Interferometry of massive stars: the next step

AbstractWe present some new and interesting results on the complementarity between asteroseismology and interferometry, the detection of non-radial pulsations in massive stars and the possibility for evidencing differential rotation on the surface of Bn stars. We also discuss the curretn interferometric facilities, namely the Very Large Telescope Interferometer (VLTI)/AMBER, VLTI/MIDI, VLTI/PIONIER within the European Southern Observatory (ESO) context and the Center for High Angular Resolution Astronomy (CHARA) array with their current limitations. The forthcoming second-generation VLTI instruments GRAVITY and MATISSE are presented as well as the FRIEND prototype in the visible spectral domain and an update of the Navy Precision Optical Interferometer (NPOI). A conclusion is presented with a special emphasis on the foreseen difficulties for a third generation of interferometric instruments within the (budget limited) Extremely Large Telescope framework and the need for strong science cases to push a future visible beam combiner.

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Constraining convection across the AGB with high-angular-resolution observations

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318007378 ◽

2018 ◽

Vol 14 (S343) ◽

pp. 27-30

Author(s):

Claudia Paladini ◽

Fabien Baron ◽

A. Jorissen ◽

J.-B. Le Bouquin ◽

B. Freytag ◽

...

Keyword(s):

Angular Resolution ◽

Granule Size ◽

Scaling Relations ◽

High Angular Resolution ◽

Large Telescope ◽

Horizontal Scale ◽

Very Large Telescope ◽

Convective Pattern ◽

Surface Convection ◽

First Time

AbstractWe present very detailed images of the photosphere of an AGB star obtained with the PIONIER instrument, installed at the Very Large Telescope Interferometer (VLTI). The images show a well defined stellar disc populated by a few convective patterns. Thanks to the high precision of the observations we are able to derive the contrast and granulation horizontal scale of the convective pattern for the first time in a direct way. Such quantities are then compared with scaling relations between granule size, effective temperature, and surface gravity that are predicted by simulations of stellar surface convection.

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Taking the Measure of Massive Stars and their Environments with the CHARA Array Long-baseline Interferometer

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317002393 ◽

2016 ◽

Vol 12 (S329) ◽

pp. 156-160

Author(s):

Douglas R. Gies

Keyword(s):

Angular Resolution ◽

Massive Stars ◽

High Angular Resolution ◽

State University ◽

Luminous Blue Variables ◽

University Center ◽

Long Baseline ◽

Multiple Stars ◽

Mount Wilson Observatory ◽

Georgia State University

AbstractMost massive stars are so distant that their angular diameters are too small for direct resolution. However, the observational situation is now much more favorable, thanks to new opportunities available with optical/IR long-baseline interferometry. The Georgia State University Center for High Angular Resolution Astronomy Array at Mount Wilson Observatory is a six-telescope instrument with a maximum baseline of 330 meters, which is capable of resolving stellar disks with diameters as small as 0.2 milliarcsec. The distant stars are no longer out of range, and many kinds of investigations are possible. Here we summarize a number of studies involving angular diameter measurements and effective temperature estimates for OB stars, binary and multiple stars (including the σ Orionis system), and outflows in Luminous Blue Variables. An enlarged visitors program will begin in 2017 that will open many opportunities for new programs in high angular resolution astronomy.

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European Extremely Large Telescope Site Characterization. II. High Angular Resolution Parameters

Publications of the Astronomical Society of the Pacific ◽

10.1086/667599 ◽

2012 ◽

Vol 124 (918) ◽

pp. 868-884 ◽

Cited By ~ 11

Author(s):

Héctor Vázquez Ramió ◽

Jean Vernin ◽

Casiana Muñoz-Tuñón ◽

Marc Sarazin ◽

Antonia M. Varela ◽

...

Keyword(s):

Angular Resolution ◽

Site Characterization ◽

High Angular Resolution ◽

Large Telescope

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Commission 9: Instruments and Techniques (Instruments et Techniques)

Transactions of the International Astronomical Union ◽

10.1017/s0251107x00009780 ◽

1991 ◽

Vol 21 (1) ◽

pp. 41-52

Author(s):

John Davis

Keyword(s):

Adaptive Optics ◽

Optical Fibers ◽

Angular Resolution ◽

New Technology ◽

High Angular Resolution ◽

Significant Progress ◽

Very Large Telescope ◽

Instruments And Techniques ◽

Telescope Optics ◽

New Generation

The period covered by this report has seen significant progress in the development of the new generation of telescopes with apertures in the 8 m plus range. The period has encompassed the major construction phase of the 10 m Keck Telescope, witnessed the commissioning of the European Southern Observatory’s (ESO) New Technology Telescope and the approval of funding for the ESO Very Large Telescope (VLT). Significant progress has been achieved in developing the necessary technology for manufacturing and figuring large mirrors. There have been major expansions of activity in the areas of active control of telescope optics and adaptive optics, and in high angular resolution interferometry with several new groups entering both fields. The use of optical fibers, particularly in the area of multiple-object spectroscopy, has continued to grow. Several telescopes can now be operated remotely and the control systems of new telescopes are being designed to facilitate remote operation.

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A CO-multilayer outer atmosphere for eight evolved stars revealed with VLTI/AMBER

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2240 ◽

2019 ◽

Vol 489 (2) ◽

pp. 2595-2614

Author(s):

M Hadjara ◽

P Cruzalèbes ◽

C Nitschelm ◽

X Chen ◽

E A Michael ◽

...

Keyword(s):

Angular Resolution ◽

High Angular Resolution ◽

Physical Parameters ◽

Fine Grid ◽

Stellar Radius ◽

Evolved Stars ◽

Very Large Telescope ◽

Outer Atmosphere ◽

Red Giant ◽

The Individual

Abstract We determine the physical parameters of the outer atmosphere of a sample of eight evolved stars, including the red supergiant α Scorpii, the red giant branch stars α Bootis and γ Crucis, the K giant λ Velorum, the normal M giants BK Virginis and SW Virginis, and the Mira star W Hydrae (in two different luminosity phases) by spatially resolving the stars in the individual carbon monoxide (CO) first overtone lines. We used the Astronomical Multi-BEam combineR (AMBER) instrument at the Very Large Telescope Interferometer (VLTI), in high-resolution mode (λ/Δλ ≈ 12 000) between 2.28 and 2.31 $\, \mu {\rm m}$ in the K band. The maximal angular resolution is 10 mas, obtained using a triplet telescope configuration, with baselines from 7 to 48 m. By using a numerical model of a molecular atmosphere in a spherical shells (MOLsphere), called pampero (an acronym for the ‘physical approach of molecular photospheric ejection at high angular resolution for evolved stars’), we add multiple extended CO layers above the photospheric marcs model at an adequate spatial resolution. We use the differential visibilities and the spectrum to estimate the size (R) of the CO molsphere, its column density (NCO) and temperature (Tmol) distributions along the stellar radius. The combining of the χ2 minimization and a fine grid approach for uncertainty analysis leads to reasonable NCO and Tmol distributions along the stellar radius of the MOLsphere.

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The Far Ultraviolet Imaging Spectrograph on Spartan-281

Symposium - International Astronomical Union ◽

10.1017/s0074180900241284 ◽

1990 ◽

Vol 139 ◽

pp. 459-460

Author(s):

George R. Carruthers ◽

Harry M. Heckathorn ◽

John C. Raymond ◽

Reginald J. Dufour ◽

Adolf N. Witt ◽

...

Keyword(s):

Spectral Range ◽

Angular Resolution ◽

Hubble Space Telescope ◽

Compact Objects ◽

High Angular Resolution ◽

Large Telescope ◽

International Ultraviolet Explorer ◽

Far Ultraviolet ◽

Compact Sources ◽

Imaging Spectrograph

The study of diffuse celestial sources in the ground-inaccessible ultraviolet spectral range is less advanced than UV studies of point and compact sources. The main reason is that the characteristics of instrumentation optimized for the two types of objects are quite different. Studies of diffuse objects are best made with fast focal ratio optics with wide fields of view, whereas studies of point and compact objects are best made with large telescope aperture and high angular resolution. As a result, most space ultraviolet instruments to date (such as the International Ultraviolet Explorer and the forthcoming Hubble Space Telescope) are not well suited to the study of faint, extended diffuse objects in the ultraviolet.

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Zooming into Eta Carinae with interferometry

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314006917 ◽

2014 ◽

Vol 9 (S307) ◽

pp. 267-272

Author(s):

Jose H. Groh

Keyword(s):

Mass Loss ◽

High Spatial Resolution ◽

Massive Stars ◽

Spatial Scales ◽

Large Telescope ◽

Rapid Rotation ◽

Eta Carinae ◽

Very Large Telescope ◽

Effects Of Rotation ◽

Circumstellar Environment

AbstractShaped by strong mass loss, rapid rotation, and/or the presence of a close companion, the circumstellar environment around the most massive stars is complex and anything but spherical. Here we provide a brief overview of the high spatial resolution observations of Eta Carinae performed with the Very Large Telescope Interferometer (VLTI). Special emphasis is given to discuss VLTI/AMBER and VLTI/VINCI observations, which directly resolve spatial scales comparable to those where mass loss originates. Studying scales as small as a few milli-arcseconds allows us to investigate kinematical effects of rotation and binarity in more detail than ever before.

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On a spatially resolving USAXS instrument for operation at a third-generation synchrotron radiation source

Journal of Synchrotron Radiation ◽

10.1107/s0909049597015665 ◽

1998 ◽

Vol 5 (3) ◽

pp. 986-988 ◽

Cited By ~ 1

Author(s):

Stephen Wilkins

Keyword(s):

Synchrotron Radiation ◽

Radiation Source ◽

Angular Resolution ◽

Synchrotron Radiation Source ◽

High Angular Resolution ◽

Third Generation ◽

Contrast Imaging ◽

Saxs Data ◽

Ccd Detector ◽

Plane Direction

A point-collimation USAXS system based on the Bonse–Hart-diffractometer concept is proposed which takes advantage of a CCD detector to rapidly obtain two-dimensional SAXS data at both high spatial and angular resolution for a line of points on the sample. The method might typically be employed using Bonse–Hart crystal optics in the horizontal plane, encompassing the high-angular-resolution scan direction, and a condensing monochromator in the out-of-diffraction-plane direction as the basis for a pinhole SAXS camera in that plane. The new system is well suited to operation at an undulator beamline on a third-generation synchrotron radiation source. Other applications of the instrument include (i) both absorption and phase-contrast imaging/tomography, (ii) polycrystalline topography, (iii) high-resolution triple-crystal measurements and (iv) diffuse scattering measurements.

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Simulation and Analysis of Telescopic Photonic Beam Combiner for Stellar Interferometry in Labview

International Journal of Innovative Technology and Exploring Engineering - Special Issue ◽

10.35940/ijitee.i1036.0789s19 ◽

2019 ◽

Vol 8 (9S) ◽

pp. 230-236

Keyword(s):

Angular Resolution ◽

Mechanical Stability ◽

Optical Interferometry ◽

Physical Contact ◽

Optical Methods ◽

High Angular Resolution ◽

Multiple Observations ◽

Beam Combiner ◽

Stellar Interferometry ◽

The Universe

The optical methods are the sensitive and subtle techniques of conducting optical investigations without any physical contact. They are both accurate and fast at the same time which provides an ease of having multiple observations. The need of optical interferometry has been increased at a very quick pace due to its high range of applications, from surface testing to locating of extra-solar planets in the universe. Optical Interferometry is a process or technique of combining light from various telescopes for calculating the angular resolution. The technique of optical interferometry helps astronomers for achieving a high angular resolution, that is not possible with the conventional telescopes. Optical approaches are the best approaches for non-contact evaluations, and these are accurate and fast. Due to optical nature of the interferometry, this process is used in various fields, and today it has become one of the important areas of research. Integrated Optics (IO) beam combiners are an efficient and compact technology to combine light interferometrically collected by multiple telescopes. IO beam combiner is based on the modal filtering properties of waveguides or fibers, and it improves thermo-mechanical stability, because of the characteristic rigidity of IO component substrate. Other advantages of this technology are miniaturization and non-existence of alignment needs. Several IO beam combiners are being proposed and tested nowadays. The purpose of this paper is to investigate different techniques used to develop interferometric instrument from previous researches and to simulate the technique suggested by Ermann in Labview.

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