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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.

    2016-08-01

    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/HIRES 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 AGB 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. 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.

  4. Apex determination and detection of stellar clumps in the open cluster M 67

    NASA Astrophysics Data System (ADS)

    Vereshchagin, S. V.; Chupina, N. V.; Sariya, Devesh P.; Yadav, R. K. S.; Kumar, Brijesh

    2014-08-01

    We determined the cluster’s apex coordinates, studied the substructures and performed membership analysis in the central part (34‧×33‧) of the open cluster M 67. We used the individual stellar apexes method developed earlier and classical technique of proper motion diagrams in coordinate system connected with apex. The neighbour-to-neighbour distance technique was applied to detect space details. The membership list was corrected and some stars were excluded from the most probable members list. The apex coordinates have been determined as: A0=132.97° ± 0.81° and D0=11.85° ± 0.90°. The 2D-space star density field was analysed and high degree of inhomogeneity was found.

  5. 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

  6. 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.

  7. Variable stars in one open cluster within the Kepler/K2-Campaign-5 field: M 67 (NGC 2682)

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    In this paper, we continue the release of high-level data products from the multiyear photometric survey collected at the 67/92 cm Schmidt Telescope in Asiago. The primary goal of the survey is to discover and to characterize variable objects and exoplanetary transits in four fields containing five nearby open clusters spanning a broad range of ages. This second paper releases a photometric catalogue, in five photometric bands, of the solar-age, solar-metallicity open cluster M 67 (NGC 2682). Proper motions are derived comparing the positions observed in 2013 at the Asiago's Schmidt Telescope with those extracted from Wide Field Imager@2.2 m Max-Planck-Gesellschaft/European Southern Obseratory images in 2000. We also analyse the variable sources within M 67. We detected 68 variables, 43 of which are new detection. Variable periods and proper-motion memberships of a large majority of sources in our catalogue are improved with respect to previous releases. The entire catalogue will be available in electronic format. Besides the general interest on an improved catalogue, this work will be particularly useful because of: (1) the imminent release of Kepler/K2 Campaign-5 data of this clusters, for which our catalogue will provide an excellent, high spatial resolution input list, and (2) characterization of the M 67 stars which are targets of intense High Accuracy Radial velocity Planet Searcher and High Accuracy Radial velocity Planet Searcher for the Northern hemisphere radial-velocity surveys for planet search.

  8. 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.

  9. A Survey of Chromospheric Activity in the Solar-Type Stars in the Open Cluster M67

    NASA Astrophysics Data System (ADS)

    Giampapa, Mark S.; Hall, Jeffrey C.; Radick, Richard R.; Baliunas, Sallie L.

    2006-11-01

    We present the results of a spectroscopic survey of the Ca II H and K core strengths in a sample of 60 solar-type stars that are members of the solar-age and solar-metallicity open cluster M67. We adopt the HK index, defined as the summed H+K core strengths in 1 Å bandpasses centered on the H and K lines, respectively, as a measure of the chromospheric activity that is present. We compare the distribution of mean HK index values for the M67 solar-type stars with the variation of this index as measured for the Sun during the contemporary solar cycle. We find that the stellar distribution in our HK index is broader than that for the solar cycle. Approximately 17% of the M67 Sun-like stars exhibit average HK indices that are less than solar minimum. About 7%-12% are characterized by relatively high activity in excess of solar maximum values, while 72%-80% of the solar analogs exhibit Ca II H+K strengths within the range of the modern solar cycle. The ranges given reflect uncertainties in the most representative value of the maximum in the HK index to adopt for the solar cycle variations observed during the period AD 1976-2004. Thus, ~20%-30% of our homogeneous sample of Sun-like stars have mean chromospheric H+K strengths that are outside the range of the contemporary solar cycle. Any cycle-like variability that is present in the M67 solar-type stars appears to be characterized by periods greater than ~6 yr. Finally, we estimate a mean chromospheric age for M67 in the range of 3.8-4.3 Gyr. The results presented herein are based on data obtained at the WIYN telescope and at the McMath-Pierce Solar Telescope. The WIYN Observatory is a joint facility of the University of Wisconsin-Madison, Indiana University, Yale University, and the National Optical Astronomy Observatory. The McMath-Pierce Solar Telescope Facility is operated by the National Solar Observatory for the National Science Foundation. This paper is WIYN Open Cluster Study XXVIII in the series.

  10. 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

  11. Deep, Low Mass Ratio Overcontact Binary Systems. VI. AH Cancri in the Old Open Cluster M67

    NASA Astrophysics Data System (ADS)

    Qian, S.-B.; Liu, L.; Soonthornthum, B.; Zhu, L.-Y.; He, J.-J.

    2006-06-01

    CCD photometric light curves in the B and V bands obtained in 2001 and in the V band obtained in 2002 of AH Cnc in the old open cluster M67 are presented. It is shown that AH Cnc is a total-eclipsing binary and its light curves correspond to a typical A type according to Binnendijk's classification. The variations of the light curve around the primary minimum and second maximum were found. Our nine epochs of light minimum monitored from 2001 to 2005, including others collected from the literature, were used to create the first study of the period changes of the binary system. A cyclic oscillation with a period of 36.5 yr and an amplitude of 0.0237 days was discovered to be superposed on a continuous period increase (dP/dt=3.99×10-7 days yr-1). Weak evidence indicates that there exists another small-amplitude period oscillation (A4=0.0035 days, P4=7.75 yr). The symmetric light curves in the B and V bands obtained in 2001 were analyzed with the 2003 version of the Wilson-Devinney code. It is confirmed that AH Cnc is a deep overcontact binary system with a high degree of overcontact f=58.5%+/-4.5% and a low mass ratio of q=0.1682+/-0.0012. The existence of the third light and the cyclic period oscillation both may suggest that AH Cnc is a triple system containing an unseen third body. The tertiary component may have played an important role in the origin of the overcontact binary star by removing angular momentum from the central system, which would cause it to have a short initial orbital period and thus evolve into an overcontact configuration by angular momentum loss. The long-term period increase can be interpreted as a mass transfer from the less massive component to the more massive one. As the orbital period increases, the decrease of the mass ratio will cause it finally to evolve into a single rapid-rotating star when the system meets the more familiar criterion that the orbital angular momentum be less than 3 times the total spin angular momentum. Therefore

  12. A PSF-based approach to Kepler/K2 data - III. Search for exoplanets and variable stars within the open cluster M 67 (NGC 2682)

    NASA Astrophysics Data System (ADS)

    Nardiello, D.; Libralato, M.; Bedin, L. R.; Piotto, G.; Borsato, L.; Granata, V.; Malavolta, L.; Nascimbeni, V.

    2016-08-01

    In the third paper of this series we continue the exploitation of Kepler/K2 data in dense stellar fields using our PSF-based method. This work is focused on a ˜720-arcmin2 region centred on the Solar-metallicity and Solar-age open cluster M 67. We extracted light curves for all detectable sources in the Kepler channels 13 and 14, adopting our technique based on the usage of a high-angular-resolution input catalogue and target-neighbour subtraction. We detrended light curves for systematic errors, and searched for variables and exoplanets using several tools. We found 451 variables, of which 299 are new detection. Three planetary candidates were detected by our pipeline in this field. Raw and detrended light curves, catalogues, and K2 stacked images used in this work will be released to the community.

  13. Rotation Periods for Cool Stars in the 4 Gyr old Open Cluster M67, The Solar–Stellar Connection, and the Applicability of Gyrochronology to at least Solar Age

    NASA Astrophysics Data System (ADS)

    Barnes, Sydney A.; Weingrill, Joerg; Fritzewski, Dario; Strassmeier, Klaus G.; Platais, Imants

    2016-05-01

    We report rotation periods for 20 cool (FGK) main sequence member stars of the 4 Gyr-old open cluster M67 (=NGC 2682), obtained by analyzing data from Campaign 5 of the K2 mission with the Kepler Space Telescope. The rotation periods delineate a sequence in the color–period diagram (CPD) of increasing period with redder color. This sequence represents a cross-section at the cluster age of the surface P = P(t, M), suggested in prior work to extend to at least solar age. The current Sun is located marginally (approximately 1σ) above M67 in the CPD, as its relative age leads us to expect, and lies on the P = P(t, M) surface to within measurement precision. We therefore conclude that the solar rotation rate is normal as compared with cluster stars, a fact that strengthens the solar–stellar connection. The agreement between the M67 rotation period measurements and prior predictions further implies that rotation periods, especially when coupled with appropriate supporting work such as spectroscopy, can provide reliable ages via gyrochronology for other similar FGK dwarfs from the early main sequence to solar age and likely until the main sequence turnoff. The M67 rotators have a rotational age of 4.2 Gyr with a standard deviation of 0.7 Gyr, implying that similar field stars can be age-dated to precisions of ∼17%. The rotational age of the M67 cluster as a whole is therefore 4.2 Gyr, but with a lower (averaged) uncertainty of 0.2 Gyr.

  14. The Sun was Not Born in M67

    NASA Astrophysics Data System (ADS)

    Pichardo, Bárbara; Moreno, Edmundo; Allen, Christine; Bedin, Luigi R.; Bellini, Andrea; Pasquini, Luca

    2012-03-01

    Using the most recent proper-motion determination of the old, solar-metallicity, Galactic open cluster M67 in orbital computations in a non-axisymmetric model of the Milky Way, including a bar and three-dimensional spiral arms, we explore the possibility that the Sun once belonged to this cluster. We have performed Monte Carlo numerical simulations to generate the present-day orbital conditions of the Sun and M67, and all the parameters in the Galactic model. We compute 3.5 × 105 pairs of orbits Sun-M67 looking for close encounters in the past with a minimum distance approach within the tidal radius of M67. In these encounters we find that the relative velocity between the Sun and M67 is larger than 20 km s-1. If the Sun had been ejected from M67 with this high velocity by means of a three-body encounter, this interaction would have either destroyed an initial circumstellar disk around the Sun or dispersed its already formed planets. We also find a very low probability, much lower than 10-7, that the Sun was ejected from M67 by an encounter of this cluster with a giant molecular cloud. This study also excludes the possibility that the Sun and M67 were born in the same molecular cloud. Our dynamical results convincingly demonstrate that M67 could not have been the birth cluster of our solar system. This work relies partly on observations of the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are The Ohio State University; The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota, and University of Virginia.

  15. 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.

  16. ON USING THE COLOR-MAGNITUDE DIAGRAM MORPHOLOGY OF M67 TO TEST SOLAR ABUNDANCES

    SciTech Connect

    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.

  17. 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.

  18. 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.

  19. Mass loss in M67 giants - Evidence from isochrone fitting

    NASA Technical Reports Server (NTRS)

    Tripicco, Michael J.; Dorman, Ben; Bell, R. A.

    1993-01-01

    A comparison between the color-magnitude diagram of M67 and a new set of theoretical evolutionary models which include all phases from the unevolved main-sequence through core-helium burning and onto the AGB is presented. The present 5-Gyr solar abundance isochrone is found to yield an excellent fit to the whole of the M67 color-magnitude diagram. A differential technique that compares the gap in color between clump giants and normal red giants, on one hand, with the temperature gap between core He-burning tracks and first-ascent RGB tracks, on the other, strongly indicates that the clump giants in M67 have masses of 0.70 solar mass or less. The extremely large amount of mass loss that is deduced is well in excess of that found for globular cluster stars. Possible resolutions of this problem are that degree of mass loss increases with total stellar mass, or with metallicity.

  20. 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.

  1. The Chemical Composition of Planet-Harboring Stars in M67

    NASA Astrophysics Data System (ADS)

    Holzer, Parker H.; Ivans, Inese; Galbraith-Frew, Jessica; Anderton, Tim; Apogee Team

    2016-03-01

    At the forefront of observational astronomy is the search for, and an understanding about the nature of, stars containing planetary companions. To contribute to this search, we have studied stars in the open cluster Messier 67 (M67), a cluster known to have many stars very comparable to the Sun. At least four dwarf stars in this cluster have shown evidence in previous studies to contain planets. We studied these, as well as about thirty four other F-dwarf stars in M67, by using high signal-to-noise infrared stellar spectra from APOGEE (Apache Point Observatory Galactic Evolution Experiment; a part of the Sloan Digital Sky Survey). Because stars in an open cluster are born from the same material and approximately at the same time, they are in general expected to all have very similar chemical compositions. However, after using spectral synthesis to derive the temperature, gravitational acceleration at the surface, and overall chemical enrichment of the stars in our sample, we have shown that the chemical composition of stars in the cluster is not homogeneous, but instead exhibits a spread. Further, we have shown that this spread may possibly be due to the presence of planet-harboring stars. Our findings suggest that planet-harboring stars are richer in refractory elements and poorer in volatile elements, giving a deeper understanding of the environments in which planets are likely to form.

  2. 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.

  3. 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.

  4. Discovery of a Long-Period Eclipsing Binary in M67

    NASA Astrophysics Data System (ADS)

    Sandquist, Eric L.; Latham, David W.; Mathieu, Robert D.; Vanderburg, Andrew; Brown, Timothy M.; M67 K2 Team

    2016-06-01

    We announce the detection of an eclipsing binary (WOCS 12009 / Sanders 1247) near the turnoff of the heavily-studied old open cluster M67 using K2 Campaign 5 data. The object was previously known to be a double-lined spectroscopic binary, and the orbit period (69.75 d) agrees with the photometric period. We present a preliminary analysis of the K2 photometry, multi-band ground-based photometry of the eclipses, and extensive radial velocity observations of the two stars. Precise measurements of the pair will begin to provide mass and radius scales for cluster stars, and will constrain the age of this iconic open cluster.We gratefully acknowledge support from NASA through grant NNX15AW24A to R.D.M.

  5. 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.

  6. 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.

  7. 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.

  8. The WIYN Open Cluster Study: A 15-Year Report

    NASA Astrophysics Data System (ADS)

    Mathieu, Robert D.; WOCS Collaboration

    2013-06-01

    The WIYN 3.5m telescope combines large aperture, wide field of view and superb image quality. The WIYN consortium includes investigators in numerous areas of open cluster research. The combination spawned the WIYN Open Cluster Study (WOCS) over a decade ago, with the goals of producing 1) comprehensive photometric, astrometric and spectroscopic data for new fundamental open clusters and 2) addressing key astrophysical problems with these data. The set of core WOCS open clusters spans age and metallicity. Low reddening, solar proximity and richness were also desirable features in selecting core open clusters. More than 50 WIYN Open Cluster Study papers have been published in refereed journals. Highlights include: deep and wide-field photometry of NGC 188, NGC 2168 (M35), and NGC 6819 (WOCS I, II, XI and LII); deep and wide-field proper-motion studies of the old open clusters NGC 188, NGC 2682 (M67) and NGC 6791 (WOCS XVII, XXXIII and XLVI); comprehensive radial-velocity surveys of NGC 188, NGC 2168 and NGC 6819 (WOCS XXXII, XXIV, and XXXVIII); metallicity and lithium abundances in NGC 2168 (WOCS V); comprehensive definition of the hard-binary populations of NGC 188 and NGC 2168 (WOCS XXII and XLVIII); rotation period distributions in NGC 1039 (M34) and NGC 2168 (WOCS XXXV, XLIII, and XLV); study of chromospheric activity in NGC 2682 (WOCS XVIII); photometric variability surveys in NGC 188 and NGC 2682 (IX and XV); new Bayesian techniques for determination of cluster parameters (WOCS XXIII); a new infrared age-diagnostic for open clusters (WOCS XL); theoretical studies of stellar rotation (WOCS XIII and XIV); sophisticated N-body simulations of NGC 188 (WOCS LI); and the discovery of a high binary frequency and white dwarf companions among NGC 188 blue stragglers. While the WIYN 3.5m telescope remains at its heart, today the WIYN Open Cluster Study collaboration extends beyond both the WIYN observatory and consortium, and continues as a vital and productive

  9. Bayesian inference of mass segregation of open clusters

    NASA Astrophysics Data System (ADS)

    Shao, Zhengyi; Chen, Li; Lin, Chien-Cheng; Zhong, Jing; Hou, Jinliang

    2015-08-01

    Based on the Bayesian inference (BI) method, the mixture-modeling approach is improved to combine all kinematic data, including the coordinative position, proper motion (PM) and radial velocity (RV), to separate the motion of the cluster from field stars in its area, as well as to describe the intrinsic kinematic status. Meanwhile, the membership probabilities of individual stars are determined as by product results. This method has been testified by simulation of toy models and it was found that the joint usage of multiple kinematic data can significantly reduce the missing rate of membership determination, say from ~15% for single data type to 1% for using all position, proper motion and radial velocity data.By combining kinematic data from multiple sources of photometric and redshift surveys, such as WIYN and APOGEE, M67 and NGC188 are revisited. Mass segregation is identified clearly for both of these two old open clusters, either in position or in PM spaces, since the Bayesian evidence (BE) of the model, which includes the segregation parameters, is much larger than that without it. The ongoing work is applying this method to the LAMOST released data which contains a large amount of RVs cover ~200 nearby open clusters. If the coming GAIA data can be used, the accuracy of tangential velocity will be largely improved and the intrinsic kinematics of open clusters can be well investigated, though they are usually less than 1 km/s.

  10. 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.

  11. THE ORIGIN OF ENHANCED ACTIVITY IN THE SUNS OF M67

    SciTech Connect

    Reiners, A.; Giampapa, M. S. E-mail: giampapa@noao.ed

    2009-12-10

    We report the results of the analysis of high-resolution photospheric line spectra obtained with the UVES instrument on the VLT for a sample of 15 solar-type stars selected from a recent survey of the distribution of H and K chromospheric line strengths in the solar-age open cluster M67. We find upper limits to the projected rotation velocities that are consistent with solar-like rotation (i.e., v sin iapprox< 2-3 km s{sup -1}) for objects with Ca II chromospheric activity within the range of the contemporary solar cycle. Two solar-type stars in our sample exhibit chromospheric emission well in excess of even solar maximum values. In one case, Sanders 1452, we measure a minimum rotational velocity of v sin i = 4 +- 0.5 km s{sup -1}, or over twice the solar equatorial rotational velocity. The other star with enhanced activity, Sanders 747, is a spectroscopic binary. We conclude that high activity in solar-type stars in M67 that exceeds solar levels is likely due to more rapid rotation rather than an excursion in solar-like activity cycles to unusually high levels. We estimate an upper limit of 0.2% for the range of brightness changes occurring as a result of chromospheric activity in solar-type stars and, by inference, in the Sun itself. We discuss possible implications for our understanding of angular momentum evolution in solar-type stars, and we tentatively attribute the rapid rotation in Sanders 1452 to a reduced braking efficiency.

  12. 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.

  13. Photometric Study of AH Cancri, a W UMa-Type System in M67

    NASA Astrophysics Data System (ADS)

    Zhang, X. B.; Zhang, R. X.; Deng, L.

    2005-02-01

    We present time-series CCD photometry of AH Cnc, a W UMa-type binary system in the old open cluster M67. Over 3500 measurements in two filters were recorded on 15 nights from 2001 to 2004. From the data, 17 new times of minima for the eclipsing binary were obtained, from which a new ephemeris was derived. The orbital period of the system is refined as 0.36045754 days. A photometric analysis for the obtained light curves is performed based on the Wilson-Devinney code. The photometric solutions reveal a totally eclipsing contact configuration for AH Cnc. The photometric mass ratio is determined to be 0.149+/-0.002. The masses and radii of the components are estimated as 1.21+/-0.08 Msolar and 1.36+/-0.03 Rsolar for the primary and 0.18+/-0.02 Msolar and 0.62+/-0.02 Rsolar for the secondary, respectively. The evolutionary status of the contact system is briefly discussed.

  14. 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.

  15. 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.

  16. Dynamics of very rich open clusters

    NASA Astrophysics Data System (ADS)

    de la Fuente Marcos, R.; de la Fuente Marcos, C.

    The oldest open clusters in our Galaxy set the lower limit to the age of the Galactic Disk (9-10 Gyr). Although they appear to be very rich now, it is clear that their primordial populations were much larger. Often considered as transitional objects, these populous open clusters show structural differences with respect to globular clusters so their dynamics and characteristic evolutionary time scales can also be different. On the other hand, their large membership lead to different dynamical evolution as compared with average open clusters. In this paper, the differential features of the evolution of rich open clusters are studied using N-body simulations, including several of the largest (10^4 stars) published direct collisional N-body calculations so far, which were performed on a CRAY YMP. The disruption rate of rich open clusters is analysed in detail and the effect of the initial spatial distribution of the stars in the cluster on its dynamics is studied. The results show that cluster life-time depends on this initial distribution, decreasing when it is more concentrated. The effect of stellar evolution on the dynamical evolution of rich clusters is an important subject that also has been considered here. We demonstrate that the cluster's life-expectancy against evaporation increases because of mass loss by evolving high-mass stars.

  17. The end of the white dwarf cooling sequence in M 67

    NASA Astrophysics Data System (ADS)

    Bellini, A.; Bedin, L. R.; Piotto, G.; Salaris, M.; Anderson, J.; Brocato, E.; Ragazzoni, R.; Ortolani, S.; Bonanos, A. Z.; Platais, I.; Gilliland, R.; Raimondo, G.; Bragaglia, A.; Tosi, M.; Gallozzi, S.; Testa, V.; Kochanek, C. S.; Giallongo, E.; Baruffolo, A.; Farinato, J.; Diolaiti, E.; Speziali, R.; Carraro, G.; Yadav, R. K. S.

    2010-04-01

    In this paper, we present for the first time a proper-motion-selected white dwarf (WD) sample of the old Galactic open cluster M 67, down to the bottom of the WD cooling sequence (CS). The color-magnitude diagram is based on data collected with the LBC-Blue camera at the prime-focus of LBT. As first epoch data, we used CFHT-archive images collected 10 years before LBC data. We measured proper motions of all the identified sources. Proper motions are then used to separate foreground and background objects from the cluster stars, including WDs. Finally, the field-object cleaned WD CS in the V vs. B-I color-magnitude diagram is compared with the models. We confirm that the age derived from the location of the bottom of the WD CS is consistent with the turn off age. Based on data acquired using the Large Binocular Telescope (LBT) at Mt. Graham, Arizona, under the Commissioning of the Large Binocular Blue Camera. The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota and University of Virginia; and on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.Visiting PhD Student at STScI under the “2008 graduate research assistantship” program.

  18. 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.

  19. 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.

  20. 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.

  1. Determination of the Core Composition of White Dwarfs in M67

    NASA Astrophysics Data System (ADS)

    Simon, Amélie; Fontaine, Gilles; Brassard, Pierre

    2015-06-01

    Since stellar helium thermonuclear burning is still not well constrained, the exact proportion of carbon and oxygen in the core of white dwarfs remains largely unknown. Given that the cooling time of these objects depends on their composition, it is thus crucial to constrain the latter in order to use white dwarfs as cosmochronometers. To address this, we compared theoretical luminosty functions built for a wide range of compositions to the observed luminosity function of the coeval white dwarfs in the M67 cluster. Theoretical luminosity functions were determined from 300 state-of-the-art evolutionary sequences, combined with models for the stellar formation rate, initial mass function, and initial-to-final mass relationship. Since the age of M67 is known to a good precision , this comparison allowed us to determine the mean carbon-to-oxygen ratio of its white dwarf population. Assuming that the white dwarfs in M67 are 80% DA's and 20% DB's with standard "thick" envelopes, we find that their core composition is dominated by oxygen.

  2. Dynamical Evolution of Open Star Clusters

    NASA Astrophysics Data System (ADS)

    de La Fuente Marcos, Raúl

    1998-09-01

    Stars are not formed independently, but instead they form in clusters. The influence of the initial mass function (IMF) on the evolution of open star clusters is analyzed using numerical integrations of N-body systems by the code NBODY5 (S. J. Aarseth, in Multiple Time Scales, ed. J. U. Brackbill & B. I. Cohen [New York: Academic, 1985], p. 377), which include tidal effects, mass loss due to stellar evolution, the realistic fraction of primordial binaries, and the formation of multiple systems. Five different IMFs (E. E. Salpeter, ApJ, 121, 161 [1955]; L. G. Taff, AJ, 79, 11 [1974]; G. E. Miller & J. M. Scalo, ApJS, 41, 513 [1979]; P. Kroupa, C. A. Tout, & G. Gilmore, MNRAS, 262, 545 [1993]; J. M. Scalo, Fundam. Cosmic Phys., 11, 1 [1986]) are used for generating stellar masses. The results confirm significant differences with single-mass models and allow us to distinguish between the standard power-law models and modern ones. An approximate analytic expression for the escape rate is derived in order to fit the data obtained. When stellar evolution is included, the results show that for all the IMF's studied, the evolution of the cluster is slowed down and the initial core collapse loses importance because of an expansion of the inner regions of the cluster. We find that the total disruption time is very IMF dependent because of different numbers of massive stars and also depends on the richness of the cluster. A differential behavior is found between poor and rich systems with respect to mass loss. Poor systems disrupt earlier than homologous ones without mass loss; the opposite is found for rich systems. The transition population is about N = 300. The binary escape rate seems preferentially due to close encounters in poor clusters, but it seems mainly exponential for populated clusters. It suggests that ejection is the main mechanism for binary escape in poor clusters and evaporation is the dominant one for rich clusters. The formation and evolution of

  3. A CHANDRA X-RAY STUDY OF THE INTERACTING BINARIES IN THE OLD OPEN CLUSTER NGC 6791

    SciTech Connect

    Van den Berg, Maureen; Verbunt, Frank

    2013-06-20

    We present the first X-ray study of NGC 6791, one of the oldest open clusters known (8 Gyr). Our Chandra observation is aimed at uncovering the population of close interacting binaries down to L{sub X} Almost-Equal-To 1 Multiplication-Sign 10{sup 30} erg s{sup -1} (0.3-7 keV). We detect 86 sources within 8' of the cluster center, including 59 inside the half-mass radius. We identify 20 sources with proper-motion cluster members, which are a mix of cataclysmic variables (CVs), active binaries (ABs), and binaries containing sub-subgiants. With follow-up optical spectroscopy, we confirm the nature of one CV. We discover one new, X-ray variable candidate CV with Balmer and He II emission lines in its optical spectrum; this is the first X-ray-selected CV in an open cluster. The number of CVs per unit mass is consistent with the field, suggesting that the 3-4 CVs observed in NGC 6791 are primordial. We compare the X-ray properties of NGC 6791 with those of a few old open (NGC 6819, M 67) and globular clusters (47 Tuc, NGC 6397). It is puzzling that the number of ABs brighter than 1 Multiplication-Sign 10{sup 30} erg s{sup -1} normalized by cluster mass is lower in NGC 6791 than in M 67 by a factor {approx}3-7. CVs, ABs, and sub-subgiants brighter than 1 Multiplication-Sign 10{sup 30} erg s{sup -1} are under-represented per unit mass in the globular clusters compared to the oldest open clusters, and this accounts for the lower total X-ray luminosity per unit mass of the former. This indicates that the net effect of dynamical encounters may be the destruction of even some of the hardest (i.e., X-ray-emitting) binaries.

  4. A Chandra X-Ray Study of the Interacting Binaries in the Old Open Cluster NGC 6791

    NASA Astrophysics Data System (ADS)

    van den Berg, Maureen; Verbunt, Frank; Tagliaferri, Gianpiero; Belloni, Tomaso; Bedin, Luigi R.; Platais, Imants

    2013-06-01

    We present the first X-ray study of NGC 6791, one of the oldest open clusters known (8 Gyr). Our Chandra observation is aimed at uncovering the population of close interacting binaries down to L X ≈ 1 × 1030 erg s-1 (0.3-7 keV). We detect 86 sources within 8' of the cluster center, including 59 inside the half-mass radius. We identify 20 sources with proper-motion cluster members, which are a mix of cataclysmic variables (CVs), active binaries (ABs), and binaries containing sub-subgiants. With follow-up optical spectroscopy, we confirm the nature of one CV. We discover one new, X-ray variable candidate CV with Balmer and He II emission lines in its optical spectrum; this is the first X-ray-selected CV in an open cluster. The number of CVs per unit mass is consistent with the field, suggesting that the 3-4 CVs observed in NGC 6791 are primordial. We compare the X-ray properties of NGC 6791 with those of a few old open (NGC 6819, M 67) and globular clusters (47 Tuc, NGC 6397). It is puzzling that the number of ABs brighter than 1 × 1030 erg s-1 normalized by cluster mass is lower in NGC 6791 than in M 67 by a factor ~3-7. CVs, ABs, and sub-subgiants brighter than 1 × 1030 erg s-1 are under-represented per unit mass in the globular clusters compared to the oldest open clusters, and this accounts for the lower total X-ray luminosity per unit mass of the former. This indicates that the net effect of dynamical encounters may be the destruction of even some of the hardest (i.e., X-ray-emitting) binaries.

  5. MOST satellite photometry of stars in the M67 field: eclipsing binaries, blue stragglers and δ Scuti variables

    NASA Astrophysics Data System (ADS)

    Pribulla, Theodor; Rucinski, Slavek; Matthews, Jaymie M.; Kallinger, Thomas; Kuschnig, Rainer; Rowe, Jason F.; Guenther, David B.; Moffat, Anthony F. J.; Sasselov, Dimitar; Walker, Gordon A. H.; Weiss, Werner W.

    2008-11-01

    We present two series of MOST (Microvariability and Oscillations of STars) space-based photometry, covering nearly continuously 10 d in 2004 and 30 d in 2007, of selected variable stars in the upper main sequence of the old open cluster M67. New high-precision light curves were obtained for the blue straggler binary/triple systems AH Cnc, ES Cnc and EV Cnc. The precision and phase coverage of ES Cnc and EV Cnc is by far superior to any previous observations. The light curve of ES Cnc is modelled in detail, assuming two dark photospheric spots and Roche geometry. An analysis of the light curve of AH Cnc indicates a low mass ratio (q ~ 0.13) and a high inclination angle for this system. Two new long-period eclipsing binaries, GSC 814-323 and HD 75638 (non-members of M67) were discovered. We also present ground-based DDO spectroscopy of ES Cnc and of the newly found eclipsing binaries. Especially interesting is HD 75638, a member of a visual binary, which must itself be a triple or a higher multiplicity system. New light curves of two δ Scuti pulsators, EX Cnc and EW Cnc, have been analysed leading to detection of 26 and eight pulsation frequencies of high temporal stability. Based on photometric data from MOST, a Canadian Space Agency mission (jointly operated by Dynacon Inc., the University of Toronto Institute for Aerospace Studies and the University of British Columbia, with the assistance of the University of Vienna), and on spectroscopic data from the David Dunlap Observatory, University of Toronto. E-mail: pribulla@ta3.sk (TP); rucinski@astro.utoronto.ca (SR)

  6. 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.

  7. Membership determination of Open Clusters with CLUSTERIX

    NASA Astrophysics Data System (ADS)

    Sezima, T.; Galadí-Enríquez, D.; Paunzen, E.; Jordi, C.; Balaguer-Núñez, L.; Jilkova, L.

    2015-05-01

    The web-based application Clusterix has been developed as a collaboration between the Masaryk University (Czech Republic) and the Universitat de Barcelona (Spain) to calculate the membership probability of open clusters on the WEBDA database using a completely non parametric method (Galadí-Enríquez et al., 1998; Balaguer-Núñez et al., 2004). WEBDA is a site devoted to observational data on stars in Galactic open clusters. Clusterix is an interactive tool where the user can define the default values to configure the membership estimation for the area of a cluster. Gaia's capabilities to study the kinematics of clusters of stars with great accuracy is one of the main motivations for the development of this tool. The applet first version can be found at: http://clusterix.cerit-sc.cz/

  8. 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.

  9. 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.

  10. FUV imaging survey of Galactic open clusters

    NASA Astrophysics Data System (ADS)

    Maiz Apellaniz, Jesus

    2007-07-01

    We propose a WFPC2 FUV imaging survey of 6 Galactic open clusters with ages ranging from 1 Myr to 300 Myr complemented with NUV/optical imaging of the same fields. No such survey has ever been attempted before in the FUV at the resolution of WFPC2 {indeed, no WFPC2 FUV images of any Galactic open cluster exist in the HST archive} and, since WFPC2 will be retired in SM4 and none of the other HST instruments can do FUV imaging of bright objects, this is the last chance to do such a survey before another UV telescope is launched. This survey will provide a new perspective on young/intermediate age Galactic clusters and a key template for the study of star formation at high redshift, where the intensity peak we observe in the optical/NIR from Earth is located in the FUV in its rest frame. For clusters still associated with an H II region, UV imaging maps the continuum emission of the ionized gas and the radiation scattered by background dust and, combined with optical nebular images, can be used to determine the 3-D structure of the H II region. For all young clusters, FUV+NUV+optical photometry can be used to study the UV excesses of T-Tauri stars. For clusters older than 40 Myr, the same photometric combination is the easiest method to detect companion white dwarfs which are invisible using only the optical and NIR. WFPC2 is also an excellent instrument to discover close companions around bright stars and improve our knowledge of their multiplicity fraction. Finally, for all clusters, the combination of high-spatial-resolution UV and optical photometry can be used to simultaneously measure the temperature, extinction, extinction law, distance, and existence of companions {resolved and unresolved} and, thus, produce clean HR diagrams with resolved cluster membership and much-reduced systematic uncertainties.

  11. Photometry and Spectroscopy of Short-Period Binary Stars in Four Old Open Clusters

    NASA Astrophysics Data System (ADS)

    Blake, R. M.; Rucinski, S. M.

    2004-12-01

    We have performed a spectroscopic and photometric study of six contact binary stars in four old open clusters, M67, Praesepe, NGC 6791 and NGC 752, in order to evaluate their suitability for measuring the distance to their respective clusters. The technique being tested uses the cosine Fourier coefficients of the light curves of the binary stars, and the mass ratios obtained spectroscopically, to provide distances to the binaries. The contact binary TX Cnc was used to obtain the distance to Praesepe, which we find to be (V - MV}){o = 6.30 ± 0.08, which is in good agreement with the values of V - MV = 6.20 - 6.35 found in color-magnitude diagram (CMD) studies. Our spectroscopic study of QX And in NGC 752 provided a distance modulus of (V - MV}){o = 8.30± 0.07 for this cluster. This compares to a value of (V - MV}){o = 7.9 ± 0.1 obtained by Milone et al. (1995) using the same star, but is in good agreement with V - MV = 8.25 ± 0.10 obtained by Daniel et al. (1994) from the CMD. We obtained a distance modulus of (V - MV}){o = 12.71 ± 0.44 for V7 in NGC 6791, the oldest cluster in our survey. This agrees within ˜ 1σ the values of 13.3 ≤ (V - MV) ≤ 13.42 obtained by isochrone fitting of the cluster CMD. EV Cnc in M67 did not yield a distance to the cluster from our procedure because of faintness of the system resulting in poor spectroscopic data. The distances to the clusters as determined from the contact binaries using our procedure do not seem to give systematically smaller or larger distances as compared to CMD fitting. However, we have measured the distances to only three clusters, and only one object per cluster, and so establishing any systematic differences may require a larger survey. R. M. Blake acknowledges the support of the Natural Science and Engineering Research Council of Canada through grants to S. M. Rucinski and C. T. Bolton.

  12. A Revised Gyro-Age for M 67 from Kepler/K2-Campaign-5 Light Curves

    NASA Astrophysics Data System (ADS)

    Gonzalez, Guillermo

    2016-09-01

    We revisit the photometric variability of stars in the M 67 field using Kepler/K2-Campaign-5 light curves. In our previous work, we limited the search area around M 67 to that of a recent ground-based study. In the present work, we expand the search area and apply a more rigorous period-finding algorithm to determine the rotation periods of 98 main sequence cluster members from the same data. In addition, we derive periods of 40 stars from the K2SC detrended light curves. We determine the mean period of single sun-like main sequence cluster members to be 29.6 ± 0.6 d. Assuming the periods correspond to stellar rotation, the corresponding mean gyro-age is 5.4 ± 0.2 Gyr.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Gravitational interactions between globular and open clusters: an introduction

    NASA Astrophysics Data System (ADS)

    de la Fuente Marcos, R.; de la Fuente Marcos, C.; Reilly, D.

    2014-01-01

    Historically, it has been assumed that globular and open clusters never interact. However, recent evidence suggests that: globular clusters passing through the disk may be able to perturb giant molecular clouds (GMCs) triggering formation of open clusters and some old open clusters may be linked to accreted globulars. Here, we further explore the existence of possible dynamical connections between globular and open clusters, and realize that the most obvious link must be in the form of gravitational interactions. If open clusters are born out of GMCs, they have to move in similar orbits. If we accept that globulars can interact with GMCs, triggering star formation, it follows that globular and open clusters must also interact. Consistently, theoretical arguments as well as observational evidence, show that globular and open clusters certainly are interacting populations and their interactions are far more common than usually thought, especially for objects part of the bulge/disk. Monte Carlo calculations confirm that conclusion. Globular clusters seem capable of not only inducing formation of open clusters but, more often, their demise. Relatively frequent high speed cluster encounters or cluster harassment may also cause, on the long-term, slow erosion and tidal truncation on the globulars involved. The disputed object FSR 1767 (2MASS-GC04) may be, statistically speaking, the best example of an ongoing interaction.

  19. Variability among stars in the M 67 field from Kepler/K2-Campaign-5 light curves

    NASA Astrophysics Data System (ADS)

    Gonzalez, Guillermo

    2016-06-01

    We examine the photometric variability of stars in the M 67 field using Kepler/K2-Campaign-5 light curves. Variabilities and periods were determined for 639 stars. The mean photometric period of 28 single Sun-like members stars in M 67 is 23.4 ± 1.2 d. This corresponds to a gyro-age of 3.7 ± 0.3 Gyr, assuming the periods can be associated with rotation. The intrinsic variabilities of the solar analogues are greater than the Sun's variability, as measure from VIRGO fluxes. We also find evidence that the single cluster members have a different distribution of variability than the binary members.

  20. 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.

  1. HR Diagrams of Open Clusters: A Virtual Observational Exercise from Project CLEA

    NASA Astrophysics Data System (ADS)

    Snyder, Glenn; Marschall, L. A.; Cooper, P. R.

    2007-12-01

    Project CLEA announces a new laboratory exercise on the analysis of HR Diagrams of Open Clusters. The new software allows students to examine plots of V vs B-V for any of 14 open clusters for which high quality data has been published in the literature. (E.g., NGC 752, Alpha Persei, M45, and M67) The clusters range in distance from about 50 to 2000 pc, and in age from 2 x 106 to 4.5 x 109 years. Students can overlay theoretical isochrones and ZAMS lines to these plots using sliders on an interactive tool to determine the distance, age, and even the metallicity of the cluster. Files of magnitudes and colors can be loaded directly into the plotting program, or students can carry out their own photometry using a simulated optical telescope and photometer or a simulated CCD camera that produces FITS files. A student manual provides information on the software and alternative exercises for in-class use and independent study. This exercise is the first that utilizes CLEA's new Virtual Educational Observatory, VIREO. VIREO is a simulated multi-wavelength observatory including optical, radio, infrared, and x-ray instrumentation very large-all-sky database, and access to catalog resources on the Web. The VIREO software provides an environment under which a wide variety of astronomical exercises can be carried out, from observations of asteroids, to searches for high-redshift quasars using a multi-slit spectrograph. The website of Project CLEA is http://public.gettysburg.edu/~marschal/clea/CLEAhome.html This research was sponsored by the National Science Foundation and Gettysburg College.

  2. HR Diagrams of Open Clusters: A Virtual Observational Exercise from Project CLEA

    NASA Astrophysics Data System (ADS)

    Snyder, Glenn; Marschall, L. A.; Cooper, P. R.

    2007-05-01

    Project CLEA announces a new laboratory exercise on the analysis of HR Diagrams of Open Clusters. The new software allows students to examine plots of V vs B-V for any of 14 open clusters for which high quality data has been published in the literature. (E.g., NGC 752, Alpha Persei, M45, and M67) The clusters range in distance from about 50 to 2000 pc, and in age from 2 x 106 to 4.5 x 109 years. Students can overlay theoretical isochrones and ZAMS lines to these plots using sliders on an interactive tool to determine the distance, age, and even the metallicity of the cluster. Files of magnitudes and colors can be loaded directly into the plotting program, or students can carry out their own photometry using a simulated optical telescope and photometer or a simulated CCD camera that produces FITS files. A student manual provides information on the software and alternative exercises for in-class use and independent study. This exercise is the first that utilizes CLEA’s new Virtual Educational Observatory, VIREO. VIREO is a simulated multi-wavelength observatory including optical, radio, infrared, and x-ray instrumentation very large-all-sky database, and access to catalog resources on the Web. The VIREO software provides an environment under which a wide variety of astronomical exercises can be carried out, from observations of asteroids, to searches for high-redshift quasars using a multi-slit spectrograph. The website of Project CLEA is http://www.gettysburg.edu/ marschal/clea/CLEAhome.html This research was sponsored by the National Science Foundation and Gettysburg College.

  3. WIYN Open Cluster Study. LXXI. Spectroscopic Membership and Orbits of NGC 6791 Sub-subgiants

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    In an optical color–magnitude diagram, sub-subgiants (SSGs) lie redward of the main sequence and fainter than the base of the red giant branch in a region not easily populated by standard stellar-evolution pathways. In this paper, we present multi-epoch radial velocities for five SSG candidates in the old and metal-rich open cluster NGC 6791 (8 Gyr, [Fe/H] = +0.30). From these data, we are able to make three-dimensional kinematic membership determinations and confirm four SSG candidates as likely cluster members. We also identify three member SSGs as short-period binary systems and present their orbital solutions. These are the first SSGs with known three-dimensional kinematic membership, binary status, and orbital parameters since the two SSGs in M67 studied by Mathieu et al. We also remark on the other properties of these stars including photometric variability, Hα emission, and X-ray luminosity. The membership confirmation of these SSGs in NGC 6791 strengthens the case that SSGs are a new class of nonstandard stellar evolution products, and that a physical mechanism must be found that explains the evolutionary paths of these stars.

  4. Dolidze-35: Results for a Possible Open Cluster

    NASA Astrophysics Data System (ADS)

    Gulledge, Deborah J.; Borges, Richard A.; Juelfs, Elizabeth; Allyn Smith, J.; Olive, Mary E.; McDonald, Christopher P.; Williams, Sarah M.; Cohen, Eden M.; Gawel, Jason D.; McCole, Bambi A.; Robertson, Jacob M.; Wilson, Tyler; Young, William J.; Buckner, Spencer L.; Allen, Nic R.; Head, H. Hope

    2016-01-01

    Dolidze-35 is an under-observed northern hemisphere open cluster. It is noted in WEBDA as "No data available for this cluster". As such, we chose this cluster as an undergraduate class project to investigate its existence. We present SDSS-ugriz magnitudes for the possible cluster and cross these with existing JHK data obtained from 2MASS. Selection of possible members is aided by the proper motion study of Krone-Martins (2010).

  5. 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

  6. 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).

  7. The Gaia-ESO Survey: Insights into the inner-disc evolution from open clusters

    NASA Astrophysics Data System (ADS)

    Magrini, L.; Randich, S.; Donati, P.; Bragaglia, A.; Adibekyan, V.; Romano, D.; Smiljanic, R.; Blanco-Cuaresma, S.; Tautvaišienė, G.; Friel, E.; Overbeek, J.; Jacobson, H.; Cantat-Gaudin, T.; Vallenari, A.; Sordo, R.; Pancino, E.; Geisler, D.; San Roman, I.; Villanova, S.; Casey, A.; Hourihane, A.; Worley, C. C.; Francois, P.; Gilmore, G.; Bensby, T.; Flaccomio, E.; Korn, A. J.; Recio-Blanco, A.; Carraro, G.; Costado, M. T.; Franciosini, E.; Heiter, U.; Jofré, P.; Lardo, C.; de Laverny, P.; Monaco, L.; Morbidelli, L.; Sacco, G.; Sousa, S. G.; Zaggia, S.

    2015-08-01

    Context. The inner disc, which links the thin disc with the bulge, has been somewhat neglected in the past because of the intrinsic difficulties in its study, among which crowding and high extinction. Open clusters located in the inner disc are among thebest tracers of its chemistry at different ages and distances. Aims: We analyse the chemical patterns of four open clusters located within 7 kpc of the Galactic centre and of field stars to infer the properties of the inner disc with the Gaia-ESO survey idr2/3 data release. Methods: We derive the parameters of the newly observed cluster, Berkeley 81, finding an age of about 1 Gyr and a Galactocentric distance of ~5.4 kpc. We construct the chemical patterns of clusters and we compare them with those of field stars in the solar neighbourhood and in the inner-disc samples. Results: Comparing the three populations we observe that inner-disc clusters and field stars are both, on average, enhanced in [O/Fe], [Mg/Fe], and [Si/Fe]. Using the idr2/3 results of M67, we estimate the non-local thermodynamic equilibrium (NLTE) effect on the abundances of Mg and Si in giant stars. After empirically correcting for NLTE effects, we note that NGC 6705 and Be 81 still have a high [α/Fe]. Conclusions: The location of the four open clusters and of the field population reveals that the evolution of the metallicity [Fe/H] and of [α/Fe] can be explained within the framework of a simple chemical evolution model: both [Fe/H] and [α/Fe] of Trumpler 20 and of NGC 4815 are in agreement with expectations from a simple chemical evolution model. On the other hand, NGC 6705, and to a lesser degree Berkeley 81, have higher [α/Fe] than expected for their ages, location in the disc, and metallicity. These differences might originate from local enrichment processes as explained in the inhomogeneous evolution framework. Based on observations collected with the FLAMES spectrograph at VLT/UT2 telescope (Paranal Observatory, ESO, Chile), for the Gaia

  8. Activity in M Dwarf Members of NGC 2516 and M67: Calibrating an Age-Activity Relation

    NASA Astrophysics Data System (ADS)

    Andersen, Jan M.; West, A. A.; Covey, K. R.; McDonald, M.; Veilleux, S.; Seth, A.

    2011-05-01

    We present preliminary results from a study of M dwarf magnetic activity in clusters of known ages with the ultimate goal of constraining the age-activity relation. The age-activity relation provides clues to the mechanisms generating magnetic dynamos, especially in late-type dwarfs where their stellar interiors become fully convective. Broadband griz photometry was obtained for four clusters with ages ranging from 150 Myrs to 4 Gyrs. Narrowband images of each cluster were acquired with the Maryland Magellan Tunable Filter, tuned to the frequency of H-alpha (including a correction for each cluster's radial velocity) and a nearby, similarly sized bandpass sampling the stellar pseudo-continuum. This permits a "photometric” measurement of the H-alpha emission for each star, and thus a measure of activity. Cluster membership is determined from broadband photometry and comparison to stellar positions from previous studies. We report on our findings for the clusters NGC 2516 and M67. H-alpha measurements are stronger for cluster stars than for field stars of the same magnitude. In NGC 2516, a clear correlation is seen between our H-alpha strengths measured by narrowband imaging and previous spectroscopic activity measurements in stars for which spectra have been obtained. J.M.A. acknowledges support through an NSF Graduate Research Fellowship.

  9. A Swift/UVOT Study of Open Clusters

    NASA Astrophysics Data System (ADS)

    LaPorte, Samuel; Siegel, Michael

    2016-01-01

    Star clusters, due to being coeval populations of similar stars, provide a convenient snapshot of a stellar population to study and compare to theoretical models of stellar evolution. They also serve as the empirical baseline for studies of distant unresolved stellar populations. However, few studies have been performed of detailed color-magnitude diagrams (CMDs) of young open clusters in the near ultraviolet. We present a sample of 92 open clusters compiled using Swift's Ultra-Violet and Optical Telescope (UVOT). We construct CMDs and perform isochrone fitting for the most luminous clusters to determine how well the theoretical models reproduce the salient features of the CMDs. We find that the isochrones provide excellent fits to the primary color-magnitude loci, lending confidence to models of unresolved stellar populations and providing, in the future, an opportunity to use open clusters to probe the UV properties of foreground dust.

  10. Looking for Interacting Binaries in Old Open Clusters

    NASA Technical Reports Server (NTRS)

    Grindley, Jonathan

    2005-01-01

    We requested a 12 ks observation of the old open cluster NGC7142 with the aim to investigate the population of interacting binaries, and compare the properties with those of interacting binaries in other old open clusters. Unfortunately, the observation suffered from long periods of background flaring, and as a result the effective exposure time was shortened to only approximately 25% of the planned exposure. The sensitivity to detect sources in the cluster was therefore much reduced, hampering a useful comparison with other clusters observed with Chandra and XMM. We detect 5 sources (all less than 300 counts) in the full field of view of the detectors; based on the large separations from the cluster center, we expect that at least 3-4 are not associated with the cluster. A brief paper that reports the results is in preparation.

  11. ZIRCONIUM, BARIUM, LANTHANUM, AND EUROPIUM ABUNDANCES IN OPEN CLUSTERS

    SciTech Connect

    Jacobson, Heather R.; Friel, Eileen D. E-mail: efriel@indiana.edu

    2013-04-15

    We present an analysis of the s-process elements Zr, Ba, and La and the r-process element Eu in a sample of 50 stars in 19 open clusters. Stellar abundances of each element are based on measures of a minimum of two lines per species via both equivalent width and spectrum synthesis techniques. We investigate cluster mean neutron-capture abundance trends as a function of cluster age and location in the Milky Way disk and compare them to results found in other studies in the literature. We find a statistically significant trend of increasing cluster [Ba/Fe] as a function of decreasing cluster age, in agreement with recent findings for other open cluster samples, supporting the increased importance of low-mass asymptotic giant branch stars to the generation of s-process elements. However, the other s-process elements, [La/Fe] and [Zr/Fe], do not show similar dependences, in contrast to theoretical expectations and the limited observational data from other studies. Conversely, cluster [Eu/Fe] ratios show a slight increase with increasing cluster age, although with marginal statistical significance. Ratios of [s/r]-process abundances, [Ba/Eu] and [La/Eu], however, show more clearly the increasing efficiency of s-process relative to r-process enrichment in open cluster chemical evolution, with significant increases among younger clusters. Last, cluster neutron-capture element abundances appear to be independent of Galactocentric distance. We conclude that a homogeneous analysis of a larger sample of open clusters is needed to resolve the apparent discrepant conclusions between different studies regarding s-process element abundance trends with age to better inform models of galactic chemical evolution.

  12. Photometry of the young open cluster Trumpler 37

    SciTech Connect

    Marschall, L.A.; Karshner, G.B.; Comins, N.F. Main, Univ., Orono )

    1990-05-01

    Photoelectric UBV observations of 120 stars in the young open cluster Trumpler 37 are presented, primarily in the magnitude range 10.0 - 13.5. An analysis of the color-magnitude diagram of the cluster yields an age of 6.7 million yr and reveals the presence of a number of possible pre-main-sequence stars in the cluster. 24 refs.

  13. Bayesian Inference of Kinematics and Memberships of Open Cluster

    NASA Astrophysics Data System (ADS)

    Shao, Z. Y.; Chen, L.; Zhong, J.; Hou, J. L.

    2014-07-01

    Based on the Bayesian Inference (BI) method, the Multiple-modelling approach is improved to combine coordinative positions, proper motions (PM) and radial velocities (RV), to separate the motion of the open cluster from field stars, as well as to describe the intrinsic kinematic status of the cluster.

  14. 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

  15. 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.

  16. X-ray sources in Galactic old Open Star Clusters

    NASA Astrophysics Data System (ADS)

    van den Berg, M.

    2013-01-01

    I review the current status of studies of the X-ray sources in Galactic old open clusters. Cataclysmic variables (CVs), magnetically-active binaries (ABs), and sub-subgiants (SSGs) dominate the X-ray emission of old open clusters. Surprisingly, the number of ABs detected inside the half-mass radius with LX ≥ 1 × 1030 erg s-1 (0.3-7 keV) does not appear to scale with cluster mass. Comparison of the numbers of CVs, ABs, and SSGs per unit mass in old open and globular clusters shows that each of these classes is under-abundant in globulars. This suggests that dense environments suppress the frequency of even some of the hardest binaries.

  17. 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.

  18. 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.

  19. Towards a photometric metallicity scale for open clusters

    NASA Astrophysics Data System (ADS)

    Netopil, M.; Paunzen, E.

    2013-09-01

    Context. Open clusters are a useful tool when investigating several topics connected with stellar evolution; for example the age or distance can be more accurately determined than for field stars. However, one important parameter, the metallicity, is only known for a marginal percentage of open clusters. Aims: We aim at a consistent set of parameters for the open clusters investigated in our photometric Δa survey of chemically peculiar stars. Special attention is paid to expanding our knowledge of cluster metallicities and verifying their scale. Methods: Making use of a previously developed method based on normalised evolutionary grids and photometric data, the distance, age, reddening, and metallicity of open clusters were derived. To transform photometric measurements into effective temperatures to use as input for our method, a set of temperature calibrations for the most commonly used colour indices and photometric systems was compiled. Results: We analysed 58 open clusters in total. Our derived metallicity values were in excellent agreement with about 30 spectroscopically studied targets. The mean value of the absolute deviations was found to be 0.03 dex, with no noticeable offset or gradient. The method was also applied using recent evolutionary models based on the currently accepted lower solar abundance value Z ~ 0.014. No significant differences were found compared to grids using the former adopted solar value Z = 0.02. Furthermore, some divergent photometric datasets were identified and discussed. Conclusions: The method provides an accurate way of obtaining properly scaled metallicity values for open clusters. In light of present and future homogeneous photometric sky surveys, the sample of stellar clusters can be extended to the outskirts of the Milky Way, where spectroscopic studies are almost impossible. This will help for determining galactic metallicity gradients in more detail. Figure 7 is available in electronic form at http://www.aanda.org

  20. 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.

  1. Two populations of open star clusters in the Galaxy

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

    Based on our compiled catalogue of fundamental astrophysical parameters for 593 open clusters, we analyze the relations between the chemical composition, spatial positions, Galactic orbital elements, age, and other physical parameters of open star clusters. We show that the population of open clusters is heterogeneous and is divided into two groups differing by their mean parameters, properties, and origin. One group includes the Galactic clusters formed mainly from the interstellar matter of the thin disk with nearly solarmetallicities ([Fe/H] > -0.2) and having almost circular orbits a short distance away from the Galactic plane, i.e., typical of the field stars of the Galactic thin disk. The second group includes the peculiar clusters formed through the interaction of extragalactic objects (such as high-velocity clouds, globular clusters, or dwarf galaxies) with the interstellar matter of the thin disk, which, as a result, derived abnormally low (for field thin-disk stars) metallicities and/or Galactic orbits typical of objects of the older Galactic subsystems. About 70% of the clusters older than 1Gyr have been found to be peculiar, suggesting a slower disruption of clusters with noncircular high orbits. Analysis of orbital elements has shown that the bulk of the clusters from both groups were formed within a Galactocentric radius of ≈10.5 kpc and closer than ≈180 pc from the Galactic plane, but owing to their high initial velocities, the peculiar clusters gradually took up the volumes occupied by the objects of the thick disk, the halo, and even the accreted halo of the Galaxy. Analysis of the relative abundances of magnesium (a representative of the α-elements) in clusters that, according to their kinematical parameters, belong to different Galactic subsystems has shown that all clusters are composed of matter incorporating the interstellar matter of a single protogalactic cloud in different proportions, i.e., reprocessed in genetically related stars of

  2. Singlet-paired coupled cluster theory for open shells.

    PubMed

    Gomez, John A; Henderson, Thomas M; Scuseria, Gustavo E

    2016-06-28

    Restricted single-reference coupled cluster theory truncated to single and double excitations accurately describes weakly correlated systems, but often breaks down in the presence of static or strong correlation. Good coupled cluster energies in the presence of degeneracies can be obtained by using a symmetry-broken reference, such as unrestricted Hartree-Fock, but at the cost of good quantum numbers. A large body of work has shown that modifying the coupled cluster ansatz allows for the treatment of strong correlation within a single-reference, symmetry-adapted framework. The recently introduced singlet-paired coupled cluster doubles (CCD0) method is one such model, which recovers correct behavior for strong correlation without requiring symmetry breaking in the reference. Here, we extend singlet-paired coupled cluster for application to open shells via restricted open-shell singlet-paired coupled cluster singles and doubles (ROCCSD0). The ROCCSD0 approach retains the benefits of standard coupled cluster theory and recovers correct behavior for strongly correlated, open-shell systems using a spin-preserving ROHF reference. PMID:27369507

  3. Primordial binary populations in low-density star clusters as seen by Chandra: globular clusters versus old open clusters

    NASA Astrophysics Data System (ADS)

    van den Berg, Maureen C.

    2015-08-01

    The binaries in the core of a star cluster are the energy source that prevents the cluster from experiencing core collapse. To model the dynamical evolution of a cluster, it is important to have constraints on the primordial binary content. X-ray observations of old star clusters are very efficient in detecting the close interacting binaries among the cluster members. The X-ray sources in star clusters are a mix of binaries that were dynamically formed and primordial binaries. In massive, dense star clusters, dynamical encounters play an important role in shaping the properties and numbers of the binaries. In contrast, in the low-density clusters the impact of dynamical encounters is presumed to be very small, and the close binaries detected in X-rays represent a primordial population. The lowest density globular clusters have current masses and central densities similar to those of the oldest open clusters in our Milky Way. I will discuss the results of studies with the Chandra X-ray Observatory that have nevertheless revealed a clear dichotomy: far fewer (if any at all) X-ray sources are detected in the central regions of the low-density globular clusters compared to the number of secure cluster members that have been detected in old open clusters (above a limiting X-ray luminosity of typically 4e30 erg/s). The low stellar encounter rates imply that dynamical destruction of binaries can be ignored at present, therefore an explanation must be sought elsewhere. I will discuss several factors that can shed light on the implied differences between the primordial close binary populations in the two types of star clusters.

  4. Properties of the Old Open Cluster Czernik 30

    NASA Astrophysics Data System (ADS)

    Hayes, Christian R.; Friel, Eileen D.; Slack, Taleah J.; Boberg, Owen M.

    2015-12-01

    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-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)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 Rgc ˜ 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.

  5. Radial velocity membership for the open cluster IC4756

    NASA Astrophysics Data System (ADS)

    Weingrill, Joerg; Geller, Aaron; Strassmeier, Klaus; Barnes, Sydney; Meibom, Soeren; Granzer, Thomas; Spada, Federico

    2013-08-01

    IC 4756 is an ~800 Myr-old nearby (500 pc) open cluster that conveniently splits the difference in age between the well-studied Hyades (625 Myr) and NGC 6811 (1 Gyr) clusters. As a result, measuring IC 4756 rotation periods offers us the chance to test the universality of the intermediate-age rotational evolution of stars independent of any theoretical models. Therefore we have performed precision time-series photometry of the IC 4756 field with the CoRoT satellite, and derived 111 main sequence rotation periods in the cluster region. We have also acquired new multicolor Stromgren photometry of the cluster. However, heavy differential reddening and imprecise membership information do not yet allow a satisfactory determination of the cluster parameters and membership, far less interpretation of the rotation periods. We propose here to use WIYN+Hydra to securely identify the cluster members, determine the cluster parameters, and to fully interpret the corresponding color-period diagram. This work will provide a new benchmark open cluster for the community, and help to develop the associated study of stellar rotation and gyrochronology.

  6. The old, massive, metal rich open cluster NGC 6791

    NASA Astrophysics Data System (ADS)

    Carraro, Giovanni

    2015-08-01

    NGC~6791 is a rich open cluster that attracted a lot of attention in the last decade. Recent estimates indicate that the mass is even larger, around 5000\\,$\\mathrm{M}_{\\odot}$. This is quite remarkable: the cluster is in fact 8\\,Gyr old, while the typical dissolution time for Galactic open clusters is a few Myr only. This might imply that the cluster managed to survive so long either because its original mass was much larger, or because it moved along a preferential orbit. In any case, such combination of old age and large mass is unique among Galactic open clusters, especially for clusters located in the inner regions of the Galactic disk. This is not the only special property of NGC 6791. Its abundance in iron is [Fe/H] $\\sim$ +0.40. again unique among Galactic star clusters of the same age range. Significant dispersions in various elements have been detected, that are not routinely found in Galactic open clusters. The combined UV flux of the few hot HB stars makes the cluster the closest proxy of an elliptical galaxy. This surprising result might indeed indicate that NGC 6791 was massive enough at origin to experience a strong burst of star formation and a fast enrichment.This pletora of unique properties renders NGC 6791 an extremely important object to study and understand.How and where could such a stellar system have formed? Is NGC 6791 just an open cluster? Did it form close to the bulge? How could have survived in the adverse, high-density, environment of the inner Galactic disk?These are difficult questions to answer to, of course. One of the still missing key observational evidence is whether the cluster suffered from tidal interaction, that could have significantly decreased its mass. We find such evidences, and use them as an argument to support a scenario in which the cluster formed as a massive object. We also estimate, using approximate analytic description based on available $N$-body models, how much mass NGC~6791 lost, and which was its

  7. Radial velocities of three poorly studied clusters and the kinematics of open clusters

    SciTech Connect

    Hayes, Christian R.; Friel, Eileen D. E-mail: efriel@indiana.edu

    2014-04-01

    We present radial velocities for stars in the field of the open star clusters Berkeley 44, Berkeley 81, and NGC 6802 from spectra obtained using the Wisconsin-Indiana-Yale-NOAO (WIYN) 3.5 m telescope. These clusters are of intermediate age (1-3 Gyr), located within the solar Galactocentric radius, and have no previous radial velocity measurements. We find mean radial velocities of –9.6 ± 3.0 km s{sup –1}, 48.1 ± 2.0 km s{sup –1}, and 12.4 ± 2.8 km s{sup –1} for Be 44, Be 81, and NGC 6802, respectively. We present an analysis of radial velocities of 134 open clusters of a wide range of ages using data obtained in this study and the literature. Assuming the system of clusters rotates about the Galactic center with a constant velocity, we find older clusters exhibit a slower rotation and larger line-of-sight (LOS) velocity dispersion than younger clusters. The gradual decrease in rotational velocity of the cluster system with age is accompanied by a smooth increase in LOS velocity dispersion, which we interpret as the effect of heating on the open cluster system over time.

  8. 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.

  9. 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.

  10. Mass-losing red giants in open clusters

    NASA Technical Reports Server (NTRS)

    Jura, M.

    1987-01-01

    Mass-losing stars in open clusters with main-sequence turn-offs at intermediate mass have been searched for by using the IRAS data base. The absence of many strong 60 micron sources in open clusters implies that intermediate-mass stars lose much of their mass during an intense wind phase of rather short duration. For stars of about seven solar masses, this phase, if it exists at all, lasts for not much more than 100,000 yr. For stars of about four solar masses, the intense wind phase appears to last considerably less than 10 million yr; it may well last for less than a million yr.

  11. A detailed study of the open cluster PISMIS 20.

    NASA Astrophysics Data System (ADS)

    Vazquez, R. A.; Will, J.-M.; Prado, P.; Feinstein, A.

    1995-05-01

    The very young open cluster Pis 20 has been investigated using CCD UBVR photometry. New blue faint members were found down to V=19mag. With them we obtain a better definition of the lower cluster main sequence. Using the fitting method, we derive a cluster distance of d=3600pc (V_0_-M_V_=12.80). The mean color excess is =1.24mag. From the observed characteristics and spatial location of the bluest cluster stars we conclude that the star WR 67 has a good chance to be a cluster member. In that case, the mass of its progenitor should be greater than 50Msun_ according to evolutionary models. We obtain for Pis 20 an age of 5(+/-1)x10^6^yr from isochrone fitting. We discuss the cluster's mass spectrum whose slope, within the observational uncertainties, appears to be similar to the one in Salpeter's law. We notice that high WR/OB and WC/WN number ratios are present not only within the cluster itself but also in the association where Pis 20 is situated. Although the cluster distance derived here places Pis 20 nearer than the supernova remnant MSH 15-52, we cannot/rule out the possibility that they are spatially related. The presently observed cluster mass is around 600Msun_.

  12. 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.

  13. Commentary on interstellar matter associated with 18 open clusters

    NASA Technical Reports Server (NTRS)

    Leisawitz, David

    1989-01-01

    Information supplementary to that contained in Section 4 of an article entitled, A CO Survey of Regions Around 34 Open Clusters, (Leisawitz, Bash, and Thaddeus) published in the Astrophysical Journal Supplement Series, Volume 70, Number 4, August 1989 is summarized. The information presented here, which describes the interstellar environments of young clusters and some cluster physical characteristics, comes from observations published in the astronomical literature and the author's carbon monoxide (CO) emission line survey, and may help clarify our understanding of the interaction of massive stars with the interstellar medium.

  14. WIYN Open Cluster Study. LXVI. Spectroscopic Binary Orbits in the Young Open Cluster M35 (NGC 2168)

    NASA Astrophysics Data System (ADS)

    Leiner, E. M.; Mathieu, R. D.; Gosnell, N. M.; Geller, A. M.

    2015-07-01

    The young (150 Myr) open cluster M35 (NGC 2168) has been one of the core clusters of the WIYN Open Cluster Study since 1997. Over these 17 years we have obtained approximately 8000 radial-velocity (RV) measurements of stars in the M35 field, which we provide here. Our target sample consists of 1355 photometrically selected stars in the field of M35 within the main sequence and binary sequence of the cluster and within 13≤slant V≤slant 16.5 and (B-V)≥slant 0.6. Using our RV measurements we cleanly separate likely cluster members from field stars. We calculate RV membership probabilities for over 1200 stars in our sample. 418 are probable cluster members, of which 64 are velocity-variable (binary) systems. Here we present 52 orbital solutions for binary members of M35. This sample defines the hard binary population of M35 that dynamically powers the cluster. We also present XMM-Newton X-ray detections within the cluster. We use our large binary sample to search for interacting binaries among the X-ray sources, investigate M35's period-eccentricity distribution, and determine binary frequency. We find a circularization period of 9.9 ± 1.2 days and a binary frequency of 24% ± 3% for main-sequence binaries with P\\lt {10}4 days. Determining these properties in a young cluster like M35 is key to defining the initial conditions used in models of cluster dynamical evolution.

  15. The Blue Stragglers of the Old Open Cluster NGC 188

    NASA Astrophysics Data System (ADS)

    Mathieu, Robert D.; Geller, Aaron M.

    The old (7 Gyr) open cluster NGC 188 has yielded a wealth of astrophysical insight into its rich blue straggler population. Specifically, the NGC 188 blue stragglers are characterised by: A binary frequency of 80 % for orbital periods less than 104 days;

  16. 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…

  17. Determining Cluster Reddenings: A New Method

    NASA Astrophysics Data System (ADS)

    Miller, Nathan A.; Hong, Linh N.; Friel, Eileen D.; Janes, Kenneth A.

    1995-12-01

    We have developed a technique for determining the reddening to open clusters by using the equivalent width of the Balmer line, Hβ , to determine the intrinsic color of early-type stars in the clusters' fields. Our technique attempts to quantify spectral classification in spectra of moderate resolution using the temperature sensitivity of the Hβ line. We also use the strength of secondary indicators like Mgb (5170 Angstroms) to help distinguish spectral type for stars near A0, where the H-line strength is double-valued with respect to color. Members of the well-studied open cluster M67 were used to develop the calibration. The moderate resolution spectra used in this project were taken with the multi-object spectrographs at the CTIO and KPNO 4-meter telescopes. The calibrating cluster M67 could be observed from both sites, allowing the two data sets to be consistently combined. The two observations of M67 also resulted in a large number of calibrating stars, giving a well-defined relationship between (Hβ ) strength and intrinsic color for stars of known luminosity class. The calibration has been applied to obtain estimates of intrinsic color and thus reddening to individual stars in the fields of a number of open clusters, and the distribution of reddening with distance then constrains the reddening along the line of sight to the clusters. For clusters whose parameters are known, the technique gives excellent agreement with previously published estimates of reddening. The method also provides reddening estimates to a number of open clusters that lack estimates of reddening by traditional methods, such as King 5 and 11, Be 17, 20, 31, 32, and 39, To 2, Pi 2, Cr 261. These clusters include the oldest and most distant open clusters known, and improved estimates of their reddening are crucial for accurate determinations of cluster age and metallicity.

  18. 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

  19. 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.

  20. Stellar multiplicity of the open cluster ASCC 113

    SciTech Connect

    Guerrero, C. A.; Orlov, V. G.; Monroy-Rodríguez, M. A.; Voitsekhovich, V. V. E-mail: orlov@astro.unam.mx E-mail: voisteko@astro.unam.mx

    2014-02-01

    We present a high angular resolution survey for binary and multiple stars in the Galactic open cluster ASCC 113. Our observations were conducted on the 2.1 m telescope of the Observatorio Astronómico Nacional, Sierra San Pedro Mártir, México. Combining our results with data taken from the literature, we found a ratio of the number of single to binary stars to be 27:7 for the most probable members, so the multiplicity fraction for this cluster is 20.6% ± 3%. We also observed field stars in the vicinity of the cluster and estimated a ratio of multiplicities to be 125:27:4:1:0:0:0:1 (between one and eight companions), equivalent to a multiplicity fraction of 20.9% ± 1%. We estimated the number of undetected companions in our sample to be very small. Comparing the multiplicity frequency of the cluster with the frequency of the field, we concluded that they are statistically indistinguishable from each other. We provide a brief review on the topic of stellar multiplicity in open clusters.

  1. Stellar Multiplicity of the Open Cluster ASCC 113

    NASA Astrophysics Data System (ADS)

    Guerrero, C. A.; Orlov, V. G.; Monroy-Rodríguez, M. A.; Voitsekhovich, V. V.

    2014-02-01

    We present a high angular resolution survey for binary and multiple stars in the Galactic open cluster ASCC 113. Our observations were conducted on the 2.1 m telescope of the Observatorio Astronómico Nacional, Sierra San Pedro Mártir, México. Combining our results with data taken from the literature, we found a ratio of the number of single to binary stars to be 27:7 for the most probable members, so the multiplicity fraction for this cluster is 20.6% ± 3%. We also observed field stars in the vicinity of the cluster and estimated a ratio of multiplicities to be 125:27:4:1:0:0:0:1 (between one and eight companions), equivalent to a multiplicity fraction of 20.9% ± 1%. We estimated the number of undetected companions in our sample to be very small. Comparing the multiplicity frequency of the cluster with the frequency of the field, we concluded that they are statistically indistinguishable from each other. We provide a brief review on the topic of stellar multiplicity in open clusters.

  2. 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).

  3. Open cluster membership probability based on K-means clustering algorithm

    NASA Astrophysics Data System (ADS)

    El Aziz, Mohamed Abd; Selim, I. M.; Essam, A.

    2016-05-01

    In the field of galaxies images, the relative coordinate positions of each star with respect to all the other stars are adapted. Therefore the membership of star cluster will be adapted by two basic criterions, one for geometric membership and other for physical (photometric) membership. So in this paper, we presented a new method for the determination of open cluster membership based on K-means clustering algorithm. This algorithm allows us to efficiently discriminate the cluster membership from the field stars. To validate the method we applied it on NGC 188 and NGC 2266, membership stars in these clusters have been obtained. The color-magnitude diagram of the membership stars is significantly clearer and shows a well-defined main sequence and a red giant branch in NGC 188, which allows us to better constrain the cluster members and estimate their physical parameters. The membership probabilities have been calculated and compared to those obtained by the other methods. The results show that the K-means clustering algorithm can effectively select probable member stars in space without any assumption about the spatial distribution of stars in cluster or field. The similarity of our results is in a good agreement with results derived by previous works.

  4. Chemical Abundances of Solar-Type Dwarfs in Open Clusters

    NASA Astrophysics Data System (ADS)

    Schuler, S. C.

    2005-12-01

    Open clusters present homogeneous samples of stars that are of the same age, distance, and initial chemical composition, making open clusters valuable observational targets for studies of stellar evolution, stellar structure, exoplanetary systems, and Galactic chemical evolution. I present an overview of my graduate dissertation research on LTE abundances of solar-type dwarfs (4200 ≲ T eff ≲ 6400 ; {K}) in the open clusters Pleiades, M34, and Hyades, as well as in the Ursa Major moving group. For the dwarfs of intermediate T eff (5500 ≲ T eff ≲ 6100 ; {K}), intracluster metal abundances are in good agreement. Conversely, we have identified excitation/ionization-related abundance anomalies among the cool dwarfs (T eff ≤ 5500 ; {K}) of all three clusters and UMa; for example, O abundances derived from the high-excitation, near-IR \\ion{O}{1} triplet show a dramatic increase with decreasing T eff, a behavior that is not predicted by current non-LTE calculations. Intercluster comparisons are suggestive of an age-related diminution of the \\ion{O}{1} triplet abundance trend, and possible causes of these observed abundance anomalies, i.e., chromospheric activity, surface inhomogeneities, etc., are explored. Using multi-component ``toy model'' stellar atmospheres, we demonstrate that the \\ion{O}{1} triplet abundance trend may be due to inhomogeneous temperature structure, possibly resulting from spots or plages, in the photospheres of cool open cluster dwarfs. I gratefully acknowledge the following agencies that have provided support during this research: NSF (through grants AST 00-86576 and AST 02-39518 to Prof. J.R. King), South Carolina Space Grant Consortium (through the Graduate Student Research Fellowship program), and the Charles Curry Foundation (through a generous grant to Clemson University).

  5. Refining the true parameters of the open cluster NGC 4852

    NASA Astrophysics Data System (ADS)

    Solivella, Gladys; Giorg, Edgard; Vázquez, Rubén; Carraro, Giovanni

    2010-01-01

    NGC 4852 is a moderately compact cluster centered at α2000 = 13 : 00 : 09; δ = -59 : 36 : 48, located near the center of an Hα superring. This cluster forms part of an extended region including young stellar aggregates inside a circle with a radius of 3 degrees, where many show an abundance of emission line stars. In the field of this cluster, two stars of known type exist: Wray 15-1039 (emission-line object) and CD -58:4845 (emission-line star). We do not yet know whether the Be phase is transient or whether it is just what randomly happens in some hot stars. It appears that Be star may be found even in clusters as old as 70 Myr with a high occurrence rate in clusters of 25-27 Myr old. A recent photometric survey in NGC 4852 down to V = 22 - 23 mag established that NGC 4852 is about 200 - 250 Myr old, located at 1.1 kpc from the Sun and with a mean E(B - V) = 0.45 mag. Since the presence of potential Be-type stars in the cluster area suggests it may be a very young object instead of moderately old, we decided to carry out spectroscopy for 33 selected stars and CCD UBVI photometry for the bright objects in the cluster area. This way, we attempt to clarify their evolutionary state and include them in the framework of emission-line stars and open clusters. From our analysis, we agree with the cluster distance and reddening determined by earlier studies, but we derive that the age of NGC 4852 is younger than 40 Myr.

  6. 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.

  7. VizieR Online Data Catalog: Open clusters in Auriga OB2 (Marco+, 2016)

    NASA Astrophysics Data System (ADS)

    Marco, A.; Negueruela, I.

    2016-05-01

    We present tables with coordinates in J2000, near IR photometry and Stromgren photometry for stars in the open cluster Stock 8 and in the two new open clusters: Alicante 11 and Alicante 12 (7 data files).

  8. 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.

  9. Studies of Open Clusters using 50BiN

    NASA Astrophysics Data System (ADS)

    Deng, Licai; Xin, Yu; Zhang, Xiaobin; Wang, Kun; Luo, Changqing

    2015-08-01

    50BiN (50cm Binocular Network) is a sub-program of SONG, funded by Chinese participating universities. The Science goals is to do simulteneous two-color widep-field photometry of Galactic open clusters in time-domain, and to study the fundamental properties of the clusters and to search variable objects in a systematic manner. The proto-type node, located in West-China, is now in operation. The science plan of the program and some preliminary results will be presented.

  10. 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.

  11. UBV Photometry of the young open cluster Berkely 87

    NASA Astrophysics Data System (ADS)

    Akinyemi, Abolaji; Eskridge, Paul B.

    2015-01-01

    We obtained UBV imaging of a field in the young open cluster Berkeley 87. From these images, we measured the brightness of ~180 stars in the cluster. Our photometry was calibrated using published photometry (Turner & Forbes 1982 PASP 94, 789) of a subset of stars in our field. The cluster is in a region of the sky with strongly varying extinction. Therefore we made a (U-B)-(B-V) color-color diagram of the field and used this to de-redden the stars on a case by case basis. We de-reddened the stars using the unreddened supergiant and main sequence colors from Astrophysical Quantities (Cox 2000).The color-magnitude diagrams of the de-reddened stars are compared to the Padova isochrones(Marigo et al 2008 A&A 482 883). The isochrones are generated for a range of ages, with solar metalicity and no α enhancement. The best fit for the isochrones was the main sequence de-reddened stars from which the age of the cluster is estimated to be 20 million years. This is older than previous age estimates (1-5 million years) from earlier studies of the cluster. This may indicate age variation in the cluster.We acknowledge the support of the Physics and Astronomy department, and the College of Science and Engineering, Minnesota State University, Mankato.

  12. 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.

  13. 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.

  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. 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.

  16. 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

  17. Photometrically determined membership of the young, open cluster IC 2391

    NASA Astrophysics Data System (ADS)

    Rolleston, W. R. J.; Byrne, P. B.

    1997-12-01

    New 4-colour BV(RI)KC CCD photometry to a limiting magnitude of V ~19 is presented for 1428 objects observed towards the direction of the young, open cluster IC 2391. We observed 36 (2' X 3') fields within 17 arcmin of the nominal cluster core. By fitting the theoretical isochrones of \\cite[D'Antona & Mazzitelli (1994]{Dan94}) to a combination of colour-magnitude and colour-colour diagrams, we have identified 17 stars as probable cluster members with a further 85 stars as possible members. The brightness distribution of low-mass members is compared with the luminosity function observed for the Pleiades and we estimate that the contamination due to background giants should be small. Figure 4 is only available in electronic form via http://www.ed-phys.fr

  18. 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.

  19. Open-Cluster Population of Sh 2-109

    NASA Astrophysics Data System (ADS)

    LeMieux, Henri; Kaltcheva, Nadia

    2016-01-01

    The prominent nebulosity Sh 2-109 that dominates the Cygnus star-forming field is probably a complex of several overlapping H II regions. Since in this direction the line of sight is along the local Orion spiral arm, the isolation of individual stellar and interstellar structures is difficult. This study is focused on the massive stellar content of Sh 2-109 with the purpose of providing new insights on its structure. We use the catalog of optically visible open clusters and candidates (Dias et al. 2014) to study the properties of the open-cluster population within the boundaries of the Sh 2-109 star-forming region. We also utilize photometric uvbyβ data for the massive stars in Sh 2-109. This data set includes more than 10 young open clusters. Since the intermediate-band uvbyβ photometry allows the derivation of stellar physical parameters with high precision, we provide homogeneous distance and age estimates to the OB-associations identified toward Sh 2-109. Based on all the data we map the structure of the field in order to further study its morphology and energetics. Acknowledgments. This work was supported by NSF grant AST- 1516932.

  20. Detailed chemical composition of the open cluster IC 4651: The iron peak, α elements, and Li

    NASA Astrophysics Data System (ADS)

    Pasquini, L.; Randich, S.; Zoccali, M.; Hill, V.; Charbonnel, C.; Nordström, B.

    2004-09-01

    We present a detailed chemical analysis of 22 stars along the colour-magnitude sequence of the intermediate-age (1.7 Gyr) open cluster IC 4651, based on high-resolution, high S/N ratio spectra from UVES/VLT. IC 4651 thus becomes one of the few open clusters for which a detailed composition analysis exists for stars spanning 3.5 mag, from solar-type main-sequence stars to giants above the RGB clump. In a strict comparison with the Sun, we find for the cluster a well-defined Fe abundance of [Fe/H] = 0.10 ± 0.03 (internal errors), with a reddening E(b-y) = 0.091. We also derive abundances for the α elements Mg, Si, Ti, and Ca and find a moderate enhancement of the three former elements, in excellent agreement with the results for field stars of similar Fe abundance. Among the Fe group elements, Cr and Ni are slightly overabundant ([X/Fe] ˜ 0.05). As also observed in M 67, the Na abundance among the giants is more than 0.2 dex higher than in the dwarfs. We interpret this effect as real, and due to dredge-up of 23Na in the giants. Four turnoff stars, all fairly rapid rotators (v sin i ≥ 25 km s-1), appear to have higher [Fe/H] than the other stars; our tests show that, while a spurious enhancement of 0.1 dex can be produced by the effect of high rotation on our spectral analysis, this cannot explain the whole difference. These stars appear overabundant because we tend to overestimate their effective temperatures by forcing excitation equilibrium. Li abundances have been computed for all the stars and show a well-defined pattern: the Solar-type stars have an almost constant Li abundance, just below that of the Hyades, and the Li-dip is pronounced and well determined. Turnoff stars just above the dip have a ``cosmic'' Li abundance, but within a very small range of magnitudes (0.25 mag) higher on the turnoff, the Li level drops by more than a factor 10. This cannot be due just to dilution; rather some extra mixing is required. Among the giants, two probable clump

  1. 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.

  2. 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.

  3. 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

  4. Spectroscopic Abundances in the Open Cluster NGC 6819

    NASA Astrophysics Data System (ADS)

    Lee-Brown, Donald B.; Anthony-Twarog, Barbara J.; Deliyannis, Constantine P.; Rich, Evan; Twarog, Bruce A.

    2015-04-01

    High-dispersion spectra of 333 stars in the open cluster NGC 6819, obtained using the HYDRA spectrograph on the WIYN 3.5 m telescope, have been analyzed to determine the abundances of iron and other metals from lines in the 400 Å region surrounding the Li 6708 Å line. Our spectra, with signal-to-noise per pixel ranging from 60 to 300, span the luminosity range from the tip of the red giant branch to a point two magnitudes below the top of the cluster turnoff. We derive radial and rotational velocities for all stars, as well as [Fe/H] based on 17 iron lines, [Ca/H], [Si/H], and [Ni/H] in the 247 most probable, single members of the cluster. Input Teff estimates for model atmosphere analysis are provided by (B-V) colors merged from several sources, with individual reddening corrections applied to each star relative to a cluster mean of E(B-V) = 0.16. Extensive use is made of ROBOSPECT, an automatic equivalent width measurement program; its effectiveness on large spectroscopic samples is discussed. From the sample of likely single members, [Fe/H] = -0.03 ± 0.06, where the error describes the median absolute deviation about the sample median value, leading to internal precision for the cluster below 0.01 dex. The final uncertainty in the cluster abundance is therefore dominated by external systematics due to the temperature scale, surface gravity, and microturbulent velocity, leading to [Fe/H] = -0.02 ± 0.02 for a sub-sample restricted to main sequence and turnoff stars. This result is consistent with our recent intermediate-band photometric determination of a slightly subsolar abundance for this cluster. [Ca/Fe], [Si/Fe], and [Ni/Fe] are determined to be solar within the uncertainties. NGC 6819 has an abundance distribution typical of solar metallicity thin disk stars in the solar neighborhood. WIYN Open Cluster study LXV.

  5. 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.

  6. 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.

  7. Open cluster detection in extensive sky regions using astrometric parameters

    NASA Astrophysics Data System (ADS)

    Paíz, L. G.; De Biasi, M. S.; Orellana, R. B.

    2014-10-01

    We developed a non-parametric method for identifying open clusters in large areas of the sky using stellar position and proper motions. Two binary codes were established from the analysis of the empirical probability density functions in position and proper motion, after eliminating field stars contamination. For each star, these codes provided a parameter indicating the star belongingness to spatial and proper motion overdensities. The method was tested in a region of 4°×5° where Collinder 140 and Collinder 132 are located. 1300 stars up to the magnitude R=11 were obtained from UCAC2 and its supplement UCAC2 BSS catalogue. We detected six stellar groups having spatial and proper motion overdensities. A detailed analysis revealed that three of them could be open clusters. We confirmed that one of them is Collinder 140, for which mean coordinates (mathaccent α,mathaccent δ)=(110.8°,-32.0°), a radius of about 12' and mean proper motion components (mathaccent μ_{α} cosδ,mathaccent μ_{δ})=(9,4) mas/yr were obtained, in good agreement with the literature. The other two possible clusters have members fainter than magnitude 10.0 and they are not found in the literature. Related to Collinder 132, the low density of the data used in the area did not allow to detect it.

  8. Open clusters in the Third Galactic Quadrant III. Alleged binary clusters

    NASA Astrophysics Data System (ADS)

    Vázquez, R. A.; Moitinho, A.; Carraro, G.; Dias, W. S.

    2010-02-01

    Aims: We aim to determine accurate distances and ages of eight open clusters in order to: (1) assess their possible binarity (2) provide probes to trace the structure of the Third Galactic Quadrant. Methods: Cluster reddenings, distances, ages and metallicities are derived from ZAMS and isochrone fits in UBVRI photometric diagrams. Field contamination is reduced by restricting analysis to stars within the cluster limits derived from star counts. Further membership control is done by requiring that stars have consistent positions in several diagrams and by using published spectral types. Results: The derived distances, ages and metallicities have shown that none of the analysed clusters compose binary/double systems. Of the four candidate pairs, only NGC 2383/NGC 2384 are close to each other, but have different metallicities and ages. Ruprecht 72 and Ruprecht 158 are not clusters but fluctuations of the field stellar density. Haffner 18 is found to be the superposition of two stellar groups at different distances: Haffner 18(1) at 4.5 kpc and Haffner 18(2) between 9.5 and 11.4 kpc from the Sun. The derived distances and ages have been used to situate the clusters in the Galactic context. In particular, young stellar groups trace spiral structure at large Galactocentric radii. At least two clusters formed during the last few 108 yr in an interstellar medium with less than solar abundances. Conclusions: In contrast with the LMC, double clusters are apparently rare, or even non existent, in the undisturbed environment of the Third Galactic Quadrant. This leaves open the question of whether binary clusters form more easily toward denser and more violent regions of the Milky Way such as the inner Galaxy. The original photometry is only available in electronic form at 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/511/A38on leave from Dipartimento di Astronomia, Università di Padova, Vicolo Osservatorio 2

  9. 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.

  10. CCD UBV(RI)C photometry of twenty open clusters

    NASA Astrophysics Data System (ADS)

    Oralhan, İnci Akkaya; Karataş, Yüksel; Schuster, William J.; Michel, Raúl; Chavarría, Carlos

    2015-01-01

    Fundamental astrophysical parameters have been derived for 20 open clusters (OCs) using CCD UBV(RI)C photometric data observed with the 84 cm telescope at the San Pedro Mártir National Astronomical Observatory, México. The interstellar reddenings, metallicities, distances, and ages have been compared to the literature values. Significant differences are usually due to the usage of diverse empirical calibrations and differing assumptions, such as concerning cluster metallicity, as well as distinct isochrones which correspond to differing element-abundance ratios, internal stellar physics, and photometric systems. Different interstellar reddenings, as well as varying reduction and cluster-membership techniques, are also responsible for these kinds of systematic differences and errors. The morphological ages, which are derived from the morphological indices (δV and δ1) in the CM diagrams, are in good agreement with the isochrone ages of 12 OCs, those with good red clump (RC) and red giant (RG) star candidates. No metal abundance gradient is detected for the range 6.82⩽RGC⩽15.37 kpc, nor any correlation between the cluster ages and metal abundances for these 20 OCs. Young, metal-poor OCs, observed here in the third Galactic quadrant, may be associated with stellar over-densities, such as that in Canis Major (Martin et al.) and the Monoceros Ring (Newberg et al.), or signatures of past accretion events, as discussed by Yong et al. and Carraro et al.

  11. 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 ☉}.

  12. 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.

  13. A new look at open cluster NGC 6520

    SciTech Connect

    Odell, Andrew P.

    2014-01-01

    We use CCD and photoelectric photometry with Strömgren filters along with medium resolution spectra to investigate NGC 6520, an open cluster very nearly in the direction of the galactic center. We find an age of 60 Myr, a distance of 2 kpc, and an average reddening E(b – y) = 0.295, which increases toward the south. The average heliocentric radial velocity of the B stars is –29 km s{sup –1}, while the velocity of the nearby Barnard 86 is about 0 (heliocentric; –11 km s{sup –1} compared to the LSR). This velocity difference amounts to about 1.8 kpc since the cluster formed, implying that it is extremely doubtful NGC 6520 is related to Barnard 86.

  14. The Galactic open cluster system: evidence of enhanced formation episodes

    NASA Astrophysics Data System (ADS)

    Piatti, A. E.

    The exciting debate about the existence of signs of enhanced formation of Galactic open clusters (OCs) is revisited here on the basis of a revised age distribution. By using the recently updated 2009 version of the Dias et al. catalogue of 1787 OCs, we found that the present OC's age distribution presents two primary excesses at t ~ 10-15 Myr and 1.5 Gyr. We interpret both excesses as signs of enhanced formation episodes similar to those that occurred in other galaxies (e.g., M 51, NGC 1705). When restricting the OC sample to those located in the solar neighbourhood, with the aim of avoiding incompleteness effects, we also find that these clusters are engraved with clear signs of enhanced formation at both ages.

  15. 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.

  16. Assembly of open clusters of colloidal dumbbells via droplet evaporation

    NASA Astrophysics Data System (ADS)

    Pham Van, Hai; Fortini, Andrea; Schmidt, Matthias

    2016-05-01

    We investigate the behavior of a mixture of asymmetric colloidal dumbbells and emulsion droplets by means of kinetic Monte Carlo simulations. The evaporation of the droplets and the competition between droplet-colloid attraction and colloid-colloid interactions lead to the formation of clusters built up of colloid aggregates with both closed and open structures. We find that stable packings and hence complex colloidal structures can be obtained by changing the relative size of the colloidal spheres and/or their interfacial tension with the droplets.

  17. A multiwavelength polarimetric study towards the open cluster NGC 1893

    NASA Astrophysics Data System (ADS)

    Eswaraiah, C.; Pandey, A. K.; Maheswar, G.; Medhi, Biman J.; Pandey, J. C.; Ojha, D. K.; Chen, W. P.

    2011-03-01

    We present multiwavelength linear polarimetric observations for 44 stars of the NGC 1893 young open cluster region along with V-band polarimetric observations of stars of four other open clusters located between l˜ 160° and 175°. We found evidence for the presence of two dust layers located at a distance of ˜170 and ˜360 pc. The dust layers produce a polarization PV˜ 2.2 per cent. It is evident from the clusters studied in this work that, in the Galactic longitude range from l˜ 160° to 175° and within the Galactic plane (|b| < 2°), the polarization angles remain almost constant, with a mean of ˜163° and a dispersion of 6°. The small dispersion in polarization angle could be due to the presence of a uniform dust layer beyond 1 kpc. Present observations reveal that in the case of NGC 1893, the foreground two dust layers, in addition to the intracluster medium, seem to be responsible for the polarization effects. It is also found that towards the direction of NGC 1893, the dust layer that exists between 2 and 3 kpc has a negligible contribution towards the total observed polarization. The weighted mean for percentage of polarization (Pmax) and the wavelength at maximum polarization (λmax) are found to be 2.59 ± 0.02 per cent and 0.55 ± 0.01 μm, respectively. The estimated mean value of λmax indicates that the average size of the dust grains within the cluster is similar to that in the general interstellar medium. The spatial variation of the polarization is found to decrease towards the outer region of the cluster. In this work, we support the notion, as has already been shown in previous studies, that polarimetry, in combination with the (U-B)-(B-V) colour-colour diagram, is a useful tool for identifying non-members in a cluster.

  18. 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

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. Cage Opening of a Carborane Ligand by Metal Cluster Complexes.

    PubMed

    Adams, Richard D; Kiprotich, Joseph; Peryshkov, Dmitry V; Wong, Yuen Onn

    2016-05-01

    The reaction of Os3 (CO)10 (NCMe)2 with closo-o-C2 B10 H10 has yielded two interconvertible isomers Os3 (CO)9 (μ3 -4,5,9-C2 B10 H8 )(μ-H)2 (1 a) and Os3 (CO)9 (μ3 -3,4,8-C2 B10 H8 )(μ-H)2 (1 b) formed by the loss of the two NCMe ligands and one CO ligand from the Os3 cluster. Two BH bonds of the o-C2 B10 H10 were activated in its addition to the osmium cluster. A second triosmium cluster was added to the 1 a/1 b mixture to yield the complex Os3 (CO)9 (μ-H)2 (μ3 -4,5,9-μ3 -7,11,12-C2 B10 H7 )Os3 (CO)9 (μ-H)3 (2) that contains two triosmium triangles attached to the same carborane cage. When heated, 2 was transformed to the complex Os3 (CO)9 (μ-H)(μ3 -3,4,8-μ3 -7,11,12-C2 B10 H8 )Os3 (CO)9 (μ-H) (3) by a novel opening of the carborane cage with loss of H2 . PMID:26971388

  5. 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

  6. WIYN OPEN CLUSTER STUDY. XXXVIII. STELLAR RADIAL VELOCITIES IN THE YOUNG OPEN CLUSTER M35 (NGC 2168)

    SciTech Connect

    Geller, Aaron M.; Mathieu, Robert D.; Braden, Ella K.; Meibom, Soeren; Dolan, Christopher J.; Platais, Imants E-mail: mathieu@astro.wisc.edu E-mail: smeibom@cfa.harvard.edu E-mail: imants@pha.jhu.edu

    2010-04-15

    We present 5201 radial-velocity (RV) measurements of 1144 stars as part of an ongoing study of the young (150 Myr) open cluster M35 (NGC 2168). We have observed M35 since 1997, using the Hydra Multi-Object Spectrograph on the WIYN 3.5 m telescope. Our stellar sample covers main-sequence stars over a magnitude range of 13.0 {<=} V {<=} 16.5 (1.6-0.8 M {sub sun}) and extends spatially to a radius of 30 arcmin (7 pc in projection at a distance of 805 pc or {approx}4 core radii). Due to its youth, M35 provides a sample of late-type stars with a range of rotation periods. Therefore, we analyze the RV measurement precision as a function of the projected rotational velocity. For narrow-lined stars (vsin i{<=} 10 km s{sup -1}), the RVs have a precision of 0.5 km s{sup -1}, which degrades to 1.0 km s{sup -1} for stars with vsin i = 50 km s{sup -1}. The RV distribution shows a well-defined cluster peak with a central velocity of -8.16 {+-} 0.05 km s{sup -1}, permitting a clean separation of the cluster and field stars. For stars with {>=}3 measurements, we derive RV membership probabilities and identify RV variables, finding 360 cluster members, 55 of which show significant RV variability. Using these cluster members, we construct a color-magnitude diagram for our stellar sample cleaned of field star contamination. We also compare the spatial distribution of the single and binary cluster members, finding no evidence for mass segregation in our stellar sample. Accounting for measurement precision, we place an upper limit on the RV dispersion of the cluster of 0.81 {+-} 0.08 km s{sup -1}. After correction for undetected binaries, we derive a true RV dispersion of 0.65 {+-} 0.10 km s{sup -1}.

  7. 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

  8. 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. PMID:23990913

  9. Be Stars in the Open Cluster NGC 6830

    NASA Astrophysics Data System (ADS)

    Yu, Po-Chieh; Lin, Chien-Cheng; Lin, Hsing-Wen; Lee, Chien-De; Konidaris, Nick; Ngeow, Chow-Choong; Ip, Wing-Huen; Chen, Wen-Ping; Chen, Hui-Chen; Malkan, Matthew A.; Chang, Chan-Kao; Laher, Russ; Huang, Li-Ching; Cheng, Yu-Chi; Edelson, Rick; Ritter, Andreas; Quimby, Robert; Ben-Ami, Sagi; Ofek, Eran. O.; Surace, Jason; Kulkarni, Shrinivas R.

    2016-05-01

    We report the discovery of two new Be stars, and re-identify one known Be star in the open cluster NGC 6830. Eleven Hα emitters were discovered using the Hα imaging photometry of the Palomar Transient Factory Survey. Stellar membership of the candidates was verified with photometric and kinematic information using 2MASS data and proper motions. The spectroscopic confirmation was carried out by using the Shane 3 m telescope at the Lick observatory. Based on their spectral types, three Hα emitters were confirmed as Be stars with Hα equivalent widths greater than ‑10 Å. Two objects were also observed by the new spectrograph spectral energy distribution-machine (SED-machine) on the Palomar 60-inch Telescope. The SED-machine results show strong Hα emission lines, which are consistent with the results of the Lick observations. The high efficiency of the SED-machine can provide rapid observations for Be stars in a comprehensive survey in the future.

  10. Oxygen in Open Cluster Dwarfs: Pleiades and M34

    NASA Astrophysics Data System (ADS)

    Schuler, S. C.; King, J. R.; Hobbs, L. M.; Pinsonneault, M. H.

    2003-12-01

    We analyze the high-excitation 7774 ; Å O 1 triplet in high-resolution, moderate signal-to-noise spectra of 15 Pleiades (HET/HRS) and 8 M34 (Keck/HIRES) open cluster dwarfs. Effective temperatures range from 5048 - 6172 K for the Pleiades sample and from 5290 - 6130 K for the M34 sample. Relative O abundances have been derived using model atmospheres interpolated from four different sets of ATLAS9 grids: with convective overshoot, without convective overshoot, with the mixing length parameter set to 0.5, and with the convective treatment of Canuto, Goldman, & Mazzitelli. In contrast to existing NLTE predictions, a dramatic increase in O 1 triplet abundance with decreasing temperature is seen for both clusters, regardless of atmospheric model. S 1 abundances of three Pleiads derived from the high-excitation λ 6052.67 feature mimic the O 1 abundance behavior. O abundances have also been derived from the 6300 Å [OI] feature in three Pleiads; the abundances exhibit a much lower mean-value than the cool dwarf triplet results. Inasmuch as the [OI] abundances are presumed to be free from NLTE effects, their mean ( {[O/H]}6300 = 0.14) provide the current best estimate of the Pleiades O abundance. Spreads in {[O/H]}Trip at a given temperature are also seen in both clusters; there is no correlation between the spreads and chromospheric activity measures. This study is supported by a Graduate Student Research Fellowship from the South Carolina Space Grant Consortium and by grants AST 00-86576 and AST 02-39518 awarded to J.R.K. from the National Science Foundation.

  11. 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.

  12. BATC 15 Band Photometry of the Open Cluster NGC 188

    NASA Astrophysics Data System (ADS)

    Wang, Jiaxin; Ma, Jun; Wu, Zhenyu; Wang, Song; Zhou, Xu

    2015-08-01

    This paper presents CCD multicolor photometry for the old open cluster NGC 188. The observations were carried out as part of the Beijing-Arizona-Taiwan-Connecticut Multicolor Sky Survey from 1995 February to 2008 March, using 15 intermediate-band filters covering 3000-10000 Å. By fitting the Padova theoretical isochrones to our data, the fundamental parameters of this cluster are derived: an age of t=7.5+/- 0.5 Gyr, a distance modulus of {(m-M)}0=11.17+/- 0.08, and a reddening of E(B-V)=0.036+/- 0.010. The radial surface density profile of NGC 188 is obtained using the star count. By fitting the King model, the structural parameters of NGC 188 are derived: a core radius of {R}c=3\\buildrel{ \\prime}\\over{.} 80, a tidal radius of {R}t=44\\buildrel{ \\prime}\\over{.} 78, and a concentration parameter of {C}0={log}({R}t/{R}c)=1.07. Fitting the mass function (MF) to a power-law function φ (m)\\propto {m}α , the slopes of the MFs for different spatial regions are derived. We find that NGC 188 presents a slope break in the MF. The break mass is {m}{break}=0.885 {M}⊙ . In the mass range above {m}{break}, the slope of the overall region is α =-0.76. The slope of the core region is α =1.09, and the slopes of the external regions are α =-0.86 and α =-2.15, respectively. In the mass range below {m}{break}, these slopes are α =0.12, α =4.91, α =1.33, and α =-1.09, respectively. The mass segregation in NGC 188 is reflected in the obvious variation of the slopes in different spatial regions of this cluster.

  13. 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.

  14. Sejong Open Cluster Survey (SOS) - III. The young open cluster NGC 1893 in the H II region W8

    NASA Astrophysics Data System (ADS)

    Lim, Beomdu; Sung, Hwankyung; Kim, Jinyoung S.; Bessell, Michael S.; Park, Byeong-Gon

    2014-09-01

    We present a UBVI and Hα photometric study of the young open cluster NGC 1893 in the H II region W8 (IC 410 or Sh 2-236). A total of 65 early-type members are selected from photometric diagrams. A mean reddening of the stars is = 0.563 ± 0.083 mag. The published photometric data in the near- and mid-infrared passbands are used to test the reddening law towards the cluster, and we confirm that the reddening law is normal (RV = 3.1). Zero-age main-sequence fitting gives a distance modulus of V0 - MV = 12.7 ± 0.2 mag, equivalent to 3.5 ± 0.3 kpc. From Hα photometry, 125 Hα emission stars and candidates are identified as pre-main-sequence (PMS). The lists of young stellar objects and X-ray sources published by previous studies allow us to select a large number of PMS members down to 1 M⊙. Isochrone fitting in the Hertzsprung-Russell diagram gives a turn-off age of 1.5 Myr and the median age of 1.9 Myr from the PMS members with a spread of ˜5 Myr. We derive the initial mass function (IMF) for stars with mass larger than 1 M⊙. The slope of the IMF (Γ = -1.3 ± 0.1) is well consistent with the Salpeter/Kroupa IMF. A total mass of the cluster appears to be in excess of 1300 M⊙. Finally, we estimate the mass accretion rate of 82 PMS members in the mass range of 0.6-5 M⊙.

  15. Experimental investigation on argon cluster sizes for conical nozzles with different opening angles

    NASA Astrophysics Data System (ADS)

    Chen, Guanglong; Kim, Byunghoon; Ahn, Byungnam; Kim, Dong Eon

    2010-09-01

    Using Rayleigh scattering measurement, we experimentally studied the effect of the opening angle of conical nozzles on the average sizes of argon clusters produced by high-pressure argon gas (up to 50 bars) expanding into vacuum. Both the scattering signal intensity and the scattering image were synchronically recorded by a photomultiplier tube and a charge-coupled device camera. These measurements allow for the comparison of average cluster sizes among conical nozzles of different opening angles. The experimental results indicate that, as expected by Hagena's scaling law, the argon cluster size is dependent on the opening angle. However, it is also found that (1) the cluster size exhibits a larger deviation from Hagena's scaling law at high backing pressure for a nozzle of a smaller opening angle and (2) the smaller the opening angle of conical nozzle gets, the weaker the pressure dependence of cluster size becomes.

  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. 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).

  18. 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

  19. IR emission and UV extinction in two open clusters

    NASA Technical Reports Server (NTRS)

    Hackwell, James A.; Hecht, James H.

    1989-01-01

    Recent models of interstellar extinction have shown the importance of understanding both the UV and IR properties of interstellar dust grains. IRAS data have shown variations in 60 and 100 micron emissions presumably due to the presence of IR cirrus, while recent observations in the UV by Fitzpatrick and Massa have identified components in the UV extinction curve which vary in different star regions. A Draine and Anderson model connects these results by proposing that different size variations in interstellar grains would cause distinct changes in both the IR emission and the UV extinction. In order to test this model it is necessary to make observations in well defined locations away from peculiar extinction regions. In the infrared this means looking away from the galactic plane so as to limit non-local sources of IR radiation. Two open clusters that are out of the galactic plane and which contain a number of late B and early A stars suitable for UV extinction studies, and whose IRAS data show variations in the 60/100 micron ratio were studied. Based on the Drain and Anderson model, variations were expected in their UV extinction curves that correlate with the IR cirrus emission.

  20. 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.

  1. 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.

  2. Do open star clusters evolve toward energy equipartition?

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    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.

  3. Massive open star clusters using the VVV survey. II. Discovery of six clusters with Wolf-Rayet stars

    NASA Astrophysics Data System (ADS)

    Chené, A.-N.; Borissova, J.; Bonatto, C.; Majaess, D. J.; Baume, G.; Clarke, J. R. A.; Kurtev, R.; Schnurr, O.; Bouret, J.-C.; Catelan, M.; Emerson, J. P.; Feinstein, C.; Geisler, D.; de Grijs, R.; Hervé, A.; Ivanov, V. D.; Kumar, M. S. N.; Lucas, P.; Mahy, L.; Martins, F.; Mauro, F.; Minniti, D.; Moni Bidin, C.

    2013-01-01

    Context. The ESO Public Survey "VISTA Variables in the Vía Láctea" (VVV) provides deep multi-epoch infrared observations for an unprecedented 562 sq. degrees 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: This is the second in a series of papers about young, massive open clusters observed using the VVV survey. We present the first study of six recently discovered clusters. These clusters contain at least one newly discovered Wolf-Rayet (WR) star. 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 for a subset of clusters. Results: We find that the six studied stellar groups are real young (2-7 Myr) and massive (between 0.8 and 2.2 × 103 M⊙) clusters. They are highly obscured (AV ~ 5-24 mag) and compact (1-2 pc). In addition to WR stars, two of the six clusters also contain at least one red supergiant star, and one of these two clusters also contains a blue supergiant. We claim the discovery of 8 new WR stars, and 3 stars showing WR-like emission lines which could be classified WR or OIf. Preliminary analysis provides initial masses of ~30-50 M⊙ for the WR stars. Finally, we discuss the spiral structure of the Galaxy using the six new clusters as tracers, together with the previously studied VVV clusters. Based on observations with ISAAC, VLT, ESO (programme 087.D-0341A), New Technology Telescope at ESO's La Silla Observatory (programme 087.D-0490A) and with the Clay telescope at the Las Campanas Observatory (programme CN2011A-086). Also based on data from the VVV survey (programme 172.B-2002).

  4. 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.

  5. Photometry using Kepler ``superstamps'' of open clusters NGC 6791 & NGC 6819

    NASA Astrophysics Data System (ADS)

    Kuehn, Charles A.; Drury, Jason; Stello, Dennis; Bedding, Timothy R.

    2014-02-01

    The Kepler space telescope has proven to be a gold mine for the study of variable stars. Unfortunately, Kepler only returns a handful of pixels surrounding each star on the target list, which omits a large number of stars in the Kepler field. For the open clusters NGC 6791 and NGC 6819, Kepler also reads out larger superstamps which contain complete images of the central region of each cluster. These cluster images can potentially be used to study additional stars in the open clusters. We present preliminary results from using traditional photometric techniques to identify and analyze additional variable stars from these images.

  6. AN UNEXPECTED DISCOVERY IN THE RICH OPEN CLUSTER NGC 6819 USING XMM-NEWTON

    SciTech Connect

    Gosnell, Natalie M.; Mathieu, Robert D.; Pooley, David; Geller, Aaron M.; Kalirai, Jason; Frinchaboy, Peter; Ramirez-Ruiz, Enrico

    2012-01-20

    We present the first study of the X-ray population of the intermediate-age rich open cluster NGC 6819 using the XMM-Newton Observatory. In the past decade, Chandra X-ray observations have shown a relationship between the X-ray population of globular clusters and their internal dynamics and encounter frequency. We investigate the role dynamics possibly play in the formation of X-ray sources in NGC 6819, and compare our results with known properties of field and globular cluster X-ray populations. We implement a multi-wavelength approach to studying the X-ray sources, utilizing X-ray and UV data from XMM observations along with the wealth of photometry and radial-velocity data from the WIYN Open Cluster Study and the CFHT Open Cluster Survey. Within the cluster half-light radius, we detect 12 X-ray sources down to a luminosity of 10{sup 30} erg s{sup -1} for cluster members. The sources include a candidate quiescent low-mass X-ray binary (qLMXB), a candidate cataclysmic variable, and two active binary systems. The presence of a qLMXB in an open cluster is previously unexpected given the known relationships between luminous X-ray sources and encounter frequency in globular clusters, and most likely has a dynamical origin.

  7. 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.

  8. A search for open cluster Cepheids in the Galactic plane

    NASA Astrophysics Data System (ADS)

    Chen, Xiaodian; de Grijs, Richard; Deng, Licai

    2015-01-01

    We analyse all potential combinations of Galactic Cepheids and open clusters (OCs) in the most up-to-date catalogues available. Isochrone fitting and proper-motion calculation are applied to all potential OC-Cepheid combinations. Five selection criteria are used to select possible OC Cepheids: (i) the Cepheid of interest must be located within 60 arcmin of the OC's centre; (ii) the Cepheid's proper motion is located within the 1σ distribution of that of its host OC; (iii) the Cepheid is located in the instability strip of its postulated host OC; (iv) the Cepheid and OC distance moduli should differ by less than 1 mag; and (v) the Cepheid and OC ages (and, where available, their metallicities) should be comparable: Δlog (t yr-1) < 0.3. 19 possible OC Cepheids are found based on our near-infrared (NIR) analysis; eight additional OC-Cepheid associations may be genuine pairs for which we lack NIR data. Six of the Cepheids analysed at NIR wavelengths are new, high-probability OC Cepheids, since they lie on the NIR period (P)-luminosity relation (PLR). These objects include TY Sct and CN Sct in Dolidze 34, XX Sgr in Dolidze 52, CK Sct in NGC 6683, VY Car in ASCC 61 and U Car in Feinstein 1. Two additional new OC Cepheids lack NIR data: V0520 Cyg in NGC 6991 and CS Mon in Juchert 18. The NIR PLR for our confirmed sample of OC Cepheids is MJ = (-3.12 ± 0.29)log (Pd-1) - (2.17 ± 0.29) mag, which is in good agreement with the best NIR PLR available for all Galactic Cepheids.

  9. Abundance analysis of an extended sample of open clusters: A search for chemical inhomogeneities

    NASA Astrophysics Data System (ADS)

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

    We have initiated a program to explore the presence of chemical inhomogeneities in the Galactic disk using the open clusters as ideal probes. We have analyzed high-dispersion echelle spectra (R ≥ 55,000) of red giant members for eleven open clusters to derive abundances for many elements. The membership to the cluster has been confirmed through their radial velocities and proper motions. The spread in temperatures and gravities being very small among the red giants, nearly the same stellar lines were employed thereby reducing the random errors. The errors of average abundance for the cluster were generally in 0.02 to 0.07 dex range. Our present sample covers galactocentric distances of 8.3 to 11.3 kpc and an age range of 0.2 to 4.3 Gyrs. Our earlier analysis of four open clusters (Reddy A.B.S. et al., 2012, MNRAS, 419,1350) indicate that abundances relative to Fe for elements from Na to Eu are equal within measurement uncertainties to published abundances for thin disk giants in the field. This supports the view that field stars come from disrupted open clusters. In the enlarged sample of eleven open clusters we find cluster to cluster abundance variations for some s- and r- process elements, with certain elements such as Zr and Ba showing large variation. These differences mark the signatures that these clusters had formed under different environmental conditions (Type II SN, Type Ia SN, AGB stars or a mixture of any of these) unique to the time and site of formation. These eleven clusters support the widely held impression that there is an abundance gradient such that the metallicity [Fe/H] at the solar galactocentric distance decreases outwards at about -0.1 dex per kpc.

  10. 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.

  11. 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.

  12. Kinematic parameters and membership probabilities of open clusters in the Bordeaux PM2000 catalogue

    NASA Astrophysics Data System (ADS)

    Krone-Martins, A.; Soubiran, C.; Ducourant, C.; Teixeira, R.; Le Campion, J. F.

    2010-06-01

    Aims: We derive lists of proper-motions and kinematic membership probabilities for 49 open clusters and possible open clusters in the zone of the Bordeaux PM2000 proper motion catalogue (+11° ≤ δ ≤ +18°). We test different parametrisations of the proper motion and position distribution functions and select the most successful one. In the light of those results, we analyse some objects individually. Methods: We differenciate between cluster and field member stars, and assign membership probabilities, by applying a new and fully automated method based on both parametrisations of the proper motion and position distribution functions, and genetic algorithm optimization heuristics associated with a derivative-based hill climbing algorithm for the likelihood optimization. Results: We present a catalogue comprising kinematic parameters and associated membership probability lists for 49 open clusters and possible open clusters in the Bordeaux PM2000 catalogue region. We note that this is the first determination of proper motions for five open clusters. We confirm the non-existence of two kinematic populations in the region of 15 previously suspected non-existent objects. Full Table 5 is also 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/516/A3

  13. On the Origin of High-altitude Open Clusters in the Milky Way

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    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. 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.

  15. The San Pedro Mártir Open Cluster Survey: Progress, Techniques, Preliminary Results

    NASA Astrophysics Data System (ADS)

    Schuster, W.; Michel, R.; Dias, W.; Tapia-Peralta, T.; Vázquez, R.; Macfarland, J.; Chavarría, C.; Santos, C.; Moitinho, A.

    2007-05-01

    A CCD UBVRI survey of northern open clusters is being undertaken at San Pedro Mártir, Mexico, and performed using always the same instrumental setup (telescope, CCD, filters), reduction methods, and system of standards (Landolt). To date more than 300 clusters (mostly unstudied previously) have been observed, and about half the data reduced using aperture-photometry and PSF techniques. Our analysis procedures are being refined by studying in detail a small subset of these clusters. For example, the heavily reddened clusters Be80 and Be95 are being examined in the color-color diagrams: (B-V,U-B) and (B-V,R-I) to better understand the problems of curvature and variable reddening. For clusters for which our U data reaches the F-type stars, such as NGC2192 and NGC7296, techniques are being examined for estimating both the reddening E(B-V) and metallicity [Fe/H] via the use of the (U-B) excess. If the clusters also have "red clump" stars, such as NGC1798 and Do02, these procedures can be iterated between the clump and main sequence stars to establish even better the values of E(B-V) and [Fe/H]. Finally, color-magnitude diagrams, such as (B-V,V) and (V-I,V), are being employed together with the Schmidt-Kaler colors and Padova isochrones to obtain distances and ages for these clusters. A java-based computer program is being developed to help in the visualization and analysis of these photometric data. This system is capable of displaying each cluster simultaneously in different color-color and color-magnitude diagrams and has an interactive way to identify a star, or group of stars, in one diagram and to see were it falls in the other diagrams, facilitating the elimination of field stars and the apperception of cluster features. This program is capable of displaying up to 16 different diagrams for one cluster and processing up to 20 clusters at the same time. Our aims are the following: (1) a common UBVRI photometric scale for open clusters, (2) an atlas of color

  16. Cluster-based representation of hydraulic systems. [stable (closed valve) and unstable (open valve) states

    NASA Technical Reports Server (NTRS)

    Farley, Arthur M.

    1988-01-01

    The authors present a technique for structural abstraction applicable to the domain of pressurized hydraulic systems. Valves, when closed, functionally isolate clusters of components; when opened, neighboring clusters are merged. A cluster can only be in the one of two qualitative states-stable, where pressures are equal throughout and no flow occurs, or unstable, where flow from high-pressure source(s) to low-pressure sink(s) occurs. Reasoning in terms of clusters is shown to facilitate the generation and explanation of plans for operating and troubleshooting hydraulic systems.

  17. 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.

  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. Basic parameters of open star clusters DOLIDZE 14 and NGC 110 in infrared bands

    NASA Astrophysics Data System (ADS)

    Joshi, Gireesh C.; Joshi, Y. C.; Joshi, S.; Tyagi, R. K.

    2015-10-01

    The basic physical parameters of a poorly studied open cluster NGC 110 and an unstudied open cluster DOLIDZE 14 are estimated in the present study using the archival PPMXL and WISE catalogues. The radius of both the clusters are estimated by fitting the modified King's empirical model on their stellar density profiles. The other basic parameters of the clusters such as distance, reddening, and age are obtained by visual fitting of the Marigo's solar metallicity isochrone on their IR colour-magnitude diagrams (CMDs). The mean-proper motion of the clusters are estimated through the individual proper motion of probable members identified through the dynamical and statistical methods. The archival catalogues (JHKW1W2) are constructed for both the clusters by compiling the extracted data from the PPMXL and WISE catalogues. The various colour-excesses, such as E (J - H), E (H - K) and E (W1 -W2) , are estimated using the best fit theoretical isochrone on the (J - H) - H, (H - K) - H and (W1 -W2) - H CMDs, respectively. The ratios of various infrared colours of the clusters are obtained through their two-colour diagrams. We also identify the most probable members in these clusters by estimating spatial, kinematic and spatio-kinematic probabilities of stars within the cluster. A correlation between the E (H - K) and E (W1 -W2) is also established.

  20. Stellar models with microscopic diffusion and rotational mixing. 2: Application to open clusters

    NASA Technical Reports Server (NTRS)

    Chaboyer, B.; Demarque, P.; Pinsonneault, M. H.

    1995-01-01

    Stellar models with masses ranging from 05.5 to 1.3 solar mass were constructed for comparison with young cluster observations of Li and of rotation velocities. The amount of Li depletion in cool stars is sensitive to the amount of overshoot at the base of the surface convection zone, and the exact metallicity of the models. Even when this is taken into account, the Li observations are a severe constraint for the models and rule out standard models and pure diffusion models. Stellar models which include diffusion and rotational mixing in the radiative regions of stars are able to simultaneously match the Li abundances observed in the Pleiades, the UMa Group, The Hyades, Praesepe, NGC 752, and M67. They also match the observed rotation periods in the Hyades. However, these models are unable to simultaneously explain the presence of the rapidly rotating late G and K stars in the Pleiades and the absence of rapidly rotating late F and early G stars.

  1. 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)).

  2. The Kepler Cluster Study: rotation period measurements for cool stars in the 2.5 billion year open cluster NGC 6819

    NASA Astrophysics Data System (ADS)

    Meibom, Soren; Barnes, Sydney A.; Platais, Imants; Gilliland, Ronald L.; Latham, David W.; Mathieu, Robert D.; Kepler Science Team, Kepler Science Operations Center

    2015-01-01

    The Kepler Cluster Study (KeCS) is a program to measure stellar rotation periods and search for planets around members of open star clusters within the field of view of NASA's Kepler mission. We present here the latest results from KeCS - measurements of stellar rotation periods in the 2.5 billion year open cluster NGC 6819 - and discuss their implications for a technique (gyrochronology) to determine stellar ages from stellar rotation.

  3. The fractal dimensions of the spatial distribution of young open clusters in the solar neighbourhood

    NASA Astrophysics Data System (ADS)

    de La Fuente Marcos, R.; de La Fuente Marcos, C.

    2006-06-01

    Context: .Fractals are geometric objects with dimensionalities that are not integers. They play a fundamental role in the dynamics of chaotic systems. Observation of fractal structure in both the gas and the star-forming sites in galaxies suggests that the spatial distribution of young open clusters should follow a fractal pattern, too. Aims: .Here we investigate the fractal pattern of the distribution of young open clusters in the Solar Neighbourhood using a volume-limited sample from WEBDA and a multifractal analysis. By counting the number of objects inside spheres of different radii centred on clusters, we study the homogeneity of the distribution. Methods: .The fractal dimension D of the spatial distribution of a volume-limited sample of young open clusters is determined by analysing different moments of the count-in-cells. The spectrum of the Minkowski-Bouligand dimension of the distribution is studied as a function of the parameter q. The sample is corrected for dynamical effects. Results: .The Minkowski-Bouligand dimension varies with q in the range 0.71-1.77, therefore the distribution of young open clusters is fractal. We estimate that the average value of the fractal dimension is < D> = 1.7± 0.2 for the distribution of young open clusters studied. Conclusions: .The spatial distribution of young open clusters in the Solar Neighbourhood exhibits multifractal structure. The fractal dimension is time-dependent, increasing over time. The values found are consistent with the fractal dimension of star-forming sites in other spiral galaxies.

  4. 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.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

    Kuehn, Charles A.; Drury, J.; Stello, D.; Bedding, T. R.

    2014-01-01

    The Kepler space telescope has proven to be a gold mine for the study of variable stars. To conserve bandwidth, Kepler only returns a handful of pixels surrounding each star on the target list. Unfortunately, this omits a large number of stars in the Kepler field. Fortunately, for the open clusters NGC 6791 and NGC 6819, Kepler also reads out larger superstamps which contain complete images of the central region of each cluster. These cluster images can be used to study additional stars in the open clusters which were not originally on Kepler's target list. We present preliminary results from using traditional photometric techniques to identify and analyze additional variable stars from these superstamp images.

  7. 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.

  8. 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

  9. Map-based trigonometric parallaxes of open clusters - The Pleiades

    NASA Technical Reports Server (NTRS)

    Gatewood, George; Castelaz, Michael; Han, Inwoo; Persinger, Timothy; Stein, John

    1990-01-01

    The multichannel astrometric photometer and Thaw refractor of the University of Pittsburgh's Allegheny Observatory have been used to determine the trigonometric parallax of the Pleiades star cluster. The distance determined, 150 with a standard error of 18 parsecs, places the cluster slightly farther away than generally accepted. This suggests that the basis of many estimations of the cosmic distance scale is approximately 20 percent short. The accuracy of the determination is limited by the number and choice of reference stars. With careful attention to the selection of reference stars in several Pleiades regions, it should be possible to examine differences in the photometric and trigonometric modulus at a precision of 0.1 magnitudes.

  10. Intrinsic Variability in Multiple Systems and Clusters: Open Questions

    NASA Astrophysics Data System (ADS)

    Lampens, P.

    2006-04-01

    It is most interesting and rewarding to probe the stellar structure of stars which belong to a system originating from the same parent cloud as this provides additional and more accurate constraints for the models. New results on pulsating components in multiple systems and clusters are beginning to emerge regularly. Based on concrete studies, I will present still unsolved problems and discuss some of the issues which may affect our understanding of the pulsation physics in such systems but also in general.

  11. Dynamical Interactions Make Hot Jupiters in Open Star Clusters

    NASA Astrophysics Data System (ADS)

    Shara, Michael M.; Hurley, Jarrod R.; Mardling, Rosemary A.

    2016-01-01

    Explaining the origin and evolution of exoplanetary hot Jupiters remains a significant challenge. One possible mechanism for the production of hot Jupiters is planet-planet interactions, which produce them from planets born far from their host stars but near their dynamical stability limits. In the much more likely case of planets born far from their dynamical stability limits, can hot Jupiters be formed in star clusters? Our N-body simulations answer this question in the affirmative, and show that hot Jupiter formation is not a rare event, occurring in ˜1% of star cluster planetary systems. We detail three case studies of the dynamics-induced births of hot Jupiters on highly eccentric orbits that can only occur inside star clusters. The hot Jupiters’ orbits bear remarkable similarities to those of some of the most extreme exoplanets known: HAT-P-32b, HAT-P-2b, HD 80606b, and GJ 876d. If stellar perturbations formed these hot Jupiters, then our simulations predict that these very hot inner planets are often accompanied by much more distant gas giants in highly eccentric orbits.

  12. 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.

  13. 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.

  14. A Study of The Binary and Anomalous Stellar Populations in Two Intermediate-Aged Open Clusters

    NASA Astrophysics Data System (ADS)

    Mathieu, Robert D.; Milliman, Katelyn; Geller, Aaron M.; Gosnell, Natalie

    2010-08-01

    ``Anomalous'' stars, such as blue stragglers and more recently sub- subgiants, have been an enduring challenge for stellar evolution theory. It is now clear that in star clusters these systems are closely linked to the binary star populations. Furthermore, sophisticated N-body models show that stellar dynamical processes play a central role in the formation of such anomalous stars. These stars trace the interface between the classical fields of stellar evolution and stellar dynamics. We propose to expand our highly successful radial-velocity survey to include two new rich open clusters NGC 7789 (1.8 Gyr, -0.1 dex) and NGC 2506 (2.1 Gyr, -0.4 dex) as part of the WIYN Open Cluster Study (WOCS). Though these two clusters are both of intermediate age and of similar richness, they have quite different blue straggler populations. NGC 2506 has only 10 known blue stragglers, while NGC 7789 has at least 27, among the largest known populations of blue stragglers in an open cluster. Defining the hard-binary populations in these two clusters is critical for understanding the factors that determine blue straggler production rates. Our proposed observations will establish the hard- binary fraction and frequency distributions of orbital parameters (periods, eccentricities, mass-ratios, etc.) for orbital periods approaching the hard-soft boundary, and will provide a comprehensive survey of the blue stragglers and other anomalous stars, including secure cluster memberships and binary properties. These data will then form direct constraints for detailed N-body open cluster simulations from which we will study the impact of the hard-binary population on the production rates and mechanisms of blue stragglers.

  15. 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.

  16. Open Cluster Radial Velocity determination from observations at Observatório Pico Dos Dias

    NASA Astrophysics Data System (ADS)

    Faria, M. A. F.; Monteiro, H.; Dias, W. S.; Lépine, J. R. D.

    2014-10-01

    In studies of the dynamics of the Galactic disk, such as the determination of the speed of the spiral pattern and the permanence of stars in the spiral arms, it is crucial to know orbits obtained from proper motions, radial velocities and the potential of the Galaxy. Aiming to improve the statistics of our catalog of open clusters, maintained by our research group, we determined the radial velocity of stars belonging to a group of open clusters using spectra with a resolution of 4000, obtained at the Pico dos Dias Observatory (LNA) with the 1.60 m telescope and the Coudé spectrograph. We observed the open cluster's member stars and calculated their radial speeds using standard techniques. The stars were selected from our own database based on relevant information concerning the clusters, obtained by statistical analysis of their proper motions and/or their position in the HR's diagram. In this work, we present the detailed analysis of the data reduction and radial velocity determination using synthetic spectra from different libraries. Finally we present the open cluster's radial (and spacial) velocities.

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

    NASA Astrophysics Data System (ADS)

    Piatti, Andrés E.

    2016-09-01

    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, multi-band photometric data sets were used to trace the cluster stellar density radial profiles and to build colour-magnitude diagrams (CMDs) and colour-colour (CC) 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 - 380M$⊙$), with higher concentration parameter values (c ˜ 0.75-1.15) and dynamically evolved ones.

  18. A search for white dwarfs in the Galactic plane: the field and the open cluster population

    NASA Astrophysics Data System (ADS)

    Raddi, R.; Catalán, S.; Gänsicke, B. T.; Hermes, J. J.; Napiwotzki, R.; Koester, D.; Tremblay, P.-E.; Barentsen, G.; Farnhill, H. J.; Mohr-Smith, M.; Drew, J. E.; Groot, P. J.; Guzman-Ramirez, L.; Parker, Q. A.; Steeghs, D.; Zijlstra, A.

    2016-04-01

    We investigated the prospects for systematic searches of white dwarfs at low Galactic latitudes, using the VLT Survey Telescope H α Photometric Survey of the Galactic plane and Bulge (VPHAS+). We targeted 17 white dwarf candidates along sightlines of known open clusters, aiming to identify potential cluster members. We confirmed all the 17 white dwarf candidates from blue/optical spectroscopy, and we suggest five of them to be likely cluster members. We estimated progenitor ages and masses for the candidate cluster members, and compare our findings to those for other cluster white dwarfs. A white dwarf in NGC 3532 is the most massive known cluster member (1.13 M⊙), likely with an oxygen-neon core, for which we estimate an 8.8_{-4.3}^{+1.2} M⊙ progenitor, close to the mass-divide between white dwarf and neutron star progenitors. A cluster member in Ruprecht 131 is a magnetic white dwarf, whose progenitor mass exceeded 2-3 M⊙. We stress that wider searches, and improved cluster distances and ages derived from data of the ESA Gaia mission, will advance the understanding of the mass-loss processes for low- to intermediate-mass stars.

  19. NGC 2309: A Relatively Young Open Cluster Projected onto a Random Stellar Concentration

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

    We have obtained CCD UBVIKC photometry down to V ~ 22.0 for the open cluster NGC 2309 and its surrounding field. Twenty three probable cluster members have been identified for the first time on the basis of sound photometric criteria. Because NGC 2309 is a relatively poor cluster projected onto a rich star field showing density fluctuations, the frequently used membership criteria based on stellar density profiles or proper motion measurements would not be enough to assess the star membership status if employed independently. We estimated a cluster radius of 7.9' and a radius at half the maximum of the cluster density profile of 1.7'. Based on the best fits of isochrones computed by the Geneva group to the cluster color-magnitude and color-color diagrams, previously shifted by the cluster reddening (E(B - V) = 0.32) and distance (d = 2.5 kpc), we derived the cluster age (250 Myr) and metallicity ([Fe/H] sime 0.0). If an 8.5 kpc distance from the Sun to the center of the Galaxy is assumed, then NGC 2309 is found to be located just in front of the Perseus spiral arm.

  20. 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.

  1. 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.

  2. Distance moduli of open cluster NGC 6819 from Red Giant Clump stars

    NASA Astrophysics Data System (ADS)

    Abedigamba, O. P.; Balona, L. A.; Medupe, R.

    2016-07-01

    In this paper we study Kepler open cluster NGC 6819 using Kepler data of Red Giant Clump (RGC) single member (SM) stars. The Kepler data spans a period of 4 years starting in 2009. In particular, we derive distance moduli for each individual RGC star, from which we get the mean distance modulus of μ0 = 11.520 ± 0.105 mag for the cluster when we use reddening from the Kepler Input Catalogue (KIC) for each RGC star. A value of μ0 = 11.747 ± 0.086 mag is obtained when uniform reddening value E(B - V) = 0.15 is used for the cluster. The values of μ0 obtained with RGC stars are in agreement with the values in the literature with other methods. We report for the case of Kepler open cluster NGC 6819 that RGC stars can be used as 'distance candles' as has been done in the literature with other open clusters.

  3. Pulsating B-type Stars in the Open Cluster NGC 884: Frequencies, Mode Identification, and Asteroseismology

    NASA Astrophysics Data System (ADS)

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

    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. 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.

  5. 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.

  6. Time-series Spectroscopy of Two Candidate Double Degenerates in the Open Cluster NGC 6633

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    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-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. The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

  7. Photometric Determination of Binary Mass Ratios in the WIYN Open Cluster Study (WOCS) Using Theoretical Isochrones

    NASA Astrophysics Data System (ADS)

    Cai, K.; Durisen, R. H.; Deliyannis, C. P.

    2003-05-01

    Binary stars in Galactic open clusters are difficult to detect without spectroscopic observations. However, from theoretical isochrones, we find that binary stars with different primary masses M1 and mass ratios q = M2/M1 have measurably different behaviors in various UBVRI color-magnitude and color-color diagrams. By using appropriate Yonsei-Yale Isochrones, in the best cases we can evaluate M1 and q to within about +/- 0.1Msun and +/- 0.1, respectively, for individual proper-motion members that have multiple WOCS UBVRI measurements of high quality. The cluster metallicity, reddening, and distance modulus and best-fit isochrones are determined self-consistently from the same WOCS data. This technique allows us to detect binaries and determine their mass ratios in open clusters without time-consuming spectrocopy, which is only sensitive to a limited range of binary separations. We will report results from this photometric technique for WOCS cluster M35 for M1 in the range of 1 to 4 Msun. For the lower main sequence, we used the empirical colors to reduce the error introduced by the problematic color transformations of Y2 Isochrones. In addition to other sources of uncertainty, we have considered effects of rapid rotation and pulsational instability. We plan to apply our method to other WOCS clusters in the future and explore differences in binary fractions and/or mass ratio distributions as a function of cluster age, metallicity, and other parameters.

  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. 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.

  10. 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.

  11. RACE-OC project: rotation and variability in the open cluster NGC 2099 (M 37)

    NASA Astrophysics Data System (ADS)

    Messina, S.; Distefano, E.; Parihar, P.; Kang, Y. B.; Kim, S.-L.; Rey, S.-C.; Lee, C.-U.

    2008-05-01

    Context: Rotation and solar-type magnetic activity are closely related to each other in main-sequence stars of G or later spectral types. The presence and level of magnetic activity depend on star's rotation, and rotation itself is strongly influenced by strength and topology of the magnetic fields. Open clusters represent especially useful targets to investigate the connection between rotation and activity. Aims: The open cluster NGC 2099 has been studied as a part of the RACE-OC project (Rotation and ACtivity Evolution in Open Clusters), which is aimed at exploring the evolution of rotation and magnetic activity in the late-type members of open clusters of different ages. Methods: We collected time series CCD photometric observations of this cluster in January 2004, and we determined the presence of periodicities in the flux variation related to the stellar rotation by Fourier analysis. We investigate the relations between activity manifestations, such as the light curve amplitude, and global stellar parameters. Results: We have discovered 135 periodic variables, 122 of which are candidate cluster members. Determination of rotation periods of G- and K-type stars has allowed us to better explore the evolution of angular momentum at an age of about 500 Myr. In our analysis, we have also identified 3 new detached eclipsing binary candidates among cluster members. Conclusions: A comparison with the older Hyades cluster (~625 Myr) shows that the newly-determined distribution of rotation periods is consistent with the scenario of rotational braking of main-sequence spotted stars as they age. However, a comparison with the younger M 34 cluster (~200 Myr) shows that the G8-K5 members of these clusters have the same rotation period distribution. That is, G8-K5 members in NGC 2099 seem to have experienced no significant braking in the age range from ~200 to ~500 Myr. Finally, NGC 2099 members have a smaller level of photospheric magnetic activity, as measured by light

  12. Global survey of star clusters in the Milky Way. III. 139 new open clusters at high Galactic latitudes.

    NASA Astrophysics Data System (ADS)

    Schmeja, S.; Kharchenko, N. V.; Piskunov, A. E.; Roeser, S.; Schilbach, E.; Froebrich, D.; Scholz, R.-D.

    <-18.5. We present: The Catalogue of new MWSC open clusters found at high galactic latitudes (|b|>18.5°) which includes several files: Catalogue of cluster parameters (confirmed clusters only); Index of all MWSC(|b|>18.5 deg) candidates; Notes for every item of index list. Within each list the entries are ordered along with MWSC number. The Catalogues of the MWSC Stars in 139 circular sky areas with confirmed clusters. Files are ordered by MWSC number; inside each sky area the entries are ordered by Ks magnitudes. The Atlas of new MWSC clusters diagrams. In the Atlas the Cluster pages are ordered by MWSC number. All the data are given in the same format as in the main MWSC catalogue (Cat. J/A+A/558/A53). (5 data files).

  13. Spherical coupled-cluster theory for open-shell nuclei

    NASA Astrophysics Data System (ADS)

    Jansen, G. R.

    2013-08-01

    Background: A microscopic description of nuclei is important to understand the nuclear shell model from fundamental principles. This is difficult to achieve for more than the lightest nuclei without an effective approximation scheme.Purpose: Define and evaluate an approximation scheme that can be used to study nuclei that are described as two particles attached to a closed (sub-)shell nucleus.Methods: The equation-of-motion coupled-cluster formalism has been used to obtain ground- and excited-state energies. This method is based on the diagonalization of a non-Hermitian matrix obtained from a similarity transformation of the many-body nuclear Hamiltonian. A chiral interaction at the next-to-next-to-next-to leading order (N3LO) using a cutoff at 500 MeV was used.Results: The ground-state energies of 6Li and 6He were in good agreement with a no-core shell-model calculation using the same interaction. Several excited states were also produced with overall good agreement. Only the Jπ=3+ excited state in 6Li showed a sizable deviation. The ground-state energies of 18O, 18F, and 18Ne were converged but underbound compared to experiment. Moreover, the calculated spectra were converged and comparable to both experiment and shell-model studies in this region. Some excited states in 18O were high or missing in the spectrum. It was also shown that the wave function for both ground and excited states separates into an intrinsic part and a Gaussian for the center-of-mass coordinate. Spurious center-of-mass excitations are clearly identified.Conclusions: Results are converged with respect to the size of the model space and the method can be used to describe nuclear states with simple structure. Especially the ground-state energies were very close to what has been achieved by exact diagonalization. To obtain a closer match with experimental data, effects of three-nucleon forces, the scattering continuum, as well as additional configurations in the coupled-cluster approximations

  14. Accurate age determinations of several nearby open clusters containing magnetic Ap stars

    NASA Astrophysics Data System (ADS)

    Silaj, J.; Landstreet, J. D.

    2014-06-01

    Context. To study the time evolution of magnetic fields, chemical abundance peculiarities, and other characteristics of magnetic Ap and Bp stars during their main sequence lives, a sample of these stars in open clusters has been obtained, as such stars can be assumed to have the same ages as the clusters to which they belong. However, in exploring age determinations in the literature, we find a large dispersion among different age determinations, even for bright, nearby clusters. Aims: Our aim is to obtain ages that are as accurate as possible for the seven nearby open clusters α Per, Coma Ber, IC 2602, NGC 2232, NGC 2451A, NGC 2516, and NGC 6475, each of which contains at least one magnetic Ap or Bp star. Simultaneously, we test the current calibrations of Te and luminosity for the Ap/Bp star members, and identify clearly blue stragglers in the clusters studied. Methods: We explore the possibility that isochrone fitting in the theoretical Hertzsprung-Russell diagram (i.e. log (L/L⊙) vs. log Te), rather than in the conventional colour-magnitude diagram, can provide more precise and accurate cluster ages, with well-defined uncertainties. Results: Well-defined ages are found for all the clusters studied. For the nearby clusters studied, the derived ages are not very sensitive to the small uncertainties in distance, reddening, membership, metallicity, or choice of isochrones. Our age determinations are all within the range of previously determined values, but the associated uncertainties are considerably smaller than the spread in recent age determinations from the literature. Furthermore, examination of proper motions and HR diagrams confirms that the Ap stars identified in these clusters are members, and that the presently accepted temperature scale and bolometric corrections for Ap stars are approximately correct. We show that in these theoretical HR diagrams blue stragglers are particularly easy to identify. Conclusions: Constructing the theoretical HR diagram

  15. 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.

  16. CCD Washington photometry of three highly field star contaminated open clusters in the third Galactic quadrant

    NASA Astrophysics Data System (ADS)

    Piatti, A. E.; Clariá, J. J.; Parisi, M. C.; Ahumada, A. V.

    2009-01-01

    We present CCD photometry in the Washington system C and T1 passbands down to T1 ˜ 19.5 magnitudes in the fields of Czernik 26, Czernik 30, and Haffner 11, three poorly studied open clusters located in the third Galactic quadrant. We measured T1 magnitudes and C - T1 colors for a total of 6472 stars distributed throughout cluster areas of 13.6' × 13.6' each. Cluster radii were estimated from star counts in appropriate-sized boxes distributed throughout the entire observed fields. Based on the best fits of isochrones computed by the Padova group to the ( C - T1, T1) color-magnitude diagrams (CMDs), we derived color excesses, heliocentric distances and ages for the three clusters. These are characterized by a relatively small angular size and by a high field star contamination. We performed a firm analysis of the field star contamination of the CMDs and examined different relationships between the position in the Galaxy of known open clusters located within 1 kpc around the three studied ones, their age and their interstellar visual absorption. We confirm previous results in the sense that the closer the cluster birthplace to the Galactic plane, the higher the interstellar visual absorption. We also found that the space velocity dispersion perpendicular to the Galactic plane diminishes as the clusters are younger. The positions, interstellar visual absorptions, ages, and metallicities of the three studied clusters favor the hypothesis that they were not born in the recently discovered Canis major (CMa) dwarf galaxy before it was accreted by the Milky Way.

  17. Open Cluster Neutron Capture Element Abundances and Milky Way Disk Evolution

    NASA Astrophysics Data System (ADS)

    Jacobson, Heather R.; Friel, E. D.

    2012-01-01

    Open clusters, whose ages and distances can be precisely determined, are useful probes of the chemical evolution of the Milky Way disk. The sample sizes of clusters subject to homogeneous analysis of high resolution spectra have grown in recent years, and increased attention has turned to measuring the abundances of neutron capture elements. The relative abundances of r-process elements (e.g., europium) to s-process elements (e.g., barium, lanthanum and zirconium) in cluster stars reveal the relative contributions of Type II supernovae and low-mass AGB stars to the chemical evolution of the galactic disk. A recent study of cluster s-process element abundances has revealed a surprising trend of increasing s-process element abundance ([s/Fe]) with decreasing cluster age, at odds with current s-process yield predictions (D'Orazi et al. 2009, Maiorca et al. 2011). We have undertaken an analysis of Zr, Ba, La, and Eu abundances in 17 open clusters based on high resolution optical spectra. The sample spans 700 Myr to 10 Gyr in age and Rgc 7-22 kpc in galactocentric distance, allowing for the exploration of neutron capture [x/Fe] ratios as a function of age and location in the disk. Preliminary results confirm the trend of enhanced [s/Fe] with decreasing cluster age found by other studies, though with a weaker correlation. Here we present the latest results of this analysis, including newly-determined abundances for the r-process element Eu for an expanded cluster sample that includes outer disk objects. This research is supported by a National Science Foundation Astronomy and Astrophysics Postdoctoral Fellowship to HRJ under award AST-0901919.

  18. VizieR Online Data Catalog: Catalogue of variable stars in open clusters (Zejda+, 2012)

    NASA Astrophysics Data System (ADS)

    Zejda, M.; Paunzen, E.; Baumann, B.; Mikulasek, Z.; Liska, J.

    2012-08-01

    The catalogue of variable stars in open clusters were prepared by cross-matching of Variable Stars Index (http://www.aavso.org/vsx) version Apr 29, 2012 (available online, Cat. B/vsx) against the version 3.1. catalogue of open clusters DAML02 (Dias et al. 2002A&A...389..871D, Cat. B/ocl) available on the website http://www.astro.iag.usp.br/~wilton. The open clusters were divided into two categories according to their size, where the limiting diameter was 60 arcmin. The list of all suspected variables and variable stars located within the fields of open clusters up to two times of given cluster radius were generated (Table 1). 8938 and 9127 variable stars are given in 461 "smaller" and 74 "larger" clusters, respectively. All found variable stars were matched against the PPMXL catalog of positions and proper motions within the ICRS (Roeser et al., 2010AJ....139.2440R, Cat. I/317). Proper motion data were included in our catalogue. Unfortunately, a homogeneous data set of mean cluster proper motions has not been available until now. Therefore we used the following sources (sorted alphabetically) to compile a new catalogue: Baumgardt et al. (2000, Cat. J/A+AS/146/251): based on the Hipparcos catalogue Beshenov & Loktin (2004A&AT...23..103B): based on the Tycho-2 catalogue Dias et al. (2001, Cat. J/A+A/376/441, 2002A&A...389..871D, Cat. B/ocl): based on the Tycho-2 catalogue Dias et al. (2006, Cat. J/A+A/446/949): based on the UCAC2 catalog (Zacharias et al., 2004AJ....127.3043Z, Cat. I/289) Frinchaboy & Majewski (2008, Cat. J/AJ/136/118): based on the Tycho-2 catalogue Kharchenko et al. (2005, J/A+A/438/1163): based on the ASCC2.5 catalogue (Kharchenko, 2001KFNT...17..409K, Cat. I/280) Krone-Martins et al. (2010, Cat. J/A+A/516/A3): based on the Bordeaux PM2000 proper motion catalogue (Ducourant et al., 2006A&A...448.1235D, Cat. I/300) Robichon et al. (1999, Cat. J/A+A/345/471): based on the Hipparcos catalogue van Leeuwen (2009A&A...497..209V): based on the new

  19. 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.

  20. Stellar open clusters' membership probabilities: an N-dimensional geometrical approach

    NASA Astrophysics Data System (ADS)

    Sampedro, Laura; Alfaro, Emilio J.

    2016-04-01

    We present a new geometrical method aimed at determining the members of open clusters. The methodology estimates, in an N-dimensional space, the membership probabilities by means of the distances between every star and the cluster central overdensity. It can handle different sets of variables, which have to satisfy the simple condition of being more densely distributed for the cluster members than for the field stars (as positions, proper motions, radial velocities and/or parallaxes are). Unlike other existing techniques, this fact makes the method more flexible and so can be easily applied to different data sets. To quantify how the method identifies the cluster members, we design series of realistic simulations recreating sky regions in both position and proper motion subspaces populated by clusters and field stars. The results, using different simulated data sets (N = 1, 2 and 4 variables), show that the method properly recovers a very high fraction of simulated cluster members, with a low number of misclassified stars. To compare the goodness of our methodology, we also run other existing algorithms on the same simulated data. The results show that our method has a similar or even better performance than the other techniques. We study the robustness of the new methodology from different subsamplings of the initial sample, showing a progressive deterioration of the capability of our method as the fraction of missing objects increases. Finally, we apply all the methodologies to the real cluster NGC 2682, indicating that our methodology is again in good agreement with preceding studies.

  1. 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.

  2. 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.

  3. VizieR Online Data Catalog: Cepheids in open clusters (Anderson+, 2013)

    NASA Astrophysics Data System (ADS)

    Anderson, R. I.; Eyer, L.; Mowlavi, N.

    2013-07-01

    Cepheids in open clusters (cluster Cepheids: CCs) are of great importance as zero-point calibrators of the Galactic Cepheid period-luminosity relationship (PLR). We perform an 8-dimensional all-sky census that aims to identify new bona-fide CCs and provide a ranking of membership confidence for known CC candidates according to membership probabilities. The probabilities are computed for combinations of known Galactic open clusters and classical Cepheid candidates, based on spatial, kinematic, and population-specific membership constraints. Data employed in this analysis are taken largely from published literature and supplemented by a year-round observing program on both hemispheres dedicated to determining systemic radial velocities of Cepheids. In total, we find 23 bona-fide CCs, 5 of which are candidates identified for the first time, including an overtone-Cepheid member in NGC 129. We discuss a subset of CC candidates in detail, some of which have been previously mentioned in the literature. Our results indicate unlikely membership for 7 Cepheids that have been previously discussed in terms of cluster membership. We furthermore revisit the Galactic PLR using our bona fide CC sample and obtain a result consistent with the recent calibration by Turner (2010). However, our calibration remains limited mainly by cluster uncertainties and the small number of long-period calibrators. In the near future, Gaia will enable our study to be carried out in much greater detail and accuracy, thanks to data homogeneity and greater levels of completeness. (4 data files).

  4. 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.

  5. uvbyβ photometry of early type open cluster and field stars

    NASA Astrophysics Data System (ADS)

    Handler, G.

    2011-04-01

    Context. The β Cephei stars and slowly pulsating B (SPB) stars are massive main sequence variables. The strength of their pulsational driving strongly depends on the opacity of iron-group elements. As many of those stars naturally occur in young open clusters, whose metallicities can be determined in several fundamental ways, it is logical to study the incidence of pulsation in several young open clusters. Aims: To provide the foundation for such an investigation, Strömgren-Crawford uvbyβ photometry of open cluster target stars was carried out to determine effective temperatures, luminosities, and therefore cluster memberships. Methods: In the course of three observing runs, uvbyβ photometry for 168 target stars was acquired and transformed into the standard system by measurements of 117 standard stars. The list of target stars also included some known cluster and field β Cephei stars, as well as β Cephei and SPB candidates that are targets of the asteroseismic part of the Kepler satellite mission. Results: The uvbyβ photometric results are presented. The data are shown to be on the standard system, and the properties of the target stars are discussed: 140 of these are indeed OB stars, a total of 101 targets lie within the β Cephei and/or SPB star instability strips, and each investigated cluster contains such potential pulsators. Conclusions: These measurements will be taken advantage of in a number of subsequent publications. Based on measurements obtained at McDonald Observatory of the University of Texas at Austin.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://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/528/A148

  6. Chemical analysis of giant stars in the young open cluster NGC 3114

    NASA Astrophysics Data System (ADS)

    Santrich, O. J. Katime; Pereira, C. B.; Drake, N. A.

    2013-06-01

    Context. Open clusters are very useful targets for examining possible trends in galactocentric distance and age, especially when young and old open clusters are compared. Aims: We carried out a detailed spectroscopic analysis to derive the chemical composition of seven red giants in the young open cluster NGC 3114. Abundances of C, N, O, Li, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, and Nd were obtained, as well as the carbon isotopic ratio. Methods: 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. Results: We found that NGC 3114 has a mean metallicity of [Fe/H] = -0.01 ± 0.03. The isochrone fit yielded a turn-off mass of 4.2 M⊙. The [N/C] ratio is in good agreement with the models predicted by first dredge-up. We found that two stars, HD 87479 and HD 304864, have high rotational velocities of 15.0 km s-1 and 11.0 km s-1; HD 87526 is a halo star and is not a member of NGC 3114. Conclusions: The carbon and nitrogen abundance in NGC 3114 agree with the field and cluster giants. The oxygen abundance in NGC 3114 is lower compared to the field giants. The [O/Fe] ratio is similar to the giants in young clusters. We detected sodium enrichment in the analyzed cluster giants. As far as the other elements are concerned, their [X/Fe] ratios follow the same trend seen in giants with the same metallicity. Based on observations made with the 2.2 m telescope at the European Southern Observatory (La Silla, Chile).Tables 2 and 5 are available in electronic form at http://www.aanda.org

  7. 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.

  8. Improved proper motion determinations for 15 open clusters based on the UCAC4 catalog

    NASA Astrophysics Data System (ADS)

    Kurtenkov, Alexander; Dimitrova, Nadezhda; Atanasov, Alexander; Aleksiev, Teodor D.

    2016-07-01

    The proper motions of 15 nearby (d > 1 kpc) open clusters (OCs) were recalculated using data from the UCAC4 catalog. Only evolved or main sequence stars inside a certain radius from the center of the cluster were used. The results significantly differ from the ones presented by Dias et al. (2014). This could be explained by a different approach in which we take the field star contamination into account. The present work aims to emphasize the importance of applying photometric criteria for the calculation of OC proper motions.

  9. 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.

  10. 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.

  11. The binary fraction and mass segregation in Alpha Persei open cluster

    NASA Astrophysics Data System (ADS)

    Sheikhi, Najmeh; Hasheminia, Maryam; Khalaj, Pouria; Haghi, Hosein; Zonoozi, Akram Hasani; Baumgardt, Holger

    2016-03-01

    We have obtained membership probabilities of stars within a field of ˜ 3° from the centre of the open cluster Alpha Persei using proper motions and photometry from the PPMXL and Wide-field Infrared Survey Explorer catalogues. We have identified 810 possible stellar members of Alpha Persei. We derived the global and radial present-day mass function (MF) of the cluster and found that they are well matched by two-stage power-law relations with different slopes at different radii. The global MF of Alpha Persei shows a turnover at m = 0.62 M⊙ with low- and high-mass slopes of αlow = 0.50 ± 0.09 (0.1 < m/ M⊙ < 0.62) and αhigh = 2.32 ± 0.14 (0.62 ≤ m/ M⊙ < 4.68), respectively. The high-mass slope of the cluster increases from 2.01 inside 1.10° to 2.63 outside 2.2°, whereas the mean stellar mass decreases from 0.95 to 0.57 M⊙ in the same regions, signifying clear evidence of mass segregation in the cluster. From an examination of the high-quality colour-magnitude data of the cluster and performing a series of Monte Carlo simulations, we obtained a binary fraction of fbin = 34 ± 12 per cent for stars with 0.70 < m/ M⊙ < 4.68. This is significantly larger than the observed binary fraction, indicating that this open cluster contains a large population of unresolved binaries. Finally, we corrected the MF slopes for the effect of unresolved binaries and found low- and high-mass slopes of αlow = 0.89 ± 0.11 and αhigh = 2.37 ± 0.09 and a total cluster mass of 352 M⊙ for Alpha Persei.

  12. Subsampled open-reference clustering creates consistent, comprehensive OTU definitions and scales to billions of sequences.

    PubMed

    Rideout, Jai Ram; He, Yan; Navas-Molina, Jose A; Walters, William A; Ursell, Luke K; Gibbons, Sean M; Chase, John; McDonald, Daniel; Gonzalez, Antonio; Robbins-Pianka, Adam; Clemente, Jose C; Gilbert, Jack A; Huse, Susan M; Zhou, Hong-Wei; Knight, Rob; Caporaso, J Gregory

    2014-01-01

    We present a performance-optimized algorithm, subsampled open-reference OTU picking, for assigning marker gene (e.g., 16S rRNA) sequences generated on next-generation sequencing platforms to operational taxonomic units (OTUs) for microbial community analysis. This algorithm provides benefits over de novo OTU picking (clustering can be performed largely in parallel, reducing runtime) and closed-reference OTU picking (all reads are clustered, not only those that match a reference database sequence with high similarity). Because more of our algorithm can be run in parallel relative to "classic" open-reference OTU picking, it makes open-reference OTU picking tractable on massive amplicon sequence data sets (though on smaller data sets, "classic" open-reference OTU clustering is often faster). We illustrate that here by applying it to the first 15,000 samples sequenced for the Earth Microbiome Project (1.3 billion V4 16S rRNA amplicons). To the best of our knowledge, this is the largest OTU picking run ever performed, and we estimate that our new algorithm runs in less than 1/5 the time than would be required of "classic" open reference OTU picking. We show that subsampled open-reference OTU picking yields results that are highly correlated with those generated by "classic" open-reference OTU picking through comparisons on three well-studied datasets. An implementation of this algorithm is provided in the popular QIIME software package, which uses uclust for read clustering. All analyses were performed using QIIME's uclust wrappers, though we provide details (aided by the open-source code in our GitHub repository) that will allow implementation of subsampled open-reference OTU picking independently of QIIME (e.g., in a compiled programming language, where runtimes should be further reduced). Our analyses should generalize to other implementations of these OTU picking algorithms. Finally, we present a comparison of parameter settings in QIIME's OTU picking workflows and

  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. WIYN Open Cluster Study. LV. Astrometry and Membership in NGC 6819

    NASA Astrophysics Data System (ADS)

    Platais, Imants; Gosnell, Natalie M.; Meibom, Søren; 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 ~0.2 mas yr-1 within 10' of the cluster center to 1.1 mas yr-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 ~ 18 and within 10' from the cluster center. The formal sum of membership probabilities indicates a total of ~2500 cluster members down to V ~ 22. We confirm the cluster membership of several variable stars, including some eclipsing binaries. The estimated absolute proper motion of NGC 6819 is \\mu _x^abs=-2.6+/- 0.5 and \\mu _y^abs=-4.2+/- 0.5 mas yr-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. Based on observations collected at the Canada-France-Hawaii Telescope.

  15. 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.

  16. 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

  17. RACE-OC project: rotation and variability in the open cluster M 11 (NGC 6705)

    NASA Astrophysics Data System (ADS)

    Messina, S.; Parihar, P.; Koo, J.-R.; Kim, S.-L.; Rey, S.-C.; Lee, C.-U.

    2010-04-01

    Context. Rotation and magnetic activity are intimately linked in main-sequence stars of G or later spectral types. The presence and level of magnetic activity depend on stellar rotation, and rotation itself is strongly influenced by the strength and topology of the magnetic fields. Open clusters represent especially useful targets for investigating the connection among rotation, activity, and age. Over time, stellar activity and rotation evolve, providing us with a promising diagnostic tool to determine the age of the field stars. Aims: The open cluster M11 has been studied as a part of the RACE-OC project (Rotation and ACtivity Evolution in Open Clusters), which aims to explore the evolution of rotation and magnetic activity in the late-type members of open clusters with different ages. Methods: Photometric observations of the open cluster M 11 were carried out in June 2004 using the LOAO 1 m telescope. The rotation periods of the cluster members were determined by Fourier analysis of photometric data time series. We investigated the relations between the surface activity, characterized by the light curve amplitude, and rotation. Results: We have discovered a total of 75 periodic variables in the M 11 FoV, of which 38 are candidate cluster members. Specifically, among cluster members we discovered 6 early-type periodic variables, 2 eclipsing binaries, and 30 bona-fide single periodic late-type variables. Considering the rotation periods of 16 G-type members of the almost coeval 200-Myr M 34 cluster, we could determine the rotation period distribution from a more numerous sample of 46 single G stars at an age of about 200-230 Myr and determine a median rotation period of P = 4.8 d. Conclusions: A comparison with the younger M 35 cluster (~150 Myr) and with the older M37 cluster (~550 Myr) shows that G stars rotate more slowly than younger M 35 stars and more rapidly than older M 37 stars. The measured variation in the median rotation period is consistent with the

  18. Photometric study of open star clusters in II quadrant: Teutsch 1 and Riddle 4

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    We present the broad band UBVI CCD photometry in the region of two open star clusters Teutsch 1 and Riddle 4 located in the second Galactic quadrant. The optical CCD data for these clusters are obtained for the first time. Radii of the clusters are estimated as 3‧.5 for both the clusters. Using two color (U - B) versus (B - V) diagram we determined the reddening as E(B - V) = 0.40 ± 0.05 mag for Teutsch 1 and 1.10 ± 0.05 mag for Riddle 4. Using 2MASS JHK and optical data, we estimated E(J - K) = 0.24 ± 0.05 mag and E(V - K) = 1.40 ± 0.05 mag for Teutsch 1 and E(J - K) = 0.47 ± 0.06 mag and E(V - K) = 2.80 ± 0.06 mag for Riddle 4. Color-excess ratio indicates normal interstellar extinction law in the direction of both the clusters. We estimated distance as 4.3 ± 0.5 Kpc for Teutsch 1 and 2.8 ± 0.2 Kpc for Riddle 4 by comparing the color-magnitude diagram of the clusters with theoretical isochrones. The age of the clusters has been estimated as 200 ± 20 Myr for Teutsch 1 and 40 ± 10 Myr for Riddle 4 using the stellar isochrones of metallicity Z = 0.02 . The Mass function slope has been derived 1.89 ± 0.43 and 1.41 ± 0.70 for Teutsch 1 and Riddle 4 respectively. Our analysis indicates that both the clusters are dynamically relaxed. A slight bend of Galactic disc towards the southern latitude is found in the longitude range l = 130-180°.

  19. Peculiarities of the abundances of neutron-capture elements in Galactic open clusters

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    The properties of the relative abundances of rapid and slow neutron-capture elements are studied using a catalog containing spectroscopic abundance determinations for 14 elements produced in various nuclear-synthesis processes for 90 open clusters. The catalog also contains the positions, ages, velocities, and elements of the Galactic orbits of the clusters. The relative abundances of both r-elements (Eu) and s-elements (Y, Ba, La, and Ce) in clusters with high, elongated orbits and in field stars of the Galactic thin disk display different dependences on metallicity, age, Galactocentric distance, and the elements of the Galactic orbits, supporting the view that these objects have different natures. In young clusters, not only barium, but also the three other studied s-elements display significantly higher relative abundances than field stars of the same metallicity. The relative abundances of Eu are lower in highmetallicity clusters ([Fe/H] > -0.1) with high, elongated orbits than in field giants, on average, while the [Eu/Fe] ratios in lower-metallicity clusters are the same as those in field stars, on average, although with a large scatter. The metallicity dependence of the [O, Mg/Eu] ratios in clusters with high, elongated orbits and in field stars are substantially different. These and other described properties of the Eu abundances, together with the properties of the abundances of primary a-elements, can be understood in a natural way if clusters with high, elongated orbits with different metallicities formed as a result of interactions of two types of high-velocity clouds with the interstellar medium of the Galactic disk: low-metallicity highvelocity clouds that formed from "primordial" gas, and high-metallicity clouds with intermediate velocities that formed in "Galactic fountains."

  20. Google Classroom and Open Clusters: An Authentic Science Research Project for High School Students

    NASA Astrophysics Data System (ADS)

    Johnson, Chelen H.; Linahan, Marcella; Cuba, Allison Frances; Dickmann, Samantha Rose; Hogan, Eleanor B.; Karos, Demetra N.; Kozikowski, Kendall G.; Kozikowski, Lauren Paige; Nelson, Samantha Brooks; O'Hara, Kevin Thomas; Ropinski, Brandi Lucia; Scarpa, Gabriella; Garmany, Catharine D.

    2016-01-01

    STEM education is about offering unique opportunities to our students. For the past three years, students from two high schools (Breck School in Minneapolis, MN, and Carmel Catholic High School in Mundelein, IL) have collaborated on authentic astronomy research projects. This past year they surveyed archival data of open clusters to determine if a clear turnoff point could be unequivocally determined. Age and distance to each open cluster were calculated. Additionally, students requested time on several telescopes to obtain original data to compare to the archival data. Students from each school worked in collaborative teams, sharing and verifying results through regular online hangouts and chats. Work papers were stored in a shared drive and on a student-designed Google site to facilitate dissemination of documents between the two schools.

  1. The RACE-OC project: Rotation and Activity Evolution in Open Clusters

    NASA Astrophysics Data System (ADS)

    Messina, S.; Distefano, E.; Parihar, Padmakar; Busà, I.; Cutispoto, G.; Lanza, A. F.; Lanzafame, A.; Pagano, I.; Biazzo, K.; Leto, G.; Hatzidimitriou, D.; Kim, S.-L.; Koo, J.-R.; Kang, Y. B.

    2009-02-01

    The RACE-OC project, standing for Rotation and Activity Evolution in Open Clusters, is a long-term project aimed at studying the evolution of rotation and magnetic activity of late-type members of stellar open clusters. Magnetic fields play a fundamental role in altering the rotational properties of late-type stars. They are responsible, e.g., for angular momentum loss in the wind or its redistribution in the stellar interior. Magnetic fields in late-type stars and their related phenomena, such as photospheric cool spots and bright faculae, chromospheric plages, and X-ray emission, in turn depend on the stellar rotation which controls the efficiency of the hydromagnetic dynamo. Thus, the evolution of angular momentum and magnetic activity offer complementary approaches to understanding the mechanisms by which rotation and magnetic fields influence each other in late-type stars.

  2. The Search for Low Mass Members of the Young Open Cluster Stock 2

    NASA Astrophysics Data System (ADS)

    Foster, D. C.; Byrne, P. B.; Rolleston, W. R. J.

    We present a combined photometric and proper motion survey of the 100Myr open cluster Stock 2. BVRI CCD photometry was obtained for 21 5 x 5 arcmin fields. Fifty-nine candidate members were selected from (B, B-V) and (R, R-I) colour magnitude diagrams using the theoretical isochrones of D'Antona & Mazzitelli (1994). We also obtained SuperCOSMOS scans of three POSS plates. From their position in a proper motion vector-point diagram we estimate that 12 of the 59 candidate members selected above are likely to be cluster members. We also present the results of analysis based only on the POSS data, and identify 311 candidate cluster members.

  3. Mass function study of open star clusters Haffner 11 and Czernik 31

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    We analysis VI CCD data of two open clusters Haffner 11 and Czernik 31 in order to determine their luminosity function, mass function and mass-segregation for the first time. The observed luminosity function is corrected for both data incompleteness and field star contamination. Theoretical stellar evolutionary isochrones are used to convert luminosity function into mass function. The Mass function slopes are derived as 1.22 ± 0.42 and 1.55 ± 0.38 for Haffner 11 and Czernik 31 respectively. They agree with the Salpeter value (x = 1.35) within the errors. The effect of mass segregation are observed in both the clusters. The estimated dynamical relaxation time is less than age of the clusters. This indicates that they are dynamically relaxed. The cause of relaxation may be due to the dynamical evolution or imprint of star formation or both.

  4. 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.

  5. Open clusters and stellar associations: recent results of the Italian community

    NASA Astrophysics Data System (ADS)

    Sciortino, S.

    Current research on open clusters and stellar associations in the Galaxy aims to answer key scientific questions at the hearth of stellar physics, such as the universality of the IMF and its shape in the sub-stellar regime, the star and disk evolution from the PMS to the MS phase, the role played by high energy radiation in the YSO (Young Stellar Object) evolution, and its coronal vs. accretion shock origin, the truly coeval origin of young cluster members and its implication on the still controversial speed of the star formation process. The study of clusters with age greater than 1 Gyr is crucial for understanding the evolution and enrichment of Galaxy disk and its implication for the occurrence of similar phenomena in outer galaxies. I will review recent selected results obtained by scientists of the Italian community in this research area.

  6. 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.

  7. Evidence of the Galactic outer ring R1R2' from young open clusters and OB-associations

    NASA Astrophysics Data System (ADS)

    Mel'nik, A. M.; Rautiainen, P.; Glushkova, E. V.; Dambis, A. K.

    2016-02-01

    The distribution of young open clusters in the Galactic plane within 3 kpc from the Sun suggests the existence of the outer ring R1R2' in the Galaxy. The optimum value of the solar position angle with respect to the major axis of the bar, θb, providing the best agreement between the distribution of open clusters and model particles is θb=35±10°. The kinematical features obtained for young open clusters and OB-associations with negative Galactocentric radial velocity VR indicate the solar location near the descending segment of the outer ring R2.

  8. An observational asteroseismic study of the pulsating B-type stars in the open cluster NGC 884

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    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 asteroseismic study based on the discovery of numerous multi-periodic and mono-periodic B-type stars in the open cluster NGC 884 (χ Persei). Our study illustrates the current status of ensemble asteroseismology of this young open cluster.

  9. 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)

  10. Cepheids in open clusters: an 8D all-sky census

    NASA Astrophysics Data System (ADS)

    Anderson, Richard I.; Eyer, Laurent; Mowlavi, Nami

    2013-09-01

    Cepheids in Galactic open clusters (CCs) are of great importance as zero-point calibrators of the Galactic Cepheid period-luminosity relationship (PLR). We perform an eight-dimensional all-sky census that aims to identify new bona fide CCs and provides a ranking of membership confidence for known CC candidates according to membership probabilities. The probabilities are computed for combinations of known Galactic open clusters and classical Cepheid candidates, based on spatial, kinematic and population-specific membership constraints. Data employed in this analysis are taken largely from published literature and supplemented by a year-round observing programme on both hemispheres dedicated to determining systemic radial velocities of Cepheids. In total, we find 23 bona fide CCs, 5 of which are candidates identified for the first time, including an overtone-Cepheid member in NGC 129. We discuss a subset of CC candidates in detail, some of which have been previously mentioned in the literature. Our results indicate unlikely membership for seven Cepheids that have been previously discussed in terms of cluster membership. We furthermore revisit the Galactic PLR using our bona fide CC sample and obtain a result consistent with the recent calibration by Turner. However, our calibration remains limited mainly by cluster uncertainties and the small number of long-period calibrators. In the near future, Gaia will enable our study to be carried out in much greater detail and accuracy, thanks to data homogeneity and greater levels of completeness.

  11. 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.

  12. Barium Surface Abundances of Blue Stragglers in the Open Cluster NGC 6819

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    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.

  13. 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. PMID:25174709

  14. 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.

  15. WIYN Open Cluster Study. LXIII. Abundances in the Super-metal-rich Open Cluster NGC 6253 from Hydra Spectroscopy of the 7774 Å Oxygen Triplet Region

    NASA Astrophysics Data System (ADS)

    Maderak, Ryan M.; Deliyannis, Constantine P.; Anthony-Twarog, Barbara J.; Twarog, Bruce A.; Cummings, Jeffery D.; King, Jeremy R.; Steiman-Cameron, Thomas Y.

    2015-04-01

    We present a spectroscopic abundance analysis of the old, super-metal-rich open cluster NGC 6253, with emphasis on its O abundance. High-dispersion, 7774 Å O i triplet region spectra of 47 stars were obtained using Hydra II on the CTIO Blanco 4 m. Radial velocity analysis confirms 39 stars consistent with single star membership, primarily at the turnoff. Thirty-six of these are included in our abundance analysis. Our differential analysis relative to the Sun yields primarily scaled-solar values, with weighted cluster averages of [O/H] = +0.440 ± 0.020, [Fe/H] = +0.445 ± 0.014, [Al/H] = +0.487 ± 0.020, [Si/H] = +0.504 ± 0.018, and [Ni/H] = +0.702 ± 0.018 (where the errors are {{σ }μ }). We discuss possible origins for the three known super-metal-rich clusters based upon their abundance patterns, Galactic locations, and space motions. The abundance patterns of NGC 6253 are very similar to those of NGC 6791 and NGC 6583. With the possible exception of oxygen, the abundances of these clusters are all close to scaled-solar, and they are similar to patterns seen in metal-rich disk dwarfs and giants. However, they also seem to differ from those of metal-rich bulge stars. We demonstrate that NGC 6253 is unusually oxygen rich (in [O/H]) for its 3.3 Gyr age. While we find [O/Fe] to be scaled-solar for NGC 6253, the more recently reported values for NGC 6791 show a large variation, from values close to scaled-solar down to values at least a factor of two below scaled-solar. We discuss the possibility that the scaled-solar [O/Fe] abundances of NGC 6253 and NGC 6791 might reflect a flattening of the Galactic [O/Fe] versus [Fe/H] relationship. This possibility may be consistent with disk star abundance data, which show an apparent “floor” at [O/Fe] ˜ -0.1 for [Fe/H] \\gt 0, and with chemical evolution model results, which may predict such a flattening due to a decrease in supernova Fe yields at super-solar-metallicities. Orbit solutions for NGC 6791 allow that it

  16. The CNO Bi-cycle in the Open Cluster NGC 752

    NASA Astrophysics Data System (ADS)

    Hawkins, Keith; Schuler, S.; King, J.; The, L.

    2011-01-01

    The CNO bi-cycle is the primary energy source for main sequence stars more massive than the sun. To test our understanding of stellar evolution models using the CNO bi-cycle, we have undertaken light-element (CNO) abundance analysis of three main sequence dwarf stars and three red giant stars in the open cluster NGC 752 utilizing high resolution (R 50,000) spectroscopy from the Keck Observatory. Preliminary results indicate, as expected, there is a depletion of carbon in the giants relative to the dwarfs. Additional analysis is needed to determine if the amount of depletion is in line with model predictions, as seen in the Hyades open cluster. Oxygen abundances are derived from the high-excitation O I triplet, and there is a 0.19 dex offset in the [O/H] abundances between the giants and dwarfs which may be explained by non-local thermodynamic equilibrium (NLTE), although further analysis is needed to verify this. The standard procedure for spectroscopically determining stellar parameters used here allows for a measurement of the cluster metallicity, [Fe/H] = 0.04 ± 0.02. In addition to the Fe abundances we have determined Na, Mg, and Al abundances to determine the status of other nucleosynthesis processes. The Na, Mg and Al abundances of the giants are enhanced relative to the dwarfs, which is consistent with similar findings in giants of other open clusters. Support for K. Hawkins was provided by the NOAO/KPNO Research Experiences for Undergraduates (REU) Program which is funded by the National Science Foundation Research Experiences for Undergraduates Program and the Department of Defense ASSURE program through Scientific Program Order No. 13 (AST-0754223) of the Cooperative Agreement No. AST-0132798 between the Association of Universities for Research in Astronomy (AURA) and the NSF.

  17. 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.

  18. New Wolf-Rayet stars in Galactic open clusters - Sher 1 and the giant H II region core Westerlund 2

    NASA Technical Reports Server (NTRS)

    Moffat, Anthony F. J.; Shara, Michael M.; Potter, Michael

    1991-01-01

    Two new Galactic Wolf-Rayet stars were found in open clusters: a WN4 star in the O9 cluster Sher 1 and a WN7 star in the O7 cluster Westerlund 2. This confirms a previous trend, namely that fainter, hotter WN stars tend to be older than brighter, cooler WN stars. This may be a consequence of evolution via extreme mass loss.

  19. Abundance analysis of B, A and F dwarfs in the M6 open cluster: Spectrum synthesis method

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    The chemical abundances of 10 stars in the M6 open cluster (˜100 Myr) were derived using spectrum synthesis. The stars were observed using the FLAMES/GIRAFFE spectrograph. We found star-to-star variations in abundances for A type stars. General enrichment of Si, Cr, and Y were obtained for the cluster.

  20. VizieR Online Data Catalog: Galactic open clusters in RAVE (Conrad+, 2014)

    NASA Astrophysics Data System (ADS)

    Conrad, C.; Scholz, R.-D.; Kharchenko, N. V.; Piskunov, A. E.; Schilbach, E.; Roser, S.; Boeche, C.; Kordopatis, G.; Siebert, A.; Williams, M.; Munari, U.; Matijevic, G.; Grebel, E. K.; Zwitter, T.; de Jong, R. S.; Steinmetz, M.; Gilmore, G.; Seabroke, G.; Freeman, K.; Navarro, J. F.; Parker, Q.; Reid, W.; Watson, F.; Gibson, B. K.; Bienayme, O.; Wyse, R.; Bland-Hawthorn, J.; Siviero, A.

    2014-01-01

    The presented tables summarise new radial velocities and average metallicities for Galactic open clusters extracted from the Catalogue of Open Cluster Data (COCD; Kharchenko et al. 2005, Cat. J/A+A/438/1163, J/A+A/440/403). The data were obtained from the RAdial Velocity Experiment (RAVE; Kordopatis et al. 2013AJ....146..134K) through a cross match with the stellar catalogues related to the COCD. The RV and [M/H] values were computed as weighted means, considering the individual uncertainties of the included members and their cluster membership probability based on position, proper motion, and photometry. The three uncertainties listed originate from different calculations: "RVRAVE" and "MetRAVE" are the weighted mean values for RV and [M/H] "errRV" and "errMet" are equivalent to the uncertainty of the mean values "sigRV" and "sigMet" are the standard deviations of the mean values "eRV" and "eMet" weighted mean values of the individual uncertainties of the included open cluster (OC) members For the calculations we primarily considered most probable OC members (best members) with a membership probability of at least 61%. Only in cases where just one or no most probable members was available we also included possible members (good members) with membership probabilities above 14%. In the table we include the numbers for both types of members separately: best members -> "bmem" and good members -> "gmem". We included reference values for RVs from the second version of the Catalogue of Radial Velocities with Astrometric Data (CRVAD-2) and the Catalogue of Radial Velocities of Open Clusters and Associations (CRVOCA) provided by Kharchenko et al. 2007, Cat. III/254). The CRVAD-2 reference values were computed according to the RAVE values for identified OC members. The CRVOCA references were directly extracted from the catalogue and number of OC members used are given in column "nmem". The reference values for [M/H] were obtained from the online compilation provided by Dias

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  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. 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.

  8. SOUNDING OPEN CLUSTERS: ASTEROSEISMIC CONSTRAINTS FROM KEPLER ON THE PROPERTIES OF NGC 6791 AND NGC 6819

    SciTech Connect

    Basu, Sarbani; Esch, Lisa; Grundahl, Frank; Brogaard, Karsten; Bruntt, Hans; Stello, Dennis; Bedding, Timothy R.; Huber, Daniel; Kallinger, Thomas; Hekker, Saskia; Chaplin, William J.; Elsworth, Yvonne; Mosser, Benoit; GarcIa, Rafael A.; Gai, Ning; Ballot, Jerome; Gruberbauer, Michael; Miglio, Andrea; Yildiz, Mutlu

    2011-03-01

    We present initial results on some of the properties of open clusters NGC 6791 and NGC 6819 derived from asteroseismic data obtained by NASA's Kepler mission. In addition to estimating the mass, radius, and log g of stars on the red giant branch (RGB) of these clusters, we estimate the distance to the clusters and their ages. Our model-independent estimate of the distance modulus of NGC 6791 is (m - M){sub 0} = 13.11 {+-} 0.06. We find (m - M){sub 0} = 11.85 {+-} 0.05 for NGC 6819. The average mass of stars on the RGB of NGC 6791 is 1.20 {+-} 0.01 M{sub sun}, while that of NGC 6819 is 1.68 {+-} 0.03 M{sub sun}. It should be noted that we do not have data that cover the entire RGB and the actual mass will be somewhat lower. We have determined model-dependent estimates of ages of these clusters. We find ages between 6.8 and 8.6 Gyr for NGC 6791, however, most sets of models give ages around 7 Gyr. We obtain ages between 2 and 2.4 Gyr for NGC 6819.

  9. Blue Straggler Stars in Galactic Open Clusters and the Simple Stellar Population Model

    NASA Astrophysics Data System (ADS)

    Xin, Y.; Deng, L.; Han, Z. W.

    2007-05-01

    The presence of blue straggler stars (BSs) as secure members of Galactic open clusters (OCs) poses a major challenge to the conventional picture of simple stellar population (SSP) models. These are based on the stellar evolution theory of single stars, whereas the major formation mechanisms of BSs are all correlated with stellar interactions. We have illustrated this in a previous study based on a small sample of old (age >=1 Gyr) Galactic OCs. However, for the purpose of demonstrating the contributions of BSs to the conventional SSP models statistically and systematically, a large database with sufficient coverage of age and metallicity is definitely needed. The working sample now includes 100 Galactic OCs with ages ranging from 0.1 to 10 Gyr. The contributions of BSs to the integrated light of their host clusters are calculated on an individual cluster basis. The general existence of BSs in our star cluster sample dramatically alters the predictions of conventional SSP models in terms of their integrated properties. Neglecting the consequences of nonstandard evolutionary products, such as BSs, in stellar populations, very large uncertainties can be made in analyzing their integrated spectral energy distributions at unresolvable conditions. The current work strongly suggests that when evolutionary population synthesis technique is used to study the properties of unresolved stellar populations in galaxies, the contributions of BSs should be taken into account.

  10. NGC6791: A case study of using CN and CH band strengths to detect chemical inhomogeneities in open clusters

    NASA Astrophysics Data System (ADS)

    Boberg, Owen; Martell, S. L.; Friel, E. D.

    2014-01-01

    We present an analysis of the CN and CH molecular band strengths for cluster members of the open cluster NGC 6791 using low resolution (R ~ 2000) SEGUE spectra. The spectra were taken as part of the validation process for the SEGUE Stellar Parameter Pipeline (SSPP) and released in the eighth SDSS data release. If there are star-to-star abundance variations present at a given evolutionary state in a stellar population, they may be observed through variations in the molecular band strengths at that stage. Characterizing these variations in globular clusters has shown that the band strengths form a bimodal distribution, indicative of cluster members with different chemical abundances and possibly multiple generations of stars. In this work, we use this technique on an open cluster (NGC 6791) to address the possibility of abundance variations present in the cluster. Performing this analysis on other open clusters has resulted in unimodal distributions of CN and CH band strengths, as expected from their typical physical characteristics. NGC 6791, however, provides an interesting case study for this analysis due to its high mass ~5 x 10 4 solar masses, old age ~ 8 Gyr, and high metallicity [Fe/H] ~ +0.4 dex, making it a less than typical open cluster. For this reason, NGC 6791 has been the subject of other studies (see Twarog, et al. 2011; Geisler, et al. 2012; Carrera, 2012) focused on detecting abundance variations in the cluster using broadband photometry, high resolution spectra, and molecular band strengths. These studies have found some evidence for abundance variations among the cluster members, but there is still debate as to whether these findings are conclusive. In this study, we do not find evidence to support abundance variations between cluster members of NGC 6791.

  11. 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

  12. CCD photometry of late-type stars in the young open cluster IC 2602

    NASA Astrophysics Data System (ADS)

    Foster, D. C.; Byrne, P. B.; Hawley, S. L.; Rolleston, W. R. J.

    1997-11-01

    We present the results of VRI photometry of the young open cluster IC 2602. Two 15 arcmin times 15 arcmin fields were observed in February and May 1991 using the 1-m Swope telescope at Las Campanas. Using theoretical isochrones obtained from \\cite[D'Antona & Mazzitelli (1994)]{dam94}, and allowing for observational and other uncertainties, we identify 78 primary candidate members with 12cluster field with an offset field of similar galactic latitude and estimate the contamination due to background stars to be large, >= 50%, as might be expected given its low galactic latitude. We also compare our photometry with that given for the X-ray detected stars of \\cite[Randich et al. (1995)]{ran95}. We present complimentary narrow band H alpha photometry for a subset of the stars.

  13. Search for transiting exoplanets and variable stars in the open cluster NGC 7243

    NASA Astrophysics Data System (ADS)

    Garai, Z.; Pribulla, T.; Hambálek, Ľ.; Errmann, R.; Adam, Ch.; Buder, S.; Butterley, T.; Dhillon, V. S.; Dincel, B.; Gilbert, H.; Ginski, Ch.; Hardy, L. K.; Kellerer, A.; Kitze, M.; Kundra, E.; Littlefair, S. P.; Mugrauer, M.; Nedoroščík, J.; Neuhäuser, R.; Pannicke, A.; Raetz, S.; Schmidt, J. G.; Schmidt, T. O. B.; Seeliger, M.; Vaňko, M.; Wilson, R. W.

    2016-03-01

    We report results of the first five observing campaigns for the open stellar cluster NGC 7243 in the frame of project Young Exoplanet Transit Initiative (YETI). The project focuses on the monitoring of young and nearby stellar clusters, with the aim to detect young transiting exoplanets and to study other variability phenomena on time-scales from minutes to years. After five observing campaigns and additional observations during 2013 and 2014, a clear and repeating transit-like signal was detected in the light curve of J221550.6+495611. Furthermore, we detected and analysed 37 new eclipsing binary stars in the studied region. The best fit parameters and light curves of all systems are given. Finally, we detected and analysed 26 new, presumably pulsating variable stars in the studied region. The follow-up investigation of these objects, including spectroscopic measurements of the exoplanet candidate, is currently planned.

  14. Evidence of enhanced formation episodes in the Galactic open cluster system

    NASA Astrophysics Data System (ADS)

    Piatti, A. E.

    2010-04-01

    Aims: The exciting debate about the existence of signs of enhanced formation of Galactic open clusters (OCs) is revisited here on the basis of a revised age distribution. Methods: The data were taken from the recently updated 2009 version of the Dias et al.'s 1787 OC catalogue. Results: We found that the present OC's age distribution presents two primary excesses at t ~ 10-15 Myr and 1.5 Gyr, which are signs of enhanced formation episodes similar to those that occurred in other galaxies (e.g., M 51, NGC 1705). When restricting the OC sample to those located in the solar neighbourhood, with the aim of avoiding incompleteness effects, we also find that these clusters are engraved with clear signs of enhanced formation at both ages.

  15. VizieR Online Data Catalog: MWSC IV. 63 new open clusters (Scholz+, 2015)

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    , heliocentric distances, colour-excesses, mean proper motions, ages, tidal parameters. This work represents the second extension of the MWSC survey (Kharchenko et al. 2012, Cat. J/A+A/543/A156, 2013, Cat. J/A+A/558/A53), which had an original input list of 3784 targets. After the first extension by Schmeja et al. (2014, Cat. J/A+A/568/A51), who investigated 782 further candidates, we analysed 692 new candidates. We have adopted for them MWSC numbers starting with 4001. We present: The Catalogue of 63 new MWSC open clusters, which includes several files: Catalogue of cluster parameters (confirmed clusters only); Index of all 692 candidates; Notes for every item of the index list. Within each list the entries are ordered by the MWSC number. The Catalogues of the MWSC Stars in 63 circular sky areas with confirmed clusters. Files are ordered by MWSC number; inside each sky area the entries are ordered by Ks magnitudes. The Atlas of 63 new MWSC clusters diagrams. In the Atlas the Cluster pages are ordered by MWSC number. All the data are given in the same format as in the main MWSC catalogue (J/A+A/558/A53). (5 data files).

  16. 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).

  17. Chemical abundances of A-type dwarfs in the young open cluster M6

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    Elemental abundance analysis of five members in the open cluster M6 (age ˜90 myr) were performed using FLAMES-GIRAFFE spectrograph mounted on 8-meter class VLT telescopes. The abundances of 14 chemical elements were derived. Johnson and Geneva photometric systems, hydrogen line profile fittings, and ionization equilibrium were used to derive the atmospheric parameters of the stars. Synthetic spectra were compared to the observed spectra to derive chemical abundances. The abundance analysis of these five members shows that these stars have an enhancement (or solar composition) of metals in general, with some exceptions. C, O, Ca, Sc, Ni, Y, and Ba exhibit the largest star-to-star abundance variations.

  18. 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.

  19. 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⊙.

  20. 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

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

    DOE PAGESBeta

    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 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

  2. 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.

  3. Spectroscopic Study of the Open Cluster Bochum 7 and the Binary System LSS 1135

    NASA Astrophysics Data System (ADS)

    Corti, M.; Morrell, N. I.; Niemela, V. S.

    1998-11-01

    We report a spectroscopic investigation of brightest stars in the open clust er Bochum 7 (l=265^deg 20, b=-2deg 18; Moffat & Vogt 1975), and a detailed anal ysis of LSS 1135, member of such cluster, using photographic and CCD spectrogra ms obtained with the 1m telescope at CTIO (Chile) and with the 2.15m telescope at CASLEO (Argentina), respectively. Orbital elements for the primary component in LSS 1135 were derived, being the orbital period P=2.7532 days, and fitting a circular orbit solution with a semi amplitude K=113 km/s, was obtained. The spectral type determined for that prima ry component is O6.5 V. Furthermore, spectral types and radial velocities for seven probable members of Bochum 7 were derived, being six of them OB main-sequence stars (one with prob able radial velocity variations) and one supergiant (LSS 1140: O9Ib). Combining our spectral types and radial velocities datasets of Bochum 7 with th e photometric ones published by Moffat & Vogt (1975), we derive a distance of 5 .8 kpc from that open cluster.

  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. 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.

  6. 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.

  7. Characterizing the Stellar Content of the Young Open Cluster Blanco 1

    NASA Astrophysics Data System (ADS)

    King, Piera Andrea Soto; James, David

    2015-01-01

    In this work we seek to derive the age of the nearby and young open cluster Blanco 1. This solar metallicity cluster, is located far from the Galactic plane making it quite unusual and astrophysically interesting. The methods that we used to determinate the age of Blanco 1 employed color magnitude diagrams and various flavors of stellar evolution models.Initially, the data that we used are a suite of F- and G-star spectra, which were acquired using the low-resolution cassegrain spectrograph installed on the 1.9m Radcliffe telescope located at the South African Astronomical Observatory. Comparing optical photometry with spectral types, we hoped to derive reddening vectors to help us with the isochrone fitting of Blanco 1. However, magnetic activity on our target stars prevented us from completing this analysis. We instead used hot, higher-mass, early-spectral type stars in thecluster to derive its reddening vectors.To fit the distance we tried with the HIPPARCOS (209 pc) distance, that have no a good fit in the main sequence. On the other hand we found that the best fit is 240 pc by isochrones D'Antona & Mazzitelli (1997).Finally, isochrones generated from theoretical stellar models were compared to the cluster's color magnitude diagrams, allowing us to estimate the distance-dependent age of Blanco 1. We find that its photometric age is ˜150 Myr, comparable to its lithium and gyrochronology age.

  8. 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.

  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. 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.

  11. Stars approaching the substellar limit in the α Persei open cluster.

    NASA Astrophysics Data System (ADS)

    Zapatero Osorio, M. R.; Rebolo, R.; Martin, E. L.; Garcia Lopez, R. J.

    1996-01-01

    We present intermediate dispersion optical spectroscopy for seven very low-mass stars in the α Per open cluster with spectral types between M3 and M6, including the brown dwarf candidate of Rebolo et al. (1992). Our radial velocity measurements are found to be generally consistent with the mean cluster velocity to within the measurement errors. Hα equivalent widths have been measured and compared to previous published data for other known members of the cluster. A turnover in chromospheric activity around spectral type M3-M4 is observed. The brown dwarf candidate, located in the cool side of the turnover, is confirmed to exhibit a strong Hα variability. It is the coolest α Per candidate member for which spectra are available and for which chromospheric activity has been measured. Using the LiI doublet at λ6707.8A, we derive upper limits to the atmospheric Li abundance in the sample and discuss them in the context of the most recent stellar evolutionary tracks. The non-detection of the Lii line in the spectrum of the brown dwarf candidate implies a mass greater than 0.08Msun_, and therefore it is not a substellar object. However, its position in the HR diagram implies that this star is indeed very close to the substellar limit.

  12. Estimating ages of open star clusters using stellar lumionosity and colour

    NASA Astrophysics Data System (ADS)

    Williams, Chris

    2004-12-01

    This paper was designed for the 'armchair' astronomer who is interested in 'amateur research' by utilising the vast amount of images placed on the Internet from various places. Open star clusters are groups of stars that are physically related, bound by mutual gravitational attraction, populate a limited region of space and are all roughly at the same distance from us. We believe they originate from large cosmic gas and dust clouds within the Milky Way and the process of formation takes only a short time, so therefore all members of the cluster are of similar age. Also, as all the stars in a cluster formed from the same cloud, they are all of similar (initial) chemical composition. This 'family' of stars may be of similar birth age but their evolutionary ages differ due to the variation in their masses. High mass stars evolve much quicker than low mass stars they consume their fuel faster, have higher luminosities and die in a very short time (astronomical speaking) compared to a fractional solar mass star.

  13. 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.

  14. 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. PMID:24401992

  15. 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.

  16. The Unique Na:O Abundance Distribution in NGC 6791: The First Open(?) Cluster with Multiple Populations

    NASA Astrophysics Data System (ADS)

    Geisler, D.; Villanova, S.; Carraro, G.; Pilachowski, C.; Cummings, J.; Johnson, C. I.; Bresolin, F.

    2012-09-01

    Almost all globular clusters investigated exhibit a spread in their light element abundances, the most studied being an Na:O anticorrelation. In contrast, open clusters show a homogeneous composition and are still regarded as Simple Stellar Populations. The most probable reason for this difference is that globulars had an initial mass high enough to retain primordial gas and ejecta from the first stellar generation and thus formed a second generation with a distinct composition, an initial mass exceeding that of open clusters. NGC 6791 is a massive open cluster and warrants a detailed search for chemical inhomogeneities. We collected high-resolution, high signal-to-noise spectra of 21 members covering a wide range of evolutionary status and measured their Na, O, and Fe content. We found [Fe/H] = +0.42 ± 0.01, in good agreement with previous values, and no evidence for a spread. However, the Na:O distribution is completely unprecedented. It becomes the first open cluster to show intrinsic abundance variations that cannot be explained by mixing, and thus the first discovered to host multiple populations. It is also the first star cluster to exhibit two subpopulations in the Na:O diagram with one being chemically homogeneous while the second has an intrinsic spread that follows the anticorrelation so far displayed only by globular clusters. NGC 6791 is unique in many aspects, displaying certain characteristics typical of open clusters, others more reminiscent of globulars, and yet others, in particular its Na:O behavior investigated here, that are totally unprecedented. It clearly had a complex and fascinating history.

  17. Observational properties of the open cluster system of the Milky Way and what they tell us about our Galaxy

    NASA Astrophysics Data System (ADS)

    Moitinho, André

    2010-01-01

    Almost 80 years have passed since Trumpler's analysis of the Galactic open cluster system laid one of the main foundations for understanding the nature and structure of the Milky Way. Since then, the open cluster system has been recognised as a key source of information for addressing a wide range of questions about the structure and evolution of our Galaxy. Over the last decade, surveys and individual observations from the ground and space have led to an explosion of astrometric, kinematic and multiwavelength photometric and spectroscopic open cluster data. In addition, a growing fraction of these data is often time-resolved. Together with increasing computing power and developments in classification techniques, the open cluster system reveals an increasingly clearer and more complete picture of our Galaxy. In this contribution, I review the observational properties of the Milky Way's open cluster system. I discuss what they can and cannot teach us now and in the near future about several topics such as the Galaxy's spiral structure and dynamics, chemical evolution, large-scale star formation, stellar populations and more.

  18. A uvbyCaHβ CCD Analysis of the Open Cluster Standard NGC 752

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    Precision uvbyCaHβ photometry of the nearby old open cluster, NGC 752, is presented. The mosaic of CCD fields covers an area ˜42‧ on a side with internal precision at the 0.005-0.010 mag level for the majority of stars down to V ˜ 15. The CCD photometry is tied to the standard system using an extensive set of published photoelectric observations adopted as secondary standards within the cluster. Multicolor indices are used to eliminate as nonmembers a large fraction of the low probability proper-motion members near the faint end of the main sequence, while identifying 24 potential dwarf members between V = 15.0 and 16.5, eight of which have been noted before from Vilnius photometry. From 68 highly probable F dwarf members, we derive a reddening estimate of E(b - y) = 0.025 ± 0.003 (E(B - V) = 0.034 ± 0.004), where the error includes the internal photometric uncertainty and the systematic error arising from the choice of the standard (b - y, Hβ) relation. With reddening fixed, [Fe/H] is derived from the F dwarf members using both m1 and hk, leading to [Fe/H] = -0.071 ± 0.014 (sem) and -0.017 ± 0.008 (sem), respectively. Taking the internal precision and possible systematics in the standard relations into account, [Fe/H] for NGC 752 becomes -0.03 ± 0.02. With the reddening and metallicity defined, we use the Victoria-Regina isochrones on the Strömgren system and find an excellent match for (m - M) = 8.30 ± 0.05 and an age of 1.45 ± 0.05 Gyr at the appropriate metallicity. WIYN Open Cluster Study LXIX.

  19. 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

  20. DETECTABILITY OF FREE FLOATING PLANETS IN OPEN CLUSTERS WITH THE JAMES WEBB SPACE TELESCOPE

    SciTech Connect

    Pacucci, Fabio; Ferrara, Andrea; D'Onghia, Elena

    2013-12-01

    Recent observations have shown the presence of extra-solar planets in Galactic open stellar clusters, such as in Praesepe (M44). These systems provide a favorable environment for planetary formation due to the high heavy-element content exhibited by the majority of their population. The large stellar density, and corresponding high close-encounter event rate, may induce strong perturbations of planetary orbits with large semimajor axes. Here we present a set of N-body simulations implementing a novel scheme to treat the tidal effects of external stellar perturbers on planetary orbit eccentricity and inclination. By simulating five nearby open clusters, we determine the rate of occurrence of bodies extracted from their parent stellar system by quasi-impulsive tidal interactions. We find that the specific free-floating planet production rate N-dot {sub o} (total number of free-floating planets per unit of time, normalized by the total number of stars), is proportional to the stellar density ρ{sub *} of the cluster: N-dot {sub o}=αρ{sub ⋆}, with α = (23 ± 5) × 10{sup –6} pc{sup 3} Myr{sup –1}. For the Pleiades (M45), we predict that ∼26% of stars should have lost their planets. This raises the exciting possibility of directly observing these wandering planets with the James Webb Space Telescope in the near-infrared band. Assuming a surface temperature for the planet of ∼500 K, a free-floating planet of Jupiter size inside the Pleiades would have a specific flux of F {sub ν} (4.4 μm) ≈4 × 10{sup 2} nJy, which would lead to a very clear detection (S/N ∼ 100) in only one hour of integration.

  1. 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.

  2. ANALYSIS OF DETACHED ECLIPSING BINARIES NEAR THE TURNOFF OF THE OPEN CLUSTER NGC 7142

    SciTech Connect

    Sandquist, Eric L.; Serio, Andrew W.; Orosz, Jerome; Shetrone, Matthew E-mail: aserio@gemini.edu E-mail: shetrone@astro.as.utexas.edu

    2013-08-01

    We analyze extensive BVR{sub C}I{sub C} photometry and radial velocity measurements for three double-lined deeply eclipsing binary stars in the field of the old open cluster NGC 7142. The short period (P = 1.9096825 days) detached binary V375 Cep is a high probability cluster member, and has a total eclipse of the secondary star. The characteristics of the primary star (M = 1.288 {+-} 0.017 M{sub Sun }) at the cluster turnoff indicate an age of 3.6 Gyr (with a random uncertainty of 0.25 Gyr), consistent with earlier analysis of the color-magnitude diagram. The secondary star (M = 0.871 {+-} 0.008 M{sub Sun }) is not expected to have evolved significantly, but its radius is more than 10% larger than predicted by models. Because this binary system has a known age, it is useful for testing the idea that radius inflation can occur in short period binaries for stars with significant convective envelopes due to the inhibition of energy transport by magnetic fields. The brighter star in the binary also produces a precision estimate of the distance modulus, independent of reddening estimates: (m - M){sub V} = 12.86 {+-} 0.07. The other two eclipsing binary systems are not cluster members, although one of the systems (V2) could only be conclusively ruled out as a present or former member once the stellar characteristics were determined. That binary is within 0. Degree-Sign 5 of edge-on, is in a fairly long-period eccentric binary, and contains two almost indistinguishable stars. The other binary (V1) has a small but nonzero eccentricity (e = 0.038) in spite of having an orbital period under 5 days.

  3. Analysis of Detached Eclipsing Binaries near the Turnoff of the Open Cluster NGC 7142

    NASA Astrophysics Data System (ADS)

    Sandquist, Eric L.; Shetrone, Matthew; Serio, Andrew W.; Orosz, Jerome

    2013-08-01

    We analyze extensive BVRCIC photometry and radial velocity measurements for three double-lined deeply eclipsing binary stars in the field of the old open cluster NGC 7142. The short period (P = 1.9096825 days) detached binary V375 Cep is a high probability cluster member, and has a total eclipse of the secondary star. The characteristics of the primary star (M = 1.288 ± 0.017 M ⊙) at the cluster turnoff indicate an age of 3.6 Gyr (with a random uncertainty of 0.25 Gyr), consistent with earlier analysis of the color-magnitude diagram. The secondary star (M = 0.871 ± 0.008 M ⊙) is not expected to have evolved significantly, but its radius is more than 10% larger than predicted by models. Because this binary system has a known age, it is useful for testing the idea that radius inflation can occur in short period binaries for stars with significant convective envelopes due to the inhibition of energy transport by magnetic fields. The brighter star in the binary also produces a precision estimate of the distance modulus, independent of reddening estimates: (m - M) V = 12.86 ± 0.07. The other two eclipsing binary systems are not cluster members, although one of the systems (V2) could only be conclusively ruled out as a present or former member once the stellar characteristics were determined. That binary is within 0.°5 of edge-on, is in a fairly long-period eccentric binary, and contains two almost indistinguishable stars. The other binary (V1) has a small but nonzero eccentricity (e = 0.038) in spite of having an orbital period under 5 days.

  4. 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.

  5. 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

  6. Stromvil CCD Photometry in Globular Cluster M 3

    NASA Astrophysics Data System (ADS)

    Boyle, Richard P.; Janusz, R.; Philip, A. G. D.; Straizys, V.; Vrba, F.

    2007-12-01

    We observed the globular cluster M 3 in the 7-band Stromvil system plus Vilnius X-band at the 1.8-m Vatican Advanced Technology Telescope with a 2K CCD giving a 6-arcmin field. We observed the open cluster M 67 in the same run. Here from the residuals of many stars fit to quality CCD Vilnius photometry (Laugalys et al., 2004, Baltic Astronomy, 13, 1) we reshape and thus correct the initial flatfields. M 67 with a wide color base gives the color transformations of the run by calibrating from about 12 photoelectric standards in the Stromvil and similar Vilnius systems. In M 3 six photoelectric standards of moderate quality, all red stars of 13th magnitude in the Vilnius system calibrate the zero-point magnitude scale. Point-spread-function fitting to the stars in the crowded M 3 field resolves blends. With relatively short exposures of minutes a limiting magnitude V=15 is obtained with a signal/noise ratio about 100. So from this new photometry we subsequently can classify all types of stars and treat questions of reddening, distances, membership and metallicity at least at the horizontal branch of the cluster.

  7. ELEMENTAL ABUNDANCE RATIOS IN STARS OF THE OUTER GALACTIC DISK. IV. A NEW SAMPLE OF OPEN CLUSTERS

    SciTech Connect

    Yong, David; Carney, Bruce W.; Friel, Eileen D. E-mail: bruce@physics.unc.edu

    2012-10-01

    We present radial velocities and chemical abundances for nine stars in the old, distant open clusters Be18, Be21, Be22, Be32, and PWM4. For Be18 and PWM4, these are the first chemical abundance measurements. Combining our data with literature results produces a compilation of some 68 chemical abundance measurements in 49 unique clusters. For this combined sample, we study the chemical abundances of open clusters as a function of distance, age, and metallicity. We confirm that the metallicity gradient in the outer disk is flatter than the gradient in the vicinity of the solar neighborhood. We also confirm that the open clusters in the outer disk are metal-poor with enhancements in the ratios [{alpha}/Fe] and perhaps [Eu/Fe]. All elements show negligible or small trends between [X/Fe] and distance (<0.02 dex kpc{sup -1}), but for some elements, there is a hint that the local (R{sub GC} < 13 kpc) and distant (R{sub GC} > 13 kpc) samples may have different trends with distance. There is no evidence for significant abundance trends versus age (<0.04 dex Gyr{sup -1}). We measure the linear relation between [X/Fe] and metallicity, [Fe/H], and find that the scatter about the mean trend is comparable to the measurement uncertainties. Comparison with solar neighborhood field giants shows that the open clusters share similar abundance ratios [X/Fe] at a given metallicity. While the flattening of the metallicity gradient and enhanced [{alpha}/Fe] ratios in the outer disk suggest a chemical enrichment history different from that of the solar neighborhood, we echo the sentiments expressed by Friel et al. that definitive conclusions await homogeneous analyses of larger samples of stars in larger numbers of clusters. Arguably, our understanding of the evolution of the outer disk from open clusters is currently limited by systematic abundance differences between various studies.

  8. Comparative assessment of bone pose estimation using Point Cluster Technique and OpenSim.

    PubMed

    Lathrop, Rebecca L; Chaudhari, Ajit M W; Siston, Robert A

    2011-11-01

    Estimating the position of the bones from optical motion capture data is a challenge associated with human movement analysis. Bone pose estimation techniques such as the Point Cluster Technique (PCT) and simulations of movement through software packages such as OpenSim are used to minimize soft tissue artifact and estimate skeletal position; however, using different methods for analysis may produce differing kinematic results which could lead to differences in clinical interpretation such as a misclassification of normal or pathological gait. This study evaluated the differences present in knee joint kinematics as a result of calculating joint angles using various techniques. We calculated knee joint kinematics from experimental gait data using the standard PCT, the least squares approach in OpenSim applied to experimental marker data, and the least squares approach in OpenSim applied to the results of the PCT algorithm. Maximum and resultant RMS differences in knee angles were calculated between all techniques. We observed differences in flexion/extension, varus/valgus, and internal/external rotation angles between all approaches. The largest differences were between the PCT results and all results calculated using OpenSim. The RMS differences averaged nearly 5° for flexion/extension angles with maximum differences exceeding 15°. Average RMS differences were relatively small (< 1.08°) between results calculated within OpenSim, suggesting that the choice of marker weighting is not critical to the results of the least squares inverse kinematics calculations. The largest difference between techniques appeared to be a constant offset between the PCT and all OpenSim results, which may be due to differences in the definition of anatomical reference frames, scaling of musculoskeletal models, and/or placement of virtual markers within OpenSim. Different methods for data analysis can produce largely different kinematic results, which could lead to the misclassification

  9. 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.

  10. 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.

  11. 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

  12. Spectroscopy of the ringlike nebula toward the open cluster NGC 3572

    NASA Astrophysics Data System (ADS)

    Noumaru, Junichi; Ogura, Katsuo

    1993-11-01

    Low-dispersion spectroscopy has been obtained for the ringlike nebula which Phelps and Janes (1991) found in the direction of the young open cluster NGC 3572 and suspected as a planetary nebula. Some nearby nebulosities have also been observed. Analyses of these data indicate that all of them, including the NGC 3572 ring, are H II regions. Morphological considerations of the region show that the nearby nebulosities are bright rims which are associated with the H II region BBW 342 and are partly hidden by the obscuring matter lying on this side. The NGC 3572 ring could be of the same nature. However, as the alternative interpretation, it could be a ring nebula (probably a wind-blown bubble) around a massive star (WR/Of star or LBV).

  13. Detection of a new phosphorus rich star in the open cluster M6

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    We present the first spectroscopic analysis of HD318101, a member of the M6 (NGC 6405, age 100 Myr) open cluster, using low and high resolution (R˜7500, R˜25000) spectra stretching from 4500 to 5840 Å. The atmospheric parameters of the star were determined from Geneva photometry and hydrogen line modeling (T_e = 15400 ± 500 K, log g = 4.0 ± 0.25). The abundances of 8 elements were determined by fitting synthetic spectral lines to the observed ones. We derived a strong overabundance of phosphorus (+1.69 dex, relative to the Sun) from several P II lines. We also found helium to be underabundant (-0.37 dex). These abundance anomalies suggest that HD318101 could be a He-weak PGa type star (CP4).

  14. KIC 8263801: A clump star in the Kepler open cluster NGC 6866 field?

    NASA Astrophysics Data System (ADS)

    Abedigamba, O. P.

    2016-07-01

    In this paper we study the field of Kepler open cluster NGC 6866 using the data obtained from Kepler mission collected for a period of 4 years. We search for the red clump (RC) stars amongst the red giant (RG) stars showing solar-like oscillations using median gravity-mode period spacings (ΔP). We find a RG star KIC 8263801 having median gravity-mode period spacing 173.7 ± 6.4 s. We claim based on the median gravity-mode period spacing that KIC 8263801 is a secondary red clump (SRC) star which is massive enough to have ignited Helium burning in a non degenerate core. In the literature, no classification for KIC 8263801 has been provided. This is the first time that a star located in the field of NGC 6866 is classified in this manner.

  15. 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

  16. CCD Photometric Study of the Contact Binary TX Cnc in the Young Open Cluster NGC 2632

    NASA Astrophysics Data System (ADS)

    Liu, Liang; Qian, Sheng-Bang; Boonrucksar, Soonthornthum; Zhu, Li-Ying; He, Jia-Jia; Yuan, J.-Z.

    2007-06-01

    TX Cnc is a member of the young open cluster NGC2632. In the present paper, four CCD epochs of light minimum and a complete V light curve of TX Cnc are presented. A period investigation based on all available photoelectric or CCD data showed that it is superimposed on a long-term increase (dP/dt=+3.97×10-8) and weak evidence suggests that it includes a small-amplitude period oscillation (A3=0d.0028; T3=26.6yr). The light curves in the V band obtained in 2004 were analyzed with the 2003 version of the W-D code. It was shown that TX Cnc is an overcontact binary system with a degree of contact factor f=24.8%. The absolute parameters of the system were calculated: M1=1.319±0.007M⊙, M2=0.600±0.01M⊙; R1=1.28±0.19R⊙, R2=0.91±0.13R⊙. TX Cnc may be on the TRO-controlled stage of the evolutionary scheme proposed by Qian (2001a, b, 2003a), and may contain an invisible tertiary component (m3≈0.097M⊙). If this is true, the tertiary component has played an important role in the formation and evolution of TX Cnc by removing angular momentum from the central system (Pribulla & Rucinski 2006). In this way the contact binary configuration can be formed in the shortlife time of a young open cluster via AML.

  17. HD 285507b: An Eccentric Hot Jupiter in the Hyades Open Cluster

    NASA Astrophysics Data System (ADS)

    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.

    2014-05-01

    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 * = 0.734 M ⊙ R * = 0.656 R ⊙) in a slightly eccentric (e=0.086^{+0.018}_{-0.019}) orbit with a period of 6.0881^{+0.0019}_{-0.0018} days. The induced stellar radial velocity corresponds to a minimum companion mass of M Psin i = 0.917 ± 0.033 M 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 P, allows us to constrain the average value for hot Jupiters to be log {Q_P} = 6.14^{+0.41}_{-0.25}.

  18. 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}.

  19. The RACE-OC project: Rotation and ACtivity Evolution in Open Clusters .

    NASA Astrophysics Data System (ADS)

    Messina, S.

    The RACE-OC (Rotation and ACtivity Evolution in Open Clusters) is a project aimed at studying the evolution of rotation and magnetic activity of the late-type members belonging to open clusters with an age in the range from about 1 to 500 Myr. In late-type stars rotation and solar-like magnetic activity are closely inter-related. In fact, presence and level of stellar magnetic activity depend on rotation. On the other hand, magnetic activity influences the evolution of the angular momentum and determines the atmospheric structure from the PMS to Post-MS evolutionary stages (Dorren & Guinan \\cite{Dorren94}; Guinan et al. \\cite{Guinan01}). Studies of the rotation and magnetic activity evolution versus time are particularly relevant to 1) determine the radiative and magnetic properties of the young Sun; 2) study its evolution history to the present; 3) construct irradiance tables to be used to model paleo-planetary atmospheres. Our aim is to describe the evolution versus time of either the stellar angular momentum and magnetic activity, by inferring from observational data accurate empirical relations between global stellar properties, rotation and activity manifestations at different atmospheric levels to be compared to current stellar evolution and hydromagnetic dynamo models. The multiband CCD photometric observations have been so far carried out with the 0.6m REM (Rapid Eye Mount) telescope (La Silla, Chile) of INAF; the 2m HCT (Himalayan Chandra Telescope) of IIA, the 1.3m Cassegrain telescope of Skinakas Observatory (University of Crete) and, finally, the 1.3m RCT (Robotic Controlled Telescope, Arizona) of Villanova University.

  20. TIME-RESOLVED SPECTROSCOPY OF THE POLAR EU CANCRI IN THE OPEN CLUSTER MESSIER 67

    SciTech Connect

    Williams, Kurtis A.; Howell, Steve B.; Bellini, Andrea; Rubin, Kate H. R.; Bolte, Michael E-mail: steve.b.howell@nasa.gov E-mail: psmith@as.arizona.edu E-mail: rubin@mpia.de

    2013-05-15

    We present time-resolved spectroscopic and polarimetric observations of the AM Her system EU Cnc. EU Cnc is located near the core of the old open cluster Messier 67; new proper motion measurements indicate that EU Cnc is indeed a member of the star cluster, and this system therefore is useful to constrain the formation and evolution of magnetic cataclysmic variables. The spectra exhibit two-component emission features with independent radial velocity variations as well as time-variable cyclotron emission indicating a magnetic field strength of 41 MG. The period of the radial velocity and cyclotron hump variations are consistent with the previously known photometric period, and the spectroscopic flux variations are consistent in amplitude with previous photometric amplitude measurements. The secondary star is also detected in the spectrum. We also present polarimetric imaging measurements of EU Cnc that show a clear detection of polarization, and the degree of polarization drops below our detection threshold at phases when the cyclotron emission features are fading or not evident. The combined data are all consistent with the interpretation that EU Cnc is a low-state polar in the cluster Messier 67. The mass function of the system gives an estimate of the accretor mass of M{sub WD} {>=} 0.68 M{sub Sun} with M{sub WD} Almost-Equal-To 0.83 M{sub Sun} for an average inclination. We are thus able to place a lower limit on the progenitor mass of the accreting white dwarf of {>=}1.43 M{sub Sun }.

  1. Strong evidences for a nonextensive behavior of the rotation period in open clusters

    NASA Astrophysics Data System (ADS)

    de Freitas, D. B.; Nepomuceno, M. M. F.; Soares, B. B.; Silva, J. R. P.

    2014-11-01

    Time-dependent nonextensivity in a stellar astrophysical scenario combines nonextensive entropic indices qK derived from the modified Kawaler's parametrization, and q, obtained from rotational velocity distribution. These q's are related through a heuristic single relation given by q≈ q0(1-Δ t/qK) , where t is the cluster age. In a nonextensive scenario, these indices are quantities that measure the degree of nonextensivity present in the system. Recent studies reveal that the index q is correlated to the formation rate of high-energy tails present in the distribution of rotation velocity. On the other hand, the index qK is determined by the stellar rotation-age relationship. This depends on the magnetic-field configuration through the expression qK=1+4aN/3 , where a and N denote the saturation level of the star magnetic field and its topology, respectively. In the present study, we show that the connection q-qK is also consistent with 548 rotation period data for single main-sequence stars in 11 open clusters aged less than 1 Gyr. The value of qK ˜ 2.5 from our unsaturated model shows that the mean magnetic-field topology of these stars is slightly more complex than a purely radial field. Our results also suggest that stellar rotational braking behavior affects the degree of anti-correlation between q and cluster age t. Finally, we suggest that stellar magnetic braking can be scaled by the entropic index q.

  2. 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.

    2016-08-01

    We present the high resolution (R ≈ 60 000), high signal-to-noise (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 dex 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 Å 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.

  3. 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

  4. λ7774 Oxygen Triplet in Open Cluster Dwarfs: Pleiades and M34,

    NASA Astrophysics Data System (ADS)

    Schuler, S. C.; King, J. R.; Hobbs, L. M.; Pinsonneault, M. H.

    2005-07-01

    We have undertaken a LTE analysis of the high-excitation 7774 Å O I triplet in high-resolution, moderate signal-to-noise spectra of 15 Pleiades (HET/HRS) and 8 M34 (Keck/HIRES) open cluster dwarfs. Effective temperatures range from 5048 - 6172 K for the Pleiades sample and from 5290 - 6130 K for the M34 sample. Relative O abundances have been derived using model atmospheres interpolated from four different sets of ATLAS9 grids: with convective overshoot, without convective overshoot, with the mixing length parameter set to 0.5, and with the convective treatment of Canuto, Goldman, & Mazzitelli. In contrast to existing NLTE predictions, a dramatic increase in O I triplet abundance with decreasing temperature is seen for both clusters, regardless of atmospheric model. S I abundances of three Pleiads derived from the high-excitation λ6052.67 feature mimic the O I abundance behavior. O abundances have also been derived from the 6300 Å [OI] feature in three Pleiads; the abundances exhibit a much lower mean value than the cool dwarf triplet results. These data suggest LTE abundances derived from the O I triplet for cool dwarfs (Teff˜5800 K) should be viewed with caution.

  5. Complex Stellar System ESO65SC03: Open Cluster or Remnant?

    NASA Astrophysics Data System (ADS)

    Joshi, Gireesh C.; Joshi, Y. C.; Joshi, S.; Chowdhury, S.; Tyagi, R. K.

    2015-06-01

    We present a complete spatial and dynamical study of the poorly populated stellar system ESO65SC03. The radial distribution of the system gives a core and cluster radii of 1.10±0.63 and 5.36±0.24 arcmin, respectively. The SNDP does not show any clear enhancement of the surface stellar number density between the stars of the system and the field regions. We derive the optimum isochrone solution for a particular grid size in the CMD using the statistical cleaning procedure. Using the statistically cleaned CMDs, we find the distance modulus, (m - M)0, and reddening, E(B - V), of the system to be 11.8±0.2 and 0.45 mag, respectively. The mean proper motion of this system is - 5.37±0.81 mas yr-1 and 0.31±0.40 in RA and DEC directions, respectively. The mean proper motion of this system is found to be almost similar to the field region. The mass function for the brighter stars is found to be too high for the system to be an open cluster. These combined results place constraints on whether stellar system ESO65SC03 is a POCR or an Asterism. Our understanding is that the ESO65SC03 is in a stage of POCR by losing their main-sequence stars in the dynamic evolution processes.

  6. 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).

  7. 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).

  8. 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).

  9. 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).

  10. An open-source software package for multivariate modeling and clustering: applications to air quality management.

    PubMed

    Wang, Xiuquan; Huang, Guohe; Zhao, Shan; Guo, Junhong

    2015-09-01

    This paper presents an open-source software package, rSCA, which is developed based upon a stepwise cluster analysis method and serves as a statistical tool for modeling the relationships between multiple dependent and independent variables. The rSCA package is efficient in dealing with both continuous and discrete variables, as well as nonlinear relationships between the variables. It divides the sample sets of dependent variables into different subsets (or subclusters) through a series of cutting and merging operations based upon the theory of multivariate analysis of variance (MANOVA). The modeling results are given by a cluster tree, which includes both intermediate and leaf subclusters as well as the flow paths from the root of the tree to each leaf subcluster specified by a series of cutting and merging actions. The rSCA package is a handy and easy-to-use tool and is freely available at http://cran.r-project.org/package=rSCA . By applying the developed package to air quality management in an urban environment, we demonstrate its effectiveness in dealing with the complicated relationships among multiple variables in real-world problems. PMID:25966889

  11. CdC-SF Catalogue.II: Application of its Proper Motions to Open Clusters

    NASA Astrophysics Data System (ADS)

    Vicente, B.; Garzón, F.

    We present an astrometric catalogue of positions and proper motions derived from the Carte du Ciel plates of the San Fernando zone, photographic material with a mean epoch 1901.4 with a limiting magnitude V˜15.Digitization has been made using a conventional flatbed scanner. Special techniques have been developed to handle the combination of plate material and the large distortion introduced by the scanner. A variety of post-scan corrections are shown to be necessary. The equatorial coordinates are on the ICRS system defined by Tycho-2. Comparison with the reference catalog indicates external errors of 0.;​​''2. The UCAC2 Catalogue was used as second-epoch positions to derive proper motions with a mean accuracy of 1.2 mas/year for the proper motions for well-measure stars. The usefulness of the resulting catalogue of proper motions is demonstrated by means of a proper-motion analysis of seven open clusters ASCC 30, BOCHUM 3, NGC 2215, NGC 2302, NGC 2311, NGC 2323 and NGC 2548, determining individual membership probabilities and characterizing the gross properties of each cluster.

  12. 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.

  13. 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.

  14. VizieR Online Data Catalog: CCD {Delta}a-photometry of 8 open clusters (Paunzen+, 2006)

    NASA Astrophysics Data System (ADS)

    Paunzen, E.; Netopil, M.; Iliev, I. K.; Maitzen, H. M.; Claret, A.; Pintado, O. I.

    2006-08-01

    Within the sample of eight open clusters, we have investigated 1698 objects using the narrow band, three filter Delta a photometric system resulting in the detection of twenty three bona-fide magnetic chemically peculiar (CP) stars, eight Be/Ae and eight metal-weak stars. (8 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. Photometry and membership for low mass stars in the young open cluster NGC 2516

    NASA Astrophysics Data System (ADS)

    Jeffries, R. D.; Thurston, M. R.; Hambly, N. C.

    2001-09-01

    We present the results of a 0.86 square degree CCD photometric survey of the open cluster NGC 2516, which has an age of about 150 Myr and may have a much lower metallicity than the similarly-aged Pleiades. Our BVI_c survey of cluster members is complete to V =~ 20 and is used to select a preliminary catalogue of 1254 low mass (0.2cluster candidates, of which about 70-80 percent are expected to be genuine. After applying corrections for contamination by non-members and adding data for higher mass stars from the literature, we investigate the cluster binarity, luminosity and mass function, mass segregation and total mass. We find a binary fraction of 26+/-5 percent, for A to M-type systems with mass ratios between 0.6 and 1, which is very similar to the Pleiades. The mass function is metallicity and evolutionary-model dependent, but consistent with a Salpeter-like law (dN/dlog M~ M-alpha , alpha =+1.47+/-0.11 or alpha =+1.67+/-0.11 for the solar and half-solar metallicity models of Siess et al. \\cite{siess00}, and alpha =+1.58+/-0.10 for the solar metallicity models of D'Antona & Mazzitelli \\cite{dantona97}), for 0.7

  17. THE OPEN CLUSTER CHEMICAL ANALYSIS AND MAPPING SURVEY: LOCAL GALACTIC METALLICITY GRADIENT WITH APOGEE USING SDSS DR10

    SciTech Connect

    Frinchaboy, Peter M.; Thompson, Benjamin; Jackson, Kelly M. E-mail: b.a.thompson1@tcu.edu; and others

    2013-11-01

    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 from this sample. This first contribution from the OCCAM survey presents analysis of 141 members stars in 28 open clusters with high-resolution metallicities derived from a large uniform sample collected as part of the Sloan Digital Sky Survey III/Apache Point Observatory Galactic Evolution Experiment. This sample includes the first high-resolution metallicity measurements for 22 open clusters. With this largest ever uniformly observed sample of open cluster stars we investigate the Galactic disk gradients of both [M/H] and [α/M]. We find basically no gradient in [α/M] across 7.9 kpc ≤ R {sub GC} ≤ 14.5 kpc, but [M/H] does show a gradient for R {sub GC} < 10 kpc and a significant flattening beyond R {sub GC} = 10 kpc. In particular, whereas fitting a single linear trend yields an [M/H] gradient of –0.09 ± 0.03 dex kpc{sup –1}—similar to previously measure gradients inside 13 kpc—by independently fitting inside and outside 10 kpc separately we find a significantly steeper gradient near the Sun (7.9 ≤ R {sub GC} ≤ 10) than previously found (–0.20 ± 0.08 dex kpc{sup –1}) and a nearly flat trend beyond 10 kpc (–0.02 ± 0.09 dex kpc{sup –1})

  18. 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.

  19. The chemical compositions and evolutionary status of red giants in the open cluster NGC 752

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    We present detailed chemical compositions of 10 red giant star members of the Galactic (open) cluster NGC 752, derived from high-resolution (R ≈ 60 000), high signal-to-noise (S/N ≥ 140) spectra. We confirmed cluster memberships by measuring the stellar radial velocities, and by deriving model atmosphere parameters (Teff, log g, [Fe/H] and ξt) from equivalent widths of Fe I, Fe II, Ti I, and Ti II lines. The metallicity we obtained for NGC 752 ([Fe/H] = -0.02 ± 0.05) is in good agreement with previous studies. We derived abundances of α (Mg, Si, Ca), light odd-Z (Na, Al), Fe-group (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn), n-capture (Y, La, Nd, Eu), and p-capture (Li, C, N, O) species for each star. Furthermore, we also derived abundances of the LiCNO p-capture element group and carbon isotopic ratios, using synthetic spectrum analyses of the Li I 6707 Å resonance doublet, the [O I] line at 6300 Å, the CH G-band features near 4311 and 4325 Å, the C2 bandheads at 5160 and 5631 Å, and 12,13CN red system lines in the 7995-8040 Å region. By applying recent isochrones to NGC 752 photometry, and comparing the colour-magnitude diagram information to our Li abundances and 12C/13C ratios, we suggest that the 10 observed red giants can be separated into three first-ascent, six red-clump and one red horizontal branch star.

  20. 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.

  1. Searching for Chemical Signatures of Multiple Stellar Populations in the Old, Massive Open Cluster NGC 6791

    NASA Astrophysics Data System (ADS)

    Bragaglia, Angela; Sneden, Christopher; Carretta, Eugenio; Gratton, Raffaele G.; Lucatello, Sara; Bernath, Peter F.; Brooke, James S. A.; Ram, Ram S.

    2014-11-01

    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.

  2. Binary Origin of Blue Straggler Stars in Star Clusters

    NASA Astrophysics Data System (ADS)

    Xin, Yu

    2015-08-01

    Close-binary evolution is one of the major formation channels of blue straggler stars (BSSs). We present binary evolution models, including case-A and/or case-B mass transfer (MT) in the intermediate- and low-mass stars, to try to understand the binary origin of BSS populations in star clusters. With the help of Monte-Carlo simulations, we compared the distribution of our synthetic MT BSSs with observations in the color-magnitude diagram (CMD) of M67 and M30. The current results show that primordial binary MT can only contribute to a small part of BSSs in M67, and it can credibly explain the formation of the red-BSS sequence observed in the CMD of M30. We also analyzed the spectral properties of BSS populations in open clusters (OCs) based on the LAMOST data, and a small part of BSSs indeed present Carbon depletion compared with the main sequence stars, which indicate their binary origin. Unfortunately, a statistical resfult of how much the binary MT can contribute to BSS fomation in OCs still requires larger working sample.

  3. 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.

  4. 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

    2016-04-01

    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.

  5. 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.

  6. VizieR Online Data Catalog: CCD Δa-photometry of 5 open clusters (Paunzen+, 2002)

    NASA Astrophysics Data System (ADS)

    Paunzen, E.; Maitzen, H. M.

    2002-04-01

    In total, more than 550 objects within the fields of five open clusters (NGC 2439, NGC 3960, NGC 6134, NGC 6192 and NGC 6451) were investigated in order to find classical chemically peculiar stars. One bona-fide CP candidate was detected in each of the open clusters NGC 3960, NGC 6192 and NGC 6451. All three objects seem to be members of the corresponding cluster taking the results from our photometry as well as from the literature. For NGC 6192 and NGC 6451 we found widely different interstellar reddening values and therefore distances and ages in the literature. From an analysis of published Johnson UBVRI photometry, we were able to rule out a rather old age for NGC 6451. This is also supported by the finding of one peculiar object in this cluster with spectral type of about A2. Five variable objects within the field of NGC 6134 were detected. The variability exceeds 10 times (or typically 0.03 mag) the standard deviation of the weighted individual measurements. But since our observations were obtained mostly during one hour (typical integration times of five minutes per filter) on several nights within 45 days, no light curves could yet be derived. For this cluster some Am candidates were reported for which we were not able to detect a significant positive Δ a-value. For a description of the Δa photometric system, see e.g. (5 data files).

  7. GeMs/GSAOI observations of La Serena 94: an old and far open cluster inside the solar circle

    NASA Astrophysics Data System (ADS)

    Santos, João F. C., Jr.; Roman-Lopes, Alexandre; Carrasco, Eleazar R.; Maia, Francisco F. S.; Neichel, Benoit

    2016-02-01

    Physical properties were derived for the candidate open cluster La Serena 94, recently unveiled by the VISTA Variables in the Vía Láctea (VVV) survey. Thanks to the exquisite angular resolution provided by Gemini South multiconjugate adaptive optics system/Gemini South Adaptive Optics Imager (GeMS/GSAOI), we could characterize this system in detail, for the first time, with deep photometry in JHKs bands. Decontaminated JHKs diagrams reach about 5 mag below the cluster turnoff in H. The locus of red clump giants in the colour-colour diagram, together with an extinction law, was used to obtain an average extinction of AV = 14.18 ± 0.71. The same stars were considered as standard candles to derive the cluster distance, 8.5 ± 1.0 kpc. Isochrones were matched to the cluster colour-magnitude diagrams to determine its age, log t(yr) = 9.12 ± 0.06, and metallicity, Z = 0.02 ± 0.01. A core radius of rc = 0.51 ± 0.04 pc was found by fitting King models to the radial density profile. By adding up the visible stellar mass to an extrapolated mass function, the cluster mass was estimated as M=(2.65± 0.57)× 10^3 M⊙, consistent with an integrated magnitude of M_{K_s}=-5.82± 0.16 and a tidal radius of rt = 17.2 ± 2.1 pc. The overall characteristics of La Serena 94 confirm that it is an old open cluster located in the Crux spiral arm towards the fourth Galactic quadrant and distant 7.30 ± 0.49 kpc from the Galactic Centre. The cluster distorted structure, mass segregation and age indicate that it is a dynamically evolved stellar system.

  8. Exploring public discourses about emerging technologies through statistical clustering of open-ended survey questions.

    PubMed

    Stoneman, Paul; Sturgis, Patrick; Allum, Nick

    2013-10-01

    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

  9. Ring opening of strained-ring heterocycles containing nitrogen by an osmium cluster complex

    SciTech Connect

    Adams, R.D.; Chen, Gong

    1992-11-01

    The osmium cluster complex Os{sub 3}(CO){sub 10}({mu}-NCH{sub 2}CH{sub 2}CH{sub 2})({mu}-H) (1) was obtained in 34% yield from the reaction of Os{sub 3}(CO){sub 10}(NCMe){sub 2} with azetidine. Complex 1 was characterized crystallographically and shown to contain a four-membered NCH{sub 2}CH{sub 2}CH{sub 2} ring bridging two of the metal atoms via the nitrogen atom. When heated to 125{degrees}C, 1 was transformed to the new complex Os{sub 3}(CO){sub 10}[{mu}-N=C(H)Et]({mu}-H) (2; 27% yield) by an opening of the four-membered ring and a hydrogen shift. Crystal data: for 1, space group P2{sub 1}/c, a = 8.793 (2) A, b = 16.265 (2) A, c = 13.766 (4) A, {Beta} = 110.56 (1){degrees}, Z = 4, 1872 reflections, R = 0.039; for 2, space group P1, a = 92.73 (2){degrees}, {Beta} = 99.03 (2){degrees}, {gamma} = 81.52 (2){degrees}, Z = 6, 4862 reflections, R = 0.024. 16 refs. 2 figs.

  10. 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.

  11. 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

  12. The Reddening Law and Distance of the Highly Reddened Massive Young Open Cluster Westerlund 2

    NASA Astrophysics Data System (ADS)

    Hur, H.; Sung, H.; Lim, B.

    2014-08-01

    Westerlund 2 is one of the most reddened massive young open clusters observable in optical bands. There is large disagreement among previous distance determinations. The main cause of the disagreement seems to be due to the abnormal reddening law. We report the reddening law and distance of Westerlund 2 using the deep UBVIC photometry data obtained with the CTIO 4m Blanco telescope and MOSAIC II CCD camera. We estimated the reddening E(B-V) using the relation E(U-B)/E(B-V)=0.72+0.025E(B-V). The foreground reddening law is found to be fairly normal, E(V-I)/E(B-V)=1.31 (i.e. RV≡ AV/E(B-V)=3.2) for E(B-V)≤ 1.05. An abnormal reddening law of RV=4.3 is determined for E(B-V)>1.05 stars using the combined optical and published near-IR data. We also report the color excess ratio E(V-I)/E(B-V) for highly reddened OB stars may not follow the relation RV=2.45E(V-I)/E(B-V) by Guetter & Vrba. Finally, we determined the distance modulus of Westerlund 2 to be V0-MV=13.9±0.2 mag (d=6.0±0.6 kpc).

  13. 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

  14. Towards A Complete Census of the Solar-Type Binaries in the Young Open Cluster M37

    NASA Astrophysics Data System (ADS)

    Geller, Aaron M.; Meibom, Soren; Barnes, Sydney A.; Mathieu, Robert D.

    2012-08-01

    Binary stars govern the dynamical evolution of star clusters and determine the formation rates and mechanisms for exotic stars like blue stragglers and X-ray sources. Understanding the near-primordial (after removal of the natal gas) binary population of star clusters is of primary importance for dynamical models of star clusters, which have the potential to revolutionize our understanding of star cluster evolution. Yet the binary frequencies and distributions of binary orbital parameters (period, eccentricity, etc.) for young coeval stellar populations are poorly known, due to a lack of necessary observations. Time-series radial-velocity surveys are essential for identifying and characterizing binary populations. Using WIYN/Hydra data, we have already identified a nearly complete sample of 329 solar-type (1.5 <=M [M_⊙] <=1.0) candidate members in the young (~540 Myr) open cluster M37. Of these stars, 82 show significant radial-velocity variability, indicative of a binary companion. Kinematic orbital solutions are crucial to define the initial binary conditions critical for dynamical star cluster models, and to understand how binaries affects stellar rotational evolution. As we have already identified the binaries in M37, we have a unique opportunity to add significantly to our knowledge of young binaries with minimal additional telescope time. We propose to initiate a WIYN/Hydra multi-epoch radial-velocity survey of the 82 velocity variables in M37.

  15. 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%.

  16. Pre-main sequence candidates in the very young open cluster NGC 6611

    NASA Astrophysics Data System (ADS)

    de Winter, D.; Koulis, C.; The, P. S.; van den Ancker, M. E.; Perez, M. R.; Bibo, E. A.

    1997-02-01

    For the search of Herbig Ae/Be objects in the extremely young open cluster NGC 6611 we have selected a sample of 52 pre-main sequence candidates, discovered by Walker (1961), Sagar & Joshi (1979), Chini & Wargau (1990) and The et al. (1990). We continue the approach of the last paper by studying each star individually with new and unpublished Walraven WULBV, Johnson/Cousins UBV(RI)_C and Johnson JHKLM photometric data as well as low resolution spectroscopy. Each object is shown to have its own extinction law, which is investigated using their spectral energy distribution (SED). There does not seem to be a clear relationship between the location of a star and the extinction law. This means that the extinction is generated locally and its correction must be taken individually. For each object accurate astrophysical parameters are then derived. Plotting the objects in an HR-diagram, together with the values for the E(B-V), the probability of membership value P and the extinction characteristics, helps to discriminate between cluster members and non-cluster members. Most foreground stars are of late spectral type and are labeled as Group III objects. Group I, to which most members of this cluster belong, contains objects of early spectral type. Part of them seem to be in their post-ZAMS phase and the other part in their pre-ZAMS stage. By comparing the evolutionary tracks of Palla & Stahler (1993) for pre-MS objects and of Maeder & Meyenet (1988) for post-MS stars we have concluded that the cluster contains objects of a few 0.1 Myr as well as objects of about 6 Myr. As most of the Group I objects do not show well-known Herbig Ae/Be characteristics, the time scale of clearing the disk material must be typically less than about 0.1 Myr for the more massive objects. Objects that show an IR-excess are found among the less luminous ones. They could still be in their pre-ZAMS phase, having an age of about 1 Myr. Such an age is appropriate for the Group II objects, which are

  17. WIYN Open Cluster Study. LVII. Oxygen Abundances of Solar-type Dwarfs in the Hyades and NGC 752

    NASA Astrophysics Data System (ADS)

    Maderak, Ryan M.; Deliyannis, Constantine P.; King, Jeremy R.; Cummings, Jeffery D.

    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 σμ 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 eff range straddling the solar T eff, the [Fe/H] cluster averages come from stars exhibiting a flat [Fe/H]-T 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 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.

  18. 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.

  19. 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

  20. Chemical composition of A and F dwarfs members of the Hyades open cluster

    NASA Astrophysics Data System (ADS)

    Gebran, M.; Vick, M.; Monier, R.; Fossati, L.

    2010-11-01

    Aims: Abundances of 15 chemical elements have been derived for 28 F and 16 A stars members of the Hyades open cluster in order to set constraints on self-consistent evolutionary models that include radiative and turbulent diffusion. Methods: A spectral synthesis, iterative procedure was applied to derive the abundances from selected high-quality lines in high-resolution, high-signal-to-noise spectra obtained with SOPHIE and AURELIE at the Observatoire de Haute Provence. Results: The abundance patterns found for A and F stars in the Hyades resemble those observed in Coma Berenices and Pleiades clusters. In graphs representing the abundances versus the effective temperature, A stars often display much more scattered abundances around their mean values than the coolest F stars do. Large star-to-star variations are detected in the Hyades A dwarfs in their abundances of C, Na, Sc, Fe, Ni, Sr, Y, and Zr, which we interpret as evidence of transport processes competing with radiative diffusion. In A and Am stars, the abundances of Cr, Ni, Sr, Y, and Zr are found to be correlated with that of Fe as in the Pleiades and in Coma Berenices. The ratios C/Fe and O/Fe are found to be anticorrelated with Fe/H as in Coma Berenices. All Am stars in the Hyades are deficient in C and O and overabundant in elements heavier than Fe but not all are deficient in Ca and/or Sc. The F stars have solar abundances for almost all elements except for Si. The overall shape of the abundance pattern of the slow rotator HD 30210 cannot be entirely reproduced by models including radiative diffusion and different amounts of turbulent diffusion. Conclusions: While part of the discrepancies between derived and predicted abundances could come from non-LTE effects, including competing processes such as rotational mixing and/or mass loss seems necessary in order to improve the agreement between the observed and predicted abundance patterns. Tables 5 to 8 are only available in electronic form at the CDS via

  1. 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.

  2. 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. PMID:25309040

  3. 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

  4. VizieR Online Data Catalog: ubvy light curves of CP stars in open clusters (Paunzen+, 2011)

    NASA Astrophysics Data System (ADS)

    Paunzen, E.; Hensberge, H.; Maitzen, H. M.; Netopil, M.; Trigilio, C.; Fossati, L.; Heiter, U.; Pranka, M.

    2010-11-01

    Photoelectric Stroemgren uvby time series for 27 CP stars are presented. A standard reduction procedure was applied to the data. Members of the following open clusters have been observed: Collinder 132, IC 4725, NGC 2516, NGC 3114, NGC 3228, NGC 3532, NGC 5460, NGC 5662, NGC 6281, NGC 6405, and NGC 6475. For each target star the HJD and the differential uvby magnitudes are given. (2 data files).

  5. 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.

  6. 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.

  7. Spectroscopic studies of yellow supergiants in the open cluster NGC 129

    NASA Astrophysics Data System (ADS)

    Usenko, I. A.

    2015-09-01

    Spectroscopic studies of three yellow supergiants in the open cluster NGC 129, the classical Cepheid DL Cas, SAO 21450, and SAO 21482, have been performed on the basis of high-resolution spectra. For the two nonvariable cluster supergiants, the atmospheric parameters and chemical composition have been determined for the first time. SAO 21450 ( T eff = 6541 ± 16 K, log g = 2.00, V t = 4.20 km s-1) has nearly solar abundances of the key elements in the evolution of yellow supergiants (CNO, Na, Mg, and Al), while SAO 21482 ( T eff = 4506 ± 50 K, log g = 1.10, V t = 9.90 km s-1) exhibits an overabundance of carbon ([C/H] = +0.34 dex) and aluminum and nearly solar N, O, Na, and Mg abundances. The abundances of the key elements in the Cepheid DL Cas are typical for an object that has passed the first dredge-up: a C underabundance, N and Na overabundances, and nearly solar O, Mg, and Al abundances. In all objects, the abundances of iron [Fe/H] = -0.01 dex, α-elements, Fe-peak elements, and r- and s-process elements are virtually identical and nearly solar. The radial velocities of SAO 21482 measured from metal absorption lines have confirmed its membership in NGC 129. The knifelike shape of the H α and H β line profiles in SAO 21482 and the asymmetry of the Mg Ib 5183.618 Å line in SAO 21482 and DL Cas as well as the absorption lines of neutral atoms and ions of metals in the Cepheid suggest the existence of extended gaseous envelopes around them. The positions of the objects on the T eff- L diagram among the tracks of evolutionary masses for the objects show the following: (1) the primary component of SAO 21450 has a mass of 6.6 M ⊙ and approaches the blue edge of the Cepheid instability strip (CIS) for the first time, while its companion of possible spectral type B5 V has a mass of 4.8 M ⊙; (2) DL Cas is on the path of its CIS with a mass of 5.8 M ⊙ and has lost ~1.5 M ⊙ after the first dredge-up; (3) SAO 21482 with a mass of no more than 7.3 M ⊙ has

  8. MAGNETIC EFFECTS AND OVERSIZED M DWARFS IN THE YOUNG OPEN CLUSTER NGC 2516

    SciTech Connect

    MacDonald, James; Mullan, Dermott J.

    2013-03-10

    By combining rotation periods with spectroscopic determinations of projected rotation velocity, Jackson et al. have found that the mean radii for low-mass M-dwarfs in the young, open cluster NGC 2516 are larger than model predictions at a given absolute I magnitude or I - K color and also larger than measured radii of magnetically inactive M-dwarfs. The relative radius difference is correlated with magnitude, increasing from a few percent at M{sub I} = 7 to greater than 50% for the lowest luminosity stars in their sample at M{sub I} {approx} 9.5. Jackson et al. have suggested that a two-temperature star spot model is capable of explaining the observations, but their model requires spot coverage fractions of at least 50% in rapidly rotating M-dwarfs. Here we examine these results in terms of stellar models that include the inhibiting effects of magnetic fields on convective energy transport, with and without the effects of star spots. We find that a pure spot model is inconsistent with the color-magnitude diagram. The observations of radii versus color and radii versus absolute magnitude in NGC 2516 are consistent with models which include only magnetic inhibition or a combination of magnetic inhibition and spots. At a given mass we find a large dispersion in the strength of the vertical component of the magnetic field in the stellar photosphere but the general trend is that the vertical field increases with decreasing mass from a few hundred Gauss at 0.65 M{sub Sun} to 600-900 G, depending on spot coverage, in the lowest mass stars in the sample at 0.25 M{sub Sun }.

  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. 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.

  12. Reddening, distance, and stellar content of the young open cluster Westerlund 2

    NASA Astrophysics Data System (ADS)

    Hur, Hyeonoh; Park, Byeong-Gon; Sung, Hwankyung; Bessell, Michael S.; Lim, Beomdu; Chun, Moo-Young; Sohn, Sangmo Tony

    2015-02-01

    We present deep UBVIC photometric data of the young open cluster Westerlund 2. An abnormal reddening law of RV, cl = 4.14 ± 0.08 was found for the highly reddened early-type members (E(B-V)≥q 1.45), whereas a fairly normal reddening law of RV, fg = 3.33 ± 0.03 was confirmed for the foreground early-type stars (E(B - V)fg < 1.05). The distance modulus was determined from zero-age main-sequence fitting to the reddening-corrected colour-magnitude diagram of the early-type members to be V0 - MV = 13.9 ± 0.14 (random error) _{-0.1}^{+0.4} (the upper limit of systematic error) mag (d = 6.0 ± 0.4 _{-0.3}^{+1.2} kpc). To obtain the initial mass function, pre-main-sequence (PMS) stars were selected by identifying the optical counterparts of Chandra X-ray sources and mid-infrared emission stars from the Spitzer GLIMPSE (Galactic Legacy Infrared Mid-Plane Survey Extraordinaire) source catalogue. The initial mass function shows a shallow slope of Γ = -1.1 ± 0.1 down to log m = 0.7. The total mass of Westerlund 2 is estimated to be at least 7 400 M⊙. The age of Westerlund 2 from the main-sequence turn-on and PMS stars is estimated to be ≲ 1.5 Myr. We confirmed the existence of a clump of PMS stars located ˜1 arcmin north of the core of Westerlund 2, but we could not find any clear evidence for an age difference between the core and the northern clump.

  13. Chemical composition of A and F dwarfs members of the Pleiades open cluster

    NASA Astrophysics Data System (ADS)

    Gebran, M.; Monier, R.

    2008-05-01

    Aims: We derive the abundances of 18 chemical elements for 16 A-dwarf, both normal and chemically-peculiar, and 5 F-dwarf members of the Pleiades open cluster to place constraints on evolutionary models. Methods: Abundances and rotational and microturbulent velocities were derived by fitting synthetic spectra to high-resolution (R ~ 42 000 and R ~ 75 000) observations of high signal-to-noise ratio (S/N). Results: The abundances exhibit correlation with neither the effective temperature nor the projected rotational velocity. Interestingly, A stars exhibit larger star-to-star variations in C, Sc, Ti, V, Cr, Mn, Sr, Y, Zr and Ba, than F stars. F stars have solar abundances of almost all elements. In A stars, the abundances of Si, Ti and Cr are correlated with that of Fe, and the [X/Fe] ratios are solar for these three elements. The derived abundances are compared with the predictions of evolutionary models for the age of Pleiades (100 Myr). For F stars, small predicted underabundances of light elements and overabundances of Cr, Fe and Ni are confirmed by our findings. For A stars, the predicted overabundances in iron-peak elements are confirmed for a few stars only. Conclusions: The large scatter in the abundances of A stars, discovered previously in the Hyades, Coma Berenices, UMa group, and in field stars, appears to be a characteristic property of dwarf A stars. Hydrodynamical processes competing with radiative diffusion in the radiative zone of A dwarfs, could account for the scatter in abundances that we determine. Based on observations performed at the Observatoire de Haute-Provence (France). Tables [see full textsee full text] and [see full textsee full text] are only available in electronic form at http://www.aanda.org

  14. Three Close Binaries in Different Evolutionary Stages in the Old Open Cluster NGC 188

    NASA Astrophysics Data System (ADS)

    Zhu, L. Y.; Qian, S. B.; Soonthornthum, B.; Liu, L.; He, J. J.; Liu, N. P.; Zhao, E. G.; Zhang, J.; Wang, J. J.

    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.

  15. 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. PMID:27208931

  16. Assessment of the accuracy of coupled cluster perturbation theory for open-shell systems. I. Triples expansions

    NASA Astrophysics Data System (ADS)

    Eriksen, Janus J.; Matthews, Devin A.; Jørgensen, Poul; Gauss, Jürgen

    2016-05-01

    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.

  17. THE SEGUE STELLAR PARAMETER PIPELINE. IV. VALIDATION WITH AN EXTENDED SAMPLE OF GALACTIC GLOBULAR AND OPEN CLUSTERS

    SciTech Connect

    Smolinski, Jason P.; Lee, Young Sun; Beers, Timothy C.; An, Deokkeun; Bickerton, Steven J.; Loomis, Craig P.; Johnson, Jennifer A.; Rockosi, Constance M.; Yanny, Brian E-mail: lee@pa.msu.edu E-mail: deokkeun@ewha.ac.kr E-mail: cloomis@astro.princeton.edu E-mail: crockosi@ucolick.org E-mail: yanny@fnal.gov

    2011-03-15

    Spectroscopic and photometric data for likely member stars of five Galactic globular clusters (M3, M53, M71, M92, and NGC 5053) and three open clusters (M35, 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 (RVs) 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 ((RV)) 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.

  18. The chromospheric emission of solar-type stars in the young open clusters IC 2391 and IC 2602

    NASA Astrophysics Data System (ADS)

    Marsden, S. C.; Carter, B. D.; Donati, J.-F.

    2009-10-01

    In this paper we present chromospheric emission levels of the solar-type stars in the young open clusters IC 2391 and IC 2602. High-resolution spectroscopic data were obtained for over 50 F, G and K stars from these clusters over several observing campaigns using the University College London Echelle Spectrograph on the 3.9-m Anglo-Australian Telescope. Unlike older clusters, the majority (28/52) of the solar-type stars in the two clusters are rapid rotators (vsini > 20kms-1) with five of the stars being classified as ultra-rapid rotators (vsini > 100 km s-1). The emission levels in the calcium infrared triplet lines were then used as a measure of the chromospheric activity of the stars. When plotted against the Rossby number (NR), the star's chromospheric emission levels show a plateau in the emission for log(NR) <~ -1.1 indicating chromospheric saturation similar to the coronal saturation seen in previously observed X-ray emission from the same stars. However, unlike the coronal emission, the chromospheric emission of the stars shows little evidence of a reduction in emission (i.e. supersaturation) for the ultra-rapid rotators in the clusters. Thus we believe that coronal supersaturation is not the result of an overall decrease in magnetic dynamo efficiency for ultra-rapid rotators.

  19. 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.

  20. Star formation in the outer Galaxy: membership and fundamental parameters of the young open cluster NGC 1893

    NASA Astrophysics Data System (ADS)

    Prisinzano, L.; Sanz-Forcada, J.; Micela, G.; Caramazza, M.; Guarcello, M. G.; Sciortino, S.; Testi, L.

    2011-03-01

    Context. Different environmental conditions can play a crucial role in determining final products of the star formation process, and in this context, less favorable activities of star formation are expected in the external regions of our Galaxy. Aims: We studied the properties of the young open cluster NGC 1893 located about 12 Kpc from the galactic center, to investigate how different physical conditions can affect the process of star formation. Methods: By adopting a multiwavelength approach, we compiled a catalog extending from X-rays to NIR data to derive the cluster membership. In addition, optical and NIR photometric properties are used to evaluate the cluster parameters. Results: We find 415 diskless candidate members and 1061 young stellar objects with a circumstellar disk or class II candidate members, 125 of which are also Hα emitters. Considering the diskless candidate members, we find that the cluster distance is 3.6 ± 0.2 kpc and the mean interstellar reddening is E(B - V) = 0.6 ± 0.1 with evidence of differential reddening in the whole surveyed region. Conclusions: NGC 1893 contains a conspicuous population of pre-main sequence stars, together with the well-studied main sequence cluster population. We found a disk fraction of about 70% similar to the one found in clusters of similar age in the solar neighbor and then, despite expected unfavorable conditions for star formation, we conclude that very rich young clusters can also form in the outer regions of our Galaxy. Full Tables 5-8 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/527/A77

  1. Massive open star clusters using the VVV survey. I. Presentation of the data and description of the approach

    NASA Astrophysics Data System (ADS)

    Chené, A.-N.; Borissova, J.; Clarke, J. R. A.; Bonatto, C.; Majaess, D. J.; Moni Bidin, C.; Sale, S. E.; Mauro, F.; Kurtev, R.; Baume, G.; Feinstein, C.; Ivanov, V. D.; Geisler, D.; Catelan, M.; Minniti, D.; Lucas, P.; de Grijs, R.; Kumar, M. S. N.

    2012-09-01

    Context. The ESO Public Survey "VISTA Variables in the Vía Láctea" (VVV) provides deep multi-epoch infrared observations for unprecedented 562 sq. degrees of the Galactic bulge, and adjacent regions of the disk. Aims: The VVV observations will foster the construction of a sample of Galactic star clusters with reliable and homogeneously derived physical parameters (e.g., age, distance, and mass, etc.). In this first paper in a series, the methodology employed to establish cluster parameters for the envisioned database are elaborated upon by analysing four known young open clusters: Danks 1, Danks 2, RCW 79, and DBS 132. The analysis offers a first glimpse of the information that can be gleaned from the VVV observations for clusters in the final database. Methods: Wide-field, deep JHKs VVV observations, combined with new infrared spectroscopy, are employed to constrain fundamental parameters for a subset of clusters. Results: Results are inferred from VVV near-infrared photometry and numerous low resolution spectra (typically more than 10 per cluster). The high quality of the spectra and the deep wide-field VVV photometry enables us to precisely and independently determine the characteristics of the clusters studied, which we compare to previous determinations. An anomalous reddening law in the direction of the Danks clusters is found, specifically E(J - H)/E(H - Ks) = 2.20 ± 0.06, which exceeds published values for the inner Galaxy. The G305 star forming complex, which includes the Danks clusters, lies beyond the Sagittarius-Carina spiral arm and occupies the Centaurus arm. Finally, the first deep infrared colour-magnitude diagram of RCW 79 is presented, which reveals a sizeable pre-main sequence population. A list of candidate variable stars in G305 region is reported. Conclusions: This study demonstrates the strength of the dataset and methodology employed, and constitutes the first step of a broader study which shall include reliable parameters for a sizeable

  2. 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

  3. 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

  4. 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

    2016-08-01

    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.

  5. 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.

  6. Elemental abundance analysis of the early-type members of the open cluster M6: Preliminary results

    NASA Astrophysics Data System (ADS)

    Kııçoǧlu, 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.

  7. Chemical composition of A and F dwarf members of the Coma Berenices open cluster

    NASA Astrophysics Data System (ADS)

    Gebran, M.; Monier, R.; Richard, O.

    2008-02-01

    Aims:Abundances of 18 chemical elements have been derived for 11 A (normal and Am) and 11 F dwarfs members of the Coma Berenices open cluster in order to set constraints on evolutionary models including transport processes (radiative and turbulent diffusion) calculated with the Montréal code. Methods: A spectral synthesis iterative procedure has been applied to derive the abundances from selected high quality lines in high resolution high signal-to-noise échelle spectra obtained with ELODIE at the Observatoire de Haute Provence. Results: The chemical pattern found for the A and F dwarfs in Coma Berenices is reminiscent of that found in the Hyades and the UMa moving group. In graphs representing the abundances [X/H] versus the effective temperature, the A stars often display abundances much more scattered around their mean values than the F stars do. Large star-to-star variations are detected for A stars in their abundances of C, O, Na, Sc, Ti, Mn, Fe, Ni, Sr, Y, Zr and Ba which we interpret as evidence of transport processes competing with radiative diffusion. The abundances of Mn, Ni, Sr and Ba are strongly correlated with that of iron for A and Am stars. In contrast the ratios [C/Fe] and [O/Fe] appear to be anticorrelated with [Fe/H] as found earlier for field A dwarfs. All Am stars in Coma Berenices are deficient in C and O and overabundant in elements heavier than Fe but not all are deficient in calcium and/or scandium. The F stars have solar abundances for almost all elements except for Mg, Si, V and Ba. The derived abundances patterns, [X/H] versus atomic number, for the slow rotator HD 108642 (A2m) and the moderately fast rotator HD 106887 (A4m) were compared to the predictions of self consistent evolutionary model codes including radiative and different amounts of turbulent diffusion. None of the models reproduces entirely the overall shape of the abundance pattern. Conclusions: While part of the discrepancies between derived and predicted abundances may

  8. The Solar-Type Hard-Binary Frequency and Distributions of Orbital Parameters in the Open Cluster M37

    NASA Astrophysics Data System (ADS)

    Geller, Aaron M.; Meibom, Soren; Barnes, Sydney A.; Mathieu, Robert D.

    2014-02-01

    Binary stars, and particularly the short-period ``hard'' binaries, govern the dynamical evolution of star clusters and determine the formation rates and mechanisms for exotic stars like blue stragglers and X-ray sources. Understanding the near-primordial hard-binary population of star clusters is of primary importance for dynamical models of star clusters, which have the potential to greatly advance our understanding of star cluster evolution. Yet the binary frequencies and distributions of binary orbital parameters (period, eccentricity, etc.) for young coeval stellar populations are poorly known, due to a lack of necessary observations. The young (~540 Myr) open cluster M37 hosts a rich binary population that can be used to empirically define these initial conditions. Importantly, this cluster has been the target of a comprehensive WIYN/Hydra radial-velocity (RV) survey, from which we have already identified a nearly complete sample of 329 solar-type (1.5 <=M [M_⊙] <=1.0) members in M37. Of these stars, 82 show significant RV variability, indicative of a binary companion. We propose to build upon these data with a multi-epoch RV survey using WIYN/Hydra to derive kinematic orbital solutions for these 82 binaries in M37. This project was granted time in 2013B and scheduled for later this year. We anticipate that about half of the detected binaries in M37 will acquire enough RV measurements (>=10) in 2013B to begin searching for orbital solutions. With this proposal and perhaps one additional semester we should achieve >=10 RV measurements for the remaining binaries.

  9. Low mass stars, brown dwarf candidates and the mass function of the young open cluster NGC 2547

    NASA Astrophysics Data System (ADS)

    Jeffries, R. D.; Naylor, Tim; Devey, C. R.; Totten, E. J.

    2004-07-01

    We present a catalogue of RcIcZ photometry over an area of 0.855 square degrees, centred on the young open cluster NGC 2547. The survey is substantially complete to limits of Rc= 21.5, Ic= 19.5, Z= 19.5. We use the catalogue to define a sample of NGC 2547 candidates with model-dependent masses of about 0.05 -1.0 Msolar. After correcting for incompleteness and estimating contamination by foreground field dwarfs, we investigate the mass function of the cluster, its binary content, and search for evidence of mass segregation among the lower mass stars. There is ample evidence for mass segregation between high (>3 Msolar) and lower mass stars, but over the range 0.1 < M < 0.7 Msolar, the data are consistent with no further mass segregation. By fitting King profiles we conclude that at least 60 per cent of the low-mass stellar population are contained within our survey. The cluster mass function is remarkably similar to the Pleiades for 0.075 < M < 0.7 Msolar. Because of its age (~= 30 Myr), we demonstrate that this mass function is robust to a number of systematic uncertainties likely to affect older and younger clusters and is therefore one of the best available estimates for the initial mass function in young disc populations. For 0.05 < M < 0.075 Msolar there is some evidence for a deficit of brown dwarfs in NGC 2547 compared with other clusters. This deficit may extend to lower masses or may only be a dip, perhaps caused by an imperfect understanding of the mass-magnitude relationship at temperatures of around 2800 K. Incompleteness in both our survey and the luminosity functions from which we estimate contamination by foreground objects leave this question open. The binary fraction for systems with mass ratios greater than about 0.5 is 20-35 per cent for M dwarfs in NGC 2547, quite consistent with that found in the field and other young clusters. The full photometric catalogue and our lists of candidate cluster members are made available in electronic format.

  10. 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.

  11. 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

  12. X-ray source populations in the region of the open clusters NGC 6633 and IC 4756

    NASA Astrophysics Data System (ADS)

    Briggs, K. R.; Pye, J. P.; Jeffries, R. D.; Totten, E. J.

    2000-12-01

    Using deep exposures (~105s) with the ROSAT High Resolution Imager, we have performed flux-limited surveys for X-ray sources in the vicinity of the Hyades-age open stellar clusters NGC 6633 and IC 4756, detecting 31 and 13 sources, respectively. Our primary aim is to search for so-far unrecognized cluster members. We propose identifications or classifications (cluster member, field star, extragalactic field object) for the X-ray sources, based on published membership lists, and on X-ray:optical flux ratios and optical colour-magnitude diagrams. Results of simulating the expected X-ray-emitting source populations are compared with the ROSAT measurements and with the expected capabilities of the XMM mission. The simulations provide a novel method of comparing the activity levels of NGC 6633 and IC 4756 with that of the Hyades. The measurements and simulations confirm that cluster members are the major class of X-ray emitter in these fields at flux levels √(N) (0.1-2.4keV), contributing ~40per cent of the total X-ray sources. We find six possible new members in NGC 6633 and four candidates in IC 4756; all require further observation to establish membership probability.

  13. Cluster hepaticojejunostomy with radial spreading anchoring traction technique for secure reconstruction of widely opened hilar bile ducts.

    PubMed

    Hwang, Shin; Ha, Tae-Yong; Song, Gi-Won; Jung, Dong-Hwan

    2016-05-01

    Secure reconstruction of multiple hepatic ducts that are severely damaged by tumor invasion or iatrogenic injury is a challenge. Failure of percutaneous or endoscopic biliary stenting requires lifelong placement of one or more percutaneous transhepatic biliary drainage (PTBD) tubes. For such difficult situations, we devised a surgical technique termed cluster hepaticojejunostomy (HJ), which can be coupled with palliative bile duct resection. The cluster HJ technique consisted of applying multiple internal biliary stents and a single wide porto-enterostomy to the surrounding connective tissues. The technique is described in detail in the present case report. Performing cluster HJ benefits from three technical tips as follows: making the multiple bile duct openings wide and parallel after sequential side-to-side unification; radially anchoring and traction of the suture materials at the anterior anastomotic suture line; and making multiple segmented continuous sutures at the posterior anastomotic suture line. Thus, cluster HJ with radial spreading anchoring traction technique is a useful surgical method for secure reconstruction of severely damaged hilar bile ducts. PMID:27212993

  14. 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. PMID:26280450

  15. Cluster hepaticojejunostomy with radial spreading anchoring traction technique for secure reconstruction of widely opened hilar bile ducts

    PubMed Central

    Ha, Tae-Yong; Song, Gi-Won; Jung, Dong-Hwan

    2016-01-01

    Secure reconstruction of multiple hepatic ducts that are severely damaged by tumor invasion or iatrogenic injury is a challenge. Failure of percutaneous or endoscopic biliary stenting requires lifelong placement of one or more percutaneous transhepatic biliary drainage (PTBD) tubes. For such difficult situations, we devised a surgical technique termed cluster hepaticojejunostomy (HJ), which can be coupled with palliative bile duct resection. The cluster HJ technique consisted of applying multiple internal biliary stents and a single wide porto-enterostomy to the surrounding connective tissues. The technique is described in detail in the present case report. Performing cluster HJ benefits from three technical tips as follows: making the multiple bile duct openings wide and parallel after sequential side-to-side unification; radially anchoring and traction of the suture materials at the anterior anastomotic suture line; and making multiple segmented continuous sutures at the posterior anastomotic suture line. Thus, cluster HJ with radial spreading anchoring traction technique is a useful surgical method for secure reconstruction of severely damaged hilar bile ducts. PMID:27212993

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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).

  1. 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.

  2. A Detached Eclipsing Binary near the Turnoff of the Open Cluster NGC 6819 and Determining Age Using Kepler

    NASA Astrophysics Data System (ADS)

    Brewer, Lauren; Sandquist, E. L.; Mathieu, R. D.; Milliman, K.; Geller, A. M.; Jeffries, M.; Orosz, J. A.; Brogaard, K. F.; Platais, I.; Bruntt, H.; Grundahl, F.; Stello, D.; Frandsen, S.

    2013-01-01

    Measurements of the mass and radius of detached eclipsing binaries (DEB) can be used to accurately determine the ages of clusters if an eclipsing star is evolved enough and sits near the cluster turnoff on the color-magnitude diagram (CMD). Multiple DEBs in a cluster can constrain the age even more tightly, and can also lead to inferences about chemical composition (such as helium abundance). As part of our study of the old 2.5 Gyr) open cluster NGC 6819 in the Kepler field, we present results for the DEB Auner 665 (WOCS 24009) with a short period of 3.6 days. We make use of photometric observations from the Kepler spacecraft and from the 1 m telescope at Mount Laguna Observatory in B, V, Rc, and Ic. Radial velocities were measured as part of a long-term study of the cluster (e.g., Hole et al. 2009) using the WIYN 3.5-meter telescope. A665 is a triple-lined system, and we verify that the brightest star is physically orbiting the eclipsing binary based on radial velocities and eclipse timing variations. The stars that make up the detached eclipsing binary are almost identical in temperature, with eclipses that are only clearly distinguishable using Kepler photometry. A new astrometric study of NGC 6819 confirms the cluster membership probability of A665 at a level of P=99%. Ultimately, we will compare the masses and radii obtained with theoretical isochrones and analyze the derived age of NGC 6819, which can also be used to improve stellar theoretical models with better constraints in the mass-radius plane. Our target is to reduce the uncertainty on the cluster age to less than 10% using results from A665 and other known DEBs. The results for this system will also help produce a valuable test of the asteroseismic mass estimates for giant stars in the cluster (Stello et al. 2011). We gratefully acknowledge funding from the National Science Foundation under grant AST-0908536 and NASA under grants NNX11AC76G and NNX12AC88G.

  3. 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

  4. C, N, O abundances and carbon isotope ratios in evolved stars of the open clusters Collinder 261 and NGC 6253

    NASA Astrophysics Data System (ADS)

    Mikolaitis, Š.; Tautvaišienė, G.; Gratton, R.; Bragaglia, A.; Carretta, E.

    2012-05-01

    Context. Investigations of abundances of carbon and nitrogen in the atmospheres of evolved stars of open clusters may provide comprehensive information on chemical composition changes caused by stellar evolution. Aims: Our main aim is to increase the number of open clusters with determined carbon-to nitrogen and carbon isotope ratios. 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 (FEROS spectra) and the C2 Swan (1, 0) band head at 4737 Å (UVES spectra). The wavelength interval 7980-8130 Å, with strong CN features was analysed to determine nitrogen abundances and 12C/13C isotope ratios. The oxygen abundances were determined from the [O i] line at 6300 Å. Results: The average value of 12C/13C isotope ratios of Cr 261 is equal to 18 ± 2 in four giants and to 12 ± 1 in two clump stars; it is equal to 16 ± 1 in four clump stars of the open cluster NGC 6253. The mean C/N ratios in Cr 261 and NGC 6253 are equal to 1.67 ± 0.06 and 1.37 ± 0.09, respectively. Conclusions: The 12C/13C and C/N values in Cr 261 and NGC 6253 within limits of uncertainties agree with the theoretical model of thermohaline-induced mixing as well as with the cool-bottom processing model. Based on observations collected at ESO telescopes under programmes 65.N-0286, 169.D-0473.

  5. 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).

  6. Opening of Carborane Cages by Metal Cluster Complexes: The Reaction of a Thiolate-Substituted Carborane with Triosmium Carbonyl Cluster Complexes.

    PubMed

    Adams, Richard D; Kiprotich, Joseph; Peryshkov, Dmitry V; Wong, Yuen Onn

    2016-08-15

    The reaction of Os3(CO)10(NCMe)2 with closo-o-(1-SCH3)C2B10H11 has yielded the complex Os3(CO)9[μ3-η(3)-C2B10H9(SCH3)](μ-H)2, 1, by the loss of the two NCMe ligands and one CO ligand from the Os3 cluster and the coordination of the sulfur atom and the activation of two B-H bonds with transfer of the hydrogen atoms to the cluster. Reaction of 1 with a second equivalent of Os3(CO)10(NCMe)2 yielded the complex Os3(CO)9(μ-H)[(μ3-η(3)-1,4,5-μ3-η(3)-6,10,11-C2B10H8S(CH3)]Os3(CO)9(μ-H)2, 2, that contains two triosmium triangles attached to the same carborane cage. The carborane cage was opened by cleavage of two B-C bonds and one B-B bond. The B-H group that was pulled out of the cage became a triply bridging group on one of the Os3 triangles but remains bonded to the cage by two B-B bonds. When heated to 150 °C, 2 was transformed into the complex Os3(CO)9(μ-H)[(μ3-η(3)-μ3-η(3)-C2B10H7S(CH3)]Os3(CO)9(μ-H), 3, by the loss of two hydrogen atoms and a rearrangement that led to further opening of the carborane cage. Reaction of 1 with a second equivalent of closo-o-(1-SCH3)C2B10H11 has yielded the complex Os3(CO)6)(μ3-η(3)-C2B10H9-R-SCH3) (μ3-η(3)-C2B10H10-S-SCH3)(μ-H)3, 4a, containing two carborane cages coordinated to one Os3 cluster. Compound 4a was isomerized to the compound Os3(CO)6(μ3-η(3)-C2B10H9-R-SCH3)(μ3-η(3)-C2B10H10-R-SCH3)(μ-H)3, 4b, by an inversion of stereochemistry at one of the sulfur atoms by heating to 174 °C. PMID:27487332

  7. 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

  8. Pre-main sequence stars in open clusters. I. The DAY-I catalogue

    NASA Astrophysics Data System (ADS)

    Delgado, A. J.; Alfaro, E. J.; Yun, J. L.

    2007-06-01

    Context: We present the basic ideas and first results from the project we are carrying out at present, the search for and characterisation of pre-main sequence (PMS) stars among the members of Galactic young clusters. The observations of 10 southern clusters, nine of them located in the Carina-Sagittarius spiral arm of the Milky Way are presented. Aims: We aim at listing candidate PMS member stars in young clusters. The catalogued stars will serve as a basis for future spectroscopic studies of individual objects to determine the properties of stellar formation in the last phases before the main sequence stage. Properties such as the presence of residual envelopes or disks, age spread among PMS members, and the possible presence of several episodes of star formation in the clusters, are to be addressed. Methods: Multicolour photometry in the UBVR_CIC system has been obtained for 10 southern young clusters in the fourth Galactic quadrant, located between Galactic longitudes l = 238° and l = 310°. For six clusters in the sample, the observations presented here provide the first published study based on CCD photometry. A quantitative comparison is performed with post-MS isochrones, and PMS isochrones from three different evolutionary models are used in the photometric membership analysis for possible PMS stars. Results: The observations produce photometric indices in the Johnson-Cousins photometric systems for a total of 26 962 stars. The matching of our pixel coordinates with corresponding fields in the 2MASS data base provides astrometric calibration for all cataloged stars and JHK 2MASS photometric indices for 60% of them. Post-MS cluster ages range from 4 to 60 Myr, whereas the photometric membership analysis assigns PMS membership to a total of 842 stars, covering an age range between 1 and 10 Myr. This information on the PMS candidate members has been collected into a catalogue, named DAY-I, which contains 16 entries for 842 stars in the field of 10 southern

  9. A photoelectric investigation of Ap-stars in open clusters. II - NGC 6475

    NASA Astrophysics Data System (ADS)

    Maitzen, H. M.; Floquet, M.

    1981-07-01

    Results are presented of photoelectric study of Ap stars in the old galactic cluster NGC 6475. Photometry was obtained in the y, g1 and g2 filters at the 50-cm ESO telescope on La Silla. Observations confirm the presence of the three silicon stars found by Abt (1975) (K 88, 55 and 59) and reveal the Ap nature of two additional stars, K 23 and K 14. A b-y reddening value of 0.050 is obtained which is somewhat lower than that found by Snowden (1976), due to evolutionary effects and the calibration used. In addition, virtually no variable reddening in the cluster is observed.

  10. 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.

  11. 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.

  12. Globular and Open Clusters Observed by SDSS/SEGUE: The Giant Stars

    NASA Astrophysics Data System (ADS)

    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.

    2016-01-01

    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 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.

  13. Main-sequence variable stars in young open cluster NGC 1893

    NASA Astrophysics Data System (ADS)

    Lata, Sneh; Yadav, Ram Kesh; Pandey, A. K.; Richichi, Andrea; Eswaraiah, C.; Kumar, Brajesh; Kappelmann, Norbert; Sharma, Saurabh

    2014-07-01

    In this paper, we present time series photometry of 104 variable stars in the cluster region NGC 1893. The association of the present variable candidates to the cluster NGC 1893 has been determined by using (U - B)/(B - V) and (J - H)/(H - K) two colour diagrams, and V/(V - I) colour-magnitude diagram. 45 stars are found to be main-sequence variables and these could be B-type variable stars associated with the cluster. We classified these objects as β Cep, slowly pulsating B stars and new class variables as discussed by Mowlavi et al. These variable candidates show ˜0.005 to ˜0.02 mag brightness variations with periods of <1.0 d. 17 new class variables are located in the H - R diagram between the slowly pulsating B stars and δ Scuti variables. Pulsation could be one of the causes for periodic brightness variations in these stars. The X-ray emission of present main-sequence variables associated with the cluster lies in the saturated region of X-ray luminosity versus period diagram and follows the general trend by Pizzolato et al.

  14. Globular and Open Clusters Observed by SDSS/SEGUE: the Giant Stars

    DOE PAGESBeta

    Morrison, Heather L.; Ma, Zhibo; Clem, James L.; An, Deokkeun; Connor, Thomas; Schechtman-Rook, Andrew; Casagrande, Luca; Rockosi, Constance; Yanny, Brian; Harding, Paul; et al

    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

  15. Wide Field Multicolor CCD Photometry in the Vicinity of the Open Cluster King 7

    NASA Astrophysics Data System (ADS)

    Zdanavičius, J.; Čepas, V.; Zdanavičius, K.; Straižys, V.

    We present the results of CCD photometry in the seven-color Vilnius system for 1549 stars down to V = 16 mag in a 1.5 square degree field around the cluster King 7, at the Perseus and Camelopardalis border. Using photometric parameters, two-dimensional spectral types, interstellar extinctions and distances for most of the stars are determined.

  16. 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.

  17. Globular and Open Clusters Observed by SDSS/SEGUE: The Giant Stars

    NASA Astrophysics Data System (ADS)

    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.

    2016-01-01

    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 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.

  18. 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).

  19. Multiplexing Precision RVs: Searching for Close-in Gas Giants in Open Clusters

    NASA Astrophysics Data System (ADS)

    Bailey, John I., III; Mateo, Mario; White, Russel J.; Shectman, Stephen A.; Crane, Jeffrey D.; Olszewski, Edward W.

    2016-07-01

    We present a multiplexed high-resolution (R ˜ 50,000 median) spectroscopic survey designed to detect exoplanet candidates in two southern star clusters (NGC 2516 and NGC 2422) using the Michigan/Magellan Fiber System (M2FS) on the Magellan/Clay telescope at Las Campanas Observatory. With 128 available fibers in our observing mode, we are able to target every star in the core half-degree of each cluster that could plausibly be a solar-analog member. Our template-based spectral fits provide precise measurements of fundamental stellar properties—T eff (±30 K), [Fe/H] and [α/Fe] (±0.02 dex), and {v}r{sin}(i) (±0.3 km s‑1)—and radial velocities (RVs) by using telluric absorption features from 7160 to 7290 Å as a wavelength reference for 251 mid-F to mid-K stars (126 in NGC 2516 and 125 in NGC 2422) that comprise our survey. In each cluster, we have obtained ˜10–12 epochs of our targets. Using repeat observations of an RV standard star, we show our approach can attain a single-epoch velocity precision of 25–60 m s‑1 over a broad range of signal-to-noise ratios throughout our observational baseline of 1.1 years. Our technique is suitable for nonrapidly rotating stars cooler than mid-F. In this paper, we describe our observational sample and analysis methodology and present a detailed study of the attainable precision and measurement capabilities of our approach. Subsequent papers will provide results for stars observed in the target clusters, analyze our data set of RV time series for stellar jitter and stellar and substellar companions, and consider the implications of our findings on the clusters themselves.

  20. The Clusters AgeS Experiment (CASE). Analysis of the Detached Eclipsing Binary V15 in the Metal-Rich Open Cluster NGC 6253

    NASA Astrophysics Data System (ADS)

    Rozyczka, M.; Kaluzny, J.; Thompson, I. B.; Dotter, A.; Pych, W.; Narloch, W.

    2014-09-01

    We present the first detailed analysis of the detached eclipsing binary V15 in the super-metal rich open cluster NGC 6253. We obtain the following absolute parameters: Mp=1.303±0.006 MSun, Rp=1.71±0.03 RSun, Lp=2.98±0.10 LSun for the primary, and Ms=1.225±0.006 MSun, Rs=1.44±0.02 RSun, Ls=2.13±0.06 LSun for the secondary. Based on Dartmouth isochrones, the age of NGC 6253 is estimated to be 3.80-4.25 Gyr from the mass-radius diagram and 3.9-4.6 Gyr from color-magnitude diagram fitting. Both of these estimates are significantly higher than those reported so far. The derived apparent distance modulus of 11.65 mag agrees well with the range of 10.9-12.2 mag derived by other authors; however our estimated reddening (0.113 mag) is lower than the lowest published value (0.15 mag). We confirm earlier observations that model atmospheres are not accurate enough to account for the whole CMD of the cluster, with the largest discrepancies appearing on the subgiant and giant branches. Although age estimation from the mass-radius diagram is a relatively safe, distance- and reddening-independent procedure, our results should be verified by photometric and spectroscopic observations of additional detached eclipsing binaries which we have discovered, at least two of which are proper-motion members of NGC 6253.

  1. 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

  2. VizieR Online Data Catalog: CCD Δa-photometry of 5 open clusters (Paunzen+, 2002)

    NASA Astrophysics Data System (ADS)

    Paunzen, E.; Maitzen, H. M.

    2002-11-01

    The time scale on which chemical peculiarity in upper main sequence stars begins is unknown. Results from the Hipparcos measurements indicate that the classical chemically peculiar (CP) stars occupy the whole area from the zero age main sequence to the terminal age main sequence. Hubrig et al. (2000ApJ...539..352H) reported that the magnetic fields appear only in stars that have already completed at least approximately 30% of their main sequence life time. Previous observations in the very young Orion OB1 and Scorpio Centaurus associations reveal a percentage of chemically peculiar stars that is significantly smaller (less than 5%) than that of the galactic field (up to 25%). This already indicates that the phenomenon needs at least several Myr to appear. Since no further observations have been published since then, we have observed the five very young (1Myropen clusters Collinder 272, Pismis 20, Lynga 14, NGC 6396 and NGC 6611. Photometry from 250 CCD frames in the three filter Delta a-system results in very low detection limits (0.008 to 0.015mag). We find no single photometrically chemically peculiar candidate in approximately 460 observed cluster members in the five program clusters. From the number of observed objects we deduce upper limits between 0.6% and 2.4% for the incidence of CP stars for the five observed aggregates.The tables presented here include all photometric observations of these five clusters. For a description of the (Delta a) photometric system, see e.g. : a = g2 - (g1+y)/2 g1 and g2 centered at 502 and 524nm. (5 data files).

  3. ValWorkBench: an open source Java library for cluster validation, with applications to microarray data analysis.

    PubMed

    Giancarlo, R; Scaturro, D; Utro, F

    2015-02-01

    The prediction of the number of clusters in a dataset, in particular microarrays, is a fundamental task in biological data analysis, usually performed via validation measures. Unfortunately, it has received very little attention and in fact there is a growing need for software tools/libraries dedicated to it. Here we present ValWorkBench, a software library consisting of eleven well known validation measures, together with novel heuristic approximations for some of them. The main objective of this paper is to provide the interested researcher with the full software documentation of an open source cluster validation platform having the main features of being easily extendible in a homogeneous way and of offering software components that can be readily re-used. Consequently, the focus of the presentation is on the architecture of the library, since it provides an essential map that can be used to access the full software documentation, which is available at the supplementary material website [1]. The mentioned main features of ValWorkBench are also discussed and exemplified, with emphasis on software abstraction design and re-usability. A comparison with existing cluster validation software libraries, mainly in terms of the mentioned features, is also offered. It suggests that ValWorkBench is a much needed contribution to the microarray software development/algorithm engineering community. For completeness, it is important to mention that previous accurate algorithmic experimental analysis of the relative merits of each of the implemented measures [19,23,25], carried out specifically on microarray data, gives useful insights on the effectiveness of ValWorkBench for cluster validation to researchers in the microarray community interested in its use for the mentioned task. PMID:25582071

  4. The Distances to Open Clusters from Main-Sequence Fitting. IV. Galactic Cepheids, the LMC, and the Local Distance Scale

    NASA Astrophysics Data System (ADS)

    An, Deokkeun; Terndrup, Donald M.; Pinsonneault, Marc H.

    2007-12-01

    We derive the basic properties of seven Galactic open clusters containing Cepheids and construct their period-luminosity (P-L) relations. For our cluster main-sequence fitting we extend previous Hyades-based empirical color-temperature corrections to hotter stars using the Pleiades as a template. We use BVICJHKs data to test the reddening law and include metallicity effects to perform a more comprehensive study for our clusters than prior efforts. The ratio of total to selective extinction RV that we derive is consistent with expectations. Assuming the LMC P-L slopes, we find =-3.93+/-0.07 (statistical)+/-0.14 (systematic) for 10 day period Cepheids, which is generally fainter than those in previous studies. Our results are consistent with recent HST and Hipparcos parallax studies when using the Wesenheit magnitudes W(VI). Uncertainties in reddening and metallicity are the major remaining sources of error in the V-band P-L relation, but a higher precision could be obtained with deeper optical and near-infrared cluster photometry. We derive distances to NGC 4258, the LMC, and M33 of (m-M)0=29.28+/-0.10, 18.34+/-0.06, and 24.55+/-0.28, respectively, with an additional systematic error of 0.16 mag in the P-L relations. The distance to NGC 4258 is in good agreement with the geometric distance derived from water masers [Δ(m-M)0=0.01+/-0.24], our value for M33 is less consistent with the distance from an eclipsing binary [Δ(m-M)0=0.37+/-0.34], and our LMC distance is moderately shorter than the adopted distance in the HST Key Project, which formally implies an increase in the Hubble constant of 7%+/-8%.

  5. 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

  6. The Gaia-ESO Survey: Reevaluation of the parameters of the open cluster Trumpler 20 using photometry and spectroscopy

    NASA Astrophysics Data System (ADS)

    Donati, P.; Cantat Gaudin, T.; Bragaglia, A.; Friel, E.; Magrini, L.; Smiljanic, R.; Vallenari, A.; Tosi, M.; Sordo, R.; Tautvaišienė, G.; Blanco-Cuaresma, S.; Costado, M. T.; Geisler, D.; Klutsch, A.; Mowlavi, N.; Muñoz, C.; San Roman, I.; Zaggia, S.; Gilmore, G.; Randich, S.; Bensby, T.; Flaccomio, E.; Koposov, S. E.; Korn, A. J.; Pancino, E.; Recio-Blanco, A.; Franciosini, E.; de Laverny, P.; Lewis, J.; Morbidelli, L.; Prisinzano, L.; Sacco, G.; Worley, C. C.; Hourihane, A.; Jofré, P.; Lardo, C.; Maiorca, E.

    2014-01-01

    Trumpler 20 is an old open cluster (OC) located toward the Galactic centre, at about 3 kpc from the Sun and ~7 kpc from the Galactic centre. Its position makes this cluster particularly interesting in the framework of the chemical properties of the Galactic disc because very few old OCs reside in the inner part of the disc. For this reason it has been selected as a cluster target of the Gaia-ESO Survey, and spectra of many stars in the main-sequence and red-clump phases are now available. Moreover, although it has been studied by several authors in the past, no consensus on the evolutionary status of Tr 20 has been reached. The heavy contamination of field stars (the line of sight of Tr 20 crosses the Carina spiral arm) complicates a correct interpretation. Another interesting aspect of the cluster is that it shows a broadened main-sequence turn-off and a prominent and extended red-clump, characteristics that are not easily explained by classical evolutionary models. Exploiting both spectroscopic information from the Gaia-ESO Survey (and the ESO archive) and literature photometry, weobtain a detailed and accurate analysis of the properties of the cluster. We make use of the first accurate metallicity measurement ever obtained from several spectra of red clump stars, and of cluster membership determination using radial velocities. According to the evolutionary models adopted, we find that Tr 20 has an age in the range 1.35-1.66 Gyr, an average reddening E(B - V) in the range 0.31-0.35 mag, and a distance modulus (m - M)0 between 12.64 and 12.72 mag. The spectroscopic metallicity is [Fe/H] = +0.17 dex. We discuss the structural properties of the object and constrain possible hypotheses for its broadened upper main sequence by estimating the effect of differential reddening and its extended red clump. Based on the data obtained at ESO telescopes under programme 188.B-3002 (the public Gaia-ESO spectroscopic survey, PIs Gilmore & Randich) and on the archive data of the

  7. VizieR Online Data Catalog: UBVI photometry of 4 open clusters (Piatti+, 2010)

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    We obtained images for the cluster sample on the nights of 2000 December 25, 27 and 29 with the UBVIKC filters and a 2048x2048-pixel Tektronix CCD attached to the 0.9-m telescope (scale 0.4arcsec/pix) at Cerro Tololo Inter-American Observatory (CTIO), Chile. Its field of view is 13.6x13.6arcmin2. (5 data files).

  8. VizieR Online Data Catalog: OCCASO survey. HRV for 12 open clusters (Casamiquela+, 2016)

    NASA Astrophysics Data System (ADS)

    Casamiquela, L.; Carrera, R.; Jordi, C.; Balaguer-Nunez, L.; Pancino, E.; Hidalgo, S. L.; Martinez-Vazquez, C. E.; Murabito, S.; Del Pino, A.; Aparicio, A.; Blanco-Cuaresma, S.; Gallart, C.

    2016-05-01

    We present results of radial velocities for stars in 12 completed clusters (77 stars), and the reference stars Arcturus and μ Leo. This is a total of 79 stars. We include radial velocities from individual spectra, and final radial velocities from combined spectra which reach a minimum signal-to-noise ratio of 70. Comparison with the literature is included in the cases which the stars had previous measurements. (2 data files).

  9. VizieR Online Data Catalog: UBVI photometry of 5 open clusters (Piatti+, 2010)

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    We obtained images for the cluster sample in 2000 December with the UBVIKC filters and a 2048x2048-pixel Tektronix CCD attached to the CTIO 0.9m telescope. The detector used has a pixel size of 24um, producing a scale of 0.4arcsec/pix on the chip (focal ratio of f/13.5) and a 13.6x13.6-arcmin2 field of view. (7 data files).

  10. 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.

  11. Map-based trigonometric parallaxes of open clusters. II - The Hyades: 51 Tauri

    NASA Technical Reports Server (NTRS)

    Gatewood, George; Castelaz, Michael; De Jonge, Joost K.; Persinger, Timothy; Stein, John; Stephenson, Bruce

    1992-01-01

    The trigonometric parallax, mass, and mass ratio of 51 Tauri, a binary member of the Hyades star cluster, are determined. The parallax solution, 19.4 mas with a standard error of 1.1 mas, is slightly greater than its generally accepted value and yields a cluster distance of 4.30 +/-2.0 pc or a distance modulus equivalent of 3.16 +/- 0.10 mag, in excellent agreement with recent photographic parallax results. The weighted mean of all trigonometric parallax determinations of the cluster is now 22.9 +/-0.6 mas or a modulus of 3.20 +/- 0.06 mag. The total mass of the 51 Tauri system was found to be 2.56 +/- 0.44 solar masses. Adopting a magnitude difference in line with the spectral types of the components yields individual masses of 1.61 +/- 0.28 and 0.95 +/- 0.18 solar masses. This result places the mass of both the A8 V primary and the G0 secondary stars within the errors of the measurement of the mass-luminosity relation established for solar-neighborhood main-sequence stars.

  12. Determining the Age of the Kepler Open Cluster NGC 6819 With a New Triple System and Other Eclipsing Binary Stars

    NASA Astrophysics Data System (ADS)

    Brewer, Lauren N.; Sandquist, Eric L.; Mathieu, Robert D.; Milliman, Katelyn; Geller, Aaron M.; Jeffries, Mark W., Jr.; Orosz, Jerome A.; Brogaard, Karsten; Platais, Imants; Bruntt, Hans; Grundahl, Frank; Stello, Dennis; Frandsen, Søren

    2016-03-01

    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 BVRCIC) 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 MB = 1.090 ± 0.010 M⊙ and MC = 1.075 ± 0.013 M⊙, and radii RB = 1.099 ± 0.006 ± 0.005 R⊙ and RC = 1.069 ± 0.006 ± 0.013 R⊙. The bright non-eclipsing star resides at the cluster turnoff, and ultimately its mass will directly constrain the turnoff mass: our preliminary determination is MA = 1.251 ± 0.057 M⊙. 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)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. This is paper 57 of the WIYN Open Cluster Study (WOCS).

  13. 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.

  14. The Young Open Clusters King 12, NGC 7788, and NGC 7790: Pre-main-sequence Stars and Extended Stellar Halos

    NASA Astrophysics Data System (ADS)

    Davidge, T. J.

    2012-12-01

    The stellar contents of the open clusters King 12, NGC 7788, and NGC 7790 are investigated using MegaCam images. Comparisons with isochrones yield an age <20 Myr for King 12, 20-40 Myr for NGC 7788, and 60-80 Myr for NGC 7790 based on the properties of stars near the main-sequence turnoff (MSTO) in each cluster. The reddening of NGC 7788 is much larger than previously estimated. The luminosity functions (LFs) of King 12 and NGC 7788 show breaks that are attributed to the onset of pre-main-sequence (PMS) objects, and comparisons with models of PMS evolution yield ages that are consistent with those measured from stars near the MSTO. In contrast, the r' LF of main-sequence stars in NGC 7790 is matched to r' = 20 by a model that is based on the solar neighborhood mass function. The structural properties of all three clusters are investigated by examining the two-point angular correlation function of blue main-sequence stars. King 12 and NGC 7788 are each surrounded by a stellar halo that extends out to a radius of 5 arcmin (~3.4 pc). It is suggested that these halos form in response to large-scale mass ejection early in the evolution of the clusters, as predicted by models. In contrast, blue main-sequence stars in NGC 7790 are traced out to a radius of ~7.5 arcmin (~5.5 pc), with no evidence of a halo. It is suggested that all three clusters may have originated in the same star-forming complex, but not in the same giant molecular cloud. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii.

  15. The synthesis of open-shell, bimetallic Mn/Fe trinuclear clusters

    PubMed Central

    Powers, Tamara M.; Gu, Nina; Fout, Alison R.; Baldwin, Anne M.; Sánchez, Raúl Hernández; Alfonso, Denise M.; Chen, Yu-Sheng; Zheng, Shao-Liang

    2013-01-01

    Concomitant deprotonation and metallation of hexadentate ligand platform tbsLH6 (tbsLH6 = 1,3,5-C6H9(NHC6H4-o-NHSiMe2 tBu)3) with divalent transition metal starting materials Fe2(Mes)4 (Mes = mesityl) or Mn3(Mes)6 in the presence of tetrahydrofuran (THF) resulted in isolation of homotrinuclear complexes (tbsL)Fe3(THF) and (tbsL)Mn3(THF) respectively. In the absence of coordinating solvent (THF) the deprotonation and metallation exclusively afforded dinuclear complexes of the type (tbsLH2)M2 (M = Fe or Mn). The resulting dinuclear species were utilized as synthons to prepare bimetallic trinuclear clusters. Treatment of (tbsLH2)Fe2 complex with divalent Mn source (Mn2(N(SiMe3)2)4) afforded the bimetallic complex (tbsL)Fe2Mn(THF) which established the ability of hexamine ligand tbsLH6 to support mixed metal clusters. The substitutional homogeneity of (tbsL)Fe2Mn(THF) was determined by 1H NMR, 57Fe Mössbauer, and X-ray fluorescence. Anomalous scattering measurements were critical for the unambiguous assignment of the trinuclear core composition. Heating a solution of (tbsLH2)Mn2 with a stoichiometric amount of Fe2(Mes)4 (0.5 mol equiv) affords a mixture of both (tbsL)Mn2Fe(THF) and (tbsL)Fe2Mn(THF) as a result of the thermodynamic preference for heavier metal substitution within the hexa-anilido ligand framework. These results demonstrate for the first time the assembly of mixed metal cluster synthesis in an unbiased ligand platform. PMID:23984911

  16. 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).

  17. VizieR Online Data Catalog: Physical parameters of pre-main sequence stars in open clusters.

    NASA Astrophysics Data System (ADS)

    Delgado, A. J.; Alfaro, E. J.; Yun, J. L.

    Photometric colors in the UBVRI system for 27040 stars, in the fields of 11 Young Open Clusters. The membership and physical parameters are listed. For MS and post MS candidate members, only the mass value is listed. It is calculated from comparison to ZAMS and isochrones by Girardi et al. (2002A&A...391..195G). For PMS candidate members, the age, mass, luminosity, and effective temperature are listed as obtained from comparison to four PMS model isochrones: D'Antona and Mazzitelli (1997MmSAI..68..807D), Palla and Stahler (1999ApJ...525..772P), Siess et al. (2000A&A...358..593S), and Yi et al. (2001ApJS..136..417Y). (2 data files).

  18. 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.

  19. 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.

  20. Pre-main sequence variable stars in young open cluster NGC 1893

    NASA Astrophysics Data System (ADS)

    Lata, Sneh; Pandey, A. K.; Chen, W. P.; Maheswar, G.; Chauhan, Neelam

    We present results of multi-epoch (14 nights during 2007-2010) V-band photometry of the cluster NGC 1893 region to identify photometric variable stars in the cluster. The study identified a total of 53 stars showing photometric variability. The members associated with the region are identified on the basis of spectral energy distribution, J-H/H-K two colour diagram and V/V-I colour-magnitude diagram. The ages and masses of the majority of pre-main-sequence sources are found to be ≲5 Myr and in the range 0.5 ≲ M/M_{⊙} ≲4, respectively. These pre-main-sequence sources hence could be T Tauri stars. We also determined the physical parameters like disk mass and accretion rate from the spectral energy distribution of these T Tauri stars. The periods of majority of the T Tauri stars range from 0.1 to 20 day. We found that the brightness of Classical T Tauri stars is varying with larger amplitude in comparison to weak line T Tauri stars. The amplitude is found to decrease with increase in mass, which could be due to the dispersal of disks of massive stars.

  1. Pre-main-sequence variable stars in young open cluster NGC 1893

    NASA Astrophysics Data System (ADS)

    Lata, Sneh; Pandey, A. K.; Chen, W. P.; Maheswar, G.; Chauhan, Neelam

    2012-12-01

    We present results of multi-epoch (14 nights during 2007-2010) V-band photometry of the cluster NGC 1893 region to identify photometric variable stars in the cluster. The study identified a total of 53 stars showing photometric variability. The members associated with the region are identified on the basis of spectral energy distribution, J - H/H - K two-colour diagram and V/V - I colour-magnitude diagram. The ages and masses of the majority of pre-main-sequence sources are found to be ≲5 Myr and in the range 0.5≲M/M≲4, respectively. These pre-main-sequence sources hence could be T Tauri stars. We also determined the physical parameters like disc mass and accretion rate from the spectral energy distribution of these T Tauri stars. The periods of majority of the T Tauri stars range from 0.1 to 20 d. The brightness of Classical T Tauri stars is found to vary with larger amplitude in comparison to weak line T Tauri stars. It is found that the amplitude decreases with increase in mass, which could be due to the dispersal of discs of massive stars.

  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. The Gaia-ESO Survey: pre-main-sequence stars in the young open cluster NGC 3293

    NASA Astrophysics Data System (ADS)

    Delgado, A. J.; Sampedro, L.; Alfaro, E. J.; Costado, M. T.; Yun, J. L.; Frasca, A.; Lanzafame, A. C.; Drew, J. E.; Eislöffel, J.; Blomme, R.; Morel, T.; Lobel, A.; Semaan, T.; Randich, S.; Jeffries, R. D.; Micela, G.; Vallenari, A.; Kalari, V.; Gilmore, G.; Flaccomio, E.; Carraro, G.; Lardo, C.; Monaco, L.; Prisinzano, L.; Sousa, S. G.; Morbidelli, L.; Lewis, J.; Koposov, S.; Hourihane, A.; Worley, C.; Casey, A.; Franciosini, E.; Sacco, G.; Magrini, L.

    2016-08-01

    The young open cluster NGC3293 is included in the observing program of the Gaia-ESO survey (GES). The radial velocity values provided have been used to assign cluster membership probabilities by means of a single-variable parametric analysis. These membership probabilities are compared to the results of the photometric membership assignment of NGC3293, based on UBVRI photometry. The agreement of the photometric and kinematic member samples amounts to 65 per cent, and could increase to 70 per cent as suggested by the analysis of the differences between both samples. A number of photometric PMS candidate members of spectral type F are found, which are confirmed by the results from VPHAS photometry and SED fitting for the stars in common with VPHAS and GES data sets. Excesses at mid- and near-infrared wavelengths, and signs of Hα emission, are investigated for them. Marginal presence of Hα emission or infilling is detected for the candidate members. Several of them exhibit moderate signs of U excess and weak excesses at mid-IR wavelengths. We suggest that these features originate from accretion discs in their last stages of evolution.

  5. 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

  6. Beryllium abundances along the evolutionary sequence of the open cluster IC 4651 - A new test for hydrodynamical stellar models

    NASA Astrophysics Data System (ADS)

    Smiljanic, R.; Pasquini, L.; Charbonnel, C.; Lagarde, N.

    2010-02-01

    Context. Previous analyses of lithium abundances in main sequence and red giant stars have revealed the action of mixing mechanisms other than convection in stellar interiors. Beryllium abundances in stars with Li abundance determinations can offer valuable complementary information on the nature of these mechanisms. Aims: Our aim is to derive Be abundances along the whole evolutionary sequence of an open cluster. We focus on the well-studied open cluster IC 4651. These Be abundances are used with previously determined Li abundances, in the same sample stars, to investigate the mixing mechanisms in a range of stellar masses and evolutionary stages. Methods: Atmospheric parameters were adopted from a previous abundance analysis by the same authors. New Be abundances have been determined from high-resolution, high signal-to-noise UVES spectra using spectrum synthesis and model atmospheres. The careful synthetic modeling of the Be lines region is used to calculate reliable abundances in rapidly rotating stars. The observed behavior of Be and Li is compared to theoretical predictions from stellar models including rotation-induced mixing, internal gravity waves, atomic diffusion, and thermohaline mixing. Results: Beryllium is detected in all the main sequence and turn-off sample stars, both slow- and fast-rotating stars, including the Li-dip stars, but is not detected in the red giants. Confirming previous results, we find that the Li dip is also a Be dip, although the depletion of Be is more modest than for Li in the corresponding effective temperature range. For post-main-sequence stars, the Be dilution starts earlier within the Hertzsprung gap than expected from classical predictions, as does the Li dilution. A clear dispersion in the Be abundances is also observed. Theoretical stellar models including the hydrodynamical transport processes mentioned above are able to reproduce all the observed features well. These results show a good theoretical understanding of the

  7. 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

  8. 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.

  9. 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. PMID:27208932

  10. 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

  11. GU Monocerotis: A high-mass eclipsing overcontact binary in the young open cluster Dolidze 25

    NASA Astrophysics Data System (ADS)

    Lorenzo, J.; Negueruela, I.; Vilardell, F.; Simón-Díaz, S.; Pastor, P.; Méndez Majuelos, M.

    2016-05-01

    Context. The eclipsing binary GU Mon is located in the star-forming cluster Dolidze 25, which has the lowest metallicity measured in a Milky Way young cluster. Aims: GU Mon has been identified as a short-period eclipsing binary with two early B-type components. We set out to derive its orbital and stellar parameters. Methods: We present a comprehensive analysis, including B and V light curves and 11 high-resolution spectra, to verify the orbital period and determine parameters. We used the stellar atmosphere code FASTWIND to obtain stellar parameters and create templates for cross-correlation. We obtained a model to fit the light and radial-velocity curves using the Wilson-Devinney code iteratively and simultaneously. Results: The two components of GU Mon are identical stars of spectral type B1 V with the same mass and temperature. The light curves are typical of an EW-type binary. The spectroscopic and photometric analyses agree on a period of 0.896640 ± 0.000007 d. We determine a mass of 9.0 ± 0.6 M⊙ for each component and for temperatures of 28 000 ± 2000 K. Both values are consistent with the spectral type. The two stars are overfilling their respective Roche lobes, sharing a common envelope and, therefore the orbit is synchronised and circularised. Conclusions: The GU Mon system has a fill-out factor above 0.8, containing two dwarf B-type stars on the main sequence. The two stars are in a very advanced stage of interaction, with their extreme physical similarity likely due to the common envelope. The expected evolution of such a system very probably leads to a merger while still on the main sequence. Photometry tables are 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/590/A45

  12. 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

  13. Series of open-framework aluminoborates containing [B5O10] clusters.

    PubMed

    Wei, Li; Wang, Guo-Ming; He, Huan; Yang, Bai-Feng; Yang, Guo-Yu

    2015-01-21

    Three new open-framework aluminoborates (ABOs), Rb2AlB5O10·4H2O (), [C5N2H16]AlB5O10 (, C5N2H16 = N-ethyl-1,3-diaminopropane) and [H2dap][(CH3)2NH]AlB5O10 (, dap = 1,2-diaminopropane) have been made under solvothermal conditions and characterized by elemental analysis, IR, TGA, UV-vis, powder XRD, single-crystal XRD, fluorescence spectra and NLO determination, respectively. These three ABOs display two structural types: and are isostructural and crystallize in acentric space groups C2221 and P212121 respectively, showing intersecting helical channels and good NLO properties; while, crystallizes in the centrosymmetric space group Pbca and has CrB4 topology, exhibiting intersecting 8-, 11- and 14-ring channels. UV-vis spectral investigation indicates that they are wide-band-gap semiconductors. PMID:25427276

  14. 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

  15. 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.

  16. 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.

  17. Massive open star clusters using the VVV survey. III. A young massive cluster at the far edge of the Galactic bar

    NASA Astrophysics Data System (ADS)

    Ramírez Alegría, S.; Borissova, J.; Chené, A. N.; O'Leary, E.; Amigo, P.; Minniti, D.; Saito, R. K.; Geisler, D.; Kurtev, R.; Hempel, M.; Gromadzki, M.; Clarke, J. R. A.; Negueruela, I.; Marco, A.; Fierro, C.; Bonatto, C.; Catelan, M.

    2014-04-01

    Context. Young massive clusters are key to map the Milky Way's structure, and near-infrared large area sky surveys have contributed strongly to the discovery of new obscured massive stellar clusters. Aims: We present the third article in a series of papers focused on young and massive clusters discovered in the VVV survey. This article is dedicated to the physical characterization of VVV CL086, using part of its OB-stellar population. Methods: We physically characterized the cluster using JHKS near-infrared photometry from ESO public survey VVV images, using the VVV-SkZ pipeline, and near-infrared K-band spectroscopy, following the methodology presented in the first article of the series. Results: Individual distances for two observed stars indicate that the cluster is located at the far edge of the Galactic bar. These stars, which are probable cluster members from the statistically field-star decontaminated CMD, have spectral types between O9 and B0 V. According to our analysis, this young cluster (1.0 Myr < age < 5.0 Myr) is located at a distance of 11+5-6 kpc, and we estimate a lower limit for the cluster total mass of (2.8+1.6-1.4) · 103 M⊙. It is likely that the cluster contains even earlier and more massive stars. Based on observations taken within the ESO VISTA Public Survey VVV (programme ID 179.B-2002), and with ISAAC, VLT, ESO (programme 087.D-0341A).Near-IR photometry of the most probable cluster members 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/564/L9

  18. Relativistic equation-of-motion coupled-cluster method using open-shell reference wavefunction: Application to ionization potential.

    PubMed

    Pathak, Himadri; Sasmal, Sudip; Nayak, Malaya K; Vaval, Nayana; Pal, Sourav

    2016-08-21

    The open-shell reference relativistic equation-of-motion coupled-cluster method within its four-component description is successfully implemented with the consideration of single- and double- excitation approximations using the Dirac-Coulomb Hamiltonian. At the first attempt, the implemented method is employed to calculate ionization potential value of heavy atomic (Ag, Cs, Au, Fr, and Lr) and molecular (HgH and PbF) systems, where the effect of relativity does really matter to obtain highly accurate results. Not only the relativistic effect but also the effect of electron correlation is crucial in these heavy atomic and molecular systems. To justify the fact, we have taken two further approximations in the four-component relativistic equation-of-motion framework to quantify how the effect of electron correlation plays a role in the calculated values at different levels of theory. All these calculated results are compared with the available experimental data as well as with other theoretically calculated values to judge the extent of accuracy obtained in our calculations. PMID:27544090

  19. Photometric studies of two W UMa type variables in the field of distant open cluster NGC 6866

    NASA Astrophysics Data System (ADS)

    Joshi, Yogesh Chandra; Jagirdar, Rukmini; Joshi, Santosh

    2016-04-01

    We present photometric analysis of the two W UMa type binaries identified in the field of distant open star cluster NGC 6866. Although these systems, namely ID487 and ID494, were reported by Joshi et al., a detailed study of these stars has not been carried out before. The orbital periods of these stars are found to be 0.415110±0.000001 day and 0.366709±0.000004 day, respectively. Based on the photometric and infrared colors, we find their respective spectral types to be K0 and K3. The photometric light variations of both stars show the O'Connell effect which can be explained by employing a dark spot on the secondary components. The V and I band light curves are analyzed using the Wilson-Devinney (WD) code and relations given by Gazeas which yield radii and masses for the binary components of star ID487 of R1 = 1.24 ± 0.01 R⊙, R2 = 1.11 ± 0.02 R⊙, and M1 = 1.24 ± 0.02 M⊙, M2 = 0.96 ± 0.05 M⊙ and for star ID494 of R1 = 1.22±0.02R⊙, R2 = 0.81±0.01 R⊙, and M1 = 1.20±0.06 M⊙, M2 = 0.47±0.01 M⊙.

  20. A Hubble Space Telescope Advanced Camera for Surveys Search for Brown Dwarf Binaries in the Pleiades Open Cluster

    NASA Astrophysics Data System (ADS)

    Bouy, H.; Moraux, E.; Bouvier, J.; Brandner, W.; Martín, E. L.; Allard, F.; Baraffe, I.; Fernández, M.

    2006-02-01

    We present the results of a high-resolution imaging survey for brown dwarf binaries in the Pleiades open cluster. The observations were carried out with the Advanced Camera for Surveys (Pavlovsky and coworkers) on board the Hubble Space Telescope. Our sample consists of 15 bona fide brown dwarfs. We confirm two binaries and detect their orbital motion, but we did not resolve any new binary candidates in the separation range between 5.4 and 1700 AU and masses in the range 0.035-0.065 Msolar. Together with the results of our previous study (Martín and coworkers), we can derive a visual binary frequency of 13.3+13.7-4.3% for separations greater than 7 AU, masses in the range 0.055-0.065 Msolar, and mass ratios in the range 0.45-0.9

  1. 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.

  2. 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. PMID:26235389

  3. A CONSTRAINT ON BROWN DWARF FORMATION VIA EJECTION: RADIAL VARIATION OF THE STELLAR AND SUBSTELLAR MASS FUNCTION OF THE YOUNG OPEN CLUSTER IC 2391

    SciTech Connect

    Boudreault, S.; Bailer-Jones, C. A. L.

    2009-12-01

    We present the stellar and substellar mass function (MF) of the open cluster IC 2391, plus its radial dependence, and use this to put constraints on the formation mechanism of brown dwarfs (BDs). Our multi-band optical and infrared photometric survey with spectroscopic follow-up covers 11 deg{sup 2}, making it the largest survey of this cluster to date. We observe a radial variation in the MF over the range 0.072-0.3 M {sub sun}, but no significant variation in the MF below the substellar boundary at the three cluster radius intervals is analyzed. This lack of radial variation for low masses is what we would expect with the ejection scenario for BD formation, although considering that IC 2391 has an age about three times older than its crossing time, we expect that BDs with a velocity greater than the escape velocity have already escaped the cluster. Alternatively, the variation in the MF of the stellar objects could be an indication that they have undergone mass segregation via dynamical evolution. We also observe a significant variation across the cluster in the color of the (background) field star locus in color-magnitude diagrams and conclude that this is due to variable background extinction in the Galactic plane. From our preliminary spectroscopic follow-up, to confirm BD status and cluster membership, we find that all candidates are M dwarfs (in either the field or the cluster), demonstrating the efficiency of our photometric selection method in avoiding contaminants (e.g., red giants). About half of our photometric candidates for which we have spectra are spectroscopically confirmed as cluster members; two are new spectroscopically confirmed BD members of IC 2391.

  4. Small-scale Interstellar Structure Toward the Open Cluster Chi Persei; Program ID: BO29 (Cycle 2)

    NASA Technical Reports Server (NTRS)

    Meyer, David M.

    2004-01-01

    The primary objective of this program was to obtain FUSE observations of the interstellar H2 absorption toward six early-type stars in the core of the open star cluster Chi Persei. High resolution optical observations of the interstellar Na I absorption toward these stars and others in the core of Chi Per have revealed a rich variety of small-scale diffuse ISM structure in both the distant Perseus and more local Orion spiral arms. At the 1 arc minute angular scales typically probed by the separations of these stars, this structure corresponds to respective physical length scales of 0.6 and 0.15 pc in the Perseus and Orion arm gas. The principal scientific goal of the FUSE observations was to determine if this small-scale Na I structure toward the core of Chi Per was reflected in the abundance and/or excitation of interstellar H2. In September 2001, we obtained FUSE observations of the Chi Per stars BD +56 563, BD +56 571, BD +56 573, BD +56 574, BD +56 575, and BD +56 578 for this program. The data reveal that the Perseus arm gas exhibits significant small-scale variations in the strength of its molecular hydrogen absorption while the Orion arm H2 absorption is relatively uniform. We presented these results at the January 2003 American Astronomical Society meeting in Seattle, WA (points, Meyer, Lauroesch, Nguyen, and Friedman 2002, Bulletin of the American Astronomical Society, 34,1229). Since Na I is not a dominant ion in H I clouds, the variations detected in the Perseus arm Na I line profiles could be due to spatial differences in either the physical structure or the physical conditions in the gas. Although many of the H2 absorption profiles are too saturated or too weak to be definitive in this regard, it is clear that small-scale variations are present in H2 gas with excitation as high as the J=4 rotational level. In contrast, lower spatial resolution H I 21 cm studies of the Perseus arm gas across the face of the h and Chi Per double cluster have shown

  5. 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).

  6. 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).

  7. Cooperative effects and strengths of hydrogen bonds in open-chain cis-triaziridine clusters (n = 2-8): a DFT investigation.

    PubMed

    Song, Hua-Jie; Xiao, He-Ming; Dong, Hai-Shan; Zhu, Wei-Hua

    2006-02-16

    We employ DFT/B3LYP method to investigate linear open-chain clusters (n = 2-8) of the cis-triaziridine molecule that is a candidate molecule for high energy density materials (HEDM). Our calculations indicate that the pervasive phenomena of cooperative effects are observed in the clusters of n = 3-8, which are reflected in changes in lengths of N...H hydrogen bonds, stretching frequencies, and intensities of N-H bonds, dipole moments, and charge transfers as cluster size increases. The n(N) --> sigma*(N-H) interactions, i.e., the charge transfers from lone pairs (n(N)) of the N atoms into antibonds (sigma*) of the N-H bonds acting as H-donors, can be used to explain the observed cooperative phenomena. The approaches based upon natural bond orbital (NBO) method and theory of atoms in molecule (AIM) to evaluating N...H strengths are found to be equivalent. In the process of N...H bonding, cooperative nature of n(N) --> sigma*(N-H) interactions promotes formation of stronger N...H bonds