scholarly journals A super lithium-rich red-clump star in the open cluster Trumpler 5

2014 ◽  
Vol 564 ◽  
pp. L6 ◽  
Author(s):  
L. Monaco ◽  
H. M. J. Boffin ◽  
P. Bonifacio ◽  
S. Villanova ◽  
G. Carraro ◽  
...  
Keyword(s):  
Open Cluster ◽  
Red Clump

scholarly journals Abundance analysis of red clump stars in the old, inner disc, open cluster NGC 4337: a twin of NGC 752?

2014 ◽  
Vol 568 ◽  
pp. A86 ◽  
Author(s):  
Giovanni Carraro ◽  
Lorenzo Monaco ◽  
Sandro Villanova
Keyword(s):  
Open Cluster ◽  
Red Clump

scholarly journals The San Pedro Mártir Open Cluster Survey: Progress, Techniques, Preliminary Results

2006 ◽  
Vol 2 (S235) ◽  
pp. 331-331 ◽  
Author(s):  
W. Schuster ◽  
R. Michel ◽  
W. Dias ◽  
T. Tapia-Peralta ◽  
R. Vázquez ◽  
...  
Keyword(s):  
Open Cluster ◽  
Open Clusters ◽  
Small Subset ◽  
Main Sequence Stars ◽  
San Pedro ◽  
Reduction Methods ◽  
Red Clump ◽  
Different Color ◽  
Photometric Scale ◽  
Selection Of

AbstractA CCD UBVRI survey of northern open clusters is being undertaken at San Pedro Mártir, México, and performed using always the same instrumental setup (telescope, CCD, filters), reduction methods, and system of standards of Landolt (1992). To date more than 300 clusters (mostly unstudied previously) have been observed, and about half the data reduced using aperture-photometry and PSF techniques. Our analysis procedures are being refined by studying in detail a small subset of these clusters. For example, the heavily reddened clusters Be80 and Be95 are being examined in the color-color diagrams: (B-V, U-B) and (B-V, R-I) to better understand the problems of curvature and variable reddening. For clusters for which our U data reaches the F-type stars, such as NGC2192 and NGC7296, techniques are being examined for estimating both the reddening E(B-V) and metallicity [Fe/H] via the use of the (U-B) excess. If the clusters also have “red clump” stars, such as NGC1798 and Do02, these procedures can be iterated between the clump and main sequence stars to establish even better the values of E(B-V) and [Fe/H]. Finally, color-magnitude diagrams, such as (B-V, V) and (V-I, V), are being employed together with the SchmidtKaler (1982) colors and Padova isochrones of Girardi et al. (2000) to obtain distances and ages for these clusters. A java-based computer program is being developed to help in the visualization and analysis of these photometric data. This system is capable of displaying each cluster simultaneously in different color-color and color-magnitude diagrams and has an interactive way to identify a star, or group of stars, in one diagram and to see were it falls in the other diagrams, facilitating the elimination of field stars and the apperception of cluster features. This program is capable of displaying up to 16 different diagrams for one cluster and processing up to 20 clusters at the same time. Our aims are the following: (1) a common UBVRI photometric scale for open clusters, (2) an atlas of color-color and color-magnitude diagrams for open clusters, (3) a homogeneous set of cluster reddenings, distances, and ages, (4) an increased number of old and distant open clusters, and (5) a selection of interesting clusters for further study.

scholarly journals The Gaia-ESO Survey: The inner disc, intermediate-age open cluster Pismis 18

2019 ◽  
Vol 626 ◽  
pp. A90 ◽  
Author(s):  
D. Hatzidimitriou ◽  
E. V. Held ◽  
E. Tognelli ◽  
A. Bragaglia ◽  
L. Magrini ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Proper Motion ◽  
Open Cluster ◽  
Open Clusters ◽  
High Resolution Spectroscopy ◽  
Distance Modulus ◽  
Chemical Abundance ◽  
High Confidence ◽  
Galactocentric Distance ◽  
Red Clump

Context. Pismis 18 is a moderately populated, intermediate-age open cluster located within the solar circle at a Galactocentric distance of about seven kpc. Few open clusters have been studied in detail in the inner disc region before the Gaia-ESO Survey. Aims. New data from the Gaia-ESO Survey allowed us to conduct an extended radial velocity membership study as well as spectroscopic metallicity and detailed chemical abundance measurements for this cluster. Methods. Gaia-ESO Survey data for 142 potential members, lying on the upper main sequence and on the red clump, yielded radial velocity measurements, which, together with proper motion measurements from the Gaia Second Data Release (Gaia DR2), were used to determine the systemic velocity of the cluster and membership of individual stars. Photometry from Gaia DR2 was used to re-determine cluster parameters based on high confidence member stars only. Cluster abundance measurements of six radial-velocity member stars with UVES high-resolution spectroscopy are presented for 23 elements. Results. The average radial velocity of 26 high confidence members is −27.5 ± 2.5 (std) km s−1 with an average proper motion of pmra = −5.65 ± 0.08 (std) mas yr−1 and pmdec = −2.29 ± 0.11 (std) mas yr−1. According to the new estimates, based on high confidence members, Pismis 18 has an age of τ = 700+40−50 Myr, interstellar reddening of E(B − V) = 0.562+0.012−0.026 mag and a de-reddened distance modulus of DM0 = 11.96+0.10−0.24 mag. The median metallicity of the cluster (using the six UVES stars) is [Fe/H] = +0.23 ± 0.05 dex, with [α/Fe] = 0.07 ± 0.13 and a slight enhancement of s- and r-neutron-capture elements. Conclusions. With the present work, we fully characterized the open cluster Pismis 18. We confirmed its present location in the inner disc. We estimated a younger age than the previous literature values and we gave, for the first time, its metallicity and its detailed abundances. Its [α/Fe] and [s-process/Fe], both slightly super-solar, are in agreement with other inner-disc open clusters observed by the Gaia-ESO survey.

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

2018 ◽  
Vol 610 ◽  
pp. A66 ◽  
Author(s):  
L. Casamiquela ◽  
R. Carrera ◽  
L. Balaguer-Núñez ◽  
C. Jordi ◽  
C. Chiappini ◽  
...  
Keyword(s):  
Spectral Synthesis ◽  
Open Cluster ◽  
High Signal ◽  
Galactic Centre ◽  
Chemical Abundances ◽  
Blue Straggler ◽  
The Galaxy ◽  
Galactic Potentials ◽  
Red Clump ◽  
Current Paradigm

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.

scholarly journals The UV Upturn in Elliptical Galaxies

1995 ◽  
Vol 164 ◽  
pp. 239-248
Author(s):  
H.C. Ferguson
Keyword(s):  
Galaxy Evolution ◽  
Open Cluster ◽  
Elliptical Galaxies ◽  
Asymptotic Giant Branch ◽  
Star Mass ◽  
Uv Emission ◽  
Stellar Component ◽  
Red Clump ◽  
Ehb Stars ◽  
Uv Upturn

The hot stellar component in elliptical galaxies offers clues to both stellar evolution and galaxy evolution. Current observations suggest that extreme horizontal branch (EHB) stars dominate the far-UV emission from galaxies with the strongest “UV upturns,” while post asymptotic giant branch (PAGB) stars are probably significant contributors for weaker galaxies. Spectra near the Lyman limit indicate that a rather narrow range of temperature (and hence EHB star mass) is required. However, other arguments suggest that most of the helium-burning stars in elliptical galaxies are in the red clump. The HB star mass distribution therefore appears to be strongly bimodal. Such bimodality is qualitatively reproduced by two radically different stellar population models, (those of Lee and Bressan et al.), both of which require that the galaxies be very old. However, the Galactic open cluster NGC 6791 also contains EHB stars and exhibits strong bimodality, indicating that old age may not necessarily be a requirement for the UV upturn phenomenon.

scholarly journals Gaia-ESO survey: Lithium abundances in open cluster Red Clump stars

2021 ◽  
Author(s):  
L. Magrini ◽  
R. Smiljanic ◽  
E. Franciosini ◽  
L. Pasquini ◽  
S. Randich ◽  
...  
Keyword(s):  
Open Cluster ◽  
Red Clump

WIYN Open Cluster Study. X. The [ITAL]K[/ITAL]-Band Magnitude of the Red Clump as a Distance Indicator

2002 ◽  
Vol 123 (3) ◽  
pp. 1603-1612 ◽  
Author(s):  
Aaron J. Grocholski ◽  
Ata Sarajedini
Keyword(s):  
Open Cluster ◽  
Distance Indicator ◽  
Red Clump

scholarly journals Variability in the Massive Open Cluster NGC 1817 from K2: A Rich Population of Asteroseismic Red Clump, Eclipsing Binary, and Main-sequence Pulsating Stars

2020 ◽  
Vol 159 (3) ◽  
pp. 96 ◽  
Author(s):  
Eric L. Sandquist ◽  
Dennis Stello ◽  
Torben Arentoft ◽  
Karsten Brogaard ◽  
Frank Grundahl ◽  
...  
Keyword(s):  
Main Sequence ◽  
Open Cluster ◽  
Eclipsing Binary ◽  
Pulsating Stars ◽  
Red Clump

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

2000 ◽  
Vol 119 (5) ◽  
pp. 2296-2302 ◽  
Author(s):  
Jorge Federico González ◽  
Emilio Lapasset
Keyword(s):  
Open Cluster ◽  
Radial Velocities
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