The blue straggler V106 in NGC6791: A prototype progenitor of old single giants masquerading as young

K. Brogaard; S. M. Christiansen; F. Grundahl; A. Miglio; R. G. Izzard; T. M. Tauris; E. L. Sandquist; D. A. Vanden Berg; J. Jessen-Hansen; T. Arentoft; H. Bruntt; S. Frandsen; J. A. Orosz; G. A. Feiden; R. Mathieu; Aaron M Geller; M. Shetrone; N. Ryde; D. Stello; I. Platais; S. Meibom

doi:10.1093/MNRAS/STY2504

The blue straggler V106 in NGC6791: A prototype progenitor of old single giants masquerading as young

K. Brogaard^*, S. M. Christiansen, F. Grundahl, A. Miglio, R. G. Izzard, T. M. Tauris, E. L. Sandquist, D. A. Vanden Berg, J. Jessen-Hansen, T. Arentoft, H. Bruntt, S. Frandsen, J. A. Orosz, G. A. Feiden, R. Mathieu, Aaron M Geller, M. Shetrone, N. Ryde, D. Stello, I. PlataisS. Meibom

^*Corresponding author for this work

CIERA - Center for Interdisciplinary Exploration and Research in Astrophysics

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Abstract

We determine the properties of the binary star V106 in the old open cluster NGC6791. We identify the system to be a blue straggler cluster member by using a combination of groundbased and Kepler photometry and multi-epoch spectroscopy. The properties of the primary component are found to be M_p ~ 1.67M_⊙, more massive than the cluster turn-off, with R_p ~ 1.91R_⊙ and T_eff = 7110 ± 100 K. The secondary component is highly oversized and overluminous for its low mass with M_s ~ 0.182M_⊙, R_⊙ ~ 0.864R_⊙, and T_⊙ =6875±200 K. We identify this secondary star as a bloated (proto) extremely low-mass helium white dwarf. These properties of V106 suggest that it represents a typical Algol-paradox system and that it evolved through a mass-transfer phase, which provides insight into its past evolution. We present a detailed binary stellar evolution model for the formation of V106 using the MESA code and find that the mass-transfer phase only ceased about 40 Myr ago. Due to the short orbital period (P = 1.4463 d), another mass-transfer phase is unavoidable once the current primary star evolves towards the red giant phase. We argue that V106 will evolve through a common-envelope phase within the next 100 Myr and merge to become a single overmassive giant. The high mass will make it appear young for its true age, which is revealed by the cluster properties. Therefore, V106 is potentially a prototype progenitor of old field giants masquerading as young.

Original language	English (US)
Pages (from-to)	5062-5072
Number of pages	11
Journal	Monthly Notices of the Royal Astronomical Society
Volume	481
Issue number	4
DOIs	https://doi.org/10.1093/MNRAS/STY2504
State	Published - Dec 1 2018

Funding

We thank the anonymous referee for useful comments and suggestions that helped improve the manuscript. We thank Simon Jeffery for useful conversations. Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (Grant DNRF106). RGI thanks the STFC for funding Rutherford grant ST/M003892/1. AM acknowledges the International Space Science Institute (ISSI) for the support provided to the asterosSTEP ISSI International Team. AM acknowledges support from the ERC Consolidator Grant funding scheme (project ASTEROCHRONOMETRY, G.A. n. 772293).

Keywords

Binaries: close
Blue stragglers
Stars: fundamental parameters
Stars: individual: V106
White dwarfs

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.1093/MNRAS/STY2504

Cite this

Brogaard, K., Christiansen, S. M., Grundahl, F., Miglio, A., Izzard, R. G., Tauris, T. M., Sandquist, E. L., Vanden Berg, D. A., Jessen-Hansen, J., Arentoft, T., Bruntt, H., Frandsen, S., Orosz, J. A., Feiden, G. A., Mathieu, R., Geller, A. M., Shetrone, M., Ryde, N., Stello, D., ... Meibom, S. (2018). The blue straggler V106 in NGC6791: A prototype progenitor of old single giants masquerading as young. Monthly Notices of the Royal Astronomical Society, 481(4), 5062-5072. https://doi.org/10.1093/MNRAS/STY2504

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title = "The blue straggler V106 in NGC6791: A prototype progenitor of old single giants masquerading as young",

abstract = "We determine the properties of the binary star V106 in the old open cluster NGC6791. We identify the system to be a blue straggler cluster member by using a combination of groundbased and Kepler photometry and multi-epoch spectroscopy. The properties of the primary component are found to be Mp ~ 1.67M⊙, more massive than the cluster turn-off, with Rp ~ 1.91R⊙ and Teff = 7110 ± 100 K. The secondary component is highly oversized and overluminous for its low mass with Ms ~ 0.182M⊙, R⊙ ~ 0.864R⊙, and T⊙ =6875±200 K. We identify this secondary star as a bloated (proto) extremely low-mass helium white dwarf. These properties of V106 suggest that it represents a typical Algol-paradox system and that it evolved through a mass-transfer phase, which provides insight into its past evolution. We present a detailed binary stellar evolution model for the formation of V106 using the MESA code and find that the mass-transfer phase only ceased about 40 Myr ago. Due to the short orbital period (P = 1.4463 d), another mass-transfer phase is unavoidable once the current primary star evolves towards the red giant phase. We argue that V106 will evolve through a common-envelope phase within the next 100 Myr and merge to become a single overmassive giant. The high mass will make it appear young for its true age, which is revealed by the cluster properties. Therefore, V106 is potentially a prototype progenitor of old field giants masquerading as young.",

keywords = "Binaries: close, Blue stragglers, Stars: fundamental parameters, Stars: individual: V106, White dwarfs",

author = "K. Brogaard and Christiansen, {S. M.} and F. Grundahl and A. Miglio and Izzard, {R. G.} and Tauris, {T. M.} and Sandquist, {E. L.} and {Vanden Berg}, {D. A.} and J. Jessen-Hansen and T. Arentoft and H. Bruntt and S. Frandsen and Orosz, {J. A.} and Feiden, {G. A.} and R. Mathieu and Geller, {Aaron M} and M. Shetrone and N. Ryde and D. Stello and I. Platais and S. Meibom",

note = "Publisher Copyright: {\textcopyright} 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.",

year = "2018",

month = dec,

day = "1",

doi = "10.1093/MNRAS/STY2504",

language = "English (US)",

volume = "481",

pages = "5062--5072",

journal = "Monthly Notices of the Royal Astronomical Society",

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Brogaard, K, Christiansen, SM, Grundahl, F, Miglio, A, Izzard, RG, Tauris, TM, Sandquist, EL, Vanden Berg, DA, Jessen-Hansen, J, Arentoft, T, Bruntt, H, Frandsen, S, Orosz, JA, Feiden, GA, Mathieu, R, Geller, AM, Shetrone, M, Ryde, N, Stello, D, Platais, I & Meibom, S 2018, 'The blue straggler V106 in NGC6791: A prototype progenitor of old single giants masquerading as young', Monthly Notices of the Royal Astronomical Society, vol. 481, no. 4, pp. 5062-5072. https://doi.org/10.1093/MNRAS/STY2504

TY - JOUR

T1 - The blue straggler V106 in NGC6791

T2 - A prototype progenitor of old single giants masquerading as young

AU - Brogaard, K.

AU - Christiansen, S. M.

AU - Grundahl, F.

AU - Miglio, A.

AU - Izzard, R. G.

AU - Tauris, T. M.

AU - Sandquist, E. L.

AU - Vanden Berg, D. A.

AU - Jessen-Hansen, J.

AU - Arentoft, T.

AU - Bruntt, H.

AU - Frandsen, S.

AU - Orosz, J. A.

AU - Feiden, G. A.

AU - Mathieu, R.

AU - Geller, Aaron M

AU - Shetrone, M.

AU - Ryde, N.

AU - Stello, D.

AU - Platais, I.

AU - Meibom, S.

PY - 2018/12/1

Y1 - 2018/12/1

N2 - We determine the properties of the binary star V106 in the old open cluster NGC6791. We identify the system to be a blue straggler cluster member by using a combination of groundbased and Kepler photometry and multi-epoch spectroscopy. The properties of the primary component are found to be Mp ~ 1.67M⊙, more massive than the cluster turn-off, with Rp ~ 1.91R⊙ and Teff = 7110 ± 100 K. The secondary component is highly oversized and overluminous for its low mass with Ms ~ 0.182M⊙, R⊙ ~ 0.864R⊙, and T⊙ =6875±200 K. We identify this secondary star as a bloated (proto) extremely low-mass helium white dwarf. These properties of V106 suggest that it represents a typical Algol-paradox system and that it evolved through a mass-transfer phase, which provides insight into its past evolution. We present a detailed binary stellar evolution model for the formation of V106 using the MESA code and find that the mass-transfer phase only ceased about 40 Myr ago. Due to the short orbital period (P = 1.4463 d), another mass-transfer phase is unavoidable once the current primary star evolves towards the red giant phase. We argue that V106 will evolve through a common-envelope phase within the next 100 Myr and merge to become a single overmassive giant. The high mass will make it appear young for its true age, which is revealed by the cluster properties. Therefore, V106 is potentially a prototype progenitor of old field giants masquerading as young.

AB - We determine the properties of the binary star V106 in the old open cluster NGC6791. We identify the system to be a blue straggler cluster member by using a combination of groundbased and Kepler photometry and multi-epoch spectroscopy. The properties of the primary component are found to be Mp ~ 1.67M⊙, more massive than the cluster turn-off, with Rp ~ 1.91R⊙ and Teff = 7110 ± 100 K. The secondary component is highly oversized and overluminous for its low mass with Ms ~ 0.182M⊙, R⊙ ~ 0.864R⊙, and T⊙ =6875±200 K. We identify this secondary star as a bloated (proto) extremely low-mass helium white dwarf. These properties of V106 suggest that it represents a typical Algol-paradox system and that it evolved through a mass-transfer phase, which provides insight into its past evolution. We present a detailed binary stellar evolution model for the formation of V106 using the MESA code and find that the mass-transfer phase only ceased about 40 Myr ago. Due to the short orbital period (P = 1.4463 d), another mass-transfer phase is unavoidable once the current primary star evolves towards the red giant phase. We argue that V106 will evolve through a common-envelope phase within the next 100 Myr and merge to become a single overmassive giant. The high mass will make it appear young for its true age, which is revealed by the cluster properties. Therefore, V106 is potentially a prototype progenitor of old field giants masquerading as young.

KW - Binaries: close

KW - Blue stragglers

KW - Stars: fundamental parameters

KW - Stars: individual: V106

KW - White dwarfs

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U2 - 10.1093/MNRAS/STY2504

DO - 10.1093/MNRAS/STY2504

M3 - Article

AN - SCOPUS:85059612803

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VL - 481

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EP - 5072

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

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The blue straggler V106 in NGC6791: A prototype progenitor of old single giants masquerading as young

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