Exploring B4: A pulsating sdB star, in a binary, in the open cluster NGC 6791

Herbert Pablo; Steven D. Kawaler; Elizabeth M. Green

doi:10.1088/2041-8205/740/2/L47

Exploring B4: A pulsating sdB star, in a binary, in the open cluster NGC 6791

Herbert Pablo, Steven D. Kawaler, Elizabeth M. Green

Steward Observatory

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38 Scopus citations

Abstract

We report on Kepler photometry of the hot subdwarf B (sdB) star B4 in the open cluster NGC 6791. We confirm that B4 is a reflection effect binary with an sdB component and a low-mass main-sequence companion with a circular 0.3985 day orbit. The sdB star is a g-mode pulsator (a V1093 Her star) with periods ranging from 2384s to 7643s. Several of the pulsation modes show symmetric splitting by 0.62 μHz. Attributing this to rotational splitting, we conclude that the sdB component has a rotation period of approximately 9.63 days, indicating that tidal synchronization has not been achieved in this system. Comparison with theoretical synchronization time provides a discriminant between various theoretical models.

Original language	English (US)
Article number	L47
Journal	Astrophysical Journal Letters
Volume	740
Issue number	2
DOIs	https://doi.org/10.1088/2041-8205/740/2/L47
State	Published - Oct 20 2011

Keywords

binaries: close
open clusters and associations: individual (NGC 6791)
stars: horizontal-branch
stars: oscillations

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.1088/2041-8205/740/2/L47

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title = "Exploring B4: A pulsating sdB star, in a binary, in the open cluster NGC 6791",

abstract = "We report on Kepler photometry of the hot subdwarf B (sdB) star B4 in the open cluster NGC 6791. We confirm that B4 is a reflection effect binary with an sdB component and a low-mass main-sequence companion with a circular 0.3985 day orbit. The sdB star is a g-mode pulsator (a V1093 Her star) with periods ranging from 2384s to 7643s. Several of the pulsation modes show symmetric splitting by 0.62 μHz. Attributing this to rotational splitting, we conclude that the sdB component has a rotation period of approximately 9.63 days, indicating that tidal synchronization has not been achieved in this system. Comparison with theoretical synchronization time provides a discriminant between various theoretical models.",

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T1 - Exploring B4

T2 - A pulsating sdB star, in a binary, in the open cluster NGC 6791

AU - Pablo, Herbert

AU - Kawaler, Steven D.

AU - Green, Elizabeth M.

PY - 2011/10/20

Y1 - 2011/10/20

N2 - We report on Kepler photometry of the hot subdwarf B (sdB) star B4 in the open cluster NGC 6791. We confirm that B4 is a reflection effect binary with an sdB component and a low-mass main-sequence companion with a circular 0.3985 day orbit. The sdB star is a g-mode pulsator (a V1093 Her star) with periods ranging from 2384s to 7643s. Several of the pulsation modes show symmetric splitting by 0.62 μHz. Attributing this to rotational splitting, we conclude that the sdB component has a rotation period of approximately 9.63 days, indicating that tidal synchronization has not been achieved in this system. Comparison with theoretical synchronization time provides a discriminant between various theoretical models.

AB - We report on Kepler photometry of the hot subdwarf B (sdB) star B4 in the open cluster NGC 6791. We confirm that B4 is a reflection effect binary with an sdB component and a low-mass main-sequence companion with a circular 0.3985 day orbit. The sdB star is a g-mode pulsator (a V1093 Her star) with periods ranging from 2384s to 7643s. Several of the pulsation modes show symmetric splitting by 0.62 μHz. Attributing this to rotational splitting, we conclude that the sdB component has a rotation period of approximately 9.63 days, indicating that tidal synchronization has not been achieved in this system. Comparison with theoretical synchronization time provides a discriminant between various theoretical models.

KW - binaries: close

KW - open clusters and associations: individual (NGC 6791)

KW - stars: horizontal-branch

KW - stars: oscillations

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JO - Astrophysical Journal Letters

JF - Astrophysical Journal Letters

SN - 2041-8205

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ER -

Exploring B4: A pulsating sdB star, in a binary, in the open cluster NGC 6791

Abstract

Keywords

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