FLAMES and XSHOOTER spectroscopy along the two blue straggler star sequences of M30

L. Lovisi, A. Mucciarelli, B. Lanzoni, F. R. Ferraro, E. Dalessandro, L. Monaco

Resultado de la investigación: Article

17 Citas (Scopus)

Resumen

We present spectroscopic observations acquired with FLAMES and XSHOOTER at the Very Large Telescope for a sample of 15 blue straggler stars (BSSs) in the globular cluster (GC) M30. The targets have been selected to sample the two BSS sequences discovered, with seven BSSs along the blue sequence and eight along the red one. No difference in the kinematical properties of the two groups of BSSs has been found. In particular, almost all the observed BSSs have projected rotational velocities lower than ∼30 km s-1, with only one (blue) fast rotating BSS (>90 km s-1), identified as a W UMa binary. This rotational velocity distribution is similar to those obtained in 47 Tucanae and NGC 6397, while M4 remains the only GC studied so far that harbors a large fraction of fast rotating BSSs. All stars hotter than ∼7800 K (regardless of the parent BSS sequence) show iron abundances larger than those measured from normal cluster stars, with a clear-cut trend with the effective temperature. This behavior suggests that particle transport mechanisms driven by radiative levitation occur in the photosphere of these stars, as already observed for the BSSs in NGC 6397. Finally, four BSSs belonging to the red sequence (not affected by radiative levitation) show a strong depletion of [O/Fe], with respect to the abundance measured in red giant branch and horizontal branch stars. This O-depletion is compatible with the chemical signature expected in BSSs formed by mass-transfer processes in binary systems, in agreement with the mechanism proposed for the formation of BSSs in the red sequence.

Idioma originalEnglish
Número de artículo148
PublicaciónAstrophysical Journal
Volumen772
N.º2
DOI
EstadoPublished - 1 ago 2013

Huella dactilar

blue stars
spectroscopy
mass transfer
harbor
iron
O stars
temperature
levitation
globular clusters
depletion
horizontal branch stars
hot stars
harbors
star clusters
photosphere
low speed
distribution
chemical
trend
particle

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Citar esto

Lovisi, L. ; Mucciarelli, A. ; Lanzoni, B. ; Ferraro, F. R. ; Dalessandro, E. ; Monaco, L. / FLAMES and XSHOOTER spectroscopy along the two blue straggler star sequences of M30. En: Astrophysical Journal. 2013 ; Vol. 772, N.º 2.
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title = "FLAMES and XSHOOTER spectroscopy along the two blue straggler star sequences of M30",
abstract = "We present spectroscopic observations acquired with FLAMES and XSHOOTER at the Very Large Telescope for a sample of 15 blue straggler stars (BSSs) in the globular cluster (GC) M30. The targets have been selected to sample the two BSS sequences discovered, with seven BSSs along the blue sequence and eight along the red one. No difference in the kinematical properties of the two groups of BSSs has been found. In particular, almost all the observed BSSs have projected rotational velocities lower than ∼30 km s-1, with only one (blue) fast rotating BSS (>90 km s-1), identified as a W UMa binary. This rotational velocity distribution is similar to those obtained in 47 Tucanae and NGC 6397, while M4 remains the only GC studied so far that harbors a large fraction of fast rotating BSSs. All stars hotter than ∼7800 K (regardless of the parent BSS sequence) show iron abundances larger than those measured from normal cluster stars, with a clear-cut trend with the effective temperature. This behavior suggests that particle transport mechanisms driven by radiative levitation occur in the photosphere of these stars, as already observed for the BSSs in NGC 6397. Finally, four BSSs belonging to the red sequence (not affected by radiative levitation) show a strong depletion of [O/Fe], with respect to the abundance measured in red giant branch and horizontal branch stars. This O-depletion is compatible with the chemical signature expected in BSSs formed by mass-transfer processes in binary systems, in agreement with the mechanism proposed for the formation of BSSs in the red sequence.",
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FLAMES and XSHOOTER spectroscopy along the two blue straggler star sequences of M30. / Lovisi, L.; Mucciarelli, A.; Lanzoni, B.; Ferraro, F. R.; Dalessandro, E.; Monaco, L.

En: Astrophysical Journal, Vol. 772, N.º 2, 148, 01.08.2013.

Resultado de la investigación: Article

TY - JOUR

T1 - FLAMES and XSHOOTER spectroscopy along the two blue straggler star sequences of M30

AU - Lovisi, L.

AU - Mucciarelli, A.

AU - Lanzoni, B.

AU - Ferraro, F. R.

AU - Dalessandro, E.

AU - Monaco, L.

PY - 2013/8/1

Y1 - 2013/8/1

N2 - We present spectroscopic observations acquired with FLAMES and XSHOOTER at the Very Large Telescope for a sample of 15 blue straggler stars (BSSs) in the globular cluster (GC) M30. The targets have been selected to sample the two BSS sequences discovered, with seven BSSs along the blue sequence and eight along the red one. No difference in the kinematical properties of the two groups of BSSs has been found. In particular, almost all the observed BSSs have projected rotational velocities lower than ∼30 km s-1, with only one (blue) fast rotating BSS (>90 km s-1), identified as a W UMa binary. This rotational velocity distribution is similar to those obtained in 47 Tucanae and NGC 6397, while M4 remains the only GC studied so far that harbors a large fraction of fast rotating BSSs. All stars hotter than ∼7800 K (regardless of the parent BSS sequence) show iron abundances larger than those measured from normal cluster stars, with a clear-cut trend with the effective temperature. This behavior suggests that particle transport mechanisms driven by radiative levitation occur in the photosphere of these stars, as already observed for the BSSs in NGC 6397. Finally, four BSSs belonging to the red sequence (not affected by radiative levitation) show a strong depletion of [O/Fe], with respect to the abundance measured in red giant branch and horizontal branch stars. This O-depletion is compatible with the chemical signature expected in BSSs formed by mass-transfer processes in binary systems, in agreement with the mechanism proposed for the formation of BSSs in the red sequence.

AB - We present spectroscopic observations acquired with FLAMES and XSHOOTER at the Very Large Telescope for a sample of 15 blue straggler stars (BSSs) in the globular cluster (GC) M30. The targets have been selected to sample the two BSS sequences discovered, with seven BSSs along the blue sequence and eight along the red one. No difference in the kinematical properties of the two groups of BSSs has been found. In particular, almost all the observed BSSs have projected rotational velocities lower than ∼30 km s-1, with only one (blue) fast rotating BSS (>90 km s-1), identified as a W UMa binary. This rotational velocity distribution is similar to those obtained in 47 Tucanae and NGC 6397, while M4 remains the only GC studied so far that harbors a large fraction of fast rotating BSSs. All stars hotter than ∼7800 K (regardless of the parent BSS sequence) show iron abundances larger than those measured from normal cluster stars, with a clear-cut trend with the effective temperature. This behavior suggests that particle transport mechanisms driven by radiative levitation occur in the photosphere of these stars, as already observed for the BSSs in NGC 6397. Finally, four BSSs belonging to the red sequence (not affected by radiative levitation) show a strong depletion of [O/Fe], with respect to the abundance measured in red giant branch and horizontal branch stars. This O-depletion is compatible with the chemical signature expected in BSSs formed by mass-transfer processes in binary systems, in agreement with the mechanism proposed for the formation of BSSs in the red sequence.

KW - blue stragglers

KW - globular clusters: individual (M30)

KW - stars: abundances

KW - stars: evolution

KW - techniques: spectroscopic

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DO - 10.1088/0004-637X/772/2/148

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