Observations of the Ultraviolet-bright Star III-60 in the Globular Cluster NGC 6723
We have analyzed archival far-ultraviolet spectra of the UV-bright star III-60 in the globular cluster NGC 6723 obtained with the Far Ultraviolet Spectroscopic Explorer and the Cosmic Origins Spectrograph. We find that the star's photospheric parameters (effective temperature T _eff = 44,800 ±...
Saved in:
| Main Author: | |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
|
| Series: | The Astrophysical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-4357/ada604 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1832581887659343872 |
|---|---|
| author | William V. Dixon |
| author_facet | William V. Dixon |
| author_sort | William V. Dixon |
| collection | DOAJ |
| description | We have analyzed archival far-ultraviolet spectra of the UV-bright star III-60 in the globular cluster NGC 6723 obtained with the Far Ultraviolet Spectroscopic Explorer and the Cosmic Origins Spectrograph. We find that the star's photospheric parameters (effective temperature T _eff = 44,800 ± 1200 K, surface gravity $\mathrm{log}g=4.89\pm 0.18$ , and helium abundance $\mathrm{log}N({\rm{He}})/N({\rm{H}})=-0.84\pm 0.29$ ) are consistent with the values derived from its optical spectrum, suggesting that optically derived values are generally accurate for evolved stars with T _eff ≲ 50,000 K. Relative to the cluster's red giant branch stars, III-60 is enhanced in nitrogen and depleted in carbon and oxygen. The star exhibits strong P Cygni profiles in both components of the N v λ 1240 doublet, but the resonance lines of other species show no evidence of a stellar wind. The star's effective temperature and luminosity place it on the evolutionary tracks of stars evolving from the blue horizontal branch, but its high mass (∼1.2 M _⊙ ) indicates that it is the product of a stellar merger. Its helium, carbon, and nitrogen abundances suggest that it is following an evolutionary path similar to that of the low-carbon, intermediate helium-rich hot subdwarfs. |
| format | Article |
| id | doaj-art-3a72a5804e1a4e4683ed81bd2327a544 |
| institution | Kabale University |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj-art-3a72a5804e1a4e4683ed81bd2327a5442025-01-30T09:32:01ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-019801510.3847/1538-4357/ada604Observations of the Ultraviolet-bright Star III-60 in the Globular Cluster NGC 6723William V. Dixon0https://orcid.org/0000-0001-9184-4716Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA ; dixon@stsci.eduWe have analyzed archival far-ultraviolet spectra of the UV-bright star III-60 in the globular cluster NGC 6723 obtained with the Far Ultraviolet Spectroscopic Explorer and the Cosmic Origins Spectrograph. We find that the star's photospheric parameters (effective temperature T _eff = 44,800 ± 1200 K, surface gravity $\mathrm{log}g=4.89\pm 0.18$ , and helium abundance $\mathrm{log}N({\rm{He}})/N({\rm{H}})=-0.84\pm 0.29$ ) are consistent with the values derived from its optical spectrum, suggesting that optically derived values are generally accurate for evolved stars with T _eff ≲ 50,000 K. Relative to the cluster's red giant branch stars, III-60 is enhanced in nitrogen and depleted in carbon and oxygen. The star exhibits strong P Cygni profiles in both components of the N v λ 1240 doublet, but the resonance lines of other species show no evidence of a stellar wind. The star's effective temperature and luminosity place it on the evolutionary tracks of stars evolving from the blue horizontal branch, but its high mass (∼1.2 M _⊙ ) indicates that it is the product of a stellar merger. Its helium, carbon, and nitrogen abundances suggest that it is following an evolutionary path similar to that of the low-carbon, intermediate helium-rich hot subdwarfs.https://doi.org/10.3847/1538-4357/ada604Stellar abundancesStellar atmospheresStellar evolutionUltraviolet spectroscopy |
| spellingShingle | William V. Dixon Observations of the Ultraviolet-bright Star III-60 in the Globular Cluster NGC 6723 The Astrophysical Journal Stellar abundances Stellar atmospheres Stellar evolution Ultraviolet spectroscopy |
| title | Observations of the Ultraviolet-bright Star III-60 in the Globular Cluster NGC 6723 |
| title_full | Observations of the Ultraviolet-bright Star III-60 in the Globular Cluster NGC 6723 |
| title_fullStr | Observations of the Ultraviolet-bright Star III-60 in the Globular Cluster NGC 6723 |
| title_full_unstemmed | Observations of the Ultraviolet-bright Star III-60 in the Globular Cluster NGC 6723 |
| title_short | Observations of the Ultraviolet-bright Star III-60 in the Globular Cluster NGC 6723 |
| title_sort | observations of the ultraviolet bright star iii 60 in the globular cluster ngc 6723 |
| topic | Stellar abundances Stellar atmospheres Stellar evolution Ultraviolet spectroscopy |
| url | https://doi.org/10.3847/1538-4357/ada604 |
| work_keys_str_mv | AT williamvdixon observationsoftheultravioletbrightstariii60intheglobularclusterngc6723 |