scholarly journals Beryllium abundances along the evolutionary sequence of the open cluster IC 4651

2009 ◽  
Vol 5 (S268) ◽  
pp. 357-358 ◽  
Author(s):  
Rodolfo Smiljanic ◽  
L. Pasquini ◽  
C. Charbonnel ◽  
N. Lagarde
Keyword(s):  
Main Sequence ◽  
Open Cluster ◽  
High Signal ◽  
Evolutionary Sequence ◽  
Main Sequence Stars ◽  
Signal To Noise ◽  
Mixing Processes ◽  
Hydrodynamical Models ◽  
Spectrum Synthesis ◽  
Hertzsprung Gap

AbstractThe simultaneous investigation of Li and Be in stars is a powerful tool in the study of the evolutionary mixing processes. Here, we present beryllium abundances in stars along the whole evolutionary sequence of the open cluster IC 4651. This cluster has a metallicity of [Fe/H] = +0.11 and an age of 1.2 or 1.7 Gyr. Abundances have been determined from high-resolution, high signal-to-noise UVES spectra using spectrum synthesis and model atmospheres. Lithium abundances for the same stars were determined in a previous work. Confirming previous results, we find that the Li dip is also a Be dip. For post-main-sequence stars, the Be dilution starts earlier within the Hertzsprung gap than expected from classical predictions, as does the Li dilution. Theoretical hydrodynamical models are able to reproduce well all the observed features.

scholarly journals A Rotational Period Study of a Large Sample of Pre-Main Sequence stars in NGC 2264

2004 ◽  
Vol 215 ◽  
pp. 125-126 ◽  
Author(s):  
M. Lamm ◽  
C.A.L. Bailer-Jones ◽  
R. Mundt ◽  
W. Herbst
Keyword(s):  
Main Sequence ◽  
Open Cluster ◽  
Monitoring Program ◽  
Bimodal Distribution ◽  
Main Sequence Stars ◽  
Lower Mass ◽  
Rotation Periods ◽  
Photometric Monitoring ◽  
Pms Stars ◽  
Mass Dependent

We present the results of a photometric monitoring program of pre-main sequence (PMS) stars in the young (2-4 Myr) open cluster NGC 2264 (d=700 pc). We find that the rotation periods are mass dependent and show a bimodal distribution for higher mass stars with M ≳ 0.3 M⊙ and a unimodal distribution for lower mass stars with M ≲ 0.3 M⊙.

scholarly journals A Spectroscopic Study of Blue Stragglers in M67

2008 ◽  
Vol 4 (S252) ◽  
pp. 391-397
Author(s):  
G. Q. Liu ◽  
L. Deng ◽  
M. Chávez ◽  
E. Bertone
Keyword(s):  
Effective Temperature ◽  
Spectral Properties ◽  
Main Sequence ◽  
Open Cluster ◽  
Observational Constraints ◽  
Photometric System ◽  
Main Sequence Stars ◽  
Complete Sample ◽  
Blue Stragglers ◽  
Fitting Method

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

scholarly journals Light elements in massive single and binary stars

2009 ◽  
Vol 5 (S268) ◽  
pp. 411-420 ◽  
Author(s):  
N. Langer ◽  
I. Brott ◽  
M. Cantiello ◽  
S. E. de Mink ◽  
R. G. Izzard ◽  
...  
Keyword(s):  
Binary Stars ◽  
Main Sequence ◽  
Diagnostic Value ◽  
Light Elements ◽  
Main Sequence Stars ◽  
Mixing Processes ◽  
Transfer Event ◽  
Internal Mixing ◽  
Early Type Stars

AbstractWe highlight the role of the light elements (Li, Be, B) in the evolution of massive single and binary stars, which is largely restricted to a diagnostic value, and foremost so for the element boron. However, we show that the boron surface abundance in massive early type stars contains key information about their foregoing evolution which is not obtainable otherwise. In particular, it allows to constrain internal mixing processes and potential previous mass transfer event for binary stars (even if the companion has disappeared). It may also help solving the mystery of the slowly rotating nitrogen-rich massive main sequence stars.

scholarly journals High Signal-To-Noise Ratio - the Spectroscopic Key to Algol Systems

1989 ◽  
Vol 107 ◽  
pp. 245-255
Author(s):  
Jocelyn Tomkin
Keyword(s):  
Main Sequence ◽  
Near Infrared ◽  
Signal To Noise Ratio ◽  
Large Fraction ◽  
High Signal ◽  
Signal To Noise ◽  
Algol System ◽  
Low Mass ◽  
Noise Ratio ◽  
Cno Abundances

AbstractThe usefulness of high signal-to-noise-ratio spectra for both radial-velocity and abundance studies of Algol systems is emphasised. It is shown that division by a hot star is a worthwhile step in pursuit of this objective. A preliminary analysis of high signal-to-noise-ratio, red and near-infrared, Reticon observations of R CMa shows that its primary has solar CNO abundances within the 0.3 dex observational error. The low-mass (0.17 m⊙) secondary of this Algol system must have lost a large fraction of its original mass. Some of this material would have been extensively processed during the secondary’s main-sequence lifetime and would therefore have had a highly non-solar CNO-abundance distribution. The lack of serious contamination of the primary’s abundances is consistent with most, but not all, plausible mass-transfer scenarios.

scholarly journals NGC 6302: high-ionization permitted lines. Applying X-SSN synthesis to VLT-UVES spectra

2011 ◽  
Vol 7 (S283) ◽  
pp. 470-471
Author(s):  
Daniel Péquignot ◽  
Christophe Morisset ◽  
Simon Casassus
Keyword(s):  
High Signal ◽  
Signal To Noise ◽  
High Ionization ◽  
Spectrum Synthesis ◽  
First Time

AbstractA preliminary VLT-UVES spectrum of NGC 6302 (Casassus et al. 2002, MN), which hosts one of the hottest PN nuclei known (Teff ~ 220000 K; Wright et al. 2011, MN), has been recently analysed by means of X-SSN, a spectrum synthesis code for nebulae (Morisset and Péquignot). Permitted recombination lines from highly-ionized species are detected/identified for the first time in a PN, and some of them probably for the first time in (astro)physics. The need for a homogeneous, high signal-to-noise UVES spectrum for NGC 6302 is advocated.

scholarly journals NIR Spectroscopy of the Most Massive Open Cluster in the Galaxy: Westerlund 1

2007 ◽  
Vol 3 (S246) ◽  
pp. 113-114 ◽  
Author(s):  
S. Mengel ◽  
L. E. Tacconi-Garman
Keyword(s):  
Cluster Expansion ◽  
Main Sequence ◽  
Velocity Dispersion ◽  
Open Cluster ◽  
Nir Spectroscopy ◽  
Radial Velocities ◽  
Main Sequence Stars ◽  
Central Wavelength ◽  
Cluster Mass ◽  
The Galaxy

AbstractUsing ISAAC/VLT, we have obtained individual spectra of all NIR-bright stars in the central 2′ × 2′ of the cluster Westerlund 1 (Wd 1) with a resolution of R ≈ 9000 at a central wavelength of 2.30 μm. This allowed us to determine radial velocities of ten post-main-sequence stars, and from these values a velocity dispersion. Assuming virial equilibrium, the dispersion of σ = 8.4 km/s leads to a total dynamical cluster mass of 1.25 × 105M⊙, comparable to the photometric mass of the cluster. There is no extra-virial motion which would have to be interpreted as a signature of cluster expansion or dissolution.

scholarly journals A Stringent Test of Magnetic Models of Stellar Evolution

Galaxies ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 3
Author(s):  
Guillermo Torres ◽  
Gregory A. Feiden ◽  
Andrew Vanderburg ◽  
Jason L. Curtis
Keyword(s):  
Stellar Evolution ◽  
Main Sequence ◽  
Open Cluster ◽  
Main Sequence Stars ◽  
Robust Estimates ◽  
Empirical Estimates ◽  
Nonstandard Models ◽  
Stringent Test ◽  
Standard Models ◽  
The Magnetic Field

Main-sequence stars with convective envelopes often appear larger and cooler than predicted by standard models of stellar evolution for their measured masses. This is believed to be caused by stellar activity. In a recent study, accurate measurements were published for the K-type components of the 1.62-day detached eclipsing binary EPIC 219511354, showing the radii and temperatures for both stars to be affected by these discrepancies. This is a rare example of a system in which the age and chemical composition are known, by virtue of being a member of the well-studied open cluster Ruprecht 147 (age~3 Gyr, [Fe/H] = +0.10). Here, we report a detailed study of this system with nonstandard models incorporating magnetic inhibition of convection. We show that these calculations are able to reproduce the observations largely within their uncertainties, providing robust estimates of the strength of the magnetic fields on both stars: 1600 ± 130 G and 1830 ± 150 G for the primary and secondary, respectively. Empirical estimates of the magnetic field strengths based on the measured X-ray luminosity of the system are roughly consistent with these predictions, supporting this mechanism as a possible explanation for the radius and temperature discrepancies.

scholarly journals Pre-main-sequence stars in the young open cluster NGC 1893

2007 ◽  
Vol 471 (2) ◽  
pp. 485-497 ◽  
Author(s):  
I. Negueruela ◽  
A. Marco ◽  
G. L. Israel ◽  
G. Bernabeu
Keyword(s):  
Main Sequence ◽  
Open Cluster ◽  
Main Sequence Stars ◽  
Young Open Cluster
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