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

International Nuclear Information System (INIS)

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

2013-01-01

Ruprecht 147 is a hitherto unappreciated open cluster that holds great promise as a standard in fundamental stellar astrophysics. We have conducted a radial velocity survey of astrometric candidates with Lick, Palomar, and MMT observatories and have identified over 100 members, including 5 blue stragglers, 11 red giants, and 5 double-lined spectroscopic binaries (SB2s). We estimate the cluster metallicity from spectroscopic analysis, using Spectroscopy Made Easy (SME), and find it to be [M/H] = +0.07 ± 0.03. We have obtained deep CFHT/MegaCam g'r'i'z' photometry and fit Padova isochrones to the (g' – i') and Two Micron All Sky Survey (J – K S ) color-magnitude diagrams, using the τ 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 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 ∼300 pc and ∼3 Gyr, Ruprecht 147 is by far the oldest nearby star cluster.

Open source clustering software.

Science.gov (United States)

de Hoon, M J L; Imoto, S; Nolan, J; Miyano, S

2004-06-12

We have implemented k-means clustering, hierarchical clustering and self-organizing maps in a single multipurpose open-source library of C routines, callable from other C and C++ programs. Using this library, we have created an improved version of Michael Eisen's well-known Cluster program for Windows, Mac OS X and Linux/Unix. In addition, we generated a Python and a Perl interface to the C Clustering Library, thereby combining the flexibility of a scripting language with the speed of C. The C Clustering Library and the corresponding Python C extension module Pycluster were released under the Python License, while the Perl module Algorithm::Cluster was released under the Artistic License. The GUI code Cluster 3.0 for Windows, Macintosh and Linux/Unix, as well as the corresponding command-line program, were released under the same license as the original Cluster code. The complete source code is available at http://bonsai.ims.u-tokyo.ac.jp/mdehoon/software/cluster. Alternatively, Algorithm::Cluster can be downloaded from CPAN, while Pycluster is also available as part of the Biopython distribution.

Wolf-Rayet stars in open clusters and associations

International Nuclear Information System (INIS)

Lundstroem, I.; Stenholm, B.

1982-01-01

The authors have made a search for line-of-sight coincidences between WR stars and open clusters using the new catalogue of galactic WR stars (van der Hucht et al., 1981, called the HCLS catalogue) and the catalogue of open cluster data (Lyngaa and Lundstroem, 1980). As a measure of the separation they used the angular distance between the WR star and the cluster centre expressed with the cluster angular radius, r', as unit. By comparing the results found from the real angular distributions of WR stars and open clusters with those found if the WR stars were redistributed by changing signs in their latitudes, it is concluded that the majority of WR stars with separations less than 3r' are true cluster members. For larger separations only a few stars can be expected to be members. The authors have therefore limited their investigation to those WR stars that were found within 5r' from an open cluster. (Auth.)

ROTATION PERIODS OF OPEN-CLUSTER STARS .3.

NARCIS (Netherlands)

PROSSER, CF; SHETRONE, MD; DASGUPTA, A; BACKMAN, DE; LAAKSONEN, BD; BAKER, SW; MARSCHALL, LA; WHITNEY, BA; KUIJKEN, K; STAUFFER, [No Value

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 slow rotators which are members of the Alpha Persei, Pleiades, and Hyades open clusters have been monitored and period estimates derived. Using

WIYN Open Cluster Study. XXXVI. Spectroscopic Binary Orbits in NGC 188

Science.gov (United States)

2009-04-01

2000; Pleiades , Mermilliod et al. 1992; M67, Mathieu et al. 1990). Today, the advent of multi-object spectrographs permits surveys of larger stellar...open clusters (e.g., M67, Mathieu et al. (1990); Praesepe, Mermilliod et al. (1994); Pleiades , Bouvier et al. (1997); Hyades, Patience et al. (1998

Sejong Open Cluster Survey (SOS). 0. Target Selection and Data Analysis

Science.gov (United States)

Sung, Hwankyung; Lim, Beomdu; Bessell, Michael S.; Kim, Jinyoung S.; Hur, Hyeonoh; Chun, Moo-Young; Park, Byeong-Gon

2013-06-01

Star clusters are superb astrophysical laboratories containing cospatial and coeval samples of stars with similar chemical composition. We initiate the Sejong Open cluster Survey (SOS) - a project dedicated to providing homogeneous photometry of a large number of open clusters in the SAAO Johnson-Cousins' UBVI system. To achieve our main goal, we pay much attention to the observation of standard stars in order to reproduce the SAAO standard system. Many of our targets are relatively small sparse clusters that escaped previous observations. As clusters are considered building blocks of the Galactic disk, their physical properties such as the initial mass function, the pattern of mass segregation, etc. give valuable information on the formation and evolution of the Galactic disk. The spatial distribution of young open clusters will be used to revise the local spiral arm structure of the Galaxy. In addition, the homogeneous data can also be used to test stellar evolutionary theory, especially concerning rare massive stars. In this paper we present the target selection criteria, the observational strategy for accurate photometry, and the adopted calibrations for data analysis such as color-color relations, zero-age main sequence relations, Sp - M_V relations, Sp - T_{eff} relations, Sp - color relations, and T_{eff} - BC relations. Finally we provide some data analysis such as the determination of the reddening law, the membership selection criteria, and distance determination.

Singlet-paired coupled cluster theory for open shells

Science.gov (United States)

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

2016-06-01

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.

Singlet-paired coupled cluster theory for open shells

International Nuclear Information System (INIS)

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

2016-01-01

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.

Open Cluster Dynamics via Fundamental Plane

Science.gov (United States)

Lin, Chien-Cheng; Pang, Xiao-Ying

2018-04-01

Open clusters (OCs) are important objects for stellar dynamics studies. The short survival timescale of OCs makes them closely related to the formation of Galactic field stars. We motivate to investigate the dynamical evolution of OCs on the aspect of internal effect and the external influence. Firstly, we make use of the known OC catalog to obtain OCs masses, effective radii. Additionally, we estimate OCs kinematics properties by OC members cross-matched with radial velocity and metallicity from SDSSIV/APOGEE2. We then establish the fundamental plane of OCs based on the radial velocity dispersion, the effective radius, and average surface brightness. The deviation of the fundamental plane from the Virial Plane, so called the tilt, and the r.m.s. dispersion of OCs around the average plane are used to indicate the dynamical status of OCs. Parameters of the fitted plane will vary with cluster age and distance.

THE YOUNG OPEN CLUSTER BERKELEY 55

Energy Technology Data Exchange (ETDEWEB)

Negueruela, Ignacio; Marco, Amparo, E-mail: ignacio.negueruela@ua.es, E-mail: amparo.marco@ua.es [Departamento de Fisica, Ingenieria de Sistemas y Teoria de la Senal, Universidad de Alicante, Apdo. 99, E-03080 Alicante (Spain)

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.

Searching for multiple stellar populations in the massive, old open cluster Berkeley 39

Science.gov (United States)

Bragaglia, A.; Gratton, R. G.; Carretta, E.; D'Orazi, V.; Sneden, C.; Lucatello, S.

2012-12-01

The most massive star clusters include several generations of stars with a different chemical composition (mainly revealed by an Na-O anti-correlation) while low-mass star clusters appear to be chemically homogeneous. We are investigating the chemical composition of several clusters with masses of a few 104 M⊙ to establish the lower mass limit for the multiple stellar population phenomenon. Using VLT/FLAMES spectra we determine abundances of Fe, O, Na, and several other elements (α, Fe-peak, and neutron-capture elements) in the old open cluster Berkeley 39. This is a massive open cluster: M ~ 104 M⊙, approximately at the border between small globular clusters and large open clusters. Our sample size of about 30 stars is one of the largest studied for abundances in any open cluster to date, and will be useful to determine improved cluster parameters, such as age, distance, and reddening when coupled with precise, well-calibrated photometry. We find that Berkeley 39 is slightly metal-poor, ⟨[Fe/H]⟩ = -0.20, in agreement with previous studies of this cluster. More importantly, we do not detect any star-to-star variation in the abundances of Fe, O, and Na within quite stringent upper limits. The rms scatter is 0.04, 0.10, and 0.05 dex for Fe, O, and Na, respectively. This small spread can be entirely explained by the noise in the spectra and by uncertainties in the atmospheric parameters. We conclude that Berkeley 39 is a single-population cluster. Based on observations collected at ESO telescopes under programme 386.B-0009.Tables 2 and 3 are available in electronic form at http://www.aanda.org

Searching for the 3.5 keV Line in the Stacked Suzaku Observations of Galaxy Clusters

Science.gov (United States)

Bulbul, Esra; Markevitch, Maxim; Foster, Adam; Miller, Eric; Bautz, Mark; Lowenstein, Mike; Randall, Scott W.; Smith, Randall K.

2016-01-01

We perform a detailed study of the stacked Suzaku observations of 47 galaxy clusters, spanning a redshift range of 0.01-0.45, to search for the unidentified 3.5 keV line. This sample provides an independent test for the previously detected line. We detect a 2sigma-significant spectral feature at 3.5 keV in the spectrum of the full sample. When the sample is divided into two subsamples (cool-core and non-cool core clusters), the cool-core subsample shows no statistically significant positive residuals at the line energy. A very weak (approx. 2sigma confidence) spectral feature at 3.5 keV is permitted by the data from the non-cool-core clusters sample. The upper limit on a neutrino decay mixing angle of sin(sup 2)(2theta) = 6.1 x 10(exp -11) from the full Suzaku sample is consistent with the previous detections in the stacked XMM-Newton sample of galaxy clusters (which had a higher statistical sensitivity to faint lines), M31, and Galactic center, at a 90% confidence level. However, the constraint from the present sample, which does not include the Perseus cluster, is in tension with previously reported line flux observed in the core of the Perseus cluster with XMM-Newton and Suzaku.

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

Science.gov (United States)

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

2017-01-01

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

Searches for 3.5 keV Absorption Features in Cluster AGN Spectra

Science.gov (United States)

Conlon, Joseph P.

2018-06-01

We investigate possible evidence for a spectral dip around 3.5 keV in central cluster AGNs, motivated by previous results for archival Chandra observations of the Perseus cluster and the general interest in novel spectral features around 3.5 keV that may arise from dark matter physics. We use two deep Chandra observations of the Perseus and Virgo clusters that have recently been made public. In both cases, mild improvements in the fit (Δχ2 = 4.2 and Δχ2 = 2.5) are found by including such a dip at 3.5 keV into the spectrum. A comparable result (Δχ2 = 6.5) is found re-analysing archival on-axis Chandra ACIS-S observations of the centre of the Perseus cluster.

Variable stars in the field of open cluster NGC 2126

International Nuclear Information System (INIS)

Liu Shunfang; Wu Zhenyu; Zhang Xiaobin; Wu Jianghua; Ma Jun; Jiang Zhaoji; Chen Jiansheng; Zhou Xu

2009-01-01

We report the results of a time-series CCD photometric survey of variable stars in the field of open cluster NGC 2126. In about a one square degree field covering the cluster, a total of 21 variable candidates are detected during this survey, of which 16 are newly found. The periods, classifications and spectral types of 14 newly discovered variables are discussed, which consist of six eclipsing binary systems, three pulsating variable stars, three long period variables, one RS CVn star, and one W UMa or δ Scuti star. In addition, there are two variable candidates, the properties of which cannot be determined. By a method based on fitting observed spectral energy distributions of stars with theoretical ones, the membership probabilities and the fundamental parameters of this cluster are determined. As a result, five variables are probably members of NGC 2126. The fundamental parameters of this cluster are determined as: metallicity to be 0.008 Z o-dot , age log(t) = 8.95, distance modulus (m - M) 0 = 10.34 and reddening value E (B - V) = 0.55 mag.

Four-color and Hβ photometry for open clusters I: NGC 2516

International Nuclear Information System (INIS)

Snowden, M.S.

1975-01-01

Extensive uvby and Hβ photometry was obtained for stars in the region of the open cluster NGC 2516. A photometric analysis revealed variable reddening and a mean reddening of E(b - y) = 0.088 m. In addition to determining a new age of 137 x 10 6 years and a new adopted distance modulus of 8.01 m, several possible new variable stars were discovered, one of which may be an eclipsing Ap star. From the photometry of the Si-lambda4200 stars in the cluster it appears the absolute magnitudes and masses for this type of star are not as restricted as previously thought

Multicolor photometric study of M31 globular clusters

International Nuclear Information System (INIS)

Fan Zhou; Ma Jun; Zhou Xu

2009-01-01

We present the photometry of 30 globular clusters (GCs) and GC candidates in 15 intermediate-band filters covering the wavelength region from ∼3000 to ∼10000 A using the archival CCD images of M31 observed as part of the Beijing - Arizona - Taiwan - Connecticut (BATC) Multicolor Sky Survey. We transform these intermediate-band photometric data into the photometry in the standard U BV RI broad-bands. These M31 GC candidates are selected from the Revised Bologna Catalog (RBC V.3.5), and most of these candidates do not have any photometric data. Therefore, the presented photometric data are a supplement to the RBC V.3.5. We find that 4 out of 61 GCs and GC candidates in RBC V.3.5 do not show any signal on the BATC images at their locations. By applying a linear fit of the distribution in the color-magnitude diagram of blue GCs and GC candidates using data from the RBC V.3.5, in this study, we find the 'blue-tilt' of blue M31 GCs with a high confidence at 99.95% or 3.47σ for the confirmed GCs, and > 99.99% or 4.87σ for GCs and GC candidates. (research papers)

New open cluster candidates discovered in the XSTPS-GAC survey

Science.gov (United States)

Guo, Jin-Cheng; Zhang, Hua-Wei; Zhang, Hui-Hua; Liu, Xiao-Wei; Yuan, Hai-Bo; Huang, Yang; Wang, Song; Chen, Li; Zhao, Hai-Bin; Liu, Ji-Feng; Chen, Bing-Qiu; Xiang, Mao-Sheng; Tian, Zhi-Jia; Huo, Zhi-Ying; Wang, Chun

2018-03-01

The Xuyi Schmidt Telescope Photometric Survey of the Galactic Anti-center (XSTPS-GAC) is a photometric sky survey that covers nearly 6000 deg2 towards the Galactic Anti-center (GAC) in the g, r, i bands. Half of its survey field is located on the Galactic Anti-center disk, which makes XSTPS-GAC highly suitable to search for new open clusters in the GAC region. In this paper, we report new open cluster candidates discovered in this survey, as well as properties of these open cluster candidates, such as age, distance and reddening, derived by isochrone fitting in the color-magnitude diagram (CMD). These open cluster candidates are stellar density peaks detected in the star density maps by applying the method from Koposov et al. Each candidate is inspected in terms of its true color image composed from three XSTPS-GAC band images. Then its CMD is checked, in order to identify whether the central region stars have a clear isochrone-like trend differing from background stars. The parameters derived from isochrone fitting for these candidates are mainly based on three band photometry of XSTPS-GAC. Moreover, when these new candidates are able to be seen clearly in 2MASS data, their parameters are also derived based on the 2MASS (J – H, J) CMD. There are a total of 320 known open clusters rediscovered and 24 new open cluster candidates discovered in this work. Furthermore, the parameters of these new candidates, as well as another 11 previously known open clusters, are properly determined for the first time.

Yellow supergiants in open clusters

International Nuclear Information System (INIS)

Sowell, J.R.

1986-01-01

Superluminous giant stars (SLGs) have been reported in young globular clusters in the Large Magellanic Cloud (LMC). These stars appear to be in the post-asymptotic-giant-branch phase of evolution. This program was an investigation of galactic SLG candidates in open clusters, which are more like the LMC young globular clusters. These were chosen because luminosity, mass, and age determinations can be made for members since cluster distances and interstellar reddenings are known. Color magnitude diagrams were searched for candidates, using the same selection criteria as for SLGs in the LMC. Classification spectra were obtained of 115 program stars from McGraw-Hill Observatory and of 68 stars from Cerro Tololo Inter-American Observatory Chile. These stars were visually classified on the MK system using spectral scans of standard stars taken at the respective observations. Published information was combined with this program's data for 83 stars in 30 clusters. Membership probabilities were assigned to these stars, and the clusters were analyzed according to age. It was seen that the intrinsically brightest supergiants are found in the youngest clusters. With increasing cluster age, the absolute luminosities attained by the supergiants decline. Also, it appears that the evolutionary tracks of luminosity class II stars are more similar to those of class I than of class III

X-ray Observations of Eight Young Open Star Clusters: I ...

Indian Academy of Sciences (India)

XMM-Newton View of Eight Young Open Star Clusters. 395 ... Multi-wavelength surveys of young open clusters provide an effective way to iden- tify young cluster .... First, the input images were built in two energy ranges, a soft band (0.3–2.0 keV) and ..... 3.2 Color-magnitude diagram of X-ray sources with NIR counterparts.

Searching for Be stars in the open cluster NGC 663

Energy Technology Data Exchange (ETDEWEB)

Yu, P. C.; Lin, C. C.; Chen, W. P.; Lee, C. D.; Ip, W. H.; Ngeow, C. C. [Graduate Institute of Astronomy, National Central University, 300 Jhongda Road, Jhongli 32001, Taiwan (China); Laher, Russ; Surace, Jason [Spitzer Science Center, California Institute of Technology, M/S 314-6, Pasadena, CA 91125 (United States); Kulkarni, Shrinivas R. [Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)

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.

The Open Cluster Chemical Abundances and Mapping (OCCAM) Survey: Galactic Neutron CaptureAbundance Gradients

Science.gov (United States)

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

2017-06-01

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

Reanalysis of 24 Nearby Open Clusters using Gaia data

Science.gov (United States)

Yen, Steffi X.; Reffert, Sabine; Röser, Siegfried; Schilbach, Elena; Kharchenko, Nina V.; Piskunov, Anatoly E.

2018-04-01

We have developed a fully automated cluster characterization pipeline, which simultaneously determines cluster membership and fits the fundamental cluster parameters: distance, reddening, and age. We present results for 24 established clusters and compare them to literature values. Given the large amount of stellar data for clusters available from Gaia DR2 in 2018, this pipeline will be beneficial to analyzing the parameters of open clusters in our Galaxy.

Integrated spectral study of small angular diameter galactic open clusters

Science.gov (United States)

Clariá, J. J.; Ahumada, A. V.; Bica, E.; Pavani, D. B.; Parisi, M. C.

2017-10-01

This paper presents flux-calibrated integrated spectra obtained at Complejo Astronómico El Leoncito (CASLEO, Argentina) for a sample of 9 Galactic open clusters of small angular diameter. The spectra cover the optical range (3800-6800 Å), with a resolution of ˜14 Å. With one exception (Ruprecht 158), the selected clusters are projected into the fourth Galactic quadrant (282o evaluate their membership status. The current cluster sample complements that of 46 open clusters previously studied by our group in an effort to gather a spectral library with several clusters per age bin. The cluster spectral library that we have been building is an important tool to tie studies of resolved and unresolved stellar content.

THE NEXT GENERATION VIRGO CLUSTER SURVEY. X. PROPERTIES OF ULTRA-COMPACT DWARFS IN THE M87, M49, AND M60 REGIONS

Energy Technology Data Exchange (ETDEWEB)

Liu, Chengze [Center for Astronomy and Astrophysics, Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Peng, Eric W.; Zhang, Hong-Xin [Department of Astronomy, Peking University, Beijing 100871 (China); Côté, Patrick; Ferrarese, Laura; Gwyn, Stephen; Blakeslee, John P. [Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria, BC V9E 2E7 (Canada); Jordán, Andrés; Muñoz, Roberto P.; Puzia, Thomas H. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago (Chile); Mihos, J. Christopher [Department of Astronomy, Case Western Reserve University, Cleveland, OH (United States); Lançon, Ariane [Observatoire Astronomique de Strasbourg, Université de Strasbourg and CNRS, UMR 7550, 11 rue de l’Université, F-67000 Strasbourg (France); Cuillandre, Jean-Charles [CEA/IRFU/SAp, Laboratoire AIM Paris-Saclay, CNRS/INSU, Université Paris Diderot, Observatoire de Paris, PSL Research University, F-91191 Gif-sur-Yvette Cedex (France); Boselli, Alessandro [Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, F-13388, Marseille (France); Durrell, Patrick R., E-mail: czliu@sjtu.edu.cn, E-mail: peng@pku.edu.cn [Department of Physics and Astronomy, Youngstown State University, One University Plaza, Youngstown, OH 44555 (United States); and others

2015-10-10

We use imaging from the Next Generation Virgo cluster Survey (NGVS) to present a comparative study of ultra-compact dwarf (UCD) galaxies associated with three prominent Virgo sub-clusters: those centered on the massive red-sequence galaxies M87, M49, and M60. We show how UCDs can be selected with high completeness using a combination of half-light radius and location in color–color diagrams (u*iK{sub s} or u*gz). Although the central galaxies in each of these sub-clusters have nearly identical luminosities and stellar masses, we find large differences in the sizes of their UCD populations, with M87 containing ∼3.5 and 7.8 times more UCDs than M49 and M60, respectively. The relative abundance of UCDs in the three regions scales in proportion to sub-cluster mass, as traced by X-ray gas mass, total gravitating mass, number of globular clusters (GCs), and number of nearby galaxies. We find that the UCDs are predominantly blue in color, with ∼85% of the UCDs having colors similar to blue GCs and stellar nuclei of dwarf galaxies. We present evidence that UCDs surrounding M87 and M49 may follow a morphological sequence ordered by the prominence of their outer, low surface brightness envelope, ultimately merging with the sequence of nucleated low-mass galaxies, and that envelope prominence correlates with distance from either galaxy. Our analysis provides evidence that tidal stripping of nucleated galaxies is an important process in the formation of UCDs.

Elemental abundances of intermediate-age open cluster NGC 3680

Science.gov (United States)

Mitschang, A. W.; De Silva, G. M.; Zucker, D. B.

2012-06-01

We present a new abundance analysis of the intermediate-age Galactic open cluster NGC 3680, based on high-resolution, high signal-to-noise ratio VLT/UVES spectroscopic data. Several element abundances are presented for this cluster for the first time, but most notably we derive abundances for the light and heavy s-process elements Y, Ba, La and Nd. The serendipitous measurement of the rare-earth r-process element Gd is also reported. This cluster exhibits a significant enhancement of Na in giants as compared to dwarfs, which may be a proxy for an O to Na anticorrelation as observed in Galactic globular clusters but not open clusters. We also observe a step-like enhancement of heavy s-process elements towards higher atomic number, contrary to expectations from asymptotic giant branch nucleosynthesis models, suggesting that the r process played a significant role in the generation of both La and Nd in this cluster.

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

Science.gov (United States)

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.

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

Science.gov (United States)

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.

Determining open cluster membership. A Bayesian framework for quantitative member classification

Science.gov (United States)

Stott, Jonathan J.

2018-01-01

Aims: My goal is to develop a quantitative algorithm for assessing open cluster membership probabilities. The algorithm is designed to work with single-epoch observations. In its simplest form, only one set of program images and one set of reference images are required. Methods: The algorithm is based on a two-stage joint astrometric and photometric assessment of cluster membership probabilities. The probabilities were computed within a Bayesian framework using any available prior information. Where possible, the algorithm emphasizes simplicity over mathematical sophistication. Results: The algorithm was implemented and tested against three observational fields using published survey data. M 67 and NGC 654 were selected as cluster examples while a third, cluster-free, field was used for the final test data set. The algorithm shows good quantitative agreement with the existing surveys and has a false-positive rate significantly lower than the astrometric or photometric methods used individually.

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

Science.gov (United States)

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

2013-07-04

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

The K2 M67 Study: A Curiously Young Star in an Eclipsing Binary in an Old Open Cluster

Science.gov (United States)

Sandquist, Eric L.; Mathieu, Robert D.; Quinn, Samuel N.; Pollack, Maxwell L.; Latham, David W.; Brown, Timothy M.; Esselstein, Rebecca; Aigrain, Suzanne; Parviainen, Hannu; Vanderburg, Andrew; Stello, Dennis; Somers, Garrett; Pinsonneault, Marc H.; Tayar, Jamie; Orosz, Jerome A.; Bedin, Luigi R.; Libralato, Mattia; Malavolta, Luca; Nardiello, Domenico

2018-04-01

We present an analysis of a slightly eccentric (e = 0.05), partially eclipsing, long-period (P = 69.73 days) main-sequence binary system (WOCS 12009, Sanders 1247) in the benchmark old open cluster M67. Using Kepler K2 and ground-based photometry, along with a large set of new and reanalyzed spectra, we derived highly precise masses (1.111 ± 0.015 and 0.748 ± 0.005 M ⊙) and radii (1.071 ± 0.008 ± 0.003 and 0.713 ± 0.019 ± 0.026 R ⊙, with statistical and systematic error estimates) for the stars. The radius of the secondary star is in agreement with theory. The primary, however, is approximately 15% smaller than reasonable isochrones for the cluster predict. Our best explanation is that the primary star was produced from the merger of two stars, as this can also account for the nondetection of photospheric lithium and its higher temperature relative to other cluster main-sequence stars at the same V magnitude. To understand the dynamical characteristics (low measured rotational line broadening of the primary star and low eccentricity of the current binary orbit), we believe that the most probable (but not the only) explanation is the tidal evolution of a close binary within a primordial triple system (possibly after a period of Kozai–Lidov oscillations), leading to merger approximately 1 Gyr ago. This star appears to be a future blue straggler that is being revealed as the cluster ages and the most massive main-sequence stars die out. Based on observations made at Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation; with the Tillinghast Reflector Echelle Spectrograph (TRES) on the 1.5 m Tillinghast telescope, located at the Smithsonian Astrophysical Observatory’s Fred L. Whipple Observatory on Mt. Hopkins in Arizona; the HARPS-N spectrograph on the Italian Telescopio Nazionale

Parameters of oscillation generation regions in open star cluster models

Science.gov (United States)

Danilov, V. M.; Putkov, S. I.

2017-07-01

We determine the masses and radii of central regions of open star cluster (OCL) models with small or zero entropy production and estimate the masses of oscillation generation regions in clustermodels based on the data of the phase-space coordinates of stars. The radii of such regions are close to the core radii of the OCL models. We develop a new method for estimating the total OCL masses based on the cluster core mass, the cluster and cluster core radii, and radial distribution of stars. This method yields estimates of dynamical masses of Pleiades, Praesepe, and M67, which agree well with the estimates of the total masses of the corresponding clusters based on proper motions and spectroscopic data for cluster stars.We construct the spectra and dispersion curves of the oscillations of the field of azimuthal velocities v φ in OCL models. Weak, low-amplitude unstable oscillations of v φ develop in cluster models near the cluster core boundary, and weak damped oscillations of v φ often develop at frequencies close to the frequencies of more powerful oscillations, which may reduce the non-stationarity degree in OCL models. We determine the number and parameters of such oscillations near the cores boundaries of cluster models. Such oscillations points to the possible role that gradient instability near the core of cluster models plays in the decrease of the mass of the oscillation generation regions and production of entropy in the cores of OCL models with massive extended cores.

WIYN OPEN CLUSTER STUDY. XXIV. STELLAR RADIAL-VELOCITY MEASUREMENTS IN NGC 6819

International Nuclear Information System (INIS)

Tabetha Hole, K.; Geller, Aaron M.; Mathieu, Robert D.; Meibom, Soeren; Platais, Imants; Latham, David W.

2009-01-01

We present the current results from our ongoing radial-velocity (RV) survey of the intermediate-age (2.4 Gyr) open cluster NGC 6819. Using both newly observed and other available photometry and astrometry, we define a primary target sample of 1454 stars that includes main-sequence, subgiant, giant, and blue straggler stars, spanning a magnitude range of 11 ≤V≤ 16.5 and an approximate mass range of 1.1-1.6 M sun . Our sample covers a 23 arcminute (13 pc) square field of view centered on the cluster. We have measured 6571 radial velocities for an unbiased sample of 1207 stars in the direction of the open cluster NGC 6819, with a single-measurement precision of 0.4 km s -1 for most narrow-lined stars. We use our RV data to calculate membership probabilities for stars with ≥3 measurements, providing the first comprehensive membership study of the cluster core that includes stars from the giant branch through the upper main sequence. We identify 480 cluster members. Additionally, we identify velocity-variable systems, all of which are likely hard binaries that dynamically power the cluster. Using our single cluster members, we find a cluster average RV of 2.34 ± 0.05 km s -1 . We use our kinematic cluster members to construct a cleaned color-magnitude diagram from which we identify rich giant, subgiant, and blue straggler populations and a well defined red clump. The cluster displays a morphology near the cluster turnoff clearly indicative of core convective overshoot. Finally, we discuss a few stars of note, one of which is a short-period red-clump binary that we suggest may be the product of a dynamical encounter.

The s-process enrichment of the globular clusters M4 and M22

Energy Technology Data Exchange (ETDEWEB)

Shingles, Luke J.; Karakas, Amanda I.; Fishlock, Cherie K.; Yong, David; Da Costa, Gary S.; Marino, Anna F. [Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia); Hirschi, Raphael, E-mail: luke.shingles@anu.edu.au [Institute for the Physics and Mathematics of the Universe (WPI), University of Tokyo, 5-1-5 Kashiwanoha, 277-8583 Kashiwa (Japan)

2014-11-01

We investigate the enrichment in elements produced by the slow neutron-capture process (s-process) in the globular clusters M4 (NGC 6121) and M22 (NGC 6656). Stars in M4 have homogeneous abundances of Fe and neutron-capture elements, but the entire cluster is enhanced in s-process elements (Sr, Y, Ba, Pb) relative to other clusters with a similar metallicity. In M22, two stellar groups exhibit different abundances of Fe and s-process elements. By subtracting the mean abundances of s-poor from s-rich stars, we derive s-process residuals or empirical s-process distributions for M4 and M22. We find that the s-process distribution in M22 is more weighted toward the heavy s-peak (Ba, La, Ce) and Pb than M4, which has been enriched mostly with light s-peak elements (Sr, Y, Zr). We construct simple chemical evolution models using yields from massive star models that include rotation, which dramatically increases s-process production at low metallicity. We show that our massive star models with rotation rates of up to 50% of the critical (break-up) velocity and changes to the preferred {sup 17}O(α, γ){sup 21}Ne rate produce insufficient heavy s-elements and Pb to match the empirical distributions. For models that incorporate asymptotic giant branch yields, we find that intermediate-mass yields (with a {sup 22}Ne neutron source) alone do not reproduce the light-to-heavy s-element ratios for M4 and M22, and that a small contribution from models with a {sup 13}C pocket is required. With our assumption that {sup 13}C pockets form for initial masses below a transition range between 3.0 and 3.5 M {sub ☉}, we match the light-to-heavy s-element ratio in the s-process residual of M22 and predict a minimum enrichment timescale of between 240 and 360 Myr. Our predicted value is consistent with the 300 Myr upper limit age difference between the two groups derived from isochrone fitting.

NGC 6705 a young α-enhanced open cluster from OCCASO data

Science.gov (United States)

Casamiquela, L.; Carrera, R.; Balaguer-Núñez, L.; Jordi, C.; Chiappini, C.; Anders, F.; Antoja, T.; Miret-Roig, N.; Romero-Gomez, M.; Blanco-Cuaresma, S.; Pancino, E.; Aguado, D. S.; del Pino, A.; Diaz-Perez, L.; Gallart, C.

2018-03-01

Context. The stellar [α/Fe] abundance is sometimes used as a proxy for stellar age, following standard chemical evolution models for the Galaxy, as seen by different observational results. Aim. In this work, we aim to show that the open cluster NGC 6705/M 11 has a significant α-enhancement [α/Fe] > 0.1 dex, despite its young age ( 300 Myr), challenging the current paradigm. Methods: We used high resolution (R > 65 000) high signal-to-noise ( 70) spectra of eight red clump stars, acquired within the OCCASO survey. We determined very accurate chemical abundances of several α elements, using an equivalent width methodology (Si, Ca and Ti), and spectral synthesis fits (Mg and O). Results: We obtain [Si/Fe] = 0.13 ± 0.05, [Mg/Fe] = 0.14 ± 0.07, [O/Fe] = 0.17 ± 0.07, [Ca/Fe] = 0.06 ± 0.05, and [Ti/Fe] = 0.03 ± 0.03. Our results place these clusters within the group of young [α/Fe]-enhanced field stars recently found by several authors in the literature. The ages of our stars have an uncertainty of around 50 Myr, much more precise than for field stars. By integrating the cluster's orbit in several non-axisymmetric Galactic potentials, we establish the M 11's most likely birth radius as lying between 6.8-7.5 kpc from the Galactic centre, not far from its current position. Conclusions: With the robust open cluster age scale, our results prove that a moderate [α/Fe]-enhancement is no guarantee for a star to be old, and that not all α-enhanced stars can be explained with an evolved blue straggler scenario. Based on our orbit calculations, we further argue against a Galactic bar origin of M 11. Full Table 2 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/610/A66

Star clusters and K2

Science.gov (United States)

Dotson, Jessie; Barentsen, Geert; Cody, Ann Marie

2018-01-01

The K2 survey has expanded the Kepler legacy by using the repurposed spacecraft to observe over 20 star clusters. The sample includes open and globular clusters at all ages, including very young (1-10 Myr, e.g. Taurus, Upper Sco, NGC 6530), moderately young (0.1-1 Gyr, e.g. M35, M44, Pleiades, Hyades), middle-aged (e.g. M67, Ruprecht 147, NGC 2158), and old globular clusters (e.g. M9, M19, Terzan 5). K2 observations of stellar clusters are exploring the rotation period-mass relationship to significantly lower masses than was previously possible, shedding light on the angular momentum budget and its dependence on mass and circumstellar disk properties, and illuminating the role of multiplicity in stellar angular momentum. Exoplanets discovered by K2 in stellar clusters provides planetary systems ripe for modeling given the extensive information available about their ages and environment. I will review the star clusters sampled by K2 across 16 fields so far, highlighting several characteristics, caveats, and unexplored uses of the public data set along the way. With fuel expected to run out in 2018, I will discuss the closing Campaigns, highlight the final target selection opportunities, and explain the data archive and TESS-compatible software tools the K2 mission intends to leave behind for posterity.

STAR CLUSTERS IN M31. IV. A COMPARATIVE ANALYSIS OF ABSORPTION LINE INDICES IN OLD M31 AND MILKY WAY CLUSTERS

International Nuclear Information System (INIS)

Schiavon, Ricardo P.; Caldwell, Nelson; Morrison, Heather; Harding, Paul; Courteau, Stéphane; MacArthur, Lauren A.; Graves, Genevieve J.

2012-01-01

We present absorption line indices measured in the integrated spectra of globular clusters both from the Galaxy and from M31. Our samples include 41 Galactic globular clusters, and more than 300 clusters in M31. The conversion of instrumental equivalent widths into the Lick system is described, and zero-point uncertainties are provided. Comparison of line indices of old M31 clusters and Galactic globular clusters suggests an absence of important differences in chemical composition between the two cluster systems. In particular, CN indices in the spectra of M31 and Galactic clusters are essentially consistent with each other, in disagreement with several previous works. We reanalyze some of the previous data, and conclude that reported CN differences between M31 and Galactic clusters were mostly due to data calibration uncertainties. Our data support the conclusion that the chemical compositions of Milky Way and M31 globular clusters are not substantially different, and that there is no need to resort to enhanced nitrogen abundances to account for the optical spectra of M31 globular clusters.

STAR CLUSTERS IN M31. IV. A COMPARATIVE ANALYSIS OF ABSORPTION LINE INDICES IN OLD M31 AND MILKY WAY CLUSTERS

Energy Technology Data Exchange (ETDEWEB)

Schiavon, Ricardo P. [Gemini Observatory, Hilo, HI 96720 (United States); Caldwell, Nelson [Smithsonian Astrophysical Observatory, Cambridge, MA 02138 (United States); Morrison, Heather; Harding, Paul [Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106-7215 (United States); Courteau, Stephane [Department of Physics, Engineering Physics and Astronomy, Queen' s University, Kingston, ON K7L 3N6 (Canada); MacArthur, Lauren A. [Herzberg Institute of Astrophysics, National Research Council of Canada/University of Victoria, Victoria, B.C. V9E 2E7 (Canada); Graves, Genevieve J., E-mail: rschiavon@gemini.edu, E-mail: caldwell@cfa.harvard.edu, E-mail: paul.harding@case.edu, E-mail: heather@vegemite.case.edu, E-mail: courteau@astro.queensu.ca, E-mail: Lauren.MacArthur@nrc-cnrc.gc.ca, E-mail: graves@astro.berkeley.edu [Department of Astronomy, University of California, Berkeley, CA 94720 (United States)

2012-01-15

We present absorption line indices measured in the integrated spectra of globular clusters both from the Galaxy and from M31. Our samples include 41 Galactic globular clusters, and more than 300 clusters in M31. The conversion of instrumental equivalent widths into the Lick system is described, and zero-point uncertainties are provided. Comparison of line indices of old M31 clusters and Galactic globular clusters suggests an absence of important differences in chemical composition between the two cluster systems. In particular, CN indices in the spectra of M31 and Galactic clusters are essentially consistent with each other, in disagreement with several previous works. We reanalyze some of the previous data, and conclude that reported CN differences between M31 and Galactic clusters were mostly due to data calibration uncertainties. Our data support the conclusion that the chemical compositions of Milky Way and M31 globular clusters are not substantially different, and that there is no need to resort to enhanced nitrogen abundances to account for the optical spectra of M31 globular clusters.

PROTOPLANETARY AND TRANSITIONAL DISKS IN THE OPEN STELLAR CLUSTER IC 2395

Energy Technology Data Exchange (ETDEWEB)

Balog, Zoltan [Max Planck Institute for Astronomy, Heidelberg, D-69117 (Germany); Siegler, Nick [NASA Exoplanet Exploration Program, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Rieke, G. H.; Su, K. Y. L.; Gáspár, András [Steward Observatory, 933 N. Cherry Ave, University of Arizona, Tucson, AZ 85721 (United States); Kiss, L. L. [Konkoly Observatory, Research Center for Astronomy and Earth Sciences, P.O. Box 67, H-1525 Budapest (Hungary); Muzerolle, James [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Gutermuth, R. A. [Department of Astronomy, University of Massachusetts, Amherst, MA (United States); Bell, Cameron P. M. [Institute for Astronomy, ETH Zürich, Wolfgang-Pauli-Strasse 27, 8093, Zürich (Switzerland); Vinkó, J. [Dept. of Optics and Quantum Electronics, University of Szeged, H-6720 Szeged (Hungary); Young, E. T., E-mail: balog@mpia-hd.mpg.de [NASA Ames SOFIA Science Center, N211, Mountain View, CA 94043 (United States)

2016-11-20

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

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

Energy Technology Data Exchange (ETDEWEB)

Martinez-Medina, L. A.; Pichardo, B.; Moreno, E.; Peimbert, A. [Instituto de Astronomía, Universidad Nacional Autónoma de México, A.P. 70-264, 04510, México, D.F., México (Mexico); Velazquez, H., E-mail: lamartinez@astro.unam.mx [Instituto de Astronomía, Universidad Nacional Autónoma de México, Apartado Postal 877, 22860 Ensenada, B.C., México (Mexico)

2016-01-20

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

Estimating the parameters of globular cluster M 30 (NGC 7099) from time-series photometry

DEFF Research Database (Denmark)

Kains, N.; Bramich, D.M.; Figuera Jaimes, R.

2013-01-01

Aims. We present the analysis of 26 nights of V and I time-series observations from 2011 and 2012 of the globular cluster M 30 (NGC 7099). We used our data to search for variable stars in this cluster and refine the periods of known variables; we then used our variable star light curves to derive...... values for the cluster's parameters. Methods. We used difference image analysis to reduce our data to obtain high-precision light curves of variable stars. We then estimated the cluster parameters by performing a Fourier decomposition of the light curves of RR Lyrae stars for which a good period estimate...... stars to derive cluster parameters using empirical relations. We find a cluster metallicity [Fe/H]ZW =-2.01 ± 0.04, or [Fe/H]UVES =-2.11 ± 0.06, and a distance of 8.32 ± 0.20 kpc (using RR0 variables), 8.10 kpc (using one RR1 variable), and 8.35 ± 0.42 kpc (using our SX Phoenicis star detection in M 30...

A CCD photometric analysis of the old open cluster NGC 2420

International Nuclear Information System (INIS)

Anthony-Twarog, B.J.; Twarog, B.A.; Kaluzny, J.; Shara, M.M.

1990-01-01

Precision CCD photometry on the BV system of the core of the old open cluster NGC 2420 is analyzed to explore the value of such an approach for open clusters, particularly in the areas of Galactic and stellar evolution. The unevolved main sequence is shown to be narrow and well defined to the completeness limit of V = 18.5, and the distribution of stars away from the main sequence is shown to be bimodal, with a secondary peak located approximately 0.7 mag above the fiducial main sequence. It is estimated that 50 percent of the cluster systems are binary. Near the turnoff the cluster exhibits some detailed structure. Fiducial relations are given for the cluster extending from the lower main sequence to the red giant branch 1.5 mag above the clump. Comparisons are made between the NGC 2420 cluster and NGC 2506, the isochrones of VandenBerg (1985), and 47 Tuc, in order to estimate cluster parameters, including reddening and metallicity. 68 refs

Lithium in Open Cluster Red Giants Hosting Substellar Companions

Science.gov (United States)

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.

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

Science.gov (United States)

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

2016-01-01

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

A survey for low-mass stellar and substellar members of the Hyades open cluster

Science.gov (United States)

Melnikov, Stanislav; Eislöffel, Jochen

2018-03-01

Context. Unlike young open clusters (with ages 2MASS JHKs photometry Results: We present a photometric and proper motion survey covering 23.4 deg2 in the Hyades cluster core region. Using optical/IR colour-magnitude diagrams, we identify 66 photometric cluster member candidates in the magnitude range 14.m7 < I < 20.m5. The proper motion measurements are based on several all-sky surveys with an epoch difference of 60-70 yr for the bright objects. The proper motions allowed us to discriminate the cluster members from field objects and resulted in 14 proper motion members of the Hyades. We rediscover Hy 6 as a proper motion member and classify it as a substellar object candidate (BD) based on the comparison of the observed colour-magnitude diagram with theoretical model isochrones. Conclusions: With our results, the mass function of the Hyades continues to be shallow below 0.15 M⊙ indicating that the Hyades have probably lost their lowest mass members by means of dynamical evolution. We conclude that the Hyades core represents the "VLM/BD desert" and that most of the substeller objects may have already left the volume of the cluster.

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

Energy Technology Data Exchange (ETDEWEB)

Hoq, Sadia; Clemens, D. P., E-mail: shoq@bu.edu, E-mail: clemens@bu.edu [Institute for Astrophysical Research, 725 Commonwealth Avenue, Boston University, Boston, MA 02215 (United States)

2015-10-15

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

High-resolution Spectroscopic Observations of Single Red Giants in Three Open Clusters: NGC 2360, NGC 3680, and NGC 5822

Science.gov (United States)

Peña Suárez, V. J.; Sales Silva, J. V.; Katime Santrich, O. J.; Drake, N. A.; Pereira, C. B.

2018-02-01

Single stars in open clusters with known distances are important targets in constraining the nucleosynthesis process since their ages and luminosities are also known. In this work, we analyze a sample of 29 single red giants of the open clusters NGC 2360, NGC 3680, and NGC 5822 using high-resolution spectroscopy. We obtained atmospheric parameters, abundances of the elements C, N, O, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, and Nd, as well as radial and rotational velocities. We employed the local thermodynamic equilibrium atmospheric models of Kurucz and the spectral analysis code MOOG. Rotational velocities and light-element abundances were derived using spectral synthesis. Based on our analysis of the single red giants in these three open clusters, we could compare, for the first time, their abundance pattern with that of the binary stars of the same clusters previously studied. Our results show that the abundances of both single and binary stars of the open clusters NGC 2360, NGC 3680, and NGC 5822 do not have significant differences. For the elements created by the s-process, we observed that the open clusters NGC 2360, NGC 3680, and NGC 5822 also follow the trend already raised in the literature that young clusters have higher s-process element abundances than older clusters. Finally, we observed that the three clusters of our sample exhibit a trend in the [Y/Mg]-age relation, which may indicate the ability of the [Y/Mg] ratio to be used as a clock for the giants. Based on the observations made with the 2.2 m telescope at the European Southern Observatory (La Silla, Chile) under an agreement with Observatório Nacional and under an agreement between Observatório Nacional and Max-Planck Institute für Astronomie.

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

Science.gov (United States)

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.

18 CFR 35.28 - Non-discriminatory open access transmission tariff.

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2010-04-01

... 18 Conservation of Power and Water Resources 1 2010-04-01 2010-04-01 false Non-discriminatory open access transmission tariff. 35.28 Section 35.28 Conservation of Power and Water Resources FEDERAL ENERGY... available supply falls short ofdemand plus the operating reserve requirement. (7) Market Monitoring Unit...

BVI photometry of star clusters in M33

International Nuclear Information System (INIS)

Christian, C.A.; Schommer, R.A.

1988-01-01

CCD images of candidate star clusters in M33 were obtained for 13 fields in the B, V, and I bandpasses. The integrated visual colors and magnitudes are used to study the clusters, and evidence for extended giant branches and possibly carbon stars in several of the intermediate-aged clusters is presented. The colors, magnitudes, and positions are used to analyze stellar population of M33 and confirm the existence of massive star clusters with a 0.1-10-Gyr age range. That is, the cluster system of M33 shares some similarities to that of the Magellanic Clouds in that relatively massive clusters are found at all ages. In addition, more than 20 true (i.e., old, massive) globulars are identified. A substantial population of intermediate-color clusters are found, and it is argued that the cluster-formation rate for clusters less than 10 Gyr old may be more continuous in M33 than in the Magellanic Clouds. The chemical evolution of M33 as traced by the clusters suggests that an abundance gradient existed at all ages, in that the outer regions of the disk (i.e., R greater than 10 arcmin or 2 kpc) follow a slow enhancement history similar to the SMC, while the inner regions were enriched more dramatically. 59 references

Cataloging the Praesepe Cluster: Identifying Interlopers and Binary Systems

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Lucey, Madeline R.; Gosnell, Natalie M.; Mann, Andrew; Douglas, Stephanie

2018-01-01

We present radial velocity measurements from an ongoing survey of the Praesepe open cluster using the WIYN 3.5m Telescope. Our target stars include 229 early-K to mid-M dwarfs with proper motion memberships that have been observed by the repurposed Kepler mission, K2. With this survey, we will provide a well-constrained membership list of the cluster. By removing interloping stars and determining the cluster binary frequency we can avoid systematic errors in our analysis of the K2 findings and more accurately determine exoplanet properties in the Praesepe cluster. Obtaining accurate exoplanet parameters in open clusters allows us to study the temporal dimension of exoplanet parameter space. We find Praesepe to have a mean radial velocity of 34.09 km/s and a velocity dispersion of 1.13 km/s, which is consistent with previous studies. We derive radial velocity membership probabilities for stars with ≥3 radial velocity measurements and compare against published membership probabilities. We also identify radial velocity variables and potential double-lined spectroscopic binaries. We plan to obtain more observations to determine the radial velocity membership of all the stars in our sample, as well as follow up on radial velocity variables to determine binary orbital solutions.

CCD BVRI and 2MASS photometry of the poorly studied open cluster NGC 6631

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A.L. Tadross

2014-12-01

Full Text Available Here we have obtained the BVRI CCD photometry down to a limiting magnitude of V∼20 for the southern poorly studied open cluster NGC 6631. It is observed from the 1.88 m Telescope of Kottamia Observatory in Egypt. About 3300 stars have been observed in an area of ∼10′×10′ around the cluster center. The main photometric parameters have been estimated and compared with the results that determined for the cluster using JHKs 2MASS photometric database. The cluster’s diameter is estimated to be 10 arcmin; the reddening E(B-V=0.68 ± 0.10 mag, E(J-H=0.21 ± 0.10 mag, the true modulus (m-Mo=12.16 ± 0.10 mag, which corresponds to a distance of 2700 ± 125 pc and age of 500 ± 50 Myr.

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

International Nuclear Information System (INIS)

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.

2013-01-01

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° < l < 265°). 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

Membership, binarity, and rotation of F-G-K stars in the open cluster Blanco 1

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Mermilliod, J.-C.; Platais, I.; James, D. J.; Grenon, M.; Cargile, P. A.

2008-07-01

Context: The nearby open cluster Blanco 1 is of considerable astrophysical interest for formation and evolution studies of open clusters because it is the third highest Galactic latitude cluster known. It has been observed often, but so far no definitive and comprehensive membership determination is readily available. Aims: An observing programme was carried out to study the stellar population of Blanco 1, and especially the membership and binary frequency of the F5-K0 dwarfs. Methods: We obtained radial-velocities with the CORAVEL spectrograph in the field of Blanco 1 for a sample of 148 F-G-K candidate stars in the magnitude range 10 rate reaches 40% (27/68) if one includes the photometric binaries. The cluster mean heliocentric radial velocity is +5.53 ± 0.11 km s-1 based on the most reliable 49 members. The V sin i distribution is similar to that of the Pleiades, confirming the age similarities between the two clusters. Conclusions: This study clearly demonstrates that, in spite of the cluster's high Galactic latitude, three membership criteria - radial velocity, proper motion, and photometry - are necessary for performing a reliable membership selection. Furthermore, even with accurate and extensive data, ambiguous cases still remain. Based on observations collected with the Danish 1.54-m and the Swiss telescopes at the European Southern Observatory, La Silla, Chile, and with the old YALO 1-m telescope at the Cerro Tololo InterAmerican Observatory, Chile. Table [see full textsee full textsee full textsee full textsee full textsee full text] 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/485/95

Density functional calculations on 13-atom Pd12M (M = Sc—Ni) bimetallic clusters

International Nuclear Information System (INIS)

Tang Chun-Mei; Chen Sheng-Wei; Zhu Wei-Hua; Tao Cheng-Jun; Zhang Ai-Mei; Gong Jiang-Feng; Zou Hua; Liu Ming-Yi; Zhu Feng

2012-01-01

The geometric structures, electronic and magnetic properties of the 3d transition metal doped clusters Pd 12 M (M = Sc—Ni) are studied using the semi-core pseudopots density functional theory. The groundstate geometric structure of the Pd 12 M cluster is probably of pseudoicosahedron. The I h -Pd 12 M cluster has the most thermodynamic stability in five different symmetric isomers. The energy gap shows that Pd 12 M cluster is partly metallic. Both the absolutely predominant metal bond and very weak covalent bond might exist in the Pd 12 M cluster. The magnetic moment of Pd 12 M varies from 0 to 5 μ B , implying that it has a potential application in new nanomaterials with tunable magnetic properties

Near-infrared photometric study of open star cluster IC 1805

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Sagar, R.; Yu, Q.Z.

1990-01-01

The JHK magnitudes of 29 stars in the region of open star cluster IC 1805 were measured. These, and the existing infrared and optical observations, indicate a normal interstellar extinction law in the direction of the cluster. Further, most of the early-type stars have near-infrared fluxes as expected from their spectral types. Patchy distribution of ionized gas and dust appears to be the cause of nonuniform extinction across the cluster face. 36 refs

TWO BARIUM STARS IN THE OPEN CLUSTER NGC 5822

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Katime Santrich, O. J.; Pereira, C. B.; De Castro, D. B., E-mail: osantrich@on.br, E-mail: claudio@on.br, E-mail: denise@on.br [Observatorio Nacional/MCT, Rua Gen. Jose Cristino, 77, 20921-400 Rio de Janeiro (Brazil)

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.

THE DISCOVERY OF REMOTE GLOBULAR CLUSTERS IN M33

International Nuclear Information System (INIS)

Huxor, A.; Ferguson, A. M. N.; Barker, M. K.; Tanvir, N. R.; Irwin, M. J.; Chapman, S. C.; Ibata, R.; Lewis, G.

2009-01-01

We present the discovery of four remote star clusters in M33, one of which is of an extended nature. Three of the clusters were discovered using survey data from the Isaac Newton Telescope Wide-Field Camera while one was discovered serendipitously in a deep image taken with the Hubble Space Telescope's Advanced Camera for Surveys. With projected radii of 38-113 arcmin (9.6-28.5 kpc for an assumed M33 distance of 870 kpc), these clusters lie significantly beyond all but one of the currently confirmed clusters in M33. The clusters have magnitudes and colors consistent with their being old to intermediate-age globular clusters (GCs). Indeed, they bear a strong resemblance to the outer halo GC population of the Milky Way and M31 in terms (V - I) 0 color. The three outermost clusters are projected on the far side of M33 with respect to M31, an asymmetry that could suggest tidal interactions have affected M33's GC distribution at large radii.

Interstellar Extinction in 20 Open Star Clusters

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Rangwal, Geeta; Yadav, R. K. S.; Durgapal, Alok K.; Bisht, D.

2017-12-01

The interstellar extinction law in 20 open star clusters namely, Berkeley 7, Collinder 69, Hogg 10, NGC 2362, Czernik 43, NGC 6530, NGC 6871, Bochum 10, Haffner 18, IC 4996, NGC 2384, NGC 6193, NGC 6618, NGC 7160, Collinder 232, Haffner 19, NGC 2401, NGC 6231, NGC 6823, and NGC 7380 have been studied in the optical and near-IR wavelength ranges. The difference between maximum and minimum values of E(B - V) indicates the presence of non-uniform extinction in all the clusters except Collinder 69, NGC 2362, and NGC 2384. The colour excess ratios are consistent with a normal extinction law for the clusters NGC 6823, Haffner 18, Haffner 19, NGC 7160, NGC 6193, NGC 2401, NGC 2384, NGC 6871, NGC 7380, Berkeley 7, Collinder 69, and IC 4996. We have found that the differential colour-excess ΔE(B - V), which may be due to the occurrence of dust and gas inside the clusters, decreases with the age of the clusters. A spatial variation of colour excess is found in NGC 6193 in the sense that it decreases from east to west in the cluster region. For the clusters Berkeley 7, NGC 7380, and NGC 6871, a dependence of colour excess E(B - V) with spectral class and luminosity is observed. Eight stars in Collinder 232, four stars in NGC 6530, and one star in NGC 6231 have excess flux in near-IR. This indicates that these stars may have circumstellar material around them.

VizieR Online Data Catalog: Kinematic study of open clusters (Vande Putte+, 2010)

Science.gov (United States)

Vande Putte, D. V.; Garnier, T. P.; Ferreras, I.; Mignani, R. P.; Cropper, M.

2011-03-01

The Galactic population of open clusters provides an insight into star formation in the Galaxy. The open cluster catalogue by Dias et al. (Cat. B/ocl) is a rich source of data, including kinematic information. This large sample made it possible to carry out a systematic analysis of 481 open cluster orbits, using parameters based on orbit eccentricity and separation from the Galactic plane. These two parameters may be indicative of origin, and we find them to be correlated. We also find them to be correlated with metallicity, another parameter suggested elsewhere to be a marker for origin in that high values of any of these two parameters generally indicate a low metallicity ([Fe/H]solar<-0.2dex). The resulting analysis points to four open clusters in the catalogue being of extragalactic origin by impact of high-velocity cloud on the disc: Berkeley 21, 32, 99 and Melotte 66, with a possible further four due to this origin (NGC 2158, 2420, 7789 and IC 1311). A further three may be due to Galactic globular cluster impact on the disc, i.e. of internal Galactic origin (NGC 6791, 1817 and 7044). (3 data files).

Clustering of near clusters versus cluster compactness

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Yu Gao; Yipeng Jing

1989-01-01

The clustering properties of near Zwicky clusters are studied by using the two-point angular correlation function. The angular correlation functions for compact and medium compact clusters, for open clusters, and for all near Zwicky clusters are estimated. The results show much stronger clustering for compact and medium compact clusters than for open clusters, and that open clusters have nearly the same clustering strength as galaxies. A detailed study of the compactness-dependence of correlation function strength is worth investigating. (author)

Radial Profile of the 3.5 kev Line Out to R200 in the Perseus Cluster

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Franse, Jeroen; Bulbul, Esra; Foster, Adam; Boyarsky, Alexey; Markevitch, Maxim; Bautz, Mark; Lakubovskyi, Dmytro; Loewenstein, Michael; McDonald, Michael; Miller, Eric;

Astrophysical parameters of ten poorly studied open star clusters

International Nuclear Information System (INIS)

Tadross, Ashraf Latif; El-Bendary, Reda; Osman, Anas; Ismail, Nader; Bakry, Abdel Aziz

2012-01-01

We present the fundamental parameters of ten open star clusters, nominated from Kronberger et al. who presented some newly discovered stellar groups on the basis of the Two Micron All Sky Survey photometry and Digitized Sky Survey visual images. Star counts and photometric parameters (radius, membership, distance, color excess, age, luminosity function, mass function, total mass, and dynamical relaxation time) have been determined for these ten clusters for the first time. In order to calibrate our procedures, the main parameters (distance, age, and color excess) have been re-estimated for another five clusters, which are also studied by Kronberger et al. (research papers)

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

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José María Mateos-Pérez

Full Text Available 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.

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

International Nuclear Information System (INIS)

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

2013-01-01

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 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 * of the cluster: N-dot o =αρ ⋆ , with α = (23 ± 5) × 10 –6 pc 3 Myr –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 ν (4.4 μm) ≈4 × 10 2  nJy, which would lead to a very clear detection (S/N ∼ 100) in only one hour of integration

Detectability of Free Floating Planets in Open Clusters with the James Webb Space Telescope

Science.gov (United States)

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 \\dot{N}_o (total number of free-floating planets per unit of time, normalized by the total number of stars), is proportional to the stellar density ρsstarf of the cluster: \\dot{N}_o = \\alpha \\rho _\\star, with α = (23 ± 5) × 10-6 pc3 Myr-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 ν (4.4 μm) ≈4 × 102 nJy, which would lead to a very clear detection (S/N ~ 100) in only one hour of integration.

Interaction between Nbp35 and Cfd1 proteins of cytosolic Fe-S cluster assembly reveals a stable complex formation in Entamoeba histolytica.

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Shadab Anwar

Full Text Available Iron-Sulfur (Fe-S proteins are involved in many biological functions such as electron transport, photosynthesis, regulation of gene expression and enzymatic activities. Biosynthesis and transfer of Fe-S clusters depend on Fe-S clusters assembly processes such as ISC, SUF, NIF, and CIA systems. Unlike other eukaryotes which possess ISC and CIA systems, amitochondriate Entamoeba histolytica has retained NIF & CIA systems for Fe-S cluster assembly in the cytosol. In the present study, we have elucidated interaction between two proteins of E. histolytica CIA system, Cytosolic Fe-S cluster deficient 1 (Cfd1 protein and Nucleotide binding protein 35 (Nbp35. In-silico analysis showed that structural regions ranging from amino acid residues (P33-K35, G131-V135 and I147-E151 of Nbp35 and (G5-V6, M34-D39 and G46-A52 of Cfd1 are involved in the formation of protein-protein complex. Furthermore, Molecular dynamic (MD simulations study suggested that hydrophobic forces surpass over hydrophilic forces between Nbp35 and Cfd1 and Van-der-Waal interaction plays crucial role in the formation of stable complex. Both proteins were separately cloned, expressed as recombinant fusion proteins in E. coli and purified to homogeneity by affinity column chromatography. Physical interaction between Nbp35 and Cfd1 proteins was confirmed in vitro by co-purification of recombinant Nbp35 with thrombin digested Cfd1 and in vivo by pull down assay and immunoprecipitation. The insilico, in vitro as well as in vivo results prove a stable interaction between these two proteins, supporting the possibility of its involvement in Fe-S cluster transfer to target apo-proteins through CIA machinery in E. histolytica. Our study indicates that initial synthesis of a Fe-S precursor in mitochondria is not necessary for the formation of Cfd1-Nbp35 complex. Thus, Cfd1 and Nbp35 with the help of cytosolic NifS and NifU proteins can participate in the maturation of non-mitosomal Fe-S proteins

Laser ionization of molecular clusters

International Nuclear Information System (INIS)

Desai, S.; Feigerle, C.S.

1995-01-01

Multiphoton ionization coupled with mass spectrometry was used to investigate molecular cluster distributions. Three examples will be discussed in this presentation. First, in studies of neat nitric oxide clusters, (NO) m , an interesting odd-even intensity alternation was observed and will be discussed in terms of electron-pairing considerations. In a separate study, the binary clusters comprising nitric oxide and methane preferentially form a stoichiometric cluster made up of repeating units of (NO) 2 CH 4 . These presumably represent a particularly strongly bound open-quotes van der Waalsclose quotes subunit. Finally, in similar studies of neat carbon disulfide clusters, (CS 2 ) m , additional photon absorption after the two-photon ionization step stimulates a series of intracluster ion-molecular reactions leading to formation of S m + and (CS) m + polymers, as well as intermediate species such as S m + (CS 2 ). This molecular cluster analogue of open-quotes laser snowclose quotes will be described in detail

Cluster expansion of the wavefunction. Symmetry-adapted-cluster expansion, its variational determination, and extension of open-shell orbital theory

International Nuclear Information System (INIS)

Nakatsuji, H.; Hirao, K.

1978-01-01

The symmetry-adapted-cluster (SAC) expansion of an exact wavefunction is given. It is constructed from the generators of the symmetry-adapted excited configurations having the symmetry under consideration, and includes their higher-order effect and self-consistency effect. It is different from the conventional cluster expansions in several important points, and is suitable for applications to open-shell systems as well as closed-shell systems. The variational equation for the SAC wavefunction has a form similar to the generalized Brillouin theorem in accordance with the inclusion of the higher-order effect and the self-consistency effect. We have expressed some existing open-shell orbital theories equivalently in the conventional cluster expansion formulas, and on this basis, we have given the pseudo-orbital theory which is an extension of open-shell orbital theory in the SAC expansion formula

CHEMICAL COMPOSITION OF INTERMEDIATE-MASS STAR MEMBERS OF THE M6 (NGC 6405) OPEN CLUSTER

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Kılıçoğlu, T.; Albayrak, B. [Ankara University, Faculty of Science, Department of Astronomy and Space Sciences, 06100, Tandoğan, Ankara (Turkey); Monier, R. [LESIA, UMR 8109, Observatoire de Paris Meudon, Place J. Janssen, Meudon (France); Richer, J. [Département de physique, Université de Montréal, 2900, Boulevard Edouard-Montpetit, Montréal QC, H3C 3J7 (Canada); Fossati, L., E-mail: tkilicoglu@ankara.edu.tr, E-mail: balbayrak@ankara.edu.tr, E-mail: Richard.Monier@obspm.fr, E-mail: Jacques.Richer@umontreal.ca, E-mail: lfossati@astro.uni-bonn.de [Argelander-Institut für Astronomie der Universität Bonn, Auf dem Hügel 71, D-53121, Bonn (Germany)

2016-03-15

We present here the first abundance analysis of 44 late B-, A-, and F-type members of the young open cluster M6 (NGC 6405, age about 75 Myr). Low- and medium-resolution spectra, covering the 4500–5840 Å wavelength range, were obtained using the FLAMES/GIRAFFE spectrograph attached to the ESO Very Large Telescopes. We determined the atmospheric parameters using calibrations of the Geneva photometry and by adjusting the H{sub β} profiles to synthetic ones. The abundances of up to 20 chemical elements, from helium to mercury, were derived for 19 late B, 16 A, and 9 F stars by iteratively adjusting synthetic spectra to the observations. We also derived a mean cluster metallicity of [Fe/H] = 0.07 ± 0.03 dex from the iron abundances of the F-type stars. We find that for most chemical elements, the normal late B- and A-type stars exhibit larger star-to-star abundance variations than the F-type stars probably because of the faster rotation of the B and A stars. The abundances of C, O, Mg, Si, and Sc appear to be anticorrelated with that of Fe, while the opposite holds for the abundances of Ca, Ti, Cr, Mn, Ni, Y, and Ba as expected if radiative diffusion is efficient in the envelopes of these stars. In the course of this analysis, we discovered five new peculiar stars: one mild Am, one Am, and one Fm star (HD 318091, CD-32 13109, GSC 07380-01211, CP1), one HgMn star (HD 318126, CP3), and one He-weak P-rich (HD 318101, CP4) star. We also discovered a new spectroscopic binary, most likely a SB2. We performed a detailed modeling of HD 318101, the new He-weak P-rich CP star, using the Montréal stellar evolution code XEVOL which self-consistently treats all particle transport processes. Although the overall abundance pattern of this star is properly reproduced, we find that detailed abundances (in particular the high P excess) resisted modeling attempts even when a range of turbulence profiles and mass-loss rates were considered. Solutions are proposed which are

A Near-Infrared Surface Compositional Analysis of Blue Straggler Stars in Open Cluster M67

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

2017-06-01

Blue straggler stars (BSSs) are stars whose evolutions have been directly impacted by binary system interactions. By obtaining additional mass from a companion, BSSs are able to live prolonged lives on the main sequence. BSSs bring confusions to studies that rely on a standard stellar evolutionary track when modeling stellar populations, since the presence of BSSs can make a population appear younger than it actually is. It is important to have a better understanding of the mechanisms that drive BSS formation so that BSSs may be correctly accounted for in future studies.Blue stagglers in clusters primarily form in one of two ways; either from a close binary system in which one star accretes mass from its companion star or from a hierarchical trinary system in which a close inner binary merges as a result of perturbations from a farther-orbiting third star. In order to investigate the nature of this mass transfer, We obtained IGRINS H-band high resolution spectra of 6 BSSs and 12 red giant stars in open cluster M67. Using a grid of synthetic spectra obtained from the line analysis code MOOG, we identified and fit abundances for absorption lines of iron, silicon, and carbon. Depending on the evolutionary stage of the donor star, the abundance of carbon in the resulting BSS can be affected by mixing during the mass transfer. By analyzing the abundance of carbon in our targets, we find that [Fe/H] ~= 0 and [C/H] ~= 0. We see no evidence of depletion of carbon from RGB-phase mass transfer or enhancement of carbon from AGB-phase mass transfer, implying that the mass transfer occured earlier in the donar star's evolution.Funding for this research comes from the John W. Cox endowment for the Advanced Studies in Astronomy. For support of this work we acknowledge NSF grants AST-1211585 and AST-1616040 to CS. The successful development of the IGRINS spectrograph has resulted from the combined efforts of teams at the University of Texas at Austin and the Korea Astronomy and

Spectroscopic Analyses of Neutron Capture Elements in Open Clusters

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O'Connell, Julia E.

The evolution of elements as a function or age throughout the Milky Way disk provides strong constraints for galaxy evolution models, and on star formation epochs. In an effort to provide such constraints, we conducted an investigation into r- and s-process elemental abundances for a large sample of open clusters as part of an optical follow-up to the SDSS-III/APOGEE-1 near infrared survey. To obtain data for neutron capture abundance analysis, we conducted a long-term observing campaign spanning three years (2013-2016) using the McDonald Observatory Otto Struve 2.1-meter telescope and Sandiford Cass Echelle Spectrograph (SES, R(lambda/Deltalambda) ˜60,000). The SES provides a wavelength range of ˜1400 A, making it uniquely suited to investigate a number of other important chemical abundances as well as the neutron capture elements. For this study, we derive abundances for 18 elements covering four nucleosynthetic families- light, iron-peak, neutron capture and alpha-elements- for ˜30 open clusters within 6 kpc of the Sun with ages ranging from ˜80 Myr to ˜10 Gyr. Both equivalent width (EW) measurements and spectral synthesis methods were employed to derive abundances for all elements. Initial estimates for model stellar atmospheres- effective temperature and surface gravity- were provided by the APOGEE data set, and then re-derived for our optical spectra by removing abundance trends as a function of excitation potential and reduced width log(EW/lambda). With the exception of Ba II and Zr I, abundance analyses for all neutron capture elements were performed by generating synthetic spectra from the new stellar parameters. In order to remove molecular contamination, or blending from nearby atomic features, the synthetic spectra were modeled by a best-fit Gaussian to the observed data. Nd II shows a slight enhancement in all cluster stars, while other neutron capture elements follow solar abundance trends. Ba II shows a large cluster-to-cluster abundance spread

Photometry Using Kepler “Superstamps” of Open Clusters NGC 6791 & NGC 6819

Directory of Open Access Journals (Sweden)

Kuehn Charles A.

2015-01-01

Full Text Available 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.

Search for and Investigation of Double Open Clusters

Directory of Open Access Journals (Sweden)

Yalyalieva L. N.

2016-12-01

Full Text Available The physical and kinematical parameters of three pairs of open clusters, NGC 6755 and Czernik 39, NGC 1857 and Czernik 20, Berkeley 70 and SAI 47, are determined using the data from several photometric catalogs in order to confirm or disprove the binarity of these pairs.

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

Science.gov (United States)

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).

Disintegration of the Aged Open Cluster Berkeley 17

Energy Technology Data Exchange (ETDEWEB)

Bhattacharya, Souradeep; Vaidya, Kaushar [Department of Physics, Birla Institute of Technology and Science, Pilani 333031, Rajasthan (India); Mishra, Ishan [Indian Institute of Technology Guwahati, Guwahati 781039, Assam (India); Chen, W. P., E-mail: f2012553@pilani.bits-pilani.ac.in [Graduate Institute of Astronomy, National Central University, 300 Jhongda Road, Jhongli 32001, Taiwan (China)

2017-10-01

We present the analysis of the morphological shape of Berkeley 17, the oldest known open cluster (∼10 Gyr), using the probabilistic star counting of Pan-STARRS point sources, and confirm its core-tail shape, plus an antitail, previously detected with the 2MASS data. The stellar population, as diagnosed by the color–magnitude diagram and theoretical isochrones, shows many massive members in the clusters core, whereas there is a paucity of such members in both of the tails. This manifests mass segregation in this aged star cluster with the low-mass members being stripped away from the system. It has been claimed that Berkeley 17 is associated with an excessive number of blue straggler candidates. A comparison of nearby reference fields indicates that about half of these may be field contamination.

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

Energy Technology Data Exchange (ETDEWEB)

Pacucci, Fabio; Ferrara, Andrea [Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa (Italy); D' Onghia, Elena [University of Wisconsin, 475 Charter St., Madison, WI 53706 (United States)

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.

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

Energy Technology Data Exchange (ETDEWEB)

Sandquist, Eric L.; Serio, Andrew W.; Orosz, Jerome [San Diego State University, Department of Astronomy, San Diego, CA 92182 (United States); Shetrone, Matthew, E-mail: esandquist@mail.sdsu.edu, E-mail: aserio@gemini.edu, E-mail: jorosz@mail.sdsu.edu, E-mail: shetrone@astro.as.utexas.edu [University of Texas, McDonald Observatory, HC75 Box 1337-L Fort Davis, TX 79734 (United States)

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.

RADIAL PROFILE OF THE 3.5 keV LINE OUT TO R 200 IN THE PERSEUS CLUSTER

International Nuclear Information System (INIS)

Franse, Jeroen; Bulbul, Esra; Bautz, Mark; McDonald, Michael; Miller, Eric; Foster, Adam; Randall, Scott W.; Smith, Randall K.; Boyarsky, Alexey; Markevitch, Maxim; Iakubovskyi, Dmytro; Ruchayskiy, Oleg; Loewenstein, Mike

2016-01-01

The recent discovery of the unidentified emission line at 3.5 keV in galaxies and clusters has attracted great interest from the community. As the origin of the line remains uncertain, we study the surface brightness distribution of the line in the Perseus cluster since that information can be used to identify its origin. We examine the flux distribution of the 3.5 keV line in the deep Suzaku observations of the Perseus cluster in detail. The 3.5 keV line is observed in three concentric annuli in the central observations, although the observations of the outskirts of the cluster did not reveal such a signal. We establish that these detections and the upper limits from the non-detections are consistent with a dark matter decay origin. However, absence of positive detection in the outskirts is also consistent with some unknown astrophysical origin of the line in the dense gas of the Perseus core, as well as with a dark matter origin with a steeper dependence on mass than the dark matter decay. We also comment on several recently published analyses of the 3.5 keV line.

STAR CLUSTERS IN M31. II. OLD CLUSTER METALLICITIES AND AGES FROM HECTOSPEC DATA

International Nuclear Information System (INIS)

Caldwell, Nelson; Schiavon, Ricardo; Morrison, Heather; Harding, Paul; Rose, James A.

2011-01-01

We present new high signal-to-noise spectroscopic data on the M31 globular cluster (GC) system, obtained with the Hectospec multifiber spectrograph on the 6.5 m MMT. More than 300 clusters have been observed at a resolution of 5 A and with a median S/N of 75 per A, providing velocities with a median uncertainty of 6 km s -1 . The primary focus of this paper is the determination of mean cluster metallicities, ages, and reddenings. Metallicities were estimated using a calibration of Lick indices with [Fe/H] provided by Galactic GCs. These match well the metallicities of 24 M31 clusters determined from Hubble Space Telescope color-magnitude diagrams, the differences having an rms of 0.2 dex. The metallicity distribution is not generally bimodal, in strong distinction with the bimodal Galactic globular distribution. Rather, the M31 distribution shows a broad peak, centered at [Fe/H] = -1, possibly with minor peaks at [Fe/H] = -1.4, -0.7, and -0.2, suggesting that the cluster systems of M31 and the Milky Way had different formation histories. Ages for clusters with [Fe/H] > - 1 were determined using the automatic stellar population analysis program EZ A ges. We find no evidence for massive clusters in M31 with intermediate ages, those between 2 and 6 Gyr. Moreover, we find that the mean ages of the old GCs are remarkably constant over about a decade in metallicity (-0.95∼< [Fe/H] ∼<0.0).

CAMPAIGN: an open-source library of GPU-accelerated data clustering algorithms.

Science.gov (United States)

Kohlhoff, Kai J; Sosnick, Marc H; Hsu, William T; Pande, Vijay S; Altman, Russ B

2011-08-15

Data clustering techniques are an essential component of a good data analysis toolbox. Many current bioinformatics applications are inherently compute-intense and work with very large datasets. Sequential algorithms are inadequate for providing the necessary performance. For this reason, we have created Clustering Algorithms for Massively Parallel Architectures, Including GPU Nodes (CAMPAIGN), a central resource for data clustering algorithms and tools that are implemented specifically for execution on massively parallel processing architectures. CAMPAIGN is a library of data clustering algorithms and tools, written in 'C for CUDA' for Nvidia GPUs. The library provides up to two orders of magnitude speed-up over respective CPU-based clustering algorithms and is intended as an open-source resource. New modules from the community will be accepted into the library and the layout of it is such that it can easily be extended to promising future platforms such as OpenCL. Releases of the CAMPAIGN library are freely available for download under the LGPL from https://simtk.org/home/campaign. Source code can also be obtained through anonymous subversion access as described on https://simtk.org/scm/?group_id=453. kjk33@cantab.net.

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

International Nuclear Information System (INIS)

Williams, Kurtis A.; Howell, Steve B.; Liebert, James; Smith, Paul S.; Bellini, Andrea; Rubin, Kate H. R.; Bolte, Michael

2013-01-01

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 WD ≥ 0.68 M ☉ with M WD ≈ 0.83 M ☉ 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 ☉ .

X-ray emission from open star clusters with Spectrum-Rontgen-Gamma

DEFF Research Database (Denmark)

Singh, K.P.; Ojha, D.K.; Schnopper, H.W.

1998-01-01

The study of X-ray emission from co-evolving populations of stars in open dusters is extremely important for understanding the dynamo activity among the stars. With this objective, we propose to observe a number of open clusters in the X-ray and UV bands using SPECTRUM-Rontgen-Gamma. The high...... throughput of SPECTRUM-Rontgen-Gamma will help detect main sequence stars like Sun in middle-aged and old clusters. We will study the relationships between various parameters - age, rotation, abundance, UBV colors, X-ray luminosity, coronal temperature etc. X-ray spectra of younger and brighter populations...

Deep CCD photometry in globular clusters. VII. M30

International Nuclear Information System (INIS)

Richer, H.B.; Fahlman, G.G.; Vandenberg, D.A.

1988-01-01

New UBV CCD photometry in a single field of the globular cluster M30 was obtained, and the data were used to obtain the color magnitude diagram (CMD) of the cluster, its luminosity function, and to derive fundamental cluster parameters. No blue stragglers were found, nor any evidence of a binary sequence in the data even though the field under study is only 21 core radii from the cluster center. The cluster reddening is observed to be 0.068 + or - 0.035, significantly higher than that adopted in most current papers on M30. An intercomparison of the CMDs of three very metal-poor clusters clearly shows that there is no evidence for any age difference between them. The age of M30 itself is found to be about 14 Gyr. The luminosity function of M30 is determined to be M(V) = 8. Comparison of this function with one found by Bolte (1987) at 65 core radii shows clear evidence of mass segregation in the low-mass stars. 44 references

Collaborative Research of Open Star Clusters Alisher S. Hojaev

Indian Academy of Sciences (India)

Some spectra of the young star candidates with dispersion 50 and 200 Å/mm were .... Color-magnitude diagram for o band and o band minus i band for stars in the region of NGC ... Statistical analysis for open cluster parameters investigation.

Red giants and yellow stragglers in the young open cluster NGC 2447

Science.gov (United States)

da Silveira, M. D.; Pereira, C. B.; Drake, N. A.

2018-06-01

In this work we analysed, using high-resolution spectroscopy, a sample of 12 single and 4 spectroscopic binary stars of the open cluster NGC 2447. For the single stars, we obtained atmospheric parameters and chemical abundances of Li, C, N, O, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, Nd, Eu. Rotational velocities were obtained for all the stars. The abundances of the light elements and Eu and the rotational velocities were derived using spectral synthesis technique. We obtained a mean metallicity of [Fe/H] = -0.17 ± 0.05. We found that the abundances of all elements are similar to field giants and/or giants of open clusters, even for the s-process elements, which are enhanced as in other young open clusters. We show that the spectroscopic binaries NGC 2447-26, 38, and 42 are yellow-straggler stars, of which the primary is a giant star and the secondary a main-sequence A-type star.

Sequence spaces M ( ϕ $M(\\phi$ and N ( ϕ $N(\\phi$ with application in clustering

Directory of Open Access Journals (Sweden)

Mohd Shoaib Khan

2017-03-01

Full Text Available Abstract Distance measures play a central role in evolving the clustering technique. Due to the rich mathematical background and natural implementation of l p $l_{p}$ distance measures, researchers were motivated to use them in almost every clustering process. Beside l p $l_{p}$ distance measures, there exist several distance measures. Sargent introduced a special type of distance measures m ( ϕ $m(\\phi$ and n ( ϕ $n(\\phi$ which is closely related to l p $l_{p}$ . In this paper, we generalized the Sargent sequence spaces through introduction of M ( ϕ $M(\\phi$ and N ( ϕ $N(\\phi$ sequence spaces. Moreover, it is shown that both spaces are BK-spaces, and one is a dual of another. Further, we have clustered the two-moon dataset by using an induced M ( ϕ $M(\\phi$ -distance measure (induced by the Sargent sequence space M ( ϕ $M(\\phi$ in the k-means clustering algorithm. The clustering result established the efficacy of replacing the Euclidean distance measure by the M ( ϕ $M(\\phi$ -distance measure in the k-means algorithm.

The peculiar radio source M17 JVLA 35

Energy Technology Data Exchange (ETDEWEB)

Rodríguez, L. F.; Carrasco-González, C. [Centro de Radioastronomía y Astrofísica UNAM, Apartado Postal 3-72 (Xangari), 58089 Morelia, Michoacán (Mexico); Montes, G. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Tapia, M. [Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 877, Ensenada, BC, CP 22830 (Mexico)

2014-07-01

M17 JVLA 35 is a radio source detected in projection against the M17 H II region. In recent observations, its spectrum between 4.96 and 8.46 GHz was found to be positive and very steep, with α ≥ 2.9 ± 0.6 (S {sub ν}∝ν{sup α}). Here we present Very Large Array observations made in the 18.5 to 36.5 GHz region that indicate a spectral turnover at ∼13 GHz and a negative spectral index (α ≅ –2.0) at higher frequencies. The spectrum is consistent with that of an extragalactic high frequency peaker (HFP). However, M17 JVLA 35 has an angular size of ∼0.''5 at 8.46 GHz, while HFPs have extremely compact, milliarcsecond dimensions. We discuss other possible models for the spectrum of the source and do not find them feasible. Finally, we propose that M17 JVLA 35 is indeed an HFP but that its angular size becomes broadened by plasma scattering as its radiation travels across M17. If our interpretation is correct, accurate measurements of the angular size of M17 JVLA 35 across the centimeter range should reveal the expected ν{sup –2} dependence.

Theoretical study of isoelectronic SinM clusters (M=Sc-,Ti,V+; n=14-18)

DEFF Research Database (Denmark)

Torres, M. B.; Fernandez Sanchez, Eva; Balbás, L. C.

2007-01-01

We study, from first-principles quantum mechanical calculations, the structural and electronic properties of several low-lying energy equilibrium structures of isoelectronic SinM clusters (M=Sc-,Ti,V+) for n=14-18. The main result is that those clusters with n=16 are more stable than its neighbors...... of the spherical potential model). The structures of the two lowest energy isomers of Si16M are nearly degenerate, and consist of the Frank-Kasper polyhedron and a distortion of that polyhedron. The first structure is the ground state for M=V+, and the second is the ground state for Ti and Sc-. For the lowest...... energy isomers of clusters SinM with n=14-18, we analyze the changes with size n, and impurity M of several quantities: binding energy, second difference of total energy, HOMO-LUMO gap, adiabatic electron affinity, addition energy of a Si atom, and addition energy of an M impurity to a pure Si-n cluster...

Investigating the usefulness of a cluster-based trend analysis to detect visual field progression in patients with open-angle glaucoma.

Science.gov (United States)

Aoki, Shuichiro; Murata, Hiroshi; Fujino, Yuri; Matsuura, Masato; Miki, Atsuya; Tanito, Masaki; Mizoue, Shiro; Mori, Kazuhiko; Suzuki, Katsuyoshi; Yamashita, Takehiro; Kashiwagi, Kenji; Hirasawa, Kazunori; Shoji, Nobuyuki; Asaoka, Ryo

2017-12-01

To investigate the usefulness of the Octopus (Haag-Streit) EyeSuite's cluster trend analysis in glaucoma. Ten visual fields (VFs) with the Humphrey Field Analyzer (Carl Zeiss Meditec), spanning 7.7 years on average were obtained from 728 eyes of 475 primary open angle glaucoma patients. Mean total deviation (mTD) trend analysis and EyeSuite's cluster trend analysis were performed on various series of VFs (from 1st to 10th: VF1-10 to 6th to 10th: VF6-10). The results of the cluster-based trend analysis, based on different lengths of VF series, were compared against mTD trend analysis. Cluster-based trend analysis and mTD trend analysis results were significantly associated in all clusters and with all lengths of VF series. Between 21.2% and 45.9% (depending on VF series length and location) of clusters were deemed to progress when the mTD trend analysis suggested no progression. On the other hand, 4.8% of eyes were observed to progress using the mTD trend analysis when cluster trend analysis suggested no progression in any two (or more) clusters. Whole field trend analysis can miss local VF progression. Cluster trend analysis appears as robust as mTD trend analysis and useful to assess both sectorial and whole field progression. Cluster-based trend analyses, in particular the definition of two or more progressing cluster, may help clinicians to detect glaucomatous progression in a timelier manner than using a whole field trend analysis, without significantly compromising specificity. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

The incidence of chemically peculiar stars in open clusters

Energy Technology Data Exchange (ETDEWEB)

Netopil, M.

2013-07-01

The formation and evolution of chemically peculiar (CP) stars is still a matter of debate, although the first representatives were detected already more than 110 years ago. From the astrophysical point of view, these objects are of particular interest, since they combine a wide variety of specific properties. This work deals with a subgroup of CP stars, showing beside overabundances of some iron-peak (e.g. Chromium) and rare earth elements like Europium, also strong ordered magnetic fields as well as a slow rotation. Based on a selection of well investigated close field stars, the possible connections of these properties were examined. However, the main research focus was the analysis of a relationship between the number of CP stars and their age. For this purpose, the results of the extensive Delta-a survey in open clusters were used. This photometric filter system allows an efficient and economic detection of magnetic CP stars due to a characteristic flux depression at 520 nm. Compared to field stars, open clusters offer the big advantage that for example the age and the distance can be determined more accurately on a statistical basis, since all member stars of an open cluster originate more or less at the same time from a single molecular cloud. After the membership analysis of all in Delta a investigated objects and the determination of the cluster parameters, it was shown that the occurrence of CP stars depend on age, but can be explained by the general evolution of stars. This entails amongst others that CP stars show their typical characteristics already as soon as they have arrived the main-sequence, or even before. Furthermore, we were able to detect at least one representative, probably still in its pre-main-sequence phase. (author) [German] Die Entstehung und Entwicklung von chemisch pekuliaren (CP) Sternen ist nach wie vor nicht restlos geklärt, und das obwohl die ersten Vertreter dieser Sterngruppe bereits vor mehr als 110 Jahren entdeckt wurden. Aus

Be STARS IN THE OPEN CLUSTER NGC 6830

International Nuclear Information System (INIS)

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

2016-01-01

We report the discovery of two new Be stars, and re-identify one known Be star in the open cluster NGC 6830. Eleven H α emitters were discovered using the H α 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 H α emitters were confirmed as Be stars with H α 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 H α 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.

Be STARS IN THE OPEN CLUSTER NGC 6830

Energy Technology Data Exchange (ETDEWEB)

Yu, Po-Chieh; Lin, Chien-Cheng; Lin, Hsing-Wen; Lee, Chien-De; Ngeow, Chow-Choong; Ip, Wing-Huen; Chen, Wen-Ping; Chang, Chan-Kao; Huang, Li-Ching; Cheng, Yu-Chi; Ritter, Andreas [Graduate Institute of Astronomy, National Central University, 300 Jhongda Road, Jhongli 32001, Taiwan (China); Konidaris, Nick [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, 1200 E. California Boulevard, Pasadena, CA 91125 (United States); Chen, Hui-Chen [Department of Natural Sciences and Sustainable Development, Ministry of Science and Technology, 106, Sec. 2, Heping E. Road, Taipei 10622, Taiwan (China); Malkan, Matthew A. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90024 (United States); Laher, Russ; Surace, Jason [Spitzer Science Center, California Institute of Technology, M/S 314-6, Pasadena, CA 91125 (United States); Edelson, Rick [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Quimby, Robert [Kavli-Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa-shi, Chiba (Japan); Ben-Ami, Sagi; Ofek, Eran O. [Department of Particle Physics and Astrophysics, The Weizmann Institute of Science, Rehovot 76100 (Israel); and others

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 H α emitters were discovered using the H α 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 H α emitters were confirmed as Be stars with H α 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 H α 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.

CCD photometry of the distant young open cluster NGC 7510

International Nuclear Information System (INIS)

Sagar, R.; Bonn Univ.; Griffiths, W.K.

1991-01-01

CCD observations in B, V and I passbands have been used to generate deep V, (B-V) and V,(V-I) colour-magnitude diagrams for the open cluster NGC 7510. The sample consists of 592 stars reaching down to V=21 mag. There appears to be non-uniform extinction over the face of the cluster with the value of colour excess, E(B-V), ranging from 1.0 to 1.3 mag. The law of interstellar extinction in the direction of the cluster is found to be normal. A broad main sequence is clearly visible in both colour-magnitude diagrams. From the bluest part of the colour-magnitude diagrams, the true distance modulus to the cluster has been estimated as 12.5±0.3 mag and an upper limit of 10 Myr has been assigned for the cluster age. (author)

Open Clusters as Tracers of the Galactic Disk

Science.gov (United States)

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

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

Science.gov (United States)

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.

Na-O abundances in M53: A Mostly First Generation Globular Cluster

Science.gov (United States)

Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico

2016-01-01

We present the Fe, Ca, Ti, Ni, Ba, Na, and O abundances for a sample of 53 red giant branch (RGB) stars in the globular cluster (GC) NGC 5024 (M53). The abundances were measured from high signal-to-noise medium resolution spectra collected with the Hydra multi-object spectrograph on the WIYN 3.5- meter telescope. M53 is of interest because previous studies based on the morphology of the cluster's horizontal branch suggested that it might be composed primarily of first generation (FG) stars and differ from the majority of other GCs withmultiple populations, which have been found to be dominated by second generation (SG) stars. Our sample has an average [Fe/H] = -2.07 with a standard deviation of 0.07 dex. This value is consistent with previouslypublished results. The alpha-element abundances in our sample are also consistent with the trends seen in Milky Way halo stars at similar metallicities, with enhanced [Ca/Fe] and [Ti/Fe] relative to solar. We find thatthe Na-O anti-correlation is not as extended as other GCs with similarly high masses. The fraction of SG to FG stars in our sample is approximately 1:3 and the SG is more centrally concentrated. These findings further support that M53 might be a mostly FG cluster and could give further insight into how GCs formed the light element abundance patterns we observe in them today.

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

DEFF Research Database (Denmark)

Brewer, Lauren; Sandquist, E. L.; Mathieu, R. D.

2013-01-01

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...... 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...

THE UNIQUE Na:O ABUNDANCE DISTRIBUTION IN NGC 6791: THE FIRST OPEN(?) CLUSTER WITH MULTIPLE POPULATIONS

International Nuclear Information System (INIS)

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

2012-01-01

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.

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

Science.gov (United States)

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.

RADIAL PROFILE OF THE 3.5 keV LINE OUT TO R {sub 200} IN THE PERSEUS CLUSTER

Energy Technology Data Exchange (ETDEWEB)

Franse, Jeroen [Leiden Observatory, Leiden University, Niels Bohrweg 2, Leiden (Netherlands); Bulbul, Esra; Bautz, Mark; McDonald, Michael; Miller, Eric [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Foster, Adam; Randall, Scott W.; Smith, Randall K. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Boyarsky, Alexey [Instituut-Lorentz for Theoretical Physics, Leiden University, Niels Bohrweg 2, Leiden (Netherlands); Markevitch, Maxim [NASA Goddard Space Flight Center, 880 Greenbelt Road, MD 20771 (United States); Iakubovskyi, Dmytro; Ruchayskiy, Oleg [Discovery Center, Niels Bohr Institute, Blegdamsvej 17, Copenhagen (Denmark); Loewenstein, Mike [CRESST and X-ray Astrophysics Laboratory NASA/GSFC, Greenbelt, MD 20771 (United States)

2016-10-01

The recent discovery of the unidentified emission line at 3.5 keV in galaxies and clusters has attracted great interest from the community. As the origin of the line remains uncertain, we study the surface brightness distribution of the line in the Perseus cluster since that information can be used to identify its origin. We examine the flux distribution of the 3.5 keV line in the deep Suzaku observations of the Perseus cluster in detail. The 3.5 keV line is observed in three concentric annuli in the central observations, although the observations of the outskirts of the cluster did not reveal such a signal. We establish that these detections and the upper limits from the non-detections are consistent with a dark matter decay origin. However, absence of positive detection in the outskirts is also consistent with some unknown astrophysical origin of the line in the dense gas of the Perseus core, as well as with a dark matter origin with a steeper dependence on mass than the dark matter decay. We also comment on several recently published analyses of the 3.5 keV line.

m-BIRCH: an online clustering approach for computer vision applications

Science.gov (United States)

Madan, Siddharth K.; Dana, Kristin J.

2015-03-01

We adapt a classic online clustering algorithm called Balanced Iterative Reducing and Clustering using Hierarchies (BIRCH), to incrementally cluster large datasets of features commonly used in multimedia and computer vision. We call the adapted version modified-BIRCH (m-BIRCH). The algorithm uses only a fraction of the dataset memory to perform clustering, and updates the clustering decisions when new data comes in. Modifications made in m-BIRCH enable data driven parameter selection and effectively handle varying density regions in the feature space. Data driven parameter selection automatically controls the level of coarseness of the data summarization. Effective handling of varying density regions is necessary to well represent the different density regions in data summarization. We use m-BIRCH to cluster 840K color SIFT descriptors, and 60K outlier corrupted grayscale patches. We use the algorithm to cluster datasets consisting of challenging non-convex clustering patterns. Our implementation of the algorithm provides an useful clustering tool and is made publicly available.

Performance Modeling of Hybrid MPI/OpenMP Scientific Applications on Large-scale Multicore Cluster Systems

KAUST Repository

Wu, Xingfu; Taylor, Valerie

2011-01-01

In this paper, we present a performance modeling framework based on memory bandwidth contention time and a parameterized communication model to predict the performance of OpenMP, MPI and hybrid applications with weak scaling on three large-scale multicore clusters: IBM POWER4, POWER5+ and Blue Gene/P, and analyze the performance of these MPI, OpenMP and hybrid applications. We use STREAM memory benchmarks to provide initial performance analysis and model validation of MPI and OpenMP applications on these multicore clusters because the measured sustained memory bandwidth can provide insight into the memory bandwidth that a system should sustain on scientific applications with the same amount of workload per core. In addition to using these benchmarks, we also use a weak-scaling hybrid MPI/OpenMP large-scale scientific application: Gyro kinetic Toroidal Code in magnetic fusion to validate our performance model of the hybrid application on these multicore clusters. The validation results for our performance modeling method show less than 7.77% error rate in predicting the performance of hybrid MPI/OpenMP GTC on up to 512 cores on these multicore clusters. © 2011 IEEE.

Performance Modeling of Hybrid MPI/OpenMP Scientific Applications on Large-scale Multicore Cluster Systems

KAUST Repository

Wu, Xingfu

2011-08-01

In this paper, we present a performance modeling framework based on memory bandwidth contention time and a parameterized communication model to predict the performance of OpenMP, MPI and hybrid applications with weak scaling on three large-scale multicore clusters: IBM POWER4, POWER5+ and Blue Gene/P, and analyze the performance of these MPI, OpenMP and hybrid applications. We use STREAM memory benchmarks to provide initial performance analysis and model validation of MPI and OpenMP applications on these multicore clusters because the measured sustained memory bandwidth can provide insight into the memory bandwidth that a system should sustain on scientific applications with the same amount of workload per core. In addition to using these benchmarks, we also use a weak-scaling hybrid MPI/OpenMP large-scale scientific application: Gyro kinetic Toroidal Code in magnetic fusion to validate our performance model of the hybrid application on these multicore clusters. The validation results for our performance modeling method show less than 7.77% error rate in predicting the performance of hybrid MPI/OpenMP GTC on up to 512 cores on these multicore clusters. © 2011 IEEE.

The CNO Bi-cycle in the Open Cluster NGC 752

Science.gov (United States)

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.

VizieR Online Data Catalog: Ages and metallicities for M31 star clusters (Fan+, 2016)

Science.gov (United States)

Fan, Z.; de Grijs, R.; Chen, B.; Jiang, L.; Bian, F.; Li, Z.

2017-05-01

We have selected 22 confirmed M31 globular clusters from Peacock et al. 2010 (Cat. J/MNRAS/402/803). Spectroscopic observations were carried out with the 6.5m MMT/Red Channel Spectrograph from 2010 October 31 to 2010 November 2 and on 2011 November 4. The telescope is located on Mt. Hopkins in Arizona (USA) at an altitude of 2581m. The exposure times used ranged from 480-1800s, depending on the cluster brightness. The median seeing was ~0.98'' and we adopted a slit aperture of 0.75''*180''. The CCD's size is 450*1032 pixels2. It is characterized by a gain of 1.3e- ADU-1, with a readout noise of 3.5e-. A grating with 600l/mm with a blaze 1st/4800 was used. The spectral resolution was R=960 for a slit of 1'' and a central wavelength of 4701Å; the dispersion was 1.63Å/pixel. (7 data files).

Comparison of Intra-cluster and M87 Halo Orphan Globular Clusters in the Virgo Cluster

Science.gov (United States)

Louie, Tiffany Kaye; Tuan, Jin Zong; Martellini, Adhara; Guhathakurta, Puragra; Toloba, Elisa; Peng, Eric; Longobardi, Alessia; Lim, Sungsoon

2018-01-01

We present a study of “orphan” globular clusters (GCs) — GCs with no identifiable nearby host galaxy — discovered in NGVS, a 104 deg2 CFHT/MegaCam imaging survey. At the distance of the Virgo cluster, GCs are bright enough to make good spectroscopic targets and many are barely resolved in good ground-based seeing. Our orphan GC sample is derived from a subset of NGVS-selected GC candidates that were followed up with Keck/DEIMOS spectroscopy. While our primary spectroscopic targets were candidate GC satellites of Virgo dwarf elliptical and ultra-diffuse galaxies, many objects turned out to be non-satellites based on a radial velocity mismatch with the Virgo galaxy they are projected close to. Using a combination of spectral characteristics (e.g., absorption vs. emission), Gaussian mixture modeling of radial velocity and positions, and extreme deconvolution analysis of ugrizk photometry and image morphology, these non-satellites were classified into: (1) intra-cluster GCs (ICGCs) in the Virgo cluster, (2) GCs in the outer halo of M87, (3) foreground Milky Way stars, and (4) background galaxies. The statistical distinction between ICGCs and M87 halo GCs is based on velocity distributions (mean of 1100 vs. 1300 km/s and dispersions of 700 vs. 400 km/s, respectively) and radial distribution (diffuse vs. centrally concentrated, respectively). We used coaddition to increase the spectral SNR for the two classes of orphan GCs and measured the equivalent widths (EWs) of the Mg b and H-beta absorption lines. These EWs were compared to single stellar population models to obtain mean age and metallicity estimates. The ICGCs and M87 halo GCs have = –0.6+/–0.3 and –0.4+/–0.3 dex, respectively, and mean ages of >~ 5 and >~ 10 Gyr, respectively. This suggests the M87 halo GCs formed in relatively high-mass galaxies that avoided being tidally disrupted by M87 until they were close to the cluster center, while IGCCs formed in relatively low-mass galaxies that were

The Open Cluster Chemical Abundances and Mapping (OCCAM) Survey: Detailed Age and Abundance Gradients using DR12

Science.gov (United States)

Frinchaboy, Peter M.; Thompson, Benjamin A.; O'Connell, Julia; Meyer, Brianne; Donor, John; Majewski, Steven R.; Holtzman, Jon A.; Zasowski, Gail; Beers, Timothy C.; Beaton, Rachael; Cunha, Katia M. L.; Hearty, Fred; Nidever, David L.; Schiavon, Ricardo P.; Smith, Verne V.; Hayden, Michael R.

2015-01-01

We present detailed abundance results for Galactic open clusters as part of the Open Cluster Chemical Abundances and Mapping (OCCAM) Survey, which is based primarily on data from the Sloan Digital Sky Survey/ Apache Point Observatory Galactic Evolution Experiment. Using 100 open clusters from the uniformly observed complete SDSS-III/APOGEE-1 DR12 dataset, we present age and multi-element abundance gradients for the disk of the Milky Way.This work is supported by an NSF AAG grant AST-1311835.

A method for determining the radius of an open cluster from stellar proper motions

Science.gov (United States)

Sánchez, Néstor; Alfaro, Emilio J.; López-Martínez, Fátima

2018-04-01

We propose a method for calculating the radius of an open cluster in an objective way from an astrometric catalogue containing, at least, positions and proper motions. It uses the minimum spanning tree in the proper motion space to discriminate cluster stars from field stars and it quantifies the strength of the cluster-field separation by means of a statistical parameter defined for the first time in this paper. This is done for a range of different sampling radii from where the cluster radius is obtained as the size at which the best cluster-field separation is achieved. The novelty of this strategy is that the cluster radius is obtained independently of how its stars are spatially distributed. We test the reliability and robustness of the method with both simulated and real data from a well-studied open cluster (NGC 188), and apply it to UCAC4 data for five other open clusters with different catalogued radius values. NGC 188, NGC 1647, NGC 6603, and Ruprecht 155 yielded unambiguous radius values of 15.2 ± 1.8, 29.4 ± 3.4, 4.2 ± 1.7, and 7.0 ± 0.3 arcmin, respectively. ASCC 19 and Collinder 471 showed more than one possible solution, but it is not possible to know whether this is due to the involved uncertainties or due to the presence of complex patterns in their proper motion distributions, something that could be inherent to the physical object or due to the way in which the catalogue was sampled.

Construction and application of Red5 cluster based on OpenStack

Science.gov (United States)

Wang, Jiaqing; Song, Jianxin

2017-08-01

With the application and development of cloud computing technology in various fields, the resource utilization rate of the data center has been improved obviously, and the system based on cloud computing platform has also improved the expansibility and stability. In the traditional way, Red5 cluster resource utilization is low and the system stability is poor. This paper uses cloud computing to efficiently calculate the resource allocation ability, and builds a Red5 server cluster based on OpenStack. Multimedia applications can be published to the Red5 cloud server cluster. The system achieves the flexible construction of computing resources, but also greatly improves the stability of the cluster and service efficiency.

Characterization of an M-Cluster-Substituted Nitrogenase VFe Protein.

Science.gov (United States)

Rebelein, Johannes G; Lee, Chi Chung; Newcomb, Megan; Hu, Yilin; Ribbe, Markus W

2018-03-13

The Mo- and V-nitrogenases are two homologous members of the nitrogenase family that are distinguished mainly by the presence of different heterometals (Mo or V) at their respective cofactor sites (M- or V-cluster). However, the V-nitrogenase is ~600-fold more active than its Mo counterpart in reducing CO to hydrocarbons at ambient conditions. Here, we expressed an M-cluster-containing, hybrid V-nitrogenase in Azotobacter vinelandii and compared it to its native, V-cluster-containing counterpart in order to assess the impact of protein scaffold and cofactor species on the differential reactivities of Mo- and V-nitrogenases toward CO. Housed in the VFe protein component of V-nitrogenase, the M-cluster displayed electron paramagnetic resonance (EPR) features similar to those of the V-cluster and demonstrated an ~100-fold increase in hydrocarbon formation activity from CO reduction, suggesting a significant impact of protein environment on the overall CO-reducing activity of nitrogenase. On the other hand, the M-cluster was still ~6-fold less active than the V-cluster in the same protein scaffold, and it retained its inability to form detectable amounts of methane from CO reduction, illustrating a fine-tuning effect of the cofactor properties on this nitrogenase-catalyzed reaction. Together, these results provided important insights into the two major determinants for the enzymatic activity of CO reduction while establishing a useful framework for further elucidation of the essential catalytic elements for the CO reactivity of nitrogenase. IMPORTANCE This is the first report on the in vivo generation and in vitro characterization of an M-cluster-containing V-nitrogenase hybrid. The "normalization" of the protein scaffold to that of the V-nitrogenase permits a direct comparison between the cofactor species of the Mo- and V-nitrogenases (M- and V-clusters) in CO reduction, whereas the discrepancy between the protein scaffolds of the Mo- and V-nitrogenases (MoFe and VFe

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

Science.gov (United States)

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

uvby and Hβ photometry of the open cluster IC 4996

International Nuclear Information System (INIS)

Alfaro, E.J.; Delgado, A.J.; Garcia-Pelayo, J.M.; Garrido, R.; Saez, M.

1985-01-01

Photoelectric uvby and Hβ observations have been obtained for 15 stars in the field of the open cluster IC 4996. An average colour excess of E(b-y)=0.473 is estimated for six observed members of the cluster, in good agreement with previous results. A comparison between the β-Msub(v) calibrations given by Crawford and by Eggen suggests that the first one takes better into account the evolutionary effects on the Hβ index. We have calculated a true distance modulus of 11.43 and an age of 7.5x10 6 years

Towards a comprehensive knowledge of the open cluster Haffner 9

Science.gov (United States)

Piatti, Andrés E.

2017-03-01

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

High-resolution Spectroscopic Observations of Binary Stars and Yellow Stragglers in Three Open Clusters : NGC 2360, NGC 3680, and NGC 5822

Science.gov (United States)

Sales Silva, J. V.; Peña Suárez, V. J.; Katime Santrich, O. J.; Pereira, C. B.; Drake, N. A.; Roig, F.

2014-11-01

Binary stars in open clusters are very useful targets in constraining the nucleosynthesis process. The luminosities of the stars are known because the distances of the clusters are also known, so chemical peculiarities can be linked directly to the evolutionary status of a star. In addition, binary stars offer the opportunity to verify a relationship between them and the straggler population in both globular and open clusters. We carried out a detailed spectroscopic analysis to derive the atmospheric parameters for 16 red giants in binary systems and the chemical composition of 11 of them in the open clusters NGC 2360, NGC 3680, and NGC 5822. We obtained abundances of C, N, O, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, and Nd. The atmospheric parameters of the studied stars and their chemical abundances were determined using high-resolution optical spectroscopy. We employ the local thermodynamic equilibrium model atmospheres of Kurucz and the spectral analysis code MOOG. The abundances of the light elements were derived using the spectral synthesis technique. We found that the stars NGC 2360-92 and 96, NGC 3680-34, and NGC 5822-4 and 312 are yellow straggler stars. We show that the spectra of NGC 5822-4 and 312 present evidence of contamination by an A-type star as a secondary star. For the other yellow stragglers, evidence of contamination is given by the broad wings of the Hα. Detection of yellow straggler stars is important because the observed number can be compared with the number predicted by simulations of binary stellar evolution in open clusters. We also found that the other binary stars are not s-process enriched, which may suggest that in these binaries the secondary star is probably a faint main-sequence object. The lack of any s-process enrichment is very useful in setting constraints for the number of white dwarfs in the open cluster, a subject that is related to the birthrate of these kinds of stars in open clusters and also to the age of a

Migration in the shearing sheet and estimates for young open cluster migration

Science.gov (United States)

Quillen, Alice C.; Nolting, Eric; Minchev, Ivan; De Silva, Gayandhi; Chiappini, Cristina

2018-04-01

Using tracer particles embedded in self-gravitating shearing sheet N-body simulations, we investigate the distance in guiding centre radius that stars or star clusters can migrate in a few orbital periods. The standard deviations of guiding centre distributions and maximum migration distances depend on the Toomre or critical wavelength and the contrast in mass surface density caused by spiral structure. Comparison between our simulations and estimated guiding radii for a few young supersolar metallicity open clusters, including NGC 6583, suggests that the contrast in mass surface density in the solar neighbourhood has standard deviation (in the surface density distribution) divided by mean of about 1/4 and larger than measured using COBE data by Drimmel and Spergel. Our estimate is consistent with a standard deviation of ˜0.07 dex in the metallicities measured from high-quality spectroscopic data for 38 young open clusters (<1 Gyr) with mean galactocentric radius 7-9 kpc.

THE STAR CLUSTER SYSTEM IN THE NEARBY STARBURST GALAXY M82

International Nuclear Information System (INIS)

Lim, Sungsoon; Lee, Myung Gyoon; Hwang, Narae

2013-01-01

We present a photometric study of star clusters in the nearby starburst galaxy M82 based on the UBVI-, YJ- and H-band Hubble Space Telescope images. We find 1105 star clusters with V 0 ≈ 0.45, and a weaker red population. The luminosity function of the disk clusters shows a power-law distribution with a power-law index α = –2.04 ± 0.03, and the scale height of their distribution is h z = 9.''64 ± 0.''40 (164 ± 7 pc), similar to that of the stellar thin disk of M82. We have derived the ages of ∼630 star clusters using the spectral energy distribution fit method by comparing UBVI(YJ)H-band photometric data with the simple stellar population models. The age distribution of the disk clusters shows that the most dominant cluster population has ages ranging from 100 Myr to 1 Gyr, with a peak at about 500 Myr. This suggests that M82 has undergone a disk-wide star formation about 500 Myr ago, probably through the interaction with M81. The brightest star clusters in the nuclear region are much brighter than those in other regions, indicating that more massive star clusters are formed in the denser environments. On the other hand, the colors of the halo clusters are similar to those of globular clusters in the Milky Way, and their ages are estimated to be older than 1 Gyr. These are probably genuine old globular clusters in M82.

X-ray Observations of Eight Young Open Star Clusters: I ...

Indian Academy of Sciences (India)

X-ray Observations of Eight Young Open Star Clusters: I. Membership and X-ray Luminosity. Himali Bhatt, J. C. Pandey, K. P. Singh, Ram Sagar & Brijesh Kumar. J. Astrophys. Astr. 34(4), December 2013, pp. 393–429, c Indian Academy of Sciences. Supplementary Material. Supplementary Table 3 follows.

The helium abundance in the metal-poor globular clusters M30 and NGC 6397

Energy Technology Data Exchange (ETDEWEB)

Mucciarelli, A.; Lovisi, L.; Lanzoni, B.; Ferraro, F. R. [Dipartimento di Fisica and Astronomia, Università degli Studi di Bologna, Viale Berti Pichat 6/2, I-40127 Bologna (Italy)

2014-05-01

We present the helium abundance of the two metal-poor clusters M30 and NGC 6397. Helium estimates have been obtained by using the high-resolution spectrograph FLAMES at the European Southern Observatory Very Large Telescope and by measuring the He I line at 4471 Å in 24 and 35 horizontal branch (HB) stars in M30 and NGC 6397, respectively. This sample represents the largest data set of He abundances collected so far in metal-poor clusters. The He mass fraction turns out to be Y = 0.252 ± 0.003 (σ = 0.021) for M30 and Y = 0.241 ± 0.004 (σ = 0.023) for NGC 6397. These values are fully compatible with the cosmological abundance, thus suggesting that the HB stars are not strongly enriched in He. The small spread of the Y distributions are compatible with those expected from the observed main sequence splitting. Finally, we find a hint of a weak anticorrelation between Y and [O/Fe] in NGC 6397 in agreement with the prediction that O-poor stars are formed by (He-enriched) gas polluted by the products of hot proton-capture reactions.

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

Energy Technology Data Exchange (ETDEWEB)

Williams, Kurtis A.; Chakraborty, Subho [Department of Physics and Astrophysics, Texas A and M University-Commerce, P.O. Box 3011, Commerce, TX, 75429 (United States); Serna-Grey, Donald [Department of Astronomy, University of Washington, Box 351580, Seattle, WA, 98195 (United States); Gianninas, A.; Canton, Paul A., E-mail: Kurtis.Williams@tamuc.edu [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks St., Norman, OK, 73019 (United States)

2015-12-15

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

MORE REMOTE GLOBULAR CLUSTERS IN THE OUTER HALO OF M31

International Nuclear Information System (INIS)

Di Tullio Zinn, Graziella; Zinn, Robert

2013-01-01

We searched the Sloan Digital Sky Survey for outer halo globular clusters (GCs) around M31. Our search of non-stellar objects, within the limits of 0.3 ≤ (g – i) 0 ≤ 1.5 and 14.0 ≤ r 0 ≤ 19.0 concentrated in some remote areas of the extended halo, to a maximum projected distance of 240 kpc, for a total of approximately 200 deg 2 . Another ∼50 deg 2 , ∼5-75 kpc from M31, were surveyed as test areas. In these areas, we identified 39 GCs and 2 GC candidates, 84% of the previously known GCs (93% of the 'classical GCs' and 40% of the 'halo extended clusters', on the cluster classification scheme of Huxor et al.). For the entire survey, we visually inspected 78,516 objects for morphological evidence of cluster status, and we identified 18 new clusters, and 75 candidate clusters. The new clusters include 15 classical globulars and 3 clusters of lower density. Six of the clusters reside in the remote areas of the outer halo, beyond projected distances of 100 kpc. Previously, only MGC1 was found beyond this limit at 117 kpc. The farthest cluster discovered in this survey lies at a projected radius of 158 kpc from M31, assuming that the M31 distance is 780 kpc.

Deep CCD photometry in globular clusters III. M15

International Nuclear Information System (INIS)

Fahlman, G.G.; Richer, H.B.; Vandenberg, D.A.

1985-01-01

CCD photometry in U, B, and V is presented for a 5' x 3' field in the globular cluster M15. The location of the main sequence in the color-magnitude diagram is found here to be significantly bluer than previous studies have indicated. The luminosity function of the cluster is studied down to V = 22.8 (Mroughly-equal7.5) and shown to be consistent with a power-law mass function, n(M) = QM/sup -alpha/ with α = 2.5 +- 1.0, to the limit of our data. The field star population brighter than V = 21.5, is examined in some detail. There appears to be about 50% more stars belonging to the disk in the field as compared with the Bahcall-Soneira standard galaxy model. The reddening to the cluster is found to be E(B-V) = 0.11 +- 0.04 from nine bright field stars. A new value for the ultraviolet excess of the cluster main-sequence stars is obtained, delta(0.6) = 0.25 +- 0.02, and confirms the well-known fact that M15 is among the metal poorest of the globular clusters

Ab Initio Molecular Dynamics Studies of Pb m Sb n ( m + n ≤ 9) Alloy Clusters

Science.gov (United States)

Song, Bingyi; Xu, Baoqiang; Yang, Bin; Jiang, Wenlong; Chen, Xiumin; Xu, Na; Liu, Dachun; Dai, Yongnian

2017-10-01

Structure, stability, and dynamics of Pb m Sb n ( m + n ≤ 9) clusters were investigated using ab initio molecular dynamics. Size dependence of binding energies, the second-order energy difference of clusters, dissociation energy, HOMO-LUMO gaps, Mayer bond order, and the diffusion coefficient of Pb m Sb n clusters were discussed. Results suggest that Pb3Sb2, Pb4Sb2, and Pb5Sb4 ( n = 2 or 4) clusters have higher stability than other clusters, which is consistent with previous findings. In case of Pb-Sb alloy, the dynamics results show that Pb4Sb2 (Pb-22.71 wt pct Sb) can exist in gas phase at 1073 K (800 °C), which reasonably explains the azeotropic phenomenon, and the calculated values are in agreement with the experimental results (Pb-22 wt pct Sb).

The Observational and Theoretical Tidal Radii of Globular Clusters in M87

Science.gov (United States)

Webb, Jeremy J.; Sills, Alison; Harris, William E.

2012-02-01

Globular clusters have linear sizes (tidal radii) which theory tells us are determined by their masses and by the gravitational potential of their host galaxy. To explore the relationship between observed and expected radii, we utilize the globular cluster population of the Virgo giant M87. Unusually deep, high signal-to-noise images of M87 are used to measure the effective and limiting radii of approximately 2000 globular clusters. To compare with these observations, we simulate a globular cluster population that has the same characteristics as the observed M87 cluster population. Placing these simulated clusters in the well-studied tidal field of M87, the orbit of each cluster is solved and the theoretical tidal radius of each cluster is determined. We compare the predicted relationship between cluster size and projected galactocentric distance to observations. We find that for an isotropic distribution of cluster velocities, theoretical tidal radii are approximately equal to observed limiting radii for R gc < 10 kpc. However, the isotropic simulation predicts a steep increase in cluster size at larger radii, which is not observed in large galaxies beyond the Milky Way. To minimize the discrepancy between theory and observations, we explore the effects of orbital anisotropy on cluster sizes, and suggest a possible orbital anisotropy profile for M87 which yields a better match between theory and observations. Finally, we suggest future studies which will establish a stronger link between theoretical tidal radii and observed radii.

THE OBSERVATIONAL AND THEORETICAL TIDAL RADII OF GLOBULAR CLUSTERS IN M87

International Nuclear Information System (INIS)

Webb, Jeremy J.; Sills, Alison; Harris, William E.

2012-01-01

Globular clusters have linear sizes (tidal radii) which theory tells us are determined by their masses and by the gravitational potential of their host galaxy. To explore the relationship between observed and expected radii, we utilize the globular cluster population of the Virgo giant M87. Unusually deep, high signal-to-noise images of M87 are used to measure the effective and limiting radii of approximately 2000 globular clusters. To compare with these observations, we simulate a globular cluster population that has the same characteristics as the observed M87 cluster population. Placing these simulated clusters in the well-studied tidal field of M87, the orbit of each cluster is solved and the theoretical tidal radius of each cluster is determined. We compare the predicted relationship between cluster size and projected galactocentric distance to observations. We find that for an isotropic distribution of cluster velocities, theoretical tidal radii are approximately equal to observed limiting radii for R gc < 10 kpc. However, the isotropic simulation predicts a steep increase in cluster size at larger radii, which is not observed in large galaxies beyond the Milky Way. To minimize the discrepancy between theory and observations, we explore the effects of orbital anisotropy on cluster sizes, and suggest a possible orbital anisotropy profile for M87 which yields a better match between theory and observations. Finally, we suggest future studies which will establish a stronger link between theoretical tidal radii and observed radii.

Ligand combination strategy for the preparation of novel low-dimensional and open-framework metal cluster materials

Science.gov (United States)

Anokhina, Ekaterina V.

Low-dimensional and open-framework materials containing transition metals have a wide range of applications in redox catalysis, solid-state batteries, and electronic and magnetic devices. This dissertation reports on research carried out with the goal to develop a strategy for the preparation of low-dimensional and open-framework materials using octahedral metal clusters as building blocks. Our approach takes its roots from crystal engineering principles where the desired framework topologies are achieved through building block design. The key idea of this work is to induce directional bonding preferences in the cluster units using a combination of ligands with a large difference in charge density. This investigation led to the preparation and characterization of a new family of niobium oxychloride cluster compounds with original structure types exhibiting 1ow-dimensional or open-framework character. Most of these materials have framework topologies unprecedented in compounds containing octahedral clusters. Comparative analysis of their structural features indicates that the novel cluster connectivity patterns in these systems are the result of complex interplay between the effects of anisotropic ligand arrangement in the cluster unit and optimization of ligand-counterion electrostatic interactions. The important role played by these factors sets niobium oxychloride systems apart from cluster compounds with one ligand type or statistical ligand distribution where the main structure-determining factor is the total number of ligands. These results provide a blueprint for expanding the ligand combination strategy to other transition metal cluster systems and for the future rational design of cluster-based materials.

Astrophysical parameters of open star clusters using 2MASS JHKs data

Science.gov (United States)

Durgapal, Alok; Bisht, Devendra; Yadav, Ramakant Singh

2018-04-01

In the present analysis we have estimated the fundamental parameters of two poorly studied open star clusters, namely Teutsch 61 and Czernik 3, using 2MASS JHKs data. We have used the color-magnitude and colour-colour diagrams to determine their fundamental parameters.

Open BPS wall crossing and M-theory

International Nuclear Information System (INIS)

Aganagic, Mina; Yamazaki, Masahito

2010-01-01

Consider the degeneracies of BPS bound states of one D6-brane wrapping Calabi-Yau X with D0-branes and D2-branes. When we include D4-branes wrapping Lagrangian cycles in addition, D2-branes can end on them. These give rise to new bound states in the d=2, N=(2,2) theory of the D4-branes. We call these 'open' BPS states, in contrast to closed BPS states that arise from D-branes without boundaries. Lifting this to M-theory, we show that the generating function is captured by free Fock space spanned by M2-brane particles ending on M5-branes wrapping the Lagrangian. This implies that the open BPS bound states are counted by the square of the open topological string partition function on X, reduced to the corresponding chamber. Our results give new predictions for open BPS invariants and their wall crossing phenomena when we change the open and closed string moduli. We relate our results to the work of Cecotti and Vafa on wall crossing in the two-dimensional N=(2,2) theories. The findings from the crystal melting model for the open BPS invariants proposed recently fit well with the M-theory predictions.

Kepler red-clump stars in the field and in open clusters

DEFF Research Database (Denmark)

Bossini, D.; Miglio, A.; Salaris, M.

2017-01-01

Convective mixing in helium-core-burning (HeCB) stars is one of the outstanding issues in stellar modelling. The precise asteroseismic measurements of gravity-mode period spacing (Delta Pi(1)) have opened the door to detailed studies of the near-core structure of such stars, which had not been...... possible before. Here, we provide stringent tests of various core-mixing scenarios against the largely unbiased population of red-clump stars belonging to the old-open clusters monitored by Kepler, and by coupling the updated precise inference on Delta Pi(1) in thousands of field stars with spectroscopic...... constraints. We find that models with moderate overshooting successfully reproduce the range observed of Delta Pi(1) in clusters. In particular, we show that there is no evidence for the need to extend the size of the adiabatically stratified core, at least at the beginning of the HeCB phase. This conclusion...

THE SUN WAS NOT BORN IN M67

International Nuclear Information System (INIS)

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

2012-01-01

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 × 10 5 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.

Tidal radii of the globular clusters M 5, M 12, M 13, M 15, M 53, NGC 5053 and NGC 5466 from automated star counts.

Science.gov (United States)

Lehmann, I.; Scholz, R.-D.

1997-04-01

We present new tidal radii for seven Galactic globular clusters using the method of automated star counts on Schmidt plates of the Tautenburg, Palomar and UK telescopes. The plates were fully scanned with the APM system in Cambridge (UK). Special account was given to a reliable background subtraction and the correction of crowding effects in the central cluster region. For the latter we used a new kind of crowding correction based on a statistical approach to the distribution of stellar images and the luminosity function of the cluster stars in the uncrowded area. The star counts were correlated with surface brightness profiles of different authors to obtain complete projected density profiles of the globular clusters. Fitting an empirical density law (King 1962) we derived the following structural parameters: tidal radius r_t_, core radius r_c_ and concentration parameter c. In the cases of NGC 5466, M 5, M 12, M 13 and M 15 we found an indication for a tidal tail around these objects (cf. Grillmair et al. 1995).

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

International Nuclear Information System (INIS)

Yong, David; Carney, Bruce W.; Friel, Eileen D.

2012-01-01

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 [α/Fe] and perhaps [Eu/Fe]. All elements show negligible or small trends between [X/Fe] and distance ( –1 ), but for some elements, there is a hint that the local (R GC GC > 13 kpc) samples may have different trends with distance. There is no evidence for significant abundance trends versus age ( –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 [α/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.

K2 and M4: A Unique Opportunity to Unlock the Mysteries of Globular Clusters

Science.gov (United States)

Kuehn, Charles A.; Stello, Dennis; Campbell, Simon; Drury, Jason; de Silva, Gayandhi; Maclean, Ben; Bedding, Timothy R.; Huber, Daniel

2016-01-01

One of the most exciting opportunities presented by K2 is the ability to study variable stars in globular clusters (GCs). The K2 observations allow us to perform ensemble asteroseismology of a population that is much older than that in the open clusters in the original Kepler field. This should help us answer long-standing questions concerning mass loss on the red giant branch and the spread in masses along the horizontal branch. By combining the asteroseismic data with chemical tagging of sub-populations from spectroscopy, we hope to better constrain stellar evolution models and potentially shed some light on the formation history of GCs. The very crowded nature of stars in GCs poses a challenge, however, due to Kepler's large pixels. M4, observed during K2's campaign 2, presents an excellent opportunity to study GCs with a combination of K2 and ground-based data. M4 is one of the two nearest GCs and thus should appear less crowded and brighter; in fact M4 is likely the only GC whose horizontal branch stars, other than RR Lyraes, will be accessible with K2. We discuss our method of obtaining photometry for the stars in M4 and present sample lightcurves for different classes of oscillating stars in the cluster. We also discuss efforts to use ground-based observations to increase the utility of the K2 dataset.

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

Energy Technology Data Exchange (ETDEWEB)

Hills, Shane; Courteau, Stéphane [Department of Physics, Engineering Physics and Astronomy, Queen’s University, Kingston, ON K7L 3N6 Canada (Canada); Von Hippel, Ted [Department of Physical Sciences, Embry-Riddle Aeronautical University, Daytona Beach, FL 32114 (United States); Geller, Aaron M., E-mail: shane.hills@queensu.ca, E-mail: courteau@astro.queensu.ca, E-mail: ted.vonhippel@erau.edu, E-mail: a-geller@northwestern.edu [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States)

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.

Spectroscopic determination of fundamental parameters of small angular diameter galactic open clusters

Science.gov (United States)

Ahumada, A. V.; Claria, J. J.; Bica, E.; Parisi, M. C.; Torres, M. C.; Pavani, D. B.

We present integrated spectra obtained at CASLEO (Argentina) for 9 galactic open clusters of small angular diameter. Two of them (BH 55 and Rup 159) have not been the target of previous research. The flux-calibrated spectra cover the spectral range approx. 3600-6900 A. Using the equivalent widths (EWs) of the Balmer lines and comparing the cluster spectra with template spectra, we determined E(B-V) colour excesses and ages for the present cluster sample. The parameters obtained for 6 of the clusters show good agreement with previous determinations based mainly on photometric methods. This is not the case, however, for BH 90, a scarcely reddened cluster, for which Moffat and Vogt (1975, Astron. and Astroph. SS, 20, 125) derived E(B-V) = 0.51. We explain and justify the strong discrepancy found for this object. According to the present analysis, 3 clusters are very young (Bo 14, Tr 15 and Tr 27), 2 are moderately young (NGC 6268 and BH 205), 3 are Hyades-like clusters (Rup 164, BH 90 and BH 55) and only one is an intermediate-age cluster (Rup 159).

Structure and stability of M6N8 clusters (M = Si, Ge, Sn, Ti).

Science.gov (United States)

Davydova, Elena I; Timoshkin, Alexey Y; Frenking, Gernot

2010-06-10

The structures and stabilities of the M(6)N(8) clusters (M = Si, Ge, Sn, Ti) have been theoretically studied at DFT and ab initio levels of theory. Two new isomers have been considered: cage-like molecules and propeller-like molecules. It is shown that only for M = Si are both isomers true minima on the potential energy surface. The thermodynamics of the dissociation process (1/6)M(6)N(8) --> (1/3)M(3)N(4) is discussed. For each M(3)N(4) molecule, four structures with different multiplicity are considered. The thermodynamic analysis shows that independently of the multiplicity of M(3)N(4) nitrides all M(6)N(8) clusters are stable in the gas phase in a wide temperature range and could be potential intermediates in chemical vapor deposition of the nitride materials.

The formation and evolution of M33 as revealed by its star clusters

Science.gov (United States)

San Roman, Izaskun

2012-03-01

Numerical simulations based on the Lambda-Cold Dark Matter (Λ-CDM) model predict a scenario consistent with observational evidence in terms of the build-up of Milky Way-like halos. Under this scenario, large disk galaxies derive from the merger and accretion of many smaller subsystems. However, it is less clear how low-mass spiral galaxies fit into this picture. The best way to answer this question is to study the nearest example of a dwarf spiral galaxy, M33. We will use star clusters to understand the structure, kinematics and stellar populations of this galaxy. Star clusters provide a unique and powerful tool for studying the star formation histories of galaxies. In particular, the ages and metallicities of star clusters bear the imprint of the galaxy formation process. We have made use of the star clusters to uncover the formation and evolution of M33. In this dissertation, we have carried out a comprehensive study of the M33 star cluster system, including deep photometry as well as high signal-to-noise spectroscopy. In order to mitigate the significant incompleteness presents in previous catalogs, we have conducted ground-based and space-based photometric surveys of M33 star clusters. Using archival images, we have analyzed 12 fields using the Advanced Camera for Surveys Wide Field Channel onboard the Hubble Space Telescope (ACS/HST) along the major axis of the galaxy. We present integrated photometry and color-magnitude diagrams for 161 star clusters in M33, of which 115 were previously uncataloged. This survey extends the depth of the existing M33 cluster catalogs by ˜ 1 mag. We have expanded our search through a photometric survey in a 1° x 1° area centered on M33 using the MegaCam camera on the 3.6m Canada-France-Hawaii Telescope (CFHT). In this work we discuss the photometric properties of the sample, including color-color diagrams of 599 new candidate stellar clusters, and 204 confirmed clusters. Comparisons with models of simple stellar populations

ADAPTIVE OPTICS OBSERVATIONS OF 3 {mu}m WATER ICE IN SILHOUETTE DISKS IN THE ORION NEBULA CLUSTER AND M43

Energy Technology Data Exchange (ETDEWEB)

Terada, Hiroshi; Pyo, Tae-Soo; Minowa, Yosuke; Hayano, Yutaka; Oya, Shin; Hattori, Masayuki; Takami, Hideki [Subaru Telescope, National Astronomical Observatory of Japan, 650 North A' ohoku Place, Hilo, HI 96720 (United States); Tokunaga, Alan T. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Watanabe, Makoto [Department of Cosmosciences, Hokkaido University, Kita 10, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810 (Japan); Saito, Yoshihiko [Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551 (Japan); Ito, Meguru [Department of Mechanical Engineering, University of Victoria, 3800 Finnerty Road, Victoria, BC, V8P 5C2 (Canada); Iye, Masanori, E-mail: terada@subaru.naoj.org [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

2012-12-01

We present the near-infrared images and spectra of four silhouette disks in the Orion Nebula Cluster (M42) and M43 using the Subaru Adaptive Optics system. While d053-717 and d141-1952 show no water ice feature at 3.1 {mu}m, a moderately deep ({tau}{sub ice} {approx} 0.7) water ice absorption is detected toward d132-1832 and d216-0939. Taking into account the water ice so far detected in the silhouette disks, the critical inclination angle to produce a water ice absorption feature is confirmed to be 65 Degree-Sign -75 Degree-Sign . As for d216-0939, the crystallized water ice profile is exactly the same as in the previous observations taken 3.63 years ago. If the water ice material is located at 30 AU, then the observations suggest it is uniform at a scale of about 3.5 AU.

Seeing deconvolution of globular clusters in M31

International Nuclear Information System (INIS)

Bendinelli, O.; Zavatti, F.; Parmeggiani, G.; Djorgovski, S.

1990-01-01

The morphology of six M31 globular clusters is examined using seeing-deconvolved CCD images. The deconvolution techniques developed by Bendinelli (1989) are reviewed and applied to the M31 globular clusters to demonstrate the methodology. It is found that the effective resolution limit of the method is about 0.1-0.3 arcsec for CCD images obtained in FWHM = 1 arcsec seeing, and sampling of 0.3 arcsec/pixel. Also, the robustness of the method is discussed. The implications of the technique for future studies using data from the Hubble Space Telescope are considered. 68 refs

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

Science.gov (United States)

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

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

Directory of Open Access Journals (Sweden)

Jai Ram Rideout

2014-08-01

Full Text Available 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

CHEMICAL ABUNDANCES IN NGC 5024 (M53): A MOSTLY FIRST GENERATION GLOBULAR CLUSTER

International Nuclear Information System (INIS)

Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico

2016-01-01

We present the Fe, Ca, Ti, Ni, Ba, Na, and O abundances for a sample of 53 red giant branch stars in the globular cluster (GC) NGC 5024 (M53). The abundances were measured from high signal-to-noise medium resolution spectra collected with the Hydra multi-object spectrograph on the Wisconsin–Indiana–Yale–NOAO 3.5 m telescope. M53 is of interest because previous studies based on the morphology of the cluster’s horizontal branch suggested that it might be composed primarily of first generation (FG) stars and differ from the majority of other GCs with multiple populations, which have been found to be dominated by the second generation (SG) stars. Our sample has an average [Fe/H] = −2.07 with a standard deviation of 0.07 dex. This value is consistent with previously published results. The alpha-element abundances in our sample are also consistent with the trends seen in Milky Way halo stars at similar metallicities, with enhanced [Ca/Fe] and [Ti/Fe] relative to solar. We find that the Na–O anti-correlation in M53 is not as extended as other GCs with similar masses and metallicities. The ratio of SG to the total number of stars in our sample is approximately 0.27 and the SG generation is more centrally concentrated. These findings further support that M53 might be a mostly FG cluster and could give further insight into how GCs formed the light element abundance patterns we observe in them today.

Chemical Abundances in NGC 5024 (M53): A Mostly First Generation Globular Cluster

Science.gov (United States)

Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico

2016-06-01

We present the Fe, Ca, Ti, Ni, Ba, Na, and O abundances for a sample of 53 red giant branch stars in the globular cluster (GC) NGC 5024 (M53). The abundances were measured from high signal-to-noise medium resolution spectra collected with the Hydra multi-object spectrograph on the Wisconsin-Indiana-Yale-NOAO 3.5 m telescope. M53 is of interest because previous studies based on the morphology of the cluster’s horizontal branch suggested that it might be composed primarily of first generation (FG) stars and differ from the majority of other GCs with multiple populations, which have been found to be dominated by the second generation (SG) stars. Our sample has an average [Fe/H] = -2.07 with a standard deviation of 0.07 dex. This value is consistent with previously published results. The alpha-element abundances in our sample are also consistent with the trends seen in Milky Way halo stars at similar metallicities, with enhanced [Ca/Fe] and [Ti/Fe] relative to solar. We find that the Na-O anti-correlation in M53 is not as extended as other GCs with similar masses and metallicities. The ratio of SG to the total number of stars in our sample is approximately 0.27 and the SG generation is more centrally concentrated. These findings further support that M53 might be a mostly FG cluster and could give further insight into how GCs formed the light element abundance patterns we observe in them today.

CHEMICAL ABUNDANCES IN NGC 5024 (M53): A MOSTLY FIRST GENERATION GLOBULAR CLUSTER

Energy Technology Data Exchange (ETDEWEB)

Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico [Astronomy Department, Indiana University, Bloomington, IN 47405 (United States)

2016-06-10

We present the Fe, Ca, Ti, Ni, Ba, Na, and O abundances for a sample of 53 red giant branch stars in the globular cluster (GC) NGC 5024 (M53). The abundances were measured from high signal-to-noise medium resolution spectra collected with the Hydra multi-object spectrograph on the Wisconsin–Indiana–Yale–NOAO 3.5 m telescope. M53 is of interest because previous studies based on the morphology of the cluster’s horizontal branch suggested that it might be composed primarily of first generation (FG) stars and differ from the majority of other GCs with multiple populations, which have been found to be dominated by the second generation (SG) stars. Our sample has an average [Fe/H] = −2.07 with a standard deviation of 0.07 dex. This value is consistent with previously published results. The alpha-element abundances in our sample are also consistent with the trends seen in Milky Way halo stars at similar metallicities, with enhanced [Ca/Fe] and [Ti/Fe] relative to solar. We find that the Na–O anti-correlation in M53 is not as extended as other GCs with similar masses and metallicities. The ratio of SG to the total number of stars in our sample is approximately 0.27 and the SG generation is more centrally concentrated. These findings further support that M53 might be a mostly FG cluster and could give further insight into how GCs formed the light element abundance patterns we observe in them today.

New Cepheid variables in the young open clusters Berkeley 51 and Berkeley 55

Science.gov (United States)

Lohr, M. E.; Negueruela, I.; Tabernero, H. M.; Clark, J. S.; Lewis, F.; Roche, P.

2018-05-01

As part of a wider investigation of evolved massive stars in Galactic open clusters, we have spectroscopically identified three candidate classical Cepheids in the little-studied clusters Berkeley 51, Berkeley 55 and NGC 6603. Using new multi-epoch photometry, we confirm that Be 51 #162 and Be 55 #107 are bona fide Cepheids, with pulsation periods of 9.83±0.01 d and 5.850±0.005 d respectively, while NGC 6603 star W2249 does not show significant photometric variability. Using the period-luminosity relationship for Cepheid variables, we determine a distance to Be 51 of 5.3^{+1.0}_{-0.8} kpc and an age of 44^{+9}_{-8} Myr, placing it in a sparsely-attested region of the Perseus arm. For Be 55, we find a distance of 2.2±0.3 kpc and age of 63^{+12}_{-11} Myr, locating the cluster in the Local arm. Taken together with our recent discovery of a long-period Cepheid in the starburst cluster VdBH222, these represent an important increase in the number of young, massive Cepheids known in Galactic open clusters. We also consider new Gaia (data release 2) parallaxes and proper motions for members of Be 51 and Be 55; the uncertainties on the parallaxes do not allow us to refine our distance estimates to these clusters, but the well-constrained proper motion measurements furnish further confirmation of cluster membership. However, future final Gaia parallaxes for such objects should provide valuable independent distance measurements, improving the calibration of the period-luminosity relationship, with implications for the distance ladder out to cosmological scales.

GLOBULAR AND OPEN CLUSTERS OBSERVED BY SDSS/SEGUE: THE GIANT STARS

Energy Technology Data Exchange (ETDEWEB)

Morrison, Heather L.; Ma, Zhibo; Connor, Thomas; Schechtman-Rook, Andrew; Harding, Paul [Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106 (United States); Clem, James L. [Department of Physics, Grove City College, 100 Campus Dr., Grove City, PA 16127 (United States); An, Deokkeun [Department of Science Education, Ewha Womans University, Seoul 120-750 (Korea, Republic of); Casagrande, Luca [Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, The Australian National University, ACT 2611 (Australia); Rockosi, Constance [UCO/Lick Observatory, University of California, Santa Cruz, 1156 High St., Santa Cruz, CA 95064 (United States); Yanny, Brian [Fermi National Accelerator Laboratory, P.O. Box 500, Batavia IL 60510 (United States); Beers, Timothy C. [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46656 (United States); Johnson, Jennifer A. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Schneider, Donald P., E-mail: hlm5@case.edu [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States)

2016-01-15

We present griz observations for the clusters M92, M13 and NGC 6791 and gr photometry for M71, Be 29 and NGC 7789. In addition we present new membership identifications for all these clusters, which have been observed spectroscopically as calibrators for the Sloan Digital Sky Survey (SDSS)/SEGUE survey; this paper focuses in particular on the red giant branch stars in the clusters. In a number of cases, these giants were too bright to be observed in the normal SDSS survey operations, and we describe the procedure used to obtain spectra for these stars. For M71, we also present a new variable reddening map and a new fiducial for the gr giant branch. For NGC 7789, we derived a transformation from T{sub eff} to g–r for giants of near solar abundance, using IRFM T{sub eff} measures of stars with good ugriz  and 2MASS photometry and SEGUE spectra. The result of our analysis is a robust list of known cluster members with correctly dereddened and (if needed) transformed gr photometry for crucial calibration efforts for SDSS and SEGUE.

THE BOTTOM OF THE WHITE DWARF COOLING SEQUENCE IN THE OLD OPEN CLUSTER NGC 2158

International Nuclear Information System (INIS)

Bedin, L. R.; Anderson, J.; Salaris, M.; King, I. R.; Piotto, G.; Cassisi, S.

2010-01-01

We use 10 orbits of Advanced Camera for Surveys observations to reach the end of the white dwarf (WD) cooling sequence in the solar-metallicity open cluster NGC 2158. Our photometry and completeness tests show that the end falls at magnitude m F606W = 27.5 ± 0.15, which implies an age between ∼1.8 and ∼2.0 Gyr, consistent with the age of 1.9 ± 0.2 Gyr obtained from fits to the main-sequence turn-off. The faintest WDs show a clear turn toward bluer colors, as predicted by theoretical isochrones.

The astrophysical behavior of open clusters along the Milky Way Galaxy

Directory of Open Access Journals (Sweden)

A.L. Tadross

2014-06-01

Full Text Available The main aim of this paper is to study the astrophysical behaviour of open clusters’ properties along the Milky Way Galaxy. Near-IR JHKS (2MASS photometry has been used for getting a homogeneous Catalog of 263 open clusters’ parameters, which are randomly selected and studied by the author through the last five years; most of them were studied for the first time. The correlations between the astrophysical parameters of these clusters have been achieved by morphological way and compared with the most recent works.

A multimembership catalogue for 1876 open clusters using UCAC4 data

Science.gov (United States)

Sampedro, L.; Dias, W. S.; Alfaro, E. J.; Monteiro, H.; Molino, A.

2017-10-01

The main objective of this work is to determine the cluster members of 1876 open clusters, using positions and proper motions of the astrometric fourth United States Naval Observatory (USNO) CCD Astrograph Catalog (UCAC4). For this purpose, we apply three different methods, all based on a Bayesian approach, but with different formulations: a purely parametric method, another completely non-parametric algorithm and a third, recently developed by Sampedro & Alfaro, using both formulations at different steps of the whole process. The first and second statistical moments of the members' phase-space subspace, obtained after applying the three methods, are compared for every cluster. Although, on average, the three methods yield similar results, there are also specific differences between them, as well as for some particular clusters. The comparison with other published catalogues shows good agreement. We have also estimated, for the first time, the mean proper motion for a sample of 18 clusters. The results are organized in a single catalogue formed by two main files, one with the most relevant information for each cluster, partially including that in UCAC4, and the other showing the individual membership probabilities for each star in the cluster area. The final catalogue, with an interface design that enables an easy interaction with the user, is available in electronic format at the Stellar Systems Group (SSG-IAA) web site (http://ssg.iaa.es/en/content/sampedro-cluster-catalog).

AN UPDATED CATALOG OF M33 CLUSTERS AND CANDIDATES: UBVRI PHOTOMETRY AND SOME STATISTICAL RESULTS

International Nuclear Information System (INIS)

Ma Jun

2012-01-01

We present UBVRI photometry for 392 star clusters and candidates in the field of M33, which are selected from the most recent star cluster catalog. In this catalog, the authors listed star clusters' parameters such as cluster positions, magnitudes, colors in the UBVRIJHK s filters, and so on. However, a large fraction of objects in this catalog do not have previously published photometry. Photometry is performed using archival images from the Local Group Galaxies Survey, which covers 0.8 deg 2 along the major axis of M33. Detailed comparisons show that, in general, our photometry is consistent with previous measurements. Positions (right ascension and declination) for some clusters are corrected here. Combined with previous literature, ours constitute a large sample of M33 star clusters. Based on this cluster sample, we present some statistical results: none of the youngest M33 clusters (∼10 7 yr) have masses approaching 10 5 M ☉ ; roughly half the star clusters are consistent with the 10 4 -10 5 M ☉ mass models; the continuous distribution of star clusters along the model line indicates that M33 star clusters have been formed continuously from the epoch of the first star cluster formation until recent times; and there are ∼50 star clusters which are overlapped with the Galactic globular clusters on the color-color diagram, and these clusters are old globular cluster candidates in M33.

Investigation on IMCP based clustering in LTE-M communication for smart metering applications

Directory of Open Access Journals (Sweden)

Kartik Vishal Deshpande

2017-06-01

Full Text Available Machine to Machine (M2M is foreseen as an emerging technology for smart metering applications where devices communicate seamlessly for information transfer. The M2M communication makes use of long term evolution (LTE as its backbone network and it results in long-term evolution for machine type communication (LTE-M network. As huge number of M2M devices is to be handled by single eNB (evolved Node B, clustering is exploited for efficient processing of the network. This paper investigates the proposed Improved M2M Clustering Process (IMCP based clustering technique and it is compared with two well-known clustering algorithms, namely, Low Energy Adaptive Clustering Hierarchical (LEACH and Energy Aware Multihop Multipath Hierarchical (EAMMH techniques. Further, the IMCP algorithm is analyzed with two-tier and three-tier M2M systems for various mobility conditions. The proposed IMCP algorithm improves the last node death by 63.15% and 51.61% as compared to LEACH and EAMMH, respectively. Further, the average energy of each node in IMCP is increased by 89.85% and 81.15%, as compared to LEACH and EAMMH, respectively.

3.5D dynamic PET image reconstruction incorporating kinetics-based clusters

International Nuclear Information System (INIS)

Lu Lijun; Chen Wufan; Karakatsanis, Nicolas A; Rahmim, Arman; Tang Jing

2012-01-01

Standard 3D dynamic positron emission tomographic (PET) imaging consists of independent image reconstructions of individual frames followed by application of appropriate kinetic model to the time activity curves at the voxel or region-of-interest (ROI). The emerging field of 4D PET reconstruction, by contrast, seeks to move beyond this scheme and incorporate information from multiple frames within the image reconstruction task. Here we propose a novel reconstruction framework aiming to enhance quantitative accuracy of parametric images via introduction of priors based on voxel kinetics, as generated via clustering of preliminary reconstructed dynamic images to define clustered neighborhoods of voxels with similar kinetics. This is then followed by straightforward maximum a posteriori (MAP) 3D PET reconstruction as applied to individual frames; and as such the method is labeled ‘3.5D’ image reconstruction. The use of cluster-based priors has the advantage of further enhancing quantitative performance in dynamic PET imaging, because: (a) there are typically more voxels in clusters than in conventional local neighborhoods, and (b) neighboring voxels with distinct kinetics are less likely to be clustered together. Using realistic simulated 11 C-raclopride dynamic PET data, the quantitative performance of the proposed method was investigated. Parametric distribution-volume (DV) and DV ratio (DVR) images were estimated from dynamic image reconstructions using (a) maximum-likelihood expectation maximization (MLEM), and MAP reconstructions using (b) the quadratic prior (QP-MAP), (c) the Green prior (GP-MAP) and (d, e) two proposed cluster-based priors (CP-U-MAP and CP-W-MAP), followed by graphical modeling, and were qualitatively and quantitatively compared for 11 ROIs. Overall, the proposed dynamic PET reconstruction methodology resulted in substantial visual as well as quantitative accuracy improvements (in terms of noise versus bias performance) for parametric DV

The luminosity function for globular clusters, 4: M3

International Nuclear Information System (INIS)

Simoda, Mahiro; Fukuoka, Takashi

1976-01-01

The subgiant-turnoff portion (V = 17.2 - 20.0 mag) of the luminosity function for the globular cluster M3 has been determined from photometry of the stars within the annuli 3'-8' and 6'-8' for V = 17.2 - 19.0 mag and 19.0 - 20.0 mag, respectively, by using plates taken with the Kitt Peak 2.1-m reflector. Our result shows that the luminosity function for M3 has a similar steep rise in the subgiant portion as other clusters so far studied (M5, M13, and M92), in direct conflict with the result by SANDAGE (1954, 1957). A probable cause of this discrepancy is given. Comparison with theoretical luminosity functions by SIMODA and IBEN (1970) suggests that theory and observation are not inconsistent if the initial helium abundance of M3 stars is taken to be about 20 percent. It is suggested that M13 has a larger helium abundance than M3 and M92 from the intercomparison of their luminosity functions and color-magnitude diagrams. (auth.)

Amplitudes of solar-like oscillations: Constraints from red giants in open clusters observed by Kepler

DEFF Research Database (Denmark)

Stello, Dennis; Huber, Daniel; Kallinger, Thomas

2011-01-01

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......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...... 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...

M31 GLOBULAR CLUSTER STRUCTURES AND THE PRESENCE OF X-RAY BINARIES

International Nuclear Information System (INIS)

Agar, J. R. R.; Barmby, P.

2013-01-01

The Andromeda galaxy, M31, has several times the number of globular clusters found in the Milky Way. It contains a correspondingly larger number of low-mass X-ray binaries (LMXBs) associated with globular clusters, and as such can be used to investigate the cluster properties that lead to X-ray binary formation. The best tracer of the spatial structure of M31 globulars is the high-resolution imaging available from the Hubble Space Telescope (HST), and we have used HST data to derive structural parameters for 29 LMXB-hosting M31 globular clusters. These measurements are combined with structural parameters from the literature for a total of 41 (of 50 known) LMXB clusters and a comparison sample of 65 non-LMXB clusters. Structural parameters measured in blue bandpasses are found to be slightly different (smaller core radii and higher concentrations) than those measured in red bandpasses; this difference is enhanced in LMXB clusters and could be related to stellar population differences. Clusters with LMXBs show higher collision rates for their mass compared to clusters without LMXBs, and collision rates estimated at the core radius show larger offsets than rates estimated at the half-light radius. These results are consistent with the dynamical formation scenario for LMXBs. A logistic regression analysis finds that, as expected, the probability of a cluster hosting an LMXB increases with increasing collision rate and proximity to the galaxy center. The same analysis finds that probability of a cluster hosting an LMXB decreases with increasing cluster mass at a fixed collision rate, although we caution that this could be due to sample selection effects. Metallicity is found to be a less important predictor of LMXB probability than collision rate, mass, or distance, even though LMXB clusters have a higher metallicity on average. This may be due to the interaction of location and metallicity: a sample of M31 LMXBs with a greater range in galactocentric distance would

BVRI main-sequence photometry of the globular cluster M4

International Nuclear Information System (INIS)

Alcaino, G.; Liller, W.

1984-01-01

We present BV and RI photographic photometry of 1421 and 189 stars, respectively, in the intermediate metallicity globular cluster M4 (NGC 6121). This investigation includes the first results of RI main-sequence photometry of a globular cluster. The use of longer wavelengths and longer color baselines provides the potential of improved isochrone fittings and underscores the urgent need for calculations of RI synthetic isochrones to be compared with observations. The Pickering-Racine wedge was used with the ESO 3.6 m telescope, the Las Campanas 2.5 m du Pont telescope, and the CTIO 1 m Yale telescope to extend the photoelectric limit from Vroughly-equal16.1 to Vroughly-equal19.1. We have determined the position of the main-sequence turnoff to lie at V = 16.6 +- 0.2 (m.e.) and B-V = 0.80 +- 0.03 (m.e.). A comparison of our BV observations with the CCD data of Richer and Fahlman shows excellent agreement: the two fifucial main sequences agree at all points to within 0.025 mag and, on average, to 0.013 mag. For the cluster we derive a distance modulus (m-M)/sub V/ = 12.52 +- 0.2 and reddening E(B-V) = 0.44 +- 0.03, results which confirm that at a distance of 2 kpc, M4 is the closest globular clusters to the Sun. Using the isochrones of VandenBerg, we deduce an age 13 +- 2 Gyr. As noted in several other investigations, there is a striking deficiency of stars in certain parts of the color-magnitude diagram; in M4 we find a pronounced gap over approx.0.6 mag at the base of the subgiant branch

SPACE VELOCITIES OF SOUTHERN GLOBULAR CLUSTERS. VII. NGC 6397, NGC 6626 (M28), AND NGC 6656 (M22)

Energy Technology Data Exchange (ETDEWEB)

Casetti-Dinescu, Dana I.; Girard, Terrence M.; Van Altena, William F. [Astronomy Department, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States); Jilkova, Lucie [Department of Theoretical Physics and Astrophysics, Faculty of Science, Masaryk University, Kotlarska 2, CZ-61137 Brno (Czech Republic); Podesta, Federico; Lopez, Carlos E., E-mail: dana.casetti@yale.edu, E-mail: terry.girard@yale.edu, E-mail: william.vanaltena@yale.edu, E-mail: jilkoval@physics.muni.cz [Universidad National de San Juan, Observatorio Astronomico ' ' Felix Aguilar' ' and Yale Southern Observatory, Chimbas, 5413 San Juan (Argentina)

2013-08-01

We have measured the absolute proper motions of globular clusters NGC 6397, NGC 6626 (M22), and NGC 6656 (M28) as part of our ongoing Southern Proper-Motion Program. The reference system is the ICRS via Hipparcos stars for these three low-Galactic-latitude clusters. Formal errors range between {approx}0.3 and 0.7 mas yr{sup -1}. Notable is the result for NGC 6397, which differs by 2.5 mas yr{sup -1} from two Hubble Space Telescope determinations while agreeing with previous ground-based ones. We determine orbits for all three clusters in an axisymmetric and barred model of the Galaxy and discuss these in the context of globular-cluster formation. M22 is a well-known cluster with an iron abundance spread; such clusters are now believed to have formed in massive parent systems that can retain ejecta of core-collapsed supernovae. We find that the five currently accepted globular clusters with iron/calcium abundance spread show orbits unrelated to each other, thus suggesting at least five independent, massive progenitors that have contributed to the build-up of the Milky-Way halo.

Chemical Abundances of Main-sequence, Turnoff, Subgiant, and Red Giant Stars from APOGEE Spectra. I. Signatures of Diffusion in the Open Cluster M67

Science.gov (United States)

Souto, Diogo; Cunha, Katia; Smith, Verne V.; Allende Prieto, C.; García-Hernández, D. A.; Pinsonneault, Marc; Holzer, Parker; Frinchaboy, Peter; Holtzman, Jon; Johnson, J. A.; Jönsson, Henrik; Majewski, Steven R.; Shetrone, Matthew; Sobeck, Jennifer; Stringfellow, Guy; Teske, Johanna; Zamora, Olga; Zasowski, Gail; Carrera, Ricardo; Stassun, Keivan; Fernandez-Trincado, J. G.; Villanova, Sandro; Minniti, Dante; Santana, Felipe

2018-04-01

Detailed chemical abundance distributions for 14 elements are derived for eight high-probability stellar members of the solar metallicity old open cluster M67 with an age of ∼4 Gyr. The eight stars consist of four pairs, with each pair occupying a distinct phase of stellar evolution: two G dwarfs, two turnoff stars, two G subgiants, and two red clump (RC) K giants. The abundance analysis uses near-IR high-resolution spectra (λ1.5–1.7 μm) from the Apache Point Observatory Galactic Evolution Experiment survey and derives abundances for C, N, O, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, and Fe. Our derived stellar parameters and metallicity for 2M08510076+1153115 suggest that this star is a solar twin, exhibiting abundance differences relative to the Sun of ≤0.04 dex for all elements. Chemical homogeneity is found within each class of stars (∼0.02 dex), while significant abundance variations (∼0.05–0.20 dex) are found across the different evolutionary phases; the turnoff stars typically have the lowest abundances, while the RCs tend to have the largest. Non-LTE corrections to the LTE-derived abundances are unlikely to explain the differences. A detailed comparison of the derived Fe, Mg, Si, and Ca abundances with recently published surface abundances from stellar models that include chemical diffusion provides a good match between the observed and predicted abundances as a function of stellar mass. Such agreement would indicate the detection of chemical diffusion processes in the stellar members of M67.

Photoelectron Spectroscopy and Density Functional Theory Studies of Iron Sulfur (FeS)m- (m = 2-8) Cluster Anions: Coexisting Multiple Spin States.

Science.gov (United States)

Yin, Shi; Bernstein, Elliot R

2017-10-05

Iron sulfur cluster anions (FeS) m - (m = 2-8) are studied by photoelectron spectroscopy (PES) at 3.492 eV (355 nm) and 4.661 eV (266 nm) photon energies, and by density functional theory (DFT) calculations. The most probable structures and ground state spin multiplicities for (FeS) m - (m = 2-8) clusters are tentatively assigned through a comparison of their theoretical and experiment first vertical detachment energy (VDE) values. Many spin states lie within 0.5 eV of the ground spin state for the larger (FeS) m - (m ≥ 4) clusters. Theoretical VDEs of these low lying spin states are in good agreement with the experimental VDE values. Therefore, multiple spin states of each of these iron sulfur cluster anions probably coexist under the current experimental conditions. Such available multiple spin states must be considered when evaluating the properties and behavior of these iron sulfur clusters in real chemical and biological systems. The experimental first VDEs of (FeS) m - (m = 1-8) clusters are observed to change with the cluster size (number m). The first VDE trends noted can be related to the different properties of the highest singly occupied molecular orbitals (NBO, HSOMOs) of each cluster anion. The changing nature of the NBO/HSOMO of these (FeS) m - (m = 1-8) clusters from a p orbital on S, to a d orbital on Fe, and to an Fe-Fe bonding orbital is probably responsible for the observed increasing trend for their first VDEs with respect to m.

OpenSubspace

DEFF Research Database (Denmark)

Müller, Emmanuel; Assent, Ira; Günnemann, Stephan

2009-01-01

Subspace clustering and projected clustering are recent research areas for clustering in high dimensional spaces. As the field is rather young, there is a lack of comparative studies on the advantages and disadvantages of the different algorithms. Part of the underlying problem is the lack...... of available open source implementations that could be used by researchers to understand, compare, and extend subspace and projected clustering algorithms. In this paper, we discuss the requirements for open source evaluation software. We propose OpenSubspace, an open source framework that meets...... these requirements. OpenSubspace integrates state-of-the-art performance measures and visualization techniques to foster research in subspace and projected clustering....

Main sequence of the metal-poor globular cluster M30 (NGC 7099)

International Nuclear Information System (INIS)

Alcaino, G.; Liller, W.

1980-01-01

We present photographic photometry for 673 stars in the metal-poor globular cluster M30 (NGC 7099). The Racine wedge was used with the CTIO 1-m Yale telescope (Δm=3/sup m/.60), the CTIO 4-m telescope (Δm=6/sup m/.83), and the ESO 3.6-m telescope (Δm=4/sup m/.12) to extend the photoelectric limit from Vapprox. =16.3 to Vapprox. =20.4. For the main-sequence turn-off, we have determined its position to lie at V=18.4 +- 0.1 (m.e.) and B-V=0.49 +- 0.03 (m.e.). From these values, we calculate the intrinsic values M/sub v/ =3.87 and (B-V) 0 =0.47. For the cluster as a whole, we derive a distance modulus (m-M)/sub V/=14.53 +- 0.15 and reddening E(B-V)=0.02 +- 0.02. Using the models of Iben and Rood [Astrophys. J. 159, 605 (1970)] and the isochrones of Demarque and McClure [(1977), in Evolution of Galaxies and Stellar Populations, edited by B. Tinsley and R. B. Larson (Yale University Observatory, New Haven), p. 199], we deduce the cluster's age to be 14.5( +- 4.0) x 10 9 yr. The large uncertainty in this value emphasizes the dire need for more work on cluster evolution

Gemini Spectra of Star Clusters in the Spiral Galaxy M101

Science.gov (United States)

Simanton-Coogan, Lesley A.; Chandar, Rupali; Miller, Bryan; Whitmore, Bradley C.

2017-12-01

We present low resolution, visible light spectra of 41 star clusters in the spiral galaxy M101, taken with the Gemini/GMOS instrument. We measure Lick indices for each cluster and compare with BaSTI models to estimate their ages and metallicities. We also measure the line-of-sight velocities. We find that 25 of the clusters are fairly young massive clusters (YMCs) with ages of hundreds of millions of years, and 16 appear to be older, globular clusters (GCs). There are at least four GCs with best-fit ages of ≈1–3 Gyr and eight with best-fit ages of ≈5–10 Gyr. The mean metallicity of the YMCs is [Fe/H] ≈ ‑0.1 and for the GCs is [Fe/H] ≈ ‑0.9. We find a near-continuous spread in both age and metallicity for our sample, which may indicate that M101 had a more-or-less continuous history of cluster and star formation. From the kinematics, we find that the YMCs rotate with the H I gas fairly well, while the GCs do not. We cannot definitively say whether the GCs sampled here lie in an inner halo, thick disk, or bulge/psuedobulge component, although given the very small bulge in M101, the last seems unlikely. The kinematics and ages of the YMCs suggest that M101 may have undergone heating of its disk or possibly a continuous merger/accretion history for the galaxy.

A new Be star in an open cluster - NGC 6871-8

Science.gov (United States)

Grigsby, James A.; Morrison, Nancy D.

1988-01-01

Spectroscopic observations of H-alpha show that star eight in the open cluster NGC 6871 is a previously-undiscovered Be star. The H-alpha profile was observed to vary from clear emission to pure absorption over a period of ten days; later observations over a five-day interval show weak emission along with asymmetries and filling in of the profile.

The M5-brane and non-commutative open strings

NARCIS (Netherlands)

Bergshoeff, E.; Berman, D.S.; Schaar, J.P. van der; Sundell, P.

2001-01-01

The M-theory origin of non-commutative open-string theory is examined by investigating the M-theory 5-brane at near critical field strength. In particular, it is argued that the open-membrane metric provides the appropriate moduli when calculating the duality relations between M and II

Complex open-framework germanate built by 8-coordinated Ge 10 clusters

KAUST Repository

Yue, Huijuan

2012-11-19

A novel open-framework germanate |(C 5H 14N 2) 2(C 5H 12N 2) 0.5(H 2O) 2.5|[Ge 12.5O 26(OH) 2] with three-dimensional 10- and 11-ring channels, denoted as SU-67, has been synthesized under hydrothermal conditions using 2-methylpiperazine (MPP) as the structure-directing agent (SDA). The synthesis is intimately related to that of JLG-5, a tubular germanate built from Ge 7 clusters. The influences of synthesis parameters are discussed. A strong influence of the hydrofluoric acid quantity on the resulting cluster building units can be concluded. The framework of SU-67 is based on an elaborate topological pattern of connected Ge 10 clusters forming intersecting 10- and 11-ring channels and has a low framework density (12.4 Ge atoms per 1000 ̊ 3). We have discovered that the topology of SU-67 is a new 8-connected nce-8-I4 1/acd net. Strong hydrogen bonding among the organic SDAs, water molecules, and Ge 10 clusters resulted in helical networks in SU-67. © 2012 American Chemical Society.

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

International Nuclear Information System (INIS)

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

2011-01-01

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.

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

International Nuclear Information System (INIS)

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

2010-01-01

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 ∼ 4400) GMOS spectra for 15 cluster candidate members with I ∼ 14-20 mag, and employed a series of membership criteria-proximity to the cluster's sequence in an I/I - K 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 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 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.

TIME-SERIES PHOTOMETRY OF GLOBULAR CLUSTERS: M62 (NGC 6266), THE MOST RR LYRAE-RICH GLOBULAR CLUSTER IN THE GALAXY?

International Nuclear Information System (INIS)

Contreras, R.; Catelan, M.; Smith, H. A.; Kuehn, C. A.; Pritzl, B. J.; Borissova, J.

2010-01-01

We present new time-series CCD photometry, in the B and V bands, for the moderately metal-rich ([Fe/H] ≅ -1.3) Galactic globular cluster M62 (NGC 6266). The present data set is the largest obtained so far for this cluster and consists of 168 images per filter, obtained with the Warsaw 1.3 m telescope at the Las Campanas Observatory and the 1.3 m telescope of the Cerro Tololo Inter-American Observatory, in two separate runs over the time span of 3 months. The procedure adopted to detect the variable stars was the optimal image subtraction method (ISIS v2.2), as implemented by Alard. The photometry was performed using both ISIS and Stetson's DAOPHOT/ALLFRAME package. We have identified 245 variable stars in the cluster fields that have been analyzed so far, of which 179 are new discoveries. Of these variables, 133 are fundamental mode RR Lyrae stars (RRab), 76 are first overtone (RRc) pulsators, 4 are type II Cepheids, 25 are long-period variables (LPVs), 1 is an eclipsing binary, and 6 are not yet well classified. Such a large number of RR Lyrae stars places M62 among the top two most RR Lyrae-rich (in the sense of total number of RR Lyrae stars present) globular clusters known in the Galaxy, second only to M3 (NGC 5272) with a total of 230 known RR Lyrae stars. Since this study covers most but not all of the cluster area, it is not unlikely that M62 is in fact the most RR Lyrae-rich globular cluster in the Galaxy. In like vein, thanks to the time coverage of our data sets, we were also able to detect the largest sample of LPVs known so far in a Galactic globular cluster. We analyze a variety of Oosterhoff type indicators for the cluster, including mean periods, period distribution, Bailey diagrams, and Fourier decomposition parameters (as well as the physical parameters derived therefrom). All of these indicators clearly show that M62 is an Oosterhoff type I system. This is in good agreement with the moderately high metallicity of the cluster, in spite of its

The murine cytomegalovirus M35 protein antagonizes type I IFN induction downstream of pattern recognition receptors by targeting NF-κB mediated transcription.

Directory of Open Access Journals (Sweden)

Baca Chan

2017-05-01

Full Text Available The type I interferon (IFN response is imperative for the establishment of the early antiviral immune response. Here we report the identification of the first type I IFN antagonist encoded by murine cytomegalovirus (MCMV that shuts down signaling following pattern recognition receptor (PRR sensing. Screening of an MCMV open reading frame (ORF library identified M35 as a novel and strong negative modulator of IFNβ promoter induction following activation of both RNA and DNA cytoplasmic PRR. Additionally, M35 inhibits the proinflammatory cytokine response downstream of Toll-like receptors (TLR. Using a series of luciferase-based reporters with specific transcription factor binding sites, we determined that M35 targets NF-κB-, but not IRF-mediated, transcription. Expression of M35 upon retroviral transduction of immortalized bone marrow-derived macrophages (iBMDM led to reduced IFNβ transcription and secretion upon activation of stimulator of IFN genes (STING-dependent signaling. On the other hand, M35 does not antagonize interferon-stimulated gene (ISG 56 promoter induction or ISG transcription upon exogenous stimulation of the type I IFN receptor (IFNAR. M35 is present in the viral particle and, upon MCMV infection of fibroblasts, is immediately shuttled to the nucleus where it exerts its immunomodulatory effects. Deletion of M35 from the MCMV genome and hence from the viral particle resulted in elevated type I IFN transcription and secretion in vitro and in vivo. In the absence of M35, lower viral titers are observed during acute infection of the host, and productive infection in the salivary glands was not detected. In conclusion, the M35 protein is released by MCMV immediately upon infection in order to deftly inhibit the antiviral type I IFN response by targeting NF-κB-mediated transcription. The identification of this novel viral protein reinforces the importance of timely countermeasures in the complex relationship between virus and host.

ARGUS laser plasma experiments at 1.06 μm, 0.53 μm and 0.35 μm

International Nuclear Information System (INIS)

Turner, R.E.; Campbell, E.M.; Mead, W.C.; Ze, F.; Max, C.; Phillion, D.W.; Lee, P.; Pruett, B.; Tirsell, G.; Lasinski, B.F.

1982-01-01

ARGUS wavelength scaling experiments have been performed on low (Be) and high (Au) Z disk targets, with laser wavelengths of 1.06 μm, 0.53 μm and 0.35 μm. The laser provided a 700 psec pulse, with up to 100J and 1.06 μm; 200J at 0.53 μm; and 40J at 0.35 μm. Laser intensities on target ranged from 3 x 10 13 to over 3 x 10 15 W/cm 2 , using an f/2.2 focusing system. Box calorimeter measurements show the expected increasing fractional absorption at shorter laser wavelengths; absolutely calibrated hard x-ray detectors show the number of suprathermal electrons to be greatly decreased. Scattered light measurements concentrated on stimulated Raman scattering, and the 3/2 harmonic. The SRS was spectrally and temporally resolved during 0.53 μm irradiations; our measurements showed the scattering to be principally from the convective instability, near tenth critical density. Near ω/2, a double peaked spectral feature is observed. The time resolved data show a number of interesting features, which are discussed

The stellar and substellar mass function in central region of the old open cluster Praesepe from deep LBT observations

Directory of Open Access Journals (Sweden)

Goldman B.

2011-07-01

Full Text Available Studies of the mass function of open clusters of different ages allow us to study the efficiency with which brown dwarfs are evaporated from clusters to populate the field. Surveys in relatively old clusters (age ≳100 Myr do not suffer from problems found in young clusters, such as intra-cluster extinction and large uncertainties in brown dwarf models. In this paper, we present the results of a photometric survey to study the mass function of the old open cluster Praesepe (age of ~590 Myr and distance of ~190 pc, down to the substellar regime. We have performed optical (riz and Y-band photometric survey of Praesepe with the Large Binocular Telescope Camera, for a spatial coverage of 0.61 deg2 from ~90 MJ down to a 5σ detection limit at 40 MJ.

Globular clusters as a source of X-ray emission from the neighbourhood of M87

International Nuclear Information System (INIS)

Fabian, A.C.; Pringle, J.E.; Rees, M.J.

1976-01-01

It is stated that the X-ray emission from globular clusters may be attributable to accretion on to compact objects, the accreting material being supplied from binary companions, or gas trapped in the potential well of the cluster. Counts of objects in the vicinity of the M87 have revealed that it has an extensive halo of globular clusters, the number of which may exceed 10,000 within a radius of 23 arc min. Most of these clusters may be explicable as a population effect, and the similarity of their optical properties to those of cluster in our own Galaxy suggests that they may also contain X-ray sources. The brighter globular clusters in M87 may, however, be substantially more X-ray luminous, and there may be proportionally more gas available in globular clusters in M87 compared with our Galaxy. The average X-ray luminosity of individual globular clusters may be of the order of 10 38 erg/sec., which raises the possibility that the integrated globular cluster emission may account for a substantial fraction of the X-ray emission observed from the region of M87. In support of this it is noted that the extended X-ray emission from the Virgo cluster is centered on M87, which lies approximately 45 arc min from the cluster centroid, and it is expected that the general X-ray emission from the globular cluster will appear to be smoothly and symmetrically distributed about M87 at moderate spatial resolution. A similar situation may apply to the elliptical galaxy NGC 3311 in Abell 1060 which, as a cluster, has been suggested as the identification for the X-ray source 3 U 1044-40, and it seems possible that that galaxy is surrounded by a similar globular cluster population to that of M87. (U.K.)

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

Science.gov (United States)

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.

Binarity and Variable Stars in the Open Cluster NGC 2126

Science.gov (United States)

Chehlaeh, Nareemas; Mkrtichian, David; Kim, Seung-Lee; Lampens, Patricia; Komonjinda, Siramas; Kusakin, Anatoly; Glazunova, Ljudmila

2018-04-01

We present the results of an analysis of photometric time-series observations for NGC 2126 acquired at the Thai National Observatory (TNO) in Thailand and the Mount Lemmon Optical Astronomy Observatory (LOAO) in USA during the years 2004, 2013 and 2015. The main purpose is to search for new variable stars and to study the light curves of binary systems as well as the oscillation spectra of pulsating stars. NGC 2126 is an intermediate-age open cluster which has a population of stars inside the δ Scuti instability strip. Several variable stars are reported including three eclipsing binary stars, one of which is an eclipsing binary star with a pulsating component (V551 Aur). The Wilson-Devinney technique was used to analyze its light curves and to determine a new set of the system’s parameters. A frequency analysis of the eclipse-subtracted light curve was also performed. Eclipsing binaries which are members of open clusters are capable of delivering strong constraints on the cluster’s properties which are in turn useful for a pulsational analysis of their pulsating components. Therefore, high-resolution, high-quality spectra will be needed to derive accurate component radial velocities of the faint eclipsing binaries which are located in the field of NGC 2126. The new Devasthal Optical Telescope, suitably equipped, could in principle do this.

The little-studied cluster Berkeley 90. I. LS III +46 11: a very massive O3.5 If* + O3.5 If* binary

Science.gov (United States)

Maíz Apellániz, J.; Negueruela, I.; Barbá, R. H.; Walborn, N. R.; Pellerin, A.; Simón-Díaz, S.; Sota, A.; Marco, A.; Alonso-Santiago, J.; Sanchez Bermudez, J.; Gamen, R. C.; Lorenzo, J.

2015-07-01

Context. It appears that most (if not all) massive stars are born in multiple systems. At the same time, the most massive binaries are hard to find owing to their low numbers throughout the Galaxy and the implied large distances and extinctions. Aims: We want to study LS III +46 11, identified in this paper as a very massive binary; another nearby massive system, LS III +46 12; and the surrounding stellar cluster, Berkeley 90. Methods: Most of the data used in this paper are multi-epoch high S/N optical spectra, although we also use Lucky Imaging and archival photometry. The spectra are reduced with dedicated pipelines and processed with our own software, such as a spectroscopic-orbit code, CHORIZOS, and MGB. Results: LS III +46 11 is identified as a new very early O-type spectroscopic binary [O3.5 If* + O3.5 If*] and LS III +46 12 as another early O-type system [O4.5 V((f))]. We measure a 97.2-day period for LS III +46 11 and derive minimum masses of 38.80 ± 0.83 M⊙ and 35.60 ± 0.77 M⊙ for its two stars. We measure the extinction to both stars, estimate the distance, search for optical companions, and study the surrounding cluster. In doing so, a variable extinction is found as well as discrepant results for the distance. We discuss possible explanations and suggest that LS III +46 12 may be a hidden binary system where the companion is currently undetected.

Quantifying opening-mode fracture spatial organization in horizontal wellbore image logs, core and outcrop: Application to Upper Cretaceous Frontier Formation tight gas sandstones, USA

Science.gov (United States)

Li, J. Z.; Laubach, S. E.; Gale, J. F. W.; Marrett, R. A.

2018-03-01

The Upper Cretaceous Frontier Formation is a naturally fractured gas-producing sandstone in Wyoming. Regionally, random and statistically more clustered than random patterns exist in the same upper to lower shoreface depositional facies. East-west- and north-south-striking regional fractures sampled using image logs and cores from three horizontal wells exhibit clustered patterns, whereas data collected from east-west-striking fractures in outcrop have patterns that are indistinguishable from random. Image log data analyzed with the correlation count method shows clusters ∼35 m wide and spaced ∼50 to 90 m apart as well as clusters up to 12 m wide with periodic inter-cluster spacings. A hierarchy of cluster sizes exists; organization within clusters is likely fractal. These rocks have markedly different structural and burial histories, so regional differences in degree of clustering are unsurprising. Clustered patterns correspond to fractures having core quartz deposition contemporaneous with fracture opening, circumstances that some models suggest might affect spacing patterns by interfering with fracture growth. Our results show that quantifying and identifying patterns as statistically more or less clustered than random delineates differences in fracture patterns that are not otherwise apparent but that may influence gas and water production, and therefore may be economically important.

Radio observations of some clusters of galaxies at lambda=3.5 and 4 mm

International Nuclear Information System (INIS)

Efanov, V.A.; Zinchenko, I.I.; Kislyakov, A.G.; Krasil'nikov, A.A.; Kukina, E.P.; Moiseev, I.G.

1980-01-01

Millimeter radio observations with the 22-m Crimean antenna are reported for the central regions of the clusters of galaxies in Virgo, Hercules, and Coma Berenices, and from the cluster Abell 2199. In two of these, Coma and A2199, sources with a flux density of several jansky have been detected. The position of the source in A2199 matches that of the radio source 3C 338, but the object in the Coma cluster does not correspond to any known radio source. The nature of the emission from the new sources is discussed

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

International Nuclear Information System (INIS)

Luo, Y. P.; Han, Z. W.; Zhang, X. B.; Deng, L. C.

2012-01-01

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 δ 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 γ Dor star candidates. We found that all these stars (18 SPB and 3 γ 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 γ 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.

Two stellar-mass black holes in the globular cluster M22.

Science.gov (United States)

Strader, Jay; Chomiuk, Laura; Maccarone, Thomas J; Miller-Jones, James C A; Seth, Anil C

2012-10-04

Hundreds of stellar-mass black holes probably form in a typical globular star cluster, with all but one predicted to be ejected through dynamical interactions. Some observational support for this idea is provided by the lack of X-ray-emitting binary stars comprising one black hole and one other star ('black-hole/X-ray binaries') in Milky Way globular clusters, even though many neutron-star/X-ray binaries are known. Although a few black holes have been seen in globular clusters around other galaxies, the masses of these cannot be determined, and some may be intermediate-mass black holes that form through exotic mechanisms. Here we report the presence of two flat-spectrum radio sources in the Milky Way globular cluster M22, and we argue that these objects are black holes of stellar mass (each ∼10-20 times more massive than the Sun) that are accreting matter. We find a high ratio of radio-to-X-ray flux for these black holes, consistent with the larger predicted masses of black holes in globular clusters compared to those outside. The identification of two black holes in one cluster shows that ejection of black holes is not as efficient as predicted by most models, and we argue that M22 may contain a total population of ∼5-100 black holes. The large core radius of M22 could arise from heating produced by the black holes.

The Globular Cluster NGC 6402 (M14). II. Variable Stars

Science.gov (United States)

Contreras Peña, C.; Catelan, M.; Grundahl, F.; Stephens, A. W.; Smith, H. A.

2018-03-01

We present time-series BVI photometry for the Galactic globular cluster NGC 6402 (M14). The data consist of ∼137 images per filter, obtained using the 0.9 and 1.0 m SMARTS telescopes at the Cerro Tololo Inter-American Observatory. The images were obtained during two observing runs in 2006–2007. The image-subtraction package ISIS, along with DAOPHOT II/ALLFRAME, was used to perform crowded-field photometry and search for variable stars. We identified 130 variables, eight of which are new discoveries. The variable star population is comprised of 56 ab-type RR Lyrae stars, 54 c-type RR Lyrae, 6 type II Cepheids, 1 W UMa star, 1 detached eclipsing binary, and 12 long-period variables. We provide Fourier decomposition parameters for the RR Lyrae, and discuss the physical parameters and photometric metallicity derived therefrom. The M14 distance modulus is also discussed, based on different approaches for the calibration of the absolute magnitudes of RR Lyrae stars. The possible presence of second-overtone RR Lyrae in M14 is critically addressed, with our results arguing against this possibility. By considering all of the RR Lyrae stars as members of the cluster, we derive =0.589 {{d}}{{a}}{{y}}{{s}}. This, together with the position of the RR Lyrae stars of both Bailey types in the period–amplitude diagram, suggests an Oosterhoff-intermediate classification for the cluster. Such an intermediate Oosterhoff type is much more commonly found in nearby extragalactic systems, and we critically discuss several other possible indications that may point to an extragalactic origin for this cluster. Based on observations obtained with the 0.9 m and 1 m telescopes at the Cerro Tololo Inter-American Observatory, Chile, operated by the SMARTS consortium.

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

Science.gov (United States)

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.

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

Energy Technology Data Exchange (ETDEWEB)

Eriksen, Janus J., E-mail: janusje@chem.au.dk; Jørgensen, Poul [qLEAP Center for Theoretical Chemistry, Department of Chemistry, Aarhus University, DK-8000 Aarhus C (Denmark); Matthews, Devin A. [The Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, Texas 78712 (United States); Gauss, Jürgen [Institut für Physikalische Chemie, Johannes Gutenberg-Universität Mainz, D-55128 Mainz (Germany)

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.

Resonant ion-dip infrared spectroscopy of benzene-(water)n-(methanol)m clusters with n+m=4, 5

International Nuclear Information System (INIS)

Hagemeister, F.C.; Gruenloh, C.J.; Zwier, T.S.

1998-01-01

Resonant two-photon ionization and resonant ion-dip infrared (RIDIR) spectra of benzene-(water) n -(methanol) m clusters (hereafter shortened to BW n M m ) have been recorded for a total of seven clusters with n+m=4 and 5. The infrared spectra in the OH and CH stretch regions show absorptions characteristic of H-bonded W n M m clusters which are bound to benzene by a π H-bond involving a dangling OH on the W n M m sub-unit. Density functional theory (DFT) calculations identify a number of conformational isomers in the n+m=4 series which meet the general criteria imposed by the experimental spectra. The structures, binding energies, harmonic vibrational frequencies, and infrared intensities for these isomers have been calculated for comparison with experiment. Based on the calculations, tentative assignments of several of the observed species are given. The calculations uncover the fact that complexation of benzene to the cyclic water tetramer imposes much the same perturbations on the cycle as substitution of methanol for water. In particular, the single-donor OH stretch spectra of W n M m and BW n+1 M m-1 are calculated to be virtually identical to one another. The comparison of experiment and theory for this series of cyclic structures is used to assess the strengths and limitations of the calculations at the DFT Becke3LYP/6-31+G * level of theory. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

A search for peculiar stars in the open cluster Hogg 16

Science.gov (United States)

Cariddi, Stefano; Azatyan, Naira M.; Kurfürst, Petr; Štofanová, Lýdia; Netopil, Martin; Paunzen, Ernst; Pintado, Olga I.; Aidelman, Yael J.

2018-01-01

The study of chemically peculiar (CP) stars in open clusters provides valuable information about their evolutionary status. Their detection can be performed using the Δa photometric system, which maps a characteristic flux depression at λ ∼ 5200 Å. This paper aims at studying the occurrence of CP stars in the earliest stages of evolution of a stellar population by applying this technique to Hogg 16, a very young Galactic open cluster ( ∼ 25 Myr). We identified several peculiar candidates: two B-type stars with a negative Δa index (CD - 60 4701, CPD - 60 4706) are likely emission-line (Be) stars, even though spectral measurements are necessary for a proper classification of the second one; a third object (CD - 60 4703), identified as a Be candidate in literature, appears to be a background B-type supergiant with no significant Δa index, which does not rule out the possibility that it is indeed peculiar as the normality line of Δa for supergiants has not been studied in detail yet. A fourth object (CD - 60 4699) appears to be a magnetic CP star of 8 M⊙, but obtained spectral data seem to rule out this hypothesis. Three more magnetic CP star candidates are found in the domain of early F-type stars. One is a probable nonmember and close to the border of significance, but the other two are probably pre-main sequence cluster objects. This is very promising, as it can lead to very strong constraints to the diffusion theory. Finally, we derived the fundamental parameters of Hogg 16 and provide for the first time an estimate of its metal content.

Optical and ultraviolet study of five stars in the Pleiades open cluster

International Nuclear Information System (INIS)

Younan, K.F.; Dufton, P.L.

1984-01-01

Optical and ultraviolet observations of five low-reddened stars in the Pleiades open cluster have been obtained with an echelle spectrograph and the IUE satellite. The observed interstellar absorption lines have been analysed with different cloud models to estimate interstellar gas abundances for each line-of-sight. These results have been discussed in the light of current models for diatomic formation. (author)

A SPECTROSCOPIC ANALYSIS OF THE GALACTIC GLOBULAR CLUSTER NGC 6273 (M19)

Energy Technology Data Exchange (ETDEWEB)

Johnson, Christian I.; Caldwell, Nelson [Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, MS-15, Cambridge, MA 02138 (United States); Rich, R. Michael [Department of Physics and Astronomy, UCLA, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547 (United States); Pilachowski, Catherine A. [Astronomy Department, Indiana University Bloomington, Swain West 319, 727 East 3rd Street, Bloomington, IN 47405-7105 (United States); Mateo, Mario; Bailey, John I. III [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Crane, Jeffrey D., E-mail: cjohnson@cfa.harvard.edu, E-mail: ncaldwell@cfa.harvard.edu, E-mail: rmr@astro.ucla.edu, E-mail: catyp@astro.indiana.edu, E-mail: mmateo@umich.edu, E-mail: baileyji@umich.edu, E-mail: crane@obs.carnegiescience.edu [The Observatories of the Carnegie Institution for Science, Pasadena, CA 91101 (United States)

2015-08-15

A combined effort utilizing spectroscopy and photometry has revealed the existence of a new globular cluster class. These “anomalous” clusters, which we refer to as “iron-complex” clusters, are differentiated from normal clusters by exhibiting large (≳0.10 dex) intrinsic metallicity dispersions, complex sub-giant branches, and correlated [Fe/H] and s-process enhancements. In order to further investigate this phenomenon, we have measured radial velocities and chemical abundances for red giant branch stars in the massive, but scarcely studied, globular cluster NGC 6273. The velocities and abundances were determined using high resolution (R ∼ 27,000) spectra obtained with the Michigan/Magellan Fiber System (M2FS) and MSpec spectrograph on the Magellan–Clay 6.5 m telescope at Las Campanas Observatory. We find that NGC 6273 has an average heliocentric radial velocity of +144.49 km s{sup −1} (σ = 9.64 km s{sup −1}) and an extended metallicity distribution ([Fe/H] = −1.80 to −1.30) composed of at least two distinct stellar populations. Although the two dominant populations have similar [Na/Fe], [Al/Fe], and [α/Fe] abundance patterns, the more metal-rich stars exhibit significant [La/Fe] enhancements. The [La/Eu] data indicate that the increase in [La/Fe] is due to almost pure s-process enrichment. A third more metal-rich population with low [X/Fe] ratios may also be present. Therefore, NGC 6273 joins clusters such as ω Centauri, M2, M22, and NGC 5286 as a new class of iron-complex clusters exhibiting complicated star formation histories.

The ellipticities of a sample of globular clusters in M31

International Nuclear Information System (INIS)

Lupton, R.H.

1989-01-01

Images for a sample of 18 globular clusters in M31 have been obtained. The mean ellipticity on the sky in the range 7-14 pc (2-4 arcsec) is 0.08 + or - 0.02 and 0.12 + or - 0.01 in the range 14-21 pc (4-6 arcsec), with corresponding true ellipticities of 0.12 and 0.18. The difference between the inner and outer parts is significant at a 99 percent level. The flattening of the inner parts is statistically indistinguishable from that of the Galactic globular clusters, while the outer parts are flatter than the Galactic clusters at a 99.8 percent confidence level. There is a significant anticorrelation of ellipticity with line strength; such a correlation may in retrospect also be seen in the Galactic globular cluster system. For the M31 data, this anticorrelation is stronger in the inner parts of the galaxy. 30 refs

SPB stars in the open SMC cluster NGC 371

Science.gov (United States)

Karoff, C.; Arentoft, T.; Glowienka, L.; Coutures, C.; Nielsen, T. B.; Dogan, G.; Grundahl, F.; Kjeldsen, H.

2008-05-01

Pulsation in β Cep and slowly pulsating B (SPB) stars are driven by the κ mechanism which depends critically on the metallicity. It has therefore been suggested that β Cep and SPB stars should be rare in the Magellanic Clouds which have lower metallicities than the solar neighbourhood. To test this prediction we have observed the open Small Magellanic Cloud (SMC) cluster NGC 371 for 12 nights in order to search for β Cep and SPB stars. Surprisingly, we find 29 short-period B-type variables in the upper part of the main sequence, many of which are probably SPB stars. This result indicates that pulsation is still driven by the κ mechanism even in low-metallicity environments. All the identified variables have periods longer than the fundamental radial period which means that they cannot be β Cep stars. Within an amplitude detection limit of 5 mmag no stars in the top of the Hertzsprung-Russell diagram show variability with periods shorter than the fundamental radial period. So if β Cep stars are present in the cluster they oscillate with amplitudes below 5 mmag, which is significantly lower than the mean amplitude of β Cep stars in the Galaxy. We see evidence that multimode pulsation is more common in the upper part of the main sequence than in the lower. We have also identified five eclipsing binaries and three periodic pulsating Be stars in the cluster field.

An Optical and Infrared Photometric Study of the Young Open Cluster IC 1805 in the Giant H II Region W4 †

Science.gov (United States)

Sung, Hwankyung; Bessell, Michael S.; Chun, Moo-Young; Yi, Jonghyuk; Nazé, Y.; Lim, Beomdu; Karimov, R.; Rauw, G.; Park, Byeong-Gon; Hur, Hyeonoh

2017-05-01

We present deep wide-field optical CCD photometry and mid-infrared Spitzer/IRAC and MIPS 24 μm data for about 100,000 stars in the young open cluster IC 1805. The members of IC 1805 were selected from their location in the various color-color and color-magnitude diagrams, and the presence of Hα emission, mid-infrared excess emission, and X-ray emission. The reddening law toward IC 1805 is nearly normal (R V = 3.05 ± 0.06). However, the distance modulus of the cluster is estimated to be 11.9 ± 0.2 mag (d=2.4+/- 0.2 kpc) from the reddening-free color-magnitude diagrams, which is larger than the distance to the nearby massive star-forming region W3(OH) measured from the radio VLBA astrometry. We also determined the age of IC 1805 ({τ }{MSTO}=3.5 Myr). In addition, we critically compared the age and mass scale from two pre-main-sequence evolution models. The initial mass function with a Salpeter-type slope of Γ = -1.3 ± 0.2 was obtained and the total mass of IC 1805 was estimated to be about 2700 ± 200 {M}⊙ . Finally, we found our distance determination to be statistically consistent with the Tycho-Gaia Astrometric Solution Data Release 1, within the errors. The proper motion of the B-type stars shows an elongated distribution along the Galactic plane, which could be explained by some of the B-type stars being formed in small clouds dispersed by previous episodes of star formation or supernova explosions. The optical imaging data in this article were gathered with two facilities: the AZT-22 1.5 m telescope at Maidanak Astronomical Observatory in Uzbekistan and 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.

Big Fish in Small Ponds: massive stars in the low-mass clusters of M83

Energy Technology Data Exchange (ETDEWEB)

Andrews, J. E.; Calzetti, D.; McElwee, Sean [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Chandar, R. [Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606 (United States); Elmegreen, B. G. [IBM T. J. Watson Research Center, Yorktown Heights, NY 10598 (United States); Kennicutt, R. C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Kim, Hwihyun [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287-1404 (United States); Krumholz, Mark R. [Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); Lee, J. C.; Whitmore, B. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); O' Connell, R. W., E-mail: jandrews@astro.umass.edu, E-mail: callzetti@astro.umass.edu [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States)

2014-09-20

We have used multi-wavelength Hubble Space Telescope WFC3 data of the starbursting spiral galaxy M83 in order to measure variations in the upper end of the stellar initial mass function (uIMF) using the production rate of ionizing photons in unresolved clusters with ages ≤ 8 Myr. As in earlier papers on M51 and NGC 4214, the uIMF in M83 is consistent with a universal IMF, and stochastic sampling of the stellar populations in the ∼<10{sup 3} M {sub ☉} clusters are responsible for any deviations in this universality. The ensemble cluster population, as well as individual clusters, also imply that the most massive star in a cluster does not depend on the cluster mass. In fact, we have found that these small clusters seem to have an over-abundance of ionizing photons when compared to an expected universal or truncated IMF. This also suggests that the presence of massive stars in these clusters does not affect the star formation in a destructive way.

HUBBLE SPACE TELESCOPE PHOTOMETRY OF GLOBULAR CLUSTERS IN M81

International Nuclear Information System (INIS)

Nantais, Julie B.; Huchra, John P.; Zezas, Andreas; Gazeas, Kosmas; Strader, Jay

2011-01-01

We perform aperture photometry and profile fitting on 419 globular cluster (GC) candidates with m V ≤ 23 mag identified in Hubble Space Telescope/Advanced Camera for Surveys BVI imaging, and estimate the effective radii of the clusters. We identify 85 previously known spectroscopically confirmed clusters, and newly identify 136 objects as good cluster candidates within the 3σ color and size ranges defined by the spectroscopically confirmed clusters, yielding a total of 221 probable GCs. The luminosity function peak for the 221 probable GCs with estimated total dereddening applied is V ∼ (20.26 ± 0.13) mag, corresponding to a distance of ∼3.7 ± 0.3 Mpc. The blue and red GC candidates, and the metal-rich and metal-poor spectroscopically confirmed clusters, respectively, are similar in half-light radius. Red confirmed clusters are about 6% larger in median half-light radius than blue confirmed clusters, and red and blue good GC candidates are nearly identical in half-light radius. The total population of confirmed and 'good' candidates shows an increase in half-light radius as a function of galactocentric distance.

The Frequency of Binary Stars in the Globular Cluster M71

Science.gov (United States)

Barden, S. C.; Armandroff, T. E.; Pryor, C. P.

1994-12-01

The frequency of binary stars is a fundamental property of a stellar population. A comparison of the frequency of binaries in globular clusters with those in the field halo and disk populations tests the similarity of star formation in those environments. Binary stars in globular clusters also act as an energy source which ``heats" the cluster through super-elastic encounters with other stars and binaries. Such encounters can not only profoundly affect the dynamical evolution of the cluster, they can disrupt the widely separated binaries and catalyze the formation of exotic objects such as blue stragglers, x-ray binaries, and milli-second pulsars. We have used the KPNO 4-m and the multi-fiber instruments Nessie and Hydra to measure radial velocities at 4 epochs over two years for a sample of 126 stars in the globular cluster M71. Velocity errors are under 1 km s(-1) for the brighter stars and under 2 km s(-1) for the majority of our data set. These velocities will be valuable for studying the kinematics of M71, but here we focus on searching for binaries. The faintest stars are at V=17, or just above the main sequence turnoff. Our sample is thus deeper than any published globular cluster binary search utilizing spectroscopic techniques. By observing smaller stars, we double the number of decades of binary periods sampled compared to previous studies and come within a factor of 4 of the shortest possible periods for turnoff stars. This wider period window has produced the largest known sample of binaries in a globular cluster. Four stars show velocity ranges larger than 20 km s(-1) , nine have ranges larger than 10 km s(-1) , and others are clearly variable. We will compare the radial distribution of these stars to that predicted by theory and derive the main-sequence binary fraction.

Linked-cluster perturbation theory for closed and open-shell systems: derivation of effective π-electron hamiltonians

International Nuclear Information System (INIS)

Brandow, B.H.

1977-01-01

The Brueckner--Goldstone form of linked-cluster perturbation theory is derived, together with its open-shell analog, by an elementary time-independent approach. This serves to focus attention on the physical interpretation of the results. The open-shell expansion is used to provide a straightforward justification for the effective π-electron Hamiltonians of planar organic molecules

High-resolution spectroscopic observations of binary stars and yellow stragglers in three open clusters: NGC 2360, NGC 3680, and NGC 5822

Energy Technology Data Exchange (ETDEWEB)

Sales Silva, J. V.; Peña Suárez, V. J.; Katime Santrich, O. J.; Pereira, C. B.; Drake, N. A.; Roig, F., E-mail: joaovictor@on.br, E-mail: jearim@on.br, E-mail: osantrich@on.br, E-mail: claudio@on.br, E-mail: drake@on.br, E-mail: froig@on.br [Observatório Nacional/MCT, Rua Gen. José Cristino, 77, 20921-400 Rio de Janeiro (Brazil)

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

Open clusters. I. Fundamental parameters of B stars in NGC 3766 and NGC 4755

Science.gov (United States)

Aidelman, Y.; Cidale, L. S.; Zorec, J.; Arias, M. L.

2012-08-01

Context. Spectroscopic investigations of galactic open clusters are scarce and limited to a reduced sample of cluster members. Aims: We intend to perform a complete study of the physical parameters of two galactic clusters as well as of their individual members. Methods: To carry out this study, we used the BCD (Barbier-Chalonge-Divan) spectrophotometric system, which is based on the study of the Balmer discontinuity and is independent of interstellar and circumstellar extinction. Additional physical properties were derived from the line profiles (FWHM) and stellar evolution models. We analyzed low-resolution spectra around the Balmer discontinuity for normal B-type and Be stars in two open clusters: NGC 3766 and NGC 4755. We determined the stellar fundamental parameters, such as effective temperatures, surface gravities, spectral types, luminosity classes, absolute and bolometric magnitudes, and color gradient excesses. The stellar rotation velocity was also determined. Complementary information, mainly stellar mass, age, and radius of the star population were calculated using stellar evolution models. In some cases, the stellar fundamental parameters were derived for the first time. The obtained results allowed us also to determine the reddening, age, and distance to the clusters. Results: The cluster parameters obtained through the BCD method agree very well with those derived from classical methods based on photometric data. The BCD system also provides physical properties of the star members. This study enables us to test the good behavior of Mbol(λ1,D)-calibrations and detect systematic discrepancies between log g estimates from model atmospheres and those derived from stellar evolution models. To improve our knowledge on the formation and evolution of the clusters, more statistical studies on the initial mass luminosity and angular momentum distributions should be addressed. Therefore, the BCD spectrophotometric system could be a powerful tool for studying

Open clusters. II. Fundamental parameters of B stars in Collinder 223, Hogg 16, NGC 2645, NGC 3114, and NGC 6025

Science.gov (United States)

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 (age between 40 Myr and 69 Myr. In

Gaia Data Release 1 Open cluster astrometry: performance, limitations, and future prospects

Czech Academy of Sciences Publication Activity Database

van Leeuwen, F.; Vallenari, A.; Jordi, C.; Lindegren, L.; Bastian, U.; Prusti, T.; de Bruijne, J.H.J.; Brown, A.G.A.; Babusiaux, C.; Bailer-Jones, C.A.L.; Fuchs, Jan; Koubský, Pavel; Votruba, Viktor

2017-01-01

Roč. 601, May (2017), A19/1-A19/65 E-ISSN 1432-0746 R&D Projects: GA MŠk(CZ) LG15010 Grant - others:ESA(XE) ESA-PECS project No. 98058 Institutional support: RVO:67985815 Keywords : astrometry * open clusters and associations * proper motion and parallax Subject RIV: BN - Astronomy , Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 5.014, year: 2016

M31 GLOBULAR CLUSTER ABUNDANCES FROM HIGH-RESOLUTION, INTEGRATED-LIGHT SPECTROSCOPY

International Nuclear Information System (INIS)

Colucci, Janet E.; Bernstein, Rebecca A.; Cameron, Scott; McWilliam, Andrew; Cohen, Judith G.

2009-01-01

We report the first detailed chemical abundances for five globular clusters (GCs) in M31 from high-resolution (R ∼ 25,000) spectroscopy of their integrated light (IL). These GCs are the first in a larger set of clusters observed as part of an ongoing project to study the formation history of M31 and its GC population. The data presented here were obtained with the HIRES echelle spectrograph on the Keck I telescope and are analyzed using a new IL spectra analysis method that we have developed. In these clusters, we measure abundances for Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Y, and Ba, ages ≥10 Gyr, and a range in [Fe/H] of -0.9 to -2.2. As is typical of Milky Way GCs, we find these M31 GCs to be enhanced in the α-elements Ca, Si, and Ti relative to Fe. We also find [Mg/Fe] to be low relative to other [α/Fe], and [Al/Fe] to be enhanced in the IL abundances. These results imply that abundances of Mg, Al (and likely O, Na) recovered from IL do display the inter- and intra-cluster abundance variations seen in individual Milky Way GC stars, and that special care should be taken in the future in interpreting low- or high-resolution IL abundances of GCs that are based on Mg-dominated absorption features. Fe-peak and the neutron-capture elements Ba and Y also follow Milky Way abundance trends. We also present high-precision velocity dispersion measurements for all five M31 GCs, as well as independent constraints on the reddening toward the clusters from our analysis.

The LAMOST spectroscopic survey of globular clusters in M31 and M33. I. catalog and new identifications

International Nuclear Information System (INIS)

Chen, Bing-Qiu; Liu, Xiao-Wei; Xiang, Mao-Sheng; Huang, Yang; Sun, Ning-Chen; Wang, Chun; Ren, Juan-Juan; Zhang, Hua-Wei; Yuan, Hai-Bo; Rebassa-Mansergas, Alberto; Huo, Zhi-Ying; Yang, Ming; Zhang, Yong; Hou, Yong-Hui; Wang, Yue-Fei

2015-01-01

We present a catalog of 908 objects observed with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) in fields in the vicinity of M31 and M33, targeted as globular clusters (GCs) and candidates. The targets include known GCs and candidates selected from the literature, as well as new candidates selected from the Sloan Digital Sky Survey (SDSS). Analysis shows that 356 of them are likely GCs with various confidence levels, while the remaining ones turn out to be background galaxies and quasars, stars and H ii regions in M31 or foreground Galactic stars. The 356 likely GCs include 298 bona fide GCs and 26 candidates known in the literature. Three candidates, selected from the Revised Bologna Catalog of M31 GCs and candidates (RBC) and one possible cluster from Johnson et al., are confirmed to be bona fide clusters. We search for new GCs in the halo of the M31 among the new candidates selected from the SDSS photometry. Based on radial velocities yielded by LAMOST spectra and visual examination of the SDSS images, we find 28 objects, 5 bona fide and 23 likely GCs. Among the five bona fide GCs, three have been recently discovered independently by others, and the remaining 25 are our new identifications, including two bona fide ones. The newly identified objects fall at projected distances ranging from 13 to 265kpc from M31. Of the two newly discovered bona fide GCs, one is located near M33, probably a GC belonging to M33. The other bona fide GC falls on the Giant Stream with a projected distance of 78 kpc from M31. Of the 23 newly identified likely GCs, one has a projected distance of about 265 kpc from M31 and could be an intergalactic cluster. (paper)

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

International Nuclear Information System (INIS)

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

2010-01-01

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

New red giant star in the Kepler open cluster NGC 6819

Science.gov (United States)

Komucyeya, E.; Abedigamba, O. P.; Jurua, E.; Anguma, S. K.

2018-05-01

A recent study indicated that 39 red giant stars showing solar-like oscillations were discovered in the field of Kepleropen cluster NGC 6819. The study was based on photometric distance estimates of 27 stars out of the 39. Using photometric method alone may not be adequate to confirm the membership of these stars. The stars were not previously known in literature to belong to the open cluster NGC 6819. In this study, Kepler data was used to study the membership of the 27 stars. A plot of apparent magnitude as a function of the large frequency separation, supplemented with the proper motion and radial velocity values from literature revealed KIC 5112840 to lie on the same plane with the well known members of the cluster. Echelle diagram was constructed, and the median gravity-mode period spacings (ΔP) calculated for KIC 5112840. A value of ΔP = 66.3 s was obtained, thus placing the red giant star KIC 5112840 on the Red Giant Branch stage of evolution. Our evolutionary status result using the approach in this paper is in agreement with what is in the available literature.

EVIDENCE FOR AN ACCRETION ORIGIN FOR THE OUTER HALO GLOBULAR CLUSTER SYSTEM OF M31

International Nuclear Information System (INIS)

Mackey, A. D.; Huxor, A. P.; Ferguson, A. M. N.; Irwin, M. J.; Chapman, S. C.; Tanvir, N. R.; McConnachie, A. W.; Ibata, R. A.; Lewis, G. F.

2010-01-01

We use a sample of newly discovered globular clusters from the Pan-Andromeda Archaeological Survey (PAndAS) in combination with previously cataloged objects to map the spatial distribution of globular clusters in the M31 halo. At projected radii beyond ∼30 kpc, where large coherent stellar streams are readily distinguished in the field, there is a striking correlation between these features and the positions of the globular clusters. Adopting a simple Monte Carlo approach, we test the significance of this association by computing the probability that it could be due to the chance alignment of globular clusters smoothly distributed in the M31 halo. We find that the likelihood of this possibility is low, below 1%, and conclude that the observed spatial coincidence between globular clusters and multiple tidal debris streams in the outer halo of M31 reflects a genuine physical association. Our results imply that the majority of the remote globular cluster system of M31 has been assembled as a consequence of the accretion of cluster-bearing satellite galaxies. This constitutes the most direct evidence to date that the outer halo globular cluster populations in some galaxies are largely accreted.

New 2MASS near-infrared photometry for globular clusters in M31

Energy Technology Data Exchange (ETDEWEB)

Wang, Song; Ma, Jun; Wu, Zhenyu; Zhou, Xu, E-mail: majun@nao.cas.cn [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

2014-07-01

We present Two Micron All Sky Survey JHK {sub s} photometry for 913 star clusters and candidates in the field of M31, which are selected from the latest Revised Bologna Catalog of M31 globular clusters (GCs) and candidates. The photometric measurements in this paper supplement this catalog, and provide the most comprehensive and homogeneous photometric catalog for M31 GCs in the JHK {sub s} bandpasses. In general, our photometry is consistent with previous measurements. The globular cluster luminosity function (GCLF) peaks for the confirmed GCs derived by fitting a t {sub 5} distribution using the maximum likelihood method are J{sub 0}=15.348{sub −0.208}{sup +0.206}, H{sub 0}=14.703{sub −0.180}{sup +0.176}, and K{sub s0}=14.534{sub −0.146}{sup +0.142}, all of which agree well with previous studies. The GCLFs are different between metal-rich (MR) and metal-poor (MP), and between inner and outer subpopulations, as MP clusters are fainter than their MR counterparts and the inner clusters are brighter than the outer ones, which confirm previous results. The NIR colors of the GC candidates are on average redder than those of the confirmed GCs, which leads to an obscure bimodal distribution of color indices. The relation of (V – K {sub s}){sub 0} and metallicity shows a notable departure from linearity, with a shallower slope toward the redder end. The color-magnitude diagram (CMD) and color-color diagram show that many GC candidates are located out of the evolutionary tracks, suggesting that some of them may be false M31 GC candidates. The CMD also shows that the initial mass function of M31 GCs covers a large range, and the majority of the clusters have initial masses between 10{sup 3} and 10{sup 6} M {sub ☉}.

The L_X-M relation of Clusters of Galaxies

Energy Technology Data Exchange (ETDEWEB)

Rykoff, E.S.; Evrard, A.E.; McKay, T.A.; Becker, M.R.; Johnston, D.E.; Koester, B.P.; Nord, B.; Rozo, E.; Sheldon, E.S.; Stanek, R.; Wechsler, R.H.

2008-05-16

We present a new measurement of the scaling relation between X-ray luminosity and total mass for 17,000 galaxy clusters in the maxBCG cluster sample. Stacking sub-samples within fixed ranges of optical richness, N200, we measure the mean 0.1-2.4 keV X-ray luminosity, , from the ROSAT All-Sky Survey. The mean mass, <M{sub 200}>, is measured from weak gravitational lensing of SDSS background galaxies (Johnston et al. 2007). For 9 {le} N{sub 200} < 200, the data are well fit by a power-law, /10{sup 42} h{sup -2} ergs{sup -1} = (12.6{sub -1.3}{sup +1.4}(stat) {+-} 1.6 (sys)) (<M{sub 200}>/10{sup 14} h{sup -1} M{sub {circle_dot}}){sup 1.65{+-}0.13}. The slope agrees to within 10% with previous estimates based on X-ray selected catalogs, implying that the covariance in L{sub X} and N{sub 200} at fixed halo mass is not large. The luminosity intercept is 30%, or 2{sigma}, lower than determined from the X-ray flux-limited sample of Reiprich & Boehringer (2002), assuming hydrostatic equilibrium. This slight difference could arise from a combination of Malmquist bias and/or systematic error in hydrostatic mass estimates, both of which are expected. The intercept agrees with that derived by Stanek et al. (2006) using a model for the statistical correspondence between clusters and halos in a WMAP3 cosmology with power spectrum normalization {sigma}{sub 8} = 0.85. Similar exercises applied to future data sets will allow constraints on the covariance among optical and hot gas properties of clusters at fixed mass.

New insights into the origin and evolution of the old, metal-rich open cluster NGC 6791

Science.gov (United States)

Martinez-Medina, Luis A.; Gieles, Mark; Pichardo, Barbara; Peimbert, Antonio

2018-02-01

NGC 6791 is one of the most studied open clusters, it is massive (˜5000 M⊙), located at the solar circle, old (˜8 Gyr) and yet the most metal-rich cluster ([Fe/H] ≃ 0.4) known in the Milky Way. By performing an orbital analysis within a Galactic model including spiral arms and a bar, we found that it is plausible that NGC 6791 formed in the inner thin disc or in the bulge, and later displaced by radial migration to its current orbit. We apply different tools to simulate NGC 6791, including direct N-body summation in time-varying potentials, to test its survivability when going through different Galactic environments. In order to survive the 8-Gyr journey moving on a migrating orbit, NGC 6791 must have been more massive, M0 ≥ 5 × 104 M⊙, when formed. We find independent confirmation of this initial mass in the stellar mass function, which is observed to be flat; this can only be explained if the average tidal field strength experienced by the cluster is stronger than what it is at its current orbit. Therefore, the birth place and journeys of NGC 6791 are imprinted in its chemical composition, in its mass-loss and in its flat stellar mass function, supporting its origin in the inner thin disc or in the bulge.

Achievement of 35 MV/m in the superconducting nine-cell cavities for TESLA

International Nuclear Information System (INIS)

Lilje, L.; Kostin, D.; Matheisen, A.; Moeller, W.D.; Proch, D.; Reschke, D.; Simrock, S.; Twarowski, K.; Kako, E.; Saito, K.; Schmueser, P.; Suzuki, T.

2004-01-01

The tera electronvolt superconducting linear accelerator TESLA is the only linear electron-positron collider project based on superconductor technology for particle acceleration. In the first stage with 500 GeV center-of-mass energy an accelerating field of 23.4 MV/m is needed in the superconducting niobium cavities which are operated at a temperature of 2 K and a quality factor Q 0 of 10 10 . This performance has been reliably achieved in the cavities of the TESLA test facility (TTF) accelerator. The upgrade of TESLA to 800 GeV requires accelerating gradients of 35 MV/m. Using an improved cavity treatment by electrolytic polishing it has been possible to raise the gradient to 35 - 43 MV/m in single cell resonators. Here we report on the successful transfer of the electropolishing technique to multi-cell cavities. Presently four nine-cell cavities have achieved 35 MV/m at Q 0 ≥ 5 x 10 9 , and a fifth cavity could be excited to 39 MV/m. In two high-power tests it could be verified that EP-cavities preserve their excellent performance after welding into the helium cryostat and assembly of the high-power coupler. One cavity has been operated for 1100 hours at the TESLA-800 gradient of 35 MV/m and 57 hours at 36 MV/m without loss in performance. (orig.)

Photoelectron spectroscopy and density functional theory studies of (FeS)mH- (m = 2-4) cluster anions: effects of the single hydrogen.

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Yin, Shi; Bernstein, Elliot R

2017-12-20

Single hydrogen containing iron hydrosulfide cluster anions (FeS) m H - (m = 2-4) are studied by photoelectron spectroscopy (PES) at 3.492 eV (355 nm) and 4.661 eV (266 nm) photon energies, and by Density Functional Theory (DFT) calculations. The structural properties, relative energies of different spin states and isomers, and the first calculated vertical detachment energies (VDEs) of different spin states for these (FeS) m H - (m = 2-4) cluster anions are investigated at various reasonable theory levels. Two types of structural isomers are found for these (FeS) m H - (m = 2-4) clusters: (1) the single hydrogen atom bonds to a sulfur site (SH-type); and (2) the single hydrogen atom bonds to an iron site (FeH-type). Experimental and theoretical results suggest such available different SH- and FeH-type structural isomers should be considered when evaluating the properties and behavior of these single hydrogen containing iron sulfide clusters in real chemical and biological systems. Compared to their related, respective pure iron sulfur (FeS) m - clusters, the first VDE trend of the diverse type (FeS) m H 0,1 - (m = 1-4) clusters can be understood through (1) the different electron distribution properties of their highest singly occupied molecular orbital employing natural bond orbital analysis (NBO/HSOMO), and (2) the partial charge distribution on the NBO/HSOMO localized sites of each cluster anion. Generally, the properties of the NBO/HSOMOs play the principal role with regard to the physical and chemical properties of all the anions. The change of cluster VDE from low to high is associated with the change in nature of their NBO/HSOMO from a dipole bound and valence electron mixed character, to a valence p orbital on S, to a valence d orbital on Fe, and to a valence p orbital on Fe or an Fe-Fe delocalized valence bonding orbital. For clusters having the same properties for NBO/HSOMOs, the partial charge distributions at the NBO/HSOMO localized sites additionally

The Gaia-ESO Survey: open clusters in Gaia-DR1 . A way forward to stellar age calibration

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Randich, S.; Tognelli, E.; Jackson, R.; Jeffries, R. D.; Degl'Innocenti, S.; Pancino, E.; Re Fiorentin, P.; Spagna, A.; Sacco, G.; Bragaglia, A.; Magrini, L.; Prada Moroni, P. G.; Alfaro, E.; Franciosini, E.; Morbidelli, L.; Roccatagliata, V.; Bouy, H.; Bravi, L.; Jiménez-Esteban, F. M.; Jordi, C.; Zari, E.; Tautvaišiene, G.; Drazdauskas, A.; Mikolaitis, S.; Gilmore, G.; Feltzing, S.; Vallenari, A.; Bensby, T.; Koposov, S.; Korn, A.; Lanzafame, A.; Smiljanic, R.; Bayo, A.; Carraro, G.; Costado, M. T.; Heiter, U.; Hourihane, A.; Jofré, P.; Lewis, J.; Monaco, L.; Prisinzano, L.; Sbordone, L.; Sousa, S. G.; Worley, C. C.; Zaggia, S.

2018-05-01

Context. Determination and calibration of the ages of stars, which heavily rely on stellar evolutionary models, are very challenging, while representing a crucial aspect in many astrophysical areas. Aims: We describe the methodologies that, taking advantage of Gaia-DR1 and the Gaia-ESO Survey data, enable the comparison of observed open star cluster sequences with stellar evolutionary models. The final, long-term goal is the exploitation of open clusters as age calibrators. Methods: We perform a homogeneous analysis of eight open clusters using the Gaia-DR1 TGAS catalogue for bright members and information from the Gaia-ESO Survey for fainter stars. Cluster membership probabilities for the Gaia-ESO Survey targets are derived based on several spectroscopic tracers. The Gaia-ESO Survey also provides the cluster chemical composition. We obtain cluster parallaxes using two methods. The first one relies on the astrometric selection of a sample of bona fide members, while the other one fits the parallax distribution of a larger sample of TGAS sources. Ages and reddening values are recovered through a Bayesian analysis using the 2MASS magnitudes and three sets of standard models. Lithium depletion boundary (LDB) ages are also determined using literature observations and the same models employed for the Bayesian analysis. Results: For all but one cluster, parallaxes derived by us agree with those presented in Gaia Collaboration (2017, A&A, 601, A19), while a discrepancy is found for NGC 2516; we provide evidence supporting our own determination. Inferred cluster ages are robust against models and are generally consistent with literature values. Conclusions: The systematic parallax errors inherent in the Gaia DR1 data presently limit the precision of our results. Nevertheless, we have been able to place these eight clusters onto the same age scale for the first time, with good agreement between isochronal and LDB ages where there is overlap. Our approach appears promising

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

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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.

The evolution of the Y-M scaling relation in MUSIC clusters

Science.gov (United States)

Sembolini, F.; Yepes, G.; De Petris, M.; Gottlöber, S.; Lamagna, L.; Comis, B.

2013-04-01

This work describes the baryon content and Sunyaev-Zeld'ovich properties of the MUSIC (Marenostrum-MultiDark SImulations of galaxy clusters) dataset and their evolution with redshift and aperture radius. The MUSIC dataset is one of the largest samples of hydrodynamically simulated galaxy clusters (more than 2000 objects, including more than 500 clusters). We show that when the effects of cooling and stellar feedbacks are properly taken into account, the gas fraction of the MUSIC clusters consistently agrees with recent observational results. Moreover, the gas fraction has a net dependence with the total mass of the cluster and increases slightly with redshift at high overdensities. The study of the Y-M relation confirms the consistence of the self-similar model, showing no evolution with redshift at low overdensities.

Hierarchical cluster analysis of progression patterns in open-angle glaucoma patients with medical treatment.

Science.gov (United States)

Bae, Hyoung Won; Rho, Seungsoo; Lee, Hye Sun; Lee, Naeun; Hong, Samin; Seong, Gong Je; Sung, Kyung Rim; Kim, Chan Yun

2014-04-29

To classify medically treated open-angle glaucoma (OAG) by the pattern of progression using hierarchical cluster analysis, and to determine OAG progression characteristics by comparing clusters. Ninety-five eyes of 95 OAG patients who received medical treatment, and who had undergone visual field (VF) testing at least once per year for 5 or more years. OAG was classified into subgroups using hierarchical cluster analysis based on the following five variables: baseline mean deviation (MD), baseline visual field index (VFI), MD slope, VFI slope, and Glaucoma Progression Analysis (GPA) printout. After that, other parameters were compared between clusters. Two clusters were made after a hierarchical cluster analysis. Cluster 1 showed -4.06 ± 2.43 dB baseline MD, 92.58% ± 6.27% baseline VFI, -0.28 ± 0.38 dB per year MD slope, -0.52% ± 0.81% per year VFI slope, and all "no progression" cases in GPA printout, whereas cluster 2 showed -8.68 ± 3.81 baseline MD, 77.54 ± 12.98 baseline VFI, -0.72 ± 0.55 MD slope, -2.22 ± 1.89 VFI slope, and seven "possible" and four "likely" progression cases in GPA printout. There were no significant differences in age, sex, mean IOP, central corneal thickness, and axial length between clusters. However, cluster 2 included more high-tension glaucoma patients and used a greater number of antiglaucoma eye drops significantly compared with cluster 1. Hierarchical cluster analysis of progression patterns divided OAG into slow and fast progression groups, evidenced by assessing the parameters of glaucomatous progression in VF testing. In the fast progression group, the prevalence of high-tension glaucoma was greater and the number of antiglaucoma medications administered was increased versus the slow progression group. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

The interstellar extinction in the open clusters Tr 14, Tr 15, Tr 16/Cr 232 and Cr 228 in NGC 3372. New near-infrared photometry

International Nuclear Information System (INIS)

Tapia, M.; Roth, M.; Ruiz, M.T.

1988-01-01

Near-infrared JHKL photometry of more than 200 stars, members of the open clusters Tr14, Tr15, Tr16, Cr228 and Cr232 in the Carina Nebula are presented. From comparing these results with the available visual photometry and spectroscopy, it is found that, except in Tr15, the intracluster reddening is characterized by a 'normal' extinction law at λ > 0.5μm but is highly anomalous and variable in the U- and B-bands. This behaviour may be explained by the presence of intracluster interstellar grains 'processed' by shock waves presumably associated with the explosive history of η Carinae. All clusters are found to be at the same distance from the Sun at d = 2.4 ± 0.2 kpc or Vsub(o) - Msub(v) 11.9 ± 0.2. The total amount of reddening, though, differs significantly from cluster to cluster. (author)

The complex lives of star clusters

CERN Document Server

Stevenson, David

2015-01-01

As with the author’s recent books Extreme Explosions and Under a Crimson Sun, the complex topic of star clusters is broken down and made accessible with clear links to other areas of astronomy in a language which the non-specialist can easily read and enjoy. The full range of a star cluster's lifespan is depicted, as both globular and open clusters are tracked from birth to eventual death. Why is it some are dense conglomerates of stars while others are looser associations? Are the young, brilliant clusters seen in neighboring galaxies such as the Large Magellanic Cloud, M33 or M82 analogous to the ancient globulars seen in the Milky Way? How will these clusters change as their stars wane and die? More interestingly, how does living in a dense star cluster affect the fates of the stars and any attendant planets that accompany them?   Star clusters form many of the most dazzling objects in the astronomers’ catalogs. Many amateur astronomers are interested in exploring how these objects are created and wh...

Charge exchange in galaxy clusters

Science.gov (United States)

Gu, Liyi; Mao, Junjie; de Plaa, Jelle; Raassen, A. J. J.; Shah, Chintan; Kaastra, Jelle S.

2018-03-01

Context. Though theoretically expected, the charge exchange emission from galaxy clusters has never been confidently detected. Accumulating hints were reported recently, including a rather marginal detection with the Hitomi data of the Perseus cluster. As previously suggested, a detection of charge exchange line emission from galaxy clusters would not only impact the interpretation of the newly discovered 3.5 keV line, but also open up a new research topic on the interaction between hot and cold matter in clusters. Aim. We aim to perform the most systematic search for the O VIII charge exchange line in cluster spectra using the RGS on board XMM-Newton. Methods: We introduce a sample of 21 clusters observed with the RGS. In order to search for O VIII charge exchange, the sample selection criterion is a >35σ detection of the O VIII Lyα line in the archival RGS spectra. The dominating thermal plasma emission is modeled and subtracted with a two-temperature thermal component, and the residuals are stacked for the line search. The systematic uncertainties in the fits are quantified by refitting the spectra with a varying continuum and line broadening. Results: By the residual stacking, we do find a hint of a line-like feature at 14.82 Å, the characteristic wavelength expected for oxygen charge exchange. This feature has a marginal significance of 2.8σ, and the average equivalent width is 2.5 × 10-4 keV. We further demonstrate that the putative feature can be barely affected by the systematic errors from continuum modeling and instrumental effects, or the atomic uncertainties of the neighboring thermal lines. Conclusions: Assuming a realistic temperature and abundance pattern, the physical model implied by the possible oxygen line agrees well with the theoretical model proposed previously to explain the reported 3.5 keV line. If the charge exchange source indeed exists, we expect that the oxygen abundance could have been overestimated by 8-22% in previous X

Metallicity Spreads in M31 Globular Clusters

Science.gov (United States)

Bridges, Terry

2003-07-01

Our recent deep HST photometry of the M31 halo globular cluster {GC} Mayall II, also called G1, has revealed a red-giant branch with a clear spread that we attribute to an intrinsic metallicity dispersion of at least 0.4 dex in [Fe/H]. The only other GC exhibiting such a metallicity dispersion is Omega Centauri, the brightest and most massive Galactic GC, whose range in [Fe/H] is about 0.5 dex. These observations are obviously linked to the fact that both G1 and Omega Cen are bright and massive GC, with potential wells deep enough to keep part of their gas, which might have been recycled, producing a metallicity scatter among cluster stars. These observations dramatically challenge the notion of chemical homogeneity as a defining characteristic of GCs. It is critically important to find out how common this phenomenon is and how it can constrain scenarios/models of GC formation. The obvious targets are other bright and massive GCs, which exist in M31 but not in our Galaxy where Omega Cen is an isolated giant. We propose to acquire, with ACS/HRC, deep imaging of 3 of the brightest M31 GCs for which we have observed velocity dispersion values similar to those observed in G1 and Omega Cen. A sample of GCs with chemical abundance dispersions will provide essential information about their formation mechanism. This would represent a major step for the studies of the origin and evolution of stellar populations.

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

International Nuclear Information System (INIS)

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

2009-01-01

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 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 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.

The next generation Virgo cluster survey. VIII. The spatial distribution of globular clusters in the Virgo cluster

Energy Technology Data Exchange (ETDEWEB)

Durrell, Patrick R.; Accetta, Katharine [Department of Physics and Astronomy, Youngstown State University, Youngstown, OH 44555 (United States); Côté, Patrick; Blakeslee, John P.; Ferrarese, Laura; McConnachie, Alan; Gwyn, Stephen [Herzberg Astronomy and Astrophysics, National Research Council, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Peng, Eric W.; Zhang, Hongxin [Department of Astronomy, Peking University, Beijing 100871 (China); Mihos, J. Christopher [Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106 (United States); Puzia, Thomas H.; Jordán, Andrés [Institute of Astrophysics, Pontificia Universidad Catolica, Av. Vicu' a Mackenna 4860, Macul 7820436, Santiago (Chile); Lançon, Ariane [Observatoire astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l' Université, F-67000 Strasbourg (France); Liu, Chengze [Center for Astronomy and Astrophysics, Department of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China); Cuillandre, Jean-Charles [Canada-France-Hawaii Telescope Corporation, Kamuela, HI 96743 (United States); Boissier, Samuel; Boselli, Alessandro [Aix Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Courteau, Stéphane [Department of Physics, Engineering Physics and Astronomy, Queen' s University, Kingston, ON K7L 3N6 (Canada); Duc, Pierre-Alain [AIM Paris Saclay, CNRS/INSU, CEA/Irfu, Université Paris Diderot, Orme des Merisiers, F-91191 Gif sur Yvette cedex (France); Emsellem, Eric [Université de Lyon 1, CRAL, Observatoire de Lyon, 9 av. Charles André, F-69230 Saint-Genis Laval (France); CNRS, UMR 5574, ENS de Lyon (France); and others

2014-10-20

We report on a large-scale study of the distribution of globular clusters (GCs) throughout the Virgo cluster, based on photometry from the Next Generation Virgo Cluster Survey (NGVS), a large imaging survey covering Virgo's primary subclusters (Virgo A = M87 and Virgo B = M49) out to their virial radii. Using the g{sub o}{sup ′}, (g' – i') {sub o} color-magnitude diagram of unresolved and marginally resolved sources within the NGVS, we have constructed two-dimensional maps of the (irregular) GC distribution over 100 deg{sup 2} to a depth of g{sub o}{sup ′} = 24. We present the clearest evidence to date showing the difference in concentration between red and blue GCs over the full extent of the cluster, where the red (more metal-rich) GCs are largely located around the massive early-type galaxies in Virgo, while the blue (metal-poor) GCs have a much more extended spatial distribution with significant populations still present beyond 83' (∼215 kpc) along the major axes of both M49 and M87. A comparison of our GC maps to the diffuse light in the outermost regions of M49 and M87 show remarkable agreement in the shape, ellipticity, and boxiness of both luminous systems. We also find evidence for spatial enhancements of GCs surrounding M87 that may be indicative of recent interactions or an ongoing merger history. We compare the GC map to that of the locations of Virgo galaxies and the X-ray intracluster gas, and find generally good agreement between these various baryonic structures. We calculate the Virgo cluster contains a total population of N {sub GC} = 67, 300 ± 14, 400, of which 35% are located in M87 and M49 alone. For the first time, we compute a cluster-wide specific frequency S {sub N,} {sub CL} = 2.8 ± 0.7, after correcting for Virgo's diffuse light. We also find a GC-to-baryonic mass fraction ε {sub b} = 5.7 ± 1.1 × 10{sup –4} and a GC-to-total cluster mass formation efficiency ε {sub t} = 2.9 ± 0.5 × 10{sup –5

Distributed Joint Cluster Formation and Resource Allocation Scheme for Cooperative Data Collection in Virtual MIMO-Based M2M Networks

Directory of Open Access Journals (Sweden)

Xi Luan

2015-01-01

Full Text Available An efficient data collection scheme plays an important role for the real-time intelligent monitoring in many machine-to-machine (M2M networks. In this paper, a distributed joint cluster formation and resource allocation scheme for data collection in cluster-based M2M networks is proposed. Specifically, in order to utilize the advantages of cooperation, we first propose a hierarchical transmission model which contains two communication phases. In the first phase, the intracluster information sharing is carried out by all the nodes within the same cluster. Then these nodes transmit the total information to the BS cooperatively with virtual-MIMO (VMIMO protocol in the second phase. To grasp the properties and advantages of this cooperative transmission strategy, the theoretical analysis results are provided. The key issue in this system is to form the clusters and allocate resources efficiently. Since the optimization problem on this issue is an NP-hard problem, a feasible joint scheme for the cluster formation and resource allocation is proposed in this paper, which is carried out via coalition formation game with a distributed algorithm. This scheme can reduce the complexity while keeping an attractive performance. Simulation results show the properties of the proposed scheme and its advantages when comparing with the noncooperative scheme for the data collection in a practical scenario.

ON THE HEATING EFFICIENCY DERIVED FROM OBSERVATIONS OF YOUNG SUPER STAR CLUSTERS IN M82

International Nuclear Information System (INIS)

Silich, Sergiy; Tenorio-Tagle, Guillermo; Torres-Campos, Ana; Munoz-Tunon, Casiana; Monreal-Ibero, Ana; Melo, Veronica

2009-01-01

Here, we discuss the mechanical feedback that massive stellar clusters provide to the interstellar medium of their host galaxy. We apply an analytic theory developed in a previous study for M82-A1 to a sample of 10 clusters located in the central zone of the starburst galaxy M82, all surrounded by compact and dense H II regions. We claim that the only way that such H II regions can survive around the selected clusters, is if they are embedded into a high-pressure ISM and if the majority of their mechanical energy is lost within the star cluster volume via strong radiative cooling. The latter implies that these clusters have a low heating efficiency, η, and evolve in the bimodal hydrodynamic regime. In this regime, the shock-heated plasma in the central zones of a cluster becomes thermally unstable, loses its pressure and is accumulated there, whereas the matter injected by supernovae and stellar winds outside this volume forms a high-velocity outflow-the star cluster wind. We calculated the heating efficiency for each of the selected clusters and found that in all cases it does not exceed 10%. Such low heating efficiency values imply a low mechanical energy output and the impact that the selected clusters provide to the ISM of M82 is thus much smaller than what one would expect using stellar cluster synthetic models.

Stellar activity with LAMOST - II. Chromospheric activity in open clusters

Science.gov (United States)

Fang, Xiang-Song; Zhao, Gang; Zhao, Jing-Kun; Bharat Kumar, Yerra

2018-05-01

We use the LAMOST spectra of member stars in Pleiades, M34, Praesepe, and Hyades to study how chromospheric activity varies as a function of mass and rotation at different age. We measured excess equivalent widths of H α, H β, and Ca II K based on estimated chromospheric contributions from old and inactive field dwarfs, and excess luminosities are obtained by normalizing bolometric luminosity, for more than 700 late-type stars in these open clusters. Results indicate two activity sequences in cool spot coverage and H α excess emission among GK dwarfs in Pleiades and M dwarfs in Praesepe and Hyades, paralleling with well-known rotation sequences. A weak dependence of chromospheric emission on rotation exists among ultrafast rotators in saturated regime with Rossby number Ro ≲ 0.1. In the unsaturated regime, chromospheric and coronal emission show similar dependence on Ro, but with a shift towards larger Ro, indicating chromospheric emission gets easily saturated than coronal emission, and/or convective turnover time-scales based on X-ray data do not work well with chromospheric emission. More interestingly, our analysis shows fully convective slow rotators obey the rotation-chromospheric activity relation similar to hotter stars, confirming the previous finding. We found correlations among H α, H β, and Ca II K emissions, in which H α losses are more important than Ca II K for cooler and more active stars. In addition, a weak correlation is seen between chromospheric emission and photospheric activity that shows dependence on stellar spectral type and activity level, which provides some clues on how spot configuration varies as a function of mass and activity level.

Investigation of Galactic open cluster remnants: the case of NGC 7193

Science.gov (United States)

de Souza Angelo, Mateus; Francisco Coelho dos Santos, João, Jr.; Barbosa Corradi, Wagner José; Ferreira de Souza Maia, Francisco; Piatti, Andrés Eduardo

2017-01-01

Galactic open clusters (OCs) that survive the early gas-expulsion phase are gradually destroyed over time by the action of disruptive dynamical processes. Their final evolutionary stages are characterized by a poorly populated concentration of stars called an open cluster remnant (OCR). This study is devoted to assessing the real physical nature of the OCR candidate NGC 7193. GMOS/Gemini spectroscopy of 53 stars in the inner target region were obtained to derive radial velocities and atmospheric parameters. We also employed photometric and proper motion data. The analysis method consists of the following steps: (i) analysis of the statistical resemblance between the cluster and a set of field samples with respect to the sequences defined in color-magnitude diagrams (CMDs); (ii) a 5-dimensional iterative exclusion routine was employed to identify outliers from kinematical and positional data; (iii) isochrone fitting to the Ks×(J-Ks) CMD of the remaining stars and the dispersion of spectral types along empirical sequences in the (J-H)×(H-Ks) diagram were checked. A group of stars was identified for which the mean heliocentric distance is compatible with that obtained via isochrone fitting and whose metallicities are compatible with each other. Fifteen of the member stars observed spectroscopically were identified together with another 19 probable members. Our results indicate that NGC 7193 is a genuine OCR, of a once very populous OC, for which the following parameters were derived: d = 501±46 pc, t=2.5+/-1.2 Gyr, =-0.17+/-0.23 and E(B-V)=0.05+/-0.05. Its luminosity and mass functions show depletion of low mass stars, confirming the OCR is in a dynamically evolved state. Based on observations obtained at the Gemini Observatory, which is operated by the AURA under a cooperative agreement with the NSF on behalf of the Gemini partnership: NSF (United States), STFC (United Kingdom), NRC (Canada), CONICYT (Chile), ARC (Australia), CNPq (Brazil) and CONICET (Argentina).

The Sun was Not Born in M67

Science.gov (United States)

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.

Catalogue of Positions and Proper Motions of Stars in the Vicinity of Open Clusters

Directory of Open Access Journals (Sweden)

Protsyuk, Yu.I.

2017-01-01

Full Text Available In the Research Institute Mykolaiv Astronomical Observatory (MAO the catalogue of position and proper motions of stars in the 544 square areas of nearly (1×1°around the Galactic open clusters was created using photographic and CCD observations. 293 plates of (5×5°obtained with the MAO Zonal Astrograph (D=116 mm, F=2040 mm in 1962-1993 and more than 20 thousands CCD frames (0.7×0.7° obtained with KT-50 telescope (D=500 mm, F=3000 mm in 2011-2015 were used. Almost 270 thousands FITS files from the IVOA image archives with observational epoch from 1953 to 2010 were downloaded and processed. The created catalogue contains more than 2.3 million stars (7.5-18.5m in the ICRS system with the accuracy of positions on both coordinates ranged from 0.02" to 0.05". Inner accuracy of proper motions is ~0.004"/year.

Catalogue of positions and proper motions of stars in the vicinity of open clusters

Science.gov (United States)

Protsyuk, Yu. I.; Kovalchuk, O. M.; Mazhaev, O. E.

2017-02-01

A catalog of positions and proper motions of stars in 544 square areas of nearly (1 × 1)° around the Galactic open clusters has been created using photographic and CCD observations, at Research Institute "Mykolaiv Astronomical Observatory" (RI "MAO"). To this end, 293 plates of (5 × 5)° obtained with the MAO Zonal Astrograph (D=116 mm, F=2040 mm) in 1962-1993 and more than 20 thousand CCD frames (0.7 × 0.7)° obtained with KT-50 telescope (D=500 mm, F=3000 mm) in 2011-2015 have been used. Almost 270 thousand FITS files from the IVOA image archives with observational epoch from 1953 to 2010 have been downloaded and processed. The created catalogue contains more than 2.3 million stars having a magnitude of (7.5-18.5)m in the ICRS system, with accuracy of positions for both coordinates ranging from 0.02" to 0.05". Internal accuracy of proper motions is estimated as ~0.004"/year.

BVRI CCD photometry of the metal-poor globular cluster M68 (NGC 4590)

International Nuclear Information System (INIS)

Alcaino, G.; Liller, W.; Alvarado, F.; Wenderoth, E.

1990-01-01

BVRI photometry of the low metallicity globular cluster M68 (NGC 4590) was obtained with a CCD camera and the 2.2-m ESO telescope. The resulting BV color-magnitude diagrams are compared with the observations of McClure et al. (1987). The observations are also compared with theoretical isochrones, yielding a cluster age of 13 Gyr with a likely external uncertainty of 2 or 3 Gyr. 25 refs

OpenStack augstas pieejamības risinājumi

OpenAIRE

Dreiže, Toms

2016-01-01

Šis bakalaura darbs ir pētījums par OpenStack IaaS mākoņpakalpojumu platformu. Tā mērķis ir sniegt ieskatu augstas pieejamības pamatprincipos un OpenStack mākoņpakalpojumu platformas piedāvātajos augstas pieejamības nodrošināšanas risinājumos. Bakalaura darba gaitā ir veikta augsti pieejamas OpenStack trīs mezglu sistēmas uzstādīšana, izmantojot Galera Cluster datubāzu klasteri un HAProxy slodzes līdzsvarotāju. Tika pārbaudīta OpenStack augsta pieejamība, testējot OpenStack Glance komponentes...

Proper Motions and Structural Parameters of the Galactic Globular Cluster M71

Energy Technology Data Exchange (ETDEWEB)

Cadelano, M.; Dalessandro, E.; Ferraro, F. R.; Miocchi, P.; Lanzoni, B.; Pallanca, C. [Dipartimento di Fisica e Astronomia, Università di Bologna, Viale Berti Pichat 6/2, I-40127 Bologna (Italy); Massari, D. [INAF—Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy)

2017-02-20

By exploiting two ACS/ HST data sets separated by a temporal baseline of ∼7 years, we have determined the relative stellar proper motions (PMs; providing membership) and the absolute PM of the Galactic globular cluster M71. The absolute PM has been used to reconstruct the cluster orbit within a Galactic, three-component, axisymmetric potential. M71 turns out to be in a low-latitude disk-like orbit inside the Galactic disk, further supporting the scenario in which it lost a significant fraction of its initial mass. Since large differential reddening is known to affect this system, we took advantage of near-infrared, ground-based observations to re-determine the cluster center and density profile from direct star counts. The new structural parameters turn out to be significantly different from the ones quoted in the literature. In particular, M71 has a core and a half-mass radii almost 50% larger than previously thought. Finally, we estimate that the initial mass of M71 was likely one order of magnitude larger than its current value, thus helping to solve the discrepancy with the observed number of X-ray sources.

Study of Remote Globular Cluster Satellites of M87

Science.gov (United States)

Sahai, Arushi; Shao, Andrew; Toloba, Elisa; Guhathakurta, Puragra; Peng, Eric W.; Zhang, Hao

2017-01-01

We present a sample of “orphan” globular clusters (GCs) with previously unknown parent galaxies, which we determine to be remote satellites of M87, a massive elliptical galaxy at the center of the Virgo Cluster of Galaxies. Because GCs were formed in the early universe along with their original parent galaxies, which were cannibalized by massive galaxies such as M87, they share similar age and chemical properties. In this study, we first confirm that M87 is the adoptive parent galaxy of our orphan GCs using photometric and spectroscopic data to analyze spatial and velocity distributions. Next, we increase the signal-to-noise ratio of our samples’ spectra through a process known as coaddition. We utilize spectroscopic absorption lines to determine the age and metallicity of our orphan GCs through comparison to stellar population synthesis models, which we then relate to the GCs’ original parent galaxies using a mass-metallicity relation. Our finding that remote GCs of M87 likely developed in galaxies with ~1010 solar masses implies that M87’s outer halo is formed of relatively massive galaxies, serving as important parameters for developing theories about the formation and evolution of massive galaxies.This research was funded in part by NASA/STScI and the National Science Foundation. Most of this work was carried out by high school students working under the auspices of the Science Internship Program at UC Santa Cruz.

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

Science.gov (United States)

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

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

Science.gov (United States)

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.

Age and helium content of the open cluster NGC 6791 from multiple eclipsing binary members. II

DEFF Research Database (Denmark)

Brogaard, K.; VandenBerg, D. A.; Bruntt, H.

2012-01-01

Models of stellar structure and evolution can be constrained by measuring accurate parameters of detached eclipsing binaries in open clusters. Multiple binary stars provide the means to determine helium abundances in these old stellar systems, and in turn, to improve estimates of their age. In th...

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

Science.gov (United States)

2014-10-13

Survey ( 2MASS ) system (Skrutskie et al. 2006) and the ratios of color excesses EV−m/EB−V , where m are the near-infrared magnitudes J, H, and K. In...andEV−K/EB−V with the J, H, and K magnitudes from 2MASS . For this aim, we used a list of B and A stars identified in the central 15′ × 15′ area. Their...V and B − V data were taken from Massey et al. (1995) and the AAVSO APASS survey, DR7,7 and the near-infrared magnitudes from 2MASS . The ratios of

Open clusters. III. Fundamental parameters of B stars in NGC 6087, NGC 6250, NGC 6383, and NGC 6530 B-type stars with circumstellar envelopes

Science.gov (United States)

Aidelman, Y.; Cidale, L. S.; Zorec, J.; Panei, J. A.

2018-02-01

Context. Stellar physical properties of star clusters are poorly known and the cluster parameters are often very uncertain. Methods: Our goals are to perform a spectrophotometric study of the B star population in open clusters to derive accurate stellar parameters, search for the presence of circumstellar envelopes, and discuss the characteristics of these stars. The BCD spectrophotometric system is a powerful method to obtain stellar fundamental parameters from direct measurements of the Balmer discontinuity. To this end, we wrote the interactive code MIDE3700. The BCD parameters can also be used to infer the main properties of open clusters: distance modulus, color excess, and age. Furthermore, we inspected the Balmer discontinuity to provide evidence for the presence of circumstellar disks and identify Be star candidates. We used an additional set of high-resolution spectra in the Hα region to confirm the Be nature of these stars. Results: We provide Teff, log g, Mv, Mbol, and spectral types for a sample of 68 stars in the field of the open clusters NGC 6087, NGC 6250, NGC 6383, and NGC 6530, as well as the cluster distances, ages, and reddening. Then, based on a sample of 230 B stars in the direction of the 11 open clusters studied along this series of three papers, we report 6 new Be stars, 4 blue straggler candidates, and 15 B-type stars (called Bdd) with a double Balmer discontinuity, which indicates the presence of circumstellar envelopes. We discuss the distribution of the fraction of B, Be, and Bdd star cluster members per spectral subtype. The majority of the Be stars are dwarfs and present a maximum at the spectral type B2-B4 in young and intermediate-age open clusters (operating under agreement of CONICET and the Universities of La Plata, Córdoba, and San Juan, Argentina.Tables 1, 2, 9-16 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/610/A30

DETERMINING THE AGE OF THE KEPLER OPEN CLUSTER NGC 6819 WITH A NEW TRIPLE SYSTEM AND OTHER ECLIPSING BINARY STARS

International Nuclear Information System (INIS)

Brewer, Lauren N.; Sandquist, Eric L.; Jeffries, Mark W. Jr.; Orosz, Jerome A.

2016-01-01

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 BVR C I C ) and spectroscopic observations of the detached eclipsing binary WOCS 24009 (Auner 665; KIC 5023948) with a short orbital period of 3.6 days. WOCS 24009 is a triple-lined system, and we verify that the brightest star is physically orbiting the eclipsing binary using radial velocities and eclipse timing variations. The eclipsing binary components have masses M B  = 1.090 ± 0.010 M ⊙ and M C  = 1.075 ± 0.013 M ⊙ , and radii R B  = 1.099 ± 0.006 ± 0.005 R ⊙ and R C  = 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 M A  = 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

Search for variable stars in the young open cluster Stock 18

Directory of Open Access Journals (Sweden)

Sinha Tirthendu

2017-01-01

Full Text Available We have carried out multi-epoch deep I band photometry of the open cluster Stock 18 to search for variable stars in star forming regions. In the present study, we report identification of 28 periodic and 165 non-periodic variables stars. The periods of most of the periodic variables are in between 2 to 20 hours and their magnitude varies between 0.05 to 0.6 mag. We have derived spectral energy distributions for 48 probable pre-main sequence variables and the average age and mass is found to be 2.7 ± 0.3 Myrs and 2.7 ± 0.2 M⊙, respectively.

The Magellanic Bridge Cluster NGC 796: Deep Optical AO Imaging Reveals the Stellar Content and Initial Mass Function of a Massive Open Cluster

Science.gov (United States)

Kalari, Venu M.; Carraro, Giovanni; Evans, Christopher J.; Rubio, Monica

2018-04-01

NGC 796 is a massive young cluster located 59 kpc from us in the diffuse intergalactic medium of the 1/5–1/10 Z⊙ Magellanic Bridge, allowing us to probe variations in star formation and stellar evolution processes as a function of metallicity in a resolved fashion, and providing a link between resolved studies of nearby solar-metallicity and unresolved distant metal-poor clusters located in high-redshift galaxies. In this paper, we present adaptive optics griHα imaging of NGC 796 (at 0.″5, which is ∼0.14 pc at the cluster distance) along with optical spectroscopy of two bright members to quantify the cluster properties. Our aim is to explore whether star formation and stellar evolution vary as a function of metallicity by comparing the properties of NGC 796 to higher-metallicity clusters. We find an age of {20}-5+12 Myr from isochronal fitting of the cluster main sequence in the color–magnitude diagram. Based on the cluster luminosity function, we derive a top-heavy stellar initial mass function (IMF) with a slope α = 1.99 ± 0.2, hinting at a metallicity and/or environmental dependence of the IMF, which may lead to a top-heavy IMF in the early universe. Study of the Hα emission-line stars reveals that classical Be stars constitute a higher fraction of the total B-type stars when compared with similar clusters at greater metallicity, providing some support to the chemically homogeneous theory of stellar evolution. Overall, NGC 796 has a total estimated mass of 990 ± 200 M⊙, and a core radius of 1.4 ± 0.3 pc, which classifies it as a massive young open cluster, unique in the diffuse interstellar medium of the Magellanic Bridge.

From WSN towards WoT: Open API Scheme Based on oneM2M Platforms

Science.gov (United States)

Kim, Jaeho; Choi, Sung-Chan; Ahn, Il-Yeup; Sung, Nak-Myoung; Yun, Jaeseok

2016-01-01

Conventional computing systems have been able to be integrated into daily objects and connected to each other due to advances in computing and network technologies, such as wireless sensor networks (WSNs), forming a global network infrastructure, called the Internet of Things (IoT). To support the interconnection and interoperability between heterogeneous IoT systems, the availability of standardized, open application programming interfaces (APIs) is one of the key features of common software platforms for IoT devices, gateways, and servers. In this paper, we present a standardized way of extending previously-existing WSNs towards IoT systems, building the world of the Web of Things (WoT). Based on the oneM2M software platforms developed in the previous project, we introduce a well-designed open API scheme and device-specific thing adaptation software (TAS) enabling WSN elements, such as a wireless sensor node, to be accessed in a standardized way on a global scale. Three pilot services are implemented (i.e., a WiFi-enabled smart flowerpot, voice-based control for ZigBee-connected home appliances, and WiFi-connected AR.Drone control) to demonstrate the practical usability of the open API scheme and TAS modules. Full details on the method of integrating WSN elements into three example systems are described at the programming code level, which is expected to help future researchers in integrating their WSN systems in IoT platforms, such as oneM2M. We hope that the flexibly-deployable, easily-reusable common open API scheme and TAS-based integration method working with the oneM2M platforms will help the conventional WSNs in diverse industries evolve into the emerging WoT solutions. PMID:27782058

From WSN towards WoT: Open API Scheme Based on oneM2M Platforms

Directory of Open Access Journals (Sweden)

Jaeho Kim

2016-10-01

Full Text Available Conventional computing systems have been able to be integrated into daily objects and connected to each other due to advances in computing and network technologies, such as wireless sensor networks (WSNs, forming a global network infrastructure, called the Internet of Things (IoT. To support the interconnection and interoperability between heterogeneous IoT systems, the availability of standardized, open application programming interfaces (APIs is one of the key features of common software platforms for IoT devices, gateways, and servers. In this paper, we present a standardized way of extending previously-existing WSNs towards IoT systems, building the world of the Web of Things (WoT. Based on the oneM2M software platforms developed in the previous project, we introduce a well-designed open API scheme and device-specific thing adaptation software (TAS enabling WSN elements, such as a wireless sensor node, to be accessed in a standardized way on a global scale. Three pilot services are implemented (i.e., a WiFi-enabled smart flowerpot, voice-based control for ZigBee-connected home appliances, and WiFi-connected AR.Drone control to demonstrate the practical usability of the open API scheme and TAS modules. Full details on the method of integrating WSN elements into three example systems are described at the programming code level, which is expected to help future researchers in integrating their WSN systems in IoT platforms, such as oneM2M. We hope that the flexibly-deployable, easily-reusable common open API scheme and TAS-based integration method working with the oneM2M platforms will help the conventional WSNs in diverse industries evolve into the emerging WoT solutions.

From WSN towards WoT: Open API Scheme Based on oneM2M Platforms.

Science.gov (United States)

Kim, Jaeho; Choi, Sung-Chan; Ahn, Il-Yeup; Sung, Nak-Myoung; Yun, Jaeseok

2016-10-06

Conventional computing systems have been able to be integrated into daily objects and connected to each other due to advances in computing and network technologies, such as wireless sensor networks (WSNs), forming a global network infrastructure, called the Internet of Things (IoT). To support the interconnection and interoperability between heterogeneous IoT systems, the availability of standardized, open application programming interfaces (APIs) is one of the key features of common software platforms for IoT devices, gateways, and servers. In this paper, we present a standardized way of extending previously-existing WSNs towards IoT systems, building the world of the Web of Things (WoT). Based on the oneM2M software platforms developed in the previous project, we introduce a well-designed open API scheme and device-specific thing adaptation software (TAS) enabling WSN elements, such as a wireless sensor node, to be accessed in a standardized way on a global scale. Three pilot services are implemented (i.e., a WiFi-enabled smart flowerpot, voice-based control for ZigBee-connected home appliances, and WiFi-connected AR.Drone control) to demonstrate the practical usability of the open API scheme and TAS modules. Full details on the method of integrating WSN elements into three example systems are described at the programming code level, which is expected to help future researchers in integrating their WSN systems in IoT platforms, such as oneM2M. We hope that the flexibly-deployable, easily-reusable common open API scheme and TAS-based integration method working with the oneM2M platforms will help the conventional WSNs in diverse industries evolve into the emerging WoT solutions.

Chemical Abundances of Red Giant Stars in the Globular Cluster M107 (NGC 6171)

Science.gov (United States)

O'Connell, Julia E.; Johnson, Christian I.; Pilachowski, Catherine A.; Burks, Geoffrey

2011-10-01

We present chemical abundances of Al and several Fe-Peak and neutron-capture elements for 13 red giant branch stars in the Galactic globular cluster NGC 6171 (M107). The abundances were determined using equivalent width and spectrum synthesis analyses of moderate-resolution ( R ˜ 15,000), moderate signal-to-noise ratio ( ˜ 80) spectra obtained with the WIYN telescope and Hydra multifiber spectrograph. A comparison between photometric and spectroscopic effective temperature estimates seems to indicate that a reddening value of E(B - V) = 0.46 may be more appropriate for this cluster than the more commonly used value of E(B - V) = 0.33. Similarly, we found that a distance modulus of (m - M)V ≈ 13.7 provided reasonable surface gravity estimates for the stars in our sample. Our spectroscopic analysis finds M107 to be moderately metal-poor with = -0.93 and also exhibits a small star-to-star metallicity dispersion (σ = 0.04). These results are consistent with previous photometric and spectroscopic studies. Aluminum appears to be moderately enhanced in all program stars ( = +0.39, σ = 0.11). The relatively small star-to-star scatter in [Al/Fe] differs from the trend found in more metal-poor globular clusters, and is more similar to what is found in clusters with [Fe/H] ≳ -1. The cluster also appears to be moderately r-process-enriched with = +0.32 (σ = 0.17).

Molecular oxygen adsorption and dissociation on Au12M clusters with M = Cu, Ag or Ir

Science.gov (United States)

Jiménez-Díaz, Laura M.; Pérez, Luis A.

2018-03-01

In this work, we present a density functional theory study of the structural and electronic properties of isolated neutral clusters of the type Au12M, with M = Cu, Ag, or Ir. On the other hand, there is experimental evidence that gold-silver, gold-copper and gold-iridium nanoparticles have an enhanced catalytic activity for the CO oxidation reaction. In order to address these phenomena, we also performed density functional calculations of the adsorption and dissociation of O2 on these nanoparticles. Moreover, to understand the effects of Cu, Ag, and Ir impurity atoms on the dissociation of O2, we also analyze this reaction in the corresponding pure gold cluster. The results indicate that the substitution of one gold atom in a Au13 cluster by Ag, Cu or Ir diminishes the activation energy barrier for the O2 dissociation by nearly 1 eV. This energy barrier is similar for Au12Ag and Au12Cu, whereas for Au12Ir is even lower. These results suggest that the addition of other transition metal atoms to gold nanoclusters can enhance their catalytic activity towards the CO oxidation reaction, independently of the effect that the substrate could have on supported nanoclusters.

Digestibilidade determinada pelo método indireto usando o n-alcano C35 Digestibility determinate by indirect method using C35 n-alkane

Directory of Open Access Journals (Sweden)

Dimas Estrásulas de Oliveira

2000-06-01

Full Text Available Foi feito um trabalho de extração e análise de n-alcanos com o objetivo de investigar o uso do n-alcano (C35 presente nas forragens como um indicador interno para determinação de digestibilidade. Foram utilizadas amostras de experimentos de digestibilidade convencional realizados previamente entre os anos de 1978 e 1982. O C35 subestimou as digestibilidades da matéria seca e orgânica, apresentando diferença média, em relação ao método in vivo, de 4,68 (± 0,69 e 4,43 (± 0,85 unidades percentuais, respectivamente. O coeficiente de regressão não diferiu da unidade, indicando que os métodos foram equivalentes, havendo, porém, a necessidade de um fator de correção. Os coeficientes de correlação para a matéria seca e orgânica, observados entre os dois métodos, foram 0,87 e 0,85, respectivamente. O C35 apresentou recuperação fecal média de 91,76% (± 7,94, que contribuiu para o vício da técnica.An experiment was conducted, on extraction and analysis of n-alkanes, to investigate the use of n-alkane (C35 present in forages as an internal marker for the digestibility determination. Samples of forages and feces were taken from conventional digestibility trials, which were previous conducted from 1978 to 1982. The C35 underestimated the dry matter and organic matter digestibilities, presenting an average difference in relation to in vivo of 4.68 (± 0.69 and 4,43 (± 0.85 perceptual units, respectively. The coefficient of regression did not differ from the unit, indicating that both methods were equivalent, having, however, the necessity of a correction factor. The coefficients of correlation observed for the dry and organic matter between the two methods were 0.87 and 0.85, respectively. The average fecal recovery of C35 was 91.76% (± 7.94, and this contributed to the bias of the method.

THERE ARE NO STARLESS MASSIVE PROTO-CLUSTERS IN THE FIRST QUADRANT OF THE GALAXY

Energy Technology Data Exchange (ETDEWEB)

Ginsburg, A.; Bally, J.; Battersby, C. [Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309 (United States); Bressert, E. [European Southern Observatory, Karl Schwarzschild str. 2, D-85748 Garching bei Muenchen (Germany)

2012-10-20

We search the {lambda} = 1.1 mm Bolocam Galactic Plane Survey for clumps containing sufficient mass to form {approx}10{sup 4} M{sub Sun} star clusters. Eighteen candidate massive proto-clusters are identified in the first Galactic quadrant outside of the central kiloparsec. This sample is complete to clumps with mass M{sub clump} > 10{sup 4} M{sub Sun} and radius r {approx}< 2.5 pc. The overall Galactic massive cluster formation rate is CFR(M{sub cluster} > 10{sup 4}) {approx}<5 Myr{sup -1}, which is in agreement with the rates inferred from Galactic open clusters and M31 massive clusters. We find that all massive proto-clusters in the first quadrant are actively forming massive stars and place an upper limit of {tau}{sub starless} < 0.5 Myr on the lifetime of the starless phase of massive cluster formation. If massive clusters go through a starless phase with all of their mass in a single clump, the lifetime of this phase is very short.

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

International Nuclear Information System (INIS)

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

2016-01-01

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 R 1 = 1.24 ± 0.01 R ⊙ , R 2 = 1.11 ± 0.02 R ⊙ , and M 1 = 1.24 ± 0.02 M ⊙ , M 2 = 0.96 ± 0.05 M ⊙ and for star ID494 of R 1 = 1.22±0.02R ⊙ , R 2 = 0.81±0.01 R ⊙ , and M 1 = 1.20±0.06 M ⊙ , M 2 = 0.47±0.01 M ⊙ . (paper)

BVI CCD photometry of the globular cluster M4

International Nuclear Information System (INIS)

Alcaino, G.; Liller, W.; Alvarado, F.

1988-01-01

CCD BV1 main-sequence (MS) photometry of M4, the globular cluster closest to the sun, is presented. The photometry is matched to the BVI isochrones of VandenBerg and Bell (1985). The MS turnoffs are found to be at V = 16.90 + or - 0.05, B-V = 0.81 + or - 0.02, V-I = 0.96 + or - 0.02, and B - I = 1.77 + or - 0.02. The magnitude difference between the MS turnoff and the horizontal branch is Delta M(V) = 3.52 + or - 0.1 for all three color indices. Using Y = 0.2, (Fe/H) = - 1.27, and alpha = 1.65, with a distance modulus of (m-M)V = 12.7 and E(B-V) = 0.41, a consistent age for M4 is deduced in all three color indices of 17 + or - 1.5 Gyr. 34 references

Mucosal immunization with the Moraxella catarrhalis porin m35 induces enhanced bacterial clearance from the lung: a possible role for opsonophagocytosis

Directory of Open Access Journals (Sweden)

Donna eEaston

2011-05-01

Full Text Available Moraxella catarrhalis is a significant cause of respiratory tract infection against which a vaccine is sought. Several outer membrane proteins are currently under investigation as potential vaccine antigens, including the porin M35. We have previously shown that the third external loop of M35 was immunodominant over the remainder of the protein for antibody produced in mice against the refolded recombinant protein. However, as this loop is predicted to fold inside the porin channel we also predicted that it would not be accessible to these antibodies when M35 is expressed on the surface of the bacteria in its native conformation. This study investigated the functional activity of antibodies against M35 and those specific for the loop 3 region of M35 in vitro and in vivo. Antisera from mice immunized with M35 or the loop 3-deletion, M35loop3–, recombinant proteins were not bactericidal but did have enhanced opsonic activity, whereas antibodies raised against the loop 3 peptide were not opsonising indicating that the immunodominant loop 3 of M35 was not accessible to antibody as we had previously predicted. Mucosal immunization with M35, M35 that had an antigenically altered loop 3 (M35(ID78 and M35loop3– enhanced the clearance of M. catarrhalis from the lungs of mice challenged with live M. catarrhalis. The in vivo clearance of bacteria in the mice with the M35-derived protein constructs correlated significantly (p<0.001 with the opsonic activity assessed an in vitro opsonophagocytosis assay. This study has demonstrated that the immunodominat B-cell epitope to loop 3 of the M. catarrhalis outer membrane protein M35 is not associated with immune protection and that M35-specific antibodies are not bactericidal but are opsonising. The opsonising activity correlated with in vivo clearance of the bacteria suggesting that opsonising antibody may be a good correlate of immune protection.

Long-term occipital nerve stimulation for drug-resistant chronic cluster headache.

Science.gov (United States)

Leone, Massimo; Proietti Cecchini, Alberto; Messina, Giuseppe; Franzini, Angelo

2017-07-01

Introduction Chronic cluster headache is rare and some of these patients become drug-resistant. Occipital nerve stimulation has been successfully employed in open studies to treat chronic drug-resistant cluster headache. Data from large group of occipital nerve stimulation-treated chronic cluster headache patients with long duration follow-up are advantageous. Patients and methods Efficacy of occipital nerve stimulation has been evaluated in an experimental monocentric open-label study including 35 chronic drug-resistant cluster headache patients (mean age 42 years; 30 men; mean illness duration: 6.7 years). The primary end-point was a reduction in number of daily attacks. Results After a median follow-up of 6.1 years (range 1.6-10.7), 20 (66.7%) patients were responders (≥50% reduction in headache number per day): 12 (40%) responders showed a stable condition characterized by sporadic attacks, five responders had a 60-80% reduction in headache number per day and in the remaining three responders chronic cluster headache was transformed in episodic cluster headache. Ten (33.3%) patients were non-responders; half of these have been responders for a long period (mean 14.6 months; range 2-48 months). Battery depletion (21 patients 70%) and electrode migration (six patients - 20%) were the most frequent adverse events. Conclusions Occipital nerve stimulation efficacy is confirmed in chronic drug-resistant cluster headaches even after an exceptional long-term follow-up. Tolerance can occur years after improvement.

A Constraint on the Formation Timescale of the Young Open Cluster NGC 2264: Lithium Abundance of Pre-main Sequence Stars

Science.gov (United States)

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

2016-11-01

The timescale of cluster formation is an essential parameter in order to understand the formation process of star clusters. Pre-main sequence (PMS) stars in nearby young open clusters reveal a large spread in brightness. If the spread were considered to be a result of a real spread in age, the corresponding cluster formation timescale would be about 5-20 Myr. Hence it could be interpreted that star formation in an open cluster is prolonged for up to a few tens of Myr. However, difficulties in reddening correction, observational errors, and systematic uncertainties introduced by imperfect evolutionary models for PMS stars can result in an artificial age spread. Alternatively, we can utilize Li abundance as a relative age indicator of PMS star to determine the cluster formation timescale. The optical spectra of 134 PMS stars in NGC 2264 have been obtained with MMT/Hectochelle. The equivalent widths have been measured for 86 PMS stars with a detectable Li line (3500\\lt {T}{eff}[{{K}}]≤slant 6500). Li abundance under the condition of local thermodynamic equilibrium (LTE) was derived using the conventional curve of growth method. After correction for non-LTE effects, we find that the initial Li abundance of NGC 2264 is A({Li})=3.2+/- 0.2. From the distribution of the Li abundances, the underlying age spread of the visible PMS stars is estimated to be about 3-4 Myr and this, together with the presence of embedded populations in NGC 2264, suggests that the cluster formed on a timescale shorter than 5 Myr.

Development of New Open-Shell Perturbation and Coupled-Cluster Theories Based on Symmetric Spin Orbitals

Science.gov (United States)

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.

USING Hα MORPHOLOGY AND SURFACE BRIGHTNESS FLUCTUATIONS TO AGE-DATE STAR CLUSTERS IN M83

International Nuclear Information System (INIS)

Whitmore, Bradley C.; Mutchler, Max; Stankiewicz, Matt; Bond, Howard E.; Chandar, Rupali; Kim, Hwihyun; Kaleida, Catherine; Calzetti, Daniela; Saha, Abhijit; O'Connell, Robert; Balick, Bruce; Carollo, Marcella; Disney, Michael J.; Dopita, Michael A.; Frogel, Jay A.; Hall, Donald N. B.; Holtzman, Jon A.; Kimble, Randy A.; McCarthy, Patrick J.; Paresce, Francesco

2011-01-01

We use new WFC3 observations of the nearby grand-design spiral galaxy M83 to develop two independent methods for estimating the ages of young star clusters. The first method uses the physical extent and morphology of Hα emission to estimate the ages of clusters younger than τ ∼ 10 Myr. It is based on the simple premise that the gas in very young (τ V 10 Myr) clusters. A by-product of this study is the identification of 22 'single-star' H II regions in M83, with central stars having ages ∼4 Myr.

The Globular Cluster NGC 6402 (M14). II. Variable Stars

DEFF Research Database (Denmark)

Contreras Peña, C.; Catelan, M.; Grundahl, F.

2018-01-01

approaches for the calibration of the absolute magnitudes of RR Lyrae stars. The possible presence of second-overtone RR Lyrae in M14 is critically addressed, with our results arguing against this possibility. By considering all of the RR Lyrae stars as members of the cluster, we derive =0.589 {{d...

A Long-Period Totally Eclipsing Binary Star at the Turnoff of the Open Cluster NGC 6819 Discovered with Kepler

DEFF Research Database (Denmark)

Sandquist, Eric L.; Mathieu, Robert D.; Brogaard, Karsten

2012-01-01

We present the discovery of the totally eclipsing long-period (P = 771.8 d) 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 Msun) star. This system was previously known to be a single-lined spectros......We present the discovery of the totally eclipsing long-period (P = 771.8 d) 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 Msun) 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 degrees. 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 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...

CCD Photometry of the Open Cluster Tombaugh 5 in the Vilnius System

Science.gov (United States)

2011-01-01

Es-v = 0.80 mag, d = 1.33 kpc and the age 251 Myr. Majaess et al. (2008) investigated the cluster using the J,H,I<s data from the 2MASS survey. By...000 stars in the compari- SOJ1 catalog. For the classification of some stars, additional information from the J-H vs. H-K, diagram of 2MASS (Skrutskie...22 16.91 2.74 1.88 0.98 0.36 0.82 1.25 35: 2MASS J03464290+5902134, the star is a close visual binary ( ~ 2") with a 613 3 48 40.0 +59 06 37 14.18

Spatial Substructure in the M87 Globular Cluster System

Science.gov (United States)

Feng, Yuting; Zhang, Yunhao; Guhathakurta, Puragra; Peng, Eric; Lim, Sungsoon

2018-01-01

Based on the observation of Next Generation Virgo Cluster Survey (NGVS) project, we obtained the u,g,r,i,z and Ks band photometric information of all the objects in the 2 degree × 2 degree area (Pilot Region) around M87, the major subcluster of Virgo. By adapting an Extreme Deconvolution method, which classifies objects into Globular Clusters (GCs), galaxies and foreground stars with their color and morphology data, we got a purer-than-ever GC distribution map with a depth to gmag=25 in Pilot Region. After masking galaxy GCs, smoothing with a 10arcmin Gaussian kernel and performing a flat field correction, we show the GC density map of M87, and got a good sersic fitting of GC radial distribution with a sersic index~2.2 in the central ellipse part (45arcmin semi major axis area of M87). We quantitatively compared our GC sample with a substructure-free mock data set, which was generated from the smoothed density map as well as the sersic fitting, by calculating the 2 point correlation function (TPCF) value in different parts of the map. After separately performing such comparison with mocks based on different galaxy masking radii which vary from 4 times g band effective radius to 10, we found signals of remarkable spatial enhancement in certain directions in the central ellipse of M87, as well as halo substructures shown as lumpiness and holes in the outer region. We present the estimated scales of these substructures from the TPCF results, and, managed to locate them with a statistical analysis of the pixelized GC map. Apart from all results listed above, we discuss the constant, extra-galactic substructure signal at a scale of ~3kpc, which does not diminish with masking sizes, as the evidence of merging and accretion history of M87.

The range of variation of the mass of the most massive star in stellar clusters derived from 35 million Monte Carlo simulations

International Nuclear Information System (INIS)

Popescu, Bogdan; Hanson, M. M.

2014-01-01

A growing fraction of simple stellar population models, in an aim to create more realistic simulations capable of including stochastic variation in their outputs, begin their simulations with a distribution of discrete stars following a power-law function of masses. Careful attention is needed to create a correctly sampled initial mass function (IMF), and here we provide a solid mathematical method, called MASSCLEAN IMF Sampling, for doing so. We use our method to perform 10 million MASSCLEAN Monte Carlo stellar cluster simulations to determine the most massive star in a mass distribution as a function of the total mass of the cluster. We find that a maximum mass range is predicted, not a single maximum mass. This range is (1) dependent on the total mass of the cluster and (2) independent of an upper stellar mass limit, M limit , for unsaturated clusters and emerges naturally from our IMF sampling method. We then turn our analysis around, starting with our new database of 25 million simulated clusters, to constrain the highest mass star from the observed integrated colors of a sample of 40 low-mass Large Magellanic Cloud stellar clusters of known age and mass. Finally, we present an analytical description of the maximum mass range of the most massive star as a function of the cluster's total mass and present a new M max -M cluster relation.

Gravitational microlensing by low-mass objects in the globular cluster M22.

Science.gov (United States)

Sahu, K C; Casertano, S; Livio, M; Gilliland, R L; Panagia, N; Albrow, M D; Potter, M

2001-06-28

Gravitational microlensing offers a means of determining directly the masses of objects ranging from planets to stars, provided that the distances and motions of the lenses and sources can be determined. A globular cluster observed against the dense stellar field of the Galactic bulge presents ideal conditions for such observations because the probability of lensing is high and the distances and kinematics of the lenses and sources are well constrained. The abundance of low-mass objects in a globular cluster is of particular interest, because it may be representative of the very early stages of star formation in the Universe, and therefore indicative of the amount of dark baryonic matter in such clusters. Here we report a microlensing event associated with the globular cluster M22. We determine the mass of the lens to be 0.13(+0.03)(-0.02) solar masses. We have also detected six events that are unresolved in time. If these are also microlensing events, they imply that a non-negligible fraction of the cluster mass resides in the form of free-floating planetary-mass objects.

The Open Cluster NGC 6811: An Eclipsing Binary, the Turnoff, and Age

DEFF Research Database (Denmark)

Sandquist, Eric L.; Jessen-Hansen, Jens; Shetrone, Matthew D.

. The cluster's turnoff also falls completely within the instability strip, and the majority of the brightest main sequence stars have now been identified as δ Scuti pulsators. The eclipsing binary KIC 9777062/Sanders 195 is a cluster member slightly fainter than the turnoff, containing one star that falls...... stars to produce an improved age determination.We gratefully acknowledge support from the NSF to E.L.S. under grant AST-0908536 and for M.L. as part of the REU program at San Diego State University under grant AST-0850564, and from NASA under grants NNX12AC88G and NNX13AC19G....

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

Czech Academy of Sciences Publication Activity Database

Chene, A.-N.; Alegria, S.R.; Borissova, J.; O'Leary, E.; Martins, F.; Hervé, Anthony; Kuhn, M.; Kurtev, R.; Consuelo Amigo Fuentes, P.; Bonatto, C.; Minniti, D.

2015-01-01

Roč. 584, December (2015), A31/1-A31/8 ISSN 0004-6361 R&D Projects: GA ČR(CZ) GA14-02385S Institutional support: RVO:67985815 Keywords : open clusters and associations * VVV CL041 * massive star s Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.378, year: 2014

SEARCH FOR PULSED {gamma}-RAY EMISSION FROM GLOBULAR CLUSTER M28

Energy Technology Data Exchange (ETDEWEB)

Wu, J. H. K.; Kong, A. K. H.; Huang, R. H. H.; Tam, P. H. T. [Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu, Taiwan (China); Hui, C. Y. [Department of Astronomy and Space Science, Chungnam National University, Daejeon (Korea, Republic of); Wu, E. M. H.; Takata, J.; Cheng, K. S., E-mail: wuhkjason@gmail.com, E-mail: cyhui@cnu.ac.kr [Department of Physics, University of Hong Kong, Pokfulam Road (Hong Kong)

2013-03-10

Using the data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope, we have searched for {gamma}-ray pulsations from the direction of the globular cluster M28 (NGC 6626). We report the discovery of a signal with a frequency consistent with that of the energetic millisecond pulsar (MSP) PSR B1821-24 in M28. A weighted H-test test statistic of 28.8 is attained, which corresponds to a chance probability of {approx}10{sup -5} (4.3{sigma} detection). With a phase-resolved analysis, the pulsed component is found to contribute {approx}25% of the total observed {gamma}-ray emission from the cluster. However, the unpulsed level provides a constraint for the underlying MSP population and the fundamental plane relations for the scenario of inverse Compton scattering. Follow-up timing observations in radio/X-ray are encouraged to further investigate this periodic signal candidate.

THE DETAILED CHEMICAL PROPERTIES OF M31 STAR CLUSTERS. I. Fe, ALPHA AND LIGHT ELEMENTS

Energy Technology Data Exchange (ETDEWEB)

Colucci, Janet E.; Bernstein, Rebecca A. [The Observatories of the Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101 (United States); Cohen, Judith G., E-mail: jcolucci@obs.carnegiescience.edu [Palomar Observatory, Mail Stop 105-24, California Institute of Technology, Pasadena, CA 91125 (United States)

2014-12-20

We present ages, [Fe/H] and abundances of the α elements Ca I, Si I, Ti I, Ti II, and light elements Mg I, Na I, and Al I for 31 globular clusters (GCs) in M31, which were obtained from high-resolution, high signal-to-noise ratio >60 echelle spectra of their integrated light (IL). All abundances and ages are obtained using our original technique for high-resolution IL abundance analysis of GCs. This sample provides a never before seen picture of the chemical history of M31. The GCs are dispersed throughout the inner and outer halo, from 2.5 kpc < R {sub M31} < 117 kpc. We find a range of [Fe/H] within 20 kpc of the center of M31, and a constant [Fe/H] ∼ – 1.6 for the outer halo clusters. We find evidence for at least one massive GC in M31 with an age between 1 and 5 Gyr. The α-element ratios are generally similar to the Milky Way GC and field star ratios. We also find chemical evidence for a late-time accretion origin for at least one cluster, which has a different abundance pattern than other clusters at similar metallicity. We find evidence for star-to-star abundance variations in Mg, Na, and Al in the GCs in our sample, and find correlations of Ca, Mg, Na, and possibly Al abundance ratios with cluster luminosity and velocity dispersion, which can potentially be used to constrain GC self-enrichment scenarios. Data presented here were obtained with the HIRES echelle spectrograph on the Keck I telescope.

The range of variation of the mass of the most massive star in stellar clusters derived from 35 million Monte Carlo simulations

Energy Technology Data Exchange (ETDEWEB)

Popescu, Bogdan; Hanson, M. M., E-mail: bogdan.popescu@uc.edu, E-mail: margaret.hanson@uc.edu [Department of Physics, University of Cincinnati, P.O. Box 210011, Cincinnati, OH 45221-0011 (United States)

2014-01-01

A growing fraction of simple stellar population models, in an aim to create more realistic simulations capable of including stochastic variation in their outputs, begin their simulations with a distribution of discrete stars following a power-law function of masses. Careful attention is needed to create a correctly sampled initial mass function (IMF), and here we provide a solid mathematical method, called MASSCLEAN IMF Sampling, for doing so. We use our method to perform 10 million MASSCLEAN Monte Carlo stellar cluster simulations to determine the most massive star in a mass distribution as a function of the total mass of the cluster. We find that a maximum mass range is predicted, not a single maximum mass. This range is (1) dependent on the total mass of the cluster and (2) independent of an upper stellar mass limit, M{sub limit} , for unsaturated clusters and emerges naturally from our IMF sampling method. We then turn our analysis around, starting with our new database of 25 million simulated clusters, to constrain the highest mass star from the observed integrated colors of a sample of 40 low-mass Large Magellanic Cloud stellar clusters of known age and mass. Finally, we present an analytical description of the maximum mass range of the most massive star as a function of the cluster's total mass and present a new M{sub max} -M{sub cluster} relation.

Detection of binaries in the core of the globular cluster M15 using calcium emission lines

Energy Technology Data Exchange (ETDEWEB)

Murphy, B W [Rijksuniversiteit Utrecht (Netherlands). Inst. of Astronomy; Rutten, R G.M. [Astronomical Inst. ' Anton Pannekoek' , Amsterdam (Netherlands); Callanan, P J [Oxford Univ. (UK). Dept. of Astrophysics; Seitzer, Patrick [Space Telescope Science Inst., Baltimore, MD (USA); Charles, P A [Oxford Univ. (UK). Dept. of Astrophysics Observatorio del Roque do los Muchachos, Santa Cruz de La Palma, Tenerife, Canary Islands (Spain); Cohn, H N; Lugger, P M [Indiana Univ., Bloomington, IN (USA). Dept. of Astronomy

1991-05-09

M12 is the prototypical collapsed-core globular cluster. Having undergone collapse, its core is believed now to be expanding, with energy for the re-expansion provided by binary stars, which turn gravitational potential energy into kinetic energy. Because these binary stars are generally more massive than single stars, they will have settled to the centre of the cluster. We report here that several of the stars at the core of M15 show Ca II H- and K-line emission characteristic of young, rapidly rotating stars and close binaries. We argue that the emission from M15 comes from primordial binaries, in which a period of spin-up has led to magnetic field generation by enhanced dynamo action, which in turn causes heating of the stellar chromospheres. If this interpretation is correct, the Ca H and K emission may provide an important diagnostic tool of the binary population in cluster cores, and thus of the cluster dynamics. (author).

Detection of binaries in the core of the globular cluster M15 using calcium emission lines

International Nuclear Information System (INIS)

Murphy, B.W.; Callanan, P.J.; Charles, P.A.; Cohn, H.N.; Lugger, P.M.

1991-01-01

M12 is the prototypical collapsed-core globular cluster. Having undergone collapse, its core is believed now to be expanding, with energy for the re-expansion provided by binary stars, which turn gravitational potential energy into kinetic energy. Because these binary stars are generally more massive than single stars, they will have settled to the centre of the cluster. We report here that several of the stars at the core of M15 show Ca II H- and K-line emission characteristic of young, rapidly rotating stars and close binaries. We argue that the emission from M15 comes from primordial binaries, in which a period of spin-up has led to magnetic field generation by enhanced dynamo action, which in turn causes heating of the stellar chromospheres. If this interpretation is correct, the Ca H and K emission may provide an important diagnostic tool of the binary population in cluster cores, and thus of the cluster dynamics. (author)

The origin and orbit of the old, metal-rich, open cluster NGC 6791. Insights from kinematics

Czech Academy of Sciences Publication Activity Database

Jílková, L.; Carraro, G.; Jungwiert, Bruno; Minchev, I.

2012-01-01

Roč. 541, April (2012), A64/1-A64/11 ISSN 0004-6361 R&D Projects: GA MŠk(CZ) LC06014; GA ČR GD205/08/H005 Institutional research plan: CEZ:AV0Z10030501 Keywords : galaxy * kinematics and dynamics * open clusters and associations Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 5.084, year: 2012

The Cluster AgeS Experiment (CASE). Variable Stars in the Field of the Globular Cluster M22

Science.gov (United States)

Rozyczka, M.; Thompson, I. B.; Pych, W.; Narloch, W.; Poleski, R.; Schwarzenberg-Czerny, A.

2017-09-01

The field of the globular cluster M22 (NGC 6656) was monitored between 2000 and 2008 in a search for variable stars. BV light curves were obtained for 359 periodic, likely periodic, and long-term variables, 238 of which are new detections. 39 newly detected variables, and 63 previously known ones are members or likely members of the cluster, including 20 SX Phe, 10 RRab and 16 RRc type pulsators, one BL Her type pulsator, 21 contact binaries, and 9 detached or semi-detached eclipsing binaries. The most interesting among the identified objects are V112 - a bright multimode SX Phe pulsator, V125 - a β Lyr type binary on the blue horizontal branch, V129 - a blue/yellow straggler with a W UMa-like light curve, located halfway between the extreme horizontal branch and red giant branch, and V134 - an extreme horizontal branch object with P=2.33 d and a nearly sinusoidal light curve. All four of them are proper motion members of the cluster. Among nonmembers, a P=2.83 d detached eclipsing binary hosting a δ Sct type pulsator was found, and a peculiar P=0.93 d binary with ellipsoidal modulation and narrow minimum in the middle of one of the descending shoulders of the sinusoid. We also collected substantial new data for previously known variables. In particular we revise the statistics of the occurrence of the Blazhko effect in RR Lyr type variables of M22.

The Lithium Depletion Boundary and the Age of the Hyades Cluster

Science.gov (United States)

Martín, Eduardo L.; Lodieu, Nicolas; Pavlenko, Yakiv; Béjar, Víctor J. S.

2018-03-01

Determination of the lithium depletion boundary (LDB), i.e., the observational limit below which the cores of very low-mass objects do not reach high enough temperatures for Li destruction, has been used to obtain ages for several open clusters and stellar associations younger than 200 Myr—which until now has been considered the practical upper limit on the range of applicability of this method. In this work, we show that the LDB method can be extended to significant older ages than previously thought. Intermediate resolution optical spectra of six L-type candidate members in the Hyades cluster obtained using Optical System for Imaging and Low Resolution Integrated Spectroscopy at the 10.4 m Gran Telescopio Canarias are presented. The {Li} {{I}} 670.8 nm resonance doublet is clearly detected only in the two faintest and coolest of these objects, which are classified as L3.5 to L4 brown dwarf (BD) cluster members with luminosities around 10‑4 solar. Lithium depletion factors are estimated for our targets with the aid of synthetic spectra and they are compared with predictions from evolutionary models. An LDB age of 650 ± 70 Myr for the Hyades provides a consistent description of our data using a set of state-of-the-art evolutionary models for BDs calculated by Baraffe et al. Based on data obtained at the Gran Telescopio Canarias.

The Detailed Chemical Properties of M31 Star Clusters. I. Fe, Alpha and Light Elements

Science.gov (United States)

Colucci, Janet E.; Bernstein, Rebecca A.; Cohen, Judith G.

2014-12-01

We present ages, [Fe/H] and abundances of the α elements Ca I, Si I, Ti I, Ti II, and light elements Mg I, Na I, and Al I for 31 globular clusters (GCs) in M31, which were obtained from high-resolution, high signal-to-noise ratio >60 echelle spectra of their integrated light (IL). All abundances and ages are obtained using our original technique for high-resolution IL abundance analysis of GCs. This sample provides a never before seen picture of the chemical history of M31. The GCs are dispersed throughout the inner and outer halo, from 2.5 kpc < R M31 < 117 kpc. We find a range of [Fe/H] within 20 kpc of the center of M31, and a constant [Fe/H] ~ - 1.6 for the outer halo clusters. We find evidence for at least one massive GC in M31 with an age between 1 and 5 Gyr. The α-element ratios are generally similar to the Milky Way GC and field star ratios. We also find chemical evidence for a late-time accretion origin for at least one cluster, which has a different abundance pattern than other clusters at similar metallicity. We find evidence for star-to-star abundance variations in Mg, Na, and Al in the GCs in our sample, and find correlations of Ca, Mg, Na, and possibly Al abundance ratios with cluster luminosity and velocity dispersion, which can potentially be used to constrain GC self-enrichment scenarios. Data presented here were obtained with the HIRES echelle spectrograph on the Keck I telescope. 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.

THE NEXT GENERATION VIRGO CLUSTER SURVEY. VI. THE KINEMATICS OF ULTRA-COMPACT DWARFS AND GLOBULAR CLUSTERS IN M87

Energy Technology Data Exchange (ETDEWEB)

Zhang, Hong-Xin; Peng, Eric W.; Li, Biao [Department of Astronomy, Peking University, Beijing 100871 (China); Côté, Patrick; Ferrarese, Laura; Gwyn, Stephen D. J.; Blakeslee, John P. [National Research Council of Canada, Herzberg Astronomy and Astrophysics Program, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Liu, Chengze [Center for Astronomy and Astrophysics, Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Cuillandre, Jean-Charles [Canada-France-Hawaii Telescope Corporation, Kamuela, HI 96743 (United States); Caldwell, Nelson [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Jordán, Andrés; Muñoz, Roberto P.; Puzia, Thomas H. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago (Chile); Lançon, Ariane [Observatoire astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l' Universite, F-67000 Strasbourg (France); Bekki, Kenji [School of Physics, University of New South Wales, Sydney 2052, NSW (Australia); Boselli, Alessandro [Aix Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Drinkwater, Michael J. [School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072 (Australia); Duc, Pierre-Alain, E-mail: hongxin@pku.edu.cn, E-mail: peng@pku.edu.cn [Laboratoire AIM Paris-Saclay, CNRS/INSU, Université Paris Diderot, CEA/IRFU/SAp, F-91191 Gif-sur-Yvette Cedex (France); and others

2015-03-20

The origin of ultra-compact dwarfs (UCDs; r{sub h} ≳ 10 pc)—objects larger and more massive than typical globular clusters (GCs), but more compact than typical dwarf galaxies—has been hotly debated in the 15 years since their discovery. Even whether UCDs should be considered galactic in origin, or simply the most extreme star clusters, is not yet settled. We present the dynamical properties of 97 spectroscopically confirmed UCDs and 911 GCs associated with the central cD galaxy of the Virgo cluster, M87. Our UCDs, of which 89% have M {sub *} ≳ 2× 10{sup 6} M {sub ☉} and 92% are as blue as the classic blue GCs, nearly triple the confirmed sample of Virgo UCDs, providing by far the best opportunity for studying global dynamics of a UCD system. We found that (1) UCDs have a surface number density profile that is shallower than that of blue GCs in the inner ∼70 kpc and as steep as that of red GCs at larger radii; (2) UCDs exhibit a significantly stronger rotation than GCs, and blue GCs seem to have a velocity field that is more consistent with that of the surrounding dwarf ellipticals than with that of UCDs; (3) UCDs have an orbital anisotropy profile that is tangentially biased at radii ≲40 kpc and radially biased farther out, whereas blue GCs become more tangentially biased at larger radii beyond ∼40 kpc; (4) GCs with M {sub *} ≳ 2 × 10{sup 6} M {sub ☉} have rotational properties indistinguishable from the less massive ones, suggesting that it is the size, instead of mass, that differentiates UCDs from GCs as kinematically distinct populations. We conclude that most UCDs in M87 are not consistent with being merely the most luminous and extended examples of otherwise normal GCs. The radially biased orbital structure of UCDs at large radii is in general agreement with the 'tidally threshed dwarf galaxy' scenario.

THE NEXT GENERATION VIRGO CLUSTER SURVEY. VI. THE KINEMATICS OF ULTRA-COMPACT DWARFS AND GLOBULAR CLUSTERS IN M87

International Nuclear Information System (INIS)

Zhang, Hong-Xin; Peng, Eric W.; Li, Biao; Côté, Patrick; Ferrarese, Laura; Gwyn, Stephen D. J.; Blakeslee, John P.; Liu, Chengze; Cuillandre, Jean-Charles; Caldwell, Nelson; Jordán, Andrés; Muñoz, Roberto P.; Puzia, Thomas H.; Lançon, Ariane; Bekki, Kenji; Boselli, Alessandro; Drinkwater, Michael J.; Duc, Pierre-Alain

2015-01-01

The origin of ultra-compact dwarfs (UCDs; r h ≳ 10 pc)—objects larger and more massive than typical globular clusters (GCs), but more compact than typical dwarf galaxies—has been hotly debated in the 15 years since their discovery. Even whether UCDs should be considered galactic in origin, or simply the most extreme star clusters, is not yet settled. We present the dynamical properties of 97 spectroscopically confirmed UCDs and 911 GCs associated with the central cD galaxy of the Virgo cluster, M87. Our UCDs, of which 89% have M *  ≳ 2× 10 6 M ☉ and 92% are as blue as the classic blue GCs, nearly triple the confirmed sample of Virgo UCDs, providing by far the best opportunity for studying global dynamics of a UCD system. We found that (1) UCDs have a surface number density profile that is shallower than that of blue GCs in the inner ∼70 kpc and as steep as that of red GCs at larger radii; (2) UCDs exhibit a significantly stronger rotation than GCs, and blue GCs seem to have a velocity field that is more consistent with that of the surrounding dwarf ellipticals than with that of UCDs; (3) UCDs have an orbital anisotropy profile that is tangentially biased at radii ≲40 kpc and radially biased farther out, whereas blue GCs become more tangentially biased at larger radii beyond ∼40 kpc; (4) GCs with M *  ≳ 2 × 10 6 M ☉ have rotational properties indistinguishable from the less massive ones, suggesting that it is the size, instead of mass, that differentiates UCDs from GCs as kinematically distinct populations. We conclude that most UCDs in M87 are not consistent with being merely the most luminous and extended examples of otherwise normal GCs. The radially biased orbital structure of UCDs at large radii is in general agreement with the 'tidally threshed dwarf galaxy' scenario

NEAR-INFRARED IMAGING AND SPECTROSCOPIC SURVEY OF THE SOUTHERN REGION OF THE YOUNG OPEN CLUSTER NGC 2264

Energy Technology Data Exchange (ETDEWEB)

Marinas, Naibi; Lada, Elizabeth A. [Astronomy Department, University of Florida, Gainesville, FL 32611 (United States); Teixiera, Paula S. [Department of Astrophysics, University of Vienna, Tuerkenschanzstrasse 17, A-1180 Vienna (Austria); Lada, Charles J. [Harvard-Smithsonian CFA, Cambridge, MA (United States)

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.

Origin of γ-rays from young open clusters

International Nuclear Information System (INIS)

Giovannelli, F.; Bednarek, W.; Karakula, S.

1996-01-01

The young open cluster Berkeley 87 was predicted to be associated with the COS B γ-ray source 2CG 075+00 on the basis of the experimental evidence of the presence of a shock front around the Wolf - Rayet star ST3 placed in the inner part of the cluster. The CGRO phase-1 data confirm this identification. Protons accelerated at the shock boundary can produce π deg. via p-p interactions and then γ-rays. With the measured flux F γ (E > 100 MeV) ≅ 9x10 -7 ph cm -2 s -1 and the power-law proton spectrum with spectral index γ = 2, the cosmic-ray-energy-density in the inner part (∼ 0.8 pc radius) of Berk 87 is about 100 times greater than that in the vicinity of the Earth. We have calculated γ-ray spectra expected from the decay of π d eg. produced in p-p interactions. The spectra have been normalized to the observed flux of Berk 87 by using different input proton spectra. The comparison of these normalized spectra with the upper limit at 140 TeV, coming from the CASA-MIA experiment, provides constraints on the initial proton spectrum in Berk 87. The calculated γ-ray spectra of Berk 87 are also compared with the sensitivities of some present and future experiments for energies greater than 100 GeV, such as the Whipple and GAMT experiments. We suggest the possibility of measuring cosmic-ray induced lines, such as the 4.44 MeV and 6.13 MeV nuclear de-excitation lines of 12 C* and 16 O*, respectively, from Berk 87 with the COMPTEL instrument on board the CGRO. Also the positrons resulting from energetic particle interactions should produce 0.511 MeV annihilation radiation from Berk 87, which could be measured by the OSSE instrument on board the CGRO. (author)

Constraints on Ωm and σ8 from the potential-based cluster temperature function

Science.gov (United States)

Angrick, Christian; Pace, Francesco; Bartelmann, Matthias; Roncarelli, Mauro

2015-12-01

The abundance of galaxy clusters is in principle a powerful tool to constrain cosmological parameters, especially Ωm and σ8, due to the exponential dependence in the high-mass regime. While the best observables are the X-ray temperature and luminosity, the abundance of galaxy clusters, however, is conventionally predicted as a function of mass. Hence, the intrinsic scatter and the uncertainties in the scaling relations between mass and either temperature or luminosity lower the reliability of galaxy clusters to constrain cosmological parameters. In this article, we further refine the X-ray temperature function for galaxy clusters by Angrick et al., which is based on the statistics of perturbations in the cosmic gravitational potential and proposed to replace the classical mass-based temperature function, by including a refined analytic merger model and compare the theoretical prediction to results from a cosmological hydrodynamical simulation. Although we find already a good agreement if we compare with a cluster temperature function based on the mass-weighted temperature, including a redshift-dependent scaling between mass-based and spectroscopic temperature yields even better agreement between theoretical model and numerical results. As a proof of concept, incorporating this additional scaling in our model, we constrain the cosmological parameters Ωm and σ8 from an X-ray sample of galaxy clusters and tentatively find agreement with the recent cosmic microwave background based results from the Planck mission at 1σ-level.

M45

Science.gov (United States)

Murdin, P.

2000-11-01

M45 is better known as the Pleiades, a young open cluster in Taurus. Again, this is a very bright (1.6 mag) object known since antiquity. The Pleiades are sometimes referred to as the `Seven Sisters' since that is the number of stars normally visible to the naked eye. In Greek mythology these represent Pleione and her daughters with Atlas: Alcyone, Asterope (a double star), Electra, Maia, Merope,...

The young star cluster population of M51 with LEGUS - I. A comprehensive study of cluster formation and evolution

Science.gov (United States)

Messa, M.; Adamo, A.; Östlin, G.; Calzetti, D.; Grasha, K.; Grebel, E. K.; Shabani, F.; Chandar, R.; Dale, D. A.; Dobbs, C. L.; Elmegreen, B. G.; Fumagalli, M.; Gouliermis, D. A.; Kim, H.; Smith, L. J.; Thilker, D. A.; Tosi, M.; Ubeda, L.; Walterbos, R.; Whitmore, B. C.; Fedorenko, K.; Mahadevan, S.; Andrews, J. E.; Bright, S. N.; Cook, D. O.; Kahre, L.; Nair, P.; Pellerin, A.; Ryon, J. E.; Ahmad, S. D.; Beale, L. P.; Brown, K.; Clarkson, D. A.; Guidarelli, G. C.; Parziale, R.; Turner, J.; Weber, M.

2018-01-01

Recently acquired WFC3 UV (F275W and F336W) imaging mosaics under the Legacy Extragalactic UV Survey (LEGUS), combined with archival ACS data of M51, are used to study the young star cluster (YSC) population of this interacting system. Our newly extracted source catalogue contains 2834 cluster candidates, morphologically classified to be compact and uniform in colour, for which ages, masses and extinction are derived. In this first work we study the main properties of the YSC population of the whole galaxy, considering a mass-limited sample. Both luminosity and mass functions follow a power-law shape with slope -2, but at high luminosities and masses a dearth of sources is observed. The analysis of the mass function suggests that it is best fitted by a Schechter function with slope -2 and a truncation mass at 1.00 ± 0.12 × 105 M⊙. Through Monte Carlo simulations, we confirm this result and link the shape of the luminosity function to the presence of a truncation in the mass function. A mass limited age function analysis, between 10 and 200 Myr, suggests that the cluster population is undergoing only moderate disruption. We observe little variation in the shape of the mass function at masses above 1 × 104 M⊙ over this age range. The fraction of star formation happening in the form of bound clusters in M51 is ∼ 20 per cent in the age range 10-100 Myr and little variation is observed over the whole range from 1 to 200 Myr.

Reactivity of Cubane-Type [(OC)(3)MFe(3)S(4)(SR)(3)](3-) Clusters (M = Mo, W): Interconversion with Cuboidal [Fe(3)S(4)](0) Clusters and Electron Transfer.

Science.gov (United States)

Raebiger, James W.; Crawford, Charles A.; Zhou, Jian; Holm, R. H.

1997-03-12

The title clusters, several examples of which have been reported earlier, have been prepared by two different methods and subjected to structural and reactivity studies. The compounds (Et(4)N)(3)[(OC)(3)MFe(3)S(4)(Smes)(3)].MeCN (M = Mo/W) are isomorphous and crystallize in monoclinic space group P2(1)/n with a = 13.412(1)/13.297(1) Å, b = 19.0380(1)/18.9376(3) Å, c = 26.4210(1)/26.2949(1) Å, beta = 97.87(1)/97.549(1) degrees, and Z = 4. The clusters contain long M-S (2.62/2.59 Å) and M-Fe (3.22/3.19 Å) bonds, consistent with the reported structure of [(OC)(3)MoFe(3)S(4)(SEt)(3)](3-) (3). Reaction of [(OC)(3)MoFe(3)S(4)(LS(3))](3-) (7) with CO in the presence of NaPF(6) affords cuboidal [Fe(3)S(4)(LS(3))](3-) (9), also prepared in this laboratory by another route as a synthetic analogue of protein-bound [Fe(3)S(4)](0) clusters. The clusters [Fe(3)S(4)(SR)(3)](3-) (R = mes, Et), of limited stability, were generated by the same reaction. Treatment of 9 with [M(CO)(3)(MeCN)(3)] affords 7 and its M = W analogue. The clusters [(OC)(3)MFe(3)S(4)(SR)(3)](3-) form a four-member electron transfer series in which the 3- cluster can be once reduced (4-) and twice oxidized (2-, 1-) to afford clusters of the indicated charges. The correct assignment of redox couple to potential in the redox series of six clusters is presented, correcting an earlier misassignment of the redox series of 3. Carbonyl stretching frequencies are shown to be sensitive to cluster oxidation state, showing that the M sites and Fe(3)S(4) fragments are electronically coupled despite the long bond distances. (LS(3) = 1,3,5-tris((4,6-dimethyl-3-mercaptophenyl)thio)-2,4,6-tris(p-tolylthio)benzenate(3-); mes = mesityl.)

Structural calculations and experimental detection of small Ga mS n clusters using time-of-flight mass spectrometry

Science.gov (United States)

BelBruno, J. J.; Sanville, E.; Burnin, A.; Muhangi, A. K.; Malyutin, A.

2009-08-01

Ga mS n clusters were generated by laser ablation of a solid sample of Ga 2S 3. The resulting molecules were analyzed in a time-of-flight mass spectrometer. In addition to atomic species, the spectra exhibited evidence for the existence of GaS3+, GaS4+, GaS5+, and GaS6+ clusters. The potential neutral and cationic structures of the observed Ga mS n clusters were computationally investigated using a density-functional approach. Reference is made to the kinetic pathways required for production of clusters from the starting point of the stoichiometric molecule or molecular ion. Cluster atomization enthalpies are compared with bulk values from the literature.

Structure of the Ebola VP35 interferon inhibitory domain.

Science.gov (United States)

Leung, Daisy W; Ginder, Nathaniel D; Fulton, D Bruce; Nix, Jay; Basler, Christopher F; Honzatko, Richard B; Amarasinghe, Gaya K

2009-01-13

Ebola viruses (EBOVs) cause rare but highly fatal outbreaks of viral hemorrhagic fever in humans, and approved treatments for these infections are currently lacking. The Ebola VP35 protein is multifunctional, acting as a component of the viral RNA polymerase complex, a viral assembly factor, and an inhibitor of host interferon (IFN) production. Mutation of select basic residues within the C-terminal half of VP35 abrogates its dsRNA-binding activity, impairs VP35-mediated IFN antagonism, and attenuates EBOV growth in vitro and in vivo. Because VP35 contributes to viral escape from host innate immunity and is required for EBOV virulence, understanding the structural basis for VP35 dsRNA binding, which correlates with suppression of IFN activity, is of high importance. Here, we report the structure of the C-terminal VP35 IFN inhibitory domain (IID) solved to a resolution of 1.4 A and show that VP35 IID forms a unique fold. In the structure, we identify 2 basic residue clusters, one of which is important for dsRNA binding. The dsRNA binding cluster is centered on Arg-312, a highly conserved residue required for IFN inhibition. Mutation of residues within this cluster significantly changes the surface electrostatic potential and diminishes dsRNA binding activity. The high-resolution structure and the identification of the conserved dsRNA binding residue cluster provide opportunities for antiviral therapeutic design. Our results suggest a structure-based model for dsRNA-mediated innate immune antagonism by Ebola VP35 and other similarly constructed viral antagonists.

KINEMATICS OF OUTER HALO GLOBULAR CLUSTERS IN M31

International Nuclear Information System (INIS)

Veljanoski, J.; Ferguson, A. M. N.; Bernard, E. J.; Peñarrubia, J.; Mackey, A. D.; Huxor, A. P.; Irwin, M. J.; Chapman, S. C.; Côté, P.; Tanvir, N. R.; McConnachie, A.; Ibata, R. A.; Martin, N. F.; Fardal, M.; Lewis, G. F.

2013-01-01

We present the first kinematic analysis of the far outer halo globular cluster (GC) population in the Local Group galaxy M31. Our sample contains 53 objects with projected radii of ∼20-130 kpc, 44 of which have no previous spectroscopic information. GCs with projected radii ∼> 30 kpc are found to exhibit net rotation around the minor axis of M31, in the same sense as the inner GCs, albeit with a smaller amplitude of 79 ± 19 km s –1 . The rotation-corrected velocity dispersion of the full halo GC sample is 106 ± 12 km s –1 , which we observe to decrease with increasing projected radius. We find compelling evidence for kinematic coherence among GCs that project on top of halo substructure, including a clear signature of infall for GCs lying along the northwest stream. Using the tracer mass estimator, we estimate the dynamical mass of M31 within 200 kpc to be M M31 = (1.2-1.5) ± 0.2 × 10 12 M ☉ . This value is highly dependent on the chosen model and assumptions within.

Density functional theory and surface reactivity study of bimetallic AgnYm (n+m = 10) clusters

Science.gov (United States)

Hussain, Riaz; Hussain, Abdullah Ijaz; Chatha, Shahzad Ali Shahid; Hussain, Riaz; Hanif, Usman; Ayub, Khurshid

2018-06-01

Density functional theory calculations have been performed on pure silver (Agn), yttrium (Ym) and bimetallic silver yttrium clusters AgnYm (n + m = 2-10) for reactivity descriptors in order to realize sites for nucleophilic and electrophilic attack. The reactivity descriptors of the clusters, studied as a function of cluster size and shape, reveal the presence of different type of reactive sites in a cluster. The size and shape of the pure silver, yttrium and bimetallic silver yttrium cluster (n = 2-10) strongly influences the number and position of active sites for an electrophilic and/or nucleophilic attack. The trends of reactivities through reactivity descriptors are confirmed through comparison with experimental data for CO binding with silver clusters. Moreover, the adsorption of CO on bimetallic silver yttrium clusters is also evaluated. The trends of binding energies support the reactivity descriptors values. Doping of pure cluster with the other element also influence the hardness, softness and chemical reactivity of the clusters. The softness increases as we increase the number of silver atoms in the cluster, whereas the hardness decreases. The chemical reactivity increases with silver doping whereas it decreases by increasing yttrium concentration. Silver atoms are nucleophilic in small clusters but changed to electrophilic in large clusters.

X ray emission experiments at 1.06 μm and 0.35 μm

International Nuclear Information System (INIS)

Babonneau, D.; Billon, D.; Bocher, J.L.; Di Bona, G.; Fortin, X.; Thiell, G.

1982-10-01

Experiments and analyses on high-Z targets X-ray emission are reported. Two kinds of targets have been used: spherical targets with Octal laser (1.06 μm; 10 13 to 10 13 to 10 15 W/cm 2 ) and planar targets with P102 laser (0.35μm; 3 x 10 13 to 3 x 10 14 W/cm 2 ). The influence of the different parameters (laser flux, laser wavelength, atomic number) on emission rates and spectra is discussed. The results about the emission rates are compared with data from other laboratories and an experimental scaling law is proposed. Temperatures can be evaluated from experimental spectra and related to the different plasma regions. Space-time resolved measurements with a streak camera, from spherical targets, in the (1 - 1.3 keV) energy range allow to determine a velocity: about 6 x 10 6 cm/s for the emission region

Room temperature continuous wave mid-infrared VCSEL operating at 3.35 μm

Science.gov (United States)

Jayaraman, V.; Segal, S.; Lascola, K.; Burgner, C.; Towner, F.; Cazabat, A.; Cole, G. D.; Follman, D.; Heu, P.; Deutsch, C.

2018-02-01

Tunable vertical cavity surface emitting lasers (VCSELs) offer a potentially low cost tunable optical source in the 3-5 μm range that will enable commercial spectroscopic sensing of numerous environmentally and industrially important gases including methane, ethane, nitrous oxide, and carbon monoxide. Thus far, achieving room temperature continuous wave (RTCW) VCSEL operation at wavelengths beyond 3 μm has remained an elusive goal. In this paper, we introduce a new device structure that has enabled RTCW VCSEL operation near the methane absorption lines at 3.35 μm. This device structure employs two GaAs/AlGaAs mirrors wafer-bonded to an optically pumped active region comprising compressively strained type-I InGaAsSb quantum wells grown on a GaSb substrate. This substrate is removed in processing, as is one of the GaAs mirror substrates. The VCSEL structure is optically pumped at room temperature with a CW 1550 nm laser through the GaAs substrate, while the emitted 3.3 μm light is captured out of the top of the device. Power and spectrum shape measured as a function of pump power exhibit clear threshold behavior and robust singlemode spectra.

Asteroseismology of old open clusters with Kepler: direct estimate of the integrated red giant branch mass-loss in NGC 6791 and 6819

DEFF Research Database (Denmark)

Miglio, A.; Brogaard, Karsten Frank; Stello, D.

2012-01-01

Mass-loss of red giant branch (RGB) stars is still poorly determined, despite its crucial role in the chemical enrichment of galaxies. Thanks to the recent detection of solar-like oscillations in G–K giants in open clusters with Kepler, we can now directly determine stellar masses...... for a statistically significant sample of stars in the old open clusters NGC 6791 and 6819. The aim of this work is to constrain the integrated RGB mass-loss by comparing the average mass of stars in the red clump (RC) with that of stars in the low-luminosity portion of the RGB [i.e. stars with L≲L(RC)]. Stellar...... masses were determined by combining the available seismic parameters νmax and Δν with additional photometric constraints and with independent distance estimates. We measured the masses of 40 stars on the RGB and 19 in the RC of the old metal-rich cluster NGC 6791. We find that the difference between...

Analyzing the anodic reactions for iron surface with a porous Al2O3 cluster with the scanning vibrating electrode

Science.gov (United States)

Eliyan, Faysal Fayez

2017-09-01

The Scanning Vibrating Electrode Technique (SVET) was used to analyze the anodic reactions inside and around a porous Al2O3 cluster embedded onto an iron foil. The tests were carried out at -0.7 V vs. Saturated Calomel Electrode, in naturally aerated solutions of 0.1, 0.2, 0.35, and 0.5 M bicarbonate concentration. During 10 h of testing, the SVET showed evidence for a formation of a passive film in and around the cluster, in the scanning area shown in the graphical abstract. In the dilute 0.1 and 0.2 M solutions, the passive films formed slower than those in 0.35 and 0.5 M solutions. In the SVET maps, the passive films showed that they could suppress dissolution to currents comparable to those of slower dissolution under the porous Al2O3 cluster.

Asteroseismology of the Open Clusters NGC 6791, NGC 6811, and NGC 6819 from 19 Months of Kepler Photometry

DEFF Research Database (Denmark)

Corsaro, Enrico; Stello, Dennis; Huber, Daniel

2012-01-01

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 δν02, δν01, and ϵ, which...

An Extremely Lithium-rich Bright Red Giant in the Globular Cluster M3

Science.gov (United States)

Kraft, Robert P.; Peterson, Ruth C.; Guhathakurta, Puragra; Sneden, Christopher; Fulbright, Jon P.; Langer, G. Edward

1999-06-01

We have serendipitously discovered an extremely lithium-rich star on the red giant branch of the globular cluster M3 (NGC 5272). An echelle spectrum obtained with the Keck I High-Resolution Echelle Spectrograph reveals a Li I λ6707 resonance doublet of 520 mÅ equivalent width, and our analysis places the star among the most Li-rich giants known: logε(Li)~=+3.0. We determine the elemental abundances of this star, IV-101, and three other cluster members of similar luminosity and color and conclude that IV-101 has abundance ratios typical of giants in M3 and M13 that have undergone significant mixing. We discuss mechanisms by which a low-mass star may be so enriched in Li, focusing on the mixing of material processed by the hydrogen-burning shell just below the convective envelope. While such enrichment could conceivably happen only rarely, it may in fact regularly occur during giant-branch evolution but be rarely detected because of rapid subsequent Li depletion. Based on observations obtained with the Keck I Telescope of the W. M. Keck Observatory, which is operated by the California Association for Research in Astronomy (CARA), Inc., on behalf of the University of California and the California Institute of Technology. This Letter is dedicated to the memory of our beloved colleague Ed Langer, who died after a brief illness on February 16, 1999. Ed brought a unique theoretical perspective to our globular cluster abundance studies. His career truly embodied the academic ideals of inspiration in both teaching and research. He made friends wherever he traveled, and was an inspiration to students. We will miss him greatly.

Cluster dynamics at different cluster size and incident laser wavelengths

International Nuclear Information System (INIS)

Desai, Tara; Bernardinello, Andrea

2002-01-01

X-ray emission spectra from aluminum clusters of diameter -0.4 μm and gold clusters of dia. ∼1.25 μm are experimentally studied by irradiating the cluster foil targets with 1.06 μm laser, 10 ns (FWHM) at an intensity ∼10 12 W/cm 2 . Aluminum clusters show a different spectra compared to bulk material whereas gold cluster evolve towards bulk gold. Experimental data are analyzed on the basis of cluster dimension, laser wavelength and pulse duration. PIC simulations are performed to study the behavior of clusters at higher intensity I≥10 17 W/cm 2 for different size of the clusters irradiated at different laser wavelengths. Results indicate the dependence of cluster dynamics on cluster size and incident laser wavelength

Red Clump stars in Kepler open cluster NGC 6819

Directory of Open Access Journals (Sweden)

Abedigamba O.P.

2015-01-01

Full Text Available We measure the large frequency separation, Δν, and the frequency of maximum amplitude, νmax, for 10 Red Clump (RC single member (SM stars in the Kepler open cluster NGC 6819. We derive luminosities and masses for each individual RC star. A comparison of the observations with an isochrone of Age = 2.5 Gyr, Z = 0.017 with no mass loss using a statistical techniques is made. A fractional mass loss of 5 ± 3 percent is obtained if we assume that no correction to Δν between RC and red-giant branch (RGB is necessary. However, models suggest that an effective correction of about 1.9 percent in Δν is required to obtain the correct mass of RC stars owing to the different internal structures of stars in the two evolutionary stages. In this case we find that the mass loss in the red giant branch is not significantly different from zero. This finding confirms that of [6]. It is clear that the mass estimate obtained by asteroseismology is not sufficient to deduce the mass loss on the red giant branch. However, it is clearly only a few percent at most.

IR emission and UV extinction in two open clusters

International Nuclear Information System (INIS)

Hackwell, J.A.; Hecht, J.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

Star clusters and associations

International Nuclear Information System (INIS)

Ruprecht, J.; Palous, J.

1983-01-01

All 33 papers presented at the symposium were inputted to INIS. They dealt with open clusters, globular clusters, stellar associations and moving groups, and local kinematics and galactic structures. (E.S.)

A model for the Lin-Shu type density-wave structure of our Galaxy: Line-of-sight and transverse-longitudinal velocities of 242 optically visible open clusters

Science.gov (United States)

Griv, E.; Jiang, I.-G.

2015-02-01

In this paper, the fourth in a series, we examine again one of the implications of the Lin-Shu density-wave theory, specifically, the noncircular systematic motion of the Galactic objects. Our previous investigation is extended by analyzing simultaneously both the line-of-sight and transversal velocities of a sample of open clusters for which velocities, distances and ages are available. The ordinary equations of the Oort-Lindblad theory of galactic differential rotation are used. The minor effects caused by the two-dimensional tightly-wound density waves are also taken into account. The published data of 242 currently known optically visible clusters having distances rsight and transversal along the Galactic longitude velocities are nearly equal. We argue that the resemblance of these Galactic wave structures is so remarkable that no doubt is felt as to the theory's truth with respect to these data. The results obtained allow us to conclude that several low-m trailing density-wave patterns with different number of spiral arms m (say, m=1, 2, 3, and 4), pitch angles (about 5o, 8o, 11o, and 14o, respectively) and amplitudes of the perturbed gravitational potential may coexist in the Galaxy. The latter suggests the asymmetric multiarm, not well-organized (``flocculent'') spiral structure of the system. In memory of Professors Alexei M. Fridman (1940-2010) and Chi Yuan (1937-2008)

CLUSTER DYNAMICS LARGELY SHAPES PROTOPLANETARY DISK SIZES

Energy Technology Data Exchange (ETDEWEB)

Vincke, Kirsten; Pfalzner, Susanne, E-mail: kvincke@mpifr-bonn.mpg.de [Max Planck Institute for Radio Astronomy, Auf dem Hügel 69, D-53121 Bonn (Germany)

2016-09-01

To what degree the cluster environment influences the sizes of protoplanetary disks surrounding young stars is still an open question. This is particularly true for the short-lived clusters typical for the solar neighborhood, in which the stellar density and therefore the influence of the cluster environment change considerably over the first 10 Myr. In previous studies, the effect of the gas on the cluster dynamics has often been neglected; this is remedied here. Using the code NBody6++, we study the stellar dynamics in different developmental phases—embedded, expulsion, and expansion—including the gas, and quantify the effect of fly-bys on the disk size. We concentrate on massive clusters (M {sub cl} ≥ 10{sup 3}–6 ∗ 10{sup 4} M {sub Sun}), which are representative for clusters like the Orion Nebula Cluster (ONC) or NGC 6611. We find that not only the stellar density but also the duration of the embedded phase matters. The densest clusters react fastest to the gas expulsion and drop quickly in density, here 98% of relevant encounters happen before gas expulsion. By contrast, disks in sparser clusters are initially less affected, but because these clusters expand more slowly, 13% of disks are truncated after gas expulsion. For ONC-like clusters, we find that disks larger than 500 au are usually affected by the environment, which corresponds to the observation that 200 au-sized disks are common. For NGC 6611-like clusters, disk sizes are cut-down on average to roughly 100 au. A testable hypothesis would be that the disks in the center of NGC 6611 should be on average ≈20 au and therefore considerably smaller than those in the ONC.

An updated survey of globular clusters in M 31. III. A spectroscopic metallicity scale for the Revised Bologna Catalog

Science.gov (United States)

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

2009-12-01

Aims. We present a new homogeneous set of metallicity estimates based on Lick indices for the old globular clusters of the M 31 galaxy. The final aim is to add homogeneous spectroscopic metallicities to as many entries as possible of the Revised Bologna Catalog of M 31 clusters, by reporting Lick index measurements from any source (literature, new observations, etc.) on the same scale. Methods: New empirical relations of [Fe/H] as a function of [MgFe] and Mg2 indices are based on the well-studied galactic globular clusters, complemented with theoretical model predictions for -0.2≤ [Fe/H]≤ +0.5. Lick indices for M 31 clusters from various literature sources (225 clusters) and from new observations by our team (71 clusters) have been transformed into the Trager et al. system, yielding new metallicity estimates for 245 globular clusters of M 31. Results: Our values are in good agreement with recent estimates based on detailed spectral fitting and with those obtained from color magnitude diagrams of clusters imaged with the Hubble Space Telescope. The typical uncertainty on individual estimates is ≃±0.25 dex, as resulted from the comparison with metallicities derived from color magnitude diagrams of individual clusters. Conclusions: The metallicity distribution of M 31 globular cluster is briefly discussed and compared with that of the Milky Way. Simple parametric statistical tests suggest that the distribution is probably not unimodal. The strong correlation between metallicity and kinematics found in previous studies is confirmed. The most metal-rich GCs tend to be packed into the center of the system and to cluster tightly around the galactic rotation curve defined by the HI disk, while the velocity dispersion about the curve increases with decreasing metallicity. However, also the clusters with [Fe/H]<-1.0 display a clear rotation pattern, at odds with their Milky Way counterparts. Based on observations made at La Palma, at the Spanish Observatorio del Roque

WIYN Open Cluster Study: Binary Orbits and Tidal Circularization in NGC 6819

Science.gov (United States)

Morscher, Meagan B.; Mathieu, R. D.; Kaeppler, S.; Hole, K. T.; Meibom, S.

2006-12-01

We are conducting a comprehensive stellar radial-velocity survey in NGC 6819, a rich, intermediate age ( 2.4 Gyr) open cluster with [Fe/H] -0.05. As of October 2006, we have obtained 7065 radial-velocity measurements of 1409 stars using the WIYN Hydra Multi-Object Spectrograph, with typical velocity measurement precisions of 0.4 km/s. Using an E/I criterion of 3, we have identified 282 velocity variables. In the past year we have expanded the number of final orbital solutions by 45 to a total of more than 80 solutions. In coeval stellar populations, circular binaries tend to have the shortest orbital periods, while longer period binaries show a distribution of non-zero eccentricities. The circularization of the shortest period orbits is the result of an exchange of stellar and orbital angular momentum due to tidal interactions. We defined a population’s tidal circularization period as the longest orbital period at which a binary of typical initial eccentricity has become circularized (e.g., has evolved to an eccentricity e = 0.01) over the lifetime of the cluster (Meibom & Mathieu, 2005, ApJ, 620, 970). We are studying the trend of increasing tidal circularization periods with population age. Preliminary results in NGC 6819 indicate a tidal circularization period of 7.5 days, which is consistent with this overall trend. We will recalculate the tidal circularization period in order to include the latest sample of orbital solutions. This comprehensive survey also allows us to investigate the relative spatial distributions of spectroscopic binaries and other constant-velocity cluster members of similar mass. We find the spectroscopic binaries to be more centrally concentrated at a statistically significant level, which we attribute to energy equipartition processes. MM was supported by REU NSF grant AST-0453442. RDM, SK, KTH, and SM were supported by NSF grant AST-0406615.

Heterometallic clusters arising from cubic Ni3M'O4 (M'=K and Na) entity: Solvothermal synthesis with/without the assistance of microwave

International Nuclear Information System (INIS)

Zhang Shuhua; Zhou Yanling; Sun Xiaojun; Wei, Lian-Qiang; Zeng Minghua; Liang Hong

2009-01-01

Solvothermal reaction assisted with microwave leads to the formation of two unique heterometallic cubic clusters [Ni 3 M'(L) 3 (OH)(CH 3 CN) 3 ] 2 .CH 3 CN (M'=K for 1 and M'=Na for 2, where L is an anion of 2-[(2-hydroxy-3-methoxy-benzylidene)-amino]-ethanesulfonate) with higher efficiency, yields and purity than those without it. The 6-metallacrown-3 [Ni 3 (OH)(L) 3 ] - groups exhibit interesting ion trapping and self-assembly of size-different Na + and K + through form recognition and coordination activity in 1 and 2. The magnetic studies for 1 and 2 suggest that the {Ni 3 M'O 4 } (M'=K and Na) cores both display dominant ferromagnetic interactions from the nature of the binding modes of μ 3 -O (oxidophenyl) and μ 3 -OH. - Graphical abstract: Solvothermal reaction assisted with microwave leads to two heterometallic cubic clusters with 6-metallacrown-3 structure [Ni 3 O 3 (OH)] - acting as a host for a K + or Na + ion. The {Ni 3 M'O 4 } (M'=K, Na) cores display dominant ferromagnetic interactions.

Electronographic photometry of star clusters in the Magellanic Clouds

International Nuclear Information System (INIS)

Walker, M.F.

1979-01-01

Electronographic magnitudes and colours of 78 stars in the cluster Hodge 11 in the Large Magellanic Cloud have been measured to V = 21.5 on electrographs taken with a Spectracon image-converter attached to the focus of the 1.5-m (60-inch) Cerro Tololo reflector. The zero point of the electronographic photometry was provided by photoelectric observations of four stars in the cluster field using the same telescope. The colour-magnitude diagram of the cluster consists of an evolved main sequence, whose termination point corresponds to an age of about 6 x 10 8 yr, but with a giant branch which is displaced blueward by about Δ(B-V) 0 = 0.4 from the positions of the giant branches of open clusters of similar age in our Galaxy. (author)

A 110-ms pulsar, with negative period derivative, in the global cluster M15

International Nuclear Information System (INIS)

Wolszczan, A.; Kulkarni, S.R.; Middleditch, J.; Backer, D.C.; Fruchter, A.S.; Dewey, R.J.

1989-01-01

We report the discovery of a 110-ms pulsar, PSR2127 + 11, in the globular cluster M15 (NGC7078). The results of nine months of timing measurements place the new pulsar about 2'' from the centre of the cluster, and indicate that it is not a member of a close binary system. The measured negative value of the period derivative, P ∼-2 x 10 -17 s s -1 , is probably the result of the pulsar being bodily accelerated in our direction by the gravitational field of the collapsed core of M15. Although PSR2127 + 11 has an unexpectedly long period, we argue that it belongs to the class of 'recycled' pulsars, which have been spun up by accretion in a binary system. (author)

A fast pulsar candidate in the globular cluster M28

International Nuclear Information System (INIS)

Mahoney, M.J.; Erickson, W.C.

1985-01-01

Recent work on radio sources in globular clusters, using the very large Array telescope at 1,465 MHz, revealed a source within the core of M28. Observations of this source at 30.9 and 57.5 MHz have also been carried out, by the authors, using the Clark lake TPT synthesis telescope. The observations show that the source has a spectral index of -2.44. Only pulsars have well-documented spectra which are as steep as this. (U.K.)

The young star cluster population of M51 with LEGUS - II. Testing environmental dependences

Science.gov (United States)

Messa, Matteo; Adamo, A.; Calzetti, D.; Reina-Campos, M.; Colombo, D.; Schinnerer, E.; Chandar, R.; Dale, D. A.; Gouliermis, D. A.; Grasha, K.; Grebel, E. K.; Elmegreen, B. G.; Fumagalli, M.; Johnson, K. E.; Kruijssen, J. M. D.; Östlin, G.; Shabani, F.; Smith, L. J.; Whitmore, B. C.

2018-06-01

It has recently been established that the properties of young star clusters (YSCs) can vary as a function of the galactic environment in which they are found. We use the cluster catalogue produced by the Legacy Extragalactic UV Survey (LEGUS) collaboration to investigate cluster properties in the spiral galaxy M51. We analyse the cluster population as a function of galactocentric distance and in arm and inter-arm regions. The cluster mass function exhibits a similar shape at all radial bins, described by a power law with a slope close to -2 and an exponential truncation around 105 M⊙. While the mass functions of the YSCs in the spiral arm and inter-arm regions have similar truncation masses, the inter-arm region mass function has a significantly steeper slope than the one in the arm region, a trend that is also observed in the giant molecular cloud mass function and predicted by simulations. The age distribution of clusters is dependent on the region considered, and is consistent with rapid disruption only in dense regions, while little disruption is observed at large galactocentric distances and in the inter-arm region. The fraction of stars forming in clusters does not show radial variations, despite the drop in the H2 surface density measured as a function of galactocentric distance. We suggest that the higher disruption rate observed in the inner part of the galaxy is likely at the origin of the observed flat cluster formation efficiency radial profile.

Real-time observation of formation and relaxation dynamics of NH4 in (CH3OH)m(NH3)n clusters.

Science.gov (United States)

Yamada, Yuji; Nishino, Yoko; Fujihara, Akimasa; Ishikawa, Haruki; Fuke, Kiyokazu

2009-03-26

The formation and relaxation dynamics of NH4(CH3OH)m(NH3)n clusters produced by photolysis of ammonia-methanol mixed clusters has been observed by a time-resolved pump-probe method with femtosecond pulse lasers. From the detailed analysis of the time evolutions of the protonated cluster ions, NH4(+)(CH3OH)m(NH3)n, the kinetic model has been constructed, which consists of sequential three-step reaction: ultrafast hydrogen-atom transfer producing the radical pair (NH4-NH2)*, the relaxation process of radical-pair clusters, and dissociation of the solvated NH4 clusters. The initial hydrogen transfer hardly occurs between ammonia and methanol, implying the unfavorable formation of radical pair, (CH3OH2-NH2)*. The remarkable dependence of the time constants in each step on the number and composition of solvents has been explained by the following factors: hydrogen delocalization within the clusters, the internal conversion of the excited-state radical pair, and the stabilization of NH4 by solvation. The dependence of the time profiles on the probe wavelength is attributed to the different ionization efficiency of the NH4(CH3OH)m(NH3)n clusters.

WHY ARE RAPIDLY ROTATING M DWARFS IN THE PLEIADES SO (INFRA)RED? NEW PERIOD MEASUREMENTS CONFIRM ROTATION-DEPENDENT COLOR OFFSETS FROM THE CLUSTER SEQUENCE

Energy Technology Data Exchange (ETDEWEB)

Covey, Kevin R. [Department of Physics and Astronomy, Western Washington University, Bellingham WA 98225-9164 (United States); Agüeros, Marcel A.; Liu, Jiyu [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Law, Nicholas M. [Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599-3255 (United States); Ahmadi, Aida [Max Planck Institute for Radioastronomy, Auf dem Hügel 69, D-53121 Bonn (Germany); Laher, Russ; Surace, Jason [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States); Levitan, David [Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Sesar, Branimir, E-mail: kevin.covey@wwu.edu [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany)

2016-05-10

Stellar rotation periods ( P {sub rot}) measured in open clusters have proved to be extremely useful for studying stars’ angular momentum content and rotationally driven magnetic activity, which are both age- and mass-dependent processes. While P {sub rot} measurements have been obtained for hundreds of solar-mass members of the Pleiades, measurements exist for only a few low-mass (<0.5 M {sub ⊙}) members of this key laboratory for stellar evolution theory. To fill this gap, we report P {sub rot} for 132 low-mass Pleiades members (including nearly 100 with M ≤ 0.45 M {sub ⊙}), measured from photometric monitoring of the cluster conducted by the Palomar Transient Factory in late 2011 and early 2012. These periods extend the portrait of stellar rotation at 125 Myr to the lowest-mass stars and re-establish the Pleiades as a key benchmark for models of the transport and evolution of stellar angular momentum. Combining our new P {sub rot} with precise BVIJHK photometry reported by Stauffer et al. and Kamai et al., we investigate known anomalies in the photometric properties of K and M Pleiades members. We confirm the correlation detected by Kamai et al. between a star's P {sub rot} and position relative to the main sequence in the cluster's color–magnitude diagram. We find that rapid rotators have redder ( V − K ) colors than slower rotators at the same V , indicating that rapid and slow rotators have different binary frequencies and/or photospheric properties. We find no difference in the photometric amplitudes of rapid and slow rotators, indicating that asymmetries in the longitudinal distribution of starspots do not scale grossly with rotation rate.

On the Absolute Age of the Globular Cluster M92

Science.gov (United States)

Di Cecco, A.; Becucci, R.; Bono, G.; Monelli, M.; Stetson, P. B.; Degl'Innocenti, S.; Prada Moroni, P. G.; Nonino, M.; Weiss, A.; Buonanno, R.; Calamida, A.; Caputo, F.; Corsi, C. E.; Ferraro, I.; Iannicola, G.; Pulone, L.; Romaniello, M.; Walker, A. R.

2010-09-01

We present precise and deep optical photometry of the globular M92. Data were collected in three different photometric systems: Sloan Digital Sky Survey (g‧, r‧, i‧, and z‧ MegaCam at CFHT), Johnson-Kron-Cousins (B, V, and I; various ground-based telescopes), and Advanced Camera for Surveys (ACS) Vegamag (F475W, F555W, and F814W; Hubble Space Telescope). Special attention was given to the photometric calibration, and the precision of the ground-based data is generally better than 0.01 mag. We computed a new set of α-enhanced evolutionary models accounting for the gravitational settling of heavy elements at fixed chemical composition ([α/Fe] = +0.3, [Fe/H] = -2.32 dex, and Y = 0.248). The isochrones—assuming the same true distance modulus (μ = 14.74 mag), the same reddening [E(B - V) = 0.025 ± 0.010 mag], and the same reddening law—account for the stellar distribution along the main sequence and the red giant branch in different color-magnitude diagrams (i‧, g‧ - i‧ i‧, and g‧ - r‧ i‧, g‧ - z‧ I, and B - I and F814W and F475W-F814W). The same outcome applies to the comparison between the predicted zero-age horizontal-branch (ZAHB) and the HB stars. We also found a cluster age of 11 ± 1.5 Gyr, in good agreement with previous estimates. The error budget accounts for uncertainties in the input physics and the photometry. To test the possible occurrence of CNO-enhanced stars, we also computed two sets of α- and CNO-enhanced (by a factor of 3) models, both at fixed total metallicity ([M/H] = -2.10 dex) and at fixed iron abundance. We found that the isochrones based on the former set give the same cluster age (11 ± 1.5 Gyr) as the canonical α-enhanced isochrones. The isochrones based on the latter set also give a similar cluster age (10 ± 1.5 Gyr). These findings support previous results concerning the weak sensitivity of cluster isochrones to CNO-enhanced chemical mixtures. This paper makes use of data obtained from the Isaac Newton

Blue stragglers in open clusters - a test of the binary hypothesis

International Nuclear Information System (INIS)

Manteiga, M.; Martinez, R.C.; Beckman, J.E.; Pickles, A.J.

1987-01-01

A search for binaries among 17 blue stragglers in five galactic clusters, NGC 7789, 6633, 6819, 6939, and M 67, has been performed using measurements of radial velocity variations. The spectra were obtained with the Intermediate Dispersion Spectrograph attached to the f/15 Cassegrain focus of the 2.5 m Isaac Newton Telescope at the Spanish Observatory of the Roque de los Muchachos. The wavelength coverage was 200 A, centered at 8510 A with a scale of 12.4 km/sec per pixel. All radial velocity determinations were made using cross-correlation techniques. A velocity resolution of about 3 km/sec/pixel was obtained for the standard radial velocity stars and the brighter program stars. For three of the blue stragglers variations in radial velocity greater than 30 km/sec are reported. 10 references

Neutron-Capture Element Abundances in the Globular Cluster M15.

Science.gov (United States)

Sneden; Johnson; Kraft; Smith; Cowan; Bolte

2000-06-20

High-resolution, high signal-to-noise ratio, blue-violet spectra of three red giant branch tip stars in M15 have been obtained with the Keck I High-Resolution Echelle Spectrograph. These spectra have been analyzed to determine the abundances of several neutron-capture elements, including the radioactive chronometer element thorium. There are two principal results of this study. First, the abundances of the heavier (Z>/=56) elements for each of the three stars is well matched by a scaled solar system r-process abundance distribution. Second, a weighted mean-observed Th/Eu ratio for the stars implies an age for the neutron-capture material in M15 stars of 14+/-3 Gyr, in reasonable agreement with other recent age estimates for Galactic globular clusters.

Liberation of methyl acrylate from metallalactone complexes via M-O ring opening (M = Ni, Pd) with methylation agents

KAUST Repository

Lee, S. Y Tina; Ghani, Amylia Abdul; D'Elia, Valerio; Cokoja, Mirza; Herrmann, Wolfgang A.; Basset, Jean-Marie; Kü hn, Fritz

2013-01-01

Ring opening of various nickela- and palladalactones induced by the cleavage of the M-O bond by methyl trifluoromethanesulfonate (MeOTf) and methyl iodide (MeI) is examined. Experimental evidence supports the mechanism of ring opening by the alkylating agent followed by β-H elimination leading to methyl acrylate and a metal-hydride species. MeOTf shows by far higher efficiency in the lactone ring opening than any other methylating agent including the previously reported methyl iodide. © 2013 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

Major cluster mergers and the location of the brightest cluster galaxy

International Nuclear Information System (INIS)

Martel, Hugo; Robichaud, Fidèle; Barai, Paramita

2014-01-01

Using a large N-body cosmological simulation combined with a subgrid treatment of galaxy formation, merging, and tidal destruction, we study the formation and evolution of the galaxy and cluster population in a comoving volume (100 Mpc) 3 in a ΛCDM universe. At z = 0, our computational volume contains 1788 clusters with mass M cl > 1.1 × 10 12 M ☉ , including 18 massive clusters with M cl > 10 14 M ☉ . It also contains 1, 088, 797 galaxies with mass M gal ≥ 2 × 10 9 M ☉ and luminosity L > 9.5 × 10 5 L ☉ . For each cluster, we identified the brightest cluster galaxy (BCG). We then computed two separate statistics: the fraction f BNC of clusters in which the BCG is not the closest galaxy to the center of the cluster in projection, and the ratio Δv/σ, where Δv is the difference in radial velocity between the BCG and the whole cluster and σ is the radial velocity dispersion of the cluster. We found that f BNC increases from 0.05 for low-mass clusters (M cl ∼ 10 12 M ☉ ) to 0.5 for high-mass clusters (M cl > 10 14 M ☉ ) with very little dependence on cluster redshift. Most of this result turns out to be a projection effect and when we consider three-dimensional distances instead of projected distances, f BNC increases only to 0.2 at high-cluster mass. The values of Δv/σ vary from 0 to 1.8, with median values in the range 0.03-0.15 when considering all clusters, and 0.12-0.31 when considering only massive clusters. These results are consistent with previous observational studies and indicate that the central galaxy paradigm, which states that the BCG should be at rest at the center of the cluster, is usually valid, but exceptions are too common to be ignored. We built merger trees for the 18 most massive clusters in the simulation. Analysis of these trees reveal that 16 of these clusters have experienced 1 or several major or semi-major mergers in the past. These mergers leave each cluster in a non-equilibrium state, but eventually the cluster

The center of the core-cusp globular cluster M15: CFHT and HST Observations, ALLFRAME reductions

Science.gov (United States)

Stetson, Peter B.

1994-03-01

The central brightness cusps seen in some globular clusters are thought to be the relics of a gravothermal core collapse that occurred sometime in the clusters' past. Recent observations show that the centers of such clusters are bluer than their outskirts, indicating that the stellar populations there are somehow different than those farther out, presumably as a result of unusual physical processes that took place in these extremely dense regions. Here I analyze a large body of digital imagery from the Canada-France-Hawaii Telescope and the Hubble Space Telescope to obtain color-magnitude and color-color diagrams for stars in the central two arcminutes of the prototypical core-cusp globular cluster M15 = NGC 7078 = C 2127 + 119. These data were reduced with a new computer program, named ALLFRAME, that is described in detail here for the first time. ALLFRAME makes simultaneous use of the geometric and photometric information from all images of a given field to derive a self-consistent set of positions and magnitudes for all detected starlike objects in that area of sky, thereby extending the range of magnitude and crowding conditions for which useful photometry is obtainable. I tentatively conclude that the color gradient in M15 is due to three distinct effects: (1) there is a deficiency of the brightest red giants in the central regions of the cluster; (2) the giant branch of the dominant cluster population shifts systematically toward the blue as the center of the cluster is approached; and (3) the very center of the cluster (radius approximately equal or less than 12 seconds) contains a large population of blue and yellow stragglers that occupy the area of the color-magnitude diagram between the main-sequence turnoff and the horizontal branch and between the extended blue horizontal branch and the subgiant branch; many of these appear to have a significant ultraviolet excess.

SERPENS CLUSTER B AND VV SER OBSERVED WITH HIGH SPATIAL RESOLUTION AT 70, 160, AND 350 μm

International Nuclear Information System (INIS)

Harvey, Paul; Dunham, Michael M.

2009-01-01

We report on diffraction-limited observations in the far-infrared (FIR) and submillimeter of the Cluster B region of Serpens (G3-G6 Cluster) and of the Herbig Be star to the south, VV Ser. The observations were made with the Spitzer/MIPS instrument in fine-scale mode at 70 μm, in a normal mapping mode at 160 μm (VV Ser only), and the Caltech Submillimeter Observatory (CSO) Submillimeter High Angular Resolution Camera II (SHARC-II) camera at 350 μm (Cluster B only). We use these data to define the spectral energy distributions of the tightly grouped members of Cluster B, many of whose spectral energy distribution (SED)'s peak in the FIR. We compare our results to those of the c2d survey of Serpens and to published models for the FIR emission from VV Ser. We find that values of L bol and T bol calculated with our new photometry show only modest changes from previous values, and that most source SED classifications remain unchanged.

Clustering with position-specific constraints on variance: Applying redescending M-estimators to label-free LC-MS data analysis

Directory of Open Access Journals (Sweden)

Mani D R

2011-08-01

Full Text Available Abstract Background Clustering is a widely applicable pattern recognition method for discovering groups of similar observations in data. While there are a large variety of clustering algorithms, very few of these can enforce constraints on the variation of attributes for data points included in a given cluster. In particular, a clustering algorithm that can limit variation within a cluster according to that cluster's position (centroid location can produce effective and optimal results in many important applications ranging from clustering of silicon pixels or calorimeter cells in high-energy physics to label-free liquid chromatography based mass spectrometry (LC-MS data analysis in proteomics and metabolomics. Results We present MEDEA (M-Estimator with DEterministic Annealing, an M-estimator based, new unsupervised algorithm that is designed to enforce position-specific constraints on variance during the clustering process. The utility of MEDEA is demonstrated by applying it to the problem of "peak matching"--identifying the common LC-MS peaks across multiple samples--in proteomic biomarker discovery. Using real-life datasets, we show that MEDEA not only outperforms current state-of-the-art model-based clustering methods, but also results in an implementation that is significantly more efficient, and hence applicable to much larger LC-MS data sets. Conclusions MEDEA is an effective and efficient solution to the problem of peak matching in label-free LC-MS data. The program implementing the MEDEA algorithm, including datasets, clustering results, and supplementary information is available from the author website at http://www.hephy.at/user/fru/medea/.

The K2 M67 Study: Establishing the Limits of Stellar Rotation Period Measurements in M67 with K2 Campaign 5 Data

Science.gov (United States)

Esselstein, Rebecca; Aigrain, Suzanne; Vanderburg, Andrew; Smith, Jeffrey C.; Meibom, Soren; Van Saders, Jennifer; Mathieu, Robert

2018-06-01

The open cluster M67 offers a unique opportunity to measure rotation periods for solar-age stars across a range of masses, potentially filling a critical gap in the understanding of angular momentum loss in older main sequence stars. The observation of M67 by NASA K2 Campaign 5 provided light curves with high enough precision to make this task possible, albeit challenging, as the pointing instability, 75 day observation window, crowded field, and typically low-amplitude signals mean that determining accurate rotation periods on the order of 25–30 days is inherently difficult. Lingering, non-astrophysical signals with power at ≥25 days found in a set of Campaign 5 A and F stars compounds the problem. To achieve a quantitative understanding of the best-case scenario limits for reliable period detection imposed by these inconveniences, we embarked on a comprehensive set of injection tests, injecting 120,000 sinusoidal signals with periods ranging from 5 to 35 days and amplitudes from 0.05% to 3.0% into real Campaign 5 M67 light curves processed using two different pipelines. We attempted to recover the signals using a normalized version of the Lomb–Scargle periodogram and setting a detection threshold. We find that, while the reliability of detected periods is high, the completeness (sensitivity) drops rapidly with increasing period and decreasing amplitude, maxing at a 15% recovery rate for the solar case (i.e., 25 day period, 0.1% amplitude). This study highlights the need for caution in determining M67 rotation periods from Campaign 5 data, but this can be extended to other clusters observed by K2 (and soon, TESS).

Towards Efficient Mobile M2M Communications: Survey and Open Challenges

Directory of Open Access Journals (Sweden)

Carlos Pereira

2014-10-01

Full Text Available Machine-to-Machine (M2M communications enable networked devices and services to exchange information and perform actions seamlessly without the need for human intervention. They are viewed as a key enabler of the Internet of Things (IoT and ubiquitous applications, like mobile healthcare, telemetry, or intelligent transport systems. We survey existing work on mobile M2M communications, we identify open challenges that have a direct impact on performance and resource usage efficiency, especially the impact on energy efficiency, and we review techniques to improve communications. We review the ETSI standard and application protocols, and draw considerations on the impact of their use in constrained mobile devices. Nowadays, smartphones are equipped with a wide range of embedded sensors, with varied local and wide area connectivity capabilities, and thus they offer a unique opportunity to serve as mobile gateways for other more constrained devices with local connectivity. At the same time, they can gather context data about users and environment from the embedded sensors. These capabilities may be crucial for mobile M2M applications. Finally, in this paper, we consider a scenario where smartphones are used as gateways that collect and aggregate data from sensors in a cellular network. We conclude that, in order for their use to the feasible in terms of a normal depletion time of a smartphone’s battery, it is a good advice to maximize the collection of data necessary to be transmitted from nearby sensors, and maximize the intervals between transmissions. More research is required to devise energy efficient transmission methods that enable the use of smartphones as mobile gateways.

Towards efficient mobile M2M communications: survey and open challenges.

Science.gov (United States)

Pereira, Carlos; Aguiar, Ana

2014-10-20

Machine-to-Machine (M2M) communications enable networked devices and services to exchange information and perform actions seamlessly without the need for human intervention. They are viewed as a key enabler of the Internet of Things (IoT) and ubiquitous applications, like mobile healthcare, telemetry, or intelligent transport systems. We survey existing work on mobile M2M communications, we identify open challenges that have a direct impact on performance and resource usage efficiency, especially the impact on energy efficiency, and we review techniques to improve communications. We review the ETSI standard and application protocols, and draw considerations on the impact of their use in constrained mobile devices. Nowadays, smartphones are equipped with a wide range of embedded sensors, with varied local and wide area connectivity capabilities, and thus they offer a unique opportunity to serve as mobile gateways for other more constrained devices with local connectivity. At the same time, they can gather context data about users and environment from the embedded sensors. These capabilities may be crucial for mobile M2M applications. Finally, in this paper, we consider a scenario where smartphones are used as gateways that collect and aggregate data from sensors in a cellular network. We conclude that, in order for their use to the feasible in terms of a normal depletion time of a smartphone's battery, it is a good advice to maximize the collection of data necessary to be transmitted from nearby sensors, and maximize the intervals between transmissions. More research is required to devise energy efficient transmission methods that enable the use of smartphones as mobile gateways.

Dynamical mass of a star cluster in M 83: a test of fibre-fed multi-object spectroscopy

NARCIS (Netherlands)

Moll, S.L.; Grijs, R.; Anders, P.; Crowther, P.A.; Larsen, S.S.; Smith, L.J.; Portegies Zwart, S.F.

2008-01-01

Aims. We obtained VLT/FLAMES+UVES high-resolution, fibre-fed spectroscopy of five young massive clusters (YMCs) in M 83 (NGC 5236). This forms the basis of a pilot study testing the feasibility of using fibre-fed spectroscopy to measure the velocity dispersions of several clusters simultaneously, in

Dynamical mass of a star cluster in M 83: A test of fibre-fed multi-object spectroscopy

NARCIS (Netherlands)

Moll, S.L.; de Grijs, R.; Anders, P.; Crowther, P.A.; Larsen, S.S.; Smith, L.J.; Portegies Zwart, S.F.

2008-01-01

Aims. We obtained VLT/FLAMES+UVES high-resolution, fibre-fed spectroscopy of five young massive clusters (YMCs) in M 83 (NGC 5236). This forms the basis of a pilot study testing the feasibility of using fibre-fed spectroscopy to measure the velocity dispersions of several clusters simultaneously, in

Globular cluster formation and evolution in the context of cosmological galaxy assembly: open questions

Science.gov (United States)

Forbes, Duncan A.; Bastian, Nate; Gieles, Mark; Crain, Robert A.; Kruijssen, J. M. Diederik; Larsen, Søren S.; Ploeckinger, Sylvia; Agertz, Oscar; Trenti, Michele; Ferguson, Annette M. N.; Pfeffer, Joel; Gnedin, Oleg Y.

2018-02-01

We discuss some of the key open questions regarding the formation and evolution of globular clusters (GCs) during galaxy formation and assembly within a cosmological framework. The current state of the art for both observations and simulations is described, and we briefly mention directions for future research. The oldest GCs have ages greater than or equal to 12.5 Gyr and formed around the time of reionization. Resolved colour-magnitude diagrams of Milky Way GCs and direct imaging of lensed proto-GCs at z˜6 with the James Webb Space Telescope (JWST) promise further insight. GCs are known to host multiple populations of stars with variations in their chemical abundances. Recently, such multiple populations have been detected in ˜2 Gyr old compact, massive star clusters. This suggests a common, single pathway for the formation of GCs at high and low redshift. The shape of the initial mass function for GCs remains unknown; however, for massive galaxies a power-law mass function is favoured. Significant progress has been made recently modelling GC formation in the context of galaxy formation, with success in reproducing many of the observed GC-galaxy scaling relations.

Link-Prediction Enhanced Consensus Clustering for Complex Networks (Open Access)

Science.gov (United States)

2016-05-20

RESEARCH ARTICLE Link-Prediction Enhanced Consensus Clustering for Complex Networks Matthew Burgess1*, Eytan Adar1,2, Michael Cafarella1 1Computer...consensus clustering algorithm to enhance community detection on incomplete networks. Our framework utilizes existing community detection algorithms that...types of complex networks exhibit community structure: groups of highly connected nodes. Communities or clusters often reflect nodes that share similar

Performance Characteristics of Hybrid MPI/OpenMP Implementations of NAS Parallel Benchmarks SP and BT on Large-Scale Multicore Clusters

KAUST Repository

Wu, X.; Taylor, V.

2011-01-01

The NAS Parallel Benchmarks (NPB) are well-known applications with fixed algorithms for evaluating parallel systems and tools. Multicore clusters provide a natural programming paradigm for hybrid programs, whereby OpenMP can be used with the data sharing with the multicores that comprise a node, and MPI can be used with the communication between nodes. In this paper, we use Scalar Pentadiagonal (SP) and Block Tridiagonal (BT) benchmarks of MPI NPB 3.3 as a basis for a comparative approach to implement hybrid MPI/OpenMP versions of SP and BT. In particular, we can compare the performance of the hybrid SP and BT with the MPI counterparts on large-scale multicore clusters, Intrepid (BlueGene/P) at Argonne National Laboratory and Jaguar (Cray XT4/5) at Oak Ridge National Laboratory. Our performance results indicate that the hybrid SP outperforms the MPI SP by up to 20.76 %, and the hybrid BT outperforms the MPI BT by up to 8.58 % on up to 10 000 cores on Intrepid and Jaguar. We also use performance tools and MPI trace libraries available on these clusters to further investigate the performance characteristics of the hybrid SP and BT. © 2011 The Author. Published by Oxford University Press on behalf of The British Computer Society. All rights reserved.

Performance Characteristics of Hybrid MPI/OpenMP Implementations of NAS Parallel Benchmarks SP and BT on Large-Scale Multicore Clusters

KAUST Repository

Wu, X.

2011-07-18

The NAS Parallel Benchmarks (NPB) are well-known applications with fixed algorithms for evaluating parallel systems and tools. Multicore clusters provide a natural programming paradigm for hybrid programs, whereby OpenMP can be used with the data sharing with the multicores that comprise a node, and MPI can be used with the communication between nodes. In this paper, we use Scalar Pentadiagonal (SP) and Block Tridiagonal (BT) benchmarks of MPI NPB 3.3 as a basis for a comparative approach to implement hybrid MPI/OpenMP versions of SP and BT. In particular, we can compare the performance of the hybrid SP and BT with the MPI counterparts on large-scale multicore clusters, Intrepid (BlueGene/P) at Argonne National Laboratory and Jaguar (Cray XT4/5) at Oak Ridge National Laboratory. Our performance results indicate that the hybrid SP outperforms the MPI SP by up to 20.76 %, and the hybrid BT outperforms the MPI BT by up to 8.58 % on up to 10 000 cores on Intrepid and Jaguar. We also use performance tools and MPI trace libraries available on these clusters to further investigate the performance characteristics of the hybrid SP and BT. © 2011 The Author. Published by Oxford University Press on behalf of The British Computer Society. All rights reserved.

To the Edge of M87 and Beyond: Spectroscopy of Intracluster Globular Clusters and Ultracompact Dwarfs in the Virgo Cluster

Energy Technology Data Exchange (ETDEWEB)

Ko, Youkyung; Lee, Myung Gyoon; Jang, In Sung [Astronomy Program, Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826 (Korea, Republic of); Hwang, Ho Seong [Quantum Universe Center, Korea Institute for Advanced Study, 85 Hoegiro, Dongdaemun-gu, Seoul 02455 (Korea, Republic of); Park, Hong Soo; Hwang, Narae; Park, Byeong-Gon [Korea Astronomy and Space Science Institute, 776 Daedeokdae-Ro, Yuseong-Gu, Daejeon 34055 (Korea, Republic of); Lim, Sungsoon [Department of Astronomy, Peking University, Beijing 100871 (China); Sohn, Jubee, E-mail: ykko@astro.snu.ac.kr, E-mail: mglee@astro.snu.ac.kr [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States)

2017-02-01

We present the results of a wide-field spectroscopic survey of globular clusters (GCs) in the Virgo cluster. We obtain spectra for 201 GCs and 55 ultracompact dwarfs (UCDs) using Hectospec on the Multiple-Mirror Telescope and derive their radial velocities. We identify 46 genuine intracluster GCs (IGCs), not associated with any Virgo galaxies, using the 3D GMM test on the spatial and radial velocity distribution. They are located at a projected distance 200 kpc≲R ≲500 kpc from the center of M87. The radial velocity distribution of these IGCs shows two peaks, one at v{sub r} = 1023 km s{sup −1}, associated with the Virgo main body, and another at v {sub r}=36 km s{sup −1}, associated with the infalling structure. The velocity dispersion of the IGCs in the Virgo main body is σ{sub GC}∼314 km s{sup −1}, which is smoothly connected to the velocity dispersion profile of M87 GCs but is much lower than that of dwarf galaxies in the same survey field, σ {sub dwarf}∼608 km s{sup −1}. The UCDs are more centrally concentrated on massive galaxies - M87, M86, and M84. The radial velocity dispersion of the UCD system is much smaller than that of dwarf galaxies. Our results confirm the large-scale distribution of Virgo IGCs indicated by previous photometric surveys. The color distribution of the confirmed IGCs shows a bimodality similar to that of M87 GCs. This indicates that most IGCs are stripped off dwarf galaxies and some off massive galaxies in the Virgo.

SIGNATURES OF DARK MATTER BURNING IN NUCLEAR STAR CLUSTERS

International Nuclear Information System (INIS)

Casanellas, Jordi; Lopes, IlIdio

2011-01-01

In order to characterize how dark matter (DM) annihilation inside stars changes the aspect of a stellar cluster, we computed the evolution until the ignition of the He burning of stars from 0.7 M sun to 3.5 M sun within halos of DM with different characteristics. We found that, when a cluster is surrounded by a dense DM halo, the positions of the cluster' stars in the H-R diagram have a brighter and hotter turnoff point than in the classical scenario without DM, therefore giving the cluster a younger appearance. The high DM densities required to produce these effects are expected only in very specific locations, such as near the center of our Galaxy. In particular, if DM is formed by the 8 GeV weakly interacting massive particles recently invoked to reconcile the results from direct detection experiments, then this signature is predicted for halos of DM with a density ρ χ = 3 x 10 5 GeV cm -3 . A DM density gradient inside the stellar cluster would result in a broader main sequence, turnoff, and red giant branch regions. Moreover, we found that for very high DM halo densities the bottom of the isochrones in the H-R diagram rises to higher luminosities, leading to a characteristic signature on the stellar cluster. We argue that this signature could be used to indirectly probe the presence of DM particles in the location of a cluster.

GALAXY CLUSTERS AT HIGH REDSHIFT AND EVOLUTION OF BRIGHTEST CLUSTER GALAXIES

International Nuclear Information System (INIS)

Wen, Z. L.; Han, J. L.

2011-01-01

Identification of high-redshift clusters is important for studies of cosmology and cluster evolution. Using photometric redshifts of galaxies, we identify 631 clusters from the Canada-France-Hawaii Telescope (CFHT) wide field, 202 clusters from the CFHT deep field, 187 clusters from the Cosmic Evolution Survey (COSMOS) field, and 737 clusters from the Spitzer Wide-area InfraRed Extragalactic Survey (SWIRE) field. The redshifts of these clusters are in the range 0.1 ∼ + - m 3.6 μ m colors of the BCGs are consistent with a stellar population synthesis model in which the BCGs are formed at redshift z f ≥ 2 and evolved passively. The g' - z' and B - m 3.6μm colors of the BCGs at redshifts z > 0.8 are systematically bluer than the passive evolution model for galaxies formed at z f ∼ 2, indicating star formation in high-redshift BCGs.

THE LUMINOSITY, MASS, AND AGE DISTRIBUTIONS OF COMPACT STAR CLUSTERS IN M83 BASED ON HUBBLE SPACE TELESCOPE/WIDE FIELD CAMERA 3 OBSERVATIONS

International Nuclear Information System (INIS)

Chandar, Rupali; Whitmore, Bradley C.; Mutchler, Max; Bond, Howard; Kim, Hwihyun; Kaleida, Catherine; Calzetti, Daniela; Saha, Abhijit; O'Connell, Robert; Balick, Bruce; Carollo, Marcella; Disney, Michael; Dopita, Michael A.; Frogel, Jay A.; Hall, Donald; Holtzman, Jon A.; Kimble, Randy A.; McCarthy, Patrick; Paresce, Francesco; Silk, Joe

2010-01-01

The newly installed Wide Field Camera 3 (WFC3) on the Hubble Space Telescope has been used to obtain multi-band images of the nearby spiral galaxy M83. These new observations are the deepest and highest resolution images ever taken of a grand-design spiral, particularly in the near-ultraviolet, and allow us to better differentiate compact star clusters from individual stars and to measure the luminosities of even faint clusters in the U band. We find that the luminosity function (LF) for clusters outside of the very crowded starburst nucleus can be approximated by a power law, dN/dL ∝ L α , with α = -2.04 ± 0.08, down to M V ∼ -5.5. We test the sensitivity of the LF to different selection techniques, filters, binning, and aperture correction determinations, and find that none of these contribute significantly to uncertainties in α. We estimate ages and masses for the clusters by comparing their measured UBVI, Hα colors with predictions from single stellar population models. The age distribution of the clusters can be approximated by a power law, dN/dτ ∝ τ γ , with γ = -0.9 ± 0.2, for M ∼> few x 10 3 M sun and τ ∼ 8 yr. This indicates that clusters are disrupted quickly, with ∼80%-90% disrupted each decade in age over this time. The mass function of clusters over the same M-τ range is a power law, dN/dM ∝ M β , with β = -1.94 ± 0.16, and does not have bends or show curvature at either high or low masses. Therefore, we do not find evidence for a physical upper mass limit, M C , or for the earlier disruption of lower mass clusters when compared with higher mass clusters, i.e., mass-dependent disruption. We briefly discuss these implications for the formation and disruption of the clusters.

Similarity transformed equation of motion coupled-cluster theory based on an unrestricted Hartree-Fock reference for applications to high-spin open-shell systems.

Science.gov (United States)

Huntington, Lee M J; Krupička, Martin; Neese, Frank; Izsák, Róbert

2017-11-07

The similarity transformed equation of motion coupled-cluster approach is extended for applications to high-spin open-shell systems, within the unrestricted Hartree-Fock (UHF) formalism. An automatic active space selection scheme has also been implemented such that calculations can be performed in a black-box fashion. It is observed that both the canonical and automatic active space selecting similarity transformed equation of motion (STEOM) approaches perform about as well as the more expensive equation of motion coupled-cluster singles doubles (EOM-CCSD) method for the calculation of the excitation energies of doublet radicals. The automatic active space selecting UHF STEOM approach can therefore be employed as a viable, lower scaling alternative to UHF EOM-CCSD for the calculation of excited states in high-spin open-shell systems.

Similarity transformed equation of motion coupled-cluster theory based on an unrestricted Hartree-Fock reference for applications to high-spin open-shell systems

Science.gov (United States)

Huntington, Lee M. J.; Krupička, Martin; Neese, Frank; Izsák, Róbert

2017-11-01

The similarity transformed equation of motion coupled-cluster approach is extended for applications to high-spin open-shell systems, within the unrestricted Hartree-Fock (UHF) formalism. An automatic active space selection scheme has also been implemented such that calculations can be performed in a black-box fashion. It is observed that both the canonical and automatic active space selecting similarity transformed equation of motion (STEOM) approaches perform about as well as the more expensive equation of motion coupled-cluster singles doubles (EOM-CCSD) method for the calculation of the excitation energies of doublet radicals. The automatic active space selecting UHF STEOM approach can therefore be employed as a viable, lower scaling alternative to UHF EOM-CCSD for the calculation of excited states in high-spin open-shell systems.

The Peculiar Radial Distribution of Multiple Populations in the Massive Globular Cluster M80

Science.gov (United States)

Dalessandro, E.; Cadelano, M.; Vesperini, E.; Salaris, M.; Ferraro, F. R.; Lanzoni, B.; Raso, S.; Hong, J.; Webb, J. J.; Zocchi, A.

2018-05-01

We present a detailed analysis of the radial distribution of light-element multiple populations (LE-MPs) in the massive and dense globular cluster M80, based on a combination of UV and optical Hubble Space Telescope data. Surprisingly, we find that first-generation (FG) stars (FG) are significantly more centrally concentrated than extreme second-generation (SG) stars out to ∼2.5r h from the cluster center. To understand the origin of such peculiar behavior, we used a set of N-body simulations following the long-term dynamical evolution of LE-MPs. We find that, given the advanced dynamical state of the cluster, the observed difference does not depend on the primordial relative distributions of FG and SG stars. On the contrary, a difference of ∼0.05–0.10 M ⊙ between the average masses of the two subpopulations is needed to account for the observed radial distributions. We argue that such a mass difference might be the result of the higher He abundance of SG stars (of the order of ΔY ∼ 0.05–0.06) with respect to FG stars. Interestingly, we find that a similar He variation is necessary to reproduce the horizontal branch morphology of M80. These results demonstrate that differences in mass among LE-MPs, due to different He content, should be properly taken into account for a correct interpretation of their radial distribution, at least in dynamically evolved systems.

A comprehensive study of the young open star cluster NGC 6611 based on deep VRI CCD images and 2MASS data

Directory of Open Access Journals (Sweden)

I.M. Selim

2016-06-01

Full Text Available In the present study, we have used Deep CCD images of the extremely young open star cluster NGC 6611, up to a limiting magnitude of V ∼ 22.86 mag in V, R and I passbands. The resulting color-magnitude V; (V–I diagram as well as their radial density profiles has been determined. Using 2MASS data, we confirmed the consistency between the 2MASS photometry, by fitting isochrones, the extinction E(V–I = 0.530 ± 0.04 mag, E(J–H = 0.31 ± 0.02, from the color magnitude diagram the cluster distance =2.2 ± 0.21 kpc and age = 3.6 Myr, based on the fitting of theoretical stellar isochrones of solar metallicity Z = 0.019. The distance modulus of the cluster is estimated at 12.3. The radial stellar density profiles and the cluster center have been determined by two methods. The core and cluster radii are determined from the radial stellar density profiles. Only about 40% of the cluster members are present in the core region. The cluster luminosity function has been calculated. The mass function slope of the entire cluster is ∼−0.67 ± 0.12. The effects of mass segregation, most probably due to dynamical evolution, have been observed in the cluster.

Design, Characterization and Analysis of a 0.35 μm CMOS SPAD

Directory of Open Access Journals (Sweden)

Khalil Jradi

2014-12-01

Full Text Available Most of the works about single-photon detectors rely on Single Photon Avalanche Diodes (SPADs designed with dedicated technological processes in order to achieve single-photon sensitivity and excellent timing resolution. Instead, this paper focuses on the implementation of high-performance SPADs detectors manufactured in a standard 0.35-micron opto-CMOS technology provided by AMS. We propose a series of low-noise SPADs designed with a variable pitch from 20 µm down to 5 µm. This opens the further way to the integration of large arrays of optimized SPAD pixels with pitch of a few micrometers in order to provide high-resolution single-photon imagers. We experimentally demonstrate that a 20-micron SPAD appears as the most relevant detector in terms of Signal-to-Noise ratio, enabling emergence of large arrays of SPAD.

Infrared photometry of open star clusters Alessi 16, Chupina1, Juchert-Saloran1 and Patchick 78

Directory of Open Access Journals (Sweden)

I.M. Selim

2016-12-01

Full Text Available In this work we present JHKs near-infrared photometric study for the poorly studied open star clusters Alessi 16, Chupina1, Juchert-Saloran1 and Patchick 78 based on 2MASS data. Astrometry and photometric parameters have been calculated using the Redial Density Profile (RDP and Color Magnitude Diagrams (CMDs fittings. Radius, distance, reddening, age, Luminosity Function (LF, Mass Function (MF, total mass and relaxation time have been calculated from the analysis of 2MASS data. The stellar memberships have been determined using a new method.

Dense Fe cluster-assembled films by energetic cluster deposition

International Nuclear Information System (INIS)

Peng, D.L.; Yamada, H.; Hihara, T.; Uchida, T.; Sumiyama, K.

2004-01-01

High-density Fe cluster-assembled films were produced at room temperature by an energetic cluster deposition. Though cluster-assemblies are usually sooty and porous, the present Fe cluster-assembled films are lustrous and dense, revealing a soft magnetic behavior. Size-monodispersed Fe clusters with the mean cluster size d=9 nm were synthesized using a plasma-gas-condensation technique. Ionized clusters are accelerated electrically and deposited onto the substrate together with neutral clusters from the same cluster source. Packing fraction and saturation magnetic flux density increase rapidly and magnetic coercivity decreases remarkably with increasing acceleration voltage. The Fe cluster-assembled film obtained at the acceleration voltage of -20 kV has a packing fraction of 0.86±0.03, saturation magnetic flux density of 1.78±0.05 Wb/m 2 , and coercivity value smaller than 80 A/m. The resistivity at room temperature is ten times larger than that of bulk Fe metal

ULTRAVIOLET-BRIGHT STELLAR POPULATIONS AND THEIR EVOLUTIONARY IMPLICATIONS IN THE COLLAPSED-CORE CLUSTER M15

International Nuclear Information System (INIS)

Haurberg, Nathalie C.; Lubell, Gabriel M. G.; Cohn, Haldan N.; Lugger, Phyllis M.; Anderson, Jay; Cool, Adrienne M.; Serenelli, Aldo M.

2010-01-01

We performed deep photometry of the central region of the Galactic globular cluster M15 from archival Hubble Space Telescope data taken on the High Resolution Channel and Solar Blind Channel of the Advanced Camera for Surveys. Our data set consists of images in far-UV (FUV 140 ; F140LP), near-UV (NUV 220 ; F220W), and blue (B 435 ; F435W) filters. The addition of an optical filter complements previous UV work on M15 by providing an additional constraint on the UV-bright stellar populations. Using color-magnitude diagrams (CMDs), we identified several populations that arise from non-canonical evolution including candidate blue stragglers, extreme horizontal branch (HB) stars, blue hook (BHk) stars, cataclysmic variables (CVs), and helium-core white dwarfs (He WDs). Due to preliminary identification of several He WD and BHk candidates, we add M15 as a cluster containing an He WD sequence and suggest it be included among clusters with a BHk population. We also investigated a subset of CV candidates that appear in the gap between the main sequence (MS) and WDs in FUV 140 -NUV 220 but lie securely on the MS in NUV 220 -B 435 . These stars may represent a magnetic CV or detached WD-MS binary population. Additionally, we analyze our candidate He WDs using model cooling sequences to estimate their masses and ages and investigate the plausibility of thin versus thick hydrogen envelopes. Finally, we identify a class of UV-bright stars that lie between the HB and WD cooling sequences, a location not usually populated on cluster CMDs. We conclude these stars may be young, low-mass He WDs.

Relics in galaxy clusters at high radio frequencies

Science.gov (United States)

Kierdorf, M.; Beck, R.; Hoeft, M.; Klein, U.; van Weeren, R. J.; Forman, W. R.; Jones, C.

2017-04-01

Aims: We investigated the magnetic properties of radio relics located at the peripheries of galaxy clusters at high radio frequencies, where the emission is expected to be free of Faraday depolarization. The degree of polarization is a measure of the magnetic field compression and, hence, the Mach number. Polarization observations can also be used to confirm relic candidates. Methods: We observed three radio relics in galaxy clusters and one radio relic candidate at 4.85 and 8.35 GHz in total emission and linearly polarized emission with the Effelsberg 100-m telescope. In addition, we observed one radio relic candidate in X-rays with the Chandra telescope. We derived maps of polarization angle, polarization degree, and Faraday rotation measures. Results: The radio spectra of the integrated emission below 8.35 GHz can be well fitted by single power laws for all four relics. The flat spectra (spectral indices of 0.9 and 1.0) for the so-called Sausage relic in cluster CIZA J2242+53 and the so-called Toothbrush relic in cluster 1RXS 06+42 indicate that models describing the origin of relics have to include effects beyond the assumptions of diffuse shock acceleration. The spectra of the radio relics in ZwCl 0008+52 and in Abell 1612 are steep, as expected from weak shocks (Mach number ≈2.4). Polarization observations of radio relics offer a method of measuring the strength and geometry of the shock front. We find polarization degrees of more than 50% in the two prominent Mpc-sized radio relics, the Sausage and the Toothbrush, which are among the highest percentages of linear polarization detected in any extragalactic radio source to date. This is remarkable because the large beam size of the Effelsberg single-dish telescope corresponds to linear extensions of about 300 kpc at 8.35 GHz at the distances of the relics. The high degree of polarization indicates that the magnetic field vectors are almost perfectly aligned along the relic structure, as expected for shock

Electronic, Magnetic, and Redox Properties of [MFe(3)S(4)] Clusters (M = Cd, Cu, Cr) in Pyrococcus furiosus Ferredoxin.

Science.gov (United States)

Staples, Christopher R.; Dhawan, Ish K.; Finnegan, Michael G.; Dwinell, Derek A.; Zhou, Zhi Hao; Huang, Heshu; Verhagen, Marc F. J. M.; Adams, Michael W. W.; Johnson, Michael K.

1997-12-03

The ground- and excited-state properties of heterometallic [CuFe(3)S(4)](2+,+), [CdFe(3)S(4)](2+,+), and [CrFe(3)S(4)](2+,+) cubane clusters assembled in Pyrococcus furiosus ferredoxin have been investigated by the combination of EPR and variable-temperature/variable-field magnetic circular dichroism (MCD) studies. The results indicate Cd(2+) incorporation into [Fe(3)S(4)](0,-) cluster fragments to yield S = 2 [CdFe(3)S(4)](2+) and S = (5)/(2) [CdFe(3)S(4)](+) clusters and Cu(+) incorporation into [Fe(3)S(4)](+,0) cluster fragments to yield S = (1)/(2) [CuFe(3)S(4)](2+) and S = 2 [CuFe(3)S(4)](+) clusters. This is the first report of the preparation of cubane type [CrFe(3)S(4)](2+,+) clusters, and the combination of EPR and MCD results indicates S = 0 and S = (3)/(2) ground states for the oxidized and reduced forms, respectively. Midpoint potentials for the [CdFe(3)S(4)](2+,+), [CrFe(3)S(4)](2+,+), and [CuFe(3)S(4)](2+,+) couples, E(m) = -470 +/- 15, -440 +/- 10, and +190 +/- 10 mV (vs NHE), respectively, were determined by EPR-monitored redox titrations or direct electrochemistry at a glassy carbon electrode. The trends in redox potential, ground-state spin, and electron delocalization of [MFe(3)S(4)](2+,+) clusters in P. furiosus ferredoxin are discussed as a function of heterometal (M = Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Tl).

Open cluster Dolidze 25: Stellar parameters and the metallicity in the Galactic anticentre

Science.gov (United States)

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.

Polyunsaturated fatty acids are potent openers of human M-channels expressed in Xenopus laevis oocytes

DEFF Research Database (Denmark)

Liin, Sara I; Karlsson, Urban; Bentzen, Bo Hjorth

2016-01-01

the threshold current to evoke action potentials in dorsal root ganglion neurons. The polyunsaturated fatty acids docosahexaenoic acid, α-linolenic acid, and eicosapentaenoic acid facilitated opening of the human M-channel, comprised of the heteromeric human KV 7.2/3 channel expressed in Xenopus oocytes......, by shifting the conductance-versus-voltage curve towards more negative voltages (by -7.4 to -11.3 mV by 70 μM). Uncharged docosahexaenoic acid methyl ester and monounsaturated oleic acid did not facilitate opening of the human KV 7.2/3 channel. CONCLUSIONS: These findings suggest that circulating...... polyunsaturated fatty acids, with a minimum requirement of multiple double bonds and a charged carboxyl group, dampen excitability by opening neuronal M-channels. Collectively, our data bring light to the molecular targets of polyunsaturated fatty acids and thus a possible mechanism by which polyunsaturated fatty...

A Framework Based on Sustainability, Open Innovation, and Value Cocreation Paradigms—A Case in an Italian Maritime Cluster

Directory of Open Access Journals (Sweden)

Daniela Rupo

2018-03-01

Full Text Available The paper deals with a case study in an Italian maritime cluster seen through a multiple paradigms framework, based on Sustainability (SUS, Open Innovation (OI, and Value Co-creation (VCc. The proposed theoretical framework helps to interpret a true phenomenon consisting of the design of a new product with a prototype created in a network of multiple actors. The approach adopted stems in part from recent writings in qualitative research methodology and is quite apt in this context considering the qualitative, confirmatory nature of this work. The prototype named “TESEO I” was realized through open innovation aimed at sustainability, not only directed at environmental aspects but synergistically with value cocreation, which emerged from interaction among the actors, while also including social and economic aspects. The work concludes with a discussion of theoretical implications related to the proposed framework and the results that emerged from the case study, with both referring to sustainability, open innovation, and value cocreation.

A 110-ms pulsar, with negative period derivative, in the globular cluster M15

Science.gov (United States)

Wolszczan, A.; Kulkarni, S. R.; Middleditch, J.; Backer, D. C.; Fruchter, A. S.; Dewey, R. J.

1989-01-01

The discovery of a 110-ms pulsar, PSR2127+11, in the globular cluster M15, is reported. The results of nine months of timing measurements place the new pulsar about 2 arcsec from the center of the cluster, and indicate that it is not a member of a close binary system. The measured negative value of the period derivative is probably the result of the pulsar being bodily accelerated in our direction by the gravitational field of the collapsed core of M15. This apparently overwhelms a positive contribution to the period derivative due to magnetic braking. Although the pulsar has an unexpectedly long period, it is argued that it belongs to the class of 'recycled' pulsars, which have been spun up by accretion in a binary system. The subsequent loss of the pulsar's companion is probably due to disruption of the system by close encounters with other stars.

PREFACE: Nuclear Cluster Conference; Cluster'07

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Freer, Martin

2008-05-01

The Cluster Conference is a long-running conference series dating back to the 1960's, the first being initiated by Wildermuth in Bochum, Germany, in 1969. The most recent meeting was held in Nara, Japan, in 2003, and in 2007 the 9th Cluster Conference was held in Stratford-upon-Avon, UK. As the name suggests the town of Stratford lies upon the River Avon, and shortly before the conference, due to unprecedented rainfall in the area (approximately 10 cm within half a day), lay in the River Avon! Stratford is the birthplace of the `Bard of Avon' William Shakespeare, and this formed an intriguing conference backdrop. The meeting was attended by some 90 delegates and the programme contained 65 70 oral presentations, and was opened by a historical perspective presented by Professor Brink (Oxford) and closed by Professor Horiuchi (RCNP) with an overview of the conference and future perspectives. In between, the conference covered aspects of clustering in exotic nuclei (both neutron and proton-rich), molecular structures in which valence neutrons are exchanged between cluster cores, condensates in nuclei, neutron-clusters, superheavy nuclei, clusters in nuclear astrophysical processes and exotic cluster decays such as 2p and ternary cluster decay. The field of nuclear clustering has become strongly influenced by the physics of radioactive beam facilities (reflected in the programme), and by the excitement that clustering may have an important impact on the structure of nuclei at the neutron drip-line. It was clear that since Nara the field had progressed substantially and that new themes had emerged and others had crystallized. Two particular topics resonated strongly condensates and nuclear molecules. These topics are thus likely to be central in the next cluster conference which will be held in 2011 in the Hungarian city of Debrechen. Martin Freer Participants and Cluster'07

Pulsed flows at the high-altitude cusp poleward boundary, and associated ionospheric convection and particle signatures, during a Cluster - FAST - SuperDARN- Søndrestrøm conjunction under a southwest IMF

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C. J. Farrugia

2004-09-01

Full Text Available Particle and magnetic field observations during a magnetic conjunction Cluster 1-FAST-Søndrestrøm within the field of view of SuperDARN radars on 21 January 2001 allow us to draw a detailed, comprehensive and self-consistent picture at three heights of signatures associated with transient reconnection under a steady south-westerly IMF (clock angle ≈130°. Cluster 1 was outbound through the high altitude (~12RE exterior northern cusp tailward of the bifurcation line (geomagnetic Bx>0 when a solar wind dynamic pressure release shifted the spacecraft into a boundary layer downstream of the cusp. The centerpiece of the investigation is a series of flow bursts observed there by the spacecraft, which were accompanied by strong field perturbations and tailward flow deflections. Analysis shows these to be Alfvén waves. We interpret these flow events as being due to a sequence of reconnected flux tubes, with field-aligned currents in the associated Alfvén waves carrying stresses to the underlying ionosphere, a view strengthened by the other observations. At the magnetic footprint of the region of Cluster flow bursts, FAST observed an ion energy-latitude disperison of the stepped cusp type, with individual cusp ion steps corresponding to individual flow bursts. Simultaneously, the SuperDARN Stokkseyri radar observed very strong poleward-moving radar auroral forms (PMRAFs which were conjugate to the flow bursts at Cluster. FAST was traversing these PMRAFs when it observed the cusp ion steps. The Søndrestrøm radar observed pulsed ionospheric flows (PIFs just poleward of the convection reversal boundary. As at Cluster, the flow was eastward (tailward, implying a coherent eastward (tailward motion of the hypothesized open flux tubes. The joint Søndrestrøm and FAST observations indicate that the open/closed field line boundary was equatorward of the convection reversal boundary by ~2°. The unprecedented accuracy of the conjunction argues strongly

Gemini/GMOS Spectroscopy of Globular Clusters in the Merger Remnant Galaxy M85

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Ko, Youkyung; Lee, Myung Gyoon; Park, Hong Soo; Sohn, Jubee; Lim, Sungsoon; Hwang, Narae

2018-06-01

M85 is a peculiar S0 galaxy in Virgo and a well-known merger remnant. We present the first spectroscopic study of globular clusters (GCs) in M85. We obtain spectra for 21 GC candidates and the nucleus of M85 using the Gemini Multi-Object Spectrograph on the Gemini North 8.1 m telescope. From their radial velocities, 20 of the GCs are found to be members of M85. We find a strong rotation signal of the M85 GC system with a rotation amplitude of 235 km s‑1. The rotation axis of the GC system has a position angle of about 161°, which is 51.°5 larger than that of the stellar light. The rotation-corrected radial velocity dispersion of the GC system is estimated to be {σ }{{r},{cor}}=160 km s‑1. The rotation parameter {{Ω }}{R}icor}/{σ }{{r},{cor}} of the GC system is derived to be {1.47}-0.48+1.05, which is one of the largest among known early-type galaxies. The ages and metallicities of the GCs, which show the same trend as the results based on Lick indices, are derived from full spectrum fitting (ULySS). About half of the GCs are an intermediate-age population whose mean age is ∼3.7 ± 1.9 Gyr, having a mean [Fe/H] value of ‑0.26. The other half are old and metal-poor. These results suggest that M85 experienced a wet merging event about 4 Gyr ago, forming a significant population of star clusters. The strong rotational feature of the GC system can be explained by an off-center major merging.

Hot HB Stars in Globular Clusters: Physical Parameters and Consequences for Theory. VI; The Second Parameter Pair M 3 and M 13

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Moehler, S.; Landsman, W. B.; Sweigart, A. V.; Grundahl, F.

2003-01-01

We present the results of spectroscopic analyses of hot horizontal branch (HB) stars in M 13 and M 3, which form a famous "second parameter" pair. F rom the spectra and Stromgren photometry we derived - for the first time in M 13 - atmospheric parameters (effective temperature and surface gravity). For stars with Stromgren temperatures between 10,000 and 12,000 K we found excellent agreement between the atmospheric parameters derived from Stromgren photometry and those derived from Balmer line profile fits. However, for cooler stars there is a disagreement in the parameters derived by the two methods, for which we have no satisfactory explanation. Stars hotter than 12,000 K show evidence for helium depletion and iron enrichment, both in M 3 and M 13. Accounting for the iron enrichment substantially improves the agreement with canonical evolutionary models, although the derived gravities and masses are still somewhat too low. This remaining discrepancy may be an indication that scaled-solar metal-rich model atmospheres do not adequately represent the highly non-solar abundance ratios found in blue HB stars affected by diffusion. We discuss the effects of an enhancement in the envelope helium abundance on the atmospheric parameters of the blue HB stars, as might be caused by deep mixing on the red giant branch or primordial pollution from an earlier generation of intermediate mass asymptotic giant branch stars. Key words. Stars: atmospheres - Stars: evolution - Stars: horizontal branch - Globular clusters: individual: M 3 - Globular clusters: individual: M 13

Expression Profile of IL-35 mRNA in Gingiva of Chronic Periodontitis and Aggressive Periodontitis Patients: A Semiquantitative RT-PCR Study

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Nagaraj B. Kalburgi

2013-01-01

Full Text Available Background. Proinflammatory and anti-inflammatory cytokines play a key role in the pathogenesis of periodontal diseases. Secretion of bioactive IL-35 has been described by T regulatory cells ( and is required for their maximal suppressive activity. are involved in the modulation of local immune response in chronic periodontitis patients. Objective. Hence, the present study was aimed to investigate the expression of IL-35 mRNA in chronic periodontitis and aggressive periodontitis patients. Materials and Methods. The present study was carried out in 60 subjects, which included 20 chronic periodontitis patients, 20 aggressive periodontitis patients, and 20 periodontally healthy controls. IL-35 mRNA expression in gingival tissue samples of all subjects was semiquantitatively analyzed using Reverse Transcriptase Polymerase Chain Reaction (RT-PCR. Results. The present study demonstrated the expression of IL-35 mRNA in gingival tissues of all the three groups. IL-35 mRNA expression was highest in chronic periodontitis subjects ( as compared to the aggressive periodontitis group ( and least seen in healthy patients (. Conclusion. The increased expression of IL-35 in chronic and aggressive periodontitis suggests its possible role in pathogenesis of periodontitis. Future studies done on large samples with intervention will strengthen our result.

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

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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.

H.E.S.S. OBSERVATIONS OF THE GLOBULAR CLUSTERS NGC 6388 AND M15 AND SEARCH FOR A DARK MATTER SIGNAL

International Nuclear Information System (INIS)

Abramowski, A.; Acero, F.; Aharonian, F.; Bernloehr, K.; Bochow, A.; Akhperjanian, A. G.; Anton, G.; Balzer, A.; Brucker, J.; Barnacka, A.; Barres de Almeida, U.; Bazer-Bachi, A. R.; Borrel, V.; Becherini, Y.; Becker, J.; Behera, B.; Boisson, C.; Bolmont, J.; Bordas, P.

2011-01-01

Observations of the globular clusters (GCs) NGC 6388 and M15 were carried out by the High Energy Stereoscopic System array of Cherenkov telescopes for a live time of 27.2 and 15.2 hr, respectively. No gamma-ray signal is found at the nominal target position of NGC 6388 and M15. In the primordial formation scenario, GCs are formed in a dark matter (DM) halo and DM could still be present in the baryon-dominated environment of GCs. This opens the possibility of observing a DM self-annihilation signal. The DM content of the GCs NGC 6388 and M15 is modeled taking into account the astrophysical processes that can be expected to influence the DM distribution during the evolution of the GC: the adiabatic contraction of DM by baryons, the adiabatic growth of a black hole in the DM halo, and the kinetic heating of DM by stars. Ninety-five percent confidence level exclusion limits on the DM particle velocity-weighted annihilation cross section are derived for these DM halos. In the TeV range, the limits on the velocity-weighted annihilation cross section are derived at the 10 -25 cm 3 s -1 level and a few 10 -24 cm 3 s -1 for NGC 6388 and M15, respectively.

NEW ISOLATED PLANETARY-MASS OBJECTS AND THE STELLAR AND SUBSTELLAR MASS FUNCTION OF THE {sigma} ORIONIS CLUSTER

Energy Technology Data Exchange (ETDEWEB)

Pena Ramirez, K.; Bejar, V. J. S. [Instituto de Astrofisica de Canarias, C/. Via Lactea s/n, E-38205 La Laguna, Tenerife (Spain); Zapatero Osorio, M. R.; Martin, E. L. [Centro de Astrobiologia (CSIC-INTA), Crta. Ajalvir km 4, E-28850 Torrejon de Ardoz, Madrid (Spain); Petr-Gotzens, M. G., E-mail: karla@iac.es, E-mail: vbejar@iac.es, E-mail: mosorio@cab.inta-csic.es, E-mail: ege@cab.inta-csic.es, E-mail: mpetr@eso.org [European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei Muenchen (Germany)

2012-07-20

We report on our analysis of the VISTA Orion ZY JHK{sub s} photometric data (completeness magnitudes of Z = 22.6 and J = 21.0 mag) focusing on a circular area of 2798.4 arcmin{sup 2} around the young {sigma} Orionis star cluster ({approx}3 Myr, {approx}352 pc, and solar metallicity). The combination of the VISTA photometry with optical, WISE and Spitzer data allows us to identify a total of 210 {sigma} Orionis member candidates with masses in the interval 0.25-0.004 M{sub Sun }, 23 of which are new planetary-mass object findings. These discoveries double the number of cluster planetary-mass candidates known so far. One object has colors compatible with a T spectral type. The {sigma} Orionis cluster harbors about as many brown dwarfs (69, 0.072-0.012 M{sub Sun }) and planetary-mass objects (37, 0.012-0.004 M{sub Sun }) as very low mass stars (104, 0.25-0.072 M{sub Sun }). Based on Spitzer data, we derive a disk frequency of {approx}40% for very low mass stars, brown dwarfs, and planetary-mass objects in {sigma} Orionis. The radial density distributions of these three mass intervals are alike: all are spatially concentrated within an effective radius of 12' (1.2 pc) around the multiple star {sigma} Ori, and no obvious segregation between disk-bearing and diskless objects is observed. Using the VISTA data and the Mayrit catalog, we derive the cluster mass spectrum ({Delta}N/{Delta}M {approx} M{sup -{alpha}}) from {approx}19 to 0.006 M{sub Sun} (VISTA ZJ completeness), which is reasonably described by two power-law expressions with indices of {alpha} = 1.7 {+-} 0.2 for M > 0.35 M{sub Sun }, and {alpha} = 0.6 {+-} 0.2 for M < 0.35 M{sub Sun }. The {sigma} Orionis mass spectrum smoothly extends into the planetary-mass regime down to 0.004 M{sub Sun }. Our findings of T-type sources (<0.004 M{sub Sun }) in the VISTA {sigma} Orionis exploration appear to be smaller than what is predicted by the extrapolation of the cluster mass spectrum down to the survey J

NEAR-INFRARED SPECTRA OF GALACTIC STELLAR CLUSTERS DETECTED ON SPITZER/GLIMPSE IMAGES

International Nuclear Information System (INIS)

Messineo, Maria; Davies, Ben; Figer, Donald F.; Ivanov, Valentin D.; Schuller, Frederic; Menten, Karl M.; Habing, Harm J.; Petr-Gotzens, Monika G.

2009-01-01

We present near-infrared spectroscopic observations of massive stars in three stellar clusters located in the direction of the inner Galaxy. One of them, the Quartet, is a new discovery while the other two were previously reported as candidate clusters identified on mid-infrared Spitzer images (GLIMPSE20 and GLIMPSE13). Using medium-resolution (R = 900-1320) H and K spectroscopy, we firmly establish the nature of the brightest stars in these clusters, yielding new identifications of an early WC and two Ofpe/WN9 stars in the Quartet and an early WC star in GLIMPSE20. We combine this information with the available photometric measurements from Two Micron All Sky Survey, to estimate cluster masses, ages, and distances. The presence of several massive stars places the Quartet and GLIMPSE20 among the small sample of known Galactic stellar clusters with masses of a few 10 3 M sun , and ages from 3 to 8 Myr. We estimate a distance of about 3.5 kpc for GLIMPSE20 and 6.0 kpc for Quartet. The large number of giant stars identified in GLIMPSE13 indicates that it is another massive (∼6500 M sun ) cluster, but older, with an age between 30 and 100 Myr, at a distance of about 3 kpc.

A UV spectroscopic survey of periodic M dwarfs in the Hyades

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Agueros, Marcel

2017-08-01

Because of its proximity, the 650-Myr-old Hyades open cluster is a unique resource for exploring the relationship between magnetic activity, rotation, and age in low-mass stars. While the cluster has been largely ignored in UV studies of the dependence of activity on rotation, we now have an extensive and growing set of complementary rotation period, Halpha, and X-ray measurements with which to examine in detail the rotation-activity relation at 650 Myr and to constrain theories of magnetic heating. We propose to measure Mg II line emission, the strongest NUV activity tracer, in COS spectra of 17 Hyads ranging in spectral type from M0 to M7 with known rotation periods and Halpha and X-ray measurements. These stars form a representative sample of M-dwarf Hyads with known periods and are a significant addition to, and expansion of, the sample of 20 mainly solar-mass rotators with existing (mostly low-resolution) International Ultravioled Explorer (IUE) NUV spectra. The Mg II measurements will contribute significantly to our goal of mapping out the rotation-activity relation star-by-star in this benchmark open cluster. This, in turn, will move us toward an improved understanding of the radiation environment and habitability of the exoplanets we continue to find around low-mass stars.

CERN Open Days The LHC demystified!

CERN Multimedia

2008-01-01

Lots of surprises are being planned for the CERN Open Days scheduled for 5 and 6 April (see 21 January edition of the Bulletin). Fred’s itinerary on 6 April 20089.00 a.m\tDeparture from SM12 at CERN (the pit down which all the LHC magnets were lowered into the tunnel)9.15 a.m. Saint-Genis theatre10.00 a.m.\tRoussillon communal hall in Crozet 10.50 a.m. La Chenaille communal hall in Echenevex 11.40 a.m. CMS Building SX5 at Cessy 2.30 p.m. La Forge communal hall in Versonnex 3.30 p.m. Le Levant communal hall in Ferney Voltaire4.40 Forum in Meyrin 5.30 p.m. Main Auditorium at CERN For instance, Fred, who fronts the French television programme "C’est pas sorcier" on France 3 will be taking part in the Open Day for the general public on Sunday, 6 April. He will be on board a CERN lorry carrying a 35 tonne 15 m long dipole magnet and will make halts at eight Swiss and French communes around the LHC Ring to meet the local inhabitants (see...

Rod cluster having improved vane configuration

International Nuclear Information System (INIS)

Shockling, L.A.; Francis, T.A.

1989-01-01

This patent describes a pressurized water reactor vessel, the vessel defining a predetermined axial direction of the flow of coolant therewithin and having plural spider assemblies supporting, for vertical movement within the vessel, respective clusters of rods in spaced, parallel axial relationship, parallel to the predetermined axial direction of coolant flow, and a rod guide for each spider assembly and respective cluster of rods. The rod guide having horizontally oriented support plates therewithin, each plate having an interior opening for accommodating axial movement therethrough of the spider assembly and respective cluster of rods. The opening defining plural radially extending channels and corresponding parallel interior wall surfaces of the support plate

GAS SURFACE DENSITY, STAR FORMATION RATE SURFACE DENSITY, AND THE MAXIMUM MASS OF YOUNG STAR CLUSTERS IN A DISK GALAXY. II. THE GRAND-DESIGN GALAXY M51

International Nuclear Information System (INIS)

González-Lópezlira, Rosa A.; Pflamm-Altenburg, Jan; Kroupa, Pavel

2013-01-01

We analyze the relationship between maximum cluster mass and surface densities of total gas (Σ gas ), molecular gas (Σ H 2 ), neutral gas (Σ H I ), and star formation rate (Σ SFR ) in the grand-design galaxy M51, using published gas data and a catalog of masses, ages, and reddenings of more than 1800 star clusters in its disk, of which 223 are above the cluster mass distribution function completeness limit. By comparing the two-dimensional distribution of cluster masses and gas surface densities, we find for clusters older than 25 Myr that M 3rd ∝Σ H I 0.4±0.2 , whereM 3rd is the median of the five most massive clusters. There is no correlation withΣ gas ,Σ H2 , orΣ SFR . For clusters younger than 10 Myr, M 3rd ∝Σ H I 0.6±0.1 and M 3rd ∝Σ gas 0.5±0.2 ; there is no correlation with either Σ H 2 orΣ SFR . The results could hardly be more different from those found for clusters younger than 25 Myr in M33. For the flocculent galaxy M33, there is no correlation between maximum cluster mass and neutral gas, but we have determined M 3rd ∝Σ gas 3.8±0.3 , M 3rd ∝Σ H 2 1.2±0.1 , and M 3rd ∝Σ SFR 0.9±0.1 . For the older sample in M51, the lack of tight correlations is probably due to the combination of strong azimuthal variations in the surface densities of gas and star formation rate, and the cluster ages. These two facts mean that neither the azimuthal average of the surface densities at a given radius nor the surface densities at the present-day location of a stellar cluster represent the true surface densities at the place and time of cluster formation. In the case of the younger sample, even if the clusters have not yet traveled too far from their birth sites, the poor resolution of the radio data compared to the physical sizes of the clusters results in measuredΣ that are likely quite diluted compared to the actual densities relevant for the formation of the clusters.