相关论文: Improved VLBI astrometry of OH maser stars

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)…

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…

Here we provide a review of Mira variables, their basic properties, and Period-Luminosity Relations with an emphasis on their role in measuring the Hubble Constant. The usage of multiple independent distance indicators and methods is…

Dynamical mass measurements to date have allowed determinations of the mass M and the distance D of a number of nearby supermassive black holes. In the case of Sgr A*, these measurements are limited by a strong correlation between the mass…

We present results of multi-epoch VLBI observations with VERA (VLBI Exploration of Radio Astrometry) of the 22 GHz H$_{2}$O masers associated with a young stellar object (YSO) IRAS 22198+6336 in a dark cloud L1204G. Based on the…

We report the first Very Long Baseline Array (VLBA) observations of 43 GHz v=1, J=1-0 SiO masers in the circumstellar envelope of the M-type semi-regular supergiant variable star AH Sco at 2 epochs separated by 12 days in March 2004. These…

We present the results of PSR$\pi$, a large astrometric project targeting radio pulsars using the Very Long Baseline Array (VLBA). From our astrometric database of 60 pulsars, we have obtained parallax-based distance measurements for all…

We report on the high-precision astrometric observations of maser sources around the Galactic Center in the SiO J=1--0 v=1 and 2 lines with the VLBA during 2001 -- 2004. With phase-referencing interferometry referred to the radio continuum…

We investigate the molecular and dusty environment of OH/IR stars in order to characterize the mass-loss process during the tip-AGB superwind phase. Employing the AMBER instrument at the VLT Interferometer we obtained near-infrared H- and…

We have carried out multi-epoch VLBI observations with VERA (VLBI Exploration of Radio Astrometry) of the 22~GHz H$_{2}$O masers associated with a Class 0 protostar L1448C in the Perseus molecular cloud. The maser features trace the base of…

Joint analysis of Cosmic Microwave Background, Baryon Acoustic Oscillation, and supernova data has enabled precision estimation of cosmological parameters. New programs will push to 1% uncertainty in the dark energy equation of state and…

We have used the NRAO Very Long Baseline Array (VLBA) to image OH(1720 MHz) masers in the supernova remnants W28 and W44 at a resolution of 40 mas. We also used MERLIN to observe the same OH(1720 MHz) masers in W44 at a resolution of 290 x…

The knowledge of the structure and dynamics of AGB-star atmospheres is crucial to better understand the mass loss. The tomographic method, that relies on the design of spectral masks containing lines forming in given ranges of optical…

The aim of this work is to improve the SBC relation for early-type stars in the $-1 \leq V-K \leq 0$ color domain, using optical interferometry. Observations of eight B- and A-type stars were secured with the VEGA/CHARA instrument in the…

Key and still largely missing parameters for measuring the mass content and distribution of the Local Group are the proper motion vectors of its member galaxies. The problem when trying to derive the gravitational potential of the Local…

We have been doing a sample survey in UBV photometry and proper motions as part of an investigation of galactic structure and evolution. The programme is based on Schmidt plates (from OCA, Tautenburg, Palomar and ESO Schmidt telescopes)…

Oxygen-rich Asymptotic Giant Branch (AGB) stars can be intense emitters of SiO ($v$=1 and 2, J=1$\rightarrow$0) and H$_2$O maser lines at 43 and 22 GHz, respectively. VLBI observations of the maser emission provide a unique tool to probe…

SiO maser emission occurs in the extended atmosphere of evolved stars and can be studied at high angular resolution. Very long baseline interferometry (VLBI) observations of Mira variables indicate that SiO masers are significantly linearly…

Using the Very Long Baseline Array (VLBA) we performed a high resolution OH maser survey in Galactic star-forming regions (SFRs). We observed all the ground state spectral lines: the main lines at 1665 and 1667 MHz and the satellite lines…

In this paper we present the results of very long baseline interferometry (VLBI) ob- servations carried out with the VLBI Exploration of Radio Astrometry (VERA) array and the Very Long Baseline Array (VLBA) toward H2O masers in a young…