First Results from the CHARA Array. II. A Description of the Instrument

Brummelaar, Theo A. ten; McAlister, Harold A.; Ridgway, Stephen T.; Bagnuolo, W. G.; Turner, N.; Sturmann, L.; Sturmann, J.; Berger, David H.; Ogden, Chad; Cadman, Robert V.; Hartkopf, William I.; Hopper, Charles H.; Shure, M. A.

doi:10.1086/430729

Cited by 449 publications

(304 citation statements)

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“…The system was observed by four different spectrointerferometers: the Mark III Stellar Interferometer 1 (Mark III) (Shao et al 1988), the Navy Precision Optical Interferometer (NPOI) , the Visible spEctroGraph and polArimeter (VEGA) (Mourard et al 2009) mounted at the Centre for High Angular Resolution Astronomy (CHARA) (ten Brummelaar et al 2005), and the Astronomical Multi-BEam combineR (AMBER) (Petrov et al 2007) attached to the Very Large Telescope Interferometer (VLTI) (Glindemann et al 2004). A journal of the spectrointerferometric observations is listed in Table 4.…”

Section: Interferometric Observationsmentioning

confidence: 99%

ξTauri: a unique laboratory to study the dynamic interaction in a compact hierarchical quadruple system

Nemravová

Harmanec

Brož

et al. 2016

A&A

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Context. Compact hierarchical systems are important because the effects caused by the dynamical interaction among its members occur on a human timescale. These interactions play a role in the formation of close binaries through Kozai cycles with tides. One such system is ξ Tauri: it has three hierarchical orbits: 7.14 d (eclipsing components Aa, Ab), 145 d (components Aa+Ab, B), and 51 yr (components Aa+Ab+B, C). Aims. We aim to obtain physical properties of the system and to study the dynamical interaction between its components. Methods. Our analysis is based on a large series of spectroscopic photometric (including space-borne) observations and long-baseline optical and infrared spectro-interferometric observations. We used two approaches to infer the system properties: a set of observation-specific models, where all components have elliptical trajectories, and an N-body model, which computes the trajectory of each component by integrating Newton's equations of motion. Results. The triple subsystem exhibits clear signs of dynamical interaction. The most pronounced are the advance of the apsidal line and eclipsetiming variations. We determined the geometry of all three orbits using both observation-specific and N-body models. The latter correctly accounted for observed effects of the dynamical interaction, predicted cyclic variations of orbital inclinations, and determined the sense of motion of all orbits. Using perturbation theory, we demonstrate that prominent secular and periodic dynamical effects are explainable with a quadrupole interaction. We constrained the basic properties of all components, especially of members of the inner triple subsystem and detected rapid low-amplitude light variations that we attribute to co-rotating surface structures of component B. We also estimated the radius of component B. Properties of component C remain uncertain because of its low relative luminosity. We provide an independent estimate of the distance to the system. Conclusions. The accuracy and consistency of our results make ξ Tau an excellent test bed for models of formation and evolution of hierarchical systems.

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Section: Interferometric Observationsmentioning

confidence: 99%

ξTauri: a unique laboratory to study the dynamic interaction in a compact hierarchical quadruple system

Nemravová

Harmanec

Brož

et al. 2016

A&A

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“…The VEGA instrument (Mourard et al 2009) at the CHARA array (ten Brummelaar et al 2005) is located on the Mount Wilson Observatory just north of Los Angeles in California, USA. It operates in the visible domain and benefits from both a highresolution spectrograph and a polarimeter.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Kinematics and geometrical study of the Be stars 48 Persei andψPersei with the VEGA/CHARA interferometer

Delaa

Stee

Meilland

et al. 2011

A&A

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Context. Five different physical processes might be responsible for the formation of decretion disks around Be stars: fast rotation of the star, stellar pulsations, binarity, stellar winds, and magnetic fields. Our observations indicate that fast rotation seems to produce a disk in Keplerian rotation, at least in the specific case of the two stars observed. We do not know if this observational result is a generality or not. Aims. We measure the size, orientation, shape, and kinematics of the disks around 2 Be stars, namely 48 Per and ψ Per. Methods. We used the VEGA/CHARA interferometer with a spectral resolution of 5000 to obtain spectrally dispersed visibility modulus and phases within the Hα emission line. Results. We were able to estimate the disk extension in the continuum and in the Hα line, as well as flattening, for both stars. Both stars rotate at nearly a critical rotation, but while the disk of 48 Per seems to be in Keplerian rotation, our preliminary data suggest that the disk of ψ Per is possibly faster than Keplerian, similarly to what has been found for κ CMa with observations carried out in the near-IR. However, more data is needed to confirm the fast rotation of the disk. Conclusions. Assuming a simple uniform disk model for the stellar photosphere in the continuum and a Gaussian brightness distribution in the line emission region, we obtain a ratio of the disk diameter over the photospheric diameter of 8 for 48 Per and 11 for and ψ Per. We also found that the major axis of 48 Per is parallel to the polarization angle and not perpendicular to it as previously observed for many Be stars, including ψ Per. This might be due to the optical thickness of the disk, which is also responsible for the incoherent scattering of a non negligible part of the Hα line emission. To our knowledge, this is the first time that this effect has been measured in a Be star.

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“…The Center for High Angular Resolution Astronomy (CHARA) of the Georgia State University operates an optical interferometric array located at Mount Wilson Observatory (ten Brummelaar et al 2005). It is formed by six telescopes placed in pairs on the arms of a Y-shaped configuration.…”

Section: Introductionmentioning

confidence: 99%

“…It yields 15 baselines ranging from 34 to 331 m. The distribution of length and orientation of these baselines, as given in Table 1 of ten Brummelaar et al (2005), allows a good coverage of the spatial frequency plane and permits the instrument to reach very high angular resolution. Operated in the near-infrared with CLASSIC (ten Brummelaar et al 2005), FLUOR (Coudé du Foresto et al 2003) or MIRC and in the visible with PAVO (Ireland et al 2008) and VEGA, the CHARA array allows a maximum angular resolution (λ/B) of 1.3 and 0.3 ms of arc in the K and V bands respectively. The 1 m diameter alt-azimuth telescopes collect the stellar light and supply a compressed Coudé beam after 7 reflections.…”

Section: Introductionmentioning

confidence: 99%

VEGA: Visible spEctroGraph and polArimeter for the CHARA array: principle and performance

Mourard

Clausse

Marcotto

et al. 2009

A&A

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Context. Among optical stellar interferometers, the CHARA Array located at Mt Wilson in California offers the potential of very long baselines (up to 330 m) and the prospect of coupling multiple beam combiners. This paper presents the principle and the measured performance of VEGA, Visible spEctroGraph and polArimeter installed in September 2007 at the coherent focus of the array. Aims. With 0.3 ms of arc of spatial resolution and up to 30 000 of spectral resolution, VEGA intends to measure fundamental parameters of stars, to study stellar activities and to image and analyze circumstellar environments. We describe the observing modes that have been implemented for this spectro-polarimeter and show actual performances measured on the sky during the first observing runs. Methods. The astrophysical programs are described in relation to the observing modes of the instrument, the presentation of the spectrograph and of the interface table is shown and finally the data is presented. We discuss the perspectives of further development in the framework of the CHARA Array. Results. We show that VEGA/CHARA is fully operational. The current limiting magnitude is nearly 7 but the results depend on the observing conditions (seeing, spectral resolution, etc.). We have validated the stability of the instrumental visibility at the level of 1 to 2% over half an hour and of the instrumental polarization for various declinations. Some examples of squared visibility and differential visibility are presented. Conclusions. The spectro-polarimeter VEGA has been installed and successfully tested on CHARA. It will permit stellar physics studies at unprecedented spectral and spatial resolutions.

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First Results from the CHARA Array. II. A Description of the Instrument

Cited by 449 publications

References 28 publications

ξTauri: a unique laboratory to study the dynamic interaction in a compact hierarchical quadruple system

ξTauri: a unique laboratory to study the dynamic interaction in a compact hierarchical quadruple system

Kinematics and geometrical study of the Be stars 48 Persei andψPersei with the VEGA/CHARA interferometer

VEGA: Visible spEctroGraph and polArimeter for the CHARA array: principle and performance

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