scholarly journals Determination of the fundamental properties of an M31 globular cluster from main-sequence photometry

2012 ◽  
Vol 8 (S289) ◽  
pp. 398-401
Author(s):  
Jun Ma
Keyword(s):  
Globular Cluster ◽  
Main Sequence ◽  
Distance Modulus ◽  
Population Synthesis ◽  
Fundamental Properties ◽  
Stellar Population Synthesis ◽  
Metal Abundance ◽  
Multicolor Photometry ◽  
Good Agreement

AbstractWe determined the age of the M31 globular cluster B379 using isochrones of the Padova stellar evolutionary models. At the same time, the cluster's metal abundance, its distance modulus, and reddening value were also obtained. The results obtained in this paper are consistent with previous determinations, including the age. Brown et al. constrained the age of B379 by comparing its color–magnitude diagram with isochrones of the 2006 VandenBerg models. Therefore, this paper confirms the consistency of the age scale of B379 between the Padova isochrones and the 2006 VandenBerg isochrones. The results of B379 obtained in this paper are: metallicity [M/H] = log(Z/Z⊙) = −0.325 dex, age τ = 11.0 ± 1.5 Gyr, reddening E(B − V) = 0.08 mag, and distance modulus (m − M)0 = 24.44 ± 0.10 mag. Using the metallicity, the reddening value and the distance modulus obtained in this paper, we constrained the age of B379 by comparing its multicolor photometry with theoretical stellar population synthesis models. The age of B379 obtained is 10.6−0.76+0.92 Gyr, which is in very good agreement with the determination from main-sequence photometry.

scholarly journals Determination of Fundamental Properties of an M31 Globular Cluster from Main-Sequence Photometry

2010 ◽  
Vol 122 (896) ◽  
pp. 1164-1170 ◽  
Author(s):  
Jun Ma ◽  
Zhenyu Wu ◽  
Song Wang ◽  
Zhou Fan ◽  
Xu Zhou ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Main Sequence ◽  
Fundamental Properties

scholarly journals The Abundance of the LMC Globular Cluster NGC 2213

1988 ◽  
Vol 126 ◽  
pp. 579-580
Author(s):  
Doug Geisler
Keyword(s):  
Globular Cluster ◽  
Main Sequence ◽  
High Accuracy ◽  
Magellanic Cloud ◽  
New Technique ◽  
Distance Modulus ◽  
Ccd Photometry ◽  
Cloud Clusters ◽  
A New Technique ◽  
Using Data

A new technique for determining accurate abundances in distant giants - Washington CCD photometry - has been applied to the intermediate-age LMC globular cluster NGC 2213. An abundance of −0.40 ± 0.15 was found from the analysis of 42 giants with V < 20, using data obtained with the 1.5 m telescope. Combined with published main-sequence photometry, the derived abundance indicates a true LMC distance modulus of 18.2 ± 0.2. A likely CN strong giant near the tip of the giant branch is identified. Abundances are also derived for a sample of 27 field giants. Results indicate that one could determine both the age and abundance of Magellanic Cloud clusters with high accuracy from Washington photometry using the 4 m in less than one hour of observing time per cluster.

scholarly journals Pal 1: A Globular Cluster Anyway?

1995 ◽  
Vol 164 ◽  
pp. 395-395
Author(s):  
J. Borissova ◽  
N. Spassova
Keyword(s):  
Globular Cluster ◽  
Luminosity Function ◽  
Main Sequence ◽  
Structural Parameters ◽  
Distance Modulus ◽  
Horizontal Branch ◽  
Ccd Photometry ◽  
Horizontal Branch Stars ◽  
Mass Estimate

CCD photometry of the halo cluster Pall in Thuan-Gunn system is presented. The color - magnitude diagrams (Fig. 1) show a well defined red horizontal branch, lower giant branch and main-sequence down to about two magnitudes below the main-sequence turnoff. The giant branch is absent and the brightest stars are horizontal-branch stars. The horizontal branch is composed of red stars only. The age of the cluster, determined by comparison with the isochrones of Bell and Vanden Berg (1987) is consistent with an age between 12 – 14 Gyr. and a metallicity [Fe/H] = −0.79. The observed luminosity function shows a deficiency of stars from about 0.5 mag below turnoff up to g = 21 mag. A distance modulus of (m – M)g0 = 15.35 ± 0.1 magnitude has been derived. An estimate of the cluster structural parameters gives rc = 1.7 pc and c = 1.46. A mass estimate of 1.6 × 103M⊙ and mass-to-light ratio 1.77 has been obtained, using King's (1966) method.

scholarly journals Asteroseismology of Delta Scuti Stars – A Parameter Study

2002 ◽  
Vol 185 ◽  
pp. 600-601
Author(s):  
M. Templeton ◽  
S. Basu ◽  
P. Demarque
Keyword(s):  
Main Sequence ◽  
Parameter Study ◽  
Period Ratio ◽  
Fundamental Properties ◽  
The Core ◽  
Stellar Parameter ◽  
Metal Abundance ◽  
Delta Scuti ◽  
Stellar Properties ◽  
Scuti Stars

AbstractWe assess the potential of asteroseismology for determining the fundamental properties of individual δ Scuti stars. We computed a grid of evolution and adiabatic pulsation models to study systematic changes in l = 0,1,2, and 3 modes as functions of fundamental stellar properties. Mass has the strongest effect on evolution and on pulsation, followed by the metal abundance. Changes to the helium content have very little effect on the frequencies until near the end of the main sequence. Changes to each of the four parameters change the p-mode frequencies more than they do the g- and mixed-mode frequencies, suggesting that these parameters have a greater effect on the outer layers of the star. We also present pulsation models of FG Virginis, outlining a possible method of locating favorable models in the stellar parameter space based upon a definitive identification of only two modes. We plot evolution models on the (period-period ratio) and (temperature-period ratio) planes to select candidate models, and modify the core overshooting parameter to fit the observed star.

scholarly journals Breaking the disc-halo degeneracy in NGC 1291 using hydrodynamic simulations

2016 ◽  
Vol 11 (S321) ◽  
pp. 111-113
Author(s):  
Francesca Fragkoudi ◽  
E. Athanassoula ◽  
A. Bosma
Keyword(s):  
Near Infrared ◽  
Height Function ◽  
Population Synthesis ◽  
Corotation Radius ◽  
Stellar Population Synthesis ◽  
The Galaxy ◽  
Pattern Speed ◽  
Gas Response ◽  
Best Fit

AbstractWe present a pilot study on the nearby massive galaxy NGC 1291, in which we aim to constrain the dark matter in the inner regions, by obtaining a dynamical determination of the disc mass-to-light ratio (M/L). To this aim, we model the bar-induced dust lanes in the galaxy, using hydrodynamic gas response simulations. The models have three free parameters, the M/L of the disc, the bar pattern speed and the disc height function. We explore the parameter space to find the best fit models, i.e. those in which the morphology of the shocks in the gas simulations matches the observed dust lanes. The best-fit models suggest that the M/L of NGC 1291 agrees with that predicted by stellar population synthesis models in the near-infrared (≈ 0.6M⊙/L⊙), which leads to a borderline maximum disc for this galaxy. The bar rotates fast, with corotation radius ⩽ 1.4 times the bar length. Additionally, we find that the height function has a significant effect on the results, and can bias them towards lower or higher M/L.

scholarly journals Red Giants in Globular Clusters and Large-Scale Variations in The Galaxy

1980 ◽  
Vol 5 ◽  
pp. 817-826
Author(s):  
B. E. J. Pagel
Keyword(s):  
Recent Work ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Large Scale ◽  
Red Giants ◽  
Mixing Effects ◽  
The Galaxy ◽  
Metal Abundance ◽  
Red Giant

SummaryThis review concerns recent work on the determination of overall metallicities [Fe/H] in a number of globular clusters and the systematics of mixing effects displayed (usually) by weak CH and strong CN. Special attention is given to the globular cluster ω Centauri, where both metal abundance variations and mixing effects occur and are closely intertwined. Recent observations carried out at the Anglo-Australian Telescope by E.A. Mallia and D.C. Watts have revealed large variations in the strength of metallic lines across the red giant branch of this cluster.

scholarly journals A precise asteroseismic age and metallicity for HD 139614: a pre-main-sequence star with a protoplanetary disc in Upper Centaurus–Lupus

2021 ◽  
Vol 502 (2) ◽  
pp. 1633-1646
Author(s):  
Simon J Murphy ◽  
Meridith Joyce ◽  
Timothy R Bedding ◽  
Timothy R White ◽  
Mihkel Kama
Keyword(s):  
Main Sequence ◽  
Main Sequence Star ◽  
Radial Pulsation ◽  
Chemical Abundance ◽  
Abundance Pattern ◽  
Intermediate Mass Stars ◽  
Metal Abundance ◽  
Ring Structures ◽  
Stellar Oscillation

ABSTRACT HD 139614 is known to be a ∼14-Myr-old, possibly pre-main-sequence star in the Sco-Cen OB association in the Upper Centaurus-Lupus subgroup, with a slightly warped circumstellar disc containing ring structures hinting at one or more planets. The star’s chemical abundance pattern is metal-deficient except for volatile elements, which places it in the λ Boo class and suggests it has recently accreted gas-rich but dust-poor material. We identify seven dipole and four radial pulsation modes among its δ Sct pulsations using the TESS light curve and an échelle diagram. Precision modelling with the mesa stellar evolution and gyre stellar oscillation programs confirms it is on the pre-main sequence. Asteroseismic, grid-based modelling suggests an age of 10.75 ± 0.77 Myr, a mass of 1.52 ± 0.02 M ⊙, and a global metal abundance of Z = 0.0100 ± 0.0010. This represents the first asteroseismic determination of the bulk metallicity of a λ Boo star. The precise age and metallicity offer a benchmark for age estimates in Upper Centaurus–Lupus, and for understanding disc retention and planet formation around intermediate-mass stars.

scholarly journals New Ages For Old Clusters

1998 ◽  
Vol 11 (1) ◽  
pp. 562-562
Author(s):  
I.N. Reid
Keyword(s):  
High Resolution ◽  
Globular Cluster ◽  
Main Sequence ◽  
Distance Scale ◽  
Distance Modulus ◽  
Systematic Bias ◽  
Major Result ◽  
Spectroscopic Analyses ◽  
Cluster Distance ◽  
Extreme Metal

A major result of the Hipparcos mission is the availability of accurate parallaxes for a much-increased sample of nearby subdwarfs. On the basis of those data, both Reid (1997-R97) and Gratton et al (1997-G97) have used main-sequence fitting techniques to obtain new estimates of globular cluster distances, deriving significantly larger moduli (by 0.15 to 0.3 mag) for extreme, metal-poor clusters such as M92 and M15. These re-calibrations are not solely the result of the revised parallax data - both D’Antona, Caloi & Mazzitelli (1997 - DCM) and Reid show that similar results can be derived from pre-Hipparcos subdwarf data if the calibrations are not tied exclusively to HD 103095. The longer distance scale leads to a brighter inferred turnoff, and, combined with the latest models (DCM), ages of only 11 to 13 Gyrs - substantially younger than the 16±2 Gyrs proposed by Bolte & Hogan (1992). Recently, Pont et al (1997) have suggested that these revised distances reflect systematic bias in the calibration, notably underestimation of subdwarf abundances. Their distance modulus for M92 ( (m-M)0=14.68) is closer to the Bolte/Hogan value (14.65 mag) than those derived byG97 (14.82 mag) or Reid (14.93 mag). While we believe that Pont et al overestimate the bias, particularly, where high-resolution spectroscopic analyses are concerned (G97, Reid, preprint), there is no question that significant uncertainties remain in the cluster distance calibration. Colours,rather than luminosities, are particularly vulnerable, and a mismatch of 0.01 in (B-V) translates to δ(m — M)0 ~ 0.05 mag.

scholarly journals Determination of Absolute Proper Motions by Use of Automated Measurements of Tautenburg Plates

1990 ◽  
Vol 141 ◽  
pp. 451-452
Author(s):  
R.-D. Scholz
Keyword(s):  
Globular Cluster ◽  
Proper Motion ◽  
Proper Motions ◽  
Automated Measurements ◽  
The Absolute ◽  
Good Agreement

From measurements of Tautenburg Schmidt plates with the APM in Cambridge positional accuracies per plate of 0.″05 for stars and of 0.″10 for galaxies were achieved. With 0.″3/100a accuracy in a single stellar proper motion we obtained the absolute proper motion of the M3 globular cluster in good agreement between the two pairs of plates used.

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