INTRODUCTION

2013 ◽  
Vol 02 (02) ◽  
pp. 1303001 ◽  
Author(s):  
T. TEN BRUMMELAAR ◽  
P. TUTHILL ◽  
G. VAN BELLE
Keyword(s):  
Near Infrared ◽  
Angular Resolution ◽  
The United States ◽  
High Angular Resolution ◽  
State University ◽  
Observational Astronomy ◽  
Georgia State University ◽  
Infrared Interferometry ◽  
Optical Astronomy ◽  
Modern Instrumentation

After nearly one and a half centuries of effort, one of the most pernicious problems in observational astronomy — obtaining resolved images of the stars — is finally yielding to advances in modern instrumentation. The exquisite precision delivered by today's interferometric observatories is rapidly being applied to more and more branches of optical astronomy. The most capable interferometers in the Northern Hemisphere, both located in the United States are the Navy Precision Optical Interferometer (NPOI) in Arizona and the Center for High Angular Resolution Astronomy Array (CHARA) run by Georgia State University and located in California. In early 2013 these two groups held a joint meeting hosted by the Lowell Observatory in Flagstaff. All major groups working in the field were represented at this meeting and it was suggested to us by this Journal that this was an excellent opportunity to put together a special issue on interferometry. In order to be as broad as possible, those who did not attend the CHARA/NPOI meeting were also solicited to make a contribution. The result is this collection of papers representing a snap shot of the state of the art of ground based optical and near infrared interferometry.

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.

Zooming into the complex dusty envelopes of C-rich AGB stars

2018 ◽  
Vol 14 (S343) ◽  
pp. 456-457
Author(s):  
Foteini Lykou ◽  
Josef Hron ◽  
Daniela Klotz
Keyword(s):  
Temperature Distribution ◽  
Near Infrared ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
Dust Formation ◽  
Agb Stars ◽  
Circumstellar Envelopes ◽  
Recent Advances ◽  
Multi Wavelength

AbstractRecent advances in high-angular resolution instruments (VLT and VLTI, ALMA) have enabled us to delve deep into the circumstellar envelopes of AGB stars from the optical to the sub-mm wavelengths, thus allowing us to study in detail the gas and dust formation zones (e.g., their geometry, chemistry and kinematics). This work focuses on four (4) C-rich AGB stars observed with a high-angular resolution technique in the near-infrared: a multi-wavelength tomographic study of the dusty layers of the circumstellar envelopes of these C-rich stars, i.e. the variations in the morphology and temperature distribution.

scholarly journals High gas-to-dust size ratio indicating efficient radial drift in the mm-faint CX Tauri disk

2019 ◽  
Vol 626 ◽  
pp. L2 ◽  
Author(s):  
S. Facchini ◽  
E. F. van Dishoeck ◽  
C. F. Manara ◽  
M. Tazzari ◽  
L. Maud ◽  
...  
Keyword(s):  
Near Infrared ◽  
Angular Resolution ◽  
Spectral Energy Distribution ◽  
Theoretical Models ◽  
Intensity Profile ◽  
Continuum Emission ◽  
Spectral Energy ◽  
High Angular Resolution ◽  
Sharp Drop ◽  
Large Program

The large majority of protoplanetary disks have very compact continuum emission (≲15 AU) at millimeter wavelengths. However, high angular resolution observations that resolve these small disks are still lacking, due to their intrinsically fainter emission compared with large bright disks. In this Letter we present 1.3 mm ALMA data of the faint disk (∼10 mJy) orbiting the TTauri star CX Tau at a resolution of ∼40 mas, ∼5 AU in diameter. The millimeter dust disk is compact, with a 68% enclosing flux radius of 14 AU, and the intensity profile exhibits a sharp drop between 10 and 20 AU, and a shallow tail between 20 and 40 AU. No clear signatures of substructure in the dust continuum are observed, down to the same sensitivity level of the DSHARP large program. However, the angular resolution does not allow us to detect substructures on the scale of the disk aspect ratio in the inner regions. The radial intensity profile closely resembles the inner regions of more extended disks imaged at the same resolution in DSHARP, but with no rings present in the outer disk. No inner cavity is detected, even though the disk has been classified as a transition disk from the spectral energy distribution in the near-infrared. The emission of 12CO is much more extended, with a 68% enclosing flux radius of 75 AU. The large difference of the millimeter dust and gas extents (> 5) strongly points to radial drift, and closely matches the predictions of theoretical models.

Near Infrared High Angular Resolution Observations of Stars and Circumstellar Regions by the Technique of Lunar Occultations

1994 ◽  
Vol 158 ◽  
pp. 376-378
Author(s):  
T. Chandrasekhar ◽  
N. M. Ashok ◽  
Sam Ragland
Keyword(s):  
High Speed ◽  
Near Infrared ◽  
Angular Resolution ◽  
Infrared Region ◽  
High Angular Resolution ◽  
Filter Bandwidth ◽  
One Dimensional ◽  
Near Infrared Region ◽  
System Frequency ◽  
Source Structure

A program of High Angular Resolution observations of stars and their circumstellar regions using the technique of lunar occultations has been initiated at the 1.2 m telescope at Gurushikhar (24°39′ N, 72°47′ E), India. A liquid nitrogen cooled InSb detector based high speed Infrared photometer with millisecond data acquisition capabilities has been developed for the near Infrared region (1–5 μm) and eight occultations have been successfully observed in the K band (2.2 μm). The sources are (IRC No. -10578, +10013, +20034, +30094, +20190, +20200, +20073 and +00198. The diffraction pattern is clearly seen in all the observations. A convolution analysis involving the system frequency response, filter bandwidth and one dimensional source structure has been carried out to fit the data. System capability has been determined to be ~ 6 milliarcseconds.

scholarly journals GALACTICNUCLEUS: A high angular resolution JHKs imaging survey of the Galactic centre

2018 ◽  
Vol 610 ◽  
pp. A83 ◽  
Author(s):  
F. Nogueras-Lara ◽  
A. T. Gallego-Calvente ◽  
H. Dong ◽  
E. Gallego-Cano ◽  
J. H. V. Girard ◽  
...  
Keyword(s):  
Near Infrared ◽  
Angular Resolution ◽  
Infrared Camera ◽  
Stellar Model ◽  
Galactic Centre ◽  
High Angular Resolution ◽  
Wide Field ◽  
Photometric Calibration ◽  
Solar Metallicity

Context. The Galactic centre (GC) is of fundamental astrophysical interest, but existing near-infrared surveys fall short covering it adequately, either in terms of angular resolution, multi-wavelength coverage, or both. Here we introduce the GALACTICNUCLEUS survey, a JHKs imaging survey of the centre of the Milky Way with a 0.2″ angular resolution. Aims. The purpose of this paper is to present the observations of Field 1 of our survey, centred approximately on SgrA* with an approximate size of 7.95′ × 3.43′. We describe the observational set-up and data reduction pipeline and discuss the quality of the data. Finally, we present the analysis of the data. Methods. The data were acquired with the near-infrared camera High Acuity Wide field K-band Imager (HAWK-I) at the ESO Very Large Telescope (VLT). Short readout times in combination with the speckle holography algorithm allowed us to produce final images with a stable, Gaussian PSF (point spread function) of 0.2″ FWHM (full width at half maximum). Astrometric calibration is achieved via the VISTA Variables in the Via Lactea (VVV) survey and photometric calibration is based on the SIRIUS/Infrared Survey Facility telescope (IRSF) survey. The quality of the data is assessed by comparison between observations of the same field with different detectors of HAWK-I and at different times. Results. We reach 5σ detection limits of approximately J = 22, H = 21, and Ks = 20. The photometric uncertainties are less than 0.05 at J ≲ 20, H ≲ 17, and Ks ≲ 16. We can distinguish five stellar populations in the colour-magnitude diagrams; three of them appear to belong to foreground spiral arms, and the other two correspond to high- and low-extinction star groups at the GC. We use our data to analyse the near-infrared extinction curve and find some evidence for a possible difference between the extinction index between J − H and H − Ks. However, we conclude that it can be described very well by a power law with an index of αJHKs = 2.30 ± 0.08. We do not find any evidence that this index depends on the position along the line of sight, or on the absolute value of the extinction. We produce extinction maps that show the clumpiness of the ISM (interstellar medium) at the GC. Finally, we estimate that the majority of the stars have solar or super-solar metallicity by comparing our extinction-corrected colour-magnitude diagrams with isochrones with different metallicities and a synthetic stellar model with a constant star formation.

scholarly journals Polarimetric imaging of NGC 1068 at high angular resolution in the near infrared

2015 ◽  
Vol 581 ◽  
pp. L8 ◽  
Author(s):  
D. Gratadour ◽  
D. Rouan ◽  
L. Grosset ◽  
A. Boccaletti ◽  
Y. Clénet
Keyword(s):  
Near Infrared ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
Polarimetric Imaging ◽  
Ngc 1068
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