technical Reports Server (NTRS)

    Lee, Timothy J.; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    Comparisons of various recently developed open-shell RHF perturbation theories will be presented. Among the aspects considered are spin-contamination, computational cost, and quality of numerical results. In addition, a new approach to avoid the disk storage and I/O bottlenecks in large scale coupled-cluster calculations will be discussed.

  7. A Search For Planets in the Metal-Rich Open Cluster Praesepe

    NASA Astrophysics Data System (ADS)

    White, Russel

    The most promising way to distinguish between competing theories of planet formation and subsequent migration is to find and determine the basic properties of short period (< 1 yr) planets with well-determined ages younger than 1 billion years. Open clusters are the most promising locations to do this, but disappointingly no main sequence open cluster stars are known to harbor planets. This is primarily a consequence of most clusters being too distant for precise radial velocity measurements at visual wavelength. A better determined frequency of planets within open clusters would also clarify if this environment inhibits their formation, as has recently been suggested. If confirmed, that would imply that most stars will not have planets since most stars are believed to form in dense clusters. Here we request funding to support a 2-year program to search for radial velocity planets in the 600 Myr Praesepe open cluster. Praesepe is the most metal rich open cluster within 1000 pc of the sun. Based on known planet frequency - metallicity correlations, its high metallicity suggests a planet frequency enhanced by nearly a factor of 4 relative to sun- like stars; approximately 1 in 20 of its members should harbor a short period (3-10 day) hot Jupiter-like planet, and 1 in 400 of its members should have a transiting planet. The observations will be carried out using the Mayall 4-m/Echelle and Keck/HIRES facilities; nearly 100 Praesepe FGK stars will be surveyed over a 1+ year baseline. Precise radial velocities will be obtained using telluric features as a wavelength reference. We have demonstrated this technique achieves a precision of at least 50 m/s, and anticipate a final precision of 10 m/s, similar to what has been previously achieved. This precision and proposed temporal sampling will enable us to confidently identify nearly all Jupiter-sized planets with periods less than ~1 yr. The discovery of the first planets orbiting dwarf stars within an open cluster with a

  8. Photometric and spectroscopic study of the intermediate-age open cluster NGC 2355

    NASA Astrophysics Data System (ADS)

    Donati, P.; Bragaglia, A.; Carretta, E.; D'Orazi, V.; Tosi, M.; Cusano, F.; Carini, R.

    2015-11-01

    In this paper we analyse the evolutionary status and properties of the old open cluster NGC 2355, located in the Galactic anticentre direction, as a part of the long-term programme Bologna Open Clusters Chemical Evolution. NGC 2355 was observed with the Large Binocular Camera at the Large Binocular Telescope using the Bessel B, V, and Ic filters. The cluster parameters have been obtained using the synthetic colour-magnitude diagram method, as done in other papers of this series. Additional spectroscopic observations with the Fibre-fed Echelle Spectrograph at the Nordic Optical Telescope of three giant stars were used to determine the chemical properties of the cluster. Our analysis shows that NGC 2355 has metallicity slightly less than solar, with [Fe/H]= -0.06 dex, age between 0.8 and 1 Gyr, reddening E(B - V) in the range 0.14-0.19 mag, and distance modulus (m - M)0 of about 11 mag. We also investigate the abundances of O, Na, Al, α, iron-peak, and neutron capture elements, showing that NGC 2355 falls within the abundance distribution of similar clusters (same age and metallicity). The Galactocentric distance of NGC 2355 places it at the border between two regimes of metallicity distribution; this makes it an important cluster for the study of the chemical properties and evolution of the disc.

  9. VizieR Online Data Catalog: Proper motions of open clusters from UCAC4 (Dias+, 2014)

    NASA Astrophysics Data System (ADS)

    Dias, W. S.; Monteiro, H.; Caetano, T. C.; Lepine, J. R. D.; Assafin, M.; Oliveira, A. F.

    2014-04-01

    We present a catalog of mean proper motions and membership probabilities of individual stars for optically visible open clusters, which have been determined using data from the UCAC4 catalog in a homogeneous way. The mean proper motion of the cluster and the membership probabilities of the stars in the region of each cluster were determined by applying the statistical method in a modified fashion. In this study, we applied a global optimization procedure to fit the observed distribution of proper motions with two overlapping normal bivariate frequency functions, which also take the individual proper motion errors into account. For 724 clusters, this is the first determination of proper motion, and for the whole sample, we present results with a much larger number of identified astrometric member stars. Furthermore, it was possible to estimate the mean radial velocity of 364 clusters (102 unpublished so far) with the stellar membership using published radial velocity catalogs. These results provide an increase of 30% and 19% in the sample of open clusters with a determined mean absolute proper motion and mean radial velocity, respectively. (5 data files).

  10. Proper motions of the optically visible open clusters based on the UCAC4 catalog

    NASA Astrophysics Data System (ADS)

    Dias, W. S.; Monteiro, H.; Caetano, T. C.; Lépine, J. R. D.; Assafin, M.; Oliveira, A. F.

    2014-04-01

    We present a catalog of mean proper motions and membership probabilities of individual stars for optically visible open clusters, which have been determined using data from the UCAC4 catalog in a homogeneous way. The mean proper motion of the cluster and the membership probabilities of the stars in the region of each cluster were determined by applying the statistical method in a modified fashion. In this study, we applied a global optimization procedure to fit the observed distribution of proper motions with two overlapping normal bivariate frequency functions, which also take the individual proper motion errors into account. For 724 clusters, this is the first determination of proper motion, and for the whole sample, we present results with a much larger number of identified astrometric member stars. Furthermore, it was possible to estimate the mean radial velocity of 364 clusters (102 unpublished so far) with the stellar membership using published radial velocity catalogs. These results provide an increase of 30% and 19% in the sample of open clusters with a determined mean absolute proper motion and mean radial velocity, respectively. Tables 2 to 1809 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/564/A79

  11. SODIUM AND OXYGEN ABUNDANCES IN THE OPEN CLUSTER NGC 6791 FROM APOGEE H-BAND SPECTROSCOPY

    SciTech Connect

    Cunha, Katia; Souto, Diogo; Smith, Verne V.; Johnson, Jennifer A.; Bergemann, Maria; Mészáros, Szabolcs; Shetrone, Matthew D.; Prieto, Carlos Allende; Schiavon, Ricardo P.; Frinchaboy, Peter; Zasowski, Gail; Bizyaev, Dmitry; Holtzman, Jon; García Pérez, Ana E.; Majewski, Steven R.; Nidever, David; Beers, Timothy; Carrera, Ricardo; Geisler, Doug; Gunn, James; and others

    2015-01-10

    The open cluster NGC 6791 is among the oldest, most massive, and metal-rich open clusters in the Galaxy. High-resolution H-band spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) of 11 red giants in NGC 6791 are analyzed for their chemical abundances of iron, oxygen, and sodium. The abundances of these three elements are found to be homogeneous (with abundance dispersions at the level of ∼0.05-0.07 dex) in these cluster red giants, which span much of the red-giant branch (T {sub eff} ∼ 3500-4600 K), and include two red clump giants. From the infrared spectra, this cluster is confirmed to be among the most metal-rich clusters in the Galaxy (([Fe/H]) = 0.34 ± 0.06) and is found to have a roughly solar value of [O/Fe] and slightly enhanced [Na/Fe]. Our non-LTE calculations for the studied Na I lines in the APOGEE spectral region (16373.86 Å and 16388.85 Å) indicate only small departures from LTE (≤0.04 dex) for the parameter range and metallicity of the studied stars. The previously reported double population of cluster members with different Na abundances is not found among the studied sample.

  12. TIME-SERIES SPECTROSCOPY OF TWO CANDIDATE DOUBLE DEGENERATES IN THE OPEN CLUSTER NGC 6633

    SciTech Connect

    Williams, Kurtis A.; Chakraborty, Subho; Serna-Grey, Donald; Gianninas, A.; Canton, Paul A.

    2015-12-15

    SNe Ia are heavily used tools in precision cosmology, yet we still are not certain what the progenitor systems are. General plausibility arguments suggest there is potential for identifying double degenerate SN Ia progenitors in intermediate-age open star clusters. We present time-resolved high-resolution spectroscopy of two white dwarfs (WDs) in the field of the open cluster NGC 6633 that had previously been identified as candidate double degenerates in the cluster. However, three hours of continuous observations of each candidate failed to detect any significant radial velocity variations at the ≳10 km s{sup −1} level, making it highly unlikely that either WD is a double degenerate that will merge within a Hubble Time. The WD LAWDS NGC 6633 4 has a radial velocity inconsistent with cluster membership at the 2.5σ level, while the radial velocity of LAWDS NGC 6633 7 is consistent with cluster membership. We conservatively conclude that LAWDS 7 is a viable massive double degenerate candidate, though unlikely to be a Type Ia progenitor. Astrometric data from GAIA will likely be needed to determine if either WD is truly a cluster member.

  13. Comparing the OpenMP, MPI, and Hybrid Programming Paradigm on an SMP Cluster

    NASA Technical Reports Server (NTRS)

    Jost, Gabriele; Jin, Hao-Qiang; anMey, Dieter; Hatay, Ferhat F.

    2003-01-01

    Clusters of SMP (Symmetric Multi-Processors) nodes provide support for a wide range of parallel programming paradigms. The shared address space within each node is suitable for OpenMP parallelization. Message passing can be employed within and across the nodes of a cluster. Multiple levels of parallelism can be achieved by combining message passing and OpenMP parallelization. Which programming paradigm is the best will depend on the nature of the given problem, the hardware components of the cluster, the network, and the available software. In this study we compare the performance of different implementations of the same CFD benchmark application, using the same numerical algorithm but employing different programming paradigms.

  14. Variable stars in the field of the open cluster NGC 6939

    NASA Astrophysics Data System (ADS)

    Maciejewski, G.; Georgiev, Ts.; Niedzielski, A.

    2008-05-01

    The results of CCD photometric survey performed with the 90/180 cm Schmidt-Cassegrain Telescope of the Nicolaus Copernicus University Astronomical Observatory in Piwnice (Poland) and the 70/172 cm Schmidt Telescope of the National Astronomical Observatory (NAO) at Rozhen (Bulgaria) of the field of the 1 Gyr old open cluster NGC 6939 are presented. Twenty two variable stars were detected, four of them previously known. Four eclipsing systems (3 detached and 1 contact binary) were found to be members of the cluster. Analysis of the brightness of the contact binary V20 strongly supports the distance to the cluster of 1.74 ± 0.20 kpc. The small population of contact binaries in NGC 6939 confirms also the relatively young age of the cluster.

  15. The Gaia-ESO Survey: the inner disk, intermediate-age open cluster Trumpler 23

    NASA Astrophysics Data System (ADS)

    Overbeek, J. C.; Friel, E. D.; Donati, P.; Smiljanic, R.; Jacobson, H. R.; Hatzidimitriou, D.; Held, E. V.; Magrini, L.; Bragaglia, A.; Randich, S.; Vallenari, A.; Cantat-Gaudin, T.; Tautvaišienė, G.; Jiménez-Esteban, F.; Frasca, A.; Geisler, D.; Villanova, S.; Tang, B.; Muñoz, C.; Marconi, G.; Carraro, G.; San Roman, I.; Drazdauskas, A.; Ženovienė, R.; Gilmore, G.; Jeffries, R. D.; Flaccomio, E.; Pancino, E.; Bayo, A.; Costado, M. T.; Damiani, F.; Jofré, P.; Monaco, L.; Prisinzano, L.; Sousa, S. G.; Zaggia, S.

    2017-02-01

    Context. Trumpler 23 is a moderately populated, intermediate-age open cluster within the solar circle at a RGC 6 kpc. It is in a crowded field very close to the Galactic plane and the color-magnitude diagram shows significant field contamination and possible differential reddening; it is a relatively understudied cluster for these reasons, but its location makes it a key object for determining Galactic abundance distributions. Aims: New data from the Gaia-ESO Survey enable the first ever radial velocity and spectroscopic metallicity measurements for this cluster. We aim to use velocities to isolate cluster members, providing more leverage for determining cluster parameters. Methods: Gaia-ESO Survey data for 167 potential members have yielded radial velocity measurements, which were used to determine the systemic velocity of the cluster and membership of individual stars. Atmospheric parameters were also used as a check on membership when available. Literature photometry was used to re-determine cluster parameters based on radial velocity member stars only; theoretical isochrones are fit in the V, V-I diagram. Cluster abundance measurements of ten radial-velocity member stars with high-resolution spectroscopy are presented for 24 elements. These abundances have been compared to local disk stars, and where possible placed within the context of literature gradient studies. Results: We find Trumpler 23 to have an age of 0.80 ± 0.10 Gyr, significant differential reddening with an estimated mean cluster E(V-I) of 1.02, and an apparent distance modulus of 14.15 ± 0.20. We find an average cluster metallicity of [Fe/H] = 0.14 ± 0.03 dex, a solar [α/Fe] abundance, and notably subsolar [s-process/Fe] abundances.

  16. Optical and Near Infrared Study of the Open Cluster Czernik 17

    NASA Astrophysics Data System (ADS)

    Sujatha, S.; Krishna, K. K.; Komala, S.; Babu, G. S. D.

    2015-09-01

    In this paper we present the fundamental physical parameters of the poorly studied open cluster Czernik 17. The parameters have been derived from the UBVRI CCD photometric observations obtained with the 2-m Himalayan Chandra Telescope as well as using data taken from the Two-Micron All Sky Survey. This cluster is located in the direction of Camelopardalis constellation with a radial extent of 4' and is estimated to be at a distance of 7 ± 0.5 kpc. The interstellar extinction in the line of sight of the cluster is found to be E(B-V) = 0.72 ± 0.05 mag. Based on the evolutionary stage of the evolved stars the log(age) of the cluster is found to be 8.05 to 8.1 making it a relatively young cluster which can be considered as a spiral arm tracer of the outer arm. We have constructed the luminosity function for the stars within the adopted cluster radius which shows the common trend of the number of stars increasing toward the fainter magnitudes. We also find the presence of Böhm-Vitense gaps in the main-sequence branch of the color-magnitude diagrams of this cluster which may be attributed to surface convection which has the effect of making the stars redder although the luminosity remains unchanged.

  17. Chemically peculiar A/F stars in open clusters of the Milky Way

    NASA Astrophysics Data System (ADS)

    Gebran, M.; Monier, R.

    2010-12-01

    Abundance anomalies have been determined at the surface of many field and open cluster A and F dwarfs. These abundance anomalies are most likely caused by microscopic diffusion at work within the stable envelopes of A stars. However diffusion can be counteracted by several other mixing processes such as convection, rotational mixing and mass loss. We present a short review of the surface abundance patterns of A/F stars in the Pleiades (100 Myr), Coma Berenices (450 Myr) and Hyades (650 Myr) open clusters. Real star-to-star variations of the abundances were found for several chemical elements in the A dwarfs in these clusters. The derived abundances are then compared to evolutionary models from the Montreal group. These comparisons strongly suggest the occurence of hydrodynamical processes at play within the radiative zones of these stars and hindering the effects of microscopic diffusion (mixing processes/mass loss). In the frame of Gaia mission, simulations are presented that predict the number of A stars and open clusters that Gaia will observe in the Galaxy.

  18. AMPLITUDES OF SOLAR-LIKE OSCILLATIONS: CONSTRAINTS FROM RED GIANTS IN OPEN CLUSTERS OBSERVED BY KEPLER

    SciTech Connect

    Stello, Dennis; Huber, Daniel; Bedding, Timothy R.; Benomar, Othman; Kallinger, Thomas; Basu, Sarbani; Mosser, BenoIt; Hekker, Saskia; Mathur, Savita; GarcIa, Rafael A.; Gilliland, Ronald L.; Verner, Graham A.; Chaplin, William J.; Elsworth, Yvonne P.; Meibom, Soeren; Molenda-Zakowicz, Joanna; Szabo, Robert

    2011-08-10

    Scaling relations that link asteroseismic quantities to global stellar properties are important for gaining understanding of the intricate physics that underpins stellar pulsations. The common notion that all stars in an open cluster have essentially the same distance, age, and initial composition implies that the stellar parameters can be measured to much higher precision than what is usually achievable for single stars. This makes clusters ideal for exploring the relation between the mode amplitude of solar-like oscillations and the global stellar properties. We have analyzed data obtained with NASA's Kepler space telescope to study solar-like oscillations in 100 red giant stars located in either of the three open clusters, NGC 6791, NGC 6819, and NGC 6811. By fitting the measured amplitudes to predictions from simple scaling relations that depend on luminosity, mass, and effective temperature, we find that the data cannot be described by any power of the luminosity-to-mass ratio as previously assumed. As a result we provide a new improved empirical relation which treats luminosity and mass separately. This relation turns out to also work remarkably well for main-sequence and subgiant stars. In addition, the measured amplitudes reveal the potential presence of a number of previously unknown unresolved binaries in the red clump in NGC 6791 and NGC 6819, pointing to an interesting new application for asteroseismology as a probe into the formation history of open clusters.

  19. Variable Stars in the 50BiN Open Cluster Survey. I. NGC 2301

    NASA Astrophysics Data System (ADS)

    Wang, Kun; Deng, Licai; Zhang, Xiaobin; Xin, Yu; Yan, Zhengzhou; Tian, Jianfeng; Luo, Yangping; Luo, Changqing; Zhang, Chunguang; Peng, Yingjiang; Pan, Yang; Sun, Jinjiang; Luo, Zhiquan

    2015-11-01

    The current work is the first contribution from the 50 cm Binocular Network, whose primary goal is to systematically detect and characterize variable stars in Galactic open clusters. In this paper, we report the results of a search for variables in the open cluster NGC 2301. Eighteen variable stars including 12 new objects were detected in a 20‧ × 20‧ field around the cluster. The physical properties, classifications, and memberships are discussed using the behaviors of the light curves, the positions on the color-magnitude diagram, and the archival proper-motion data. Among the 12 new objects, 5 are low-amplitude δ Scuti stars, 4 of which are probable members of the cluster. One of them is discovered to be a δ Scuti star in an eclipsing binary system. One γ Doradus candidate is identified as a cluster member, but is apparently located very close to the blue edge of the γ Doradus instability strip and therefore can be used to pin down the blue edge of the instability strip. The remaining five new variables are classified as an EW-type eclipsing binary with an orbital period of 0.5785 days and four unknown type variable stars. In addition, revised basic data for the six known variables are given according to our observations.

  20. The OCCASO survey: presentation and radial velocities of 12 Milky Way open clusters

    NASA Astrophysics Data System (ADS)

    Casamiquela, L.; Carrera, R.; Jordi, C.; Balaguer-Núñez, L.; Pancino, E.; Hidalgo, S. L.; Martínez-Vázquez, C. E.; Murabito, S.; del Pino, A.; Aparicio, A.; Blanco-Cuaresma, S.; Gallart, C.

    2016-05-01

    Open clusters (OCs) are crucial for studying the formation and evolution of the Galactic disc. However, the lack of a large number of OCs analysed homogeneously hampers the investigations about chemical patterns and the existence of Galactocentric radial and vertical gradients, or an age-metallicity relation. To overcome this, we have designed the Open Cluster Chemical Abundances from Spanish Observatories (OCCASO) survey. We aim to provide homogeneous radial velocities, physical parameters and individual chemical abundances of six or more red clump stars for a sample of 25 old and intermediate-age OCs visible from the Northern hemisphere. To do so, we use high-resolution spectroscopic facilities (R ≥ 62 000) available at Spanish observatories. We present the motivation, design and current status of the survey, together with the first data release of radial velocities for 77 stars in 12 OCs, which represents about 50 per cent of the survey. We include clusters never studied with high-resolution spectroscopy before (NGC 1907, NGC 6991, NGC 7762), and clusters in common with other large spectroscopic surveys like the Gaia-ESO Survey (NGC 6705) and Apache Point Observatory Galactic Evolution Experiment (NGC 2682 and NGC 6819). We perform internal comparisons between instruments to evaluate and correct internal systematics of the results, and compare our radial velocities with previous determinations in the literature, when available. Finally, radial velocities for each cluster are used to perform a preliminary kinematic study in relation with the Galactic disc.

  1. The Open Cluster Chemical Abundances and Mapping (OCCAM) Survey: Galactic Neutron Capture Abundance Gradients

    NASA Astrophysics Data System (ADS)

    O'Connell, Julia; Frinchaboy, Peter M.; Shetrone, Matthew D.; Melendez, Matthew; Cunha, Katia M. L.; Majewski, Steven R.; Zasowski, Gail; APOGEE Team

    2017-01-01

    The evolution of elements, as a function or age, throughout the Milky Way disk provides a key constraint for galaxy evolution models. In an effort to provide these constraints, we have conducted an investigation into the r- and s- process elemental abundances for a large sample of open clusters as part of an optical follow-up to the SDSS-III/APOGEE-1 survey. Stars were identified as cluster members by the Open Cluster Chemical Abundance & Mapping (OCCAM) survey, which culls member candidates by radial velocity, metallicity, and proper motion from the observed APOGEE sample. To obtain data for neutron capture elements in these clusters, we conducted a long-term observing campaign covering three years (2013-2016) using the McDonald Observatory Otto Struve 2.1-m telescope and Sandiford Cass Echelle Spectrograph (R ~ 60,000). We present Galactic neutron-capture abundance gradients using 30+ clusters, within 6 kpc of the Sun, covering a range of ages from ~80 Myr to ~10 Gyr .

  2. The Detached Eclipsing Binary KV 29 and the Age of the Open Cluster M11

    NASA Astrophysics Data System (ADS)

    Bavarsad, Ernest A.; Sandquist, Eric L.; Shetrone, Matthew D.; Orosz, Jerome A.

    2016-11-01

    We present an extensive set of photometry and radial velocities for the detached eclipsing binary KV 29 in the intermediate-aged open cluster M11 (NGC 6705). Spectroscopy shows that the system is double lined, and all available evidence (proper motion, photometry, and position on the color-magnitude diagram) indicates that it is a member of the cluster. We find the period of the binary to be 4.64276 ± 0.00001 days. We find masses {3.604}-0.011+0.002{M}⊙ and {1.837}-0.006+0.001{M}⊙ and radii {5.392}-0.035+0.018{R}⊙ and {1.656}-0.044+0.007{R}⊙ for the primary and secondary stars, respectively. Because the primary star in the binary is rapidly evolving and is brighter than the cluster turnoff in a color-magnitude diagram, the measurement of its mass leads to a strong constraint on the cluster age. We find the age of M11 to be {222}-3+2+/- 15 Myr, where the quoted uncertainties come from statistical errors in the calculated masses and radii, and systematic uncertainties due to the ambiguity of the metallicity of the open cluster and variations within the isochrone models concerning heavy elements and convective overshooting.

  3. The X-ray properties of the young open cluster around alpha Persei

    NASA Technical Reports Server (NTRS)

    Randich, S.; Schmitt, J. H. M. M.; Prosser, C. F.; Stauffer, J. R.

    1995-01-01

    The observations of the 50 Myr old alpha Persei open cluster, performed by the Rosat's position sensitive proportional counter (PSPC), are discussed. The X-ray observations cover an area of about 10 sq deg. A total of 160 X-ray sources were detected. The comparison between the X-ray luminosity distribution functions of the alpha Persei sample and the Pleiades indicated that F and G-type stars in the alpha Persei are more X-ray luminous than their older counterparts in the Pleiades. No significant difference was found between the distributions of the K and M-type dwarfs in the two clusters.

  4. Isochrone Fittings for the Open Star Clusters NGC 3680 and Melotte 66

    NASA Astrophysics Data System (ADS)

    Guillemaud, Nikolas; Frinchaboy, P. M.; Thompson, B. A.

    2013-01-01

    I will be displaying the results from isochrone fittings on two open star clusters. The stellar evolution models used to generate the isochrones are from Dartmouth (Dotter et al. 2007) and Padova (Mango et al. 2008). Both of the models were applied to two star clusters: NGC 3680 and Melotte 66. The analysis is performed by utilizing infrared observations from the CPAPIR instrument; which is operated in conjunction with CTIO’s 1.5m telescope. This research was made possible by the NSF’s REU grant; award number 0851558.

  5. VizieR Online Data Catalog: CCD UBVRI photometry of 7 open star clusters (Sagar+, 2001)

    NASA Astrophysics Data System (ADS)

    Sagar, R.; Munari, U.; de Boer, K. S.

    2002-01-01

    We derive cluster parameters and mass functions from new UBVRI CCD photometric observations of ~3500 stars reaching down to V~20mag for the distant southern open star clusters NGC 3105, NGC 3603, Melotte 105, Hogg 15, NGC 4815, Pismis 20 and NGC 6253. For NGC 3105 and Hogg 15, CCD data are presented for the first time. The observations were carried out in 1992 between February 28 and March 8, June 5 and 9, and July 9 and 12 in the Cousins U, B, V, R and I photometric bands using CCD detector at the 1.0-m Elizabeth Telescope at the South African Astronomical Observatory (SAAO), Sutherland. (8 data files).

  6. NGC2587: a sparse open cluster projected on to a populous star field

    NASA Astrophysics Data System (ADS)

    Piatti, Andrés E.; Clariá, Juan J.; Ahumada, Andrea V.

    2009-08-01

    We present CCD photometry in the Johnson U, B and V and Kron-Cousins I passbands for the open cluster NGC2587. The sample consists of 4406 stars reaching down to V ~ 21.0. We developed a new method to clean statistically the colour-magnitude diagrams. NGC2587 appears to be a sparse, relatively bright open cluster, with a few tens of members projected on to a populous star field. The comparatively bright F7/8 II type star HD70927, located close to the cluster centre, seems not to be a member. Our analysis suggests that NGC2587 is slightly younger than the Hyades and probably of solar metallicity. A cluster radius of roughly 8 arcmin was estimated from the radial stellar density profile. From 18 probable cluster members with measured proper motions, we derive the following mean values for NGC2587: μα = -4.3 +/- 3.6masyr-1 and μδ = -2.5 +/- 3.4masyr-1. Adopting the theoretical metal content Z = 0.02, which provides the best global fit, we derive a cluster age of 500+60-50. Simultaneously, colour excesses E(B - V) = 0.10 and E(V - I) = 0.15 and an apparent distance modulus of V - MV = 12.50 are obtained. The interstellar extinction in the cluster direction is found to follow the normal law. NGC2587 is located at a distance of (2.70 +/- 0.70) kpc from the Sun and ~9.8 kpc from the Galactic centre.

  7. A uvbyCaHβ Analysis of the Old Open Cluster, NGC 6819

    NASA Astrophysics Data System (ADS)

    Anthony-Twarog, Barbara J.; Deliyannis, Constantine P.; Twarog, Bruce A.

    2014-09-01

    NGC 6819 is a richly populated, older open cluster situated within the Kepler field. A CCD survey of the cluster on the uvbyCaHβ system, coupled with proper-motion membership, has been used to isolate 382 highly probable, single-star unevolved main-sequence members over a 20' field centered on the cluster. From 278 F dwarfs with high precision photometry in all indices, a mean reddening of E(b - y) = 0.117 ± 0.005 or E(B - V) = 0.160 ± 0.007 is derived, where the standard errors of the mean include both internal errors and the photometric zero-point uncertainty. With the reddening fixed, the metallicity derived from the same 278 stars is [Fe/H] = -0.116 ± 0.101 from m 1 and -0.055 ± 0.033 from hk, for a weighted average of [Fe/H] = -0.06 ± 0.04, where the quoted standard errors of the mean include the internal errors from the photometric scatter plus the uncertainty in the photometric zero points. If metallicity is derived using individual reddening values for each star to account for potential reddening variation across the face of the cluster, the analogous result is unchanged. The cluster members at the turnoff of the color-magnitude diagram are used to test and confirm the recently discovered variation in reddening across the face of the cluster, with a probable range in the variation of ΔE(B - V) = 0.045 ± 0.015. With the slightly higher reddening and lower [Fe/H] compared to commonly adopted values, isochrone fitting leads to an age of 2.3 ± 0.2 Gyr for an apparent modulus of (m - M) = 12.40 ± 0.12. WIYN Open Cluster study LXI.

  8. IDENTIFICATION OF THE LITHIUM DEPLETION BOUNDARY AND AGE OF THE SOUTHERN OPEN CLUSTER BLANCO 1

    SciTech Connect

    Cargile, P. A.; James, D. J.; Jeffries, R. D.

    2010-12-20

    We present results from a spectroscopic study of the very low mass members of the Southern open cluster Blanco 1 using the Gemini-N telescope. We obtained intermediate resolution (R {approx} 4400) GMOS spectra for 15 cluster candidate members with I {approx} 14-20 mag, and employed a series of membership criteria-proximity to the cluster's sequence in an I/I - K{sub s} color-magnitude diagram (CMD), kinematics agreeing with the cluster systemic motion, magnetic activity as a youth indicator-to classify 10 of these objects as probable cluster members. For these objects, we searched for the presence of the Li I 6708 A feature to identify the lithium depletion boundary (LDB) in Blanco 1. The I/I - K{sub s} CMD shows a clear mass segregation in the Li distribution along the cluster sequence; namely, all higher mass stars are found to be Li poor, while lower mass stars are found to be Li rich. The division between Li-poor and Li-rich (i.e., the LDB) in Blanco 1 is found at I = 18.78 {+-} 0.24 and I - K{sub s} = 3.05 {+-} 0.10. Using current pre-main-sequence evolutionary models, we determine an LDB age of 132 {+-} 24 Myr. Comparing our derived LDB age to upper-main-sequence isochrone ages for Blanco 1, as well as for other open clusters with identified LDBs, we find good chronometric consistency when using stellar evolution models that incorporate a moderate degree of convective core overshoot.

  9. OpenACC programs of the Swendsen-Wang multi-cluster spin flip algorithm

    NASA Astrophysics Data System (ADS)

    Komura, Yukihiro

    2015-12-01

    We present sample OpenACC programs of the Swendsen-Wang multi-cluster spin flip algorithm. OpenACC is a directive-based programming model for accelerators without requiring modification to the underlying CPU code itself. In this paper, we deal with the classical spin models as with the sample CUDA programs (Komura and Okabe, 2014), that is, two-dimensional (2D) Ising model, three-dimensional (3D) Ising model, 2D Potts model, 3D Potts model, 2D XY model and 3D XY model. We explain the details of sample OpenACC programs and compare the performance of the present OpenACC implementations with that of the CUDA implementations for the 2D and 3D Ising models and the 2D and 3D XY models.

  10. The young open cluster NGC 7067 using Strömgren photometry

    NASA Astrophysics Data System (ADS)

    Monguió, M.; Negueruela, I.; Marco, A.; González-Fernández, C.; Alonso-Santiago, J.; Costado, M. T.; Casamiquela, L.; López-Corredoira, M.; Molgó, J.; Vilardell, F.; Alfaro, E. J.; Antoja, T.; Figueras, F.; Garcia, M.; Jordi, C.; Romero-Gómez, M.

    2017-04-01

    NGC 7067 is a young open cluster located in the direction between the first and the second Galactic quadrants and close to the Perseus spiral arm. This makes it useful for studies of the nature of the Milky Way spiral arms. Strömgren photometry taken with the Wide Field Camera at the Isaac Newton Telescope allowed us to compute individual physical parameters for the observed stars and hence to derive the cluster's physical parameters. Spectra from the 1.93-m telescope at the Observatoire de Haute-Provence helped to check and improve the results. We obtained photometry for 1233 stars, individual physical parameters for 515 and spectra for 9 of them. The 139 selected cluster members lead to a cluster distance of 4.4 ± 0.4 kpc, with an age below log10(t(yr)) = 7.3 and a present mass of 1260 ± 160 M⊙. The morphology of the data reveals that the centre of the cluster is at (α, δ) = (21: 24: 13.69, +48: 00: 39.2) J2000, with a radius of 6.1 arcmin. Strömgren and spectroscopic data allowed us to improve the previous parameters available for the cluster in the literature.

  11. DETECTION OF SOLAR-LIKE OSCILLATIONS FROM KEPLER PHOTOMETRY OF THE OPEN CLUSTER NGC 6819

    SciTech Connect

    Stello, Dennis; Bedding, Timothy R.; Huber, Daniel; Basu, Sarbani; Bruntt, Hans; Mosser, BenoIt; Barban, Caroline; Goupil, Marie-Jo; Stevens, Ian R.; Chaplin, William J.; Elsworth, Yvonne P.; Hekker, Saskia; Brown, Timothy M.; Christensen-Dalsgaard, Joergen; Kjeldsen, Hans; Arentoft, Torben; Gilliland, Ronald L.; Ballot, Jerome; GarcIa, Rafael A.

    2010-04-20

    Asteroseismology of stars in clusters has been a long-sought goal because the assumption of a common age, distance, and initial chemical composition allows strong tests of the theory of stellar evolution. We report results from the first 34 days of science data from the Kepler Mission for the open cluster NGC 6819-one of the four clusters in the field of view. We obtain the first clear detections of solar-like oscillations in the cluster red giants and are able to measure the large frequency separation, {delta}{nu}, and the frequency of maximum oscillation power, {nu}{sub max}. We find that the asteroseismic parameters allow us to test cluster membership of the stars, and even with the limited seismic data in hand, we can already identify four possible non-members despite their having a better than 80% membership probability from radial velocity measurements. We are also able to determine the oscillation amplitudes for stars that span about 2 orders of magnitude in luminosity and find good agreement with the prediction that oscillation amplitudes scale as the luminosity to the power of 0.7. These early results demonstrate the unique potential of asteroseismology of the stellar clusters observed by Kepler.

  12. The Be Population in 10 Galactic Open Clusters From the Discovery Channel Telescope

    NASA Astrophysics Data System (ADS)

    Chia Thao, Pa; Richardson, Noel; Gerhartz, Cody; Bjorkman, Karen S.; Bjorkman, Jon Eric; Wisniewski, John P.; Burrow, Anthony; Lomax, Jamie R.; Covey, Kevin R.

    2017-01-01

    As part of a multi-site, multi-epoch campaign to study the time-scales of disk growth and dissipation for classical Be stars, we have studied ten Galactic open clusters with multi-color photometry (Johnson BVRIJK and narrow band H-alpha and an adjacent continuum filter). We have created color-color diagrams to isolate the Be stars in the targeted clusters. These clusters have previously been determined to contain multiple Be stars. From our early analysis of the clusters we have found a number of new candidate Be stars, as well as a few stars in each cluster that appear to have lost their gaseous disks. Such studies of clusters will provide a statistical basis for understanding the evolution of the disks around these stars and may provide insights into the formation processes for the Be stars. We are grateful for support of the NSF REU program at the University of Toledo through NSF grant 1262810, as well as for support from NSF AST 1411563, 1412110, and 1412135.

  13. WIYN OPEN CLUSTER STUDY. LV. ASTROMETRY AND MEMBERSHIP IN NGC 6819

    SciTech Connect

    Platais, Imants; Gosnell, Natalie M.; Meibom, Soren; Kozhurina-Platais, Vera; Bellini, Andrea; Veillet, Christian; Burkhead, Martin S.

    2013-08-01

    We present proper motions and astrometric membership analysis for 15,750 stars around the intermediate-age open cluster NGC 6819. The accuracy of relative proper motions for well-measured stars ranges from {approx}0.2 mas yr{sup -1} within 10' of the cluster center to 1.1 mas yr{sup -1} outside this radius. In the proper motion vector-point diagram, the separation between the cluster members and field stars is convincing down to V {approx} 18 and within 10' from the cluster center. The formal sum of membership probabilities indicates a total of {approx}2500 cluster members down to V {approx} 22. We confirm the cluster membership of several variable stars, including some eclipsing binaries. The estimated absolute proper motion of NGC 6819 is {mu}{sub x}{sup abs}=-2.6{+-}0.5 and {mu}{sub y}{sup abs}=-4.2{+-}0.5 mas yr{sup -1}. A cross-identification between the proper motion catalog and a list of X-ray sources in the field of NGC 6819 resulted in a number of new likely optical counterparts, including a candidate CV. For the first time we show that there is significant differential reddening toward NGC 6819.

  14. Integrated spectral properties of 22 small angular diameter galactic open clusters

    NASA Astrophysics Data System (ADS)

    Ahumada, A. V.; Clariá, J. J.; Bica, E.

    2007-10-01

    Aims:Flux-calibrated integrated spectra of a sample of 22 Galactic open clusters of small angular diameter are presented. With one exception (ESO 429-SC2), all objects have Galactic longitudes in the range 208° < l < 33°. The spectra cover the range ≈3600-6800 Å, with a resolution of ≈14 Å. The properties of the present cluster sample are compared with those of well-studied clusters located in two 90° sectors, centred at l = 257° and l = 347°. The dissolution rate of Galactic open clusters in these two sectors is examined. Methods: Using the equivalent widths of the Balmer lines and comparing line intensities and continuum distribution of the cluster spectra with those of template cluster spectra with known properties, we derive both foreground reddening values and ages. Thus, we provide information independent of that determined through colour-magnitude diagrams. Results: The derived E(B-V) values for the whole sample vary from 0.0 in ESO 445-SC74 to 1.90 in Pismis 24, while the ages range from ~3 Myr (NGC 6604 and BH 151) to ~3.5 Gyr (Ruprecht 2). For six clusters (Dolidze 34, ESO 429-SC2, ESO 445-SC74, Ruprecht 2, BH 151 and Hogg 9) the foreground E(B-V) colour excesses and ages are determined for the first time. The results obtained for the remaining clusters show, in general terms, good agreement with previous photometric results. Conclusions: The age and reddening distributions of the present sample match those of known clusters in the two selected Galactic sectors. The present results would favour a major dissolution rate of star clusters in these two sectors. Two new solar-metallicity templates are defined corresponding to the age groups of (4-5) Myr and 30 Myr among those of Piatti et al. (2002, MNRAS, 335, 233). The Piatti et al. templates of 20 Myr and (3-4) Gyr are here redefined. Based on observations made at Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y T

  15. X-ray Source Populations in Old Open Clusters - Collinder 261

    NASA Astrophysics Data System (ADS)

    Vats, Smriti

    2014-11-01

    We are carrying out an X-ray survey of old open clusters (OCs) with the Chandra X-ray Observatory. Single old stars emit very faint X-rays, making X-rays produced by mass transfer in CVs, or by rapid rotation of the stars in tidally-locked, detached binaries detectable, without contamination from single stars. By comparing properties of interacting binaries in different environments, we aim to study binary evolution, and how dynamical encounters with other cluster members affect it. Collinder (Cr) 261 is an old OC(~7Gyr), with one of the richest populations inferred, of close binary populations and blue stragglers of all OCs. We will present the first results, detailing the X-ray population of Cr 261, in conjugation with other OCs, and in comparison with populations in globular clusters.

  16. Open and Globular Cluster Distances for Extragalactic, Galactic, and Stellar Astrophysics

    NASA Technical Reports Server (NTRS)

    Worthey, Guy S.

    2004-01-01

    One of the hallmarks of SIM's few-milliarcsecond astrometric precision is its ability to obtain accurate parallax measurements across more than half of the Galaxy. The "open and globular" project obtains parallax distances to a set of star clusters. One important, goal is to pinpoint the zeropoint of the distance scale for main-sequence fitting. Another goal is to improve stellar evolutionary isochrones and integrated light models. Another goal is to use the clusters themselves to address unsolved problems of late-stage stellar evolution and Galactic and extragalactic chemical evolution. The clusters to be observed are chosen to span the widest possible range of abundance and age, to be as rich as possible, and to be as well-studied as possible.

  17. Galactic Structure from Open Clusters: Photometric Characterization of Reddening, Distance and Abundance

    NASA Astrophysics Data System (ADS)

    Anthony-Twarog, Barbara; Twarog, Bruce A.; Schuster, William

    1999-02-01

    Our recent work with open clusters has indicated a surprising demarcation of the Milky Way disk's metallicity as a function of distance from the Galactic center - an apparently abrupt drop in [Fe/H] from solar to -0.3 at R_GC=10 kpc (Twarog, Ashman & Anthony- Twarog 1997). We have asserted that due to uncertain reddenings, distances and abundance data, the step-down in [Fe/H] at 10 kpc has long been masked in previous studies or interpreted as a declining radial gradient in the disk's metallicity. Current work, including observations proposed here, will address these issues for disk clusters by using uvbyCaH(beta) photometry to determine foreground reddenings, abundances and cluster distances.

  18. Evidences of tidal distortion and mass loss from the old open cluster NGC 6791

    NASA Astrophysics Data System (ADS)

    Carraro, Giovanni; Dalessandro, Emanuele

    2017-03-01

    We present the first evidence of clear signatures of tidal distortions in the density distribution of the fascinating open cluster NGC 6791. We find that the 2D density map shows a clear elongation and an irregular distribution starting from ~ 300'' from the cluster center and two tails extending in opposite directions beyond the tidal radius. These features are aligned to both the absolute proper motion and to the Galactic centre directions. Accordingly we find that both the surface brightness and star count density profiles reveal a departure from a King model starting from ~ 600''. These observational evidences suggest that NGC 6791 is currently undergoing mass-loss likely due to gravitational shocking and interactions with the tidal field of the Milky Way. We derive the expected mass-loss due to stellar evolution and tidal interactions and we estimate the initial cluster mass to be Mini = (1.5 - 4.0) × 105 M ⊙.

  19. The ODD Old, Super-Metal-Rich Open Cluster, NGC 6791

    NASA Astrophysics Data System (ADS)

    Boesgaard, Ann Merchant; Lum, Michael G.; Deliyannis, Constantine P.

    2017-03-01

    We report on the composition of turn-off stars in the intriguing open cluster, NGC 6791, which is old, but super-metal-rich using Keck/HIRES spectra. We find [Fe/H] = +0.30 +/-0.02[O/Fe]n -0.06 +/-0.02,[Mg/Fe], [Si/Fe], [Ca/Fe], and [Ti/Fe] near solar and the two Fe-peak elements, Cr and Ni, are consistent with Fe.

  20. CONFIGURATIONS OF BOUNDED AND FREE-FLOATING PLANETS IN VERY YOUNG OPEN CLUSTERS

    SciTech Connect

    Liu Huigen; Zhang Hui; Zhou Jilin

    2013-08-01

    Open clusters (OCs) are usually young and suitable for studying the formation and evolution of planetary systems. So far, only four planets have been found with radial velocity measurements in OCs. Meanwhile, a lot of free-floating planets (FFPs) have been detected. We utilize N-body simulations to investigate the evolution and final configurations of multi-planetary systems in very young open clusters with an age <10 Myr. After an evolution of 10 Myr, 61%-72% of the planets remain bounded and more than 55% of the planetary systems will maintain their initial orbital configurations. For systems with one planet ejected, more than 25% of them have the surviving planets in misaligned orbits. In the clusters, the fraction of planetary systems with misalignment is >6%, and only 1% have planets in retrograde orbits. We also obtain a positive correlation between the survival planet number and the distance from the cluster center r: planetary systems with a larger r tend to be more stable. Moreover, stars with a mass >2.5 M{sub Sun} are likely unstable and lose their planets. These results are roughly consistent with current observations. Planetary systems in binaries are less stable and we achieve a rough criterion: most of the binary systems with a{sub b}(1-e{sub b}{sup 2})>100 AU can retain all the initial planets. Finally, 80% of the FFPs are ejected out of the clusters, while the rest ({approx}20%) still stay in host clusters and most of them are concentrated in the center (<2 pc)

  1. Fundamental parameters of the highly reddened young open clusters Westerlund 1 and 2

    NASA Astrophysics Data System (ADS)

    Piatti, A. E.; Bica, E.; Claria, J. J.

    1998-02-01

    We study the compact open clusters Westerlund1 (BH197) and Westerlund2. We present CCD integrated spectroscopy for both clusters, and CCD imaging in the V and I bands for the former one. So far, Westerlund1 is possibly the most reddened open cluster studied in detail (Av ~ 13.0). It has an age of 8 +/- 3 Myr and a distance from the Sun of d_sun ~ 1.0 +/- 0.4 kpc. For Westerlund2 we derive a visual absorption AV~ 5.0 mag, an age of 2-3 Myr, and d_sun=5.7+/- 0.3 kpc. From luminosity and structural arguments we conclude that Westerlund1, although young and compact, it is a massive cluster, in contrast to Westerlund2. Based on observations made at Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Cientificas y Tecnicas de la Republica Argentina and the Universities of La Plata, Cordoba and San Juan, Argentina, and at the University of Toronto (David Dunlap Observatory) 24-inch telescope, Las Campanas, Chile. The photometric observations are available at CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

  2. Calibrating the lithium-age relation with open clusters observed with GES (Gaia-ESO Survey)

    NASA Astrophysics Data System (ADS)

    Gutiérrez Albarrán, M. L.; Montes, D.; Gómez Garrido, M.; Tabernero, H. M..; González Hernández, J. I.; GES Survey Builders

    2017-03-01

    Li depletion is strongly age-dependent but currently available data have shown a complex pattern of Li depletion on the pre- and main-sequence stars that is not yet understood. The lithium abundance observed in late-type stars depend not only of the age and the temperature but also on metallicity, mixing mechanisms, convection structure, rotation and magnetic activity. The large number of stars observed within the Gaia-ESO survey (GES - https://www.gaia-eso.eu/) for many open clusters and associations can be used to calibrate the lithium-age relation and its dependence with other parameters that can be derived from the UVES and GIRAFFE spectroscopic observations. We present here the preliminary results of the analysis of membership and Li abundance of the young clusters and associations, as well as of the intermediate-age and old open clusters, observed until now in GES (iDR4) in order to conduct a comparative study. All this information allowed us to characterize the properties of the members of these clusters and identify a series of field contaminant stars, both lithium-rich giants and non-giant outliers.

  3. DISCOVERY OF 14 NEW SLOWLY PULSATING B STARS IN THE OPEN CLUSTER NGC 7654

    SciTech Connect

    Luo, Y. P.; Han, Z. W.

    2012-02-10

    We carried out time-series BV CCD photometric observations of the open cluster NGC 7654 (Messier 52) to search for variable stars. Eighteen slowly pulsating B (SPB) stars have been detected, among which 14 candidates are newly discovered, three known ones are confirmed, and a previously found {delta} Scuti star is also identified as an SPB candidate. Twelve SPBs are probable cluster members based on membership analysis. This makes NGC 7654 the richest galactic open cluster in terms of SPB star content. It is also a new discovery that NGC 7654 hosts three {gamma} Dor star candidates. We found that all these stars (18 SPB and 3 {gamma} Dor stars) have periods longer than their corresponding fundamental radial mode. With such a big sample of g-mode pulsators in a single cluster, it is clear that multi-mode pulsation is more common in the upper part of the main sequence than in the lower part. All the stars span a narrow strip on the period-luminosity plane, which also includes the {gamma} Dor stars at the low-luminosity extension. This result implies that there may be a single period-luminosity relation applicable to all g-mode main-sequence pulsators. As a by-product, three EA-type eclipsing binaries and an EW-type eclipsing binary are also discovered.

  4. BARIUM SURFACE ABUNDANCES OF BLUE STRAGGLERS IN THE OPEN CLUSTER NGC 6819

    SciTech Connect

    Milliman, Katelyn E.; Mathieu, Robert D.; Schuler, Simon C.

    2015-09-15

    We present a barium surface abundance of 12 blue stragglers (BSs) and 18 main-sequence (MS) stars in the intermediate-age open cluster NGC 6819 (2.5 Gyr) based on spectra obtained from the Hydra Multi-object Spectrograph on the WIYN 3.5 m telescope. For the MS stars we find [Fe/H] = +0.05 ± 0.04 and [Ba/Fe] = −0.01 ± 0.10. The majority of the BS stars are consistent with these values. We identify five BSs with significant barium enhancement. These stars most likely formed through mass transfer from an asymptotic giant branch star that polluted the surface of the BS with the nucleosynthesis products generated during thermal pulsations. This conclusion aligns with the results from the substantial work done on the BSs in old open cluster NGC 188 that identifies mass transfer as the dominant mechanism for BS formation in that open cluster. However, four of the BSs with enhanced barium show no radial-velocity evidence for a companion. The one star that is in a binary is a double-lined system, meaning the companion is not a white dwarf and not the remnant of a prior AGB star. In this paper we attempt to develop a consistent scenario to explain the origin of these five BSs.

  5. A deep survey for transiting hot planets in the open cluster M37 with the MMT

    NASA Astrophysics Data System (ADS)

    Hartman, Joel David

    This thesis presents the results of a deep (14.5 [Special characters omitted.] the intermediate age open cluster M37 (NGC 2099) using the 6.5m MMT. We combine spectroscopic and photometric observations of the cluster to refine estimates of the cluster fundamental parameters, identify variable stars, study stellar rotation, and place limits on the fraction of stars with planets as small as Neptune. We determine new estimates of the fundamental cluster parameters: t 550 ± 30 Myr, E ( B - V ) = 0.227 ± 0.038, ( m - M ) v = 11.57 ± 0.13 and [ M/ H ] = +0.045 ± 0.044. We obtain light curves for ~ 23,000 stars and identify 1445 variable stars, 99% of which are new discoveries. These variables include 575 rotational variables that are potential cluster members. Using this rich sample we investigate a number of relations between rotation period, color and the amplitude of photometric variability, and we combine these results with published observations of other open clusters to test the standard theory of lower-main sequence stellar angular momentum evolution. Notably we find that the period of the Sun and the periods of solar mass stars in M37, and the Hyades do not follow the "Skumanich law", i.e. they cannot be related by a simple model invoking solid-body rotation with a standard wind angular momentum-loss law. Finally, we do not detect any transiting planets among the ~ 1450 observed cluster members. We do, however, identify a ~ 1 R J candidate planet transiting a Galactic field star. We use this null result to place 95% confidence upper limits on the fraction of cluster members and field stars with planets as a function of planetary radius and orbital period. We find that < 25% of cluster members have 0.35 R J planets with periods shorter than 1 day, and < 16% of field stars have 0.3 R J planets with periods shorter than 1 day. This is the first transit survey to place limits on the fraction of stars with planets as small as Neptune.

  6. The Substellar Mass Function in the Central Region of the Open Cluster Praesepe from Deep LBT Observations

    NASA Astrophysics Data System (ADS)

    Wang, W.; Boudreault, S.; Goldman, B.; Henning, Th.; Caballero, J. A.; Bailer-Jones, C. A. L.

    2011-12-01

    Studies of the mass function (MF) of open clusters of different ages allow us to probe the efficiency with which brown dwarfs (BDs) are evaporated from clusters to populate the field. Surveys in old clusters (age gtrsim 100 Myr) do not suffer so severely from several problems encountered in young clusters, such as intra-cluster extinction and large uncertainties in BD models. Here we present the results of a deep photometric survey to study the MF of the old open cluster Praesepe (age 590+150-120 Myr and distance 190+6.0-5.8 pc), down to a 5σ detection limit at i˜25.6 mag (˜40 MJup). We identify 62 cluster member candidates, of which 40 are substellar, from comparison with predictions from a dusty atmosphere model. The MF rises from the substellar boundary until ˜60 MJup and then declines. This is quite different from the form inferred for other open clusters older than 50 Myr, but seems to be similar to those found in very young open cluster, whose MFs peak at ˜10 MJup. Either Praesepe really does have a different MF from other clusters or they had similar initial MFs but have differed in their dynamical evolution. We further have identified six foreground T dwarf candidates towards Praesepe, which require follow-up spectroscopy to confirm their nature.

  7. BRIGHT VARIABLE STARS IN NGC 6819: AN OPEN CLUSTER IN THE KEPLER FIELD

    SciTech Connect

    Talamantes, Antonio; Sandquist, Eric L.; Clem, James L.; Robb, Russell M.; Balam, David D.; Shetrone, Matthew E-mail: erics@mintaka.sdsu.ed E-mail: robb@uvic.c E-mail: shetrone@astro.as.utexas.ed

    2010-11-15

    We describe a variability study of the moderately old open cluster NGC 6819. We have detected four new detached eclipsing binaries near the cluster turnoff (one of which may be in a triple system). Several of these systems should be able to provide mass and radius information, and can therefore constrain the age of the cluster. We have also newly detected one possible detached binary member about 3.5 mag below the turnoff. One EW-type binary (probably not a cluster member) shows unusually strong night-to-night light curve variations in sets of observations separated by eight years. According to the best current information, the three brightest variables we detected (two of them new) are cluster members, making them blue stragglers. The first one is a {delta} Scu pulsating variable, the second one is a close but detached binary, and the third one contains a detached short-period binary that shows total eclipses. In each case, however, there is evidence hinting that the system may have been produced through the interaction of more than two stars.

  8. Early turbulent mixing as the origin of chemical homogeneity in open star clusters.

    PubMed

    Feng, Yi; Krumholz, Mark R

    2014-09-25

    The abundances of elements in stars are critical clues to stars' origins. Observed star-to-star variations in logarithmic abundance within an open star cluster--a gravitationally bound ensemble of stars in the Galactic plane--are typically only about 0.01 to 0.05 over many elements, which is noticeably smaller than the variation of about 0.06 to 0.3 seen in the interstellar medium from which the stars form. It is unknown why star clusters are so homogenous, and whether homogeneity should also prevail in regions of lower star formation efficiency that do not produce bound clusters. Here we report simulations that trace the mixing of chemical elements as star-forming clouds assemble and collapse. We show that turbulent mixing during cloud assembly naturally produces a stellar abundance scatter at least five times smaller than that in the gas, which is sufficient to explain the observed chemical homogeneity of stars. Moreover, mixing occurs very early, so that regions with star formation efficiencies of about 10 per cent are nearly as well mixed as those with formation efficiencies of about 50 per cent. This implies that even regions that do not form bound clusters are likely to be well mixed, and improves the prospects of using 'chemical tagging' to reconstruct (via their unique chemical signatures, or tags) star clusters whose constituent stars have become unbound from one another and spread across the Galactic disk.

  9. Radial Velocities, Binarity, and Kinematic Membership in the Open Cluster NGC 2516

    NASA Astrophysics Data System (ADS)

    González, Jorge Federico; Lapasset, Emilio

    2000-05-01

    We present echelle spectroscopic observations for 36 bright (V<9.6) stars in the open cluster NGC 2516, including several blue straggler candidates and four red giants. Radial velocities are derived by cross-correlations using high signal-to-noise ratio standard spectra as templates. From 22 cluster members a mean cluster velocity of +22.0+/-0.2 km s-1 was derived. Membership probabilities of the observed stars are computed on the basis of their distance to the cluster center and kinematic criteria. We report the discovery of three double-lined spectroscopic binaries and several probable binaries among main-sequence stars. A binary frequency of more than 26% is found among the high-mass main-sequence stars. The blue straggler HD 66341 is a slowly rotating cluster member with constant velocity, while HD 66194 is a fast-rotating Be star with probable variations in radial velocity. Other blue straggler candidates, such as HD 65663, 65950, 66066, and 65987, must be considered turnoff stars. The observations presented here were obtained at the Complejo Astronómico El Leoncito (CASLEO), which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina (CONICET) and the national universities of La Plata, Córdoba, and San Juan.

  10. The Evolutionary Status of Be Stars: Results from a Photometric Study of Southern Open Clusters

    NASA Astrophysics Data System (ADS)

    McSwain, M. Virginia; Gies, Douglas R.

    2005-11-01

    Be stars are a class of rapidly rotating B stars with circumstellar disks that cause Balmer and other line emission. There are three possible reasons for the rapid rotation of Be stars: they may have been born as rapid rotators, spun up by binary mass transfer, or spun up during the main-sequence (MS) evolution of B stars. To test the various formation scenarios, we have conducted a photometric survey of 55 open clusters in the southern sky. Of these, five clusters are probably not physically associated groups and our results for two other clusters are not reliable, but we identify 52 definite Be stars and an additional 129 Be candidates in the remaining clusters. We use our results to examine the age and evolutionary dependence of the Be phenomenon. We find an overall increase in the fraction of Be stars with age until 100 Myr, and Be stars are most common among the brightest, most massive B-type stars above the zero-age main sequence (ZAMS). We show that a spin-up phase at the terminal-age main sequence (TAMS) cannot produce the observed distribution of Be stars, but up to 73% of the Be stars detected may have been spun-up by binary mass transfer. Most of the remaining Be stars were likely rapid rotators at birth. Previous studies have suggested that low metallicity and high cluster density may also favor Be star formation. Our results indicate a possible increase in the fraction of Be stars with increasing cluster distance from the Galactic center (in environments of decreasing metallicity). However, the trend is not significant and could be ruled out due to the intrinsic scatter in our data. We also find no relationship between the fraction of Be stars and cluster density.

  11. DEEP, WIDE-FIELD CCD PHOTOMETRY FOR THE OPEN CLUSTER NGC 3532

    SciTech Connect

    Clem, James L.; Landolt, Arlo U.; Hoard, D. W.; Wachter, Stefanie E-mail: landolt@phys.lsu.edu E-mail: wachter@ipac.caltech.edu

    2011-04-15

    We present the results of a deep, wide-field CCD survey for the open cluster NGC 3532. Our new BV(RI){sub c} photometry effectively covers a one square degree area and reaches an unprecedented depth of V {approx} 21 to reveal that NGC 3532 is a rich open cluster that harbors a large number of faint, low-mass stars. We employ a number of methods to reduce the impact of field star contamination in the cluster color-magnitude diagrams (CMDs), including supplementing our photometry with JHK{sub s} data from the 2MASS catalog. These efforts allow us to define a robust sample of candidate main-sequence stars suitable for a purely empirical determination of the cluster's parameters by comparing them to the well-established Hyades main sequence. Our results confirm previous findings that NGC 3532 lies fairly near to the Sun [(m - M){sub 0} = 8.46 {+-} 0.05; 492{sup +12}{sub -11} pc] and has an extremely low reddening for its location near the Galactic plane [E(B - V) = 0.028 {+-} 0.006]. Moreover, an age of {approx}300 Myr has been derived for the cluster by fitting a set of overshooting isochrones to the well-populated upper main sequence. This new photometry also extends faint enough to reach the cluster white dwarf sequence, as confirmed by our photometric recovery of eight spectroscopically identified members of the cluster. Using the location of these eight members, along with the latest theoretical cooling tracks, we have identified {approx}30 additional white dwarf stars in the [V, (B - V)] CMD that have a high probability of belonging to NGC 3532. Reassuringly, the age we derive from fitting white dwarf isochrones to the locus of these stars, 300 {+-} 100 Myr, is consistent with the age derived from the turnoff. Our analysis of the photometry also includes an estimation of the binary star fraction as well as a determination of the cluster's luminosity and mass functions.

  12. A study of the two northern open clusters NGC 1582 and NGC 1663

    NASA Astrophysics Data System (ADS)

    Baume, G.; Villanova, S.; Carraro, G.

    2003-08-01

    We present CCD UBV(I)C observations obtained in the field of the previously unstudied northern open clusters NGC 1582 and NGC 1663. For the former, we also provide high-resolution spectra of the brightest stars and complement our data with Two-Micron All-Sky-Survey (2MASS) near-infrared photometry and with astrometric data from the Tycho-2 catalog. From the analysis of all these data, we argue that NGC 1582 is a very poor, quite large and heavily contaminated open cluster. It turns out to have a reddening EB-V = 0.35 +/- 0.03, to be situated 1100 +/- 100 pc from the Sun and to have an age of 300 +/- 100 Myr. On the other hand, we were not able to unambiguously clarify the nature of NGC 1663. By assuming it is a real cluster and from the analysis of its photometric diagrams, we found a color excess value EB-V = 0.20, an intermediate age value ( ~ 2000 Myr) and a distance of about 700 pc. The distribution of the stars in the region however suggests we are probably facing an open cluster remnant. As an additional result, we obtained aperture photometry of three previously unclassified galaxies placed in the field of NGC 1663 and performed a preliminary morphological classification of them. Based on observations carried out at Mt Ekar, Asiago, Italy. Data are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/407/527

  13. An X-Ray Survey of the Open Cluster NGC 6475 (M7) with ROSAT

    NASA Technical Reports Server (NTRS)

    Prosser, Charles F.; Stauffer, John R.; Caillault, J.-P.; Balachandran, Suchitra; Stern, Robert A.; Randich, Sofia

    1995-01-01

    A ROSAT x-ray survey, with complimentary optical photometry, of the open cluster NGC 6475 has enabled the detection of approx. 50 late-F to K0 and approx. 70 K/M dwarf new candidate members, providing the first reliable detection of low-mass stars in this low. galactic latitude, 220 Myr old cluster. The x-ray observations reported here have a typical limiting sensitivity of L(sub x) approx. equal to 10(exp 29) erg/s. The detection frequency of early type cluster members is consistent with the hypothesis that the x-ray emitting early type stars are binary systems with an unseen, low-mass secondary producing the x rays. The ratio between x-ray and bolometric luminosity among NGC 6475 members saturates at a spectral-type/color which is intermediate between that in much younger and in much older clusters, consistent with rotational spindown of solar-type stars upon their arrival on the ZAMS. The upper envelope of x-ray luminosity as a function of spectral type is comparable to that of the Pleiades, with the observed spread in x-ray luminosity among low-mass members being likely due to the presence of binaries and relatively rapid rotators. However, the list of x-ray selected candidate members is likely biased against low-mass, slowly rotating single stars. While some preliminary spectroscopic information is given in an appendix, further spectroscopic observations of the new candidate members will aid in interpreting the coronal activity among solar-type NGC 6475 members and their relation to similar stars in older and younger open clusters.

  14. The Enigma of the Open Cluster M29 (NGC 6913) Solved

    NASA Astrophysics Data System (ADS)

    Straižys, V.; Milašius, K.; Boyle, R. P.; Vrba, F. J.; Munari, U.; Walborn, N. R.; Černis, K.; Kazlauskas, A.; Zdanavičius, K.; Janusz, R.; Zdanavičius, J.; Laugalys, V.

    2014-11-01

    Determining the distance to the open cluster M29 (NGC 6913) has proven difficult, with distances determined by various authors differing by a factor of two or more. To solve this problem, we have initiated a new photometric investigation of the cluster in the Vilnius seven-color photometric system, supplementing it with available data in the BV and JHK s photometric systems and spectra of the nine brightest stars of spectral classes O and B. Photometric spectral classes and luminosities of 260 stars in a 15' × 15' area down to V = 19 mag are used to investigate the interstellar extinction run with distance and to estimate the distance of the Great Cygnus Rift, ~ 800 pc. The interstellar reddening law in the optical and near-infrared regions is found to be close to normal, with the ratio of extinction to color excess RBV = 2.87. The extinction AV of cluster members is between 2.5 and 3.8 mag, with a mean value of 2.97 mag, or E B - V = 1.03. The average distance of eight stars of spectral types O9-B2 is 1.54 ± 0.15 kpc. Two stars from the seven brightest stars are field stars: HDE 229238 is a background B0.5 supergiant and HD 194378 is a foreground F star. In the intrinsic color-magnitude diagram, seven fainter stars of spectral classes B3-B8 are identified as possible members of the cluster. The 15 selected members of the cluster of spectral classes O9-B8 plotted on the log L/L ⊙ versus log T eff diagram, together with the isochrones from the Padova database, give the age of the cluster as 5 ± 1 Myr.

  15. A uvbyCaHβ analysis of the old open cluster, NGC 6819

    SciTech Connect

    Anthony-Twarog, Barbara J.; Twarog, Bruce A.; Deliyannis, Constantine P. E-mail: btwarog@ku.edu

    2014-09-01

    NGC 6819 is a richly populated, older open cluster situated within the Kepler field. A CCD survey of the cluster on the uvbyCaHβ system, coupled with proper-motion membership, has been used to isolate 382 highly probable, single-star unevolved main-sequence members over a 20' field centered on the cluster. From 278 F dwarfs with high precision photometry in all indices, a mean reddening of E(b – y) = 0.117 ± 0.005 or E(B – V) = 0.160 ± 0.007 is derived, where the standard errors of the mean include both internal errors and the photometric zero-point uncertainty. With the reddening fixed, the metallicity derived from the same 278 stars is [Fe/H] = –0.116 ± 0.101 from m {sub 1} and –0.055 ± 0.033 from hk, for a weighted average of [Fe/H] = –0.06 ± 0.04, where the quoted standard errors of the mean include the internal errors from the photometric scatter plus the uncertainty in the photometric zero points. If metallicity is derived using individual reddening values for each star to account for potential reddening variation across the face of the cluster, the analogous result is unchanged. The cluster members at the turnoff of the color-magnitude diagram are used to test and confirm the recently discovered variation in reddening across the face of the cluster, with a probable range in the variation of ΔE(B – V) = 0.045 ± 0.015. With the slightly higher reddening and lower [Fe/H] compared to commonly adopted values, isochrone fitting leads to an age of 2.3 ± 0.2 Gyr for an apparent modulus of (m – M) = 12.40 ± 0.12.

  16. Be Stars and Physical Properties of the Young Open Cluster NGC 6834

    NASA Astrophysics Data System (ADS)

    Miller, G. J.; Grebel, E. K.; Yoss, K. M.

    1996-12-01

    We present initial results for the young open cluster NGC 6834 obtained with the 1-m telescope at Mount Laguna Observatory. We observed this cluster as part of a CCD-photometric survey for Be stars using B,V filters and two narrow-band interference filters at Hα and Hα continuum. Through a census of Be stars in clusters, where stars are coeval, equidistant, have the same metallicities, and share a common origin, we hope to gain a better understanding of the properties and origins of the still enigmatic Be phenomenon. Our B,V color-magnitude diagram of NGC 6834 shows an extended blue main sequence widened at fainter magnitudes by field star contamination. Fitting Geneva isochrones with solar metallicity to the cluster population, we find an age of ~ 50 Myr, a mean reddening of E(B-V)~ 0.7 mag, and a distance modulus of 12.2 mag (i.e. a distance of ~ 2750 pc). Our data reach roughly 4 magnitudes fainter in V than previous photographic or photoelectric studies. For the detection of Be stars, we use a two-color diagram. The most prominent feature distinguishing Be stars from B stars is their Balmer emission. The (Hα \\ continuum - Hα ) index allows us to find stars bright in Hα . The (B-V) color index serves to distinguish blue stars from red giants and red supergiants, which also may exhibit Hα emission. We find six Be star candidates in NGC 6834, that stand out clearly through their enhanced Balmer emission. Only one was known previously in this cluster. The brightness in Hα is well-correlated with reddened (B-V) colors. The relatively small number of Be stars in NGC 6834 is consistent with the young age of the cluster and the spectral type (B5) at the main-sequence turnoff.

  17. Radial Velocities and Kinematic Membership in the Open Cluster NGC 3114

    NASA Astrophysics Data System (ADS)

    González, Jorge Federico; Lapasset, Emilio

    2001-05-01

    Echelle spectroscopic observations for 30 bright stars in the field of the sparse open cluster NGC 3114 are presented. The sample includes main-sequence stars, yellow and red giants, and blue straggler candidates. Radial velocities are derived by cross-correlations using high signal-to-noise ratio standard spectra as templates. The cluster mean velocity is well defined from eight giants and several main-sequence stars whose average is =-3.52+/-0.25 km s-1. The membership probabilities of the observed stars are computed on the basis of the velocity distributions of the cluster and field stars, and the expected percentage of contamination at each position. We classified 19 cluster members and 10 nonmembers; the remaining star is a known spectroscopic binary for which no membership probability was assigned. Among the members, there is a bright yellow giant, seven red giants, and four blue straggler candidates, although they should be considered as turn-off stars. The location of two of them in the color-magnitude diagram (slightly blueward of the turn-off) can be explained by their low rotational velocities. No velocity variations were detected in the 16 stars measured more than once, which indicates that NGC 3114 possess an abnormally low binary frequency. From spectral types of cluster members, a distance modulus (V-Mv)=9.8+/-0.2 mag and a reddening E(B-V)=0.07+/-0.01 mag are derived. The cluster age is estimated to be 1.6×108 yr. The observations presented here were obtained at the Complejo Astronómico El Leoncito (CASLEO), which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina (CONICET) and the National Universities of La Plata, Córdoba and San Juan.

  18. The enigma of the open cluster M29 (NGC 6913) solved

    SciTech Connect

    Straižys, V.; Milašius, K.; Černis, K.; Kazlauskas, A.; Zdanavičius, K.; Zdanavičius, J.; Laugalys, V.; Boyle, R. P.; Vrba, F. J.; Munari, U.; Walborn, N. R.; Janusz, R.

    2014-11-01

    Determining the distance to the open cluster M29 (NGC 6913) has proven difficult, with distances determined by various authors differing by a factor of two or more. To solve this problem, we have initiated a new photometric investigation of the cluster in the Vilnius seven-color photometric system, supplementing it with available data in the BV and JHK {sub s} photometric systems and spectra of the nine brightest stars of spectral classes O and B. Photometric spectral classes and luminosities of 260 stars in a 15' × 15' area down to V = 19 mag are used to investigate the interstellar extinction run with distance and to estimate the distance of the Great Cygnus Rift, ∼ 800 pc. The interstellar reddening law in the optical and near-infrared regions is found to be close to normal, with the ratio of extinction to color excess R{sub BV} = 2.87. The extinction A{sub V} of cluster members is between 2.5 and 3.8 mag, with a mean value of 2.97 mag, or E {sub B–V} = 1.03. The average distance of eight stars of spectral types O9-B2 is 1.54 ± 0.15 kpc. Two stars from the seven brightest stars are field stars: HDE 229238 is a background B0.5 supergiant and HD 194378 is a foreground F star. In the intrinsic color-magnitude diagram, seven fainter stars of spectral classes B3-B8 are identified as possible members of the cluster. The 15 selected members of the cluster of spectral classes O9-B8 plotted on the log L/L {sub ☉} versus log T {sub eff} diagram, together with the isochrones from the Padova database, give the age of the cluster as 5 ± 1 Myr.

  19. Membership and Coronal Activity in the NGC 2232 and Cr 140 Open Clusters

    NASA Technical Reports Server (NTRS)

    Patten, Brian M.; Oliversen, Ronald J. (Technical Monitor)

    2001-01-01

    This is the second annual performance report for our grant "Membership and Coronal Activity in the NGC 2232 and Cr 140 Open Clusters." We propose to identify X-ray sources and extract net source counts in 8 archival ROSAT HRI images in the regions of the NGC 2232 and Cr 140 open clusters. These X-ray data will be combined with ground-based photometry and spectroscopy in order to identify G, K, and early-M type cluster members. At present, no members later than approximately F5 are currently known for either cluster. With ages of approximately 25 Myr and at a distance of just 320 - 360 pc, the combined late-type membership of the NGC 2232 and Cr 140 clusters will yield an almost unique sample of solar-type stars in the post-T Tauri/pre-main sequence phase of evolution. These stars will be used to assess the level and dispersion in coronal activity levels, as part of a probe of the importance of magnetic braking and the level of magnetic dynamo activity, for solar-type stars just before they reach the ZAMS. Over the past year we have successfully acquired all of the ground-based data necessary to support the analysis of the archival ROSAT X-ray data in the regions around both of these clusters. By the end of 2001 we expect to have completed the reduction and analysis of the ground-based photometry and spectroscopy and will begin the integration of these data with the ROSAT X-ray data. A certain amount of pressure to complete the work on NGC 2232 is coming from the SIRTF project, as this cluster may be a key component to a circumstellar disk evolution GTO program. We are only too happy to try to help and have worked to speed the analysis as much as possible. The primary activity to be undertaken in the next few months is the integration of the groundbased photometry and spectroscopy with the archival ROSAT X-ray data and then writing the paper summarizing our results. The most time consuming portion of this next phase is, of course, seeing the paper through

  20. The Internal Proper Motions of Stars in the Open Cluster M35

    NASA Astrophysics Data System (ADS)

    McNamara, Bernard J.; Harrison, Thomas E.; McArthur, Barbara E.; Benedict, G. Fritz

    2011-08-01

    Relative proper motions, based on 108 orbits of Hubble Space Telescope Fine Guidance Sensor data extending from 1992 to 2006, are reported for 74 stars in the open cluster M35 (NGC 2168). A subset of 22 of these objects are then used to compute the cluster's internal proper motion dispersions in both right ascension and declination. We find that these dispersions are equal to within their measurement errors. The average one-dimensional dispersion is 0.018 ± 0.002 arcsec century-1. When combined with the M35 radial velocity dispersion of 0.65 ± 0.10 km s-1 found by Geller et al., this produces a cluster distance of 762 ± 145 pc. Using isochrone fits to the cluster main sequence, this distance suggests that M35 has an age of about 133 Myr. Although this age is consistent with that typically found for M35, the formal error in the dynamical distance of ±19% can accommodate ages between 65 Myr and 201 Myr.

  1. Ruprecht 147: The Oldest Nearby Open Cluster as a New Benchmark for Stellar Astrophysics

    NASA Astrophysics Data System (ADS)

    Curtis, Jason L.; Wolfgang, Angie; Wright, Jason T.; Brewer, John M.; Johnson, John Asher

    2013-05-01

    Ruprecht 147 is a hitherto unappreciated open cluster that holds great promise as a standard in fundamental stellar astrophysics. We have conducted a radial velocity survey of astrometric candidates with Lick, Palomar, and MMT observatories and have identified over 100 members, including 5 blue stragglers, 11 red giants, and 5 double-lined spectroscopic binaries (SB2s). We estimate the cluster metallicity from spectroscopic analysis, using Spectroscopy Made Easy (SME), and find it to be [M/H] = +0.07 ± 0.03. We have obtained deep CFHT/MegaCam g'r'i'z' photometry and fit Padova isochrones to the (g' - i') and Two Micron All Sky Survey (J - KS ) color-magnitude diagrams, using the τ2 maximum-likelihood procedure of Naylor, and an alternative method using two-dimensional cross-correlations developed in this work. We find best fits for Padova isochrones at age t = 2.5 ± 0.25 Gyr, m - M = 7.35 ± 0.1, and AV = 0.25 ± 0.05, with additional uncertainty from the unresolved binary population and possibility of differential extinction across this large cluster. The inferred age is heavily dependent on our choice of stellar evolution model: fitting Dartmouth and PARSEC models yield age parameters of 3 Gyr and 3.25 Gyr, respectively. At ~300 pc and ~3 Gyr, Ruprecht 147 is by far the oldest nearby star cluster.

  2. RUPRECHT 147: THE OLDEST NEARBY OPEN CLUSTER AS A NEW BENCHMARK FOR STELLAR ASTROPHYSICS

    SciTech Connect

    Curtis, Jason L.; Wright, Jason T.; Wolfgang, Angie; Brewer, John M.; Johnson, John Asher

    2013-05-15

    Ruprecht 147 is a hitherto unappreciated open cluster that holds great promise as a standard in fundamental stellar astrophysics. We have conducted a radial velocity survey of astrometric candidates with Lick, Palomar, and MMT observatories and have identified over 100 members, including 5 blue stragglers, 11 red giants, and 5 double-lined spectroscopic binaries (SB2s). We estimate the cluster metallicity from spectroscopic analysis, using Spectroscopy Made Easy (SME), and find it to be [M/H] = +0.07 {+-} 0.03. We have obtained deep CFHT/MegaCam g'r'i'z' photometry and fit Padova isochrones to the (g' - i') and Two Micron All Sky Survey (J - K{sub S} ) color-magnitude diagrams, using the {tau}{sup 2} maximum-likelihood procedure of Naylor, and an alternative method using two-dimensional cross-correlations developed in this work. We find best fits for Padova isochrones at age t = 2.5 {+-} 0.25 Gyr, m - M = 7.35 {+-} 0.1, and A{sub V} = 0.25 {+-} 0.05, with additional uncertainty from the unresolved binary population and possibility of differential extinction across this large cluster. The inferred age is heavily dependent on our choice of stellar evolution model: fitting Dartmouth and PARSEC models yield age parameters of 3 Gyr and 3.25 Gyr, respectively. At {approx}300 pc and {approx}3 Gyr, Ruprecht 147 is by far the oldest nearby star cluster.

  3. Iron Abundances and Atmospheric Parameters of Red Giants in the Open Cluster IC 4756

    NASA Astrophysics Data System (ADS)

    Djordjevic, Julie O.

    Three red giants were investigated within the open cluster IC 4756 using observations taken from the McDonald Observatory's 2.1m Otto Struve Telescope and the Sandiford Cassegrain Echelle Spectrometer (SES). Iron abundances were calculated for each star based on the equivalent widths of Fe I and Fe II lines measured using the line lists of Bubar and King (2010) and Schuler et al. (2005). Also derived were the basic atmospheric parameters: effective temperature, surface gravity, metallicity, and microturbulence. Her 35, Her 85, and Her 249 were found to have corresponding [Fe I/H] of 0.06 +/- 0.04, -0.16 +/- 0.03, and -0.16 +/- 0.06 as derived from the neutral lines. These values, when compared to the results of other studies, suggest that the cluster has an overall metallicity within the solar to subsolar value. This would indicate IC 4756 as a slightly metal-poor object. The star Her 85 is also examined to determine if derived atmospheric parameters support the classification of more recent studies as a nonmember of the cluster. The studies base their decisions on its deviation in radial velocity from the cluster mean. It is concluded that there is little solid evidence to support the dismissal of Her 85 from metallicity studies of IC 4756 and present-day membership and proper motion studies with modern equipment are required to confirm or reject this theory.

  4. UBVI CCD Photometry of the Open Clusters NGC 4609 and Hogg 15

    NASA Astrophysics Data System (ADS)

    Kook, Seung-Hwa; Sung, Hwankyung; Bessell, M. S.

    2010-10-01

    {UBVI CCD photometry is obtained for the open clusters NGC 4609 and Hogg 15 in Crux. For NGC 4609, CCD data are presented for the first time. From new photometry we derive the reddening, distance modulus and age of each cluster - NGC 4609 : E(B-V) = 0.37 ± 0.03, V_0 - M_V = 10.60 ± 0.08, log τ= 7.7 ± 0.1; Hogg 15 : E(B-V) = 1.13 ± 0.11, V_0 - M_V = 12.50 ± 0.15, log τ ≲ 6.6. The young age of Hogg 15 strongly implies that WR 47 is a member of the cluster. We also determine the mass function of these clusters and obtain a slope Γ = -1.2 (± 0.3) for NGC 4609 which is normal and a somewhat shallow slope (Γ = -0.95 ± 0.5) for Hogg 15.

  5. A study of variable stars in the open cluster NGC 1582 and its surrounding field

    NASA Astrophysics Data System (ADS)

    Song, Fang-Fang; Esamdin, Ali; Ma, Lu; Liu, Jin-Zhong; Zhang, Yu; Niu, Hu-Biao; Yang, Tao-Zhi

    2016-10-01

    This paper presents Charge-Coupled Device time-series photometric observations of the open cluster NGC 1582 and its surrounding field with Johnson B, V and R filters by using the Nanshan 1 m telescope administered by Xinjiang Astronomical Observatory. 19 variable stars and three variable candidates were detected in a 45‧ × 48.75‧ field around the cluster. 12 of the variable stars are newly-discovered variable objects. The physical properties, classifications and memberships of these 22 objects are studied through their light curves, their positions on the color-magnitude diagram and with archival data from the Naval Observatory Merged Astrometric Dataset. Among these objects, five are eclipsing binary systems, six are pulsating variable stars including one known δ Scuti star and one newly-discovered RR Lyrae star. The distance to the RR Lyrae star is estimated to be 7.9 ± 0.3 kpc, indicating that the star is located far behind the cluster. Four variable stars are probable members of the cluster, and 13 of the 22 objects are confirmed to be field stars.

  6. Membership and Coronal Activity in the NGC 2232 and Cr 140 Open Clusters

    NASA Technical Reports Server (NTRS)

    Oliversen, Ronald J. (Technical Monitor); Patten, Brian M.

    2004-01-01

    Making use of eight archival ROSAT HRI images in the regions of the NGC 2232 and Cr 140, this project's primary focus is to identify X-ray sources and to extract net source counts for these sources in these two open clusters. These X-ray data would be combined with ground-based photometry and spectroscopy in order to identify G, K, and early-M type cluster members. Such membership data are important because, at present, no members later than spectral type approx. F5 are currently known for either cluster. With ages estimated to be approx. 25 Myr and at distances of just approx. 350 pc, the combined late-type membership of the NGC 2232 and Cr 140 clusters would yield an almost unique sample of solar-type stars in the post-T Tauri/pre-main sequence phase of evolution. These stars could be used to assess the level and dispersion of coronal activity levels, as a part of a probe of the importance of magnetic braking and the level of magnetic dynamo activity, for solar-type stars just before they reach the zero-age main sequence.

  7. Protoplanetary and Transitional Disks in the Open Stellar Cluster IC 2395

    NASA Astrophysics Data System (ADS)

    Balog, Zoltan; Siegler, Nick; Rieke, G. H.; Kiss, L. L.; Muzerolle, James; Gutermuth, R. A.; Bell, Cameron P. M.; Vinkó, J.; Su, K. Y. L.; Young, E. T.; Gáspár, András

    2016-11-01

    We present new deep UBVRI images and high-resolution multi-object optical spectroscopy of the young (˜6-10 Myr old), relatively nearby (800 pc) open cluster IC 2395. We identify nearly 300 cluster members and use the photometry to estimate their spectral types, which extend from early B to middle M. We also present an infrared imaging survey of the central region using the IRAC and MIPS instruments on board the Spitzer Space Telescope, covering the wavelength range from 3.6 to 24 μm. Our infrared observations allow us to detect dust in circumstellar disks originating over a typical range of radii from ˜0.1 to ˜10 au from the central star. We identify 18 Class II, 8 transitional disk, and 23 debris disk candidates, respectively, 6.5%, 2.9%, and 8.3% of the cluster members with appropriate data. We apply the same criteria for transitional disk identification to 19 other stellar clusters and associations spanning ages from ˜1 to ˜18 Myr. We find that the number of disks in the transitional phase as a fraction of the total with strong 24 μm excesses ([8] - [24] ≥ 1.5) increases from (8.4 ± 1.3)% at ˜3 Myr to (46 ± 5)% at ˜10 Myr. Alternative definitions of transitional disks will yield different percentages but should show the same trend.

  8. Stellar rotation, binarity, and lithium in the open cluster IC 4756

    NASA Astrophysics Data System (ADS)

    Strassmeier, K. G.; Weingrill, J.; Granzer, T.; Bihain, G.; Weber, M.; Barnes, S. A.

    2015-08-01

    Context. An important aspect in the evolutionary scenario of cool stars is their rotation and the rotationally induced magnetic activity and interior mixing. Stars in open clusters are particularly useful tracers for these aspects because of their known ages. Aims: We aim to characterize the open cluster IC 4756 and measure stellar rotation periods and surface differential rotation for a sample of its member stars. Methods: Thirty-seven cluster stars were observed continuously with the CoRoT satellite for 78 days in 2010. Follow-up high-resolution spectroscopy of the CoRoT targets and deep Strömgren uvbyβ and Hα photometry of the entire cluster were obtained with our robotic STELLA facility and its echelle spectrograph and wide-field imager, respectively. Results: We determined high-precision photometric periods for 27 of the 37 CoRoT targets and found values between 0.155 and 11.4 days. Twenty of these are rotation periods. Twelve targets are spectroscopic binaries of which 11 were previously unknown; orbits are given for six of them. Six targets were found that show evidence of differential rotation with ΔΩ/Ω in the range 0.04-0.15. Five stars are non-radially pulsating stars with fundamental periods of below 1 d, two stars are semi-contact binaries, and one target is a micro-flaring star that also shows rotational modulation. Nine stars in total were not considered members because of much redder color(s) and deviant radial velocities with respect to the cluster mean. Hα photometry indicates that the cluster ensemble does not contain magnetically over-active stars. The cluster average metallicity is -0.08 ± 0.06 (rms) and its logarithmic lithium abundance for 12 G-dwarf stars is 2.39 ± 0.17 (rms). Conclusions: The cluster is 890 ± 70 Myrs old with an average turn-off mass of 1.8 M⊙ and a solar or slightly subsolar metallicity. The distance modulus is 8m.02 and the average reddening E(b - y) = 0m.16.. The cluster is masked by a very inhomogeneous

  9. The Role of Collybistin in Gephyrin Clustering at Inhibitory Synapses: Facts and Open Questions

    PubMed Central

    Papadopoulos, Theofilos; Soykan, Tolga

    2011-01-01

    Collybistin (Cb) is a brain-specific GDP/GTP-exchange factor, which interacts with the inhibitory receptor anchoring protein gephyrin. Data from mice carrying an inactivated Cb gene indicate that Cb is required for the formation and maintenance of gephyrin and gephyrin-dependent GABAA receptor (GABAAR) clusters at inhibitory postsynapses in selected regions of the mammalian forebrain. However, important aspects of how Cb’s GDP/GTP-exchange activity, structure, and regulation contribute to gephyrin and GABAAR clustering, as well as its role in synaptic plasticity, remain poorly understood. Here we review the current state of knowledge about Cb’s function and address open questions concerning its contribution to synapse formation, maintenance, plasticity, and adaptive changes in response to altered network activity. PMID:21738498

  10. Is the Hogg 12-NGC 3590 pair a new open cluster binary system?

    NASA Astrophysics Data System (ADS)

    Piatti, A. E.; Clariá, J. J.; Ahumada, A. V.

    Based on CCD UBVI_(KC) images obtained at Cerro Tololo Inter-American Observatory (CTIO, Chile) and on morphological criteria, as well as on the stellar density in the region, we confirm that Hogg 12 is a genuine open cluster (OC) separated in the sky from NGC 3590 by scarcely 3.6 pc. The colour-magnitude diagrams of Hogg 12, cleaned from field star contamina- tion, reveal that this is a solar metal content cluster, affected by E(B-V) = 0.40 ± 0.05, located at a heliocentric distance d = 2.0 ± 0.5 kpc, and of an age similar to that of NGC 3590. Evidence that these two objects form an OC binary system is presented. A detailed version of this work can be seen in PASP, 122, 516 (2010).

  11. Pulsation of Pre-Main Sequence Stars in Young Open Clusters

    NASA Astrophysics Data System (ADS)

    Zwintz, Konstanze; Weiss, Werner W.

    2001-08-01

    The aim of this proposal is to determine observationally the parameter space of the pre-main sequence instability strip. For that purpose we intend to obtain photometric timeseries with high time resolution and low noise level of the stars in young open clusters (IC 4996, NGC 6910 and NGC 6383) and to identify pre-main sequence pulsators. Several cluster members have the spectral types of interest (A-F) and lie between the birthline and the zero-age main sequence. Up to now the number of pre-main sequence pulsators is absolutely inadequate to determine reliably the hot and cool border of the according instability region. Its definition is indispensable for a better understanding of the internal structure and evolution of such stars.

  12. VizieR Online Data Catalog: On the metallicity of open clusters. III. (Netopil+, 2016)

    NASA Astrophysics Data System (ADS)

    Netopil, M.; Paunzen, E.; Heiter, U.; Soubiran, C.

    2016-03-01

    In Paper II (Heiter et al., Paper II 2014A&A...561A..93H) we have evaluated available spectroscopic iron abundance determinations of open cluster stars and presented mean values for 78 open clusters. The results are based on high-resolution data (R>=25000) with high signal-to-noise ratios (S/N>=50). Furthermore, quality criteria were introduced by adopting only [Fe/H] measurements of stars with Teff=4400-6500K and logg>=2.0dex. We have to note that the mean iron abundance for Berkeley 29, listed in Paper II, also incorporates some measurements based upon lower S/N data. In the present paper we therefore list the correct values for the higher and lower quality data. Since publication of Paper II, some new studies were made (Boesgaard et al., 2013ApJ...775...58B; Bocek Topcu et al., 2015, Cat. J/MNRAS/446/3562; Carraro et al., 2014A&A...568A..86C; Donati et al., 2015, Cat. J/MNRAS/446/1411; Magrini et al.. 2014A&A...563A..44M, 2015A&A...580A..85M; Molenda-Zakowicz et al., 2014MNRAS.445.2446M; Monaco et al., 2014A&A...564L...6M; Reddy et al., 2015MNRAS.450.4301R), which we examined the same way as described in Paper II. This adds ten open clusters to our list (Berkeley 81, NGC 1342, NGC 1662, NGC 1912, NGC 2354, NGC 4337, NGC 4815, NGC 6811, Trumpler 5, and Trumpler 20) and supplementary data for NGC 752, NGC 2447, NGC 2632, and NGC 6705. (1 data file).

  13. Pushing up the size limit of chalcogenide supertetrahedral clusters: two- and three-dimensional photoluminescent open frameworks from (Cu(5)In(30)S(54))(13-) clusters.

    PubMed

    Bu, Xianhui; Zheng, Nanfeng; Li, Yuqi; Feng, Pingyun

    2002-10-30

    Direct band gap copper indium chalcogenides are of great technological importance in part because of their high photovoltaic conversion efficiency. Covalent superlattices constructed from copper indium chalcogenide clusters are of particular interest because they may combine open framework architecture with semiconducting properties. Here two photoluminescent covalent superlattices built from core-shell type copper indium sulfide supertetrahedral clusters are reported. Each cluster consists of 35 metal cations and is so far the largest known supertetrahedral cluster with a metal-to-metal distance of 1.6 nm. In addition, this is the first example of supertetrahedral clusters in heterometallic copper indium chalcogenides. The preparation of these large clusters has narrowed down the size gap between colloidal nanoclusters and small supertetrahedral clusters and revealed new possibilities in the construction of nanoporous semiconducting superlattices with tunable pore size. Through the combination of metal ions with different oxidation states to provide both overall and local charge neutrality, an effective approach has been demonstrated in the rational synthesis of chalcogenide open framework materials with large and unprecedented supertetrahedral clusters.

  14. Chemical Abundances in a Sample of Red Giants in the Open Cluster NGC 2420 from APOGEE

    NASA Astrophysics Data System (ADS)

    Souto, Diogo; Cunha, K.; Smith, V.; Allende Prieto, C.; Pinsonneault, M.; Zamora, O.; García-Hernández, D. A.; Mészáros, Sz.; Bovy, J.; García Pérez, A. E.; Anders, F.; Bizyaev, D.; Carrera, R.; Frinchaboy, P. M.; Holtzman, J.; Ivans, I.; Majewski, S. R.; Shetrone, M.; Sobeck, J.; Pan, K.; Tang, B.; Villanova, S.; Geisler, D.

    2016-10-01

    NGC 2420 is a ˜2 Gyr old well-populated open cluster that lies about 2 kpc beyond the solar circle, in the general direction of the Galactic anti-center. Most previous abundance studies have found this cluster to be mildly metal-poor, but with a large scatter in the obtained metallicities. Detailed chemical abundance distributions are derived for 12 red-giant members of NGC 2420 via a manual abundance analysis of high-resolution (R = 22,500) near-infrared (λ1.5-1.7 μm) spectra obtained from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. The sample analyzed contains six stars that are identified as members of the first-ascent red giant branch (RGB), as well as six members of the red clump (RC). We find small scatter in the star-to-star abundances in NGC 2420, with a mean cluster abundance of [Fe/H] = -0.16 ± 0.04 for the 12 red giants. The internal abundance dispersion for all elements (C, N, O, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Co and Ni) is also very small (˜0.03-0.06 dex), indicating a uniform cluster abundance distribution within the uncertainties. NGC 2420 is one of the clusters used to calibrate the APOGEE Stellar Parameter and Chemical Abundance Pipeline (ASPCAP). The results from this manual analysis compare well with ASPCAP abundances for most of the elements studied, although for Na, Al, and V there are more significant offsets. No evidence of extra-mixing at the RGB luminosity bump is found in the 12C and 14N abundances from the pre-luminosity-bump RGB stars in comparison to the post-He core-flash RC stars.

  15. Proper motions and CCD photometry of stars in the region of the open cluster NGC 6866

    NASA Astrophysics Data System (ADS)

    Frolov, V. N.; Ananjevskaja, Yu. K.; Gorshanov, D. L.; Polyakov, E. V.

    2010-05-01

    We present the results of our comprehensive study of the Galactic open star cluster NGC 6866. The positions of stars in the investigated region have been obtained with the “Fantasy” automatic measuring machine from 10 plates of the normal astrograph at the Pulkovo Astronomical Observatory. The size of the investigated field is 40' × 40', the limiting magnitude is B ˜ 16{·/ m }6, and the maximum epoch difference is 79 yr. For 1202 field stars, we have determined the relative proper motions with an rms error of 2.5 mas yr-1. Out of them, 423 stars may be considered cluster members with a probability P > 70% according to the astrometric criterion. Photometric diagrams have been used as an additional criterion. We have performed two-color BV CCD photometry of stars with the Pulkovo ZA-320M mirror astrograph. The U magnitudes from the literature have also been used to construct the two-color diagrams. A total of 267 stars have turned out to be members of NGC 6866 according to the two criteria. We present refined physical parameters of the cluster and its age estimate (5.6 × 108 yr). The cluster membership of red and blue giants, variable, double, and multiple stars is considered. We have found an almost complete coincidence of the positions of one of the stars in the region (a cluster nonmember) and a soft X-ray source in the ROSAT catalog. The “Fantasy” automatic measuring machine is described in the Appendix.

  16. Evidence of tidal distortions and mass-loss from the old open cluster NGC 6791

    NASA Astrophysics Data System (ADS)

    Dalessandro, E.; Miocchi, P.; Carraro, G.; Jílková, L.; Moitinho, A.

    2015-05-01

    We present the first evidence of clear signatures of tidal distortions in the density distribution of the fascinating open cluster NGC 6791. We used deep and wide-field data obtained with the Canada-France-Hawaii Telescope covering a 2° × 2° area around the cluster. The 2D density map obtained with the optimal matched filter technique shows a clear elongation and an irregular distribution starting from ˜300 arcsec from the cluster centre. At larger distances, two tails extending in opposite directions beyond the tidal radius are also visible. These features are aligned to both the absolute proper motion and to the Galactic Centre directions. Moreover, other overdensities appear to be stretched in a direction perpendicular to the Galactic plane. Accordingly to the behaviour observed in the density map, we find that both the surface brightness and the star count density profiles reveal a departure from a King model starting from ˜600 arcsec from the centre. These observational evidence suggest that NGC 6791 is currently experiencing mass-loss likely due to gravitational shocking and interactions with the tidal field. We use this evidence to argue that NGC 6791 should have lost a significant fraction of its original mass. A larger initial mass would in fact explain why the cluster survived so long. Using available recipes based on analytic studies and N-body simulations, we derived the expected mass-loss due to stellar evolution and tidal interactions and estimated the initial cluster mass to be Mini = (1.5-4) × 105 M⊙.

  17. The age-mass-metallicity-activity relation for solar-type stars: comparisons with asteroseismology and the NGC 188 open cluster

    NASA Astrophysics Data System (ADS)

    Lorenzo-Oliveira, D.; Porto de Mello, G. F.; Schiavon, R. P.

    2016-10-01

    Context. The Mount Wilson Ca ii index log(R'_HK) is the accepted standard metric of calibration for the chromospheric activity versus age relation for FGK stars. Recent results claim its inability to discern activity levels, and thus ages, for stars older than ~2 Gyr, which would severely hamper its application to date disk stars older than the Sun. Aims: We present a new activity-age calibration of the Mt. Wilson index that explicitly takes mass and [Fe/H] biases into account; these biases are implicit in samples of stars selected to have precise ages, which have so far not been appreciated. Methods: We show that these selection biases tend to blur the activity-age relation for large age ranges. We calibrate the Mt. Wilson index for a sample of field FGK stars with precise ages, covering a wide range of mass and [Fe/H] , augmented with data from the Pleiades, Hyades, M 67 clusters, and the Ursa Major moving group. Results: We further test the calibration with extensive new Gemini/GMOS log ()R'HK) data of the old, solar [Fe/H] clusters, M 67 and NGC 188. The observed NGC 188 activity level is clearly lower than M 67. We correctly recover the isochronal age of both clusters and establish the viability of deriving usable chromospheric ages for solar-type stars up to at least ~6 Gyr, where average errors are ~0.14 dex provided that we explicitly account for the mass and [Fe/H] dimensions. We test our calibration against asteroseismological ages, finding excellent correlation (ρ = + 0.89). We show that our calibration improves the chromospheric age determination for a wide range of ages, masses, and metallicities in comparison to previous age-activity relations.

  18. Ab initio Bogoliubov coupled cluster theory for open-shell nuclei

    DOE PAGES

    Signoracci, Angelo J.; Duguet, Thomas; Hagen, Gaute; ...

    2015-06-29

    Background: Ab initio many-body methods have been developed over the past 10 yr to address closed-shell nuclei up to mass A≈130 on the basis of realistic two- and three-nucleon interactions. A current frontier relates to the extension of those many-body methods to the description of open-shell nuclei. Several routes to address open-shell nuclei are currently under investigation, including ideas that exploit spontaneous symmetry breaking. Purpose: Singly open-shell nuclei can be efficiently described via the sole breaking of U(1) gauge symmetry associated with particle-number conservation as a way to account for their superfluid character. While this route was recently followed withinmore » the framework of self-consistent Green's function theory, the goal of the present work is to formulate a similar extension within the framework of coupled cluster theory. Methods: We formulate and apply Bogoliubov coupled cluster (BCC) theory, which consists of representing the exact ground-state wave function of the system as the exponential of a quasiparticle excitation cluster operator acting on a Bogoliubov reference state. Equations for the ground-state energy and the cluster amplitudes are derived at the singles and doubles level (BCCSD) both algebraically and diagrammatically. The formalism includes three-nucleon forces at the normal-ordered two-body level. The first BCC code is implemented in m scheme, which will permit the treatment of doubly open-shell nuclei via the further breaking of SU(2) symmetry associated with angular momentum conservation. Results: Proof-of-principle calculations in an Nmax=6 spherical harmonic oscillator basis for 16,18O and 18Ne in the BCCD approximation are in good agreement with standard coupled cluster results with the same chiral two-nucleon interaction, while 20O and 20Mg display underbinding relative to experiment. The breaking of U(1) symmetry, monitored by computing the variance associated with the particle-number operator, is

  19. Ab initio Bogoliubov coupled cluster theory for open-shell nuclei

    SciTech Connect

    Signoracci, Angelo J.; Duguet, Thomas; Hagen, Gaute; Jansen, G. R.

    2015-06-29

    Background: Ab initio many-body methods have been developed over the past 10 yr to address closed-shell nuclei up to mass A≈130 on the basis of realistic two- and three-nucleon interactions. A current frontier relates to the extension of those many-body methods to the description of open-shell nuclei. Several routes to address open-shell nuclei are currently under investigation, including ideas that exploit spontaneous symmetry breaking. Purpose: Singly open-shell nuclei can be efficiently described via the sole breaking of U(1) gauge symmetry associated with particle-number conservation as a way to account for their superfluid character. While this route was recently followed within the framework of self-consistent Green's function theory, the goal of the present work is to formulate a similar extension within the framework of coupled cluster theory. Methods: We formulate and apply Bogoliubov coupled cluster (BCC) theory, which consists of representing the exact ground-state wave function of the system as the exponential of a quasiparticle excitation cluster operator acting on a Bogoliubov reference state. Equations for the ground-state energy and the cluster amplitudes are derived at the singles and doubles level (BCCSD) both algebraically and diagrammatically. The formalism includes three-nucleon forces at the normal-ordered two-body level. The first BCC code is implemented in m scheme, which will permit the treatment of doubly open-shell nuclei via the further breaking of SU(2) symmetry associated with angular momentum conservation. Results: Proof-of-principle calculations in an Nmax=6 spherical harmonic oscillator basis for 16,18O and 18Ne in the BCCD approximation are in good agreement with standard coupled cluster results with the same chiral two-nucleon interaction, while 20O and 20Mg display underbinding relative to experiment. The breaking of U(1) symmetry, monitored by computing the variance

  20. WIYN Open Cluster Study. XLVIII. The Hard-binary Population of NGC 188

    NASA Astrophysics Data System (ADS)

    Geller, Aaron M.; Mathieu, Robert D.

    2012-08-01

    We present an in-depth study of the hard-binary population of the old (7 Gyr) open cluster NGC 188. Utilizing 85 spectroscopic binary orbits out of a complete sample of 129 detected binary members, we study the cluster binary frequency and the distributions of binary orbital elements among the main-sequence (MS), giant, and blue straggler (BS) populations. The results are derived from our ongoing radial velocity survey of the cluster, which spans in magnitude from the brightest stars in the cluster to V = 16.5 (about 1.1-0.9 M ⊙), and extends to a projected radius of 17 pc (~13 core radii). Our detectable binaries have periods ranging from a few days to of order 104 days, and thus are hard binaries that dynamically power the cluster. The MS solar-type hard binaries in NGC 188 are nearly indistinguishable from similar binaries in the Galactic field. We observe a global solar-type MS hard-binary frequency in NGC 188 of 23% ± 2%, which when corrected for incompleteness results in a frequency of 29% ± 3% for binaries with periods less than 104 days. For MS hard binaries in the cluster, we observe a log-period distribution that rises toward our detection limit, a roughly Gaussian eccentricity distribution centered on e = 0.35 (for binaries with periods longer than the circularization period), and a secondary-mass distribution that rises toward lower-mass companions. Importantly, the NGC 188 BS binaries show significantly different characteristics than the solar-type MS binaries in NGC 188. We observe a BS hard-binary frequency of 76% ± 19%, three times that of the MS. The excess of this binary frequency over the normal MS binary frequency is valid at the >99% confidence level. Furthermore, the BS binary eccentricity-log-period distribution is distinct from that of the MS at the 99% confidence level, with the majority of the BS binaries having periods of order 1000 days and lower eccentricities. The secondary-mass distribution for these long-period BS binaries is

  1. The Design, Synthesis, and Characterization of Open Sites on Metal Clusters

    NASA Astrophysics Data System (ADS)

    Nigra, Michael Mark

    undercoordinated sites led me to synthesize small gold clusters consisting of a high fraction of coordinatively unsaturated open sites. This was enabled through an approach that utilized bulky calix[4]arene ligands that are bound to a gold core. Since the size of the calix[4]arene ligand is commensurate with the size of the gold cluster core, the calix[4]arene ligand does not pack closely together on the gold cluster surface. This in turn results in areas of accessible gold atom sites between ligands. Additionally, these calix[4]arene ligands prevent cluster aggregation and electronically tune the gold core in a manner conceptually similar to enzymes affecting reactivity through organic side-chains acting as ligands. I quantified the number of open sites that result from this packing problem on the gold cluster surface, using fluorescence probe chemisorption experiments. The results of these chemisorption measurements support the mechanical model of accessibility whereby accessibility is not dependent on the identity of the functional group, whether it be calixarene phosphines or N-heterocyclic carbenes, bound to the gold surface, but rather to the relative radii of curvature of bound ligands and the gold cluster core. Additional materials characterization was completed with transmission electron microscopy in both bright-field imaging of zeolites, in MCM-22 and delaminated ITQ-2 and UCB-1 materials, and in dark field imaging of glucan coatings on oxide particles. These materials could prove to be interesting materials as to use as supports for the calixarene-bound metal clusters described above or for other metal clusters.

  2. The WFI Hα spectroscopic survey of the Magellanic Clouds: Be stars in SMC open clusters

    NASA Astrophysics Data System (ADS)

    Martayan, Christophe; Baade, Dietrich; Fabregat, Juan

    2009-03-01

    At low metallicity, B-type stars show lower loss of mass and, therefore, angular momentum so that it is expected that there are more Be stars in the Magellanic Clouds than in the Milky Way. However, till now, searches for Be stars were only performed in a very small number of open clusters in the Magellanic Clouds. Using the ESO/WFI in its slitless spectroscopic mode, we performed a Hα survey of the Large and Small Magellanic Cloud. Eight million low-resolution spectra centered on Hα were obtained. For their automatic analysis, we developed the ALBUM code. Here, we present the observations, the method to exploit the data and first results for 84 open clusters in the SMC. In particular, cross-correlating our catalogs with OGLE positional and photometric data, we classified more than 4000 stars and were able to find the B and Be stars in them. We show the evolution of the rates of Be stars as functions of area density, metallicity, spectral type, and age.

  3. ACCRETION RATES ON PRE-MAIN-SEQUENCE STARS IN THE YOUNG OPEN CLUSTER NGC 6530

    SciTech Connect

    Gallardo, Jose; Del Valle, Luciano; Ruiz, Maria Teresa E-mail: ldelvall@das.uchile.cl

    2012-01-15

    It is well accepted that during the star formation process, material from a protoplanetary disk is accreted onto the central object during the first {approx}1-5 Myr. Different authors have published measurements of accretion rates for young low- and intermediate-mass stars in several nearby star-forming regions (SFRs). Due to its somewhat larger distance, the SFR M8 (the Lagoon Nebula) has not been studied to the same extent, despite its abundant population of young stellar objects. We have obtained optical band low-resolution spectra of a sample of pre-main-sequence stars in the open cluster NGC 6530 located in the aforementioned nebulae using the Gemini Multi Object Spectrograph at Gemini-South in multi-object mode. Spectra cover the H{sub {alpha}} emission line used to measure the accretion rate, following the method presented by Natta et al. The observed spectral characteristics are fully consistent with pre-main-sequence stars, showing lithium absorption lines, which are very common in young stellar objects, as well as prominent and broad H{sub {alpha}} emission lines, indicating a T Tauri evolutionary stage. This work presents the first determinations of mass accretion rates of young stellar objects in the open cluster NGC 6530, confirming that they are classical T Tauri stars going through the accretion phase. These observations contribute to a better understanding of the stellar content and evolutionary phase of the very active Lagoon Nebula SFR.

  4. Spectroscopy and Strömgren Photometry in the Young Open Cluster NGC 2169

    NASA Astrophysics Data System (ADS)

    Yost, C. C.; Gray, R. O.; Murdick, L.; Robinson, P.

    2000-12-01

    NGC 2169 is a young (1.5 x 107 yr) open cluster in Orion with no associated nebulosity. As part of our program of searching for peculiar stars in open clusters, we have obtained classification--resolution (1.8Å/2 pixels) spectra for 23 stars, low--resolution (20Å/2 pixels) spectra for an additional 9 stars, and Strömgren uvby photometry for 40 stars in the field of NGC 2169 down to V ~ 15.5. The observations were made on the 0.8 meter telescope of Appalachian State University's Dark Sky Observatory. NGC 2169 appears to have very few members later than spectral type A3. However, the Strömgren photometry yields 5 new candidate members of NGC 2169, plus a population of possible but not probable pre--main--sequence stars. The spectroscopy shows that most stars in NGC 2169 are normal, except for two helium--weak B--type stars, and a mild Silicon Bp star. More spectroscopy and photometry is planned in the field. This project has been partially funded by a small AAS Grant, plus an Undergraduate Research Scholarship from the Graduate School of Appalachian State University to C.C. Yost. We would also like to acknowledge a grant from the Fund for Astrophysical Research.

  5. Photometric and Proper Motion Study of the Neglected Open Cluster NGC 2215

    NASA Astrophysics Data System (ADS)

    Fitzgerald, M. T.; Inwood, L.; McKinnon, D. H.; Dias, W. S.; Sacchi, M.; Scott, B.; Zolinski, M.; Danaia, L.; Edwards, R.

    2015-06-01

    Optical UBVRI photometric measurements using the Faulkes Telescope North were taken in early 2011 and combined with 2MASS JHKs and WISE infrared photometry as well as UCAC4 proper motion data in order to estimate the main parameters of the galactic open cluster NGC 2215 of which large uncertainty exists in the current literature. Fitting a King model we estimate a core radius of 1.‧12 ± 0.‧04 (0.24 ± 0.01 pc) and a limiting radius of 4.‧3 ± 0.‧5 (0.94 ± 0.11 pc) for the cluster. The results of isochrone fits indicates an age of log (t)=8.85+/- 0.10 with a distance of d=790+/- 90 pc, a metallicity of [Fe/H]=-0.40+/- 0.10 dex, and a reddening of E(B-V)=0.26+/- 0.04. A proportion of the work in this study was undertaken by Australian and Canadian upper secondary school students involved in the Space to Grow astronomy education project, and is the first scientific publication to have utilized our star cluster photometry curriculum materials.

  6. The Open Connectome Project Data Cluster: Scalable Analysis and Vision for High-Throughput Neuroscience.

    PubMed

    Burns, Randal; Roncal, William Gray; Kleissas, Dean; Lillaney, Kunal; Manavalan, Priya; Perlman, Eric; Berger, Daniel R; Bock, Davi D; Chung, Kwanghun; Grosenick, Logan; Kasthuri, Narayanan; Weiler, Nicholas C; Deisseroth, Karl; Kazhdan, Michael; Lichtman, Jeff; Reid, R Clay; Smith, Stephen J; Szalay, Alexander S; Vogelstein, Joshua T; Vogelstein, R Jacob

    2013-01-01

    We describe a scalable database cluster for the spatial analysis and annotation of high-throughput brain imaging data, initially for 3-d electron microscopy image stacks, but for time-series and multi-channel data as well. The system was designed primarily for workloads that build connectomes- neural connectivity maps of the brain-using the parallel execution of computer vision algorithms on high-performance compute clusters. These services and open-science data sets are publicly available at openconnecto.me. The system design inherits much from NoSQL scale-out and data-intensive computing architectures. We distribute data to cluster nodes by partitioning a spatial index. We direct I/O to different systems-reads to parallel disk arrays and writes to solid-state storage-to avoid I/O interference and maximize throughput. All programming interfaces are RESTful Web services, which are simple and stateless, improving scalability and usability. We include a performance evaluation of the production system, highlighting the effec-tiveness of spatial data organization.

  7. On the lithium dip in the metal poor open cluster NGC 2243

    SciTech Connect

    François, P.; Pasquini, L.; Palsa, R.; Biazzo, K.; Bonifacio, P.

    2014-05-02

    Lithium is a key element for studying the mixing mechanisms operating in stellar interiors. It can also be used to probe the chemical evolution of the Galaxy and the Big Bang nucleosynthesis. Measuring the abundance of Lithium in stars belonging to Open Clusters (hereafter OC) allows a detailed comparison with stellar evolutionary models. NGC 2243 is particularly interesting thanks to its relative low metallicity ([Fe/H]=−0.54 ± 0.10 dex). We performed a detailed analysis of high-resolution spectra obtained with the multi-object facility FLAMES at the VLT 8.2m telescope. Lithium abundance has been measured in 27 stars. We found a Li dip center of 1.06 M{sub ⊙}, which is significantly smaller than that observed in solar metallicity and metal-rich clusters. This finding confirms and strengthens the conclusion that the mass of the stars in the Li dip strongly depends on stellar metallicity. The mean Li abundance of the cluster is log n(Li) = 2.70 dex, which is substantially higher than that observed in 47 Tue. We derived an iron abundance of [Fe/H]=−0.54±0.10 dex for NGC 2243, in agreement (within the errors) with previous findings.

  8. The Open Connectome Project Data Cluster: Scalable Analysis and Vision for High-Throughput Neuroscience

    PubMed Central

    Burns, Randal; Roncal, William Gray; Kleissas, Dean; Lillaney, Kunal; Manavalan, Priya; Perlman, Eric; Berger, Daniel R.; Bock, Davi D.; Chung, Kwanghun; Grosenick, Logan; Kasthuri, Narayanan; Weiler, Nicholas C.; Deisseroth, Karl; Kazhdan, Michael; Lichtman, Jeff; Reid, R. Clay; Smith, Stephen J.; Szalay, Alexander S.; Vogelstein, Joshua T.; Vogelstein, R. Jacob

    2013-01-01

    We describe a scalable database cluster for the spatial analysis and annotation of high-throughput brain imaging data, initially for 3-d electron microscopy image stacks, but for time-series and multi-channel data as well. The system was designed primarily for workloads that build connectomes— neural connectivity maps of the brain—using the parallel execution of computer vision algorithms on high-performance compute clusters. These services and open-science data sets are publicly available at openconnecto.me. The system design inherits much from NoSQL scale-out and data-intensive computing architectures. We distribute data to cluster nodes by partitioning a spatial index. We direct I/O to different systems—reads to parallel disk arrays and writes to solid-state storage—to avoid I/O interference and maximize throughput. All programming interfaces are RESTful Web services, which are simple and stateless, improving scalability and usability. We include a performance evaluation of the production system, highlighting the effec-tiveness of spatial data organization. PMID:24401992

  9. High-resolution elemental abundance analysis of the open cluster IC 4756

    NASA Astrophysics Data System (ADS)

    Ting, Yuan-Sen; De Silva, Gayandhi M.; Freeman, Kenneth C.; Parker, Stacey Jo

    2012-11-01

    We present detailed elemental abundances of 12 subgiants in the open cluster IC 4756 including Na, Al, Mg, Si, Ca, Ti, Cr, Ni, Fe, Zn and Ba. We measure the cluster to have [Fe/H] = -0.01 ± 0.10. Most of the measured star-to-star [X/H] abundance variation is below σ < 0.03, as expected from a coeval stellar population preserving natal abundance patterns, supporting the use of elemental abundances as a probe to reconstruct dispersed clusters. We find discrepancies between Cr I and Cr II abundances as well as between Ti I and Ti II abundances, where the ionized abundances are larger by about 0.2 dex. This follows other such studies which demonstrate the effects of overionization in cool stars. IC 4756 are supersolar in Mg, Si, Na and Al, but are solar in the other elements. The fact that IC 4756 is supersolar in some α-elements (Mg, Si) but solar in the others (Ca, Ti) suggests that the production of α-elements is not simply one dimensional and could be exploited for chemical tagging.

  10. Spectroscopic Binaries and Kinematic Membership in the Open Cluster NGC 3532

    NASA Astrophysics Data System (ADS)

    González, Jorge Federico; Lapasset, Emilio

    2002-06-01

    We report spectroscopic observations for bright stars in the open cluster NGC 3532 up to 1 mag below the turnoff point. We compute radial velocities by cross-correlations and determine spectral types and rotational velocities. Using 21 stars identified as certain members, we derive a mean cluster velocity of +3.4+/-0.3 km s-1. From radial velocities and angular distances to the cluster center, we compute membership probabilities for all but two stars that are radial velocity variables. Only one out of 34 program stars is a clear kinematic nonmember. Three spectroscopic binaries and three additional possible radial velocity variables are detected among the 23 stars measured more than once. We report the star HD 96609 as a double-lined spectroscopic binary. Using the two-dimensional cross-correlation technique TODCOR developed by Zucker & Mazeh, we derive the radial velocity curves for both components and obtain the orbital parameters with errors of 0.3% and 0.7% for the projected orbital semiaxis and masses, respectively. This system is composed of two main-sequence stars in a circular orbit, with a period of 8.19 days. The observations presented here were obtained at the Complejo Astronómico El Leoncito (CASLEO), which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina (CONICET) and the National Universities of La Plata, Córdoba, and San Juan.

  11. New Neutron-capture Measurements in 23 Open Clusters. I. The r-Process

    NASA Astrophysics Data System (ADS)

    Overbeek, Jamie C.; Friel, Eileen D.; Jacobson, Heather R.

    2016-06-01

    Neutron-capture elements, those with Z > 35, are the least well understood in terms of nucleosynthesis and formation environments. The rapid neutron-capture, or r-process, elements are formed in the environments and/or remnants of massive stars, while the slow neutron-capture, or s-process, elements are primarily formed in low-mass AGB stars. These elements can provide much information about Galactic star formation and enrichment, but observational data are limited. We have assembled a sample of 68 stars in 23 open clusters that we use to probe abundance trends for six neutron-capture elements (Eu, Gd, Dy, Mo, Pr, and Nd) with cluster age and location in the disk of the Galaxy. In order to keep our analysis as homogeneous as possible, we use an automated synthesis fitting program, which also enables us to measure multiple (3-10) lines for each element. We find that the pure r-process elements (Eu, Gd, and Dy) have positive trends with increasing cluster age, while the mixed r- and s-process elements (Mo, Pr, and Nd) have insignificant trends consistent with zero. Pr, Nd, Eu, Gd, and Dy have similar, slight (although mostly statistically significant) gradients of ˜0.04 dex kpc-1. The mixed elements also appear to have nonlinear relationships with R GC.

  12. The Initial-Final Mass Relation: Analysis of White Dwarfs in the M7 Open Cluster

    NASA Astrophysics Data System (ADS)

    Cummings, Jeff D.; Kalirai, Jason S.; Geisler, Douglas; Tremblay, Pier-Emmanuel; Mauro, Francesco; Deliyannis, Constantine P.

    2017-01-01

    The initial-final mass relation (IFMR) is a direct comparison of the mass a star forms with on the main sequence to its final mass as a white dwarf. This provides critical information for our understanding of stellar evolution and mass loss, and how these are dependent on initial mass. Our group has done detailed analysis of the known white dwarfs in star clusters to improve the semi-empirical IFMR, but limited data (most importantly at the highest masses) causes remaining uncertainties. Our new wide-field photometric and spectroscopic observations of the young and nearby M7 open cluster have discovered and confirmed five new white dwarfs consistent with single-star membership. Four are intermediate-mass white dwarfs (0.65 to 0.85 Msun) and the final is a white dwarf estimated to be at 1.25 Msun and with an estimated initial mass of 6.75 Msun. Higher signal-to-noise follow-up spectra are required, but these and similar observations of other young and nearby clusters will begin to characterize the poorly explored ultra-high-mass end of the IFMR.

  13. A super lithium-rich red-clump star in the open cluster Trumpler 5

    NASA Astrophysics Data System (ADS)

    Monaco, L.; Boffin, H. M. J.; Bonifacio, P.; Villanova, S.; Carraro, G.; Caffau, E.; Steffen, M.; Ahumada, J. A.; Beletsky, Y.; Beccari, G.

    2014-04-01

    Context. The existence of lithium-rich low-mass red giant stars still represents a challenge for stellar evolution models. Stellar clusters are privileged environments for this kind of investigation. Aims: To investigate the chemical abundance pattern of the old open cluster Trumpler 5, we observed a sample of four red-clump stars with high-resolution optical spectrographs. One of them (#3416) reveals extremely strong lithium lines in its spectrum. Methods: One-dimensional, local thermodynamic equilibrium analysis was performed on the spectra of the observed stars. A 3D-NLTE analysis was performed to derive the lithium abundance of star #3416. Results: Star #3416 is super Li-rich with A(Li) = 3.75 dex. The lack of 6Li enrichment (6Li/7Li < 2%), the low carbon isotopic ratio (12C/13C = 14 ± 3), and the lack of evidence for radial velocity variation or enhanced rotational velocity (vsini = 2.8 km s-1) all suggest that lithium production has occurred in this star through the Cameron & Fowler mechanism. Conclusions: We identified a super Li-rich core helium-burning, red-clump star in an open cluster. Internal production is the most likely cause of the observed enrichment. Given the expected short duration of a star's Li-rich phase, enrichment is likely to have occurred at the red clump or in the immediately preceding phases, namely during the He-flash at the tip of the red giant branch (RGB) or while ascending the brightest portion of the RGB. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under program ID 088.D-0045(A).Appendix A is available in electronic form at http://www.aanda.org

  14. WOCS 40007: A DETACHED ECLIPSING BINARY NEAR THE TURNOFF OF THE OPEN CLUSTER NGC 6819

    SciTech Connect

    Jeffries, Mark W. Jr.; Sandquist, Eric L.; Orosz, Jerome A.; Brewer, Lauren N. E-mail: erics@mintaka.sdsu.edu E-mail: lbrewer@rohan.sdsu.edu; and others

    2013-09-15

    We analyze extensive BVR{sub c}I{sub c} time-series photometry and radial-velocity measurements for WOCS 40007 (Auner 259; KIC 5113053), a double-lined detached eclipsing binary and a member of the open cluster NGC 6819. Utilizing photometric observations from the 1 m telescope at Mount Laguna Observatory and spectra from the WIYN 3.5 m telescope, we measure precise and accurate masses ({approx}1.6% uncertainty) and radii ({approx}0.5%) for the binary components. In addition, we discover a third star orbiting the binary with a period greater than 3000 days using radial velocities and Kepler eclipse timings. Because the stars in the eclipsing binary are near the cluster turnoff, they are evolving rapidly in size and are sensitive to age. With a metallicity of [Fe/H] = +0.09 {+-} 0.03, we find the age of NGC 6819 to be about 2.4 Gyr from color-magnitude diagram (CMD) isochrone fitting and 3.1 {+-} 0.4 Gyr by analyzing the mass-radius (M-R) data for this binary. The M-R age is above previous determinations for this cluster, but consistent within 1{sigma} uncertainties. When the M-R data for the primary star of the additional cluster binary WOCS 23009 is included, the weighted age estimate drops to 2.5 {+-} 0.2 Gyr, with a systematic uncertainty of at least 0.2 Gyr. The age difference between our CMD and M-R findings may be the result of systematic error in the metallicity or helium abundance used in models, or due to slight radius inflation of one or both stars in the WOCS 40007 binary.

  15. The evolution of the Milky Way: new insights from open clusters

    NASA Astrophysics Data System (ADS)

    Reddy, Arumalla B. S.; Lambert, David L.; Giridhar, Sunetra

    2016-12-01

    We have collected high-dispersion echelle spectra of red giant members in the 12 open clusters (OCs) and derived stellar parameters and chemical abundances for 26 species by either line equivalent widths or synthetic spectrum analyses. We confirm the lack of an age-metallicity relation for OCs but argue that such a lack of trend for OCs arise from the limited coverage in metallicity compared to that of field stars which span a wide range in metallicity and age. We confirm that the radial metallicity gradient of OCs is steeper (flatter) for Rgc < 12 kpc (>12 kpc). We demonstrate that the sample of clusters constituting a steep radial metallicity gradient of slope -0.052 ± 0.011 dex kpc-1 at Rgc < 12 kpc are younger than 1.5 Gyr and located close to the Galactic mid-plane (| z| < 0.5 kpc) with kinematics typical of the thin disc. Whereas the clusters describing a shallow slope of -0.015 ± 0.007 dex kpc-1 at Rgc > 12 kpc are relatively old, thick disc members with a striking spread in age and height above the mid-plane (0.5 < | z| < 2.5 kpc). Our investigation reveals that the OCs and field stars yield consistent radial metallicity gradients if the comparison is limited to samples drawn from the similar vertical heights. We argue via the computation of Galactic orbits that all the outer disc clusters were actually born inwards of 12 kpc but the orbital eccentricity has taken them to present locations very far from their birthplaces.

  16. Bayesian investigation of isochrone consistency using the old open cluster NGC 188

    SciTech Connect

    Hills, Shane; Courteau, Stéphane; Von Hippel, Ted; Geller, Aaron M. E-mail: courteau@astro.queensu.ca E-mail: a-geller@northwestern.edu

    2015-03-01

    This paper provides a detailed comparison of the differences in parameters derived for a star cluster from its color–magnitude diagrams (CMDs) depending on the filters and models used. We examine the consistency and reliability of fitting three widely used stellar evolution models to 15 combinations of optical and near-IR photometry for the old open cluster NGC 188. The optical filter response curves match those of theoretical systems and are thus not the source of fit inconsistencies. NGC 188 is ideally suited to this study thanks to a wide variety of high-quality photometry and available proper motions and radial velocities that enable us to remove non-cluster members and many binaries. Our Bayesian fitting technique yields inferred values of age, metallicity, distance modulus, and absorption as a function of the photometric band combinations and stellar models. We show that the historically favored three-band combinations of UBV and VRI can be meaningfully inconsistent with each other and with longer baseline data sets such as UBVRIJHK{sub S}. Differences among model sets can also be substantial. For instance, fitting Yi et al. (2001) and Dotter et al. (2008) models to UBVRIJHK{sub S} photometry for NGC 188 yields the following cluster parameters: age = (5.78 ± 0.03, 6.45 ± 0.04) Gyr, [Fe/H] = (+0.125 ± 0.003, −0.077 ± 0.003) dex, (m−M){sub V} = (11.441 ± 0.007, 11.525 ± 0.005) mag, and A{sub V} = (0.162 ± 0.003, 0.236 ± 0.003) mag, respectively. Within the formal fitting errors, these two fits are substantially and statistically different. Such differences among fits using different filters and models are a cautionary tale regarding our current ability to fit star cluster CMDs. Additional modeling of this kind, with more models and star clusters, and future Gaia parallaxes are critical for isolating and quantifying the most relevant uncertainties in stellar evolutionary models.

  17. Phase Transition for the Large-Dimensional Contact Process with Random Recovery Rates on Open Clusters

    NASA Astrophysics Data System (ADS)

    Xue, Xiaofeng

    2016-12-01

    In this paper we are concerned with the contact process with random recovery rates on open clusters of bond percolation on Z^d. Let ξ be a random variable such that P(ξ ≥ 1)=1, which ensures E1/ξ <+∞, then we assign i. i. d. copies of ξ on the vertices as the random recovery rates. Assuming that each edge is open with probability p and the infection can only spread through the open edges, then we obtain that limsup _{d→ +∞}λ _d≤ λ _c=1/pE{1}/{ξ}, where λ _d is the critical value of the process on Z^d, i.e., the maximum of the infection rates with which the infection dies out with probability one when only the origin is infected at t=0. To prove the above main result, we show that the following phase transition occurs. Assuming that lceil log drceil vertices are infected at t=0, where these vertices can be located anywhere, then when the infection rate λ >λ _c, the process survives with high probability as d→ +∞ while when λ <λ _c, the process dies out at time O(log d) with high probability.

  18. Formation history of old open clusters constrained by detailed asteroseismology of red giant stars observed by Kepler

    NASA Astrophysics Data System (ADS)

    Corsaro, E.; Lee, Y.-N.; García, R. A.; Hennebelle, P.; Mathur, S.; Beck, P. G.; Mathis, S.; Stello, D.; Bouvier, J.

    2016-12-01

    Stars originate by the gravitational collapse of a turbulent molecular cloud, often forming clusters of thousands of stars. Stellar clusters therefore play an important role in our understanding of star formation, a fundamental problem in astrophysics that is difficult to investigate because pre-stellar cores are typically obscured by dust. Thanks to a Bayesian analysis of about 50 red giants of NGC 6791 and NGC 6819, two old open clusters observed by NASA Kepler, we characterize thousands of individual oscillation modes. We show for the first time how the measured asteroseismic properties lead us to a discovery about the rotation history of these clusters. Finally, our findings are compared to 3D hydrodynamical simulations for stellar cluster formation to put strong constraints on the physical processes of turbulence and rotation, which are in action in the early formation stage of the stellar clusters.

  19. Proper motions and CCD-photometry of stars in the region of the open cluster Trumpler 2

    NASA Astrophysics Data System (ADS)

    Frolov, V. N.; Ananjevskaja, J. K.; Jilinski, E. G.; Gorshanov, D. L.; Bronnikova, N. M.

    2006-06-01

    The results of a complex study of the galactic open cluster Trumpler 2 are presented. In order to obtain the proper motions, the positions of approximately 3000 stars up to the limit magnitude B˜16.25 mag in the area 80 arcmin×80 arcmin around the cluster were measured on 6 plates with a maximal epoch difference of 63 years. The root-mean error of the relative proper motions is 4.2 mas yr-1. The catalogue of {BV} magnitudes of all the stars in the investigated area was compiled. The selection of the cluster members within the region of R<16 arcmin from the center of the cluster was made. Altogether, 148 stars were considered to be cluster members by both astrometrical and photometrical criteria. We present the estimated age (8.91×107 yr) and physical parameters of the cluster and append the catalogues of the proper motions and of the photometry of the stars.

  20. A Survey of Open Clusters in the u'g'r'i'z' Filter System. 3. Results for the Cluster NGC 188

    SciTech Connect

    Fornal, Bartosz; Tucker, Douglas L.; Smith, J.Allyn; Allam, Sahar S.; Rider, Cristin J.; Sung, Hwankyung; /Jagiellonian U. /Fermilab /Austin Peay State U. /Wyoming U. /Johns Hopkins U. /Sejong U.

    2006-11-01

    The authors continue the series of papers describing the results of a photometric survey of open star clusters, primarily in the southern hemisphere, taken in the u'g'r'i'z' filter system. The entire observed sample covered more than 100 clusters, but here they present data only on NGC 188, which is one of the oldest open clusters known in the Milky Way. They fit the Padova theoretical isochrones to the data. Assuming a solar metallicity for NGC 188, they find a distance of 1700 {+-} 100 pc, an age of 7.5 {+-} 0.7 Gyr, and a reddening E(B-V) of 0.025 {+-} 0.005. This yields a distance modulus of 11.23 {+-} 0.14.

  1. Nucleophilic ring opening of bridging thietane ligands in trirhenium carbonyl cluster complexes

    SciTech Connect

    Adams, R.D.; Cortopassi, J.E.; Falloon, S.B.

    1992-11-01

    The reactions of 3,3-dimethylthietane, SCH{sub 2}CMe{sub 2}CH{sub 2} (3,3-DMT), and thietane, SCH{sub 2}CH{sub 2}CH{sub 2}, with Re{sub 3}(CO){sub 10}[{mu}-SCH{sub 2}CH{sub 2}CH{sub 2}]({mu}-H){sub 3}, 2b. Compound 2a was characterized crystallographically and was found to consist of a trirhenium cluster with three bridging hydride ligands and a bridging thietane ligand coordinated through its sulfur atom. 2a and 2b react with halide ions by ring-opening additions to the 3,3-DMT ligand to yield the complex anions [Re{sub 3}(CO){sub 10}({mu}-SCH{sub 2}CMe{sub 2}CH{sub 2}x)({mu}-h){sub 3}]{sup -} 3A-6A, X = F (71%), Cl(71%), Br(84%), I(87%) and [Re{sub 3}(CO){sub 10}({mu}-SCH{sub 2}CH{sub 2}CH{sub 2}Cl)({mu}-H){sub 3}]{sup -}, 4b (67%). Similarly, addition of NMe{sub 3} to 2a and 2b yielded the ring-opened zwitterions Re{sub 3}(CO){sub 10}({mu}-SCH{sub 2}CMe{sub 2}CH{sub 2}NMe{sub 3})({mu}-H){sub 3}, 7 a crystographically. They are zwitterions positively charged at the nitrogen atoms and negatively charged on the trirhenium clusters. Complex 7b was also obtained in a 48% yield from the reaction of Re{sub 3}(C){sub 12}({mu}-H){sub 3} with Me{sub 3}NO in the presence of thietane, but the corresponding reaction using 3,3-DMT yielded only 2a and Re{sub 3}(CO){sub 11}(SCH{sub 2}CMe{sub 2}CH{sub 2})({mu}-H){sub 3}, 8. Attempts to obtain a ring-opening addition to 2a by reaction with PMe{sub 2}Ph yielded only Re{sub 3}(CO){sub 10}(PMe{sub 2}PH){sub 2}({mu}-H){sub 3} by ligand substitution. Attempts to obtain ring opening addition to 8 by reaction with I{sup -} yielded only [Re{sub 3}(CO){sub 11}I({mu}-H){sub 3}]{sup -} by ligand substitution. 20 refs., 3 figs., 10 tabs.

  2. Entrapment of Metal Clusters in MOF Channels by Extended Hooks Anchored at Open Metal Sites

    PubMed Central

    Zheng, Shou-Tian; Zhao, Xiang; Lau, Samuel; Fuhr, Addis; Feng, Pingyun; Bu, Xianhui

    2015-01-01

    Reported here is a new concept and its practical implementation that involves the novel utilization of open metal sites (OMS) for architectural pore design. Specifically, it is shown here that OMS can be used to run extended hooks (isonicotinate in this work) from the framework wall to channel centers to effect the capture of single metal ions or clusters, with the concurrent partition of the large channel space into multiple domains, alteration of host-guest charge relationship and associated guest-exchange properties, as well as the transfer of OMS from the wall to the channel centers. The concept of the extended hook, demonstrated here in the multi-component dual-metal and dual-ligand system, should be generally applicable to a range of framework types. PMID:23826752

  3. Nucleosynthesis in the Hyades Open Cluster: Evidence for the Enhanced Depletion of 12C

    NASA Astrophysics Data System (ADS)

    Schuler, Simon C.; King, Jeremy R.; The, Lih-Sin

    2010-03-01

    We present the results of a light element abundance analysis of three solar-type main sequence (MS) dwarfs and three red giant branch (RGB) clump stars in the Hyades open cluster using high-resolution and high signal-to-noise spectroscopy. The CNO abundances of each group (MS or RGB) are in excellent star-to-star agreement and confirm that the giants have undergone first dredge-up mixing. The observed abundances are compared to predictions of a standard stellar model based on the Clemson-American University of Beirut (CAUB) stellar evolution code. The model reproduces the observed evolution of the N and O abundances, as well as the previously derived 12C/13C ratio, but it fails to predict the observed level of 12C depletion in the giants. More tellingly, the sum of the observed giant CNO abundances does not equal that of the dwarfs.

  4. A homogeneous photometric and spectroscopic survey of open clusters in the Perseus Arm

    NASA Astrophysics Data System (ADS)

    Marco, Amparo; Negueruela, Ignacio; Monguió, Maria

    2015-08-01

    We are carrying out a homogeneous photometric survey of all young (< 100 Ma) open clusters in the Perseus Arm between Galactic longitudes 90º and 140º, using Strömgren filters at the Isaac Newton Telescope in La Palma. We intend to derive relative ages and distances with typical accuracies of 5 Ma and 200 pc. Our data will allow us to test the predictions of different models for the main mechanism producing the spiral structure of the Milky Way. In addition, we will enormously improve our knowledge of stellar evolution for stars in the 6-15 Msolar range. Moreover, the huge dataset of homogeneous photometry for thousands of stars (including ~2000 B-type stars) will have an enormous legacy value

  5. Observation Of New Variable Stars In The Field Of Open Cluster M23

    NASA Astrophysics Data System (ADS)

    Wilkerson, Jeffrey A.; Brown, T. S.; Frank, K. A.; Joshi, U.; Lacoul, B. K.; Rengstorf, N. P.; Schiefelbein, A. M.

    2007-05-01

    In 2002 a program of surveying regions containing bright open star clusters was initiated using the observing facilities at Luther College. As part of this program the half degree square field containing open cluster M23 was observed in 2003, 2005 and 2006, resulting in approximately 45,000 2.5-second images, 45,000 3.5-second images and 65,000 5.0-second images. The data set contains images from 94 nights spanning a time range from JD 2452810 to JD 2454005. We have searched for stellar variability on timescales from seconds to years in approximately 1600 stars in this field. Unambiguous variability is apparent in 30 stars ranging in magnitude from about 10 to 17. Twenty-eight of these stars have not been previously reported as variable. Seven of the stars are eclipsing binaries, including two apparent W UMa-type contact binaries and one additional eclipsing binary with a period shorter than 0.6 days. The remaining 23 variables are red pulsating stars with long periods. Most of these stars have amplitudes smaller than two magnitudes and periods between 200 and 400 days. Thus, they are likely Semi-Regular variables. We present celestial coordinates, estimated amplitude and estimated period for each of these stars, as well as several selected light curves. Finally, we have performed low-precision BVRI photometry of the field and have placed most of the observed variables on color magnitude diagrams. We are grateful for support from the Roy J. Carver Charitable Trust and the R. J. McElroy Trust.

  6. HD 285507b: An eccentric hot Jupiter in the hyades open cluster

    SciTech Connect

    Quinn, Samuel N.; White, Russel J.; Latham, David W.; Buchhave, Lars A.; Torres, Guillermo; Stefanik, Robert P.; Berlind, Perry; Bieryla, Allyson; Calkins, Michael C.; Esquerdo, Gilbert A.; Fűrész, Gabor; Geary, John C.; Szentgyorgyi, Andrew H.

    2014-05-20

    We report the discovery of the first hot Jupiter in the Hyades open cluster. HD 285507b orbits a V = 10.47 K4.5V dwarf (M {sub *} = 0.734 M {sub ☉}; R {sub *} = 0.656 R {sub ☉}) in a slightly eccentric (e=0.086{sub −0.019}{sup +0.018}) orbit with a period of 6.0881{sub −0.0018}{sup +0.0019} days. The induced stellar radial velocity corresponds to a minimum companion mass of M {sub P}sin i = 0.917 ± 0.033 M {sub Jup}. Line bisector spans and stellar activity measures show no correlation with orbital phase, and the radial velocity amplitude is independent of wavelength, supporting the conclusion that the variations are caused by a planetary companion. Follow-up photometry indicates with high confidence that the planet does not transit. HD 285507b joins a small but growing list of planets in open clusters, and its existence lends support to a planet formation scenario in which a high stellar space density does not inhibit giant planet formation and migration. We calculate the circularization timescale for HD 285507b to be larger than the age of the Hyades, which may indicate that this planet's non-zero eccentricity is the result of migration via interactions with a third body. We also demonstrate a significant difference between the eccentricity distributions of hot Jupiters that have had time to tidally circularize and those that have not, which we interpret as evidence against Type II migration in the final stages of hot Jupiter formation. Finally, the dependence of the circularization timescale on the planetary tidal quality factor, Q {sub P}, allows us to constrain the average value for hot Jupiters to be logQ{sub P}=6.14{sub −0.25}{sup +0.41}.

  7. Photometric investigation of two contact binaries in the young open cluster NGC 957

    NASA Astrophysics Data System (ADS)

    Luo, ChangQing; Zhang, XiaoBin; Deng, Licai; Wang, Kun; Luo, Yangping; Fang, Xiangsong

    2017-04-01

    We present V- and R- band time-series CCD photometry of two contact binaries in the region of the young open cluster NGC 957. The two eclipsing binaries were discovered by Bukowiecki et al., 2009. OEJV 112, 1 and named as V4 and V5, respectively. In the present paper, the first detailed studies of the two contact binary systems are carried out. Firstly, based on the light curves, 28 times of minimum light were detected for V4 and 21 times of minimum light for V5, respectively. Secondly, the orbital periods of V4 and V5 were redetermined as PV4 = 0.40032(5) days and PV5 = 0.30752 (4)days, respectively. The photometric solutions were analyzed by using Wilson Decinny Code. The results reveal that both V4 and V5 are W UMa-type contact binaries with a degree of fV4 = 31(± 1)% and fV5 = 65(± 1)%. The mass ratios were determined to be qV4 = 0.30 and qV5 = 0.19. For V5, the well known O'Connell effect was detected in the dataset, which effect can be explained by employing a dark spot placed on the more massive primary component. Finally, based on the distances of the two contact binaries, which were calculated by using an relation given by Gettel et al., the two contact binaries are judged to be foreground stars in the open cluster NGC 957.

  8. Accretion Rates on Pre-main-sequence Stars in the Young Open Cluster NGC 6530

    NASA Astrophysics Data System (ADS)

    Gallardo, José; del Valle, Luciano; Ruiz, María Teresa

    2012-01-01

    It is well accepted that during the star formation process, material from a protoplanetary disk is accreted onto the central object during the first ~1-5 Myr. Different authors have published measurements of accretion rates for young low- and intermediate-mass stars in several nearby star-forming regions (SFRs). Due to its somewhat larger distance, the SFR M8 (the Lagoon Nebula) has not been studied to the same extent, despite its abundant population of young stellar objects. We have obtained optical band low-resolution spectra of a sample of pre-main-sequence stars in the open cluster NGC 6530 located in the aforementioned nebulae using the Gemini Multi Object Spectrograph at Gemini-South in multi-object mode. Spectra cover the Hα emission line used to measure the accretion rate, following the method presented by Natta et al. The observed spectral characteristics are fully consistent with pre-main-sequence stars, showing lithium absorption lines, which are very common in young stellar objects, as well as prominent and broad Hα emission lines, indicating a T Tauri evolutionary stage. This work presents the first determinations of mass accretion rates of young stellar objects in the open cluster NGC 6530, confirming that they are classical T Tauri stars going through the accretion phase. These observations contribute to a better understanding of the stellar content and evolutionary phase of the very active Lagoon Nebula SFR. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciencia e Tecnologia (Brazil), and Ministerio de Ciencia, Tecnología e Innovación Productiva

  9. The chemical compositions and evolutionary status of red giants in the open cluster NGC 6940

    NASA Astrophysics Data System (ADS)

    Böcek Topcu, G.; Afşar, M.; Sneden, C.

    2016-11-01

    We present the high-resolution (R ≈ 60 000), high signal-to-noise ratio (S/N ≃ 120) spectroscopic analysis of 12 red giant members of the Galactic open cluster NGC 6940. We applied Yonsei-Yale isochrones to the colour-magnitude diagram, which suggested an age of 1.1 Gyr for the cluster with a turn-off mass of 2 M⊙. Atmospheric parameters (Teff, log g, [Fe/H], and ξt) were determined via equivalent widths of Fe I, Fe II, Ti I, and Ti II lines. Calculated mean metallicity of the cluster is <[Fe/H]> = 0.04 ± 0.02. We derived abundances of α (Mg, Si, Ca), Fe-group (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn), and n-capture (Y, La, Nd, Eu) elements to be about solar. Light odd-Z elements Na and Al are slightly enhanced in MMU 108 and MMU 152 by ˜0.34 and ˜0.16 dex, respectively. Abundances of light elements Li, C, N, O, and 12C/13C ratios were derived from spectrum syntheses of the Li I resonance doublet at 6707 Å, [O I] line at 6300 Å, C2 Swan bandheads at 5164 and 5635 Å, and strong 12,13CN system lines in the 7995-8040 Å region. Most carbon isotopic ratios are similar to those found in other solar-metallicity giants, but MMU 152 has an unusual value of 12C/13C = 6. Evaluation of the LiCNO abundances and 12C/13C ratios along with the present theoretical models suggests that all the red giants in our sample are core-helium-burning clump stars.

  10. Climatological analyses of LMA data with an open-source lightning flash-clustering algorithm

    NASA Astrophysics Data System (ADS)

    Fuchs, Brody R.; Bruning, Eric C.; Rutledge, Steven A.; Carey, Lawrence D.; Krehbiel, Paul R.; Rison, William

    2016-07-01

    Approximately 63 million lightning flashes have been identified and analyzed from multiple years of Washington, D. C., northern Alabama, and northeast Colorado lightning mapping array (LMA) data using an open-source flash-clustering algorithm. LMA networks detect radiation produced by lightning breakdown processes, allowing for high-resolution mapping of lightning flashes. Similar to other existing clustering algorithms, the algorithm described herein groups lightning-produced radiation sources by space and time to estimate total flash counts and information about each detected flash. Various flash characteristics and their sensitivity to detection efficiency are investigated to elucidate biases in the algorithm, detail detection efficiencies of various LMAs, and guide future improvements. Furthermore, flash density values in each region are compared to corresponding satellite estimates. While total flash density values produced by the algorithm in Washington, D. C. ( 20 flashes km-2 yr-1), and Alabama ( 35 flashes km-2 yr-1) are within 50% of satellite estimates, LMA-based estimates are approximately a factor of 3 larger (50 flashes km-2 yr-1) than satellite estimates in northeast Colorado. Accordingly, estimates of the ratio of in-cloud to cloud-to-ground flashes near the LMA network ( 20) are approximately a factor of 3 larger than satellite estimates in Colorado. These large differences between estimates may be related to the distinct environment conducive to intense convection, low-altitude flashes, and unique charge structures in northeast Colorado.

  11. Open clusters as laboratories for stellar spin-down and magnetic activity decay

    NASA Astrophysics Data System (ADS)

    Douglas, Stephanie; Agueros, Marcel A.; Covey, Kevin R.

    2017-01-01

    The oldest open clusters within 250 pc of the Sun, the Hyades and Praesepe, are important benchmarks for calibrating stellar properties such as rotation and magnetic activity. As they have the same age and roughly solar metallicity, these clusters serve as an ideal laboratory for testing the agreement between theoretical and empirical rotation-activity relations at ~600 Myr. The repurposed Kepler mission, K2, has allowed us to measure rotation periods for dozens of Hyads and hundreds of Praesepe members, including the first periods measured for fully convective Hyads. These data have enabled new tests of models describing the evolution of stellar rotation; discrepancies with these models imply that we still do not fully understand how magnetic fields affect stellar spin-down. I will present rotation periods measured for 48 Hyads and 699 Praesepe members with K2, along with associated Halpha and X-ray fluxes. I will also show how we can compare the dependence of H-alpha and X-ray emission on rotation in order to test theories of magnetic field topology and stellar dynamos. These tests inform models of stellar wind-driven angular momentum loss and the age-rotation-activity relation.

  12. CHEMICAL ABUNDANCES OF MEMBER STARS IN THE OPEN CLUSTER NGC 2632 (PRAESEPE)

    SciTech Connect

    Yang, X. L.; Chen, Y. Q.; Zhao, G.

    2015-11-15

    Based on high-resolution, high signal-to-noise ratio spectra, we present abundances of 17 elements (Fe, O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Co, Ni, Y, Zr, Ba, La) for six stars (one Am star, one F dwarf star, and four GK giant stars) and radial velocities for 18 proper-motion selected member stars in the open cluster NGC 2632. In the Am star, s-process elements Y and Ba are clearly overabundant, which may be considered as an indicator of a peculiar Am star. The average [Fe/H] is 0.16 ± 0.06 from four GK giant member stars, which is similar to that of solar-type stars in the literature. As compared with dwarf stars, significant overabundances are found for Na, Mg, and Ba elements in our giant stars, which can be explained by the evolutionary effect. We also detect a star-to-star scatter of [Na/Fe] ratios among four giants which locate approximately at the same position in the CMD. Finally, we perform an analysis on the possible connection between the abundance and spatial structure of NGC 2632, but we find no inhomogeneous abundance among different clumps of stars in this cluster based on our limited sample.

  13. Chemical Abundances of Member Stars in the Open Cluster NGC 2632 (Praesepe)

    NASA Astrophysics Data System (ADS)

    Yang, X. L.; Chen, Y. Q.; Zhao, G.

    2015-11-01

    Based on high-resolution, high signal-to-noise ratio spectra, we present abundances of 17 elements (Fe, O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Co, Ni, Y, Zr, Ba, La) for six stars (one Am star, one F dwarf star, and four GK giant stars) and radial velocities for 18 proper-motion selected member stars in the open cluster NGC 2632. In the Am star, s-process elements Y and Ba are clearly overabundant, which may be considered as an indicator of a peculiar Am star. The average [Fe/H] is 0.16 ± 0.06 from four GK giant member stars, which is similar to that of solar-type stars in the literature. As compared with dwarf stars, significant overabundances are found for Na, Mg, and Ba elements in our giant stars, which can be explained by the evolutionary effect. We also detect a star-to-star scatter of [Na/Fe] ratios among four giants which locate approximately at the same position in the CMD. Finally, we perform an analysis on the possible connection between the abundance and spatial structure of NGC 2632, but we find no inhomogeneous abundance among different clumps of stars in this cluster based on our limited sample.

  14. NSVS 1908107, an EB-type eclipsing binary in the open cluster NGC 869

    NASA Astrophysics Data System (ADS)

    Pan, Yang; Luo, Zhi-Quan; Zhang, Xiao-Bin; Deng, Li-Cai; Wang, Kun; Luo, Yang-Ping; Fang, Wei-Jing; Peng, Yin-Jiang; Sun, Jin-Jiang; Liu, Qi-Li; Zhou, Qiang

    2016-07-01

    We present a time-series BV CCD photometry for an EB-type eclipsing binary NSVS 1908107, a member of the young open cluster NGC 869. The photometric solution was obtained by using the 2003 version of the Wilson-Devinney code. It reveals that the system is a semi-detached binary with the secondary component filling its Roche lobe. The mass ratio was determined to be 0.059±0.001. With the physical parameters of the cluster, the masses, radii and luminosities of the two components of NSVS 1908107 are estimated to be M 1 = 10.34±2.29 M ⊙, R 1 = 4.65±0.34 R ⊙, L 1 = 8076±371 L ⊙ and M 2 = 0.61±0.13 M ⊙, R 2 = 2.40±0.17 R ⊙, L 2 = 1054±48 L ⊙ respectively. The results show that the secondary component could be a giant or subgiant star with the outer envelope being stripped.

  15. VizieR Online Data Catalog: UBVR photometry of the open cluster King 2 (Aparicio+ 1990)

    NASA Astrophysics Data System (ADS)

    Aparicio, A.; Bertelli, G.; Chiosi, C.; Garcia-Pelayo, J. M.

    2003-06-01

    In this paper we present the Johnson-Cousins UBVR CCD photometry of the stars in King 2, an old open cluster towards the galactic anticenter. We have obtained the colour-magnitude diagram, the colour excess, the reddening, an estimate of the metallicity, and the distance modulus. The comparison of the observational colour-magnitude diagram with the theoretical simulations based on stellar models with convective overshoot shows that a major revision of the model structure is required. To this aim, we explore the possibility that the formulation of convective overshoot for stars in the mass range 1 to 2M{sun} ought to be different from the one currently in use. The point of major uncertainty that we see to affect the stars in this domain is whether or not convective overshoot may erode the gradient in molecular weight in the regions surrounding the convective core. We find that models, in which this is not allowed to occur, better fit the overall morphology of the colour-magnitude diagram of King 2. In addition to this, analyzing the width of the main sequence band we suggest that a significant fraction of the stars are members of binary systems, and evaluate the range spanned by their mass ratios. Finally, we derive the luminosity function and the mass function for the main sequence stars of the cluster. (1 data file).

  16. VizieR Online Data Catalog: Optically visible open clusters and Candidates (Dias+ 2002-2010)

    NASA Astrophysics Data System (ADS)

    Dias, W. S.; Alessi, B. S.; Moitinho, A.; Lepine, J. R. D.

    2010-04-01

    We have compiled a new catalogue of open clusters in the Galaxy which updates the previous catalogues of Lynga (1987, Cat. ) and of Mermilliod (1995, in Information and On-Line Data in Astronomy, ed. D. Egret & M. A. Albrecht (Dordrecht: Kluwer), 127) (included in the WEBDA database, http://obswww.unige.ch/webda). New objects and new data, in particular, data on kinematics (proper motions) that were not present in the old catalogues, have been included. Virtually all the clusters (1629) presently known were included, which represents an increment of about 476 objects relative to the Lynga (1987, Cat. ) catalogue. The catalogue is presented in a single table containing all the important data, which makes it easy to use. In total, 99% of the objects have estimates of their apparent diameters, and 38% have distance, E(B-V) and age determinations. Concerning the data on kinematics, 22% have their mean proper motions listed, 14% their mean radial velocities, and 11% have both information simultaneously. (5 data files).

  17. VizieR Online Data Catalog: Optically visible open clusters and Candidates (Dias+ 2002-2015)

    NASA Astrophysics Data System (ADS)

    Dias, W. S.; Alessi, B. S.; Moitinho, A.; Lepine, J. R. D.

    2014-10-01

    We have compiled a new catalogue of open clusters in the Galaxy which updates the previous catalogues of Lynga (1987, Cat. VII/92) and of Mermilliod (1995, in Information and On-Line Data in Astronomy, ed. D. Egret & M. A. Albrecht (Dordrecht: Kluwer), 127) (included in the WEBDA database, http://obswww.unige.ch/webda). New objects and new data, in particular, data on kinematics (proper motions) that were not present in the old catalogues, have been included. Virtually all the clusters (2167) presently known were included, which represents an increment of about 986 objects relative to the Lynga (1987, VII/92) catalogue. The catalogue is presented in a single table containing all the important data, which makes it easy to use. In total, 99.7% of the objects have estimates of their apparent diameters, and 74.5% have distance, E(B-V) and age determinations. Concerning the data on kinematics, 54.7% have their mean proper motions listed, 25% their mean radial velocities, and 24.2% have both information simultaneously. (6 data files).

  18. VizieR Online Data Catalog: Optically visible open clusters and Candidates (Dias+ 2002-2013)

    NASA Astrophysics Data System (ADS)

    Dias, W. S.; Alessi, B. S.; Moitinho, A.; Lepine, J. R. D.

    2012-01-01

    We have compiled a new catalogue of open clusters in the Galaxy which updates the previous catalogues of Lynga (1987, Cat. ) and of Mermilliod (1995, in Information and On-Line Data in Astronomy, ed. D. Egret & M. A. Albrecht (Dordrecht: Kluwer), 127) (included in the WEBDA database, http://obswww.unige.ch/webda). New objects and new data, in particular, data on kinematics (proper motions) that were not present in the old catalogues, have been included. Virtually all the clusters (1629) presently known were included, which represents an increment of about 476 objects relative to the Lynga (1987, Cat. ) catalogue. The catalogue is presented in a single table containing all the important data, which makes it easy to use. In total, 99% of the objects have estimates of their apparent diameters, and 38% have distance, E(B-V) and age determinations. Concerning the data on kinematics, 22% have their mean proper motions listed, 14% their mean radial velocities, and 11% have both information simultaneously. (6 data files).

  19. VizieR Online Data Catalog: Optically visible open clusters and Candidates (Dias+ 2002-2007)

    NASA Astrophysics Data System (ADS)

    Dias, W. S.; Alessi, B. S.; Moitinho, A.; Lepine, J. R. D.

    2007-09-01

    We have compiled a new catalogue of open clusters in the Galaxy which updates the previous catalogues of Lynga (1987, Cat. ) and of Mermilliod (1995, in Information and On-Line Data in Astronomy, ed. D. Egret & M. A. Albrecht (Dordrecht: Kluwer), 127) (included in the WEBDA database, http://obswww.unige.ch/webda). New objects and new data, in particular, data on kinematics (proper motions) that were not present in the old catalogues, have been included. Virtually all the clusters (1629) presently known were included, which represents an increment of about 476 objects relative to the Lynga (1987, Cat. ) catalogue. The catalogue is presented in a single table containing all the important data, which makes it easy to use. In total, 99% of the objects have estimates of their apparent diameters, and 38% have distance, E(B-V) and age determinations. Concerning the data on kinematics, 22% have their mean proper motions listed, 14% their mean radial velocities, and 11% have both information simultaneously. (5 data files).

  20. Basic physical properties of the close binary V497 Cep in the open cluster NGC 7160

    NASA Astrophysics Data System (ADS)

    Yakut, K.; Tarasov, A. E.; İbanoğlu, C.; Harmanec, P.; Kalomeni, B.; Holmgren, D. E.; Božić, H.; Eenens, P.

    2003-07-01

    New light and radial-velocity curves of V497 Cep , a binary in the open cluster NGC 7160, were obtained and the linear ephemeris of the system was refined to HJD (Min I) = (2 446 299.1596 +/- 0.0064) + (1.2028287d +/- 0.0000015d ) x E. The first light and radial-velocity curve solutions allowed us to derive the basic physical properties of this astrophysically important binary. It was found that the observed light variation of V497 Cep consists of a strong ellipticity effect and a small contribution from grazing eclipses. A comparison of masses and radii of V497 Cep with theoretical evolutionary tracks indicates that both binary components are very close to the zero-age main sequence. A comparison of disentangled line profiles of the He I 6678 line with synthetic, rotationally broadened line profiles indicates that the rotation of both stars is synchronized with the orbital revolution as expected. This finding increases the credibility of our solutions. We find E(B-V)=0fm39 . The distance to the cluster NGC 7160 was found to be about 760 (+/- 100) pc which agrees well with other available estimates. Tables 1 and 2 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/405/1087

  1. X-ray and optical spectroscopy of the massive young open cluster IC 1805

    NASA Astrophysics Data System (ADS)

    Rauw, G.; Nazé, Y.

    2016-10-01

    Context. Very young open clusters are ideal places to study the X-ray properties of a homogeneous population of early-type stars. In this respect, the IC 1805 open cluster is very interesting as it hosts the O4 If+ star HD 15570 thought to be in an evolutionary stage intermediate between a normal O-star and a Wolf-Rayet star. Aims: Such a star could provide a test for theoretical models aiming at explaining the empirical scaling relation between the X-ray and bolometric luminosities of O-type stars. Methods: We have observed IC 1805 with XMM-Newton and further collected optical spectroscopy of some of the O-star members of the cluster. Results: The optical spectra allow us to revisit the orbital solutions of BD+60° 497 and HD 15558, and provide the first evidence of binarity for BD+60° 498. X-ray emission from colliding winds does not appear to play an important role among the O-stars of IC 1805. Notably, the X-ray fluxes do not vary significantly between archival X-ray observations and our XMM-Newton pointing. The very fast rotator BD+60° 513, and to a lesser extent the O4 If+ star HD 15570 appear somewhat underluminous. Whilst the underluminosity of HD 15570 is only marginally significant, its amplitude is found to be compatible with theoretical expectations based on its stellar and wind properties. A number of other X-ray sources are detected in the field, and the brightest objects, many of which are likely low-mass pre-main sequence stars, are analyzed in detail. Based on observations collected with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and the USA (NASA), and with the TIGRE telescope (La Luz, Mexico).Table A.1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/594/A82

  2. Investigation of Galactic open cluster remnants: the case of NGC 7193

    NASA Astrophysics Data System (ADS)

    de Souza Angelo, Mateus; Francisco Coelho dos Santos, João, Jr.; José Barbosa Corradi, Wagner; Ferreira de Souza Maia, Francisco; Piatti, Andrés Eduardo

    2017-01-01

    Galactic open clusters (OCs) that survive the early gas-expulsion phase are gradually destroyed over time by the action of disruptive dynamical processes. Their final evolutionary stages are characterized by a poorly populated concentration of stars called an open cluster remnant (OCR). This study is devoted to assessing the real physical nature of the OCR candidate NGC 7193. GMOS/Gemini spectroscopy of 53 stars in the inner target region were obtained to derive radial velocities and atmospheric parameters. We also employed photometric and proper motion data. The analysis method consists of the following steps: (i) analysis of the statistical resemblance between the cluster and a set of field samples with respect to the sequences defined in color-magnitude diagrams (CMDs); (ii) a 5-dimensional iterative exclusion routine was employed to identify outliers from kinematical and positional data; (iii) isochrone fitting to the Ks×(J-Ks) CMD of the remaining stars and the dispersion of spectral types along empirical sequences in the (J-H)×(H-Ks) diagram were checked. A group of stars was identified for which the mean heliocentric distance is compatible with that obtained via isochrone fitting and whose metallicities are compatible with each other. Fifteen of the member stars observed spectroscopically were identified together with another 19 probable members. Our results indicate that NGC 7193 is a genuine OCR, of a once very populous OC, for which the following parameters were derived: d = 501±46 pc, t=2.5+/-1.2 Gyr, < [Fe/H] >=-0.17+/-0.23 and E(B-V)=0.05+/-0.05. Its luminosity and mass functions show depletion of low mass stars, confirming the OCR is in a dynamically evolved state. Based on observations obtained at the Gemini Observatory, which is operated by the AURA under a cooperative agreement with the NSF on behalf of the Gemini partnership: NSF (United States), STFC (United Kingdom), NRC (Canada), CONICYT (Chile), ARC (Australia), CNPq (Brazil) and CONICET

  3. PHR 1315-6555: a bipolar planetary nebula in the compact Hyades-age open cluster ESO 96-SC04

    NASA Astrophysics Data System (ADS)

    Parker, Quentin A.; Frew, David J.; Miszalski, Brent; Kovacevic, Anna V.; Frinchaboy, Peter M.; Dobbie, Paul D.; Köppen, Joachim

    2011-05-01

    We present a detailed study of a bipolar, possible Type I planetary nebula (PN), PHR 1315-6555 (PN G305.3-03.1), which was discovered as part of the Macquarie/AAO/Strasbourg Hα planetary nebula project (MASH), and that we considered at the time was an excellent candidate for membership of the distant, compact, intermediate-age open cluster, ESO 96-SC04. The strong evidence for this association is presented here, making this the only known example of a PN physically associated with a Galactic open cluster. Cluster membership is extremely important as it allows for very precise estimates of the fundamental properties of the PN as the cluster is at a known distance. The PN was discovered by one of us (QAP) during systematic MASH searches for new Galactic PNe of the AAO United Kingdom Schmidt Telescope (UKST) Hα survey and had been missed in earlier broad-band surveys, including specific CCD studies of the host cluster. We present original discovery images and Cerro Tololo Inter-American Observatory (CTIO) 4-m MOSAIC-II camera follow-up narrow-band images that reveal its bipolar morphology. We also present (i) low-resolution optical spectra that spectroscopically confirm the PN, (ii) accurate radial velocities of PN and cluster stars from high-resolution spectroscopy which show they are consistent and (iii) a reliable, independent distance estimate to the PN using a robust PN distance indicator which agrees with the published cluster distance to within the errors. We also provide preliminary estimates of basic PN properties and abundance estimates from deeper spectra that show it to be of possible Type I chemistry. This is also consistent with its estimated turn-off mass. Taken together, these findings present a powerful case for clear physical association between the PN and host cluster. Results for this association will be of considerable interest to specialists across differing astrophysical disciplines, including PNe, white dwarfs and open clusters.

  4. Two "b"s in the Beehive: The Discovery of the First Hot Jupiters in an Open Cluster

    NASA Astrophysics Data System (ADS)

    Quinn, Samuel N.; White, Russel J.; Latham, David W.; Buchhave, Lars A.; Cantrell, Justin R.; Dahm, Scott E.; Fűrész, Gabor; Szentgyorgyi, Andrew H.; Geary, John C.; Torres, Guillermo; Bieryla, Allyson; Berlind, Perry; Calkins, Michael C.; Esquerdo, Gilbert A.; Stefanik, Robert P.

    2012-09-01

    We report the discovery of two giant planets orbiting stars in Praesepe (also known as the Beehive Cluster). These are the first known hot Jupiters in an open cluster and the only planets known to orbit Sun-like, main-sequence stars in a cluster. The planets are detected from Doppler-shifted radial velocities; line bisector spans and activity indices show no correlation with orbital phase, confirming the variations are caused by planetary companions. Pr0201b orbits a V = 10.52 late F dwarf with a period of 4.4264 ± 0.0070 days and has a minimum mass of 0.540 ± 0.039 M Jup, and Pr0211b orbits a V = 12.06 late G dwarf with a period of 2.1451 ± 0.0012 days and has a minimum mass of 1.844 ± 0.064 M Jup. The detection of two planets among 53 single members surveyed establishes a lower limit of 3.8+5.0 - 2.4% on the hot Jupiter frequency in this metal-rich open cluster. Given the precisely known age of the cluster, this discovery also demonstrates that, in at least two cases, giant planet migration occurred within 600 Myr after formation. As we endeavor to learn more about the frequency and formation history of planets, environments with well-determined properties—such as open clusters like Praesepe—may provide essential clues to this end.

  5. Open cluster Dolidze 25: Stellar parameters and the metallicity in the Galactic anticentre

    NASA Astrophysics Data System (ADS)

    Negueruela, I.; Simón-Díaz, S.; Lorenzo, J.; Castro, N.; Herrero, A.

    2015-12-01

    Context. The young open cluster Dolidze 25, in the direction of the Galactic anticentre, has been attributed a very low metallicity, with typical abundances between -0.5 and -0.7 dex below solar. Aims: We intend to derive accurate cluster parameters and accurate stellar abundances for some of its members. Methods: We have obtained a large sample of intermediate- and high-resolution spectra for stars in and around Dolidze 25. We used the fastwind code to generate stellar atmosphere models to fit the observed spectra. We derive stellar parameters for a large number of OB stars in the area, and abundances of oxygen and silicon for a number of stars with spectral types around B0. Results: We measure low abundances in stars of Dolidze 25. For the three stars with spectral types around B0, we find 0.3 dex (Si) and 0.5 dex (O) below the values typical in the solar neighbourhood. These values, even though not as low as those given previously, confirm Dolidze 25 and the surrounding H ii region Sh2-284 as the most metal-poor star-forming environment known in the Milky Way. We derive a distance 4.5 ± 0.3 kpc to the cluster (rG ≈ 12.3 kpc). The cluster cannot be older than ~3 Myr, and likely is not much younger. One star in its immediate vicinity, sharing the same distance, has Si and O abundances at most 0.15 dex below solar. Conclusions: The low abundances measured in Dolidze 25 are compatible with currently accepted values for the slope of the Galactic metallicity gradient, if we take into account that variations of at least ±0.15 dex are observed at a given radius. The area traditionally identified as Dolidze 25 is only a small part of a much larger star-forming region that comprises the whole dust shell associated with Sh2-284 and very likely several other smaller H ii regions in its vicinity. Based on observations made with the Nordic Optical Telescope, the Mercator Telescope, and the telescopes of the Isaac Newton Group.

  6. A probabilistic spatial-temporal model for vent opening clustering at Campi Flegrei caldera (Italy)

    NASA Astrophysics Data System (ADS)

    Bevilacqua, A.; Isaia, R.; Flandoli, F.; Neri, A.; Quaranta, D.

    2014-12-01

    Campi Flegrei (CF) is a densely urbanized caldera with a very high volcanic risk. Its more recent volcanic activity was characterized in the last 15 kyrs by more than 70 explosive events of variable scale and vent location. The sequence of eruptive events at CF is remarkably inhomogeneous, both in space and time. Eruptions concentred over periods from a few centuries to a few millennia, and were alternated by periods of quiescence lasting up to several millennia. As a consequence, activity has been subdivided into three distinct epochs, i.e. Epoch I, 15 - 9.5 kyrs, Epoch II, 8.6 - 8.2 kyrs, and Epoch III, 4.8 - 3.7 kyrs BP [e.g. Orsi et al., 2004; Smith et al., 2011]. The eruptive record also shows the presence of clusters of events in space-time, i.e. the opening of a new vent in a particular location and at a specific time seems to increase the probability of another vent opening in the nearby area and in the next decades-centuries (self-exciting effect). Probabilistic vent opening mapping conditional the occurrence of a new event and able to account for some of the intrinsic uncertainties affecting the system, has been investigated in some recent studies [e.g. Selva et al. 2011, Bevilacqua et al. 2014, in preparation], but a spatial-temporal model of the sequence of volcanic activity remains an open issue. Hence we have developed a time-space mathematical model that takes into account both the self-exciting behaviour of the system and the significant uncertainty affecting the eruptive record. Based on the past eruptive record of the volcano, the model allows to simulate sequences of future events as well as to better understand the spatial and temporal evolution of the system. In addition, based on the assumption that the last eruptive event occurred in 1538 AD (Monte Nuovo eruption) is the first event of a new epoch of activity, the model can estimate the probability of new vent opening at CF in the next decades.

  7. Properties of the Open Cluster Tombaugh 1 from High-resolution Spectroscopy and uvbyCaHβ Photometry

    NASA Astrophysics Data System (ADS)

    Sales Silva, João V.; Carraro, Giovanni; Anthony-Twarog, Barbara J.; Moni Bidin, Christian; Costa, Edgardo; Twarog, Bruce A.

    2016-01-01

    Open clusters can be the key to deepening our knowledge on various issues involving the structure and evolution of the Galactic disk and details of stellar evolution because a cluster’s properties are applicable to all its members. However, the number of open clusters with detailed analysis from high-resolution spectroscopy or precision photometry imposes severe limitations on studies of these objects. To expand the number of open clusters with well-defined chemical abundances and fundamental parameters, we investigate the poorly studied, anticenter open cluster Tombaugh 1. Using precision uvbyCaHβ photometry and high-resolution spectroscopy, we derive the cluster’s reddening, obtain photometric metallicity estimates, and, for the first time, present a detailed abundance analysis of 10 potential cluster stars (nine clump stars and one Cepheid). Using the radial position from the cluster center and multiple color indices, we have isolated a sample of unevolved, probable single-star members of Tombaugh 1. From 51 stars, the cluster reddening is found to be E(b-y) = 0.221 ± 0.006 or E(B-V) = 0.303 ± 0.008, where the errors refer to the internal standard errors of the mean. The weighted photometric metallicity from m1 and hk is [Fe/H] = -0.10 ± 0.02, while a match to the Victoria-Regina Strömgren isochrones leads to an age of 0.95 ± 0.10 Gyr and an apparent modulus of (m-M) = 13.10 ± 0.10. Radial velocities identify six giants as probable cluster members, and the elemental abundances of Fe, Na, Mg, Al, Si, Ca, Ti, Cr, Ni, Y, Ba, Ce, and Nd have been derived for both the cluster and the field stars. Tombaugh 1 appears to be a typical inner thin disk, intermediate-age open cluster of slightly subsolar metallicity, located just beyond the solar circle, with solar elemental abundance ratios except for the heavy s-process elements, which are a factor of two above solar. Its metallicity is consistent with a steep metallicity gradient in the galactocentric region

  8. Searching for chemical signatures of multiple stellar populations in the old, massive open cluster NGC 6791

    SciTech Connect

    Bragaglia, Angela; Carretta, Eugenio; Sneden, Christopher; Gratton, Raffaele G.; Lucatello, Sara; Bernath, Peter F.; Brooke, James S. A.; Ram, Ram S. E-mail: eugenio.carretta@oabo.inaf.it E-mail: raffaele.gratton@oapd.inaf.it E-mail: pbernath@odu.edu E-mail: rr662@york.ac.uk

    2014-11-20

    Galactic open and globular clusters (OCs, GCs) appear to inhabit separate regions of the age-mass plane. However, the transition between them is not easily defined because there is some overlap between high-mass, old OCs and low-mass, young GCs. We are exploring the possibility of a clear-cut separation between OCs and GCs using an abundance feature that has been found so far only in GCs: (anti)correlations between light elements. Among the coupled abundance trends, the Na-O anticorrelation is the most widely studied. These anticorrelations are the signature of self-enrichment, i.e., of a formation mechanism that implies multiple generations of stars. Here we concentrate on the old, massive, metal-rich OC NGC 6791. We analyzed archival Keck/HIRES spectra of 15 NGC 6791 main-sequence turnoff and evolved stars, concentrating on the derivation of C, N, O, and Na abundances. We also used WIYN/Hydra spectra of 21 evolved stars (one is in common). Given the spectral complexity of the very metal-rich NGC 6791 stars, we employed spectrum synthesis to measure most of the abundances. We confirmed the cluster super-solar metallicity and abundances of Ca and Ni that have been derived in past studies. More importantly, we did not detect any significant star-to-star abundance dispersion in C, N, O, and Na. Based on the absence of a clear Na-O anticorrelation, NGC 6791 can still be considered a true OC, hosting a single generation of stars and not a low-mass GC.

  9. Chemical composition of evolved stars in the young open clusters NGC 4609 and NGC 5316

    NASA Astrophysics Data System (ADS)

    Drazdauskas, Arnas; Tautvaišienė, Gražina; Smiljanic, Rodolfo; Bagdonas, Vilius; Chorniy, Yuriy

    2016-10-01

    High-resolution spectral analysis is performed for the first time in evolved stars of two young open clusters: NGC 4609 and NGC 5316, of about 80 and 100 Myr in age, respectively, and turn-off masses above 5 M⊙. Stellar evolution models predict an extra-mixing event in evolved stars, which follows the first dredge-up and happens later on the red giant branch. However, it is still not understood how this process affects stars of different masses. In this study, we determine abundances of the mixing sensitive elements carbon and nitrogen, carbon isotope 12C/13C ratios, as well as 20 other elements produced by different nucleosynthetic processes (O, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Co, Ni, Y, Zr, Ba, La, Ce, Pr, Nd, and Eu). We compared our results with the latest theoretical models of evolutionary mixing processes. We find that the obtained 12C/13C and C/N ratios and [Na/Fe] agree quite well with the model which takes into account thermohaline- and rotation-induced mixing but within error limits also agree with the standard first dredge-up model. Comparison of oxygen, magnesium, and other α-elements with theoretical models of Galactic chemical evolution revealed that both clusters follow the thin disc α-element trends. Neutron-capture element abundances in NGC 4609 are apparently reflecting its birthplace in the thin disc, while NGC 5316 has marginally higher abundances, which would indicate its birthplace in an environment more enriched with neutron-capture elements.

  10. New variable stars discovered in the fields of three Galactic open clusters using the VVV survey

    NASA Astrophysics Data System (ADS)

    Palma, T.; Minniti, D.; Dékány, I.; Clariá, J. J.; Alonso-García, J.; Gramajo, L. V.; Ramírez Alegría, S.; Bonatto, C.

    2016-11-01

    This project is a massive near-infrared (NIR) search for variable stars in highly reddened and obscured open cluster (OC) fields projected on regions of the Galactic bulge and disk. The search is performed using photometric NIR data in the J-, H- and Ks- bands obtained from the Vista Variables in the Vía Láctea (VVV) Survey. We performed in each cluster field a variability search using Stetson's variability statistics to select the variable candidates. Later, those candidates were subjected to a frequency analysis using the Generalized Lomb-Scargle and the Phase Dispersion Minimization algorithms. The number of independent observations range between 63 and 73. The newly discovered variables in this study, 157 in total in three different known OCs, are classified based on their light curve shapes, periods, amplitudes and their location in the corresponding color-magnitude (J -Ks ,Ks) and color-color (H -Ks , J - H) diagrams. We found 5 possible Cepheid stars which, based on the period-luminosity relation, are very likely type II Cepheids located behind the bulge. Among the newly discovered variables, there are eclipsing binaries, δ Scuti, as well as background RR Lyrae stars. Using the new version of the Wilson & Devinney code as well as the "Physics Of Eclipsing Binaries" (PHOEBE) code, we analyzed some of the best eclipsing binaries we discovered. Our results show that these studied systems turn out to be ranging from detached to double-contact binaries, with low eccentricities and high inclinations of approximately 80°. Their surface temperatures range between 3500 K and 8000 K.

  11. Communication: spin densities within a unitary group based spin-adapted open-shell coupled-cluster theory: analytic evaluation of isotropic hyperfine-coupling constants for the combinatoric open-shell coupled-cluster scheme.

    PubMed

    Datta, Dipayan; Gauss, Jürgen

    2015-07-07

    We report analytical calculations of isotropic hyperfine-coupling constants in radicals using a spin-adapted open-shell coupled-cluster theory, namely, the unitary group based combinatoric open-shell coupled-cluster (COSCC) approach within the singles and doubles approximation. A scheme for the evaluation of the one-particle spin-density matrix required in these calculations is outlined within the spin-free formulation of the COSCC approach. In this scheme, the one-particle spin-density matrix for an open-shell state with spin S and MS = + S is expressed in terms of the one- and two-particle spin-free (charge) density matrices obtained from the Lagrangian formulation that is used for calculating the analytic first derivatives of the energy. Benchmark calculations are presented for NO, NCO, CH2CN, and two conjugated π-radicals, viz., allyl and 1-pyrrolyl in order to demonstrate the performance of the proposed scheme.

  12. Stellar variability in open clusters. I. A new class of variable stars in NGC 3766

    NASA Astrophysics Data System (ADS)

    Mowlavi, N.; Barblan, F.; Saesen, S.; Eyer, L.

    2013-06-01

    Aims: We analyze the population of periodic variable stars in the open cluster NGC 3766 based on a 7-year multiband monitoring campaign conducted on the 1.2 m Swiss Euler telescope at La Silla, Chili. Methods: The data reduction, light curve cleaning, and period search procedures, combined with the long observation time line, allowed us to detect variability amplitudes down to the millimagnitude (mmag) level. The variability properties were complemented with the positions in the color-magnitude and color-color diagrams to classify periodic variable stars into distinct variability types. Results: We find a large population (36 stars) of new variable stars between the red edge of slowly pulsating B (SPB) stars and the blue edge of δ Sct stars, a region in the Hertzsprung-Russell (HR) diagram where no pulsation is predicted to occur based on standard stellar models. The bulk of their periods ranges from 0.1 to 0.7 d, with amplitudes between 1 and 4 mmag for the majority of them. About 20% of stars in that region of the HR diagram are found to be variable, but the number of members of this new group is expected to be higher, with amplitudes below our mmag detection limit. The properties of this new group of variable stars are summarized and arguments set forth in favor of a pulsation origin of the variability, with g-modes sustained by stellar rotation. Potential members of this new class of low-amplitude periodic (most probably pulsating) A and late-B variables in the literature are discussed. We additionally identify 16 eclipsing binary, 13 SPB, 14 δ Sct, and 12 γ Dor candidates, as well as 72 fainter periodic variables. All are new discoveries. Conclusions: We encourage searching for this new class of variables in other young open clusters, especially in those hosting a rich population of Be stars. Appendices are available in electronic form at http://www.aanda.orgReduced photometry of the variable stars is only available at the CDS via anonymous ftp to http

  13. The extent of mixing in stellar interiors: the open clusters Collinder 261 and Melotte 66

    NASA Astrophysics Data System (ADS)

    Drazdauskas, Arnas; Tautvaišienė, Gražina; Randich, Sofia; Bragaglia, Angela; Mikolaitis, Šarūnas; Janulis, Rimvydas

    2016-05-01

    Context. Determining carbon and nitrogen abundances in red giants provides useful diagnostics to test mixing processes in stellar atmospheres. Aims: Our main aim is to determine carbon-to-nitrogen and carbon isotope ratios for evolved giants in the open clusters Collinder 261 and Melotte 66 and to compare the results with predictions of theoretical models. Methods: High-resolution spectra were analysed using a differential model atmosphere method. Abundances of carbon were derived using the C2 Swan (0, 1) band head at 5635.5 Å. The wavelength interval 7940-8130 Å, which contains CN features, was analysed to determine nitrogen abundances and carbon isotope ratios. The oxygen abundances were determined from the [O i] line at 6300 Å. Results: The mean values of the elemental abundances in Collinder 261, as determined from seven stars, are: [ C/Fe ] = -0.23 ± 0.02 (s.d.), [ N/Fe ] = 0.18 ± 0.09, [ O/Fe ] = -0.03 ± 0.07. The mean 12C /13C ratio is 11 ± 2, considering four red clump stars and 18 for one star above the clump. The mean C/N ratios are 1.60 ± 0.30 and 1.74, respectively. For the five stars in Melotte 66 we obtained: [ C/Fe ] = -0.21 ± 0.07 (s.d.), [ N/Fe ] = 0.17 ± 0.07, [ O/Fe ] = 0.16 ± 0.04. The 12C /13C and C/N ratios are 8 ± 2 and 1.67 ± 0.21, respectively. Conclusions: The 12C /13C and C/N ratios of stars in the investigated open clusters were compared with the ratios predicted by stellar evolution models. The mean values of 12C /13C ratios in Collinder 261 and Melotte 66 agree well with models of thermohaline-induced extra-mixing for the corresponding stellar turn-off masses of about 1.1-1.2 M⊙. The mean C/N ratios are not decreased as much as predicted by the model in which the thermohaline- and rotation-induced extra-mixing act together. Based on observations collected at ESO telescopes under Guaranteed Time Observation programmes 071.D-0065, 072.D-0019, and 076.D-0220.

  14. VizieR Online Data Catalog: UBV(RI)c photometry of 6 open clusters (Glushkova+, 2013)

    NASA Astrophysics Data System (ADS)

    Glushkova, E. V.; Zabolotskikh, M. V.; Koposov, S. E.; Spiridonova, O. I.; Leonova, S. I.; Vlasyuk, V. V.; Rastorguev, A. S.

    2014-03-01

    We observed six open clusters in the Johnson/Kron-Cousins broad band BVRcIc using the Zeiss-1000 telescope at the Special Astrophysical Observatory of the Russian Academy of Sciences equipped with a photometer based on an EEV 42-40 2Kx2K CCD. (6 data files).

  15. VizieR Online Data Catalog: CaIIK spectra of 7 Galactic and MC open clusters (Smoker+, 2015)

    NASA Astrophysics Data System (ADS)

    Smoker, J.; Keenan, F. P.; Fox, A. J.

    2015-07-01

    The data on which the current paper is based were extracted from the ESO archive and are FLAMES-GIRAFFE observations towards three open clusters located in the Milky Way, and two in each of the Large and Small Magellanic Clouds, plus FEROS and UVES observations towards stars located in the Magellanic system and Milky Way. (18 data files).

  16. Physical parameters of NGC6705 (M11) open cluster using Strömgren photometry

    NASA Astrophysics Data System (ADS)

    Casamiquela, L.; Balaguer-Núñez, L.; Jordi, C.; Masana, E.

    2015-05-01

    NGC 6705 (M11) is a middle-age well-studied open cluster. Its location in an area where the interstellar extinction is relatively low, its exceptional stellar density and richness, and the presence of both early type and evolved stars makes this cluster an interesting target for many scientific issues. Although NGC 6705 has been widely studied, Strömgren photometry was missing. The observations by our team have yielded uvbyH photometry for 51293 stars in an area of 34'×34' and with V_{lim}˜21. Observed stars with complete photometry (9308) are classified into photometric regions and their physical parameters are determined using standard relations among color indices for each of the photometric regions of the HR diagram. That allows us to provide an astrophysical characterization of the cluster: E(b-y)=0.31±0.05 (E(B-V)=0.42); V_{0}-M_{V}=11.9±0.7 (d˜2000pc); [Fe/H]=-0.2±0.4 (Z=0.009). In addition, we discuss the accuracy of the physical parameters through comparison with those recently determined by Beaver et al. (2013) with Strömgren photometry. We find mean systematic differences of Δ V=-0.015±0.038, Δ (b-y)=-0.017±0.046, Δ m_{1}=-0.014±0.092, Δ c_{1}=+0.014±0.131, and Δ β=-0.036±0.042. These are caused by different selection of reference stars for the instrumental-to-standard transformation. We also compare our results with those from the spectroscopic Gaia-ESO Survey (GES) to assess the quality of the photometric determinations. This work can be useful to give input astrophysical parameters to the spectral analyses being made by GES. We find out clear different trends for the stars bluer and redder than (b-y)=0.4 (T_{eff}˜8000 K), due to the different instrumental setups used for the GIRAFFE observations (HR3 and HR15N). We find that mean differences in effective temperatures and gravities for both works are compatible within the errors. However, mean difference in metallicity for stars with (b-y)>0.4 is discrepant by -0.65 dex.

  17. Massive open star clusters using the VVV survey. IV. WR 62-2, a new very massive star in the core of the VVV CL041 cluster

    NASA Astrophysics Data System (ADS)

    Chené, A.-N.; Ramírez Alegría, S.; Borissova, J.; O'Leary, E.; Martins, F.; Hervé, A.; Kuhn, M.; Kurtev, R.; Consuelo Amigo Fuentes, P.; Bonatto, C.; Minniti, D.

    2015-12-01

    Context. The ESO Public Survey VISTA Variables in the Vía Láctea (VVV) provides deep multi-epoch infrared observations for an unprecedented 562 sq. deg of the Galactic bulge and adjacent regions of the disk. Nearly 150 new open clusters and cluster candidates have been discovered in this survey. Aims: We present the fourth article in a series of papers focussed on young and massive clusters discovered in the VVV survey. This article is dedicated to the cluster VVV CL041, which contains a new very massive star candidate, WR 62-2. Methods: Following the methodology presented in the first paper of the series, wide-field, deep JHKs VVV observations, combined with new infrared spectroscopy, are employed to constrain fundamental parameters (distance, reddening, mass, age) of VVV CL041. Results: We confirm that the cluster VVV CL041 is a young (less than 4 Myr) and massive (3 ± 2 × 103 M⊙) cluster, and not a simple asterism. It is located at a distance of 4.2 ± 0.9 kpc, and its reddening is AV = 8.0 ± 0.2 mag, which is slightly lower than the average for the young clusters towards the centre of the Galaxy. Spectral analysis shows that the most luminous star of the cluster, of the WN8h spectral type, is a candidate to have an initial mass larger than 100 M⊙. Based on observations taken within the ESO VISTA Public Survey VVV, Programme ID 179.B-2002, and on observations with VLT/ISAAC at ESO (programme 087.D.0341A) and Flamingos-2 at Gemini (programme GS-2014A-Q-72).The photometric catalogue is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/584/A31

  18. BVI photometry and integrated spectroscopy of the very young open clusters Ruprecht 119, NGC 6318 and BH 245

    NASA Astrophysics Data System (ADS)

    Piatti, A. E.; Bica, E.; Clariá, J. J.

    2000-10-01

    We present CCD BVI observations obtained for stars in the fields of the unstudied or poorly studied open clusters Ruprecht 119, NGC 6318, and BH 245 projected close to the direction towards the Galactic centre. We measured V magnitude and B-V and V-I colours for about 600 stars reaching down to V ~ 19 mag. From the analysis of the colour magnitude diagrams, we confirmed the physical reality of the clusters and derived their reddening, distance and age for the first time. In addition, we obtained flux-calibrated integrated spectra in the range 3500-9200 Å for the cluster sample. Using the equivalent widths of the Balmer lines and comparing the cluster spectra with template spectra we derive both foreground reddening and age. The photometric and spectroscopic results reveal that the three studied objects are very young open clusters with ages ranging between 10 and 15 Myr, which have already undergone the HII region evolutionary phase and are dominated by the upper MS stars. The clusters, located between 1.1 kpc and 3.3 kpc from the Sun, are affected by different amounts of interstellar visual absorption (2.4 <= A_v <= 7.0). In particular, BH 245 turned out to be a highly reddened open cluster located at a distance of scarcely 1.1 kpc. Based on observations made at the University of Toronto (David Dunlap Observatory) 24inch telescope, Las Campanas, Chile, and at the Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnics de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan, Argentina.

  19. Proper motions and CCD-photometry of stars in the region of the open cluster NGC 1513

    NASA Astrophysics Data System (ADS)

    Frolov, V. N.; Jilinski, E. G.; Ananjevskaja, J. K.; Poljakov, E. V.; Bronnikova, N. M.; Gorshanov, D. L.

    2002-12-01

    The results of astrometric and photometric investigations of the poorly studied open cluster NGC 1513 are presented. The proper motions of 333 stars with a root-mean-square error of 1.9;mas yr-1 were obtained by means of the automated measuring complex ``Fantasy''. Eight astrometric plates covering the time interval of 101 years were measured and a total of 141 astrometric cluster members identified. BV CCD-photometry was obtained for stars in an area 17arcminx 17arcmin centered on the cluster. Altogether 33 stars were considered to be cluster members with high reliability by two criteria. The estimated age of NGC 1513 is 2.54x 108 years. Tables 2 and 3 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/396/125.

  20. WIYN open cluster study. LX. Spectroscopic binary orbits in NGC 6819

    SciTech Connect

    Milliman, Katelyn E.; Mathieu, Robert D.; Gosnell, Natalie M.; Geller, Aaron M.; Meibom, Søren; Platais, Imants

    2014-08-01

    We present the current state of the WOCS radial-velocity (RV) survey for the rich open cluster NGC 6819 (2.5 Gyr) including 93 spectroscopic binary orbits with periods ranging from 1.5 to 8000 days. These results are the product of our ongoing RV survey of NGC 6819 using the Hydra Multi-Object Spectrograph on the WIYN 3.5 m telescope. We also include a detailed analysis of multiple prior sets of optical photometry for NGC 6819. Within a 1° field of view, our stellar sample includes the giant branch, the red clump, and blue straggler candidates, and extends to almost 2 mag below the main sequence (MS) turnoff. For each star observed in our survey we present all RV measurements, the average RV, and velocity variability information. Additionally, we discuss notable binaries from our sample, including eclipsing binaries (WOCS 23009, WOCS 24009, and WOCS 40007), stars noted in Kepler asteroseismology studies (WOCS 4008, WOCS 7009, and WOCS 8007), and potential descendants of past blue stragglers (WOCS 1006 and WOCS 6002). We find the incompleteness-corrected binary fraction for all MS binaries with periods less than 10{sup 4} days to be 22% ± 3% and a tidal circularization period of 6.2{sub −1.1}{sup +1.1} days for NGC 6819.

  1. Exploring public discourses about emerging technologies through statistical clustering of open-ended survey questions

    PubMed Central

    Stoneman, Paul; Sturgis, Patrick; Allum, Nick

    2013-01-01

    The primary method by which social scientists describe public opinion about science and technology is to present frequencies from fixed response survey questions and to use multivariate statistical models to predict where different groups stand with regard to perceptions of risk and benefit. Such an approach requires measures of individual preference which can be aligned numerically in an ordinal or, preferably, a continuous manner along an underlying evaluative dimension – generally the standard 5- or 7-point attitude question. The key concern motivating the present paper is that, due to the low salience and “difficult” nature of science for members of the general public, it may not be sensible to require respondents to choose from amongst a small and predefined set of evaluative response categories. Here, we pursue a different methodological approach: the analysis of textual responses to “open-ended” questions, in which respondents are asked to state, in their own words, what they understand by the term “DNA.” To this textual data we apply the statistical clustering procedures encoded in the Alceste software package to detect and classify underlying discourse and narrative structures. We then examine the extent to which the classifications, thus derived, can aid our understanding of how the public develop and use “everyday” images of, and talk about, biomedicine to structure their evaluations of emerging technologies. PMID:23825238

  2. Catalogue of positions and proper motions of stars in the vicinity of open clusters

    NASA Astrophysics Data System (ADS)

    Protsyuk, Yu. I.; Kovalchuk, O. M.; Mazhaev, O. E.

    2017-02-01

    In the Research Institute "Mykolaiv Astronomical Observatory" (RI "MAO") the catalogue of position and proper motions of stars in the 544 square areas of nearly (1 × 1)° around the Galactic open clusters was created using photographic and CCD observations. 293 plates of (5 × 5)° obtained with the MAO Zonal Astrograph (D=116 mm, F=2040 mm) in 1962-1993 and more than 20 thousands CCD frames (0.7 × 0.7)° obtained with KT-50 telescope (D = 500 mm, F = 3000 mm) in 2011-2015 were used. Almost 270 thousands FITS files from the IVOA image archives with observational epoch from 1953 to 2010 were downloaded and processed. The created catalogue contains more than 2.3 million stars (7.5-18.5)m in the ICRS system with the accuracy of positions on both coordinates ranged from 0.02" to 0.05". Inner accuracy of pro per motions is 0.004"/year.

  3. Small-Scale Interstellar Structure Toward the Open Cluster CHI Persei-Fuse II

    NASA Technical Reports Server (NTRS)

    Sonneborn, George (Technical Monitor); Friedman, Scott

    2003-01-01

    The purpose of this study was to measure the physical conditions of gas along sight lines toward 6 stars in the core Chi Persei open cluster. These sight lines traverse gas in both the Orion and Perseus spiral arms of the Galaxy, at distances of 500 and 2000 pc, respectively. The stars have angular separations ranging from 45 to 280 arcsec; 60 arcsec corresponds to linear distances of 0.15 and 0.6 pc in the two arms. Thus, abundance variations in these observations would constitute evidence for small-scale variations in the properties of the interstellar medium. Ground-based Na I observations at high resolution (approx. 15 km/sec) toward 172 stars (including the 6 in this study) in the double open cluster h and Chi Persei have revealed complex spatial variation. These variations are especially evident in the gas at velocities of -40 and -55 km/sec, corresponding to the Perseus spiral arm. 21 cm observations of HI emission using the Low Resolution DRAO Survey, with a 12-arcmin beam, also show variations. Averaging the Na I apparent optical depth profiles of neighboring sight lines in order to mimic such a beam size reduces the variation, as compared to the individual Na I measurements, but still show variations larger than seen in the 21 cm profiles. Na I is not the dominant ionization state of Na in the interstellar medium. Thus, it is possible that the variations seen really trace physical structures in the interstellar medium, or they may simply result from variations in the radiation field seen by the gas, or be due to some other environmental circumstance. To distinguish among these possibilities in the present study we obtained FUSE spectra toward the 6 targets in order to measure the molecular hydrogen absorption profiles along these sight lines. The higher J states of H2 are populated by the ambient W radiation field, and thus can provide insight into the environment affecting the gas. If both the high and low J states reveal absorption line profiles with

  4. WIYN Open Cluster Study. LXXV. Testing the Metallicity Dependence of Stellar Lithium Depletion Using Hyades-aged Clusters. I. Hyades and Praesepe

    NASA Astrophysics Data System (ADS)

    Cummings, Jeffrey D.; Deliyannis, Constantine P.; Maderak, Ryan M.; Steinhauer, Aaron

    2017-03-01

    WIYN/Hydra spectroscopy (at R ∼ 15,000) of the moderately metal-rich Praesepe and Hyades open clusters was used to study their main-sequence (MS) iron ([Fe/H]) and lithium (A(Li)) abundances. Self-consistent [Fe/H] and Li analyses of these clusters of consistent age, which we re-evaluate, confirms that they have consistent [Fe/H] and provides a foundation to investigate the poorly understood G-dwarf and F-dwarf Li-depletions. Neither phenomenon agrees with standard stellar evolution theory, but possible explanations abound. We supplement our A(Li) with previously published results placed on a uniform abundance scale. This creates the largest self-consistently analyzed sample of A(Li) in both the Hyades (90) and Praesepe (110). For each star, high-precision UBVRI photometry was used to determine a 10-color-based {T}{eff} and then to test for photometric peculiarities indicated by a large {σ }{Teff} (>75 K). The stars that have large {σ }{Teff} were predominantly found to be binaries or stars with peculiar (apparent) A(Li). When considering only proper-motion members that have low {σ }{Teff} and are also photometrically consistent with the cluster MS fiducial, each cluster has a more tightly defined Li morphology than previously observed and the two clusters’ A(Li) are indistinguishable. This suggests that clusters of consistent age and metallicity may have consistent Li-depletion trends across a broad range of {T}{eff}; no additional major parameters are required, at least for these two clusters. We propose that the combined Hyades and Praesepe data offer more rigorous constraints than does either cluster alone, and we discuss newly revealed features of the combined Li–{T}{eff} trend.

  5. CHEMICAL COMPOSITION OF INTERMEDIATE-MASS STAR MEMBERS OF THE M6 (NGC 6405) OPEN CLUSTER

    SciTech Connect

    Kılıçoğlu, T.; Albayrak, B.; Monier, R.; Richer, J.; Fossati, L. E-mail: balbayrak@ankara.edu.tr E-mail: Jacques.Richer@umontreal.ca

    2016-03-15

    We present here the first abundance analysis of 44 late B-, A-, and F-type members of the young open cluster M6 (NGC 6405, age about 75 Myr). Low- and medium-resolution spectra, covering the 4500–5840 Å wavelength range, were obtained using the FLAMES/GIRAFFE spectrograph attached to the ESO Very Large Telescopes. We determined the atmospheric parameters using calibrations of the Geneva photometry and by adjusting the H{sub β} profiles to synthetic ones. The abundances of up to 20 chemical elements, from helium to mercury, were derived for 19 late B, 16 A, and 9 F stars by iteratively adjusting synthetic spectra to the observations. We also derived a mean cluster metallicity of [Fe/H] = 0.07 ± 0.03 dex from the iron abundances of the F-type stars. We find that for most chemical elements, the normal late B- and A-type stars exhibit larger star-to-star abundance variations than the F-type stars probably because of the faster rotation of the B and A stars. The abundances of C, O, Mg, Si, and Sc appear to be anticorrelated with that of Fe, while the opposite holds for the abundances of Ca, Ti, Cr, Mn, Ni, Y, and Ba as expected if radiative diffusion is efficient in the envelopes of these stars. In the course of this analysis, we discovered five new peculiar stars: one mild Am, one Am, and one Fm star (HD 318091, CD-32 13109, GSC 07380-01211, CP1), one HgMn star (HD 318126, CP3), and one He-weak P-rich (HD 318101, CP4) star. We also discovered a new spectroscopic binary, most likely a SB2. We performed a detailed modeling of HD 318101, the new He-weak P-rich CP star, using the Montréal stellar evolution code XEVOL which self-consistently treats all particle transport processes. Although the overall abundance pattern of this star is properly reproduced, we find that detailed abundances (in particular the high P excess) resisted modeling attempts even when a range of turbulence profiles and mass-loss rates were considered. Solutions are proposed which are

  6. Chemical Composition of Intermediate-mass Star Members of the M6 (NGC 6405) Open Cluster

    NASA Astrophysics Data System (ADS)

    Kılıçoğlu, T.; Monier, R.; Richer, J.; Fossati, L.; Albayrak, B.

    2016-03-01

    We present here the first abundance analysis of 44 late B-, A-, and F-type members of the young open cluster M6 (NGC 6405, age about 75 Myr). Low- and medium-resolution spectra, covering the 4500-5840 Å wavelength range, were obtained using the FLAMES/GIRAFFE spectrograph attached to the ESO Very Large Telescopes. We determined the atmospheric parameters using calibrations of the Geneva photometry and by adjusting the Hβ profiles to synthetic ones. The abundances of up to 20 chemical elements, from helium to mercury, were derived for 19 late B, 16 A, and 9 F stars by iteratively adjusting synthetic spectra to the observations. We also derived a mean cluster metallicity of [Fe/H] = 0.07 ± 0.03 dex from the iron abundances of the F-type stars. We find that for most chemical elements, the normal late B- and A-type stars exhibit larger star-to-star abundance variations than the F-type stars probably because of the faster rotation of the B and A stars. The abundances of C, O, Mg, Si, and Sc appear to be anticorrelated with that of Fe, while the opposite holds for the abundances of Ca, Ti, Cr, Mn, Ni, Y, and Ba as expected if radiative diffusion is efficient in the envelopes of these stars. In the course of this analysis, we discovered five new peculiar stars: one mild Am, one Am, and one Fm star (HD 318091, CD-32 13109, GSC 07380-01211, CP1), one HgMn star (HD 318126, CP3), and one He-weak P-rich (HD 318101, CP4) star. We also discovered a new spectroscopic binary, most likely a SB2. We performed a detailed modeling of HD 318101, the new He-weak P-rich CP star, using the Montréal stellar evolution code XEVOL which self-consistently treats all particle transport processes. Although the overall abundance pattern of this star is properly reproduced, we find that detailed abundances (in particular the high P excess) resisted modeling attempts even when a range of turbulence profiles and mass-loss rates were considered. Solutions are proposed which are still under

  7. Ring opening and carbonylation of 3,3-dimethylthietane ligands in ruthenium carbonyl cluster complexes

    SciTech Connect

    Adams, R.D.; Belinski, J.A.; Yamamoto, J.H.

    1992-10-01

    When heated to 97{degrees}C, the complex Ru{sub 4}(CO){sub 12}[{mu}-SCH{sub 2}CMe{sub 2}CH{sub 2}]2 (1) was transformed into two new hexaruthenium cluster complexes, Ru{sub 6}(CO){sub 13}({mu}{sub 3}-SCH{sub 2}CMe{sub 2}CH{sub 2}){sub 4} (2) and Ru{sub 6}(CO){sub 12}({mu}-SCH{sub 2}CMe{sub 2}CH{sub 2})({mu}{sub 3}-SCH{sub 2}CMe{sub 2}CH{sub 2}){sub 3}[{mu}{sub 3}-SCH{sub 2}C(Me)(CH{sub 2})CH{sub 2}] ({mu}-H) (3), that contain four and five ring-opened 3,3-dimethylthietane (3,3-DMT) ligands, respectively. In compound 3 one of the ring-opened DMT ligands has also undergone a CH activation on one of the methyl groups. Compound 2 reacts with additional 3,3-DMT at 97{degrees}C to form 3 in 18% yield. When treated with CO at 95{degrees}C (500 psi), compound 2 yielded 4,4-dimethylthiobutyrolactone and Ru{sub 3}(CO){sub 12}. It was also found that the complex Os{sub 3}(CO){sub 11-}(SCH{sub 2}CMe{sub 2}CH{sub 2}C{double_bond}O) (4) yields 4,4-dimethylthiobutyrolactone when treated with CO at 120{degrees}C (1200 psi). Crystal data for 2: space group P2{sub 1}/n, {alpha} = 22.652 (7) A, {beta} = 11.712 (2) A, c = 19.965 (6) A, {Beta} = 115.75 (2){degrees} Z = 4, 3665 reflections, R = 0.021. Crystal data for 3: space group P2{sub 1}/c, {alpha} = 17.332 (8) A, {Beta} = 14.668 (9) A, c = 19.823 (9) A, {Beta} = 91.27 (4){degrees}, Z = 4, 1875 reflections, R = 0.050. 13 refs., 2 figs., 13 refs.

  8. Spectroscopy of the open cluster remnant candidate ESO429-SC02

    NASA Astrophysics Data System (ADS)

    Angelo, M. S.; Corradi, W. J. B.; Santos, J. F. C., Jr.; Maia, F. F. S.

    2014-10-01

    In this study we intend to assess the physical nature of the open cluster remnant (OCR) candidate ESO429-SC02. In a previous work, the method of characterization devised by Pavani & Bica (2007) failed to characterize the object as an OCR or as an asterism, classifying it as a possible OCR. We carried out multi-object spectroscopy of 31 stars in its inner area (r lesssim 4^{'}) using GMOS/GEMINI-S (resolution R≍ 2000). We cross-correlated (IRAF's FXCOR task) our science spectra with all templates from ELODIE and PHOENIX libraries to obtain radial velocities and atmospheric parameters. We also employed 2MASS photometric data and proper motions from UCAC4. Individual distances via spectroscopic parallax and reddening values were derived for our science stars. In order to identify candidate member stars, we performed a 5-dimensional sigma-clipping routine using positional an kinematical data to interactively reject outliers and selected those stars well fitted by a Padova isochrone in K_{s} × (J-K_{s}) and (J-H) × (H-K_{s}) diagrams. Although a isochrone fitting solution was found, individual distances of stars close to the turnoff point or to the RGB range from 1.5 kpc to 4.4 kpc; E(B-V) values range from 0.0 to 0.46; [Fe/H] from -0.95 to 0.61 dex and radial velocities from 9 to 64 km/s. Besides, spectral types distribution of candidate member stars along the main sequence and the high dispersion in the parameters derived for them are inconsistent with what is expected for a coeval system. Our results suggest that ESO429-SC02 is a random overdensity of field stars along the line of sight.

  9. Three close binaries in different evolutionary stages in the old open cluster NGC 188

    SciTech Connect

    Zhu, L. Y.; Qian, S. B.; Liu, L.; He, J. J.; Liu, N. P.; Zhao, E. G.; Zhang, J.; Wang, J. J.; Soonthornthum, B.

    2014-02-01

    NGC 188 is a good laboratory for studying the formation and evolution of W UMa type contact binaries due to its rich populations of them. We present a detailed photometric study of three short-period close binaries, EP Cep, ES Cep, and V369 Cep, in the old open cluster NGC 188 based on our two-set photometric observations. We discovered that both EP Cep and ES Cep are shallow-contact binaries with continuously decreasing periods. The difference is in their mass ratios. EP Cep has an extremely low-mass ratio, q = 0.15, while ES Cep has a relatively high-mass ratio, q = 0.69, indicating that they lie in different evolutionary stages. ES Cep is likely a newly formed contact binary via a Case A mass transfer, while EP Cep is an evolved system and may be on the oscillations caused by the combined effect of the thermal relaxation oscillation and the variable angular momentum loss. For another system, V369 Cep, we found that it is a primary-filling near-contact binary. Both the semidetached configuration and the continuous decrease in the orbital period indicate that it is undergoing a mass transfer from the primary component to the secondary one. This conclusion is in agreement with the excess luminosity seen in the light curves on the ingress of the secondary minimum produced by the impact of the mass transfer. All of the results suggest that V369 Cep is evolving into contact, and a shallow-contact high-mass ratio system similar to ES Cep will be formed. Then, it will evolve into a low-mass ratio contact binary just like EP Cep, and finally merge into a rapidly rotating single star.

  10. Giant Planets in Open Clusters and Binaries: Observational Constraints on Migration

    NASA Astrophysics Data System (ADS)

    Quinn, Samuel N.; White, Russel J.; Latham, David W.; Buchhave, Lars A.; Torres, Guillermo

    2016-01-01

    Some giant planets migrate from their birthplace beyond the ice line to short-period orbits just a fraction of an AU from their host stars. Though many theories have been proposed, it is not yet clear which mechanism is most important for migration, and by extension, in which types of planetary system we can expect a greater prevalence of disruptive gas giant migration. One way to constrain this process is to observe the orbital properties of migrating planets, which are expected to be shaped according to the mode of migration: in general, interaction with the gas disk should produce circular, coplanar orbits, while multi-body processes stir up eccentricities and inclinations. Unfortunately, tidal and magnetic interactions between hot Jupiters and their host stars can obscure these differences by damping eccentricities and inclinations over time, so the most direct constraints will come from difficult-to-observe young systems. Additional constraints on migration can be obtained by observing the architectures of systems containing short-period giant planets: if an outer companion is often responsible for driving migration, there should be a higher incidence of massive companions on wide orbits in hot Jupiter systems than in systems not hosting a short-period giant planet. Further, the properties of these outer companions can help differentiate between multi-body migration mechanisms. We describe two complementary surveys that we have carried out to address these problems. The first, a precise radial-velocity survey in nearby adolescent (100-600 Myr) open clusters, characterizes the orbits of giant planets soon after migration. The second, an adaptive optics imaging survey of hot Jupiter host stars, constrains the population of wide companions in hot Jupiter systems. We present the results from these two surveys and discuss the orbital properties and system architectures of our discoveries in the context of giant planet migration.

  11. A LONG-PERIOD TOTALLY ECLIPSING BINARY STAR AT THE TURNOFF OF THE OPEN CLUSTER NGC 6819 DISCOVERED WITH KEPLER

    SciTech Connect

    Sandquist, Eric L.; Orosz, Jerome A.; Jeffries, Mark W. Jr.; Brewer, Lauren N. E-mail: orosz@sciences.sdsu.edu; and others

    2013-01-01

    We present the discovery of the totally eclipsing long-period (P = 771.8 days) binary system WOCS 23009 in the old open cluster NGC 6819 that contains both an evolved star near central hydrogen exhaustion and a low-mass (0.45 M {sub Sun }) star. This system was previously known to be a single-lined spectroscopic binary, but the discovery of an eclipse near apastron using data from the Kepler space telescope makes it clear that the system has an inclination that is very close to 90 Degree-Sign . Although the secondary star has not been identified in spectra, the mass of the primary star can be constrained using other eclipsing binaries in the cluster. The combination of the total eclipses and a mass constraint for the primary star allows us to determine a reliable mass for the secondary star and radii for both stars, and to constrain the cluster age. Unlike well-measured stars of similar mass in field binaries, the low-mass secondary is not significantly inflated in radius compared to model predictions. The primary star characteristics, in combination with cluster photometry and masses from other cluster binaries, indicate a best age of 2.62 {+-} 0.25 Gyr, although stellar model physics may introduce systematic uncertainties at the {approx}10% level. We find preliminary evidence that the asteroseismic predictions for red giant masses in this cluster are systematically too high by as much as 8%.

  12. UB CCD Photometry of the Old, Metal-rich, Open Clusters NGC 6791, NGC 6819, and NGC 7142

    NASA Astrophysics Data System (ADS)

    Carraro, G.; Buzzoni, A.; Bertone, E.; Buson, L.

    2013-11-01

    We report on a UV-oriented imaging survey in the fields of the old, metal-rich open clusters NGC 6791, NGC 6819, and NGC 7142. With their super-solar metallicity and ages >~ 3-8 Gyr, these three clusters represent both very near and ideal stellar aggregates to match the distinctive properties of the evolved stellar populations, as in elliptical galaxies and bulges of spirals. Following a first discussion of NGC 6791 observations in an accompanying paper, here we complete our analysis, also presenting for NGC 6819 and NGC 7142 the first-ever U CCD photometry. The color-magnitude diagram of the three clusters is analyzed in detail, with special emphasis on the hot stellar component. We report, in this regard, one new extreme horizontal-branch star candidate in NGC 6791. For NGC 6819 and 7142, the stellar luminosity function clearly points to a looser radial distribution of faint lower main sequence stars, either as a consequence of cluster dynamical interaction with the Galaxy or as an effect of an increasing fraction of binary stars toward the cluster core, as also observed in NGC 6791. Compared to a reference theoretical model for the Galaxy disk, the analysis of the stellar field along the line of sight of each cluster indicates that a more centrally concentrated thick disk, on a scale length shorter than ~2.8 kpc, might better reconcile the lower observed fraction of bright field stars and their white-dwarf progeny.

  13. UB CCD PHOTOMETRY OF THE OLD, METAL-RICH, OPEN CLUSTERS NGC 6791, NGC 6819, AND NGC 7142

    SciTech Connect

    Carraro, G.; Buzzoni, A.; Bertone, E.; Buson, L. E-mail: alberto.buzzoni@oabo.inaf.it E-mail: lucio.buson@oapd.inaf.it

    2013-11-01

    We report on a UV-oriented imaging survey in the fields of the old, metal-rich open clusters NGC 6791, NGC 6819, and NGC 7142. With their super-solar metallicity and ages ∼> 3-8 Gyr, these three clusters represent both very near and ideal stellar aggregates to match the distinctive properties of the evolved stellar populations, as in elliptical galaxies and bulges of spirals. Following a first discussion of NGC 6791 observations in an accompanying paper, here we complete our analysis, also presenting for NGC 6819 and NGC 7142 the first-ever U CCD photometry. The color-magnitude diagram of the three clusters is analyzed in detail, with special emphasis on the hot stellar component. We report, in this regard, one new extreme horizontal-branch star candidate in NGC 6791. For NGC 6819 and 7142, the stellar luminosity function clearly points to a looser radial distribution of faint lower main sequence stars, either as a consequence of cluster dynamical interaction with the Galaxy or as an effect of an increasing fraction of binary stars toward the cluster core, as also observed in NGC 6791. Compared to a reference theoretical model for the Galaxy disk, the analysis of the stellar field along the line of sight of each cluster indicates that a more centrally concentrated thick disk, on a scale length shorter than ∼2.8 kpc, might better reconcile the lower observed fraction of bright field stars and their white-dwarf progeny.

  14. WIYN OPEN CLUSTER STUDY. LVII. OXYGEN ABUNDANCES OF SOLAR-TYPE DWARFS IN THE HYADES AND NGC 752

    SciTech Connect

    Maderak, Ryan M.; Deliyannis, Constantine P.; Cummings, Jeffery D.; King, Jeremy R. E-mail: con@astro.indiana.edu E-mail: jcummings@astro-udec.cl

    2013-12-01

    Oxygen has been proposed to be a superior tracer, compared to iron, for studying galactic chemical evolution. In the context of improving our understanding of the evolution of Galactic oxygen using open clusters, we present a spectroscopic analysis of oxygen and iron abundances in the 650 Myr old Hyades cluster and in the 1.45 Gyr old cluster NGC 752, using high-dispersion 7774 Å O I triplet region spectra of dwarfs in these clusters acquired with the Hydra MOS on the WIYN 3.5 m telescope. Motivated by recent improvements in analysis of the triplet, we use a strictly differential analysis in solar-type stars to obtain reliable O abundances. Using stars whose radial velocities and spectral cross-correlation analyses are consistent with single-star membership, we report Hyades cluster averages of [O/H] = 0.195 ± 0.010 and [Fe/H] = 0.130 ± 0.009 based on 22 stars, and NGC 752 cluster averages of [O/H] = –0.077 ± 0.02 and [Fe/H] = –0.063 ± 0.013 based on 36 stars (where the errors are σ{sub μ}; we discuss possible additional systematic errors). These cluster abundance averages are in very good agreement with most previous determinations. Whereas the [O/H] cluster averages utilize only stars found in the ''prime'' T {sub eff} range straddling the solar T {sub eff}, the [Fe/H] cluster averages come from stars exhibiting a flat [Fe/H]-T {sub eff} relation of over 1000 K for the Hyades and nearly 2000 K for NGC 752. Previous studies of open clusters younger than NGC 752 have reported oxygen triplet over abundances in cool dwarfs, as compared to oxygen abundances of the prime-T {sub eff} range. We report that NGC 752 also shows such overabundances, at a higher level than the Hyades overabundances, and thus contradicts the idea of a decline of such overabundances with increasing age. We discuss evidence for and against correlations of the oxygen overabundances with rotation, X-ray luminosity, chromospheric activity, and metallicity.

  15. CURious Variables Experiment (CURVE). CCD Photometry and Variable Stars in the Field of Open Cluster NGC637

    NASA Astrophysics Data System (ADS)

    Pietrukowicz, P.; Olech, A.; Wisniewski, M.; Kedzierski, P.; Mularczyk, K.; Zloczewski, K.; Starczewski, S.; Szaruga, K.

    2006-09-01

    We present VI photometry for the open cluster NGC 637 which is located in the Cassiopeia region. Morphology of cluster color-magnitude diagram indicates that it is a young object with age of a few million years. The apparent distance modulus of the cluster is 13.9<(m-M)_V<14.3 mag, while reddening is 0.69

  16. Evolution of the chemical element abundances with age in open clusters: The Hyades, Pleiades, Coma Berenices and M6

    NASA Astrophysics Data System (ADS)

    Kiliçoǧlu, T.; Monier, R.; Gebran, M.; Fossati, L.

    2014-12-01

    We compare the averaged photospheric abundances of A and F stars in open clusters of different ages: M6 (˜80 Myr), Pleiades (˜100 Myr), Coma Berenices (˜450 Myr), and the Hyades (˜800 Myr). The variation in the averaged abundances among F stars generally reflects the differences between the initial compositions of the clusters in their various birthplaces. The differences of the averaged chemical composition of A stars may also reveal the effects of radiative difussion for the stars of different ages. We also discuss the methods, resolutions and wavelength coverages of spectra and discrepancies in the derived microturbulent velocities among the various studies to check if these studies are comparable. We also present the pattern of mean abundances and metallicity for the M6 cluster determined by spectral analysis of GIRAFFE spectra acquired with the VLT, Paranal Observatory.

  17. High Performance Data Clustering: A Comparative Analysis of Performance for GPU, RASC, MPI, and OpenMP Implementations*

    PubMed Central

    Yang, Luobin; Chiu, Steve C.; Liao, Wei-Keng; Thomas, Michael A.

    2013-01-01

    Compared to Beowulf clusters and shared-memory machines, GPU and FPGA are emerging alternative architectures that provide massive parallelism and great computational capabilities. These architectures can be utilized to run compute-intensive algorithms to analyze ever-enlarging datasets and provide scalability. In this paper, we present four implementations of K-means data clustering algorithm for different high performance computing platforms. These four implementations include a CUDA implementation for GPUs, a Mitrion C implementation for FPGAs, an MPI implementation for Beowulf compute clusters, and an OpenMP implementation for shared-memory machines. The comparative analyses of the cost of each platform, difficulty level of programming for each platform, and the performance of each implementation are presented. PMID:25309040

  18. High Performance Data Clustering: A Comparative Analysis of Performance for GPU, RASC, MPI, and OpenMP Implementations.

    PubMed

    Yang, Luobin; Chiu, Steve C; Liao, Wei-Keng; Thomas, Michael A

    2014-10-01

    Compared to Beowulf clusters and shared-memory machines, GPU and FPGA are emerging alternative architectures that provide massive parallelism and great computational capabilities. These architectures can be utilized to run compute-intensive algorithms to analyze ever-enlarging datasets and provide scalability. In this paper, we present four implementations of K-means data clustering algorithm for different high performance computing platforms. These four implementations include a CUDA implementation for GPUs, a Mitrion C implementation for FPGAs, an MPI implementation for Beowulf compute clusters, and an OpenMP implementation for shared-memory machines. The comparative analyses of the cost of each platform, difficulty level of programming for each platform, and the performance of each implementation are presented.

  19. VizieR Online Data Catalog: CCD {Delta}a-photometry of 5 open clusters (Paunzen+, 2003)

    NASA Astrophysics Data System (ADS)

    Paunzen, E.; Pintado, O. I.; Maitzen, H. M.

    2004-01-01

    Observations of the five open clusters were performed with the Bochum 61cm (ESO-La Silla), the Helen-Sawyer-Hogg 61cm telescope (UTSO-Las Campanas Observatory), the 2.15m telescope at the Complejo Astronomico el Leoncito (CASLEO) and the L. Figl Observatory (FOA) with the 150cm telescope on Mt. Schopfl (Austria) using the multimode instrument OEFOSC (see the observation log in Table 1). (5 data files).

  20. CCD Photometry of the Old Open Clusters ESO 093-SC08 and VandenBerg-Hagen 176

    NASA Astrophysics Data System (ADS)

    Phelps, R. L.

    2002-05-01

    Faint-magnitude CCD photometry has been obtained for the clusters ESO 093-SC08 and VandenBerg-Hagen 176. These data reveal ESO 093-SC08 to be an old open cluster, with a derived age of 5.5 +/- 1.0 Gyr, a heliocentric distance of 14.00 +/- 0.75 kpc, an inferred metallicity between -0.60 < [Fe/H] < -0.20 dex, and Galactocentric positions Rgc = 13.0 +/- 0.7 kpc and Z = -1000 +/- 50 pc. For VandenBerg-Hagen 176, a derived age of 7.0 +/- 1.5 Gyr, a heliocentric distance of 18.00 +/- 1.00 kpc, an inferred metallicity between -0.20 < [Fe/H] < 0.20 dex, and Galactocentric positions Rgc = 12.0 +/- 0.9 kpc and Z = +1350 +/- 100 pc are found. The current results for ESO 093-SC08 are in good agreement with a study by Bica et al. VandenBerg-Hagen 176 appears to be a massive metal-rich old open cluster, similar to NGC 6791, or a young, metal-rich globular cluster. This research was supported by NSF grant AST-9800216, an Oberlin College Grant-In-Aid award, and grants from the California State University, Sacramento Research and Creative Activities program. An allocation of telescope time from the Carnegie Observatories, that made this research possible, is also gratefully acknowledged.

  1. Rotational and Radial Velocities of 1.3-2.2 M ⊙ Red Giants in Open Clusters

    NASA Astrophysics Data System (ADS)

    Carlberg, Joleen K.

    2014-06-01

    This study presents the rotational distribution of red giant (RG) stars in 11 old to intermediate age open clusters. The masses of these stars are all above the Kraft break, so they lose negligible amounts of their birth angular momentum (AM) during the main-sequence (MS) evolution. However, they do span a mass range with quite different AM distributions imparted during formation, with the stars less massive than ~1.6M ⊙ arriving on the MS with lower rotation rates than the more massive stars. The majority of RGs in this study are slow rotators across the entire red giant branch regardless of mass, supporting the picture that intermediate-mass stars rapidly spin down when they evolve off the MS and develop convection zones capable of driving a magnetic dynamo. Nevertheless, a small fraction of RGs in open clusters show some level of enhanced rotation, and faster rotators are as common in these clusters as in the field RG population. Most of these enhanced rotators appear to be red clump stars, which is also true of the underlying stellar sample, while others are clearly RGs that are above or below the clump. In addition to rotational velocities, the radial velocities (RVs) and membership probabilities of individual stars are also presented. Cluster heliocentric RVs for NGC 6005 and Pismis 18 are reported for the first time.

  2. Rotational and radial velocities of 1.3-2.2 M {sub ☉} red giants in open clusters

    SciTech Connect

    Carlberg, Joleen K.

    2014-06-01

    This study presents the rotational distribution of red giant (RG) stars in 11 old to intermediate age open clusters. The masses of these stars are all above the Kraft break, so they lose negligible amounts of their birth angular momentum (AM) during the main-sequence (MS) evolution. However, they do span a mass range with quite different AM distributions imparted during formation, with the stars less massive than ∼1.6M {sub ☉} arriving on the MS with lower rotation rates than the more massive stars. The majority of RGs in this study are slow rotators across the entire red giant branch regardless of mass, supporting the picture that intermediate-mass stars rapidly spin down when they evolve off the MS and develop convection zones capable of driving a magnetic dynamo. Nevertheless, a small fraction of RGs in open clusters show some level of enhanced rotation, and faster rotators are as common in these clusters as in the field RG population. Most of these enhanced rotators appear to be red clump stars, which is also true of the underlying stellar sample, while others are clearly RGs that are above or below the clump. In addition to rotational velocities, the radial velocities (RVs) and membership probabilities of individual stars are also presented. Cluster heliocentric RVs for NGC 6005 and Pismis 18 are reported for the first time.

  3. Variable stars in two open clusters within the Kepler/K2-Campaign-0 field: M35 and NGC 2158

    NASA Astrophysics Data System (ADS)

    Nardiello, D.; Bedin, L. R.; Nascimbeni, V.; Libralato, M.; Cunial, A.; Piotto, G.; Bellini, A.; Borsato, L.; Brogaard, K.; Granata, V.; Malavolta, L.; Marino, A. F.; Milone, A. P.; Ochner, P.; Ortolani, S.; Tomasella, L.; Clemens, M.; Salaris, M.

    2015-03-01

    We present a multiyear survey aimed at collecting (1) high-precision (˜5 milli-mag), (2) fast-cadence (˜3 min), and (3) relatively long duration (˜10 d) multiband photometric series. The goal of the survey is to discover and characterize efficiently variable objects and exoplanetary transits in four fields containing five nearby open clusters spanning a broad range of ages. More in detail, our project will (1) constitute a preparatory survey for the High Accuracy Radial velocity Planet Searcher for the Northern hemisphere (HARPS-N) mounted at the Telescopio Nazionale Galileo (TNG), which will be used for spectroscopic follow-up of any target of interest that this survey discovers or characterizes, (2) measure rotational periods and estimate the activity level of targets we are already monitoring with HARPS and HARPS-N for exoplanet transit search, and (3) long-term characterization of selected targets of interest in open clusters within the planned K2 fields. In this first paper, we give an overview of the project, and report on the variability of objects within the first of our selected fields, which contains two open clusters: M35 and NGC 2158. We detect 519 variable objects, 273 of which are new discoveries, while the periods of most of the previously known variables are considerably improved.

  4. Genome-Wide Prediction of Metabolic Enzymes, Pathways, and Gene Clusters in Plants1[OPEN

    PubMed Central

    Zhang, Peifen; Kim, Taehyong; Banf, Michael; Chavali, Arvind K.; Nilo-Poyanco, Ricardo; Bernard, Thomas

    2017-01-01

    Plant metabolism underpins many traits of ecological and agronomic importance. Plants produce numerous compounds to cope with their environments but the biosynthetic pathways for most of these compounds have not yet been elucidated. To engineer and improve metabolic traits, we need comprehensive and accurate knowledge of the organization and regulation of plant metabolism at the genome scale. Here, we present a computational pipeline to identify metabolic enzymes, pathways, and gene clusters from a sequenced genome. Using this pipeline, we generated metabolic pathway databases for 22 species and identified metabolic gene clusters from 18 species. This unified resource can be used to conduct a wide array of comparative studies of plant metabolism. Using the resource, we discovered a widespread occurrence of metabolic gene clusters in plants: 11,969 clusters from 18 species. The prevalence of metabolic gene clusters offers an intriguing possibility of an untapped source for uncovering new metabolite biosynthesis pathways. For example, more than 1,700 clusters contain enzymes that could generate a specialized metabolite scaffold (signature enzymes) and enzymes that modify the scaffold (tailoring enzymes). In four species with sufficient gene expression data, we identified 43 highly coexpressed clusters that contain signature and tailoring enzymes, of which eight were characterized previously to be functional pathways. Finally, we identified patterns of genome organization that implicate local gene duplication and, to a lesser extent, single gene transposition as having played roles in the evolution of plant metabolic gene clusters. PMID:28228535

  5. Assessment of the accuracy of coupled cluster perturbation theory for open-shell systems. I. Triples expansions.

    PubMed

    Eriksen, Janus J; Matthews, Devin A; Jørgensen, Poul; Gauss, Jürgen

    2016-05-21

    The accuracy at which total energies of open-shell atoms and organic radicals may be calculated is assessed for selected coupled cluster perturbative triples expansions, all of which augment the coupled cluster singles and doubles (CCSD) energy by a non-iterative correction for the effect of triple excitations. Namely, the second- through sixth-order models of the recently proposed CCSD(T-n) triples series [J. J. Eriksen et al., J. Chem. Phys. 140, 064108 (2014)] are compared to the acclaimed CCSD(T) model for both unrestricted as well as restricted open-shell Hartree-Fock (UHF/ROHF) reference determinants. By comparing UHF- and ROHF-based statistical results for a test set of 18 modest-sized open-shell species with comparable RHF-based results, no behavioral differences are observed for the higher-order models of the CCSD(T-n) series in their correlated descriptions of closed- and open-shell species. In particular, we find that the convergence rate throughout the series towards the coupled cluster singles, doubles, and triples (CCSDT) solution is identical for the two cases. For the CCSD(T) model, on the other hand, not only its numerical consistency, but also its established, yet fortuitous cancellation of errors breaks down in the transition from closed- to open-shell systems. The higher-order CCSD(T-n) models (orders n > 3) thus offer a consistent and significant improvement in accuracy relative to CCSDT over the CCSD(T) model, equally for RHF, UHF, and ROHF reference determinants, albeit at an increased computational cost.

  6. The SEGUE Stellar Parameter Pipeline. IV. Validation with an Extended Sample of Galactic Globular and Open Clusters

    SciTech Connect

    Smolinski, Jason P.; Beers, Timothy C.; Lee, Young Sun; An, Deokkeun; Bickerton, Steven J.; Johnson, Jennifer A.; Loomis, Craig P.; Rockosi, Constance M.; Sivarani, Thirupathi; Yanny, Brian; /Fermilab

    2010-08-01

    Spectroscopic and photometric data for likely member stars of five Galactic globular clusters (M 3, M 53, M 71, M 92, and NGC 5053) and three open clusters (M 35, NGC 2158, and NGC 6791) are processed by the current version of the SEGUE Stellar Parameter Pipeline (SSPP), in order to determine estimates of metallicities and radial velocities for the clusters. These results are then compared to values from the literature. We find that the mean metallicity (<[Fe/H]>) and mean radial velocity (hRVi) estimates for each cluster are almost all within 2{sigma} of the adopted literature values; most are within 1{sigma}. We also demonstrate that the new version of the SSPP achieves small, but noteworthy, improvements in <[Fe/H]> estimates at the extrema of the cluster metallicity range, as compared to a previous version of the pipeline software. These results provide additional confidence in the application of the SSPP for studies of the abundances and kinematics of stellar populations in the Galaxy.

  7. On the stability of ion water clusters at atmospheric conditions: Open system Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Zidi, Zouhaier S.

    2012-09-01

    The formation of water clusters on Li+, Na+, K+, Cl-, and I- ions from water vapor at atmospheric conditions have been studied using Monte Carlo simulations. The extended simple point charge model has been employed for water molecules. The polarization of ions in the field of molecules and the polarization of molecules in the field of ions have been considered explicitly in the total Hamiltonian of the molecular system. The cluster formation work and the Gibbs free energy and enthalpy of attachment reactions of one water molecule to the cluster have been calculated via the bicanonical ensemble method. Our results reveal the formation of stable clusters in equilibrium with the moist atmosphere in a wide range of vapor pressure values, with largest clusters are formed around cations. Decreasing the temperature, from 293 K to 253 K, leads to the formation of larger equilibrium clusters, and enhances the stability of systems as whole. According to clusters' molecular structures, negative ions are expected to be more active in atmospheric processes, including chemical reactions and cloud formation, than positive ones.

  8. A color-period diagram for the open cluster M 48 (NGC 2548), and its rotational age

    NASA Astrophysics Data System (ADS)

    Barnes, Sydney A.; Weingrill, Joerg; Granzer, Thomas; Spada, Federico; Strassmeier, Klaus G.

    2015-11-01

    Rotation periods are increasingly being used to derive ages for cool single field stars. Such ages are based on an empirical understanding of how cool stars spin down, acquired by constructing color-period diagrams (CPDs) for a series of open clusters. Our main aims here are to construct a CPD for M 48, to compare this with other clusters of similar age to check for consistency, and to derive a rotational age for M 48 using gyrochronology. We monitored M 48 photometrically for over 2 months with AIP's STELLA I 1.2 m telescope and the WiFSIP 4K imager in Tenerife. Light curves with 3 mmag precision for bright (V ~ 14 mag) stars were produced and then analysed to provide rotation periods. A cluster CPD has then been constructed. We report 62 rotation periods for cool stars in M 48. The CPD displays a clear slow/I-sequence of rotating stars, similar to those seen in the 625 Myr-old Hyades and 590 Myr-old Praesepe clusters, and below both, confirming that M 48 is younger. A similar comparison with the 250 Myr-old M 34 cluster shows that M 48 is older and does not possess any fast/C-sequence G or early K stars like those in M 34, although relatively fast rotators do seem to be present among the late-K and M stars. A more detailed comparison of the CPD with rotational evolution models shows that the cluster stars have a mean age of 450 Myr, and its (rotating) stars can be individually dated to ± 117 Myr (26%). Much of this uncertainty stems from intrinsic astrophysical spread in initial periods, and almost all stars are consistent with a single age of 450 Myr. The gyro-age of M 48 as a whole is 450 ± 50 Myr, in agreement with the previously determined isochrone age of 400 ± 100 Myr. Based on data obtained with the STELLA robotic telescopes in Tenerife, an AIP facility jointly operated by AIP and IAC; this paper presents results for the STELLA Open Cluster Survey (SOCS).Appendices A and B are available in electronic form at http://www.aanda.orgThe cluster photometry

  9. Open clusters. II. Fundamental parameters of B stars in Collinder 223, Hogg 16, NGC 2645, NGC 3114, and NGC 6025

    NASA Astrophysics Data System (ADS)

    Aidelman, Y.; Cidale, L. S.; Zorec, J.; Panei, J. A.

    2015-05-01

    Context. The knowledge of accurate values of effective temperature, surface gravity, and luminosity of stars in open clusters is very important not only to derive cluster distances and ages but also to discuss the stellar structure and evolution. Unfortunately, stellar parameters are still very scarce. Aims: Our goal is to study five open clusters to derive stellar parameters of the B and Be star population and discuss the cluster properties. In a near future, we intend to gather a statistically relevant samples of Be stars to discuss their origin and evolution. Methods: We use the Barbier-Chalonge-Divan spectrophotometric system, based on the study of low-resolution spectra around the Balmer discontinuity, since it is independent of the interstellar and circumstellar extinction and provides accurate Hertzsprung-Russell diagrams and stellar parameters. Results: We determine stellar fundamental parameters, such as effective temperatures, surface gravities, spectral types, luminosity classes, absolute and bolometric magnitudes and colour gradient excesses of the stars in the field of Collinder 223, Hogg 16, NGC 2645, NGC 3114, and NGC 6025. Additional information, mainly masses and ages of cluster stellar populations, is obtained using stellar evolution models. In most cases, stellar fundamental parameters have been derived for the first time. We also discuss the derived cluster properties of reddening, age and distance. Conclusions: Collinder 223 cluster parameters are overline{E(B-V) = 0.25 ± 0.03} mag and overline{(mv - M_v)0 = 11.21 ± 0.25} mag. In Hogg 16, we clearly distinguish two groups of stars (Hogg 16a and Hogg 16b) with very different mean true distance moduli (8.91 ± 0.26 mag and 12.51 ± 0.38 mag), mean colour excesses (0.26 ± 0.03 mag and 0.63 ± 0.08 mag), and spectral types (B early-type and B late-/A-type stars, respectively). The farthest group could be merged with Collinder 272. NGC 2645 is a young cluster (<14 Myr) with overline{E(B-V) = 0

  10. Photometric and integrated spectral study of the young open clusters Pismis 22, NGC 6178, NGC 6216 and Ruprecht 130

    NASA Astrophysics Data System (ADS)

    Piatti, A. E.; Clariá, J. J.; Bica, E.

    2000-08-01

    We present CCD observations in the B, V , and I passbands obtained for stars in the fields of the open clusters Pismis 22, NGC 6178, NGC 6216, and Ruprecht 130, projected not far from the Galactic centre (|l| < 30̂, |b| < 2̂). The sample consists of about 790 stars reaching down to V ~ 18-19 mag. From the analysis of the colour magnitude diagrams, we confirmed the physical reality of the clusters and derived their reddening, distance and age. In addition, we obtained flux-calibrated integrated spectra in the range 3500-9200 Å for the cluster sample. The equivalent widths of the Balmer lines provided us with age estimates, while the comparison with template spectra allowed us to derive both foreground reddening and age. The photometric and spectroscopic results reveal that the four studied objects are young open clusters with ages ranging between 35 and 50 Myr. The clusters, located between 1.0 kpc and 4.3 kpc from the Sun, are affected by different amounts of interstellar visual absorption (0.6 ≃ Av ≃ 6.0). Based on observations made at Complejo Astronómico El Leoncito, which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la Repúbica Argentina and the National Universities of La Plata, Córdoba, and San Juan, Argentina, and at the University of Toronto (David Dunlap Observatory) 24-inch telescope, Las Campanas, Chile. Tables 3-6 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

  11. Transdermal clonidine in the prophylaxis of episodic cluster headache: an open study.

    PubMed

    Leone, M; Attanasio, A; Grazzi, L; Libro, G; D'Amico, D; Moschiano, F; Bussone, G

    1997-10-01

    Transdermal clonidine has recently been reported to be efficacious in the prophylaxis of cluster headache. A 2-week course of transdermal clonidine (5 mg the first week, 7.5 mg the second week) preceded by a 5-day run-in period, was administered to 16 patients with episodic cluster headache in an active cluster period. In 5 patients, the painful attacks disappeared after the seventh day of treatment. For the group as a whole, no significant variations in headache frequency, pain intensity, or attack duration were observed between the run-in period and the first and second weeks of treatment (ANOVA). Further studies are necessary to clarify the effectiveness of transdermal clonidine in the prophylaxis of episodic cluster headache.

  12. The complex stellar populations in the background of open clusters in the third Galactic quadrant

    NASA Astrophysics Data System (ADS)

    Carraro, Giovanni; Seleznev, Anton F.; Baume, Gustavo; Turner, David. G.

    2016-02-01

    Multicolour photometry of the stellar populations in five fields in the third Galactic quadrant centred on the clusters NGC 2215, NGC 2354, Haffner 22, Ruprecht 11, and ESO489 SC01 is interpreted in terms of a warped and flared Galactic disc, without resort to an external entity such as the popular Monoceros or Canis Major overdensities. Except for NGC 2215, the clusters are poorly or unstudied previously. The data generate basic parameters for each cluster, including the distribution of stars along the line of sight. We use star counts and photometric analysis, without recourse to Galactic-model-based predictions or interpretations, and confirms earlier results for NGC 2215 and NGC 2354. ESO489 SC01 is not a real cluster, while Haffner 22 is an overlooked cluster aged ˜2.5 Gyr. Conclusions for Ruprecht 11 are preliminary, evidence for a cluster being marginal. Fields surrounding the clusters show signatures of young and intermediate-age stellar populations. The young population background to NGC 2354 and Ruprecht 11 lies ˜8-9 kpc from the Sun and ˜1 kpc below the formal Galactic plane, tracing a portion of the Norma-Cygnus arm, challenging Galactic models that adopt a sharp cut-off of the disc 12-14 kpc from the Galactic Centre. The old population is metal-poor with an age of ˜2-3 Gyr, resembling star clusters like Tombaugh 2 or NGC 2158. It has a large colour spread and is difficult to locate precisely. Young and old populations follow a pattern that depends critically on the vertical location of the thin and/or thick disc, and whether or not a particular line of sight intersects one, both, or none.

  13. Communication: Spin densities within a unitary group based spin-adapted open-shell coupled-cluster theory: Analytic evaluation of isotropic hyperfine-coupling constants for the combinatoric open-shell coupled-cluster scheme

    SciTech Connect

    Datta, Dipayan Gauss, Jürgen

    2015-07-07

    We report analytical calculations of isotropic hyperfine-coupling constants in radicals using a spin-adapted open-shell coupled-cluster theory, namely, the unitary group based combinatoric open-shell coupled-cluster (COSCC) approach within the singles and doubles approximation. A scheme for the evaluation of the one-particle spin-density matrix required in these calculations is outlined within the spin-free formulation of the COSCC approach. In this scheme, the one-particle spin-density matrix for an open-shell state with spin S and M{sub S} = + S is expressed in terms of the one- and two-particle spin-free (charge) density matrices obtained from the Lagrangian formulation that is used for calculating the analytic first derivatives of the energy. Benchmark calculations are presented for NO, NCO, CH{sub 2}CN, and two conjugated π-radicals, viz., allyl and 1-pyrrolyl in order to demonstrate the performance of the proposed scheme.

  14. Electrocrystallization of Monolayer-Protected Gold Clusters: Opening the Door to Quality, Quantity, and New Structures.

    PubMed

    Antonello, Sabrina; Dainese, Tiziano; Pan, Fangfang; Rissanen, Kari; Maran, Flavio

    2017-03-22

    Thiolate-protected metal clusters are materials of ever-growing importance in fundamental and applied research. Knowledge of their single-crystal X-ray structures has been instrumental to enable advanced molecular understanding of their intriguing properties. So far, however, a general, reliable, chemically clean approach to prepare single crystals suitable for accurate crystallographic analysis was missing. Here we show that single crystals of thiolate-protected clusters can be grown in large quantity and very high quality by electrocrystallization. This method relies on the fact that charged clusters display a higher solubility in polar solvents than their neutral counterparts. Nucleation of the electrogenerated insoluble clusters directly onto the electrode surface eventually leads to the formation of a dense forest of millimeter-long single crystals. Electrocrystallization of three known Au25(SR)18(0) clusters is described. A new cluster, Au25(S-nC5H11)18, was also prepared and found to crystallize by forming bundles of millimeter-long Au25 polymers.

  15. VizieR Online Data Catalog: Dynamical parameters of open clusters (Danilov+, 2012)

    NASA Astrophysics Data System (ADS)

    Danilov, V. M.; Putkov, S. I.

    2012-11-01

    α0 - is the mean value of a virial factor, δ{alp the amplitude of virial factor oscillations, ν={rho}c/{rho}0-is the density contrast ({rho}c - is the mean density of a cluster core, {rho}0 - is the cluster centre density), NK/N - is the ratio of the stars number in a cluster received by King's distribution and by stellar counts, P1-is the period of cluster core oscillations, P2 - is the period of cluster oscillations, δR1/R10-is the relative amplitude of core radius oscillations, λ=σ/σiz, σiz2 - is the velocity dispersion of an isolated virialized cluster, σ2, σ12, σ22 - are the velocity dispersions of nonisolated nonsteady clusters with spherical halo; with ellipsoidal halo elongated to the centre of Galaxy; with ellipsoidal halo elongated to the direction of cluster motion correspondingly. Errors of values α0, δα, δR1/R10, P1 have been estimated by the assumption of the normal distribution of the values M (the mass of a cluster), R2 (the radius of a cluster), {xi} (the ratio of core radius to halo radius), μ (the ratio of core mass to halo mass). Assuming a deviation of one of the four values equal to zero we receive four sections of 1σ-errors ellipsoid. These sections are the spheres of radius 20.5. Taking points on each sphere with the step 0.25*π on angular coordinates we receive 96 points on a surface of the 1σ-errors ellipsoid. The values α0, δα, δR1/R10, P1 were calculated in the 96 points. The centre of the ellipsoidal was used for calculation of the mean values. The errors of the values were computed as root-mean-squire deviations of 96 values from the same mean values. The errors of the others values of the catalog were computed by the errors calculation rule of indirect measuring. (3 data files).

  16. Blue stragglers and X -ray binaries in open clusters: An observational study of alternative pathways in stellar evolution

    NASA Astrophysics Data System (ADS)

    Gosnell, Natalie Marie

    Membership studies of evolved open clusters reveal many alternative pathway stellar products whose evolution cannot be explained using single-star evolutionary models. These stars are neither rare nor anomalous, and in fact are a common occurrence in cluster populations. The goal of this thesis is to investigate the origin and evolutionary pathways of such stars through the careful study of X-ray binaries in NGC 6819 and white dwarf (WD) companions of mass transfer-formed blue straggler stars (BSSs) in NGC 188. I present the first X-ray study of the intermediate-age open cluster NGC 6819, using observations from XMM-Newton. This study of NGC 6819 is part of a systematic survey to investigate the relationship between the number of X-ray sources and cluster dynamics in the regime of massive open clusters. Of the 12 X-ray sources within the half-light radius of NGC 6819, four sources challenge single-star evolutionary models, including a candidate quiescent low-mass X-ray binary. Next, I present the first results from a Hubble Space Telescope (HST) far-ultraviolet (FUV) campaign to search for WD companions of BSSs as indicators of mass transfer formation. I find direct observational detections of young (< 250 Myr), hot WD companions in three BSS binaries. Their presence in a well-studied cluster environment allows for unparalleled constraints on the pre-mass transfer system. I outline potential formation timelines for these three BSSs, which all formed through recent mass transfer. Finally, I use HST photometry of the complete NGC 188 BSS population to place limits on the mass transfer BSS formation frequency. Comparison of the observations with models for BSS FUV emission reveals seven WD companions with temperatures greater than 11,000 K. The location of the young BSSs on an optical color-magnitude diagram suggests that using single-star evolutionary models to age luminous BSSs may be problematic. Considering other formation scenarios, the total mass transfer

  17. Elemental abundance analysis of the early-type members of the open cluster M6: Preliminary results

    NASA Astrophysics Data System (ADS)

    Kılıçoǧlu, T.; Monier, R.; Fossati, L.

    2014-11-01

    Differences in chemical composition among main sequence stars within a given cluster are probably due to differences in their masses and other effects such as radiative diffusion, magnetic field, rotation, mixing mechanisms, mass loss, accretion and multiplicity. The early type main-sequence members of open clusters of different ages support studies of the competition between radiative diffusion and mixing mechanisms. We have analysed low- and high-resolution spectra covering the spectral range λ 4500-5840 Å of late B-, A- and F-type members of the open cluster M6 (age ˜100 Myr). The spectra were obtained with the FLAMES/GIRAFFE spectrograph mounted at UT2, the 8-m VLT telescope. The effective temperatures, surface gravities and microturbulent velocities of the stars were derived from both photometric and spectral methods. We have also performed a chemical abundance analysis using synthetic spectra. Abundances were determined for the elements C, O, Mg, Si, Ca, Sc, Ti, Cr, Mn, Fe, Ni, Y and Ba. The star-to-star variations in element abundances among the members of M6 are discussed.

  18. Single stars in the Hyades open cluster. Fiducial sequence for testing stellar and atmospheric models

    NASA Astrophysics Data System (ADS)

    Kopytova, Taisiya G.; Brandner, Wolfgang; Tognelli, Emanuele; Prada Moroni, Pier Giorgio; Da Rio, Nicola; Röser, Siegfried; Schilbach, Elena

    2016-01-01

    Context. Age and mass determinations for isolated stellar objects remain model-dependent. While stellar interior and atmospheric theoretical models are rapidly evolving, we need a powerful tool to test them. Open clusters are good candidates for this role. Aims: We aim to create a fiducial sequence of stellar objects for testing stellar and atmospheric models. Methods: We complement previous studies on the Hyades multiplicity by Lucky Imaging observations with the AstraLux Norte camera. This allows us to exclude possible binary and multiple systems with companions outside a 2-7 AU separation and to create a single-star sequence for the Hyades. The sequence encompasses 250 main-sequence stars ranging from A5V to M6V. Using the Tool for Astrophysical Data Analysis (TA-DA), we create various theoretical isochrones applying different combinations of interior and atmospheric models. We compare the isochrones with the observed Hyades single-star sequence on J vs. J-Ks, J vs. J-H, and Ks vs. H-Ks color-magnitude diagrams. As a reference we also compute absolute fluxes and magnitudes for all stars from X-ray to mid-infrared based on photometric measurements available in the literature(ROSAT X-ray, GALEX UV, APASS gri, 2MASS JHKs, and WISE W1 to W4). Results: We find that combinations of both PISA and DARTMOUTH stellar interior models with BT-Settl 2010 atmospheric models describe the observed sequence well. We use PISA in combination with BT-Settl 2010 models to derive theoretical predictions for physical parameters (Teff, mass, log g) of 250 single stars in the Hyades. The full sequence covers the mass range of 0.13-2.30 M⊙, and effective temperatures between 3060 K and 8200 K. Conclusions: Within the measurement uncertainties, the current generation of models agree well with the single-star sequence. The primary limitations are the uncertainties in the measurement of the distances to individual Hyades members, and uncertainties in the photometry. Gaia parallaxes

  19. ASTEROSEISMOLOGY OF THE OPEN CLUSTERS NGC 6791, NGC 6811, AND NGC 6819 FROM 19 MONTHS OF KEPLER PHOTOMETRY

    SciTech Connect

    Corsaro, Enrico; Stello, Dennis; Huber, Daniel; Bedding, Timothy R.; Benomar, Othman; White, Timothy R.; Bonanno, Alfio; Brogaard, Karsten; Kallinger, Thomas; Mosser, Benoit; Basu, Sarbani; Chaplin, William J.; Elsworth, Yvonne P.; Mathur, Savita; Christensen-Dalsgaard, Jorgen; Garcia, Rafael A.; Hekker, Saskia; Kjeldsen, Hans; Meibom, Soren; Hall, Jennifer R. [Orbital Sciences Corporation and others

    2012-10-01

    We studied solar-like oscillations in 115 red giants in the three open clusters, NGC 6791, NGC 6811, and NGC 6819, based on photometric data covering more than 19 months with NASA's Kepler space telescope. We present the asteroseismic diagrams of the asymptotic parameters {delta}{nu}{sub 02}, {delta}{nu}{sub 01}, and {epsilon}, which show clear correlation with fundamental stellar parameters such as mass and radius. When the stellar populations from the clusters are compared, we see evidence for a difference in mass of the red giant branch stars and possibly a difference in structure of the red clump stars, from our measurements of the small separations {delta}{nu}{sub 02} and {delta}{nu}{sub 01}. Ensemble echelle diagrams and upper limits to the linewidths of l = 0 modes as a function of {Delta}{nu} of the clusters NGC 6791 and NGC 6819 are also shown, together with the correlation between the l = 0 ridge width and the T{sub eff} of the stars. Lastly, we distinguish between red giant branch and red clump stars through the measurement of the period spacing of mixed dipole modes in 53 stars among all the three clusters to verify the stellar classification from the color-magnitude diagram. These seismic results also allow us to identify a number of special cases, including evolved blue stragglers and binaries, as well as stars in late He-core burning phases, which can be potentially interesting targets for detailed theoretical modeling.

  20. Development of New Open-Shell Perturbation and Coupled-Cluster Theories Based on Symmetric Spin Orbitals

    NASA Technical Reports Server (NTRS)

    Lee, Timothy J.; Arnold, James O. (Technical Monitor)

    1994-01-01

    A new spin orbital basis is employed in the development of efficient open-shell coupled-cluster and perturbation theories that are based on a restricted Hartree-Fock (RHF) reference function. The spin orbital basis differs from the standard one in the spin functions that are associated with the singly occupied spatial orbital. The occupied orbital (in the spin orbital basis) is assigned the delta(+) = 1/square root of 2(alpha+Beta) spin function while the unoccupied orbital is assigned the delta(-) = 1/square root of 2(alpha-Beta) spin function. The doubly occupied and unoccupied orbitals (in the reference function) are assigned the standard alpha and Beta spin functions. The coupled-cluster and perturbation theory wave functions based on this set of "symmetric spin orbitals" exhibit much more symmetry than those based on the standard spin orbital basis. This, together with interacting space arguments, leads to a dramatic reduction in the computational cost for both coupled-cluster and perturbation theory. Additionally, perturbation theory based on "symmetric spin orbitals" obeys Brillouin's theorem provided that spin and spatial excitations are both considered. Other properties of the coupled-cluster and perturbation theory wave functions and models will be discussed.

  1. Dust discs around intermediate-mass and Sun-like stars in the 16 Myr old NGC 1960 open cluster

    NASA Astrophysics Data System (ADS)

    Smith, R.; Jeffries, R. D.

    2012-03-01

    We present an analysis of Spitzer IRAC (3.6-8 μm) and MIPS (24 μm) imaging of members of the 16? Myr old open cluster NGC 1960 (M36). Models of terrestrial planet formation indicate that rocky planets are likely to achieve their final masses at around 10-30 Myr, and thus this cluster is at an interesting epoch for planet formation. We find 21 B-F5 type stars and 14 F6-K9 type stars which have 24 μm excess emission, and thus determine that >30 per cent of B-F5 type stars and >23 per cent of F6-K9 type stars in this cluster have 24 μm excess emission. These excess frequencies are similar to those observed in other clusters of similar age. Three early-type stars have excesses at near-infrared wavelengths. Analysis of their spectral energy distributions confirms that these are true debris discs and not remnant primordial or transitional discs. None of the 61 Sun-like stars has confirmed near-infrared excess, and we can place a limit on the frequency of 8 μm excess emission around Sun-like stars of <7 per cent. All of the detected excesses are consistent with emission from debris discs and are not primordial.

  2. JMS: An Open Source Workflow Management System and Web-Based Cluster Front-End for High Performance Computing.

    PubMed

    Brown, David K; Penkler, David L; Musyoka, Thommas M; Bishop, Özlem Tastan

    2015-01-01

    Complex computational pipelines are becoming a staple of modern scientific research. Often these pipelines are resource intensive and require days of computing time. In such cases, it makes sense to run them over high performance computing (HPC) clusters where they can take advantage of the aggregated resources of many powerful computers. In addition to this, researchers often want to integrate their workflows into their own web servers. In these cases, software is needed to manage the submission of jobs from the web interface to the cluster and then return the results once the job has finished executing. We have developed the Job Management System (JMS), a workflow management system and web interface for high performance computing (HPC). JMS provides users with a user-friendly web interface for creating complex workflows with multiple stages. It integrates this workflow functionality with the resource manager, a tool that is used to control and manage batch jobs on HPC clusters. As such, JMS combines workflow management functionality with cluster administration functionality. In addition, JMS provides developer tools including a code editor and the ability to version tools and scripts. JMS can be used by researchers from any field to build and run complex computational pipelines and provides functionality to include these pipelines in external interfaces. JMS is currently being used to house a number of bioinformatics pipelines at the Research Unit in Bioinformatics (RUBi) at Rhodes University. JMS is an open-source project and is freely available at https://github.com/RUBi-ZA/JMS.

  3. Binary open clusters in the Milky Way: photometric and spectroscopic analysis of NGC 5617 and Trumpler 22

    NASA Astrophysics Data System (ADS)

    De Silva, G. M.; Carraro, G.; D'Orazi, V.; Efremova, V.; Macpherson, H.; Martell, S.; Rizzo, L.

    2015-10-01

    Using photometry and high-resolution spectroscopy we investigate for the first time the physical connection between the open clusters NGC 5617 and Trumpler 22. Based on new CCD photometry we report their spatial proximity and common age of ˜70 Myr. Based on high-resolution spectra collected using the HERMES and UCLES spectrographs on the Anglo-Australian telescope, we present radial velocities and abundances for Fe, Na, Mg, Al, Si, Ca, and Ni. The measured radial velocities are -38.63 ± 2.25 km s-1 for NGC 5617 and -38.46 ± 2.08 km s-1 for Trumpler 22. The mean metallicity of NGC 5617 was found to be [Fe/H] = -0.18 ± 0.02 and for Trumpler 22 was found to be [Fe/H] = -0.17 ± 0.04. The two clusters share similar abundances across the other elements, indicative of a common chemical enrichment history of these clusters. Together with common motions and ages we confirm that NGC 5617 and Trumpler 22 are a primordial binary cluster pair in the Milky Way.

  4. JMS: An Open Source Workflow Management System and Web-Based Cluster Front-End for High Performance Computing

    PubMed Central

    Brown, David K.; Penkler, David L.; Musyoka, Thommas M.; Bishop, Özlem Tastan

    2015-01-01

    Complex computational pipelines are becoming a staple of modern scientific research. Often these pipelines are resource intensive and require days of computing time. In such cases, it makes sense to run them over high performance computing (HPC) clusters where they can take advantage of the aggregated resources of many powerful computers. In addition to this, researchers often want to integrate their workflows into their own web servers. In these cases, software is needed to manage the submission of jobs from the web interface to the cluster and then return the results once the job has finished executing. We have developed the Job Management System (JMS), a workflow management system and web interface for high performance computing (HPC). JMS provides users with a user-friendly web interface for creating complex workflows with multiple stages. It integrates this workflow functionality with the resource manager, a tool that is used to control and manage batch jobs on HPC clusters. As such, JMS combines workflow management functionality with cluster administration functionality. In addition, JMS provides developer tools including a code editor and the ability to version tools and scripts. JMS can be used by researchers from any field to build and run complex computational pipelines and provides functionality to include these pipelines in external interfaces. JMS is currently being used to house a number of bioinformatics pipelines at the Research Unit in Bioinformatics (RUBi) at Rhodes University. JMS is an open-source project and is freely available at https://github.com/RUBi-ZA/JMS. PMID:26280450

  5. Rotational Periods and Starspot Activity of Young Solar-Type Dwarfs in the Open Cluster IC 4665

    NASA Technical Reports Server (NTRS)

    Allain, S.; Bouvier, J.; Prosser, C.; Marschall, L. A.; Laaksonen, B. D.

    1995-01-01

    We present the results of a V-band photometric monitoring survey of 15 late-type dwarfs in the young open cluster IC 4665. Low-amplitude periodic light variations are found for 8 stars and ascribed to the modulation by starspots that cover typically a few percent of the stellar disk. Periods range from 0.6 to 3.7 d, translating to equatorial velocities between 13 and 93 km/s. That no period longer than 4 d was detected suggests a relative paucity of extremely slow rotators (V(sub eq) much less than 10 km/s) among late-type dwarfs in IC 4665. The fractional number of slow rotators in IC 4665 is similar to that of Alpha Per cluster, suggesting that IC 4665 is close in age to Alpha Per (approx. 50 Myr).

  6. DETECTION OF WHITE DWARF COMPANIONS TO BLUE STRAGGLERS IN THE OPEN CLUSTER NGC 188: DIRECT EVIDENCE FOR RECENT MASS TRANSFER

    SciTech Connect

    Gosnell, Natalie M.; Mathieu, Robert D.; Geller, Aaron M.; Sills, Alison; Leigh, Nathan; Knigge, Christian

    2014-03-01

    Several possible formation pathways for blue straggler stars have been developed recently, but no one pathway has yet been observationally confirmed for a specific blue straggler. Here we report the first findings from a Hubble Space Telescope Advanced Camera for Surveys/Solar Blind Channel far-UV photometric program to search for white dwarf companions to blue straggler stars. We find three hot and young white dwarf companions to blue straggler stars in the 7 Gyr open cluster NGC 188, indicating that mass transfer in these systems ended less than 300 Myr ago. These companions are direct and secure observational evidence that these blue straggler stars were formed through mass transfer in binary stars. Their existence in a well-studied cluster environment allows for observational constraints of both the current binary system and the progenitor binary system, mapping the entire mass transfer history.

  7. Asteroseismology of the Hyades with K2: first detection of main-sequence solar-like oscillations in an open cluster

    NASA Astrophysics Data System (ADS)

    Lund, Mikkel N.; Basu, Sarbani; Silva Aguirre, Víctor; Chaplin, William J.; Serenelli, Aldo M.; García, Rafael A.; Latham, David W.; Casagrande, Luca; Bieryla, Allyson; Davies, Guy R.; Viani, Lucas S.; Buchhave, Lars A.; Miglio, Andrea; Soderblom, David R.; Valenti, Jeff A.; Stefanik, Robert P.; Handberg, Rasmus

    2016-12-01

    The Hyades open cluster was targeted during Campaign 4 (C4) of the NASA K2 mission, and short-cadence data were collected on a number of cool main-sequence stars. Here, we report results on two F-type stars that show detectable oscillations of a quality that allows asteroseismic analyses to be performed. These are the first ever detections of solar-like oscillations in main-sequence stars in an open cluster.

  8. Photometric monitoring of open clusters: Low-mass eclipsing binary stars and the stellar mass-luminosity-radius relation

    NASA Astrophysics Data System (ADS)

    Hebb, Leslie

    2006-06-01

    This thesis describes a photometric monitoring survey of Galactic star clusters designed to detect low-mass eclipsing binary star systems through variations in their relative lightcurves. The aim is to use cluster eclipsing binaries to measure the masses and radii of M-dwarf stars with ages and metallicities known from studies of brighter cluster stars. This information will provide an improved calibration of the mass-luminosity-radius relation for low-mass stars, be used to test stellar structure and evolution models, and help quantify the contribution of low-mass stars to the global mass census in the Galaxy. The survey is designed to detect eclipse events in stars of ~0.3 M_sun and consists of 600 Gbytes of raw imaging data on six open clusters with a range of ages (~ 0.15 - 4 Gyr) and metallicites (~ -0.2 - 0.0 dex). The clusters NGC 1647 and M 35 contain excellent candidate systems showing eclipse like variations in brightness and photometry consistent with cluster membership. The analysis of these clusters and the eclipsing M-dwarf stars detected in them are presented. Analysis of the candidate system in NGC 1647 confirms the object as a newly discovered M-dwarf eclipsing binary in the cluster with compenent masses of M 1 = 0.47 ± 0.05[Special characters omitted.] and M 2 = 0.19 ± 0.02[Special characters omitted.] . The small mass ratio ( M 2 / M 1 ) and low secondary mass of this object provide an unprecedented opportunity to test stellar models. We find that no stellar evolution models are consistent with all the properties of both M-dwarf stars in the eclipsing binary. The candidate in M 35 has been confirmed as an M-dwarf eclipsing binary, and the masses of the individual components are estimated to be M 1 ~ 0.25 M_sun and M 2 ~ 0.15 M_sun . Additional high resolution spectroscopic and photometric observations, for which we have applied and been awarded time, are necessary to accurately derive the intrinsic properties of the individual stellar

  9. GLOBULAR AND OPEN CLUSTERS OBSERVED BY SDSS/SEGUE: THE GIANT STARS

    SciTech Connect

    Morrison, Heather L.; Ma, Zhibo; Connor, Thomas; Schechtman-Rook, Andrew; Harding, Paul; Clem, James L.; An, Deokkeun; Casagrande, Luca; Rockosi, Constance; Beers, Timothy C.; Johnson, Jennifer A.; Schneider, Donald P.

    2016-01-15

    We present griz observations for the clusters M92, M13 and NGC 6791 and gr photometry for M71, Be 29 and NGC 7789. In addition we present new membership identifications for all these clusters, which have been observed spectroscopically as calibrators for the Sloan Digital Sky Survey (SDSS)/SEGUE survey; this paper focuses in particular on the red giant branch stars in the clusters. In a number of cases, these giants were too bright to be observed in the normal SDSS survey operations, and we describe the procedure used to obtain spectra for these stars. For M71, we also present a new variable reddening map and a new fiducial for the gr giant branch. For NGC 7789, we derived a transformation from T{sub eff} to g–r for giants of near solar abundance, using IRFM T{sub eff} measures of stars with good ugriz  and 2MASS photometry and SEGUE spectra. The result of our analysis is a robust list of known cluster members with correctly dereddened and (if needed) transformed gr photometry for crucial calibration efforts for SDSS and SEGUE.

  10. Globular and Open Clusters Observed by SDSS/SEGUE: the Giant Stars

    SciTech Connect

    Morrison, Heather L.; Ma, Zhibo; Clem, James L.; An, Deokkeun; Connor, Thomas; Schechtman-Rook, Andrew; Casagrande, Luca; Rockosi, Constance; Yanny, Brian; Harding, Paul; Beers, Timothy C.; Johnson, Jennifer A.; Schneider, Donald P.

    2015-12-18

    We present griz observations for the clusters M92, M13 and NGC 6791 and gr photometry for M71, Be 29 and NGC 7789. In addition we present new membership identifications for all these clusters, which have been observed spectroscopically as calibrators for the SDSS/SEGUE survey; this paper focuses in particular on the red giant branch stars in the clusters. In a number of cases, these giants were too bright to be observed in the normal SDSS survey operations, and we describe the procedure used to obtain spectra for these stars. For M71, also present a new variable reddening map and a new fiducial for the gr giant branch. For NGC 7789, we derived a transformation from Teff to g-r for giants of near solar abundance, using IRFM Teff measures of stars with good ugriz and 2MASS photometry and SEGUE spectra. The result of our analysis is a robust list of known cluster members with correctly dereddened and (if needed) transformed gr photometry for crucial calibration efforts for SDSS and SEGUE.

  11. Globular and Open Clusters Observed by SDSS/SEGUE: the Giant Stars

    DOE PAGES

    Morrison, Heather L.; Ma, Zhibo; Clem, James L.; ...

    2015-12-18

    We present griz observations for the clusters M92, M13 and NGC 6791 and gr photometry for M71, Be 29 and NGC 7789. In addition we present new membership identifications for all these clusters, which have been observed spectroscopically as calibrators for the SDSS/SEGUE survey; this paper focuses in particular on the red giant branch stars in the clusters. In a number of cases, these giants were too bright to be observed in the normal SDSS survey operations, and we describe the procedure used to obtain spectra for these stars. For M71, also present a new variable reddening map and amore » new fiducial for the gr giant branch. For NGC 7789, we derived a transformation from Teff to g-r for giants of near solar abundance, using IRFM Teff measures of stars with good ugriz and 2MASS photometry and SEGUE spectra. The result of our analysis is a robust list of known cluster members with correctly dereddened and (if needed) transformed gr photometry for crucial calibration efforts for SDSS and SEGUE.« less

  12. VizieR Online Data Catalog: New Variables in 3 Galactic open clusters (Palma+, 2016)

    NASA Astrophysics Data System (ADS)

    Palma, T.; Minniti, D.; Dekany, I.; Claria, J. J.; Alonso-Garcia, J.; Gramajo, L. V.; Ramirez Alegria, S.; Bonatto, C.

    2016-11-01

    The observations were made as part of the VVV Survey. For each cluster field, we extracted and analyzed VVV data for objects that best matched the positions of previously reported variable stars (Zejda et al., 2012, Cat. J/A+A/548/A97), and also performed a blind variability search. (3 data files).

  13. VizieR Online Data Catalog: The young open cluster NGC 7067 (Monguio+, 2017)

    NASA Astrophysics Data System (ADS)

    Monguio, M.; Negueruela, I.; Marco, A.; Gonzalez-Fernandez, C.; Alonso-Santiago, J.; Costado, M. T.; Casamiquela, L.; Lopez-Corredoira, M.; Molgo, J.; Vilardell, F.; Alfaro, E. J.; Antoja, T.; Figueras, F.; Garcia, M.; Jordi, C.; Romero-Gomez, M.

    2017-02-01

    The Wide Field Camera (WFC) at the Isaac Newton Telescope (INT, 2.5m) - located at El Roque de los Muchachos in the Canary Islands - was used to obtain Stroemgren uvbyβ CCD photometry for this cluster. The observations were acquired during the nights of 2014 July 6-8. (3 data files).

  14. The mass-ratio and eccentricity distributions of barium and S stars, and red giants in open clusters

    NASA Astrophysics Data System (ADS)

    Van der Swaelmen, M.; Boffin, H. M. J.; Jorissen, A.; Van Eck, S.

    2017-01-01

    Context. A complete set of orbital parameters for barium stars, including the longest orbits, has recently been obtained thanks to a radial-velocity monitoring with the HERMES spectrograph installed on the Flemish Mercator telescope. Barium stars are supposed to belong to post-mass-transfer systems. Aims: In order to identify diagnostics distinguishing between pre- and post-mass-transfer systems, the properties of barium stars (more precisely their mass-function distribution and their period-eccentricity (P-e) diagram) are compared to those of binary red giants in open clusters. As a side product, we aim to identify possible post-mass-transfer systems among the cluster giants from the presence of s-process overabundances. We investigate the relation between the s-process enrichment, the location in the (P-e) diagram, and the cluster metallicity and turn-off mass. Methods: To invert the mass-function distribution and derive the mass-ratio distribution, we used the method pioneered by Boffin et al. (1992) that relies on a Richardson-Lucy deconvolution algorithm. The derivation of s-process abundances in the open-cluster giants was performed through spectral synthesis with MARCS model atmospheres. Results: A fraction of 22% of post-mass-transfer systems is found among the cluster binary giants (with companion masses between 0.58 and 0.87 M⊙, typical for white dwarfs), and these systems occupy a wider area than barium stars in the (P-e) diagram. Barium stars have on average lower eccentricities at a given orbital period. When the sample of binary giant stars in clusters is restricted to the subsample of systems occupying the same locus as the barium stars in the (P-e) diagram, and with a mass function compatible with a WD companion, 33% (=4/12) show a chemical signature of mass transfer in the form of s-process overabundances (from rather moderate - about 0.3 dex - to more extreme - about 1 dex). The only strong barium star in our sample is found in the cluster with

  15. The Problem of Hipparcos Distances to Open Clusters. II. Constraints from Nearby Field Theory. Report 2; ClustersConstraints from nearly Field Stars

    NASA Technical Reports Server (NTRS)

    Soderblom, David R.; King, Jeremy R.; Hanson, Robert B.; Jones, Burton F.; Fischer, Debra; Stauffer, John R.; Pinsonneault, Marc H.

    1998-01-01

    This paper examines the discrepancy between distances to nearby open clusters as determined by parallaxes from Hipparcos compared to traditional main-sequence fitting. The biggest difference is seen for the Pleiades, and our hypothesis is that if the Hipparcos distance to the Pleiades is correct, then similar subluminous zero-age main-sequence (ZAMS) stars should exist elsewhere, including in the immediate solar neighborhood. We examine a color-magnitude diagram of very young and nearby solar-type stars and show that none of them lie below the traditional ZAMS, despite the fact that the Hipparcos Pleiades parallax would place its members 0.3 mag below that ZAMS. We also present analyses and observations of solar-type stars that do lie below the ZAMS, and we show that they are subluminous because of low metallicity and that they have the kinematics of old stars.

  16. A High Angular Resolution Multiplicity Survey of the Open Clusters α Persei and Praesepe

    NASA Astrophysics Data System (ADS)

    Patience, J.; Ghez, A. M.; Reid, I. N.; Matthews, K.

    2002-03-01

    Two hundred forty-two members of the Praesepe and α Persei clusters have been surveyed with high angular resolution 2.2 μm speckle imaging on the 3 m Infrared Telescope Facility, the 5 m Hale, and the 10 m Keck telescopes, along with direct imaging using the near-infrared camera (NICMOS) aboard the Hubble Space Telescope. The observed stars range in spectral type from B (~5 Msolar) to early M (~0.5 Msolar), with the majority of the targets more massive than ~0.8 Msolar. The one quadruple and 39 binary systems detected encompass separations from 0.053" to 7.28" 28 of the systems are new detections, and there are nine candidate substellar companions. The results of the survey are used to test binary star formation and evolution scenarios and to investigate the effects of companion stars on X-ray emission and stellar rotation. The main results are as follows:1. Over the projected separation range of 26 to 581 AU and magnitude differences of ΔK<4.0 (comparable to mass ratios q=Msec/Mprim>0.25), the companion-star fraction (CSF) for α Per is 0.09+/-0.03, and that for Praesepe is 0.10+/-0.03. This fraction is consistent with the field G dwarf value, implying that there is not a systematic decline in multiplicity with age at these separations on timescales of a few times 107 yr. The combination of previous spectroscopic work and the current cluster survey results in a cluster binary separation distribution that peaks at 4+1-1.5 AU, a significantly smaller value than the peaks of both the field G dwarf and the nearby T Tauri distributions. If the field G dwarf distribution represents a superposition of distributions from the populations that contributed to the field, then the data imply that ~30% of field binaries formed in dark clouds like the nearby T Tauri stars and the remaining ~70% formed in denser regions.2. An exploration of the binary star properties reveals a cluster CSF that increases with decreasing target mass, and a cluster mass ratio distribution that

  17. A UBVI AND uvbyCaH{beta} ANALYSIS OF THE INTERMEDIATE-AGE OPEN CLUSTER, NGC 5822

    SciTech Connect

    Carraro, Giovanni; Anthony-Twarog, Barbara J.; Jones, Bryce J.; Twarog, Bruce A.; Costa, Edgardo E-mail: bjat@ku.edu E-mail: btwarog@ku.edu

    2011-10-15

    NGC 5822 is a richly populated, moderately nearby, intermediate-age open cluster covering an area larger than the full moon on the sky. A CCD survey of the cluster on the UBVI and uvbyCaH{beta} systems shows that the cluster is superposed upon a heavily reddened field of background stars with E(B - V) > 0.35 mag, while the cluster has small and uniform reddening at E(b - y) = 0.075 {+-} 0.008 mag or E(B - V) = 0.103 {+-} 0.011 mag, based upon 48 and 61 probable A and F dwarf single-star members, respectively. The errors quoted include both internal photometric precision and external photometric uncertainties. The metallicity derived from 61 probable single F-star members is [Fe/H] = -0.058 {+-} 0.027 (sem) from m{sub 1} and 0.010 {+-} 0.020 (sem) from hk, for a weighted average of [Fe/H] = -0.019 {+-} 0.023, where the errors refer to the internal errors from the photometry alone. With reddening and metallicity fixed, the cluster age and apparent distance modulus are obtained through a comparison to appropriate isochrones in both VI and BV, producing 0.9 {+-} 0.1 Gyr and 9.85 {+-} 0.15, respectively. The giant branch remains dominated by two distinct clumps of stars, though the brighter clump seems a better match to the core-He-burning phase while the fainter clump straddles the first-ascent red giant branch. Four potential new clump members have been identified, equally split between the two groups. Reanalysis of the UBV two-color data extending well down the main sequence shows it to be optimally matched by reddening near E(B - V) = 0.10 rather than the older value of 0.15, leading to [Fe/H] between -0.16 and 0.00 from the ultraviolet excess of the unevolved dwarfs. The impact of the lower reddening and younger age of the cluster on previous analyses of the cluster is discussed.

  18. BOCCE, The Bologna Open Clusters Chemical Evolution Project: a large, homogeneous sample of Galactic open clusters. (Spanish Title: %t Proyecto BOCCE (The Bologna Open Clusters Chemical Evolution Project): una gran muestra homogénea de cúmulos abiertos galácticos)

    NASA Astrophysics Data System (ADS)

    Ahumada, A. V.; Bragaglia, A.; Tosi, M.; Marconi, G.

    The BOCCE project is a photometric and spectroscopic survey of Galactic open clusters (OCs), to be used as tracers of the properties and evolution of the Galactic disk. The main OCs parameters are derived in a precise and homogeneous way, and they will be used, for example, to determine the metallicity distribution in the Galactic disk and how it has evolved with time. We have presently data for about 40 OCs. We present here part of our last effort, concerning the photometric data obtained for NGC 2849.

  19. Computer-aided cluster expansion: An efficient algebraic approach for open quantum many-particle systems

    NASA Astrophysics Data System (ADS)

    Foerster, A.; Leymann, H. A. M.; Wiersig, J.

    2017-03-01

    We introduce an equation of motion approach that allows for an approximate evaluation of the time evolution of a quantum system, where the algebraic work to derive the equations of motion is done by the computer. The introduced procedures offer a variety of different types of approximations applicable for finite systems with strong coupling as well as for arbitrary large systems where augmented mean-field theories like the cluster expansion can be applied.

  20. CoRoT observations of the young open cluster Dolidze 25

    NASA Astrophysics Data System (ADS)

    Ripepi, V.; Leccia, S.; Baglin, A.; Ruoppo, A.; Bernabei, S.; Zwintz, K.; Cusano, F.; Gandolfi, D.; Guenter, E. W.; Alencar, S.; Marconi, M.; Monteiro, M. J. P. F. G.; Palla, F.; Alcalá, J. M.; Boehm, T.; Catala, C.; Chavero, C.; Corradi, W. S.; Degl'Innocenti, S.; de La Reza, R.; Deluil, M.; Favata, F.; Fernandez, M.; Gregorio-Hetem, J.; Lepine, J. D. R.; Pinheiro, F. J. G.; Prada Moroni, P. G.; Quast, G.; Torres, C. A. O.; Weiss, W.

    2010-07-01

    We present some preliminary results based on the CoRoT observations of the young distant cluster Dolidze 25. The light curve for the 28 stars observed by the satellite have been analyzed and the relevant periodogram presented. As a result we have found two binary, three Pulsating Be, three SPB, two Spotted and one ellipsoidal variables. Noteworthy, we have also identified one PMS δ Scuti candidate.

  1. The Effect of Metallicity on Surface Lithium Abundance in Hyades-Aged Open Clusters

    NASA Astrophysics Data System (ADS)

    Gayetsky, Lisa; Cummings, J.; Deliyannis, C. P.; Steinhauer, A.; James, D.; Sarajedini, A.

    2007-12-01

    Two of the most important predictions from standard stellar evolution theory about the lithium depletion of solar-type F and G dwarfs are that it occurs primarily during the pre-main sequence and that it depends on metallicity. Abundant evidence from star clusters shows that Li depletion does indeed occur during the pre-main sequence, but then also continues during the main sequence, perhaps due to the effects of (non-standard) rotationally-induced or wave-induced mixing. However, little is known about whether Li depletion depends on metallicity. To test the predicted dependence of standard Li depletion on metallicity, a program has begun that compares the Li-Teff relation in Hyades-aged clusters of different metallicities. Here, we present high resolution results from WIYN/Hydra observations of IC 4756. We find, first, that our data qualitatively support the prediction that stars with higher metallicity have depleted more Li. Second, if a reasonable adjustment is made to the (unknown) initial cluster Li abundances that is consistent with knowledge of Galactic Li production from the field dwarf Li-Fe relation, then our data are also in good quantitative agreement with the metallicity-dependence of the Li depletion from standard theory. This work has been supported by the National Science Foundation under grants AST-0452975 and AST-0206202.

  2. Comparing the OpenMP, MPI, and Hybrid Programming Paradigm on an SMP Cluster

    NASA Technical Reports Server (NTRS)

    Jost, Gabriele; Jin, Haoqiang; anMey, Dieter; Hatay, Ferhat F.

    2003-01-01

    With the advent of parallel hardware and software technologies users are faced with the challenge to choose a programming paradigm best suited for the underlying computer architecture. With the current trend in parallel computer architectures towards clusters of shared memory symmetric multi-processors (SMP), parallel programming techniques have evolved to support parallelism beyond a single level. Which programming paradigm is the best will depend on the nature of the given problem, the hardware architecture, and the available software. In this study we will compare different programming paradigms for the parallelization of a selected benchmark application on a cluster of SMP nodes. We compare the timings of different implementations of the same CFD benchmark application employing the same numerical algorithm on a cluster of Sun Fire SMP nodes. The rest of the paper is structured as follows: In section 2 we briefly discuss the programming models under consideration. We describe our compute platform in section 3. The different implementations of our benchmark code are described in section 4 and the performance results are presented in section 5. We conclude our study in section 6.

  3. Open reading frame 176 in the photosynthesis gene cluster of Rhodobacter capsulatus encodes idi, a gene for isopentenyl diphosphate isomerase.

    PubMed Central

    Hahn, F M; Baker, J A; Poulter, C D

    1996-01-01

    Isopentenyl diphosphate (IPP) isomerase catalyzes an essential activation step in the isoprenoid biosynthetic pathway. A database search based on probes from the highly conserved regions in three eukaryotic IPP isomerases revealed substantial similarity with ORF176 in the photosynthesis gene cluster in Rhodobacter capsulatus. The open reading frame was cloned into an Escherichia coli expression vector. The encoded 20-kDa protein, which was purified in two steps by ion exchange and hydrophobic interaction chromatography, catalyzed the interconversion of IPP and dimethylallyl diphosphate. Thus, the photosynthesis gene cluster encodes all of the enzymes required to incorporate IPP into the ultimate carotenoid and bacteriochlorophyll metabolites in R. capsulatus. More recent searches uncovered additional putative open reading frames for IPP isomerase in seed-bearing plants (Oryza sativa, Arabadopsis thaliana, and Clarkia breweri), a worm (Caenorhabiditis elegans), and another eubacterium (Escherichia coli). The R. capsulatus enzyme is the smallest of the IPP isomerases to be identified thus far and may consist mostly of a fundamental catalytic core for the enzyme. PMID:8550491

  4. Multiplexing Precision Radial Velocities with the Michigan/Magellan Fiber System: Searching for Hot Jupiters in Southern Open Star Clusters

    NASA Astrophysics Data System (ADS)

    Bailey, John Ira; Mateo, Mario L.; White, Russel J.; Crane, Jeffrey D.; Shectman, Stephen A.; M2FS Instrument Team

    2017-01-01

    The Michigan/Magellan Fiber System enables multiplexed, precision radial velocity surveys of open star clusters for warm- and hot-Jupiter exoplanetary companions while simultaneously allowing detailed study of stellar properties to V~17. To create this capability, we developed a novel mechanism to improve its maximum resolving power from ~20,000 to ~60,000 along with an automated control system that enables users to rapidly reconfigure M2FS for different scientific programs. We report the results of a survey of 126 photometric FGK members of the young (141 Myr), nearby (346 pc) open star cluster NGC 2516 and 100 photometric FGK members plus 25 candidate members of the young (72 Myr), nearby (491 pc) open cluster NGC 2422 (M 47). Our results show M2FS can achieve RV precisions in the 20-60 m/s range for up to 128 stars simultaneously while our median RV precision of 80 m/s on individual epochs, which span a temporal baseline of 1.1 yrs, enables us to investigate membership and stellar binarity and search for sub-stellar companions. We also report the methods developed to make precise spectroscopic measurements of Teff (±30 K), [Fe/H] and [α/Fe] (±0.02 dex), and vr sin(i) (±0.3 km/s). We determine membership probabilities and RV variability probabilities for our sample along with candidate companion orbital periods for a select subset of stars. We identify 81 RV members in NGC 2516, 27 spectroscopic binaries (17 previously identified as photometric binaries), and 16 other stars that show significant RV variability after accounting for average stellar jitter found to be at the 74 m/s level. In NGC 2422 we identify 57 members, 11 spectroscopic binaries, and 3 other stars that show significant RV variability after accounting for an average jitter of 138 m/s. We use Monte Carlo simulations to verify our stellar jitter measurements, determine the proportion of exoplanets and stellar companions to which we are sensitive, and estimate companion mass limits for our

  5. New Candidate Ehb Stars in the Open Cluster NGC 6791: Looking Locally Into the Uv-Upturn Phenomenon

    NASA Astrophysics Data System (ADS)

    Buson, L. M.; Bertone, E.; Buzzoni, A.; Carraro, G.

    Relying on U and B imagery at the Italian Telescopio Nazionale Galileo (TNG), we report here the discovery of a sample of 13 new UV-bright post-HB candidate stars in the field of the Galactic open cluster NGC 6791. Owing to its super-solar metal content ([Fe/H] ≳ 0.2 dex) and estimated age (t ≳ 8 Gyr), this cluster represents the nearest and ideal stellar aggregate to match the distinctive properties of the evolved stellar populations possibly ruling the UV-upturn phenomenon in elliptical galaxies and bulges of spirals. Our ongoing spectroscopic follow-up of this unique UV-bright sample will allow us to assess -- once cluster membership of the candidates is properly checked -- the real nature (e.g., sdB, sdO, AGB-manqué or EHB stars) of these hot sources and their link with the ultraviolet excess emerging from low-mass, metal-rich evolutionary environments of external galaxies.

  6. A revision of the fundamental parameters of the open cluster Hogg 15 and the projected star WR 47

    NASA Astrophysics Data System (ADS)

    Piatti, A. E.; Bica, E.; Santos, J. F. C., Jr.; Clariá, J. J.

    2002-05-01

    We revise the fundamental parameters of the faint open cluster Hogg 15, for which two recent colour-magnitude diagram (CMD) studies have obtained significantly different ages. In the present study, we combine a series of methods trying to constrain age, together with other fundamental parameters. We employ spatial extractions to construct the CMDs, and the cluster integrated spectrum to compare it with those of templates of known age. We derive fundamental parameters, in particular, distance, of the closely projected Wolf-Rayet star HDE 311884 (WR 47) - often proposed to be physically related to Hogg 15. Based on the WR 47 spectrum and available photometry, we conclude that the short distance implied by the Hipparcos parallax (216 pc) is affected by binary motion. From the WR 47 spectrum we estimate a reddening E(B-V) and a distance of 1.10 +/- 0.05 and 5.2 +/- 0.9 kpc, respectively. For Hogg 15 we derive an age of 20 +/- 10 Myr, a reddening of 1.10 +/- 0.05, and a distance of 3.1 +/- 0.5 kpc. We conclude that Hogg 15 is not related to WR 47 from the point of view of origin, since the cluster and the star do not belong to the same formation event.

  7. CCD UBVR photometry of two old open clusters: King 11 and Be42 - Comparison with theoretical models

    NASA Astrophysics Data System (ADS)

    Aparicio, A.; Bertelli, G.; Chiosi, C.; Garcia-Pelayo, J. M.

    1991-04-01

    This paper presents the Johnson-Cousins UBVR CCD photometry of two old rich open clusters toward the galactic anticenter: King 11 and Be 42. Included are the color-magnitude (C-M) diagrams of King 11 and Be 42; the color excess; and the reddening, metallicity, and distance modulus of the two clusters. Also given are the ages of King 11 and Be 42, as determined from the turn-off luminosity by means of theoretical isochromes, and the results for the luminosity function and the present-day mass function of the two clusters, derived from star counts in the V(V - R) C-M diagrams. The C-M diagram of King 11 is discussed in detail with the aid of models incorporating convective overshoot, according to the revised prescription proposed by Aparicio et al. (1990). It is shown that these models fit the overall morphology of the C-M diagram of King 11 much better than does the Bressan et al. (1981) model.

  8. The Gaia-ESO Survey: Inhibited extra mixing in two giants of the open cluster Trumpler 20?

    NASA Astrophysics Data System (ADS)

    Smiljanic, R.; Franciosini, E.; Randich, S.; Magrini, L.; Bragaglia, A.; Pasquini, L.; Vallenari, A.; Tautvaišienė, G.; Biazzo, K.; Frasca, A.; Donati, P.; Delgado Mena, E.; Casey, A. R.; Geisler, D.; Villanova, S.; Tang, B.; Sousa, S. G.; Gilmore, G.; Bensby, T.; François, P.; Koposov, S. E.; Lanzafame, A. C.; Pancino, E.; Recio-Blanco, A.; Costado, M. T.; Hourihane, A.; Lardo, C.; de Laverny, P.; Lewis, J.; Monaco, L.; Morbidelli, L.; Sacco, G. G.; Worley, C. C.; Zaggia, S.; Martell, S.

    2016-06-01

    Aims: We report the discovery of two Li-rich giants, with A(Li) ~ 1.50, in an analysis of a sample of 40 giants of the open cluster Trumpler 20 (with turnoff mass ~1.8 M⊙). The cluster was observed in the context of the Gaia-ESO Survey. Methods: The atmospheric parameters and Li abundances were derived using high-resolution UVES spectra. The Li abundances were corrected for nonlocal thermodynamical equilibrium (non-LTE) effects. Results: Only upper limits of the Li abundance could be determined for the majority of the sample. Two giants with detected Li turned out to be Li rich: star MG 340 has A(Li)non-LTE = 1.54 ± 0.21 dex and star MG 591 has A(Li)non-LTE = 1.60 ± 0.21 dex. Star MG 340 is on average ~0.30 dex more rich in Li than stars of similar temperature, while for star MG 591 this difference is on average ~0.80 dex. Carbon and nitrogen abundances indicate that all stars in the sample have completed the first dredge-up. Conclusions: The Li abundances in this unique sample of 40 giants in one open cluster clearly show that extra mixing is the norm in this mass range. Giants with Li abundances in agreement with the predictions of standard models are the exception. To explain the two Li-rich giants, we suggest that all events of extra mixing have been inhibited. This includes rotation-induced mixing during the main sequence and the extra mixing at the red giant branch luminosity bump. Such inhibition has been suggested in the literature to occur because of fossil magnetic fields in red giants that are descendants of main-sequence Ap-type stars. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 188.B-3002 (The Gaia-ESO Public Spectroscopic Survey).

  9. Tombaugh 2: the first open cluster with a significant abundance spread or embedded in a cold stellar stream?

    NASA Astrophysics Data System (ADS)

    Frinchaboy, P. M.; Marino, A. F.; Villanova, S.; Carraro, G.; Majewski, S. R.; Geisler, D.

    2008-11-01

    We present new high-resolution spectroscopy from which we derive abundances and radial velocities for stars in the field of the open cluster Tombaugh 2 (To2), which has been suggested to be one of a group of clusters previously identified with the Galactic Anticenter Stellar Structure (GASS) (also known as the Monoceros stream). Using Very Large Telescope/Fibre Large Array Multi-Element Spectrograph (VLT/FLAMES) with the Ultra-Violet and Visible Echelle Spectrograph (UVES) and GIRAFFE spectrographs, we find a radial velocity (RV) of = 121 +/- 0.4kms-1 using 18 To2 cluster stars; this is in agreement with previous studies, but at higher precision. We also make the first measurement of To2's velocity dispersion, which is σint = 1.8 +/- 0.3kms-1. Our abundance analysis of RV-selected members finds that To2 is more metal rich than previous studies have found; moreover, unlike the previous work, our larger sample also reveals that stars with the velocity of the cluster show a relatively large spread in chemical properties (e.g. Δ[Fe/H] > 0.2). This is the first time a possible abundance spread has been observed in an open cluster, though this is one of several possible explanations for our observations. While there is an apparent trend of [α/Fe] with [Fe/H], the distribution of abundances of these `RV cluster members' also may hint at a possible division into two primary groups with different mean chemical characteristics - namely (<[Fe/H]>, <[Ti/Fe]>) ~ (-0.06, +0.02) and (-0.28, +0.36). Isochrone fitting to the colour-magnitude distribution of apparent To2 members yields an age of 2.0Gyr, E(B - V) = 0.3, and (m - M)0 = 14.5 or d = 7.9kpc for both populations - parameters that are within the range of previous findings. Based on position and kinematics To2 is a likely member of the GASS/Monoceros stream, which makes To2 the second star cluster within the originally proposed GASS/Monoceros family after NGC 2808 to show some evidence for internal population

  10. The implementation of binned Kernel density estimation to determine open clusters' proper motions: validation of the method

    NASA Astrophysics Data System (ADS)

    Priyatikanto, R.; Arifyanto, M. I.

    2015-01-01

    Stellar membership determination of an open cluster is an important process to do before further analysis. Basically, there are two classes of membership determination method: parametric and non-parametric. In this study, an alternative of non-parametric method based on Binned Kernel Density Estimation that accounts measurements errors (simply called BKDE- e) is proposed. This method is applied upon proper motions data to determine cluster's membership kinematically and estimate the average proper motions of the cluster. Monte Carlo simulations show that the average proper motions determination using this proposed method is statistically more accurate than ordinary Kernel Density Estimator (KDE). By including measurement errors in the calculation, the mode location from the resulting density estimate is less sensitive to non-physical or stochastic fluctuation as compared to ordinary KDE that excludes measurement errors. For the typical mean measurement error of 7 mas/yr, BKDE- e suppresses the potential of miscalculation by a factor of two compared to KDE. With median accuracy of about 93 %, BKDE- e method has comparable accuracy with respect to parametric method (modified Sanders algorithm). Application to real data from The Fourth USNO CCD Astrograph Catalog (UCAC4), especially to NGC 2682 is also performed. The mode of member stars distribution on Vector Point Diagram is located at μ α cos δ=-9.94±0.85 mas/yr and μ δ =-4.92±0.88 mas/yr. Although the BKDE- e performance does not overtake parametric approach, it serves a new view of doing membership analysis, expandable to astrometric and photometric data or even in binary cluster search.

  11. Radial velocities of blue stragglers in the old open cluster NGC 7789

    NASA Astrophysics Data System (ADS)

    Drilling, J. S.; Schoenberner, D.

    NGC 7789 is a populous, old galactic cluster with a large number of blue stragglers. In an attempt to determine the stellar parameters of as many of these objects as possible in order to unravel their origin, the brighter blue stragglers of NGC 7789 were observed with the 4-meter echelle spectrograph at Kitt Peak and the 2.2-meter coude spectrograph at Calar Alto. This paper reports on the determination of radial velocities from these high resolution spectra. The results are compared with the previous radial velocity studies of Strom and Strom (1970) and Stryker and Hrivnak (1984).

  12. THE COLOR-PERIOD DIAGRAM AND STELLAR ROTATIONAL EVOLUTION-NEW ROTATION PERIOD MEASUREMENTS IN THE OPEN CLUSTER M34

    SciTech Connect

    Meibom, Soeren; Saar, Steven H.; Mathieu, Robert D.; Stassun, Keivan G.; Liebesny, Paul

    2011-06-01

    We present the results of a 5 month photometric time-series survey for stellar rotation periods combined with a 4 year radial-velocity survey for membership and binarity in the 220 Myr open cluster M34. We report surface rotation periods for 120 stars, 83 of which are kinematic and photometric late-type cluster members. A comparison to previous work serves to illustrate the importance of high-cadence long baseline photometric observations and membership information. The new M34 periods are less biased against slow rotation and cleaned for non-members. The rotation periods of the cluster members span over more than an order of magnitude from 0.5 days up to 11.5 days, and trace two distinct rotational sequences-fast (C) and moderate-to-slow (I)-in the color-period diagram. The sequences represent two different states (fast and slow) in the rotational evolution of the late-type cluster members. We use the color-period diagrams for M34 and for younger and older clusters to estimate the timescale for the transition from the C to the I sequence and find {approx}<150 Myr, {approx}150-300 Myr, and {approx}300-600 Myr for G, early-mid K, and late K dwarfs, respectively. The small number of stars in the gap between C and I suggests a quick transition. We estimate a lower limit on the maximum spin-down rate (dP/dt) during this transition to be {approx}0.06 days Myr{sup -1} and {approx}0.08 days Myr{sup -1} for early and late K dwarfs, respectively. We compare the I sequence rotation periods in M34 and the Hyades for G and K dwarfs and find that K dwarfs spin down slower than the Skumanich {radical}t rate. We determine a gyrochronology age of 240 Myr for M34. The gyro-age has a small formal uncertainty of 2% which reflects the tight I sequence in the M34 color-period diagram. We measure the effect of cluster age uncertainties on the gyrochronology age for M34 and find the resulting error on the gyro-age to be consistent with the {approx}15% error estimate for the technique in

  13. X-ray Properties of the Young Open Clusters HM1 and IC 2944-2948

    NASA Technical Reports Server (NTRS)

    Naze, Y.; Rauw, G.; Sana, H.; Corcoran, Michael F.

    2013-01-01

    Using XMM-Newton data, we study for the first time the X-ray emission of HM1 and IC 2944/2948. Low-mass, pre-main-sequence objects with an age of a few Myr are detected, as well as a few background or foreground objects. Most massive stars in both clusters display the usual high-energy properties of that type of objects, though with log [L(sub X)/L(sub BOL)] apparently lower in HM1 than in IC2944/2948. Compared with studies of other clusters, it seems that a low signal-to-noise ratio at soft energies, due to the high extinction, may be the main cause of this difference. In HM1, the two Wolf-Rayet stars show contrasting behaviors:WR89 is extremely bright, but much softer than WR87. It remains to be seen whether wind-wind collisions or magnetically confined winds can explain these emissions. In IC 2944/2948, the X-ray sources concentrate around HD 101205; a group of massive stars to the north of this object is isolated, suggesting that there exist two subclusters in the field-of-view.

  14. The OPD photometric survey of open clusters I. Techniques, program details and first results of robust determination of the fundamental parameters

    NASA Astrophysics Data System (ADS)

    Caetano, T. C.; Dias, W. S.; Lépine, J. R. D.; Monteiro, H. S.; Moitinho, A.; Hickel, G. R.; Oliveira, A. F.

    2015-07-01

    Open clusters are considered valuable objects for the investigation of galactic structure and dynamics since their distances, ages and velocities can be determined with good precision. According to the New Catalog of Optically Visible Open Clusters and Candidates (Dias et al., 2002) about 10% of the optically revealed open clusters remain unstudied. However, previous analysis (Moitinho, 2010) has indicated that not considering this unstudied population introduces significant biases in the study of the structure and evolution of the Milky Way. In addition, a systematic revision of the data contained in the catalog, collected from the literature, is needed, due to its inhomogeneity. In this first paper of a series, we present the observational strategy, data reduction and analysis procedures of a UBRVI photometric survey of southern open star clusters carried out at Pico dos Dias Observatory (Brazil). The aim of the program is to contribute to an unbiased, homogenous collection of cluster fundamental parameters. We show that the implementation of a sequence of systematic procedures considerably improves the quality of the results. To illustrate the methods we present the first results based on one night of observations. The parameters, reddening, distance, age and metallicity, were obtained by fitting theoretical isochrones to cluster color-color and multidimensional color-magnitude diagrams, applying a cross-entropy optimization algorithm developed by our group, which takes into account UBVRI photometric data weighted using a membership-likelihood estimation.

  15. Chemical Abundance Comparisons Between ASPCAP and Manual Analyses in Open Cluster Red Giants

    NASA Astrophysics Data System (ADS)

    Smith, Verne V.; Cunha, Katia M. L.; Souto, Diogo; Shetrone, Matthew D.; Meszaros, Szabolcs; Allende-Prieto, Carlos; Bizyaev, Dmitry; Carlberg, Joleen K.; García Pérez, Ana; Hasselquist, Sten; Holtzman, Jon A.; Johnson, Jennifer; Majewski, Steven R.; Schiavon, Ricardo P.; Sobeck, Jennifer; Troup, Nicholas William

    2015-01-01

    The APOGEE Stellar Parameter and Chemical Abundance Pipeline (ASPCAP) has now produced individual chemical abundances for 15 different elements: C, N, O, Na, Mg, Al, Si, S, K, Ca, Ti, V, Mn, Fe, and Ni. We will present comparisons of the ASPCAP abundances for stars in clusters with those derived from manual stellar parameter and abundance analyses of the same stars using the APOGEE spectra. These comparisons can be used to assess whether any of the elemental results from the automated pipeline contain larger than expected scatter, systematic offsets, or trends with stellar parameters, such as effective temperature, surface gravity, or metallicity. Using the subset of trustworthy abundances, we present early results of peculiar chemical substructures found in the APOGEE dataset.

  16. X-ray properties of the young open clusters HM1 and IC 2944/2948

    NASA Astrophysics Data System (ADS)

    Nazé, Y.; Rauw, G.; Sana, H.; Corcoran, M. F.

    2013-07-01

    Using XMM-Newton data, we study for the first time the X-ray emission of HM1 and IC 2944/2948. Low-mass, pre-main-sequence objects with an age of a few Myr are detected, as well as a few background or foreground objects. Most massive stars in both clusters display the usual high-energy properties of that type of objects, though with log [LX/LBOL] apparently lower in HM1 than in IC 2944/2948. Compared with studies of other clusters, it seems that a low signal-to-noise ratio at soft energies, due to the high extinction, may be the main cause of this difference. In HM1, the two Wolf-Rayet stars show contrasting behaviors: WR89 is extremely bright, but much softer than WR87. It remains to be seen whether wind-wind collisions or magnetically confined winds can explain these emissions. In IC 2944/2948, the X-ray sources concentrate around HD 101205; a group of massive stars to the north of this object is isolated, suggesting that there exist two subclusters in the field-of-view. Tables 2, 5, and Figs. 5, 9 are available in electronic form at http://www.aanda.orgBased on observations collected with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).Tables 1, 3 and 4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/555/A83

  17. NEAR-INFRARED IMAGING AND SPECTROSCOPIC SURVEY OF THE SOUTHERN REGION OF THE YOUNG OPEN CLUSTER NGC 2264

    SciTech Connect

    Marinas, Naibi; Lada, Elizabeth A.; Teixiera, Paula S.; Lada, Charles J.

    2013-08-01

    We have obtained JHK near-IR images and JH band low-resolution spectra of candidate members of the southern region of the young open cluster NGC 2264. We have determined spectral types from H-band spectra for 54 sources, 25 of which are classified for the first time. The stars in our sample cover a large range of spectral types (A8-M8). Using a cluster distance of 780 pc, we determined a median age of 1 Myr for this region of NGC 2264, with 90% of the stars being 5 Myr or younger. To improve the statistical significance of our sample, we included 66 additional cluster members within our field of view with optical spectral classification in the literature. We derived infrared excesses using stellar properties to model the photospheric emission for each source and the extinction to correct FLAMINGOS near-IR and Spitzer mid-IR photometry, and obtained a disk fraction of 51% {+-} 5% for the region. Binning the stars by stellar mass, we find a disk fraction of 38% {+-} 9% for the 0.1-0.3 solar mass group, 55% {+-} 6% for 0.3-1 solar masses, and 58% {+-} 10% for the higher than 1 solar mass group. The lower disk fraction for the lower mass stars is similar to the results found in non-cluster regions like Taurus and Chamaeleon, but differs from the older 3 Myr cluster IC 348 in which the disk fraction is lower for the higher mass stars. This mass-dependent disk fraction is accentuated in the sample with isochrone ages younger than 2 Myr. Here, we find that 45% {+-} 11% of the 0.1-0.3 solar mass stars have disks, 60% {+-} 7% of the 0.3-1 solar mass stars have disks, and all 1-3 solar mass stars have disks. Stellar masses might be an important factor in the ability of a system to form or retain a disk early on. However, regardless of the stellar mass, the large infrared excesses expected from optically thick disks disappear within the first 2 Myr for all stars in our study and small excesses from optically thin disks are found mostly in sources younger than 4 Myr.

  18. Near-infrared Imaging and Spectroscopic Survey of the Southern Region of the Young Open Cluster NGC 2264

    NASA Astrophysics Data System (ADS)

    Mariñas, Naibí; Lada, Elizabeth A.; Teixeira, Paula S.; Lada, Charles J.

    2013-08-01

    We have obtained JHK near-IR images and JH band low-resolution spectra of candidate members of the southern region of the young open cluster NGC 2264. We have determined spectral types from H-band spectra for 54 sources, 25 of which are classified for the first time. The stars in our sample cover a large range of spectral types (A8-M8). Using a cluster distance of 780 pc, we determined a median age of 1 Myr for this region of NGC 2264, with 90% of the stars being 5 Myr or younger. To improve the statistical significance of our sample, we included 66 additional cluster members within our field of view with optical spectral classification in the literature. We derived infrared excesses using stellar properties to model the photospheric emission for each source and the extinction to correct FLAMINGOS near-IR and Spitzer mid-IR photometry, and obtained a disk fraction of 51% ± 5% for the region. Binning the stars by stellar mass, we find a disk fraction of 38% ± 9% for the 0.1-0.3 solar mass group, 55% ± 6% for 0.3-1 solar masses, and 58% ± 10% for the higher than 1 solar mass group. The lower disk fraction for the lower mass stars is similar to the results found in non-cluster regions like Taurus and Chamaeleon, but differs from the older 3 Myr cluster IC 348 in which the disk fraction is lower for the higher mass stars. This mass-dependent disk fraction is accentuated in the sample with isochrone ages younger than 2 Myr. Here, we find that 45% ± 11% of the 0.1-0.3 solar mass stars have disks, 60% ± 7% of the 0.3-1 solar mass stars have disks, and all 1-3 solar mass stars have disks. Stellar masses might be an important factor in the ability of a system to form or retain a disk early on. However, regardless of the stellar mass, the large infrared excesses expected from optically thick disks disappear within the first 2 Myr for all stars in our study and small excesses from optically thin disks are found mostly in sources younger than 4 Myr. Based on observations

  19. Membership and binarity of solar-type dwarfs in the nearby open cluster Alpha Persei (Mel 20)

    NASA Astrophysics Data System (ADS)

    Mermilliod, J.-C.; Queloz, D.; Mayor, M.

    2008-09-01

    Context: The Alpha Persei open cluster (Melotte 20) is one of the nearby clusters (d < 500 pc) for which a long-term systematic radial-velocity monitoring of the solar-type stars has not been published so far. Aims: We undertook an observing program in 1982 to study the membership, duplicity, and rotation of the main-sequence stars and to compare the results with those of the other nearby clusters. Methods: Radial-velocity observations of 60 solar-type stars in Mel 20 were obtained with CORAVEL, and of 44 fainter stars with ELODIE spectrographs, in the magnitude range 9.5 < V < 13.85 Results: The membership of 37 stars from the list compiled by Heckmann is confirmed according to their proper motions, radial velocities, and photometry. We discovered twelve spectroscopic binaries (3 double-lined, 8 single-lined, 1 suspected) among the members and determined an orbit for the double-lined binary He 848. The observed frequency of spectroscopic binaries is therefore 32% (12/37). Four stars are photometric binaries. In addition, the membership of 33 stars with AP numbers is supported by the present radial velocities. Two single-lined and three double-lined binaries were detected in this sample. The cluster mean radial velocity is -1.39 ± 0.17 km s-1 based on 18 stars within 2σ. We found a systematic difference of 3.67 ± 1.48 km s-1 between observed- and astrometric radial velocities. Conclusions: The Alpha Persei cluster members define a tight main sequence in the colour-magnitude diagrams. The remaining scatter observed in the colour-magnitude diagrams and in radial velocities may be due to the difficulty of separating the core Alpha Persei stars from the extended comoving stream. based on observations collected at the Haute-Provence Observatory (France). Table 5 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/488/409

  20. Photometric investigation of the totally eclipsing contact binary V12 in the intermediate-age open cluster NGC 7789

    SciTech Connect

    Qian, S.-B.; Wang, J.-J.; Liu, L.; Zhou, X.; Essam, A.; Ali, G. B.; Haroon, A.-A.

    2015-02-01

    NGC 7789 is an intermediate-age open cluster with an age similar to the mean age of contact binary stars. V12 is a bright W UMa-type binary star with an orbital period of 0.3917 days. The first complete light curves of V12 in the V, R, and I bands are presented and analyzed with the Wilson–Devinney (W-D) method. The results show that V12 is an intermediate-contact binary (f=43.0(±2.2)%) with a mass ratio of 3.848, and it is a W-type contact binary where the less massive component is slightly hotter than the more massive one. The asymmetry of the light curves is explained by the presence of a dark spot on the more massive component. The derived orbital inclination (i=83{sub .}{sup ∘}6) indicates that it is a totally eclipsing binary, which suggests that the determined parameters are reliable. The orbital period may show a long-term increase at a rate of P-dot =+2.48(±0.17)×10{sup −6} days yr{sup −1} that reveals a rapid mass transfer from the less massive component to the more massive one. However, more observations are needed to confirm this conclusion. The presence of an intermediate-contact binary in an intermediate-age open cluster may suggest that some contact binaries have a very short pre-contact timescale. The presence of a third body and/or stellar collision may help to shorten the pre-contact evolution.

  1. Image Subtraction Reduction of Open Clusters M35 & NGC 2158 in the K2 Campaign 0 Super Stamps

    NASA Astrophysics Data System (ADS)

    Soares-Furtado, M.; Hartman, J. D.; Bakos, G. Á.; Huang, C. X.; Penev, K.; Bhatti, W.

    2017-04-01

    We observed the open clusters M35 and NGC 2158 during the initial K2 campaign (C0). Reducing these data to high-precision photometric timeseries is challenging due to the wide point-spread function (PSF) and the blending of stellar light in such dense regions. We developed an image-subtraction-based K2 reduction pipeline that is applicable to both crowded and sparse stellar fields. We applied our pipeline to the data-rich C0 K2 super stamp, containing the two open clusters, as well as to the neighboring postage stamps. In this paper, we present our image subtraction reduction pipeline and demonstrate that this technique achieves ultra-high photometric precision for sources in the C0 super stamp. We extract the raw light curves of 3960 stars taken from the UCAC4 and EPIC catalogs and de-trend them for systematic effects. We compare our photometric results with the prior reductions published in the literature. For de-trended TFA-corrected sources in the 12–12.25 {{{K}}}{{p}} magnitude range, we achieve a best 6.5-hour window running rms of 35 ppm, falling to 100 ppm for fainter stars in the 14–14.25 {{{K}}}{{p}} magnitude range. For stars with {K}p> 14, our de-trended and 6.5-hour binned light curves achieve the highest photometric precision. Moreover, all our TFA-corrected sources have higher precision on all timescales investigated. This work represents the first published image subtraction analysis of a K2 super stamp. This method will be particularly useful for analyzing the Galactic bulge observations carried out during K2 campaign 9. The raw light curves and the final results of our de-trending processes are publicly available at http://k2.hatsurveys.org/archive/.

  2. The Problem of Hipparcos Distances to Open Clusters. Report 1; Constraints from Multicolor a Main-Sequence Fitting

    NASA Technical Reports Server (NTRS)

    Pinsonneault, Marc H.; Stauffer, John; Soderblom, David R.; King, Jeremy R.; Hanson, Robert B.

    1998-01-01

    Parallax data from the Hipparcos mission allow the direct distance to open clusters to be compared with the distance inferred from main-sequence (MS) fitting. There are surprising differences between the two distance measurements. indicating either the need for changes in the cluster compositions or reddening, underlying problems with the technique of MS fitting, or systematic errors in the Hipparcos parallaxes at the 1 mas level. We examine the different possibilities, focusing on MS fitting in both metallicity-sensitive B-V and metallicity-insensitive V-I for five well-studied systems (the Hyades, Pleiades, alpha Per, Praesepe, and Coma Ber). The Hipparcos distances to the Hyades and alpha Per are within 1 sigma of the MS-fitting distance in B-V and V-I, while the Hipparcos distances to Coma Ber and the Pleiades are in disagreement with the MS-fitting distance at more than the 3 sigma level. There are two Hipparcos measurements of the distance to Praesepe; one is in good agreement with the MS-fitting distance and the other disagrees at the 2 sigma level. The distance estimates from the different colors are in conflict with one another for Coma but in agreement for the Pleiades. Changes in the relative cluster metal abundances, age related effects, helium, and reddening are shown to be unlikely to explain the puzzling behavior of the Pleiades. We present evidence for spatially dependent systematic errors at the 1 mas level in the parallaxes of Pleiades stars. The implications of this result are discussed.

  3. The anticentre old open clusters Berkeley 27, Berkeley 34 and Berkeley 36: new additions to the BOCCE project

    NASA Astrophysics Data System (ADS)

    Donati, P.; Bragaglia, A.; Cignoni, M.; Cocozza, G.; Tosi, M.

    2012-08-01

    In this paper, we present the investigation of the evolutionary status of three open clusters: Berkeley 27, Berkeley 34 and Berkeley 36, all located in the Galactic anticentre direction. All of them were observed with SUperb Seeing Imager 2 at the New Technology Telescope using the Bessel B, V and I filters. The cluster parameters have been obtained using the synthetic colour-magnitude diagram (CMD) method, i.e. the direct comparison of the observational CMDs with a library of synthetic CMDs generated with different evolutionary sets (Padova, FRANEC and FST). This analysis shows that Berkeley 27 has an age between 1.5 and 1.7 Gyr, a reddening E(B-V) in the range 0.40-0.50 and a distance modulus (m-M)0 between 13.1 and 13.3; Berkeley 34 is older with an age in the range 2.1-2.5 Gyr, E(B-V) between 0.57 and 0.64 and (m-M)0 between 14.1 and 14.3; Berkeley 36, with an age between 7.0 and 7.5 Gyr, has a reddening of E(B-V) ˜ 0.50 and a distance modulus (m-M)0 between 13.1 and 13.2. For all the clusters, our analysis suggests a subsolar metallicity in accord with their position in the outer Galactic disc. This work is based on data collected at the European Southern Observatory (ESO) telescopes under programme 076.D-0119.

  4. VizieR Online Data Catalog: Nine new open clusters within 500pc from the Sun (Roser+, 2016)

    NASA Astrophysics Data System (ADS)

    Roser, S.; Schilbach, E.; Goldman, B.

    2017-03-01

    We used URAT1 (Zacharias et al., 2015, Cat. I/329) to improve the Tycho-2 proper motions and to test what proper motions, which are more precise than those of Tycho-2 (Hog et al., 2000, Cat. I/259), can do for open cluster studies. URAT1 contains 228 million objects down to about R=18.5 mag, north of about -20° declination. For the bulk of the Tycho-2 stars, URAT1 gives positions at a mean epoch around 2013.5 and an accuracy level of about 20mas per co-ordinate. We cross-matched URAT1 with Tycho-2 (the original data set tyc2.dat from CDS), and obtained new proper motions via a least-squares adjustment as described, for example in PPMXL (Roeser et al., 2010, Cat. I/317). To avoid formally ultra-precise astrometry for a small number of stars, we chose a 10mas floor for the precision of a URAT1 position. The newly detected clusterings are located in the solar neighbourhood at distances below 500pc from the Sun. The candidates RSG1 to RSG8 are very probably genuine physical groups. Membership and astrophysical parameters could be determined sufficiently well. Nevertheless, accurate parallaxes of at least several reliable cluster stars could improve the quality of parameter determination. A definite age cannot be derived for RSG9; this critically depends on the secure membership status of the two brightest stars. Table 1 summarises the astrophysical parameters of the newly found objects. (1 data file).

  5. EPIC 219388192b—An Inhabitant of the Brown Dwarf Desert in the Ruprecht 147 Open Cluster

    NASA Astrophysics Data System (ADS)

    Nowak, Grzegorz; Palle, Enric; Gandolfi, Davide; Dai, Fei; Lanza, Antonino F.; Hirano, Teruyuki; Barragán, Oscar; Fukui, Akihiko; Bruntt, Hans; Endl, Michael; Cochran, William D.; Prada Moroni, Pier G.; Prieto-Arranz, Jorge; Kiilerich, Amanda; Nespral, David; Hatzes, Artie P.; Albrecht, Simon; Deeg, Hans; Winn, Joshua N.; Yu, Liang; Kuzuhara, Masayuki; Grziwa, Sascha; Smith, Alexis M. S.; Guenther, Eike W.; Van Eylen, Vincent; Csizmadia, Szilard; Fridlund, Malcolm; Cabrera, Juan; Eigmüller, Philipp; Erikson, Anders; Korth, Judith; Narita, Norio; Pätzold, Martin; Rauer, Heike; Ribas, Ignasi

    2017-03-01

    We report the discovery of EPIC 219388192b, a transiting brown dwarf in a 5.3 day orbit around a member star of Ruprecht 147, the oldest nearby open cluster association, which was photometrically monitored by K2 during its Campaign 7. We combine the K2 time-series data with ground-based adaptive optics imaging and high-resolution spectroscopy to rule out false positive scenarios and determine the main parameters of the system. EPIC 219388192b has a radius of {R}{{b}}=0.937+/- 0.032 R Jup and mass of {M}{{b}}=36.84+/- 0.97 M Jup, yielding a mean density of 59.6+/- 7.6 {{g}} {{cm}}-3. The host star is nearly a solar twin with mass {M}\\star =1.01+/- 0.04 M ⊙, radius {R}\\star =1.01+/- 0.03 R ⊙, effective temperature T eff = 5850 ± 85 K, and iron abundance [Fe/H] = 0.03 ± 0.08 dex. Its age, spectroscopic distance, and reddening are consistent with those of Ruprecht 147, corroborating its cluster membership. EPIC 219388192b is the first mature brown dwarf with precise determinations of mass, radius, and age, and serves as benchmark for evolutionary models in the substellar regime.

  6. The iron-sulfur cluster assembly machineries in plants: current knowledge and open questions

    PubMed Central

    Couturier, Jérémy; Touraine, Brigitte; Briat, Jean-François; Gaymard, Frédéric; Rouhier, Nicolas

    2013-01-01

    Many metabolic pathways and cellular processes occurring in most sub-cellular compartments depend on the functioning of iron-sulfur (Fe-S) proteins, whose cofactors are assembled through dedicated protein machineries. Recent advances have been made in the knowledge of the functions of individual components through a combination of genetic, biochemical and structural approaches, primarily in prokaryotes and non-plant eukaryotes. Whereas most of the components of these machineries are conserved between kingdoms, their complexity is likely increased in plants owing to the presence of additional assembly proteins and to the existence of expanded families for several assembly proteins. This review focuses on the new actors discovered in the past few years, such as glutaredoxin, BOLA and NEET proteins as well as MIP18, MMS19, TAH18, DRE2 for the cytosolic machinery, which are integrated into a model for the plant Fe-S cluster biogenesis systems. It also discusses a few issues currently subjected to an intense debate such as the role of the mitochondrial frataxin and of glutaredoxins, the functional separation between scaffold, carrier and iron-delivery proteins and the crosstalk existing between different organelles. PMID:23898337

  7. The Association Between Primary Open Angle Glaucoma and Clustered Components of Metabolic Syndrome

    PubMed Central

    Rasoulinejad, Seyed Ahmad; Kasiri, Ali; Montazeri, Mahdi; Rashidi, Negin; Montazeri, Maryam; Montazeri, Mohammad; Hedayati, Hesam

    2015-01-01

    Purpose : There is conflicting evidence whether components of metabolic syndrome (MetS) increase or decrease the risk of primary open-angle glaucoma (POAG). The aim of the present study was to determine the association between metabolic syndrome and primary open-angle glaucoma. Methods : A total of 200 participants comprising 100 controls and 100 patients with POAG documented by clinical tests and examined by an experienced ophthalmologist using standard ophthalmologic equipment were included in the study. MetS was defined and based on ATP III criteria and POAG was defined by the criteria of the International Society of Geographic and Epidemiological Ophthalmology (ISGEO). The data were entered into the SPSS software and analyzed. Results : The prevalence of MetS in the glaucoma group was 53% in comparison to 38% in the control group (p=0.037). MetS was associated with an increased odds ratio for an IOP higher than 21 mmHg (OR: 1.72; 95% CI 1.03-2.79; p=0.034). The mean IOP was 24.91±4.29 mmHg in the patients without MetS, and 27.23±4.81 mmHg in those with MetS (p=0.027). The mean values of CCT were 603.64±63.16 µm in MetS patients and 579.27±72.87 µm in controls (p=0.018). Conclusion : Data showed an increased prevalence of components of metabolic syndrome in patients with glaucoma. The mechanisms underlying these associations need to be established in future studies. Our results support the recommendation that patients with metabolic syndrome undergo regular ophthalmological exams to monitor for the onset or progression of glaucoma. PMID:26535072

  8. UV variability and accretion dynamics in the young open cluster NGC 2264

    NASA Astrophysics Data System (ADS)

    Venuti, L.; Bouvier, J.; Irwin, J.; Stauffer, J. R.; Hillenbrand, L. A.; Rebull, L. M.; Cody, A. M.; Alencar, S. H. P.; Micela, G.; Flaccomio, E.; Peres, G.

    2015-09-01

    Context. Photometric variability is a distinctive feature of young stellar objects; exploring variability signatures at different wavelengths provides insight into the physical processes at work in these sources. Aims: We explore the variability signatures at ultraviolet (UV) and optical wavelengths for several hundred accreting and non-accreting members of the star-forming region NGC 2264 (~3 Myr). Methods: We performed simultaneous monitoring of u- and r-band variability for the cluster population with CFHT/MegaCam. The survey extended over two full weeks, with several flux measurements per observing night. A sample of about 750 young stars is probed in our study, homogeneously calibrated and reduced, with internally consistently derived stellar parameters. Objects span the mass range 0.1-2 M⊙; about 40% of them show evidence for active accretion based on various diagnostics (Hα, UV, and IR excesses). Results: Statistically distinct variability properties are observed for accreting and non-accreting cluster members. The accretors exhibit a significantly higher level of variability than the non-accretors, in the optical and especially in the UV. The amount of u-band variability is found to correlate statistically with the median amount of UV excess in disk-bearing objects, which suggests that mass accretion and star-disk interaction are the main sources of variability in the u band. Spot models are applied to account for the amplitudes of variability of accreting and non-accreting members, which yields different results for each group. Cool magnetic spots, several hundred degrees colder than the stellar photosphere and covering from 5 to 30% of the stellar surface, appear to be the leading factor of variability for the non-accreting stars. In contrast, accretion spots with a temperature a few thousand degrees higher than the photospheric temperature and that extend over a few percent of the stellar surface best reproduce the variability of accreting objects

  9. Glutaredoxin GRXS17 Associates with the Cytosolic Iron-Sulfur Cluster Assembly Pathway1[OPEN

    PubMed Central

    Durand, Astrid Nagels; Ritter, Andrés; Klassen, Roland; Tohge, Takayuki; Fernie, Alisdair R.; Leidel, Sebastian A.; Pauwels, Laurens

    2016-01-01

    Cytosolic monothiol glutaredoxins (GRXs) are required in iron-sulfur (Fe-S) cluster delivery and iron sensing in yeast and mammals. In plants, it is unclear whether they have similar functions. Arabidopsis (Arabidopsis thaliana) has a sole class II cytosolic monothiol GRX encoded by GRXS17. Here, we used tandem affinity purification to establish that Arabidopsis GRXS17 associates with most known cytosolic Fe-S assembly (CIA) components. Similar to mutant plants with defective CIA components, grxs17 loss-of-function mutants showed some degree of hypersensitivity to DNA damage and elevated expression of DNA damage marker genes. We also found that several putative Fe-S client proteins directly bind to GRXS17, such as XANTHINE DEHYDROGENASE1 (XDH1), involved in the purine salvage pathway, and CYTOSOLIC THIOURIDYLASE SUBUNIT1 and CYTOSOLIC THIOURIDYLASE SUBUNIT2, both essential for the 2-thiolation step of 5-methoxycarbonylmethyl-2-thiouridine (mcm5s2U) modification of tRNAs. Correspondingly, profiling of the grxs17-1 mutant pointed to a perturbed flux through the purine degradation pathway and revealed that it phenocopied mutants in the elongator subunit ELO3, essential for the mcm5 tRNA modification step, although we did not find XDH1 activity or tRNA thiolation to be markedly reduced in the grxs17-1 mutant. Taken together, our data suggest that plant cytosolic monothiol GRXs associate with the CIA complex, as in other eukaryotes, and contribute to, but are not essential for, the correct functioning of client Fe-S proteins in unchallenged conditions. PMID:27503603

  10. The open cluster IC 1805 and its vicinity: investigation of stars in the Vilnius, IPHAS, 2MASS, and WISE systems

    NASA Astrophysics Data System (ADS)

    Straižys, V.; Boyle, R. P.; Janusz, R.; Laugalys, V.; Kazlauskas, A.

    2013-06-01

    The results of CCD photometry in the Vilnius seven-color system down to V = 18 mag are presented for 242 stars in the direction of the young open cluster IC 1805 that is located in the active star-forming region W4 in the Cas OB6 association. Photometric data were used to classify stars into spectral and luminosity classes, and to determine their interstellar reddenings, extinctions and distances. We confirm the CH3OH and H2O maser VLBA parallax results that the cluster is located close to the front side of the Perseus arm, at a distance about 2.0 kpc. In the color-magnitude diagram, zero-age main sequence (ZAMS) stars of the cluster extend to spectral class A0. The extinction values for the majority of the cluster stars are between 2.2 and 2.7 mag, with a mean value of 2.46 mag. This extinction originates mainly between the Sun and the outer edge of the Local arm, in accordance with the distribution of CO clouds. In the Perseus arm and beyond, the extinction was investigated using the classification and reddening determination for A0-F0 stars measured in the r, i, Hα system of the IPHAS survey to r = 19 mag. The extinction AV within the Perseus arm ranges from 2.5-4.5 mag at the front edge to 3.0-5.0 mag at the far edge. Possibly, we have found about 20 early A-type stars located in the Outer arm. The 2MASS JHKs photometry for red giants gives much higher extinction values (up to about 6 mag), which would correspond to the stars located behind dense clouds of both arms. In the area, using the WISE, 2MASS, and IPHAS photometry data, 18 possible young stellar objects (YSOs) of low masses are identified. Six high-mass YSOs (five Ae/Be stars and a F6e star) are known from previous investigations. Full Table 1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/554/A3

  11. Assessment of the accuracy of coupled cluster perturbation theory for open-shell systems. II. Quadruples expansions.

    PubMed

    Eriksen, Janus J; Matthews, Devin A; Jørgensen, Poul; Gauss, Jürgen

    2016-05-21

    We extend our assessment of the potential of perturbative coupled cluster (CC) expansions for a test set of open-shell atoms and organic radicals to the description of quadruple excitations. Namely, the second- through sixth-order models of the recently proposed CCSDT(Q-n) quadruples series [J. J. Eriksen et al., J. Chem. Phys. 140, 064108 (2014)] are compared to the prominent CCSDT(Q) and ΛCCSDT(Q) models. From a comparison of the models in terms of their recovery of total CC singles, doubles, triples, and quadruples (CCSDTQ) energies, we find that the performance of the CCSDT(Q-n) models is independent of the reference used (unrestricted or restricted (open-shell) Hartree-Fock), in contrast to the CCSDT(Q) and ΛCCSDT(Q) models, for which the accuracy is strongly dependent on the spin of the molecular ground state. By further comparing the ability of the models to recover relative CCSDTQ total atomization energies, the discrepancy between them is found to be even more pronounced, stressing how a balanced description of both closed- and open-shell species-as found in the CCSDT(Q-n) models-is indeed of paramount importance if any perturbative CC model is to be of chemical relevance for high-accuracy applications. In particular, the third-order CCSDT(Q-3) model is found to offer an encouraging alternative to the existing choices of quadruples models used in modern computational thermochemistry, since the model is still only of moderate cost, albeit markedly more costly than, e.g., the CCSDT(Q) and ΛCCSDT(Q) models.

  12. Assessment of the accuracy of coupled cluster perturbation theory for open-shell systems. II. Quadruples expansions

    NASA Astrophysics Data System (ADS)

    Eriksen, Janus J.; Matthews, Devin A.; Jørgensen, Poul; Gauss, Jürgen

    2016-05-01

    We extend our assessment of the potential of perturbative coupled cluster (CC) expansions for a test set of open-shell atoms and organic radicals to the description of quadruple excitations. Namely, the second- through sixth-order models of the recently proposed CCSDT(Q-n) quadruples series [J. J. Eriksen et al., J. Chem. Phys. 140, 064108 (2014)] are compared to the prominent CCSDT(Q) and ΛCCSDT(Q) models. From a comparison of the models in terms of their recovery of total CC singles, doubles, triples, and quadruples (CCSDTQ) energies, we find that the performance of the CCSDT(Q-n) models is independent of the reference used (unrestricted or restricted (open-shell) Hartree-Fock), in contrast to the CCSDT(Q) and ΛCCSDT(Q) models, for which the accuracy is strongly dependent on the spin of the molecular ground state. By further comparing the ability of the models to recover relative CCSDTQ total atomization energies, the discrepancy between them is found to be even more pronounced, stressing how a balanced description of both closed- and open-shell species—as found in the CCSDT(Q-n) models—is indeed of paramount importance if any perturbative CC model is to be of chemical relevance for high-accuracy applications. In particular, the third-order CCSDT(Q-3) model is found to offer an encouraging alternative to the existing choices of quadruples models used in modern computational thermochemistry, since the model is still only of moderate cost, albeit markedly more costly than, e.g., the CCSDT(Q) and ΛCCSDT(Q) models.

  13. Radial velocities and metallicities from infrared Ca ii triplet spectroscopy of open clusters. II. Berkeley 23, King 1, NGC 559, NGC 6603, and NGC 7245

    NASA Astrophysics Data System (ADS)

    Carrera, R.; Casamiquela, L.; Ospina, N.; Balaguer-Núñez, L.; Jordi, C.; Monteagudo, L.

    2015-06-01

    Context. Open clusters are key to studying the formation and evolution of the Galactic disc. However, there is a deficiency of radial velocity and chemical abundance determinations for open clusters in the literature. Aims: We intend to increase the number of determinations of radial velocities and metallicities from spectroscopy for open clusters. Methods: We acquired medium-resolution spectra (R ~ 8000) in the infrared region Ca ii triplet lines (~8500 Å) for several stars in five open clusters with the long-slit IDS spectrograph on the 2.5 m Isaac Newton Telescope (Roque de los Muchachos Observatory, Spain). Radial velocities were obtained by cross-correlation fitting techniques. The relationships available in the literature between the strength of infrared Ca ii lines and metallicity were also used to derive the metallicity for each cluster. Results: We obtain ⟨Vr⟩ = 48.6 ± 3.4, -58.4 ± 6.8, 26.0 ± 4.3, and -65.3 ± 3.2 km s-1 for Berkeley 23, NGC 559, NGC 6603, and NGC 7245, respectively. We found [ Fe/H ] = -0.25 ± 0.14 and -0.15 ± 0.18 for NGC 559 and NGC 7245, respectively. Berkeley 23 has low metallicity, [ Fe/H ] = -0.42 ± 0.13, which is similar to other open clusters in the outskirts of the Galactic disc. In contrast, we derived high metallicity ([ Fe/H ] = +0.43 ± 0.15) for NGC 6603, which places this system among the most metal-rich known open clusters. To our knowledge, this is the first determination of radial velocities and metallicities from spectroscopy for these clusters, except NGC 6603, for which radial velocities had been previously determined. We have also analysed ten stars in the line of sight to King 1. Because of the large dispersion obtained in both radial velocity and metallicity, we cannot be sure that we have sampled true cluster members. Based on observations made with the 2.5 m Isaac Newton Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the

  14. An XMM-Newton Observation of the Lagoon Nebula and the Very Young Open Cluster NGC 6530

    NASA Technical Reports Server (NTRS)

    Rauw, G.; Naze, Y.; Gosset, E.; Stevens, I. R.; Blomme, R.; Corcoran, M. F.; Pittard, J. M.; Runacres, M. C.

    2002-01-01

    We report the results of an XMM-Newton observation of the Lagoon Nebula (M 8). Our EPIC images of this region reveal a cluster of point sources, most of which have optical counterparts inside the very young open cluster NGC 6530. The bulk of these X-ray sources are probably associated with low and intermediate mass pre-main sequence stars. One of the sources experiences a flare-like increase of its X-ray flux making it the second brightest source in M 8 after the O4 star 9 Sgr. The X-ray spectra of most of the brightest sources can be fitted with thermal plasma models with temperatures of kT approximately a few keV. Only a few of the X-ray selected PMS candidates are known to display H(alpha) emission and were previously classified as classical T Tauri stars. This suggests that most of the X-ray emitting PMS stars in NGC 6530 are weak line T Tauri stars. In addition to 9 Sgr, our EPIC field of view contains also a few early-type stars. The X-ray emission from HD 164816 is found to be typical for an O9.5III-IV star. At least one of the known Herbig Be stars in NGC 6530 (LkH(alpha) 115) exhibits a relatively strong X-ray emission, while most of the main sequence stars of spectral type B1 and later are not detected. We also detect (probably) diffuse X-ray emission from the Hourglass Region that might reveal a hot bubble blown by the stellar wind of Herschel 36, the ionizing star of the Hourglass Region.

  15. New insights on Ba overabundance in open clusters. Evidence for the intermediate neutron-capture process at play?

    NASA Astrophysics Data System (ADS)

    Mishenina, T.; Pignatari, M.; Carraro, G.; Kovtyukh, V.; Monaco, L.; Korotin, S.; Shereta, E.; Yegorova, I.; Herwig, F.

    2015-02-01

    Recently, an increasing number of studies were devoted to measure the abundances of neutron-capture elements heavier than iron in stars belonging to Galactic Open Clusters (OCs). OCs span a sizeable range in metallicity (-0.6 ≤ [Fe/H] ≤ +0.4), and they show abundances of light elements similar to disc stars of the same age. A different pattern is observed for heavy elements. A large scatter is observed for Ba, with most OCs showing [Ba/Fe] and [Ba/La] overabundant with respect to the Sun. The origin of this overabundance is not clearly understood. With the goal of providing new observational insights, we determined radial velocities, atmospheric parameters and chemical composition of 27 giant stars members of five OCs: Cr 110, Cr 261, NGC 2477, NGC 2506 and NGC 5822. We used high-resolution spectra obtained with the UVES spectrograph at European Southern Observatory Paranal. We perform a detailed spectroscopic analysis of these stars to measure the abundance of up to 22 elements per star. We study the dependence of element abundance on metallicity and age with unprecedented detail, complementing our analysis with data culled from the literature. We confirm the trend of Ba overabundance in OCs, and show its large dispersion for clusters younger than ˜4 Gyr. Finally, the implications of our results for stellar nucleosynthesis are discussed. We show in this work that the Ba enrichment compared to other neutron-capture elements in OCs cannot be explained by the contributions from the slow neutron-capture process and the rapid neutron-capture process. Instead, we argue that this anomalous signature can be explained by assuming an additional contribution by the intermediate neutron-capture process.

  16. CNO abundances and carbon isotope ratios in evolved stars of the open clusters NGC 2324, NGC 2477, and NGC 3960

    NASA Astrophysics Data System (ADS)

    Tautvaišienė, Gražina; Drazdauskas, Arnas; Bragaglia, Angela; Randich, Sofia; Ženovienė, Renata

    2016-10-01

    Aims: Our main aim is to determine carbon-to-nitrogen and carbon isotope ratios for evolved giants in the open clusters NGC 2324, NGC 2477, and NGC 3960, which have turn-off masses of about 2 M⊙, and to compare them with predictions of theoretical models. Methods: High-resolution spectra were analysed using a differential synthetic spectrum method. Abundances of carbon were derived using the C2 Swan (0, 1) band heads at 5135 and 5635.5 Å. The wavelength interval 7940-8130 Å with strong CN features was analysed to determine nitrogen abundances and carbon isotope ratios. The oxygen abundances were determined from the [O i] line at 6300 Å. Results: The mean values of the CNO abundances are [C/Fe] = -0.35 ± 0.06 (s.d.), [N/Fe] = 0.28 ± 0.05, and [O/Fe] = -0.02 ± 0.10 in seven stars of NGC 2324; [C/Fe] = -0.26 ± 0.02, [N/Fe] = 0.39 ± 0.04, and [O/Fe] = -0.11 ± 0.06 in six stars of NGC 2477; and [C/Fe] = -0.39 ± 0.04, [N/Fe] = 0.32 ± 0.05, and [O/Fe] = -0.19 ± 0.06 in six stars of NGC 3960. The mean C/N ratio is equal to 0.92 ± 0.12, 0.91 ± 0.09, and 0.80 ± 0.13, respectively. The mean 12C /13C ratio is equal to 21 ± 1, 20 ± 1, and 16 ± 4, respectively. The 12C /13C and C/N ratios of stars in the investigated open clusters were compared with the ratios predicted by stellar evolution models. Conclusions: The mean values of the 12C /13C and C/N ratios in NGC 2324 and NGC 2477 agree well with the first dredge-up and thermohaline-induced extra-mixing models, which are similar for intermediate turn-off mass stars. The 12C /13C ratios in the investigated clump stars of NGC 3960 span from 10 to 20. The mean carbon isotope and C/N ratios in NGC 3960 are close to predictions of the model in which the thermohaline- and rotation-induced (if rotation velocity at the zero-age main sequence was 30% of the critical velocity) extra-mixing act together. Based on observations collected at ESO telescopes under programmes 072.D-0550 and 074.D-0571.

  17. DETERMINING THE AGE OF THE KEPLER OPEN CLUSTER NGC 6819 WITH A NEW TRIPLE SYSTEM AND OTHER ECLIPSING BINARY STARS

    SciTech Connect

    Brewer, Lauren N.; Sandquist, Eric L.; Jeffries, Mark W. Jr.; Orosz, Jerome A.; and others

    2016-03-15

    As part of our study of the old (∼2.5 Gyr) open cluster NGC 6819 in the Kepler field, we present photometric (Kepler and ground-based BVR{sub C}I{sub C}) and spectroscopic observations of the detached eclipsing binary WOCS 24009 (Auner 665; KIC 5023948) with a short orbital period of 3.6 days. WOCS 24009 is a triple-lined system, and we verify that the brightest star is physically orbiting the eclipsing binary using radial velocities and eclipse timing variations. The eclipsing binary components have masses M{sub B} = 1.090 ± 0.010 M{sub ⊙} and M{sub C} = 1.075 ± 0.013 M{sub ⊙}, and radii R{sub B} = 1.099 ± 0.006 ± 0.005 R{sub ⊙} and R{sub C} = 1.069 ± 0.006 ± 0.013 R{sub ⊙}. The bright non-eclipsing star resides at the cluster turnoff, and ultimately its mass will directly constrain the turnoff mass: our preliminary determination is M{sub A} = 1.251 ± 0.057 M{sub ⊙}. A careful examination of the light curves indicates that the fainter star in the eclipsing binary undergoes a very brief period of total eclipse, which enables us to precisely decompose the light of the three stars and place them in the color–magnitude diagram (CMD). We also present improved analysis of two previously discussed detached eclipsing stars in NGC 6819 (WOCS 40007 and WOCS 23009) en route to a combined determination of the cluster’s distance modulus (m − M){sub V} = 12.38 ± 0.04. Because this paper significantly increases the number of measured stars in the cluster, we can better constrain the age of the CMD to be 2.21 ± 0.10 ± 0.20 Gyr. Additionally, using all measured eclipsing binary star masses and radii, we constrain the age to 2.38 ± 0.05 ± 0.22 Gyr. The quoted uncertainties are estimates of measurement and systematic uncertainties (due to model physics differences and metal content), respectively.

  18. High-resolution spectroscopic observations of binary stars and yellow stragglers in three open clusters: NGC 2360, NGC 3680, and NGC 5822

    SciTech Connect

    Sales Silva, J. V.; Peña Suárez, V. J.; Katime Santrich, O. J.; Pereira, C. B.; Drake, N. A.; Roig, F. E-mail: jearim@on.br E-mail: claudio@on.br E-mail: froig@on.br

    2014-11-01

    Binary stars in open clusters are very useful targets in constraining the nucleosynthesis process. The luminosities of the stars are known because the distances of the clusters are also known, so chemical peculiarities can be linked directly to the evolutionary status of a star. In addition, binary stars offer the opportunity to verify a relationship between them and the straggler population in both globular and open clusters. We carried out a detailed spectroscopic analysis to derive the atmospheric parameters for 16 red giants in binary systems and the chemical composition of 11 of them in the open clusters NGC 2360, NGC 3680, and NGC 5822. We obtained abundances of C, N, O, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, and Nd. The atmospheric parameters of the studied stars and their chemical abundances were determined using high-resolution optical spectroscopy. We employ the local thermodynamic equilibrium model atmospheres of Kurucz and the spectral analysis code MOOG. The abundances of the light elements were derived using the spectral synthesis technique. We found that the stars NGC 2360-92 and 96, NGC 3680-34, and NGC 5822-4 and 312 are yellow straggler stars. We show that the spectra of NGC 5822-4 and 312 present evidence of contamination by an A-type star as a secondary star. For the other yellow stragglers, evidence of contamination is given by the broad wings of the Hα. Detection of yellow straggler stars is important because the observed number can be compared with the number predicted by simulations of binary stellar evolution in open clusters. We also found that the other binary stars are not s-process enriched, which may suggest that in these binaries the secondary star is probably a faint main-sequence object. The lack of any s-process enrichment is very useful in setting constraints for the number of white dwarfs in the open cluster, a subject that is related to the birthrate of these kinds of stars in open clusters and also to the age of a

  19. High-resolution Spectroscopic Observations of Binary Stars and Yellow Stragglers in Three Open Clusters : NGC 2360, NGC 3680, and NGC 5822

    NASA Astrophysics Data System (ADS)

    Sales Silva, J. V.; Peña Suárez, V. J.; Katime Santrich, O. J.; Pereira, C. B.; Drake, N. A.; Roig, F.

    2014-11-01

    Binary stars in open clusters are very useful targets in constraining the nucleosynthesis process. The luminosities of the stars are known because the distances of the clusters are also known, so chemical peculiarities can be linked directly to the evolutionary status of a star. In addition, binary stars offer the opportunity to verify a relationship between them and the straggler population in both globular and open clusters. We carried out a detailed spectroscopic analysis to derive the atmospheric parameters for 16 red giants in binary systems and the chemical composition of 11 of them in the open clusters NGC 2360, NGC 3680, and NGC 5822. We obtained abundances of C, N, O, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, and Nd. The atmospheric parameters of the studied stars and their chemical abundances were determined using high-resolution optical spectroscopy. We employ the local thermodynamic equilibrium model atmospheres of Kurucz and the spectral analysis code MOOG. The abundances of the light elements were derived using the spectral synthesis technique. We found that the stars NGC 2360-92 and 96, NGC 3680-34, and NGC 5822-4 and 312 are yellow straggler stars. We show that the spectra of NGC 5822-4 and 312 present evidence of contamination by an A-type star as a secondary star. For the other yellow stragglers, evidence of contamination is given by the broad wings of the Hα. Detection of yellow straggler stars is important because the observed number can be compared with the number predicted by simulations of binary stellar evolution in open clusters. We also found that the other binary stars are not s-process enriched, which may suggest that in these binaries the secondary star is probably a faint main-sequence object. The lack of any s-process enrichment is very useful in setting constraints for the number of white dwarfs in the open cluster, a subject that is related to the birthrate of these kinds of stars in open clusters and also to the age of a

  20. Membership, lithium and chromospheric activity of the young open clusters IC 2391, IC 2602 and IC 4665 from GES (Gaia-ESO Survey) observations

    NASA Astrophysics Data System (ADS)

    Gómez Garrido, M.; Montes, D.; Gutiérrez Albarrán, M. L.; Tabernero, H. M.; Gónzalez Hernández, J. I.; GES Survey Builders

    2017-03-01

    We conduct a comparative study of the main properties of the of the young open clusters IC 2391, IC 2602 and IC 4665, focusing on their membership, lithium abundance and level of chromospheric activity and possible accretion. We use the fundamental parameters (effective temperature, surface gravity, and radial velocity) delivered by the Gaia-ESO survey (GES - https://www.gaia-eso.eu/) consortium in the four internal data release (iDR4) to select the members of these clusters among the UVES and GIRAFFE spectroscopic observations. Chromospheric activity criterium, and iterative process between radial velocity distribution and lithium-temperature diagram are applied to determinate what objects are members or non members of the clusters. All this information allowed us to characterize the properties of the members of these clusters and identify some field contaminant lithium-rich giants.

  1. New open cluster Cepheids in the VVV survey tightly constrain near-infrared period-luminosity relations

    NASA Astrophysics Data System (ADS)

    Chen, Xiaodian; de Grijs, Richard; Deng, Licai

    2017-01-01

    Classical Cepheids are among the most useful Galactic and nearby extragalactic distance tracers because of their well-defined period-luminosity relations (PLRs). Open cluster (OC) Cepheids are important objects to independently calibrate these PLRs. Based on Data Release 1 of the VISTA Variables in the Vía Láctea VVV survey, we have discovered four new, faint, and heavily reddened OC Cepheids, including the longest period OC Cepheid known, ASAS J180342-2211.0 in Teutsch 14a. The other OC-Cepheid pairs include NGC 6334 and V0470 Sco, Majaess 170 and ASAS J160125-5150.3, and Teutsch 77 and BB Cen. ASAS J180342-2211.0, with a period of log P = 1.623 (d) is important to constrain the slope of the PLR. The currently most complete JHKs Galactic Cepheid PLRs are obtained based on a significantly increased sample of 31 OC Cepheids, with associated uncertainties that are improved by 40 per cent compared with previous determinations (in the J band). The near-infrared PLRs are in good agreement with previous PLRs determined based on other methods.

  2. A search for flares and mass ejections on young late-type stars in the open cluster Blanco-1

    NASA Astrophysics Data System (ADS)

    Leitzinger, M.; Odert, P.; Greimel, R.; Korhonen, H.; Guenther, E. W.; Hanslmeier, A.; Lammer, H.; Khodachenko, M. L.

    2014-09-01

    We present a search for stellar activity (flares and mass ejections) in a sample of 28 stars in the young open cluster Blanco-1. We use optical spectra obtained with European Southern Observatory's Visible Multi-Object Spectrograph installed on the Very Large Telescope. From the total observing time of ˜5 h, we find four Hα flares but no distinct indication of coronal mass ejections (CMEs) on the investigated dK-dM stars. Two flares show `dips' in their light curves right before their impulsive phases which are similar to previous discoveries in photometric light curves of active dMe stars. We estimate an upper limit of <4 CMEs per day per star and discuss this result with respect to a empirical estimation of the CME rate of main-sequence stars. We find that we should have detected at least one CME per star with a mass of ≤ 3 × 1017 g depending on the star's X-ray luminosity, but the estimated Hα fluxes associated with these masses are below the detection limit of our observations. We conclude that the parameter which mainly influences the detection of stellar CMEs using the method of Doppler-shifted emission caused by moving plasma is not the spectral resolution/velocity but the flux/mass of the CME.

  3. An explicitly spin-free compact open-shell coupled cluster theory using a multireference combinatoric exponential ansatz: formal development and pilot applications.

    PubMed

    Datta, Dipayan; Mukherjee, Debashis

    2009-07-28

    In this paper, we present a comprehensive account of an explicitly spin-free compact state-universal multireference coupled cluster (CC) formalism for computing the state energies of simple open-shell systems, e.g., doublets and biradicals, where the target open-shell states can be described by a few configuration state functions spanning a model space. The cluster operators in this formalism are defined in terms of the spin-free unitary generators with respect to the common closed-shell component of all model functions (core) as vacuum. The spin-free cluster operators are either closed-shell-like n hole-n particle excitations (denoted by T(mu)) or involve excitations from the doubly occupied (nonvalence) orbitals to the singly occupied (valence) orbitals (denoted by S(e)(mu)). In addition, there are cluster operators with exchange spectator scatterings involving the valence orbitals (denoted by S(re)(mu)). We propose a new multireference cluster expansion ansatz for the wave operator with the above generally noncommuting cluster operators which essentially has the same physical content as the Jeziorski-Monkhorst ansatz with the commuting cluster operators defined in the spin-orbital basis. The T(mu) operators in our ansatz are taken to commute with all other operators, while the S(e)(mu) and S(re)(mu) operators are allowed to contract among themselves through the spectator valence orbitals. An important innovation of this ansatz is the choice of an appropriate automorphic factor accompanying each contracted composite of cluster operators in order to ensure that each distinct excitation generated by this composite appears only once in the wave operator. The resulting CC equations consist of two types of terms: a "direct" term and a "normalization" term containing the effective Hamiltonian operator. It is emphasized that the direct term is almost quartic in the cluster amplitudes, barring only a handful of terms and termination of the normalization term depends on

  4. On the determination of age and mass functions of stars in young open star clusters from the analysis of their luminosity functions

    NASA Astrophysics Data System (ADS)

    Piskunov, A. E.; Belikov, A. N.; Kharchenko, N. V.; Sagar, R.; Subramaniam, A.

    2004-04-01

    We construct the observed luminosity functions of the remote young open clusters NGC 2383, 2384, 4103, 4755, 7510 and Hogg 15 from CCD observations of them. The observed LFs are corrected for field star contamination determined with the help of a Galactic star count model. In the case of Hogg 15 and NGC 2383 we also consider the additional contamination from neighbouring clusters NGC 4609 and 2384, respectively. These corrections provide a realistic pattern of cluster LF in the vicinity of the main-sequence (MS) turn-on point and at fainter magnitudes reveal the so-called H-feature arising as a result of the transition of the pre-MS phase to the MS, which is dependent on the cluster age. The theoretical LFs are constructed representing a cluster population model with continuous star formation for a short time-scale and a power-law initial mass function (IMF), and these are fitted to the observed LF. As a result, we are able to determine for each cluster a set of parameters describing the cluster population (the age, duration of star formation, IMF slope and percentage of field star contamination). It is found that in spite of the non-monotonic behaviour of observed LFs, cluster IMFs can be described as power-law functions with slopes similar to Salpeter's value. The present main-sequence turn-on cluster ages are several times lower than those derived from the fitting of theoretical isochrones to the turn-off region of the upper main sequences.

  5. A Constraint on the Formation Timescale of the Young Open Cluster NGC 2264: Lithium Abundance of Pre-main Sequence Stars

    NASA Astrophysics Data System (ADS)

    Lim, Beomdu; Sung, Hwankyung; Kim, Jinyoung S.; Bessell, Michael S.; Hwang, Narae; Park, Byeong-Gon

    2016-11-01

    The timescale of cluster formation is an essential parameter in order to understand the formation process of star clusters. Pre-main sequence (PMS) stars in nearby young open clusters reveal a large spread in brightness. If the spread were considered to be a result of a real spread in age, the corresponding cluster formation timescale would be about 5-20 Myr. Hence it could be interpreted that star formation in an open cluster is prolonged for up to a few tens of Myr. However, difficulties in reddening correction, observational errors, and systematic uncertainties introduced by imperfect evolutionary models for PMS stars can result in an artificial age spread. Alternatively, we can utilize Li abundance as a relative age indicator of PMS star to determine the cluster formation timescale. The optical spectra of 134 PMS stars in NGC 2264 have been obtained with MMT/Hectochelle. The equivalent widths have been measured for 86 PMS stars with a detectable Li line (3500\\lt {T}{eff}[{{K}}]≤slant 6500). Li abundance under the condition of local thermodynamic equilibrium (LTE) was derived using the conventional curve of growth method. After correction for non-LTE effects, we find that the initial Li abundance of NGC 2264 is A({Li})=3.2+/- 0.2. From the distribution of the Li abundances, the underlying age spread of the visible PMS stars is estimated to be about 3-4 Myr and this, together with the presence of embedded populations in NGC 2264, suggests that the cluster formed on a timescale shorter than 5 Myr.

  6. Lithium Inventory of 2 Solar Mass Red Clump Stars in Open Clusters: A Test of the Helium Flash Mechanism

    NASA Technical Reports Server (NTRS)

    Carlberg, Joleen K.; Cunha, Katia; Smith, Verne V.

    2016-01-01

    The temperature distribution of field Li-rich red giants suggests the presence of a population of Li-rich red clump (RC) stars. One proposed explanation for this population is that all stars with masses near 2 solar mass experience a shortlived phase of Li-richness at the onset of core He-burning. Many of these stars have low C-12/C-13, a signature of deep mixing that is presumably associated with the Li regeneration. To test this purported mechanism of Li enrichment, we measured abundances in 38 RC stars and 6 red giant branch (RGB) stars in four open clusters selected to have RC masses near 2 solar mass. We find six Li-rich stars (A(Li) greater than or equal to 1.50 dex) of which only two may be RC stars. None of the RC stars have Li exceeding the levels observed in the RGB stars, but given the brevity of the suggested Li-rich phase and the modest sample size, it is probable that stars with larger Li-enrichments were missed simply by chance. However, we find very few stars in our sample with low C-12/C-13. Such low C-12/C-13, seen in many field Li-rich stars, should persist even after lithium has returned to normal low levels. Thus, if Li synthesis during the He flash occurs, it is a rare, but potentially long-lived occurrence rather than a short-lived phase for all stars. We estimate a conservative upper limit of the fraction of stars going through a Li-rich phase to be less than 47%, based on stars that have low C-12/C-13 for their observed A(Li).

  7. Lithium Inventory of 2 M ⊙ Red Clump Stars in Open Clusters: A Test of the Helium Flash Mechanism

    NASA Astrophysics Data System (ADS)

    Carlberg, Joleen K.; Cunha, Katia; Smith, Verne V.

    2016-08-01

    The temperature distribution of field Li-rich red giants suggests the presence of a population of Li-rich red clump (RC) stars. One proposed explanation for this population is that all stars with masses near 2 M ⊙ experience a short-lived phase of Li-richness at the onset of core He-burning. Many of these stars have low 12C/13C, a signature of deep mixing that is presumably associated with the Li regeneration. To test this purported mechanism of Li enrichment, we measured abundances in 38 RC stars and 6 red giant branch (RGB) stars in four open clusters selected to have RC masses near 2 M ⊙. We find six Li-rich stars (A(Li) ≥ 1.50 dex) of which only two may be RC stars. None of the RC stars have Li exceeding the levels observed in the RGB stars, but given the brevity of the suggested Li-rich phase and the modest sample size, it is probable that stars with larger Li-enrichments were missed simply by chance. However, we find very few stars in our sample with low 12C/13C. Such low 12C/13C, seen in many field Li-rich stars, should persist even after lithium has returned to normal low levels. Thus, if Li synthesis during the He flash occurs, it is a rare, but potentially long-lived occurrence rather than a short-lived phase for all stars. We estimate a conservative upper limit of the fraction of stars going through a Li-rich phase to be \\lt 47 % , based on stars that have low 12C/13C for their observed A(Li).

  8. Hydrogen-bonded ring closing and opening of protonated methanol clusters H(+)(CH3OH)(n) (n = 4-8) with the inert gas tagging.

    PubMed

    Li, Ying-Cheng; Hamashima, Toru; Yamazaki, Ryoko; Kobayashi, Tomohiro; Suzuki, Yuta; Mizuse, Kenta; Fujii, Asuka; Kuo, Jer-Lai

    2015-09-14

    The preferential hydrogen bond (H-bond) structures of protonated methanol clusters, H(+)(MeOH)n, in the size range of n = 4-8, were studied by size-selective infrared (IR) spectroscopy in conjunction with density functional theory calculations. The IR spectra of bare clusters were compared with those with the inert gas tagging by Ar, Ne, and N2, and remarkable changes in the isomer distribution with the tagging were found for clusters with n≥ 5. The temperature dependence of the isomer distribution of the clusters was calculated by the quantum harmonic superposition approach. The observed spectral changes with the tagging were well interpreted by the fall of the cluster temperature with the tagging, which causes the transfer of the isomer distribution from the open and flexible H-bond network types to the closed and rigid ones. Anomalous isomer distribution with the tagging, which has been recently found for protonated water clusters, was also found for H(+)(MeOH)5. The origin of the anomaly was examined by the experiments on its carrier gas dependence.

  9. Chromospheric and Coronal Activity in the 500 Myr old Open Cluster M37: Evidence for Coronal Stripping?

    NASA Astrophysics Data System (ADS)

    Núñez, Alejandro; Agüeros, Marcel A.; Covey, Kevin R.; López-Morales, Mercedes

    2017-01-01

    We present the results of a spectroscopic survey to characterize chromospheric activity, as measured by {{H}}α emission, in low-mass members of the 500 Myr old open cluster M37. Combining our new measurements of {{H}}α luminosities ({L}{{H}α }) with previously cataloged stellar properties, we identify saturated and unsaturated regimes in the dependence of the {L}{{H}α }-to-bolometric luminosity ratio, {L}{{H}α }/{L}{bol}, on the Rossby number Ro. All rotators with Ro smaller than 0.03 ± 0.01 converge to an activity level of {L}{{H}α }/{L}{bol}=(1.27+/- 0.02)× {10}-4. This saturation threshold ({R}o,{sat}=0.03+/- 0.01) is statistically smaller than that found in most studies of the rotation–activity relation. In the unsaturated regime, slower rotators have lower levels of chromospheric activity, with {L}{{H}α }/{L}{bol}(Ro) following a power-law of index β =-0.51+/- 0.02, slightly shallower than that found for a combined ≈650 Myr old sample of Hyades and Praesepe stars. By comparing this unsaturated behavior to that previously found for coronal activity in M37 (as measured via the X-ray luminosity, {L}{{X}}), we confirm that chromospheric activity decays at a much slower rate than coronal activity with increasing Ro. While a comparison of {L}{{H}α } and {L}{{X}} for M37 members with measurements of both reveals a nearly 1:1 relation, removing the mass-dependencies by comparing instead {L}{{H}α }/{L}{bol} and {L}{{X}}/{L}{bol} does not provide clear evidence for such a relation. Finally, we find that {R}o,{sat} is smaller for our chromospheric than for our coronal indicator of activity ({R}o,{sat}=0.03+/- 0.01 versus 0.09 ± 0.01). We interpret this as possible evidence for coronal stripping.

  10. The Mass-Transfer Formation Frequency of Blue Straggler Stars in the Old Open Cluster NGC 188

    NASA Astrophysics Data System (ADS)

    Gosnell, Natalie M.; Mathieu, Robert D.; Sills, Alison; Geller, Aaron M.; Leigh, Nathan; Knigge, Christian

    2015-01-01

    The formation of blue straggler stars (BSSs), commonly categorized as stars bluer and brighter than the main sequence turnoff, has puzzled astronomers since their first detection over sixty years ago. The well-studied BSS population of the old (7 Gyr) open cluster NGC 188 has the potential to settle outstanding issues surrounding the frequency of different BSS formation mechanisms. NGC 188 contains 21 BSSs: 15 long-period single-lined binaries, two short-period double-lined binaries, and four non-velocity variables. We present results of the Hubble Space Telescope far-ultraviolet (FUV) ACS/SBC survey of the NGC 188 BSS population. This survey aims to detect white dwarf (WD) companions of BSSs that are indicative of a mass-transfer formation history. We directly detect FUV excesses consistent with four hot WD companions (Teff ≥ 12,000 K). We infer the presence of three additional WD companions with temperatures between 11,000-12,000 K. Since WDs cool as they age, these results indicate that seven BSSs formed through mass transfer within the past 400 Myr. These WD detections set a lower limit mass-transfer formation frequency of 33%. After taking into account other potential formation mechanisms we conclude that 14 long-period binary BSSs likely formed through mass transfer, setting a total NGC 188 BSS mass-transfer formation frequency of 67%. Comparing these results to a sophisticated N-body model of NGC 188 implies that binary population synthesis models underproduce mass transfer products, and the parameterization of stable mass transfer may need to be revisited. Finally, when comparing the optical CMD position of young BSSs to the zero-age main sequence (ZAMS), we find that distance from the ZAMS is not necessarily equivalent to BSS age. One must use caution before using standard single-star isochrones to age luminous BSSs.Support for Program number 12492 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the

  11. STELLAR LIFETIME AND ULTRAVIOLET PROPERTIES OF THE OLD METAL-RICH GALACTIC OPEN CLUSTER NGC 6791: A PATHWAY TO UNDERSTAND THE ULTRAVIOLET UPTURN OF ELLIPTICAL GALAXIES

    SciTech Connect

    Buzzoni, Alberto; Bertone, Emanuele; Carraro, Giovanni; Buson, Lucio

    2012-04-10

    The evolutionary properties of the old metal-rich Galactic open cluster NGC 6791 are assessed based on deep UB photometry and Two Micron All Sky Survey JK data. For the 4739 stars in the cluster, bolometric luminosity and effective temperature have been derived from theoretical (U - B) and (J - K) color fitting. The derived H-R diagram has been matched with the UVBLUE grid of synthetic stellar spectra to obtain the integrated spectral energy distribution (SED) of the system, together with a full set of UV (Fanelli) and optical (Lick) narrowband indices. The total bolometric magnitude of NGC 6791 is M{sup bol}{sub 6791} = -6.29, with a color (B - V){sub 6791} = 0.97. The cluster appears to be a fairly good proxy of standard elliptical galaxies, although with significantly bluer infrared colors, a shallower 4000 A Balmer break, and a lower Mg{sub 2} index. The confirmed presence of a dozen hot stars along their extreme horizontal-branch evolution leads the cluster SED to consistently match the properties of the most active UV-upturn galaxies, with 1.7% {+-} 0.4% of the total bolometric luminosity emitted shortward of 2500 Angstrom-Sign . The cluster helium abundance results in Y{sub 6791} = 0.30 {+-} 0.04, while the post-main-sequence (PMS) implied stellar lifetime from star number counts fairly agrees with the theoretical expectations from both the PADOVA and BASTI stellar tracks. A PMS fuel consumption of 0.43 {+-} 0.01 M{sub Sun} is found for NGC 6791 stars, in close agreement with the estimated mass of cluster He-rich white dwarfs. Such a tight figure may lead one to suspect that a fraction of the cluster stellar population does not actually reach the minimum mass required to effectively ignite He in the stellar core.

  12. Stellar Lifetime and Ultraviolet Properties of the Old Metal-rich Galactic Open Cluster NGC 6791: A Pathway to Understand the Ultraviolet Upturn of Elliptical Galaxies

    NASA Astrophysics Data System (ADS)

    Buzzoni, Alberto; Bertone, Emanuele; Carraro, Giovanni; Buson, Lucio

    2012-04-01

    The evolutionary properties of the old metal-rich Galactic open cluster NGC 6791 are assessed based on deep UB photometry and Two Micron All Sky Survey JK data. For the 4739 stars in the cluster, bolometric luminosity and effective temperature have been derived from theoretical (U - B) and (J - K) color fitting. The derived H-R diagram has been matched with the UVBLUE grid of synthetic stellar spectra to obtain the integrated spectral energy distribution (SED) of the system, together with a full set of UV (Fanelli) and optical (Lick) narrowband indices. The total bolometric magnitude of NGC 6791 is M bol 6791 = -6.29, with a color (B - V)6791 = 0.97. The cluster appears to be a fairly good proxy of standard elliptical galaxies, although with significantly bluer infrared colors, a shallower 4000 Å Balmer break, and a lower Mg2 index. The confirmed presence of a dozen hot stars along their extreme horizontal-branch evolution leads the cluster SED to consistently match the properties of the most active UV-upturn galaxies, with 1.7% ± 0.4% of the total bolometric luminosity emitted shortward of 2500 Å. The cluster helium abundance results in Y 6791 = 0.30 ± 0.04, while the post-main-sequence (PMS) implied stellar lifetime from star number counts fairly agrees with the theoretical expectations from both the PADOVA and BASTI stellar tracks. A PMS fuel consumption of 0.43 ± 0.01 M ⊙ is found for NGC 6791 stars, in close agreement with the estimated mass of cluster He-rich white dwarfs. Such a tight figure may lead one to suspect that a fraction of the cluster stellar population does not actually reach the minimum mass required to effectively ignite He in the stellar core. Based on observations carried out at the Italian Telescopio Nazionale Galileo, operated by INAF at the Roque de los Muchachos Observatory (La Palma, Spain).

  13. VI CCD Photometry Of The Old Open Clusters Arp-madore 2, Tombaugh 2 And Saurer 1

    NASA Astrophysics Data System (ADS)

    Phelps, Randy L.

    2007-05-01

    Faint-magnitude VI CCD photometry has been obtained for the clusters Arp-Madore 2, Tombaugh 2 and Saurer 1 with the DuPont 2.5-meter telescope at Las Campanas Observatory. These three clusters are among a handful that have been proposed to be associated with the so-called “Galactic Anticenter Stellar Structure” (GASS). Using the Padova isochrones (Girardi et al. 2000, 2002), we have self-consistently determined the ages, distances and Galactocentric positions of these clusters. In this contribution the newly determined parameters will be discussed, as will the potential association of the clusters with the “GASS”. This work is supported, in part, by a Research and Creative Activities award from the California State University, Sacramento and a grant (AST-0652742) from the National Science Foundation.

  14. CHARACTERIZATION OF THE YOUNG OPEN CLUSTER G144.9+0.4 IN THE CAMELOPARDALIS OB1 ASSOCIATION

    SciTech Connect

    Lin, Chien-Cheng; Chen, W. P.; Panwar, Neelam

    2013-10-01

    Our star-count analysis of the Two Micron All Sky Survey point sources resulted in an identification of the star cluster G144.9+0.4. The cluster was found, but not characterized, by Glushkova et al. We show that the cluster is physically associated with the Cam OB1 association at a distance of about 1 kpc and with an age of 1-2 Myr. Pre-main sequence stars are identified on the basis of photometric and proper motion data. A total of 91 additional OB star candidates was found in subgroups 1A and 1B, a significant increase from the currently known 43 OB stars. The OB members show an age spread that indicates a sustained star formation for at least the last 10-15 Myr. The young cluster G144.9+0.4 represents the latest episode of sequential star formation in this cloud complex.

  15. Stellar-mass black holes in young massive and open stellar clusters and their role in gravitational-wave generation

    NASA Astrophysics Data System (ADS)

    Banerjee, Sambaran

    2017-01-01

    Stellar-remnant black holes (BH) in dense stellar clusters have always drawn attention due to their potential in a number of phenomena, especially the dynamical formation of binary black holes (BBH), which potentially coalesce via gravitational-wave (GW) radiation. This study presents a preliminary set of evolutionary models of compact stellar clusters with initial masses ranging over 1.0 × 104M⊙ - 5.0 × 104M⊙, and half-mass radius of 2 or 1 pc, that is typical for young massive and starburst clusters. They have metallicities between 0.05Z⊙ - Z⊙. Including contemporary schemes for stellar wind and remnant formation, such model clusters are evolved, for the first time, using the state-of-the-art direct N-body evolution program NBODY7, until their dissolution or at least for 10 Gyr. That way, a self-regulatory behaviour in the effects of dynamical interactions among the BHs is demonstrated. In contrast to earlier studies, the BBH coalescences obtained in these models show a prominence in triple-mediated coalescences while being bound to the clusters, compared to those occurring among the BBHs that are dynamically ejected from the clusters. A broader mass spectrum of the BHs and lower escape velocities of the clusters explored here might cause this difference, which is yet to be fully understood. Among the BBH coalescences obtained here, there are ones that resemble the detected GW151226, LVT151012, and GW150914 events and also ones which are even more massive. A preliminary estimate suggests few 10s-100s of BBH coalescences per year, originating due to dynamics in stellar clusters, that can be detected by the LIGO at its design sensitivity.

  16. Searching for and Characterization of Galactic Open Clusters toward the Galactic Anti-Center with Pan-STARRS1

    NASA Astrophysics Data System (ADS)

    Lin, Chien-Cheng; Chen, Wen-Ping; Hou, Jinliang; Chen, Li; Shao, Zhengyi

    2015-08-01

    Hundreds of thousands star clusters were suggested to exist in the Galactic disk, but so far only a few thousands had been catalogued, all in the solar neighborhood (less than 2 kpc). We therefore aim to use Pan-STARRS1 3π data with its wide-field sky and sensitive camera to search for and to characterize star clusters. We used a star-counting algorithm to identify stellar density enhancements toward the Galactic anti-center. The detection rate of known star clusters in this region with radii less than 10' from the algorithm used was approximately 83%. In the field of 400 square degrees, we identified 491 stellar cluster candidates, 50 of which were matched with known star cluster catalog. The remaining 441 candidates were characterized with radius, reddening, distance, age, and lowest mass members, along with PPMXL proper motions and 2MASS and Pan-STARRS1 multi-band photometry. The revised star cluster sample was estimated to be complete up to a heliocentric distance of 5 kpc toward the Galactic anti-center. Moreover, this sample allowed us to estimate the separation between Sagittarius and Perseus arms was about 3.2 kpc with 0.2 kpc uncertainty and the widths of the nearby spiral arms---Sagittarius, Orion, and Perseus---with the full-width-half-maximum to be 1.4±0.1, 1.6±0.1, and 3.3±0.2 kpc, respectively.

  17. PICK2: Planets in Clusters with K2

    NASA Astrophysics Data System (ADS)

    Cochran, William D.; Endl, Michael; Johnson, Marshall C.; Lee, Byeong-Cheol; Park, Chan; Han, Inwoo; Rauer, Heike; Cabrera, Juan; Csizmadia, Szilard; Paetzold, Martin; Yong, David; Asplund, Martin; Hatzes, Artie P.

    2015-11-01

    Open clusters are remarkable laboratories for a wide variety of astrophysical investigations. They comprise the most homogeneous samples of stars that we can ever hope to find. They are stars that share the same age, initial chemical composition, distance and dynamical environment. The fundamental property that distinguishes one star from another in a cluster is simply the stellar mass. This gives us the very rare opportunity to conduct well controlled astrophysical studies of stars, and as a result there is a vast astronomical literature focused on understanding and characterizing the members of stellar clusters.We are searching for transiting planets in five open clusters in the NASA K2 mission Fields 4, 5 and 7. These clusters range in age from 125My (Pleiades) through the 625My ages of the Hyades and Praesepe, up to the much older Ruprecht 147 (2.5 Gyr) and M67 (3-5 Gyr) clusters. Examination of the distribution of planetary orbital parameters as well as the planetary multiplicity, radius and mass distributions as a function of stellar age (and in comparison with field stars from both K2 and Kepler) will provide a powerful test of theories of planetary system formation and dynamical evolution. The radii of hot Jupiters and Saturns as a function of cluster age will provide a sensitive test of theories to explain the population of inflated hot Jupiters.Our team will process the K2 pixel files into light curves for each target star, and will then search these light curves for possible planet transit events. We will apply standard vetting procedures to remove likely false-positives and we will then model the transit profiles. We will then conduct an extensive set of ground-based follow-up observations using a wide range of observational facilities at our disposal. These will include imaging, high resolution visible and near-IR spectroscopy, precise radial velocity measurement, and ground-based observations of further transits, as appropriate.

  18. CCD photometric search for peculiar stars in open clusters. VIII. King 21, NGC 3293, NGC 5999, NGC 6802, NGC 6830, Ruprecht 44, Ruprecht 115, and Ruprecht 120

    NASA Astrophysics Data System (ADS)

    Netopil, M.; Paunzen, E.; Maitzen, H. M.; Pintado, O. I.; Claret, A.; Miranda, L. F.; Iliev, I. Kh.; Casanova, V.

    2007-02-01

    Context: We continue our survey of magnetic chemically peculiar (CP2) stars in galactic open clusters to shed more light on their origin and evolution. Aims: To study the group of CP2 stars, it is essential to find these objects in different galactic environments and at a wide range of evolutionary stages. The knowledge of open cluster ages and metallicities can help for finding a correlation between these parameters and the (non-)presence of peculiarities, which has to be taken into account in stellar evolution models. Methods: The intermediate band Δ a photometric system samples the depth of the 5200 Å flux depression by comparing the flux at the centre with the adjacent regions with bandwidths of 110 Å to 230 Å. It is capable of detecting magnetic CP2 and CP4 stars with high efficiency, but also the groups of (metal-weak) λ Bootis and classical Be/shell stars can be successfully investigated. In addition, it allows the age, reddening, and distance modulus to be determined with appropriate accuracy by fitting isochrones. Results: From the 1677 observed members of the eight open clusters, one Ae and twenty-five CP2 stars were identified. Furthermore nineteen deviating stars are designated as questionable for several reasons. The estimated age, reddening, and distance for the programme clusters were compared with published values of the literature and discussed in this context. Conclusions: .The current paper shows that CP2 stars are continuously present in very young (7 Myr) to intermediate age (500 Myr) open clusters at distances greater than 2 kpc from the Sun. Based on observations at CASLEO, CTIO (Proposal 2003A-0057), and OSN. The Observatorio de Sierra Nevada is operated by the Consejo Superior de Investigaciones Científicas through the Instituto de Astrofísica de Andalucía (Granada, Spain). Photometric data are only avaialable in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb

  19. Investigation of the open star cluster NGC 2323 (M50) based on the proper motions and photometry of its constituent stars

    NASA Astrophysics Data System (ADS)

    Frolov, V. N.; Ananjevskaja, Yu. K.; Polyakov, E. V.

    2012-02-01

    The results of a comprehensive study of the Galactic open cluster NGC 2323 (M50) are presented. The positions of stars to a limiting magnitude {ie74-1} in a {ie74-2} area centered on the cluster were measured on six plates from the Pulkovo normal astrograph with a maximum epoch difference of 60 yr. The measurements were performed with the Pulkovo "Fantasy" automated measuring system upgraded in 2010. The corresponding areas from the USNO-A2.0, USNO-B1, and 2MASS catalogues were used as additional plates. As a result, the relative proper motions of stars were obtained with a root-mean-square error of 5.85 mas yr-1. A catalogue of UBV and JHK magnitudes for objects in the investigated area was compiled from available published resources. The astrometric selection of cluster members was made by the maximum likelihood method. A high individual cluster membership probability of a star ( P ≥ 80%) served as the first selection criterion. The position of a star on the photometric color-magnitude ( V ∝ ( B-V), J ∝ ( J-K)) diagrams of the cluster was considered as the second criterion. The position of an object on the color-color (( U-B)-( B-V), ( J-H)-( J-K)) diagrams served as the third criterion. On the basis of these criteria, it was established that 508 stars are members of NGC 2323. These data were used to refine the physical parameters of the cluster: the mean reddening {ie74-3}, the true distance modulus {ie74-4}, and the cluster age of about 140 Myr from the grid of isochrones computed by the Padova group for solar chemical composition. Two tables contain the catalogues of proper motions and photometry for stars in the area. The luminosity and mass functions were constructed. The cluster membership of red and blue giants, variable, double, and multiple stars was considered. The position of the cluster center was improved: {ie74-5}, δ = -08°20'16″(2000.0).

  20. Evaluating gyrochronology on the zero-age-main-sequence: rotation periods in the southern open cluster Blanco 1 from the Kelt-South survey

    SciTech Connect

    Cargile, P. A.; Pepper, J.; Siverd, R.; Stassun, K. G.; James, D. J.; Kuhn, R. B.

    2014-02-10

    We report periods for 33 members of Blanco 1 as measured from Kilodegree Extremely Little Telescope-South light curves, the first reported rotation periods for this benchmark zero-age-main-sequence open cluster. The distribution of these stars spans from late-A or early-F dwarfs to mid-K with periods ranging from less than a day to ∼8 days. The rotation period distribution has a m