Binary star speckle photometry. I - The colors and spectral types of the Capella stars

Bagnuolo, W. G.; Sowell, James R.

doi:10.1086/114865

Cited by 17 publications

(17 citation statements)

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“…Calibration for atmospherically induced biases in speckle data is also a non-trivial task. Perhaps the best speckle photometric analysis is that of Bagnuolo & Sowell (1988) for the components of Capella. However, the overall brightness and near-zero ∆m of that system make it an ideal candidate for careful speckle analysis.…”

Section: Observational and Data Reduction Techniquesmentioning

confidence: 99%

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Binary Star Differential Photometry Using the Adaptive Optics System at Mount Wilson Observatory

Brummelaar

Mason

McAlister

et al. 2000

The Astronomical Journal

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We present photometric and astrometric results for 36 binary systems observed with the natural guide star adaptive optics system of the Mount Wilson Institute on the Hooker 100-in telescope. The measurements consist of differential photometry in U, B, V, R and I filters along with astrometry of the relative positions of system components. Magnitude differences were combined with absolute photometry found in the literature of the combined light for systems to obtain apparent magnitudes for the individual components at standard bandpasses, which in turn led to color determinations and spectral types. The combination of these results with Hipparcos parallax measurements yielded absolute magnitudes and allowed us to plot the components on an HR diagram. To further examine the reliability and self-consistency of these data, we also estimated system masses from the spectral types.

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Section: Observational and Data Reduction Techniquesmentioning

confidence: 99%

“…For close binary systems it is extremely challenging to obtain accurate photometric measurements of the individual components using standard techniques for, except in exceptional seeing conditions, the images of the two stars overlap. One exception to this statement is the analysis of the Capella system by Bagnuolo & Sowell (1988).…”

Section: Introductionmentioning

confidence: 99%

Binary Star Differential Photometry Using the Adaptive Optics System at Mount Wilson Observatory

Brummelaar

Mason

McAlister

et al. 2000

The Astronomical Journal

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“…2.1.1. Capella Capella (a Aurigae A: G8/K0 III [Aa] + GO III [Ab]: Bagnuolo & Sowell 1988) is a 104 day spectroscopic binary consisting of a rare combination of a postflash giant (the primary) and a Hertzsprung gap star (the secondary). The ultraviolet emissions of the system are dominated by the fast-rotating secondary (Ayres & Linsky 1980).…”

Section: Introductionmentioning

confidence: 99%

The many faces of F stars - A rotational modulation study of Capella, Procyon, and Caph with the International Ultraviolet Explorer

Ayres

1991

ApJ

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I monitored the far-ultraviolet emissions of three bright "F" stars-the Capella secondary (a Aur Ah: GO III), Procyon (a CMi A: F5 IV-V), and Caph (ß Cas: F2 III-IV)-over one or more rotational cycles with the International Ultraviolet Explorer. Strong rotational modulations produced by isolated "active regions" are a characteristic signature of the hydromagnetic dynamo, believed to be the root of the nonclassical hot outer atmospheres-chromospheres and coronae-of late-type stars. Although all three stars are regarded as chromospherically "active" (with C iv A1549 surface flux densities up to 20 times solar), none exhibited any sensible rotational modulations, even at the high sensitivity achieved by pseudo-trailing low-dispersion spectra on the SWP camera (precisions of 2%-5% [1

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“…Wavelength [Å] k = start end l G8 /l G0 Bagnuolo & Sowell (1988) 3996.5 4219.5 0.61 ± 0.02 Griffin & Griffin (1986) 3931 4919 0.69 Hummel et al (1994) 4400 4600 0.77 ± 0.07 Bagnuolo & Sowell (1988) 4568 4770 0.82 ± 0.02 Torres et al (2009) 5165.5 5210.5 0.677 ± 0.023 Hege et al (1983) 5150 5250 0.64 ± 0.03 Torres et al (2009) 4086 6464 0.854 ± 0.041 Bagnuolo & Sowell (1988) 5351.5 5604.5 0.93 ± 0.02 Bagnuolo & Sowell (1988) 5351.5 5604.5 0.87 ± 0.02 Bagnuolo & Sowell (1988) 5351.5 5604.5 0.92 ± 0.02 Bagnuolo & Sowell (1988) 5351.5 5604.5 0.91 ± 0.02 Hummel et al (1994) 5383 5583 0.87 ± 0.04 Hege et al (1983) 5450 5550 0.82 ± 0.02 Hege et al (1983) 5420 5620 0.89 ± 0.01 Griffin & Griffin (1986) 5095 5993 0.87 Huby et al (2013) 6112 8430 λ-dependent Hummel et al (1994) 8003 8203 1.05 ± 0.05…”

Section: Referencementioning

confidence: 99%

Carbon¹²C/¹³C isotope ratio ofαAurigae revised

Sablowski

Järvinen

Ilyin

et al. 2019

A&A

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Context. Capella (α Aur) is one of the few binaries in the sky with two cool giant stars. With spectral types of G8III and G0III, the two components appear at different but distinct stages in their evolution. The G0 secondary star is a Hertzsprung-gap giant, and the G8 primary star is thought to be a clump giant. Aims. We present a new measure of the carbon 12 C/ 13 C isotope ratio of the primary component of Capella using high-resolution R ≈250 000 spectra obtained with the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) with both the Vatican Advanced Technology Telescope (VATT) and the Large Binocular Telescope (LBT). Methods. Signal-to-noise ratios of up to 2 700 were obtained by averaging nightly spectra. These average spectra were used to disentangle the two binary components. The isotope ratio was derived with the use of spectrum synthesis from the CN lines at 8004 Å. Results. We found that the 12 C/ 13 C ratio of the primary component of Capella is 17.8±1.9. Our measurement precision is now primarily limited by the spectral-line data and by the grid-step size of the model atmospheres rather than the data. The separated spectrum of the secondary component does not show distinguishable 12 CN and 13 CN lines because of its v sin i and higher temperature. Conclusions. Our new 12 C/ 13 C value is significantly lower than the previous value of 27±4 but now agrees better with the recent model prediction of 18.8 -20.7.

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Binary star speckle photometry. I - The colors and spectral types of the Capella stars

Cited by 17 publications

References 0 publications

Binary Star Differential Photometry Using the Adaptive Optics System at Mount Wilson Observatory

Binary Star Differential Photometry Using the Adaptive Optics System at Mount Wilson Observatory

The many faces of F stars - A rotational modulation study of Capella, Procyon, and Caph with the International Ultraviolet Explorer

Carbon¹²C/¹³C isotope ratio ofαAurigae revised

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Binary star speckle photometry. I - The colors and spectral types of the Capella stars

Cited by 17 publications

References 0 publications

Binary Star Differential Photometry Using the Adaptive Optics System at Mount Wilson Observatory

Binary Star Differential Photometry Using the Adaptive Optics System at Mount Wilson Observatory

The many faces of F stars - A rotational modulation study of Capella, Procyon, and Caph with the International Ultraviolet Explorer

Carbon12C/13C isotope ratio ofαAurigae revised

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Carbon¹²C/¹³C isotope ratio ofαAurigae revised