scholarly journals Michelson-Spectro-Interferometry (MSI) of Be stars envelopes with the GI2T Interferometer

1995 ◽  
Vol 149 ◽  
pp. 365-368
Author(s):  
Ph. Stee ◽  
D. Bonneau ◽  
P. Lawson ◽  
F. Morand ◽  
D. Mourard ◽  
...  
Keyword(s):  
Angular Resolution ◽  
Michelson Interferometer ◽  
Numerical Code ◽  
High Angular Resolution ◽  
Be Stars ◽  
Wind Model ◽  
Long Baseline ◽  
Balmer Lines ◽  
Extended Sources ◽  
Resolution Data

AbstractThe GI2T is an optical long-baseline Michelson interferometer which analyses dispersed stellar fringes in the multi-speckle mode with a spectral resolution of one Angstrom while the spatial resolution is about one milliarcsecond. This makes the GI2T a powerful instrument able to perform MSI of extended sources like Be stars or shell stars. In order to interpret these data we have developed a latitude dependent radiative wind model for Be stars. This numerical code enables us to compare directly computed 2D maps in some Balmer lines (Hα and Hβ) with high angular resolution data of some Be stars.

scholarly journals Interferometry and Stellar Magnetism

2000 ◽  
Vol 175 ◽  
pp. 174-177 ◽  
Author(s):  
O. Chesneau ◽  
K. Rousselet-Perraut ◽  
F. Vakili
Keyword(s):  
Spectral Resolution ◽  
Angular Resolution ◽  
Zeeman Effect ◽  
High Spectral Resolution ◽  
Sensitivity Threshold ◽  
High Angular Resolution ◽  
Be Stars ◽  
Long Baseline ◽  
Instrumental Polarisation ◽  
Very High

AbstractThe classical detection of magnetic fields in Be stars remains a challenge due to the sensitivity threshold and geometrical cancelation of the field effects. We propose to study the Zeeman effect using Spectro-Polarimetric INterferometry (SPIN) which consists of the simultaneous use of polarimetry and very high angular resolution provided by long baseline interferometers. As monitoring of the instrumental polarisation is mandatory in order to calibrate interferometric observations in any case, the polarised signal is a natural by-product of interferometers. This method will be tested on the GI2T interferometer thanks to its high spectral resolution and its polarimetric capabilities.

scholarly journals Constraining VLBI−optical offsets in high redshift galaxies using strong gravitational lensing

2020 ◽  
Vol 494 (2) ◽  
pp. 2312-2326 ◽  
Author(s):  
Cristiana Spingola ◽  
Anna Barnacka
Keyword(s):  
Gravitational Lensing ◽  
Angular Resolution ◽  
Hubble Space Telescope ◽  
High Redshift ◽  
Monte Carlo Sampling ◽  
High Angular Resolution ◽  
Radio Emissions ◽  
High Redshift Galaxies ◽  
Long Baseline ◽  
Redshift Galaxies

ABSTRACT We present a multiwavelength analysis of two highly magnified strong gravitationally lensed galaxies, CLASS B0712+472 and CLASS B1608+656, at redshifts 1.34 and 1.394, respectively, using new VLBI (very long baseline interferometry) and archival Hubble Space Telescope observations. We reconstruct the positions of the radio and optical emissions with their uncertainties using Monte Carlo sampling. We find that in CLASS B0712+472 the optical and radio emissions are co-spatial within 2 ± 5 mas (17 ± 42 pc at redshift of 1.34). But, in CLASS B1608+656, we reconstruct an optical–radio offset of 25 ± 16 mas (214 ± 137 pc at redshift of 1.394), among the smallest offsets measured for an AGN (active galactic nucleus) at such high redshift. The spectral features indicate that CLASS B1608+656 is a post-merger galaxy, which, in combination with the optical–VLBI offset reported here, makes CLASS B1608+656 a promising candidate for a high- z offset–AGN. Furthermore, the milliarcsecond angular resolution of the VLBI observations combined with the precise lens models allow us to spatially locate the radio emission at 0.05 mas precision (0.4 pc) in CLASS B0712+472, and 0.009 mas precision (0.08 pc) in CLASS B1608+656. The search for optical–radio offsets in high redshift galaxies will be eased by the upcoming synoptic all-sky surveys, including Extremely Large Telescope and Square Kilometre Array, which are expected to find ∼105 strongly lensed galaxies, opening an era of large strong lensing samples observed at high angular resolution.

scholarly journals Herbig Ae/Be Star Disks at High Angular Resolution

2004 ◽  
Vol 221 ◽  
pp. 389-394
Author(s):  
C. P. Dullemond ◽  
C. Dominik ◽  
R. van Boekel ◽  
R. Waters ◽  
M. van den Ancker
Keyword(s):  
Angular Resolution ◽  
Protoplanetary Disks ◽  
Spectral Energy ◽  
High Angular Resolution ◽  
Be Stars ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
Spatially Resolved ◽  
Be Star ◽  
Geometric Picture

We show that there exists a simple geometric picture for the geometries of protoplanetary disks around Herbig Ae/Be stars that explains the two main kinds of spectral energy distributions found for these objects, and that makes predictions that are qualitatively in agreement with currently available spatially resolved images and/or interferometric measurements. Also it qualitatively explains the phenomenon of UX Orionis variability.

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

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.

scholarly journals The circumstellar discs of Be stars

2010 ◽  
Vol 6 (S272) ◽  
pp. 325-336 ◽  
Author(s):  
Alex C. Carciofi
Keyword(s):  
Angular Resolution ◽  
Central Star ◽  
High Angular Resolution ◽  
Be Stars ◽  
Keplerian Orbit ◽  
Physical Processes ◽  
Simple Description ◽  
Model Predictions ◽  
Mass Ejection ◽  
Very High

AbstractCircumstellar discs of Be stars are thought to be formed from material ejected from a fast-spinning central star. This material possesses large amounts of angular momentum and settles in a quasi-Keplerian orbit around the star. This simple description outlines the basic issues that a successful disc theory must address: 1) What is the mechanism responsible for the mass ejection? 2) What is the final configuration of the material? 3) How the disc grows? With the very high angular resolution that can be achieved with modern interferometers operating in the optical and infrared we can now resolve the photosphere and immediate vicinity of nearby Be stars. Those observations are able to provide very stringent tests for our ideas about the physical processes operating in those objects. This paper discusses the basic hydrodynamics of viscous decretion discs around Be stars. The model predictions are quantitatively compared to observations, demonstrating that the viscous decretion scenario is currently the most viable theory to explain the discs around Be stars.

Investigation of the Chromosphere–Corona Interface with the Upgraded Very High Angular Resolution Ultraviolet Telescope (VAULT2.0)

2016 ◽  
Vol 05 (01) ◽  
pp. 1640003 ◽  
Author(s):  
Angelos Vourlidas ◽  
Samuel Tun Beltran ◽  
Georgios Chintzoglou ◽  
Kevin Eisenhower ◽  
Clarence Korendyke ◽  
...  
Keyword(s):  
High Resolution ◽  
Angular Resolution ◽  
Solar Spectrum ◽  
High Angular Resolution ◽  
High Resolution Data ◽  
Lyman Alpha ◽  
And Performance ◽  
White Sands ◽  
Very High ◽  
Resolution Data

Very high angular resolution ultraviolet telescope (VAULT2.0) is a Lyman-alpha (Ly[Formula: see text]; 1216[Formula: see text]Å) spectroheliograph designed to observe the upper chromospheric region of the solar atmosphere with high spatial ([Formula: see text]) and temporal (8[Formula: see text]s) resolution. Besides being the brightest line in the solar spectrum, Ly[Formula: see text] emission arises at the temperature interface between coronal and chromospheric plasmas and may, hence, hold important clues about the transfer of mass and energy to the solar corona. VAULT2.0 is an upgrade of the previously flown VAULT rocket and was launched successfully on September 30, 2014 from White Sands Missile Range (WSMR). The target was AR12172 midway toward the southwestern limb. We obtained 33 images at 8[Formula: see text]s cadence at arc second resolution due to hardware problems. The science campaign was a resounding success, with all space and ground-based instruments obtaining high-resolution data at the same location within the AR. We discuss the science rationale, instrument upgrades, and performance during the first flight and present some preliminary science results.

scholarly journals The MWA long baseline Epoch of reionisation survey—I. Improved source catalogue for the EoR 0 field

2021 ◽  
Vol 38 ◽  
Author(s):  
C. R. Lynch ◽  
T. J. Galvin ◽  
J. L. B. Line ◽  
C. H. Jordan ◽  
C. M. Trott ◽  
...  
Keyword(s):  
Angular Resolution ◽  
Low Frequency ◽  
Calibration Model ◽  
Spectral Measurements ◽  
Long Baseline ◽  
Source Models ◽  
Extended Sources ◽  
Murchison Widefield Array ◽  
Foreground Calibration ◽  
Good Agreement

Abstract One of the principal systematic constraints on the Epoch of Reionisation (EoR) experiment is the accuracy of the foreground calibration model. Recent results have shown that highly accurate models of extended foreground sources, and including models for sources in both the primary beam and its sidelobes, are necessary for reducing foreground power. To improve the accuracy of the source models for the EoR fields observed by the Murchison Widefield Array (MWA), we conducted the MWA Long Baseline Epoch of Reionisation Survey (LoBES). This survey consists of multi-frequency observations of the main MWA EoR fields and their eight neighbouring fields using the MWA Phase II extended array. We present the results of the first half of this survey centred on the MWA EoR0 observing field (centred at RA (J2000) $0^\mathrm{h}$ , Dec (J2000) $-27^{\circ}$ ). This half of the survey covers an area of 3 069 degrees $^2$ , with an average rms of 2.1 mJy beam–1. The resulting catalogue contains a total of 80 824 sources, with 16 separate spectral measurements between 100 and 230 MHz, and spectral modelling for 78 $\%$ of these sources. Over this region we estimate that the catalogue is 90 $\%$ complete at 32 mJy, and 70 $\%$ complete at 10.5 mJy. The overall normalised source counts are found to be in good agreement with previous low-frequency surveys at similar sensitivities. Testing the performance of the new source models we measure lower residual rms values for peeled sources, particularly for extended sources, in a set of MWA Phase I data. The 2-dimensional power spectrum of these data residuals also show improvement on small angular scales—consistent with the better angular resolution of the LoBES catalogue. It is clear that the LoBES sky models improve upon the current sky model used by the Australian MWA EoR group for the EoR0 field.

scholarly journals Projections of Brodmann Area 6 to the Pyramidal Tract in Humans: Quantifications Using High Angular Resolution Data

2019 ◽  
Vol 13 ◽  
Author(s):  
Zhen-Ming Wang ◽  
Yi Shan ◽  
Miao Zhang ◽  
Peng-Hu Wei ◽  
Qiong-Ge Li ◽  
...  
Keyword(s):  
Angular Resolution ◽  
Pyramidal Tract ◽  
Brodmann Area ◽  
High Angular Resolution ◽  
Area 6 ◽  
Resolution Data
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