Related papers: Re-analysis of the First Fringe with 2-Beam in the…

We present the results of first dual-beam observations with VERA (VLBI Exploration of Radio Astrometry). The first dual-beam observations of a pair of H2O maser sources W49N and OH43.8-0.1 have been carried out on 2002 May 29 and July 23,…

We present the results of multi-epoch VERA observations of W49N - OH43.8-0.1 water maser pair. Based on the dual-beam VLBI observation with VERA, we successfully obtained the phase-referenced maps of OH43.8-0.1 with respect to the W49N…

We present results of phase-referencing VLBI observations of water maser sources in Orion-Monoceros Molecular Clouds with VERA (VLBI Exploration of Radio Astrometry), which is newly constructed Japanese VLBI network. Main topics of this…

From 43GHz VLBA observations of the pair of radio sources 1928+738 and 2007+777 we have demonstrated the feasibility of precision phase-delay differential astrometric techniques at millimeter wavelengths. For a pair of sources with 5…

In this document we layout a new method to achieve "bona fide" high precision Very-Long-Baseline-Interferometry (VLBI) astrometric measurements of frequency-dependent positions of celestial sources (even) in the high (mm-wavelength)…

Space Very-Long-Baseline-Interferometry (S-VLBI) observations at high frequencies hold the prospect of achieving the highest angular resolutions and astrometric accuracies, resulting from the long baselines between ground and satellite…

We present the results of radio monitoring observations of Sgr A* at 7 mm (i.e. 43 GHz) with VLBI Exploration of Radio Astrometry (VERA), which is a VLBI array in Japan. VERA provides angular resolutions on millisecond scales, resolving…

Studying transient phenomena with the Very Long Baseline Interferometry (VLBI) technique faces severe difficulties because the turnaround time of the experiments from the observations to the scientific result is rather long. The e-VLBI…

We present Very Long Baseline Interferometry (VLBI) observations of 22 GHz H$_2$O masers in the high-mass star-forming region of \objectname{W75N}, carried out with VLBI Exploration of Radio Astrometry (VERA) for three-epochs in 2007 with…

We report VLBA observations of maser emission from the rotationally excited doublet Pi 1/2, J=1/2 state of OH at 4765 MHz. We made phase-referenced observations of W3(OH) at both 4765 MHz and 1720 MHz and found emission in three fields…

The VLA was used to determine precise positions for 4765-MHz OH maser emission sources toward star-forming regions which had been observed about seven months earlier with the Effelsberg 100-meter telescope. The observations were successful…

We report on the results of multi-epoch VLBI observations with VERA (VLBI Exploration of Radio Astrometry) of the 22 GHz H2O masers associated with the young stellar object SVS 13 in the NGC 1333 region. We have carried out…

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…

While conventional imaging in VLBI provides information only about the relative position between different features of a given source, phase-referenced observations can provide precise positional information with respect to an external…

Very long baseline interferometry (VLBI) technique allows us to determine positions of thousands of radio sources using the absolute astrometry approach. I have investigated the impact of a selection of observing frequencies in a range from…

VLBI is unique, among the space geodetic techniques, in its contribution to defining and maintaining the International Celestial Reference Frame, providing precise measurements of coordinates of extragalactic radiosources. The quest for…

Context: Phase referencing is a standard calibration technique in radio interferometry, particularly suited for the detection of weak sources close to the sensitivity limits of the interferometers. However, effects from a changing…

The Gaia celestial reference frame (Gaia-CRF) will benefit from a close assessment with independent methods, such as Very Long Baseline Interferometry (VLBI) measurements of radio stars at bright magnitudes. However, obtaining full…

We report imaging observations of the symbotic long-period Mira variable R Aquarii (R Aqr) at near-infrared and radio wavelengths. The near-infrared observations were made with the IOTA imaging interferometer in three narrow-band filters…

Modern interferometric imaging relies on advanced calibration that incorporates direction-dependent effects. Their increasing number of antennas (e.g. in LOFAR, VLA, MeerKAT/SKA) and sensitivity are often tempered with the accuracy of their…