scholarly journals Space-VLBI observations of OH masers

2002 ◽  
Vol 206 ◽  
pp. 105-111 ◽  
Author(s):  
Vyacheslav I. Slysh ◽  
Maxim A. Voronkov ◽  
Irina E. Val'tts ◽  
Victor Migenes ◽  
K.M. Shibata ◽  
...  
Keyword(s):  
Brightness Temperature ◽  
Lower Limit ◽  
Radio Telescope ◽  
Angular Resolution ◽  
Main Line ◽  
Radio Telescopes ◽  
Space Radio Telescope ◽  
Vlbi Observations ◽  
Interstellar Scattering

We report on the first space-VLBI observations of the OH masers in two main-line OH transitions at 1665 and 1667 MHz. The observations involved the space radio telescope on board the Japanese satellite HALCA and an array of ground radio telescopes. The maps of the maser region and images of individual maser spots were produced with an angular resolution of 1 mas, which is several times higher than the angular resolution available on the ground. The maser spots were only partly resolved and a lower limit to the brightness temperature 6 × 1012 K was obtained. The masers seem to be located in the direction of low interstellar scattering.

scholarly journals Lunar Occultations of the SiO Masers in RLeo

1994 ◽  
Vol 140 ◽  
pp. 154-155
Author(s):  
J. Cernicharo ◽  
W. Brunswig ◽  
G. Paubert ◽  
S. Liechti
Keyword(s):  
Radio Telescope ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
Linear Antenna ◽  
The Moon ◽  
Moderate Size ◽  
Millimeter Wavelengths ◽  
Vlbi Observations ◽  
The Ideal

VLBI observations show that the SiO maser emitting regions in oxygen-rich stars are very clumpy and that these clumps extend over a few stellar radii (Mclntosh et al. 1987; Colomer et al. 1992). These observations indicate that the ideal instrument for the study of the SiO masers is an interferometer with baselines covering between a few and several hundreds/thousands km. Such an instrument is so far unavailable.A classical way to get high angular resolution and a full beam synthesis with a single telescope of moderate size is through lunar occultations. This observing technique provides the angular resolution of a single linear antenna several kilometers long. However, at millimeter wavelengths the Fresnel fringes produced by the Moon limb as the source under study is occulted have never been observed. We present here the observation with the 30-m IRAM radio telescope of the v=1 J=2-1 line of SiO during an occultation (and reappearance) of R Leo by the Moon.

scholarly journals A Tri-band Low-noise Cryogenic Receiver for Geodetic VLBI Observations with VGOS Radio Telescopes

2019 ◽  
Author(s):  
José A. López-Pérez ◽  
Félix Tercero-Martínez ◽  
José M. Serna-Puente ◽  
Beatriz Vaquero-Jiménez ◽  
María Patino-Esteban ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Very Long Baseline Interferometry ◽  
Low Noise ◽  
Radio Telescopes ◽  
Geospatial Information ◽  
Ka Band ◽  
Geodetic Vlbi ◽  
Long Baseline ◽  
Vlbi Observations ◽  
X Band

This paper shows the development of a simultaneous tri-band (S: 2.2 - 2.7 GHz, X: 7.5 - 9 GHz and Ka: 28 - 33 GHz) low-noise cryogenic receiver for geodetic Very Long Baseline Interferometry (geo-VLBI) which has been developed by the technical staff of Yebes Observatory (IGN) laboratories in Spain. The receiver was installed in the first radio telescope of the Red Atlántica de Estaciones Geodinámicas y Espaciales (RAEGE) project, which is located in Yebes Observatory, in the frame of the VLBI Global Observing System (VGOS). After this, the receiver was borrowed by the Norwegian Mapping Autorithy (NMA) for the commissioning of two VGOS radiotelescopes in Svalbard (Norway). A second identical receiver was built for the Ishioka VGOS station of the Geospatial Information Authority (GSI) of Japan, and a third one for the second RAEGE VGOS station, located in Santa María (Açores Archipelago, Portugal). The average receiver noise temperatures are 21, 23 and 25 Kelvin and the measured antenna efficiencies are 70%, 75% and 60% in S-band, X-band and Ka-band, respectively.

scholarly journals Vlbi research in the ”Radioastron” project: structure of the H2O maser in NGC 2071 IRS 1

2021 ◽  
Author(s):  
M. A. Shchurov ◽  
◽  
I. E. Valtts ◽  
N. N. Shakhvorostova ◽  
◽  
...  
Keyword(s):  
Spatial Structure ◽  
Observational Data ◽  
Radio Telescope ◽  
Dependence Analysis ◽  
Scientific Program ◽  
Radio Telescopes ◽  
Space Radio Telescope ◽  
Visibility Function ◽  
Maser Spot ◽  
Project Structure

Within the Radioastron interferometer scientific program, observational data of the H2O maser at a frequency of 22.2280 GHz in the NGC 2071 nebula were processed. A space radio telescope (SRT — 10 m) and three radio telescopes of the ground network: RT — 32 m (Medicina, Italy), RT — 32 m (Torun, Poland) and RT —64 m (Kalyazin, RF) took part in the observations. A map of the maser spot distribution has been obtained, where there are 13 spatial components with VLSR in the range 4.7 — 20.5 km/s. Correlation is observed on ground-space baselines for the component on VLSR = 14.3 km/s. Based on the visibility function dependence analysis from the baseline projection values, there was proposed a twocomponent model of this component spatial structure with the dimensions of the extended and compact constituent of 4 and 0.06 msec, i.e. 1.56 and 0.023 au, respectively.

The Llanherne Low Frequency Radio Telescope

1972 ◽  
Vol 2 (3) ◽  
pp. 135-137 ◽  
Author(s):  
G. R. A. Ellis
Keyword(s):  
Lower Limit ◽  
Radio Telescope ◽  
Radio Astronomy ◽  
Angular Resolution ◽  
Low Frequency ◽  
Earth Satellite ◽  
The Sun ◽  
Frequency Range ◽  
Interstellar Absorption ◽  
The Galaxy

A large proportion of the easily accessible radio astronomy spectrum lies between 50 MHz and a lower limit of about 1 MHz set by interstellar absorption. The features of the spectrum in this frequency range, from sources such as the galaxy, extragalactic sources, pulsars, the Sun and Jupiter, remain only partially explored mainly owing to the large sizes of telescopes necessary to obtain adequate angular resolution and sensitivity. In addition, below 20 MHz, interference from man-made radiation and from the ionosphere severely hinders observations. At the lowest frequencies, the effects of the ionosphere can be overcome by using earth satellite telescopes at the expense of greatly increased difficulty in attaining sufficient telescope aperture.

scholarly journals 0″.4 BIMA Array Mapping of the 107 GHz Methanol Maser in W3(OH)

1998 ◽  
Vol 164 ◽  
pp. 379-380
Author(s):  
V. I. Slysh ◽  
I. E. Val’tts ◽  
S. V. Kalenskii ◽  
G. M. Larionov ◽  
L. G. Mundy
Keyword(s):  
Brightness Temperature ◽  
Lower Limit ◽  
Angular Resolution ◽  
Class Ii ◽  
Methanol Maser ◽  
H Ii Region ◽  
Methanol Masers

AbstractUsing A-configuration of the BIMA-array with 0″.4 angular resolution maps were obtained of the 107 GHz methanol line in W3(OH). The 107 GHz masers have their counterparts in another methanol transition at 6.7 GHz. The strongest maser spots are unresolved with the BIMA-array and are less than , which corresponds to the lower limit of the brightness temperature 5×105 K. A model of Class II methanol masers emitted in the extended atmosphere of icy planets orbiting around the O-star which excites H ɪɪ region is proposed.

scholarly journals The Study of Scattering Effects by VLBI Observations of PSR 0329+54 with HALCA at 1650 MHZ

2001 ◽  
Vol 182 ◽  
pp. 39-42
Author(s):  
A.K. Yangalov ◽  
M.V. Popov ◽  
V.A. Soglasnov ◽  
K.V. Semenkov ◽  
H. Hirabayashi ◽  
...  
Keyword(s):  
Data Processing ◽  
Radio Telescope ◽  
Radio Interferometer ◽  
Space Radio Telescope ◽  
Vlbi Observations ◽  
Scattering Effects ◽  
Initial Results

AbstractPSR0329+54 was observed at 1.6 GHz with a space-ground radio interferometer with HALCA as a space radio telescope. The initial results of data processing are discussed.

scholarly journals Effelsberg Monitoring of a Sample of RadioAstron Blazars

2017 ◽  
Author(s):  
Jun Liu ◽  
Thomas P. Krichbaum ◽  
Xiang Liu ◽  
Alex Kraus ◽  
Hayley Bignall ◽  
...  
Keyword(s):  
Brightness Temperature ◽  
Flux Density ◽  
Radio Telescope ◽  
Galactic Nuclei ◽  
High Brightness ◽  
Space Radio Telescope ◽  
Long Baseline ◽  
Interstellar Scintillation ◽  
Flux Monitoring ◽  
Long Baselines

The launch of the RadioAstron space radio telescope provides a unique opportunity to study the extreme high brightness temperature of Active Galactic Nuclei (AGNs) with unprecedented long baselines of up to 28 Earth diameters. A coordinated ground-based flux density monitoring of RadioAstron targets is essential to determine the effect of interstellar scintillation (ISS) on the Space Very Long Baseline Interferometry (SVLBI) visibilities. Moreover, a combination/comparison of scintillation with SVLBI observations is expected to reveal the relative influence of source brightness temperature, compactness, and properties of the interstellar medium on the observed variability at centimeter wavelengths. In 2014 we started a RadioAstron target triggered flux monitoring with the Effelsberg 100-m radio telescope in support of this SVLBI mission. A total of 112 targets were observed during the five-session monitoring performed so far. In this paper we present a statistical study on the short-term flux density variability of the sample, which is focused on the variability characteristics and derived physical properties of the observed sources.

scholarly journals Interstellar Scattering And The Einstein Ring PKS 1830-211

1996 ◽  
Vol 173 ◽  
pp. 345-346
Author(s):  
D.L. Jones ◽  
R.A. Preston ◽  
D.W. Murphy ◽  
D.L. Meier ◽  
D.L. Jauncey ◽  
...  
Keyword(s):  
Brightness Temperature ◽  
Flux Density ◽  
Angular Size ◽  
Gravitational Lens ◽  
Radio Sources ◽  
Brightness Temperatures ◽  
Vlbi Observations ◽  
Data Support ◽  
Interstellar Scattering ◽  
Lower Frequencies

The remarkably strong radio gravitational lens PKS 1830-211 consists of a one arcsecond diameter Einstein ring with two bright compact components located on opposite sides of the ring. We have obtained 22 GHz VLBA data on this source to determine the intrinsic angular sizes of the compact components. Previous VLBI observations at lower frequencies indicate that the brightness temperatures of these components are significantly lower than 1010 K (Jauncey et al. 1991), less than is typical for compact synchrotron radio sources and less than is implied by flux density variations. A possible explanation is that interstellar scattering is broadening the apparent angular size of the source and thereby reducing the observed brightness temperature. Our VLBA data support this hypothesis.

scholarly journals Phase referencing VLBI astrometry observation system: VERA

2007 ◽  
Vol 3 (S248) ◽  
pp. 148-155
Author(s):  
H. Kobayashi ◽  
N. Kawaguchi ◽  
S. Manabe ◽  
K. M. Shibata ◽  
M. Honma ◽  
...  
Keyword(s):  
Observation System ◽  
Baseline Length ◽  
Radio Telescopes ◽  
Proper Motions ◽  
3 Dimensional ◽  
Japanese Archipelago ◽  
Vlbi Observations ◽  
The Future ◽  
The Galaxy

AbstractVERA aims at astrometric observations using phase referencing VLBI techniques, whose goal is a 10 micro arc-second accuracy for annual parallax measurements. VERA has four 20-m diameter VLBI radio telescopes in Japanese archipelago with the maximum baseline length of 2,300 km. They have the two-beam observing system, which makes simultaneous observations of two objects possible. This leads to very accurate phase referencing VLBI observations. An important science goal is to make a 3-dimensional map of the Galaxy and reveal its dynamics. In order to achieve this, VERA has the 22GHz and 43GHz bands for H2O and SiO maser objects, respectively. Maser objects are compact and suitable for astrometry observations. VERA's construction was started in 2000 and the array became operational in 2004. We have already measured annual parallaxes and proper motions of some galactic objects. In the future, VERA will collaborate with Korean and Chinese VLBI stations.

scholarly journals Pulsar science with the CHIME telescope

2017 ◽  
Vol 13 (S337) ◽  
pp. 179-182 ◽  
Author(s):  
Cherry Ng
Keyword(s):  
Northern Hemisphere ◽  
Radio Telescope ◽  
Field Of View ◽  
Radio Bursts ◽  
Radio Telescopes ◽  
Acoustic Oscillations ◽  
Daily Monitoring ◽  
Intensity Mapping ◽  
Pulsar Timing ◽  
Pulsar Timing Array

AbstractThe CHIME telescope (the Canadian Hydrogen Intensity Mapping Experiment) recently built in Penticton, Canada, is currently being commissioned. Originally designed as a cosmology experiment, it was soon recognized that CHIME has the potential to simultaneously serve as an incredibly useful radio telescope for pulsar science. CHIME operates across a wide bandwidth of 400–800 MHz and will have a collecting area and sensitivity comparable to that of the 100-m class radio telescopes. CHIME has a huge field of view of ~250 square degrees. It will be capable of observing 10 pulsars simultaneously, 24-hours per day, every day, while still accomplishing its missions to study Baryon Acoustic Oscillations and Fast Radio Bursts. It will carry out daily monitoring of roughly half of all pulsars in the northern hemisphere, including all NANOGrav pulsars employed in the Pulsar Timing Array project. It will cycle through all pulsars in the northern hemisphere with a range of cadence of no more than 10 days.

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