Observations of the Ultraviolet-bright Star Y453 in the Globular Cluster M4 (NGC 6121)

Autores
Dixon, William V.; Chayer, Pierre; Latour, Marilyn; Miller Bertolami, Marcelo Miguel; Benjamin, Robert A.
Año de publicación
2017
Idioma
inglés
Tipo de recurso
artículo
Estado
versión publicada
Descripción
We present a spectral analysis of the UV-bright star Y453 in M4. Model fits to the star's optical spectrum yield Teff ∼ 56,000 K. Fits to the star's FUV spectrum, obtained with the Cosmic Origins Spectrograph on board the Hubble Space Telescope, reveal it to be considerably hotter, with Teff ∼ 72,000 K. We adopt Teff = 72,000 ± 2000 K and log g = 5.7 ± 0.2 as our best-fit parameters. Scaling the model spectrum to match the star's optical and near-infrared magnitudes, we derive a mass M∗ = 0.53±0.24 M⊙ and luminosity = log L/L⊙ 2.84±0.05, consistent with the values expected of an evolved star in a globular cluster. Comparing the star with post-horizontal-branch evolutionary tracks, we conclude that it most likely evolved from the blue horizontal branch, departing the asymptotic giant branch before third dredge-up. It should thus exhibit the abundance pattern (O-poor and Na-rich) characteristic of the second-generation (SG) stars in M4. We derive the star's photospheric abundances of He, C, N, O, Si, S, Ti, Cr, Fe, and Ni. CNO abundances are roughly 0.25 dex greater than those of the cluster's SG stars, while the Si and S abundances match the cluster values. Abundances of the iron-peak elements (except for iron itself) are enhanced by 1-3 dex. Rather than revealing the star's origin and evolution, this pattern reflects the combined effects of diffusive and mechanical processes in the stellar atmosphere.
Instituto de Astrofísica de La Plata
Materia
Ciencias Astronómicas
stars: abundances
stars: atmospheres
stars: individual (NGC 6121 Y453)
ultraviolet: stars
Nivel de accesibilidad
acceso abierto
Condiciones de uso
http://creativecommons.org/licenses/by-nc-sa/4.0/
Repositorio
SEDICI (UNLP)
Institución
Universidad Nacional de La Plata
OAI Identificador
oai:sedici.unlp.edu.ar:10915/87767

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oai_identifier_str oai:sedici.unlp.edu.ar:10915/87767
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network_name_str SEDICI (UNLP)
spelling Observations of the Ultraviolet-bright Star Y453 in the Globular Cluster M4 (NGC 6121)Dixon, William V.Chayer, PierreLatour, MarilynMiller Bertolami, Marcelo MiguelBenjamin, Robert A.Ciencias Astronómicasstars: abundancesstars: atmospheresstars: individual (NGC 6121 Y453)ultraviolet: starsWe present a spectral analysis of the UV-bright star Y453 in M4. Model fits to the star's optical spectrum yield Teff ∼ 56,000 K. Fits to the star's FUV spectrum, obtained with the Cosmic Origins Spectrograph on board the Hubble Space Telescope, reveal it to be considerably hotter, with Teff ∼ 72,000 K. We adopt Teff = 72,000 ± 2000 K and log g = 5.7 ± 0.2 as our best-fit parameters. Scaling the model spectrum to match the star's optical and near-infrared magnitudes, we derive a mass M∗ = 0.53±0.24 M⊙ and luminosity = log L/L⊙ 2.84±0.05, consistent with the values expected of an evolved star in a globular cluster. Comparing the star with post-horizontal-branch evolutionary tracks, we conclude that it most likely evolved from the blue horizontal branch, departing the asymptotic giant branch before third dredge-up. It should thus exhibit the abundance pattern (O-poor and Na-rich) characteristic of the second-generation (SG) stars in M4. We derive the star's photospheric abundances of He, C, N, O, Si, S, Ti, Cr, Fe, and Ni. CNO abundances are roughly 0.25 dex greater than those of the cluster's SG stars, while the Si and S abundances match the cluster values. Abundances of the iron-peak elements (except for iron itself) are enhanced by 1-3 dex. Rather than revealing the star's origin and evolution, this pattern reflects the combined effects of diffusive and mechanical processes in the stellar atmosphere.Instituto de Astrofísica de La Plata2017info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionArticulohttp://purl.org/coar/resource_type/c_6501info:ar-repo/semantics/articuloapplication/pdfhttp://sedici.unlp.edu.ar/handle/10915/87767enginfo:eu-repo/semantics/altIdentifier/issn/0004-6256info:eu-repo/semantics/altIdentifier/doi/10.3847/1538-3881/aa8450info:eu-repo/semantics/openAccesshttp://creativecommons.org/licenses/by-nc-sa/4.0/Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)reponame:SEDICI (UNLP)instname:Universidad Nacional de La Platainstacron:UNLP2025-09-29T11:17:13Zoai:sedici.unlp.edu.ar:10915/87767Institucionalhttp://sedici.unlp.edu.ar/Universidad públicaNo correspondehttp://sedici.unlp.edu.ar/oai/snrdalira@sedici.unlp.edu.arArgentinaNo correspondeNo correspondeNo correspondeopendoar:13292025-09-29 11:17:14.137SEDICI (UNLP) - Universidad Nacional de La Platafalse
dc.title.none.fl_str_mv Observations of the Ultraviolet-bright Star Y453 in the Globular Cluster M4 (NGC 6121)
title Observations of the Ultraviolet-bright Star Y453 in the Globular Cluster M4 (NGC 6121)
spellingShingle Observations of the Ultraviolet-bright Star Y453 in the Globular Cluster M4 (NGC 6121)
Dixon, William V.
Ciencias Astronómicas
stars: abundances
stars: atmospheres
stars: individual (NGC 6121 Y453)
ultraviolet: stars
title_short Observations of the Ultraviolet-bright Star Y453 in the Globular Cluster M4 (NGC 6121)
title_full Observations of the Ultraviolet-bright Star Y453 in the Globular Cluster M4 (NGC 6121)
title_fullStr Observations of the Ultraviolet-bright Star Y453 in the Globular Cluster M4 (NGC 6121)
title_full_unstemmed Observations of the Ultraviolet-bright Star Y453 in the Globular Cluster M4 (NGC 6121)
title_sort Observations of the Ultraviolet-bright Star Y453 in the Globular Cluster M4 (NGC 6121)
dc.creator.none.fl_str_mv Dixon, William V.
Chayer, Pierre
Latour, Marilyn
Miller Bertolami, Marcelo Miguel
Benjamin, Robert A.
author Dixon, William V.
author_facet Dixon, William V.
Chayer, Pierre
Latour, Marilyn
Miller Bertolami, Marcelo Miguel
Benjamin, Robert A.
author_role author
author2 Chayer, Pierre
Latour, Marilyn
Miller Bertolami, Marcelo Miguel
Benjamin, Robert A.
author2_role author
author
author
author
dc.subject.none.fl_str_mv Ciencias Astronómicas
stars: abundances
stars: atmospheres
stars: individual (NGC 6121 Y453)
ultraviolet: stars
topic Ciencias Astronómicas
stars: abundances
stars: atmospheres
stars: individual (NGC 6121 Y453)
ultraviolet: stars
dc.description.none.fl_txt_mv We present a spectral analysis of the UV-bright star Y453 in M4. Model fits to the star's optical spectrum yield Teff ∼ 56,000 K. Fits to the star's FUV spectrum, obtained with the Cosmic Origins Spectrograph on board the Hubble Space Telescope, reveal it to be considerably hotter, with Teff ∼ 72,000 K. We adopt Teff = 72,000 ± 2000 K and log g = 5.7 ± 0.2 as our best-fit parameters. Scaling the model spectrum to match the star's optical and near-infrared magnitudes, we derive a mass M∗ = 0.53±0.24 M⊙ and luminosity = log L/L⊙ 2.84±0.05, consistent with the values expected of an evolved star in a globular cluster. Comparing the star with post-horizontal-branch evolutionary tracks, we conclude that it most likely evolved from the blue horizontal branch, departing the asymptotic giant branch before third dredge-up. It should thus exhibit the abundance pattern (O-poor and Na-rich) characteristic of the second-generation (SG) stars in M4. We derive the star's photospheric abundances of He, C, N, O, Si, S, Ti, Cr, Fe, and Ni. CNO abundances are roughly 0.25 dex greater than those of the cluster's SG stars, while the Si and S abundances match the cluster values. Abundances of the iron-peak elements (except for iron itself) are enhanced by 1-3 dex. Rather than revealing the star's origin and evolution, this pattern reflects the combined effects of diffusive and mechanical processes in the stellar atmosphere.
Instituto de Astrofísica de La Plata
description We present a spectral analysis of the UV-bright star Y453 in M4. Model fits to the star's optical spectrum yield Teff ∼ 56,000 K. Fits to the star's FUV spectrum, obtained with the Cosmic Origins Spectrograph on board the Hubble Space Telescope, reveal it to be considerably hotter, with Teff ∼ 72,000 K. We adopt Teff = 72,000 ± 2000 K and log g = 5.7 ± 0.2 as our best-fit parameters. Scaling the model spectrum to match the star's optical and near-infrared magnitudes, we derive a mass M∗ = 0.53±0.24 M⊙ and luminosity = log L/L⊙ 2.84±0.05, consistent with the values expected of an evolved star in a globular cluster. Comparing the star with post-horizontal-branch evolutionary tracks, we conclude that it most likely evolved from the blue horizontal branch, departing the asymptotic giant branch before third dredge-up. It should thus exhibit the abundance pattern (O-poor and Na-rich) characteristic of the second-generation (SG) stars in M4. We derive the star's photospheric abundances of He, C, N, O, Si, S, Ti, Cr, Fe, and Ni. CNO abundances are roughly 0.25 dex greater than those of the cluster's SG stars, while the Si and S abundances match the cluster values. Abundances of the iron-peak elements (except for iron itself) are enhanced by 1-3 dex. Rather than revealing the star's origin and evolution, this pattern reflects the combined effects of diffusive and mechanical processes in the stellar atmosphere.
publishDate 2017
dc.date.none.fl_str_mv 2017
dc.type.none.fl_str_mv info:eu-repo/semantics/article
info:eu-repo/semantics/publishedVersion
Articulo
http://purl.org/coar/resource_type/c_6501
info:ar-repo/semantics/articulo
format article
status_str publishedVersion
dc.identifier.none.fl_str_mv http://sedici.unlp.edu.ar/handle/10915/87767
url http://sedici.unlp.edu.ar/handle/10915/87767
dc.language.none.fl_str_mv eng
language eng
dc.relation.none.fl_str_mv info:eu-repo/semantics/altIdentifier/issn/0004-6256
info:eu-repo/semantics/altIdentifier/doi/10.3847/1538-3881/aa8450
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
http://creativecommons.org/licenses/by-nc-sa/4.0/
Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)
eu_rights_str_mv openAccess
rights_invalid_str_mv http://creativecommons.org/licenses/by-nc-sa/4.0/
Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)
dc.format.none.fl_str_mv application/pdf
dc.source.none.fl_str_mv reponame:SEDICI (UNLP)
instname:Universidad Nacional de La Plata
instacron:UNLP
reponame_str SEDICI (UNLP)
collection SEDICI (UNLP)
instname_str Universidad Nacional de La Plata
instacron_str UNLP
institution UNLP
repository.name.fl_str_mv SEDICI (UNLP) - Universidad Nacional de La Plata
repository.mail.fl_str_mv alira@sedici.unlp.edu.ar
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