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 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.

scholarly journals The Molecular Outflow and CO Bullets in HH111

1997 ◽  
Vol 182 ◽  
pp. 141-152 ◽  
Author(s):  
J. Cernicharo ◽  
R. Neri ◽  
Bo Reipurth
Keyword(s):  
High Velocity ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
Molecular Gas ◽  
Kinetic Temperature ◽  
Low Velocity ◽  
Molecular Outflow ◽  
Hh Objects ◽  
Physical Phenomena ◽  
First Time

We present high angular resolution observations of the molecular outflow associated with the optical jet and HH objects of the HH111 system. Interferometric observations in the CO J =2–1 and J =1–0 lines of the high velocity bullets associated with HH111 are presented for the first time. The molecular gas in these high velocity clumps has a moderate kinetic temperature and a mass of a few 10–4 M⊙ per bullet. We favor the view that HH jets and CO bullets, which represent different manifestations of the same physical phenomena, are driving the low-velocity molecular outflow.

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

2012 ◽  
Vol 124 (918) ◽  
pp. 868-884 ◽  
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

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.

scholarly journals η Carinae: high angular resolution continuum, H30α and He30α ALMA images

2020 ◽  
Vol 499 (2) ◽  
pp. 2493-2512
Author(s):  
Zulema Abraham ◽  
Pedro P B Beaklini ◽  
Pierre Cox ◽  
Diego Falceta-Gonçalves ◽  
Lars-Åke Nyman
Keyword(s):  
Angular Resolution ◽  
Line Emission ◽  
High Angular Resolution ◽  
Proper Motions ◽  
Recombination Line ◽  
Compact Source ◽  
Continuum Source ◽  
Velocity Images ◽  
First Time ◽  
Compact Sources

ABSTRACT We present images of η Carinae in the recombination lines H30α and He30α and the underlying continuum with 50 mas resolution (110 au), obtained with ALMA. For the first time, the 230 GHz continuum image is resolved into a compact core, coincident with the binary system position, and a weaker extended structure to the NW of the compact source. Iso-velocity images of the H30α recombination line show at least 16 unresolved sources with velocities between −30 and −65 km s−1 distributed within the continuum source. A NLTE model, with density and temperature of the order of 107 cm−3 and 104 K, reproduce both the observed H30α line profiles and their underlying continuum flux densities. Three of these sources are identified with Weigelt blobs D, C, and B; estimating their proper motions, we derive ejection times (in years) of 1952.6, 1957.1, and 1967.6, respectively, all of which are close to periastron passage. Weaker H30α line emission is detected at higher positive and negative velocities, extending in the direction of the Homunculus axis. The He30α recombination line is also detected with the same velocity of the narrow H30α line. Finally, the close resemblance of the H30α image with that of an emission line that was reported in the literature as HCO+(4–3) led us to identify this line as H40δ instead, an identification that is further supported by modelling results. Future observations will enable to determine the proper motions of all the compact sources discovered in the new high angular resolution data of η Carinae.

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 The Far Ultraviolet Imaging Spectrograph on Spartan-281

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.

scholarly journals Classification of Wolf-Rayet stars in NGC 595 in M 33 through high-spatial resolution observations

2003 ◽  
Vol 212 ◽  
pp. 572-573 ◽  
Author(s):  
Pierre Royer ◽  
Ingemar Lundström ◽  
Jean-Marie Vreux
Keyword(s):  
Stellar Population ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
Photometric Technique ◽  
H Ii Region ◽  
The One ◽  
First Time ◽  
Rayet Star

NGC 595 is, after NGC 604, the second most luminous H ii region in the Milky Way's neighbouring spiral galaxy M 33. Its Wolf-Rayet star content has mainly been unveiled by two different channels. On the one hand, the stellar population of NGC 595 has been resolved and its WR stars identified through online/off-line H ii λ4686 observations realised with the HST. Nevertheless, due to the limited number of filters used, this did not give any information on the WR spectral subtypes. On the other hand, spectroscopic observations of NGC 595, realised at optical and ultraviolet wavelengths, have enabled the determination of some spectral subtypes, but this time, the lack of angular resolution did not allow to resolve the whole population. Thanks to our photometric technique, based on five dedicated narrow-band filters, we present here a determination of the spectral subtypes of NGC 595 WR stars which for the first time combines high-angular resolution and high-‘spectroscopic’ discrimination capabilities.

scholarly journals New limit on a varying proton-to-electron mass ratio from high-resolution optical quasar spectra

2009 ◽  
Vol 5 (H15) ◽  
pp. 321-321
Author(s):  
A. L. Malec ◽  
R. Buning ◽  
M. T. Murphy ◽  
N. Milutinovic ◽  
S. L. Ellison ◽  
...  
Keyword(s):  
Optical Spectrum ◽  
Resolving Power ◽  
Electron Mass ◽  
Mass Ratio ◽  
Large Telescope ◽  
Relative Deviation ◽  
Quasar Spectra ◽  
Very Large Telescope ◽  
Free Parameters ◽  
First Time

AbstractMolecular transitions recently discovered at redshift zabs=2.059 toward the bright background quasar J2123-0050 are analysed to limit cosmological variation in the proton-to-electron mass ratio, μ ≡ mp/me. Observed with the Keck telescope, the optical spectrum has the highest resolving power and largest number (86) of H2 transitions in such analyses so far. Also, (7) HD transitions are used for the first time to constrain μ-variation. These factors, and an analysis employing the fewest possible free parameters, strongly constrain μ's relative deviation from the current laboratory value: Δμ/μ =(+5.6±5.5stat±2.7sys)×10−6. This is the first Keck result to complement recent constraints from three systems at zabs>2.5 observed with the Very Large Telescope.

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