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

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.

scholarly journals Spatially resolving the thermally inhomogeneous outer atmosphere of the red giant Arcturus in the 2.3 μm CO lines

2018 ◽  
Vol 620 ◽  
pp. A23 ◽  
Author(s):  
K. Ohnaka ◽  
C. A. L. Morales Marín
Keyword(s):  
Spectral Resolution ◽  
Column Density ◽  
High Spectral Resolution ◽  
Molecular Gas ◽  
Very Large Telescope ◽  
Extended Component ◽  
Outer Atmosphere ◽  
Red Giant ◽  
The Individual ◽  
Photospheric Model

Aim. The outer atmosphere of K giants shows thermally inhomogeneous structures consisting of the hot chromospheric gas and the cool molecular gas. We present spectro-interferometric observations of the multicomponent outer atmosphere of the well-studied K1.5 giant Arcturus (α Boo) in the CO first overtone lines near 2.3 μm. Methods. We observed Arcturus with the AMBER instrument at the Very Large Telescope Interferometer (VLTI) at 2.28–2.31 μm with a spectral resolution of 12 000 and at projected baselines of 7.3, 14.6, and 21.8 m. Results. The high spectral resolution of the VLTI/AMBER instrument allowed us to spatially resolve Arcturus in the individual CO lines. Comparison of the observed interferometric data with the MARCS photospheric model shows that the star appears to be significantly larger than predicted by the model. It indicates the presence of an extended component that is not accounted for by the current photospheric models for this well-studied star. We found out that the observed AMBER data can be explained by a model with two additional CO layers above the photosphere. The inner CO layer is located just above the photosphere, at 1.04 ± 0.02 R⋆, with a temperature of 1600 ± 400 K and a CO column density of 1020 ± 0.3 cm−2. On the other hand, the outer CO layer is found to be as extended as to 2.6 ± 0.2 R⋆ with a temperature of 1800 ± 100 K and a CO column density of 1019 ± 0.15 cm−2. Conclusions. The properties of the inner CO layer are in broad agreement with those previously inferred from the spatially unresolved spectroscopic analyses. However, our AMBER observations have revealed that the quasi-static cool molecular component extends out to 2–3 R⋆, within which region the chromospheric wind steeply accelerates.

scholarly journals Improved modelling for spatially resolved spectroscopy of a P Cyg envelope

1994 ◽  
Vol 162 ◽  
pp. 502-504
Author(s):  
M. Bourguine ◽  
A. Chalabaev
Keyword(s):  
Angular Resolution ◽  
Theoretical Models ◽  
Progress Report ◽  
High Angular Resolution ◽  
Physical Parameters ◽  
Base Length ◽  
Spatially Resolved ◽  
Wide Range ◽  
Spatially Resolved Spectroscopy ◽  
Stellar Envelopes

Our study, of which we give here a progress report, addresses two problems. The first is to develop methods and software permitting to compare a wide range of theoretical models of stars with envelopes with observational data produced or expected to be produced by high angular resolution optical interferometry combined with spectroscopy. The second problem is to find out the modes of interferometric observations (base length, spectral resolution etc) that are most informative for determining the physical parameters of stellar envelopes.

scholarly journals Radio Continuum Observations of Large Supernova Remnants

1983 ◽  
Vol 101 ◽  
pp. 377-379
Author(s):  
W. Reich ◽  
E. Fürst ◽  
W. Sieber
Keyword(s):  
Supernova Remnants ◽  
Angular Resolution ◽  
Field Structure ◽  
Radio Continuum ◽  
High Angular Resolution ◽  
Physical Parameters ◽  
Field Orientation ◽  
Low Frequencies ◽  
Magnetic Field Orientation ◽  
Polarization Characteristics

Radio observations of large supernova remnants (SNRs) with high angular resolution have been provided by modern synthesis instruments preferentially at frequencies below 2 GHz. Since these instruments are sensitive mainly to unresolved emission spots, weak extended SNRs usually remain undetected. Besides this, there are numerous physical parameters, which can be studied more properly at higher frequencies. In particular, the polarization characteristics can be more easily analyzed and reduced to the intrinsic magnetic field orientation. In some cases foreground effects substantially disturb the SNR's field structure at low frequencies.

scholarly journals Commission 9: Instruments and Techniques (Instruments et Techniques)

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.

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

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.

scholarly journals Infrared Differential Photometry of Selected Orbital Binaries

2004 ◽  
Vol 191 ◽  
pp. 75-76
Author(s):  
Patricia Lampens ◽  
Jean-Louis Prieur ◽  
Robert Argyle
Keyword(s):  
Near Infrared ◽  
Angular Resolution ◽  
Broad Band ◽  
High Angular Resolution ◽  
High Quality ◽  
Mass Ratios ◽  
Differential Photometry ◽  
The Mean ◽  
The Individual

AbstractHigh-angular resolution observations were acquired for a sample of F-G and K nearby orbital binaries, making use of the ADONIS instrument mounted at the 3.6m ESO telescope from La Silla observatory. The aim is to derive broad-band near-infrared colours for the individual components of those binaries which do not fit well the mean mass-luminosity relation, but which have accurate parallaxes (from the Hipparcos satellite) and high-quality orbits, thanks to many previous efforts. Such colour determinations allow component temperatures and photometric mass ratios to be derived.

scholarly journals Spatially resolving the atmosphere of the non-Mira-type AGB star SW Vir in near-infrared molecular and atomic lines with VLTI/AMBER

2018 ◽  
Vol 621 ◽  
pp. A6 ◽  
Author(s):  
K. Ohnaka ◽  
M. Hadjara ◽  
M. Y. L. Maluenda Berna
Keyword(s):  
Near Infrared ◽  
Asymptotic Giant Branch ◽  
High Spectral Resolution ◽  
Spectral Window ◽  
Asymptotic Giant Branch Star ◽  
Spatially Resolved ◽  
Very Large Telescope ◽  
Outer Atmosphere ◽  
Atomic Lines ◽  
The Individual

Aims. We present a near-infrared spectro-interferometric observation of the non-Mira-type, semiregular asymptotic giant branch star SW Vir. Our aim is to probe the physical properties of the outer atmosphere with spatially resolved data in individual molecular and atomic lines. Methods. We observed SW Vir in the spectral window between 2.28 and 2.31 μm with the near-infrared interferometric instrument AMBER at ESO’s Very Large Telescope Interferometer (VLTI). Results. Thanks to AMBER’s high spatial resolution and high spectral resolution of 12 000, the atmosphere of SW Vir has been spatially resolved not only in strong CO first overtone lines but also in weak molecular and atomic lines of H2O, CN, HF, Ti, Fe, Mg, and Ca. While the uniform-disk diameter of the star is 16.23 ± 0.20 mas in the continuum, it increases up to 22–24 mas in the CO lines. Comparison with the MARCS photospheric models reveals that the star appears larger than predicted by the hydrostatic models not only in the CO lines but also even in the weak molecular and atomic lines. We found that this is primarily due to the H2O lines (but also possibly due to the HF and Ti lines) originating in the extended outer atmosphere. Although the H2O lines manifest themselves very little in the spatially unresolved spectrum, the individual rovibrational H2O lines from the outer atmosphere can be identified in the spectro-interferometric data. Our modeling suggests an H2O column density of 1019–1020 cm−2 in the outer atmosphere extending out to ~2 R⋆. Conclusions. Our study has revealed that the effects of the nonphotospheric outer atmosphere are present in the spectro-interferometric data not only in the strong CO first overtone lines but also in the weak molecular and atomic lines. Therefore, analyses of spatially unresolved spectra, such as, for example, analyses of the chemical composition, should be carried out with care even if the lines appear to be weak.

scholarly journals SPHERE view of Wolf-Rayet 104

2018 ◽  
Vol 618 ◽  
pp. A108 ◽  
Author(s):  
A. Soulain ◽  
F. Millour ◽  
B. Lopez ◽  
A. Matter ◽  
E. Lagadec ◽  
...  
Keyword(s):  
Physical Properties ◽  
Angular Resolution ◽  
Spatial Scales ◽  
Binary Star ◽  
Central Star ◽  
Opening Angle ◽  
High Angular Resolution ◽  
Spiral Coil ◽  
Very Large Telescope ◽  
First Time

Context. WR104 is an emblematic dusty Wolf-Rayet star and the prototypical member of a sub-group hosting spirals that are mainly observable with high-angular resolution techniques. Previous aperture masking observations showed that WR104 is likely to be an interacting binary star at the end of its life. However, several aspects of the system are still unknown. This includes the opening angle of the spiral, the dust formation locus, and the link between the central binary star and a candidate companion star detected with the Hubble Space Telescope (HST) at 1′′. Aims. Our aim was to directly image the dusty spiral or “pinwheel” structure around WR104 for the first time and determine its physical properties at large spatial scales. We also wanted to address the characteristics of the candidate companion detected by the HST. Methods. For this purpose, we used SPHERE and VISIR at the Very Large Telescope to image the system in the near- and mid-infrared, respectively. Both instruments furnished an excellent view of the system at the highest angular resolution a single, ground-based telescope can provide. Based on these direct images, we then used analytical and radiative transfer models to determine several physical properties of the system. Results. Employing a different technique than previously used, our new images have allowed us to confirm the presence of the dust pinwheel around the central star. We have also detected up to five revolutions of the spiral pattern of WR104 in the K band for the first time. The circumstellar dust extends up to 2 arcsec from the central binary star in the N band, corresponding to the past 20 yr of mass loss. Moreover, we found no clear evidence of a shadow of the first spiral coil onto the subsequent ones, which likely points to a dusty environment less massive than inferred in previous studies. We have also confirmed that the stellar candidate companion previously detected by the HST is gravitationally bound to WR104 and herein provide information about its nature and orbital elements.

scholarly journals Interferometry of massive stars: the next step

2014 ◽  
Vol 9 (S307) ◽  
pp. 480-489
Author(s):  
Ph. Stee ◽  
A. Meilland ◽  
O. L. Creevey
Keyword(s):  
Differential Rotation ◽  
Angular Resolution ◽  
Massive Stars ◽  
High Angular Resolution ◽  
Third Generation ◽  
Optical Interferometer ◽  
Large Telescope ◽  
Very Large Telescope ◽  
Beam Combiner ◽  
Radial Pulsations

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.

Sign in / Sign up

Export Citation Format

Share Document