The First VERA Astrometry Catalog

Abstract We present the first astrometry catalog from the Japanese VLBI (very long baseline interferometer) project VERA (VLBI Exploration of Radio Astrometry). We have compiled all the astrometry results from VERA, providing accurate trigonometric-annual-parallax and proper-motion measurements. In total, 99 maser sources are listed in the VERA catalog. Among them, 21 maser sources are newly reported, while the rest of the 78 sources are referred to in previously published results or those in preparation for forthcoming papers. The accuracy in the VERA astrometry is revisited and compared with that from the other VLBI astrometry projects such as BeSSeL (The Bar and Spiral Structure Legacy) Survey and GOBELINS (the Gould’s Belt Distances Survey) with the VLBA (Very Long Baseline Array). We have confirmed that most of the astrometry results are consistent with each other, and the largest error sources are due to source structure of the maser features and their rapid variation, along with the systematic calibration errors and different analysis methods. Combined with the BeSSeL results, we estimate the up-to-date fundamental Galactic parameters of $R_{0}=7.92\pm 0.16_{\rm {stat.}}\pm 0.3_{\rm {sys.}}\:$kpc and $\Omega _{\odot }=30.17\pm 0.27_{\rm {stat.}}\pm 0.3_{\rm {sys.}}\:$km$\:$s$^{-1}\:$kpc$^{-1}$, where $R_{0}$ and $\Omega _{\odot }$ are the distance from the Sun to the Galactic center and the Sun’s angular velocity of the Galactic circular rotation, respectively.

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Source structure: an essential piece of information for generating the next ICRF

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308019534 ◽

2007 ◽

Vol 3 (S248) ◽

pp. 344-347 ◽

Cited By ~ 2

Author(s):

P. Charlot ◽

A. L. Fey ◽

A. Collioud ◽

R. Ojha ◽

D. A. Boboltz ◽

...

Keyword(s):

Reference Frame ◽

Structural Evolution ◽

Limiting Factors ◽

Radio Structure ◽

Long Baseline ◽

Ongoing Work ◽

The World ◽

Very Long Baseline Array ◽

Celestial Reference Frame ◽

Source Structure

AbstractThe intrinsic radio structure of the extragalactic sources is one of the limiting factors in defining the International Celestial Reference Frame (ICRF). This paper reports about the ongoing work to monitor the structural evolution of the ICRF sources by using the Very Long Baseline Array and other VLBI telescopes around the world. Based on more than 5000 VLBI images produced from such observations, we have assessed the astrometric suitability of 80% of the ICRF sources. The number of VLBI images for a given source varies from 1 for the least-observed sources to more than 20 for the intensively-observed sources. Overall, we identify a subset of 194 sources that are highly compact at any of the available epochs and which are prime candidates for the realization of the next ICRF with the highest accuracy.

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The use of astronomy VLBA campaign MOJAVE for geodesy

Journal of Geodesy ◽

10.1007/s00190-021-01551-3 ◽

2021 ◽

Vol 95 (9) ◽

Author(s):

Hana Krásná ◽

Leonid Petrov

Keyword(s):

Baseline Length ◽

Earth Orientation Parameters ◽

Earth Orientation ◽

Long Baseline ◽

Station Coordinates ◽

The Difference ◽

Very Long Baseline Array ◽

Orientation Parameters ◽

Source Structure ◽

Selection Of

AbstractWe investigated the suitability of the astronomical 15 GHz Very Long Baseline Array (VLBA) observing program MOJAVE-5 for estimation of geodetic parameters, such as station coordinates and Earth orientation parameters. We processed a concurrent dedicated VLBA geodesy program observed at 2.3 GHz and 8.6 GHz starting on September 2016 through July 2020 as reference dataset. We showed that the baseline length repeatability from MOJAVE-5 experiments is only a factor of 1.5 greater than from the dedicated geodetic dataset and still below 1 ppb. The wrms of the difference of estimated Earth orientation parameters with respect to the reference IERS C04 time series are a factor of 1.3 to 1.8 worse. We isolated three major differences between the datasets in terms of their possible impact on the geodetic results, i.e. the scheduling approach, treatment of the ionospheric delay, and selection of target radio sources. We showed that the major factor causing discrepancies in the estimated geodetic parameters is the different scheduling approach of the datasets. We conclude that systematic errors in MOJAVE-5 dataset are low enough for these data to be used as an excellent testbed for further investigations on the radio source structure effects in geodesy and astrometry.

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VEDA: VERA data analysis software for VLBI phase-referencing astrometry

Publications of the Astronomical Society of Japan ◽

10.1093/pasj/psaa044 ◽

2020 ◽

Vol 72 (4) ◽

Cited By ~ 2

Author(s):

Takumi Nagayama ◽

Tomoya Hirota ◽

Mareki Honma ◽

Tomoharu Kurayama ◽

Yuuki Adachi ◽

...

Keyword(s):

Data Analysis ◽

High Precision ◽

Very Long Baseline Interferometry ◽

Phase Fluctuation ◽

Structural Effect ◽

Analysis Software ◽

Long Baseline ◽

Vlbi Data ◽

Motion Measurements ◽

Maser Sources

Abstract We present the VEra Data Analyzer (VEDA) software package for Very Long Baseline Interferometry (VLBI) phase-referencing observations and parallax measurements. The Japanese VLBI project VLBI Exploration of Radio Astrometry (VERA) provides high-precision astrometric results at the 10 μas level. To achieve this precision, accurate calibration of the atmospheric phase fluctuation, the instrumental phase, and the source structural effect is required. VEDA specializes in phase-referencing data analysis, including these calibrations. In order to demonstrate its performance we analyzed H2O maser observations of W 3(OH) and Orion KL with VERA. Their parallaxes were obtained to be 0.527 ± 0.016 mas and 2.459 ± 0.029 mas, respectively. We also analyzed their data using AIPS, which is widely used for VLBI data analysis, and confirmed that the parallaxes obtained using VEDA and AIPS are coincident within 10 μas. VEDA is available for high-precision parallax and proper motion measurements of Galactic maser sources.

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OH MASER SOURCES IN W49N: PROBING MAGNETIC FIELD AND DIFFERENTIAL ANISOTROPIC SCATTERING WITH ZEEMAN PAIRS USING THE VERY LONG BASELINE ARRAY

The Astrophysical Journal ◽

10.1088/0004-637x/775/1/36 ◽

2013 ◽

Vol 775 (1) ◽

pp. 36 ◽

Cited By ~ 1

Author(s):

Avinash A. Deshpande ◽

W. M. Goss ◽

J. E. Mendoza-Torres

Keyword(s):

Magnetic Field ◽

Anisotropic Scattering ◽

Long Baseline ◽

Very Long Baseline Array ◽

Maser Sources

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A broadband VLBI system using transportable stations for geodesy and metrology: an alternative approach to the VGOS concept

Journal of Geodesy ◽

10.1007/s00190-021-01479-8 ◽

2021 ◽

Vol 95 (4) ◽

Author(s):

Mamoru Sekido ◽

Kazuhiro Takefuji ◽

Hideki Ujihara ◽

Tetsuro Kondo ◽

Masanori Tsutsumi ◽

...

Keyword(s):

Large Diameter ◽

Small Diameter ◽

High Sensitivity ◽

Error Sources ◽

Long Baseline ◽

Amplitude Data ◽

Alternative Approach ◽

Increased Sensitivity ◽

Frequency Comparison ◽

Source Structure

AbstractWe have developed a broadband VLBI (very long baseline interferometry) system inspired by the concept of the VLBI Global Observing System (VGOS). The new broadband VLBI system was implemented in the Kashima 34 m antenna and in two transportable stations utilizing 2.4 m diameter antennas. The transportable stations have been developed as a tool for intercontinental frequency comparison but are equally useful for geodesy. To enable practical use of such small VLBI stations in intercontinental VLBI, we have developed the procedure of node-hub style VLBI: In joint observation with a large, high sensitivity ‘hub’ antenna, the closure delay relation provides a virtual delay observable between ‘node’ stations. This overcomes the limited sensitivity of the small diameter node antennas, while error sources associated with large diameter antennas, such as gravitational deformation and delay changes in necessarily long signal cables, are eliminated. We show that this scheme does not result in an increased sensitivity to radio source structure if one side of the baseline triangle is kept short. We have performed VLBI experiments utilizing this approach over both short range and intercontinental distance. This article describes the system components, signal processing procedure, experiment, and results in terms of baseline repeatability. Our measurements reveal signatures of structure effects in the correlation amplitude of several of the observed radio sources. We present a model of the frequency-dependent source size for 1928+738 derived from correlation amplitude data observed in four frequency bands.

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Event Horizon Telescope observations of the jet launching and collimation in Centaurus A

Nature Astronomy ◽

10.1038/s41550-021-01417-w ◽

2021 ◽

Author(s):

Michael Janssen ◽

Heino Falcke ◽

Matthias Kadler ◽

Eduardo Ros ◽

Maciek Wielgus ◽

...

Keyword(s):

Black Holes ◽

Event Horizon ◽

Galactic Nuclei ◽

Galactic Centre ◽

Radio Jets ◽

Long Baseline ◽

Wide Range ◽

Terahertz Frequencies ◽

Source Structure ◽

Centaurus A

AbstractVery-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimetre wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to 10–100 gravitational radii (rg ≡ GM/c2) scales in nearby sources1. Centaurus A is the closest radio-loud source to Earth2. It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our Galactic Centre. A large southern declination of −43° has, however, prevented VLBI imaging of Centaurus A below a wavelength of 1 cm thus far. Here we show the millimetre VLBI image of the source, which we obtained with the Event Horizon Telescope at 228 GHz. Compared with previous observations3, we image the jet of Centaurus A at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. We reveal a highly collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. We find that the source structure of Centaurus A resembles the jet in Messier 87 on ~500 rg scales remarkably well. Furthermore, we identify the location of Centaurus A’s SMBH with respect to its resolved jet core at a wavelength of 1.3 mm and conclude that the source’s event horizon shadow4 should be visible at terahertz frequencies. This location further supports the universal scale invariance of black holes over a wide range of masses5,6.

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A radio parallax to the black hole X-ray binary MAXI J1820+070

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slaa010 ◽

2020 ◽

Vol 493 (1) ◽

pp. L81-L86 ◽

Cited By ~ 12

Author(s):

P Atri ◽

J C A Miller-Jones ◽

A Bahramian ◽

R M Plotkin ◽

A T Deller ◽

...

Keyword(s):

Black Hole ◽

Inclination Angle ◽

Precise Measurement ◽

Very Long Baseline Interferometry ◽

X Ray ◽

Long Baseline ◽

Model Independent ◽

Jet Velocity ◽

Very Long Baseline Array

ABSTRACT Using the Very Long Baseline Array and the European Very Long Baseline Interferometry Network, we have made a precise measurement of the radio parallax of the black hole X-ray binary MAXI J1820+070, providing a model-independent distance to the source. Our parallax measurement of (0.348 ± 0.033) mas for MAXI J1820+070 translates to a distance of (2.96 ± 0.33) kpc. This distance implies that the source reached (15 ± 3) per cent of the Eddington luminosity at the peak of its outburst. Further, we use this distance to refine previous estimates of the jet inclination angle, jet velocity, and the mass of the black hole in MAXI J1820+070 to be (63 ± 3)°, (0.89 ± 0.09) c, and (9.2 ± 1.3) M⊙, respectively.

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