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dc.contributor.author
Dixon, William V.
dc.contributor.author
Chayer, Pierre
dc.contributor.author
Latour, Marilyn
dc.contributor.author
Miller Bertolami, Marcelo Miguel
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dc.contributor.author
Benjamin, Robert A.
dc.date.available
2018-04-19T12:26:34Z
dc.date.issued
2017-09
dc.identifier.citation
Dixon, William V.; Chayer, Pierre; Latour, Marilyn; Miller Bertolami, Marcelo Miguel; Benjamin, Robert A.; Observations of the ultraviolet-bright star Y453 in the globular cluster M4 (NGC 6121); IOP Publishing; Astronomical Journal; 154; 3; 9-2017
dc.identifier.issn
0004-6256
dc.identifier.uri
http://hdl.handle.net/11336/42581
dc.description.abstract
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.
dc.format
application/pdf
dc.language.iso
eng
dc.publisher
IOP Publishing
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dc.rights
info:eu-repo/semantics/openAccess
dc.rights.uri
https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
dc.subject
Abundances
dc.subject
Atmospheres
dc.subject
Ultraviolet
dc.subject
Stars
dc.subject
Ngc 6121 (Estrella)
dc.subject
Y453 (Estrella)
dc.subject.classification
Astronomía
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dc.subject.classification
Ciencias Físicas
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dc.subject.classification
CIENCIAS NATURALES Y EXACTAS
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dc.title
Observations of the ultraviolet-bright star Y453 in the globular cluster M4 (NGC 6121)
dc.type
info:eu-repo/semantics/article
dc.type
info:ar-repo/semantics/artículo
dc.type
info:eu-repo/semantics/publishedVersion
dc.date.updated
2018-04-16T14:58:30Z
dc.journal.volume
154
dc.journal.number
3
dc.journal.pais
Estados Unidos
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dc.description.fil
Fil: Dixon, William V.. Space Telescope Science Institute; Estados Unidos
dc.description.fil
Fil: Chayer, Pierre. Space Telescope Science Institute; Estados Unidos
dc.description.fil
Fil: Latour, Marilyn. Friedrich-alexander University Erlangen-nuremberg; Estados Unidos
dc.description.fil
Fil: Miller Bertolami, Marcelo Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina
dc.description.fil
Fil: Benjamin, Robert A.. University Of Wisconsin Whitewater; Estados Unidos
dc.journal.title
Astronomical Journal
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dc.relation.alternativeid
info:eu-repo/semantics/altIdentifier/doi/http://dx.doi.org/10.3847/1538-3881/aa8450
dc.relation.alternativeid
info:eu-repo/semantics/altIdentifier/url/http://iopscience.iop.org/article/10.3847/1538-3881/aa8450/meta
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