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

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 Te...

Descripción completa

Guardado en:
Detalles Bibliográficos
Autores principales: Dixon, William V., Chayer, Pierre, Latour, Marilyn, Miller Bertolami, Marcelo Miguel, Benjamin, Robert A.
Formato: Articulo
Lenguaje:Inglés
Publicado: 2017
Materias:
Ciencias Astronómicas
stars: abundances
stars: atmospheres
stars: individual (NGC 6121 Y453)
ultraviolet: stars
Acceso en línea:http://sedici.unlp.edu.ar/handle/10915/87767
Aporte de:
SEDICI (UNLP) de Universidad Nacional de La Plata
id I19-R120-10915-87767
record_format dspace
institution Universidad Nacional de La Plata
institution_str I-19
repository_str R-120
collection SEDICI (UNLP)
language Inglés
topic Ciencias Astronómicas
stars: abundances
stars: atmospheres
stars: individual (NGC 6121 Y453)
ultraviolet: stars
spellingShingle Ciencias Astronómicas
stars: abundances
stars: atmospheres
stars: individual (NGC 6121 Y453)
ultraviolet: stars
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)
topic_facet Ciencias Astronómicas
stars: abundances
stars: atmospheres
stars: individual (NGC 6121 Y453)
ultraviolet: stars
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.
format Articulo
Articulo
author Dixon, William V.
Chayer, Pierre
Latour, Marilyn
Miller Bertolami, Marcelo Miguel
Benjamin, Robert A.
author_facet Dixon, William V.
Chayer, Pierre
Latour, Marilyn
Miller Bertolami, Marcelo Miguel
Benjamin, Robert A.
author_sort Dixon, William V.
title Observations of the Ultraviolet-bright Star Y453 in the Globular Cluster M4 (NGC 6121)
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)
publishDate 2017
url http://sedici.unlp.edu.ar/handle/10915/87767
work_keys_str_mv AT dixonwilliamv observationsoftheultravioletbrightstary453intheglobularclusterm4ngc6121
AT chayerpierre observationsoftheultravioletbrightstary453intheglobularclusterm4ngc6121
AT latourmarilyn observationsoftheultravioletbrightstary453intheglobularclusterm4ngc6121
AT millerbertolamimarcelomiguel observationsoftheultravioletbrightstary453intheglobularclusterm4ngc6121
AT benjaminroberta observationsoftheultravioletbrightstary453intheglobularclusterm4ngc6121
bdutipo_str Repositorios
_version_ 1764820489376628736

Ejemplares similares