scholarly journals Gemini/Phoenix H-band analysis of the globular cluster AL 3

2021 ◽  
Vol 648 ◽  
pp. A16
Author(s):  
B. Barbuy ◽  
H. Ernandes ◽  
S. O. Souza ◽  
R. Razera ◽  
T. Moura ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Wavelength Range ◽  
Globular Cluster ◽  
Spectral Region ◽  
Wavelength Region ◽  
Individual Stars ◽  
Synthetic Spectra ◽  
Cool Stars ◽  
Magnitude Diagram ◽  
The Phoenix

Context. The globular cluster AL 3 is old and located in the inner bulge. Three individual stars were observed with the Phoenix spectrograph at the Gemini South telescope. The wavelength region contains prominent lines of CN, OH, and CO, allowing the derivation of C, N, and O abundances of cool stars. Aims. We aim to derive C, N, O abundances of three stars in the bulge globular cluster AL 3, and additionally in stars of NGC 6558 and HP 1. The spectra of AL 3 allows us to derive the cluster’s radial velocity. Methods. For AL 3, we applied a new code to analyse its colour-magnitude diagram. Synthetic spectra were computed and compared to observed spectra for the three clusters. Results. We present a detailed identification of lines in the spectral region centred at 15 555 Å, covering the wavelength range 15 525–15 590 Å. C, N, and O abundances are tentatively derived for the sample stars.

scholarly journals Derivation of Abundances Through Photometric and Spectroscopic Methods

1976 ◽  
Vol 72 ◽  
pp. 49-65
Author(s):  
R. A. Bell
Keyword(s):  
Globular Cluster ◽  
Spectroscopic Methods ◽  
Intermediate Band ◽  
Carbon And Nitrogen ◽  
Giant Stars ◽  
A Value ◽  
Synthetic Spectra ◽  
Isotopic Shifts ◽  
Cool Stars ◽  
K Giants

Several points of detail which affect stellar abundance determinations are discussed. In particular, the importance of including the effects of hyperfine structure and isotopic shifts when considering the lines of some elements is stressed.The abundance determinations for F dwarfs by Bell and Peytremann, who use theoretical calibrations for intermediate band photometry, and Nissen, who observes very narrow spectral intervals, are intercompared. The agreement between Bell and Nissen, who have 46 stars in common, is quite satisfactory.Recent work on carbon and nitrogen abundances in cool stars is described. The suggestion of Hearnshaw, that [C/H] = 1.5 [Fe/H] for disc stars with −0.7 < [Fe/H] < 0.4, is compared with recent results by Clegg. Whilst Clegg's results are quite precise, they neither confirm nor deny Hearnshaw's suggestion. Work by Branch and Bell on K giants shows that [C/Fe] = 0, or a constant, for the stars in the sample. A value of about 7 for the C12/C13 ratio in the atmosphere of Arcturus has now been confirmed by several authors and Lambert and his collaborators have determined this ratio for several K giants.The suggestion by Spinrad, Taylor and others that the M67 dwarfs are more metal-rich than the Hyades, i.e. that they are super-metal-rich or SMR, seems to be erroneous. However some SMR stars, such as 31 Aql, certainly exist even though there is still some uncertainty in the precise abundance of strong CN stars such as μ Leo.Examples of synthetic spectra for metal-deficient giant stars are given and a theoretical colour-colour diagram is compared with observations of globular cluster and Draco stars.

scholarly journals Synthetic Spectra for Single-Aged Populations

1995 ◽  
Vol 164 ◽  
pp. 458-458
Author(s):  
A. Milone ◽  
B. Barbuy
Keyword(s):  
Wavelength Range ◽  
Globular Clusters ◽  
Main Sequence ◽  
Stellar Populations ◽  
The Other ◽  
Individual Stars ◽  
Synthetic Spectra ◽  
Galactic Globular Clusters

Spectra of single-aged old stellar populations of metallicities in the range −1.0 ≤ [Fe/H] ≤ +0.5 are built in the wavelength range 6950-7550 Å including TiO bands, by combining synthetic spectra of individual stars. Two approaches are applied: one for moderately metal-poor populations, entirely based on isochrones, and the other one applied to the metal-rich Galactic globular clusters, based on isochrones for the main sequence and data of observed colour-magnitude diagrams for the evolved stages. Abundance ratios of [α/Fe] = +0.3 are adopted for populations of [Fe/H] = −1.0, −0.5, and both 0.0 and +0.3 for the more metal-rich ones.

B,V Photometry of the Variable Star V9 in the Globular Cluster 47 Tuc

1993 ◽  
Vol 139 ◽  
pp. 421-421
Author(s):  
Michael Corwin ◽  
Bruce Carney
Keyword(s):  
Radial Velocity ◽  
Globular Cluster ◽  
Variable Star ◽  
Light Curves ◽  
Horizontal Branch ◽  
Ccd Photometry ◽  
Magnitude Diagram

AbstractWe present BV CCD photometry of the variable star V9 in the globular cluster 47 Tuc. V, B, and (B – V) light curves are given. A colour-magnitude diagram based on four V and four B frames is given. V9's location on the diagram is considerably brighter and bluer than the edge of the red horizontal branch. Its radial velocity indicates that V9 is a member of the cluster.

Radial Velocity Variations in Cool Supergiants

1984 ◽  
Vol 88 ◽  
pp. 283-288
Author(s):  
Hugh C. Harris
Keyword(s):  
Radial Velocity ◽  
Main Sequence ◽  
Short Period ◽  
Cool Stars ◽  
Synchronous Rotation ◽  
Red Supergiants ◽  
Velocity Variations ◽  
Orbital Periods ◽  
Low Amplitude ◽  
Good Agreement

AbstractA survey of F, G, and W supergiants has been carried out with the DAO radial velocity spectrometer, an efficient instrument for detecting low-amplitude velocity variations in cool stars. Observations of 78 stars over five seasons show generally good agreement with OORAVEL results for spectroscopie binaries. The majority of supergiants show low-amplitude variability, with amplitudes typically 1 to 2 km s−1. The width of the cross-correlation profile has been measured for 58 supergiants. It reveals 14 stars with unusually broad lines, indicative of rotation velocities of 15 to 35 km s−1. Several have short-period binary companions and may be in synchronous rotation. The other broad-lined stars are apparently single or with long orbital periods; they may be making their first transition from the main sequence to become red supergiants.

scholarly journals Tests of effective temperature – colour relations

1997 ◽  
Vol 189 ◽  
pp. 159-168
Author(s):  
R.A. Bell
Keyword(s):  
Globular Cluster ◽  
Effective Temperature ◽  
Average Difference ◽  
Flux Method ◽  
Synthetic Spectra ◽  
Stellar Temperatures ◽  
Angular Diameters

This paper discusses some tests of synthetic spectra used in the calculation of synthetic colours, as well as some of the problems which arise in these calculations. Synthetic colours are tested in two ways. Firstly, observed angular diameters of stars are compared with ones predicted from stellar temperatures derived from synthetic colours and the infrared flux method. The average difference is less than 2%. Secondly, a very metal-poor isochrone is transformed to the Mv, B–V and Mv, V–I colour planes and compared with observations of stars in the globular cluster M92. The agreement is good in both colour–magnitude diagrams.

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