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Sample records for vlba radio telescope

  1. V-FASTR: The VLBA Fast Radio Transients Experiment

    CERN Document Server

    Wayth, Randall B; Deller, Adam T; Majid, Walid A; Thompson, David R; Tingay, Steven J; Wagstaff, Kiri L

    2011-01-01

    Recent discoveries of dispersed, non-periodic impulsive radio signals with single-dish radio telescopes have sparked significant interest in exploring the relatively uncharted space of fast transient radio signals. Here we describe V-FASTR, an experiment to perform a blind search for fast transient radio signals using the Very Long Baseline Array (VLBA). The experiment runs entirely in a commensal mode, alongside normal VLBA observations and operations. It is made possible by the features and flexibility of the DiFX software correlator that is used to process VLBA data. Using the VLBA for this type of experiment offers significant advantages over single-dish experiments, including a larger field of view, the ability to easily distinguish local radio-frequency interference (RFI) from real signals and the possibility to localize detected events on the sky to milli-arcsecond accuracy. We describe our software pipeline, which accepts short integration (~ms) spectrometer data from each antenna in real-time during ...

  2. VLBA imaging of radio-loud Broad Absorption Line QSOs

    CERN Document Server

    Montenegro-Montes, F M; Benn, C R; Carballo, R; Dallacasa, D; González-Serrano, J I; Holt, J; Jiménez-Luján, F

    2009-01-01

    Broad Absorption Line Quasars (BAL QSOs) have been found to be associated with extremely compact radio sources. These reduced dimensions can be either due to projection effects or these objects might actually be intrinsically small. Exploring these two hypotheses is important to understand the nature and origin of the BAL phenomenon because orientation effects are an important discriminant between the different models proposed to explain this phenomenon. In this work we present VLBA observations of 5 BAL QSOs and discuss their pc-scale morphology.

  3. NRAO Very Long Baseline Array (VLBA)

    Data.gov (United States)

    Federal Laboratory Consortium — The Very Long Baseline Array (VLBA) comprises ten radio telescopes spanning 5,351 miles. It's the world's largest, sharpest, dedicated telescope array. With an eye...

  4. VLBA Observations of Low Luminosity Flat Spectrum Radio Galaxies and BL Lac Objects: Polarisation Properties

    Science.gov (United States)

    Bondi, M.; Dallacasa, D.; Stanghellini, C.; Marchã, M. J. M.

    We obtained two-epoch VLBA observations at 5 GHz of a list of radio galaxies drawn from the 200 mJy sample (Marcha et al. 1996). The objects selected for milli-arcsecond scale observations are classified, on the basis of their optical spectroscopic and polarimetric properties, as BL Lac objects, normal weak line radio galaxies, broad line radio galaxies, and transition objects (those with intermediate properties). We present preliminary results on the radio polarization properties, on the milli-arcsecond scale, of objects with different optical properties and discuss structural variations detected from the two epochs.

  5. Everyday Radio Telescope

    CERN Document Server

    Mandal, Pranshu; Kumar, Pratik; Yelikar, Anjali; Soni, Kanchan; T, Vineeth Krishna

    2016-01-01

    We have developed an affordable, portable college level radio telescope for amateur radio astronomy which can be used to provide hands-on experience with the fundamentals of a radio telescope and an insight into the realm of radio astronomy. With our set-up one can measure brightness temperature and flux of the Sun at 11.2 GHz and calculate the beam width of the antenna. The set-up uses commercially available satellite television receiving system and parabolic dish antenna. We report the detection of point sources like Saturn and extended sources like the galactic arm of the Milky way. We have also developed python pipeline, which are available for free download, for data acquisition and visualization.

  6. VLBA observations of radio faint Fermi-LAT sources above 10 GeV

    CERN Document Server

    Lico, R; Orienti, M; D'Ammando, F

    2016-01-01

    The first Fermi-LAT High-energy source catalog (1FHL), containing gamma-ray sources detected above 10 GeV, is an ideal sample to characterize the physical properties of the most extreme gamma-ray sources. We investigate the pc scale properties of a sub-sample of radio faint 1FHL sources with the aim to confirm the proposed blazar associations, by revealing a compact high brightness temperature radio core, and we propose new low-frequency counterparts for the unassociated gamma-ray sources (UGS). Moreover, we increase the number of 1FHL sources with high resolution observations to explore the possible connection between radio and gamma rays at E >10 GeV. We observed 84 1FHL sources, mostly blazars of High Synchrotron Peaked (HSP) type, in the northern sky with the Very Long Baseline Array (VLBA) at 5 GHz. These sources lack high resolution radio observations and have at least one NVSS counterpart within the 95% confidence radius. For those sources without a well identified radio counterpart we exploit the VLBA...

  7. Uzaybimer Radio Telescope Control System

    Science.gov (United States)

    Balbay, R.; Öz, G. K.; Arslan, Ö.; Özeren, F. F.; Küçük, İ.

    2016-12-01

    A 13 meters former NATO radar is being converted into a radio telescope. The radio telescope is controlled by a system which has been developed at UZAYBİMER. The Telescope Control System(TCS) has been designed using modern industrial systems. TCS has been developed in LabView platform in which works Windows embedded OS. The position feedback used on radio telescopes is an industrial EtherCAT standard. ASCOM library is used for astronomical calculations.

  8. Astronomers Make First Images With Space Radio Telescope

    Science.gov (United States)

    1997-07-01

    Marking an important new milestone in radio astronomy history, scientists at the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico, have made the first images using a radio telescope antenna in space. The images, more than a million times more detailed than those produced by the human eye, used the new Japanese HALCA satellite, working in conjunction with the National Science Foundation's (NSF) Very Long Baseline Array (VLBA) and Very Large Array (VLA) ground-based radio telescopes. The landmark images are the result of a long-term NRAO effort supported by the National Aeronautics and Space Administration (NASA). "This success means that our ability to make detailed radio images of objects in the universe is no longer limited by the size of the Earth," said NRAO Director Paul Vanden Bout. "Astronomy's vision has just become much sharper." HALCA, launched on Feb. 11 by Japan's Institute of Space and Astronautical Science (ISAS), is the first satellite designed for radio astronomy imaging. It is part of an international collaboration led by ISAS and backed by NRAO; Japan's National Astronomical Observatory; NASA's Jet Propulsion Laboratory (JPL); the Canadian Space Agency; the Australia Telescope National Facility; the European VLBI Network and the Joint Institute for Very Long Baseline Interferometry in Europe. On May 22, HALCA observed a distant active galaxy called PKS 1519-273, while the VLBA and VLA also observed it. Data from the satellite was received by a tracking station at the NRAO facility in Green Bank, West Virginia. Tape-recorded data from the satellite and from the radio telescopes on the ground were sent to NRAO's Array Operations Center (AOC) in Socorro, NM. In Socorro, astronomers and computer scientists used a special-purpose computer to digitally combine the signals from the satellite and the ground telescopes to make them all work together as a single, giant radio telescope. This dedicated machine, the VLBA Correlator, built as

  9. Radio Telescopes "Save the Day," Produce Data on Titan's Winds

    Science.gov (United States)

    2005-02-01

    In what some scientists termed "a surprising, almost miraculous turnabout," radio telescopes, including major facilities of the National Science Foundation's National Radio Astronomy Observatory (NRAO), have provided data needed to measure the winds encountered by the Huygens spacecraft as it descended through the atmosphere of Saturn's moon Titan last month -- measurements feared lost because of a communication error between Huygens and its "mother ship" Cassini. The Green Bank Telescope The Robert C. Byrd Green Bank Telescope CREDIT: NRAO/AUI/NSF (Click on image for GBT gallery) A global network of radio telescopes, including the NRAO's Robert C. Byrd Green Bank Telescope (GBT) in West Virginia and eight of the ten antennas of the Very Long Baseline Array (VLBA), recorded the radio signal from Huygens during its descent on January 14. Measurements of the frequency shift caused by the craft's motion, called Doppler shift, are giving planetary scientists their first direct information about Titan's winds. "When we began working with our international partners on this project, we thought our telescopes would be adding to the wind data produced by the two spacecraft themselves. Now, with the ground-based telescopes providing the only information about Titan's winds, we are extremely proud that our facilities are making such a key contribution to our understanding of this fascinating planetary body," said Dr. Fred K.Y. Lo, Director of the National Radio Astronomy Observatory (NRAO). Early analysis of the radio-telescope data shows that Titan's wind flows from west to east, in the direction of the moon's rotation, at all altitudes. The highest wind speed, nearly 270 mph, was measured at an altitude of about 75 miles. Winds are weak near Titan's surface and increase in speed slowly up to an altitude of about 37 miles, where the spacecraft encountered highly-variable winds that scientists think indicate a region of vertical wind shear. The ground-based Doppler

  10. VLBA AND CHANDRA OBSERVATIONS OF JETS IN FRI RADIO GALAXIES: CONSTRAINTS ON JET EVOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    Kharb, P.; O' Dea, C. P. [Department of Physics, Rochester Institute of Technology (RIT), 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Tilak, A. [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Baum, S. A. [Center for Imaging Science, Rochester Institute of Technology (RIT), 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Haynes, E.; Noel-Storr, J.; Fallon, C.; Christiansen, K. [Radcliffe Institute for Advanced Study, 10 Garden Street, Cambridge, MA 02138 (United States)

    2012-07-20

    We present here the results from new Very Long Baseline Array (VLBA) observations at 1.6 and 5 GHz of 19 galaxies of a complete sample of 21 Uppasala General Catalog (UGC) Fanaroff-Riley type I (FRI) radio galaxies. New Chandra data of two sources, viz., UGC 00408 and UGC 08433, are combined with the Chandra archival data of 13 sources. The 5 GHz observations of 10 'core-jet' sources are polarization-sensitive, while the 1.6 GHz observations constitute second-epoch total intensity observations of nine 'core-only' sources. Polarized emission is detected in the jets of seven sources at 5 GHz, but the cores are essentially unpolarized, except in M87. Polarization is detected at the jet edges in several sources, and the inferred magnetic field is primarily aligned with the jet direction. This could be indicative of magnetic field 'shearing' due to jet-medium interaction, or the presence of helical magnetic fields. The jet peak intensity I{sub {nu}} falls with distance d from the core, following the relation, I{sub {nu}}{proportional_to}d{sup a} , where a is typically {approx} - 1.5. Assuming that adiabatic expansion losses are primarily responsible for the jet intensity 'dimming,' two limiting cases are considered: (1) the jet has a constant speed on parsec scales and is expanding gradually such that the jet radius r{proportional_to}d 0{sup .4}; this expansion is, however, unobservable in the laterally unresolved jets at 5 GHz, and (2) the jet is cylindrical and is accelerating on parsec scales. Accelerating parsec-scale jets are consistent with the phenomenon of 'magnetic driving' in Poynting-flux-dominated jets. While slow jet expansion as predicted by case (1) is indeed observed in a few sources from the literature that are resolved laterally, on scales of tens or hundreds of parsecs, case (2) cannot be ruled out in the present data, provided the jets become conical on scales larger than those probed by VLBA. Chandra

  11. Launch Will Create a Radio Telescope Larger than Earth

    Science.gov (United States)

    universe, where the extremely sharp radio "vision" of the new system can provide much-needed information about a number of astronomical mysteries. For years, astronomers have known that powerful "engines" in the hearts of quasars and many galaxies are pouring out tremendous amounts of energy. They suspect that supermassive black holes, with gravitational fields so strong that not even light can escape them, lie in the centers of these "engines." The mechanism at work in the centers of quasars and active galaxies, however, remains a mystery. Ground-based radio telescopes, notably NRAO's Very Long Baseline Array (VLBA), have revealed fascinating new details in recent years, and VSOP is expected to add a wealth of new information on these objects, millions or billions of light-years distant from Earth. Many of these same objects act as super-powerful particle accelerators to eject "jets" of subatomic particles at nearly the speed of light. Scientists plan to use VSOP to monitor the changes and motions in these jets to learn more about how they originate and interact with their surroundings. The satellite also will aim at regions in the sky where giant collections of water and other molecules act as natural amplifiers of radio emission much as lasers amplify light. These regions, called cosmic masers, are found in areas where new stars are forming and near the centers of galaxies. Observations can provide the detail needed to measure motions of individual maser "spots" within these regions, and provide exciting new information about the star-forming regions and the galaxies where the masers reside. In addition, high-resolution studies of cosmic masers can allow astronomers to calculate distances to them with unprecedented accuracy, and thus help resolve continuing questions about the size and age of the universe. The project is a major international undertaking, with about 40 radio telescopes from more than 15 countries having committed time to co-observe with the satellite

  12. Radio Telescopes Will Add to Cassini-Huygens Discoveries

    Science.gov (United States)

    2004-12-01

    When the European Space Agency's Huygens spacecraft makes its plunge into the atmosphere of Saturn's moon Titan on January 14, radio telescopes of the National Science Foundation's National Radio Astronomy Observatory (NRAO) will help international teams of scientists extract the maximum possible amount of irreplaceable information from an experiment unique in human history. Huygens is the 700-pound probe that has accompanied the larger Cassini spacecraft on a mission to thoroughly explore Saturn, its rings and its numerous moons. The Green Bank Telescope The Robert C. Byrd Green Bank Telescope CREDIT: NRAO/AUI/NSF (Click on image for GBT gallery) The Robert C. Byrd Green Bank Telescope (GBT) in West Virginia and eight of the ten telescopes of the continent-wide Very Long Baseline Array (VLBA), located at Pie Town and Los Alamos, NM, Fort Davis, TX, North Liberty, IA, Kitt Peak, AZ, Brewster, WA, Owens Valley, CA, and Mauna Kea, HI, will directly receive the faint signal from Huygens during its descent. Along with other radio telescopes in Australia, Japan, and China, the NRAO facilities will add significantly to the information about Titan and its atmosphere that will be gained from the Huygens mission. A European-led team will use the radio telescopes to make extremely precise measurements of the probe's position during its descent, while a U.S.-led team will concentrate on gathering measurements of the probe's descent speed and the direction of its motion. The radio-telescope measurements will provide data vital to gaining a full understanding of the winds that Huygens encounters in Titan's atmosphere. Currently, scientists know little about Titan's winds. Data from the Voyager I spacecraft's 1980 flyby indicated that east-west winds may reach 225 mph or more. North-south winds and possible vertical winds, while probably much weaker, may still be significant. There are competing theoretical models of Titan's winds, and the overall picture is best summarized as

  13. The LWA1 Radio Telescope

    CERN Document Server

    Ellingson, S W; Craig, J; Hartman, J; Dowell, J; Wolfe, C N; Clarke, T E; Hicks, B C; Kassim, N E; Ray, P S; Rickard, L J; Schinzel, F K; Weiler, K W

    2012-01-01

    LWA1 is a new radio telescope operating in the frequency range 10-88 MHz, located in central New Mexico. The telescope consists of 258 pairs of dipole-type antennas whose outputs are individually digitized and formed into beams. Simultaneously, signals from all dipoles can be recorded using one of the instrument's "all dipoles" modes, facilitating all-sky imaging. Notable features of the instrument include high intrinsic sensitivity (about 6 kJy zenith system equivalent flux density), large instantaneous bandwidth (up to 78 MHz), and 4 independently-steerable beams utilizing digital "true time delay" beamforming. This paper summarizes the design of LWA1 and its performance as determined in commissioning experiments. We describe the method currently in use for array calibration, and report on measurements of sensitivity and beamwidth.

  14. Multi-epoch VLBA observations of radio galaxy 0932+075: is this a compact symmetric object?

    CERN Document Server

    Marecki, A

    2014-01-01

    A part of the radio structure of the galaxy 0932+075 emerged as a possible compact symmetric object (CSO) after the observation with the Very Long Baseline Array (VLBA) at 5 GHz in 1997. More than a decade later, we carried out observations at 5, 15.4, and 22.2 GHz using the VLBA to test this possibility. We report here that we have found a component whose spectrum is inverted in the whole range from 5 GHz to 22 GHz and we label it a high-frequency peaker (HFP). Using a set of 5 GHz images from two epochs separated by 11.8 years and a set of 15.4 GHz images separated by 8.2 years, we were able to examine the proper motions of the three components of the CSO candidate with respect to the HFP. We found that their displacements cannot be reconciled with the CSO paradigm. This has led to the rejection of the hypothesis that the western part of the arcsecond-scale radio structure of 0932+075 is a CSO anchored at the HFP. Consequently, the HFP cannot be labelled a core and its role in this system is unclear.

  15. Can Radio Telescopes Find Axions?

    Science.gov (United States)

    Kohler, Susanna

    2017-08-01

    axions. Now scientists Katharine Kelley and Peter Quinn at ICRAR, University of Western Australia, have explored how we might use next-generation radio telescopes to search for photons that were created by axions interacting with the magnetic fields of our galaxy.Hope for Next-Gen TelescopesPotential axion coupling strengths vs. mass (click for a closer look). The axion mass is thought to lie between a eV and a meV; two theoretical models are shown with dashed lines. The plot shows the sensitivity of the upcoming SKA and its precursors, ASKAP and MEERKAT. [KelleyQuinn 2017]By using a simple galactic halo model and reasonable assumptions for the central galactic magnetic field even taking into account the time dependence of the field Kelley and Quinn estimate the radio-frequency power density that we would observe at Earth from axions being converted to photons within the Milky Ways magnetic field.The authors then compare this signature to the detection capabilities of upcoming radio telescope arrays. They show that the upcoming Square Kilometer Array and its precursors should have the capability to detect signs of axions across large parts of parameter space.Kelley and Quinn conclude that theres good cause for optimism about future radio telescopes ability to detect axions. And if we did succeed in making a detection, it would be a triumph for both particle physics and astrophysics, finally providing an explanation for the universes dark matter.CitationKatharine Kelley and P. J. Quinn 2017 ApJL 845 L4. doi:10.3847/2041-8213/aa808d

  16. Contemporaneous VLBA 5 GHz Observations of Large Area Telescope Detected Blazars

    Science.gov (United States)

    2012-01-10

    on board the Fermi Gamma-ray Space Telescope is a wide-field telescope covering the energy range from about 20 MeV to more than 300 GeV. It has been... energies via inverse Compton processes (e.g., Björnsson 2010; Tavecchio et al. 2011; Abdo et al. 2011). Meier (2005) expected several reconnection...Astrophys. Space Sci. Libr ., 285, 109 Healey, S. E., Romani, R. W., Cotter, G., et al. 2008, ApJS, 175, 97 Healey, S. E., Romani, R. W., Taylor, G. B

  17. Goldstone Apple Valley Radio Telescope Project.

    Science.gov (United States)

    Ibe, Mary; MacLaren, Dave

    2003-01-01

    Describes the Goldstone Apple Valley Radio Telescope (GAVRT) project as a way of teaching astronomy concepts to middle school students. The project provides students opportunities to work with professional scientists. (SOE)

  18. The nuclear accretion in the FR I radio galaxy IC4296 from CHANDRA and VLBA observations

    CERN Document Server

    Pellegrini, S; Comastri, A; Fabbiano, G; Fiore, F; Vignali, C; Morganti, R; Trinchieri, G

    2003-01-01

    A high angular resolution study of the nucleus of the FR I galaxy IC4296 using Chandra ACIS-S and VLBA observations is presented, with the aim of studying the nature of the accretion process. Pointlike and hard X-ray emission is found, well described by a moderately absorbed power law of Gamma=1.48^{+0.42}_{-0.34}; no iron fluorescence line from cold material is detected. The 0.3-10 keV luminosity is 2.4\\times 10^{41} erg/s, that is \\sim 400 times lower than the accretion luminosity resulting from the estimated Bondi mass accretion rate and a radiative efficiency of 10%. On the parsec scale a jet and a counter-jet extend out from a central unresolved ``core'' in the 8.4 GHz image. Their orientation is in good agreement with that of the large scale jets and their bulk speed is relativistic. The parsec scale spectrum is convex over 2-22 GHz. The observed nuclear luminosity is not likely to be reconciled with the accretion luminosity by assuming that Compton thick material surrounds the nucleus. Low radiative ef...

  19. A Machine Learning Classifier for Fast Radio Burst Detection at the VLBA

    CERN Document Server

    Wagstaff, Kiri L; Thompson, David R; Khudikyan, Shakeh; Wyngaard, Jane; Deller, Adam T; Palaniswamy, Divya; Tingay, Steven J; Wayth, Randall B

    2016-01-01

    Time domain radio astronomy observing campaigns frequently generate large volumes of data. Our goal is to develop automated methods that can identify events of interest buried within the larger data stream. The V-FASTR fast transient system was designed to detect rare fast radio bursts (FRBs) within data collected by the Very Long Baseline Array. The resulting event candidates constitute a significant burden in terms of subsequent human reviewing time. We have trained and deployed a machine learning classifier that marks each candidate detection as a pulse from a known pulsar, an artifact due to radio frequency interference, or a potential new discovery. The classifier maintains high reliability by restricting its predictions to those with at least 90% confidence. We have also implemented several efficiency and usability improvements to the V-FASTR web-based candidate review system. Overall, we found that time spent reviewing decreased and the fraction of interesting candidates increased. The classifier now c...

  20. Undergraduate Research with a Small Radio Telescope

    Science.gov (United States)

    Fisher, P. L.; Williams, G. J.

    2001-11-01

    We describe the construction of a small radio telescope system at ULM and the role of radio astronomy in undergraduate education. The heart of the system is the Small Radio Telescope (SRT), which is a modified satellite TV antenna and custom receiver purchased from MIT Haystack Observatory. This telescope measures the brightness of many celestial objects at wavelengths near 21 cm. The system consists of various components to control dish movement, as well as perform analog to digital conversions allowing analysis of collected data. Undergraduate students have participated in the construction of the hardware and the task of interfacing the hardware to software on two GNU/Linux computer systems. The construction of the telescope and analysis of data allow the students to employ key concepts from mechanics, optics, electrodynamics, and thermodynamics, as well as computer and electronics skills. We will report preliminary results of solar observations conducted with this instrument and with the MIT Haystack Observatory 37m radio telescope. This work was supported by Louisiana Board of Regents grant LEQSF-ENH-UG-16, NASA/LaSPACE LURA R109139 and ULM Development Foundation Grant 97317.

  1. A Machine Learning Classifier for Fast Radio Burst Detection at the VLBA

    Science.gov (United States)

    Wagstaff, Kiri L.; Tang, Benyang; Thompson, David R.; Khudikyan, Shakeh; Wyngaard, Jane; Deller, Adam T.; Palaniswamy, Divya; Tingay, Steven J.; Wayth, Randall B.

    2016-08-01

    Time domain radio astronomy observing campaigns frequently generate large volumes of data. Our goal is to develop automated methods that can identify events of interest buried within the larger data stream. The V-FASTR fast transient system was designed to detect rare fast radio bursts within data collected by the Very Long Baseline Array. The resulting event candidates constitute a significant burden in terms of subsequent human reviewing time. We have trained and deployed a machine learning classifier that marks each candidate detection as a pulse from a known pulsar, an artifact due to radio frequency interference, or a potential new discovery. The classifier maintains high reliability by restricting its predictions to those with at least 90% confidence. We have also implemented several efficiency and usability improvements to the V-FASTR web-based candidate review system. Overall, we found that time spent reviewing decreased and the fraction of interesting candidates increased. The classifier now classifies (and therefore filters) 80%-90% of the candidates, with an accuracy greater than 98%, leaving only the 10%-20% most promising candidates to be reviewed by humans.

  2. Teaching radio astronomy with Affordable Small Radio Telescope (ASRT)

    Science.gov (United States)

    Joshi, Bhal Chandra

    A simple, easy to build and portable radio telescope, called Affordable Small Radio Telescope (ASRT), has been developed by the Radio Physics Laboratory (RPL), a radio astronomy teaching unit associated with the National Centre for Radio Astrophysics (TIFR) and Inter-University Centre for Astronomy and Astrophysics (IUCAA), which are two premier astronomy institutes in India. ASRT consists of off-the-shelf available Direct to Home television dishes and is easy to assemble. Our design is scalable from simple very low cost telescope to more complex yet moderately costing instrument. ASRT provides a platform for demonstrating radio physics concepts through simple hands-on experiment as well as for carrying out solar monitoring by college/University students. The presentation will highlight the concept of ASRT and the different experiments that can be carried out using it. The solar monitoring observations will be discussed along-with details of methods for calibrating these measurements. The pedagogical usefulness of ASRT in introducing undergraduatephysics students to astrophysics, measurements and analysis methods used in radio astronomy will also be discussed. Use of ASRT in the last three years in the programs of RPL, namely the annual Radio Astronomy Winter School for College students (RAWSC) and Pulsar Observing for Students (POS) is also presented. This year a new program was initiated to form a virtual group of an ASRT community, which will not only share their measurements, but also think of improving the pedagogical usefulness of ASRT by innovative experiments. This initiative is presented with the best practices drawn from our experience in using ASRT as a tool for student training in space sciences. The talk will also point out future ideas in involving a larger body of students in simple radio astronomy experiments with the ASRT, which RPL is likely to nucleate as part of its mandate.

  3. South African Student Constructed Indlebe Radio Telescope

    Science.gov (United States)

    McGruder, Charles H.; MacPherson, Stuart; Janse Van Vuuren, Gary Peter

    2017-01-01

    The Indlebe Radio Telescope (IRT) is a small transit telescope with a 5 m diameter parabolic reflector working at 21 cm. It was completely constructed by South African (SA) students from the Durban University of Technology (DUT), where it is located. First light occurred on 28 July 2008, when the galactic center, Sagittarius A, was detected. As a contribution to the International Year of Astronomy in 2009, staff members in the Department of Electronic Engineering at DUT in 2006 decided to have their students create a fully functional radio telescope by 2009. The specific project aims are to provide a visible project that could generate interest in science and technology in high school students and to provide a real world system for research in radio astronomy in general and an optimization of low noise radio frequency receiver systems in particular. These aims must be understood in terms of the SA’s government interests in radio astronomy. SA is a partner in the Square Kilometer Array (SKA) project, has constructed the Karoo Array Telescope (KAT) and MeerKat, which is the largest and most sensitive radio telescope in the southern hemisphere. SA and its partners in Africa are investing in the construction of the African Very Long Baseline Interferometry Network (AVN), an array of radio telescopes throughout Africa as an extension of the existing global Very Long Baseline Interferometry Network (VLBI). These projects will allow SA to make significant contributions to astronomy and enable astronomy to contribute to the scientific education and development goals of the country. The IRT sees on a daily basis the transit of Sag A. The transit time is influenced by precession, nutation, polar motion, aberration, celestial pole offset, proper motion, length of the terrestrial day and variable ionospheric refraction. Of these eight factors six are either predictable or measureable. To date neither celestial pole offset nor variable ionospheric refraction are predicable

  4. LOFAR, a new low frequency radio telescope

    CERN Document Server

    Röttgering, H J A

    2003-01-01

    LOFAR, the Low Frequency Array, is a large radio telescope consisting of approximately 100 soccer-field sized antenna stations spread over a region of 400 km in diameter. It will operate at frequencies from ~10 to 240 MHz, with a resolution at 240 MHz of better than an arcsecond. Its superb sensitivity will allow for studies of a broad range of astrophysical topics, including reionisation, transient radio sources and cosmic rays, distant galaxies and AGNs. In this contribution a status rapport of the LOFAR project and an overview of the science case is presented.

  5. Astrophysical results of the Mauritius radio telescope

    Science.gov (United States)

    Somanah, R.; Issur, N.; Oozeer, N.

    2013-04-01

    One of the first scientific justifications of building the Mauritius Radio Telescope (hereafter referred to as MRT) was to complement the Cambridge 6C survey, which is a radio map of most of the northern sky at 150 MHz [1]; the MRT would then be the equivalent of the 6C survey for the southern sky and together we would obtain a whole sky radio map at 150 MHz. When the MRT was built, there were no radio surveys of the southern sky at frequencies less than 408 MHz; the frequency of 150 MHz was also chosen to complement the other radio surveys of the southern sky, which have been done at higher frequencies. Furthermore low radio frequencies like 150 MHz are bound to see new sources that would have been missed at higher frequencies due to the form of their spectra. Interesting features of resolved objects can also be studied in more details. In this paper, a brief description of the MRT will be made as well as the observations and imaging with the MRT data, and some astrophysical results obtained since its commissioning in 1992 (20 years of existence this year 2012).

  6. New Radio Telescope Makes First Scientific Observations

    Science.gov (United States)

    2001-05-01

    The world's two largest radio telescopes have combined to make detailed radar images of the cloud-shrouded surface of Venus and of a tiny asteroid that passed near the Earth. The images mark the first scientific contributions from the National Science Foundation's (NSF) new Robert C. Byrd Green Bank Telescope in West Virginia, which worked with the NSF's recently-upgraded Arecibo telescope in Puerto Rico. The project used the radar transmitter on the Arecibo telescope and the huge collecting areas of both telescopes to receive the echoes. GBT-Arecibo Radar Image of Maxwell Montes on Venus "These images are the first of many scientific contributions to come from the Robert C. Byrd Green Bank Telescope, and a great way for it to begin its scientific career," said Paul Vanden Bout, director of the National Radio Astronomy Observatory (NRAO). "Our congratulations go to the scientists involved in this project as well as to the hard-working staffs at Green Bank and Arecibo who made this accomplishment possible," Vanden Bout added. To the eye, Venus hides behind a veil of brilliant white clouds, but these clouds can be penetrated by radar waves, revealing the planet's surface. The combination of the Green Bank Telescope (GBT), the world's largest fully-steerable radio telescope, and the Arecibo telescope, the world's most powerful radar, makes an unmatched tool for studying Venus and other solar-system bodies. "Having a really big telescope like the new Green Bank Telescope to receive the radar echoes from small asteroids that are really close to the Earth and from very distant objects like Titan, the large moon of Saturn, will be a real boon to radar studies of the solar system." said Cornell University professor Donald Campbell, leader of the research team. Ten years ago, the radar system on NASA's Magellan spacecraft probed though the clouds of Venus to reveal in amazing detail the surface of the Earth's twin planet. These new studies using the GBT and Arecibo, the

  7. Beam calibration of radio telescopes with drones

    CERN Document Server

    Chang, Chihway; Refregier, Alexandre; Amara, Adam; Glauser, Adrian; Casura, Sarah

    2015-01-01

    We present a multi-frequency far-field beam map for the 5m dish telescope at the Bleien Observatory measured using a commercially available drone. We describe the hexacopter drone used in this experiment, the design of the flight pattern, and the data analysis scheme. This is the first application of this calibration method to a single dish radio telescope in the far-field. The high signal-to-noise data allows us to characterise the beam pattern with high accuracy out to at least the 4th side-lobe. The resulting 2D beam pattern is compared with that derived from a more traditional calibration approach using an astronomical calibration source. We discuss the advantages of this method compared to other beam calibration methods. Our results show that this drone-based technique is very promising for ongoing and future radio experiments, where the knowledge of the beam pattern is key to obtaining high-accuracy cosmological and astronomical measurements.

  8. Beam Calibration of Radio Telescopes with Drones

    Science.gov (United States)

    Chang, Chihway; Monstein, Christian; Refregier, Alexandre; Amara, Adam; Glauser, Adrian; Casura, Sarah

    2015-11-01

    We present a multi-frequency far-field beam map for the 5m dish telescope at the Bleien Observatory measured using a commercially available drone. We describe the hexacopter drone used in this experiment, the design of the flight pattern, and the data analysis scheme. This is the first application of this calibration method to a single dish radio telescope in the far-field. The high signal-to-noise data allows us to characterise the beam pattern with high accuracy out to at least the 4th side-lobe. The resulting 2D beam pattern is compared with that derived from a more traditional calibration approach using an astronomical calibration source. We discuss the advantages of this method compared to other beam calibration methods. Our results show that this drone-based technique is very promising for ongoing and future radio experiments, where the knowledge of the beam pattern is key to obtaining high-accuracy cosmological and astronomical measurements.

  9. Abu Simbel Radio Telescope Project in the upper Egypt.

    Science.gov (United States)

    Shaltout, M.

    1999-03-01

    This paper shows the importance of building a radio telescope at Abu Simbel in the south of Egypt as part of the European VLBI Network (EVN) to cover the gap between the radio telescopes in Western Europe and the radio telescope at Hartebeesthoek in South Africa. The telescope can be used for solar and stellar observations at wavelengths ranging between centimetres and millimetres, and for geodetic VLBI studies. The suggested diameter is 32 meters for the telescope and it is expected to work in the frequency range from 1.4 to 43 GHz. Abu Simbel is characterised by excellent atmospheric transparency, dry climate, and low population without any artificial interference.

  10. Integrated modeling of submillimeter radio telescopes

    Science.gov (United States)

    Moraru, Dan; Andersen, Torben

    2002-07-01

    Integrated models are inherently complex and often obscure to any but those who write them. Their usefulness can be greatly enhanced through well-structured, object-oriented design. A robust and computationally efficient Simulink/C++ library of optics, control, finite-element, and visualization routines for modeling radio telescope performance under various operating conditions is being developed and is described. The library is being developed in conjunction with an end-to-end model of the Atacama Large Millimeter Array (ALMA) antennas. The model includes the mechanical structure, optics, servos, and potential laser gyros, and can be used to investigate such issues as tracking performance, compliance with error budgets, wind sensitivity, and effectiveness of an internal metrology system. It will also be a good tool for comparison of different antenna designs.

  11. VLBA Locates Origin of Superenergetic Bursts Near Giant Black Hole

    Science.gov (United States)

    2009-07-01

    Using a worldwide combination of diverse telescopes, astronomers have discovered that a giant galaxy's bursts of very high energy gamma rays are coming from a region very close to the supermassive black hole at its core. The discovery provides important new information about the mysterious workings of the powerful "engines" in the centers of innumerable galaxies throughout the Universe. M87 Zooming in on the powerful core of the galaxy M87 CREDIT: Bill Saxton, NRAO/AUI/NSF Full Page of Graphics The galaxy M87, 50 million light-years from Earth, harbors at its center a black hole more than six billion times more massive than the Sun. Black holes are concentrations of matter so dense that not even light can escape their gravitational pull. The black hole is believed to draw material from its surroundings -- material that, as it falls toward the black hole, forms a tightly-rotating disk. Processes near this accretion disk, powered by the immense gravitational energy of the black hole, propel energetic material outward for thousands of light-years. This produces the "jets" seen emerging from many galaxies. In 1998, astronomers found that M87 also was emitting flares of gamma rays a trillion times more energetic than visible light. However, the telescopes that discovered these bursts of very high energy gamma rays could not determine exactly where in the galaxy they originated. In 2007 and 2008, the astronomers using these gamma-ray telescopes combined forces with a team using the National Science Foundation's continent-wide Very Long Baseline Array (VLBA), a radio telescope with extremely high resolving power, or ability to see fine detail. "Combining the gamma-ray observations with the supersharp radio 'vision' of the VLBA allowed us to see that the gamma rays are coming from a region very near the black hole itself," said Craig Walker, of the National Radio Astronomy Observatory (NRAO). "Pinning down this location addresses what was an open question and provides

  12. 32 Meter Radio Telescopes in the Arabian Region

    Science.gov (United States)

    Shaltout, M.

    2002-06-01

    This paper presents the importance of building two new radio telescopes of diameter 32 meters to work in the frequency range from 1.4 to 43 GHz, one in the South of Egypt (Abu-Simbel), and the other in the South of the Arabian Peninsula. Both telescopes would be of great interest for the International Radio Astronomy Community from the beginning, especially for EVN.

  13. Construction of largest aperture radio telescope starts in southwest China

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    @@ While observing the world around us via an optical telescope with information carried by visible light,which constitutes only a small portion of the electromagnetic spectrum,astronomers use the remainder of the spectrum to reveal extensive data about celestial objects. For instance,they use telescopes operating in the radio spectrum to explore the An artist's rendition of FAST.

  14. VLBA Reveals Closest Pair of Supermassive Black Holes

    Science.gov (United States)

    2006-05-01

    Astronomers using the National Science Foundation's Very Long Baseline Array (VLBA) radio telescope have found the closest pair of supermassive black holes ever discovered in the Universe -- a duo of monsters that together are more than 150 million times more massive than the Sun and closer together than the Earth and the bright star Vega. The VLBA The VLBA CREDIT: NRAO/AUI/NSF "These two giant black holes are only about 24 light-years apart, and that's more than 100 times closer than any pair found before," said Cristina Rodriguez, of the University of New Mexico (UNM) and Simon Bolivar University in Venezuela. Black holes are concentrations of mass with gravity so strong that not even light can escape them. The black hole pair is in the center of a galaxy called 0402+379, some 750 million light-years from Earth. Astronomers presume that each of the supermassive black holes was once at the core of a separate galaxy, then the two galaxies collided, leaving the black holes orbiting each other. The black holes orbit each other about once every 150,000 years, the scientists say. "If two black holes like these were to collide, that event would create the type of strong gravitational waves that physicists hope to detect with instruments now under construction," said Gregory Taylor, of UNM. The physicists will need to wait, though: the astronomers calculate that the black holes in 0402+379 won't collide for about a billion billion years. "There are some things that might speed that up a little bit," Taylor remarked. An earlier VLBA study of 0402+379, an elliptical galaxy, showed the pair of radio-wave-emitting objects near its core. Further studies using the VLBA and the Hobby-Eberly Telescope in Texas, revealed that the pair of objects is indeed a pair of supermassive black holes. "We needed the ultra-sharp radio 'vision' of the VLBA, particularly at the high radio frequencies of 22 and 43 GigaHertz, to get the detail needed to show that those objects are a pair of

  15. Recent Radio Monitoring of Microquasars with RATAN-600 Radio Telescope

    CERN Document Server

    Trushkin, S A; Kotani, T; Nizhelskij, N A; Namiki, M; Tsuboi, M; Voitsik, P A

    2007-01-01

    We report about the multi-frequency (1-30 GHz) daily monitoring of the radio flux variability of the three microquasars: SS433, GRS1915+105 and Cyg X-3 during the period from September 2005 to May 2006. 1. We detected clear correlation of the flaring radio fluxes and X-rays 'spikes' at 2-12 keV emission detected in RXTE ASM from GRS1915+105 during eight relatively bright (200-600 mJy) radio flares in October 2005. The 1-22 GHz spectra of these flares in maximum were optically thick at frequencies lower 2.3 GHz and optically thin at the higher frequencies. During the radio flares the spectra of the X-ray spikes become softer than those of the quiescent phase. Thus these data indicated the transitions from very high/hard states to high/soft ones during which massive ejections are probably happened. These ejections are visible as the detected radio flares. 2. After of the quiescent radio emission we have detected a drop down of the fluxes (~20 mJy) from Cyg X-3. That is a sign of the following bright flare. Inde...

  16. FPGA applications for single dish activity at Medicina radio telescopes

    Science.gov (United States)

    Bartolin, M.; Nald, G.; Mattan, A.; Maccaferr, A.; De Biagg, M.

    FPGA technologies are gaining major attention in the recent years in the field of radio astronomy. At Medicina radio telescopes, FPGAs have been used in the last ten years for a number of purposes and in this article we will take into exam the applications developed and installed for the Medicina Single Dish 32m Antenna: these range from high performance digital signal processing to instrument control developed on top of smaller FPGAs.

  17. Synergy Between Radio and Optical Telescopes: Optical Followup of Extragalactic Radio Sources

    Indian Academy of Sciences (India)

    C. H. Ishwara-Chandra

    2013-06-01

    Distance measurement is a must to characterize any source in the sky. In the radio band, it is rarely possible to get distance or redshift measurements. The optical band is the most used band to get distance estimate of sources, even for those originally discovered in other bands of the electromagnetic spectrum. However, the spectroscopic redshift measurements even for fairly bright radio sample is grossly incomplete, implying un-explored discovery space. Here we discuss the scope of optical follow up of radio sources, in particular the radio loud AGNs, from the present generation radio telescopes.

  18. Solar system radio emissions studies with the largest low-frequency radio telescopes

    Science.gov (United States)

    Zakharenko, V.; Konovalenko, A.; Litvinenko, G.; Kolyadin, V.; Zarka, P.; Mylostna, K.; Vasylieva, I.; Griessmeier, J.-M.; Sidorchuk, M.; Rucker, H.; Fischer, G.; Cecconi, B.; Coffre, A.; Denis, L.; Shevchenko, V.; Nikolaenko, V.

    2014-04-01

    We describe the trends and tasks in the field of lowfrequency studies of radio emission from the Solar system's objects. The world's largest decameter radio telescopes UTR-2 and URAN have a unique combination of sensitivity and time/frequency resolution parameters, providing the capability of the most detailed studies of various types of solar and planetary emissions.

  19. The Five-hundred-meter Aperture Spherical Radio Telescope Project

    Science.gov (United States)

    Li, Di; Pan, Zhichen

    2016-07-01

    The Five-hundred-meter Aperture Spherical Radio Telescope (FAST) is a Chinese megascience project funded by the National Development and Reform Commission (NDRC) of the People's Republic of China. The National Astronomical Observatories of China (NAOC) is in charge of its construction and subsequent operation. Upon its expected completion in September 2016, FAST will surpass the 305 m Arecibo Telescope and the 100 m Green Bank Telescope in terms of absolute sensitivity in the 70 MHz to 3 GHz bands. In this paper, we report on the project, its current status, the key science goals, and plans for early science.

  20. Fundamental Imaging Limits of Radio Telescope Arrays

    CERN Document Server

    Wijnholds, Stefan J; 10.1109/JSTSP.2008.2004216

    2010-01-01

    The fidelity of radio astronomical images is generally assessed by practical experience, i.e. using rules of thumb, although some aspects and cases have been treated rigorously. In this paper we present a mathematical framework capable of describing the fundamental limits of radio astronomical imaging problems. Although the data model assumes a single snapshot observation, i.e. variations in time and frequency are not considered, this framework is sufficiently general to allow extension to synthesis observations. Using tools from statistical signal processing and linear algebra, we discuss the tractability of the imaging and deconvolution problem, the redistribution of noise in the map by the imaging and deconvolution process, the covariance of the image values due to propagation of calibration errors and thermal noise and the upper limit on the number of sources tractable by self calibration. The combination of covariance of the image values and the number of tractable sources determines the effective noise ...

  1. Five hundred meter aperture spherical radio telescope (FAST)

    Institute of Scientific and Technical Information of China (English)

    NAN; Rendong

    2006-01-01

    Five hundred meter aperture spherical radio telescope (FAST) will be the largest radio telescope in the world. The innovative engineering concept and design pave a new road to realizing a huge single dish in the most effective way. Three outstanding features of the telescope are the unique karst depressions as the sites, the active main reflector which corrects spherical aberration on the ground to achieve full polarization and a wide band without involving a complex feed system, and the light focus cabin driven by cables and servomechanism plus a parallel robot as secondary adjustable system to carry the most precise parts of the receivers. Being the most sensitive radio telescope, FAST will enable astronomers to jumpstart many of the science goals, for example, the neutral hydrogen line surveying in distant galaxies out to very large redshifts, looking for the first shining star, detecting thousands of new pulsars, etc. Extremely interesting and exotic objects may yet await discovery by FAST. As a multi-science platform, the telescope will provide treasures to astronomers, as well as bring prosperity to other research, e.g. space weather study, deep space exploration and national security. The construction of FAST itself is expected to promote the development in high technology of relevant fields.

  2. High-precision pointing with the Sardinia Radio Telescope

    Science.gov (United States)

    Poppi, Sergio; Pernechele, Claudio; Pisanu, Tonino; Morsiani, Marco

    2010-07-01

    We present here the systems aimed to measure and minimize the pointing errors for the Sardinia Radio Telescope: they consist of an optical telescope to measure errors due to the mechanical structure deformations and a lasers system for the errors due to the subreflector displacement. We show here the results of the tests that we have done on the Medicina 32 meters VLBI radio telescope. The measurements demonstrate we can measure the pointing errors of the mechanical structure, with an accuracy of about ~1 arcsec. Moreover, we show the technique to measure the displacement of the subreflector, placed in the SRT at 22 meters from the main mirror, within +/-0.1 mm from its optimal position. These measurements show that we can obtain the needed accuracy to correct also the non repeatable pointing errors, which arise on time scale varying from seconds to minutes.

  3. VLBA Changes Picture of Famous Star-Forming Region

    Science.gov (United States)

    2007-10-01

    Using the supersharp radio "vision" of the National Science Foundation's Very Long Baseline Array (VLBA), astronomers have made the most precise measurement ever of the distance to a famous star-forming region. The measurement -- to the heavily studied Orion Nebula -- changes scientists' understanding of the characteristics of the young stars in the region. Parallax Diagram Trigonometric Parallax method determines distance to star by measuring its slight shift in apparent position as seen from opposite ends of Earth's orbit. CREDIT: Bill Saxton, NRAO/AUI/NSF Star Track Apparent track of star GMR A in the Orion Nebula Cluster, showing shift caused by Earth's orbital motion and star's movement in space. CREDIT: Sandstrom et al., NRAO/AUI/NSF Click on Images for Larger Files "This measurement is four times more precise than previous distance estimates. Because our measurement reduces the distance to this region, it tells us that the stars there are less bright than thought before, and changes the estimates of their ages," said Geoff Bower, an astronomer at the University of California at Berkeley. Bower, along with Karin Sandstrom, J.E.G. Peek, Alberto Bolatto and Richard Plambeck, all of Berkeley, published their findings in the October 10 edition of the Astrophysical Journal. The scientists determined the distance to a star called GMR A, one of a cluster of stars in the Orion Nebula, by measuring the slight shift in the star's apparent position in the sky caused by the Earth's motion around the Sun. Observing the star when the Earth is on opposite sides of its annual orbit allows astronomers to measure the angle of this small shift and thus provides a direct trigonometric calculation of its distance. "By using this technique, called parallax, we get a direct measurement that does not depend on various assumptions that are required to use less-direct methods," Bower said. "Only a telescope with the remarkable ability to see fine detail that is provided by the VLBA is

  4. An African VLBI network of radio telescopes

    CERN Document Server

    Gaylard, M J; Combrinck, L; Booth, R S; Buchner, S J; Fanaroff, B L; MacLeod, G C; Nicolson, G D; Quick, J F H; Stronkhorst, P; Venkatasubramani, T L

    2014-01-01

    The advent of international wideband communication by optical fibre has produced a revolution in communications and the use of the internet. Many African countries are now connected to undersea fibre linking them to other African countries and to other continents. Previously international communication was by microwave links through geostationary satellites. These are becoming redundant in some countries as optical fibre takes over, as this provides 1000 times the bandwidth of the satellite links. In the 1970's and 1980's some two dozen large (30 m diameter class) antennas were built in various African countries to provide the satellite links. Twenty six are currently known in 19 countries. As these antennas become redundant, the possibility exists to convert them for radio astronomy at a cost of roughly one tenth that of a new antenna of similar size. HartRAO, SKA Africa and the South African Department of Science and Technology (DST) have started exploring this possibility with some of the African countries...

  5. Detecting cosmic rays with the LOFAR radio telescope

    CERN Document Server

    Schellart, P; Buitink, S; Corstanje, A; Enriquez, J E; Falcke, H; Frieswijk, W; Hörandel, J R; Horneffer, A; James, C W; Krause, M; Mevius, M; Scholten, O; ter Veen, S; Thoudam, S; Akker, M van den; Alexov, A; Anderson, J; Avruch, I M; Bähren, L; Beck, R; Bell, M E; Bennema, P; Bentum, M J; Bernardi, G; Best, P; Bregman, J; Breitling, F; Brentjens, M; Broderick, J; Brüggen, M; Ciardi, B; Coolen, A; de Gasperin, F; de Geus, E; de Jong, A; de Vos, M; Duscha, S; Eislöffel, J; Fallows, R A; Ferrari, C; Garrett, M A; Grießmeier, J; Grit, T; Hamaker, J P; Hassall, T E; Heald, G; Hessels, J W T; Hoeft, M; Holties, H A; Iacobelli, M; Juette, E; Karastergiou, A; Klijn, W; Kohler, J; Kondratiev, V I; Kramer, M; Kuniyoshi, M; Kuper, G; Maat, P; Macario, G; Mann, G; Markoff, S; McKay-Bukowski, D; McKean, J P; Miller-Jones, J C A; Mol, J D; Mulcahy, D D; Munk, H; Nijboer, R; Norden, M J; Orru, E; Overeem, R; Paas, H; Pandey-Pommier, M; Pizzo, R; Polatidis, A G; Renting, A; Romein, J W; Röttgering, H; Schoenmakers, A; Schwarz, D; Sluman, J; Smirnov, O; Sobey, C; Stappers, B W; Steinmetz, M; Swinbank, J; Tang, Y; Tasse, C; Toribio, C; van Leeuwen, J; van Nieuwpoort, R; van Weeren, R J; Vermaas, N; Vermeulen, R; Vocks, C; Vogt, C; Wijers, R A M J; Wijnholds, S J; Wise, M W; Wucknitz, O; Yatawatta, S; Zarka, P; Zensus, A

    2013-01-01

    The low frequency array (LOFAR), is the first radio telescope designed with the capability to measure radio emission from cosmic-ray induced air showers in parallel with interferometric observations. In the first $\\sim 2\\,\\mathrm{years}$ of observing, 405 cosmic-ray events in the energy range of $10^{16} - 10^{18}\\,\\mathrm{eV}$ have been detected in the band from $30 - 80\\,\\mathrm{MHz}$. Each of these air showers is registered with up to $\\sim1000$ independent antennas resulting in measurements of the radio emission with unprecedented detail. This article describes the dataset, as well as the analysis pipeline, and serves as a reference for future papers based on these data. All steps necessary to achieve a full reconstruction of the electric field at every antenna position are explained, including removal of radio frequency interference, correcting for the antenna response and identification of the pulsed signal.

  6. SETI reloaded, Next Generation Radio Telescopes, Transients and Cognitive Computing

    CERN Document Server

    Garrett, Michael A

    2015-01-01

    The Search for Extra-terrestrial Intelligence (SETI) using radio telescopes is an area of research that is now more than 50 years old. Thus far, both targeted and wide-area surveys have yet to detect artificial signals from intelligent civilisations. In this paper, I argue that the incidence of co-existing intelligent and communicating civilisations is probably small in the Milky Way. While this makes successful SETI searches a very difficult pursuit indeed, the huge impact of even a single detection requires us to continue the search. A substantial increase in the overall performance of radio telescopes (and in particular future wide-field instruments such as the Square Kilometre Array, SKA), provide renewed optimism in the field. Evidence for this is already to be seen in the success of SETI researchers in acquiring observations on some of the world's most sensitive radio telescope facilities via open, peer-reviewed processes. The increasing interest in the dynamic radio sky, and our ability to detect new a...

  7. The Allen Telescope Array: The First Widefield, Panchromatic, Snapshot Radio Camera for Radio Astronomy and SETI

    CERN Document Server

    Welch, Jack; Blitz, Leo; Bock, Douglas; Bower, Geoffrey C; Cheng, Calvin; Croft, Steve; Dexter, Matt; Engargiola, Greg; Fields, Ed; Forster, James; Gutierrez-Kraybill, Colby; Heiles, Carl; Helfer, Tamara; Jorgensen, Susanne; Keating, Garrett; Lugten, John; MacMahon, Dave; Milgrome, Oren; Thornton, Douglas; Urry, Lynn; van Leeuwen, Joeri; Werthimer, Dan; Williams, Peter H; Tarter, Melvin Wright Jill; Ackermann, Robert; Atkinson, Shannon; Backus, Peter; Barott, William; Bradford, Tucker; Davis, Michael; DeBoer, Dave; Dreher, John; Harp, Gerry; Jordan, Jane; Kilsdonk, Tom; Pierson, Tom; Randall, Karen; Ross, John; Fleming, Seth Shostak Matt; Cork, Chris; Wadefalk, Artyom Vitouchkine Niklas; Weinreb, Sander

    2009-01-01

    The first 42 elements of the Allen Telescope Array (ATA-42) are beginning to deliver data at the Hat Creek Radio Observatory in Northern California. Scientists and engineers are actively exploiting all of the flexibility designed into this innovative instrument for simultaneously conducting surveys of the astrophysical sky and conducting searches for distant technological civilizations. This paper summarizes the design elements of the ATA, the cost savings made possible by the use of COTS components, and the cost/performance trades that eventually enabled this first snapshot radio camera. The fundamental scientific program of this new telescope is varied and exciting; some of the first astronomical results will be discussed.

  8. Searching for Transient Pulses with the ETA Radio Telescope

    CERN Document Server

    Patterson, Cameron D; Martin, Brian S; Deshpande, Kshitija; Simonetti, John H; Kavic, Michael; Cutchin, Sean E

    2008-01-01

    Array-based, direct-sampling radio telescopes have computational and communication requirements unsuited to conventional computer and cluster architectures. Synchronization must be strictly maintained across a large number of parallel data streams, from A/D conversion, through operations such as beamforming, to dataset recording. FPGAs supporting multi-gigabit serial I/O are ideally suited to this application. We describe a recently-constructed radio telescope called ETA having all-sky observing capability for detecting low frequency pulses from transient events such as gamma ray bursts and primordial black hole explosions. Signals from 24 dipole antennas are processed by a tiered arrangement of 28 commercial FPGA boards and 4 PCs with FPGA-based data acquisition cards, connected with custom I/O adapter boards supporting InfiniBand and LVDS physical links. ETA is designed for unattended operation, allowing configuration and recording to be controlled remotely.

  9. The Goldstone Apple Valley Radio Telescope (GAVRT) Jupiter Radio Data: Online Access and Analysis Tools

    Science.gov (United States)

    Arballo, J. K.; Levin, S.; Dorcey, R.; Hofstadter, M. D.; Leflang, J.; Jauncey, D.

    2016-12-01

    K-12 students have been collecting GHz radio data on Jupiter with a 34-meter dish in support of the Juno mission. These observations are part of the Goldstone Apple Valley Radio Telescope (GAVRT) project and the raw data are now freely available online. In this poster we describe the newly developed data access and analysis tools which allow both students and professional astronomers to access and analyze the data.

  10. Control of active reflector system for radio telescope

    Science.gov (United States)

    Zhou, Guo-hua; Li, Guo-ping; Zhang, Yong; Zhang, Zhen-chao

    2016-10-01

    According to the control requirements of the active reflector surface in the 110 m radio telescope at QiTai(QTT) Xinjiang, a new displacement actuator and a new displacement control system were designed and manufactured and then their characteristics were tested by a dual-frequency laser interferometer in the micro-displacement laboratory. The displacement actuator was designed by a scheme of high precision worm and roller screw structures, and the displacement control system was based on a ARM micro-processor. Finally, the S curve acceleration control methods were used to design the hardware platform and software algorithm for the active reflection surface of the control system. The test experiments were performed based on the laser metrology system on an active reflector close-loop antenna prototype for large radio telescope. Experimental results indicate that it achieves a 30 mm working stroke and 5 μm RMS motion resolution. The accuracy (standard deviation) is 3.67 mm, and the error between the determined and theoretical values is 0.04% when the rated load is 300 kg, the step is 2 mm and the stroke is 30mm. Furthermore, the active reflector integrated system was tested by the laser sensors with the accuracy of 0.25 μm RMS on 4-panel radio telescope prototype, the measurement results show that the integrated precision of the active reflector closed-loop control system is less than 5 μm RMS, and well satisfies the technical requirements of active reflector control system of the QTT radio telescope in 3 mm wavelength.

  11. An atmosphere monitoring system for the Sardinia radio telescope

    Science.gov (United States)

    Buffa, F.; Bolli, P.; Sanna, G.; Serra, G.

    2017-01-01

    The Sardinia radio telescope (SRT) is a new facility managed by the Italian National Institute for Astrophysics (INAF). SRT will detect the extremely faint radio wave signals emitted by astronomical objects in a wide frequency range from decimeter to millimeter wavelengths. Especially at high frequencies (>10 GHz), specific weather conditions and interactions between signal and atmospheric constituents (mainly water and oxygen molecules) affect the radio astronomic observation reducing the antenna performances. Thus, modern ground-based telescopes are usually equipped with systems able to examine in real-time several atmospheric parameters (opacity, integrated water vapor, etc.), and in some cases to forecast the weather conditions (wind, rain, snow, etc.), in order to ensure the antenna safety and support the schedule of the telescope observations. Here, we describe the atmosphere monitoring system (AMS) realized with the aim to improve the SRT operative efficiency. It consists of a network of different sensors such as radiometers, radiosondes, weather stations, GPS and some well-established weather models. After a validation of the scheme, we successfully tested the AMS in two real practical scenarios, comparing the AMS outcomes with those of independent techniques. In the first one we were able to detect an incoming storm front applying different techniques (GPS, radiometer and the weather forecast model), while in the last one we modeled the SRT antenna system temperature at 22 GHz processing the AMS data set.

  12. Phase Retrieval for Radio Telescope and Antenna Control

    Science.gov (United States)

    Dean, Bruce

    2011-01-01

    Phase-retrieval is a general term used in optics to describe the estimation of optical imperfections or "aberrations." The purpose of this innovation is to develop the application of phase retrieval to radio telescope and antenna control in the millimeter wave band. Earlier techniques do not approximate the incoherent subtraction process as a coherent propagation. This approximation reduces the noise in the data and allows a straightforward application of conventional phase retrieval techniques for radio telescope and antenna control. The application of iterative-transform phase retrieval to radio telescope and antenna control is made by approximating the incoherent subtraction process as a coherent propagation. Thus, for systems utilizing both positive and negative polarity feeds, this approximation allows both surface and alignment errors to be assessed without the use of additional hardware or laser metrology. Knowledge of the antenna surface profile allows errors to be corrected at a given surface temperature and observing angle. In addition to imperfections of the antenna surface figure, the misalignment of multiple antennas operating in unison can reduce or degrade the signal-to-noise ratio of the received or broadcast signals. This technique also has application to the alignment of antenna array configurations.

  13. Design and Commissioning of the LWA1 Radio Telescope

    CERN Document Server

    Ellingson, S W; Dowell, J; Taylor, G B; Helmboldt, J F

    2013-01-01

    LWA1 is a new large radio telescope array operating in the frequency range 10-88 MHz, located in central New Mexico. The telescope consists of 260 pairs of dipole-type antennas whose outputs are individually digitized and formed into beams. Simultaneously, signals from all dipoles can be recorded using one of the telescope's "all dipoles" modes, facilitating all-sky imaging. Notable features of the instrument include four independently-steerable beams utilizing digital "true time delay" beamforming, high intrinsic sensitivity (about 6 kJy zenith system equivalent flux density), large instantaneous bandwidth (up to 78 MHz), and large field of view (about 3-10 degrees, depending on frequency and zenith angle of pointing). This paper summarizes the design of LWA1, its performance as determined in commissioning experiments, and results from early science observations demonstrating the capabilities of the instrument.

  14. The control software for the Sardinia Radio Telescope

    Science.gov (United States)

    Orlati, A.; Buttu, M.; Melis, A.; Migoni, C.; Poppi, S.; Righini, S.

    2012-09-01

    The Sardinia Radio Telescope (SRT) is a new 64-meter shaped antenna designed to carry out observations up to 100 GHz. This large instrument has been built in Sardinia, 35 km north of Cagliari, and is now facing the technical commissioning phase. This paper describes the architecture, the implementation solutions and the development status of NURAGHE, the SRT control software. Aim of the project was to produce a software which is reliable, easy to keep up to date and flexible against other telescopes. The most ambitious goal will be to install NURAGHE at all the three italian radio telescopes, allowing the astronomers to access these facilities through a common interface with very limited extra effort. We give a description of all the control software subsystems (servo systems, backends, receivers, etc.) focusing on the resulting design, which is based on the ACS (Alma Common Software) patterns and comes from linux-based, LGPL, Object-Oriented development technologies. We also illustrate how NURAGHE deals with higher level requirements, coming from the telescope management or from the system users.

  15. Observations of Supernova Remnants with the Sardinia Radio Telescope

    CERN Document Server

    Egron, E; Loru, S; Iacolina, M N; Marongiu, M; Righini, S; Mulas, S; Murtas, G; Bachetti, M; Concu, R; Melis, A; Trois, A; Ricci, R; Pilia, M

    2016-01-01

    In the frame of the Astronomical Validation activities for the 64m Sardinia Radio Telescope, we performed 5-22 GHz imaging observations of the complex-morphology supernova remnants (SNRs) W44 and IC443. We adopted innovative observing and mapping techniques providing unprecedented accuracy for single-dish imaging of SNRs at these frequencies, revealing morphological details typically available only at lower frequencies through interferometry observations. High-frequency studies of SNRs in the radio range are useful to better characterize the spatially-resolved spectra and the physical parameters of different regions of the SNRs interacting with the ISM. Furthermore, synchrotron-emitting electrons in the high-frequency radio band are also responsible for the observed high-energy phenomenology as -e.g.- Inverse Compton and bremsstrahlung emission components observed in gamma-rays, to be disentangled from hadron emission contribution (providing constraints on the origin of cosmic rays).

  16. Solar and Planetary Observations with a Lunar Radio Telescope

    Science.gov (United States)

    Kassim, N.; Weiler, K. W.; Lazio, J. W.; MacDowall, R. J.; Jones, D. L.; Bale, S. D.; Demaio, L.; Kasper, J. C.

    2006-05-01

    Ground-based radio telescopes cannot observe at frequencies below about 10 MHz (wavelengths longer than 30 m) because of ionospheric absorption. The Lunar Imaging Radio Array (LIRA) is a mission concept in which an array of radio telescopes is deployed on the Moon, as part of the Vision for Space Exploration, with the aim of extending radio observations to lower frequencies than are possible from the Earth. LIRA would provide the capability for dedicated monitoring of solar and planetary bursts as well as the search for magnetospheric emissions from extrasolar planets. The highest sensitivity observations can be accomplished by locating LIRA on the far side of the Moon. The array would be composed of 10-12 radial arms, each 1-2 km in length. Each arm would have several hundred dipole antennas and feedlines printed on a very thin sheet of kapton with a total mass of about 300 kg. This would provide a convenient way to deploy thousands of individual antennas and a centrally condensed distribution of array baselines. The lunar farside provides shielding from terrestrial natural and technological radio interference and freedom from the corrupting influence of Earth's ionosphere. This paper will describe the science case for LIRA as well as various options for array deployment and data transmission to Earth. Part of this work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Basic research in radio astronomy at the NRL is supported by the Office of Naval Research.

  17. Youngest Radio Pulsar Revealed with Green Bank Telescope

    Science.gov (United States)

    2002-04-01

    Astronomers using the National Science Foundation's (NSF) newly commissioned Robert C. Byrd Green Bank Telescope (GBT) have detected remarkably faint radio signals from an 820 year-old pulsar, making it the youngest radio-emitting pulsar known. This discovery pushes the boundaries of radio telescope sensitivity for discovering pulsars, and will enable scientists to conduct observations that could lead to a better understanding of how these stars evolve. The Robert C. Byrd Green Bank Telescope Robert C. Byrd Green Bank Telescope "Important questions about pulsars may be answered by long-term monitoring of objects such as the one we just detected," said Fernando Camilo of Columbia University in New York City. "Young pulsars are particularly rare, and being able to study such a young one at radio wavelengths provides an outstanding opportunity to learn critical facts about their evolution and workings." The results of this research, based on observations conducted on February 22-23, 2002, were accepted for publication in the Astrophysical Journal Letters. Scientists have long suspected that a pulsar - a rapidly spinning, superdense neutron star - was born when a giant star ended its life in a cataclysmic supernova explosion observed in late summer of 1181, as suggested by Japanese and Chinese historical records. For the past 20 years, astronomers have searched this supernova remnant (3C58), located 10,000 light-years away in the constellation Cassiopeia, for the telltale pulsations of a newly born pulsar. Late in 2001, data from NASA's Chandra X-ray satellite confirmed its existence, but it remained an elusive quarry for radio telescopes. "We believed from historical records and certainly knew from recent X-ray observations that this star was there," Camilo remarked, "but despite many attempts, no one had been able to find any radio pulsations from it because the signals are, it turns out, incredibly weak." For comparison, this pulsar's radio emission is some 250

  18. A New Astronomical Facility for Peru: Converting a Telecommunication's 32 Meter Parabolic Antenna into a Radio Telescope

    Science.gov (United States)

    Ishitsuka, J. K.; Ishitsuka, M.; Inoue, M.; Kaifu, N.; Miyama, S.; Tsuboi, M.; Ohishi, M.; Fujisawa, K.; Kasuga, T.; Kondo, T.; Horiuchi, S.; Umemoto, T.; Miyoshi, M.; Miyazawa, K.; Bushimata, T.; Vidal, E. D.

    2006-08-01

    In 1984 Nippon Electric Company constructed an INTELSAT antenna at 3,370 meters above the sea level on the Peruvian Andes. Entel Peru, the Peruvian telecommunications company, managed the antenna station until 1993. This year the government transferred the station to a private telecommunications company, Telefónica del Peru. Since the satellite communications were rapidly replaced by transoceanic fiber optics, the beautiful 32 meters parabolic antenna has been unused since 2002.. In cooperation with the National Astronomical Observatory of Japan we began to convert the antenna into a radio telescope. Because researches on interstellar medium around Young Stellar Objects (YSO) will be able to observe the methanol masers that emit at 6.7 GHz, initially we will monitor the 6.7 GHz methanol masers and survey the southern sky. An ambient temperature receiver with Trx= 60 K was developed at Nobeyama Radio Observatory and is ready to be installed. The antenna control system is the Field System FS9 software installed in a Linux PC. An interface between the antenna and the PC was developed at Kashima Space Research Center in Japan. In the near future we plan to install the 2 GHz, 8 GHz, 12 GHz and 22 GHz receivers. The unique location and altitude of the Peruvian Radio Observatory will be useful for VLBI observations in collaboration with global arrays such as the VLBA array for astronomical observation and geodetic measurements. For Peru where few or almost no astronomical observational instruments are available for research, the implementation of the first radio observatory is a big and challenging step, and foster sciences at graduate and postgraduate levels of universities. Worldwide telecommunications antennas possibly are unused and with relative few investment could be transformed into a useful observational instrument.

  19. Scale challenges of the MeerKAT Radio Telescope

    CERN Document Server

    CERN. Geneva; Ratcliffe, Simon

    2017-01-01

    A discussion on the MeerKAT Radio Telescope, currently nearing completion in the Karoo desert region of South Africa. This talk covers a quick introduction to radio astronomy data processing and the scale challenges inherent therein. The solutions to the challenges posed will be discussed, including coverage of our MESOS based execution framework and the role of the various data storage regimes in our processing and analysis pipelines. The final third will highlight our multiple uses of CEPH, including our self-build hardware, 20PB science archive. About the speakers Simon Ratcliffe has a background in astrophysics and computer science, and is currently the technical lead for scientific computing at SKA South Africa. In this role he oversees the architecture and technical direction of the science processor for the MeerKAT radio telescope. Thomas Bennett has a masters degree in electronic engineering and is currently a developer in the scientific computing as SKA South Africa. In this role he overs...

  20. A lunar radio experiment with the Parkes radio telescope for the LUNASKA project

    CERN Document Server

    Bray, J D; Roberts, P; Reynolds, J E; James, C W; Phillips, C J; Protheroe, R J; McFadden, R A; Aartsen, M G

    2014-01-01

    We describe an experiment using the Parkes radio telescope in the 1.2-1.5 GHz frequency range as part of the LUNASKA project, to search for nanosecond-scale pulses from particle cascades in the Moon, which may be triggered by ultra-high-energy astroparticles. Through the combination of a highly sensitive multi-beam radio receiver, a purpose-built backend and sophisticated signal-processing techniques, we achieve sensitivity to radio pulses with a threshold electric field strength of 0.0053 $\\mu$V/m/MHz, lower than previous experiments by a factor of three. We observe no pulses in excess of this threshold in observations with an effective duration of 127 hours. The techniques we employ, including compensating for the phase, dispersion and spectrum of the expected pulse, are relevant for future lunar radio experiments.

  1. Square Kilometre Array: The radio telescope of the XXI century

    Science.gov (United States)

    Grainge, K.; Alachkar, B.; Amy, Shaun; Barbosa, D.; Bommineni, M.; Boven, P.; Braddock, R.; Davis, J.; Diwakar, P.; Francis, V.; Gabrielczyk, R.; Gamatham, R.; Garrington, S.; Gibbon, T.; Gozzard, D.; Gregory, S.; Guo, Y.; Gupta, Y.; Hammond, J.; Hindley, D.; Horn, U.; Hughes-Jones, R.; Hussey, M.; Lloyd, S.; Mammen, S.; Miteff, S.; Mohile, V.; Muller, J.; Natarajan, S.; Nicholls, J.; Oberland, R.; Pearson, M.; Rayner, T.; Schediwy, S.; Schilizzi, R.; Sharma, S.; Stobie, S.; Tearle, M.; Wang, B.; Wallace, B.; Wang, L.; Warange, R.; Whitaker, R.; Wilkinson, A.; Wingfield, N.

    2017-04-01

    The Square Kilometre Array (SKA) will be the world's largest and most sensitive radio telescope. It will address fundamental unanswered questions about our Universe including how the first stars and galaxies formed after the Big Bang, how dark energy is accelerating the expansion of theUniverse, the role of magnetism in the cosmos, the nature of gravity, and the search for life beyond Earth. This project envisages the construction of 133 15-m antennas in South Africa and 131072 log-periodic antennas in Australia, together with the associated infrastructure in the two desert sites. In addition, the SKA is an exemplar Big Data project, with data rates of over 10 Tbps being transported from the telescope to HPC/HTC facilities.

  2. Probing Magnetic Fields using the Giant Metrewave Radio Telescope

    CERN Document Server

    Farnes, J S; Kantharia, N G

    2013-01-01

    We present the first spectropolarimetric radio observations that apply Rotation Measure (RM) Synthesis to interferometric data from the Giant Metrewave Radio Telescope (GMRT) at 610 MHz. Spectropolarimetry requires measurement of a large number of instrumental systematics so that their effects can be calibrated - a technical problem that is currently being faced by the upcoming SKA pathfinders. Our fully-calibrated data allow for the peak Faraday depth and polarisation fraction to be measured for sub-mJy compact sources in the field of M51 at 610 MHz. The diffuse extended emission in the interacting galaxy pair is shown to be depolarised below the sensitivity limit. A survey of linear polarisation with the GMRT is now feasible and could be used to place constraints on the prevailing depolarisation mechanisms at low frequencies - improving polarised source count estimates and constraining the RM-grid observable with next generation facilities such as the SKA.

  3. Engineering and science highlights of the KAT-7 radio telescope

    Science.gov (United States)

    Foley, A. R.; Alberts, T.; Armstrong, R. P.; Barta, A.; Bauermeister, E. F.; Bester, H.; Blose, S.; Booth, R. S.; Botha, D. H.; Buchner, S. J.; Carignan, C.; Cheetham, T.; Cloete, K.; Coreejes, G.; Crida, R. C.; Cross, S. D.; Curtolo, F.; Dikgale, A.; de Villiers, M. S.; du Toit, L. J.; Esterhuyse, S. W. P.; Fanaroff, B.; Fender, R. P.; Fijalkowski, M.; Fourie, D.; Frank, B.; George, D.; Gibbs, P.; Goedhart, S.; Grobbelaar, J.; Gumede, S. C.; Herselman, P.; Hess, K. M.; Hoek, N.; Horrell, J.; Jonas, J. L.; Jordaan, J. D. B.; Julie, R.; Kapp, F.; Kotzé, P.; Kusel, T.; Langman, A.; Lehmensiek, R.; Liebenberg, D.; Liebenberg, I. J. V.; Loots, A.; Lord, R. T.; Lucero, D. M.; Ludick, J.; Macfarlane, P.; Madlavana, M.; Magnus, L.; Magozore, C.; Malan, J. A.; Manley, J. R.; Marais, L.; Marais, N.; Marais, S. J.; Maree, M.; Martens, A.; Mokone, O.; Moss, V.; Mthembu, S.; New, W.; Nicholson, G. D.; van Niekerk, P. C.; Oozeer, N.; Passmoor, S. S.; Peens-Hough, A.; Pińska, A. B.; Prozesky, P.; Rajan, S.; Ratcliffe, S.; Renil, R.; Richter, L. L.; Rosekrans, D.; Rust, A.; Schröder, A. C.; Schwardt, L. C.; Seranyane, S.; Serylak, M.; Shepherd, D. S.; Siebrits, R.; Sofeya, L.; Spann, R.; Springbok, R.; Swart, P. S.; Thondikulam, Venkatasubramani L.; Theron, I. P.; Tiplady, A.; Toruvanda, O.; Tshongweni, S.; van den Heever, L.; van der Merwe, C.; van Rooyen, R.; Wakhaba, S.; Walker, A. L.; Welz, M.; Williams, L.; Wolleben, M.; Woudt, P. A.; Young, N. J.; Zwart, J. T. L.

    2016-08-01

    The construction of the seven-dish Karoo Array Telescope (KAT-7) array in the Karoo region of the Northern Cape in South Africa was intended primarily as an engineering prototype for technologies and techniques applicable to the MeerKAT telescope. This paper looks at the main engineering and scientific highlights from this effort, and discusses their applicability to both MeerKAT and other next-generation radio telescopes. In particular, we found that the composite dish surface works well, but it becomes complicated to fabricate for a dish lacking circular symmetry; the Stirling cycle cryogenic system with ion pump to achieve vacuum works but demands much higher maintenance than an equivalent Gifford-McMahon cycle system; the ROACH (Reconfigurable Open Architecture Computing Hardware)-based correlator with SPEAD (Streaming Protocol for Exchanging Astronomical Data) protocol data transfer works very well and KATCP (Karoo Array Telescope Control Protocol) control protocol has proven very flexible and convenient. KAT-7 has also been used for scientific observations where it has a niche in mapping low surface-brightness continuum sources, some extended H I haloes and OH masers in star-forming regions. It can also be used to monitor continuum source variability, observe pulsars, and make Very Long Baseline Interferometry observations.

  4. A Small-Radio-Telescope Network for VLBI

    Science.gov (United States)

    Shaffer, D. B.; Cobb, M. L.

    2004-12-01

    In the last several years, high schools, colleges, universities, and even some private amateur radio astronomers have put some 120 copies of the commercially-available Haystack Small Radio Telescope (SRT) into operation. Haystack Observatory is now working on a new version of the SRT, designed to be used in an interferometer (see paper by Vats and Rogers, this conference). We show how the new SRT, or other similar small radio telescopes, could be adapted for educational and scientific VLBI observations of continuum and OH line sources, with a relatively small additional investment. We propose that one or more large radio telescopes join a network of the small antennas, so that fringes would be readily detected between the large antenna(s) and the small antennas. An 85-foot antenna such as those at PARI or the 40-meter antenna of the Owens Valley Radio Observatory would serve nicely as a base station. Eventually, as data storage and transmission capacity continue to improve, the small antennas should be able to operate on their own. Our emphasis is on a simple, inexpensive VLBI system. The most critical item is good frequency standard. For observations at 21 or 18 cm, a rubidium standard is good enough. (Inexpensive Rb standards can be found on E-bay!) Local time at each station would come from GPS receivers which readily provide sub-microsecond timing accuracy. One-bit data sampling at rates on the order of 10 megasamples per second could be performed with a simple box interfaced to a PC via USB. Sampled data would first be recorded to the PC hard drive, and then sent on CD-ROM or DVD through the mail or by internet to a central correlation facility. Correlation and data analysis for the network would be performed on PCs as well. We suggest an observing scenario comprised of scans that are several minutes long and taken several times per hour during the apparition of a compact source. The total data for the 10-12 hours that a source is "up" for a USA network would

  5. Thermal Design and Thermal Behaviour of Radio Telescopes and their Enclosures

    CERN Document Server

    Greve, Albert

    2010-01-01

    Radio telescopes as well as communication antennas operate under the influence of gravity, temperature and wind. Among those, temperature influences may degrade the performance of a radio telescope through transient changes of the focus, pointing, path length and sensitivity, often in an unpredictable way. Thermal Design and Thermal Behaviour of Radio Telescopes and their Enclosures reviews the design and construction principles of radio telescopes in view of thermal aspects and heat transfer with the variable thermal environment; it explains supporting thermal model calculations and the application and efficiency of thermal protection and temperature control; it presents many measurements illustrating the thermal behaviour of telescopes in the environment of their observatory sites. The book benefits scientists and radio/communication engineers, telescope designers and construction firms as well as telescope operators, observatory staff, but also the observing astronomer who is directly confronted with the t...

  6. Fine spectral structures in Jovian decametric radio emission observed by ground-based radio telescope.

    Science.gov (United States)

    Panchenko, M.; Brazhenko, A. I.; Shaposhnikov, V. E.; Konovalenko, A. A.; Rucker, H. O.

    2014-04-01

    Jupiter with the largest planetary magnetosphere in the solar system emits intense coherent non-thermal radio emission in a wide frequency range. This emission is a result of a complicated interaction between the dynamic Jovian magnetosphere and energetic particles supplying the free energy from planetary rotation and the interaction between Jupiter and the Galilean moons. Decametric radio emission (DAM) is the strongest component of Jovian radiation observed in a frequency range from few MHz up to 40 MHz. This emission is generated via cyclotron maser mechanism in sources located along Jovian magnetic field lines. Depending on the time scales the Jovian DAMexhibits different complex spectral structures. We present the observations of the Jovian decametric radio emission using the large ground-based radio telescope URAN- 2 (Poltava, Ukraine) operated in the decametric frequency range. This telescope is one of the largest low frequency telescopes in Europe equipped with high performance digital radio spectrometers. The antenna array of URAN-2 consists of 512 crossed dipoles with an effective area of 28 000m2 and beam pattern size of 3.5 x 7 deg. (at 25 MHz). The instrument enables continuous observations of the Jovian radio during long period of times. Jovian DAM was observed continuously since Sep. 2012 (depending on Jupiter visibility) with relatively high time-frequency resolution (4 kHz - 100ms) in the broad frequency range (8-32MHz). We have detected a big amount of the fine spectral structures in the dynamic spectra of DAM such as trains of S-bursts, quasi-continuous narrowband emission, narrow-band splitting events and zebra stripe-like patterns. We analyzed mainly the fine structures associated with non-Io controlled DAM. We discuss how the observed narrowband structures which most probably are related to the propagation of the decametric radiation in the Jupiter's ionosphere can be used to study the plasma parameters in the inner Jovian magnetosphere.

  7. First Results from VLBA Astrometry of Juno

    Science.gov (United States)

    Jones, Dayton L.; Folkner, William M.; Jacobs, Christopher S.; Romney, Jonathan D.; Dhawan, Vivek

    2017-06-01

    We have used the Very Long Baseline Array (VLBA) to determine precise positions of the Juno spacecraft during its approach to Jupiter and during its third perijove pass after orbit insertion. VLBA observations will continue during several perijove passes until the end of Juno’s mission. The orbit of Juno about Jupiter is most accurately determined by Doppler tracking near perijove, allowing our Juno position measurements to be transferred to the Jupiter system barycenter. We use angularly nearby extragalactic radio sources with known positions in the International Celestial Reference Frame as phase reference sources during VLBA observations to obtain accurate positions for Jupiter in an inertial reference frame. The planned series of Jupiter position measurements will be used to improve the accuracy of Jupiter’s orbit in the JPL planetary ephemeris. The improvement is most dramatic in orbit inclination and ascending node; spacecraft ranging provides the best constraints on semi-major axis and eccentricity. Similar VLBA observations of the Cassini spacecraft orbiting Saturn during the past decade have improved our knowledge of Saturn’s orbit by nearly an order of magnitude, and we expect a similar improvement for Jupiter. This research is partially funded by a grant from NASA’s Planetary Astronomy program to the Space Science Institute, Boulder, CO. Part of this work is being carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. The Long Baseline Observatory and the National Radio Astronomy Observatory are facilities of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

  8. International Agreement Will Advance Radio Astronomy

    Science.gov (United States)

    2007-12-01

    Two of the world's leading astronomical institutions have formalized an agreement to cooperate on joint efforts for the technical and scientific advancement of radio astronomy. The National Radio Astronomy Observatory (NRAO) in the United States and the Max-Planck Institute for Radioastronomy (MPIfR) in Germany concluded a Memorandum of Understanding outlining planned collaborative efforts to enhance the capabilities of each other's telescopes and to expand their cooperation in scientific research. The VLBA The VLBA CREDIT: NRAO/AUI/NSF In the first project pursued under this agreement, the MPIfR will contribute $299,000 to upgrade the continent-wide Very Long Baseline Array's (VLBA) capability to receive radio emissions at a frequency of 22 GHz. This improvement will enhance the VLBA's scientific productivity and will be particularly important for cutting-edge research in cosmology and enigmatic cosmic objects such as gamma-ray blazars. "This agreement follows many years of cooperation between our institutions and recognizes the importance of international collaboration for the future of astronomical research," said Fred K.Y. Lo, NRAO Director. "Our two institutions have many common research goals, and joining forces to keep all our telescopes at the forefront of technology will be highly beneficial for the science," said Anton Zensus, Director at MPIfR. In addition to the VLBA, the NRAO operates the Very Large Array (VLA) in New Mexico and the Robert C. Byrd Green Bank Telescope (GBT) in West Virginia. The MPIfR operates the 100-meter Effelsberg Radio Telescope in Germany and the 12-meter APEX submillimeter telescope in 5100 m altitude in the Cilean Atacama desert (together with the European Southern Observatory and the Swedish Onsala Space Observatory). With the 100-meter telescope, it is part of the VLBA network in providing transatlantic baselines. Both institutions are members of a global network of telescopes (the Global VLBI Network) that uses simultaneous

  9. LOFAR: A new radio telescope for low frequency radio observations: Science and project status

    CERN Document Server

    Röttgering, H J A; Fender, R P; Kuijpers, J; Van Haarlem, M P; Johnston-Hollitt, M; Miley, G K

    2003-01-01

    LOFAR, the Low Frequency Array, is a large radio telescope consisting about 100 soccer field sized antenna stations spread over a region of 400 km in diameter. It will operate in the frequency range from ~10 to 240 MHz, with a resolution at 240 MHz of better than an arcsecond. Its superb sensitivity will allow for a broad range of astrophysical studies. In this contribution we first discuss four major areas of astrophysical research in which LOFAR will undoubtedly make important contributions: reionisation, distant galaxies and AGNs, transient radio sources and cosmic rays. Subsequently, we will discuss the technical concept of the instrument and the status of the LOFAR project

  10. Sardinia Radio Telescope: General Description, Technical Commissioning and First Light

    CERN Document Server

    Bolli, P; Stringhetti, L; Orfei, A; Righini, S; Ambrosini, R; Bartolini, M; Bortolotti, C; Buffa, F; Buttu, M; Cattani, A; D'Amico, N; Deiana, G; Fara, A; Fiocchi, F; Gaudiomonte, F; Maccaferri, A; Mariotti, S; Marongiu, P; Melis, A; Migoni, C; Morsiani, M; Nanni, M; Nasyr, F; Pellizzoni, A; Pisanu, T; Poloni, M; Poppi, S; Porceddu, I; Prandoni, I; Roda, J; Roma, M; Scalambra, A; Serra, G; Trois, A; Valente, G; Vargiu, G P; Zacchiroli, G

    2016-01-01

    In the period 2012 June - 2013 October, the Sardinia Radio Telescope (SRT) went through the technical commissioning phase. The characterization involved three first-light receivers, ranging in frequency between 300MHz and 26GHz, connected to a Total Power back-end. It also tested and employed the telescope active surface installed in the main reflector of the antenna. The instrument status and performance proved to be in good agreement with the expectations in terms of surface panels alignment (at present 300 um rms to be improved with microwave holography), gain (~0.6 K/Jy in the given frequency range), pointing accuracy (5 arcsec at 22 GHz) and overall single-dish operational capabilities. Unresolved issues include the commissioning of the receiver centered at 350 MHz, which was compromised by several radio frequency interferences, and a lower-than-expected aperture efficiency for the 22-GHz receiver when pointing at low elevations. Nevertheless, the SRT, at present completing its Astronomical Validation ph...

  11. Engineering and Science Highlights of the KAT-7 Radio Telescope

    CERN Document Server

    Foley, A R; Armstrong, R P; Barta, A; Bauermeister, E F; Bester, H; Blose, S; Booth, R S; Botha, D H; Buchner, S J; Carignan, C; Cheetham, T; Cloete, K; Coreejes, G; Crida, R C; Cross, S D; Curtolo, F; Dikgale, A; de Villiers, M S; Toit, L J du; Esterhuyse, S W P; Fanaroff, B; Fender, R P; Fijalkowski, M; Fourie, D; Frank, B; George, D; Gibbs, P; Goedhart, S; Grobbelaar, J; Gumede, S C; Herselman, P; Hess, K M; Hoek, N; Horrell, J; Jonas, J L; Jordaan, J D B; Julie, R; Kapp, F; Kotzé, P; Kusel, T; Langman, A; Lehmensiek, R; Liebenberg, D; Liebenberg, I J V; Loots, A; Lord, R T; Lucero, D M; Ludick, J; Macfarlane, P; Madlavana, M; Magnus, L; Magozore, C; Malan, J A; Manley, J R; Marais, L; Marais, N; Marais, S J; Maree, M; Martens, A; Mokone, O; Moss, V; Mthembu, S; New, W; Nicholson, G D; van Niekerk, P C; Oozeer, N; Passmoor, S S; Peens-Hough, A; Pińska, A B; Prozesky, P; Rajan, S; Ratcliffe, S; Renil, R; Richter, L L; Rosekrans, D; Rust, A; Schröder, A C; Schwardt, L C; Seranyane, S; Serylak, M; Shepherd, D S; Siebrits, R; Sofeya, L; Spann, R; Springbok, R; Swart, P S; Thondikulam, Venkatasubramani L; Theron, I P; Tiplady, A; Toruvanda, O; Tshongweni, S; Heever, L van den; van der Merwe, C; van Rooyen, R; Wakhaba, S; Walker, A L; Welz, M; Williams, L; Wolleben, M; Woudt, P A; Young, N J; Zwart, J T L

    2016-01-01

    The construction of the KAT-7 array in the Karoo region of the Northern Cape in South Africa was intended primarily as an engineering prototype for technologies and techniques applicable to the MeerKAT telescope. This paper looks at the main engineering and scien- tific highlights from this effort, and discusses their applicability to both MeerKAT and other next-generation radio telescopes. In particular we found that the composite dish surface works well, but it becomes complicated to fabricate for a dish lacking circular symmetry; the Stir- ling cycle cryogenic system with ion pump to achieve vacuum works but demands much higher maintenance than an equivalent Gifford-McMahon cycle system; the ROACH (Recon- figurable Open Architecture Computing Hardware)-based correlator with SPEAD (Stream- ing Protocol for Exchanging Astronomical Data) protocol data transfer works very well and KATCP (Karoo Array Telescope Control Protocol) control protocol has proven very flexible and convenient. KAT-7 has also been used f...

  12. A database of phase calibration sources and their radio spectra for the Giant Metrewave Radio Telescope

    Science.gov (United States)

    Lal, Dharam V.; Dubal, Shilpa S.; Sherkar, Sachin S.

    2016-12-01

    We are pursuing a project to build a database of phase calibration sources suitable for Giant Metrewave Radio Telescope (GMRT). Here we present the first release of 45 low frequency calibration sources at 235 MHz and 610 MHz. These calibration sources are broadly divided into quasars, radio galaxies and unidentified sources. We provide their flux densities, models for calibration sources, ( u, v) plots, final deconvolved restored maps and clean-component lists/files for use in the Astronomical Image Processing System ( aips) and the Common Astronomy Software Applications ( casa). We also assign a quality factor to each of the calibration sources. These data products are made available online through the GMRT observatory website. In addition we find that (i) these 45 low frequency calibration sources are uniformly distributed in the sky and future efforts to increase the size of the database should populate the sky further, (ii) spectra of these calibration sources are about equally divided between straight, curved and complex shapes, (iii) quasars tend to exhibit flatter radio spectra as compared to the radio galaxies or the unidentified sources, (iv) quasars are also known to be radio variable and hence possibly show complex spectra more frequently, and (v) radio galaxies tend to have steeper spectra, which are possibly due to the large redshifts of distant galaxies causing the shift of spectrum to lower frequencies.

  13. A database of phase calibration sources and their radio spectra for the Giant Metrewave Radio Telescope

    Science.gov (United States)

    Lal, Dharam V.; Dubal, Shilpa S.; Sherkar, Sachin S.

    2016-10-01

    We are pursuing a project to build a database of phase calibration sources suitable for Giant Metrewave Radio Telescope (GMRT). Here we present the first release of 45 low frequency calibration sources at 235 MHz and 610 MHz. These calibration sources are broadly divided into quasars, radio galaxies and unidentified sources. We provide their flux densities, models for calibration sources, (u,v) plots, final deconvolved restored maps and uc(clean)-component lists/files for use in the Astronomical Image Processing System (uc(aips)) and the Common Astronomy Software Applications (uc(casa)). We also assign a quality factor to each of the calibration sources. These data products are made available online through the GMRT observatory website. In addition we find that (i) these 45 low frequency calibration sources are uniformly distributed in the sky and future efforts to increase the size of the database should populate the sky further, (ii) spectra of these calibration sources are about equally divided between straight, curved and complex shapes, (iii) quasars tend to exhibit flatter radio spectra as compared to the radio galaxies or the unidentified sources, (iv) quasars are also known to be radio variable and hence possibly show complex spectra more frequently, and (v) radio galaxies tend to have steeper spectra, which are possibly due to the large redshifts of distant galaxies causing the shift of spectrum to lower frequencies.

  14. The search of radio transients in the RATAN-600 radio telescope surveys

    Science.gov (United States)

    Zhelenkova, Olga P.; Majorova, Elena K.

    2017-06-01

    We present the results of the search of variable sources and transient events in the archive data of the sky surveys conducted on 3.9 GHz on the RATAN-600 radio telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) in 1980-1994. 17% of the total studied sources can be attributed to the variables in radio range. About half of them has significant variations in optical brightness according to the data of the catalogs. At the level of 3-5 r.m.s. we found three transient events. Two weak events probably associated with AGN activities or with cataclysmic events such as GRB and a supernova flash. The nature of the third event has not been established. According to our estimation the surface density of radio transients is 0.03 on one square angular degree with the detection level 8-11 mJy on 3.94 GHz.

  15. The VLBA correlator: Real-time in the distributed era

    Science.gov (United States)

    Wells, D. C.

    1992-01-01

    The correlator is the signal processing engine of the Very Long Baseline Array (VLBA). Radio signals are recorded on special wideband (128 Mb/s) digital recorders at the 10 telescopes, with sampling times controlled by hydrogen maser clocks. The magnetic tapes are shipped to the Array Operations Center in Socorro, New Mexico, where they are played back simultaneously into the correlator. Real-time software and firmware controls the playback drives to achieve synchronization, compute models of the wavefront delay, control the numerous modules of the correlator, and record FITS files of the fringe visibilities at the back-end of the correlator. In addition to the more than 3000 custom VLSI chips which handle the massive data flow of the signal processing, the correlator contains a total of more than 100 programmable computers, 8-, 16- and 32-bit CPUs. Code is downloaded into front-end CPU's dependent on operating mode. Low-level code is assembly language, high-level code is C running under a RT OS. We use VxWorks on Motorola MVME147 CPU's. Code development is on a complex of SPARC workstations connected to the RT CPU's by Ethernet. The overall management of the correlation process is dependent on a database management system. We use Ingres running on a Sparcstation-2. We transfer logging information from the database of the VLBA Monitor and Control System to our database using Ingres/NET. Job scripts are computed and are transferred to the real-time computers using NFS, and correlation job execution logs and status flow back by the route. Operator status and control displays use windows on workstations, interfaced to the real-time processes by network protocols. The extensive network protocol support provided by VxWorks is invaluable. The VLBA Correlator's dependence on network protocols is an example of the radical transformation of the real-time world over the past five years. Real-time is becoming more like conventional computing. Paradoxically, 'conventional

  16. Coordinated observations using the world largest low-frequency radio telescopes and space misiions

    Science.gov (United States)

    Konovalenko, A. A.; Zarka, Ph.; Kolyadin, V. L.; Zakharenko, V. V.; Stepkin, S. V.; Panchenko, M.; Lecacheux, A.; Rucker, H. O.; Fischer, G.; Ulyanov, O. M.; Melnik, V. N.; Litvinenko, G. V.; Sidorchuk, M. A.; Bubnov, I. N.; Vasilyeva, Ya. Yu.; Bojko, A. I.; Shaposhnikov, V.; Mann, G.; Kalinichenko, N. N.; Falkovich, I. S.; Koval, A. A.; Mylostna, K.; Pylaev, O. S.; Shepelev, V. A.; Reznik, A. P.

    2013-09-01

    The positive possibilities of astrophysical objects studies(including the Solar system investigations) using coordinated observations with the largest existing and coming low frequency radio telescopes are shown. The observations of the Sun, Jupiter, Saturn, ant others with UTR-2, URAN, NDA radio telescopes, and WIND, Cassini and STEREO space missions at frequencies lower than 40 MHz have been carried out.

  17. Lunar Radio Telescopes: A Staged Approach for Lunar Science, Heliophysics, Astrobiology, Cosmology, and Exploration

    Science.gov (United States)

    Lazio, Joseph; Bowman, Judd D.; Burns, Jack O.; Farrell, W. M.; Jones, D. L.; Kasper, J. C.; MacDowall, R. J.; Stewart, K. P.; Weiler, K.

    2012-01-01

    Observations with radio telescopes address key problems in cosmology, astrobiology, heliophysics, and planetary science including the first light in the Universe (Cosmic Dawn), magnetic fields of extrasolar planets, particle acceleration mechanisms, and the lunar ionosphere. The Moon is a unique science platform because it allows access to radio frequencies that do not penetrate the Earth's ionosphere and because its far side is shielded from intense terrestrial emissions. The instrument packages and infrastructure needed for radio telescopes can be transported and deployed as part of Exploration activities, and the resulting science measurements may inform Exploration (e.g., measurements of lunar surface charging). An illustrative roadmap for the staged deployment of lunar radio telescopes

  18. L-band orthomode transducer for the Sardinia Radio Telescope

    Science.gov (United States)

    Navarrini, Alessandro; Pisanu, Tonino

    2008-07-01

    We describe the design, construction, and characterization results of a compact L-band (1.3-1.8 GHz) Orthomode Transducer (OMT) for the Sardinia Radio Telescope (SRT), a 64 m diameter telescope which is being built in the Sardinia island, Italy. The OMT consists of three distinct mechanical parts connected through ultra low loss coaxial cables: a turnstile junction and two identical 180° hybrid power combiners. The turnstile junction is based on a circular waveguide input (diameter of 190 mm,) and on four WR650 rectangular waveguide cavities from which the RF signals are extracted using coaxial probes. The OMT was optimized using a commercial 3D electromagnetic simulator. The main mechanical part of the turnstile junction was machined out of an Aluminum block whose final external shape is a cylinder with diameter 450 mm and height 98 mm. From 1.3 to 1.8 GHz the measured reflection coefficient was less than -22 dB, the isolation between the outputs was less than -45 dB, and the cross polarization was less than -50 dB for both polarization channels.

  19. Thermal behavior of the Medicina 32-meter radio telescope

    Science.gov (United States)

    Pisanu, Tonino; Buffa, Franco; Morsiani, Marco; Pernechele, Claudio; Poppi, Sergio

    2010-07-01

    We studied the thermal effects on the 32 m diameter radio-telescope managed by the Institute of Radio Astronomy (IRA), Medicina, Bologna, Italy. The preliminary results show that thermal gradients deteriorate the pointing performance of the antenna. Data has been collected by using: a) two inclinometers mounted near the elevation bearing and on the central part of the alidade structure; b) a non contact laser alignment optical system capable of measuring the secondary mirror position; c) twenty thermal sensors mounted on the alidade trusses. Two series of measurements were made, the first series was performed by placing the antenna in stow position, the second series was performed while tracking a circumpolar astronomical source. When the antenna was in stow position we observed a strong correlation between the inclinometer measurements and the differential temperature. The latter was measured with the sensors located on the South and North sides of the alidade, thus indicating that the inclinometers track well the thermal deformation of the alidade. When the antenna pointed at the source we measured: pointing errors, the inclination of the alidade, the temperature of the alidade components and the subreflector position. The pointing errors measured on-source were 15-20 arcsec greater than those measured with the inclinometer.

  20. Identifying the source of perytons at the Parkes radio telescope

    CERN Document Server

    Petroff, E; Barr, E D; Reynolds, J E; Sarkissian, J; Edwards, P G; Stevens, J; Brem, C; Jameson, A; Burke-Spolaor, S; Johnston, S; Bhat, N D R; Chandra, P; Kudale, S; Bhandari, S

    2015-01-01

    "Perytons" are millisecond-duration transients of terrestrial origin, whose frequency-swept emission mimics the dispersion of an astrophysical pulse that has propagated through tenuous cold plasma. In fact, their similarity to FRB 010724 had previously cast a shadow over the interpretation of "fast radio bursts," which otherwise appear to be of extragalactic origin. Until now, the physical origin of the dispersion-mimicking perytons had remained a mystery. We have identified strong out-of-band emission at 2.3--2.5 GHz associated with several peryton events. Subsequent tests revealed that a peryton can be generated at 1.4 GHz when a microwave oven door is opened prematurely and the telescope is at an appropriate relative angle. Radio emission escaping from microwave ovens during the magnetron shut-down phase neatly explain all of the observed properties of the peryton signals. Now that the peryton source has been identified, we furthermore demonstrate that the microwaves on site could not have caused FRB 01072...

  1. Metric Observations of Saturn with the Giant Metrewave Radio Telescope

    Science.gov (United States)

    Courtin, R.; Pandey-Pommier, M.; Gautier, D.; Zarka, P.; Hofstadter, M.; Hersant, F.; Girard, J.

    2015-12-01

    We used the Giant Metrewave Radio Telescope (GMRT, India) to observe Saturn in the metric domain – at 0.49 m (610 MHz), 1.28 m (235 MHz), and 2.0 m (150 MHz) -with the aim of constraining the deep atmospheric ammonia and water vapor concentrations around 10-20 kbar. We have obtained a clean detection at 610 MHz, with a disk brightness temperature Tb= 216 ± 32 K, and no significant emission outside of the disk, thus confirming model predictions about the weakness of synchrotron radiation by magnetospheric electrons (Lorenzato et al. 2012, Lorenzato et al. 2012). A marginal detection was obtained at 235 MHz, with Tb= 404 ± 249 K, while an upper limit of 1210 K was set at 150 MHz. Unfortunately, some of the GMRT measurements were affected by strong ionospheric scintillation or radio frequency interferences (RFI). Although the reduction of the LOFAR measurements is much more complex, results are expected in the near future and they will complement nicely with those obtained with the GMRT. We will discuss the constraints resulting from these observations on Saturn's deep atmospheric composition.

  2. A Database of Phase Calibration Sources and their Radio Spectra for the Giant Metrewave Radio Telescope

    CERN Document Server

    Lal, Dharam V; Sherkar, Sachin S

    2016-01-01

    We are pursuing a project to build a database of phase calibration sources suitable for Giant Metrewave Radio Telescope (GMRT). Here we present the first release of 45 low frequency calibration sources at 235 MHz and 610 MHz. These calibration sources are broadly divided into quasars, radio galaxies and unidentified sources. We provide their flux densities, models for calibration sources, (u,v) plots, final deconvolved restored maps and clean-component lists/files for use in the Astronomical Image Processing System (AIPS) and the Common Astronomy Software Applications (CASA). We also assign a quality factor to each of the calibration sources. These data products are made available online through the GMRT observatory website. In addition we find that (i) these 45 low frequency calibration sources are uniformly distributed in the sky and future efforts to increase the size of the database should populate the sky further, (ii) spectra of these calibration sources are about equally divided between straight, curve...

  3. INTERPLANETARY SCINTILLATION RADIO SOURCES DETECTED WITH THE MEXICAN ARRAY RADIO TELESCOPE (MEXART)

    Science.gov (United States)

    Mejia Ambriz, J. C.; Villanueva-Hernandez, P.; Gonzalez-Esparza, A.; Aguilar-Rodriguez, E.; Andrade-Mascote, E.; Carrillo-Vargas, A.

    2009-12-01

    The Mexican Array Radio Telescope (MEXART) has an antenna composed by 4096 full-wavelength dipoles, covering about 9800 square meters. The instrument is primary devoted to carry out observations of compact stelar radio sources presenting Interplanetary Scintillation (IPS) at 140 MHz. The IPS technique is a very useful tool to perform observations of large-scale solar wind density disturbances in the inner heliosphere at heliocentric ranges where no other instruments can cover. These observations can help to track the evolution of CMEs and shocks in the interplanetary medium. We present the first catalog of IPS sources detected with the MEXART. We show the power spectrum analysis to obtain information of solar wind velocity and density.

  4. Hubble Space Telescope NICMOS observations of the host galaxies of powerful radio sources : Does size matter?

    NARCIS (Netherlands)

    de Vries, WH; O'Dea, CP; Barthel, PD; Fanti, C; Fanti, R; Lehnert, MD

    2000-01-01

    We present near-infrared J- and K-band imaging of a sample of powerful radio source host galaxies with the Hubble Space Telescope NICMOS2 camera. These sources have been selected on their double-lobed radio structure and include a wide range of projected radio source sizes. The largest projected

  5. VLBA "Movie" Gives Scientists New Insights On Workings of Mysterious Microquasars

    Science.gov (United States)

    2004-01-01

    Astronomers have made a 42-day movie showing unprecedented detail of the inner workings of a strange star system that has puzzled scientists for more than two decades. Their work is providing new insights that are changing scientists' understanding of the enigmatic stellar pairs known as microquasars. SS 433 Frame from SS 433 Movie: End to end is some 200 billion miles. CREDIT: Mioduszewski et al., NRAO/AUI/NSF Image Files Single Frame Overall Jet View (above image) VLBA Movie (animated gif, 2.3 MB) Animated graphic of SS 433 System (18MB) (Created using software by Robert Hynes, U.Texas) Annotated brightening graphic Unannotated brightening Frame 1 Unannotated brightening Frame 2 "This once-a-day series of exquisitely-detailed images is the best look anyone has ever had at a microquasar, and already has made us change our thinking about how these things work," said Amy Mioduszewski, of the National Radio Astronomy Observatory (NRAO), in Socorro, New Mexico. The astronomers used the National Science Foundation's Very Long Baseline Array (VLBA), a system of radio telescopes stretching from Hawaii to the Caribbean, to follow daily changes in a binary-star system called SS 433, some 15,000 light-years from Earth in the constellation Aquila. Mioduszewski worked with Michael Rupen, Greg Taylor and Craig Walker, all of NRAO. They reported their findings to the American Astronomical Society's meeting in Atlanta, Georgia. SS 433 consists of a neutron star or black hole orbited by a "normal" companion star. The powerful gravity of the neutron star or black hole is drawing material from the stellar wind of its companion into an accretion disk of material tightly circling the dense, central object prior to being pulled onto that object. This disk propels jets of subatomic particles outward from its poles. In SS 433, the particles in the jets move at 26 percent of the speed of light; in other microquasars, the jet material moves at 90-95 percent of light speed. The disk in SS

  6. FIRST-based survey of Compact Steep Spectrum sources, IV. Multifrequency VLBA observations of very compact objects

    CERN Document Server

    Kunert-Bajraszewska, M; Thomasson, P; Kunert-Bajraszewska, Magdalena; Marecki, Andrzej; Thomasson, Peter

    2006-01-01

    Evidence has been mounting recently that activity in some radio loud AGNs (RLAGNs) can cease shortly after ignition and that perhaps even a majority of very compact sources may be short-lived phenomena because of a lack of stable fuelling from the black hole. Thus, they can fade out before having evolved to large, extended objects. Re-ignition of the activity in such objects is not ruled out. With the aim of finding more examples of these objects and to investigate if they could be RLAGNs switched off at very early stages of their evolution, multifrequency VLBA observations of six sources with angular sizes significantly less than an arcsecond, yet having steep spectra, have been made. Observations were initially made at 1.65 GHz using the VLBA with the inclusion of Effelsberg telescope. The sources were then re-observed with the VLBA at 5, 8.4 and 15.4 GHz. All the observations were carried out in a snapshot mode with phase referencing. One of the sources studied, 0809+404, is dominated by a compact componen...

  7. The VLBA Correlator---Real-Time in the Distributed ERA

    Science.gov (United States)

    Wells, Donald C.

    1993-01-01

    The Correlator is the signal processing engine of the Very Long Baseline Array [VLBA]. Radio signals are recorded on special wideband digital recorders at the 10 VLBA antennas and are shipped to the Array Operations Center in Socorro, New Mexico, where they are played back simultaneously into the Correlator. Real-time software and firmware controls the playback drives to achieve synchronization, compute models of the wavefront delay, control the numerous modules of the Correlator, and record FITS files of the fringe visibilities at the back-end of the Correlator. The Correlator system contains a total of more than 100 programmable computers, which communicate by means of various protocols. The VLBA Correlator's dependence on network protocols is an example of the radical transformation of the real-time world over the past five years: real-time is becoming more like conventional computing.

  8. Exploring the Dynamic Radio Sky with the Allen Telescope Array

    Science.gov (United States)

    Williams, Peter Kelsey George

    The revolution in digital technology that has had so many obvious effects in recent decades has not spared the field of astronomy. It has led to an enormous improvement in astronomers' ability to study the "time domain," the expected and unexpected ways in which celestial objects change on timescales ranging from milliseconds to centuries. In the field of radio astronomy a variety of advances have led to a new breed of observatories that are orders of magnitude more efficient at surveying the sky than previous facilities. These new observatories produce data at prodigous rates, however, and require sophisticated analysis to take full advantage of their capabilities. With several major facilities coming online in the next few years, there is an urgent need to prove that terabytes of data can be reliably turned into genuine astrophysical results. This dissertation develops tools and techniques for coping with this challenge and applies them to data obtained with the Allen Telescope Array (ATA), a pioneering next-generation radio observatory located in Northern California. The ATA was built from the ground up to be a fast survey instrument, incorporating a suite of the new technologies that figure prominently in the new telescopes. I develop and describe miriad-python, a framework for the rapid development of interferometric analysis software that is used in a variety of ways in my subsequent research. I also present a robust software system for executing multiple observing campaigns cooperatively ("commensally") at the ATA. Data from the ATA are difficult to analyze due to nontraditional features such as a large instantaneous field of view; continuous coverage of a large, interference-prone frequency range; and broadband, movable feeds; I describe and implement several methods for coping with these challenges. This technical work is driven by the needs of a variety of astrophysical applications. I use broadband spectra of starforming galaxies to investigate the

  9. Gravitational redshift test with the space radio telescope "RadioAstron"

    Science.gov (United States)

    Biriukov, A. V.; Kauts, V. L.; Kulagin, V. V.; Litvinov, D. A.; Rudenko, V. N.

    2014-11-01

    The space radio telescope "RadioAstron" is equipped with a high performance hydrogen maser frequency standard and thus provides a unique opportunity for a gravitational redshift test. We consider various modes of operation of the on-board scientific equipment and their impact on accuracy of the anticipated experiment. We find that the accuracy of the test is limited by ˜10-2 for the hardware configuration routinely used in radio astronomical observations, which is a consequence of using ballistic data to remove the nonrelativistic Doppler frequency shift from the analyzed signal. On the other hand, the so-called "Semi-coherent" mode of the on-board hardware provides for combining the space and ground maser signals in such a way that the resulting signal carries information about the useful effect but is free from the nonrelativistic Doppler and tropospheric frequency shifts. The proposed compensation scheme, which is different from the one used in the Gravity Probe A experiment, allows for testing the gravitational redshift effect with ˜10-6 accuracy.

  10. Large Radio Telescopes for Anomalous Microwave Emission Observations

    CERN Document Server

    Battistelli, E S; de Bernardis, P; Masi, S

    2013-01-01

    We discuss in this paper the problem of the Anomalous Microwave Emission (AME) in the light of ongoing or future observations to be performed with the largest fully steerable radio telescope in the world. High angular resolution observations of the AME will enable astronomers to drastically improve the knowledge of the AME mechanisms as well as the interplay between the different constituents of the interstellar medium in our galaxy. Extragalactic observations of the AME have started as well, and high resolution is even more important in this kind of observations. When cross-correlating with IR-dust emission, high angular resolution is also of fundamental importance in order to obtain unbiased results. The choice of the observational frequency is also of key importance in continuum observation. We calculate a merit function that accounts for the signal-to-noise ratio (SNR) in AME observation given the current state-of-the-art knowledge and technology. We also include in our merit functions the frequency depen...

  11. Software Spectral Correlator for the 44-Element Ooty Radio Telescope

    CERN Document Server

    Prasad, Peeyush

    2011-01-01

    A Spectral Correlator is the main component of the real time signal processing for a Radio Telescope array. The correlation of signals received at each element with every other element of the array is a classic case of an application requiring a complete graph connectivity between its data sources, as well as a very large number of simple operations to carry out the correlation. Datarates can be extremely large in order to achieve high sensitivities required for the detection of weak celestial signals. Hence, correlators are prime targets for HPC implementations. In this paper, we present the design and implementation of a massively parallel software spectral Correlator for a 44 element array. The correlator handles ~735 MB/s of incoming data from the 44 spatially distributed sources, and concurrently sustains a computational load of ~100 Gflops. We first describe how we partition the large incoming data stream into grouped datasets suited for transport over high speed serial networks, as well as ideal for pr...

  12. System performance testing of the DVA1 radio telescope

    Science.gov (United States)

    Knee, Lewis B. G.; Baker, Lynn A.; Gray, Andrew D.; Hovey, Gary J.; Kesteven, Michael J.; Lacy, Gordon; Robishaw, Timothy

    2016-07-01

    DVA1 (Dish Verification Antenna 1) is a highly innovative rim-supported single-piece composite-material dish radio telescope developed at the National Research Council Canada (NRC). It has a feed-high offset Gregorian optical design with a primary effective diameter of 15 m. DVA1 has been undergoing mechanical and astronomical system tests since 2014. Astronomical measurements were made in L band using a prototype front end developed for MeerKAT by EMSS Antennas (South Africa), including aperture efficiency, beam profiles, sensitivity, and tipping curves. The clean shaped optics, careful attention to feed design, and high sensitivity of the L band receiver (Trx 6 K) yield a system with high aperture efficiency ( 0.8), excellent sensitivity ( 9 m2/K), and low spillover ( 4 K). Observations of 21 cm atomic hydrogen lines towards standard sources demonstrate the low stray radiation pickup of the antenna. Ku band holography has measured the effective surface accuracy and stability of the dual-reflector antenna. The effective RMS of 0.85 mm implies a Ruze efficiency of 0.88 at 10 GHz and 0.60 at 20 GHz. The surface is stable ( 10% variation in surface RMS) over the limited range of environmental conditions tested. Testing continues for characterization of pointing, low frequency performance (antenna, DVA3, which will have a more accurate surface and be usable at frequencies at least up to Q band (30 - 50 GHz).

  13. Conversion of a New Zealand 30-Metre Telecommunications Antenna into a Radio Telescope

    Science.gov (United States)

    Woodburn, Lewis; Natusch, Tim; Weston, Stuart; Thomasson, Peter; Godwin, Mark; Granet, Christophe; Gulyaev, Sergei

    2015-05-01

    The conversion of a former 100-foot (30-m) telecommunications antenna (Earth Station) in New Zealand into a radio telescope is described. A specification of the antenna and the priorities for its actual conversion are initially presented. In describing the actual conversion, particular emphasis is given to mechanical and electrical components, as well as to the design of the telescope control system, telescope networking for VLBI operations, and telescope maintenance. Plans for RF, front- and back-end developments based upon radio astronomical priorities are outlined.

  14. Gain and Polarization Properties of a Large Radio Telescope from Calculation and Measurement: The John A. Galt Telescope

    CERN Document Server

    Du, Xuan; Robishaw, Timothy; Gray, Andrew D; Douglas, Kevin A; Wolleben, Maik

    2016-01-01

    Measurement of the brightness temperature of extended radio emission demands knowledge of the gain (or aperture efficiency) of the telescope and measurement of the polarized component of the emission requires correction for the conversion of unpolarized emission from sky and ground to apparently polarized signal. Radiation properties of the John A. Galt Telescope at the Dominion Radio Astrophysical Observatory were studied through analysis and measurement in order to provide absolute calibration of a survey of polarized emission from the entire northern sky from 1280 to 1750 MHz, and to understand the polarization performance of the telescope. Electromagnetic simulators CST and GRASP-10 were used to compute radiation patterns of the telescope in all Stokes parameters, and aperture efficiency. Aperture efficiency was also evaluated using geometrical optics and was measured using Cyg A. Measured aperture efficiency varied smoothly with frequency between values of 0.49 and 0.54; GRASP-10 yielded values 6.5% high...

  15. Digital Receivers for Low-Frequency Radio Telescopes UTR-2, URAN, GURT

    Science.gov (United States)

    Zakharenko, V.; Konovalenko, A.; Zarka, P.; Ulyanov, O.; Sidorchuk, M.; Stepkin, S.; Koliadin, V.; Kalinichenko, N.; Stanislavsky, A.; Dorovskyy, V.; Shepelev, V.; Bubnov, I.; Yerin, S.; Melnik, V.; Koval, A.; Shevchuk, N.; Vasylieva, I.; Mylostna, K.; Shevtsova, A.; Skoryk, A.; Kravtsov, I.; Volvach, Y.; Plakhov, M.; Vasilenko, N.; Vasylkivskyi, Y.; Vavriv, D.; Vinogradov, V.; Kozhin, R.; Kravtsov, A.; Bulakh, E.; Kuzin, A.; Vasilyev, A.; Ryabov, V.; Reznichenko, A.; Bortsov, V.; Lisachenko, V.; Kvasov, G.; Mukha, D.; Litvinenko, G.; Brazhenko, A.; Vashchishin, R.; Pylaev, O.; Koshovyy, V.; Lozinsky, A.; Ivantyshyn, O.; Rucker, H. O.; Panchenko, M.; Fischer, G.; Lecacheux, A.; Denis, L.; Coffre, A.; Grießmeier, J.-M.

    This paper describes digital radio astronomical receivers used for decameter and meter wavelength observations. Since 1998, digital receivers performing on-the-fly dynamic spectrum calculations or waveform data recording without data loss have been used at the UTR-2 radio telescope, the URAN VLBI system, and the GURT new generation radio telescope. Here, we detail these receivers developed for operation in the strong interference environment that prevails in the decameter wavelength range. Data collected with these receivers allowed us to discover numerous radio astronomical objects and phenomena at low frequencies, a summary of which is also presented.

  16. Initial Results Obtained with the First TWIN VLBI Radio Telescope at the Geodetic Observatory Wettzell.

    Science.gov (United States)

    Schüler, Torben; Kronschnabl, Gerhard; Plötz, Christian; Neidhardt, Alexander; Bertarini, Alessandra; Bernhart, Simone; la Porta, Laura; Halsig, Sebastian; Nothnagel, Axel

    2015-07-30

    Geodetic Very Long Baseline Interferometry (VLBI) uses radio telescopes as sensor networks to determine Earth orientation parameters and baseline vectors between the telescopes. The TWIN Telescope Wettzell 1 (TTW1), the first of the new 13.2 m diameter telescope pair at the Geodetic Observatory Wettzell, Germany, is currently in its commissioning phase. The technology behind this radio telescope including the receiving system and the tri-band feed horn is depicted. Since VLBI telescopes must operate at least in pairs, the existing 20 m diameter Radio Telescope Wettzell (RTW) is used together with TTW1 for practical tests. In addition, selected long baseline setups are investigated. Correlation results portraying the data quality achieved during first initial experiments are discussed. Finally, the local 123 m baseline between the old RTW telescope and the new TTW1 is analyzed and compared with an existing high-precision local survey. Our initial results are very satisfactory for X-band group delays featuring a 3D distance agreement between VLBI data analysis and local ties of 1 to 2 mm in the majority of the experiments. However, S-band data, which suffer much from local radio interference due to WiFi and mobile communications, are about 10 times less precise than X-band data and require further analysis, but evidence is provided that S-band data are well-usable over long baselines where local radio interference patterns decorrelate.

  17. Initial Results Obtained with the First TWIN VLBI Radio Telescope at the Geodetic Observatory Wettzell

    Directory of Open Access Journals (Sweden)

    Torben Schüler

    2015-07-01

    Full Text Available Geodetic Very Long Baseline Interferometry (VLBI uses radio telescopes as sensor networks to determine Earth orientation parameters and baseline vectors between the telescopes. The TWIN Telescope Wettzell 1 (TTW1, the first of the new 13.2 m diameter telescope pair at the Geodetic Observatory Wettzell, Germany, is currently in its commissioning phase. The technology behind this radio telescope including the receiving system and the tri-band feed horn is depicted. Since VLBI telescopes must operate at least in pairs, the existing 20 m diameter Radio Telescope Wettzell (RTW is used together with TTW1 for practical tests. In addition, selected long baseline setups are investigated. Correlation results portraying the data quality achieved during first initial experiments are discussed. Finally, the local 123 m baseline between the old RTW telescope and the new TTW1 is analyzed and compared with an existing high-precision local survey. Our initial results are very satisfactory for X-band group delays featuring a 3D distance agreement between VLBI data analysis and local ties of 1 to 2 mm in the majority of the experiments. However, S-band data, which suffer much from local radio interference due to WiFi and mobile communications, are about 10 times less precise than X-band data and require further analysis, but evidence is provided that S-band data are well-usable over long baselines where local radio interference patterns decorrelate.

  18. Multi-beaming propertieis of reflector antennas used in radio telescopes with wide field of view

    CERN Document Server

    Iupikov, O

    2016-01-01

    The given work is devoted to the modern developments in the field of radio astronomy instrumentation. In particular, the sensitivity of the multi-beam reflector radio telescope which is fed by phased array (PAF) is considered. Using PAF as reflector feed allows obtaining wide and continuous field of view (FOV) of the telescope. This has several advantages with compare to horn-cluster feeds which are described in this work. The sensitivity inside whole FOV was computed using three different beamforming schemes.

  19. Real Time Event Detection in Astronomical Data Streams: Lessons from the VLBA

    CERN Document Server

    Thompson, David R; Deller, Adam T; Majid, Walid A; Palaniswamy, Divya; Tingay, Steven J; Wagstaff, Kiri L; Wayth, Randall B

    2013-01-01

    A new generation of observational science instruments is dramatically increasing collected data volumes in a range of fields. These instruments include the Square Kilometre Array (SKA), Large Synoptic Survey Telescope (LSST), terrestrial sensor networks, and NASA satellites participating in "decadal survey" missions. Their unprecedented coverage and sensitivity will likely reveal wholly new categories of unexpected and transient events. Commensal methods passively analyze these data streams, recognizing anomalous events of scientific interest and reacting in real time. We report on a case example: V-FASTR, an ongoing commensal experiment at the Very Long Baseline Array (VLBA) that uses online adaptive pattern recognition to search for anomalous fast radio transients. V-FASTR triages a millisecond-resolution stream of data and promotes candidate anomalies for further offline analysis. It tunes detection parameters in real time, injecting synthetic events to continually retrain itself for optimum performance. T...

  20. Observation of two coronal mass ejections on April 7, 2011 by radio telescope URAN-2

    Science.gov (United States)

    Brazhenko, A.; Melnik, V.; Konovalenko, A.; Dorovskyy, V.; Vashchishin, V.; Franzusenko, A.; Rucker, H.

    2012-09-01

    Two CME's (coronal mass ejection) were registered by SOHO and STEREO on April 7, 2011. The results of observations obtained by radio telescope URAN-2 of different CME manifestations in radio emission at decameter wavelengths are discussed in this paper. Particularly we report about registration of new type of fine structure of type II bursts.

  1. Search for molecular bremsstrahlung radiation signals in Ku band with coincidental operations of radio telescopes with air shower detectors

    Directory of Open Access Journals (Sweden)

    Fukushima Masaki

    2013-06-01

    Full Text Available Microwave radiation from extensive air showers is expected to provide a new technique to observe UHECR. We insatlled and operate radio telescopes in Osaka and at Telescope Array site in Utah, USA. In Osaka, we are coincidentally operating two Ku band radio telescopes with an air shower array which consists of nine plastic scintillators with about 10 m separation. In Utah, we installed two telescopes just beside the Black Rock Mesa fluorescence detector (FD station of the Telescope Array experiment, and we operated the radio telescopes coincidentally with FD event triggers. We report the experimental setups and the results of these measurements.

  2. Blind search for 21-cm absorption systems using a new generation of Chinese radio telescopes

    Science.gov (United States)

    Yu, Hao-Ran; Pen, Ue-Li; Zhang, Tong-Jie; Li, Di; Chen, Xuelei

    2017-05-01

    Neutral hydrogen clouds are known to exist in the Universe, however their spatial distributions and physical properties are poorly understood. Such missing information can be studied by the new generation of Chinese radio telescopes through a blind search of 21-cm absorption systems. We forecast the capabilities of surveys of 21-cm absorption systems by two representative radio telescopes in China -the Five-hundred-meter Aperture Spherical radio Telescope (FAST) and Tianlai 21-cm cosmology experiment (Tianlai). Facilitated by either the high sensitivity (FAST) or wide field of view (Tianlai) of these telescopes, more than a thousand 21-cm absorption systems can be discovered in a few years, representing orders of magnitude improvement over the cumulative discoveries in the past half a century.

  3. Engineering and science highlights of the KAT-7 radio telescope

    NARCIS (Netherlands)

    Foley, A. R.; Alberts, T.; Armstrong, R. P.; Barta, A.; Bauermeister, E. F.; Bester, H.; Blose, S.; Booth, R. S.; Botha, D. H.; Buchner, S. J.; Carignan, C.; Cheetham, T.; Cloete, K.; Coreejes, G.; Crida, R. C.; Cross, S. D.; Curtolo, F.; Dikgale, A.; de Villiers, M. S.; du Toit, L. J.; Esterhuyse, S. W. P.; Fanaroff, B.; Fender, R. P.; Fijalkowski, M.; Fourie, D.; Frank, B.; George, D.; Gibbs, P.; Goedhart, S.; Grobbelaar, J.; Gumede, S. C.; Herselman, P.; Hess, K. M.; Hoek, N.; Horrell, J.; Jonas, J. L.; Jordaan, J. D. B.; Julie, R.; Kapp, F.; Kotzé, P.; Kusel, T.; Langman, A.; Lehmensiek, R.; Liebenberg, D.; Liebenberg, I. J. V.; Loots, A.; Lord, R. T.; Lucero, D. M.; Ludick, J.; Macfarlane, P.; Madlavana, M.; Magnus, L.; Magozore, C.; Malan, J. A.; Manley, J. R.; Marais, L.; Marais, N.; Marais, S. J.; Maree, M.; Martens, A.; Mokone, O.; Moss, V.; Mthembu, S.; New, W.; Nicholson, G. D.; van Niekerk, P. C.; Oozeer, N.; Passmoor, S. S.; Peens-Hough, A.; Pińska, A. B.; Prozesky, P.; Rajan, S.; Ratcliffe, S.; Renil, R.; Richter, L. L.; Rosekrans, D.; Rust, A.; Schröder, A. C.; Schwardt, L. C.; Seranyane, S.; Serylak, M.; Shepherd, D. S.; Siebrits, R.; Sofeya, L.; Spann, R.; Springbok, R.; Swart, P. S.; Thondikulam, Venkatasubramani L.; Theron, I. P.; Tiplady, A.; Toruvanda, O.; Tshongweni, S.; van den Heever, L.; van der Merwe, C.; van Rooyen, R.; Wakhaba, S.; Walker, A. L.; Welz, M.; Williams, L.; Wolleben, M.; Woudt, P. A.; Young, N. J.; Zwart, J. T. L.

    2016-01-01

    The construction of the seven-dish Karoo Array Telescope (KAT-7) array in the Karoo region of the Northern Cape in South Africa was intended primarily as an engineering prototype for technologies and techniques applicable to the MeerKAT telescope. This paper looks at the main engineering and

  4. Engineering and science highlights of the KAT-7 radio telescope

    NARCIS (Netherlands)

    Foley, A. R.; Alberts, T.; Armstrong, R. P.; Barta, A.; Bauermeister, E. F.; Bester, H.; Blose, S.; Booth, R. S.; Botha, D. H.; Buchner, S. J.; Carignan, C.; Cheetham, T.; Cloete, K.; Coreejes, G.; Crida, R. C.; Cross, S. D.; Curtolo, F.; Dikgale, A.; de Villiers, M. S.; du Toit, L. J.; Esterhuyse, S. W. P.; Fanaroff, B.; Fender, R. P.; Fijalkowski, M.; Fourie, D.; Frank, B.; George, D.; Gibbs, P.; Goedhart, S.; Grobbelaar, J.; Gumede, S. C.; Herselman, P.; Hess, K. M.; Hoek, N.; Horrell, J.; Jonas, J. L.; Jordaan, J. D. B.; Julie, R.; Kapp, F.; Kotzé, P.; Kusel, T.; Langman, A.; Lehmensiek, R.; Liebenberg, D.; Liebenberg, I. J. V.; Loots, A.; Lord, R. T.; Lucero, D. M.; Ludick, J.; Macfarlane, P.; Madlavana, M.; Magnus, L.; Magozore, C.; Malan, J. A.; Manley, J. R.; Marais, L.; Marais, N.; Marais, S. J.; Maree, M.; Martens, A.; Mokone, O.; Moss, V.; Mthembu, S.; New, W.; Nicholson, G. D.; van Niekerk, P. C.; Oozeer, N.; Passmoor, S. S.; Peens-Hough, A.; Pińska, A. B.; Prozesky, P.; Rajan, S.; Ratcliffe, S.; Renil, R.; Richter, L. L.; Rosekrans, D.; Rust, A.; Schröder, A. C.; Schwardt, L. C.; Seranyane, S.; Serylak, M.; Shepherd, D. S.; Siebrits, R.; Sofeya, L.; Spann, R.; Springbok, R.; Swart, P. S.; Thondikulam, Venkatasubramani L.; Theron, I. P.; Tiplady, A.; Toruvanda, O.; Tshongweni, S.; van den Heever, L.; van der Merwe, C.; van Rooyen, R.; Wakhaba, S.; Walker, A. L.; Welz, M.; Williams, L.; Wolleben, M.; Woudt, P. A.; Young, N. J.; Zwart, J. T. L.

    2016-01-01

    The construction of the seven-dish Karoo Array Telescope (KAT-7) array in the Karoo region of the Northern Cape in South Africa was intended primarily as an engineering prototype for technologies and techniques applicable to the MeerKAT telescope. This paper looks at the main engineering and scienti

  5. Synchronized observations by using the STEREO and the largest ground-based decametre radio telescope

    Science.gov (United States)

    Konovalenko, A. A.; Stanislavsky, A. A.; Rucker, H. O.; Lecacheux, A.; Mann, G.; Bougeret, J.-L.; Kaiser, M. L.; Briand, C.; Zarka, P.; Abranin, E. P.; Dorovsky, V. V.; Koval, A. A.; Mel'nik, V. N.; Mukha, D. V.; Panchenko, M.

    2013-08-01

    We consider the approach to simultaneous (synchronous) solar observations of radio emission by using the STEREO-WAVES instruments (frequency range 0.125-16 MHz) and the largest ground-based low-frequency radio telescope. We illustrate it by the UTR-2 radio telescope implementation (10-30 MHz). The antenna system of the radio telescope is a T-shape-like array of broadband dipoles and is located near the village Grakovo in the Kharkiv region (Ukraine). The third observation point on the ground in addition to two space-based ones improves the space-mission performance capabilities for the determination of radio-emission source directivity. The observational results from the high sensitivity antenna UTR-2 are particularly useful for analysis of STEREO data in the condition of weak event appearances during solar activity minima. In order to improve the accuracy of flux density measurements, we also provide simultaneous observations with a large part of the UTR-2 radio telescope array and its single dipole close to the STEREO-WAVES antennas in sensitivity. This concept has been studied by comparing the STEREO data with ground-based records from 2007-2011 and shown to be effective. The capabilities will be useful in the implementation of new instruments (LOFAR, LWA, MWA, etc.) and during the future Solar Orbiter mission.

  6. Characteristics of Gamma-Ray Loud Blazars in the VLBA Imaging and Polarimetry Survey

    Science.gov (United States)

    Linford, J. D.; Taylor, G. B.; Romani, R. W.; Healey, S. E.; Helmboldt, J. F.; Readhead, A. C.; Reeves, R.; Richards, J. L.; Cotter, G.

    2010-01-01

    The radio properties of blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been observed as part of the VLBA Imaging and Polarimetry Survey. This large, flux-limited sample of active galactic nuclei (AGNs) provides insights into the mechanism that produces strong gamma-ray emission. At lower flux levels, radio flux density does not directly correlate with gamma-ray flux. We find that the LAT-detected BL Lac objects tend to be similar to the non-LAT BL Lac objects, but that the LAT-detected FSRQs are often significantly different from the non-LAT FSRQs. The differences between the gamma-ray loud and quiet FSRQS can be explained by Doppler boosting; these objects appear to require larger Doppler factors than those of the BL Lac objects. It is possible that the gamma-ray loud FSRQs are fundamentally different from the gamma-ray quiet FSRQs. Strong polarization at the base of the jet appears to be a signature for gamma-ray loud AGNs.

  7. Characteristics of Gamma-Ray Loud Blazars in the VLBA Imaging and Polarimetry Survey

    Science.gov (United States)

    Linford, J. D.; Taylor, G. B.; Romani, R. W.; Healey, S. E.; Helmboldt, J. F.; Readhead, A. C.; Reeves, R.; Richards, J. L.; Cotter, G.

    2010-01-01

    The radio properties of blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been observed as part of the VLBA Imaging and Polarimetry Survey. This large, flux-limited sample of active galactic nuclei (AGNs) provides insights into the mechanism that produces strong gamma-ray emission. At lower flux levels, radio flux density does not directly correlate with gamma-ray flux. We find that the LAT-detected BL Lac objects tend to be similar to the non-LAT BL Lac objects, but that the LAT-detected FSRQs are often significantly different from the non-LAT FSRQs. The differences between the gamma-ray loud and quiet FSRQS can be explained by Doppler boosting; these objects appear to require larger Doppler factors than those of the BL Lac objects. It is possible that the gamma-ray loud FSRQs are fundamentally different from the gamma-ray quiet FSRQs. Strong polarization at the base of the jet appears to be a signature for gamma-ray loud AGNs.

  8. System of the optic-electronic sensors for control position of the radio telescope elements

    Science.gov (United States)

    Konyakhin, Igor; Stepashkin, Ivan; Petrochenko, Andrey

    2016-04-01

    A promising area of modern astronomy is the study of the field of millimeter waves. The use of this band is due to a large extent the spectrum characteristics of the propagation of waves in the atmosphere, short wavelength. Currently, Russia jointly with Uzbekistan is implementing a project to build a radio astronomy observatory on the Suffa plateau (Uzbekistan). The main instrument of the observatory is fully steerable radio telescope RT-70 type. Main mirror telescope is a fragment of an axisymmetric parabolic with a focal length of 21 m, consisting of 1200 reflecting panels; main mirror diameter - 70 m; diameter of counter reflector - 3 m. A feature of the radio telescope as a means of research in the millimeter wavelength range are high for the quality requirements parabolic surface of the primary mirror (standard deviation of points on the surface of the theoretical parabolic is not more than 0.05 mm), to the stability of the mutual arrangement of the primary mirror and the counter reflector (not more than 0, 07 mm) for precision guidance in the corners of the mirror system azimuth and elevation (margin of error 1.5-2"). Weight of structure, temperature changes and air shock result in significant deformation elements radio telescope construction (progressive linear displacements of points of the surface of the main mirror), reaching in the marginal zone of 30 mm; counter reflector shift of up to 60 mm; Unlike the angular position of the axis of the beam pattern of the radio telescope of the measured angle transducers can reach 10 ". Therefore, to ensure the required quality of the reflective elements RT-70 systems, as well as the implementation of precision-guided munitions needs complex measuring deformation elements telescope design. This article deals with the construction of opto-electronic system of remote optoelectronic displacement sensor control elements mirror telescope system.

  9. The Radio Structure of Source 1803÷784

    Science.gov (United States)

    Chuprikov, A. A.

    Results of processing of data of ground-space VLBI experiment titled V053 are presented. These observations were made in 1997 October with 10 antennas of American interferometer VLBA and with Japan space telescope VSOP (VLBI Space Orbit Program). Data were transferred from the NRAO archive and processed with the software "Astro Space Locator" (ASL for Windows). The main result is radio image of the known quasar 1803+784. Properties of the ground-space VLBI data processing are discussed.

  10. A Study of the Fitting Accuracy of the Active Reflector for a Large Spherical Radio Telescope

    Institute of Scientific and Technical Information of China (English)

    Xiao-Qiang Tang; Jin-Song Wang; Qi-Ming Wang

    2003-01-01

    We propose a spatial three-degree-of-freedom (DOF) parallel mechanism combining two degrees of rotations and one degree of translation to support the active reflector units of a large spherical radio telescope. The kinematics, workspace and accuracy of the mechanism are analyzed. One-dimensional and two-dimensional fitting errors to the working region of active reflector are investigated. Dimensional parameters of the mechanism and active reflector unit are examined with respect to the requirement of fitting accuracy. The result of accuracy analysis shows the effectiveness and feasibility of the proposed mechanism, and gives a design rule to guarantee the highest working frequency required by large radio telescope.

  11. Surface Accuracy and Pointing Error Prediction of a 32 m Diameter Class Radio Astronomy Telescope

    Science.gov (United States)

    Azankpo, Severin

    2017-03-01

    The African Very-long-baseline interferometry Network (AVN) is a joint project between South Africa and eight partner African countries aimed at establishing a VLBI (Very-Long-Baseline Interferometry) capable network of radio telescopes across the African continent. An existing structure that is earmarked for this project, is a 32 m diameter antenna located in Ghana that has become obsolete due to advances in telecommunication. The first phase of the conversion of this Ghana antenna into a radio astronomy telescope is to upgrade the antenna to observe at 5 GHz to 6.7 GHz frequency and then later to 18 GHz within a required performing tolerance. The surface and pointing accuracies for a radio telescope are much more stringent than that of a telecommunication antenna. The mechanical pointing accuracy of such telescopes is influenced by factors such as mechanical alignment, structural deformation, and servo drive train errors. The current research investigates the numerical simulation of the surface and pointing accuracies of the Ghana 32 m diameter radio astronomy telescope due to its structural deformation mainly influenced by gravity, wind and thermal loads.

  12. The Position and Attitude of Sub-reflector Modeling for TM65 m Radio Telescope

    Science.gov (United States)

    Sun, Z. X.; Chen, L.; Wang, J. Q.

    2016-01-01

    In the course of astronomical observations, with changes in angle of pitch, the large radio telescope will have different degrees of deformation in the sub-reflector support, back frame, main reflector etc, which will lead to the dramatic decline of antenna efficiency in both high and low elevation. A sub-reflector system of the Tian Ma 65 m radio telescope has been installed in order to compensate for the gravitational deformations of the sub-reflector support and the main reflector. The position and attitude of the sub-reflector are variable in order to improve the pointing performance and the efficiency at different elevations. In this paper, it is studied that the changes of position and attitude of the sub-reflector have influence on the efficiency of antenna in the X band and Ku band. A model has been constructed to determine the position and attitude of the sub-reflector with elevation, as well as the point compensation model, by observing the radio source. In addition, antenna efficiency was tested with sub-reflector position adjusted and fixed. The results show that the model of sub-reflector can effectively improve the efficiency of the 65 m radio telescope. In X band, the aperture efficiency of the radio telescope reaches more than 60% over the entire elevation range.

  13. The Role of the Goldstone Apple Valley Radio Telescope Project in Promoting Scientific Efficacy among Middle and High School Students.

    Science.gov (United States)

    Ibe, Mary; Deutscher, Rebecca

    This study investigated the effects on student scientific efficacy after participation in the Goldstone Apple Valley Radio Telescope (GAVRT) project. In the GAVRT program, students use computers to record extremely faint radio waves collected by the telescope and analyze real data. Scientific efficacy is a type of self-knowledge a person uses to…

  14. Calibration of low-frequency radio telescopes using the galactic background radiation

    Science.gov (United States)

    Dulk, G. A.; Erickson, W. C.; Manning, R.; Bougeret, J.-L.

    2001-01-01

    We consider the calibration of flux densities of radio bursts from decametric to kilometric wavelengths using ground-based and space-based data. The method we derive is applicable to low-frequency radio telescopes where galactic background radiation is the principal contribution to system temperature. It can be particularly useful for telescopes of low angular resolution observing spectra of radio bursts from the Sun and the planets because absolute calibration of these telescopes is very difficult with conventional techniques. Here we apply the method to observations from about 7 to 47 MHz that were made on the ground with the Bruny Island Radio Spectrometer located in Tasmania, Australia, and those from about 20 kHz to 13.8 MHz were made with the radio experiment WAVES on the WIND spacecraft. The spectrum of the galactic background radiation from 30 MHz has been carefully measured with low-resolution telescopes, starting more than a decade ago. We use this known spectrum to calibrate both BIRS and WAVES on an absolute scale. The accuracy we achieve is about a factor of two, whereas the flux densities of solar and planetary radio sources vary by many orders of magnitude. Our method permits inter-calibration of ground-based and space-based observations, and allows corrections to be made for instrumental uncertainties on both radio experiments. In addition, on the ground, it allows the spectra to be corrected for ionospheric absorption and partial ground reflections. As an application we show the spectrum of a solar type III burst observed from 47 MHz to 20 kHz. Its flux density was largest, S~ 10-17 W m-2 Hz-1, at about 3 MHz, while at 60 kHz and at 47 MHz it was lower by a factor of about 300.

  15. Modelling high-resolution spatially-resolved Supernova Remnant spectra with the Sardinia Radio Telescope

    CERN Document Server

    Loru, Sara; Egron, Elise; Iacolina, Noemi; Righini, Simona; Marongiu, Marco; Mulas, Sara; Murtas, Giulia; Simeone, Davide; Pilia, Maura; Bachetti, Matteo; Trois, Alessio; Ricci, Roberto; Melis, Andrea; Concu, Raimondo

    2016-01-01

    Supernova Remnants (SNRs) exhibit spectra featured by synchrotron radio emission arising from the relativistic electrons, and high-energy emission from both leptonic (Bremsstrahlung and Inverse Compton) and hadronic processes (${\\pi}^0$ mesons decay) which are a direct signature of cosmic rays acceleration. Thanks to radio single-dish imaging observations obtained in three frequency bands (1.6, 7, 22 GHz) with the Sardinia Radio Telescope (www.srt.inaf.it), we can model different SNR regions separately. Indeed, in order to disentangle interesting and peculiar hadron contributions in the high-energy spectra (gamma-ray band) and better constrain SNRs as cosmic rays emitters, it is crucial to fully constrain lepton contributions first through radio-observed parameters. In particular, the Bremsstrahlung and Inverse Compton bumps observed in gamma-rays are bounded to synchrotron spectral slope and cut-off in the radio domain. Since these parameters vary for different SNR regions and electron populations, spatially...

  16. PuMa-II: A wide band pulsar machine for the Westerbork Synthesis Radio Telescope

    NARCIS (Netherlands)

    Karuppusamy, R.; Stappers, B.; van Straten, W.

    2008-01-01

    The Pulsar Machine II (PuMa-II) is the new flexible pulsar processing back-end system at the Westerbork Synthesis Radio Telescope (WSRT), specifically designed to take advantage of the upgraded WSRT. The instrument is based on a computer cluster running the Linux operating system, with minimal custo

  17. Modelling, simulation and testing of an optomechatronics design of a large radio telescope

    Science.gov (United States)

    Duan, B. Y.; Qiu, Y. Y.; Su, Y. X.; Wang, W. L.; Nan, R. D.; Peng, B.

    An innovative design for a feed support structure for the next generation large radio telescope, based on the idea of integrating mechanical, electronic and optical technologies (OPTOMECHATRONICS), is considered. Theoretical analyses and simulations are carried out. A 5 m experimental model is built to demonstrate the idea.

  18. Revealing the Hidden Wave: Using the Very Small Radio Telescope to Teach High School Physics

    Science.gov (United States)

    Doherty, Michael; Fish, Vincent L.; Needles, Madeleine

    2011-01-01

    Scientists and teachers have worked together to produce teaching materials for the Very Small Radio Telescope (VSRT), an easy-to-use, low-cost apparatus that can be used in multiple laboratory experiments in high school and university physics and astronomy classes. In this article, we describe the motivation for the VSRT and several of the…

  19. Communicating astronomy in a small island state: The unique role of the Mauritius Radio Telescope

    Science.gov (United States)

    Saddul-Hauzaree, S.

    2008-06-01

    The Mauritius Radio Telescope (MRT) is a 2 km x 1 km T-shaped aperture synthesis array that can generate radio images of the southern sky at 151.6 MHz. The sky surveyed can be in the declination range of -70o to -10o. It is located at Bras d'Eau, northeast of Mauritius at latitude 20oS and longitude 60oE. The MRT is a joint project of the University of Mauritius, the Indian Institute of Astrophysics and the Raman Research Institute. One of the main objectives of the MRT is to generate public interest in astronomy. Thus, it is involved in a wide range of onsite outreach activities for young school children. More mature students visiting the telescope learn about sky observation with a radio telescope, get to explore some sets of data, interact with the scientific personnel, get the opportunity to have hands-on experience with image manipulation and can ask a lot of questions on astronomy. This poster gives an overview of the Mauritius Radio Telescope and the attempts of MRT ito communicate astronomy to students as a process and not just as a vast expanse of knowledge. The challenges and dilemmas faced by MRT in conveying astronomy to the general public in a small island state are investigated and presented.

  20. The Allen Telescope Array : The First Widefield, Panchromatic, Snapshot Radio Camera

    NARCIS (Netherlands)

    Leeuwen, Joeri van

    2009-01-01

    The first 42 elements of the Allen Telescope Array (ATA-42) are beginning to deliver data at the Hat Creek Radio Observatory in Northern California. Scientists and engineers are actively exploiting all of the flexibility designed into this innovative instrument for simultaneously conducting panorami

  1. The Five-Hundred-Meter Aperture Spherical Radio Telescope (FAST) Project

    CERN Document Server

    Nan, Rendong; Jin, Chengjin; Wang, Qiming; Zhu, Lichun; Zhu, Wenbai; Zhang, Haiyan; Yue, Youling; Qian, Lei

    2011-01-01

    Five-hundred-meter Aperture Spherical radio Telescope (FAST) is a Chinese mega-science project to build the largest single dish radio telescope in the world. Its innovative engineering concept and design pave a new road to realize a huge single dish in the most effective way. FAST also represents Chinese contribution in the international efforts to build the square kilometer array (SKA). Being the most sensitive single dish radio telescope, FAST will enable astronomers to jump-start many science goals, for example, surveying the neutral hydrogen in the Milky Way and other galaxies, detecting faint pulsars, looking for the first shining stars, hearing the possible signals from other civilizations, etc. The idea of sitting a large spherical dish in a karst depression is rooted in Arecibo telescope. FAST is an Arecibo-type antenna with three outstanding aspects: the karst depression used as the site, which is large to host the 500-meter telescope and deep to allow a zenith angle of 40 degrees; the active main re...

  2. The Five-hundred-meter Aperture Spherical radio Telescope project and its early science opportunities

    CERN Document Server

    Li, Di; Pan, Zhichen

    2012-01-01

    The National Astronomical Observatories, Chinese Academy of Science (NAOC), has started building the largest antenna in the world. Known as FAST, the Five-hundred-meter Aperture Spherical radio Telescope is a Chinese mega-science project funded by the National Development and Reform Commission (NDRC). FAST also represents part of Chinese contribution to the international efforts to build the square kilometer array (SKA). Upon its finishing around September of 2016, FAST will be the most sensitive single-dish radio telescope in the low frequency radio bands between 70 MHz and 3 GHz. The design specifications of FAST, its expected capabilities, and its main scientific aspirations were described in an overview paper by Nan et al. (2011). In this paper, we briefly review the design and the key science goals of FAST, speculate the likely limitations at the initial stages of FAST operation, and discuss the opportunities for astronomical discoveries in the so-called early science phase.

  3. Radio Telescope Focal Container for the Russian VLBI Network of New Generation

    Science.gov (United States)

    Ipatov, Alexander; Mardyshkin, Vyacheslav; Cherepanov, Andrey; Chernov, Vitaly; Diky, Dmitry; Khvostov, Evgeny; Yevstigneyev, Alexander

    2010-01-01

    This article considers the development of the structure of receivers for Russian radio telescopes. The development of these radio telescopes is undertaken within the project for creating a Russian small-antenna-based radio interferometer of new generation. It is shown that for small antennas (10. 12 meter) the principal unit, which provides the best SNR, is the so-called focal container placed at primary focus. It includes the primary feed, HEMT LNA, and cryogenic cooling system down to 20. K. A new multi-band feed based on traveling wave resonators is used. It has small dimensions, low weight, and allows working with circular polarizations. Thus it can be placed into focal container and cooled with the LNA. A sketch of the focal container, with traveling-wave-resonator feed, and calculations of the expected parameters of the multi-band receiver are presented.

  4. A synthetic aperture radio telescope for ICME observations as a potential payload of SPORT

    Science.gov (United States)

    Zhang, C.; Sun, W.; Liu, H.; Xiong, M.; Liu, Y. D.; Wu, J.

    2013-12-01

    We introduce a potential payload for the Solar Polar ORbit Telescope (SPORT), a space weather mission proposed by the National Space Science Center, Chinese Academy of Sciences. This is a synthetic aperture radio imager designed to detect radio emissions from interplanetary coronal mass ejections (ICMEs), which is expected to be an important instrument to monitor the propagation and evolution of ICMEs. The radio telescope applies a synthetic aperture interferometric technique to measure the brightness temperature of ICMEs. Theoretical calculations of the brightness temperature utilizing statistical properties of ICMEs and the background solar wind indicate that ICMEs within 0.35 AU from the Sun are detectable by a radio telescope at a frequency <= 150 MHz with a sensitivity of <=1 K. The telescope employs a time shared double rotation scan (also called a clock scan), where two coplanar antennas revolve around a fixed axis at different radius and speed, to fulfill sampling of the brightness temperature. An array of 4+4 elements with opposite scanning directions are developed for the radio telescope to achieve the required sensitivity (<=1K) within the imaging refreshing time (~30 minutes). This scan scheme is appropriate for a three-axis stabilized spacecraft platform while keeping a good sampling pattern. We also discuss how we select the operating frequency, which involves a trade-off between the engineering feasibility and the scientific goal. Our preliminary results indicate that the central frequency of 150 MHz with a bandwidth of 20 MHz, which requires arm lengths of the two groups of 14m and 16m, respectively, gives an angular resolution of 2°, a field of view of ×25° around the Sun, and a time resolution of 30 minutes.

  5. Probing Ionospheric Structures using the LOFAR radio telescope

    CERN Document Server

    Mevius, M; Pandey, V N; Vedantham, H K; Brentjens, M A; de Bruyn, A G; Abdalla, F B; Asad, K M B; Bregman, J D; Brouw, W N; Bus, S; Chapman, E; Ciardi, B; Fernandez, E R; Ghosh, A; Harker, G; Iliev, I T; Jelić, V; Kazemi, S; Koopmans, L V E; Noordam, J E; Offringa, A R; Patil, A H; van Weeren, R J; Wijnholds, S; Yatawatta, S; Zaroubi, S

    2016-01-01

    LOFAR is the LOw Frequency Radio interferometer ARray located at mid-latitude ($52^{\\circ} 53'N$). Here, we present results on ionospheric structures derived from 29 LOFAR nighttime observations during the winters of 2012/2013 and 2013/2014. We show that LOFAR is able to determine differential ionospheric TEC values with an accuracy better than 1 mTECU over distances ranging between 1 and 100 km. For all observations the power law behavior of the phase structure function is confirmed over a long range of baseline lengths, between $1$ and $80$ km, with a slope that is in general larger than the $5/3$ expected for pure Kolmogorov turbulence. The measured average slope is $1.89$ with a one standard deviation spread of $0.1$. The diffractive scale, i.e. the length scale where the phase variance is $1\\, \\mathrm{rad^2}$, is shown to be an easily obtained single number that represents the ionospheric quality of a radio interferometric observation. A small diffractive scale is equivalent to high phase variability ove...

  6. An efficient feedback calibration algorithm for direct imaging radio telescopes

    Science.gov (United States)

    Beardsley, Adam P.; Thyagarajan, Nithyanandan; Bowman, Judd D.; Morales, Miguel F.

    2017-10-01

    We present the E-field Parallel Imaging Calibration (EPICal) algorithm, which addresses the need for a fast calibration method for direct imaging radio astronomy correlators. Direct imaging involves a spatial fast Fourier transform of antenna signals, alleviating an O(Na ^2) computational bottleneck typical in radio correlators, and yielding a more gentle O(Ng log _2 Ng) scaling, where Na is the number of antennas in the array and Ng is the number of gridpoints in the imaging analysis. This can save orders of magnitude in computation cost for next generation arrays consisting of hundreds or thousands of antennas. However, because antenna signals are mixed in the imaging correlator without creating visibilities, gain correction must be applied prior to imaging, rather than on visibilities post-correlation. We develop the EPICal algorithm to form gain solutions quickly and without ever forming visibilities. This method scales as the number of antennas, and produces results comparable to those from visibilities. We use simulations to demonstrate the EPICal technique and study the noise properties of our gain solutions, showing they are similar to visibility-based solutions in realistic situations. By applying EPICal to 2 s of Long Wavelength Array data, we achieve a 65 per cent dynamic range improvement compared to uncalibrated images, showing this algorithm is a promising solution for next generation instruments.

  7. Implementation of an Optimised Cassegrain System for Radio Telescopes

    CERN Document Server

    Holler, C M; Jones, M E; Grainge, K; Kaneko, T

    2007-01-01

    We present the antenna design for a radio interferometer, the Arcminute Microkelvin Imager, together with its beam pattern measurement. Our aim was to develop a low-cost system with high aperture efficiency and low ground-spill across the frequency range 12-18GHz. We use a modified cassegrain system consisting of a commercially-available paraboloidal primary mirror with a diameter of 3.7m, and a shaped secondary mirror. The secondary mirror is oversized with respect to a ray-optics design and has a surface that is bent towards the primary near its outer edge using a square term for the shaping. The antennas are simple to manufacture and therefore their cost is low. The design increased the antenna gain by approximately 10 per cent compared to a normal Cassegrain system while still maintaining low contamination from ground-spill and using a simple design for the horn.

  8. Simultaneous observations of periodic non-Io decametric radio emission by ground radio telescope URAN-2 and STEREO/WAVES

    Science.gov (United States)

    Panchenko, M.; Brazhenko, A. I.; Rucker, H. O.; Frantzusenko, A.; Shaposhnikov, V. E.; Konovalenko, A. A.

    2013-09-01

    Periodic bursts of the non-Io component of Jovian decametric radio emission (non-Io DAM) is observed as (1) series of arc-like radio bursts with negative frequency drift which reoccur with 1.5% longer period than the Jovian magnetosphere rotation rate, (2) series of bursts with positive frequency drift which reoccur with Jupiter's rotation period and (3) periodic non-arc like radio features [1, 2]. These bursts are typically detected during several Jupiter rotations in decametric frequency range from 4 MHz to 12 - 16 MHz between 300° and 60° of CML. We present simultaneous observations of the periodic non-Io controlled DAM performed by the WAVES radio experiment onboard the two STEREO spacecraft and the groundbased radio telescope URAN-2 (Poltava, Ukraine) operated in the decametric frequency range. URAN-2 with an effective area of about 30000 m2 consists of 512 broadband crossed dipoles and equipped with the high performance digital radio spectrometer with polarization measurement capability. During the observation campaign Sep., 2012 - Apr., 2013 URAN-2 recorded a large amount of Jovian DAM events with the high time-frequency resolution (4 kHz - 100 ms) in a frequency range 8-32 MHz. In the same time the two spatially separated STEREO spacecraft was able to observe DAM in the frequency range up to 16 MHz. The first analysis of the acquired stereoscopic observations is presented. In particular, we show one episode when the periodic non-arc DAM was recorded together with long lasting Jovian narrow band (NB) emissions. These NB emission was observed at the high frequency cutoff of DAM and can be interpreted as propagation of the decametric radiation in the Jovian ionosphere [3]. We discuss the possible relations between the observed NB events and the periodic non-Io controlled Jovian decametric radio emission.

  9. A High Speed Networked Signal Processing Platform for Multi-element Radio Telescopes

    CERN Document Server

    Prasad, Peeyush; 10.1007/s10686-011-9216-7

    2011-01-01

    A new architecture is presented for a Networked Signal Processing System (NSPS) suitable for handling the real-time signal processing of multi-element radio telescopes. In this system, a multi-element radio telescope is viewed as an application of a multi-sensor, data fusion problem which can be decomposed into a general set of computing and network components for which a practical and scalable architecture is enabled by current technology. The need for such a system arose in the context of an ongoing program for reconfiguring the Ooty Radio Telescope (ORT) as a programmable 264-element array, which will enable several new observing capabilities for large scale surveys on this mature telescope. For this application, it is necessary to manage, route and combine large volumes of data whose real-time collation requires large I/O bandwidths to be sustained. Since these are general requirements of many multi-sensor fusion applications, we first describe the basic architecture of the NSPS in terms of a Fusion Tree ...

  10. Reducing Effects of Cross-Talk in a Radio Telescope Using Walsh Modulation

    Science.gov (United States)

    Chaudhari, Sandeep C.; Gupta, Yashwant; Kumar, Ajith; Shinde, Navnath D.; Gupta, Sweta; Vishwakarma, Ajay

    Traditional Walsh technique is used to eliminate cross-talk in a array of radio telescope where achieving synchronization between modulator and demodulator without compromising sensitivity is a real challenge. The paper describes a novel approach named Walsh Delay Hunting (WDH) to synchronize independently running modulator and demodulator with no additional hardware. This approach is unique and can easily be implemented in any existing radio telescope with minimal changes, thus by putting Walsh modulator at telescope and demodulation can be done in digital back-end. The scheme greatly reduces antenna electronics and overhead of sending synchronizing Walsh start pulse back to center station and vice versa. The paper describes WDH method and its feasibility study for Giant Meterwave Radio Telescope (GMRT) along with test results. The modulator is a low cost CPLD-based module and demodulation is done in a Reconfigurable Open Architecture Computing Hardware (ROACH)-based digitizer and packetizer. The scheme requires noise injection facility before modulator, which GMRT has for antenna calibration.

  11. Modeling the rail surface unevenness of a high-precision radio telescope

    Science.gov (United States)

    Li, Na; Li, Peng; Wu, Jiang; Duan, Bao-Yan

    2017-02-01

    This study proposed a coarse-fine mixed model for describing the rail surface unevenness of an ultra-large fully steerable radio telescope (Qi Tai Telescope) with a diameter of 110 meters. The rail surface unevenness includes information on error arising from two different scales, i.e., the long-period-short-change and the short-period-long-change. Consequently, in this study an idea of a mixed model was proposed, in which trigonometric and fractal functions were, respectively, used to describe information on error from two scales. Key parameters were determined by using the least squares method and the wavelet transform method, and finally, a specific mathematical expression of the model was obtained by optimization. To validate the effectiveness of the new modeling method, the mixed model was then used to describe the rails of the Green Bank Telescope, the Large Millimeter Telescope, and a radio telescope in Miyun, Beijing. A comparative study revealed that the maximum error was less than 15%, thus the result was superior to those of existing modeling methods.

  12. Improving the Planetary Ephemeris with VLBA Astrometry of Spacecraft

    Science.gov (United States)

    Jones, Dayton; Folkner, William M.; Jacobson, Robert A.; Jacobs, Christopher S.; Dhawan, Vivek; Romney, Jon; Fomalont, Ed

    2016-10-01

    Improvements to the planetary ephemeris support dynamical studies of the solar system, pulsar timing, tests of general relativity, occultation and eclipse predictions, and interplanetary spacecraft navigation. We have been observing the Cassini spacecraft orbiting Saturn for over a decade using the NRAO Very Long Baseline Array to obtain positions with nano-radian precision. These radio positions are tied to the extragalactic International Celestial Reference Frame (ICRF), and are combined with solutions for Cassini's orbit about Saturn from DSN Doppler tracking to obtain ICRF positions for the Saturn system barycenter. These observations have improved our knowledge of the orientation of Saturn's orbital plane, which had been the dominant error in Saturn's orbit, to a level of 0.25 milli-arcseconds. This is comparable to the accuracy of inner planet orbits in the ephemeris, and an order of magnitude improvement over Saturn's pre-VLBA orbit accuracy. We will continue periodic VLBA astrometric observations of Cassini until the end of mission in late 2017. We are about to begin a series of similar VLBA observations of the Juno spacecraft while it orbits Jupiter. As with Cassini and Saturn, Juno will provide the first long-term series of high precision position measurements of Jupiter. (Although the Galileo spacecraft orbited Jupiter for several years, the loss of its high gain antenna prevented high precision VLBI astrometry.) Combining Juno observations with a single-epoch position measurement from the Ulysses spacecraft flyby in 1992 will allow us to cover nearly a quarter of Jupiter's orbit. We expect to obtain a factor of several improvement in the accuracy of Jupiter's orbit from VLBA observations of Juno. This work has been supported by NASA grant NNX15AJ11G to the Space Science Institute in Boulder, CO. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. The VLBA is part of the

  13. RadioAstron -- a Telescope with a Size of 300 000 km: Main Parameters and First Observational Results

    CERN Document Server

    Kardashev, N S; 10.1134/S1063772913030025

    2013-01-01

    The Russian Academy of Sciences and Federal Space Agency, together with the participation of many international organizations, worked toward the launch of the RadioAstron orbiting space observatory with its onboard 10-m reflector radio telescope from the Baikonur cosmodrome on July 18, 2011. Together with some of the largest ground-based radio telescopes and a set of stations for tracking, collecting, and reducing the data obtained, this space radio telescope forms a multi-antenna ground-space radio interferometer with extremely long baselines, making it possible for the first time to study various objects in the Universe with angular resolutions a million times better than is possible with the human eye. The project is targeted at systematic studies of compact radio-emitting sources and their dynamics. Objects to be studied include supermassive black holes, accretion disks, and relativistic jets in active galactic nuclei, stellar-mass black holes, neutron stars and hypothetical quark stars, regions of format...

  14. Measurements of electronic properties of the Miyun 50 m Radio Telescope

    Institute of Scientific and Technical Information of China (English)

    Xi-Zhen Zhang; Xin-Ying Zhu; De-Qing Kong; Lei Zheng; Cheng Yao; Hong-Bo Zhang; Yan Su; Ting-Yi Piao

    2009-01-01

    Measurement results of some properties of the Miyun 50 m radio telescope (MRT50) of the National Astronomical Observatories, such as pointing calibration, an-tenna beams, system noise temperature, gain and gain variations with elevation are intro-duced. By using a new de-convolution technique developed by our group, the broadening effect on measured beams caused by the width of an extended radio source has been re-moved so that we obtained higher accuracy on the measurements of MRT50 beams.

  15. Single-Dish Radio Polarimetry in the F-GAMMA Program with the Effelsberg 100-m Radio Telescope

    Directory of Open Access Journals (Sweden)

    Beuchert Tobias

    2013-12-01

    Full Text Available Studying the variability of polarized AGN jet emission in the radio band is crucial for understanding the dynamics of moving shocks as well as the structure of the underlying magnetic field. The 100-m Effelsberg Telescope is a high-quality instrument for studying the long-term variability of both total and polarized intensity as well as the electric-vector position angle. Since 2007, the F-GAMMA program has been monitoring the linear polarized emission of roughly 60 blazars at 11 frequencies between 2.7 and 43 GHz. Here, we describe the calibration of the polarimetric data at 5 and 10 GHz and the resulting F-GAMMA full-Stokes light curves for the exemplary case of the radio galaxy 3C 111.

  16. A survey of Radio Recombination Lines using Ooty Radio Telescope at 328 MHz in the Inner Galaxy

    CERN Document Server

    Baddi, Raju

    2012-01-01

    A survey of radio recombination lines in the Galactic plane with longitude $-32^o < l < +80^o$ and latitude $b<\\pm3^o$ using Ooty Radio Telescope(ORT) at 328 MHz has been reported. ORT observations were made using a New Digital Backend(NDB) augmented to it recently. With NDB ORT had a beam of $2^o.3 \\times 2^o.2 sec(\\delta)$ and a passband of $\\sim$1 MHz in the spectral line mode. The above mentioned Galactic region was divided into $\\sim 2^o \\times 2^o$ patches with the ORT beam pointed to the center. The ORT observations form a study of distribution of extended low-density warm-ionized medium(ELDWIM) in the inner Galaxy using H271$\\alpha$ RL. By obtaining kinematical distances using $V_{LSR}$ of the H271$\\alpha$ RLs the distribution of ELDWIM clouds within the inner Galaxy has been deduced for the region given above.

  17. Error analysis and distribution of the driving mechanism for large spherical radio telescope active reflector

    Institute of Scientific and Technical Information of China (English)

    Huang Peng; Tang Xiaoqiang; Wang Liping; Yao Rui

    2008-01-01

    In order to reduce the cost, 3-PRS mechanism is introduced into the application of supporting the active reflector unit of large radio telescope. The kinematic model of 3-PRS mechanism with rotational joint errors is derived to solve the error problem in actual engineering application. Then based on the error model, inverse and forward kinematics are analyzed. Because the solutions can not be analytically expressed, a numerical method is applied. Afterwards, the parasitic motion errors are analyzed using search method and empirical formulas of the maximum parasitic motion error are put forward. Finally, the tolerance is distributed using empirical formulas to avoid interference between adjacent reflector units. The analyses provide a theoretical basis for the design and installation of large radio telescope active reflector.

  18. Correlated Oscillations Due to Similar Multipath Effects Seen in Two Widely Separated Radio Telescopes

    Science.gov (United States)

    Diep, P. N.; Phuong, N. T.; Darriulat, P.; Nhung, P. T.; Anh, P. T.; Dong, P. N.; Hoai, D. T.; Thao, N. T.

    2014-07-01

    A multipath mechanism similar to that used in Australia sixty years ago by the Sea-cliff Interferometer is shown to generate correlations between the periods of oscillations observed by two distant radio telescopes pointed to the Sun. The oscillations are the result of interferences between the direct wave detected in the main antenna lobe and its reflection on ground detected in a side lobe. A model is made of such oscillations in the case of two observatories located at equal longitudes and opposite tropical latitudes, respectively in Ha Noi (Viet Nam) and Learmonth (Australia), where similar radio telescopes are operated at 1.4 GHz. Simple specular reflection from ground is found to give a good description of the observed oscillations and to explain correlations that had been previously observed and for which no satisfactory interpretation, instrumental or other, had been found.

  19. PONDER - A Real time software backend for pulsar and IPS observations at the Ooty Radio Telescope

    CERN Document Server

    Naidu, Arun; Manoharan, P K; Krishnakumar, M A

    2015-01-01

    This paper describes a new real-time versatile backend, the Pulsar Ooty Radio Telescope New Digital Efficient Receiver (PONDER), which has been designed to operate along with the legacy analog system of the Ooty Radio Telescope (ORT). PONDER makes use of the current state of the art computing hardware, a Graphical Processing Unit (GPU) and sufficiently large disk storage to support high time resolution real-time data of pulsar observations, obtained by coherent dedispersion over a bandpass of 16 MHz. Four different modes for pulsar observations are implemented in PONDER to provide standard reduced data products, such as time-stamped integrated profiles and dedispersed time series, allowing faster avenues to scientific results for a variety of pulsar studies. Additionally, PONDER also supports general modes of interplanetary scintillation (IPS) measurements and very long baseline interferometry data recording. The IPS mode yields a single polarisation correlated time series of solar wind scintillation over a b...

  20. Testing a modified ASKAP Mark II phased array feed on the 64 m Parkes radio telescope

    CERN Document Server

    Chippendale, A P; Deng, X; Leach, M; Reynolds, J E; Kramer, M; Tzioumis, T

    2016-01-01

    We present the first installation and characterization of a phased array feed (PAF) on the 64 m Parkes radio telescope. The combined system operates best between 0.8 GHz and 1.74 GHz where the beamformed noise temperature is between 45 K and 60 K, the aperture efficiency ranges from 70% to 80%, and the effective field of view is 1.4 deg$^2$ at 1310 MHz. After a 6-month trial observing program at Parkes, the PAF will be installed on the 100 m antenna at Effelsberg. This is the first time a PAF has been installed on a large single-antenna radio telescope and made available to astronomers.

  1. Correlated oscillations due to similar multi-path effects seen in two widely separated radio telescopes

    CERN Document Server

    Diep, P N; Darriulat, P; Nhung, P T; Anh, P T; Dong, P N; Hoai, D T; Thao, N T

    2014-01-01

    A multipath mechanism similar to that used in Australia sixty years ago by the Sea-cliff Interferometer is shown to generate correlations between the periods of oscillations observed by two distant radio telescopes pointed to the Sun. The oscillations are the result of interferences between the direct wave detected in the main antenna lobe and its reflection on ground detected in a side lobe. A model is made of such oscillations in the case of two observatories located at equal longitudes and opposite tropical latitudes, respectively in Ha Noi (Viet Nam) and Learmonth (Australia), where similar radio telescopes are operated at 1.4 GHz. Simple specular reflection from ground is found to give a good description of the observed oscillations and to explain correlations that had been previously observed and for which no satisfactory interpretation, instrumental or other, had been found.

  2. Simultaneous observations of solar sporadic radio emission by the radio telescopes UTR-2, URAN-2 and NDA within the frequency range 8-42 MHz

    Science.gov (United States)

    Melnik, V.; Konovalenko, A.; Brazhenko, A.; Briand, C.; Dorovskyy, V.; Zarka, P.; Denis, L.; Bulatzen, V.; Frantzusenko, A.; Rucker, H.; Stanislavskyy, A.

    2012-09-01

    From 25 June till 12 August 2011 sporadic solar radio emission was observed simultaneously by three separate radio telescopes: UTR-2 (Kharkov, Ukraine), URAN-2 (Poltava, Ukraine) and NDA (Nancay, France). During these observations some interesting phenomena were observed. Some of them are discussed in this paper.

  3. MECHANICAL ANALYSIS OF ORBIT TRACKING MOVEMENT OF FEED SYSTEM IN LARGE SPHERICAL RADIO-TELESCOPE

    Institute of Scientific and Technical Information of China (English)

    LIU Ming-zhi; SHEN Yu-ru; LIU Jun; NA Bai

    2005-01-01

    The curve equation and its mechanics analysis of suspended-cable under the condition of end load are given. Then on the basis of it, the mechanical analysis of suspended-cable system for large spherical radio-telescope is studied, and procedures of the control for the orbit tracking movement of the line feed in large spherical radiotelescope are given. The validity of the results mentioned above is confirmed by means of computer simulations.

  4. Reliability-centered maintenance for ground-based large optical telescopes and radio antenna arrays

    Science.gov (United States)

    Marchiori, G.; Formentin, F.; Rampini, F.

    2014-07-01

    In the last years, EIE GROUP has been more and more involved in large optical telescopes and radio antennas array projects. In this frame, the paper describes a fundamental aspect of the Logistic Support Analysis (LSA) process, that is the application of the Reliability-Centered Maintenance (RCM) methodology for the generation of maintenance plans for ground-based large optical telescopes and radio antennas arrays. This helps maintenance engineers to make sure that the telescopes continue to work properly, doing what their users require them to do in their present operating conditions. The main objective of the RCM process is to establish the complete maintenance regime, with the safe minimum required maintenance, carried out without any risk to personnel, telescope and subsystems. At the same time, a correct application of the RCM allows to increase the cost effectiveness, telescope uptime and items availability, and to provide greater understanding of the level of risk that the organization is managing. At the same time, engineers shall make a great effort since the initial phase of the project to obtain a telescope requiring easy maintenance activities and simple replacement of the major assemblies, taking special care on the accesses design and items location, implementation and design of special lifting equipment and handling devices for the heavy items. This maintenance engineering framework is based on seven points, which lead to the main steps of the RCM program. The initial steps of the RCM process consist of: system selection and data collection (MTBF, MTTR, etc.), definition of system boundaries and operating context, telescope description with the use of functional block diagrams, and the running of a FMECA to address the dominant causes of equipment failure and to lay down the Critical Items List. In the second part of the process the RCM logic is applied, which helps to determine the appropriate maintenance tasks for each identified failure mode. Once

  5. First observations of the water masers with the Urumqi 25m radio telescope

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A new radio spectral receiving system has been installed on the 25 m radio telescope of the Urumqi Astronomical Observatory. The back end is a surface acoustic wave chirp transform spectrometer (SAW CZT), used for the first time in radio astronomy. The calibration of the line observations has carefully been investigated for the new-type spectrometer. In order to test the feasibility of the prototype spectrometer, we observed water maser emission from a number of known Galactic sources. We describe the observed spectra of W49N, W3(OH), 2248+600 and 1909+090. We found that W49N spectrum showed high-velocity features ranging from -330 to 146 km s-1. In comparison with the spectra observed by Medicina, the feature at the LSR velocity -52 km s-1 in the W3(OH) presented the rapid variation in flux density.

  6. The Goldstone-Apple Valley Radio Telescope (GAVRT) Science Education Partnership

    Science.gov (United States)

    MacLaren, D. C.; Klein, M. J.; Wolff, S. E.

    2004-12-01

    The Goldstone Apple Valley Radio Telescope Project (GAVRT) offers a unique opportunity for students in grades K through 12 to not only learn about science through radio astronomy, but to actually do it. GAVRT is a science education partnership involving NASA, the Jet Propulsion Laboratory (JPL) and the Lewis Center for Educational Research (LCER). Following a preparation period using curriculum especially written for the Project, teachers connect to the Operations Control Center at LCER where trained operators assist the students to conduct remotely controlled radio astronomy observations using a 34-m diameter antenna located at the Goldstone Deep Space Communications Complex. Students use computers to record extremely faint radio waves collected by the radio telescope and analyze real data. Scientists at JPL and other research institutions ultimately validate and incorporate the data into their research. Through this process students have the opportunity to become part of a science/education team, participating with scientists in ongoing missions and special observing campaigns. Their measurements are often included in papers appearing in major scientific journals. They learn that they can make valuable contributions to the world of science. This presentation will detail the types of data and the "campaigns" in which the students are conducting observations of the radiation belts of Jupiter, the deep atmosphere of Uranus and Saturn, and the time variations in the radio emission from distant Quasars. It will describe how the student-produced data are valued by the scientists and how the involvement of the scientists impacts the attitudes and abilities of students in the classroom. The JPL contribution to this paper was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  7. The VLBA Imaging and Polarimetry Survey

    Data.gov (United States)

    National Aeronautics and Space Administration — The VLBA Imaging and Polarimetry Survey, VIPS for short, is a combined 5 GHz and 15 GHz survey with the Very Long Baseline Array of ~1100 active galactic nuclei...

  8. The Likelihood Ratio as a tool for Radio Continuum Surveys with SKA precursor telescopes

    CERN Document Server

    McAlpine, Kim; Jarvis, Matthew J; Bonfield, David G; Fleuren, Simone

    2012-01-01

    In this paper we investigate the performance of the likelihood ratio method as a tool for identifying optical and infrared counterparts to proposed radio continuum surveys with SKA precursor and pathfinder telescopes. We present a comparison of the infrared counterparts identified by the likelihood ratio in the VISTA Deep Extragalactic Observations (VIDEO) survey to radio observations with 6, 10 and 15 arcsec resolution. We cross-match a deep radio catalogue consisting of radio sources with peak flux density $>$ 60 $\\mu$Jy with deep near-infrared data limited to $K_{\\mathrm{s}}\\lesssim$ 22.6. Comparing the infrared counterparts from this procedure to those obtained when cross-matching a set of simulated lower resolution radio catalogues indicates that degrading the resolution from 6 arcsec to 10 and 15 arcsec decreases the completeness of the cross-matched catalogue by approximately 3 and 7 percent respectively. When matching against shallower infrared data, comparable to that achieved by the VISTA Hemisphere...

  9. A low frequency radio telescope at Mauritius for a Southern sky survey

    CERN Document Server

    Golap, K; Sachdev, S; Dodson, R; Sastry, C V; Sastry, Ch. V.

    1998-01-01

    A new, meter-wave radio telescope has been built in the North-East of Mauritius, an island in the Indian ocean, at a latitude of -20.14 deg. The Mauritius Radio Telescope (MRT) is a Fourier Synthesis T-shaped array, consisting of a 2048 m long East-West arm and a 880 m long South arm. In the East-West arm 1024 fixed helices are arranged in 32 groups and in the South arm 16 trolleys, with four helices on each, which move on a rail are used. A 512 channel digital complex correlation receiver is used to measure the visibility function. At least 60 days of observing are required for obtaining the visibilities up to 880 m spacing. The Fourier transform of the calibrated visibilities produces a map of the area of the sky under observation with a synthesized beam width 4'X 4.6'sec(dec+20.14) at 151.5 MHz. The primary objective of the telescope is to produce a sky survey in the declination range -70 deg to -10 deg with a point source sensitivity of about 200 mJy (3-sigma level). This will be the southern sky equivale...

  10. Discovery of two millisecond pulsars in Fermi sources with the Nancay Radio Telescope

    CERN Document Server

    Cognard, I; Johnson, T J; Smith, D A; Venter, C; Harding, A K; Wolff, M T; Cheung, C C; Donato, D; Abdo, A A; Ballet, J; Camilo, F; Desvignes, G; Dumora, D; Ferrara, E C; Freire, P C C; Grove, J E; Keith, M; Kramer, M; Lyne, A G; Michelson, P F; Parent, D; Ransom, S M; Ray, P S; Romani, R W; Parkinson, P M Saz; Stappers, B W; Theureau, G; Thompson, D J; Weltevrede, P; Wood, K S

    2011-01-01

    We report the discovery of two millisecond pulsars in a search for radio pulsations at the positions of \\emph{Fermi Large Area Telescope} sources with no previously known counterparts, using the Nan\\c{c}ay radio telescope. The two millisecond pulsars, PSRs J2017+0603 and J2302+4442, have rotational periods of 2.896 and 5.192 ms and are both in binary systems with low-eccentricity orbits and orbital periods of 2.2 and 125.9 days respectively, suggesting long recycling processes. Gamma-ray pulsations were subsequently detected for both objects, indicating that they power the associated \\emph{Fermi} sources in which they were found. The gamma-ray light curves and spectral properties are similar to those of previously-detected gamma-ray millisecond pulsars. Detailed modeling of the observed radio and gamma-ray light curves shows that the gamma-ray emission seems to originate at high altitudes in their magnetospheres. Additionally, X-ray observations revealed the presence of an X-ray source at the position of PSR ...

  11. "RadioAstron"-A telescope with a size of 300 000 km: Main parameters and first observational results

    Science.gov (United States)

    Kardashev, N. S.; Khartov, V. V.; Abramov, V. V.; Avdeev, V. Yu.; Alakoz, A. V.; Aleksandrov, Yu. A.; Ananthakrishnan, S.; Andreyanov, V. V.; Andrianov, A. S.; Antonov, N. M.; Artyukhov, M. I.; Arkhipov, M. Yu.; Baan, W.; Babakin, N. G.; Babyshkin, V. E.; Bartel', N.; Belousov, K. G.; Belyaev, A. A.; Berulis, J. J.; Burke, B. F.; Biryukov, A. V.; Bubnov, A. E.; Burgin, M. S.; Busca, G.; Bykadorov, A. A.; Bychkova, V. S.; Vasil'kov, V. I.; Wellington, K. J.; Vinogradov, I. S.; Wietfeldt, R.; Voitsik, P. A.; Gvamichava, A. S.; Girin, I. A.; Gurvits, L. I.; Dagkesamanskii, R. D.; D'Addario, L.; Giovannini, G.; Jauncey, D. L.; Dewdney, P. E.; D'yakov, A. A.; Zharov, V. E.; Zhuravlev, V. I.; Zaslavskii, G. S.; Zakhvatkin, M. V.; Zinov'ev, A. N.; Ilinen, Yu.; Ipatov, A. V.; Kanevskii, B. Z.; Knorin, I. A.; Casse, J. L.; Kellermann, K. I.; Kovalev, Yu. A.; Kovalev, Yu. Yu.; Kovalenko, A. V.; Kogan, B. L.; Komaev, R. V.; Konovalenko, A. A.; Kopelyanskii, G. D.; Korneev, Yu. A.; Kostenko, V. I.; Kotik, A. N.; Kreisman, B. B.; Kukushkin, A. Yu.; Kulishenko, V. F.; Cooper, D. N.; Kut'kin, A. M.; Cannon, W. H.; Larionov, M. G.; Lisakov, M. M.; Litvinenko, L. N.; Likhachev, S. F.; Likhacheva, L. N.; Lobanov, A. P.; Logvinenko, S. V.; Langston, G.; McCracken, K.; Medvedev, S. Yu.; Melekhin, M. V.; Menderov, A. V.; Murphy, D. W.; Mizyakina, T. A.; Mozgovoi, Yu. V.; Nikolaev, N. Ya.; Novikov, B. S.; Novikov, I. D.; Oreshko, V. V.; Pavlenko, Yu. K.; Pashchenko, I. N.; Ponomarev, Yu. N.; Popov, M. V.; Pravin-Kumar, A.; Preston, R. A.; Pyshnov, V. N.; Rakhimov, I. A.; Rozhkov, V. M.; Romney, J. D.; Rocha, P.; Rudakov, V. A.; Räisänen, A.; Sazankov, S. V.; Sakharov, B. A.; Semenov, S. K.; Serebrennikov, V. A.; Schilizzi, R. T.; Skulachev, D. P.; Slysh, V. I.; Smirnov, A. I.; Smith, J. G.; Soglasnov, V. A.; Sokolovskii, K. V.; Sondaar, L. H.; Stepan'yants, V. A.; Turygin, M. S.; Turygin, S. Yu.; Tuchin, A. G.; Urpo, S.; Fedorchuk, S. D.; Finkel'shtein, A. M.; Fomalont, E. B.; Fejes, I.; Fomina, A. N.; Khapin, Yu. B.; Tsarevskii, G. S.; Zensus, J. A.; Chuprikov, A. A.; Shatskaya, M. V.; Shapirovskaya, N. Ya.; Sheikhet, A. I.; Shirshakov, A. E.; Schmidt, A.; Shnyreva, L. A.; Shpilevskii, V. V.; Ekers, R. D.; Yakimov, V. E.

    2013-03-01

    The Russian Academy of Sciences and Federal Space Agency, together with the participation of many international organizations, worked toward the launch of the RadioAstron orbiting space observatory with its onboard 10-m reflector radio telescope from the Baikonur cosmodrome on July 18, 2011. Together with some of the largest ground-based radio telescopes and a set of stations for tracking, collecting, and reducing the data obtained, this space radio telescope forms a multi-antenna ground-space radio interferometer with extremely long baselines, making it possible for the first time to study various objects in the Universe with angular resolutions a million times better than is possible with the human eye. The project is targeted at systematic studies of compact radio-emitting sources and their dynamics. Objects to be studied include supermassive black holes, accretion disks, and relativistic jets in active galactic nuclei, stellar-mass black holes, neutron stars and hypothetical quark stars, regions of formation of stars and planetary systems in our and other galaxies, interplanetary and interstellar plasma, and the gravitational field of the Earth. The results of ground-based and inflight tests of the space radio telescope carried out in both autonomous and ground-space interferometric regimes are reported. The derived characteristics are in agreement with the main requirements of the project. The astrophysical science program has begun.

  12. GREEN BANK TELESCOPE AND SWIFT X-RAY TELESCOPE OBSERVATIONS OF THE GALACTIC CENTER RADIO MAGNETAR SGR J1745–2900

    Energy Technology Data Exchange (ETDEWEB)

    Lynch, Ryan S.; Archibald, Robert F.; Kaspi, Victoria M.; Scholz, Paul, E-mail: rlynch@physics.mcgill.ca [Department of Physics, McGill University, 3600 University Street, Montreal, Quebec, H3A 2T8 (Canada)

    2015-06-20

    We present results from eight months of Green Bank Telescope 8.7 GHz observations and nearly 18 months of Swift X-ray telescope observations of the radio magnetar SGR J1745–2900. We tracked the radio and X-ray flux density, polarization properties, profile evolution, rotation, and single-pulse behavior. We identified two main periods of activity. The first is characterized by approximately 5.5 months of relatively stable evolution in radio flux density, rotation, and profile shape, while in the second these properties varied substantially. Specifically, a third profile component emerged and the radio flux also became more variable. The single pulse properties also changed, most notably with a larger fraction of pulses with pulse widths ∼5–20 ms in the erratic state. Bright single pulses are well described by a log-normal energy distribution at low energies, but with an excess at high energies. The 2–10 keV flux decayed steadily since the initial X-ray outburst, while the radio flux remained stable to within ∼20% during the stable state. A joint pulsar timing analysis of the radio and X-ray data shows a level of timing noise unprecedented in a radio magnetar, though during the time covered by the radio data alone the timing noise was at a level similar to that observed in other radio magnetars. While SGR J1745–2900 is similar to other radio magnetars in many regards, it differs by having experienced a period of relative stability in the radio that now appears to have ended, while the X-ray properties evolved independently.

  13. VLBA Movies Reveal New Details of Cosmic Jets

    Science.gov (United States)

    2008-01-01

    individual objects. "Before the VLBA was built, we were hindered in our studies of extragalactic jets by the lack of a facility that could do high-quality, regularly-spaced images showing very great detail. The VLBA's capabilities have made it a premier facility for studying these objects out to very large distances, and thus getting a large sample," Lister said. The MOJAVE observations are showing new details about the structures of magnetic fields in the jets. This is important, because magnetic fields are thought to play vital roles in the acceleration of the particles and in shaping the jets. The time-lapse movies have revealed a variety of interesting behavior in the jets. For example, the powerful radio galaxy called 3C279 emitted a bright feature that moved along a straight path for 15 years, then suddenly brightened, showed a change in its magnetic field, and sped off in a new direction. Other jets shoot successive bright features that move outward in curved paths. Some features in jets are seen to break apart. "These detailed movies of complex motions are real-world data that allow researchers to refine their computer simulations of the jets, leading to a far better understanding of the physics involved in such impressive cosmic particle accelerators," Lister said. The MOJAVE data will prove valuable for comparison with the gamma-ray information to be collected by NASA's upcoming GLAST satellite. "Using the MOJAVE data along with data from other ground-based and orbiting observatories at different wavelengths is bringing the studies of galactic jets into a new era," Lister concluded. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

  14. Radio properties of the magnetar near Sagittarius A* from observations with the Australia Telescope Compact Array

    CERN Document Server

    Shannon, Ryan M

    2013-01-01

    We have carried out observations of the newly-discovered magnetar in the direction of Sagittarius A* using the Australia Telescope Compact Array in four frequency bands from 4.5 to 20 GHz. Radio pulsations are clearly detected at all frequencies. We measure the pulsar's dispersion measure to be 1650 +/- 50 cm^-3 pc, the highest of any of the known pulsars. Once Faraday rotation has been taken into account, the pulse profile is almost completely linearly polarized at all frequencies and has a small degree of circular polarization. The rotation measure of -67000 +/- 500 rad m^-2 is the largest ever measured in an astronomical object. The combination of the dispersion and rotation measures imples an integrated magnetic field strength of -50 uG along the line of sight. This object therefore joins the small class of radio emitting magnetars. Follow-up observations using single dishes are underway and will no doubt characterise this object further.

  15. A Real-Time, GPU-Based, Non-Imaging Back-End for Radio Telescopes

    CERN Document Server

    Magro, Alessio

    2014-01-01

    Since the discovery of RRATs, interest in single pulse radio searches has increased dramatically. Due to the large data volumes generated by these searches, especially in planned surveys for future radio telescopes, such searches have to be conducted in real-time. This has led to the development of a multitude of search techniques and real-time pipeline prototypes. In this work we investigated the applicability of GPUs. We have designed and implemented a scalable, flexibile, GPU-based, transient search pipeline composed of several processing stages, including RFI mitigation, dedispersion, event detection and classification, as well as data quantisation and persistence. These stages are encapsulated as a standalone framework. The optimised GPU implementation of direct dedispersion achieves a speedup of more than an order of magnitude when compared to an optimised CPU implementation. We use a density-based clustering algorithm, coupled with a candidate selection mechanism to group detections caused by the same ...

  16. SPAN512: A new mid-latitude pulsar survey with the Nancay Radio Telescope

    CERN Document Server

    Desvignes, Gregory; Champion, David; Lazarus, Patrick; Lespagnol, Patrice; Smith, David A; Theureau, Gilles

    2012-01-01

    We present an ongoing survey with the Nan\\c{c}ay Radio Telescope at L-band. The targeted area is $74^\\circ \\lesssim l <150^\\circ$ and $3.5^\\circ < |b| < 5^\\circ$. This survey is characterized by a long integration time (18 min), large bandwidth (512 MHz) and high time and frequency resolution (64 $\\mu$s and 0.5 MHz) giving a nominal sensitivity limit of 0.055 mJy for long period pulsars. This is about 2 times better than the mid-latitude HTRU survey, and is designed to be complementary with current large scale surveys. This survey will be more sensitive to transients (RRATs, intermittent pulsars), distant and faint millisecond pulsars as well as scintillating sources (or any other kind of radio faint sources) than all previous short-integration surveys.

  17. Rayleigh beacon for measuring the surface profile of a radio telescope.

    Science.gov (United States)

    Padin, S

    2014-12-01

    Millimeter-wavelength Rayleigh scattering from water droplets in a cloud is proposed as a means of generating a bright beacon for measuring the surface profile of a radio telescope. A λ=3  mm transmitter, with an output power of a few watts, illuminating a stratiform cloud, can generate a beacon with the same flux as Mars in 10 GHz bandwidth, but the beacon has a narrow line width, so it is extremely bright. The key advantage of the beacon is that it can be used at any time, and positioned anywhere in the sky, as long as there are clouds.

  18. Design and implementation of an error-compensating subreflector for the NRAO 12-m radio telescope.

    Science.gov (United States)

    Mayer, C. E.; Emerson, D. T.; Davis, J. H.

    1994-05-01

    This paper describes the measurement of the surface shape of the primary reflector of the NRAO 12-m radio telescope and the use of the measurements to machine the shape of a secondary mirror to compensate for the primary reflector errors. The method known as holography was used with the 38.04-GHz transmitter onboard the geosynchronous Lincoln Experimental Satellite to map the main reflector. The machining of the secondary compensated for the errors in the primary shape, and as a result, at 345 GHz, the axial gain of the instrument was increased by about 50% and the antenna pattern correspondingly improved.

  19. The OH Maser Line Receiving System for the Urumqi 25m Radio Telescope

    Institute of Scientific and Technical Information of China (English)

    Hong-Bo Zhang; Jarken Esimbek; Jian-Jun Zhou; Xing-Wu Zhen; Xi-Zhen Zhang; Wen-Jie Yang

    2005-01-01

    A maser spectral line system is newly implemented on the Urumqi 25m Radio Telescope. The system consists mainly of a cooling receiver and a 4096channels digital correlation spectrometer. The frequency resolution of the spectrometer at the maximum signal bandwidth of 80 MHz is 19.5 kHz. After careful calibrations observation at the 1665MHz OH maser emission was made towards a number of sources, including W49N and W75N. The observed results demonstrate that the digital correlation spectrometer is suitable for astronomical spectral line observations.

  20. The control system of the 3 mm band SIS receiver for the Sardinia Radio Telescope

    Science.gov (United States)

    Ladu, A.; Ortu, P.; Saba, A.; Pili, M.; Guadiomonte, F.; Navarrini, A.; Urru, E.; Pisanu, T.; Valente, G.; Marongiu, P.; Mazzarella, G.

    2016-07-01

    We present the control system of the 84-116 GHz (3 mm band) Superconductor-Insulator-Superconductor (SIS) heterodyne receiver to be installed at the Gregorian focus of the Sardinia Radio Telescope (SRT). The control system is based on a single-board computer from Raspberry, on microcontrollers from Arduino, and on a Python program for communication between the receiver and the SRT antenna control software, which remotely controls the backshorttuned SIS mixer, the receiver calibration system and the Local Oscillator (LO) system.

  1. Identifying Compact Symmetric Objects from the VLBA Imaging and Polarization Survey

    CERN Document Server

    Tremblay, S E; Helmboldt, J F; Fassnacht, C D; Romani, R W; 10.1002/asna.200811157

    2009-01-01

    Compact Symmetric Objects (CSOs) are small (less than 1 kpc) radio sources which have symmetric double lobes or jets. The dominant theory for the small size of these objects is that they are young radio sources which could grow into larger radio galaxies, but the currently small population of known CSOs makes it difficult to definitively determine whether or not this is the case. While a greater number of Gigahertz peaked sources can be identified by sifting through spectral surveys, this yields none of the dynamics of the sources, and also brings Quasars into the sample, which although interesting are peaked around 1 Gigahertz for very different reasons. We have used the 5 GHz VLBA Imaging and Polarization Survey (VIPS) to identify 103 CSO candidates morphologically, and are following up on these sources with multifrequency VLBA observations to confirm CSO identifications and to study their dynamics. The identification of candidates from within the survey will be discussed, as well as preliminary results fro...

  2. Development of a Multi-frequency Interferometer Telescope for Radio Astronomy (MITRA)

    Science.gov (United States)

    Ingala, Dominique Guelord Kumamputu

    2015-03-01

    This dissertation describes the development and construction of the Multi-frequency Interferometer Telescope for Radio Astronomy (MITRA) at the Durban University of Technology. The MITRA station consists of 2 antenna arrays separated by a baseline distance of 8 m. Each array consists of 8 Log-Periodic Dipole Antennas (LPDAs) operating from 200 MHz to 800 MHz. The design and construction of the LPDA antenna and receiver system is described. The receiver topology provides an equivalent noise temperature of 113.1 K and 55.1 dB of gain. The Intermediate Frequency (IF) stage was designed to produce a fixed IF frequency of 800 MHz. The digital Back-End and correlator were implemented using a low cost Software Defined Radio (SDR) platform and Gnu-Radio software. Gnu-Octave was used for data analysis to generate the relevant received signal parameters including total power, real, and imaginary, magnitude and phase components. Measured results show that interference fringes were successfully detected within the bandwidth of the receiver using a Radio Frequency (RF) generator as a simulated source. This research was presented at the IEEE Africon 2013 / URSI Session Mauritius, and published in the proceedings.

  3. Back to the future: science and technology directions for radio telescopes of the twenty-first century

    Science.gov (United States)

    Cordes, James M.

    2009-08-01

    The early days of radio astronomy showed incredibly diverse experimentation in ways to sample the electromagnetic spectrum at radio wavelengths. In addition to obtaining adequate sensitivity by building large collection areas, a primary goal also was to achieve sufficient angular resolution to localize radio sources for multi-wavelength identification. This led to many creative designs and the invention of aperture synthesis and VLBI. Some of the basic telescope types remain to the present day, now implemented across the entire radio spectrum from wavelengths of tens of meters to submillimeter wavelengths. In recent years, as always, there is still the drive for greater sensitivity but a primary goal is now to achieve very large fields of view to complement high resolution and frequency coverage, leading to a new phase of experimentation. This is the “back to the future” aspect of current research and development for next-generation radio telescopes. In this paper I summarize the scientific motivations for development of new technology and telescopes since about 1990 and going forward for the next decade and longer. Relevant elements include highly optimized telescope optics and feed antenna designs, innovative fabrication methods for large reflectors and dipole arrays, digital implementations, and hardware vs. software processing. The emphasis will be on meter and centimeter wavelength telescopes but I include a brief discussion of millimeter wavelengths to put the longer wavelength enterprises into perspective. I do not discuss submillimeter wavelengths because they are covered in other papers.

  4. The Engineering Development Array: A Low Frequency Radio Telescope Utilising SKA Precursor Technology

    Science.gov (United States)

    Wayth, Randall; Sokolowski, Marcin; Booler, Tom; Crosse, Brian; Emrich, David; Grootjans, Robert; Hall, Peter J.; Horsley, Luke; Juswardy, Budi; Kenney, David; Steele, Kim; Sutinjo, Adrian; Tingay, Steven J.; Ung, Daniel; Walker, Mia; Williams, Andrew; Beardsley, A.; Franzen, T. M. O.; Johnston-Hollitt, M.; Kaplan, D. L.; Morales, M. F.; Pallot, D.; Trott, C. M.; Wu, C.

    2017-08-01

    We describe the design and performance of the Engineering Development Array, which is a low-frequency radio telescope comprising 256 dual-polarisation dipole antennas working as a phased array. The Engineering Development Array was conceived of, developed, and deployed in just 18 months via re-use of Square Kilometre Array precursor technology and expertise, specifically from the Murchison Widefield Array radio telescope. Using drift scans and a model for the sky brightness temperature at low frequencies, we have derived the Engineering Development Array's receiver temperature as a function of frequency. The Engineering Development Array is shown to be sky-noise limited over most of the frequency range measured between 60 and 240 MHz. By using the Engineering Development Array in interferometric mode with the Murchison Widefield Array, we used calibrated visibilities to measure the absolute sensitivity of the array. The measured array sensitivity matches very well with a model based on the array layout and measured receiver temperature. The results demonstrate the practicality and feasibility of using Murchison Widefield Array-style precursor technology for Square Kilometre Array-scale stations. The modular architecture of the Engineering Development Array allows upgrades to the array to be rolled out in a staged approach. Future improvements to the Engineering Development Array include replacing the second stage beamformer with a fully digital system, and to transition to using RF-over-fibre for the signal output from first stage beamformers.

  5. An innovative, highly sensitive receiver system for the Square Kilometre Array Mid Radio Telescope

    Science.gov (United States)

    Tan, Gie Han; Lehmensiek, Robert; Billade, Bhushan; Caputa, Krzysztof; Gauffre, Stéphane; Theron, Isak P.; Pantaleev, Miroslav; Ljusic, Zoran; Quertier, Benjamin; Peens-Hough, Adriaan

    2016-07-01

    The Square Kilometre Array (SKA) Project is a global science and engineering project realizing the next-generation radio telescopes operating in the metre and centimetre wavelengths regions. This paper addresses design concepts of the broadband, exceptionally sensitive receivers and reflector antennas deployed in the SKA1-Mid radio telescope to be located in South Africa. SKA1-Mid (350 MHz - 13.8 GHz with an option for an upper limit of 24 GHz) will consist of 133 reflector antennas using an unblocked aperture, offset Gregorian configuration with an effective diameter of 15 m. Details on the unblocked aperture Gregorian antennas, low noise front ends and advanced direct digitization receivers, are provided from a system design perspective. The unblocked aperture results in increased aperture efficiency and lower side-lobe levels compared to a traditional on-axis configuration. The low side-lobe level reduces the noise contribution due to ground pick-up but also makes the antenna less susceptible to ground-based RFI sources. The addition of extra shielding on the sub-reflector provides a further reduction of ground pick-up. The optical design of the SKA1-Mid reflector antenna has been tweaked using advanced EM simulation tools in combination with sophisticated models for sky, atmospheric and ground noise contributions. This optimal antenna design in combination with very low noise, partially cryogenic, receivers and wide instantaneous bandwidth provide excellent receiving sensitivity in combination with instrumental flexibility to accommodate a wide range of astronomical observation modes.

  6. Measurements of Antenna Surface for Millimeter-Wave Space Radio Telescope

    CERN Document Server

    Kamegai, Kazuhisa; Doi, Akihiro; Sato, Eiichi

    2011-01-01

    In the construction of a space radio telescope, it is essential to use materials with a low noise factor and high mechanical robustness for the antenna surface. We present the results of measurements of the reflection performance of two candidates for antenna surface materials for use in a radio telescope installed in a new millimeter-wave astronomical satellite, ASTRO-G. To estimate the amount of degradation caused by fluctuations in the thermal environment in the projected orbit of the satellite, a thermal cycle test was carried out for two candidates, namely, copper foil carbon fiber reinforced plastic (CFRP) and aluminum-coated CFRP. At certain points during the thermal cycle test, the reflection loss of the surfaces was measured precisely by using a radiometer in the 41-45 GHz band. In both candidates, cracks appeared on the surface after the thermal cycle test, where the number density of the cracks increased as the thermal cycle progressed. The reflection loss also increased in proportion to the number...

  7. PONDER - A Real time software backend for pulsar and IPS observations at the Ooty Radio Telescope

    Science.gov (United States)

    Naidu, Arun; Joshi, Bhal Chandra; Manoharan, P. K.; Krishnakumar, M. A.

    2015-06-01

    This paper describes a new real-time versatile backend, the Pulsar Ooty Radio Telescope New Digital Efficient Receiver (PONDER), which has been designed to operate along with the legacy analog system of the Ooty Radio Telescope (ORT). PONDER makes use of the current state of the art computing hardware, a Graphical Processing Unit (GPU) and sufficiently large disk storage to support high time resolution real-time data of pulsar observations, obtained by coherent dedispersion over a bandpass of 16 MHz. Four different modes for pulsar observations are implemented in PONDER to provide standard reduced data products, such as time-stamped integrated profiles and dedispersed time series, allowing faster avenues to scientific results for a variety of pulsar studies. Additionally, PONDER also supports general modes of interplanetary scintillation (IPS) measurements and very long baseline interferometry data recording. The IPS mode yields a single polarisation correlated time series of solar wind scintillation over a bandwidth of about four times larger (16 MHz) than that of the legacy system as well as its fluctuation spectrum with high temporal and frequency resolutions. The key point is that all the above modes operate in real time. This paper presents the design aspects of PONDER and outlines the design methodology for future similar backends. It also explains the principal operations of PONDER, illustrates its capabilities for a variety of pulsar and IPS observations and demonstrates its usefulness for a variety of astrophysical studies using the high sensitivity of the ORT.

  8. 21-cm Observations with the Morehead Radio Telescope: Involving Undergraduates in Observing Programs

    Science.gov (United States)

    Malphrus, B. K.; Combs, M. S.; Kruth, J.

    2000-12-01

    Herein we report astronomical observations made by undergraduate students with the Morehead Radio Telescope (MRT). The MRT, located at Morehead State University, Morehead, Kentucky, is small aperture (44-ft.) instrument designed by faculty, students, and industrial partners to provide a research instrument and active laboratory for undergraduate astronomy, physics, pre-engineering, and computer science students. Small aperture telescopes like the MRT have numerous advantages as active laboratories and as research instruments. The benefits to students are based upon a hands-on approach to learning concepts in astrophysics and engineering. Students are provided design and research challenges and are allowed to pursue their own solutions. Problem-solving abilities and research design skills are cultivated by this approach. Additionally, there are still contributions that small aperture centimeter-wave instruments can make. The MRT operates over a 6 MHz bandwidth centered at 1420 MHz (21-cm), which corresponds to the hyperfine transition of atomic hydrogen (HI). The HI spatial distribution and flux density associated with cosmic phenomena can be observed and mapped. The dynamics and kinematics of celestial objects can be investigated by observing over a range of frequencies (up to 2.5 MHz) with a 2048-channel back-end spectrometer, providing up to 1 KHz frequency resolution. The sensitivity and versatility of the telescope design facilitate investigation of a wide variety of cosmic phenomena, including supernova remnants, emission and planetary nebulae, extended HI emission from the Milky Way, quasars, radio galaxies, and the sun. Student observations of galactic sources herein reported include Taurus A, Cygnus X, and the Rosette Nebula. Additionally, we report observations of extragalactic phenomena, including Cygnus A, 3C 147, and 3C 146. These observations serve as a performance and capability test-bed of the MRT. In addition to the astronomical results of these

  9. Study on a novel panel support concept for radio telescopes with active surface

    Science.gov (United States)

    Yang, Dehua; Zhou, Guohua; Okoh, Daniel; Li, Guoping; Cheng, Jingquan

    2010-07-01

    Generally, panels of radio telescopes are mainly shaped in trapezoid and each is supported/positioned by four adjustors beneath its vertexes. Such configuration of panel supporting system is essentially hyper-static, and the panel is overconstrained from a kinematic point of view. When the panel is to be adjusted and/or actuated, it will suffer stress from its adjusters and hence its shape is to be distorted. This situation is not desirable for high precision panels, such as glass based panels especially used for sub-millimeter and shorter wavelength telescopes with active optics/active panel technology. This paper began with a general overview of panel patterns and panel supports of existing radio telescopes. Thereby, we proposed a preferable master-slave active surface concept for triangular and/or hexagonal panel pattern. In addition, we carry out panel error sensitivity analysis for all the 6 degrees of freedom (DOF) of a panel to identify what DOFs are most sensitive for an active surface. And afterwards, based on the error sensitivity analysis, we suggested an innovative parallel-series concept hexapod well fitted for an active panel to correct for all of its 6 rigid errors. A demonstration active surface using the master-slave concept and the hexapod manifested a great save in cost, where only 486 precision actuators are needed for 438 panels, which is 37% of those actuators needed by classic segmented mirror active optics. Further, we put forward a swaying-arm based design concept for the related connecting joints between panels, which ensures that all the panels attached on to it free from over-constraints when they are positioned and/or actuated. Principle and performance of the swaying-arm connecting mechanism are elaborated before a practical cablemesh based prototype active surface is presented with comprehensive finite element analysis and simulation.

  10. Novel technology for the the Effelsberg 100-m Radio Telescope and MeerKAT

    Science.gov (United States)

    Kramer, Michael; Kraus, Alex; Wieching, Gundolf

    2015-08-01

    The 100-m radio telescope of the Max-Planck-Institut für Radioastronomie (MPIfR) is a unique European astronomical facility that combines superb sensitivity and wide frequency coverage (300 MHz - 95 GHz) with distinct versatility, making the telescope not only a cutting edge instrument for front-line research but also a testbed for emerging and future technology.Even more than 40 years old, the telescope has been continuously modernized and is heavily involved in various kinds of astronomical research as stand-alone instrument as well as in several VLBI networks. Currently, a large upgrade of the receiver suite at the telescope is ongoing. Several new, state-of-the-are broad-band receivers have been installed recently or are under constructions. Along with the new receivers, modern digital backends are being designed. We report on the current status of these upgrades by presenting some „highlights" and giving an outlook on the activities planned for the future.The technology developed and tested during these upgrades also finds application in the MeerKAT observatory in South Africa. MeerKAT is a fully funded radio observatory under construction in the Northern Cape of South Africa. When complete, MeerKAT’s 64 13.5-m dishes will form the - by far - most sensitive telescope in the Southern hemisphere, being equivalent to a 110 m dish. Due to the dish design with an offset Gregorian feed it will be 60%more sensitive than large center feed single dishes of comparable size.MPIfR is designing and constructing a 1.75- 3.44 GHz Receiver system for MeerKAT. The receiver will allow observations at a frequency range at currently unavailable sensitivity and spatial resolution in the Southern hemisphere. Combined with its powerful MPIfR Pulsar search backend it is expected to detect more than 1600 normal and 270 millisecond pulsars. In addition MeerKat will open up science that stays for its own but also prepares future observations with SKA and complements future SKA

  11. An Efficient Real-time Data Pipeline for the CHIME Pathfinder Radio Telescope X-Engine

    CERN Document Server

    Recnik, Andre; Denman, Nolan; Hincks, Adam D; Hinshaw, Gary; Klages, Peter; Vanderlinde, Keith

    2015-01-01

    The CHIME Pathfinder is a new interferometric radio telescope that uses a hybrid FPGA/GPU FX correlator. The GPU-based X-engine of this correlator processes over 819 Gb/s of 4+4-bit complex astronomical data from N=256 inputs across a 400 MHz radio band. A software framework is presented to manage this real-time data flow, which allows each of 16 processing servers to handle 51.2 Gb/s of astronomical data, plus 8 Gb/s of ancillary data. Each server receives data in the form of UDP packets from an FPGA F-engine over the eight 10 GbE links, combines data from these packets into large (32MB-256MB) buffered frames, and transfers them to multiple GPU co-processors for correlation. The results from the GPUs are combined and normalized, then transmitted to a collection server, where they are merged into a single file. Aggressive optimizations enable each server to handle this high rate of data; allowing the efficient correlation of 25 MHz of radio bandwidth per server. The solution scales well to larger values of N ...

  12. ALFABURST: A realtime fast radio burst monitor for the Arecibo telescope

    CERN Document Server

    Chennamangalam, Jayanth; MacMahon, David; Armour, Wes; Cobb, Jeff; Lorimer, Duncan; Rajwade, Kaustubh; Siemion, Andrew; Werthimer, Dan; Williams, Christopher

    2015-01-01

    Fast radio bursts (FRBs) constitute an emerging class of fast radio transient whose origin continues to be a mystery. Realizing the importance of increasing coverage of the search parameter space, we have designed, built, and deployed a realtime monitor for FRBs at the 305-m Arecibo radio telescope. Named 'ALFABURST', it is a commensal instrument that is triggered whenever the 1.4 GHz seven-beam Arecibo $L$-Band Feed Array (ALFA) receiver commences operation. The ongoing commensal survey we are conducting using ALFABURST has an instantaneous field of view of 0.02 sq. deg. within the FWHM of the beams, with the realtime software configurable to use up to 300 MHz of bandwidth. We search for FRBs with dispersion measure up to 2560 cm$^{-3}$ pc and pulse widths ranging from 0.128 ms to 16.384 ms. Commissioning observations performed over the past few months have demonstrated the capability of the instrument in detecting single pulses from known pulsars. In this paper, I describe the instrument and the associated ...

  13. Discovery and Follow-up of Rotating Radio Transients with the Green Bank and LOFAR Telescopes

    CERN Document Server

    Karako-Argaman, C; Lynch, R S; Hessels, J W T; Kondratiev, V I; McLaughlin, M A; Ransom, S M; Archibald, A M; Boyles, J; Jenet, F A; Kaplan, D L; Levin, L; Lorimer, D R; Madsen, E C; Roberts, M S E; Siemens, X; Stairs, I H; Stovall, K; Swiggum, J K; van Leeuwen, J

    2015-01-01

    We have discovered 21 Rotating Radio Transients (RRATs) in data from the Green Bank Telescope (GBT) 350-MHz Drift-scan and the Green Bank North Celestial Cap pulsar surveys using a new candidate sifting algorithm. RRATs are pulsars with sporadic emission that are detected through their bright single pulses rather than Fourier domain searches. We have developed {\\tt RRATtrap}, a single-pulse sifting algorithm that can be integrated into pulsar survey data analysis pipelines in order to find RRATs and Fast Radio Bursts. We have conducted follow-up observations of our newly discovered sources at several radio frequencies using the GBT and Low Frequency Array (LOFAR), yielding improved positions and measurements of their periods, dispersion measures, and burst rates, as well as phase-coherent timing solutions for four of them. The new RRATs have dispersion measures (DMs) ranging from 15 to 97 pc cm$^{-3}$, periods of 240 ms to 3.4 s, and estimated burst rates of 20 to 400 pulses hr$^{-1}$ at 350 MHz. We use this ...

  14. The Morehead State University 21 M Space Tracking Antenna and Radio Telescope: an Instrument for Undergraduate Research

    Science.gov (United States)

    Malphrus, B. K.

    2004-12-01

    The Space Science Center at Morehead State University has developed a full motion 21-meter class radio telescope which is engaged in a rigorous research program in radio astronomy and also serves as a ground station with the capability to track low earth orbiting (LEO) satellites and as a test-bed for advanced RF systems. The new instrument achieved "First Light" in December 2004 and provides a unique educational tool that will serve as an active laboratory for students to have hands-on learning experiences with the intricacies of satellite telecommunications and radio astronomy. The instrument provides a state-of-the art laboratory for researchers and students in astrophysics, satellite telecommunications, engineering (including electrical, mechanical, and computer architecture), and software development. The 21 m telescope has achieved excellent sensitivity and spatial resolution and supports operations over a number of frequency regimes including: L-Band, S-Band, X-Band, Ku-Band, and ultimately Ka-Band. The gain of the large 21 meter antenna combined with a variety of state-of-the-art receivers and back-end electronics together provide a powerful telescope for teaching and research in radio frequency astrophysics. The 21 m telescope operates primarily in the radio regime at a central frequency of 1420 MHz (HI line) and ultimately at higher frequencies that will incorporate transition lines of hydroxyl, ammonia, and water. The sensitivity and versatility of the telescope design facilitate the investigation of a wide variety of astrophysically interesting phenomena. These objects include galactic sources such as supernova remnants, emission nebula, planetary nebula, extended HI emission from the Milky Way, and the sun. Extragalactic sources such as quasars, radio galaxies, and supernova remnants (SNRs) will also be observed. A long-term AGN monitoring campaign will be undertaken, beginning in 2005. Funding for the 21m telescope has been provided by NASA, the SBA

  15. ADDING CONTEXT TO JAMES WEBB SPACE TELESCOPE SURVEYS WITH CURRENT AND FUTURE 21 cm RADIO OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Beardsley, A. P.; Morales, M. F. [Department of Physics, University of Washington Seattle, WA 98195 (United States); Lidz, A.; Malloy, M. [Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 (United States); Sutter, P. M., E-mail: beards@phys.washington.edu [INFN - National Institute for Nuclear Physics via Valerio 2, I-34127, Trieste (Italy)

    2015-02-20

    Infrared and radio observations of the Epoch of Reionization promise to revolutionize our understanding of the cosmic dawn, and major efforts with the JWST, MWA, and HERA are underway. While measurements of the ionizing sources with infrared telescopes and the effect of these sources on the intergalactic medium with radio telescopes should be complementary, to date the wildly disparate angular resolutions and survey speeds have made connecting proposed observations difficult. In this paper we develop a method to bridge the gap between radio and infrared studies. While the radio images may not have the sensitivity and resolution to identify individual bubbles with high fidelity, by leveraging knowledge of the measured power spectrum we are able to separate regions that are likely ionized from largely neutral, providing context for the JWST observations of galaxy counts and properties in each. By providing the ionization context for infrared galaxy observations, this method can significantly enhance the science returns of JWST and other infrared observations.

  16. An integral monitoring of GRS1915+105: simultaneous observations with INTEGRAL, RXTE, the Ryle and Nancay radio telescopes

    CERN Document Server

    Rodríguez, J; Hannikainen, D C; Lehto, H J

    2006-01-01

    Since the launch of INTEGRAL in late 2002 we have monitored the Galactic microquasar GRS 1915+105 with long exposures (~100 ks) pointings. All the observations have been conducted simultaneously with other instruments, in particular RXTE and the Ryle Telescope, and in some cases with others (Spitzer, Nancay, GMRT, Suzaku,...). We report here the results of 3 observations performed simultaneously with INTEGRAL, RXTE, the Ryle and Nancay radio telescopes. These observations show the so-called $\

  17. The Hitachi and Takahagi 32 m radio telescopes: Upgrade of the antennas from satellite communication to radio astronomy

    Science.gov (United States)

    Yonekura, Yoshinori; Saito, Yu; Sugiyama, Koichiro; Soon, Kang Lou; Momose, Munetake; Yokosawa, Masayoshi; Ogawa, Hideo; Kimura, Kimihiro; Abe, Yasuhiro; Nishimura, Atsushi; Hasegawa, Yutaka; Fujisawa, Kenta; Ohyama, Tomoaki; Kono, Yusuke; Miyamoto, Yusuke; Sawada-Satoh, Satoko; Kobayashi, Hideyuki; Kawaguchi, Noriyuki; Honma, Mareki; Shibata, Katsunori M.; Sato, Katsuhisa; Ueno, Yuji; Jike, Takaaki; Tamura, Yoshiaki; Hirota, Tomoya; Miyazaki, Atsushi; Niinuma, Kotaro; Sorai, Kazuo; Takaba, Hiroshi; Hachisuka, Kazuya; Kondo, Tetsuro; Sekido, Mamoru; Murata, Yasuhiro; Nakai, Naomasa; Omodaka, Toshihiro

    2016-10-01

    The Hitachi and Takahagi 32 m radio telescopes (former satellite communication antennas) were so upgraded as to work at 6, 8, and 22 GHz. We developed the receiver systems, IF systems, back-end systems (including samplers and recorders), and reference systems. We measured the performance of the antennas. The system temperature including the atmosphere toward the zenith, T_sys^{ast }, is measured to be ˜30-40 K for 6 GHz and ˜25-35 K for 8 GHz. T_sys^{ast } for 22 GHz is measured to be ˜40-100 K in winter and ˜150-500 K in summer seasons, respectively. The aperture efficiency is 55%-75% for Hitachi at 6 GHz and 8 GHz, and 55%-65% for Takahagi at 8 GHz. The beam sizes at 6 GHz and 8 GHz are ˜4.6° and ˜3.8°, respectively. The side-lobe level is less than 3%-4% at 6 and 8 GHz. Pointing accuracy was measured to be better than ˜0.3° for Hitachi and ˜0.6° for Takahagi. We succeeded in VLBI observations in 2010 August, indicating good performance of the antenna. We started single-dish monitoring observations of 6.7 GHz methanol maser sources in 2012 December, and found several new sources showing short-term periodic variation of the flux density.

  18. The Morehead State University 18 Meter Radio Telescope Project: Involving Undergraduates in Observational Astrophysics

    Science.gov (United States)

    Malphrus, B. K.; Combs, M. S.; Kruth, J.

    2002-12-01

    The Space Science Center at Morehead State University is in the process of developing a large aperture (18-21 meter) cm-wave radio telescope, the Morehead Radio Telescope (MRT). The telescope will be located in the mountainous region of Eastern Kentucky. The instrument will serve as a research instrument and active laboratory for undergraduate astronomy, physics, pre-engineering, and computer science students. The antenna system will be engaged in science programs (in astrophysics) and in satellite mission support services (telemetry, tracking, and control). The benefits to students are based upon a hands-on approach to learning concepts in astrophysics and engineering. Additionally, there are still research contributions that small aperture centimeter-wave instruments can make including long-term observations of microvariability in AGNs, observations of transient events, and surveys. The MRT will operate three receiver systems including an L-band receiver (1.4-1.7 GHz) covering the "water hole", an S-band receiver (2.2-2.4 GHz) and a Ku-band receiver (11.2- 12.7 GHz) for continuum observations and satellite telemetry. The technical specifications for the instrument have been developed and an RFP has been issued inviting antenna vendors to submit proposals. The reflector will have a surface accuracy of 0.020 inches RMS over the entire surface, which will support relatively high frequency (Ku-band) observations. The antenna system will be full-motion and have a slew speed of 2 deg per second and an acceleration of 2 deg per second2. The HI and OH spatial distribution associated with cosmic phenomena will be investigated as well as dynamics and kinematics (particularly in HI) by observing over a range of frequencies (up to 2.5 MHz) with a 2048-channel back-end spectrometer, providing up to 1 KHz frequency resolution. The sensitivity and versatility of the telescope design will facilitate investigation of a wide variety of cosmic phenomena. The MRT is funded by

  19. VLBA Teams With Optical Interferometer to Study Star's Layers

    Science.gov (United States)

    2007-05-01

    Structure of S Ori (Artist's Impression) "Astronomers are like medical doctors, who use various instruments to examine different parts of the human body," said co-author David Boboltz. "While the mouth can be checked with a simple light, a stethoscope is required to listen to the heart beat. Similarly the heart of the star can be observed in the optical, the molecular and dust layers can be studied in the infrared and the maser emission can be probed with radio instruments. Only the combination of the three gives us a more complete picture of the star and its envelope." The maser emission comes from silicon monoxide (SiO) molecules and can be used to image and track the motion of gas clouds in the stellar envelope roughly 10 times the size of the Sun. The astronomers observed S Ori with two of the largest interferometric facilities available: the ESO Very Large Telescope Interferometer (VLTI) at Paranal, observing in the near- and mid-infrared, and the NRAO-operated Very Long Baseline Array (VLBA), that takes measurements in the radio wave domain. Because the star's luminosity changes periodically, the astronomers observed it simultaneously with both instruments, at several different epochs. The first epoch occurred close to the stellar minimum luminosity and the last just after the maximum on the next cycle. ESO PR Photo 25c/07 ESO PR Photo 25c/07 S Ori to Scale (Artist's Impression) The astronomers found the star's diameter to vary between 7.9 milliarcseconds and 9.7 milliarcseconds. At the distance of S Ori, this corresponds to a change of the radius from about 1.9 to 2.3 times the distance between the Earth and the Sun, or between 400 and 500 solar radii! As if such sizes were not enough, the inner dust shell is found to be about twice as big. The maser spots, which also form at about twice the radius of the star, show the typical structure of partial to full rings with a clumpy distribution. Their velocities indicate that the gas is expanding radially, moving away at a

  20. VLBA observations of the nuclear transient AT 2017gbl in IRAS 23436+5257

    Science.gov (United States)

    Perez-Torres, Miguel; Kool, Erik; Ryder, Stuart; Mattila, Seppo; Fraser, Morgan; Kankare, Erkki

    2017-09-01

    We report on simultaneous radio interferometric observations of the luminous nuclear transient AT 2017gbl, carried out at 4.4 and 7.6 GHz with the Very Long Baseline Array (VLBA) on 2017 August 15.38 UT. AT 2017gbl was discovered in the near-infrared on MJD 57942.56 (ATel #10651) superimposed on the nucleus of the galaxy IRAS 23436+5257 (D= 146 Mpc).

  1. Deep 610-MHz Giant Metrewave Radio Telescope observations of the Spitzer extragalactic First Look Survey field - III. The radio properties of Infrared-Faint Radio Sources

    CERN Document Server

    Garn, Timothy

    2008-01-01

    Infrared-Faint Radio Sources (IFRSs) are a class of source which are bright at radio frequencies, but do not appear in deep infrared images. We report the detection of 14 IFRSs within the Spitzer extragalactic First Look Survey field, eight of which are detected near to the limiting magnitude of a deep R-band image of the region, at R ~ 24.5. Sensitive Spitzer Space Telescope images are stacked in order to place upper limits on their mid-infrared flux densities, and using recent 610-MHz and 1.4-GHz observations we find that they have spectral indices which vary between alpha = 0.05 and 1.38, where we define alpha such that S = S_0 nu^(- alpha), and should not be thought of as a single source population. We place constraints on the luminosity and linear size of these sources, and through comparison with well-studied local objects in the 3CRR catalogue demonstrate that they can be modelled as being compact ( 4).

  2. Variable Correlation Digital Noise Source on FPGA — A Versatile Tool for Debugging Radio Telescope Backends

    Science.gov (United States)

    Buch, Kaushal D.; Gupta, Yashwant; Ajith Kumar, B.

    Contemporary wideband radio telescope backends are generally developed on Field Programmable Gate Arrays (FPGA) or hybrid (FPGA+GPU) platforms. One of the challenges faced while developing such instruments is the functional verification of the signal processing backend at various stages of development. In the case of an interferometer or pulsar backend, the typical requirement is for one independent noise source per input, with provision for a common, correlated signal component across all the inputs, with controllable level of correlation. This paper describes the design of a FPGA-based variable correlation Digital Noise Source (DNS), and its applications to built-in testing and debugging of correlators and beamformers. This DNS uses the Central Limit Theorem-based approach for generation of Gaussian noise, and the architecture is optimized for resource requirements and ease of integration with existing signal processing blocks on FPGA.

  3. A Generic and Efficient E-field Parallel Imaging Correlator for Next-Generation Radio Telescopes

    CERN Document Server

    Thyagarajan, Nithyanandan; Bowman, Judd D; Morales, Miguel F

    2015-01-01

    Modern radio telescopes are favoring densely packed array layouts consisting of large numbers of antennas ($N_\\textrm{a}\\gtrsim 1000$). Since the complexity of traditional correlators scales as $\\mathcal{O}(N_\\textrm{a}^2)$, there will be a steep cost for realizing the full imaging potential of these powerful instruments. Through our generic and efficient E-field Parallel Imaging Correlator (EPIC), we present the first software demonstration of a generalized direct imaging algorithm known as the Modular Optimal Frequency Fourier (MOFF) imager. It takes advantage of the multiplication-convolution theorem of Fourier transforms. Not only does it bring down the cost for dense layouts to $\\mathcal{O}(N_\\textrm{a}\\log_2 N_\\textrm{a})$ but can also image from irregularly arranged heterogeneous antenna arrays. EPIC is highly modular and parallelizable, implemented in object oriented Python, and publicly available. We have verified the images produced to be equivalent to those produced using traditional techniques. We...

  4. A limit on the ultra-high-energy neutrino flux from lunar observations with the Parkes radio telescope

    CERN Document Server

    Bray, J D; Roberts, P; Reynolds, J E; James, C W; Phillips, C J; Protheroe, R J; McFadden, R A; Aartsen, M G

    2015-01-01

    We report a limit on the ultra-high-energy neutrino flux based on a non-detection of radio pulses from neutrino-initiated particle cascades in the Moon, in observations with the Parkes radio telescope undertaken as part of the LUNASKA project. Due to the improved sensitivity of these observations, which had an effective duration of 127 hours and a frequency range of 1.2-1.5 GHz, this limit extends to lower neutrino energies than those from previous lunar radio experiments, with a detection threshold below 10^20 eV. The calculation of our limit allows for the possibility of lunar-origin pulses being misidentified as local radio interference, and includes the effect of small-scale lunar surface roughness. The targeting strategy of the observations also allows us to place a directional limit on the neutrino flux from the nearby radio galaxy Centaurus A.

  5. Calibrating high-precision Faraday rotation measurements for LOFAR and the next generation of low-frequency radio telescopes

    NARCIS (Netherlands)

    Sotomayor-Beltran, C.; Sobey, C.; Hessels, J.W.T.; Bruyn, de G.; Noutsos, A.; Alexov, A.; Anderson, J.; Asgekar, A.; Avruch, I.M.; Beck, R.; Bell, M.E.; Bell, M.R.; Bentum, M.J.; Bernardi, G.; Best, P.; Birzan, L.; Bonafede, A.; Breitling, F.; Broderick, J.; Brouw, W.N.; Brüggen, M.; Ciardi, B.; Gasperin, de F.; Dettmar, R.-J.; Duin, van A.; Duscha, S.; Eislöffel, J.; Falcke, H.; Fallows, R.A.; Fender, R.; Ferrari, C.; Frieswijk, W.; Garrett, M.A.; Griessmeier, J.; Grit, T.; Gunst, A.W.; Hassall, T.E.; Heald, G.; Hoeft, M.; Horneffer, A.; Iacobelli, M.; Juette, E.; Karastergiou, A.; Keane, E.; Kohler, J; Kramer, M.; Kondratiev, V.I.; Koopmans, L.V.E.; Kuniyoshi, M.; Kuper, G.; Leeuwen, van J.; Maat, P.; Macario, G.; Markoff, S.; McKean, J.P.; Mulcahy, D.D.; Munk, H.; Orrú, E.; Paas, H.; Pandey-Pommier, M.; Pilia, M.; Pizzo, R.; Polatidis, A.G.; Reich, W.; Röttgering, H.; Serylak, M.; Sluman, J.; Stappers, B.W.; Tagger, M.; Tang, Y.; Tasse, C.; Veen, ter S.; Vermeulen, R.; Weeren, van R.J.; Wijers, R.A.M.J.; Wijnholds, S.J.; Wise, M.W.; Wucknitz, O.; Yatawatta, S.; Zarka, P.

    2013-01-01

    Faraday rotation measurements using the current and next generation of low-frequency radio telescopes will provide a powerful probe of astronomical magnetic fields. However, achieving the full potential of these measurements requires accurate removal of the time-variable ionospheric Faraday rotation

  6. Calibrating high-precision Faraday rotation measurements for LOFAR and the next generation of low-frequency radio telescopes

    NARCIS (Netherlands)

    Sotomayor-Beltran, C.; et al., [Unknown; Hessels, J.W.T.; Alexov, A.; van Leeuwen, J.; Markoff, S.; Wijers, R.A.M.J.; Wise, M.W.

    2013-01-01

    Faraday rotation measurements using the current and next generation of low-frequency radio telescopes will provide a powerful probe of astronomical magnetic fields. However, achieving the full potential of these measurements requires accurate removal of the time-variable ionospheric Faraday rotation

  7. Primary Beam and Dish Surface Characterization at the Allen Telescope Array by Radio Holography

    CERN Document Server

    Atkinson, Shannon; Backus, P R; Barott, William; Bauermeister, Amber; Blitz, Leo; Bock, D C -J; Bower, Geoffrey C; Bradford, Tucker; Cheng, Calvin; Croft, Steve; Dexter, Matt; Dreher, John; Engargiola, Greg; Fields, Ed; Heiles, Carl; Helfer, Tamara; Jordan, Jane; Jorgensen, Susan; Kilsdonk, Tom; Gutierrez-Kraybill, Colby; Keating, Garrett; Law, Casey; Lugten, John; MacMahon, D H E; McMahon, Peter; Milgrome, Oren; Siemion, Andrew; Smolek, Ken; Thornton, Douglas; Pierson, Tom; Randall, Karen; Ross, John; Shostak, Seth; Tarter, J C; Urry, Lynn; Werthimer, Dan; Williams, Peter K G; Whysong, David; Harp, G R; Ackermann, R F; Nadler, Z J; Blair, Samantha K; Davis, M M; Wright, M C H; Forster, J R; DeBoer, D R; Welch, W J

    2012-01-01

    The Allen Telescope Array (ATA) is a cm-wave interferometer in California, comprising 42 antenna elements with 6-m diameter dishes. We characterize the antenna optical accuracy using two-antenna interferometry and radio holography. The distortion of each telescope relative to the average is small, with RMS differences of 1 percent of beam peak value. Holography provides images of dish illumination pattern, allowing characterization of as-built mirror surfaces. The ATA dishes can experience mm-scale distortions across -2 meter lengths due to mounting stresses or solar radiation. Experimental RMS errors are 0.7 mm at night and 3 mm under worst case solar illumination. For frequencies 4, 10, and 15 GHz, the nighttime values indicate sensitivity losses of 1, 10 and 20 percent, respectively. The ATA.s exceptional wide-bandwidth permits observations over a continuous range 0.5 to 11.2 GHz, and future retrofits may increase this range to 15 GHz. Beam patterns show a slowly varying focus frequency dependence. We prob...

  8. Panel positioning error and support mechanism for a 30-m THz radio telescope

    Institute of Scientific and Technical Information of China (English)

    De-Hua Yang; Daniel Okoh; Guo-Hua Zhou; Ai-Hua Li; Guo-Ping Li; Jing-Quan Cheng

    2011-01-01

    A 30-m TeraHertz (THz) radio telescope is proposed to operate at 200 μm with an active primary surface. This paper presents sensitivity analysis of active surface panel positioning errors with optical performance in terms of the Strehl ratio.Based on Ruze's surface error theory and using a Monte Carlo simulation, the effects of six rigid panel positioning errors, such as piston, tip, tilt, radial, azimuthal and twist displacements, were directly derived. The optical performance of the telescope was then evaluated using the standard Strehl ratio. We graphically illustrated the various panel error effects by presenting simulations of complete ensembles of full reflector surface errors for the six different rigid panel positioning errors. Study of the panel error sensitivity analysis revealed that the piston error and tilt/tip errors are dominant while the other rigid errors are much less important. Furthermore, as indicated by the results, we conceived of an alternative Master-Slave Concept-based (MSC-based) active surface by implementating a special Series-Parallel Concept-based (SPC-based) hexapod as the active panel support mechanism. A new 30-m active reflector based on the two concepts was demonstrated to achieve correction for all the six rigid panel positioning errors in an economically feasible way.

  9. The Standing Wave Phenomenon in Radio Telescopes; Frequency Modulation of the WSRT Primary Beam

    CERN Document Server

    Popping, Attila

    2007-01-01

    Inadequacies in the knowledge of the primary beam response of current interferometric arrays often form a limitation to the image fidelity. We hope to overcome these limitations by constructing a frequency-resolved, full-polarization empirical model for the primary beam of the Westerbork Synthesis Radio Telescope (WSRT). Holographic observations, sampling angular scales between about 5 arcmin and 11 degrees, were obtained of a bright compact source (3C147). These permitted measurement of voltage response patterns for seven of the fourteen telescopes in the array and allowed calculation of the mean cross-correlated power beam. Good sampling of the main-lobe, near-in, and far-side-lobes out to a radius of more than 5 degrees was obtained. A robust empirical beam model was detemined in all polarization products and at frequencies between 1322 and 1457 MHz with 1 MHz resolution. Substantial departures from axi-symmetry are apparent in the main-lobe as well as systematic differences between the polarization proper...

  10. Observations of IntraDay Variable sources with the Effelsberg and Urumqi Radio Telescopes

    CERN Document Server

    Marchili, N; Liu, X; Song, H G; Gabányi, K É; Fuhrmann, L; Müller, P; Witzel, A; Zensus, J A; Han, J L

    2008-01-01

    A sample of classical IntraDay Variable (IDV) and IDV candidate sources has been monitored with the Urumqi 25m telescope and the Effelsberg 100m telescope. Aim of the project is to investigate the origin of IntraDay Variability, a phenomenon which has been observed in about 30% of flat spectrum radio quasars. Simultaneous Effelsberg-Urumqi observations demonstrated that the Urumqi antenna, although relatively small in diameter, is well suitable for IDV experiments. A few Urumqi datasets, however, turned out to be affected by a spurious $\\sim 24$ hours modulation, an effect which has been removed by means of a new procedure for data reduction. In about 14 months, 12 epochs of observation have been collected, for a total observing time of more than 45 days. The epochs are regularly distributed over the whole year, in order to check for the presence of systematic annual changes in the variability time scales - a crucial test for verifying the consistency of source-extrinsic models of the variability. Preliminary...

  11. Detection, Excision and Statistics of Interference at the Mauritius Radio Telescope

    Indian Academy of Sciences (India)

    S. Sachdev; N. Udaya Shankar

    2001-06-01

    A technique to detect man-made interference in the visibility data of the Mauritius Radio Telescope (MRT) has been developed. This technique is based on the understanding that the interference is generally ‘spiky’ in nature and has Fourier components beyond the maximum frequency which can arise from the radio sky and can therefore be identified. We take the sum of magnitudes of visibilities on all the baselines measured at a given time to improve detectability. This is then high-pass filtered to get a time series from which the contribution of the sky is removed. Interference is detected in the high-pass data using an iterative scheme. In each iteration, interference with amplitudes beyond a certain threshold is detected. These points are then removed from the original time series and the resulting data are high-pass filtered and the process repeated. We have also studied the statistics of the strength, numbers, time of occurrence and duration of the interference at the MRT. The statistics indicate that most often the interference excision can be carried out while post-integrating the visibilities by giving a zero weight to the interference points.

  12. The Atacama Cosmology Telescope: measuring radio galaxy bias through cross-correlation with lensing

    CERN Document Server

    Allison, Rupert; Sherwin, Blake D; de Bernardis, Francesco; Bond, J Richard; Calabrese, Erminia; Devlin, Mark J; Dunkley, Joanna; Gallardo, Patricio; Henderson, Shawn; Hincks, Adam D; Hlozek, Renee; Jarvis, Matt; Kosowsky, Arthur; Louis, Thibaut; Madhavacheril, Mathew; McMahon, Jeff; Moodley, Kavilan; Naess, Sigurd; Newburgh, Laura; Niemack, Michael D; Page, Lyman A; Partridge, Bruce; Sehgal, Neelima; Spergel, David N; Staggs, Suzanne T; van Engelen, Alexander; Wollack, Edward J

    2015-01-01

    We correlate the positions of radio galaxies in the FIRST survey with the CMB lensing convergence estimated from the Atacama Cosmology Telescope over 470 square degrees to determine the bias of these galaxies. We remove optically cross-matched sources below redshift $z=0.2$ to preferentially select Active Galactic Nuclei (AGN). We measure the angular cross-power spectrum $C_l^{\\kappa g}$ at $4.4\\sigma$ significance in the multipole range $100radio-loud AGN: we find $\\l...

  13. How many radio-loud quasars can be detected by the Gamma-Ray Large Area Space Telescope?

    CERN Document Server

    Cao, Xinwu

    2007-01-01

    In the unification scheme, radio quasars and FR II radio galaxies come from the same parent population, but viewed at different angles. Based on the Comptonization models for the gamma-ray emission from active galactic nuclei (AGNs), we estimate the number of radio quasars and FR II radio galaxies to be detected by the Gamma-Ray Large Area Space Telescope (GLAST) using the luminosity function (LF) of their parent population derived from the flat-spectrum radio quasar (FSRQ) LF. We find that ~1200 radio quasars will be detected by GLAST, if the soft seed photons for Comptonization come from the regions outside the jets. We also consider the synchrotron self-Comptonization (SSC) model, and find it unlikely to be responsible for gamma-ray emission from radio quasars. We find that no FR II radio galaxies will be detected by GLAST. Our results show that most radio AGNs to be detected by GLAST will be FSRQs (~99 % for the external Comptonization model, EC model), while the remainder (~1 %) will be steep-spectrum ra...

  14. The large adaptive reflector: a 200-m diameter wideband centimeter- to meter-wave radio telescope

    Science.gov (United States)

    Carlson, Brent; Bauwens, Luc; Belostotski, Leonid; Cannon, Elizabeth; Chang, Ya-Ying; Deng, Xiaohui; Dewdney, Peter E.; Fitzsimmons, Joeleff T.; Halliday, David; Kuerschner, Kai; Lachapelle, Gerard; Lo, David; Mousavi, Pedram; Nahon, Meyer; Shafai, Lot; Stiemer, Sigfried F.; Taylor, Russell; Veidt, Bruce

    2000-07-01

    The Large Adaptive Reflector (LAR) is a concept for a low- cost, large aperture, wideband, radio telescope, designed to operate over the wavelength range from 2 m to 1.4 cm. It consists of a 200-m diameter actuated-surface parabolic reflector with a focal length of 500 m, mounted flat on the ground. The feed is held in place by a tension-structure, consisting of three or more tethers tensioned by the lift of a large, helium-filled aerostat -- a stiff structure that effectively resists wind forces. The telescope is steered by simultaneously changing the lengths of the tethers with winches (thus the position of the feed) and by modifying the shape of the reflector. At all times the reflector configuration is that of an offset parabolic antenna, with the capability to point anywhere in the sky above approximately 15 degree Elevation Angle. At mid-range wavelengths, the feed is a multi-beam prime-focus phased array, about 5 m diameter; at meter wavelengths, it is a single-beam phased array of up to 10 m diameter. Simulations have shown that in operating wind conditions (10 m/s average speed with 2.5 m/s gusts), the position of the feed platform can be stabilized to within a few cm over time scales of approximately 20 s. Research indicates that the telescope concept is feasible and that an order of magnitude improvement in cost per m2 of collecting area over traditional designs of large parabolic antennas can be achieved.

  15. Super-Sharp Radio 'Eye' Remeasuring the Universe

    Science.gov (United States)

    2011-02-01

    Using the super-sharp radio "vision" of astronomy's most precise telescope, scientists have extended a directly-measured "yardstick" three times farther into the cosmos than ever before, an achievement with important implications for numerous areas of astrophysics, including determining the nature of Dark Energy, which constitutes 70 percent of the Universe. The continent-wide Very Long Baseline Array (VLBA) also is redrawing the map of our home Galaxy and is poised to yield tantalizing new information about extrasolar planets, among many other cutting-edge research projects. The VLBA provides the greatest ability to see fine detail, called resolving power, of any telescope in the world. It can produce images hundreds of times more detailed than those from the Hubble Space Telescope -- power equivalent to sitting in New York and reading a newspaper in Los Angeles. This power allows astronomers to make precise cosmic measurements with far-ranging implications for research within our own Galaxy and far beyond. New measurements with the VLBA have placed a galaxy called NGC 6264 at a distance of 450 million light-years from Earth, with an uncertainty of no more than 9 percent. This is the farthest distance ever directly measured, surpassing a measurement of 160 million light-years to another galaxy in 2009. Previously, distances beyond our own Galaxy have been estimated through indirect methods. "Our direct, geometric measurements are independent of the assumptions and complications inherent in other techniques," said James Braatz, of the National Radio Astronomy Observatory (NRAO), who worked with Cheng-Yu Kuo, of the University of Virginia and NRAO. Fine-tuning the measurement of ever-greater distances is vital to determining the expansion rate of the Universe, which helps theorists narrow down possible explanations for the nature of Dark Energy. Different models of Dark Energy predict different values for the expansion rate, known as the Hubble Constant. "Solving

  16. Limits on the event rates of fast radio transients from the V-FASTR experiment

    CERN Document Server

    Wayth, Randall B; Deller, Adam T; Brisken, Walter F; Thompson, David R; Wagstaff, Kiri L; Majid, Walid A

    2012-01-01

    We present the first results from the V-FASTR experiment, a commensal search for fast transient radio bursts using the Very Long Baseline Array (VLBA). V-FASTR is unique in that the widely spaced VLBA antennas provide a discriminant against non-astronomical signals and a mechanism for the localization and identification of events that is not possible with single dishes or short baseline interferometers. Thus far V-FASTR has accumulated over 1300 hours of observation time with the VLBA, between 90 cm and 3 mm wavelength (327 MHz - 86 GHz), providing the first limits on fast transient event rates at high radio frequencies (>1.4 GHz). V-FASTR has blindly detected bright individual pulses from seven known pulsars but has not detected any single-pulse events that would indicate high redshift impulsive bursts of radio emission. At 1.4 GHz, V-FASTR puts limits on fast transient event rates comparable with the PALFA survey at the Arecibo telescope, but generally at lower sensitivities, and comparable to the "fly's ey...

  17. The Expanded Very Large Array: A Radio Telescope for the 21st Century

    Science.gov (United States)

    2000-06-01

    The world's most productive and widely-used radio telescope, the National Science Foundation's Very Large Array (VLA), can be improved tenfold with an expansion project proposed by the National Radio Astronomy Observatory (NRAO). "This project will ensure that the scientific community has a state-of-the-art research tool to meet the astronomical research challenges of the 21st Century," said Paul Vanden Bout, NRAO Director. Aerial View of the VLA Plans for the Expanded VLA (EVLA) and its potential for new scientific contributions were described today in a series of presentations at the American Astronomical Society's meeting in Rochester, NY. The EVLA project plans to replace dated equipment left over from the VLA's original construction in the 1970s and add eight new radio- telescope dish antennas to the current, 27-dish system. It received a strong endorsement last month when the Astronomy and Astrophysics Survey Committee of the National Academy of Sciences gave the project one of its highest ratings as a priority for the next decade in its report entitled "Astronomy and Astrophysics in the New Millennium." "The Survey Committee's endorsement shows that the astronomical research community strongly supports the Expanded VLA," said NRAO astronomer Jim Ulvestad, who spoke to reporters at the AAS meeting. "The VLA has long been a unique and critical resource for all of astronomy, and we look forward to turning it into a dramatic, new research tool." The VLA Expansion Project will use modern electronics and computer technology to greatly improve the VLA's ability to observe faint celestial objects and to analyze their radio emissions. A set of eight new dish antennas, added to the current 27-antenna system, will allow the VLA to produce images with ten times greater detail. The project will build on the VLA's current infrastructure, including its 230-ton dish antennas, the railroad tracks for moving those antennas, and the existing buildings and access roads. The

  18. Conversion of a 30-m former satellite communications antenna to a radio telescope

    Science.gov (United States)

    Deboer, David R.; Steffes, Paul G.; Glowacki, John M.

    1998-05-01

    A class of large satellite communication antennas built in the mid-1970's comprise a potential set of large antennas available for use by radio astronomers upon upgrade. With the advent of low noise technology these facilities have been superseded in the communications industry by smaller, more manageable facilities. Although many have sat idle and decaying over the intervening years, these facilities remain a potential resource for research and education. A pair of such dishes has been acquired by Georgia Tech and one of the 30 meter antennas has been completely mechanically and electrically stripped and new mechanical, control, RF, and electrical systems installed. The antenna is now driven by four continuous-speed vector-controlled three-phase AC induction motors with variable frequency vector motor drives. Sixteen bit resolution optical absolute position encoders on each axis provide telescope pointing data. Sixteen bit resolution optical absolute position encoders on each axis provide telescope pointing data. A programmable logic controller provides interlock monitoring and control. The antenna is controllable both manually via a portable remote control unit and via a Pentium PC running control software on a real-time UNIX-based platform. The manual unit allows limited control at two user-selectable speeds while computer control allows full tracking capability with accuracies of better than 0.3 arcminutes. The facility can be remotely controlled via the internet, although currently only a dedicated line is used. The antenna has been refitted with an ultra-broadband feed system capable of operating from 1-7 GHz.

  19. Compact Symmetric Objects and Supermassive Binary Black Holes in the VLBA Imaging and Polarimetry Survey

    CERN Document Server

    Tremblay, S E; Ortiz, A A; Tremblay, C D; Helmboldt, J F; Romani, R W

    2016-01-01

    We present multi-frequency Very Long Baseline Array (VLBA) follow-up observations of VLBA Imaging and Polarimetry Survey sources identified as likely compact symmetric objects (CSOs) or super-massive binary black holes (SBBHs). We also present new spectroscopic redshifts for 11 sources observed with the Hobby-Eberly Telescope. While no new SBBHs can be confirmed from these observations, we have identified 24 CSOs in the sample, 15 of which are newly designated, and refuted 52 candidates leaving 33 unconfirmed candidates. This is the first large uniform sample of CSOs which can be used to elicit some of the general properties of these sources, including morphological evolution and environmental interaction. We have detected polarised emission from two of these CSOs the properties of which are consistent with Active Galactic Nuclei unification schemes.

  20. A Generic and Efficient E-field Parallel Imaging Correlator for Next-Generation Radio Telescopes

    Science.gov (United States)

    Thyagarajan, Nithyanandan; Beardsley, Adam P.; Bowman, Judd D.; Morales, Miguel F.

    2017-05-01

    Modern radio telescopes are favouring densely packed array layouts with large numbers of antennas (NA ≳ 1000). Since the complexity of traditional correlators scales as O(N_A^2), there will be a steep cost for realizing the full imaging potential of these powerful instruments. Through our generic and efficient E-field Parallel Imaging Correlator (epic), we present the first software demonstration of a generalized direct imaging algorithm, namely the Modular Optimal Frequency Fourier imager. Not only does it bring down the cost for dense layouts to O(N_A log _2N_A) but can also image from irregular layouts and heterogeneous arrays of antennas. epic is highly modular, parallelizable, implemented in object-oriented python, and publicly available. We have verified the images produced to be equivalent to those from traditional techniques to within a precision set by gridding coarseness. We have also validated our implementation on data observed with the Long Wavelength Array (LWA1). We provide a detailed framework for imaging with heterogeneous arrays and show that epic robustly estimates the input sky model for such arrays. Antenna layouts with dense filling factors consisting of a large number of antennas such as LWA, the Square Kilometre Array, Hydrogen Epoch of Reionization Array, and Canadian Hydrogen Intensity Mapping Experiment will gain significant computational advantage by deploying an optimized version of epic. The algorithm is a strong candidate for instruments targeting transient searches of fast radio bursts as well as planetary and exoplanetary phenomena due to the availability of high-speed calibrated time-domain images and low output bandwidth relative to visibility-based systems.

  1. A Generic and Efficient E-field Parallel Imaging Correlator for Next-Generation Radio Telescopes

    Science.gov (United States)

    Thyagarajan, Nithyanandan; Beardsley, Adam P.; Bowman, Judd D.; Morales, Miguel F.

    2017-01-01

    Modern radio telescopes are favouring densely packed array layouts with large numbers of antennas (NA ≳ 1000). Since the complexity of traditional correlators scales as O(N_{A}^2), there will be a steep cost for realizing the full imaging potential of these powerful instruments. Through our generic and efficient E-field Parallel Imaging Correlator (EPIC), we present the first software demonstration of a generalized direct imaging algorithm, namely, the Modular Optimal Frequency Fourier (MOFF) imager. Not only does it bring down the cost for dense layouts to O(N_{A} log _2N_{A}) but can also image from irregular layouts and heterogeneous arrays of antennas. EPIC is highly modular, parallelizable, implemented in object-oriented Python, and publicly available. We have verified the images produced to be equivalent to those from traditional techniques to within a precision set by gridding coarseness. We have also validated our implementation on data observed with the Long Wavelength Array (LWA1). We provide a detailed framework for imaging with heterogeneous arrays and show that EPIC robustly estimates the input sky model for such arrays. Antenna layouts with dense filling factors consisting of a large number of antennas such as LWA, the Square Kilometre Array, Hydrogen Epoch of Reionization Array, and Canadian Hydrogen Intensity Mapping Experiment will gain significant computational advantage by deploying an optimized version of EPIC. The algorithm is a strong candidate for instruments targeting transient searches of Fast Radio Bursts (FRB) as well as planetary and exoplanetary phenomena due to the availability of high-speed calibrated time-domain images and low output bandwidth relative to visibility-based systems.

  2. Resolving the Shocks in Radio Galaxy Nebulae: Hubble Space Telescope and Radio Imaging of 3C 171, 3C 277.3, and PKS 2250-41

    Science.gov (United States)

    Tilak, Avanti; O'Dea, Christopher P.; Tadhunter, Clive; Wills, Karen; Morganti, Raffaella; Baum, Stefi A.; Koekemoer, Anton M.; Dallacasa, Daniele

    2005-12-01

    We present the results of Hubble Space Telescope (HST) WFPC2 medium-band and narrowband imaging and Very Large Array and MERLIN2 radio imaging of three powerful radio galaxies: 3C 171, 3C 277.3, and PKS 2250-41. We obtained images of the rest frame [O III] λ5007 and [O II] λ3727 line emission using the linear ramp filters on WFPC2. The correlations of the emission-line morphology and the [O III]/[O II] line ratios with the radio emission seen in ground-based observations are clarified by the HST imaging. We confirm that the radio lobes and hot spots are preferentially associated with lower ionization gas. The galaxy 3C 171 exhibits high surface brightness emission-line gas mainly along the radio source axis. The lowest ionization gas is seen at the eastern hot spot. In 3C 277.3 there is bright high-ionization gas (and continuum) offset just to the east of the radio knot K1. Our observations are consistent with previous work suggesting that this emission is produced by precursor gas ionized by the shock being driven into the cloud by the deflected radio jet. In PKS 2250-41 we resolve the emission-line arc that wraps around the outer rim of the western lobe. The lower ionization [O II] emission is nested just interior to the higher ionization [O III] emission, suggesting that we have resolved the cooling region behind the bow shock. We also detect possible continuum emission from the secondary hot spot. Thus, our observations support the hypothesis that in these sources the interaction between the expanding radio source and the ambient gas strongly influences the morphology, kinematics, and ionization of the gas. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated with program 6657 (principal investigator C. Tadhunter).

  3. The VLBA Calibrator Search for the BeSSeL Survey

    CERN Document Server

    Immer, K; Reid, M J; Bartkiewicz, A; Choi, Y K; Menten, K M; Moscadelli, L; Sanna, A; Wu, Y W; Xu, Y; Zhang, B; Zheng, X W

    2011-01-01

    We present the results of a survey of radio continuum sources near the Galactic plane using the Very Long Baseline Array (VLBA). Our observations are designed to identify compact extragalactic sources of milliarcsecond size that can be used for parallax measurements in the Bar and Spiral Structure Legacy Survey. We selected point sources from the NVSS and CORNISH catalogs with flux densities above 30 mJy and within $1.5\\degr$ of known maser targets. Of the 1529 sources observed, 199 were detected. For sources detected on 3 or more baselines, we determined accurate positions and evaluated their quality as potential calibrators. Most of the 1330 sources that were not detected with the VLBA are probably of extragalactic origin.

  4. Sardinia Radio Telescope wide-band spectral-polarimetric observations of the galaxy cluster 3C 129

    CERN Document Server

    Murgia, M; Carretti, E; Melis, A; Concu, R; Trois, A; Loi, F; Vacca, V; Tarchi, A; Castangia, P; Possenti, A; Bocchinu, A; Burgay, M; Casu, S; Pellizzoni, A; Pisanu, T; Poddighe, A; Poppi, S; D'Amico, N; Bachetti, M; Corongiu, A; Egron, E; Iacolina, N; Ladu, A; Marongiu, P; Migoni, C; Perrodin, D; Pilia, M; Valente, G; Vargiu, G

    2016-01-01

    We present new observations of the galaxy cluster 3C 129 obtained with the Sardinia Radio Telescope in the frequency range 6000-7200 MHz, with the aim to image the large-angular-scale emission at high-frequency of the radio sources located in this cluster of galaxies. The data were acquired using the recently-commissioned ROACH2-based backend to produce full-Stokes image cubes of an area of 1 deg x 1 deg centered on the radio source 3C 129. We modeled and deconvolved the telescope beam pattern from the data. We also measured the instrumental polarization beam patterns to correct the polarization images for off-axis instrumental polarization. Total intensity images at an angular resolution of 2.9 arcmin were obtained for the tailed radio galaxy 3C 129 and for 13 more sources in the field, including 3C 129.1 at the galaxy cluster center. These data were used, in combination with literature data at lower frequencies, to derive the variation of the synchrotron spectrum of 3C 129 along the tail of the radio source...

  5. Spectropolarimetry with the Allen Telescope Array: Faraday Rotation toward Bright Polarized Radio Galaxies

    CERN Document Server

    Law, C J; Bower, G C; Backer, D C; Bauermeister, A; Croft, S; Forster, R; Gutierrez-Kraybill, C; Harvey-Smith, L; Heiles, C; Hull, C; Keating, G; MacMahon, D; Whysong, D; Williams, P K G; Wright, M

    2010-01-01

    We have observed 37 bright, polarized radio sources with the Allen Telescope Array (ATA) to present a novel analysis of their Faraday rotation properties. Each source was observed during the commissioning phase with 2 to 4 100-MHz bands at frequencies ranging from 1 to 2 GHz. These observations demonstrate how the continuous frequency coverage of the ATA's log-periodic receiver can be applied to the study of Faraday rotation measures (RMs). We use RM synthesis to show that wide-bandwidth data can find multiple RM components toward a single source. Roughly a quarter of the sources studied have extra RM components with high confidence (brighter than ~40 mJy), when observing with a RM resolution of roughly 100 rad/m2. These extra components contribute 10%-70% of the total polarized flux. This is the first time multiple RM components have been identified in a large sample of point sources. For our observing configuration, these extra RM components bias the measurement of the peak RM by 10-15 rad/m2 ; more general...

  6. 12 GHz Radio-Holographic surface measurement of the RRI 10.4 m telescope

    CERN Document Server

    Balasubramanyam, Ramesh; Raju, Sharath B

    2009-01-01

    A modern Q-band low noise amplifier (LNA) front-end is being fitted to the 10.4 m millimeter-wave telescope at the Raman Research Institute (RRI) to support observations in the 40-50 GHz frequency range. To assess the suitability of the surface for this purpose, we measured the deviations of the primary surface from an ideal paraboloid using radio holography. We used the 11.6996 GHz beacon signal from the GSAT3 satellite, a 1.2 m reference antenna, commercial Ku-band Low Noise Block Convereters (LNBC) as the receiver front-ends and a Stanford Research Systems (SRS) lock-in amplifier as the backend. The LNBCs had independent free-running first local oscillators (LO). Yet, we recovered the correlation by using a radiatively injected common tone that served as the second local oscillator. With this setup, we mapped the surface deviations on a 64 x 64 grid and measured an rms surface deviation of ~350 um with a measurement accuracy of ~50 um.

  7. A Real-time Coherent Dedispersion Pipeline for the Giant Metrewave Radio Telescope

    CERN Document Server

    De, Kishalay

    2015-01-01

    A fully real-time coherent dedispersion system has been developed for the pulsar back-end at the Giant Metrewave Radio Telescope (GMRT). The dedispersion pipeline uses the single phased array voltage beam produced by the existing GMRT software back-end (GSB) to produce coherently dedispersed intensity output in real time, for the currently operational bandwidths of 16 MHz and 32 MHz. Provision has also been made to coherently dedisperse voltage beam data from observations recorded on disk. We discuss the design and implementation of the real-time coherent dedispersion system, describing the steps carried out to optimise the performance of the pipeline. Presently functioning on an Intel Xeon X5550 CPU equipped with a NVIDIA Tesla C2075 GPU, the pipeline allows dispersion free, high time resolution data to be obtained in real-time. We illustrate the significant improvements over the existing incoherent dedispersion system at the GMRT, and present some preliminary results obtained from studies of pulsars using t...

  8. The Role of Goldstone Apple Valley Radio Telescope Project in Promoting Scientific Efficacy Among Middle and High School Students

    Science.gov (United States)

    Ibe, M.; Deutscher, R.

    2004-12-01

    This study investigated the effects on student scientific efficacy after participation in the Goldstone Apple Valley Radio Telescope (GAVRT) project. In the GAVRT program, students use computers to record extremely faint radio waves collected by the telescope and analyze real data. Scientific efficacy is a type of self-knowledge a person uses to determine his or her ability to understand and work within the scientific community. An attitudinal survey was administered to all students nationwide who participated in the GAVRT program during the 2000-2001 and 2001-2002 years and had 480 and 562 respondents respectively. The students completed a pre-survey prior to beginning the GAVRT program and then completed a follow-up survey immediately after working on the Jupiter Quest GAVRT program. Between the pre- and post- surveys, students received instruction in the GAVRT curriculum and participated in operation of the radio telescope. During the 2000-2001 school year, increases in students' scientific efficacy occurred in their feelings of efficacy associated with the value they placed on the work they produced in science. During the 2001-2002 school year, the following areas of efficacy increased: students' perceived ability to use scientific equipment, students' feelings about how other people valued their work and students' abilities to think scientifically.

  9. New Mexico Fiber-Optic Link Marks Giant Leap Toward Future of Radio Astronomy

    Science.gov (United States)

    1998-12-01

    SOCORRO, NM -- Scientists and engineers at the National Radio Astronomy Observatory (NRAO) have made a giant leap toward the future of radio astronomy by successfully utilizing the Very Large Array (VLA) radio telescope in conjunction with an antenna of the continent-wide Very Long Baseline Array (VLBA) using the longest fiber-optic data link ever demonstrated in radio astronomy. The 65-mile fiber link will allow scientists to use the two National Science Foundation (NSF) facilities together in real time, and is the first step toward expanding the VLA to include eight proposed new radio-telescope antennas throughout New Mexico. LEFT: Miller Goss, NRAO's director of VLA/VLBA Operations, unveils graphic showing success of the Pie Town-VLA fiber link. The project, funded by the NSF and Associated Universities, Inc. (AUI), which operates NRAO for the NSF, links the VLA and the VLBA antenna in Pie Town, NM, using a Western New Mexico Telephone Co. fiber-optic cable. The successful hookup was announced at a ceremony that also marked the 10th anniversary of NRAO's Operations Center in Socorro. "Linking the Pie Town antenna to the VLA quadruples the VLA's ability to make detailed images of astronomical objects," said Paul Vanden Bout, NRAO's Director. "This alone makes the link an advance for science, but its greater importance is that it clearly demonstrates the technology for improving the VLA's capabilities even more in the future." "Clearly, the big skies and wide open spaces in New Mexico create near perfect conditions for the incredible astronomical assets located in our state. This new fiber-optic link paves the way for multiplying the already breathtaking scientific capabilities of the VLA," Senator Pete Domenici (R-NM) said. The VLA is a system of 27 radio-telescope antennas distributed over the high desert west of Socorro, NM, in the shape of a giant "Y." Made famous in movies, commercials and numerous published photos, the VLA has been one of the most productive

  10. The Second VLBA Calibrator Survey: VCS2

    Science.gov (United States)

    Fomalont, E. B.; Petrov, L.; MacMillan, D. S.; Gordon, D.; Ma, C.

    2003-11-01

    This paper presents an extension of the Very Long Baseline Array Calibrator Survey, called VCS2, containing 276 sources. This survey fills in regions of the sky that were not completely covered by the previous VCS1 calibrator survey. The VCS2 survey includes calibrator sources near the Galactic plane, -30deganalysis of the group delays measured at 2.3 and 8.4 GHz using the Goddard Space Flight Center CALC/SOLVE package. From the VLBA snapshot observations, images of the calibrators are available, and each source is given a quality code for anticipated use. The VCS2 catalog is available from the NRAO Web site.

  11. Discovery of the Millisecond Pulsar PSR J2043+1711 in a Fermi Source with the Nancay Radio Telescope

    Science.gov (United States)

    Guillemot, L.; Freire, P. C. C.; Cognard, I.; Johnson, T. J.; Takahashi, Y.; Kataoka, J.; Desvignes, G.; Camilo, F.; Ferrara, E. C.; Harding, A. K.; hide

    2012-01-01

    We report the discovery of the millisecond pulsar PSR J2043+1711 in a search of a Fermi Large Area Telescope (LAT) source with no known associations, with the Nancay Radio Telescope. The new pulsar, confirmed with the Green Bank Telescope, has a spin period of 2.38 ms, is relatively nearby (d approx. system have made PSR J2043+1711 one of the first new Fermi-selected millisecond pulsars to be added to pulsar gravitational wave timing arrays. It has also allowed a significant measurement of relativistic delays in the times of arrival of the pulses due to the curvature of space-time near the companion, but not yet with enough precision to derive useful masses for the pulsar and the companion. Nevertheless, a mass for the pulsar between 1.7 and 2.0 solar Mass can be derived if a standard millisecond pulsar formation model is assumed. In this paper, we also present a comprehensive summary of pulsar searches in Fermi LAT sources with the Nancay Radio Telescope to date.

  12. Radio Follow-up on All Unassociated Gamma-Ray Sources from the Third Fermi Large Area Telescope Source Catalog

    Science.gov (United States)

    Schinzel, Frank K.; Petrov, Leonid; Taylor, Gregory B.; Edwards, Philip G.

    2017-04-01

    The third Fermi Large Area Telescope γ-ray source catalog (3FGL) contains over 1000 objects for which there is no known counterpart at other wavelengths. The physical origin of the γ-ray emission from those objects is unknown. Such objects are commonly referred to as unassociated and mostly do not exhibit significant γ-ray flux variability. We performed a survey of all unassociated γ-ray sources found in 3FGL using the Australia Telescope Compact Array and Very Large Array in the range 4.0–10.0 GHz. We found 2097 radio candidates for association with γ-ray sources. The follow-up with very long baseline interferometry for a subset of those candidates yielded 142 new associations with active galactic nuclei that are γ-ray sources, provided alternative associations for seven objects, and improved positions for another 144 known associations to the milliarcsecond level of accuracy. In addition, for 245 unassociated γ-ray sources we did not find a single compact radio source above 2 mJy within 3σ of their γ-ray localization. A significant fraction of these empty fields, 39%, are located away from the Galactic plane. We also found 36 extended radio sources that are candidates for association with a corresponding γ-ray object, 19 of which are most likely supernova remnants or H ii regions, whereas 17 could be radio galaxies.

  13. A Search for Rapidly Spinning Pulsars and Fast Transients in Unidentified Radio Sources with the NRAO 43-Meter Telescope

    CERN Document Server

    Schmidt, Deborah; Langston, Glen; Gilpin, Claire

    2013-01-01

    We have searched 75 unidentified radio sources selected from the NRAO VLA Sky Survey (NVSS) catalog for the presence of rapidly spinning pulsars and short, dispersed radio bursts. The sources are radio bright, have no identifications or optical source coincidences, are more than 5% linearly polarized, and are spatially unresolved in the catalog. If these sources are fast-spinning pulsars (e.g. sub-millisecond pulsars), previous large-scale pulsar surveys may have missed detection due to instrumental and computational limitations, eclipsing effects, or diffractive scintillation. The discovery of a sub-millisecond pulsar would significantly constrain the neutron star equation of state and would have implications for models predicting a rapid slowdown of highly recycled X-ray pulsars to millisecond periods from, e.g., accretion disk decoupling. These same sources were previously searched unsuccessfully for pulsations at 610 MHz with the Lovell Telescope at Jodrell Bank. This new search was conducted at a differe...

  14. VLBA Observations of HI in the Archetype Compact Symmetric Object B2352+495

    CERN Document Server

    Araya, E D; Pihlstrom, Y; Taylor, G B; Tremblay, S; Vermeulen, R C

    2009-01-01

    B2352+495 is a prototypical example of a Compact Symmetric Object (CSO). It has a double radio lobe symmetrically located with respect to a central flat spectrum radio core (the location of the AGN) and has a physical extent of less than 200 pc. In this work we report VLBA observation of 21 cm HI absorption toward B2352+495 to investigate the properties of this remarkable radio source, in particular, to explore whether the radio emission can be confined by circumnuclear material (frustration scenario) or whether the source is likely to be young. We confirmed the two HI absorption features previously detected toward B2352+495 - a broad line nearly centered at the systemic velocity of the galaxy and a narrow redshifted component. The atomic gas from the broad absorption component is likely associated with circumnuclear material, consistent with the current paradigm of clumpy HI distribution in toroidal structures around supermassive black holes.

  15. A real-time coherent dedispersion pipeline for the giant metrewave radio telescope

    Science.gov (United States)

    De, Kishalay; Gupta, Yashwant

    2016-02-01

    A fully real-time coherent dedispersion system has been developed for the pulsar back-end at the Giant Metrewave Radio Telescope (GMRT). The dedispersion pipeline uses the single phased array voltage beam produced by the existing GMRT software back-end (GSB) to produce coherently dedispersed intensity output in real time, for the currently operational bandwidths of 16 MHz and 32 MHz. Provision has also been made to coherently dedisperse voltage beam data from observations recorded on disk. We discuss the design and implementation of the real-time coherent dedispersion system, describing the steps carried out to optimise the performance of the pipeline. Presently functioning on an Intel Xeon X5550 CPU equipped with a NVIDIA Tesla C2075 GPU, the pipeline allows dispersion free, high time resolution data to be obtained in real-time. We illustrate the significant improvements over the existing incoherent dedispersion system at the GMRT, and present some preliminary results obtained from studies of pulsars using this system, demonstrating its potential as a useful tool for low frequency pulsar observations. We describe the salient features of our implementation, comparing it with other recently developed real-time coherent dedispersion systems. This implementation of a real-time coherent dedispersion pipeline for a large, low frequency array instrument like the GMRT, will enable long-term observing programs using coherent dedispersion to be carried out routinely at the observatory. We also outline the possible improvements for such a pipeline, including prospects for the upgraded GMRT which will have bandwidths about ten times larger than at present.

  16. Inspiring the next generation of scientists with their observations of quasars, black holes, Jupiter, and SETI with the Goldstone Apple Valley Radio Telescope, GAVRT

    Science.gov (United States)

    Jauncey, D. L.; Levin, S.; Teitelbaum, L.; Hofstadter, M.; Arballo, J.; McConnell, S.; Dorcey, R.; Cole, K.; Kreuser-Jenkins, N.; Leflang, J.; Kruzins, E.; Ricardo, L.; Horiuchi, S.; Nagle, G.; Miro, C. G.

    2017-04-01

    This paper describes a radio astronomy programfor schools, the Goldstone-AppleValley Radio Telescope,GAVRT. The GAVRT program is designed to bring the inspiration and enthusiasm to a younger generation of teachers and children who learn about science by doing real science, just as Iosif Shklovsky brought to an older generation.

  17. Exploring Systems Engineering (and the Universe) Through the RadioJOVE telescope

    Science.gov (United States)

    Aditi Raj, Anya

    2017-01-01

    Amateur projects in radio astronomy are popular methods to engage in what often seems to be an inaccessible field, and pre-made kits are becoming increasingly available to hobbyists and educators. One such kit is the RadioJOVE, which is attractive due to its simplicity, accessibility and its extensive support network and community of users. When coupled with an education in project management, building the RadioJOVE provides a perfect framework to learn about best practices in completing a project. We will primarily discuss the use of the RadioJOVE project to enhance study in project management and systems engineering. We also intend to discuss the importance of amateur projects such as the RadioJOVE in gaining a holistic understanding of radio astronomy and the project’s potential to spark interest in radio astronomy in students of various disciplines.

  18. Gamma-ray Bursts: Radio Afterglow and Host Galaxy Study with The FAST Telescope

    Science.gov (United States)

    Li, L. B.; Huang, Y. F.; Kong, S. W.; Zhang, Z. B.; Li, D.; Luo, J. J.

    2016-02-01

    For four types of GRBs, namely high-luminosity, low-luminosity, standard and failed GRBs, we calculated their radio afterglow light curves. Meanwhile, considering contributions from host galaxies in radio bands, we statistically investigated the effect of hosts on radio afterglows. It is found that a tight anti-correlation exists between the ratio of radio flux (RRF) of host galaxy to the total radio afterglow peak flux and the observed frequency. Using this method, the host flux densities of those bursts without host measurements can be estimated at low or medium frequencies. We predicted that almost all types of radio afterglows, except that of low-luminosity GRBs, can be observed by FAST up to z = 15 or even more. FAST is expected to significantly expand the samples of GRB radio afterglows and host galaxies.

  19. A SEARCH FOR RAPIDLY SPINNING PULSARS AND FAST TRANSIENTS IN UNIDENTIFIED RADIO SOURCES WITH THE NRAO 43 METER TELESCOPE

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Deborah; Crawford, Fronefield; Gilpin, Claire [Department of Physics and Astronomy, Franklin and Marshall College, P.O. Box 3003, Lancaster, PA 17604 (United States); Langston, Glen [National Radio Astronomy Observatory, P.O. Box 2, Green Bank, WV 24944 (United States)

    2013-04-15

    We have searched 75 unidentified radio sources selected from the NRAO VLA Sky Survey catalog for the presence of rapidly spinning pulsars and short, dispersed radio bursts. The sources are radio bright, have no identifications or optical source coincidences, are more than 5% linearly polarized, and are spatially unresolved in the catalog. If these sources are fast-spinning pulsars (e.g., sub-millisecond pulsars), previous large-scale pulsar surveys may have missed detection due to instrumental and computational limitations, eclipsing effects, or diffractive scintillation. The discovery of a sub-millisecond pulsar would significantly constrain the neutron star equation of state and would have implications for models predicting a rapid slowdown of highly recycled X-ray pulsars to millisecond periods from, e.g., accretion disk decoupling. These same sources were previously searched unsuccessfully for pulsations at 610 MHz with the Lovell Telescope at Jodrell Bank. This new search was conducted at a different epoch with a new 800 MHz backend on the NRAO 43 m Telescope at a center frequency of 1200 MHz. Our search was sensitive to sub-millisecond pulsars in highly accelerated binary systems and to short transient pulses. No periodic or transient signals were detected from any of the target sources. We conclude that diffractive scintillation, dispersive smearing, and binary acceleration are unlikely to have prevented detection of the large majority of the sources if they are pulsars, though we cannot rule out eclipsing, nulling or intermittent emission, or radio interference as possible factors for some non-detections. Other (speculative) possibilities for what these sources might include radio-emitting magnetic cataclysmic variables or older pulsars with aligned magnetic and spin axes.

  20. Radio-Gamma-ray connection and spectral evolution in 4C +49.22 (S4 1150+49): the Fermi, Swift and Planck view

    CERN Document Server

    Cutini, S; Orienti, M; Tramacere, A; D'Ammando, F; Verrecchia, F; Polenta, G; Carrasco, L; D'Elia, V; Giommi, P; Gonzalez-Nuevo, J; Grandi, P; Harrison, D; Hays, E; Hoversten, E; Larsson, S; Lahteenmaki, A; Leon-Tavares, J; Lopez-Caniego, M; Natoli, P; Ojha, R; Partridge, B; Porras, A; Reyes, L; Recillas, E; Torresi, E

    2014-01-01

    The Large Area Telescope on board the Fermi Gamma-ray Space Telescope detected a strong gamma-ray flare on 2011 May 15 from a source identified as 4C 49.22, a flat spectrum radio quasar also known as S4 1150+49. This blazar, characterised by a prominent radio-optical-X-ray jet, was in a low gamma-ray activity state during the first years of Fermi observations. Simultaneous observations during the quiescent, outburst and post-flare gamma-ray states were obtained by Swift, Planck and optical-IR-radio telescopes (INAOE, Catalina CSS, VLBA, Metsahovi). The flare is observed from microwave to X-ray bands with correlated variability and the Fermi, Swift and Planck data for this FSRQ show some features more typical of BL Lac objects, like the synchrotron peak in the optical band that outshines the thermal blue-bump emission, and the X-ray spectral softening. Multi-epoch VLBA observations show the ejection of a new component close in time with the GeV gamma-ray flare. The radio-to-gamma-ray spectral energy distributi...

  1. Study on the temperature field effect analysis and test of the five-hundred-meter aperture spherical radio telescope

    Science.gov (United States)

    Song, Li-qiang; Wang, Qi-ming

    2016-10-01

    The thermal problem is one of the important research contents of the design and operation about giant radio antenna. This kind of influence to the antenna has been concerned in the astronomy field. Due to the instantaneous temperature load and uncertainty, it is difficult to accurately analysis and effectively control about its effect. It has important significance to analyze the thermal problem of giant radio antenna to its design and operation. The research of solar cookers and temperature field on Five-hundred-meter Aperture Spherical radio Telescope (FAST) were preceded in detail. The tests of temperature distribute about 30 meters antenna in Mi-yun observatory station were performed. The research work including the parameters related to the sun, the flow algorithm of telescope site, mathematical model of solar cooker, analysis results of temperature field and corresponding control strategy, the temperature distribution test of 30 meters model. The results showed that: solar cookers could be weakened and controlled effectively of FAST. This work will provide a reference to design and operation of the FAST and same big antenna. It has certain theory significance, engineering significance and application value.

  2. VERITAS and VLBA Observations of HESS J1943+213

    CERN Document Server

    Shahinyan, Karlen

    2016-01-01

    HESS J1943+213 is a very high energy (VHE; 100 GeV) {\\gamma}-ray source in the direction of the Galactic plane. 38 hours of deep VERITAS observations taken over two seasons detect the source with ~20 {\\sigma} significance. Monitoring observations of HESS J1943+213 show a remarkably stable flux and spectrum in VHE {\\gamma}-rays. Studies exploring the classification of HESS J1943+213 are converging towards accepting the source as an extreme synchrotron BL Lac object. Specifically, overall SED characteristics of the source, the detection of a potential host galaxy in near-IR imaging, and VLBI observations of the HESS J1943+213 radio counterpart showing extended jet-like emission at milliarcsecond scale and core flux density variability establish the source as a blazar. Recent Very Long Baseline Array (VLBA) observations of the source (shown here for the first time) confirm the extended structure found in the 1.6 GHz band and detect the jet-like component in the 4.6 GHz and the 7.3 GHz bands. The spectral indices...

  3. Fast launch speeds in radio flares, from a new determination of the intrinsic motions of SS 433's jet bolides

    Science.gov (United States)

    Jeffrey, Robert M.; Blundell, Katherine M.; Trushkin, Sergei A.; Mioduszewski, Amy J.

    2016-09-01

    We present new high-resolution, multi-epoch, Very Long Baseline Array (VLBA) radio images of the Galactic microquasar SS 433. We are able to observe plasma knots in the milliarcsecond-scale jets more than 50 d after their launch. This unprecedented baseline in time allows us to determine the bulk launch speed of the radio-emitting plasma during a radio flare, using a new method which we present here, and which is completely independent of optical spectroscopy. We also apply this method to an earlier sequence of 39 short daily VLBA observations, which cover a period in which SS 433 moved from quiescence into a flare. In both data sets we find, for the first time at radio wavebands, clear evidence that the launch speeds of the milliarcsecond-scale jets rise as high as 0.32c during flaring episodes. By comparing these images of SS 433 with photometric radio monitoring from the RATAN-600 telescope, we explore further properties of these radio flares.

  4. Fast launch speeds in radio flares, from a new determination of the intrinsic motions of SS 433's jet bolides

    CERN Document Server

    Jeffrey, Robert M; Trushkin, Sergei A; Mioduszewski, Amy J

    2016-01-01

    We present new high-resolution, multi-epoch, VLBA radio images of the Galactic microquasar SS 433. We are able to observe plasma knots in the milliarcsecond-scale jets more than 50 days after their launch. This unprecedented baseline in time allows us to determine the bulk launch speed of the radio-emitting plasma during a radio flare, using a new method which we present here, and which is completely independent of optical spectroscopy. We also apply this method to an earlier sequence of 39 short daily VLBA observations, which cover a period in which SS 433 moved from quiescence into a flare. In both datasets we find, for the first time at radio wavebands, clear evidence that the launch speeds of the milliarcsecond-scale jets rise as high as 0.32c during flaring episodes. By comparing these images of SS 433 with photometric radio monitoring from the RATAN telescope, we explore further properties of these radio flares.

  5. Europe, Japan and North America Prepare for Joint Construction of the Giant Radio Telescope "ALMA" in Chile

    Science.gov (United States)

    2001-04-01

    Caption : PR Photo 14/01 shows how the ALMA facility may look like when it is ready at Chajnantor. Courtesy NAOJ . Representatives from Europe, Japan, and North America met in Tokyo today and signed a Resolution affirming their mutual intent to construct and operate a giant radio telescope in co-operation with the Republic of Chile, where the telescope will be located. The Atacama Large Millimeter/Submillimeter Array (ALMA) is conceived as a radio telescope comprised of sixty-four transportable 12-meter diameter antennas distributed over an area 14 km in extent. Japanese participation will allow enhanced imaging and spectroscopy, especially at submillimeter wavelengths. By pointing all the antennas in unison toward a single astronomical object, and combining the signals detected by all the antennas with a super-fast digital signal processor, this gigantic radio telescope achieves an imaging detail 10 times better than that of the Hubble Space Telescope. The combined area of all 64 antennas used to collect signals from celestial objects is more than 40 times larger than that available to astronomers using existing submillimeter telescopes. ALMA will be built on the Andean plateau at 5,000 meters altitude near the Atacama Desert of northern Chile. This site provides the exceptionally dry atmospheric conditions necessary for astronomical observations at millimeter and submillimeter wavelengths (wavelengths between the radio and far-infrared spectral regions). Observations with this telescope will have a profound impact on virtually all fields of astrophysical research. The most important targets include the most distant (i.e., the youngest) galaxies as they emerged in the early Universe. These are expected to have become rapidly enshrouded in the dust produced by the first stars; the dust absorbs much of the starlight making the galaxies difficult to see in the optical wavebands, but these same galaxies shine brightly at millimeter and submillimeter wavelengths. In

  6. Calibrating High-Precision Faraday Rotation Measurements for LOFAR and the Next Generation of Low-Frequency Radio Telescopes

    CERN Document Server

    Sotomayor-Beltran, C; Hessels, J W T; de Bruyn, G; Noutsos, A; Alexov, A; Anderson, J; Asgekar, A; Avruch, I M; Beck, R; Bell, M E; Bell, M R; Bentum, M J; Bernardi, G; Best, P; Birzan, L; Bonafede, A; Breitling, F; Broderick, J; Brouw, W N; Brueggen, M; Ciardi, B; de Gasperin, F; Dettmar, R -J; van Duin, A; Duscha, S; Eisloeffel, J; Falcke, H; Fallows, R A; Fender, R; Ferrari, C; Frieswijk, W; Garrett, M A; Griessmeier, J; Grit, T; Gunst, A W; Hassall, T E; Heald, G; Hoeft, M; Horneffer, A; Iacobelli, M; Juette, E; Karastergiou, A; Keane, E; Kohler, J; Kramer, M; Kondratiev, V I; Koopmans, L V E; Kuniyoshi, M; Kuper, G; van Leeuwen, J; Maat, P; Macario, G; Markoff, S; McKean, J P; Mulcahy, D D; Munk, H; Orru, E; Paas, H; Pandey-Pommier, M; Pilia, M; Pizzo, R; Polatidis, A G; Reich, W; Roettgering, H; Serylak, M; Sluman, J; Stappers, B W; Tagger, M; Tang, Y; Tasse, C; ter Veen, S; Vermeulen, R; van Weeren, R J; Wijers, R A M J; Wijnholds, S J; Wise, M W; Wucknitz, O; Yatawatta, S; Zarka, P; 10.1051/0004-6361/201220728

    2013-01-01

    Faraday rotation measurements using the current and next generation of low-frequency radio telescopes will provide a powerful probe of astronomical magnetic fields. However, achieving the full potential of these measurements requires accurate removal of the time-variable ionospheric Faraday rotation contribution. We present ionFR, a code that calculates the amount of ionospheric Faraday rotation for a specific epoch, geographic location, and line-of-sight. ionFR uses a number of publicly available, GPS-derived total electron content maps and the most recent release of the International Geomagnetic Reference Field. We describe applications of this code for the calibration of radio polarimetric observations, and demonstrate the high accuracy of its modeled ionospheric Faraday rotations using LOFAR pulsar observations. These show that we can accurately determine some of the highest-precision pulsar rotation measures ever achieved. Precision rotation measures can be used to monitor rotation measure variations - e...

  7. Measurements of Antenna Surface for a Millimeter-Wave Space Radio Telescope II; Metal Mesh Surface for Large Deployable Reflector

    CERN Document Server

    Kamegai, Kazuhisa

    2012-01-01

    Large deployable antennas with a mesh surface woven by fine metal wires are an important technology for communications satellites and space radio telescopes. However, it is difficult to make metal mesh surfaces with sufficient radio-frequency (RF) performance for frequencies higher than millimeter waves. In this paper, we present the RF performance of metal mesh surfaces at 43 GHz. For this purpose, we developed an apparatus to measure the reflection coefficient, transmission coefficient, and radiative coefficient of the mesh surface. The reflection coefficient increases as a function of metal mesh surface tension, whereas the radiative coefficient decreases. The anisotropic aspects of the reflection coefficient and the radiative coefficient are also clearly seen. They depend on the front and back sides of the metal mesh surface and the rotation angle. The transmission coefficient was measured to be almost constant. The measured radiative coefficients and transmission coefficients would cause significant degr...

  8. Single dish performance of KVN 21-m radio telescopes:Simultaneous observations at 22 and 43 GHz

    CERN Document Server

    Lee, Sang-Sung; Oh, Chung Sik; Han, Seog-Tae; Je, Do-Heung; Kim, Kee-Tae; Wi, Seog-Oh; Cho, Se-Hyung; Sohn, Bong Won; Kim, Jaeheon; Lee, Jeewon; Oh, Se-Jin; Song, Min-Gyu; Kang, Jiman; Jung, Moon-Hee; Lee, Jeong Ae; Oh, Junghwan; Bae, Jae-Han; Yun, So-Young; Lee, Jung-Won; Kim, Bong Gyu; Chung, Hyunsoo; Roh, Duk-Gyoo; Lee, Chang Hoon; Kim, Hyun Goo; Kim, Hyo Ryoung; Yeom, Jae-Hwan; Kurayama, Tomoharu; Jung, Taehyun; Park, Pulun; Kim, Min Joong; Yoon, Dong-Hwan; Kim, Won-Ju

    2011-01-01

    We report simultaneous multi-frequency observing performance at 22 and 43 GHz of the 21-m shaped-Cassegrain radio telescopes of the Korean VLBI Network (KVN). KVN is the first millimeter-dedicated VLBI network in Korea having a maximum baseline length of 480 km. It currently operates at 22 and 43 GHz and planed to operate in four frequency bands, 22, 43, 86, and 129 GHz. The unique quasioptics of KVN enable simultaneous multi-frequency observations based on efficient beam filtering and accuarate antenna-beam alignment at 22 and 43 GHz. We found that the offset of the beams is within 20 degrees.

  9. The panels for primary and secondary mirror reflectors and the Active Surface System for the new Sardinia Radio Telescope

    Science.gov (United States)

    Zacchiroli, G.; Fiocchi, F.; Maccaferri, G.; Morsiani, M.; Orfei, A.; Pernechele, C.; Pisanu, T.; Roda, J.; Vargiu, G.

    In this paper we will describe the panels for the primary and secondary mirror reflectors and the active surface system that will be provided on the Sardinia Radio Telescope. The panels for the primary and secondary mirror have been designed to allow an operating frequency up to 100 GHz. The active surface system will be used to overcome the effect of gravity deformation on the antenna gain and to re-shape the primary mirror in a parabolic form, in order to avoid large phase error contribution on the gain for the highest frequencies placed in the primary focus.

  10. Fermi Large Area Telescope Detection of Extended Gamma-Ray Emission from the Radio Galaxy Fornax A

    CERN Document Server

    ,

    2016-01-01

    We report the Fermi Large Area Telescope detection of extended gamma-ray emission from the lobes of the radio galaxy Fornax A using 6.1 years of Pass 8 data. After Centaurus A, this is now the second example of an extended gamma-ray source attributed to a radio galaxy. Both an extended flat disk morphology and a morphology following the extended radio lobes were preferred over a point-source description, and the core contribution was constrained to be 100 MeV gamma-ray emission established, we model the source broadband emission considering currently available total lobe radio and millimeter flux measurements, as well as X-ray detections attributed to inverse Compton (IC) emission off the cosmic microwave background (CMB). Unlike the Centaurus A case, we find that a leptonic model involving IC scattering of CMB and extragalactic background light (EBL) photons underpredicts the gamma-ray fluxes by factors of about ~ 2 - 3, depending on the EBL model adopted. An additional gamma-ray spectral component is thus ...

  11. PSRPI Mapping the Galactic distribution of pulsars with the VLBA

    Data.gov (United States)

    National Aeronautics and Space Administration — Observations for the initial PSRPI sample of 60 pulsars have now concluded. 84.7 hours were observed on the VLBA (plus 12 hours from a pilot project) searching for...

  12. Terrestrial monitoring of a radio telescope reference point using comprehensive uncertainty budgeting. Investigations during CONT14 at the Onsala Space Observatory

    Science.gov (United States)

    Lösler, Michael; Haas, Rüdiger; Eschelbach, Cornelia

    2016-05-01

    During the 15-day-long global very long baseline interferometry campaign CONT14, a terrestrial monitoring campaign was carried out at the Onsala Space Observatory. The goal of these efforts was to monitor the reference point of the Onsala 20 m radio telescope during normal telescope operations. Parts of the local site network as well as a number of reflectors that were mounted on the 20 m radio telescope were observed in an automated and continual way using the in-house-developed software package HEIMDALL. The analysis of the observed data was performed using a new concept for a coordinate-based network adjustment to allow the full adjustment process in a true Cartesian global reference frame. The Akaike Information Criterion was used to select the preferable functional model for the network adjustment. The comprehensive stochastic model of this network adjustment process considers over 25 parameters, and, to describe the persistence of the observations performed during the monitoring with a very high measurement frequency, includes also time-dependent covariances. In total 15 individual solutions for the radio telescope reference point were derived, based on monitoring observations during the normal operation of the radio telescope. Since the radio telescope was moving continually, the influence of timing errors was studied and considered in the adjustment process. Finally, recursive filter techniques were introduced to combine the 15 individual solutions. Accuracies at the sub-millimeter level could be achieved for the radio telescope reference point. Thus, the presented monitoring concept fulfills the requirement proposed by the global geodetic observing system.

  13. Beaming structures of Jupiter's decametric common S-bursts observed from LWA1, NDA, and URAN2 radio telescopes

    CERN Document Server

    Imai, Masafumi; Clarke, Tracy E; Higgins, Charles A; Panchenko, Mykhaylo; Dowell, Jayce; Imai, Kazumasa; Brazhenko, Anatolii I; Frantsuzenko, Anatolii V; Konovalenko, Alexandr A

    2016-01-01

    On 2015 February 21, simultaneous observations of Jupiter's decametric radio emission between 10 and 33 MHz were carried out using three powerful low-frequency radio telescopes: Long Wavelength Array Station One (LWA1) in USA; Nan\\c{c}ay Decameter Array (NDA) in France; and URAN2 telescope in Ukraine. We measure lag times of short-bursts (S-bursts) for 105-minutes of data over effective baselines up to 8460 km by using cross-correlation analysis of the spectrograms from each instrument. Of particular interest is the measurement of the beaming thickness of S-bursts, testing if either flashlight- or beacon-like beaming is emanating from Jupiter. We find that the lag times for all pairs drift slightly as time elapses, in agreement with expectations from the flashlight-like beaming model. This leads to a new constraint of the minimum beaming thickness of 2.66". Also, we find that most of the analyzed data abound with S-bursts, whose occurrence probability peaks at 17-18 MHz.

  14. a Simulation Tool Assisting the Design of a Close Range Photogrammetry System for the Sardinia Radio Telescope

    Science.gov (United States)

    Buffa, F.; Pinna, A.; Sanna, G.

    2016-06-01

    The Sardinia Radio Telescope (SRT) is a 64 m diameter antenna, whose primary mirror is equipped with an active surface capable to correct its deformations by means of a thick network of actuators. Close range photogrammetry (CRP) was used to measure the self-load deformations of the SRT primary reflector from its optimal shape, which are requested to be minimized for the radio telescope to operate at full efficiency. In the attempt to achieve such performance, we conceived a near real-time CRP system which requires the cameras to be installed in fixed positions and at the same time to avoid any interference with the antenna operativeness. The design of such system is not a trivial task, and to assist our decision we therefore developed a simulation pipeline to realistically reproduce and evaluate photogrammetric surveys of large structures. The described simulation environment consists of (i) a detailed description of the SRT model, included the measurement points and the camera parameters, (ii) a tool capable of generating realistic images accordingly to the above model, and (iii) a self-calibrating bundle adjustment to evaluate the performance in terms of RMSE of the camera configurations.

  15. Infrared-faint radio sources are at high redshifts. Spectroscopic redshift determination of infrared-faint radio sources using the Very Large Telescope

    Science.gov (United States)

    Herzog, A.; Middelberg, E.; Norris, R. P.; Sharp, R.; Spitler, L. R.; Parker, Q. A.

    2014-07-01

    Context. Infrared-faint radio sources (IFRS) are characterised by relatively high radio flux densities and associated faint or even absent infrared and optical counterparts. The resulting extremely high radio-to-infrared flux density ratios up to several thousands were previously known only for high-redshift radio galaxies (HzRGs), suggesting a link between the two classes of object. However, the optical and infrared faintness of IFRS makes their study difficult. Prior to this work, no redshift was known for any IFRS in the Australia Telescope Large Area Survey (ATLAS) fields which would help to put IFRS in the context of other classes of object, especially of HzRGs. Aims: This work aims at measuring the first redshifts of IFRS in the ATLAS fields. Furthermore, we test the hypothesis that IFRS are similar to HzRGs, that they are higher-redshift or dust-obscured versions of these massive galaxies. Methods: A sample of IFRS was spectroscopically observed using the Focal Reducer and Low Dispersion Spectrograph 2 (FORS2) at the Very Large Telescope (VLT). The data were calibrated based on the Image Reduction and Analysis Facility (IRAF) and redshifts extracted from the final spectra, where possible. This information was then used to calculate rest-frame luminosities, and to perform the first spectral energy distribution modelling of IFRS based on redshifts. Results: We found redshifts of 1.84, 2.13, and 2.76, for three IFRS, confirming the suggested high-redshift character of this class of object. These redshifts and the resulting luminosities show IFRS to be similar to HzRGs, supporting our hypothesis. We found further evidence that fainter IFRS are at even higher redshifts. Conclusions: Considering the similarities between IFRS and HzRGs substantiated in this work, the detection of IFRS, which have a significantly higher sky density than HzRGs, increases the number of active galactic nuclei in the early universe and adds to the problems of explaining the formation of

  16. System and method for phase retrieval for radio telescope and antenna control

    Science.gov (United States)

    Dean, Bruce H. (Inventor)

    2013-01-01

    Disclosed herein are systems, methods, and non-transitory computer-readable storage media for radio phase retrieval. A system practicing the method gathers first data from radio waves associated with an object observed via a first aperture, gathers second data from radio waves associated with the object observed via an introduced second aperture associated with the first aperture, generates reduced noise data by incoherently subtracting the second data from the first data, and performs phase retrieval for the radio waves by modeling the reduced noise data using a single Fourier transform. The first and second apertures are at different positions, such as side by side. This approach can include determining a value Q which represents a ratio of wavelength times a focal ratio divided by pixel spacing. This information can be used to accurately measure and correct alignment errors or other optical system flaws in the apertures.

  17. Practical Limits in the Sensitivity-Linearity Trade-off for Radio Telescope Front Ends in the HF and VHF-low Bands

    CERN Document Server

    Tillman, R H; Brendler, J

    2016-01-01

    Radio telescope front ends must have simultaneously low noise and sufficiently-high linearity to accommodate interfering signals. Typically these are opposing design goals. For modern radio telescopes operating in the HF (3-30 MHz) and VHF-low (30-88 MHz) bands, the problem is more nuanced in that front end noise temperature may be a relatively small component of the system temperature, and increased linearity may be required due to the particular interference problems associated with this spectrum. In this paper we present an analysis of the sensitivity-linearity trade off at these frequencies, applicable to existing commercially-available monolithic microwave integrated circuit (MMIC) amplifiers in single-ended, differential, and parallelized configurations. This analysis and associated findings should be useful in the design and upgrade of front ends for low frequency radio telescopes. The analysis is demonstrated explicitly for one of the better-performing amplifiers encountered in this study, the Mini-Ci...

  18. Near-infrared Hubble Space Telescope polarimetry of a complete sample of narrow-line radio galaxies

    CERN Document Server

    Ramírez, E A; Axon, D; Batcheldor, D; Packham, C; Lopez-Rodriguez, E; Sparks, W; Young, S

    2014-01-01

    We present an analysis of 2.05 $\\mu$m Hubble Space Telescope (HST) polarimetric data for a sample of 13 nearby Fanaroff-Riley type II (FRII) 3CR radio sources ($0.03radio galaxies (NLRG) at optical wavelengths. We find that the compact cores of the NLRG in our sample are intrinsically highly polarised in the near-IR ($6 < P_{2.05\\mu m} < 60$ per cent), with the electric-vector (E-vector) perpendicular to the radio axis in 54 per cent of the sources. The levels of extinction required to produce near-infrared polarisation by the dichroic extinction mechanism are consistent with the measured values reported in Ram\\'irez et al. (2014), provided that this mechanism has its maximum efficiency. This consistency suggests that the nuclear polarisation could be due to dichroic extinction. In this case, toroidal magnetic fields that are highly coherent would be required in the circumnuclear tori to align the elongated dust grains responsible for the dichroic extin...

  19. Effect of the rail unevenness on the pointing accuracy of large radio telescope

    Science.gov (United States)

    Li, Na; Wu, Jiang; Duan, Bao-Yan; Wang, Cong-Si

    2017-03-01

    Considering the stringent requirement of the pointing accuracy up to 2.5″ of the World largest full steerable telescope, this paper presents a coarse-fine mixed model to describe the azimuth rail unevenness. First, the coarse-fine mixed model is proposed. In the model, the trigonometric function is utilized to describe the error with long wavelength whilst the fractal function is used for the short wavelength errors, separately. Then the mathematic model of the pointing accuracy is developed mathematically. Finally, the coarse-fine model and point accuracy model are applied to Green Bank Telescope with valuable result. This paved the way for predicting point error of Qi Tai Telescope.

  20. Simultaneous observations of solar sporadic radio emission by the radio telescopes UTR-2, URAN-2 and NDA within the frequency range 8-41MHz

    Science.gov (United States)

    Melnik, V. N.; Konovalenko, A. A.; Rucker, H. O.; Brazhenko, A. I.; Briand, C.; Dorovskyy, V. V.; Zarka, P.; Denis, L.; Bulatzen, V. G.; Frantzusenko, A. V.; Stanislavskyy, A. A.

    2012-04-01

    From 25 June till 12 August 2011 sporadic solar radio emission was observed simultaneously by three separate radio telescopes: UTR-2 (Kharkov, Ukraine), URAN-2 (Poltava, Ukraine) and NDA (Nancay, France). During these observations several type II bursts with double and triple harmonics were registered, as well as type II bursts with complex herringbone structure. The events of particular interest were type II bursts registered on 9 and 11 August 2011. These bursts had opposite sign of circular polarization at different parts of their dynamic spectra. In our opinion we registered the emissions, which came from the different parts of the shock propagating through the solar corona. We have observed also groups of type III bursts merged into one burst, type III bursts with triple harmonics and type III bursts with "split" polarization. In addition some unusual solar bursts were registered: storms of strange narrow-band (up to 500kHz) bursts with high polarization degree (about 80%), decameter spikes of extremely short durations (200-300ms), "tadpole-like" bursts with durations of 1-2s and polarization degree up to 60%.

  1. Imaging of SNR IC443 and W44 with the Sardinia Radio Telescope at 1.5 and 7 GHz

    Science.gov (United States)

    Egron, E.; Pellizzoni, A.; Iacolina, M. N.; Loru, S.; Marongiu, M.; Righini, S.; Cardillo, M.; Giuliani, A.; Mulas, S.; Murtas, G.; Simeone, D.; Concu, R.; Melis, A.; Trois, A.; Pilia, M.; Navarrini, A.; Vacca, V.; Ricci, R.; Serra, G.; Bachetti, M.; Buttu, M.; Perrodin, D.; Buffa, F.; Deiana, G. L.; Gaudiomonte, F.; Fara, A.; Ladu, A.; Loi, F.; Marongiu, P.; Migoni, C.; Pisanu, T.; Poppi, S.; Saba, A.; Urru, E.; Valente, G.; Vargiu, G. P.

    2017-09-01

    Observations of supernova remnants (SNRs) are a powerful tool for investigating the later stages of stellar evolution, the properties of the ambient interstellar medium and the physics of particle acceleration and shocks. For a fraction of SNRs, multiwavelength coverage from radio to ultra-high energies has been provided, constraining their contributions to the production of Galactic cosmic rays. Although radio emission is the most common identifier of SNRs and a prime probe for refining models, high-resolution images at frequencies above 5 GHz are surprisingly lacking, even for bright and well-known SNRs such as IC443 and W44. In the frameworks of the Astronomical Validation and Early Science Program with the 64-m single-dish Sardinia Radio Telescope, we provided, for the first time, single-dish deep imaging at 7 GHz of the IC443 and W44 complexes coupled with spatially resolved spectra in the 1.5-7 GHz frequency range. Our images were obtained through on-the-fly mapping techniques, providing antenna beam oversampling and resulting in accurate continuum flux density measurements. The integrated flux densities associated with IC443 are S1.5 GHz = 134 ± 4 Jy and S7 GHz = 67 ± 3 Jy. For W44, we measured total flux densities of S1.5 GHz = 214 ± 6 Jy and S7 GHz = 94 ± 4 Jy. Spectral index maps provide evidence of a wide physical parameter scatter among different SNR regions: a flat spectrum is observed from the brightest SNR regions at the shock, while steeper spectral indices (up to ˜ 0.7) are observed in fainter cooling regions, disentangling in this way different populations and spectra of radio/gamma-ray-emitting electrons in these SNRs.

  2. No Radio Flaring Detected from Cygnus X-3 at 3 GHz by Allen Telescope Array

    Science.gov (United States)

    Williams, P. K. G.; Bower, G. C.; Tomsick, J. A.; Bodaghee, A.; Corbet, R. H. D.

    2011-01-01

    Following the announcement of a 98 GHz flare from the microquasar Cygnus X-3 (ATel #3130), we observed it with the Allen Telescope Array (Welch et al., 2009 Proc. IEEE 97 1438 for 2.5 hours beginning at 2011 January 28.848 UT (MJD 55589.848), about 4.0 hours after the 98 GHz observations concluded.

  3. Ray-tracing and physical-optics analysis of the aperture efficiency in a radio telescope.

    Science.gov (United States)

    Olmi, Luca; Bolli, Pietro

    2007-07-01

    The performance of telescope systems working at microwave or visible-IR wavelengths is typically described in terms of different parameters according to the wavelength range. Most commercial ray-tracing packages have been specifically designed for use with visible-IR systems and thus, though very flexible and sophisticated, do not provide the appropriate parameters to fully describe microwave antennas and to compare with specifications. We demonstrate that the Strehl ratio is equal to the phase efficiency when the apodization factor is taken into account. The phase efficiency is the most critical contribution to the aperture efficiency of an antenna and the most difficult parameter to optimize during the telescope design. The equivalence between the Strehl ratio and the phase efficiency gives the designer/user of the telescope the opportunity to use the faster commercial ray-tracing software to optimize the design. We also discuss the results of several tests performed to check the validity of this relationship that we carried out using a ray-tracing software, ZEMAX, and a full Physical Optics software, GRASP9.3, applied to three different telescope designs that span a factor of approximately 10 in terms of D/lambda. The maximum measured discrepancy between phase efficiency and Strehl ratio varies between approximately 0.4% and 1.9% up to an offset angle of >40 beams, depending on the optical configuration, but it is always less than 0.5% where the Strehl ratio is >0.95.

  4. Monitoring of Cyg X-3 giant flare with Medicina and the Sardinia Radio Telescope

    Science.gov (United States)

    Egron, E.; Pellizzoni, A.; Giroletti, M.; Righini, S.; Orlati, A.; Iacolina, M. N.; Navarrini, A.; Buttu, M.; Migoni, C.; Melis, A.; Concu, R.; Vargiu, G. P.; Bachetti, M.; Pilia, M.; Trois, A.; Loru, S.; Marongiu, M.

    2016-09-01

    Following the detection of Cyg X-3 entering in an ultra soft X-ray state, a forthcoming giant flare was predicted by Trushkin et al. (ATel #9416). In fact, a significant radio flux increase was detected three weeks later, on 14-16 September 2016 (ATel #9502).

  5. VLBA 24 and 43 GHz observations of massive binary black hole candidate PKS 1155 + 251

    Science.gov (United States)

    Yang, Xiaolong; Liu, Xiang; Yang, Jun; Mi, Ligong; Cui, Lang; An, Tao; Hong, Xiaoyu; Ho, Luis C.

    2017-10-01

    PKS 1155+251 is a radio-loud quasar source at z = 0.203. Observations using very long baseline interferometry (VLBI) at ∼2, 5, 8 and 15 GHz show that the structure of the radio source is quite complicated on parsec scales and that the outer hotspots are apparently undergoing a significant contraction. Because these results cannot be fully explained based on the compact symmetric object (CSO) scenario with a radio core located between the northern and southern complexes, we made observations with the Very Long Baseline Array (VLBA) at 24 and 43 GHz to search for compact substructures and alternative interpretations. The results show that the radio core revealed in the previous VLBI observations remains compact with a flat spectrum in our sub-milli-arcsecond-resolution images; the northern lobe emission becomes faint at 24 GHz and is mostly resolving out at 43 GHz; the southern complex is more bright but has been resolved into the brightest southern-end (S1) and jet or tail alike components westwards. Explaining the southern components aligned westward with a standard CSO scenario alone remains a challenge. As for the flatter spectral index of the southern-end component S1 between 24 and 43 GHz in our observations and the significant 15 GHz VLBA flux variability of S1, an alternative scenario is that the southern complex may be powered by a secondary black hole residing at S1. But more sensitive and high-resolution VLBI monitoring is required to discriminate the CSO and the binary black hole scenarios.

  6. Big-Data Perspective to Operating an SKA-Type Synthesis Array Radio Telescope

    Science.gov (United States)

    Shanmugha Sundaram, GA

    2015-08-01

    Of the two forerunner sites, viz. Australia and South Africa, where pioneering advancements to state-of-the-art in synthesis array radio astronomy instrumentation are being attempted in the form of pathfinders to the Square Kilometer Array (SKA), for its eventual deployment, a diversity of site-dependent topology and design metrics exists. Towards addressing some of the fundamental mysteries in physics at the micro- and macro-cosm levels, that form the Key Science Projects (KSPs) for the SKA, and interfacing them to an optimally designed array conguration, a critical evaluation of their radio imaging capabilities and metrics becomes paramount. Here, the various KSPs and instrument design specifications are discussed, for relative merits and adaptability to either site, from invoking well-founded and established array-design and optimization principles designed into a customized software tool. Since the problem of array design is one that encompasses variables on several scales such as separation distances between the radio interferometric pair (termed the baseline), factors such as redundancy, flux and phase calibration, bandwidth, integration time, clock synchronization for the correlation process at the detector, and many other ambient-defined parameters, there is a significant component of big data involved in the complex visibilities that are to be Fourier transformed from the spatial to the radio-sky domain (to generate a radio sky map) using vast computational infrastructure, with robust data connectivity and data handling facilities to support this. A crucial requirement exists to make the general public aware of the implications of such a massive scale scientific and technological venture, which shall be the focus of this presentation.

  7. Prospects for Detecting the 326.5MHz Redshifted 21-cm HI Signal with the Ooty Radio Telescope (ORT)

    Indian Academy of Sciences (India)

    Sk. Saiyad Ali; Somnath Bharadwaj

    2014-06-01

    Observations of the redshifted 21-cm HI fluctuations promise to be an important probe of the post-reionization era ( ≤ 6). In this paper we calculate the expected signal and foregrounds for the upgraded Ooty Radio Telescope (ORT) which operates at frequency = 326.5MHz which corresponds to redshift = 3.35. Assuming that the visibilities contain only the HI signal and system noise, we show that a 3 detection of the HI signal (∼ 1 mK) is possible at angular scales 11' to 3° with ≈ 1000 h of observation. Foreground removal is one of the major challenges for a statistical detection of the redshifted 21 cm HI signal. We assess the contribution of different foregrounds and find that the 326.5MHz sky is dominated by the extragalactic point sources at the angular scales of our interest. The expected total foregrounds are 104−105 times higher than the HI signal.

  8. An evaluation of the effectiveness of observation camera placement within the MeerKAT radio telescope project

    Directory of Open Access Journals (Sweden)

    Heyns, Andries

    2015-08-01

    Full Text Available A recent development within the MeerKAT sub-project of the Square Kilometre Array radio telescope network was the placement of a network of three observation cameras in pursuit of two specific visibility objectives. In this paper, we evaluate the effectiveness of the locations of the MeerKAT observation camera network according to a novel multi-objective geographic information systems-based facility location framework. We find that the configuration chosen and implemented by the MeerKAT decision-makers is of very high quality, although we are able to uncover slightly superior alternative placement configurations. A significant amount of time and effort could, however, have been saved in the process of choosing the appropriate camera sites, had our solutions been available to the decision-makers.

  9. Australia telescope compact array observations of radio recombination lines toward 30 Doradus

    NARCIS (Netherlands)

    Peck, AB; Goss, WM; Dickel, HR; Roelfsema, PR; Kesteven, MJ; Dickel, [No Value; Milne, DK; Points, SD

    1997-01-01

    Three hydrogen recombination lines-H90 alpha at 8.9 GHz, H92 alpha at 8.3 GHz, and H109 alpha at 5.0 GHz-have been observed with the Australia Telescope Compact Array toward the 30 Doradus Nebula, the giant H II region in the Large Magellanic Cloud. In this paper, emphasis is placed on the more sens

  10. The extreme flare in III Zw 2: evolution of a radio jet in a Seyfert galaxy

    NARCIS (Netherlands)

    Brunthaler, A.; Falcke, H.D.E.; Bower, G.C.; Aller, M.F.; Aller, H.D.; Teräsranta, H.

    2005-01-01

    A very detailed monitoring of a radio flare in the Seyfert I galaxy III Zw 2 with the VLA and the VLBA is presented. The relative astrometry in the VLBA observations was precise to a few muas. The spectral and spatial evolutions of the source are closely linked, and these observations allowed us to

  11. The extreme flare in III Zw 2: evolution of a radio jet in a Seyfert galaxy

    NARCIS (Netherlands)

    Brunthaler, A.; Falcke, H.D.E.; Bower, G.C.; Aller, M.F.; Aller, H.D.; Teräsranta, H.

    2005-01-01

    A very detailed monitoring of a radio flare in the Seyfert I galaxy III Zw 2 with the VLA and the VLBA is presented. The relative astrometry in the VLBA observations was precise on a level of a few microarcseconds. Spectral and spatial evolution of the source are closely linked and these observation

  12. Analysis of the GPS Observations of the Site Survey at Sheshan 25-m Radio Telescope in August 2008

    Science.gov (United States)

    Liu, L.; Cheng, Z. Y.; Li, J. L.

    2010-01-01

    The processing of the GPS observations of the site survey at Sheshan 25-m radio telescope in August 2008 is reported. Because each session in this survey is only about six hours, not allowing the subdaily high frequency variations in the station coordinates to be reasonably smoothed, and because there are serious cycle slips in the observations and a large volume of data would be rejected during the software automatic adjustment of slips, the ordinary solution settings of GAMIT needed to be adjusted by loosening the constraints in the a priori coordinates to 10 m, adopting the "quick" mode in the solution iteration, and combining Cview manual operation with GAMIT automatic fixing of cycle slips. The resulting coordinates of the local control polygon in ITRF2005 are then compared with conventional geodetic results. Due to large rotations and translations in the two sets of coordinates (geocentric versus quasi-topocentric), the seven transformation parameters cannot be solved for directly. With various trial solutions it is shown that with a partial pre-removal of the large parameters, high precision transformation parameters can be obtained with post-fit residuals at the millimeter level. This analysis is necessary to prepare the follow-on site and transformation survey of the VLBI and SLR telescopes at Sheshan

  13. A return to strong radio flaring by Circinus X-1 observed with the Karoo Array Telescope test array KAT-7

    CERN Document Server

    Armstrong, R P; Nicolson, G D; Ratcliffe, S; Linares, M; Horrell, J; Richter, L; Schurch, M P E; Coriat, M; Woudt, P; Jonas, J; Booth, R; Fanaroff, B

    2013-01-01

    Circinus X-1 is a bright and highly variable X-ray binary which displays strong and rapid evolution in all wavebands. Radio flaring, associated with the production of a relativistic jet, occurs periodically on a ~17-day timescale. A longer-term envelope modulates the peak radio fluxes in flares, ranging from peaks in excess of a Jansky in the 1970s to an historic low of milliJanskys during the years 1994 to 2007. Here we report first observations of this source with the MeerKAT test array, KAT-7, part of the pathfinder development for the African dish component of the Square Kilometre Array (SKA), demonstrating successful scientific operation for variable and transient sources with the test array. The KAT-7 observations at 1.9 GHz during the period 13 December 2011 to 16 January 2012 reveal in temporal detail the return to the Jansky-level events observed in the 1970s. We compare these data to contemporaneous single-dish measurements at 4.8 and 8.5 GHz with the HartRAO 26-m telescope and X-ray monitoring from...

  14. New millisecond pulsars detected by the Fermi Large Area Telescope and the radio/gamma-ray connection

    CERN Document Server

    Espinoza, C M; Celik, O; Weltevrede, P; Stappers, B W; Smith, D A; Kerr, M; Zavlin, V E; Cognard, I; Eatough, R P; Freire, P C C; Janssen, G H; Camilo, F; Desvignes, G; Hewitt, J W; Hou, X; Johnston, S; Keith, M; Kramer, M; Lyne, A; Manchester, R N; Ransom, S M; Ray, P S; Shannon, R; Theureau, G; Webb, N

    2012-01-01

    We report on the discovery of gamma-ray pulsations from five millisecond pulsars (MSPs) using the Fermi Large Area Telescope (LAT) and timing ephemerides provided by various radio observatories. We also present confirmation of the gamma-ray pulsations from a sixth source, PSR J2051-0827. Five of these six MSPs are in binary systems: PSRs J1713+0747, J1741+1351, J1600-3053 and the two black widow binary pulsars PSRs J0610-2100 and 2051-0827. The only isolated MSP is the nearby PSR J1024-0719, which is also known to emit X-rays. We present X-ray observations in the direction of PSRs J1600-3053 and J2051-0827. While the latter is firmly detected, we an only give upper limits for the X-ray flux of the former. There are no dedicated X-ray observations available for the other 3 objects. The MSPs mentioned above, together with most of the MSPs detected by Fermi, are used to put together a sample of 30 gamma-ray MSPs which is used to study the morphology and phase connection of radio and gamma-ray pulse profiles. We ...

  15. Providing hydrogen maser timing stability to orbiting VLBI radio telescope observations by post-measurement compensation of linked frequency standard imperfections

    Science.gov (United States)

    Springett, James C.

    1994-01-01

    Orbiting VLBI (OVLBI) astronomical observations are based upon measurements acquired simultaneously from ground-based and earth-orbiting radio telescopes. By the mid-1990s, two orbiting VLBI observatories, Russia's Radioastron and Japan's VSOP, will augment the worldwide VLBI network, providing baselines to earth radio telescopes as large as 80,000 km. The challenge for OVLBI is to effectuate space to ground radio telescope data cross-correlation (the observation) to a level of integrity currently achieved between ground radio telescopes. VLBI radio telescopes require ultrastable frequency and timing references in order that long term observations may be made without serious cross-correlation loss due to frequency source drift and phase noise. For this reason, such instruments make use of hydrogen maser frequency standards. Unfortunately, space-qualified hydrogen maser oscillators are currently not available for use on OVLBI satellites. Thus, the necessary long-term stability needed by the orbiting radio telescope may only be obtained by microwave uplinking a ground-based hydrogen maser derived frequency to the satellite. Although the idea of uplinking the frequency standard intrinsically seems simple, there are many 'contaminations' which degrade both the long and short term stability of the transmitted reference. Factors which corrupt frequency and timing accuracy include additive radio and electronic circuit thermal noise, slow or systematic phase migration due to changes of electronic circuit temporal operating conditions (especially temperature), ionosphere and troposphere induced scintillations, residual Doppler-incited components, and microwave signal multipath propagation. What is important, though, is to realize that ultimate stability does not have to be achieved in real-time. Instead, information needed to produce a high degree of coherence in the subsequent cross-correlation operation may be derived from a two-way coherent radio link, recorded and later

  16. New technologies and new performances of the JCMT radio-telescope: a preliminary design study

    Science.gov (United States)

    Mian, S.; De Lorenzi, S.; Ghedin, L.; Rampini, F.; Marchiori, G.; Craig, S.

    2012-09-01

    With a diameter of 15m the James Clerk Maxwell Telescope (JCMT) is the largest astronomical telescope in the world designed specifically to operate in the submillimeter wavelength region of the spectrum. It is situated close to the summit of Mauna Kea, Hawaii, at an altitude of 4092m. Its primary reflector currently consists of a steel geodesic supporting structure and pressed aluminium panels on a passive mount. The major issues of the present reflector are its thermal stability and its panels deterioration. A preliminary design study for the replacement of the JCMT antenna dish is here presented. The requested shape error for the new reflector is antenna performance in terms of both stiffness and thermal stability, so that the required surface accuracy of the primary can be achieved even by adopting a passive panels system. Moreover thanks to CFRP, a considerable weight reduction of the elevation structure can be attained. The performance of the proposed solution for the JCMT antenna has been investigated through FE analyses and the assessed deformation of the structure under different loading cases has been taken into account for subsequent error budgeting. Results show that the proposed solution is in line with the requested performance. With this new backing structure, the JCMT would have the largest CFRP reflector ever built.

  17. Analysis of Segmented Reflector Antenna for a Large Millimeter Wave Radio Telescope.

    Science.gov (United States)

    Cortes-Medellin, German

    1993-11-01

    We have developed a computational tool which serves to characterize the performance of large segmented reflector antennas under different sets of conditions. We have applied this tool to the characterization of a large millimeter telescope. A 50 meter diameter instrument of this type specified to operate to wavelengths as short as 1 mm is being design with an actively controlled main surface consisting of 126 hexagonal segments. To simulate the effect of the necessarily imperfect control system, we generate samples of tilt and piston errors for the segments from which the antenna radiation patterns and aperture efficiencies are calculated. We make a comparison of these results with models of antenna tolerance theory developed by Ruze, which relates the aperture efficiency to the rms phase error. We find that Ruze's formula have a different range of validity when the aperture rms phase error, rather than the rms surface error, is used as a parameter. When appreciable tilt errors are present in large segmented antennas, the aperture rms phase error tends to a constant value, independent of the aperture illumination and of the shape of the segments. We conclude that the antenna rms surface error is a better tracer of the aperture efficiency than is the aperture rms phase error when Ruze's formula is used. We find that this well -known expression stands as a lower limit to the performance of large segmented reflector antennas. We have analyzed the effect that gaps between the segments of the active surface of this antenna as well as the imperfect positioning of the subreflector surface have on the aperture efficiency, antenna gain and radiation pattern of this antenna. We have found that the gaps produce a series of grating lobes distributed in a regular pattern in the far field of this antenna, whose relative position is correlated with the size and shape of the segments. We have found that the large millimeter telescope is very sensitive to axial subreflector

  18. A 3mm band dual polarization MMIC receiver for the 30-m Pico Veleta Radio Telescope

    Science.gov (United States)

    Serres, Patrice; Garnier, Olivier; Bortolotti, Yves; Navarro, Santiago; John, Dave; Pissard, Bruno; Navarrini, Alessandro; Schuster, Karl F.

    2012-09-01

    We present the design, construction and test results of a prototype MMIC receiver for the 3 mm band (84-116 GHz). The receiver cryogenic module consists of a single corrugated feed horn cascaded with an Ortho Mode Traducer (OMT) that splits the two incoming linear polarized signals in two independent single-mode rectangular waveguides. Low noise MMIC HEMT amplification modules, attached to the OMT WR10 waveguide outputs, amplify the signal of each polarization channel. Outside the dewar, each signal is filtered, down-converted, and further amplified to provide a final 8 GHz IF bandwidth across 4-12 GHz. The receiver was installed on the Pico Veleta 30 m telescope in August 2010 where it was used to perform spectral line surveys of astronomical sources. The measured receiver noise temperature was below 75 K with an average value of ~55 K for both polarization channels across 84-116 GHz.

  19. The Progress of Science Preparation for the Five-hundred-meter Aperture Spherical radio Telescope

    Science.gov (United States)

    Li, Di

    2015-08-01

    By early 2015, the FAST project has reached a major landmark-finishing laying its cable-mesh system.The primary panels, actuators, and the first receiver platform will be in place by early 2016. We expect an intense period of system testing followed by the first light toward the end of 2016. The early science focus will be to explore opportunities provided by two main receivers, the L-band system and the ultra-wide band receiver covering 280 MHz to 1.6 GHz.I will report here the progress being made in early science project definition, including a pathfinding pulsar search, quasar absorption studies, radio-band line surveys, and megamaser surveys.

  20. Radio Astronomy Data Model for Single-Dish Multiple-Feed Telescopes, and Robledo Archive Architecture

    CERN Document Server

    Santander-Vela, J D; Gómez, J F; Verdes-Montenegro, L; Leon, S; Gutíerrez, R; Rodrigo, C; Morata, O; Solano, E; Suárez, O

    2008-01-01

    All the effort that the astrophysical community has put into the development of the Virtual Observatory (VO) has surpassed the non-return point: the VO is a reality today, and an initiative that will self-sustain, and to which all archival projects must adhere. We have started the design of the scientific archive for the DSS-63 70-m antenna at NASA's DSN station in Robledo de Chavela (Madrid). Here we show how we can use all VO proposed data models to build a VO-compliant single-dish, multiple-feed, radio astronomical archive data model (RADAMS) suitable for the archival needs of the antenna. We also propose an exhaustive list of Universal Content Descriptors (UCDs) and FITS keywords for all relevant metadata. We will further refine this data model with the experience that we will gain from that implementation.

  1. First observations of the water masers with the Urumqi 25m radio telescope

    Institute of Scientific and Technical Information of China (English)

    ZHENG; Xingwu

    2001-01-01

    [1]Moran, J. M., Cosmic masers—— A powerful tool for astrophysics, in Modern Radio Science (ed. Hamelin, J. H.), Oxford: Oxford University Press, 1996, 275.[2]Miyoshi, M., Moran, J. M., Herrnstein J. Et al., Evidence for a massive black hole from high rotational velocities in a sub-parsec region of NGC 4258, Nature, 1995, 373: 127.[3]Comoretto, G., Palagi, F., Cesaroni, R. Et al., The Arccetri atlas of H2O maser sources, A & As, 1996, 84: 17.[4]Braatz, J. A., Wilson, A. S., Henkel, C., A survey for H2O megamasers in active galactic nuclei, ApJS, 1996, 106: 51.[5]Wang, J., Zheng, X., Liang, Z. Et al., Interstellar H2O masers a tracer of galactic spiral structure, Ap. & Sp. S., 1992, 200: 163.[6]Greenhill, L. J., Hernstein, J. R., Moran, J. M. Et al., A search for H2O maser emission toward AGN, Ap. J., 1997, 481: L23.[7]Jack, M. A., Paige, E. G. S., Fourier transformation processors based on surface acoustic wave chirp filters, Wave Electronics, 1978, 3: 329.[8]Jack, M. A., Grant, P. M., Collins, J. H., The theory, design, and application of surface-acoustic-wave Fourier-transform processor, Proc. Of IEEE, 1989, 68: 4.[9]Liljestrom, T., Mattila, K., Toriseva, M. Et al., W49N water maser: spectral atlas of time variability during 1981-1985, A & Ap. Sup., 1989, 79: 19-39.[10]Chen, D., Gong, J., Zhou, X. Et al., A new type of radio astronomical spectrometer-saw spectrometer, Acta Astrophysica Sinica, 1990, 13: 85.

  2. The VLBA-BU-BLAZAR Multi-Wavelength Monitoring Program

    Directory of Open Access Journals (Sweden)

    Svetlana Jorstad

    2016-10-01

    Full Text Available We describe a multiwavelength program of monitoring of a sample of bright γ-ray blazars, which the Boston University (BU group has being carrying out since June 2007. The program includes monthly monitoring with the Very Long Baseline Array at 43 GHz, optical photometric and polarimetric observations, construction and analysis of UV and X-ray light curves obtained with the Rossi X-ray Timing Explorer (RXTE and Swift satellites, and construction and analysis of γ-ray light curves based on data provided by the Large Area Telescope of the Fermi Gamma-ray Space Telescope. We present general results about the kinematics of parsec-scale radio jets, as well as the connection between γ-ray outbursts and jet events.

  3. A VLBA Upgrade Conforming to VSOP-2 Specifications

    Science.gov (United States)

    Romney, J. D.

    2009-08-01

    The VLBA was a major participant in the original VSOP mission. NRAO hopes to play a similar role in the VSOP-2 mission, if commensurate support can be obtained for VLBA operations in such a collaboration. While the VLBA's original data system is not compatible with the planned VSOP-2 specifications, the current VLBA Sensitivity Upgrade project will produce a new system that is well-matched to VSOP-2. This upgrade involves replacement of the entire data path downstream from the IFs, and includes a digital sub-band processor, a wideband recording system, and a software correlator. The project's goal is to achieve sustained 4-Gbps operation by 2011, with wideband operation available much earlier for the most scientifically compelling observations. These goals appear to be well matched to the VSOP-2 timeline. This paper presents an overview of the new systems under development, and compares the capabilities of each to the requirements for VSOP-2. Further topics include adaptation of the entire system, and the correlator in particular, to Space VLBI operations, and upgrade aspects that should minimize the data-format incompatibilities that were a substantial difficulty in the first VSOP mission.

  4. Linking the central engine to the jet properties in radio loud AGN

    CERN Document Server

    Olguín-Iglesias, A; Chavushyan, V; Valtaoja, E; Añorve, C; Nilsson, K; Kotilainen, J; Tornikoski, M

    2015-01-01

    We explore the connection between the black hole mass and its relativistic jet for a sample of radio-loud AGN (z < 1), in which the relativistic jet parameters are well estimated by means of long term monitoring with the 14m Mets\\"ahovi millimeter wave telescope and the Very Long Base-line Array (VLBA). NIR host galaxy images taken with the NOTCam on the Nordic Optical Telescope (NOT) and retrieved from the 2MASS all-sky survey allowed us to perform a detailed surface brightness decomposition of the host galaxies in our sample and to estimate reliable black hole masses via their bulge luminosities. We present early results on the correlations between black hole mass and the relativistic jet parameters. Our preliminary results suggest that the more massive the black hole is, the faster and the more luminous jet it produces.

  5. Linking the central engine to the jet properties in radio loud AGN

    Science.gov (United States)

    Olguín-Iglesias, A.; León-Tavares, J.; Chavushyan, V.; Valtaoja, E.; Añorve, C.; Nilsson, K.; Kotilainen, J.; Tornikoski, M.

    2015-03-01

    We explore the connection between the black hole mass and its relativistic jet for a sample of radio-loud AGN (z < 1), in which the relativistic jet parameters are well estimated by means of long term monitoring with the 14m Metsähovi millimeter wave telescope and the Very Long Base-line Array (VLBA). NIR host galaxy images taken with the NOTCam on the Nordic Optical Telescope (NOT) and retrieved from the 2MASS all-sky survey allowed us to perform a detailed surface brightness decomposition of the host galaxies in our sample and to estimate reliable black hole masses via their bulge luminosities. We present early results on the correlations between black hole mass and the relativistic jet parameters. Our preliminary results suggest that the more massive the black hole is, the faster and the more luminous jet it produces.

  6. All-Stokes Parameterization of the Main Beam and First Sidelobe for the Arecibo Radio Telescope

    CERN Document Server

    Heiles, C; Nolan, M L; Lorimer, D; Bhat, R; Ghosh, T K; Howell, E; Lewis, M; O'Neil, K; Salter, C; Stanimirovic, S; Heiles, Carl; Perillat, Phil; Nolan, Michael; Lorimer, Duncan; Bhat, Ramesh; Ghosh, Tapasi; Howell, Ellen; Lewis, Murray; Neil, Karen O'; Salter, Chris; Stanimirovic, Snezana

    2001-01-01

    We describe a scheme that characterizes the main beam and sidelobe in all Stokes parameters employing parameters that allow reconstruction of the complete beam patterns and, also, afford an easy way to see how the beam changes with azimuth, zenith angle, and time. For the main beam in Stokes I the parameters include the beam width, ellipticity and its orientation, coma and its orientation, the point-source gain, the integrated gain (or, equivalently, the main beam efficiency); for the other Stokes parameters the beam parameters include beam squint and beam squash. For the first sidelobe ring in Stokes I the parameters include an 8-term Fourier series describing the height, radius, and radial width; for the other Stokes parameters they include only the sidelobe's fractional polarization. We illustrate the technique by applying it to the Arecibo telescope. The main beam width is smaller and the sidelobe levels higher than for a uniformly-illuminated aperture of the same effective area. These effects are modeled...

  7. Analysis of active surface reflector antenna for a large millimeter wave radio telescope

    Science.gov (United States)

    Cortes-Medellin, G.; Goldsmith, P. F.

    1994-02-01

    The authors analyze the effects of imperfect segment alignment on the aperture efficiency of a large millimeter telescope. A 50 meter diameter instrument of this type specified to operate to wavelengths as short as 1 mm is being designed with an actively controlled main surface. By simulating the performance of the control system, they generate samples of tilt and piston errors for the segments from which the antenna radiation patterns and aperture efficiencies are calculated. They make a comparison of these results with models of antenna tolerance theory developed by Ruze (1966), which relate the aperture efficiency to the RMS phase error. They find that Ruze's formulas have a different range of validity when the aperture RMS phase error, rather than the RMS surface error, is used as a parameter. When appreciable tilt errors are present in large segmented antennas, the aperture RMS phase error tends to a constant value, independent of the aperture illumination and of the shape of the segments. They conclude that the antenna RMS surface error is a better tracer of the aperture efficiency than is the aperture RMS phase error when Ruze's formula is used. They find that this well-known expression stands as a lower limit to the performance of large segmented reflector antennas.

  8. Probing Fine-Scale Ionospheric Structure with the Very Large Array Radio Telescope

    CERN Document Server

    Cohen, A S

    2009-01-01

    High resolution (~1 arcminute) astronomical imaging at low frequency (below 150 MHz) has only recently become practical with the development of new calibration algorithms for removing ionospheric distortions. In addition to opening a new window in observational astronomy, the process of calibrating the ionospheric distortions also probes ionospheric structure in an unprecedented way. Here we explore one aspect of this new type of ionospheric measurement, the differential refraction of celestial source pairs as a function of their angular separation. This measurement probes variations in the spatial gradient of the line-of-sight total electron content (TEC) to 0.001 TECU/km accuracy over spatial scales of under 10 km to over 100 km. We use data from the VLA Low-frequency Sky Survey (VLSS; Cohen et al. 2007, AJ 134, 1245), a nearly complete 74 MHz survey of the entire sky visible to the Very Large Array (VLA) telescope in Socorro, New Mexico. These data comprise over 500 hours of observations, all calibrated in...

  9. Radio and IR interferometry of SiO maser stars

    CERN Document Server

    Wittkowski, M; Gray, M D; Humphreys, E M L; Karovicova, I; Scholz, M

    2012-01-01

    Radio and infrared interferometry of SiO maser stars provide complementary information on the atmosphere and circumstellar environment at comparable spatial resolution. Here, we present the latest results on the atmospheric structure and the dust condensation region of AGB stars based on our recent infrared spectro-interferometric observations, which represent the environment of SiO masers. We discuss, as an example, new results from simultaneous VLTI and VLBA observations of the Mira variable AGB star R Cnc, including VLTI near- and mid-infrared interferometry, as well as VLBA observations of the SiO maser emission toward this source. We present preliminary results from a monitoring campaign of high-frequency SiO maser emission toward evolved stars obtained with the APEX telescope, which also serves as a precursor of ALMA images of the SiO emitting region. We speculate that large-scale long-period chaotic motion in the extended molecular atmosphere may be the physical reason for observed deviations from poin...

  10. Modeling and optimization of the antenna system with focal plane array for the new generation radio telescopes with wide field of view

    CERN Document Server

    Iupikov, O

    2016-01-01

    The model of the reflector antenna system with focal plane array, low-noise amplifier and beamformer is developed in the work. The beamformer strategy is suggested to reduce the receiving sensitivity ripple inside field of view of the telescope, while the sensitivity itself drops slightly (less than 10%). The system APERTIF (which is currently under development in Netherlands Institute For Radioastronomy, ASTRON) has been analyzed using developed model, and numerical results are presented. The obtained numerical results have been verified experimentally in anechoic chamber as well as on one of the dishes of the Westerbork Synthesis Radio Telescope (all measurements have been done in ASTRON).

  11. Study of galaxies in the Lynx-Cancer void. VI. HI-observations with the Nancay Radio Telescope

    CERN Document Server

    Pustilnik, S A

    2016-01-01

    Context. Void population consists mainly of late-type and low surface brightness (LSB) dwarf galaxies whose atomic hydrogen is the main component of their baryonic matter. Therefore, observations of void galaxy HI are mandatory in order to understand their evolution and dynamics. Aims. Our aim was to obtain integrated HI parameters for a fainter part of the nearby Lynx-Cancer void galaxy sample (total of 45 objects) with the Nancay Radio Telescope (NRT) and to conduct the comparative analysis of all the 103 void galaxies with known HI data with a sample of similar galaxies residing in denser environments of the Local Volume. Methods. For HI observations we used the NRT with its sensitive antenna/receiver system FORT and standard processing. The comparison of the void and control samples on the parameter M(HI)/L_B is conducted with the non-parametric method `The 2x2 Contingency Table test'. Results. We obtained new HI data for about 40% of the Lynx-Cancer galaxy sample. Along with data from the literature, we ...

  12. The initial characterization of a revised 10-Gsps analog-to-digital converter board for radio telescopes

    Science.gov (United States)

    Jiango, Homin; Liuo, Howard; Guzzino, Kim

    2016-07-01

    In this study, the design of a 4 bit, 10-gigasamples-per-second analog-to-digital converter (ADC) printed circuit board assembly (PCBA) was revised, manufactured, and tested. It is used for digitizing radio telescopes. An Adsantec ANST7120-KMA flash ADC chip was used, as in the original design. Associated with the field-programmable gate array platform developed by the Collaboration for Astronomy Signal Processing and Electronics Research community, the developed PCBA provides data acquisition systems with a wider bandwidth and simplifies the intermediate frequency section. The current version of the PCBA exhibits an analog bandwidth of up to 10 GHz (3 dB loss), and the chip exhibits an analog bandwidth of up to 18 GHz. This facilitates second and third Nyquist sampling. The following worstcase performance parameters were obtained from the revised PCBA at over 5 GHz: spurious-free dynamic range of 12 dB, signal-to-noise and distortion ratio of 2 dB, and effective number of bits of 0.7. The design bugs in the ADC chip caused the poor performance. The vendor created a new batch run and confirmed that the ADC chips of the new batch will meet the specifications addressed in its data sheet.

  13. Bent-Tailed Radio Sources in the Australia Telescope Large Area Survey of the Chandra Deep Field-South

    CERN Document Server

    Dehghan, Siamak; Franzen, Thomas M O; Norris, Ray P; Miller, Neal A

    2015-01-01

    Using the 1.4 GHz Australia Telescope Large Area Survey (ATLAS), supplemented with the 1.4 GHz Very Large Array images, we undertook a search for bent-tailed (BT) radio galaxies in the Chandra Deep Field-South (CDFS). Here we present a catalog of 56 detections, which include 45 bent-tailed sources, four diffuse low-surface-brightness objects (one relic, two halos, and one unclassified object), and a further seven complex, multi-component sources. We report BT sources with rest-frame powers in the range $10^{22} \\leq$ $\\textrm{P}_{1.4 \\textrm{ GHz}} \\leq 10^{26}$ W Hz$^{-1}$, redshifts up to 2 and linear extents from tens of kpc up to about one Mpc. This is the first systematic study of such sources down to such low powers and high redshifts and demonstrates the complementary nature of searches in deep, limited area surveys as compared to shallower, large surveys. Of the sources presented here one is the most distant bent-tailed source yet detected at a redshift of 2.1688. Two of the sources are found to be as...

  14. A 65 nm CMOS broadband self-calibrated power detector for the square kilometre array radio telescope

    Directory of Open Access Journals (Sweden)

    Ge Wu

    2014-08-01

    Full Text Available In this study, a 65 nm complementary metal oxide semiconductor (CMOS broadband self-calibrated high-sensitivity power detector for use in the Square Kilometre Array (SKA, the next-generation high-sensitivity radio telescope, is presented. The power detector calibration is performed by adjusting voltages at the bulk terminals of the input transistors to compensate for mismatches in the output voltages because of process, voltage and temperature variations. Measurements show that the power detector, preceded by an input power-match circuit with 6 dB gain, has an input signal range from −48 to −11 dBm over which a 0.95 dB maximum error in the detected power is observed when the calibration rate is 20 kHz. The proposed broadband power detector has a 3 dB upper band edge of 1.8 GHz, which adequately covers the midband SKA frequency range from 0.7 to 1.4 GHz. The settling time and the calibration time are both <5 μs. The circuit consumes 1.2 mW from a 1.2 V power supply and the input-match circuit consumes another 5.8 mW. The presented power detector achieves the best combination of the detection range and sensitivity of previously published circuits.

  15. Methanol Masers Observations in the 3-mm Bandwidth at the Radio Telescope RT-22 CrAO

    CERN Document Server

    Zubrin, S Yu; Myshenko, V V; Shulga, V M

    2007-01-01

    We report the beginning of the astronomical masers investigations in the 3-mm bandwidth at the radio telescope RT-22 (CrAO, Ukraine). For this purpose the special complex for maser lines investigation in 85...115 GHz frequency band is developed. It is made on the base of the low noise cryogenic Shottky-diode receiver and the high resolution Fourier-spectrometer. The cryogenic receiver has the DSB noise temperature less than 100K. The spectral channel separation of the Fourier-spectrometer is about 4kHz and the spectrometer bandwidth is 8 MHz. Results of maser observations of 8$^{0}-7^{1} $A$^{+}$ transition of methanol (95.169 GHz) towards DR-21(OH), DR-21W and NGC7538 are in good agreement with early obtained results by other authors. On the basis of the analysis of the location of masers in the NGC7538 direction we can assume that the origin of all known class I methanol masers in this region is connected with existing molecular outflows from young stars.

  16. The History of Radio Astronomy and the National Radio Astronomy Observatory: Evolution Toward Big Science

    Science.gov (United States)

    Malphrus, Benjamin Kevin

    1990-01-01

    The purpose of this study is to examine the sequence of events that led to the establishment of the NRAO, the construction and development of instrumentation and the contributions and discovery events and to relate the significance of these events to the evolution of the sciences of radio astronomy and cosmology. After an overview of the resources, a brief discussion of the early days of the science is given to set the stage for an examination of events that led to the establishment of the NRAO. The developmental and construction phases of the major instruments including the 85-foot Tatel telescope, the 300-foot telescope, the 140-foot telescope, and the Green Bank lnterferometer are examined. The technical evolution of these instruments is traced and their relevance to scientific programs and discovery events is discussed. The history is told in narrative format that is interspersed with technical and scientific explanations. Through the use of original data technical and scientific information of historical concern is provided to elucidate major developments and events. An interpretive discussion of selected programs, events and technological developments that epitomize the contributions of the NRAO to the science of radio astronomy is provided. Scientific programs conducted with the NRAO instruments that were significant to galactic and extragalactic astronomy are presented. NRAO research programs presented include continuum and source surveys, mapping, a high precision verification of general relativity, and SETI programs. Cosmic phenomena investigated in these programs include galactic and extragalactic HI and HII, emission nebula, supernova remnants, cosmic masers, giant molecular clouds, radio stars, normal and radio galaxies, and quasars. Modern NRAO instruments including the VLA and VLBA and their scientific programs are presented in the final chapter as well as plans for future NRAO instruments such as the GBT.

  17. Europe and US to Collaborate on the Design and Development of a Giant Radio Telescope Project in Chile

    Science.gov (United States)

    1999-06-01

    High Goals for the Atacama Large Millimeter Array (ALMA) Representatives from the U.S. and Europe signed an agreement today in Washington to continue collaboration on the first phase of a giant new telescope project. The telescope will image the Universe with unprecedented sensitivity and sharpness at millimeter wavelengths (between the radio and infrared spectral regions). It will be a major step for astronomy, making it possible to study the origins of galaxies, stars and planets. This project is a prime example of a truly global project, an essential development in view of the ever-increasing complexity and cost of front-line astronomical facilities. The U.S. side of the project is run by the National Radio Astronomy Observatory (NRAO) , operated by Associated Universities, Inc. (AUI) under a cooperative agreement with the National Science Foundation (NSF). The European side of the project is a collaboration between the European Southern Observatory (ESO) , the Centre National de la Recherche Scientifique (CNRS) , the Max-Planck-Gesellschaft (MPG) , the Netherlands Foundation for Research in Astronomy (NFRA) and Nederlandse Onderzoekschool Voor Astronomie (NOVA) , and the United Kingdom Particle Physics and Astronomy Research Council (PPARC). The Europe-U.S. agreement signed today may be formally extended in the very near future to include Japan, following an already existing tripartite declaration of intent. Dr. Robert Eisenstein, NSF's Assistant Director Mathematical and Physical Sciences, called the project "a path-breaking international partnership that will open far-reaching opportunities for astronomical observations. This array would enable astronomers to explore the detailed processes through which the stars and planets form and give us a vastly improved understanding of the formation of the first galaxies in the very early universe." Eisenstein welcomed the collaboration with Europe and Japan's interest in becoming a major partner. Speaking on behalf of

  18. Simultaneous Observations of Giant Pulses from the Crab Pulsar, with the Murchison Widefield Array and Parkes Radio Telescope: Implications for the Giant Pulse Emission Mechanism

    CERN Document Server

    Oronsaye, S I; Bhat, N D R; Tremblay, S E; McSweeney, S J; Tingay, S J; van Straten, W; Jameson, A; Bernardi, G; Bowman, J D; Briggs, F; Cappallo, R J; Deshpande, A A; Greenhill, L J; Hazelton, B J; Johnston-Hollitt, M; Kaplan, D L; Lonsdale, C J; McWhirter, S R; Mitchell, D A; Morales, M F; Morgan, E; Oberoi, D; Prabu, T; Shankar, N Udaya; Srivani, K S; Subrahmanyan, R; Wayth, R B; Webster, R L; Williams, A; Williams, C L

    2015-01-01

    We report on observations of giant pulses from the Crab pulsar performed simultaneously with the Parkes radio telescope and the incoherent combination of the Murchison Widefield Array (MWA) antenna tiles. The observations were performed over a duration of approximately one hour at a center frequency of 1382 MHz with 340 MHz bandwidth at Parkes, and at a center frequency of 193 MHz with 15 MHz bandwidth at the MWA. Our analysis has led to the detection of 55 giant pulses at the MWA and 2075 at Parkes above a threshold of 3.5$\\sigma$ and 6.5$\\sigma$ respectively. We detected 51$\\%$ of the MWA giant pulses at the Parkes radio telescope, with spectral indices in the range of $-3.6>\\alpha> -4.9$ ($S_{\\rm \

  19. Calibrating short-timescale tropospheric phase fluctuations seen by a radio telescope: Limits from subreflector and Cassegrain feed ring radiometer placement

    Science.gov (United States)

    Linfield, Roger

    2002-10-01

    Water vapor radiometers (WVRs) measure tropospheric brightness temperatures and use those measurements to infer path delay. Calibration of short-timescale phase fluctuations at a radio telescope requires that the WVR and radio telescope sample a similar volume of the troposphere. Using a statistical (Kolmogorov frozen flow) model of tropospheric fluctuations, the short-timescale calibration capability of two WVR configurations has been quantified. The first configuration is a WVR mounted, with its own antenna, on the back side of the main radio telescope subreflector, giving a conical beam that is coaxial with the main cylindrical near-field beam of the large telescope. The second configuration uses a Cassegrain feed ring, with the WVR and radio astronomy feeds at different positions on the ring. This second configuration gives a cylindrical calibration near-field beam, offset in angle to the main cylindrical beam. An important application of short-timescale phase calibration is improving the coherence of high-frequency interferometric observations. For two cases of current/near future interest (86 GHz very long baseline interferometry with the Very Long Baseline Array; 350 GHz observations with the Atacama Large Millimeter Array, ALMA), useful calibration could be achieved with either geometry (coaxial conical beam or offset cylindrical beam). For a coaxial conical beam, a 2° WVR beam width would allow significant coherence improvement, but a beam width performance. For an offset cylindrical beam, the desired angular offset (on the sky) is 43 GHz Very Large Array observations, or <=0.3° for 350 GHz ALMA observations.

  20. Prospects for detection of the lunar Cerenkov emission by the UHE Cosmic Rays and Neutrinos using the GMRT and the Ooty Radio Telescope

    CERN Document Server

    Swarup, Govind

    2008-01-01

    Searching for the Ultra high energy Cosmic rays and Neutrinos of $> 10^{20} eV$ is of great cosmological importance. A powerful technique is to search for the \\v{C}erenkov radio emission caused by UHECR or UHE neutrinos impinging on the lunar regolith. We examine in this paper feasibility of detecting these events by observing with the Giant Metrewave Radio Telescope (GMRT) which has a large collecting area and operates over a wide frequency range with an orthogonal polarisation capability. We discuss here prospects of observations of the \\v{C}erenkov radio emission with the GMRT at 140 MHZ with 32 MHz bandwidth using the incoherent array and also forming 25 beams of the Central Array to cover the moon. We also consider using the Ooty Radio Telescope (ORT) which was specially designed in 1970 for tracking the Moon. With the ORT (530m long and 30m wide parabolic cylinder) it becomes possible to track the Moon for 9.5 hours on a given day by a simple rotation along the long axis of the parabolic cylinder. ORT o...

  1. Giant Metrewave Radio Telescope Monitoring of the Black Hole X-Ray Binary, V404 Cygni during Its 2015 June Outburst

    Science.gov (United States)

    Chandra, Poonam; Kanekar, Nissim

    2017-09-01

    We report results from a Giant Metrewave Radio Telescope (GMRT) monitoring campaign of the black hole X-ray binary V404 Cygni during its 2015 June outburst. The GMRT observations were carried out at observing frequencies of 1280, 610, 325, and 235 MHz, and extended from June 26.89 UT (a day after the strongest radio/X-ray outburst) to July 12.93 UT. We find the low-frequency radio emission of V404 Cygni to be extremely bright and fast-decaying in the outburst phase, with an inverted spectrum below 1.5 GHz and an intermediate X-ray state. The radio emission settles to a weak, quiescent state ≈11 days after the outburst, with a flat radio spectrum and a soft X-ray state. Combining the GMRT measurements with flux density estimates from the literature, we identify a spectral turnover in the radio spectrum at ≈1.5 GHz on ≈ June 26.9 UT, indicating the presence of a synchrotron self-absorbed emitting region. We use the measured flux density at the turnover frequency with the assumption of equipartition of energy between the particles and the magnetic field to infer the jet radius (≈4.0 × 1013 cm), magnetic field (≈0.5 G), minimum total energy (≈7 × 1039 erg), and transient jet power (≈8 × 1034 erg s‑1). The relatively low value of the jet power, despite V404 Cygni’s high black hole spin parameter, suggests that the radio jet power does not correlate with the spin parameter.

  2. MAGIC observations and multifrequency properties of the Flat Spectrum Radio Quasar 3C 279 in 2011

    CERN Document Server

    Aleksić, J; Antonelli, L A; Antoranz, P; Babic, A; Bangale, P; de Almeida, U Barres; Barrio, J A; González, J Becerra; Bednarek, W; Berger, K; Bernardini, E; Biland, A; Blanch, O; Bock, R K; Bonnefoy, S; Bonnoli, G; Borracci, F; Bretz, T; Carmona, E; Carosi, A; Fidalgo, D Carreto; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Covino, S; Da Vela, P; Dazzi, F; De Angelis, A; De Caneva, G; De Lotto, B; Mendez, C Delgado; Doert, M; Domínguez, A; Prester, D Dominis; Dorner, D; Doro, M; Einecke, S; Eisenacher, D; Elsaesser, D; Farina, E; Ferenc, D; Fonseca, M V; Font, L; Frantzen, K; Fruck, C; López, R J García; Garczarczyk, M; Terrats, D Garrido; Gaug, M; Giavitto, G; Godinović, N; Muñoz, A González; Gozzini, S R; Hadasch, D; Herrero, A; Hildebrand, D; Hose, J; Hrupec, D; Idec, W; Kadenius, V; Kellermann, H; Knoetig, M L; Kodani, K; Konno, Y; Krause, J; Kubo, H; Kushida, J; La Barbera, A; Lelas, D; Lewandowska, N; Lindfors, E; Lombardi, S; López, M; López-Coto, R; López-Oramas, A; Lorenz, E; Lozano, I; Makariev, M; Mallot, K; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Marcote, B; Mariotti, M; Martínez, M; Mazin, D; Menzel, U; Meucci, M; Miranda, J M; Mirzoyan, R; Moralejo, A; Munar-Adrover, P; Nakajima, D; Niedzwiecki, A; Nilsson, K; Nishijima, K; Nowak, N; Orito, R; Overkemping, A; Paiano, S; Palatiello, M; Paneque, D; Paoletti, R; Paredes, J M; Paredes-Fortuny, X; Partini, S; Persic, M; Prada, F; Moroni, P G Prada; Prandini, E; Preziuso, S; Puljak, I; Reinthal, R; Rhode, W; Ribó, M; Rico, J; Garcia, J Rodriguez; Rügamer, S; Saggion, A; Saito, T; Saito, K; Salvati, M; Satalecka, K; Scalzotto, V; Scapin, V; Schultz, C; Schweizer, T; Shore, S N; Sillanpää, A; Sitarek, J; Snidaric, I; Sobczynska, D; Spanier, F; Stamatescu, V; Stamerra, A; Steinbring, T; Storz, J; Sun, S; Surić, T; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzić, T; Tescaro, D; Teshima, M; Thaele, J; Tibolla, O; Torres, D F; Toyama, T; Treves, A; Vogler, P; Wagner, R M; Zandanel, F; Zanin, R; Berdyugin, A; Vornanen, T; Lähteenmäki, A; Tammi, J; Tornikoski, M; Hovatta, T; Max-Moerbeck, W; Readhead, A; Richards, J; Hayashida, M; Sanchez, D A; Fermi-LAT, on behalf of the; Marscher, A; Jorstad, S

    2013-01-01

    We study the multifrequency emission and spectral properties of the quasar 3C 279. We observed 3C 279 in very high energy (VHE, E>100GeV) gamma rays, with the MAGIC telescopes during 2011, for the first time in stereoscopic mode. We combine these measurements with observations at other energy bands: in high energy (HE, E>100MeV) gamma rays from Fermi-LAT, in X-rays from RXTE, in the optical from the KVA telescope and in the radio at 43GHz, 37GHz and 15GHz from the VLBA, Mets\\"ahovi and OVRO radio telescopes and optical polarisation measurements from the KVA and Liverpool telescopes. During the MAGIC observations (February to April 2011) 3C 279 was in a low state in optical, X-ray and gamma rays. The MAGIC observations did not yield a significant detection. These upper limits are in agreement with the extrapolation of the HE gamma-ray spectrum, corrected for extragalactic background light absorption, from Fermi-LAT. The second part of the MAGIC observations in 2011 was triggered by a high activity state in the...

  3. Discovery of Pulsed Gamma Rays from the Young Radio Pulsar PSR J1028-5819 with the Fermi Large Area Telescope

    Energy Technology Data Exchange (ETDEWEB)

    Abdo, Aous A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Atwood, W.B.; /UC, Santa Cruz; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, Guido; /INFN, Trieste /Trieste U.; Baring, Matthew G.; /Rice U.; Bastieri, Denis; /INFN, Padua /Padua U.; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bloom, Elliott D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bregeon, J.; /INFN, Pisa; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Burnett, Thompson H.; /Washington U., Seattle; Caliandro, G.A.; /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /IASF, Milan /DAPNIA, Saclay /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /George Mason U. /Naval Research Lab, Wash., D.C. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Sonoma State U. /Stockholm U., OKC /Royal Inst. Tech., Stockholm /Stockholm U. /Naval Research Lab, Wash., D.C. /INFN, Trieste /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /NASA, Goddard /UC, Santa Cruz /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /CENBG, Gradignan /CENBG, Gradignan /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Bari U. /INFN, Bari /Ecole Polytechnique /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Trieste /Hiroshima U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; /more authors..

    2009-05-15

    Radio pulsar PSR J1028-5819 was recently discovered in a high-frequency search (at 3.1 GHz) in the error circle of the Energetic Gamma-Ray Experiment Telescope (EGRET) source 3EG J1027-5817. The spin-down power of this young pulsar is great enough to make it very likely the counterpart for the EGRET source. We report here the discovery of {gamma}-ray pulsations from PSR J1028-5819 in early observations by the Large Area Telescope (LAT) on the Fermi Gamma-Ray Space Telescope. The {gamma}-ray light curve shows two sharp peaks having phase separation of 0.460 {+-} 0.004, trailing the very narrow radio pulse by 0.200 {+-} 0.003 in phase, very similar to that of other known {gamma}-ray pulsars. The measured {gamma}-ray flux gives an efficiency for the pulsar of {approx}10-20% (for outer magnetosphere beam models). No evidence of a surrounding pulsar wind nebula is seen in the current Fermi data but limits on associated emission are weak because the source lies in a crowded region with high background emission. However, the improved angular resolution afforded by the LAT enables the disentanglement of the previous COS-B and EGRET source detections into at least two distinct sources, one of which is now identified as PSR J1028-5819.

  4. A New 100-GHz Band Two-Beam Sideband-Separating SIS Receiver for Z-Machine on the NRO 45-m Radio Telescope

    CERN Document Server

    Nakajima, Taku; Nishimura, Atsushi; Iwashita, Hiroyuki; Miyazawa, Chieko; Sakai, Takeshi; Iono, Daisuke; Kohno, Kotaro; Kawabe, Ryohei; Kuno, Nario; Ogawa, Hideo; Asayama, Shin'ichiro; Tamura, Tomonori; Noguchi, Takashi

    2013-01-01

    We have developed a two-beam waveguide-type dual-polarization sideband-separating SIS receiver system in the 100-GHz band for {\\it z}-machine on the 45-m radio telescope at the Nobeyama Radio Observatory. The receiver is intended for astronomical use in searching for highly redshifted spectral lines from galaxies of unknown redshift. This receiver has two beams, which have 45$^{\\prime\\prime}$ of beam separation and allow for observation with the switch in the on-on position. The receiver of each beam is composed of an ortho-mode transducer and two sideband-separating SIS mixers, which are both based on a waveguide technique, and the receiver has four intermediate frequency bands of 4.0--8.0 GHz. Over the radio frequency range of 80--116 GHz, the single-sideband receiver noise temperature is lower than about 50 K, and the image rejection ratios are greater than 10 dB in most of the same frequency range. The new receiver system has been installed in the telescope, and we successfully observed a $^{12}$CO ({\\it ...

  5. Radio follow-up of the gamma-ray flaring gravitational lens JVAS B0218+357

    CERN Document Server

    Spingola, Cristiana; Orienti, M; Giroletti, M; McKean, J P; Cheung, C C; Hovatta, T; Ciprini, S; D'Ammando, F; Falco, E; Larsson, S; Max-Moerbeck, W; Ojha, R; Readhead, A C S; Richards, J L; Scargle, J

    2016-01-01

    We present results on multifrequency Very Long Baseline Array (VLBA) monitoring observations of the double-image gravitationally lensed blazar JVAS B0218+357. Multi-epoch observations started less than one month after the gamma-ray flare detected in 2012 by the Large Area Telescope on board Fermi, and spanned a 2-month interval. The radio light curves did not reveal any significant flux density variability, suggesting that no clear correlation between the high energy and low-energy emission is present. This behaviour was confirmed also by the long-term Owens Valley Radio Observatory monitoring data at 15 GHz. The milliarcsecond-scale resolution provided by the VLBA observations allowed us to resolve the two images of the lensed blazar, which have a core-jet structure. No significant morphological variation is found by the analysis of the multi-epoch data, suggesting that the region responsible for the gamma-ray variability is located in the core of the AGN, which is opaque up to the highest observing frequenc...

  6. A Comprehensive Study of the Radio Properties of Brightest Cluster Galaxies

    CERN Document Server

    Hogan, M T; Hlavacek-Larrondo, J; Grainge, K J B; Hamer, S L; Mahony, E K; Russell, H R; Fabian, A C; McNamara, B R; Wilman, R J

    2015-01-01

    We examine the radio properties of the Brightest Cluster Galaxies (BCGs) in a large sample of X-ray selected galaxy clusters comprising the Brightest Cluster Sample (BCS), the extended BCS (eBCS) and ROSAT-ESO Flux Limited X-ray (REFLEX) cluster catalogues. We have multi-frequency radio observations of the BCG using a variety of data from the Australia Telescope Compact Array (ATCA), Jansky Very Large Array (VLA) and Very Long Baseline Array (VLBA) telescopes. The radio spectral energy distributions (SEDs) of these objects are decomposed into a component attributed to on-going accretion by the active galactic nuclei (AGN) that we refer to as the 'core', and a more diffuse, ageing component we refer to as the 'non-core'. These BCGs are matched to previous studies to determine whether they exhibit emission lines (principally H-alpha), indicative of the presence of a strong cooling cluster core. We consider how the radio properties of the BCGs vary with cluster environmental factors. Line emitting BCGs are shown...

  7. Innovative and Improved Efficiency on the Design of a control System SOftware for CBSS 6m Radio Telescope using LabView in Nigeria

    Science.gov (United States)

    EKEOMA Opara, Fidelis

    2015-08-01

    Software has been provided for controlling the antenna and selection of sources in a 6m radio telescope. In this work the most challenging aspect is the maintainance of the pointing accuracy of the final structure with pointing tolerance of about 0.0003 or 1 arcsecond. Using LabView, the voltage through the I/Q is read with a DAQ virtual instrument. The values are then calculated with the dish at its zero position, hence the control system is fully implemented and tested to work at full efficiency.

  8. Infrared Imaging of z = 2.43 Radio Galaxy B3 0731+438 with the Subaru Telescope Detection of H$\\alpha$ Ionization Cones of a Powerful Radio Galaxy

    CERN Document Server

    Motohara, K; Terada, H; Goto, M; Iwai, J; Tanabe, H; Taguchi, T; Hata, R; Maihara, T; Oya, S; Iye, M; Kosugi, G; Noumaru, J; Ogasawara, R; Sasaki, T; Takata, T; Motohara, Kentaro; Iwamuro, Fumihide; Terada, Hiroshi; Goto, Miwa; Iwai, Jun'ichi; Tanabe, Hirohisa; Taguchi, Tomoyuki; Hata, Ryuji; Maihara, Toshinori; Oya, Shin; Iye, Masanori; Kosugi, George; Noumaru, Jun'ichi; Ogasawara, Ryusuke; Sasaki, Toshinori; Takata, Tadafumi

    2000-01-01

    We report on infrared imaging observations of the z=2.429 radio galaxy B3 0731+438 with the Subaru telescope. The images were taken with the K'-band filter and the 2.25 um narrow-band filter to examine the structure and properties of the Ha+[N II] 6548,6583 emission-line components. The Ha+[N II] emission-line image shows biconical lobes with an extent of 40 kpc, which are aligned with the radio axis. The rest-frame equivalent widths of the emission lines at these cones are as large as 1100 AA, and can be well explained by a gas-cloud model photoionized by power-law continuum radiation. The isotropic ionizing photon luminosity necessary to ionize the hydrogen gas in these cones amounts to 1e57(photons/s), which is larger than that in the majority of radio-loud QSOs. From these results, we propose that the Ha alignment effect in this object is produced by biconical gas clouds, which are swept up by the passage of radio jets, and are ionized by strong UV radiation from a hidden AGN. The continuum image consists...

  9. Astronomers Make "Movie" of Radio Images Showing Supernova Explosion

    Science.gov (United States)

    1995-11-01

    Astronomers using an international network of radio telescopes have produced a "movie" showing details of the expansion of debris from an exploding star. Their sequence of images constitutes the best determination yet made of the details of a new supernova remnant, and already has raised new questions about such events. The scientists used radio telescopes in Europe and the United States, including the National Science Foundation's Very Large Array (VLA) and Very Long Baseline Array (VLBA), to make very high- resolution images of Supernova 1993J, which was discovered by a Spanish amateur astronomer on March 28, 1993 in the galaxy M81, some 11 million light-years distant in the constellation Ursa Major. Their results are reported in the December 1 issue of the journal Science. The "movie" is based on five images of the supernova, made during 1993 and 1994. The work was done by: Jon Marcaide and Eduardo Ros of the University of Valencia, Spain; Antxon Alberdi of the Special Laboratory for Astrophysics and Fundamental Physics of Madrid, Spain and the Institute of Astrophysics at Andalucia, Spain; Philip Diamond of the National Radio Astronomy Observatory in Socorro, NM; Irwin Shapiro of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA; Jose-Carlos Guirado, Dayton Jones and Robert Preston of the Jet Propulsion Laboratory in Pasadena, CA; Thomas Krichbaum and Arno Witzel of the Max-Planck Institute for Radioastronomy in Bonn, Germany; Franco Mantovani of the Institute of Radioastronomy in Bologna, Italy; Antonio Rius of the Special Laboratory for Astrophysics and Fundamental Physics of Madrid, Spain and the Center for Advanced Studies at Blanes, Spain; Richard Schilizzi of the Joint Institute for VLBI in Europe and Leiden Observatory in the Netherlands; Corrado Trigilio of the Institute of Radioastronomy in Noto, Italy; and Alan Whitney of the MIT- Haystack Observatory in Massachusetts. The capability to make such high-quality images with widely

  10. A Framework for Interpreting Fast Radio Transients Search Experiments: Application to the V-FASTR Experiment

    Science.gov (United States)

    Trott, Cathryn M.; Tingay, Steven J.; Wayth, Randall B.; Thompson, David R.; Deller, Adam T.; Brisken, Walter F.; Wagstaff, Kiri L.; Majid, Walid A.; Burke-Spolaor, Sarah; Macquart, Jean-Pierre R.; Palaniswamy, Divya

    2013-04-01

    We define a framework for determining constraints on the detection rate of fast transient events from a population of underlying sources, with a view to incorporate beam shape, frequency effects, scattering effects, and detection efficiency into the metric. We then demonstrate a method for combining independent data sets into a single event rate constraint diagram, using a probabilistic approach to the limits on parameter space. We apply this new framework to present the latest results from the V-FASTR experiment, a commensal fast transients search using the Very Long Baseline Array (VLBA). In the 20 cm band, V-FASTR now has the ability to probe the regions of parameter space of importance for the observed Lorimer and Keane fast radio transient candidates by combining the information from observations with differing bandwidths, and properly accounting for the source dispersion measure, VLBA antenna beam shape, experiment time sampling, and stochastic nature of events. We then apply the framework to combine the results of the V-FASTR and Allen Telescope Array Fly's Eye experiments, demonstrating their complementarity. Expectations for fast transients experiments for the SKA Phase I dish array are then computed, and the impact of large differential bandwidths is discussed.

  11. VLBA polarimetric observations of the CSS quasar 3C147

    CERN Document Server

    Rossetti, A; Dallacasa, D; Junor, W; Salter, C J; Saikia, D J; 10.1051/0004-6361/200811190

    2009-01-01

    Aims. We report new VLBA polarimetric observations of the compact steep-spectrum (CSS) quasar 3C147 (B0538+498) at 5 and 8.4GHz. Methods. By using multifrequency VLBA observations, we derived milliarcsecond-resolution images of the total intensity, polarisation, and rotation measure distributions, by combining our new observations with archival data. Results. The source shows a one-sided structure, with a compact region, and a component extending about 200 mas to the south-west. The compact region is resolved into two main components with polarised emission, a complex rotation measure distribution, and a magnetic field dominated by components perpendicular to the source axis. Conclusions. By considering all the available data, we examine the possible location of the core component, and discuss two possible interpretations of the observed structure of this source: core-jet and lobe-hot spot. Further observations to unambiguously determine the location of the core would help distinguish between the two possibil...

  12. Discovery of Pulsed Gamma Rays from the Young Radio Pulsar PSR J1028-5819 with the Fermi Large Area Telescope

    CERN Document Server

    2009-01-01

    Radio pulsar PSR J1028-5819 was recently discovered in a high-frequency search (at 3.1 GHz)in the error circle of the EGRET source 3EG J1027-5817. The spin-down power of this young pulsar is great enough to make it very likely the counterpart for the EGRET source. We report here the discovery of gamma-ray pulsations from PSR J1028-5819 in early observations by the Large Area Telescope (LAT) on the Fermi Gamma-Ray Space Telescope. The gamma-ray light curve shows two sharp peaks having phase separation of 0.460 +- 0.004, trailing the very narrow radio pulse by 0.200 +- 0.003 in phase, very similar to that of other known $\\gamma$-ray pulsars. The measured gamma-ray flux gives an efficiency for the pulsar of 10-20% (for outer magnetosphere beam models). No evidence of a surrounding pulsar wind nebula is seen in the current Fermi data but limits on associated emission are weak because the source lies in a crowded region with high background emission. However, the improved angular resolution afforded by the LAT ena...

  13. Robust constraint on a drifting proton-to-electron mass ratio at z=0.89 from methanol observation at three radio telescopes.

    Science.gov (United States)

    Bagdonaite, J; Daprà, M; Jansen, P; Bethlem, H L; Ubachs, W; Muller, S; Henkel, C; Menten, K M

    2013-12-06

    A limit on a possible cosmological variation of the proton-to-electron mass ratio μ is derived from methanol (CH3OH) absorption lines in the benchmark PKS1830-211 lensing galaxy at redshift z=0.89 observed with the Effelsberg 100-m radio telescope, the Institute de Radio Astronomie Millimétrique 30-m telescope, and the Atacama Large Millimeter/submillimeter Array. Ten different absorption lines of CH3OH covering a wide range of sensitivity coefficients K(μ) are used to derive a purely statistical 1σ constraint of Δμ/μ=(1.5±1.5)×10(-7) for a lookback time of 7.5 billion years. Systematic effects of chemical segregation, excitation temperature, frequency dependence, and time variability of the background source are quantified. A multidimensional linear regression analysis leads to a robust constraint of Δμ/μ=(-1.0±0.8(stat)±1.0(sys))×10(-7).

  14. The Beaming Structures of Jupiter’s Decametric Common S-bursts Observed from the LWA1, NDA, and URAN2 Radio Telescopes

    Science.gov (United States)

    Imai, Masafumi; Lecacheux, Alain; Clarke, Tracy E.; Higgins, Charles A.; Panchenko, Mykhaylo; Dowell, Jayce; Imai, Kazumasa; Brazhenko, Anatolii I.; Frantsuzenko, Anatolii V.; Konovalenko, Alexandr A.

    2016-08-01

    On 2015 February 21, simultaneous observations of Jupiter's decametric radio emission between 10 and 33 MHz were carried out using three powerful low-frequency radio telescopes: the Long Wavelength Array Station One in the USA, the Nançay Decameter Array in France, and the URAN2 telescope in Ukraine. We measured the lag times of short-bursts (S-bursts) for 105 minutes of data over effective baselines of up to 8460 km by using cross-correlation analysis of the spectrograms from each instrument. Of particular interest is the measurement of the beaming thickness of S-bursts, testing if either flashlight- or beacon-like beaming is emanating from Jupiter. We find that the lag times for all pairs drift slightly as time elapses, in agreement with expectations from the flashlight-like beaming model. This leads to a new constraint of the minimum beaming thickness of 2.″66. Also, we find that most of the analyzed data abound with S-bursts, whose occurrence probability peaks at 17-18 MHz.

  15. The Radio JOVE Project - Shoestring Radio Astronomy

    Science.gov (United States)

    Thieman, J.; Flagg, R.; Greenman, W.; Higgins, C.; Reyes, F.; Sky, J.

    2010-01-01

    Radio JOVE is an education and outreach project intended to give students and other interested individuals hands-on experience in learning radio astronomy. They can do this through building a radio telescope from a relatively inexpensive kit that includes the parts for a receiver and an antenna as well as software for a computer chart recorder emulator (Radio Skypipe) and other reference materials

  16. The Radio JOVE Project - Shoestring Radio Astronomy

    Science.gov (United States)

    Thieman, J.; Flagg, R.; Greenman, W.; Higgins, C.; Reyes, F.; Sky, J.

    2010-01-01

    Radio JOVE is an education and outreach project intended to give students and other interested individuals hands-on experience in learning radio astronomy. They can do this through building a radio telescope from a relatively inexpensive kit that includes the parts for a receiver and an antenna as well as software for a computer chart recorder emulator (Radio Skypipe) and other reference materials

  17. Giant Metrewave Radio Telescope detection of associated H I 21-cm absorption at z = 1.2230 towards TXS 1954+513

    Science.gov (United States)

    Aditya, J. N. H. S.; Kanekar, Nissim; Prochaska, J. Xavier; Day, Brandon; Lynam, Paul; Cruz, Jocelyn

    2017-03-01

    We have used the 610-MHz receivers of the Giant Metrewave Radio Telescope (GMRT) to detect associated H I 21-cm absorption from the z = 1.2230 blazar TXS 1954+513. The GMRT H I 21-cm absorption is likely to arise against either the milliarcsecond-scale core or the one-sided milliarcsecond-scale radio jet, and is blueshifted by ≈328 km s-1 from the blazar redshift. This is consistent with a scenario in which the H I cloud giving rise to the absorption is being driven outwards by the radio jet. The integrated H I 21-cm optical depth is (0.716 ± 0.037) km s-1, implying a high H I column density, N_{H I} = (1.305 ± 0.067) × ({ T_s/100 K}) × 10^{20} cm-2, for an assumed H I spin temperature of 100 K. We use Nickel Telescope photometry of TXS 1954+513 to infer a high rest-frame 1216 Å luminosity of (4.1 ± 1.2) × 1023 W Hz-1. The z = 1.2230 absorber towards TXS 1954+513 is only the fifth case of a detection of associated H I 21-cm absorption at z > 1, and is also the first case of such a detection towards an active galactic nucleus (AGN) with a rest-frame ultraviolet (UV) luminosity ≫1023 W Hz-1, demonstrating that neutral hydrogen can survive in AGN environments in the presence of high UV luminosities.

  18. Atmospheric Refractions and Radio Telescope Pointing Corrections%大气折射对射电望远镜高精度指向的影响

    Institute of Scientific and Technical Information of China (English)

    肖明; 王娜; 刘志勇

    2016-01-01

    针对中性大气的物理属性以及大气折射对射电望远镜指向的影响进行了模型分析和计算, 以改进型的 "三段式" 标准指向改正模型为基础, 着重研究了由大气折射造成高阶指向误差的改正方案, 目的是不断提高射电望远镜的指向精度, 尤其针对大口径、 高分辨率的射电望远镜. 在此模型的基础上, 模拟南山观测基地的气候特征, 给出合理的计算结果.通过分析和评估这些结果与射电望远镜指向精度的要求, 为将来大口径射电望远镜的指向修正提供参考.%In this article we discuss the effects of the atmospheric refraction, particularly, the method of accurate corrections to the pointing error of radio telescopes. The position of the telescope beam is somewhat different from the beam position as indicated by the encoders, which is due to the structural deformations caused by the wind, gravity, temperature, and the atmospheric distortion. Accurate refractive corrections which depend on astronomical pointing measurements are required by observations using large aperture radio telescopes, especially at higher frequency bands. This article presents the advanced model for atmospheric refraction corrections and shows the improvements compared to traditional methods, particularly at low elevations. In addition, the real-time refraction corrections, in which the higher-order refraction corrections of telescope pointing errors are involved, for example, the effect of the uneven temperature distribution over a wide scale range, or the differential refraction across a large aperture telescopes, are also analyzed in this article.

  19. Robust Constraint on a Drifting Proton-to-Electron Mass Ratio at z=0.89 from Methanol Observation at Three Radio Telescopes

    CERN Document Server

    Bagdonaite, Julija; Jansen, Paul; Bethlem, Hendrick L; Ubachs, Wim; Muller, Sébastien; Henkel, Christian; Menten, Karl M

    2013-01-01

    A limit on a possible cosmological variation of the proton-to-electron mass ratio $\\mu$ is derived from methanol (CH$_3$OH) absorption lines in the benchmark PKS1830$-$211 lensing galaxy at redshift $z \\sim 0.89$ observed with the Effelsberg 100-m radio telescope, the IRAM 30-m telescope, and the ALMA telescope array. Ten different absorption lines of CH$_3$OH covering a wide range of sensitivity coefficients $K_{\\mu}$ are used to derive a purely statistical 1-$\\sigma$ constraint of $\\Delta\\mu/\\mu = (1.5 \\pm 1.5) \\times 10^{-7}$ for a lookback time of 7.5 billion years. Systematic effects of chemical segregation, excitation temperature, frequency dependence and time variability of the background source are quantified. A multi-dimensional linear regression analysis leads to a robust constraint of $\\Delta\\mu/\\mu = (-1.0 \\pm 0.8_{\\rm stat} \\pm 1.0_{\\rm sys}) \\times 10^{-7}$.

  20. Multi-Epoch VLBA Observations of EGRET-Detected Quasars and BL Lac Objects Connection between Superluminal Ejections and Gamma-Ray Flares in Blazars

    CERN Document Server

    Jorstad, S G; Mattox, J R; Aller, M F; Aller, H D; Wehrle, A E; Bloom, S D; Jorstad, Svetlana G; Marscher, Alan P; Mattox, John R; Aller, Margo F; Aller, Hugh D; Wehrle, Ann E; Bloom, Steven D

    2001-01-01

    We examine the coincidence of times of high $\\gamma$-ray flux and ejections of superluminal components from the core in EGRET blazars based on a VLBA monitoring program at 22 and 43 GHz from November 1993 to July 1997. In 23 cases of $\\gamma$-ray flares for which sufficient VLBA data exist, 16 of the flares (in 14 objects) fall within 3$\\sigma$ and 9 of these within 1$\\sigma$ uncertainties of the extrapolated epoch of zero separation from the core of a superluminal radio component. In each of two sources (0528+134 and 1730-130) two successive $\\gamma$-ray flares were followed by the appearance of new superluminal components. We carried out statistical simulations which show that if the number of coincidences $\\ge$ 7 the radio and $\\gamma$-ray events are associated with each other at >99.999% confidence. Our analysis of the observed behavior, including variability of the polarized radio flux, of the sources before, during, and after the $\\gamma$-ray flares suggests that the $\\gamma$-ray events occur in the sup...

  1. Radio Astronomers Set New Standard for Accurate Cosmic Distance Measurement

    Science.gov (United States)

    1999-06-01

    A team of radio astronomers has used the National Science Foundation's Very Long Baseline Array (VLBA) to make the most accurate measurement ever made of the distance to a faraway galaxy. Their direct measurement calls into question the precision of distance determinations made by other techniques, including those announced last week by a team using the Hubble Space Telescope. The radio astronomers measured a distance of 23.5 million light-years to a galaxy called NGC 4258 in Ursa Major. "Ours is a direct measurement, using geometry, and is independent of all other methods of determining cosmic distances," said Jim Herrnstein, of the National Radio Astronomy Observatory (NRAO) in Socorro, NM. The team says their measurement is accurate to within less than a million light-years, or four percent. The galaxy is also known as Messier 106 and is visible with amateur telescopes. Herrnstein, along with James Moran and Lincoln Greenhill of the Harvard- Smithsonian Center for Astrophysics; Phillip Diamond, of the Merlin radio telescope facility at Jodrell Bank and the University of Manchester in England; Makato Inoue and Naomasa Nakai of Japan's Nobeyama Radio Observatory; Mikato Miyoshi of Japan's National Astronomical Observatory; Christian Henkel of Germany's Max Planck Institute for Radio Astronomy; and Adam Riess of the University of California at Berkeley, announced their findings at the American Astronomical Society's meeting in Chicago. "This is an incredible achievement to measure the distance to another galaxy with this precision," said Miller Goss, NRAO's Director of VLA/VLBA Operations. "This is the first time such a great distance has been measured this accurately. It took painstaking work on the part of the observing team, and it took a radio telescope the size of the Earth -- the VLBA -- to make it possible," Goss said. "Astronomers have sought to determine the Hubble Constant, the rate of expansion of the universe, for decades. This will in turn lead to an

  2. Prediction of solar particle events and geomagnetic activity using interplanetary scintillation observations from the iowa cocoa-cross radio telescope. Final report April 1, 1976--March 31, 1978

    Energy Technology Data Exchange (ETDEWEB)

    Roelof, E.C.; Gotwols, B.L.; Mitchell, D.G.; Cronyn, W.M.; Shawhan, S.D.

    1978-05-01

    Synoptic interplanetary scintillation (IPS) observations were taken during the summer of 1976 and autumn of 1977 on the University of Iowa COCOA-Cross radio telescope (34.3 MHz), with supplementary observations from the University of Maryland TPT array (38 MHz). A new high sampling rate (10 times per second) digital system made it possible to reconstruct the IPS power spectrum between 0.1-3.0 Hz. The observations, combined with earlier (1974) measurements of integrated IPS power (scintillation index), have led to the conclusion (based on theoretical modelling) that prediction of activity and associated variations in energetic solar particle events is feasible with a lead time of about 24 hours. The technique depends on the observed broadening of the IPS power spectrum as solar wind density enhancements approach the earth. This effect has been documented for both co-rotating and solar flare-associated plasma disturbances.

  3. Developments of FPGA-based digital back-ends for low frequency antenna arrays at Medicina radio telescopes

    Science.gov (United States)

    Naldi, G.; Bartolini, M.; Mattana, A.; Pupillo, G.; Hickish, J.; Foster, G.; Bianchi, G.; Lingua, A.; Monari, J.; Montebugnoli, S.; Perini, F.; Rusticelli, S.; Schiaffino, M.; Virone, G.; Zarb Adami, K.

    In radio astronomy Field Programmable Gate Array (FPGA) technology is largely used for the implementation of digital signal processing techniques applied to antenna arrays. This is mainly due to the good trade-off among computing resources, power consumption and cost offered by FPGA chip compared to other technologies like ASIC, GPU and CPU. In the last years several digital backend systems based on such devices have been developed at the Medicina radio astronomical station (INAF-IRA, Bologna, Italy). Instruments like FX correlator, direct imager, beamformer, multi-beam system have been successfully designed and realized on CASPER (Collaboration for Astronomy Signal Processing and Electronics Research, https://casper.berkeley.edu) processing boards. In this paper we present the gained experience in this kind of applications.

  4. The radio/gamma-ray connection in Active Galactic Nuclei in the era of the Fermi Large Area Telescope

    CERN Document Server

    Ackermann, M; Allafort, A; Angelakis, E; Axelsson, M; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bouvier, A; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Cannon, A; Caraveo, P A; Casandjian, J M; Cavazzuti, E; Cecchi, C; Charles, E; Chekhtman, A; Cheung, C C; Ciprini, S; Claus, R; Cohen-Tanugi, J; Cutini, S; de Palma, F; Dermer, C D; Silva, E do Couto e; Drell, P S; Dubois, R; Dumora, D; Escande, L; Favuzzi, C; Fegan, S J; Focke, W B; Fortin, P; Frailis, M; Fuhrmann, L; Fukazawa, Y; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Giglietto, N; Giommi, P; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Grandi, P; Grenier, I A; Guiriec, S; Hadasch, D; Hayashida, M; Hays, E; Healey, S E; J, G; Johnson, A S; Kamae, T; Katagiri, H; Kataoka, J; Kn, J; Kuss, M; Lande, J; Lee, S -H; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Makeev, A; Max-Moerbeck, W; Mazziotta, M N; McEnery, J E; Mehault, J; Michelson, P F; Mizuno, T; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Naumann-Godo, M; Nishino, S; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Okumura, A; Omodei, N; Orlando, E; Ormes, J F; Ozaki, M; Paneque, D; Pavlidou, V; Pelassa, V; Pepe, M; Pesce-Rollins, M; Pierbattista, M; Piron, F; Porter, T A; Rain, S; Razzano, M; Readhead, A; Reimer, A; Reimer, O; Richards, J L; Romani, R W; Sadrozinski, H F -W; Scargle, J D; Sgr, C; Siskind, E J; Smith, P D; Spandre, G; Spinelli, P; Strickman, M S; Suson, D J; Takahashi, H; Tanaka, T; Taylor, G B; Thayer, J G; Thayer, J B; Thompson, D J; Torres, D F; Tosti, G; Tramacere, A; Troja, E; Vandenbroucke, J; Vianello, G; Vitale, V; Waite, A P; Wang, P; Winer, B L; Wood, K S; Yang, Z; Ziegler, M

    2011-01-01

    We present a detailed statistical analysis of the correlation between radio and gamma-ray emission of the Active Galactic Nuclei (AGN) detected by Fermi during its first year of operation, with the largest datasets ever used for this purpose. We use both archival interferometric 8.4 GHz data (from the VLA and ATCA, for the full sample of 599 sources) and concurrent single-dish 15 GHz measurements from the Owens Valley Radio Observatory (OVRO, for a sub sample of 199 objects). Our unprecedentedly large sample permits us to assess with high accuracy the statistical significance of the correlation, using a surrogate-data method designed to simultaneously account for common-distance bias and the effect of a limited dynamical range in the observed quantities. We find that the statistical significance of a positive correlation between the cm radio and the broad band (E>100 MeV) gamma-ray energy flux is very high for the whole AGN sample, with a probability <1e-7 for the correlation appearing by chance. Using the...

  5. Associated Absorption Lines in the Radio-Loud Quasar 3C 351 Far-Ultraviolet Echelle Spectroscopy from the Hubble Space Telescope

    CERN Document Server

    Yuan, Q; Brotherton, M; Tripp, T M; Kaiser, M E; Kriss, G A

    2002-01-01

    As one of the most luminous radio-loud quasars showing intrinsic ultraviolet (UV) and X-ray absorption, 3C 351 provides a laboratory for studying the kinematics and physical conditions of such ionized absorbers. We present an analysis of the intrinsic absorption lines in the high-resolution ($\\sim$ 7 km/s) far-UV spectrum which was obtained from observations with the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST). The spectrum spans wavelengths from 1150 \\AA to 1710 \\AA, and shows strong emission lines from O VI and Ly$\\alpha$. Associated absorption lines are present on the blue wings of the high-ionization emission doublets O VI $\\lambda\\lambda$ 1032,1038 and N V $\\lambda\\lambda$ 1238,1242, as well as the Lyman lines through Ly$\\epsilon$. These intrinsic absorption features are resolved into several distinct kinematic components, covering rest-frame velocities from -40 to -2800 km/s, with respect to the systemic redshift of $z_{em}=0.3721$. For the majority of these abs...

  6. H I observations of galaxies in the southern filament of the Virgo Cluster with the Square Kilometre Array Pathfinder KAT-7 and the Westerbork Synthesis Radio Telescope

    Science.gov (United States)

    Sorgho, A.; Hess, K.; Carignan, C.; Oosterloo, T. A.

    2017-01-01

    We map the H I distribution of galaxies in a ˜1.5 × 2.5° region located at the virial radius south of the Virgo Cluster using the KAT-7 and the Westerbork Synthesis Radio Telescope interferometers. Because of the different beam sizes of the two telescopes, a similar column density sensitivity of NH I ˜ 1 × 1018 atoms cm- 2 was reached with the two observations over 16.5 km s-1. We pioneer a new approach to combine the observations and take advantage of their sensitivity to both the large- and small-scale structures. Out to an unprecedented extent, we detect an H I tail of ˜60 kpc being stripped off NGC 4424, a peculiar spiral galaxy. The properties of the galaxy, together with the shape of the tail, suggest that NGC 4424 is a post-merger galaxy undergoing ram pressure stripping as it falls towards the centre of the Virgo Cluster. We detect a total of 14 galaxies and three H I clouds lacking optical counterparts. One of the clouds is a new detection with an H I mass of 7 × 107 M⊙ and a strong H I profile with W50 = 73 km s-1. We find that 10 out of the 14 galaxies present H I deficiencies not higher than those of the cluster's late spirals, suggesting that the environmental effects are not more pronounced in the region than elsewhere in the cluster.

  7. A deep Giant Metre-wave Radio Telescope 610-MHz survey of the 1H XMM-Newton/Chandra survey field

    Science.gov (United States)

    Moss, D.; Seymour, N.; McHardy, I. M.; Dwelly, T.; Page, M. J.; Loaring, N. S.

    2007-07-01

    We present the results of a deep 610-MHz survey of the 1H XMM-Newton/Chandra survey area with the Giant Metre-wave Radio Telescope. The resulting maps have a resolution of ~7 arcsec and an rms noise limit of 60 μJy. To a 5σ detection limit of 300 μJy, we detect 223 sources within a survey area of 64 arcmin in diameter. We compute the 610-MHz source counts and compare them to those measured at other radio wavelengths. The well-known flattening of the Euclidean-normalized 1.4-GHz source counts below ~2 mJy, usually explained by a population of starburst galaxies undergoing luminosity evolution, is seen at 610 MHz. The 610-MHz source counts can be modelled by the same populations that explain the 1.4-GHz source counts, assuming a spectral index of -0.7 for the starburst galaxies and the steep spectrum active galactic nucleus (AGN) population. We find a similar dependence of luminosity evolution on redshift for the starburst galaxies at 610 MHz as is found at 1.4 GHz (i.e. `Q' = 2.45+0.3-0.4).

  8. Development of a Smooth Taper Double-Ridge Waveguide Orthomode Transducer for a New 100 GHz Band Z-Machine Receiver for the NRO 45-m Radio Telescope

    Science.gov (United States)

    Asayama, Shin’ichiro; Nakajima, Taku

    2013-02-01

    A smooth taper double-ridge waveguide orthomode transducer (OMT) has been designed for the new 100 GHz band receiver system on the Nobeyama Radio Observatory (NRO) 45-m radio telescope. The OMT consists of a smooth taper double-ridge waveguide followed by a Bøifot type junction with a main arm and two side arms. The main arm output is a smoothed tapered transformer followed by an E-plane bend and an oval waveguide. This design facilitates the fabrication of the OMT using split blocks machined on a CNC (computer numerical control) machine. The OMT shows a return loss of better than 18 dB, a polarization isolation of better than 28 dB, and an insertion loss of less than 0.5 dB across the 74–116 GHz, and also demonstrated the excellent performance on the NRO 45-m radio telescope.

  9. B1524-136 A CSS quasar with two-sided radio jets

    CERN Document Server

    Mantovani, F; Bondi, M; Junor, W; Salter, C J; Ricci, R

    2002-01-01

    We present MERLIN, global VLBI and VLBA observations of the high-luminosity, compact steep-spectrum quasar B1524$-$136 at cm wavelengths. These observations reveal well-defined radio jets on both sides of the active nucleus, a situation which is almost unique amongst high-luminosity radio quasars. However, the radio jets on opposite sides are very dissimilar, and the overall radio structure appears highly distorted. We discuss possible implications of these observations.

  10. Multifrequency VLBA polarimetry of the high-redshift GPS quasar OQ172

    Science.gov (United States)

    Liu, Yi; Jiang, D. R.; Gu, Minfeng; Gurvits, L. I.

    2017-07-01

    Multifrequency Very Long Baseline Array (VLBA) polarimetry observation of the GHz-peaked spectrum (GPS) quasar OQ172 (J1445+0958) has been performed at 1.6, 2.2, 4.8, 8.3 and 15.3 GHz in 2005. Core-jet structures are detected in all bands with the jet strongly bent at about 3 mas from the core. The radio emission of the source is polarized at all five bands. We study the Faraday rotation in the core and jet components at all five bands, and find good linear fits of Faraday rotation in the core and jet components at 4.8 and 8.3 GHz. At these two frequencies, the rotation measure (RM) is ˜ 2000 rad m- 2 in the core and ˜ 700 rad m- 2 in the inner jet components and continues to decrease at the outer jet parts. We find that the depolarization at 4.8 and 8.3 GHz might be caused by the internal medium in the source. We investigate consistency of the turnover spectra of VLBI components with the synchrotron self-absorption and free-free absorption models. Although these two models cannot be easily distinguished due to the lack of low-frequency data, the physical parameters can be constrained for each model. We find that the large width of the [O III]_{5007} line is likely caused by a jet interaction with a narrow line region (NLR) medium. The jet bending, significant RM variations, Faraday depolarization, spectral turnover and broad line width of [O III]_{5007} could be closely related, likely caused by the same nucleus medium, presumably NLR.

  11. Research on large radio telescope structure scheme%大型射电望远镜结构总体方案研究

    Institute of Scientific and Technical Information of China (English)

    刘岩; 钱宏亮; 范峰

    2015-01-01

    Aiming at the 110 m fully-steerable radio telescope(which is called QTT for short ) to be built in the future, in order to improve the main reflector precision, the traditional structural concepts were analyzed based on the best fit paraboloid. It is the uneven deformation of the reflector that results in the lower precision. It is mainly due to the following three aspects: the concentrated loads exist on the main reflecting surface, the back frame supporting system is unreasonable and the back frame structure has a poor performance. Based on this, the catching points of the secondary reflector supporting legs were changed, the space truss structure combining cones and quadrangular pyramids were adopted as the back frame structure design, and a kind of polar symmetry umbrella structure was proposed as the supporting system for the back frame structure. Finally the introduced scheme for the fully-steerable radio telescope significantly improved the main reflector precision, its maximal RMS was reduced to 0.306 mm. Compared with the fully-steerable radio telescope GBT which has the largest diameter in the world, the reflective surface area of QTT increases 10%, the surface precision improves 12.6% and the total weightdecreases 40%. The QTT performance reaches the international advanced level.%针对我国待建的110 m全可动射电望远镜(QTT)的工作特点,以提高主反射面精度为目标,以最佳吻合抛物面为拟合标准,分析了传统结构方案致使精度较低的本质原因为反射体变形不均匀,主要源于如下三方面:主反射面存在集中荷载作用、背架结构支承方案不合理、背架结构体系空间受力性能不佳。基于此,改变副反射面撑腿坐落位置,对背架结构采用三角锥、四角锥相结合的网架式结构方案,并对其引入一种高度极对称的伞撑式支承方案。最终提出的全可动望远镜结构总体方案显著提高了主反射面

  12. The Allen Telescope Array Twenty-centimeter Survey -- A 700-Square-Degree, Multi-Epoch Radio Dataset -- II: Individual Epoch Transient Statistics

    CERN Document Server

    Croft, Steve; Keating, Garrett; Law, Casey; Whysong, David; Williams, Peter K G; Wright, Melvyn

    2011-01-01

    We present our second paper on the Allen Telescope Array Twenty-centimeter Survey (ATATS), a multi-epoch, ~700 sq. deg. radio image and catalog at 1.4 GHz. The survey is designed to detect rare, bright transients as well as to commission the ATA's wide-field survey capabilities. ATATS explores the challenges of multi-epoch transient and variable source surveys in the domain of dynamic range limits and changing (u,v) coverage. Here we present images made using data from the individual epochs, as well as a revised image combining data from all ATATS epochs. The combined image has RMS noise 3.96 mJy / beam, with a circular beam of 150 arcsec FWHM. The catalog, generated using a false detection rate algorithm, contains 4984 sources, and is >90% complete to 37.9 mJy. The catalogs generated from snapshot images of the individual epochs contain between 1170 and 2019 sources over the 564 sq. deg. area in common to all epochs. The 90% completeness limits of the single epoch catalogs range from 98.6 to 232 mJy. We comp...

  13. The Allen Telescope Array Twenty-centimeter Survey - A 690-Square-Degree, 12-Epoch Radio Dataset - I: Catalog and Long-Duration Transient Statistics

    CERN Document Server

    Croft, Steve; Ackermann, Rob; Atkinson, Shannon; Backer, Don; Backus, Peter; Barott, William C; Bauermeister, Amber; Blitz, Leo; Bock, Douglas; Bradford, Tucker; Cheng, Calvin; Cork, Chris; Davis, Mike; DeBoer, Dave; Dexter, Matt; Dreher, John; Engargiola, Greg; Fields, Ed; Fleming, Matt; Forster, James R; Gutierrez-Kraybill, Colby; Harp, Gerry; Helfer, Tamara; Hull, Chat; Jordan, Jane; Jorgensen, Susanne; Keating, Garrett; Kilsdonk, Tom; Law, Casey; van Leeuwen, Joeri; Lugten, John; MacMahon, Dave; McMahon, Peter; Milgrome, Oren; Pierson, Tom; Randall, Karen; Ross, John; Shostak, Seth; Siemion, Andrew; Smolek, Ken; Tarter, Jill; Thornton, Douglas; Urry, Lynn; Vitouchkine, Artyom; Wadefalk, Niklas; Welch, Jack; Werthimer, Dan; Whysong, David; Williams, Peter K G; Wright, Melvyn

    2010-01-01

    We present the Allen Telescope Array Twenty-centimeter Survey (ATATS), a multi-epoch (12 visits), 690 square degree radio image and catalog at 1.4GHz. The survey is designed to detect rare, very bright transients as well as to verify the capabilities of the ATA to form large mosaics. The combined image using data from all 12 ATATS epochs has RMS noise sigma = 3.94mJy / beam and dynamic range 180, with a circular beam of 150 arcsec FWHM. It contains 4408 sources to a limiting sensitivity of S = 20 mJy / beam. We compare the catalog generated from this 12-epoch combined image to the NRAO VLA Sky Survey (NVSS), a legacy survey at the same frequency, and find that we can measure source positions to better than ~20 arcsec. For sources above the ATATS completeness limit, the median flux density is 97% of the median value for matched NVSS sources, indicative of an accurate overall flux calibration. We examine the effects of source confusion due to the effects of differing resolution between ATATS and NVSS on our abi...

  14. The 26 December 2001 Solar Event Responsible for GLE63. I. Observations of a Major Long-Duration Flare with the Siberian Solar Radio Telescope

    CERN Document Server

    Grechnev, V V

    2016-01-01

    Ground Level Enhancements (GLEs) of cosmic-ray intensity occur, on average, once a year. Due to their rareness, studying the solar sources of GLEs is especially important to approach understanding their origin. The SOL2001-12-26 eruptive-flare event responsible for GLE63 seems to be challenging in some aspects. Deficient observations limited its understanding. Analysis of extra observations found for this event provided new results shading light on the flare. This article addresses the observations of this flare with the Siberian Solar Radio Telescope (SSRT). Taking advantage of its instrumental characteristics, we analyze the detailed SSRT observations of a major long-duration flare at 5.7 GHz without cleaning the images. The analysis confirms that the source of GLE63 was associated with an event in active region 9742 that comprised two flares. The first flare (04:30-05:03 UT) reached a GOES importance of about M1.6. Two microwave sources were observed, whose brightness temperatures at 5.7 GHz exceeded 10 MK...

  15. Imaging of the solar atmosphere by the Siberian Solar Radio Telescope at 5.7 GHz with an enhanced dynamic range

    CERN Document Server

    Kochanov, Alexey; Prosovetsky, Dmitry; Rudenko, George; Grechnev, Victor

    2013-01-01

    The Siberian Solar Radio Telescope (SSRT) is a solar-dedicated directly-imaging interferometer observing the Sun at 5.7 GHz. The SSRT operates in the two-dimensional mode since 1996. The imaging principle of the SSRT restricts its opportunities in observations of very bright flare sources, while it is possible to use `dirty' images in studies of low brightness features, which do not overlap with side lobes from bright sources. The interactive CLEAN technique routinely used for the SSRT data provides imaging of active regions but consumes much time and efforts and does not reveal low-brightness features below the CLEAN threshold. The newly developed technique combines the CLEAN routine with the directly imaging capability of the SSRT and provides clean images with an enhanced dynamic range automatically. These elaborations considerably extend the range of tasks, which can be solved with the SSRT. We show some examples of the present opportunities of the SSRT and compare its data with the images produced by the...

  16. Astrometry of Cassini with the VLBA to improve the Saturn ephemeris

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Dayton L.; Folkner, William M.; Jacobson, Robert A.; Jacobs, Christopher S. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Dhawan, Vivek; Romney, Jon [National Radio Astronomy Observatory, Socorro, NM 87801 (United States); Fomalont, Ed, E-mail: dayton.jones@jpl.nasa.gov [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States)

    2015-01-01

    Planetary ephemerides have been developed and improved over centuries. They are a fundamental tool for understanding solar system dynamics, and essential for planetary and small body mass determinations, occultation predictions, high-precision tests of general relativity, pulsar timing, and interplanetary spacecraft navigation. This paper presents recent results from a continuing program of high-precision astrometric very long baseline interferometry (VLBI) observations of the Cassini spacecraft orbiting Saturn, using the Very Long Baseline Array (VLBA). We have previously shown that VLBA measurements can be combined with spacecraft orbit determinations from Doppler and range tracking and VLBI links to the inertial extragalactic reference frame to provide the most accurate barycentric positions currently available for Saturn. Here we report an additional five years of VLBA observations along with improved phase reference source positions, resulting in an improvement in residuals with respect to the Jet Propulsion Laboratory's dynamical ephemeris.

  17. VLBA determination of the distance to nearby star-forming regions I. The distance to T Tauri with 0.4% accuracy

    CERN Document Server

    Loinard, Laurent; Mioduszewski, Amy J; Rodriguez, Luis F; Gonzalez-Lopezlira, Rosa A; Lachaume, Regis; Vazquez, Virgilio; Gonzalez, Erandy

    2007-01-01

    In this article, we present the results of a series of twelve 3.6-cm radio continuum observations of T Tau Sb, one of the companions of the famous young stellar object T Tauri. The data were collected roughly every two months between September 2003 and July 2005 with the Very Long Baseline Array (VLBA). Thanks to the remarkably accurate astrometry delivered by the VLBA, the absolute position of T Tau Sb could be measured with a precision typically better than about 100 micro-arcseconds at each of the twelve observed epochs. The trajectory of T Tau Sb on the plane of the sky could, therefore, be traced very precisely, and modeled as the superposition of the trigonometric parallax of the source and an accelerated proper motion. The best fit yields a distance to T Tau Sb of 147.6 +/- 0.6 pc. The observed positions of T Tau Sb are in good agreement with recent infrared measurements, but seem to favor a somewhat longer orbital period than that recently reported by Duchene et al. (2006) for the T Tau Sa/T Tau Sb sy...

  18. MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. VI. Kinematics Analysis of a Complete Sample of Blazar Jets

    CERN Document Server

    Lister, M L; Homan, D C; Kadler, M; Kellermann, K I; Kovalev, Y Y; Ros, E; Savolainen, T; Zensus, J A

    2009-01-01

    We discuss the jet kinematics of a complete flux-density-limited sample of 135 radio-loud active galactic nuclei (AGN) resulting from a 13 year program to investigate the structure and evolution of parsec-scale jet phenomena. Our analysis is based on new 2 cm Very Long Baseline Array (VLBA) images obtained between 2002 and 2007, but includes our previously published observations made at the same wavelength, and is supplemented by VLBA archive data. In all, we have used 2424 images spanning the years 1994-2007 to study and determine the motions of 526 separate jet features in 127 jets. The data quality and temporal coverage (a median of 15 epochs per source) of this complete AGN jet sample represents a significant advance over previous kinematics surveys. In all but five AGNs, the jets appear one-sided, most likely the result of differential Doppler boosting. In general the observed motions are directed along the jet ridge line, outward from the optically thick core feature. We directly observe changes in spee...

  19. The Africa Millimetre Telescope

    Science.gov (United States)

    Backes, M.; Müller, C.; Conway, J. E.; Deane, R.; Evans, R.; Falcke, H.; Fraga-Encinas, R.; Goddi, C.; Klein Wolt, M.; Krichbaum, T. P.; MacLeod, G.; Ribeiro, V. A. R. M.; Roelofs, F.; Shen, Z. Q.; van Langevelde, H. J.

    It is believed that supermassive black holes are found in the centres of galaxies, including the Milky Way. Still, only indirect evidence has been gathered for the existence of these enigmatic objects that are predicted by the general theory of relativity. With the Event Horizon Telescope, a Very Long Baseline Interferometry network of millimetre-wave (radio) telescopes, it will be possible to directly image the 'shadow' of the event horizon of the black hole at the centre of the Milky Way, Sgr A*. Although the Event Horizon Telescope utilises an extensive network of telescopes, there is a huge gap in the coverage of the u-v-plane for these observations across Africa. We discuss the benefits of adding the Africa Millimetre Telescope to the Event Horizon Telescope and present Mt. Gamsberg in Namibia as the best site for this new and first mm-wave telescope in Africa.

  20. Pinpointing the TeV gamma-ray emission region in M87 using TeV and 43 GHz radio monitoring

    CERN Document Server

    Wagner, R M; Davies, F; Hardee, P; Krawczynski, H; Mazin, D; Walker, R C; Raue, M; Wagner, S; Ly, C; Junor, W; VERITAS,

    2009-01-01

    The TeV radio galaxy M87 is the first radio galaxy detected in the TeV regime. The structure of its jet, which is not pointing towards our line of sight, is spatially resolved in X-ray (by Chandra), optical and radio observations. In 2008, the three main Atmospheric Cherenkov Telescope observatories VERITAS, MAGIC and H.E.S.S. coordinated their observations in a joint campaign from January to May with a total observation time of approx. 120 hours. In February, strong and rapid day-scale TeV flares were detected. VLBA monitoring observations during the same period showed that the 43 GHz radio flux density of the unresolved core began to rise at the time of the TeV flares and eventually reached levels above any previously seen with VLBI. New jet components appeared during the flare. The localization accuracy of the TeV instruments of many arcseconds, even for strong sources, is inadequate to constrain the origin of the emission in the inner jets of AGNs. For M87, with a 6 billion solar mass black hole and a dis...

  1. 中阿40m射电望远镜选址与电磁环境监测%Site Testing and RFI Measurements for China-Argentina Radio Telescope

    Institute of Scientific and Technical Information of China (English)

    赵卫普; 夏跃兵; MALLAMACI CC; PODESTA RC; PACHECO AM; ACTIS E; CASTRO JI; ALVIS RH; LOPEZ CE; FRANCILE C; PODESTA F; 李建斌; PEREZ J; 李金增; 孙建民; 齐力; 罗滔; 马晓耘; 莫铠玮; 李鹏程

    2014-01-01

    优良站址的选择是射电望远镜完成既定科学目标并实现高效运行的重要保障。影响射电望远镜选址的主要因素包括电磁环境、水文、气象、地质条件、隔离性与可及性等。对于射电天文观测而言,来自宇宙天体的射电信号往往极其微弱,对望远镜系统及设备的灵敏度要求极高。然而,随着人类活动的不断加强,人们日常工作和生活中使用的电子通讯设备越来越多,无线电干扰源呈爆炸式涌现。在射电望远镜选址工作中,进行电磁环境监测,选择一个电磁环境良好的站址,对于射电望远镜实现常规观测运行、获取有效数据资料至关重要。同时,电磁环境监测结果也是射电望远镜接收机系统研制、站址电磁环境及无线电宁静区立法保护的重要依据。中阿天文学者和技术人员历时1年半完成了16个候选站址的初步勘察,并对优选出的3个主要候选站址进行了深入细致的电磁环境监测工作,获得了大量可靠数据。中阿双方依据电磁环境监测结果并结合各主要候选站址的水文、气象、地质及道路等条件,最终将位于Talacasto戈壁的3号候选站址确定为中阿CART射电望远镜的建设站点。%The China-Argentina Radio Telescope (CART) with a diameter of 40-m will be located in the San Juan province of Argentina. CART is destined to be eventually equipped with L, S, C, X, Ku, K, Ka, and possibly also Q bands. Up to date, radio telescopes are usually designed with high sensitivities eligible for detecting extremely weak radio signals from astronomical ob jects. However, the explosive utilization of large mass of electronics and radio communication facilities in human activities has significantly ruined the working environment of radio telescopes. Therefore, the selection of a radio quiet site is one of the most critical issues for locating radio telescopes such as CART. Measurements of

  2. VizieR Online Data Catalog: AGN in IFRS. VLBA observations (Herzog+, 2015)

    Science.gov (United States)

    Herzog, A.; Middelberg, E.; Norris, R. P.; Spitler, L. R.; Deller, A. T.; Collier, J. D.; Parker, Q. A.

    2015-09-01

    We selected all IFRS from the catalogue from Collier et al. (2014MNRAS.439..545C, Cat. J/MNRAS/439/545) which were located within 1° of a VLBA calibrator. Out of the 1317 IFRS presented by Collier et al., 110 were found to provide a calibrator which fulfills the given conditions. (1 data file).

  3. A decelerating jet observed by the EVN and VLBA in the X-ray transient XTE J1752-223

    CERN Document Server

    Yang, J; Corbel, S; Paragi, Z; Tzioumis, T; Fender, R P

    2010-01-01

    The recently discovered Galactic X-ray transient XTE J1752-223 entered its first known outburst in 2010, emitting from the X-ray to the radio regimes. Its general X-ray properties were consistent with those of a black hole candidate in various spectral states, when ejection of jet components is expected. To verify this, we carried out very long baseline interferometry (VLBI) observations. The measurements were carried out with the European VLBI Network (EVN) and the Very Long Baseline Array (VLBA) at four epochs in 2010 February. The images at the first three epochs show a moving jet component that is significantly decelerated by the last epoch, when a new jet component appears that is likely to be associated with the receding jet side. The overall picture is consistent with an initially mildly relativistic jet, interacting with the interstellar medium or with swept-up material along the jet. The brightening of the receding ejecta at the final epoch can be well explained by initial Doppler deboosting of the e...

  4. Shoestring Budget Radio Astronomy

    Science.gov (United States)

    Hoot, John E.

    2017-06-01

    The commercial exploitation of microwave frequencies for cellular, WiFi, Bluetooth, HDTV, and satellite digital media transmission has brought down the cost of the components required to build an effective radio telescope to the point where, for the cost of a good eyepiece, you can construct and operate a radio telescope. This paper sets forth a family of designs for 1421 MHz telescopes. It also proposes a method by which operators of such instruments can aggregate and archive data via the Internet. With 90 or so instruments it will be possible to survey the entire radio sky for transients with a 24 hour cadence.

  5. Dwingeloo - the golden radio telescope

    NARCIS (Netherlands)

    van Woerden, H.; Strom, R. G.

    2007-01-01

    The Dwingeloo 25-m telesope, inaugurated in 1956, has played a major role in research for half a century. We trace its history back to its conception in 1944, and summarize its main achievements. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  6. Kinematics of the Local Universe XIV. Measurements from the 21 cm line and the HI mass function from a homogeneous catalog gathered with the Nan\\c{c}ay radio telescope

    CERN Document Server

    Theureau, Gilles; Hallet, Nicole; Hanski, Mikko; Poulain, Mélina

    2016-01-01

    This paper presents 828 new 21 cm neutral hydrogen line measurements carried out with the FORT receiver of the meridian transit Nan\\c{c}ay radio telescope (NRT) in the years 2000 -- 2007. This observational program was part of a larger project aimed at collecting an exhaustive and magnitude-complete HI extragalactic catalog for Tully-Fisher applications. Through five massive data releases, the KLUN series has collected a homogeneous sample of 4876 HI-spectra of spiral galaxies, complete down to a flux of 5 Jy.km.s^{-1} and with declination delta > -40{\\deg}. We publish here the last release of the KLUN HI observational program, corresponding to the faint end of the survey, with HI masses ranging from 5 10^8 to 5 10^{10} solar masses. The size of this final sample is comparable to the catalogs based on the Arecibo and Parkes radio telescope campaigns, and it allows general HI mass distribution studies from a set of homogeneous radio measurements.

  7. Kinematics of the Local Universe. XIV. Measurements from the 21 cm line and the HI mass function from a homogeneous catalog gathered with the Nançay radio telescope

    Science.gov (United States)

    Theureau, G.; Coudreau, N.; Hallet, N.; Hanski, M. O.; Poulain, M.

    2017-03-01

    Aims: This paper presents 828 new 21 cm neutral hydrogen line measurements carried out with the FORT receiver of the meridian transit Nançay radio telescope (NRT) in the years 2000-2007. Methods: This observational program was part of a larger project aimed at collecting an exhaustive and magnitude-complete HI extragalactic catalog for Tully-Fisher applications. Through five massive data releases, the KLUN series has collected a homogeneous sample of 4876 HI-spectra of spiral galaxies, complete down to a flux of 5 Jy km s-1 and with declination δ > -40°. Results: We publish here the last release of the KLUN HI observational program, corresponding to the faint end of the survey, with HI masses ranging from 5 × 108 to 5 × 1010 solar masses. The size of this final sample is comparable to the catalogs based on the Arecibo and Parkes radio telescope campaigns, and it allows general HI mass distribution studies from a set of homogeneous radio measurements. Full Tables 2 and 3, together with HI profiles in ascii format, are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/599/A104

  8. Motion and properties of nuclear radio components in Seyfert galaxies seen with VLBI

    NARCIS (Netherlands)

    Middelberg, E; Nagar, NM; Krichbaum, TP; Norris, RP; Wilson, AS; Falcke, H; Colbert, EJM; Witzel, A; Fricke, KJ

    2004-01-01

    We report EVN, MERLIN and VLBA observations at 18 cm, 6 cm and 3.6 cm of the Seyfert galaxies NGC 7674, NGC 5506, NGC 2110 and Mrk 1210 to study their structure and proper motions on pc scales and to add some constraints on the many possible causes of the radio-quietness of Seyferts. The component c

  9. Simulations of cm-wavelength Sunyaev-Zel'dovich galaxy cluster and point source blind sky surveys and predictions for the RT32/OCRA-f and the Hevelius 100-m radio telescope

    Energy Technology Data Exchange (ETDEWEB)

    Lew, Bartosz; Kus, Andrzej [Toruń Centre for Astronomy, Nicolaus Copernicus University, ul. Gagarina 11, 87-100 Toruń (Poland); Birkinshaw, Mark [HH Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Wilkinson, Peter, E-mail: blew@astro.uni.torun.pl, E-mail: Mark.Birkinshaw@bristol.ac.uk, E-mail: peter.wilkinson@manchester.ac.uk, E-mail: ajk@astro.uni.torun.pl [Jodrell Bank Centre for Astrophysics, The University of Manchester, Alan Turing Building, Manchester M13 9PL (United Kingdom)

    2015-02-01

    We investigate the effectiveness of blind surveys for radio sources and galaxy cluster thermal Sunyaev-Zel'dovich effects (TSZEs) using the four-pair, beam-switched OCRA-f radiometer on the 32-m radio telescope in Poland. The predictions are based on mock maps that include the cosmic microwave background, TSZEs from hydrodynamical simulations of large scale structure formation, and unresolved radio sources. We validate the mock maps against observational data, and examine the limitations imposed by simplified physics. We estimate the effects of source clustering towards galaxy clusters from NVSS source counts around Planck-selected cluster candidates, and include appropriate correlations in our mock maps. The study allows us to quantify the effects of halo line-of-sight alignments, source confusion, and telescope angular resolution on the detections of TSZEs. We perform a similar analysis for the planned 100-m Hevelius radio telescope (RTH) equipped with a 49-beam radio camera and operating at frequencies up to 22 GHz.We find that RT32/OCRA-f will be suitable for small-field blind radio source surveys, and will detect 33{sup +17}{sub −11} new radio sources brighter than 0.87 mJy at 30 GHz in a 1 deg{sup 2} field at > 5σ CL during a one-year, non-continuous, observing campaign, taking account of Polish weather conditions. It is unlikely that any galaxy cluster will be detected at 3σ CL in such a survey. A 60-deg{sup 2} survey, with field coverage of 2{sup 2} beams per pixel, at 15 GHz with the RTH, would find <1.5 galaxy clusters per year brighter than 60 μJy (at 3σ CL), and would detect about 3.4 × 10{sup 4} point sources brighter than 1 mJy at 5σ CL, with confusion causing flux density errors ∼< 2% (20%) in 68% (95%) of the detected sources.A primary goal of the planned RTH will be a wide-area (π sr) radio source survey at 15 GHz. This survey will detect nearly 3 × 10{sup 5} radio sources at 5σ CL down to 1.3 mJy, and tens of galaxy

  10. Research and design on solar radio telescope observations automatic control platform%太阳射电望远镜自动观测控制平台的研究与设计

    Institute of Scientific and Technical Information of China (English)

    王冉; 殷兴辉

    2015-01-01

    In order to achieve an observer sitting in front of a computer without leaving home can be completed using a radio telescope observations the astronomical, based on laboratory radio spectrum analyzer, we propose an automatic observing solar radio telescope control platform for the overall solution. In VC++6.0 designed PC interface , MSP430F169 MCU as the next crew, PC control of MCU, lower machine control laboratory antenna azimuth and elevation movement, truly achieve the automatic control for the telescope. Experimental results show that the system is stable, we can achieve the purpose of the design.%为了实现观测者足不出户的坐在计算机面前就可以完成使用射电望远镜观测天体的任务,在实验室射电频谱仪的基础上,提出了一种太阳射电望远镜自动观测控制平台的整体解决方案。以 VC++6.0设计上位机界面,以MSP430F169单片机为下位机,上位机控制下位机使其控制实验室电机方位和俯仰的转动,真正实现对望远镜的自动控制。实验结果表明,该系统工作稳定,可以达到设计的目的。

  11. Unveiling the radio cosmos

    Science.gov (United States)

    Vanderlinde, Keith

    2017-02-01

    Using a radio telescope with no moving parts, the dark energy speeding up the expansion of the Universe can be probed in unprecedented detail, says Keith Vanderlinde, on behalf of the CHIME collaboration.

  12. Near real-time astrometry for spacecraft navigation with the VLBA: A demonstration with the Mars Reconnaissance Orbiter and Odyssey

    CERN Document Server

    Max-Moerbeck, W; Romney, J D

    2015-01-01

    We present a demonstration of near real-time spacecraft astrometry with the VLBA. We detect the X-band downlink signal from Mars Reconnaissance Orbiter and Odyssey with the VLBA and transmit the data over the internet for correlation at the VLBA correlator in near real-time. Quasars near Mars in the plane of the sky are used as position references. In the demonstration we were able to obtain initial position measurements within about 15 minutes of the start of the observation. The measured positions differ from the projected ephemerides by a few milliarcseconds, and the repeatability of the measurement is better than 0.3 milliarcseconds as determined from measurements from multiple scans. We demonstrate that robust and repeatable offsets are obtained even when removing half of the antennas. These observations demonstrate the feasibility of astrometry with the VLBA with a low latency and sub-milliarcsecond repeatability.

  13. Monthly 43 GHz VLBA Polarimetric Monitoring of 3C120 over 16 Epochs Evidence for Trailing Shocks in a Relativistic Jet

    CERN Document Server

    Gómez, J L; Alberdi, A; Jorstad, S G; Agudo, I; Gomez, Jose-Luis; Marscher, Alan P.; Alberdi, Antonio; Jorstad, Svetlana G.; Agudo, Ivan

    2001-01-01

    We present a 16-month sequence of monthly polarimetric 43 GHz VLBA images of the radio galaxy 3C 120. The images probe the inner regions of the radio jet of this relatively nearby superluminal radio galaxy at a linear resolution of 0.07 $h_{65}^{-1}$ pc ($H_o= 65 h_{65}$ km s$^{-1}$ Mpc$^{-1}$). We follow the motion of a number of features with apparent velocities between 4.01$\\pm$0.08 and $5.82\\pm 0.13 h_{65}^{-1} c$. A new superluminal knot, moving at $4.29\\pm 0.16 h_{65}^{-1} c$, is observed to be ejected from the core at a time coincident with the largest flare ever observed for this source at millimeter wavelengths. Changes in the position angle of this component, as well as a progressive rotation of its magnetic polarization vector, suggest the presence of a twisted (resembling a helix in projection) configuration of the underlying jet magnetic field and jet geometry. We identify several knots that appear in the wake of the new superluminal component, moving at proper motions $\\sim 4$ times slower than ...

  14. Milliarcsecond Imaging of the Radio Emission from the Quasar with the Most Massive Black Hole at Reionization

    Science.gov (United States)

    Wang, Ran; Momjian, Emmanuel; Carilli, Chris L.; Wu, Xue-Bing; Fan, Xiaohui; Walter, Fabian; Strauss, Michael A.; Wang, Feige; Jiang, Linhua

    2017-02-01

    We report Very Long Baseline Array (VLBA) observations of the 1.5 GHz radio continuum emission of the z = 6.326 quasar SDSS J010013.02+280225.8 (hereafter J0100+2802). J0100+2802 is by far the most optically luminous and is a radio-quiet quasar with the most massive black hole known at z > 6. The VLBA observations have a synthesized beam size of 12.10 mas ×5.36 mas (FWHM), and detected the radio continuum emission from this object with a peak surface brightness of 64.6 ± 9.0 μJy beam‑1 and a total flux density of 88 ± 19 μJy. The position of the radio peak is consistent with that from SDSS in the optical and Chandra in the X-ray. The radio source is marginally resolved by the VLBA observations. A 2D Gaussian fit to the image constrains the source size to (7.1 ± 3.5) mas × (3.1 ± 1.7) mas. This corresponds to a physical scale of (40 ± 20) pc × (18 ± 10) pc. We estimate the intrinsic brightness temperature of the VLBA source to be TB = (1.6 ± 1.2) × 107 K. This is significantly higher than the maximum value in normal star-forming galaxies, indicating an active galactic nucleus (AGN) origin for the radio continuum emission. However, it is also significantly lower than the brightness temperatures found in highest-redshift radio-loud quasars. J0100+2802 provides a unique example for studying the radio activity in optically luminous and radio-quiet AGNs in the early universe. Further observations at multiple radio frequencies will accurately measure the spectral index and address the dominant radiation mechanism of the radio emission.

  15. Radio Emission from Exoplanets

    OpenAIRE

    George, Samuel J.; Stevens, Ian R.

    2008-01-01

    We present results from new low frequency observations of two extrasolar planetary systems (Epsilon Eridani and HD128311) taken at 150 MHz with the Giant Metrewave Radio Telescope (GMRT). We do not detect either system, but are able to place tight upper limits on their low frequency radio emission.

  16. MAGIC gamma-ray and multifrequency observations of flat spectrum radio quasar PKS 1510-089 in early 2012

    CERN Document Server

    Aleksić, J; Antonelli, L A; Antoranz, P; Babic, A; Bangale, P; de Almeida, U Barres; Barrio, J A; González, J Becerra; Bednarek, W; Bernardini, E; Biland, A; Blanch, O; Bonnefoy, S; Bonnoli, G; Borracci, F; Bretz, T; Carmona, E; Carosi, A; Carreto-Fidalgo, D; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Covino, S; Da Vela, P; Dazzi, F; De Angelis, A; De Caneva, G; De Lotto, B; Mendez, C Delgado; Doert, M; Domínguez, A; Prester, D Dominis; Dorner, D; Doro, M; Einecke, S; Eisenacher, D; Elsaesser, D; Farina, E; Ferenc, D; Fonseca, M V; Font, L; Frantzen, K; Fruck, C; López, R J García; Garczarczyk, M; Terrats, D Garrido; Gaug, M; Godinović, N; Muñoz, A González; Gozzini, S R; Hadasch, D; Hayashida, M; Herrera, J; Herrero, A; Hildebrand, D; Hose, J; Hrupec, D; Idec, W; Kadenius, V; Kellermann, H; Kodani, K; Konno, Y; Krause, J; Kubo, H; Kushida, J; La Barbera, A; Lelas, D; Lewandowska, N; Lindfors, E; Lombardi, S; López, M; López-Coto, R; López-Oramas, A; Lorenz, E; Lozano, I; Makariev, M; Mallot, K; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Marcote, B; Mariotti, M; Martínez, M; Mazin, D; Menzel, U; Meucci, M; Miranda, J M; Mirzoyan, R; Moralejo, A; Munar-Adrover, P; Nakajima, D; Niedzwiecki, A; Nilsson, K; Nishijima, K; Noda, K; Nowak, N; Orito, R; Overkemping, A; Paiano, S; Palatiello, M; Paneque, D; Paoletti, R; Paredes, J M; Paredes-Fortuny, X; Partini, S; Persic, M; Prada, F; Moroni, P G Prada; Prandini, E; Preziuso, S; Puljak, I; Reinthal, R; Rhode, W; Ribó, M; Rico, J; Garcia, J Rodriguez; Rügamer, S; Saggion, A; Saito, T; Saito, K; Satalecka, K; Scalzotto, V; Scapin, V; Schultz, C; Schweizer, T; Shore, S N; Sillanpää, A; Sitarek, J; Snidaric, I; Sobczynska, D; Spanier, F; Stamatescu, V; Stamerra, A; Steinbring, T; Storz, J; Strzys, M; Sun, S; Surić, T; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzić, T; Tescaro, D; Teshima, M; Thaele, J; Tibolla, O; Torres, D F; Toyama, T; Treves, A; Uellenbeck, M; Vogler, P; Wagner, R M; Zandanel, F; Zanin, R; Lucarelli, F; Pittori, C; Vercellone, S; Verrecchia, F; Buson, S; D'Ammando, F; Stawarz, L; Giroletti, M; Orienti, M; Mundell, C; Steele, I; Zarpudin, B; Raiteri, C M; Villata, M; Sandrinelli, A; Lähteenäki, A; Tammi, J; Tornikoski, M; Hovatta, T; Readhead, A C S; Max-Moerbeck, W; Richards, J L; Jorstad, S; Marscher, A; Gurwell, M A; Larionov, V M; Blinov, D A; Konstantinova, T S; Kopatskaya, E N; Larionova, L V; Larionova, E G; Morozova, D A; Troitsky, I S; Mokrushina, A A; Pavlova, Yu V; Chen, W P; Lin, H C; Panwar, N; Agudo, I; Casadio, C; Gómez, J L; Molina, S N; Kurtanidze, O M; Nikolashvili, M G; Kurtanidze, S O; Chigladze, R A; Acosta-Pulido, J A; Carnerero, M I; Manilla-Robles, A; Ovcharov, E; Bozhilov, V; Metodieva, I; Aller, M F; Aller, H D; Fuhrmann, L; Angelakis, E; Nestoras, I; Krichbaum, T P; Zensus, J A; Ungerechts, H; Sievers, A; Riquelme, D

    2014-01-01

    Among more than fifty blazars detected in very high energy (VHE, E>100GeV) gamma-rays, only three belong to the subclass of Flat Spectrum Radio Quasars (FSRQs). MAGIC observed FSRQ PKS 1510-089 in February-April 2012 during a high activity state in the high energy (HE, E>100 MeV) gamma-ray band observed by AGILE and Fermi. MAGIC observations result in the detection of a source with significance of 6.0 sigma. In agreement with the previous VHE observations of the source, we find no statistically significant variability during the MAGIC observations in daily, weekly or monthly time scales. The other two known VHE FSRQs have shown daily scale to sub-hour variability. We study the multifrequency behaviour of the source at the epoch of MAGIC observation, collecting quasi-simultaneous data at radio and optical (GASP-WEBT and F-Gamma collaborations, REM, Steward, Perkins, Liverpool, OVRO and VLBA telescopes), X-ray (Swift satellite) and HE gamma-ray frequencies. The gamma-ray SED combining AGILE, Fermi and MAGIC dat...

  17. Radio Band Observations of Blazar Variability

    Indian Academy of Sciences (India)

    Margo F. Aller; Hugh D. Aller; Philip A. Hughes

    2011-03-01

    The properties of blazar variability in the radio band are studied using the unique combination of temporal resolution from single dish monitoring and spatial resolution from VLBA imaging. Such measurements now available in all four Stokes parameters, together with theoretical simulations, identify the origin of radio band variability and probe the characteristics of the radio jet where the broadband blazar emission originates. Outbursts in total flux density and linear polarization in the optical-to-radio bands are attributed to shocks propagating within the jet spine, in part, based on limited modelling invoking transverse shocks; new radiative transfer simulations allowing for shocks at arbitrary angle to the flow direction confirm this picture by reproducing the observed centimeter-band variations observed more generally, and are of current interest since these shocks may play a role in the -ray flaring detected by Fermi. Recent UMRAO multifrequency Stokes V studies of bright blazars identify the spectral variability properties of circular polarization for the first time and demonstrate that polarity flips are relatively common. All-Stokes data are consistent with the production of circular polarization by linear-to-circular mode conversion in a region that is at least partially selfabsorbed. Detailed analysis of single-epoch, multifrequency, all-Stokes VLBA observations of 3C 279 support this physical picture and are best explained by emission from an electron-proton plasma.

  18. Radio Band Observations of Blazar Variability

    CERN Document Server

    Aller, Margo F; Hughes, Philip A

    2010-01-01

    The properties of blazar variability in the radio band are studied using the unique combination of temporal resolution from single dish monitoring and spatial resolution from VLBA imaging; such measurements, now available in all four Stokes parameters, together with theoretical simulations, identify the origin of radio band variability and probe the characteristics of the radio jet where the broadband blazar emission originates. Outbursts in total flux density and linear polarization in the optical-to-radio bands are attributed to shocks propagating within the jet spine, in part based on limited modeling invoking transverse shocks; new radiative transfer simulations allowing for shocks at arbitrary angle to the flow direction confirm this picture by reproducing the observed centimeter-band variations observed more generally, and are of current interest since these shocks may play a role in the gamma-ray flaring detected by Fermi. Recent UMRAO multifrequency Stokes V studies of bright blazars identify the spec...

  19. Distribution of inhomogeneities in the interstellar plasma in the directions of three distant pulsars from observations with the RadioAstron ground-space interferometer

    Science.gov (United States)

    Popov, M. V.; Andrianov, A. S.; Bartel, N.; Gwinn, C.; Joshi, B. C.; Jauncey, D.; Kardashev, N. S.; Rudnitskii, A. G.; Smirnova, T. V.; Soglasnov, V. A.; Fadeev, E. N.; Shishov, V. I.

    2016-09-01

    The RadioAstron ground-space interferometer has been used to measure the angular sizes of the scattering disks of the three distant pulsars B1641-45, B1749-28, and B1933+16. The observations were carried out with the participation of the Westerbork Synthesis Radio Telescope; two 32-m telescopes at Torun, Poland and Svetloe, Russia (the latter being one antenna of the KVAZAR network); the Saint Croix VLBA antenna; the Arecibo radio telescope; the Parkes, Narrabri (ATCA), Mopra, Hobart, and Ceduna Australian radio telescopes; and the Hartebeesthoek radio telescope in South Africa. The full widths at half maximum of the scattering disks were 27 mas at 1668 MHz for B1641-45, 0.5 mas at 1668 MHz for B1749-28, and 12.3 at 316 MHz and 0.84 mas at 1668 MHz for B1933+16. The characteristic time scales for scatter-broadening of the pulses on inhomogeneities in the interstellar plasma τsc were also measured for these pulsars using various methods. Joint knowledge of the size of the scattering disk and the scatter-broadening time scale enables estimation of the distance to the effective scattering screen d. For B1641-45, d = 3.0 kpc for a distance to the pulsar D = 4.9 kpc, and for B1749-28, d = 0.95 kpc for D = 1.3 kpc. Observations of B1933+16 were carried out simultaneously at 316 and 1668 MHz. The positions of the screen derived using the measurements at the two frequencies agree: d 1 = 2.6 and d 2 = 2.7 kpc, for a distance to the pulsar of 3.7 kpc. Two screens were detected for this pulsar from an analysis of parabolic arcs in the secondary dynamic spectrum at 1668 MHz, at 1.3 and 3.1 kpc. The scattering screens for two of the pulsars are identified with real physical objects located along the lines of sight toward the pulsars: G339.1-04 (B1641-45) and G0.55-0.85 (B1749-28).

  20. Radio observations of Planck clusters

    CERN Document Server

    Kale, Ruta

    2012-01-01

    Recently, a number of new galaxy clusters have been detected by the ESA-Planck satellite, the South Pole Telescope and the Atacama Cosmology Telescope using the Sunyaev-Zeldovich effect. Several of the newly detected clusters are massive, merging systems with disturbed morphology in the X-ray surface brightness. Diffuse radio sources in clusters, called giant radio halos and relics, are direct probes of cosmic rays and magnetic fields in the intra-cluster medium. These radio sources are found to occur mainly in massive merging clusters. Thus, the new SZ-discovered clusters are good candidates to search for new radio halos and relics. We have initiated radio observations of the clusters detected by Planck with the Giant Metrewave Radio Telescope. These observations have already led to the detection of a radio halo in PLCKG171.9-40.7, the first giant halo discovered in one of the new Planck clusters.

  1. Exploring thc Radio Sky with an Giant Eye

    Institute of Scientific and Technical Information of China (English)

    NAN Rendong

    2011-01-01

    With eyes, mankind look at the world. With telescopes, we look into the universe. Radio telescopes are special eyes of mankind with special vision. In particular, large radio telescopes are super eyes built by radio astronomers aiming tbr a clear vision of the distant universe.

  2. Six Years of Fermi-LAT and Multi-Wavelength Monitoring of the Broad-Line Radio Galaxy 3c 120: Jet Dissipation At Sub-Parsec Scales from the Central Engine

    Science.gov (United States)

    Tanaka, Y. T.; Doi, A.; Inoue, Y.; Cheung, C. C.; Stawarz, L.; Fukazawa, Y.; Gurwell, M. A.; Tahara, M.; Kataoka, J.; Itoh, R.

    2015-02-01

    We present multi-wavelength monitoring results for the broad-line radio galaxy 3C 120 in the MeV/GeV, sub-millimeter, and 43 GHz bands over 6 yr. Over the past 2 yr, the Fermi-Large Area Telescope sporadically detected 3C 120 with high significance and the 230 GHz data also suggest an enhanced activity of the source. After the MeV/GeV detection from 3C 120 in MJD 56240-56300, 43 GHz Very Long Baseline Array (VLBA) monitoring revealed a brightening of the radio core, followed by the ejection of a superluminal knot. Since we observed the γ-ray and VLBA phenomena in temporal proximity to each other, it is naturally assumed that they are physically connected. This assumption was further supported by the subsequent observation that the 43 GHz core brightened again after a γ-ray flare occurred around MJD 56560. We can then infer that the MeV/GeV emission took place inside an unresolved 43 GHz core of 3C 120 and that the jet dissipation occurred at sub-parsec distances from the central black hole (BH), if we take the distance of the 43 GHz core from the central BH as ˜0.5 pc, as previously estimated from the time lag between X-ray dips and knot ejections. Based on our constraints on the relative locations of the emission regions and energetic arguments, we conclude that the γ rays are more favorably produced via the synchrotron self-Compton process, rather than inverse Compton scattering of external photons coming from the broad line region or hot dusty torus. We also derived the electron distribution and magnetic field by modeling the simultaneous broadband spectrum.

  3. SIX YEARS OF FERMI-LAT AND MULTI-WAVELENGTH MONITORING OF THE BROAD-LINE RADIO GALAXY 3C 120: JET DISSIPATION AT SUB-PARSEC SCALES FROM THE CENTRAL ENGINE

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Y. T. [Hiroshima Astrophysical Science Center, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526 (Japan); Doi, A.; Inoue, Y.; Stawarz, L. [Institute of Space and Astronautical Science, JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Cheung, C. C. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Fukazawa, Y.; Itoh, R. [Department of Physical Sciences, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Gurwell, M. A. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Tahara, M.; Kataoka, J., E-mail: ytanaka@hep01.hepl.hiroshima-u.ac.jp [Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan)

    2015-01-30

    We present multi-wavelength monitoring results for the broad-line radio galaxy 3C 120 in the MeV/GeV, sub-millimeter, and 43 GHz bands over 6 yr. Over the past 2 yr, the Fermi-Large Area Telescope sporadically detected 3C 120 with high significance and the 230 GHz data also suggest an enhanced activity of the source. After the MeV/GeV detection from 3C 120 in MJD 56240–56300, 43 GHz Very Long Baseline Array (VLBA) monitoring revealed a brightening of the radio core, followed by the ejection of a superluminal knot. Since we observed the γ-ray and VLBA phenomena in temporal proximity to each other, it is naturally assumed that they are physically connected. This assumption was further supported by the subsequent observation that the 43 GHz core brightened again after a γ-ray flare occurred around MJD 56560. We can then infer that the MeV/GeV emission took place inside an unresolved 43 GHz core of 3C 120 and that the jet dissipation occurred at sub-parsec distances from the central black hole (BH), if we take the distance of the 43 GHz core from the central BH as ∼0.5 pc, as previously estimated from the time lag between X-ray dips and knot ejections. Based on our constraints on the relative locations of the emission regions and energetic arguments, we conclude that the γ rays are more favorably produced via the synchrotron self-Compton process, rather than inverse Compton scattering of external photons coming from the broad line region or hot dusty torus. We also derived the electron distribution and magnetic field by modeling the simultaneous broadband spectrum.

  4. Next-generation radio telescope of the 12- to 15-m class for the future large-interferometer arrays in the southern hemisphere

    Science.gov (United States)

    Plathner, Dietmar E.

    1998-07-01

    Based on the quality proven technologies applied on the IRAM 15 m Plateau de Bure telescopes strategies have been developed to design antennas for the future large arrays in the southern hemisphere which shall operate at frequencies as high as 850 GHz and have a very large collecting area. For this type of antenna space frames were applied wherever possible as the full cross-section of their push-pull members is used for load transfer. Thus giving maximum stiffness at minimum weight to the proposed telescope structures. The lowest eigenfrequency is therefore predicted to be in the order of 12 Hz. Similar high performances are expected under the specified windloads at the chosen site in the Atacama Desert probably at an altitude of 5000 m. Such an exposed location requires simple, low maintenance telescopes despite of their high performance requirements, so that e.g. all active thermal stabilization is avoided by the use of low expansion carbon fiber composite material for critical members. Finally an opto-mechanical metrology system is applied which replaces the standard 'on- bord' encoders and makes the control of the telescopes independent of structural deformations in the mount. An overall surface error of 25 micrometer rms for a 12 to 15 m class telescope can be obtained and the resulting pointing error under wind load is in the order of 0.4 arcsec.

  5. Multi-Epoch VLBA Observations of EGRET-Detected Quasars and BL Lac Objects Superluminal Motion of Gamma-Ray Bright Blazars

    CERN Document Server

    Jorstad, S G; Mattox, J R; Wehrle, A E; Bloom, S D; Yurchenko, A V; Jorstad, Svetlana G; Marscher, Alan P; Mattox, John R; Wehrle, Ann E; Bloom, Steven D; Yurchenko, Alexei V

    2001-01-01

    We present the results of a program to monitor the structure of the radio emission in 42 $\\gamma$-ray bright blazars (31 quasars and 11 BL Lac objects) with the VLBA at 43, 22, and occasionally 15 and 8.4 GHz, over the period from November 1993 to July 1997. We determine proper motions in 33 sources and find that the apparent superluminal motions in $\\gamma$-ray sources are much faster than for the general population of bright compact radio sources. This follows the strong dependence of the $\\gamma$-ray flux on the level of relativistic beaming for both external-radiation Compton and synchrotron self-Compton emission. There is a positive correlation (correlation coefficient $r$=0.45) between the flux density of the VLBI core and the $\\gamma$-ray flux and a moderate correlation (partial correlation coefficient $r$=0.31) between $\\gamma$-ray apparent luminosity and superluminal velocities of jet components, as expected if the $\\gamma$-ray emission originates in a very compact region of the relativistic jet and ...

  6. THE RADIO PROPERTIES OF RADIO-LOUD NARROW-LINE SEYFERT 1 GALAXIES ON PARSEC SCALES

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Minfeng; Chen, Yongjun; Shen, Zhiqiang [Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030 (China); Komossa, S.; Zensus, J. A. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Yuan, Weimin [Key Lab for Space Astronomy and Technology, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Wajima, Kiyoaki [Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong, Daejeon 305-348 (Korea, Republic of); Zhou, Hongyan, E-mail: gumf@shao.ac.cn [Polar Research Institute of China, 451 Jinqiao Road, Shanghai 200136 (China)

    2015-11-15

    We present the detection of the compact radio structures of 14 radio-loud narrow-line Seyfert 1 (NLS1) galaxies from Very Long Baseline Array (VLBA) observations at 5 GHz performed in 2013. While 50% of the sources of our sample show a compact core only, the remaining 50% exhibit a core-jet structure. The measured brightness temperatures of the cores range from 10{sup 8.4} to 10{sup 11.4} K with a median value of 10{sup 10.1} K, indicating that the radio emission is from non-thermal jets, and that, likely, most sources are not strongly beamed, thus implying a low jet speed in these radio-loud NLS1 galaxies. In combination with archival data taken at multiple frequencies, we find that seven sources show flat or even inverted radio spectra, while steep spectra are revealed in the remaining seven objects. Although all of these sources are very radio-loud with R > 100, their jet properties are diverse in terms of their milliarcsecond (mas) scale (parsec scale) morphology and their overall radio spectral shape. The evidence for slow jet speeds (i.e., less relativistic jets), in combination with the low kinetic/radio power, may offer an explanation for the compact VLBA radio structure in most sources. The mildly relativistic jets in these high accretion rate systems are consistent with a scenario where jets are accelerated from the hot corona above the disk by the magnetic field and the radiation force of the accretion disk. Alternatively, a low jet bulk velocity can be explained by low spin in the Blandford–Znajek mechanism.

  7. The Principles of Astronomical Telescope Design

    CERN Document Server

    Cheng, Jingquan

    2009-01-01

    Presents a summary of the author's twenty five years of experience in telescope design. This work provides a general introduction to various aspects of telescope design. It discusses the theory behind telescope design. It covers Radio, Infrared, Optical, X-Ray and Gamma-Ray wavelengths

  8. VizieR Online Data Catalog: Second epoch VLBA Calibrator Survey (VCS-II) (Gordon+, 2016)

    Science.gov (United States)

    Gordon, D.; Jacobs, C.; Beasley, A.; Peck, A.; Gaume, R.; Charlot, P.; Fey, A.; Ma, C.; Titov, O.; Boboltz, D.

    2016-07-01

    Six Very Long Baseline Array (VLBA) calibrator survey campaigns were run between 1994 and 2007 (VCS1, Beasley et al. 2002, cat. J/ApJS/141/13; VCS2, Fomalont et al. 2003, cat. J/AJ/126/2562; VCS3, Petrov et al. 2005, cat. J/AJ/129/1163; VCS4, Petrov et al. 2006, cat. J/AJ/131/1872; VCS5, Kovalev et al. 2007, cat. J/AJ/133/1236; VCS6, Petrov et al. 2008, cat. J/AJ/136/580) We report on the results of a second epoch VLBA Calibrator Survey campaign (VCS-II) in which 2400 VCS sources were re-observed in the X and S bands. The VLBA S/X (S band~2.3GHz and X band~8.6GHz) dual frequency system was used. We used the VLBA RDBE/Mark5C system, which has 16 32MHz channels and records 2 Gbits/s using 2 bit sampling. Due to S-band filters below 2200MHz and above 2400MHz at most of the VLBA antennas, and a broad area of RFI from SiriusXM satellites (2320-2345MHz), only four channels could be deployed in the S band (2220.0, 2252.0, 2284.0, and 2348.0MHz). The other 12 channels were deployed in the X band (8460.0, 8492.0, 8524.0, 8556.0, 8620.0, 8652.0, 8716.0, 8748.0, 8812.0, 8844.0, 8876.0, and 8908.0MHz). We set a target of 300 sources per session, or 2400 total sources for the 8 VLBA sessions. We selected all sources from the Goddard Space Flight Center (GSFC) S/X astrometric/geodetic catalog (available at http://gemini.gsfc.nasa.gov/solutions/ or by following the links at http://lupus.gsfc.nasa.gov/) between -50° and +90° decl. that had been observed in only 1 or 2 sessions as of mid 2013. This amounted to ~2060 sources. To fill out the list, we added ~340 additional sources that had been observed but not detected in the original VCS1-6 analysis. The eight schedules were run between 2014 January and 2015 March (VCS-II-A/BG219A on 2014 01/04 10:04-01/05 10:02; VCS-II-B/BG219B1 on 2014 05/31 17:12-06/01 17:05; VCS-II-D/BG219D on 2014 06/09 09:13-06/10 09:10; VCS-II-C/BG219C on 2014 08/05 13:03-08/06 13:00; VCS-II-E/BG219E on 2014 08/09 00:00-08/09 23:55; VCS-II-F/BG219F on 2014

  9. Space Telescope.

    Science.gov (United States)

    National Aeronautics and Space Administration, Huntsville, AL. George C. Marshall Space Flight Center.

    This pamphlet describes the Space Telescope, an unmanned multi-purpose telescope observatory planned for launch into orbit by the Space Shuttle in the 1980s. The unique capabilities of this telescope are detailed, the major elements of the telescope are described, and its proposed mission operations are outlined. (CS)

  10. Correlations between radio emission of the parsec-scale jet and optical nuclear emission of host AGN

    CERN Document Server

    Torrealba, Janet; Chavushyan, Vahram; Cruz-Gonzalez, Irene

    2011-01-01

    We study the relation between the VLBA (Very Long Baseline Array) radio emission at 15 GHz and the optical nuclear emission at 5100 A for a sample of 233 core-dominated AGN with relativistic jets. For 181 quasars, there is a significant positive correlation between optical nuclear emission and total radio (VLBA) emission of unresolved cores (on milliarcsecond scales) of the jet at 15 GHz. Optical continuum emission correlates with radio emission of the jet for 31 BL Lacs. These correlations confirm that the radio and optical emission are beamed and originate at sub-parsec scales in the innermost part of the jet in quasars, while they are generated in the parsec-scale jet in BL Lacs. These results are in agreement with that reported earlier by Arshakian et al. 2010 for a sample of 135 AGN.

  11. High Velocity Precessing Jets from the Water Fountain IRAS 18286-0959 Revealed by VLBA Observations

    OpenAIRE

    Yung, Bosco; Nakashima, Jun-ichi; Imai, Hiroshi; Deguchi, Shuji; Diamond, Philip; Kwok, Sun

    2011-01-01

    We report the results of multi-epoch VLBA observations of the 22.2GHz water maser emission associated with the "water fountain" IRAS 18286-0959. We suggest that this object is the second example of a highly collimated bipolar precessing outflow traced by water maser emission, the other is W43A. The detected water emission peaks are distributed over a velocity range from -50km/s to 150km/s. The spatial distribution of over 70% of the identified maser features is found to be highly collimated a...

  12. Orientation of the cores of hybrid morphology radio sources

    CERN Document Server

    Ceglowski, Maciej; Kunert-Bajraszewska, Magdalena

    2013-01-01

    The FRI/FRII dichotomy is a much debated issue in the astrophysics of extragalactic radio sources. Study of the properties of HYbrid MOrphology Radio Sources (HYMORS) may bring crucial information and lead to a step forward in understanding the origin of FRI/FRII dichotomy. HYMORS are a rare class of double-lobed radio sources where each of the two lobes clearly exhibits a different FR morphology. This article describes follow-up high resolution VLBA observations of the five discovered by us HYMORS. The main aim of the observations was to answer the questions of whether the unusual radio morphology is connected to the orientation of objects towards the observer. We obtained the high resolution radio maps of five hybrid radio morphology objects with the VLBA at C-band and L-band. Two of them revealed milliarcsecond core-jet structures, the next two objects showed hints of parsec-scale jets, and the last one remained point-like at both frequencies. We compared properties of observed milliarcsecond structures of...

  13. 射电望远镜天线副反射面并联调整机构设计%Configuration Design of the Adjusting Parallel Mechanism for Sub-Reflector of Antenna of Radio Telescope Antenna

    Institute of Scientific and Technical Information of China (English)

    段艳宾; 李建军; 侯雨雷; 赵永生

    2013-01-01

    According to the specific requirements of the sub-reflector adjustment mechanism when the 65m diameter round movable radio telescope system observes,the Stewart platform as the Shanghai 65m radio telescope antenna sub-reflector adjustment system is proposed.Based on the optimal force of the rods when the main reflector and the sub-reflector is on the whole workspace,the configuration parameters integrated design method about the consideration to the workspace and to avoid interference between the bar and other factors is researched.Configuration parameters met the real requirements are obtained.The workspace is solved under the configuration.And the feasibility of the project is verified compared to the required workspace.The research work has an important significance in the parallel mechanism for engineering practice.%紧密结合上海天文台65m射电望远镜副反射面位姿调整任务要求,提出采用并联式Stewart平台作为副反射面调整机构,基于天线主面和副面全位姿工作状态下各杆受力最优,并兼顾工作空间及避免杆件间干涉等因素,开展副面调整机构构型综合设计,获得了满足预期性能要求的机构构型参数,并求解出该构型下机构的工作空间,验证了构型参数综合设计方法的有效性.面向实际任务进行机构设计,研究内容对并联机构真正应用于工程实践具有重要的指导意义.

  14. LUNASKA simultaneous neutrino searches with multiple telescopes

    CERN Document Server

    Bray, J D; James, C W; Roberts, P; Brown, A; Phillips, C J; Protheroe, R J; Reynolds, J E; McFadden, R A; Aartsen, M

    2011-01-01

    The most sensitive method for detecting neutrinos at the very highest energies is the lunar Cherenkov technique, which employs the Moon as a target volume, using conventional radio telescopes to monitor it for nanosecond-scale pulses of Cherenkov radiation from particle cascades in its regolith. Multiple-antenna radio telescopes are difficult to effectively combine into a single detector for this purpose, while single antennas are more susceptible to false events from radio interference, which must be reliably excluded for a credible detection to be made. We describe our progress in excluding such interference in our observations with the single-antenna Parkes radio telescope, and our most recent experiment (taking place the week before the ICRC) using it in conjunction with the Australia Telescope Compact Array, exploiting the advantages of both types of telescope.

  15. An Initial Look at the Far Infrared-Radio Correlation within Nearby Star-forming Galaxies using the Spitzer Space Telescope

    CERN Document Server

    Murphy, E J; Helou, G; Armus, L; Kenney, J D P; Gordon, K D; Bendo, G J; Dale, D A; Walter, F; Oosterloo, T A; Kennicutt, R C; Calzetti, D; Cannon, J M; Draine, B T; Engelbracht, C W; Hollenbach, D J; Jarrett, T H; Kewley, L J; Leitherer, C; Li, A; Meyer, M J; Regan, M W; Rieke, G H; Rieke, M J; Roussel, H; Sheth, K; Smith, J D T; Thornley, M D

    2006-01-01

    (Abridged) We present an initial look at the far infrared-radio correlation within the star-forming disks of four nearby, nearly face-on galaxies (NGC 2403, NGC 3031, NGC 5194, and NGC 6946). Using Spitzer MIPS imaging and WSRT radio continuum data, observed as part of the Spitzer Infrared Nearby Galaxies Survey (SINGS), we are able to probe variations in the logarithmic 24mu/22cm (q_24) and 70mu/22cm (q_70) surface brightness ratios across each disk at sub-kpc scales. We find general trends of decreasing q_24 and q_70 with declining surface brightness and with increasing radius. The residual dispersion around the trend of q_24 and q_70 versus surface brightness is smaller than the residual dispersion around the trend of q_24 and q_70 versus radius, on average by ~0.1 dex, indicating that the distribution of star formation sites is more important in determining the infrared/radio disk appearance than the exponential profiles of disks. We have also performed preliminary phenomenological modeling of cosmic ray ...

  16. Probing the innermost regions of AGN jets and their magnetic fields with RadioAstron. II. Observations of 3C 273 at minimum activity

    Science.gov (United States)

    Bruni, G.; Gómez, J. L.; Casadio, C.; Lobanov, A.; Kovalev, Y. Y.; Sokolovsky, K. V.; Lisakov, M. M.; Bach, U.; Marscher, A.; Jorstad, S.; Anderson, J. M.; Krichbaum, T. P.; Savolainen, T.; Vega-García, L.; Fuentes, A.; Zensus, J. A.; Alberdi, A.; Lee, S.-S.; Lu, R.-S.; Pérez-Torres, M.; Ros, E.

    2017-08-01

    Context. RadioAstron is a 10 m orbiting radio telescope mounted on the Spektr-R satellite, launched in 2011, performing Space Very Long Baseline Interferometry (SVLBI) observations supported by a global ground array of radio telescopes. With an apogee of 350 000 km, it is offering for the first time the possibility to perform μas-resolution imaging in the cm-band. Aims: The RadioAstron active galactic nuclei (AGN) polarization Key Science Project (KSP) aims at exploiting the unprecedented angular resolution provided by RadioAstron to study jet launching/collimation and magnetic-field configuration in AGN jets. The targets of our KSP are some of the most powerful blazars in the sky. Methods: We present observations at 22 GHz of 3C 273, performed in 2014, designed to reach a maximum baseline of approximately nine Earth diameters. Reaching an angular resolution of 0.3 mas, we study a particularly low-activity state of the source, and estimate the nuclear region brightness temperature, comparing with the extreme one detected one year before during the RadioAstron early science period. We also make use of the VLBA-BU-BLAZAR survey data, at 43 GHz, to study the kinematics of the jet in a 1.5-yr time window. Results: We find that the nuclear brightness temperature is two orders of magnitude lower than the exceptionally high value detected in 2013 with RadioAstron at the same frequency (1.4 × 1013 K, source-frame), and even one order of magnitude lower than the equipartition value. The kinematics analysis at 43 GHz shows that a new component was ejected 2 months after the 2013 epoch, visible also in our 22 GHz map presented here. Consequently this was located upstream of the core during the brightness temperature peak. Fermi-LAT observations for the period 2010-2014 do not show any γ-ray flare in conjunction with the passage of the new component by the core at 43 GHz. Conclusions: These observations confirm that the previously detected extreme brightness temperature in

  17. Neutrino telescopes

    CERN Document Server

    Carr, J

    2002-01-01

    This review presents the scientific objectives and status of Neutrino Telescope Projects. The science program of these projects covers: neutrino astronomy, dark matter searches and measurements of neutrino oscillations. The two neutrino telescopes in operation: AMANDA and BAIKAL will be described together with the ANTARES neutrino telescope being built in the Mediterranean. (18 refs).

  18. Telescopes and Techniques

    CERN Document Server

    Kitchin, C R

    2013-01-01

    Telescopes and Techniques has proved itself in its first two editions, having become probably one of the most widely used astronomy texts, both for amateur astronomers and astronomy and astrophysics undergraduates. Both earlier editions of the book were widely used for introductory practical astronomy courses in many universities. In this Third Edition the author guides the reader through the mathematics, physics and practical techniques needed to use today's telescopes (from the smaller models to the larger instruments installed in many colleges) and how to find objects in the sky. Most of the physics and engineering involved is described fully and requires little prior knowledge or experience. Both visual and electronic imaging techniques are covered, together with an introduction to how data (measurements) should be processed and analyzed. A simple introduction to radio telescopes is also included. Brief coverage of the more advanced topics of photometry and spectroscopy are included, but mainly to enable ...

  19. Radio monitoring of the hard state jets in the 2011 outburst of MAXI J1836-194

    CERN Document Server

    Russell, T D; Curran, P A; Soria, R; Altamirano, D; Corbel, S; Coriat, M; Moin, A; Russell, D M; Sivakoff, G R; Slaven-Blair, T J; Belloni, T M; Fender, R P; Heinz, S; Jonker, P G; Krimm, H A; Kording, E G; Maitra, D; Markoff, S; Middleton, M; Migliari, S; Remillard, R A; Rupen, M P; Sarazin, C L; Tetarenko, A J; Torres, M A P; Tudose, V; Tzioumis, A K

    2015-01-01

    MAXI J1836-194 is a Galactic black hole candidate X-ray binary that was discovered in 2011 when it went into outburst. In this paper, we present the full radio monitoring of this system during its `failed' outburst, in which the source did not complete a full set of state changes, only transitioning as far as the hard intermediate state. Observations with the Karl G. Jansky Very Large Array (VLA) and Australia Telescope Compact Array (ATCA) show that the jet properties changed significantly during the outburst. The VLA observations detected linearly polarised emission at a level of ~1% early in the outburst, increasing to ~3% as the outburst peaked. High-resolution images with the Very Long Baseline Array (VLBA) show a ~15 mas jet along the position angle $-21 \\pm 2^\\circ$, in agreement with the electric vector position angle found from our polarisation results ($-21 \\pm 4^\\circ$), implying that the magnetic field is perpendicular to the jet. Astrometric observations suggest that the system required an asymme...

  20. A Radio Astronomy Science Education Partnership - GAVRT and Radio JOVE

    Science.gov (United States)

    Higgins, C. A.; Thieman, J. R.; Bunnell, K.; Soholt, G.

    2009-12-01

    The planet Jupiter provides an excellent subject to educate, engage, and inspire students and teachers to learn science. The Goldstone Apple-Valley Radio Telescope (GAVRT) program (http://www.lewiscenter.org/gavrt) and The Radio JOVE project (http://radiojove.gsfc.nasa.gov) each have a long history of allowing students and teachers to interact with scientists and real radio telescopes. The upcoming Juno mission to Jupiter (2011 launch) allows both GAVRT and Radio JOVE to combine efforts and engage with the NASA Juno mission, thus increasing the excitement and learning potential for teachers, students, and the general public. Teachers can attend workshops for training to operate a 34-meter radio telescope and/or build their own simple radio telescope, both of which can be used directly in the classroom. We will overview some classroom activities and highlight some teacher-student experiences. In addition, we will update our efforts on greater Web-based control of the radio telescopes, as well as highlight our upcoming workshops to allow better access for teachers in different parts of the Country.

  1. 2 years of INTEGRAL monitoring of GRS 1915+105. I. Multiwavelength coverage with INTEGRAL, RXTE, and the Ryle radio telescope

    DEFF Research Database (Denmark)

    Rodriguez, J.; Hannikainen, D.C.; Shaw, S.E.;

    2008-01-01

    We report the results of simultaneous monitoring observations of the Galactic microquasar GRS 1915+105 with INTEGRAL and RXTE from 3 up to similar to 300 keV, and the Ryle Telescope at 15 GHz. We first identify the classes of variability in which GRS 1915+105 is found, and report some direct...... generalize the fact that a (nonmajor) discrete ejection always occurs, in GRS 1915+105, as a response to an X-ray sequence composed of a spectrally hard X-ray dip terminated by an X-ray spike marking the disappearance of the emission above 18 keV. We identify the trigger of the ejection as the X-ray spike...

  2. The Connection between the Radio Jet and the γ-ray Emission in the Radio Galaxy 3C 120 and the Blazar CTA 102

    Directory of Open Access Journals (Sweden)

    Carolina Casadio

    2016-09-01

    Full Text Available We present multi-wavelength studies of the radio galaxy 3C 120 and the blazar CTA 102 during unprecedented γ-ray flares for both sources. In both studies the analysis of γ-ray data has been compared with a series of 43 GHz VLBA images from the VLBA-BU-BLAZAR program, providing the necessary spatial resolution to probe the parsec scale jet evolution during the high energy events. To extend the radio dataset for 3C 120 we also used 15 GHz VLBA data from the MOJAVE sample. These two objects which represent very different classes of AGN, have similar properties during the γ-ray events. The γ-ray flares are associated with the passage of a new superluminal component through the mm VLBI core, but not all ejections of new components lead to γ-ray events. In both sources γ-ray events occurred only when the new components are moving in a direction closer to our line of sight. We locate the γ-ray dissipation zone a short distance from the radio core but outside of the broad line region, suggesting synchrotron self-Compton scattering as the probable mechanism for the γ-ray production.

  3. An Accurate and Efficient Algorithm for Detection of Radio Bursts with an Unknown Dispersion Measure, for Single-dish Telescopes and Interferometers

    Science.gov (United States)

    Zackay, Barak; Ofek, Eran O.

    2017-01-01

    Astronomical radio signals are subjected to phase dispersion while traveling through the interstellar medium. To optimally detect a short-duration signal within a frequency band, we have to precisely compensate for the unknown pulse dispersion, which is a computationally demanding task. We present the “fast dispersion measure transform” algorithm for optimal detection of such signals. Our algorithm has a low theoretical complexity of 2{N}f{N}t+{N}t{N}{{Δ }}{{log}}2({N}f), where Nf, Nt, and NΔ are the numbers of frequency bins, time bins, and dispersion measure bins, respectively. Unlike previously suggested fast algorithms, our algorithm conserves the sensitivity of brute-force dedispersion. Our tests indicate that this algorithm, running on a standard desktop computer and implemented in a high-level programming language, is already faster than the state-of-the-art dedispersion codes running on graphical processing units (GPUs). We also present a variant of the algorithm that can be efficiently implemented on GPUs. The latter algorithm’s computation and data-transport requirements are similar to those of a two-dimensional fast Fourier transform, indicating that incoherent dedispersion can now be considered a nonissue while planning future surveys. We further present a fast algorithm for sensitive detection of pulses shorter than the dispersive smearing limits of incoherent dedispersion. In typical cases, this algorithm is orders of magnitude faster than enumerating dispersion measures and coherently dedispersing by convolution. We analyze the computational complexity of pulsed signal searches by radio interferometers. We conclude that, using our suggested algorithms, maximally sensitive blind searches for dispersed pulses are feasible using existing facilities. We provide an implementation of these algorithms in Python and MATLAB.

  4. Space Telescopes

    Science.gov (United States)

    2010-01-01

    Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 166 9. Space telescopes Figure 9.1: Paraboloid telescope. In the following sections, NI...planets nearby a brighter star. Normal-incidence telescopes One-mirror telescope The one-mirror telescope (mostly an off-axis paraboloid ; Figure 9.1) has...rotation of the whole instrument (see SUMER/SOHO, Wilhelm et al (1995) and EIS/Hinode, Culhane et al (2007)). The paraboloid field curvature (Petzval

  5. A Statistical Description of AGN Jet Evolution from the VLBA Imaging and Polarimetry Survey (VIPS)

    CERN Document Server

    Helmboldt, J F; Walker, R C; Blanford, R D

    2008-01-01

    A detailed analysis of the evolution of the properties of core-jet systems within the VLBA Imaging and Polarimetry Survey (VIPS) is presented. We find a power-law relationship between jet intensity and width that suggests for the typical jet, little if any energy is lost as it moves away from its core. Using VLA images at 1.5 GHz, we have found evidence that parsec-scale jets tend to be aligned with the the direction of emission on kiloparsec scales. We also found that this alignment improves as the jets move farther from their cores on projected scales as small as ~50-100 pc. This suggests that realignment of jets on these projected scales is relatively common. We typically find a modest amount of bending (a change in jet position angle of ~5 deg.) on these scales, suggesting that this realignment may typically occur relatively gradually.

  6. A VLBA movie of the jet launch region in M87

    Energy Technology Data Exchange (ETDEWEB)

    Junor, William [Los Alamos National Laboratory; Walker, Robert C [NRAO, SOCORRO; Ly, Chun [UCLA; Hardee, Philip J [UNIV. OF ALABAMA

    2008-01-01

    M87 has one of the largest angular size black holes known. It also has a bright jet that is well resolved across the jet near the core using high frequency VLBI. As such it is the best object to observe to study the launch region of jets where the physical sizes of structures of interest scale with the gravitational radius. Modern numerical simulations suggest that the jet formation extends over 100-1000 R{sub s}. M87 has been observed with a resolution of about 60 R{sub s} at 43 GHz with the VLBA every 3 weeks through 2007, and every 5 days between January and April 2008. A preliminary movie, made from the first 11 observations in 2007, shows fast (thicksim2c) and complex motions in an edge brightened structure with a wide opening angle at the base.

  7. A study of the distant activity of comet C/2006 W3 (Christensen) using Herschel and ground-based radio telescopes

    CERN Document Server

    Bockelée-Morvan, D; Crovisier, J; Vandenbussche, B; Swinyard, B M; Biver, N; Lis, D C; Jarchow, C; Moreno, R; Hutsemékers, D; Jehin, E; Küppers, M K; Lara, L M; Lellouch, E; Manfroid, J; de Val-Borro, M; Szutowicz, S; Banaszkiewicz, M; Bensch, F; Blecka, M I; Emprechtinger, M; Encrenaz, T; Fulton, T; Kidger, M; Rengel, M; Waelkens, C; Bergin, E; Blake, G A; Blommaert, J A D L; Cernicharo, J; Decin, L; Encrenaz, P; de Graauw, T; Leeks, S; Medvedev, A S; Naylor, D; Schieder, R; Thomas, N

    2010-01-01

    Comet C/2006 W3 (Christensen) was observed in November 2009 at 3.3 AU from the Sun with Herschel. The PACS instrument acquired images of the dust coma in 70- and 160-micrometers filters, and spectra covering several H2O rotational lines. Spectra in the range 450-1550 GHz were acquired with SPIRE. The comet emission continuum from 70 to 672 micrometers was measured, but no lines were detected. The spectral energy distribution indicates thermal emission from large particles and provides a measure of the size distribution index and dust production rate. The upper limit to the water production rate is compared to the production rates of other species (CO, CH3OH, HCN, H2S, OH) measured with the IRAM 30-m and Nancay telescopes. The coma is found to be strongly enriched in species more volatile than water, in comparison to comets observed closer to the Sun. The CO to H2O production rate ratio exceeds 220%. The dust to gas production rate ratio is on the order of 1.

  8. A Search for TeV Gamma-Ray Emission from High-Peaked Flat Spectrum Radio Quasars Using the Whipple Air-Cherenkov Telescope

    CERN Document Server

    Falcone, A D; Boyle, P J; Bradbury, S M; Buckley, J H; Carter-Lewis, D A; Celik, O; Cui, W; Dowdall, C; Duke, C; Fegan, D J; La Perez, I C; Fegan, S J; Finley, J P; Fortson, L F; Gaidos, J A; Gibbs, K; Gammell, S; Hall, J; Hall, T A; Hillas, A M; Holder, J; Horan, D; Jordan, M; Kertzman, M; Kieda, D; Kildea, J; Knapp, J; Kosack, K; Krawczynski, H; Krennrich, F; Le Bohec, S; Linton, E T; Lloyd-Evans, J; Moriarty, P; Müller, D; Nagai, T N; Ong, R A; Page, M; Pallassini, R; Petry, D; Power-Mooney, B; Quinn, J; Rebillot, P; Reynolds, P T; Rose, H J; Schroedter, M; Sembroski, G H; Swordy, S P; Vasilev, V V; Wakely, S P; Walker, G; Weekes, T C

    2004-01-01

    Blazars have traditionally been separated into two broad categories based upon their optical emission characteristics; BL Lacs, with faint or no emission lines, and flat spectrum radio quasars (FSRQs) with prominent, broad emission lines. The spectral energy distribution of FSRQs has generally been thought of as being more akin to the low-peaked BL Lacs, which exhibit a peak in the infrared region of the spectrum, as opposed to high-peaked BL Lacs (HBLs), which exhibit a peak in UV/X-ray region of the spectrum. All blazars currently confirmed as sources of TeV emission are HBLs. Recent surveys have found several FSRQs exhibiting spectral properties similar to HBLs, particularly the synchrotron peak frequency. These objects are potential sources of TeV emission according to several models of blazar jet emission and blazar evolution. Measurements of TeV flux or upper limits could impact existing theories explaining the links between different blazar types and could have a significant impact on our understanding...

  9. An accurate and efficient algorithm for detection of radio bursts with an unknown dispersion measure, for single dish telescopes and interferometers

    CERN Document Server

    Zackay, Barak

    2014-01-01

    Astronomical radio bursts disperse while traveling through the interstellar medium. To optimally detect a short-duration signal within a frequency band, we have to precisely compensate for the pulse dispersion, which is a computationally demanding task. We present the Fast Dispersion Measure Transform (FDMT) algorithm for optimal detection of such signals. Our algorithm has a low theoretical complexity of 2N_f N_t+ N_t N_d log_2(N_f) where N_f, N_t and N_d are the numbers of frequency bins, time bins, and dispersion measure bins, respectively. Unlike previously suggested fast algorithms our algorithm conserves the sensitivity of brute force dedispersion. Our tests indicate that this algorithm, running on a standard desktop computer, and implemented in a high-level programming language, is already faster than the state of the art dedispersion codes running on graphical processing units (GPUs). We also present a variant of the algorithm that can be efficiently implemented on GPUs. The latter algorithm's computa...

  10. Radio Frequency Interference Mitigation at the WSRT

    CERN Document Server

    Fridman, P A; Millenaar, R P

    2010-01-01

    The sensitivity of radio astronomical stations is often limited by man-made radio frequency interference (RFI) due to a variety of terrestrial activities. An RFI mitigation subsystem (RFIMS) based on real-time digital signalprocessing is proposed here for the Westerbork Synthesis Radio Telescope based on a powerful field programmable gate array processor. In this system the radio astronomy signals polluted by RFI are "cleaned" with the RFIMS before routine back-end correlation processing takes place. The high temporal and frequency resolution of RFIMS allows the detection and excision of RFI better than do standard radio telescope back-end configurations.

  11. Research on the Resultant Actions of the Stewart Platform of a Large Radio Telescope%Stewart平台对大型射电望远镜反作用力的研究

    Institute of Scientific and Technical Information of China (English)

    仇原鹰; 段宝岩; 魏强; 彭勃; 南仁东

    2001-01-01

    Stewart平台作为馈源位置和姿态精调系统被安装在大型射电望远镜的悬挂馈源舱中。本文推导了计算馈源舱中的Stewart平台对舱体反作用力的公式,分析了馈源舱体姿态,Stewart平台的质量、调整速度与反作用力间的关系。研究结果为设计馈源舱与Stewart平台的质量比,消除平台对舱体的动力影响打下了基础。%A Stewart platform is assembled in the suspended feed cabin of the large radio telescope as a precise adjusting system for the position and orientation of the feed. The formulae are deduced to calculate the resultant actions of the Stewart platform to the feed cabin. Furthermore the effects of the orientation of the cabin, the adjusting velocity and the mass of the Stewart platform to the resultant actions are analyzed. The research serves as a foundation for designing the mass ratio between the feed cabin and the Stewart platform to eliminate the dynamic effect of the Stewart platform on the feed cabin.

  12. Fast radio flashes observed with LOFAR prototypes

    NARCIS (Netherlands)

    Nigl, A.

    2008-01-01

    This thesis consists of a detailed analysis of several observations with prototype stations of the Low Frequency Array (LOFAR). Chapter 1 introduces the field of radio astronomy, briefly describes the radio telescopes which were used and discusses radio frequency interference (RFI) and important too

  13. Optical and radio astrometry of the galaxy associated with FRB150418

    CERN Document Server

    Bassa, C G; Tingay, S J; Keane, E F; Bhandari, S; Johnston, S; Totani, T; Tominaga, N; Yasuda, N; Stappers, B W; Barr, E D; Kramer, M; Possenti, A

    2016-01-01

    A fading radio source, coincident in time and position with the fast radio burst FRB150418, has been associated with the galaxy WISE J071634.59-190039.2. Subsequent observations of this galaxy have revealed that it contains a persistent, but variable, radio source. We present e-MERLIN, VLBA, and ATCA radio observations and Subaru optical observations of WISE J071634.59-190039.2 and find that the persistent radio source is unresolved and must be compact (<0.01 kpc), and that its location is consistent with the optical centre of the galaxy. We conclude that it is likely that WISE J071634.59-190039.2 contains a weak radio AGN.

  14. MOJAVE XIII. Parsec-Scale AGN Jet Kinematics Analysis Based on 19 years of VLBA Observations at 15 GHz

    CERN Document Server

    Lister, M L; Aller, H D; Homan, D C; Kellermann, K I; Kovalev, Y Y; Pushkarev, A B; Richards, J L; Ros, E; Savolainen, T

    2016-01-01

    We present 1625 new 15 GHz (2 cm) VLBA images of 295 jets associated with active galactic nuclei (AGNs) from the MOJAVE and 2 cm VLBA surveys, spanning observations between 1994 Aug 31 and 2013 Aug 20. For 274 AGNs with at least 5 VLBA epochs, we have analyzed the kinematics of 961 individual bright features in their parsec-scale jets. A total of 122 of these jets have not been previously analyzed by the MOJAVE program. In the case of 451 jet features that had at least 10 epochs, we also examined their kinematics for possible accelerations. At least half of the well-sampled features have non-radial and/or accelerating trajectories, indicating that non-ballistic motion is common in AGN jets. Since it is impossible to extrapolate any accelerations that occurred before our monitoring period, we could only determine reliable ejection dates for about 24% of those features that had significant proper motions. The distribution of maximum apparent jet speeds in all 295 AGNs measured by our program to date is peaked b...

  15. Radio outburst of BL Lacertae

    Science.gov (United States)

    Buemi, C. S.; Leto, P.; Trigilio, C.; Umana, G.; Giroletti, M.; Orienti, M.; Raiteri, C. M.; Villata, M.; Bach, U.

    2013-04-01

    We report on extremely high radio flux of BL Lacertae at 43 and 8 GHz. Observations at 43 GHz with the 32 m radio telescope in Noto (Italy) revealed a flux density of 10.5 +/- 0.2 Jy on 2013 April 10.65, while observations at 8 GHz with the 32 m radio telescope in Medicina (Italy) detected a flux density of 8.2 +/- 0.7 Jy on April 12.22. These extremely high radio fluxes show that the radio activity likely correlated to the strong optical, near-infrared, and gamma-ray activity of 2011-2012 (see ATels #4028, #4031, #4155, #4271, #4277, #4349, #4565, #4600), and X-ray activity of late 2012 (ATels #4557, #4627), is far to be exhausted.

  16. Multi-Frequency Monitoring of the Flat Spectrum Radio Quasar PKS 1222+216 in 2008–2015

    Directory of Open Access Journals (Sweden)

    Ivan Troitskiy

    2016-11-01

    Full Text Available We analyze the broadband activity of the flat spectrum radio quasar PKS 1222+216 from 2008 to 2015 using multi-frequency monitoring which involves γ-ray data from the Fermi Large Area Telescope, total intensity and linear polarization observations from different optical telescopes in R band, and imaging of the inner jet structure with the Very Long Baseline Array (VLBA at 43 GHz. During the observations, the source showed several dramatic flares at γ rays and optical bands, with the rising branch of a γ-ray flare accompanied by a rapid rotation of the polarization position angle (EVPA, a fast increase of the degree of polarization in the optical band, brightening of the VLBI core, and appearance of a new superluminal component in the parsec-scale jet. The rapid variability of the optical linear polarization may be explained by a strong turbulence in the jet plasma. We find a correlation between the γ rays, optical R band, and 43 GHz variability on a long-term scale (months and years, and a good general alignment between EVPAs in R band and at 43 GHz, while the correlation between short-term variations (days and weeks is weaker. Synchronous activity across the bands supports the idea that the emission regions responsible for the γ-ray and optical flares are co-spatial and located in the vicinity of the mm-wave core of the parsec-scale jet. However, these connections do not completely explain the challenging behaviour of PKS 1222+216, since there are some γ-ray flares which are not accompanied by jet events, and vice versa. We need a continuation of multi-frequency monitoring along with high resolution imaging of the parsec-scale jet to understand in detail the origin of high energy emission in blazars.

  17. Small jets in radio-loud hot DOGs

    Science.gov (United States)

    Lonsdale, C. J.; Whittle, M.; Trapp, A.; Patil, P.; Lonsdale, C. J.; Thorp, R.; Lacy, M.; Kimball, A. E.; Blain, A.; Jones, S.; Kim, M.

    2016-02-01

    We address the impact of young radio jets on the ISM and star formation in a sample of radiatively efficient, highly obscured, radio AGN with look back times that place them near the peak of the galaxy and BH building era, z˜ 1-3. By selecting systems with a high mid-infrared (MIR) luminosity we aim to identify radiatively efficient (``quasar-mode'' or ``radiative-mode") AGN in a peak fueling phase, and by selecting compact radio sources we favor young or re-generated radio jets which are confined within the hosts. By selecting AGN which are very red through the optical-MIR we favor highly obscured systems likely to have been recently merger-triggered and still in the pre-blow-out phase of AGN feedback into the surrounding ISM. ALMA imaging at 345 GHz of 49 sources has revealed that they are accretion dominated, relative to star formation, with luminosities reaching 1014 L⊙. Extensive VLA imaging at 8-10 GHz in both A-array and B-array for 155 sources reveals that the majority of these powerful radio systems are compact on < 2-5 kpc scales while some have resolved structures on 3-25 kpc scales, and a small number have giant radio lobes on hundreds of kpc scales. The majority of the GHz range radio SEDs are typical of optically thin synchrotron, however for the 34 sources with data at more than 2 frequencies, 40 % are likely to be CSS, GPS, or HFP sources. VLBA imaging of 62 sources reveals varied morphologies, from unresolved sources to complex multicomponent 1-10 mas scale structures. Data from ALMA, VLA, and VLBA

  18. THE LARGE MILLIMETER TELESCOPE

    Directory of Open Access Journals (Sweden)

    D. H. Hughes

    2009-01-01

    Full Text Available This paper, presented on behalf of the Large Millimeter Telescope (LMT project team, describes the status and near-term plans for the telescope and its initial instrumentation. The LMT is a bi-national collaboration between M xico and the USA, led by the Instituto Nacional de Astrof sica, ptica y Electr nica (INAOE and the University of Massachusetts at Amherst, to construct, commission and operate a 50 m diameter millimeterwave radio telescope. Construction activities are nearly complete at the LMT site, at an altitude of 4600 m on the summit of Sierra Negra, an extinct volcano in the Mexican state of Puebla. Full movement of the telescope, under computer control in both azimuth and elevation, has been achieved. First-light at centimeter wavelengths on astronomical sources was obtained in November 2006. Installation of precision surface segments for millimeter-wave operation is underway, with the inner 32 m diameter of the surface now complete and ready to be used to obtain rst-light at millimeter wavelengths in 2008. Installation of the remainder of the re ector will continue during the next year and be completed in 2009 for nal commissioning of the antenna. The full LMT antenna, out ted with its initial complement of scienti c instruments, will be a world-leading scienti c research facility for millimeter-wave astronomy.

  19. Division x: Radio Astronomy

    Science.gov (United States)

    Taylor, Russ; Chapman, Jessica; Rendong, Nan; Carilli, Christopher; Giovannini, Gabriele; Hills, Richard; Hirabayashi, Hisashi; Jonas, Justin; Lazio, Joseph; Morganti, Raffaella; Rubio, Monica; Shastri, Prajval

    2012-04-01

    This triennium has seen a phenomenal investment in development of observational radio astronomy facilities in all parts of the globe at a scale that significantly impacts the international community. This includes both major enhancements such as the transition from the VLA to the EVLA in North America, and the development of new facilities such as LOFAR, ALMA, FAST, and Square Kilometre Array precursor telescopes in Australia and South Africa. These developments are driven by advances in radio-frequency, digital and information technologies that tremendously enhance the capabilities in radio astronomy. These new developments foreshadow major scientific advances driven by radio observations in the next triennium. We highlight these facility developments in section 3 of this report. A selection of science highlight from this triennium are summarized in section 2.

  20. SNAP telescope

    Energy Technology Data Exchange (ETDEWEB)

    Lampton, Michael L.; Akerlof, C.W.; Aldering, G.; Amanullah, R.; Astier, P.; Barrelet, E.; Bebek, C.; Bergstrom, L.; Bercovitz, J.; Bernstein, G.; Bester, M.; Bonissent, A.; Bower, C.; Carithers Jr., W.C.; Commins, E.D.; Day, C.; Deustua, S.E.; DiGennaro, R.; Ealet, A.; Ellis,R.S.; Eriksson, M.; Fruchter, A.; Genat, J.-F.; Goldhaber, G.; Goobar,A.; Groom, D.; Harris, S.E.; Harvey, P.R.; Heetderks, H.D.; Holland,S.E.; Huterer, D.; Karcher, A.; Kim, A.G.; Kolbe, W.; Krieger, B.; Lafever, R.; Lamoureux, J.; Levi, M.E.; Levin, D.S.; Linder, E.V.; Loken,S.C.; Malina, R.; Massey, R.; McKay, T.; McKee, S.P.; Miquel, R.; Mortsell, E.; Mostek, N.; Mufson, S.; Musser, J.; Nugent, P.; Oluseyi,H.; Pain, R.; Palaio, N.; Pankow, D.; Perlmutter, S.; Pratt, R.; Prieto,E.; Refregier, A.; Rhodes, J.; Robinson, K.; Roe, N.; Sholl, M.; Schubnell, M.; Smadja, G.; Smoot, G.; Spadafora, A.; Tarle, G.; Tomasch,A.; von der Lippe, H.; Vincent, R.; Walder, J.-P.; Wang, G.; Wang, G.

    2002-07-29

    The SuperNova/Acceleration Probe (SNAP) mission will require a two-meter class telescope delivering diffraction limited images spanning a one degree field in the visible and near infrared wavelength regime. This requirement, equivalent to nearly one billion pixel resolution, places stringent demands on its optical system in terms of field flatness, image quality, and freedom from chromatic aberration. We discuss the advantages of annular-field three-mirror anastigmat (TMA) telescopes for applications such as SNAP, and describe the features of the specific optical configuration that we have baselined for the SNAP mission. We discuss the mechanical design and choice of materials for the telescope. Then we present detailed ray traces and diffraction calculations for our baseline optical design. We briefly discuss stray light and tolerance issues, and present a preliminary wavefront error budget for the SNAP Telescope. We conclude by describing some of tasks to be carried out during the upcoming SNAP research and development phase.

  1. VLBA Survey of OH Masers in Star-Forming Regions II: Satellite Lines

    CERN Document Server

    Ruiz-Velasco, A E; Migenes, V; Wiggins, B K

    2016-01-01

    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 at 1612 and 1720 MHz. Due to the exceptionality of finding satellite lines in SFRs, we will focus our discussion on those lines. In our sample of 41 OH maser sources, five (12%) showed the 1612 MHz line and ten (24%) showed the 1720 MHz line, with only one source showing both lines. We find that 1720 MHz emission is correlated with the presence of HII regions, suggesting that this emission could be used to diagnose or trace high-mass star formation. We include an analysis of the possible mechanisms that could be causing this correlation as well as assessing the possible relationships between lines in our sample. In particular, the presence of magnetic fields seems to play an important role, as we found Zeeman splitting in four of our sources (W75 N, W3(OH), W51 and NGC 7538)...

  2. 中德亚毫米波望远镜的伺服系统设计%Servo System Design for Sino-German Sub-millimeter Wave Radio Telescope

    Institute of Scientific and Technical Information of China (English)

    郑万章

    2014-01-01

    According to the high performance specification requirement of Sino-German Sub-millimeter Wave Radio Telescope,after a mass of research and simulation analysis,the two axes design schemebased on German Rexroth AC servo is selected for antenna servo system. The main framework of this system is based on motion logical controller and full digital AC drive,and reinforced by security protection device. Azimuth and elevation axis both adopt PID controlled force moment difference anti-backlash technique, improving antenna motion accuracy and stability. This design utilizes the powerful performance of the motion logical controller to realize trajectory tracking function,which solvesa key technical problem of antenna software.%针对中德亚毫米波望远镜的高性能指标要求,经过大量的调研和仿真分析,天线伺服系统采用了基于德国Rexroth交流伺服的两轴设计方案。系统以运动逻辑控制器和全数字交流驱动器为主体框架,并附加了安全保护措施装置。方位轴和俯仰轴均采用对力矩差值进行PID控制的双电机消隙技术,提高了天线运动的精度和天线转向时的平稳性。利用运动逻辑控制器强大的性能设计了轨迹跟踪功能,解决了天线软件部分的关键技术难题。

  3. Unseen cosmos the universe in radio

    CERN Document Server

    Graham-Smith, Francis

    2013-01-01

    Radio telescopes have transformed our understanding of the Universe. Pulsars, quasars, Big Bang cosmology: all are discoveries of the new science of radio astronomy. Here, Francis Graham-Smith describes the birth, development, and maturity of radio astronomy, from the first discovery of cosmic radio waves to its present role as a major part of modern astronomy. Radio is part of the electromagnetic spectrum, covering infra-red, visible light, ultraviolet, X-rays, and gamma-rays, and Graham-Smith explains why it is that radio waves give us a unique view of the Universe. Tracing the development o

  4. Radio data archiving system

    Science.gov (United States)

    Knapic, C.; Zanichelli, A.; Dovgan, E.; Nanni, M.; Stagni, M.; Righini, S.; Sponza, M.; Bedosti, F.; Orlati, A.; Smareglia, R.

    2016-07-01

    Radio Astronomical Data models are becoming very complex since the huge possible range of instrumental configurations available with the modern Radio Telescopes. What in the past was the last frontiers of data formats in terms of efficiency and flexibility is now evolving with new strategies and methodologies enabling the persistence of a very complex, hierarchical and multi-purpose information. Such an evolution of data models and data formats require new data archiving techniques in order to guarantee data preservation following the directives of Open Archival Information System and the International Virtual Observatory Alliance for data sharing and publication. Currently, various formats (FITS, MBFITS, VLBI's XML description files and ancillary files) of data acquired with the Medicina and Noto Radio Telescopes can be stored and handled by a common Radio Archive, that is planned to be released to the (inter)national community by the end of 2016. This state-of-the-art archiving system for radio astronomical data aims at delegating as much as possible to the software setting how and where the descriptors (metadata) are saved, while the users perform user-friendly queries translated by the web interface into complex interrogations on the database to retrieve data. In such a way, the Archive is ready to be Virtual Observatory compliant and as much as possible user-friendly.

  5. A framework for interpreting fast radio transients search experiments: application to the V-FASTR experiment

    CERN Document Server

    Trott, Cathryn M; Wayth, Randall B; Thompson, David R; Deller, Adam T; Brisken, Walter F; Wagstaff, Kiri L; Majid, Walid A; Burke-Spolaor, Sarah; Macquart, Jean-Pierre R; Palaniswamy, Divya

    2013-01-01

    We define a framework for determining constraints on the detection rate of fast transient events from a population of underlying sources, with a view to incorporating beam shape, frequency effects, scattering effects, and detection efficiency into the metric. We then demonstrate a method for combining independent datasets into a single event rate constraint diagram, using a probabilistic approach to the limits on parameter space. We apply this new framework to present the latest results from the V-FASTR experiment, a commensal fast transients search using the Very Long Baseline Array (VLBA). In the 20 cm band, V-FASTR now has the ability to probe the regions of parameter space of importance for the observed Lorimer and Keane fast radio transient candidates, by combining the information from observations with differing bandwidths, and properly accounting for the source dispersion measure, VLBA antenna beam shape, experiment time sampling, and stochastic nature of events. We then apply the framework to combine ...

  6. The importance of Radio Quiet Zone (RQZ) for radio astronomy

    Science.gov (United States)

    Umar, Roslan; Abidin, Zamri Zainal; Ibrahim, Zainol Abidin

    2013-05-01

    Most of radio observatories are located in isolated areas. Since radio sources from the universe is very weak, astronomer need to avoid radio frequency interference (RFI) from active spectrum users and radio noise produced by human made (telecommunication, mobile phone, microwave user and many more. There are many observatories around the world are surrounded by a Radio Quiet Zone (RQZ), which is it was set up using public or state laws. A Radio Quiet Zone normally consists of two areas: an exclusive area in which totally radio emissions are forbidden, with restrictions for residents and business developments, and a larger (radius up to 100 km above) coordination area where the power of radio transmission limits to threshold levels. Geographical Information System (GIS) can be used as a powerful tool in mapping large areas with varying RQZ profiles. In this paper, we report the initial testing of the usage of this system in order to identify the areas were suitable for Radio Quiet Zone. Among the important parameters used to develop the database for our GIS are population density, information on TV and telecommunication (mobile phones) transmitters, road networks (highway), and contour shielding. We will also use other information gathered from on-site RFI level measurements on selected 'best' areas generated by the GIS. The intention is to find the best site for the purpose of establishing first radio quiet zones for radio telescope in Malaysia.

  7. Very large Arecibo-type telescopes

    Science.gov (United States)

    Drake, Frank D.

    1988-03-01

    The Arecibo-type radio telescope, based on a fixed spherical reflector, is a very effective design for a large radio telescope on the Moon. In such telescopes, major structural members are provided by the ground on which they are built, and thus are provided at no cost in materials or transportation. The strong compression members, the tall towers which support the suspended platform, are an expensive part of the Arecibo telescope. The need for such towers can be eliminated if a suitable valley or crater can be found wherein the rim of the depression can be used as the support point for the cables which support the suspended platform. With an Arecibo-type radio telescope on the Moon, there are no changing gravity loads because of the design and no changing wind loads because of the location; therefore, the only source of time variation in the telescope geometry is thermal changes. Calculations show that with conventional materials, such as steel, it should be possible to construct an Arecibo-type telescope with a reflector diameter of some 30 km on the Moon, and with a reflector diameter of some 60 to 90 km if materials of high specific strength are used.

  8. Selecting Your First Telescope.

    Science.gov (United States)

    Harrington, Sherwood

    1982-01-01

    Designed for first-time telescope purchasers, provides information on how a telescope works; major telescope types (refractors, reflectors, compound telescopes); tripod, pier, altazimuth, and equatorial mounts; selecting a telescope; visiting an astronomy club; applications/limitations of telescope use; and tips on buying a telescope. Includes a…

  9. Radio Journalism.

    Science.gov (United States)

    Bittner, John R.; Bittner, Denise A.

    This book, a how-to-do-it guide for the novice and the professional alike, deals with several aspects of radio journalism: producing documentaries, preparing and announcing radio news, ethics and responsibility, regulation of radio journalism, and careers. It traces the history and growth of radio news, shows its impact on the public, and…

  10. Verification of the Astrometric Performance of the Korean VLBI Network, using comparative SFPR studies with the VLBA at 14/7 mm

    CERN Document Server

    Rioja, Mar\\'\\ia J; Jung, TaeHyun; Sohn, Bong Won; Byun, Do-Young; Agudo, Iván; Cho, Se-Hyung; Lee, Sang-Sung; Kim, Jongsoo; Kim, Kee-Tae; Oh, Chung Sik; Han, Seog-Tae; Je, Do-Heung; Chung, Moon-Hee; Wi, Seog-Oh; Kang, Jiman; Lee, Jung-Won; Chung, Hyunsoo; Kim, Hyo Ryoung; Kim, Hyun-Goo; Lee, Chang-Hoon; Roh, Duk-Gyoo; Oh, Se-Jin; Yeom, Jae-Hwan; Song, Min-Gyu; Kang, Yong-Woo

    2014-01-01

    The Korean VLBI Network (KVN) is a new mm-VLBI dedicated array with capability for simultaneous observations at multiple frequencies, up to 129 GHz. The innovative multi-channel receivers present significant benefits for astrometric measurements in the frequency domain. The aim of this work is to verify the astrometric performance of the KVN using a comparative study with the VLBA, a well established instrument. For that purpose, we carried out nearly contemporaneous observations with the KVN and the VLBA, at 14/7 mm, in April 2013. The KVN observations consisted of simultaneous dual frequency observations, while the VLBA used fast frequency switching observations. We used the Source Frequency Phase Referencing technique for the observational and analysis strategy. We find that having simultaneous observations results in a superior performance for compensation of all atmospheric terms in the observables, in addition to offering other significant benefits for astrometric analysis. We have compared the KVN astr...

  11. Verification of the astrometric performance of the Korean VLBI network, using comparative SFPR studies with the VLBA AT 14/7 mm

    Energy Technology Data Exchange (ETDEWEB)

    Rioja, María J.; Dodson, Richard; Jung, TaeHyun; Sohn, Bong Won; Byun, Do-Young; Cho, Se-Hyung; Lee, Sang-Sung; Kim, Jongsoo; Kim, Kee-Tae; Oh, Chung Sik; Han, Seog-Tae; Je, Do-Heung; Chung, Moon-Hee; Wi, Seog-Oh; Kang, Jiman; Lee, Jung-Won; Chung, Hyunsoo; Kim, Hyo Ryoung; Kim, Hyun-Goo [Korea Astronomy and Space Science Institute, Daedeokdae-ro 776, Yuseong-gu, Daejeon 305-348 (Korea, Republic of); Agudo, Iván, E-mail: maria.rioja@icrar.org [Joint Institute for VLBI in Europe, Postbus 2, NL-7990 AA Dwingeloo (Netherlands); and others

    2014-11-01

    The Korean VLBI Network (KVN) is a new millimeter VLBI dedicated array with the capability to simultaneously observe at multiple frequencies, up to 129 GHz. The innovative multi-channel receivers present significant benefits for astrometric measurements in the frequency domain. The aim of this work is to verify the astrometric performance of the KVN using a comparative study with the VLBA, a well-established instrument. For that purpose, we carried out nearly contemporaneous observations with the KVN and the VLBA, at 14/7 mm, in 2013 April. The KVN observations consisted of simultaneous dual frequency observations, while the VLBA used fast frequency switching observations. We used the Source Frequency Phase Referencing technique for the observational and analysis strategy. We find that having simultaneous observations results in superior compensation for all atmospheric terms in the observables, in addition to offering other significant benefits for astrometric analysis. We have compared the KVN astrometry measurements to those from the VLBA. We find that the structure blending effects introduce dominant systematic astrometric shifts, and these need to be taken into account. We have tested multiple analytical routes to characterize the impact of the low-resolution effects for extended sources in the astrometric measurements. The results from the analysis of the KVN and full VLBA data sets agree within 2σ of the thermal error estimate. We interpret the discrepancy as arising from the different resolutions. We find that the KVN provides astrometric results with excellent agreement, within 1σ, when compared to a VLBA configuration that has a similar resolution. Therefore, this comparative study verifies the astrometric performance of the KVN using SFPR at 14/7 mm, and validates the KVN as an astrometric instrument.

  12. Comets at radio wavelengths

    CERN Document Server

    Crovisier, Jacques; Colom, Pierre; Biver, Nicolas

    2016-01-01

    Comets are considered as the most primitive objects in the Solar System. Their composition provides information on the composition of the primitive solar nebula, 4.6 Gyr ago. The radio domain is a privileged tool to study the composition of cometary ices. Observations of the OH radical at 18 cm wavelength allow us to measure the water production rate. A wealth of molecules (and some of their isotopologues) coming from the sublimation of ices in the nucleus have been identified by observations in the millimetre and submillimetre domains. We present an historical review on radio observations of comets, focusing on the results from our group, and including recent observations with the Nan\\c{c}ay radio telescope, the IRAM antennas, the Odin satellite, the Herschel space observatory, ALMA, and the MIRO instrument aboard the Rosetta space probe.

  13. CONSTRAINING RADIO EMISSION FROM MAGNETARS

    Energy Technology Data Exchange (ETDEWEB)

    Lazarus, P.; Kaspi, V. M.; Dib, R. [Department of Physics, Rutherford Physics Building, McGill University, 3600 University Street, Montreal, Quebec H3A 2T8 (Canada); Champion, D. J. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn (Germany); Hessels, J. W. T., E-mail: plazar@physics.mcgill.ca [Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo (Netherlands)

    2012-01-10

    We report on radio observations of five magnetars and two magnetar candidates carried out at 1950 MHz with the Green Bank Telescope in 2006-2007. The data from these observations were searched for periodic emission and bright single pulses. Also, monitoring observations of magnetar 4U 0142+61 following its 2006 X-ray bursts were obtained. No radio emission was detected for any of our targets. The non-detections allow us to place luminosity upper limits of L{sub 1950} {approx}< 1.60 mJy kpc{sup 2} for periodic emission and L{sub 1950,single} {approx}< 7.6 Jy kpc{sup 2} for single pulse emission. These are the most stringent limits yet for the magnetars observed. The resulting luminosity upper limits together with previous results are discussed, as is the importance of further radio observations of radio-loud and radio-quiet magnetars.

  14. Constraining Radio Emission from Magnetars

    CERN Document Server

    Lazarus, Patrick; Champion, David J; Hessels, Jason W T; Dib, Rim

    2011-01-01

    We report on radio observations of five magnetars and two magnetar candidates carried out at 1950 MHz with the Green Bank Telescope in 2006-2007. The data from these observations were searched for periodic emission and bright single pulses. Also, monitoring observations of magnetar 4U0142+61 following its 2006 X-ray bursts were obtained. No radio emission was detected was detected for any of our targets. The non-detections allow us to place luminosity upper limits (at 1950 MHz) of approximately L < 1.60 mJy kpc^2 for periodic emission and L < 7.6 Jy kpc^2 for single pulse emission. These are the most stringent limits yet for the magnetars observed. The resulting luminosity upper limits together with previous results are discussed, as is the importance of further radio observations of radio-loud and radio-quiet magnetars.

  15. Radio continuum jet in NGC 7479

    OpenAIRE

    Laine, Seppo; Beck, Rainer

    2008-01-01

    The barred galaxy NGC 7479 hosts a remarkable jet-like radio continuum feature: bright, 12-kpc long in projection, and hosting an aligned magnetic field. The degree of polarization is 6%-8% along the jet, and remarkably constant, which is consistent with helical field models. The radio brightness of the jet suggests strong interaction with the ISM and hence a location near the disk plane. We observed NGC 7479 at four wavelengths with the VLA and Effelsberg radio telescopes. The equipartition ...

  16. The Highest Redshift Radio Galaxies

    CERN Document Server

    Van Breugel, W

    2000-01-01

    At low redshifts powerful radio sources are uniquely associated with massive galaxies, and are thought to be powered by supermassive black holes. Modern 8m -- 10m telescopes may be used used to find their likely progenitors at very high redshifts to study their formation and evolution.

  17. Constraining Radio Emission from Magnetars

    NARCIS (Netherlands)

    Lazarus, P.; Kaspi, V.M.; Champion, D.; Hessels, J.W.T.; Dib, R.

    2012-01-01

    We report on radio observations of five magnetars and two magnetar candidates carried out at 1950 MHz with the Green Bank Telescope in 2006-2007. The data from these observations were searched for periodic emission and bright single pulses. Also, monitoring observations of magnetar 4U 0142+61 follow

  18. Internet Resources for Radio Astronomy

    Science.gov (United States)

    Andernach, H.

    A subjective overview of Internet resources for radio-astronomical information is presented. Basic observing techniques and their implications for the interpretation of publicly available radio data are described, followed by a discussion of existing radio surveys, their level of optical identification, and nomenclature of radio sources. Various collections of source catalogues and databases for integrated radio source parameters are reviewed and compared, as well as the web interfaces to interrogate the current and ongoing large-area surveys. Links to radio observatories with archives of raw (uv-) data are presented, as well as services providing images, both of individual objects or extracts (``cutouts'') from large-scale surveys. While the emphasis is on radio continuum data, a brief list of sites providing spectral line data, and atomic or molecular information is included. The major radio telescopes and surveys under construction or planning are outlined. A summary is given of a search for previously unknown optically bright radio sources, as performed by the students as an exercise, using Internet resources only. Over 200 different links are mentioned and were verified, but despite the attempt to make this report up-to-date, it can only provide a snapshot of the situation as of mid-1998.

  19. Searching for neutrino radio flashes from the Moon with LOFAR

    NARCIS (Netherlands)

    Buitink, Stijn; Corstanje, Arthur; Enriquez, Emilio; Falcke, Heino; Frieswijk, Wilfred; Hörandel, Jörg; Mevius, Maaijke; Nelles, Anna; Thoudam, Satyendra; Schellart, Pim; Scholten, Olaf; ter Veen, Sander; van den Akker, Martin; LOFAR Collaboration, [No Value

    2013-01-01

    Ultra-high-energy neutrinos and cosmic rays produce short radio flashes through the Askaryan effect when they impact on the Moon. Earthbound radio telescopes can search the Lunar surface for these signals. A new generation of lowfrequency, digital radio arrays, spearheaded by LOFAR, will allow for s

  20. Division X, XII / Commission 40, 41 / Working Group Radio Astronomy

    NARCIS (Netherlands)

    Kellermann, Kenneth; Orchiston, Wayne; Davies, Rod; Gurvits, Leonid; Ishiguro, Masato; Lequeux, James; Swarup, Govind; Wall, Jasper; Wielebinski, Richard; van Woerden, Hugo

    2012-01-01

    The IAU Working Group on Historical Radio Astronomy (WGHRA) was formed at the 2003 General Assembly of the IAU as a Joint Working Group of Commissions 40 (Radio Astronomy) and 41 (History of Astronomy), in order to: a) assemble a master list of surviving historically-significant radio telescopes and

  1. Division X, XII / Commission 40, 41 / Working Group Radio Astronomy

    NARCIS (Netherlands)

    Kellermann, Kenneth; Orchiston, Wayne; Davies, Rod; Gurvits, Leonid; Ishiguro, Masato; Lequeux, James; Swarup, Govind; Wall, Jasper; Wielebinski, Richard; van Woerden, Hugo

    The IAU Working Group on Historical Radio Astronomy (WGHRA) was formed at the 2003 General Assembly of the IAU as a Joint Working Group of Commissions 40 (Radio Astronomy) and 41 (History of Astronomy), in order to: a) assemble a master list of surviving historically-significant radio telescopes and

  2. Astronomical observations with the University College London balloon borne telescope

    Science.gov (United States)

    Jennings, R. E.

    1974-01-01

    The characteristics of a telescope system which was developed for high altitude balloon astronomy are discussed. A drawing of the optical system of the telescope is provided. A sample of the signals recorded during one of the flights is included. The correlation between the infrared flux and the radio continuum flux is analyzed. A far infrared map of the radio and infrared peaks of selected stars is developed. The spectrum of the planet Saturn is plotted to show intensity as compared with wavenumber.

  3. China's participation in the SKA-the world's largest synthesis radio telescope%持续参与世界最大综合孔径望远镜SKA国际合作

    Institute of Scientific and Technical Information of China (English)

    彭勃; 金乘进; 杜彪; 秦波; 郑元鹏; 卢雨; 梁赞明; 徐海光; 赵公博

    2012-01-01

    The SKA (Square Kilometer Array) will be the world's largest synthesis radio telescope, which will address many fundamental questions about our universe. Scientists and Engineers from 67 institutions in 20 countries have joined the pre-study of the SKA since 1993. China has been playing an important role, from various SKA concepts in the early years, to the current site selection as well as the technical development. The SKA has now entered the pre-construction phase, and many countries including China are involved into the key technology development, such as antenna prototyping and Phased Array Feed. With China's continuous participation into the SKA, including the establishment of a science team aiming at limited scientific objectives, technical studies and designs of high-precision light antennas and broadband wide-field receivers, the Chinese Astronomy and related technologies will be greatly promoted. The SKA will provide a great opportunity for China to play an active role in international mega-science projects.%平方公里阵SKA (Square Kilometre Array)是计划建造的世界最大综合孔径射电望远镜,致力于回答宇宙起源和基本力等问题.自1993年概念提出,全球已有20个国家67个科研机构的天文学家和工程师参与SKA预研究.中国在SKA发起、选址、工程概念及技术研发等方面起到了重要推进作用.目前SKA已进入建设准备阶段,包括中国在内的许多国家正在进行先导天线、相位阵馈源等SKA关键技术试验研究.中国持续参与SKA国际合作,组建团队探索有限科学目标、致力于高精度轻型天线设计与工艺研究、宽频带大视场接收机技术研究,将跨越式提升我国天文学和技术水平、我国工程和制造业水平,实现国际重大科学工程的“中国创造”里程碑.其可行性已通过多方分析和论证,SKA是中国参与21世纪国际重大科学工程千载难逢的机遇.

  4. Multi-Frequency VLBA Studies of the Parsec-Scale Jets in 3C 66A and 3C 66B

    Indian Academy of Sciences (India)

    G.-Y. Zhao; Y.-J. Chen; Z.-Q. Shen; H. Sudou; S. Iguchi; F. Gao; Y. Murata; Y. Taniguchi

    2014-09-01

    We report multi-frequency VLBA phase-referencing observation results of 3C 66A and 3C 66B, including high resolution maps and relative position measurements. The resulting images show similar morphology with that presented in previous works. We find core shift variations in both sources, indicating some physical condition changes in the jets.

  5. The jet-cloud interacting radio galaxy PKS B2152-699-I. Structures revealed in new deep radio and X-ray observations

    NARCIS (Netherlands)

    Worrall, D. M.; Birkinshaw, M.; Young, A. J.; Momtahan, K.; Fosbury, R. A. E.; Morganti, R.; Tadhunter, C. N.; Kleijn, G. Verdoes

    PKS B2152-699, which has radio power characteristic of sources that dominate radio feedback, is exceptional in showing a wide range of features associated with radio-galaxy/gas interactions. We present new deep radio (Australia Telescope Compact Array), X-ray (Chandra) and ground-based optical

  6. A Repeating Fast Radio Burst

    CERN Document Server

    Spitler, L G; Hessels, J W T; Bogdanov, S; Brazier, A; Camilo, F; Chatterjee, S; Cordes, J M; Crawford, F; Deneva, J; Ferdman, R D; Freire, P C C; Kaspi, V M; Lazarus, P; Lynch, R; Madsen, E C; McLaughlin, M A; Patel, C; Ransom, S M; Seymour, A; Stairs, I H; Stappers, B W; van Leeuwen, J; Zhu, W W

    2016-01-01

    Fast Radio Bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measures (i.e. integrated column density of free electrons between source and telescope) and sky position as the original detections. The apparent non-repeating nature of the fast radio bursts has led several authors to hypothesise that they originate in cataclysmic astrophysical events. Here we report the detection of ten additional bursts from the direction of FRB121102, using the 305-m Arecibo telescope. These new bursts have dispersion measures and sky positions consistent with the original burst. This unambiguously identifies FRB121102 as repeating and demonstrates that its source survives the energetic events that cause the bursts. Additionally, the bursts from FRB121102 show a wide range of spectral shapes that appear to be predominantly intrinsic to the source and wh...

  7. Robotic Telescopes

    Science.gov (United States)

    Akerlof, C. W.

    2001-05-01

    Since the discovery of gamma-ray bursts, a number of groups have attempted to detect correlated optical transients from these elusive objects. Following the flight of the BATSE instrument on the Compton Gamma-Ray Observatory in 1991, a prompt burst coordinate alert service, BACODINE (now GCN) became available to ground-based telescopes. Several instruments were built to take advantage of this facility, culminating in the discovery of a bright optical flash associated with GRB990123. To date, that single observation remains unique - no other prompt flashes have been seen for a dozen or so other bursts observed with comparably short response times. Thus, GRB prompt optical luminosities may be considerably dimmer than observed for the GRB990123 event or even absent altogether. A new generation of instruments is prepared to explore these possibilties using burst coordinates provided by HETE-2, Swift, Ballerina, Agile and other satellite missions. These telescopes have response times as short as a few seconds and reach limiting magnitudes, m_v 20, guaranteeing a sensitivity sufficient to detect the afterglow many hours later. Results from these experiments should provide important new data about the dynamics and locale of GRBs.

  8. Construction Milestone Announced on Green Bank Telescope

    Science.gov (United States)

    2000-04-01

    The National Radio Astronomy Observatory announces completion of a major construction milestone on the world's largest fully steerable radio telescope - the National Science Foundation's Green Bank Telescope (GBT). The last of 2,004 aluminum surface panels was recently installed on the GBT's two-acre (100 m x 110 m) collecting dish. The telescope is located at NRAO's Green Bank site, in rural Pocahontas County, West Virginia. The GBT will be used to study everything from the formation of galaxies in the early universe, to the chemical make-up of the dust and gas inside galaxies and in the voids that separate them, to the birth processes of stars. In conjunction with other instruments, it will help make highly accurate radar maps of some familiar objects in our own solar system. The GBT is an engineering marvel. At 485 feet tall, it is comparable in height to the Washington Monument. It weighs 16 million pounds, yet by swiveling the dish in both azimuth and elevation, it can be pointed to any point in the sky with exquisite accuracy. Additionally, the telescope's two-acre collecting dish has many novel features. Most radio telescopes in use today use receivers suspended above the dish by four struts. These struts block some of the surface of the dish, scattering some of the incoming radio waves from celestial objects under study. The GBT's offset feedarm has no struts to block incoming radio waves. The GBT also boasts an active surface. The surface of the dish is composed of 2,004 panels. On the underside of the dish, actuators are located at each corner (i.e., intersection of four panels). These actuators are motors that move the surface panels up and down, keeping the (paraboloid) shape of the dish precisely adjusted, no matter what the tilt of the telescope. The combination of its unblocked aperture and active surface promise that the GBT will display extremely high sensitivity to faint radio signals. The GBT itself is not the only precious national resource in

  9. Building the Green Bank Telescope

    Science.gov (United States)

    Kellermann, Kenneth I.

    2017-01-01

    In a previous presentation, I reported on how the freak collapse of the NRAO 300-ft transit radio telescope led to the inclusion of $75 million for a new radio telescope in the 1989 Congressional Emergency Supplemental Appropriations Act. But, this was only the beginning. NRAO was faced with challenging specifications and an unworkable schedule, but there was no design and no project team. Only one bid was even close to the Congressional appropriation. In an attempt to meet the unrealistic antenna delivery date, the contractor started construction of the foundation and fabrication of antenna members before the design was finished, leading to retrofits, redesign, and multiple delays. The antenna contractor was twice sold to other companies leading to further delays and cost escalation. In order to recoup their mounting losses, the new owners sued NRAO for $29 million for claimed design changes, and NRAO countersued demanding to be reimbursed for added project management costs and lost scientific data resulting from the seven-year delay in the completion of the telescope. Legal fees and a small net award in favor of the contractor left NRAO and the NSF with a nine million dollar bill which NSF handled by an innovative accounting adjustment.

  10. Holographic telescope

    Science.gov (United States)

    Odhner, Jefferson E.

    2016-07-01

    Holographic optical elements (HOEs) work on the principal of diffraction and can in some cases replace conventional optical elements that work on the principal of refraction. An HOE can be thinner, lighter, can have more functionality, and can be lower cost than conventional optics. An HOE can serve as a beam splitter, spectral filter, mirror, and lens all at the same time. For a single wavelength system, an HOE can be an ideal solution but they have not been widely accepted for multispectral systems because they suffer from severe chromatic aberration. A refractive optical system also suffers from chromatic aberration but it is generally not as severe. To color correct a conventional refractive optical system, a flint glass and a crown glass are placed together such that the color dispersion of the flint and the crown cancel each other out making an achromatic lens (achromat) and the wavelengths all focus to the same point. The color dispersion of refractive lenses and holographic lenses are opposite from each other. In a diffractive optical system, long wavelengths focus closer (remember for HOEs: RBM "red bends more") than nominal focus while shorter wavelengths focus further out. In a refractive optical system, it is just the opposite. For this reason, diffractives can be incorporated into a refractive system to do the color correction and often cut down on the number of optical elements used [1.]. Color correction can also be achieved with an all-diffractive system by combining a holographic optical element with its conjugate. In this way the color dispersion of the first holographic optical element can be cancelled by the color dispersion of the second holographic optic. It is this technique that will be exploited in this paper to design a telescope made entirely of holographic optical elements. This telescope could be more portable (for field operations) the same technique could be used to make optics light enough for incorporation into a UAV.

  11. Radio Galaxy Zoo: host galaxies and radio morphologies derived from visual inspection

    Science.gov (United States)

    Banfield, J. K.; Wong, O. I.; Willett, K. W.; Norris, R. P.; Rudnick, L.; Shabala, S. S.; Simmons, B. D.; Snyder, C.; Garon, A.; Seymour, N.; Middelberg, E.; Andernach, H.; Lintott, C. J.; Jacob, K.; Kapińska, A. D.; Mao, M. Y.; Masters, K. L.; Jarvis, M. J.; Schawinski, K.; Paget, E.; Simpson, R.; Klöckner, H.-R.; Bamford, S.; Burchell, T.; Chow, K. E.; Cotter, G.; Fortson, L.; Heywood, I.; Jones, T. W.; Kaviraj, S.; López-Sánchez, Á. R.; Maksym, W. P.; Polsterer, K.; Borden, K.; Hollow, R. P.; Whyte, L.

    2015-11-01

    We present results from the first 12 months of operation of Radio Galaxy Zoo, which upon completion will enable visual inspection of over 170 000 radio sources to determine the host galaxy of the radio emission and the radio morphology. Radio Galaxy Zoo uses 1.4 GHz radio images from both the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) and the Australia Telescope Large Area Survey (ATLAS) in combination with mid-infrared images at 3.4 μm from the Wide-field Infrared Survey Explorer (WISE) and at 3.6 μm from the Spitzer Space Telescope. We present the early analysis of the WISE mid-infrared colours of the host galaxies. For images in which there is >75 per cent consensus among the Radio Galaxy Zoo cross-identifications, the project participants are as effective as the science experts at identifying the host galaxies. The majority of the identified host galaxies reside in the mid-infrared colour space dominated by elliptical galaxies, quasi-stellar objects and luminous infrared radio galaxies. We also find a distinct population of Radio Galaxy Zoo host galaxies residing in a redder mid-infrared colour space consisting of star-forming galaxies and/or dust-enhanced non-star-forming galaxies consistent with a scenario of merger-driven active galactic nuclei (AGN) formation. The completion of the full Radio Galaxy Zoo project will measure the relative populations of these hosts as a function of radio morphology and power while providing an avenue for the identification of rare and extreme radio structures. Currently, we are investigating candidates for radio galaxies with extreme morphologies, such as giant radio galaxies, late-type host galaxies with extended radio emission and hybrid morphology radio sources.

  12. 18–22 cm VLBA Observational Evidence for Toroidal B-Field Components in Six AGN Jets

    Directory of Open Access Journals (Sweden)

    Juliana Cristina Motter

    2016-08-01

    Full Text Available The formation of relativistic jets in Active Galactic Nuclei (AGN is related to accretion onto their central supermassive black holes, and magnetic (B fields are believed to play a central role in launching, collimating, and accelerating the jet streams from very compact regions out to kiloparsec scales. We present results of Faraday rotation studies based on Very Long Baseline Array (VLBA data obtained at 18–22 cm for six well known AGN (OJ 287, 3C 279, PKS 1510-089, 3C 345, BL Lac, and 3C 454.3, which probe projected distances out to tens of parsecs from the observed cores. We have identified statistically significant, monotonic, transverse Faraday rotation gradients across the jets of all but one of these sources, indicating the presence of toroidal B fields, which may be one component of helical B fields associated with these AGN jets.

  13. Characteristics of Gamma-Ray Loud Blazars in the VLBA Imaging and Polarimetry Survey

    Science.gov (United States)

    2010-01-01

    It has a peak radio flux density of 131 mJy at 8.5 GHz. It has a very short jet extending to the southeast (see Figure 9). The spectrum in Marcha et...et al. 2009b, ApJ, 696, L22 Marcha , M. J. M., Brown, I. W. A., Impey, C. D., & Smith, P. S. 1996, MNRAS, 281, 425 Marscher, A. P. 2006, in AIP Conf

  14. Fermi Large Area Telescope Observations of Markarian 421: The Missing Piece of its Spectral Energy Distribution

    Science.gov (United States)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Cannon, A.; Caraveo, P. A.; Carrigan, S.; Casandjian, J. M.; Cavazzuti, E.; Cecchi, C.; Çelik, Ö.; Charles, E.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Cutini, S.; de Angelis, A.; de Palma, F.; Dermer, C. D.; Silva, E. do Couto e.; Drell, P. S.; Dubois, R.; Dumora, D.; Escande, L.; Favuzzi, C.; Fegan, S. J.; Finke, J.; Focke, W. B.; Fortin, P.; Frailis, M.; Fuhrmann, L.; Fukazawa, Y.; Fukuyama, T.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Georganopoulos, M.; Germani, S.; Giebels, B.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Guiriec, S.; Hadasch, D.; Hayashida, M.; Hays, E.; Horan, D.; Hughes, R. E.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Kadler, M.; Kamae, T.; Katagiri, H.; Kataoka, J.; Knödlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S.-H.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Makeev, A.; Max-Moerbeck, W.; Mazziotta, M. N.; McEnery, J. E.; Mehault, J.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Naumann-Godo, M.; Nishino, S.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paneque, D.; Panetta, J. H.; Parent, D.; Pavlidou, V.; Pearson, T. J.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Readhead, A.; Reimer, A.; Reimer, O.; Reyes, L. C.; Richards, J. L.; Ritz, S.; Roth, M.; Sadrozinski, H. F.-W.; Sanchez, D.; Sander, A.; Sgrò, C.; Siskind, E. J.; Smith, P. D.; Spandre, G.; Spinelli, P.; Stawarz, Ł.; Stevenson, M.; Strickman, M. S.; Suson, D. J.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Troja, E.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Wehrle, A. E.; Winer, B. L.; Wood, K. S.; Yang, Z.; Yatsu, Y.; Ylinen, T.; Zensus, J. A.; Ziegler, M.; Fermi LAT Collaboration; Aleksić, J.; Antonelli, L. A.; Antoranz, P.; Backes, M.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Berdyugin, A.; Berger, K.; Bernardini, E.; Biland, A.; Blanch, O.; Bock, R. K.; Boller, A.; Bonnoli, G.; Bordas, P.; Borla Tridon, D.; Bosch-Ramon, V.; Bose, D.; Braun, I.; Bretz, T.; Camara, M.; Carmona, E.; Carosi, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Dazzi, F.; de Angelis, A.; De Cea del Pozo, E.; Delgado Mendez, C.; De Lotto, B.; De Maria, M.; De Sabata, F.; Diago Ortega, A.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Elsaesser, D.; Ferenc, D.; Fonseca, M. V.; Font, L.; García López, R. J.; Garczarczyk, M.; Gaug, M.; Giavitto, G.; Godinovi, N.; Hadasch, D.; Herrero, A.; Hildebrand, D.; Höhne-Mönch, D.; Hose, J.; Hrupec, D.; Jogler, T.; Klepser, S.; Krähenbühl, T.; Kranich, D.; Krause, J.; La Barbera, A.; Leonardo, E.; Lindfors, E.; Lombardi, S.; López, M.; Lorenz, E.; Majumdar, P.; Makariev, E.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Miyamoto, H.; Moldón, J.; Moralejo, A.; Nieto, D.; Nilsson, K.; Orito, R.; Oya, I.; Paoletti, R.; Paredes, J. M.; Partini, S.; Pasanen, M.; Pauss, F.; Pegna, R. G.; Perez-Torres, M. A.; Persic, M.; Peruzzo, J.; Pochon, J.; Prada, F.; Prada Moroni, P. G.; Prandini, E.; Puchades, N.; Puljak, I.; Reichardt, T.; Rhode, W.; Ribó, M.; Rico, J.; Rissi, M.; Rügamer, S.; Saggion, A.; Saito, K.; Saito, T. Y.; Salvati, M.; Sánchez-Conde, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shayduk, M.; Shore, S. N.; Sierpowska-Bartosik, A.; Sillanpää, A.; Sitarek, J.; Sobczynska, D.; Spanier, F.; Spiro, S.; Stamerra, A.; Steinke, B.; Storz, J.; Strah, N.; Struebig, J. C.; Suric, T.; Takalo, L. O.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Vankov, H.; Wagner, R. M.; Weitzel, Q.; Zabalza, V.; Zandanel, F.; Zanin, R.; MAGIC Collaboration; Villata, M.; Raiteri, C.; Aller, H. D.; Aller, M. F.; Chen, W. P.; Jordan, B.; Koptelova, E.; Kurtanidze, O. M.; Lähteenmäki, A.; McBreen, B.; Larionov, V. M.; Lin, C. S.; Nikolashvili, M. G.; Reinthal, R.; Angelakis, E.; Capalbi, M.; Carramiñana, A.; Carrasco, L.; Cassaro, P.; Cesarini, A.; Falcone, A.; Gurwell, M. A.; Hovatta, T.; Kovalev, Yu. A.; Kovalev, Y. Y.; Krichbaum, T. P.; Krimm, H. A.; Lister, M. L.; Moody, J. W.; Maccaferri, G.; Mori, Y.; Nestoras, I.; Orlati, A.; Pace, C.; Pagani, C.; Pearson, R.; Perri, M.; Piner, B. G.; Ros, E.; Sadun, A. C.; Sakamoto, T.; Tammi, J.; Zook, A.

    2011-08-01

    We report on the γ-ray activity of the high-synchrotron-peaked BL Lacertae object Markarian 421 (Mrk 421) during the first 1.5 years of Fermi operation, from 2008 August 5 to 2010 March 12. We find that the Large Area Telescope (LAT) γ-ray spectrum above 0.3 GeV can be well described by a power-law function with photon index Γ = 1.78 ± 0.02 and average photon flux F(> 0.3 GeV) = (7.23 ± 0.16) × 10-8 ph cm-2 s-1. Over this time period, the Fermi-LAT spectrum above 0.3 GeV was evaluated on seven-day-long time intervals, showing significant variations in the photon flux (up to a factor ~3 from the minimum to the maximum flux) but mild spectral variations. The variability amplitude at X-ray frequencies measured by RXTE/ASM and Swift/BAT is substantially larger than that in γ-rays measured by Fermi-LAT, and these two energy ranges are not significantly correlated. We also present the first results from the 4.5 month long multifrequency campaign on Mrk 421, which included the VLBA, Swift, RXTE, MAGIC, the F-GAMMA, GASP-WEBT, and other collaborations and instruments that provided excellent temporal and energy coverage of the source throughout the entire campaign (2009 January 19 to 2009 June 1). During this campaign, Mrk 421 showed a low activity at all wavebands. The extensive multi-instrument (radio to TeV) data set provides an unprecedented, complete look at the quiescent spectral energy distribution (SED) for this source. The broadband SED was reproduced with a leptonic (one-zone synchrotron self-Compton) and a hadronic model (synchrotron proton blazar). Both frameworks are able to describe the average SED reasonably well, implying comparable jet powers but very different characteristics for the blazar emission site.

  15. Multi-frequency radio observations of BAL quasar 1045+352

    CERN Document Server

    Kunert-Bajraszewska, M; Kunert-Bajraszewska, Magdalena; Marecki, Andrzej

    2006-01-01

    Multi-frequency 1.7, 5 and 8.4-GHz VLBA observations of a radio-loud broad absorption line (BAL) quasar 1045+352 are presented. It is a young compact steep spectrum (CSS) object and its asymmetric, two-sided morphology on a scale of several hundred parsecs, extending in two different directions, may suggest intermittent activity. The young age and unusual morphology of 1045+352 are arguments in favour of an evolution scenario for BAL quasars, in which the BAL features appear at a very early stage of their evolution.

  16. Radio detection of air showers with LOFAR and AERA

    CERN Document Server

    Hörandel, Jörg R

    2015-01-01

    High-energy cosmic rays impinging onto the atmosphere of the Earth initiate extensive air showers. With the LOFAR radio telescope and the Auger Engineering Radio Array (AERA) at the Pierre Auger Observatory radio emission from air showers is detected. Recent results are presented from both experiments. The measured properties of the radio emission are described. The measurements are used to derive the properties of high-energy cosmic rays: their arrival direction, energy, and particle type (mass).

  17. Radio communications with extra-terrestrial civilizations

    Science.gov (United States)

    Kotelnikov, V. A.

    1974-01-01

    Communications between civilizations within our galaxy at the present level of radio engineering is possible, although civilizations must begin to search for each other to achieve this. If an extra-terrestrial civilization possessing a technology at our level wishes to make itself known and will transmit special radio signals to do this, then it can be picked up by us at a distance of several hundreds of light years using already existing radio telescopes and specially built radio receivers. If it wishes, this civilization can also send us information without awaiting our answer.

  18. Radio archive

    OpenAIRE

    Street, Sean

    2008-01-01

    The Centre for Broadcasting History Research, in association with the\\ud British Universities Film and Video Council, is developing an online\\ud audio archive of UK commercial radio, from 1973 to 1992. Work produced\\ud before the Broadcasting Act 1990 represents a different ethos to the role\\ud commercial radio played, and subsequently,continues to play, in the UK.\\ud The change in commercial radio since this period is extraordinary. It is\\ud impossible for the young student of radio, born si...

  19. Measuring Nearby Star Forming Regions with the VLBA: from the Distance to the Dynamics

    CERN Document Server

    Torres, Rosa M

    2010-01-01

    This thesis is part of a large ongoing effort to determine the distance and structure of all star-forming regions within several hundred parsecs of the Sun using radio-interferometric observations. The main goals of this thesis were: (1) Find the mean distance to the two best-studied nearby regions of low-mass star-formation (Taurus and Ophiuchus) with accuracies (a few percent or better) one to two orders of magnitude better than the present values, (2) Explore the structure and dynamics of these star-forming regions, and (3) Study the stars themselves.

  20. Are the infrared-faint radio sources pulsars?

    Science.gov (United States)

    Cameron, A. D.; Keith, M.; Hobbs, G.; Norris, R. P.; Mao, M. Y.; Middelberg, E.

    2011-07-01

    Infrared-faint radio sources (IFRS) are objects which are strong at radio wavelengths but undetected in sensitive Spitzer observations at infrared wavelengths. Their nature is uncertain and most have not yet been associated with any known astrophysical object. One possibility is that they are radio pulsars. To test this hypothesis we undertook observations of 16 of these sources with the Parkes Radio Telescope. Our results limit the radio emission to a pulsed flux density of less than 0.21 mJy (assuming a 50 per cent duty cycle). This is well below the flux density of the IFRS. We therefore conclude that these IFRS are not radio pulsars.

  1. Are the infrared-faint radio sources pulsars?

    CERN Document Server

    Keith, A D Cameron M J; Norris, R P; Mao, M Y; Middelberg, E

    2011-01-01

    Infrared-Faint Radio Sources (IFRS) are objects which are strong at radio wavelengths but undetected in sensitive Spitzer observations at infrared wavelengths. Their nature is uncertain and most have not yet been associated with any known astrophysical object. One possibility is that they are radio pulsars. To test this hypothesis we undertook observations of 16 of these sources with the Parkes Radio Telescope. Our results limit the radio emission to a pulsed flux density of less than 0.21 mJy (assuming a 50% duty cycle). This is well below the flux density of the IFRS. We therefore conclude that these IFRS are not radio pulsars.

  2. Structure in the Radio Counterpart to the 2004 Dec 27 Giant Flare From SGR1806-20

    Energy Technology Data Exchange (ETDEWEB)

    Fender, Rob P.; Muxlow, T.W.B.; Garrett, M.A.; Kouveliotou, C.; Gaensler, B.M.; Garrington, S.T.; Paragi, Z.; Tudose, V.; Miller-Jones, J.C.A.; Spencer, R.E.; Wijers,; Taylor, G.B.; /Southampton U. /Jodrell Bank /JIVE, Dwingeloo /NASA, Marshall /Harvard-Smithsonian Ctr. Astrophys. /Amsterdam U., Astron. Inst. /Astron. Inst. Romanian

    2006-01-11

    The formation of an expanding, moving, and fading radio source. We report observations of this radio source with the Multi-Element Radio-Linked Interferometer Network (MERLIN) and the Very Long Baseline Array (VLBA). The observations confirm the elongation and expansion already reported based on observations at lower angular resolutions, but suggest that at early epochs the structure is not consistent with the very simplest models such as a smooth flux distribution. In particular there appears to be significant structure on small angular scales, with {approx}10% of the radio flux arising on angular scales <= 100 milliarcsec. This structure may correspond to localized sites of particle acceleration during the early phases of expansion and interaction with the ambient medium.

  3. Development of Radio Astronomy at Centre for Basic Space Science Observatory, Nsukka Nigeria

    Science.gov (United States)

    Aliyu, Nasiru; Okere, Bonaventure I.; Lanre, Daniyan O.; Ezechi, Nwachukwu E.

    2015-08-01

    Radio telescopes for research, teaching and learning at Centre for Basic Space Science (CBSS) observatory are currently in place of development. A small parabolic radio telescope with diameter of 3.0 m working at 1420 MHz is already available for general purpose of radio astronomical observations. In addition, a Radio Jove telescope with dual dipole antenna working at 20 MHz and Sudden Ionospheric Disturbance (SID) monitor working at 24 KHz are also available. It is suitable to monitor daily solar burst, solar flares as well as Jupiter decametric emission. More over, CBSS radio interferometers are now under construction. It consists of non-tracking Radio Jove array and SID monitor as well as two radio telescope tracking interferometers. The latter is planned to utilize up to 4 antennas. Multi frequency receivers are made available at 24 KHz, 20 and 1420 MHz and will be used for VLBI in the near future.

  4. High-Redshift Radio Galaxies from Deep Fields

    Indian Academy of Sciences (India)

    C. H. Ishwara-Chandra; S. K. Sirothia; Y. Wadadekar; S. Pal

    2011-12-01

    Most of the radio galaxies with > 3 have been found using the red-shift spectral index correlation.We have started a programme with the Giant Metrewave Radio Telescope (GMRT) to exploit this correlation at flux density levels about 100 times deeper than the known high-redshift radio galaxies, with an aim to detect candidate high-redshift radio galaxies. Here we present results from the deep 150 MHz observations of LBDS-Lynx field, which has been imaged at 327, 610 and 1412 MHz with the Westerbork Synthesis Radio Telescope (WSRT) and at 1400 and 4860 MHz with the Very Large Array (VLA). We find about 150 radio sources with spectra steeper than 1. About two-thirds of these are not detected in Sloan Digital Sky Survey (SDSS), hence are strong candidate high-redshift radio galaxies, which need to be further explored with deep infra-red imaging and spectroscopy to estimate the red-shift.

  5. SKA Telescope Manager (TM): status and architecture overview

    Science.gov (United States)

    Natarajan, Swaminathan; Barbosa, Domingos; Barraca, Joao P.; Bridger, Alan; Choudhury, Subhrojyoti R.; Di Carlo, Matteo; Dolci, Mauro; Gupta, Yashwant; Guzman, Juan; Van den Heever, Lize; Le Roux, Gerhard; Nicol, Mark; Patil, Mangesh; Smareglia, Riccardo; Swart, Paul; Thompson, Roger; Vrcic, Sonja; Williams, Stewart

    2016-07-01

    The SKA radio telescope project is building two telescopes, SKA-Low in Australia and SKA-Mid in South Africa respectively. The Telescope Manager is responsible for the observations lifecycle and for monitoring and control of each instrument, and is being developed by an international consortium. The project is currently in the design phase, with the Preliminary Design Review having been successfully completed, along with re-baselining to match project scope to available budget. This report presents the status of the Telescope Manager work, key architectural challenges and our approach to addressing them.

  6. Radio Eska Lodz, Commercial Radio As a Local Radio

    OpenAIRE

    Szews, Przemysław

    2015-01-01

    The article discusses aspects of network-based local radio using the example of Radio Eska Lodz. The author responds to questions about whether a commercial network radio station can fulfill the functions of local radio and on what this locality is actually based. In this respect, Radio Eska Lodz is characterized as part of the most popular commercial radio network in Poland. The introduction focuses on the process of transformation that local radio stations are undergoing, along with its gen...

  7. Radio Halos in future surveys in the radio continuum

    CERN Document Server

    Cassano, R; Norris, Ray P; Roettgering, H J A; Johnston-Hollitt, M; Trasatti, M

    2012-01-01

    Giant radio halos (RH) are Mpc-scale synchrotron sources detected in a significant fraction of massive and merging galaxy clusters.Their statistical properties can be used to discriminate among various models for their origin. Theoretical predictions are important as new radio telescopes are about to begin to survey the sky at low and high frequencies with unprecedented sensitivity. We carry out Monte Carlo simulations to model the formation and evolution of RH in a cosmological framework by assuming that RH are either generated in turbulent merging clusters, or are purely hadronic sources generated in more relaxed clusters, "off-state" halos. The models predict that the luminosity function of RH at high radio luminosities is dominated by the contribution of RH generated in turbulent clusters. The generation of these RH becomes less efficient in less massive systems causing a flattening of the luminosity function at lower luminosities. This flattening is compensated by the contribution of "off-state" RH that ...

  8. Solar Radio

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Scientists monitor the structure of the solar corona, the outer most regions of the Sun's atmosphere, using radio waves (100?s of MHz to 10?s of GHz). Variations in...

  9. Connection between the Accretion Disk and Jet in the Radio Galaxy 3C 111

    CERN Document Server

    Chatterjee, Ritaban; Jorstad, Svetlana G; Markowitz, Alex; Rivers, Elizabeth; Rothschild, Richard E; McHardy, Ian M; Aller, Margo F; Aller, Hugh D; Lahteenmaki, Anne; Tornikoski, Merja; Harrison, Brandon; Agudo, Iv'an; Gomez, Jos'e L; Taylor, Brian W; Gurwell, Mark

    2011-01-01

    We present the results of extensive multi-frequency monitoring of the radio galaxy 3C 111 between 2004 and 2010 at X-ray (2.4--10 keV), optical (R band), and radio (14.5, 37, and 230 GHz) wave bands, as well as multi-epoch imaging with the Very Long Baseline Array (VLBA) at 43 GHz. Over the six years of observation, significant dips in the X-ray light curve are followed by ejections of bright superluminal knots in the VLBA images. This shows a clear connection between the radiative state near the black hole, where the X-rays are produced, and events in the jet. The X-ray continuum flux and Fe line intensity are strongly correlated, with a time lag shorter than 90 days and consistent with zero. This implies that the Fe line is generated within 90 light-days of the source of the X-ray continuum. The power spectral density function of X-ray variations contains a break, with steeper slope at shorter timescales. The break timescale of 13 (+12,-6) days is commensurate with scaling according to the mass of the centr...

  10. Erratic Jet Wobbling in the BL Lacertae Object OJ287 Revealed by Sixteen Years of 7mm VLBA Observations

    CERN Document Server

    Agudo, Ivan; Jorstad, Svetlana G; Gomez, Jose L; Perucho, Manel; Piner, B Glenn; Rioja, Maria; Dodson, Richard

    2011-01-01

    We present the results from an ultra-high-resolution 7mm Very Long Baseline Array (VLBA) study of the relativistic jet in the BL Lacertae object OJ287 from 1995 to 2011 containing 136 total intensity images. Analysis of the image sequence reveals a sharp jet-position-angle swing by >100 deg. during [2004,2006], as viewed in the plane of the sky, that we interpret as the crossing of the jet from one side of the line of sight to the other during a softer and longer term swing of the inner jet. Modulating such long term swing, our images also show for the first time a prominent erratic wobbling behavior of the innermost ~0.4mas of the jet with fluctuations in position angle of up to ~40 deg. over time scales ~2yr. This is accompanied by highly superluminal motions along non-radial trajectories, which reflect the remarkable non-ballistic nature of the jet plasma on these scales. The erratic nature and short time scales of the observed behavior rules out scenarios such as binary black hole systems, accretion disk ...

  11. The Jets of TeV Blazars at Higher Resolution: 43 GHz and Polarimetric VLBA Observations from 2005-2009

    CERN Document Server

    Piner, B Glenn; Edwards, Philip G

    2010-01-01

    We present 23 new VLBA images of the six established TeV blazars Markarian 421, Markarian 501, H 1426+428, 1ES 1959+650, PKS 2155-304, and 1ES 2344+514, obtained from 2005 to 2009. Most images were obtained at 43 GHz, and they reveal the parsec-scale structures of three of these sources (1ES 1959+650, PKS 2155-304, and 1ES 2344+514) at factors of two to three higher resolution than has previously been attained. Most of the remaining images map the linear polarization structures at a lower frequency of 22 GHz. We discuss the transverse structures of the jets as revealed by the high-frequency and polarimetric imaging. The transverse structures include significant limb-brightening in Mrk 421, and spine-sheath structures in the electric vector position angle (EVPA) and fractional polarization distributions in Mrk 421, Mrk 501, and 1ES 1959+650. We use new measured component positions to update measured apparent jet speeds, in many cases significantly reducing the statistical error over previously published result...

  12. LOFAR and APERTIF Surveys of the Radio Sky : Probing Shocks and Magnetic Fields in Galaxy Clusters

    NARCIS (Netherlands)

    Rottgering, Huub; Afonso, Jose; Barthel, Peter; Batejat, Fabien; Best, Philip; Bonafede, Annalisa; Brueggen, Marcus; Brunetti, Gianfranco; Chyzy, Krzysztof; Conway, John; De Gasperin, Francesco; Ferrari, Chiara; Haverkorn, Marijke; Heald, George; Hoeft, Matthias; Jackson, Neal; Jarvis, Matt; Ker, Louise; Lehnert, Matt; Macario, Giulia; McKean, John; Miley, George; Morganti, Raffaella; Oosterloo, Tom; Orru, Emanuela; Pizzo, Roberto; Rafferty, David; Shulevski, Alexander; Tasse, Cyril; van Bemmel, Ilse; van der Tol, Bas; van Weeren, Reinout; Verheijen, Marc; White, Glenn; Wise, Michael

    2011-01-01

    At very low frequencies, the new pan-European radio telescope LOFAR is opening the last unexplored window of the electromagnetic spectrum for astrophysical studies. The revolutionary APERTIF-phased arrays that are about to be installed on the Westerbork radio telescope (WSRT) will dramatically incre

  13. Non-thermal emission from extragalactic radio sources a high resolution broad band (radio to X-rays) approach

    CERN Document Server

    Brunetti, G

    2002-01-01

    In the framework of the study of extragalactic radio sources, we will focus on the importance of the spatial resolution at different wavelengths, and of the combination of observations at different frequency bands. In particular, a substantial step forward in this field is now provided by the new generation X-ray telescopes which are able to image radio sources in between 0.1--10 keV with a spatial resolution comparable with that of the radio telescopes (VLA) and of the optical telescopes. After a brief description of some basic aspects of acceleration mechanisms and of the radiative processes at work in the extragalactic radio sources, we will focus on a number of recent radio, optical and X-ray observations with arcsec resolution, and discuss the deriving constraints on the physics of these sources.

  14. Optical Spectra of Candidate International Celestial Reference Frame (ICRF) Flat-spectrum Radio Sources. III.

    Science.gov (United States)

    Titov, O.; Pursimo, T.; Johnston, Helen M.; Stanford, Laura M.; Hunstead, Richard W.; Jauncey, David L.; Zenere, Katrina A.

    2017-04-01

    In extending our spectroscopic program, which targets sources drawn from the International Celestial Reference Frame (ICRF) Catalog, we have obtained spectra for ˜160 compact, flat-spectrum radio sources and determined redshifts for 112 quasars and radio galaxies. A further 14 sources with featureless spectra have been classified as BL Lac objects. Spectra were obtained at three telescopes: the 3.58 m European Southern Observatory New Technology Telescope, and the two 8.2 m Gemini telescopes in Hawaii and Chile. While most of the sources are powerful quasars, a significant fraction of radio galaxies is also included from the list of non-defining ICRF radio sources.

  15. Fast radio burst tied to distant dwarf galaxy (Image 2)

    National Science Foundation

    2017-06-07

    Full Text Available Radio telescope at Arecibo only localized the fast radio burst to the area inside the two circles in this image, but the Very Large Array was able to pinpoint it as a dwarf galaxy within the square (shown at intersection of cross hairs in enlarged box)

  16. Giant Radio Galaxies: I. Intergalactic Barometers

    CERN Document Server

    Malarecki, J M; Saripalli, L; Subrahmanyan, R; Jones, D H; Duffy, A R; Rioja, M

    2013-01-01

    We present new wideband radio observations with the Australia Telescope Compact Array of a sample of 12 giant radio galaxies. The radio observations are part of a larger radio-optical study aimed at relating the radio structures with the ambient medium on large scales. With projected linear sizes larger than 0.7 Mpc, these objects are ideal candidates for the study of the Warm-Hot Intergalactic Medium (WHIM). The sample includes sources with sizes spanning 0.8 to 3.2 Mpc and total powers of 1.2*10^24 to 4.0*10^26 W Hz^-1 at 2.1 GHz. Redshifts were limited to z<0.15 to permit spectroscopic observations of the hosts and neighbouring galaxies, which were obtained using the AAOmega spectrograph on the Anglo-Australian Telescope. We derive lobe energy densities from the radio observations via equipartition arguments. The inferred pressures in the lobes of the giant radio sources, which range from 1.1*10^-15 to 2.0*10^-14 Pa (80 to 1500 cm^-3 K), are lower than previously inferred from X-ray observations of dens...

  17. The SOFIA Telescope

    CERN Document Server

    Krabbe, A

    2000-01-01

    The SOFIA telescope as the heart of the observatory is a major technological challenge. I present an overview on the astro-nomical and scientific requirements for such a big airborne observatory and demonstrate the impact of these requirements on the layout of SOFIA, in particular on the telescope design as it is now. Selected components of the telescope will be de-scribed in their context and functionality. The current status of the telescope is presented.

  18. Optical spectroscopy of four young radio sources

    Science.gov (United States)

    Fan, Xu-Liang; Bai, Jin-Ming; Hu, Chen; Wang, Jian-Guo

    2017-01-01

    We report the optical spectroscopy of four young radio sources which are observed with the Lijiang 2.4 m telescope. The Eddington ratios of these sources are similar with those of narrow-line Seyfert 1 galaxies (NLS1s). Their Fe II emission is strong while [O III] strength is weak. These results confirm the NLS1 features of young radio sources, except that the width of broad Hβ of young radio sources is larger than that of NLS1s. We thus suggest that the young radio sources are the high black hole mass counterparts of steep-spectrum radio-loud NLS1s. In addition, the broad Hβ component of 4C 12.50 is the blue wing of the narrow component, but not from the broad line region.

  19. Optical Spectroscopy of Four Young Radio Sources

    CERN Document Server

    Fan, Xu-Liang; Hu, Chen; Wang, Jian-Guo

    2016-01-01

    We report the optical spectroscopy of four young radio sources which are observed with the Lijiang 2.4m telescope. The Eddington ratios of these sources are similar with those of narrow-line Seyfert 1 galaxies (NLS1s). Their Fe {\\sc ii} emission is strong while [O {\\sc iii}] strength is weak. These results confirm the NLS1 features of young radio sources, except that the width of broad H$\\beta$ of young radio sources is larger than that of NLS1s. We thus suggest that the young radio sources are the high black hole mass counterparts of steep-spectrum radio-loud NLS1s. In addition, the broad H$\\beta$ component of \\astrobj{4C 12.50} is the blue wing of the narrow component, but not from the broad line region.

  20. Infrared imaging of WENSS radio sources

    CERN Document Server

    Villani, D

    1999-01-01

    We have performed deep imaging in the IR J- and K-bands for three sub-samples of radio sources extracted from the Westerbork Northern Sky Survey, a large low-frequency radio survey containing Ultra Steep Spectrum (USS), Gigahertz Peaked Spectrum (GPS) and Flat Spectrum (FS) sources. We present the results of these IR observations, carried out with the ARcetri Near Infrared CAmera (ARNICA) at the Nordic Optical Telescope (NOT), providing photometric and morphologic information on high redshift radio galaxies and quasars. We find that the radio galaxies contained in our sample do not show the pronounced radio/IR alignment claimed for 3CR sources. IR photometric measurements of the gravitational lens system 1600+434 are also presented.

  1. High-Flying Telescope

    Institute of Scientific and Technical Information of China (English)

    1995-01-01

    Scientists at the Space Telescope Science Institute,which operates the Hubble Space Telescope,have proposed a new telescope that would have twice the resolution of Hubble at about one-tenth the cost. It would hover seven miles above Earth,dangling below a football-field-size helium balloon

  2. Auto Adjusting Astronomical Telescope

    Directory of Open Access Journals (Sweden)

    Rohit R. Ghalsasi

    2014-04-01

    Full Text Available Astronomical telescope is powerful and basic tool for star or celestial observation. Here we proposed integrated system using Raspberry Pi for auto adjusting astronomical telescope. This integrated circuit helps to control stellar monitoring, stellar targeting, and tracking functions of telescope. Astro compass gives the direction of the celestial objects.

  3. Adaptive Real Time Imaging Synthesis Telescopes

    CERN Document Server

    Wright, Melvyn

    2012-01-01

    The digital revolution is transforming astronomy from a data-starved to a data-submerged science. Instruments such as the Atacama Large Millimeter Array (ALMA), the Large Synoptic Survey Telescope (LSST), and the Square Kilometer Array (SKA) will measure their accumulated data in petabytes. The capacity to produce enormous volumes of data must be matched with the computing power to process that data and produce meaningful results. In addition to handling huge data rates, we need adaptive calibration and beamforming to handle atmospheric fluctuations and radio frequency interference, and to provide a user environment which makes the full power of large telescope arrays accessible to both expert and non-expert users. Delayed calibration and analysis limit the science which can be done. To make the best use of both telescope and human resources we must reduce the burden of data reduction. Our instrumentation comprises of a flexible correlator, beam former and imager with digital signal processing closely coupled...

  4. The radio properties of infrared-faint radio sources

    CERN Document Server

    Middelberg, Enno; Hales, Christopher A; Seymour, Nick; Johnston-Hollitt, Melanie; Huynh, Minh T; Lenc, Emil; Mao, Minnie Y

    2010-01-01

    Infrared-faint radio sources (IFRS) are objects that have flux densities of several mJy at 1.4GHz, but that are invisible at 3.6um when using sensitive Spitzer observations with uJy sensitivities. Their nature is unclear and difficult to investigate since they are only visible in the radio. High-resolution radio images and comprehensive spectral coverage can yield constraints on the emission mechanisms of IFRS and can give hints to similarities with known objects. We imaged a sample of 17 IFRS at 4.8GHz and 8.6GHz with the Australia Telescope Compact Array to determine the structures on arcsecond scales. We added radio data from other observing projects and from the literature to obtain broad-band radio spectra. We find that the sources in our sample are either resolved out at the higher frequencies or are compact at resolutions of a few arcsec, which implies that they are smaller than a typical galaxy. The spectra of IFRS are remarkably steep, with a median spectral index of -1.4 and a prominent lack of spec...

  5. Axis Offset Estimation of VLBI Telescopes

    Science.gov (United States)

    Krásná, Hana; Nickola, Marisa; Böhm, Johannes

    2014-12-01

    Axis offset models have to be applied for VLBI telescopes with pointing axes which do not intersect. In this work, we estimated the axis offsets for VLBI antennas in a global adjustment of suitable IVS 24-hour sessions (1984.0-2014.0) with the Vienna VLBI Software (VieVS). In particular, we focused on the two radio telescopes of the Hartebeesthoek Radio Astronomy Observatory (HartRAO) in South Africa. For the older 26-m telescope we compared the estimated axis offset values before (6699.2 ± 0.5 mm) and after (6707.3 ± 0.8 mm) the bearing repair in 2010. A comparison with axis offset estimates from other geodetic techniques, such as GNSS or conventional local survey, was made. The estimated axis offset for the newer 15-m telescope (1495.0 ± 3.4 mm) agrees with the estimated value from the GPS survey in 2007. Furthermore, we assessed the influence of differences in the axis offsets on the estimated geodetic parameters, such as station coordinates or Earth Orientation Parameters.

  6. Radio astronomy

    CERN Document Server

    Alder, Berni

    1975-01-01

    Methods in Computational Physics, Volume 14: Radio Astronomy is devoted to the role of the digital computer both as a control device and as a calculator in addressing problems related to galactic radio noise. This volume contains four chapters and begins with a technical description of the hardware and the special data-handling problems of using radioheliography, with an emphasis on a selection of observational results obtained with the Culgoora radioheliograph and their significance to solar physics and to astrophysics in general. The subsequent chapter examines interstellar dispersion, i

  7. ATST telescope mount: telescope of machine tool

    Science.gov (United States)

    Jeffers, Paul; Stolz, Günter; Bonomi, Giovanni; Dreyer, Oliver; Kärcher, Hans

    2012-09-01

    The Advanced Technology Solar Telescope (ATST) will be the largest solar telescope in the world, and will be able to provide the sharpest views ever taken of the solar surface. The telescope has a 4m aperture primary mirror, however due to the off axis nature of the optical layout, the telescope mount has proportions similar to an 8 meter class telescope. The technology normally used in this class of telescope is well understood in the telescope community and has been successfully implemented in numerous projects. The world of large machine tools has developed in a separate realm with similar levels of performance requirement but different boundary conditions. In addition the competitive nature of private industry has encouraged development and usage of more cost effective solutions both in initial capital cost and thru-life operating cost. Telescope mounts move relatively slowly with requirements for high stability under external environmental influences such as wind buffeting. Large machine tools operate under high speed requirements coupled with high application of force through the machine but with little or no external environmental influences. The benefits of these parallel development paths and the ATST system requirements are being combined in the ATST Telescope Mount Assembly (TMA). The process of balancing the system requirements with new technologies is based on the experience of the ATST project team, Ingersoll Machine Tools who are the main contractor for the TMA and MT Mechatronics who are their design subcontractors. This paper highlights a number of these proven technologies from the commercially driven machine tool world that are being introduced to the TMA design. Also the challenges of integrating and ensuring that the differences in application requirements are accounted for in the design are discussed.

  8. TINY SCALE OPACITY FLUCTUATIONS FROM VLBA, MERLIN, AND VLA OBSERVATIONS OF H I ABSORPTION TOWARD 3C 138

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Nirupam; Goss, W. M. [National Radio Astronomy Observatory, 1003 Lopezville Road, Socorro, NM 87801 (United States); Minter, Anthony H. [National Radio Astronomy Observatory, P.O. Box 2, Green Bank, WV 24944 (United States); Brogan, Crystal L. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Lazio, T. J. W., E-mail: nroy@aoc.nrao.edu [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2012-04-20

    The structure function of opacity fluctuations is a useful statistical tool to study tiny scale structures of neutral hydrogen. Here we present high-resolution observation of H I absorption toward 3C 138, and estimate the structure function of opacity fluctuations from the combined VLA, MERLIN, and VLBA data. The angular scales probed in this work are {approx}10-200 mas (about 5-100 AU). The structure function in this range is found to be well represented by a power law S{sub {tau}}(x) {approx} x{sup {beta}} with index {beta} {approx} 0.33 {+-} 0.07 corresponding to a power spectrum P{sub {tau}}(U) {approx} U{sup -2.33}. This is slightly shallower than the earlier reported power-law index of {approx}2.5-3.0 at {approx}1000 AU to few pc scales. The amplitude of the derived structure function is a factor of {approx}20-60 times higher than the extrapolated amplitude from observation of Cas A at larger scales. On the other hand, extrapolating the AU scale structure function for 3C 138 predicts the observed structure function for Cas A at the pc scale correctly. These results clearly establish that the atomic gas has significantly more structures in AU scales than expected from earlier pc scale observations. Some plausible reasons are identified and discussed here to explain these results. The observational evidence of a shallower slope and the presence of rich small-scale structures may have implications for the current understanding of the interstellar turbulence.

  9. Hartebeesthoek Radio Astronomy Observatory (HartRAO)

    Science.gov (United States)

    Nickola, Marisa; Gaylard, Mike; Quick, Jonathan; Combrinck, Ludwig

    2013-01-01

    HartRAO provides the only fiducial geodetic site in Africa, and it participates in global networks for VLBI, GNSS, SLR, and DORIS. This report provides an overview of geodetic VLBI activities at HartRAO during 2012, including the conversion of a 15-m alt-az radio telescope to an operational geodetic VLBI antenna.

  10. Fast Radio Bursts: Searches, Sensitivities & Implications

    CERN Document Server

    Keane, E F

    2016-01-01

    Fast radio bursts (FRBs) are millisecond-duration transient signals discovered over the past decade. Here we describe the scientific usefulness of FRBs, consider ongoing work at the Parkes telescope, and examine some relevant search sensitivity and completeness considerations. We also look ahead to the results from ongoing and future planned studies in the field.

  11. The Cherenkov Telescope Array Large Size Telescope

    CERN Document Server

    Ambrosi, G; Baba, H; Bamba, A; Barceló, M; de Almeida, U Barres; Barrio, J A; Bigas, O Blanch; Boix, J; Brunetti, L; Carmona, E; Chabanne, E; Chikawa, M; Colin, P; Conteras, J L; Cortina, J; Dazzi, F; Deangelis, A; Deleglise, G; Delgado, C; Díaz, C; Dubois, F; Fiasson, A; Fink, D; Fouque, N; Freixas, L; Fruck, C; Gadola, A; García, R; Gascon, D; Geffroy, N; Giglietto, N; Giordano, F; Grañena, F; Gunji, S; Hagiwara, R; Hamer, N; Hanabata, Y; Hassan, T; Hatanaka, K; Haubold, T; Hayashida, M; Hermel, R; Herranz, D; Hirotani, K; Inoue, S; Inoue, Y; Ioka, K; Jablonski, C; Kagaya, M; Katagiri, H; Kishimoto, T; Kodani, K; Kohri, K; Konno, Y; Koyama, S; Kubo, H; Kushida, J; Lamanna, G; Flour, T Le; López-Moya, M; López, R; Lorenz, E; Majumdar, P; Manalaysay, A; Mariotti, M; Martínez, G; Martínez, M; Mazin, D; Miranda, J M; Mirzoyan, R; Monteiro, I; Moralejo, A; Murase, K; Nagataki, S; Nakajima, D; Nakamori, T; Nishijima, K; Noda, K; Nozato, A; Ohira, Y; Ohishi, M; Ohoka, H; Okumura, A; Orito, R; Panazol, J L; Paneque, D; Paoletti, R; Paredes, J M; Pauletta, G; Podkladkin, S; Prast, J; Rando, R; Reimann, O; Ribó, M; Rosier-Lees, S; Saito, K; Saito, T; Saito, Y; Sakaki, N; Sakonaka, R; Sanuy, A; Sasaki, H; Sawada, M; Scalzotto, V; Schultz, S; Schweizer, T; Shibata, T; Shu, S; Sieiro, J; Stamatescu, V; Steiner, S; Straumann, U; Sugawara, R; Tajima, H; Takami, H; Tanaka, S; Tanaka, M; Tejedor, L A; Terada, Y; Teshima, M; Totani, T; Ueno, H; Umehara, K; Vollhardt, A; Wagner, R; Wetteskind, H; Yamamoto, T; Yamazaki, R; Yoshida, A; Yoshida, T; Yoshikoshi, T

    2013-01-01

    The two arrays of the Very High Energy gamma-ray observatory Cherenkov Telescope Array (CTA) will include four Large Size Telescopes (LSTs) each with a 23 m diameter dish and 28 m focal distance. These telescopes will enable CTA to achieve a low-energy threshold of 20 GeV, which is critical for important studies in astrophysics, astroparticle physics and cosmology. This work presents the key specifications and performance of the current LST design in the light of the CTA scientific objectives.

  12. Radio Galaxy Zoo: host galaxies and radio morphologies derived from visual inspection

    CERN Document Server

    Banfield, J K; Willett, K W; Norris, R P; Rudnick, L; Shabala, S S; Simmons, B D; Snyder, C; Garon, A; Seymour, N; Middelberg, E; Andernach, H; Lintott, C J; Jacob, K; Kapinska, A D; Mao, M Y; Masters, K L; Jarvis, M J; Schawinski, K; Paget, E; Simpson, R; Klockner, H R; Bamford, S; Burchell, T; Chow, K E; Cotter, G; Fortson, L; Heywood, I; Jones, T W; Kaviraj, S; Lopez-Sanchez, A R; Maksym, W P; Polsterer, K; Borden, K; Hollow, R P; Whyte, L

    2015-01-01

    We present results from the first twelve months of operation of Radio Galaxy Zoo, which upon completion will enable visual inspection of over 170,000 radio sources to determine the host galaxy of the radio emission and the radio morphology. Radio Galaxy Zoo uses $1.4\\,$GHz radio images from both the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) and the Australia Telescope Large Area Survey (ATLAS) in combination with mid-infrared images at $3.4\\,\\mu$m from the {\\it Wide-field Infrared Survey Explorer} (WISE) and at $3.6\\,\\mu$m from the {\\it Spitzer Space Telescope}. We present the early analysis of the WISE mid-infrared colours of the host galaxies. For images in which there is $>\\,75\\%$ consensus among the Radio Galaxy Zoo cross-identifications, the project participants are as effective as the science experts at identifying the host galaxies. The majority of the identified host galaxies reside in the mid-infrared colour space dominated by elliptical galaxies, quasi-stellar objects (QSOs), and l...

  13. The radio spectral energy distribution of infrared-faint radio sources

    CERN Document Server

    Herzog, A; Middelberg, E; Seymour, N; Spitler, L R; Emonts, B H C; Franzen, T M O; Hunstead, R; Intema, H T; Marvil, J; Parker, Q A; Sirothia, S K; Hurley-Walker, N; Bell, M; Bernardi, G; Bowman, J D; Briggs, F; Cappallo, R J; Callingham, J R; Deshpande, A A; Dwarakanath, K S; For, B -Q; Greenhill, L J; Hancock, P; Hazelton, B J; Hindson, L; Johnston-Hollitt, M; Kapinska, A D; Kaplan, D L; Lenc, E; Lonsdale, C J; McKinley, B; McWhirter, S R; Mitchell, D A; Morales, M F; Morgan, E; Morgan, J; Oberoi, D; Offringa, A; Ord, S M; Prabu, T; Procopio, P; Shankar, N Udaya; Srivani, K S; Staveley-Smith, L; Subrahmanyan, R; Tingay, S J; Wayth, R B; Webster, R L; Williams, A; Williams, C L; Wu, C; Zheng, Q; Chippendale, A P; Harvey-Smith, L; Heywood, I; Indermuehle, B; Popping, A; Sault, R J; Whiting, M T

    2016-01-01

    Infrared-faint radio sources (IFRS) are a class of radio-loud (RL) active galactic nuclei (AGN) at high redshifts (z > 1.7) that are characterised by their relative infrared faintness, resulting in enormous radio-to-infrared flux density ratios of up to several thousand. We aim to test the hypothesis that IFRS are young AGN, particularly GHz peaked-spectrum (GPS) and compact steep-spectrum (CSS) sources that have a low frequency turnover. We use the rich radio data set available for the Australia Telescope Large Area Survey fields, covering the frequency range between 150 MHz and 34 GHz with up to 19 wavebands from different telescopes, and build radio spectral energy distributions (SEDs) for 34 IFRS. We then study the radio properties of this class of object with respect to turnover, spectral index, and behaviour towards higher frequencies. We also present the highest-frequency radio observations of an IFRS, observed with the Plateau de Bure Interferometer at 105 GHz, and model the multi-wavelength and radio...

  14. Classical radio source propagating into outer H I disc in NGC 3801

    NARCIS (Netherlands)

    Emonts, B. H. C.; Burnett, C.; Morganti, R.; Struve, C.

    2012-01-01

    We present observations of a large-scale disc of neutral hydrogen (H I) in the nearby Fanaroff-Riley type I (FR I) radio galaxy NGC 3801 with the Westerbork Synthesis Radio Telescope. The H I disc (34 kpc in diameter and with ?) is aligned with the radio jet axis. This makes NGC 3801 an ideal system

  15. Classical radio source propagating into outer HI disc in NGC 3801

    NARCIS (Netherlands)

    Emonts, B. H. C.; Burnett, C.; Morganti, R.; Struve, C.

    2012-01-01

    We present observations of a large-scale disc of neutral hydrogen (H I) in the nearby Fanaroff-Riley type I (FR I) radio galaxy NGC 3801 with the Westerbork Synthesis Radio Telescope. The H I disc (34 kpc in diameter and with ?) is aligned with the radio jet axis. This makes NGC 3801 an ideal system

  16. Charting the Transient Radio Sky on Sub-Second Time-Scales with LOFAR

    NARCIS (Netherlands)

    Hessels, J.W.T.

    2012-01-01

    The LOw Frequency ARray (LOFAR) is a radio interferometric telescope that promises to open a largely unexplored window on transient sources in the "radio sky", from time-scales of nanoseconds to years. An important aspect of this will be the study of radio-emitting neutron stars in their various inc

  17. The radio properties of infrared-faint radio sources

    Science.gov (United States)

    Middelberg, E.; Norris, R. P.; Hales, C. A.; Seymour, N.; Johnston-Hollitt, M.; Huynh, M. T.; Lenc, E.; Mao, M. Y.

    2011-02-01

    Context. Infrared-faint radio sources (IFRS) are objects that have flux densities of several mJy at 1.4 GHz, but that are invisible at 3.6 μm when using sensitive Spitzer observations with μJy sensitivities. Their nature is unclear and difficult to investigate since they are only visible in the radio. Aims: High-resolution radio images and comprehensive spectral coverage can yield constraints on the emission mechanisms of IFRS and can give hints to similarities with known objects. Methods: We imaged a sample of 17 IFRS at 4.8 GHz and 8.6 GHz with the Australia Telescope Compact Array to determine the structures on arcsecond scales. We added radio data from other observing projects and from the literature to obtain broad-band radio spectra. Results: We find that the sources in our sample are either resolved out at the higher frequencies or are compact at resolutions of a few arcsec, which implies that they are smaller than a typical galaxy. The spectra of IFRS are remarkably steep, with a median spectral index of -1.4 and a prominent lack of spectral indices larger than -0.7. We also find that, given the IR non-detections, the ratio of 1.4 GHz flux density to 3.6 μm flux density is very high, and this puts them into the same regime as high-redshift radio galaxies. Conclusions: The evidence that IFRS are predominantly high-redshift sources driven by active galactic nuclei (AGN) is strong, even though not all IFRS may be caused by the same phenomenon. Compared to the rare and painstakingly collected high-redshift radio galaxies, IFRS appear to be much more abundant, but less luminous, AGN-driven galaxies at similar cosmological distances.

  18. Radio spectrum evolution and magnetic field in extreme GPS radio sources. The case of RXJ1459+3337

    CERN Document Server

    Orienti, M

    2007-01-01

    Aims: The knowledge of the properties of the youngest radio sources is very important in order to trace the earliest phase of the evolution of the radio emission. RXJ1459+3337, with its high turnover frequency (~25 GHz) provides a unique opportunity to study this class of extreme objects. Methods: High-sensitivity multi-frequency VLA observations have been carried out to measure the flux-density with high accuracy, while multi-frequency VLBA observations were performed, aimed at determining the pc-scale structure. Archival ROSAT data have been used to infer the X-ray luminosity. Results: The comparison between our new VLA data and those available in the literature shows a steady increment of the flux-density in the optically-thick part of the spectrum and a decrement of the turnover frequency. In the optically-thin regime, the source flux density has already started to decrease. Such a variability can be explained in terms of an adiabatically-expanding homogeneous radio component. The frequency range spanned ...

  19. Digitale radio

    NARCIS (Netherlands)

    Schiphorst, Roel; Zondervan, L.

    2007-01-01

    Als eerste in Europa heeft Nederland begin december 2006 de omschakeling van analoge naar digitale ethertelevisie gemaakt. Voor de analoge FM-radio is er ook een digitale variant, T-DAB. T-DAB staat voor 'Terrestrial Digital Audio Broadcasting'. Dit artikel gaat verder in op deze techniek en de veld

  20. Liverpool Telescope and Liverpool Telescope 2

    Science.gov (United States)

    Copperwheat, C. M.; Steele, I. A.; Barnsley, R. M.; Bates, S. D.; Clay, N. R.; Jermak, H.; Marchant, J. M.; Mottram, C. J.; Piascik, A.; Smith, R. J.

    2016-12-01

    The Liverpool Telescope is a fully robotic optical/near-infrared telescope with a 2-metre clear aperture, located at the Observatorio del Roque de los Muchachos on the Canary Island of La Palma. The telescope is owned and operated by Liverpool John Moores University, with financial support from the UK's Science and Technology Facilities Council. The telescope began routine science operations in 2004 and is a common-user facility with time available through a variety of committees via an open, peer reviewed process. Seven simultaneously mounted instruments support a broad science programme, with a focus on transient follow-up and other time domain topics well suited to the characteristics of robotic observing. Development has also begun on a successor facility, with the working title `Liverpool Telescope 2', to capitalise on the new era of time domain astronomy which will be brought about by the next generation of survey facilities such as LSST. The fully robotic Liverpool Telescope 2 will have a 4-metre aperture and an improved response time. In this paper we provide an overview of the current status of both facilities.

  1. THE VOLATILE COMPOSITION OF COMET C/2003 K4 (LINEAR) AT NEAR-IR WAVELENGTHS—COMPARISONS WITH RESULTS FROM THE NANÇAY RADIO TELESCOPE AND FROM THE ODIN, SPITZER, AND SOHO SPACE OBSERVATORIES

    Energy Technology Data Exchange (ETDEWEB)

    Paganini, L.; Mumma, M. J.; Villanueva, G. L.; DiSanti, M. A.; Bonev, B. P., E-mail: lucas.paganini@nasa.gov [Goddard Center for Astrobiology, NASA GSFC, MS 690, Greenbelt, MD 20771 (United States)

    2015-07-20

    We observed comet C/2003 K4 (LINEAR) using NIRSPEC at the Keck Observatory on UT 2004 November 28, when the comet was at 1.28 AU from the Sun (post-perihelion) and 1.38 AU from Earth. We detected six gaseous species (H{sub 2}O, OH*, C{sub 2}H{sub 6}, CH{sub 3}OH, CH{sub 4}, and HCN) and obtained upper limits for three others (H{sub 2}CO, C{sub 2}H{sub 2}, and NH{sub 3}). Our results indicate a water production rate of (1.72 ± 0.18) × 10{sup 29} molecules s{sup −1}, in reasonable agreement with production rates from SOHO (on the same day), Odin (one day earlier), and Nançay (about two weeks earlier). We also report abundances (relative to water) for seven trace species: CH{sub 3}OH (∼1.8%), CH{sub 4} (∼0.9%), and C{sub 2}H{sub 6} (∼0.4%) that were consistent with mean values among Oort cloud (OC) comets, while NH{sub 3} (<0.55%), HCN (∼0.07%), H{sub 2}CO (<0.07%), and C{sub 2}H{sub 2} (<0.04%) were “lower” than the mean values in other OC comets. We extracted inner-coma rotational temperatures for four species (H{sub 2}O, C{sub 2}H{sub 6}, CH{sub 3}OH, and CH{sub 4}), all of which are consistent with 70 K (within 1σ). The extracted ortho-para ratio for water was 3.0 ± 0.15, corresponding to spin temperatures larger than 39 K (at the 1σ level) and agreeing with those obtained with the Spitzer Space Telescope at the 2σ level.

  2. The search for exomoon radio emissions

    Science.gov (United States)

    Noyola, Joaquin P.

    The field of exoplanet detection has seen many new developments since the discovery of the first exoplanet. Observational surveys by the NASA Kepler Mission and several other instrument have led to the confirmation of over 1900 exoplanets, and several thousands of exoplanet potential candidates. All this progress, however, has yet to provide the first confirmed exomoon. Since all previous attempts to discover exomoons have failed, a novel method to detect them is proposed in this dissertation, which describes development of the method and its applications to select the best exomoon candidates for observational searches. The main goal of these searches is to verify the validity and effectiveness of the method, and discover the first exomoon by using the world largest and most suitable radio telescopes. The discovery of first exomoon would begin a new era of exploratory research in exoplanetary systems. The idea that exomoons can be discovered with radio telescopes was proposed by Noyola, Satyal and Musielak et al. (2014), who suggested that the interaction between Io and the Jovian magnetosphere could also be found in exoplanet-exomoon pairs, and the resulting radio emissions could be used to directly detect these systems. The main results of the original study obtained for single prograde exomoons are also described in this dissertation, which in addition extends the previous study to multiple exomoon systems, as well as retrograde orbits. The main objective of these studies is to identify the best exomoon candidates for detection by chosen radio telescopes. One such candidates, Epsilon Eridani b, was selected and observed by the Giant Metre Radio Telescope (GMRT) in India. The preliminary results of these observations do not show any expected radio emission from the chosen systems. Thus, implementation of several important improvements to the method is discussed in details in this dissertation.

  3. Radio astronomy from space

    Science.gov (United States)

    Woan, G.

    2011-04-01

    At frequencies below about 30 MHz, radio astronomy becomes increasingly difficult from the Earth's surface, mainly due to a combination of poor ionospheric seeing and strong terrestrial interference. The obvious move is to space, either as free-flying spacecraft or with a telescope located somewhere on the Moon. All the major space agencies have a renewed interest in the Moon as a site for exploration and science, and low-frequency radio astronomy is probably the strongest of the astronomical objectives put forward in these programmes. Although the Sun is a strong source of interference in extra-solar system work, it is also a prime target for study in itself. A constellation of satellites (as proposed for the SIRA mission) would be able to image both the Sun and the inner heliosphere over the entire low-frequency band. Here we investigate some of the advantages and limitations of astronomy at these very low frequencies, using space- and lunar-based antennas.

  4. 关于口径65 m射电天文望远镜单片反射镜测量方法的讨论%Discussion on inspection method of single-chip reflector in 65 m diameter radio telescope

    Institute of Scientific and Technical Information of China (English)

    孔飞

    2013-01-01

    The performance of the radio telescope with 65 m diameter is determined by 1 008 pieces of mirrors assembly. The monolithic mirror produced by compound process with molded by vacuum adsorption and ejected by mould pressing must be taken full inspection for quality control. Based on the molding characteristics of the mirror, we established the measuring plane of it by the use of high precision mechanical gantry coordinate plane, got the measurement origin with approximation method and the benefit of the mirror's four-corner characteristics and created a more reasonable measurement system to get the measured data of the part.%口径65 m的射电天文望远镜的工作性能由1008片反射镜组装决定.对采用真空吸附再模压顶出成形复合工艺制成的单片反射镜,必须采取全检进行质量控制.根据反射镜的成形特点,利用龙门三坐标的高精度机械坐标面建立反射镜的测量平面,并借助反射镜的四角特点采用逼近法求得测量原点,较合理地建立起测量系统,获取了零件的测量数据.

  5. The SKA1 LOW telescope: system architecture and design performance

    Science.gov (United States)

    Waterson, Mark F.; Labate, Maria Grazia; Schnetler, Hermine; Wagg, Jeff; Turner, Wallace; Dewdney, Peter

    2016-07-01

    The SKA1-LOW radio telescope will be a low-frequency (50-350 MHz) aperture array located in Western Australia. Its scientific objectives will prioritize studies of the Epoch of Reionization and pulsar physics. Development of the telescope has been allocated to consortia responsible for the aperture array front end, timing distribution, signal and data transport, correlation and beamforming signal processors, infrastructure, monitor and control systems, and science data processing. This paper will describe the system architectural design and key performance parameters of the telescope and summarize the high-level sub-system designs of the consortia.

  6. The School of Galactic Radio Astronomy: An Internet Classroom

    Science.gov (United States)

    Castelaz, M. W.; Cline, J. D.; Osborne, C. S.; Moffett, D. A.; Case, J.

    2001-12-01

    The School of Galactic Radio Astronomy (SGRA) takes its name from the source SGR-A, the center of the Milky Way Galaxy. SGRA is based at the Pisgah Astronomical Research Institute (PARI) as an experience-based school room for use by middle and high school teachers and their students. Their scientific educational experience at SGRA relies on Internet access to PARI's remote-controlled 4.6-m radio telescope which is equipped with a 1420 MHz receiver. The 1420 MHz signal may either be recorded as a spectrum over a 4 MHz bandpass, or mapped over extended regions. Teachers, classes, and Independent Study students access the 4.6-m radio telescope via the SGRA webpage. The SGRA webpage has four components: Radio Astronomy Basics, Observing, Guides, and Logbook. The Radio Astronomy Basics section summarizes the concepts of electromagnetic waves, detection of electromagnetic waves, sources of astronomical radio waves, and how astronomers use radio telescopes. The Observing section is the link to controlling the radio telescope and receiver. The Observing page is designed in the same way a control room at an observatory is designed. Controls include options of source selection, coordinate entry, slew, set, and guide selection, and tracking. Also within the Observing section is the curriculum which presents eight modules based on relevant radio astronomy topics and objects. The Guides webpage contains atlases of the astronomical sky, catalogs, examples of observing sessions, and data reduction software that can be downloaded for analysis offline. The LOGBOOK page is primarily a guestbook, and evaluation form. We acknowledge support from the Space Telescope Science Institute IDEAS Program, and the South Carolina State University PAIR Program.

  7. A Radio-Frequency-over-Fiber link for large-array radio astronomy applications

    CERN Document Server

    Mena, Juan; Cliche, Jean-Francois; Dobbs, Matt; Gilbert, Adam; Tang, Qing Yang

    2013-01-01

    A prototype 425-850 MHz Radio-Frequency-over-Fiber (RFoF) link for the Canadian Hydrogen Intensity Mapping Experiment (CHIME) is presented. The design is based on a directly modulated Fabry-Perot (FP) laser, operating at ambient temperature, and a single-mode fiber. The dynamic performance, gain stability, and phase stability of the RFoF link are characterized. Tests on a two-element interferometer built at the Dominion Radio Astrophysical Observatory for CHIME prototyping demonstrate that RFoF can be successfully used as a cost-effective solution for analog signal transport on the CHIME telescope and other large-array radio astronomy applications

  8. CORRELATIONS BETWEEN RADIO EMISSION OF THE PARSEC-SCALE JET AND OPTICAL NUCLEAR EMISSION OF HOST AGN

    Directory of Open Access Journals (Sweden)

    J. Torrealba

    2011-01-01

    Full Text Available Estudiamos las relaciones entre la emisión VLBA (Very Long Base Array en radio a 15 GHz y la emisión nuclear óptica a 5100 °A, para una muestra de 233 AGN dominados por el core con jets relativistas. Para 181 cuasares, hay una correlación positiva significativa entre la luminosidad nuclear óptica y las luminosidades VLBA totales del los núcleos no resueltos (en escalas de mili-arcosegundos de los jets a 15 GHz. La emisión del continuo óptico correlaciona con la emisión del jet a 15 GHz para 31 BL Lacs. Estas correlaciones confirman que la emisión en radio y en óptico están amplificadas y se originan en la parte más interna del jet a escalas de sub-parsecs en los cuasares, mientras que en los BL Lacs estas emisiones son generadas en el jet a escalas de parsecs. Estos resultados están de acuerdo con lo reportado previamente por Arshakian et al. (2010 para una muestra de 135 AGN.

  9. Testing Potential New Sites for Optical Telescopes in Australia

    CERN Document Server

    Hotan, Claire E; Glazebrook, Karl

    2012-01-01

    In coming years, Australia may find the need to build new optical telescopes to continue local programmes, contribute to global survey projects, and form a local multi-wavelength connection for the new radio telescopes being built. In this study, we refine possible locations for a new optical telescope by studying remotely sensed meteorological infrared data to ascertain expected cloud coverage rates across Australia, and combine these data with a Digital Elevation Model using a Geographic Information System. We find that the best sites within Australia for building optical telescopes are likely to be on the highest mountains in the Hamersley Range in Northwest Western Australia, while the MacDonnell Ranges in the Northern Territory may also be appropriate. We believe that similar seeing values to Siding Spring should be obtainable and with significantly more observing time at the identified sites. We expect to find twice as many clear nights as at current telescope sites. These sites are thus prime locations...

  10. The Solar Telescope GREGOR

    Science.gov (United States)

    Volkmer, R.

    2008-09-01

    During the last years the new 1.5m solar telescope GREGOR was assembled at Izania on Tenerife, Spain. The telescope is designed for high-precision measurements of the magnetic field in the solar photosphere and chromosphere with a resolution of 70km on the Sun. The telescope concept offers also high resolution stellar spectroscopy. The telescope is build by a consortium of the Kiepenheuer-Institut für Sonnenphysik, the Astrophysikalische Institut Potsdam, the Institut für Astrophysik Göttingen, Max-Plank-Institut für Sonnensystemforschung and additional international Partners. The telescope is a complete open structure with active cooled main mirror. High performance post-focus instruments in the visible and near IR wavelength acquire high resolution spectra with 2 dimensional spatial resolution and polarimetric information. The commissioning of the telescope will start in 2008 to allow first science observations at the end of 2009.

  11. JWST Pathfinder Telescope Integration

    Science.gov (United States)

    Matthews, Gary W.; Kennard, Scott H.; Broccolo, Ronald T.; Ellis, James M.; Daly, Elizabeth A.; Hahn, Walter G.; Amon, John N.; Mt. Pleasant, Stephen M.; Texter, Scott; Atkinson, Charles B.; McKay, Andrew; Levi, Joshua; Keski-Kuha, Ritva; Feinberg, Lee

    2015-01-01

    The James Webb Space Telescope (JWST) is a 6.5m, segmented, IR telescope that will explore the first light of the universe after the big bang. In 2014, a major risk reduction effort related to the Alignment, Integration, and Test (AI&T) of the segmented telescope was completed. The Pathfinder telescope includes two Primary Mirror Segment Assemblies (PMSA's) and the Secondary Mirror Assembly (SMA) onto a flight-like composite telescope backplane. This pathfinder allowed the JWST team to assess the alignment process and to better understand the various error sources that need to be accommodated in the flight build. The successful completion of the Pathfinder Telescope provides a final integration roadmap for the flight operations that will start in August 2015.

  12. Signal Processing Techniques Applied in RFI Mitigation of Radio Astronomy

    Directory of Open Access Journals (Sweden)

    Sixiu Wang

    2012-08-01

    Full Text Available Radio broadcast and telecommunications are present at different power levels everywhere on Earth. Radio Frequency Interference (RFI substantially limits the sensitivity of existing radio telescopes in several frequency bands and may prove to be an even greater obstacle for next generation of telescopes (or arrays to overcome. A variety of RFI detection and mitigation techniques have been developed in recent years. This study describes various signal process methods of RFI mitigation in radio astronomy, choose the method of Time-frequency domain cancellation to eliminate certain interference and effectively improve the signal to noise ratio in pulsar observations. Finally, RFI mitigation researches and implements in China radio astronomy will be also presented.

  13. The Jets of TeV Blazars at Higher Resolution: 43 GHz and Polarimetric VLBA Observations from 2005 to 2009

    Science.gov (United States)

    Piner, B. Glenn; Pant, Niraj; Edwards, Philip G.

    2010-11-01

    We present 23 new VLBA images of the six established TeV blazars Markarian 421, Markarian 501, H 1426+428, 1ES 1959+650, PKS 2155-304, and 1ES 2344+514, obtained from 2005 to 2009. Most images were obtained at 43 GHz (7 mm), and they reveal the parsec-scale structures of three of these sources (1ES 1959+650, PKS 2155-304, and 1ES 2344+514) at factors of 2-3 higher resolution than has previously been attained. These images reveal new morphological details, including a high degree of jet bending in the inner milliarcsecond in PKS 2155-304. This establishes strong apparent jet bending on VLBI scales as a common property of TeV blazars, implying viewing angles close to the line of sight. Most of the remaining images map the linear polarization structures at a lower frequency of 22 GHz (1 cm). We discuss the transverse structures of the jets as revealed by the high-frequency and polarimetric imaging. The transverse structures include significant limb brightening in Mrk 421, and "spine-sheath" structures in the electric vector position angle and fractional polarization distributions in Mrk 421, Mrk 501, and 1ES 1959+650. We use new measured component positions to update measured apparent jet speeds, in many cases significantly reducing the statistical error over previously published results. With the increased resolution at 43 GHz, we detect new components within 0.1-0.2 mas of the core in most of these sources. No motion is apparent in these new components over the time span of our observations, and we place upper limits on the apparent speeds of the components near the core of <2c. From those limits, we conclude that Γ2 < (Γ1)1/2 at ~105 Schwarzschild radii, where Γ1 and Γ2 are the bulk Lorentz factors in the TeV emitting and 43 GHz emitting regions, respectively, assuming that their velocity vectors are aligned.

  14. The road to OLFAR - a roadmap to interferometric long-wavelength radio astronomy using miniaturized distributed space systems

    NARCIS (Netherlands)

    Engelen, Steven; Quillien, Kevin A.; Verhoeven, Chris; Noroozi, Arash; Sundaramoorthy, Prem; Veen, van der Alle-Jan; Rajan, Raj Thilak; Boonstra, Albert-Jan; Bentum, Mark; Meijerink, Arjan; Budianu, Alex

    2013-01-01

    The Orbiting Low Frequency Antennas for Radio Astronomy (OLFAR) project aims to develop a space-based low frequency radio telescope that will explore the universe's so-called dark ages, map the interstellar medium, and discover planetary and solar bursts in other solar systems. The telescope, compos

  15. The road to OLFAR - a roadmap to interferometric long-wavelength radio astronomy using miniaturized distributed space systems

    NARCIS (Netherlands)

    Engelen, Steven; Quillien, Kevin A.; Verhoeven, Chris; Noroozi, Arash; Sundaramoorthy, Prem; van der Veen, Alle-Jan; Rajan, Raj; Rajan, Raj Thilak; Boonstra, Albert Jan; Bentum, Marinus Jan; Meijerink, Arjan; Budianu, A.

    2013-01-01

    The Orbiting Low Frequency Antennas for Radio Astronomy (OLFAR) project aims to develop a space-based low frequency radio telescope that will explore the universe's so-called dark ages, map the interstellar medium, and discover planetary and solar bursts in other solar systems. The telescope,

  16. The great Melbourne telescope

    CERN Document Server

    Gillespie, Richard

    2011-01-01

    Erected at Melbourne Observatory in 1869, the telescope was the second largest in the world, designed to explore the nature of the nebulae in the southern skies. Richard Gillespie, head of the History and Technology department at the Melbourne museum has written an entertaining account of the telescope's extraordinary history and tells the story through an amazing cast of characters whose lives intersected with the telescope.

  17. Pointing a solar telescope

    Science.gov (United States)

    Wallace, Patrick

    2016-07-01

    As far as pointing is concerned, a solar telescope is merely an ordinary astronomical telescope but with enhancements for observing solar and coronal features. The paper discusses the additional coordinate systems that need to be supported, shows how to generate the required solar ephemerides (both orbital and physical), and sets out a suitable application programming interface for the telescope control system to use when making solar observations.

  18. Space Telecommunications Radio System STRS Cognitive Radio

    Science.gov (United States)

    Briones, Janette C.; Handler, Louis M.

    2013-01-01

    Radios today are evolving from awareness toward cognition. A software defined radio (SDR) provides the most capability for integrating autonomic decision making ability and allows the incremental evolution toward a cognitive radio. This cognitive radio technology will impact NASA space communications in areas such as spectrum utilization, interoperability, network operations, and radio resource management over a wide range of operating conditions. NASAs cognitive radio will build upon the infrastructure being developed by Space Telecommunication Radio System (STRS) SDR technology. This paper explores the feasibility of inserting cognitive capabilities in the NASA STRS architecture and the interfaces between the cognitive engine and the STRS radio. The STRS architecture defines methods that can inform the cognitive engine about the radio environment so that the cognitive engine can learn autonomously from experience, and take appropriate actions to adapt the radio operating characteristics and optimize performance.

  19. The First VERITAS Telescope

    CERN Document Server

    Holder, J; Badran, H M; Blaylock, G; Bradbury, S M; Buckley, J H; Byrum, K L; Carter-Lewis, D A; Celik, O; Chow, Y C K; Cogan, P; Cui, W; Daniel, M K; De la Calle-Perez, I; Dowdall, C; Dowkontt, P; Duke, C; Falcone, A D; Fegan, S J; Finley, J P; Fortin, P; Fortson, L F; Gibbs, K; Gillanders, G; Glidewell, O J; Grube, J; Gutíerrez, K J; Gyuk, G; Hall, J; Hanna, D; Hays, E; Horan, D; Hughes, S B; Humensky, T B; Imran, A; Jung, I; Kaaret, Philip; Kenny, G E; Kieda, D; Kildea, J; Knapp, J; Krawczynski, H; Krennrich, F; Lang, M J; Le Bohec, S; Linton, E; Little, E K; Maier, G; Manseri, H; Milovanovic, A; Moriarty, P; Mukherjee, R; Ogden, P A; Ong, R A; Perkins, J S; Pizlo, F; Pohl, M; Quinn, J; Ragan, K; Reynolds, P T; Roache, E T; Rose, H J; Schroedter, M; Sembroski, G H; Sleege, G A; Steele, D; Swordy, S P; Syson, A; Toner, J A; Valcarcel, L; Vasilev, V V; Wagner, R; Wakely, S P; Weekes, T C; White, R J; Williams, D A

    2006-01-01

    The first atmospheric Cherenkov telescope of VERITAS (the Very Energetic Radiation Imaging Telescope Array System) has been in operation since February 2005. We present here a technical description of the instrument and a summary of its performance. The calibration methods are described, along with the results of Monte Carlo simulations of the telescope and comparisons between real and simulated data. The analysis of TeV $\\gamma$-ray observations of the Crab Nebula, including the reconstructed energy spectrum, is shown to give results consistent with earlier measurements. The telescope is operating as expected and has met or exceeded all design specifications.

  20. Intelligent Cognitive Radio Models for Enhancing Future Radio Astronomy Observations

    Directory of Open Access Journals (Sweden)

    Ayodele Abiola Periola

    2016-01-01

    Full Text Available Radio astronomy organisations desire to optimise the terrestrial radio astronomy observations by mitigating against interference and enhancing angular resolution. Ground telescopes (GTs experience interference from intersatellite links (ISLs. Astronomy source radio signals received by GTs are analysed at the high performance computing (HPC infrastructure. Furthermore, observation limitation conditions prevent GTs from conducting radio astronomy observations all the time, thereby causing low HPC utilisation. This paper proposes mechanisms that protect GTs from ISL interference without permanent prevention of ISL data transmission and enhance angular resolution. The ISL transmits data by taking advantage of similarities in the sequence of observed astronomy sources to increase ISL connection duration. In addition, the paper proposes a mechanism that enhances angular resolution by using reconfigurable earth stations. Furthermore, the paper presents the opportunistic computing scheme (OCS to enhance HPC utilisation. OCS enables the underutilised HPC to be used to train learning algorithms of a cognitive base station. The performances of the three mechanisms are evaluated. Simulations show that the proposed mechanisms protect GTs from ISL interference, enhance angular resolution, and improve HPC utilisation.

  1. Active galactic nuclei cores in infrared-faint radio sources: Very long baseline interferometry observations using the Very Long Baseline Array

    CERN Document Server

    Herzog, Andreas; Norris, Ray P; Spitler, Lee R; Deller, Adam T; Collier, Jordan D; Parker, Quentin A

    2015-01-01

    Infrared-faint radio sources (IFRS) form a new class of galaxies characterised by radio flux densities between tenths and tens of mJy and faint or absent infrared counterparts. It has been suggested that these objects are radio-loud active galactic nuclei (AGNs) at significant redshifts (z >~ 2). Whereas the high redshifts of IFRS have been recently confirmed based on spectroscopic data, the evidence for the presence of AGNs in IFRS is mainly indirect. So far, only two AGNs have been unquestionably confirmed in IFRS based on very long baseline interferometry (VLBI) observations. In this work, we test the hypothesis that IFRS contain AGNs in a large sample of sources using VLBI. We observed 57 IFRS with the Very Long Baseline Array (VLBA) down to a detection sensitivity in the sub-mJy regime and detected compact cores in 35 sources. Our VLBA detections increase the number of VLBI-detected IFRS from 2 to 37 and provide strong evidence that most - if not all - IFRS contain AGNs. We find that IFRS have a marginal...

  2. High-Precision Radio and Infrared Astrometry of LSPM J1314+1320AB - I: Parallax, Proper Motions, and Limits on Planets

    CERN Document Server

    Forbrich, Jan; Reid, Mark J; Berger, Edo; Rizzuto, Aaron; Mann, Andrew W; Liu, Michael C; Aller, Kimberly; Kraus, Adam L

    2016-01-01

    We present multi-epoch astrometric radio observations with the Very Long Baseline Array (VLBA) of the young ultracool-dwarf binary LSPM J1314+1320AB . The radio emission comes from the secondary star. Combining the VLBA data with Keck near-infrared adaptive-optics observations of both components, a full astrometric fit of parallax ($\\pi_{\\rm abs}=57.975\\pm0.045$ mas, corresponding to a distance of $d=17.249\\pm0.013$ pc), proper motion ($\\mu_{\\rm \\alpha cos \\delta}=-247.99\\pm0.10$ mas yr$^{-1}$, $\\mu_{\\delta}=-183.58\\pm0.22$ mas yr$^{-1}$), and orbital motion is obtained. Despite the fact that the two components have nearly identical masses to within $\\pm2$%, the secondary's radio emission exceeds that of the primary by a factor of $\\gtrsim$30, suggesting a difference in stellar rotation history, which could result in different magnetic field configurations. Alternatively, the emission could be anisotropic and beamed toward us for the secondary but not for the primary. Using only reflex motion, we exclude plan...

  3. Simultaneous X-Ray, Gamma-Ray, and Radio Observations of the Repeating Fast Radio Burst FRB 121102

    Science.gov (United States)

    Scholz, P.; Bogdanov, S.; Hessels, J. W. T.; Lynch, R. S.; Spitler, L. G.; Bassa, C. G.; Bower, G. C.; Burke-Spolaor, S.; Butler, B. J.; Chatterjee, S.; Cordes, J. M.; Gourdji, K.; Kaspi, V. M.; Law, C. J.; Marcote, B.; McLaughlin, M. A.; Michilli, D.; Paragi, Z.; Ransom, S. M.; Seymour, A.; Tendulkar, S. P.; Wharton, R. S.

    2017-09-01

    We undertook coordinated campaigns with the Green Bank, Effelsberg, and Arecibo radio telescopes during Chandra X-ray Observatory and XMM-Newton observations of the repeating fast radio burst FRB 121102 to search for simultaneous radio and X-ray bursts. We find 12 radio bursts from FRB 121102 during 70 ks total of X-ray observations. We detect no X-ray photons at the times of radio bursts from FRB 121102 and further detect no X-ray bursts above the measured background at any time. We place a 5σ upper limit of 3 × 10‑11 erg cm‑2 on the 0.5–10 keV fluence for X-ray bursts at the time of radio bursts for durations fast radio bursts in general.

  4. Interpretation of Tadpole Structures in the Solar Radio Radiation

    Science.gov (United States)

    Mann, Gottfried; Melnik, Valentin; Rucker, Helmut; Konovalenko, Alexander

    2016-04-01

    The new spectrometer on the Ukrainian radio telescope UTR-2 allows to observe the solar radio radiation at low frequencies (10-30 MHz) with a high spectral and temporal resolution. Tadpole structures were observed as special fine structures in the solar radio radiation. They show a fast drift (-2.13 MHz/s) in the dynamic radio spectrum. They appear as an ensemble of tadpoles drifting slowly (-8.3 kHz/s) from high to low frequencies. The tadpoles are interpreted as electron beams accelerated at shocks in the high corona.

  5. Sensivity studies for the Cherenkov Telescope Array

    Science.gov (United States)

    Collado, Tarek Hassan

    2015-06-01

    Since the creation of the first telescope in the 17th century, every major discovery in astrophysics has been the direct consequence of the development of novel observation techniques, opening new windows in the electromagnetic spectrum. After Karl Jansky discovered serendipitously the first radio source in 1933, Grote Reber built the first parabolic radio telescope in his backyard, planting the seed of a whole new field in astronomy. Similarly, new technologies in the 1950s allowed the establishment of other fields, such as the infrared, ultraviolet or the X-rays. The highest energy end of the electromagnetic spectrum, the γ-ray range, represents the last unexplored window for astronomers and should reveal the most extreme phenomena that take place in the Universe. Given the technical complexity of γ-ray detection and the extremely relative low fluxes, γ-ray astronomy has undergone a slower development compared to other wavelengths. Nowadays, the great success of consecutive space missions together with the development and refinement of new detection techniques from the ground, has allowed outstanding scientific results and has brought gamma-ray astronomy to a worthy level in par with other astronomy fields. This work is devoted to the study and improvement of the future Cherenkov Telescope Array (CTA), the next generation of ground based γ-ray detectors, designed to observe photons with the highest energies ever observed from cosmic sources.

  6. Variable low-frequency radio emission of the solar system and galactic objects

    Science.gov (United States)

    Konovalenko, Alexander; Kolyadin, Vladimir; Rucker, Helmut; Zakharenko, Vyacheslav; Zarka, Philippe; Griessmeier, Jean-M.; Denis, Loran; Melnik, Valentin; Litvinenko, Galina; Zaitsev, Valerij; Falkovich, Igor; Ulyanov, Oleg; Sidorchuk, Mikhail; Stepkin, Sergej; Stanislavskij, Alexander; Kalinichenko, Nikolaj; Boiko, Nastja; Vasiljiva, Iaroslavna; Mukha, Dmytro; Koval, Artem

    2013-04-01

    There are many physical processes and propagation effects for the producing the time variable radio emission just at the low frequencies (at the decameter wavelength). The study of this radio emission is the important part of the modern radio astronomy. Strong progress in the development of the radio telescopes, methods and instrumentation allowed to start the corresponding investigations at new quality and quantity levels. It related to the implementation of the world largest UTR-2 radio telescope (effective area is more than 100 000 sq.m) more high sensitive at frequencies less than 30 MHz. During last years many new observations were carried out with this radio telescope and many new effects have been detected for the Sun, planets, interplanetary medium, exoplanets as well as various kinds of the stars.

  7. Observations of Radio Giant Pulses with GAVRT

    CERN Document Server

    Jones, Glenn

    2015-01-01

    Radio giant pulses provide a unique opportunity to study the pulsar radio emission mechanism in exquisite detail. Previous studies have revealed a wide range of properties and phenomena, including extraordinarily high brightness temperatures, sub-nanosecond emission features, and banded dynamic spectra. New measurements of giant pulse characteristics can help guide and test theoretical emission models. To this end, an extensive observation campaign has begun which will provide more than 500 hours on the Crab with a 34-meter antenna located in California, USA. The observations are being done as part of an educational outreach program called the Goldstone-Apple Valley Radio Telescope (GAVRT). This antenna has a novel wide bandwidth receiver which provides up to 8 GHz of instantaneous bandwidth in the range of 2.5 to 14 GHz. These observations will provide detailed information about the variability, amplitude distribution, and detailed frequency structure of radio giant pulses. In addition, a database of pulses ...

  8. Radio VLBI and the quantum interference paradox

    CERN Document Server

    Singal, Ashok K

    2016-01-01

    We address here the question of interference of radio signals from astronomical sources like distant quasars, in a very long baseline interferometer (VLBI), where two (or more) distantly located radio telescopes (apertures), receive simultaneous signal from the sky. In an equivalent optical two-slit experiment, it is generally argued that for the photons involved in the interference pattern on the screen, it is not possible, even in principle, to ascertain which of the two slits a particular photon went through. It is argued that any procedure to ascertain this destroys the interference pattern. But in the case of the modern radio VLBI, it is a routine matter to record the phase and amplitude of the voltage outputs from the two radio antennas on a recording media separately and then do the correlation between the two recorded signals later in an offline manner. Does this not violate the quantum interference principle? We provide a resolution of this problem here.

  9. LUTE telescope structural design

    Science.gov (United States)

    Ruthven, Gregory

    1993-01-01

    The major objective of the Lunar Ultraviolet Transit Experiment (LUTE) Telescope Structural Design Study was to investigate the feasibility of designing an ultralightweight 1-m aperture system within optical performance requirements and mass budget constraints. This study uses the results from our previous studies on LUTE as a basis for further developing the LUTE structural architecture. After summarizing our results in Section 2, Section 3 begins with the overall logic we used to determine which telescope 'structural form' should be adopted for further analysis and weight estimates. Specific telescope component analysis showing calculated fundamental frequencies and how they compare with our derived requirements are included. 'First-order' component stress analyses to ensure telescope optical and structural component (i.e. mirrors & main bulkhead) weights are realistic are presented. Layouts of both the primary and tertiary mirrors showing dimensions that are consistent with both our weight and frequency calculations also form part of Section 3. Section 4 presents our calculated values for the predicted thermally induced primary-to-secondary mirror despace motion due to the large temperature range over which LUTE must operate. Two different telescope design approaches (one which utilizes fused quartz metering rods and one which assumes the entire telescope is fabricated from beryllium) are considered in this analysis. We bound the secondary mirror focus mechanism range (in despace) based on these two telescope configurations. In Section 5 we show our overall design of the UVTA (Ultraviolet Telescope Assembly) via an 'exploded view' of the sub-system. The 'exploded view' is annotated to help aid in the understanding of each sub-assembly. We also include a two view layout of the UVTA from which telescope and telescope component dimensions can be measured. We conclude our study with a set of recommendations not only with respect to the LUTE structural architecture

  10. Simultaneous X-ray and radio observations of the radio-mode-switching pulsar PSR B1822-09

    Science.gov (United States)

    Hermsen, W.; Kuiper, L.; Hessels, J. W. T.; Mitra, D.; Rankin, J. M.; Stappers, B. W.; Wright, G. A. E.; Basu, R.; Szary, A.; van Leeuwen, J.

    2017-04-01

    We report on simultaneous X-ray and radio observations of the radio-mode-switching pulsar PSR B1822-09 with ESA's XMM-Newton and the Westerbork Synthesis Radio Telescope, Giant Metrewave Radio Telescope and Lovell radio telescopes. PSR B1822-09 switches between a radio-bright and radio-quiet mode, and we discovered a relationship between the durations of its modes and a known underlying radio-modulation time-scale within the modes. We discovered X-ray (energies 0.2-1.4 keV) pulsations with a broad sinusoidal pulse, slightly lagging the radio main pulse in phase by 0.094 ± 0.017, with an energy-dependent pulsed fraction varying from ∼0.15 at 0.3 keV to ∼0.6 at 1 keV. No evidence is found for simultaneous X-ray and radio mode switching. The total X-ray spectrum consists of a cool component (T ∼0.96 × 106 K, hotspot radius R ∼2.0 km) and a hot component (T ∼2.2 × 106 K, R ∼100 m). The hot component can be ascribed to the pulsed emission and the cool component to the unpulsed emission. The high-energy characteristics of PSR B1822-09 resemble those of middle-aged pulsars such as PSR B0656+14, PSR B1055-52 and Geminga, including an indication for pulsed high-energy gamma-ray emission in Fermi Large Area Telescope data. Explanations for the high pulsed fraction seem to require different temperatures at the two poles of this orthogonal rotator, or magnetic anisotropic beaming effects in its strong magnetic field. In our X-ray skymap, we found a harder source at only 5.1 ± 0.5 arcsec from PSR B1822-09, which might be a pulsar wind nebula.

  11. Low Frequency Radio Experiment (LORE)

    Science.gov (United States)

    Manoharan, P. K.; Naidu, Arun; Joshi, B. C.; Roy, Jayashree; Kate, G.; Pethe, Kaiwalya; Galande, Shridhar; Jamadar, Sachin; Mahajan, S. P.; Patil, R. A.

    2016-03-01

    In this paper, we present a case study of Low Frequency Radio Experiment (LORE) payload to probe the corona and the solar disturbances at solar offsets greater than 2 solar radii, i.e., at frequencies below 30 MHz. The LORE can be complimentary to the planned Indian solar mission, “Aditya-L1” and its other payloads as well as synergistic to ground-based interplanetary scintillation (IPS) observations, which are routinely carried out by the Ooty Radio Telescope. We discuss the baseline design and technical details of the proposed LORE and its particular suitability for providing measurements on the detailed time and frequency structure of fast drifting type-III and slow drifting type-II radio bursts with unprecedented time and frequency resolutions. We also brief the gonio-polarimetry, which is possible with better-designed antennas and state-of-the-art electronics, employing FPGAs and an intelligent data management system. These would enable us to make a wide range of studies, such as nonlinear plasma processes in the Sun-Earth distance, in-situ radio emission from coronal mass ejections (CMEs), interplanetary CME driven shocks, nature of ICMEs driving decelerating IP shocks and space weather effects of solar wind interaction regions.

  12. Radio Monitoring of Protoplanetary Discs

    Science.gov (United States)

    Ubach, C.; Maddison, S. T.; Wright, C. M.; Wilner, D. J.; Lommen, D. J. P.; Koribalski, B.

    2017-01-01

    Protoplanetary disc systems observed at radio wavelengths often show excess emission above that expected from a simple extrapolation of thermal dust emission observed at short millimetre wavelengths. Monitoring the emission at radio wavelengths can be used to help disentangle the physical mechanisms responsible for this excess, including free-free emission from a wind or jet, and chromospheric emission associated with stellar activity. We present new results from a radio monitoring survey conducted with Australia Telescope Compact Array over the course of several years with observation intervals spanning days, months and years, where the flux variability of 11 T Tauri stars in the Chamaeleon and Lupus star forming regions was measured at 7 and 15 mm and 3 and 6 cm. Results show that for most sources are variable to some degree at 7 mm, indicating the presence of emission mechanisms other than thermal dust in some sources. Additionally, evidence of grain growth to cm-sized pebbles was found for some sources that also have signs of variable flux at 7 mm. We conclude that multiple processes contributing to the emission are common in T Tauri stars at 7 mm and beyond, and that a detection at a single epoch at radio wavelengths should not be used to determine all processes contributing to the emission.

  13. Effect of Parasitic Element on 408 MHz Antenna for Radio Astronomy Application

    Directory of Open Access Journals (Sweden)

    Radial Anwar

    2014-01-01

    Full Text Available Antenna is one of the important subsystem components in a radio telescope system. In this paper, analysis on the effect of parasitic element on 408 MHz antenna in a radio telescope system is presented. Higher gain up to 10.24 dBi with reduction on beamwidth size has been achieved by optimizing the position of parasitic element relative to the driven element. The proposed antenna is suitable to be utilized in a transient radio telescope array.

  14. The MOJAVE Chandra Sample: A Correlation Study of Blazars and Radio Galaxies in X-ray and Radio Wavelengths

    Science.gov (United States)

    Hogan, Brandon Scott

    2011-05-01

    The Chandra X-ray observatory has increased the quality and number of detections the X-ray regime since its launch in 1999. It is an important tool for studying the jets which are associated with Active Galactic Nuclei (AGN) and their possible emission mechanisms. The MOJAVE Chandra Sample (MCS) is a sample of 27 AGN which have been selected from the radio flux-limited MOJAVE (Monitoring of Jets in AGN with VLBA Experiments) sample. The objects contained in the MOJAVE sample are traditionally associated with relativistically beamed jets that have small viewing angles. The MCS was created to study the correlation of X-ray and radio emission on kiloparsec scales. The complete sample is made up of all MOJAVE Fanaroff & Riley type II objects which have over 100 mJy of extended radio emission at 1.4 GHz and a radio structure of at least 3" in extent. Chandra observations have revealed X-ray and radio correlation in 21 of the 27 jets, bringing the detection rate to ˜78%. The selection criteria provides a quantitative method of discovering new X-ray jets associated with AGN from radio observations. The X-ray morphologies are usually well correlated with the radio emission, except for the sources which show extreme bending on the kiloparsec scale. The emission mechanism for these relativistically beamed quasars and radio galaxies can be interpreted as inverse Compton scattering off of the cosmic microwave background by the electrons in the jets (IC/CMB). The emission mechanism is reinforced by spectral energy distributions (SED) which model the emission mechanisms for sources with sufficient X-ray, optical, and radio data available. I have explored the effects of jet bending and jet deceleration in conjunction with the inverse Compton emission model and used different scenarios to derive best fit viewing angles and bulk Lorentz factors, which were calculated by using the superluminal speeds along with parameters that were derived from the IC/CMB model. The range of

  15. HUBBLE SPACE TELESCOPE Snapshot Survey of 3CR Quasars: The Data

    Science.gov (United States)

    Lehnert, Matthew D.; Miley, George K.; Sparks, William B.; Baum, Stefi A.; Biretta, John; Golombek, Daniel; de Koff, Sigrid; Macchetto, Ferdinando D.; McCarthy, Patrick J.

    1999-08-01

    We present images taken with the Wide Field Planetary Camera (WFPC-2) on the Hubble Space Telescope (HST) of 43 quasars selected from the 3CR radio catalog. The redshift range of the targets is large--0.3Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

  16. Timing of Events in the Central Engine and Jets of the Radio Galaxies 3c 111 and 3c 120 (core Program)

    Science.gov (United States)

    The investigators request continuation of their long-term monitoring of the X-ray flux of the radio galaxies 3C 111 (FR 2) and 3C 120 (FR 1) 2 and 4 times per week, respectively, throughout Cycle 12, as well as a 90 days of daily monitoring of 3C 111. In both objects, dips in X-ray flux precede the appearance of bright superluminal knots in the radio jet. The long-term multiwaveband light curves and sequences of 7 mm VLBA images will record the changing pattern of multiwaveband emission in these two AGN. 3C 111 is a probable EGRET source; if the ID is correct, GLAST will measure its flux daily, allowing relative timing of gamma-ray variations with X-ray and optical events from the central engine plus radio events in the jet.

  17. Water-filled telescopes

    CERN Document Server

    Antonello, E

    2014-01-01

    In this short note we discuss the case of the thought experiments on water-filled telescopes and their realizations during 18th and 19th century. The story of those instruments shows that the scientific progress occurs in a curious way, since there was no stringent reason for the construction of a water-filled telescope.

  18. Athermal laser launch telescopes

    NARCIS (Netherlands)

    Kamphues, F.G.; Henselmans, R.; Rijnveld, N.; Lemmen, M.H.J.; Doelman, N.J.; Nijkerk, M.D.

    2011-01-01

    ESO has developed a concept for a compact laser guide star unit for use in future Adaptive Optics (AO) systems. A small powerful laser is combined with a telescope that launches the beam, creating a single modular unit that can be mounted directly on a large telescope. This approach solves several

  19. Athermal laser launch telescopes

    NARCIS (Netherlands)

    Kamphues, F.G.; Henselmans, R.; Rijnveld, N.; Lemmen, M.H.J.; Doelman, N.J.; Nijkerk, M.D.

    2011-01-01

    ESO has developed a concept for a compact laser guide star unit for use in future Adaptive Optics (AO) systems. A small powerful laser is combined with a telescope that launches the beam, creating a single modular unit that can be mounted directly on a large telescope. This approach solves several o

  20. A search for dispersed radio bursts in archival Parkes Multibeam Pulsar Survey data

    CERN Document Server

    Bagchi, Manjari; McLaughlin, Maura

    2012-01-01

    A number of different classes of potentially extra-terrestrial bursts of radio emission have been observed in surveys with the Parkes 64m radio telescope, including "Rotating Radio Transients", the "Lorimer burst" and "perytons". Rotating Radio Transients are radio pulsars which are best detectable in single-pulse searches. The Lorimer burst is a highly dispersed isolated radio burst with properties suggestive of extragalactic origin. Perytons share the frequency-swept nature of the Rotating Radio Transients and Lorimer burst, but unlike these events appear in all thirteen beams of the Parkes Multibeam receiver and are probably a form of peculiar radio frequency interference. In order to constrain these and other radio source populations further, we searched the archival Parkes Multibeam Pulsar Survey data for events similar to any of these. We did not find any new Rotating Radio Transients or bursts like the Lorimer burst. We did, however, discover four peryton-like events. Similar to the perytons, these fou...