Selecting High-Precision Photometry on Uniform Zero Points for Five Benchmark Galactic Clusters

Taylor, Benjamin J.; Joner, M. D.

doi:10.48550/arxiv.1109.2230

Cited by 2 publications

(2 citation statements)

References 33 publications

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“…A critical focus of current and future cluster comparisons is the need to ensure that all cluster photometry is on a common system, supplying confidence that differences among the indices between clusters are signatures of true differences in the relative cluster parameters rather than by-products of calibration offsets. Fortunately, the two clusters of interest have been exhaustively investigated in a series of papers designed specifically to detect and minimize any zero-point differences in broadband VRI (Joner et al 2008;Taylor et al 2008;Taylor & Joner 2011) and uvbyHβ (Joner & Taylor 1995, 1997 photometry. As with NGC 752 (Paper I), we will first compile a set of internal M67 uvbyCaHβ photoelectric standards tied to the established systems.…”

Section: Transforming the Ccd Photometrymentioning

confidence: 99%

A uvbyCaHβ CCD Analysis of the Open Cluster Standard, M67, and Its Relation to NGC 752

Twarog¹,

Anthony-Twarog²,

Deliyannis³

2023

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Precision CCD uvbyCaHβ photometry is presented of the old cluster, M67, covering one square degree with typical internal precision at the 0.005–0.020 mag level to V ∼ 17. The photometry is calibrated using standards over a wide range in luminosity and temperature from NGC 752 and zeroed to the standard system via published photoelectric observations. Relative to NGC 752, differential offsets in reddening and metallicity are derived using astrometric members, supplemented by radial velocity information. From single-star members, offsets in the sense (M67−NGC 752) are δ E(b − y) = −0.005 ± 0.001 (sem) mag from 327 F/G dwarfs and δ[Fe/H] = 0.062 ± 0.006 (sem) dex from the combined m 1 and hk indices of 249 F dwarfs, leading to E(b − y) = 0.021 ± 0.004 (sem) and [Fe/H]M67 = +0.030 ± 0.016 (sem) assuming [Fe/H]Hyades = +0.12. With probable binaries eliminated using c 1, (b − y) indices, 83 members with (π/σ π ) > 50 generate (m − M)0 = 8.220 ± 0.005 (sem) for NGC 752 and an isochronal age of 1.45 ± 0.05 Gyr. Using the same parallax restriction for 312 stars, M67 has (m − M) = 9.77 ± 0.02 (sem), leading to an age tied solely to the luminosity of the subgiant branch of 3.70 ± 0.03 Gyr. The turnoff color spread implies ±0.1 Gyr, but the turnoff morphology defines a younger age/higher mass for the stars, consistent with recent binary analysis and broadband photometry indicating possible missing physics in the isochrones. Anomalous stars positioned blueward of the turnoff are discussed.

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Section: Transforming the Ccd Photometrymentioning

confidence: 99%

A uvbyCaHβ CCD Analysis of the Open Cluster Standard, M67, and Its Relation to NGC 752

Twarog¹,

Anthony-Twarog²,

Deliyannis³

2023

View full text Add to dashboard Cite

show abstract

“…A critical focus of current and future cluster comparisons is the need to ensure that all cluster photometry is on a common system, supplying confidence that differences among the indices between clusters are signatures of true differences in the relative cluster parameters rather than byproducts of calibration offsets. Fortunately, the two clusters of interest have been exhaustively investigated in a series of papers designed specifically to detect and minimize any zero-point differences in broad-band VRI (Joner et al 2008;Taylor, Joner, & Jeffery 2008;Taylor & Joner 2011) and uvbyHβ (Joner & Taylor 1995, 1997 photometry. As with NGC 752 (Paper I), we will first compile a set of internal M67 uvbyCaHβ photoelectric standards tied to the established systems.…”

Section: Transforming the Ccd Photometrymentioning

confidence: 99%

A uvbyCaHbeta CCD Analysis of the Open Cluster Standard, M67,and its Relation to NGC 752

Twarog¹,

Anthony-Twarog²,

Deliyannis³

2023

Preprint

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Precision CCD uvbyCaHβ photometry is presented of the old cluster, M67, covering one square degree with typical internal precision at the 0.005-0.020 mag level to V ∼ 17. The photometry is calibrated using standards over a wide range in luminosity and temperature from NGC 752 and zeroed to the standard system via published photoelectric observations. Relative to NGC 752, differential offsets in reddening and metallicity are derived using astrometric members, supplemented by radial-velocity information. From single-star members, offsets in the sense (M67 -NGC 752) are δE(b − y) = -0.005 ± 0.001 (sem) mag from 327 F/G dwarfs and δ[Fe/H] = 0.062 ± 0.006 (sem) dex from the combined m 1 and hk indices of 249 F dwarfs, leading to E(b − y) = 0.021 ± 0.004 (sem), and [Fe/H] M 67 = +0.030 ± 0.016 (sem) assuming [Fe/H] Hyades = +0.12. With probable binaries eliminated using c 1 , (b − y) indices, 83 members with (π/σ π ) > 50 generate (m − M ) 0 = 8.220 ± 0.005 (sem) for NGC 752 and an isochronal age of 1.45 ± 0.05 Gyr. Using the same parallax restriction for 312 stars, M67 has (m − M ) = 9.77 ± 0.02 (sem), leading to an age tied solely to the luminosity of the subgiant branch of 3.70 ± 0.03 Gyr. The turnoff color spread implies ± 0.1 Gyr, but the turnoff morphology defines a younger age/higher mass for the stars, consistent with recent binary analysis and broad-band photometry indicating possible missing physics in the isochrones. Anomalous stars positioned blueward of the turnoff are discussed.

show abstract

Selecting High-Precision Photometry on Uniform Zero Points for Five Benchmark Galactic Clusters

Cited by 2 publications

References 33 publications

A uvbyCaHβ CCD Analysis of the Open Cluster Standard, M67, and Its Relation to NGC 752

A uvbyCaHβ CCD Analysis of the Open Cluster Standard, M67, and Its Relation to NGC 752

A uvbyCaHbeta CCD Analysis of the Open Cluster Standard, M67,and its Relation to NGC 752

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