Observations of Nova Cygni 1992 with a long-baseline optical interferometer

Quirrenbach, A.; Elias, N. M.; Mozurkewich, David; Armstrong, J. T.; Buscher, David F.; Hummel, C. A.

doi:10.1086/116710

Cited by 73 publications

(89 citation statements)

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“…Unfortunately, these data/results were not conclusive (Monnier, private communication). Quirrenbach et al (1996) found a good agreement between their optical interferometric data on Arcturus and theoretical limbdarkening profiles. The very low visibility measured around the first null (their Fig.…”

Section: The Literaturesupporting

confidence: 56%

“…Our newly derived diameters are slightly (but significantly) larger than the LD diameters determined in the K broadband (20.91 ± 0.08, Perrin et al 1998) and in the optical wavelengths (21.0 ± 0.2 mas, Quirrenbach et al 1996). The bias introduced by the use of a single calibrator is taken into account in the error determination and should thus not be responsible for this discrepancy.…”

Section: Diameter Definitionscontrasting

confidence: 52%

“…Postdoctoral Fellow of the Fund for Scientific Research, Flanders. the calibration process), and hence to investigate the need for sophisticated models to calibrate interferometric measurements if high-accuracy visibilities are sought. Such a detailed study of Arcturus was already performed in the visible wavelength regime by Quirrenbach et al (1996), who found good agreement with theoretical wavelength-dependent limb-darkening predictions. In this paper, we investigate the near-IR part of the spectrum.…”

Section: Introductionmentioning

confidence: 57%

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Is Arcturus a well-understood K giant?

Verhoelst

Bordé

Perrin

et al. 2005

A&A

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Abstract. We present near-IR interferometric measurements of the K1.5 giant Arcturus (α Bootis), obtained at the IOTA interferometer with the FLUOR instrument, in four narrow filters with central wavelengths ranging from 2.03 µm to 2.39 µm. These observations were expected to allow us to quantify the wavelength dependence of the diameter of a typical K giant. They are compared to predictions from both plane-parallel and spherical model atmospheres. Unexpectedly, neither can explain the observed visibilities. We show that these data suggest the presence of a companion, in accordance with the Hipparcos data on this star, and discuss this solution with respect to Arcturus' single star status.

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Section: The Literaturesupporting

confidence: 56%

Section: Diameter Definitionscontrasting

confidence: 52%

Section: Introductionmentioning

confidence: 57%

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Is Arcturus a well-understood K giant?

Verhoelst

Bordé

Perrin

et al. 2005

A&A

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“…The uniform disk diameter is wavelength-dependent due to the limb-darkening effect (see, e.g. Quirrenbach et al 1996, Wittkowski et al 2001. Stellar model atmospheres are used to transform wavelength-dependent uniform disk diameters at the observational wavelength into wavelength-independent limb-darkened diameters.…”

Section: Concepts To Study Stellar Atmospheresmentioning

confidence: 99%

“…Unfortunately, direct measurements of the limb-darkening effect are rare because of the observational difficulties mentioned above. While diameters have so far been obtained for several hundred stars with interferometric and lunar occultation techniques, limb-darkening has been directly observed for only a very limited number of stars (Hanbury Brown et al 1974, Haniff et al 1995, Quirrenbach et al 1996, Burns et al 1997, Hajian et al 1998, Wittkowski et al 2001). Wittkowski (this volume) present multi-wavelength limb-darkening measurements on the giant star "y Sge, obtained with the NPOI, which succeeded not only in discriminating between uniform disks and limbdarkened disks, but also in constraining Kurucz model atmosphere parameters (Wittkowski et al 2001).…”

Section: Concepts To Study Stellar Atmospheresmentioning

confidence: 99%

Round Table Summary: Stellar Interferometry as a Tool to Investigate Atmospheres and to Compare Observations with Models

Wittkowski¹

2003

Symp. - Int. Astron. Union

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Abstract. Long-baseline interferometry at optical and near-infrared wavelengths is an emerging technology which is quickly becoming a useful tool to investigate stellar atmospheres and to compare observations with models. Stellar atmosphere models have so far mainly been constrained by comparisons with stellar spectra which are integrated over the stellar disks. Interferometric observations provide spatially and spectrally resolved information and can thus provide important complementary observational information which can be compared to model predictions. Here, I summarize the different aspects on this topic which were discussed at a round table on Thursday, June 20, 2002, during lAD Symposium 210. This summary gives an overview on discussed interferometric facilities and techniques, concepts to study atmospheres by optical interferometry, and particular classes of objects. We conclude that more frequent interactions between the efforts of atmosphere modelling and interferometric observations promise to lead to increased confidence in stellar model atmospheres and to further advancement of the field in the next years. IntroductionLong-baseline interferometry at optical and near-infrared wavelengths is an emerging technology which is quickly becoming a useful tool to investigate stellar atmospheres and to compare observations with models. A round table on this topic was held on June 20, 2002, during the lAD Symposium 210 "Modelling of stellar atmospheres". The goal of this round table was to discuss and stimulate interactions between observations obtained by optical interferometers and theoretical modelling in the field of stellar atmospheres. Here, I summarize aspects that were discussed at the round table, or during the course of the symposium. This summary is based on the individual contributions which can be found in this volume, supplemented by some further literature that was cited at the symposium, without any claim of completeness. This round table summary is, hence, not intended to be a complete review of the field. Optical interferometry, including interferometric techniques as well as scientific studies, have recently been reviewed by Shao & Colavita (1992), Quirrenbach (2001), and Haniff (2002). aLBIN (optical long baseline interferometry news, edited by P. Lawson, and available at olbin.jpl.nasa.gov) is an excellent source of up-to-313 use, available at https://www.cambridge.org/core/terms. https://doi

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Measuring starspots on magnetically active stars with the VLTI

et al. 2002

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We present feasibility studies to directly image stellar surface features, which are caused by magnetic activity, with the Very Large Telescope Interferometer (VLTI). We concentrate on late type magnetically active stars, for which the distribution of starspots on the surface has been inferred from photometric and spectroscopic imaging analysis. The study of the surface spot evolution during consecutive rotation cycles will allow first direct measurements (apart from the Sun) of differential rotation which is the central ingredient of magnetic dynamo processes. The VLTI will provide baselines of up to 200 m, and two scientific instruments for interferometric studies at near-and mid-infrared wavelengths. Imaging capabilities will be made possible by closure-phase techniques. We conclude that a realistically modeled cool surface spot can be detected on stars with angular diameters exceeding ∼ 2 mas using the VLTI with the first generation instrument AMBER. The spot parameters can then be derived with reasonable accuracy. We discuss that the lack of knowledge of magnetically active stars of the required angular size, especially in the southern hemisphere, is a current limitation for VLTI observations of these surface features.

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Observations of Nova Cygni 1992 with a long-baseline optical interferometer

Cited by 73 publications

References 0 publications

Is Arcturus a well-understood K giant?

Is Arcturus a well-understood K giant?

Round Table Summary: Stellar Interferometry as a Tool to Investigate Atmospheres and to Compare Observations with Models

Measuring starspots on magnetically active stars with the VLTI

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